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This study was conducted to investigate the effect of core sampling on Warner-Bratzler shear force evaluations of beef and pork loins (Longissimus thoracis et lumborum muscles) and to determine the relationship between them. Steaks of 2.54cm from beef and pork loins were cooked and five round cross-section cores and five square cross-section cores of each steak were taken for shear force evaluation. Core sampling influenced both beef and pork shear force values with higher (Psquare cross-section cores. There was a strong and linear relationship (Psquare cross-section cores for beef (R(2)=0.78), pork (R(2)=0.70) and for beef+pork (R(2)=0.82) samples. These results indicate that it is feasible to use square cross-section cores in Warner-Bratzler shear force protocol as an alternative and potential method to standardize sampling for shear force measurements. PMID:25569815
Silva, Douglas R G; Torres Filho, Robledo A; Cazedey, Henrique P; Fontes, Paulo R; Ramos, Alcin�ia L S; Ramos, Eduardo M
Significant SNPs associated with Warner-Bratzler (WB) shear force and sensory traits were confirmed for Hanwoo beef (Korean cattle). A Bonferroni-corrected genome-wide significant association (p<1.3�10?6) was detected with only one single nucleotide polymorphism (SNP) on chromosome 5 for WB shear force. A slightly higher number of SNPs was significantly (p<0.001) associated with WB shear force than with other sensory traits. Further, 50, 25, 29, and 34 SNPs were significantly associated with WB shear force, tenderness, juiciness, and flavor likeness, respectively. The SNPs between p = 0.001 and p = 0.0001 thresholds explained 3% to 9% of the phenotypic variance, while the most significant SNPs accounted for 7% to 12% of the phenotypic variance. In conclusion, because WB shear force and sensory evaluation were moderately affected by a few loci and minimally affected by other loci, further studies are required by using a large sample size and high marker density. PMID:25178377
Dang, C. G.; Cho, S. H.; Sharma, A.; Kim, H. C.; Jeon, G. J.; Yeon, S. H.; Hong, S. K.; Park, B. Y.; Kang, H. S.; Lee, S. H.
Sun-dried beef is a frequently consumed and valued product in Brazil, however, there have been no scientific studies on its texture. To assess the tenderness of sun-dried beef, an instrumental analysis (Warner-Bratzler Shear Force; WBSF), a sensory analysis (Quantitative Descriptive Analysis; QDA) and the sarcomere length (SL) were used as indicators. Significant differences were observed among the sun-dried beef samples. Sample 3 (composed of sun-dried meat purchased at three fairs from Regi...
Marta Madruga; Geany de Souza; Ricardo Moreira; Yuri Ishihara; Alanne Salviano
Forty USDA Select and 40 upper two-thirds USDA Choice beef carcasses were used to determine the effects of postmortem aging on tenderness of 17 individual beef muscles. Biceps femoris-long head, complexus, gluteus medius, infraspinatus, longissimus dorsi, psoas major, rectus femoris, semimembranosus, semitendinosus, serratus ventralis, spinalis dorsi, supraspinatus, tensor fasciae latae, teres major, triceps brachii-long head, vastus lateralis, and vastus medialis muscles were removed from each carcass. Seven steaks (2.54-cm thick) were cut from every muscle, and each steak was assigned to one of the following postmortem aging periods: 2, 4, 6, 10, 14, 21, or 28 d postmortem. After completion of the designated aging period, steaks were removed from storage (2 degrees C, never frozen), cooked to a peak internal temperature of 71 degrees C, and evaluated using Warner-Bratzler shear force (WBSF). Analysis of WBSF revealed a 3-way interaction (P = 0.004) among individual muscle, USDA quality grade, and postmortem aging period. With the exception of the Select teres major, WBSF of all muscles (both quality grades) decreased with increasing time of postmortem storage. Nonlinear regression was used to characterize the extent (aging response) and rate of decrease in WBSF from 2 through 28 d postmortem for each muscle within each quality grade. In general, WBSF of upper two-thirds Choice muscles decreased more rapidly from 2 to 10 d postmortem than did corresponding Select muscles. Muscles that had greater aging responses generally had greater 2-d WBSF values. The upper two-thirds Choice psoas major, serratus ventralis, and vastus lateralis muscles required similar aging times to complete a majority of the aging response (head, and vastus medialis muscles required 4 to 6 d less time to complete a majority of the aging response than did comparable Select muscles. Aging times for Select biceps femoris-long head, infraspinatus, longissimus dorsi, rectus femoris, semimembranosus, spinalis dorsi, supraspinatus, and tensor fasciae latae muscles were > or =7 d longer than those for corresponding upper two-thirds Choice muscles. Results from this study suggest that muscle-to-muscle tenderness differences depend on quality grade and aging time and that postmortem aging should be managed with respect to individual muscle and USDA quality grade. PMID:17093232
Gruber, S L; Tatum, J D; Scanga, J A; Chapman, P L; Smith, G C; Belk, K E
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Full Text Available Sun-dried beef is a frequently consumed and valued product in Brazil, however, there have been no scientific studies on its texture. To assess the tenderness of sun-dried beef, an instrumental analysis (Warner-Bratzler Shear Force; WBSF, a sensory analysis (Quantitative Descriptive Analysis; QDA and the sarcomere length (SL were used as indicators. Significant differences were observed among the sun-dried beef samples. Sample 3 (composed of sun-dried meat purchased at three fairs from Region 3 in the city of Jo�o Pessoa-PB was considered the most tender by the assessors, with a score of 6.7, and its WBSF analysis revealed a maximum value of 2.70 kgf. Additionally, this sample exhibited the highest SL value (1.89 �m. Samples 1 and 2 (composed of sun-dried meat purchased at three fairs from Regions 1 and 2, respectively, in the city of Jo�o Pessoa exhibited very similar tenderness values (WBSF and QDA but differed in their SL values, which suggested that sample 2 was the least tender. In conclusion, these results demonstrate that the studied parameters are complementary and can be used as tenderness indicators for sun-dried beef. However, although the difference was beyond the detection limit of the assessors and the texturometer, the SL analysis appears to have been the most effective.
Marta Madruga
Aging patterns of nine muscles from the chuck and round from two quality classifications of beef: USDA Select and upper 2/3 of USDA Choice grade were determined. The following muscles were evaluated: infraspinatus, triceps brachii - lateral head, triceps brachii - long head, serratus ventralis, complexus, splenius, rhomboideus, vastus lateralis and rectus femoris. Muscles were divided into four portions, progressing from anterior to posterior or dorsal to ventral orientation to the carcass depending on muscle fiber orientation. One steak was removed from each portion and aged for 7, 14, 21, or 28 d postmortem, then Warner-Bratzler shear force (WBSF) analysis was conducted. Consistent aging recommendations can be given for all muscles studied, as there was no aging by muscle interaction. An aging by USDA grade interaction was noted (P<0.05). The upper 2/3 of USDA Choice need not be aged beyond 7 d. USDA Select should be aged at least 14 d. Steak location within muscle had an effect (P<0.05) on WBSF values in four muscles. These data indicate that fabrication and merchandizing decisions should be made on an individual muscle basis. PMID:22063484
Bratcher, C L; Johnson, D D; Littell, R C; Gwartney, B L
Raw samples of 14 muscles: Mm. biceps femoris (BF), quadriceps femoris (CF), diaphragm (DI), flexor digitorum (FD), gluteus medius (GM), infraspinatus (IE), longissimus lumborum (LL), longissimus thoracis (LT), psoas major (PM), pectoralis profundus (PP), semimembranosus (SM), semitendinosus (ST), sternomandibularis (STER) and triceps brachii (TB) from four Swiss Brown (485�15 days old) young bull carcasses and weighing approximately 300 kg were evaluated for some chemical and physical properties. PM (2.11 kg) and DI (2.24 kg) were the muscles which had the lowest Warner-Bratzler shear force values, while PP (6.66 kg) had the greatest shear force (PWarner-Bratzler shear force of raw samples was found (r=0.723; PWarner-Bratzler shear force was (r=0.661; P<0.01). Significant differences (P<0.05) were observed among muscles for differential scanning calorimetry, sarcomere length, pH and colour parameters. PMID:22062666
Torrescano, Gast�n; S�nchez-Escalante, Armida; Gim�nez, Bego�a; Roncal�s, Pedro; Beltr�n, Jos� Antonio
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Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A padroniza��o da textura � um dos principais problemas relacionados � qualidade da carne bovina. Por isso, a avalia��o objetiva da maciez, por m�todos mec�nicos, vem sendo estudada h� muitos anos. Para que a avalia��o instrumental da textura seja uma ferramenta efetiva nos estudos envolvendo a maci [...] ez da carne, � necess�rio minimizar as causas de varia��o envolvidas na an�lise. Atualmente, a for�a de cisalhamento Warner-Bratzler � o m�todo mais amplamente empregado para essa finalidade. O protocolo padr�o dessa t�cnica anal�tica preconiza a utiliza��o de uma l�mina de cisalhamento de 1,016mm de espessura. Neste trabalho, foram comparados dados de textura de carne bovina obtidos com a l�mina de cisalhamento padr�o Warner-Bratzler, de 1,016mm de espessura, e uma l�mina mais grossa, de 3,05mm de espessura. Ap�s o abate, amostras de m�sculo Longissimus dorsi, semelhantes em rela��o aos teores de umidade, lip�deos e prote�nas, foram submetidas a duas diferentes temperaturas de resfriamento, atingindo diferentes velocidades de queda de temperatura e, consequentemente, diferentes graus de contra��o do tecido muscular, o que foi confirmado pela determina��o do comprimento dos sarc�meros. Os resultados demonstraram uma maior sensibilidade da l�mina padr�o Warner-Bratzler na detec��o de varia��es da textura da carne, em fun��o da velocidade de resfriamento. Abstract in english Standardization of texture is one of the main problems related to beef quality. Because of that, objective evaluation of tenderness performed by mechanic methodologies has been studied for years. In order to count on instrumental texture evaluation as a valuable tool in meat tenderness studies, it i [...] s necessary to minimize the causes of variation that might be involved in the trial. Nowadays, Warner-Bratzler shear force is widely used for meat tenderness determination. The standard protocol of this methodology establishes the utilization of shear blade 1.016mm tick. The aim of this study was to compare beef texture data provided by Warner-Bratzler standard shear blade, 1.016mm thick, with those provided by a thicker one, 3.05mm thick. After slaughtering, Longissimus dorsi muscle samples with similar contents of moisture, lipids and proteins were subjected to two different cooling temperatures,reaching different rates of temperature drop and hence different muscle contraction extents, which were confirmed by the determination of sarcomere length. Results indicated the superior sensibility of the Warner-Bratzler standard shear blade to detect variations in meat texture due to cooling velocity.
Marcos Franke, Pinto; Elisa Helena Giglio, Ponsano; Ana Paula da Silva, Almeida.
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Full Text Available A padroniza��o da textura � um dos principais problemas relacionados � qualidade da carne bovina. Por isso, a avalia��o objetiva da maciez, por m�todos mec�nicos, vem sendo estudada h� muitos anos. Para que a avalia��o instrumental da textura seja uma ferramenta efetiva nos estudos envolvendo a maciez da carne, � necess�rio minimizar as causas de varia��o envolvidas na an�lise. Atualmente, a for�a de cisalhamento Warner-Bratzler � o m�todo mais amplamente empregado para essa finalidade. O protocolo padr�o dessa t�cnica anal�tica preconiza a utiliza��o de uma l�mina de cisalhamento de 1,016mm de espessura. Neste trabalho, foram comparados dados de textura de carne bovina obtidos com a l�mina de cisalhamento padr�o Warner-Bratzler, de 1,016mm de espessura, e uma l�mina mais grossa, de 3,05mm de espessura. Ap�s o abate, amostras de m�sculo Longissimus dorsi, semelhantes em rela��o aos teores de umidade, lip�deos e prote�nas, foram submetidas a duas diferentes temperaturas de resfriamento, atingindo diferentes velocidades de queda de temperatura e, consequentemente, diferentes graus de contra��o do tecido muscular, o que foi confirmado pela determina��o do comprimento dos sarc�meros. Os resultados demonstraram uma maior sensibilidade da l�mina padr�o Warner-Bratzler na detec��o de varia��es da textura da carne, em fun��o da velocidade de resfriamento.Standardization of texture is one of the main problems related to beef quality. Because of that, objective evaluation of tenderness performed by mechanic methodologies has been studied for years. In order to count on instrumental texture evaluation as a valuable tool in meat tenderness studies, it is necessary to minimize the causes of variation that might be involved in the trial. Nowadays, Warner-Bratzler shear force is widely used for meat tenderness determination. The standard protocol of this methodology establishes the utilization of shear blade 1.016mm tick. The aim of this study was to compare beef texture data provided by Warner-Bratzler standard shear blade, 1.016mm thick, with those provided by a thicker one, 3.05mm thick. After slaughtering, Longissimus dorsi muscle samples with similar contents of moisture, lipids and proteins were subjected to two different cooling temperatures,reaching different rates of temperature drop and hence different muscle contraction extents, which were confirmed by the determination of sarcomere length. Results indicated the superior sensibility of the Warner-Bratzler standard shear blade to detect variations in meat texture due to cooling velocity.
Marcos Franke Pinto
This study is a meta-analysis of the effects of the beta-agonists zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RAC) on feedlot performance, carcase characteristics of cattle and Warner Bratzler shear force (WBSF) of muscles. It was conducted to evaluate the effect of the use of these agents on beef production and meat quality and to provide data that would be useful in considerations on the effect of these agents on meat quality in Meat Standards Australia evaluations. We cond...
Lean, Ian J.; Thompson, John M.; Dunshea, Frank R.
Warner Brothers Online is a nicely-done entertainment site for both kids and adults. It includes episodes of the original Superman Radio show (via RealAudio), a singalong with Looney Toons Karaoke, clips of Madonna songs, and the Kids WB, with downloadable games, a history of Warner Brothers animation, and the "Sylvester and Tweety mysteries". However, the most interesting feature of the entire site is "Send a WeB card to a friend", which allows you to send a personalized e-mail "postcard" to a friend. The friend receives a message, with a URL and a "secret key" allowing them to retrieve their postcard. Time and bandwidth spent having fun. http://www.warnerbros.com/
In the December 16, 1999 issue of Nature, researchers from Australia and California used chemical tests to show that coral reef fish often spend their life cycle close to home, rather than drifting in the open ocean. These findings have important implications for global fisheries management. This site provides further information on Robert Warner, one of the lead researchers on the UC Santa Barbara paper, and an established professor of Marine Biology.
It is with great sadness that we learned that our friend and former colleague, David Warner, passed away on Christmas Eve. The funeral was held the following Monday. David was a "linac man". His career centred around linacs, but with a multitude of different subjects. He began at CERN by building the 3 MeV linac in the extension of the South Hall. He did pioneering work on this machine, which paved the way towards the design of the Alvarez cavities for the CERN Linac 2, for which he was responsible. After this challenge was successfully finished, David was the first member of the small but growing team, that was in charge of building the LEP Injector Linacs (LIL). After having been recognised as a proton linac expert, he quickly converted to electron linacs where he soon became the respected key expert for the design, parameters and ultimate performance of LIL. His predilection for precise and detailed documentation, and his vision that the know-how acquired with LIL should be preserved a...
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Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Avaliaram-se as caracter�sticas sensoriais e determinou-se a for�a de cisalhamento de cortes de carne de paca (Agouti paca). As an�lises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por coc��o at� a temperatura interna de 70�C. A avalia��o de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplica��o de teste afetivo a 146 provadores, utilizando-se escala hed�nica, e a for�a de cisalhamento foi determinada pela t�cnica Warner Bratzler. Na avalia��o sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferen�a significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante � carne su�na e com boa aceita��o pelos consumidores. O estudo evidenciou o potencial da paca como uma esp�cie silvestre para a produ��o comercial de carne para o mercado de carnes vermelhas ou ex�ticas. Abstract in english Sensory characteristics and shear force of paca meat (Agouti paca) were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70�C. The evaluation of flavor, aroma, color, appea [...] rance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05) among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca) asa wild species for meat production in the red or exotic meat market.
C., Gomes; L.B., Karam; R.E.F., Macedo.
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Full Text Available Avaliaram-se as caracter�sticas sensoriais e determinou-se a for�a de cisalhamento de cortes de carne de paca (Agouti paca. As an�lises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por coc��o at� a temperatura interna de 70�C. A avalia��o de aspecto, cor, sabor, odor e maciez foi realizada pela aplica��o de teste afetivo a 146 provadores, utilizando-se escala hed�nica, e a for�a de cisalhamento foi determinada pela t�cnica Warner Bratzler. Na avalia��o sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferen�a significativa (p0,05 entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante � carne su�na e com boa aceita��o pelos consumidores. O estudo evidenciou o potencial da paca como uma esp�cie silvestre para a produ��o comercial de carne para o mercado de carnes vermelhas ou ex�ticas.Sensory characteristics and shear force of paca meat (Agouti paca were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70�C. The evaluation of flavor, aroma, color, appearance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05 among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca asa wild species for meat production in the red or exotic meat market.
C. Gomes
The Myth of "Pop Warner": Carlisle Revisited.
The myth of Pop Warner's sterling character hides the distasteful story behind the closure of Warner's Carlisle School for Indians on the grounds of moral corruption and misuse of athletic funds. (LH)
Howell, Reet A; Howell, Maxwell L.
Four replications were conducted to compare quality measurements, cook loss, shear force, and sensory quality attributes of cooked boneless skinless white meat, broiler breast fillets (pectoralis major) prepared directly from a frozen state or prepared from a thawed state. In each replication, fresh broiler fillets (removed from carcasses 6-8 h postmortem) were procured from a local commercial processing plant and stored in a -20�C freezer until use. On the sensory evaluation date, fillets were cooked to an endpoint temperature of 78�C either directly from the frozen state (thawing during cooking) or after the frozen samples were thawed in a refrigerator (2�C) overnight (thawing before cooking). Cook loss and Warner-Bratzler (WB) shear force were used as indicators for instrumental quality measurements. Sensory quality measurements were conducted by trained descriptive panelists using 0 to 15 universal intensity scales for 8 texture and 10 flavor attributes. Results show that there were no differences (P > 0.05) in measurements for sensory descriptive flavor attributes of cooked fillets between the 2 sample thawing methods, indicating that the sensory flavor profiles of both methods were similar to each other. However, WB shear force (36.98 N), cook loss (21.2%), sensory texture attributes of cohesiveness (intensity score was 5.59), hardness (5.14), rate of breakdown (5.50), and chewiness (5.21) of the breast fillets cooked directly from the frozen state were significantly higher (P compared with cookery after frozen fillets are thawed. PMID:24135605
Zhuang, Hong; Savage, Elizabeth M
Beef steers (n = 1,914) were assigned to 1 of 3 ?-adrenergic agonist (?AA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg�head(-1)�d(-1) for 28 d), or no ?AA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by ?AA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P 0.05). In steaks aged 21 d, feeding ?AA influenced (P 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of ?AA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON. PMID:24879757
Garmyn, A J; Brooks, J C; Hodgen, J M; Nichols, W T; Hutcheson, J P; Rathmann, R J; Miller, M F
Effect of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on LM shear force and sensory attributes was determined using pens (n = 40) British � Continental crossbred steers randomly allocated to one of the following treatments: control; RH fed at 200 (RH 200) or 300 mg � steer(-1) � d(-1) (RH 300), or 400 mg � steer(-1) � d(-1) (RH 400) top-dressed for the final 30 d of feeding; or ZH fed at 7.5 mg/kg, beginning 23 d before slaughter with a 3-d withdrawal. Two replicates (pens) per treatment were represented in four blocks. Eighteen carcasses per pen were randomly selected and one 5-cm LM sample was removed from both carcass sides to be used for shear force and sensory evaluation. Samples were aged for 14 d, frozen at -28.8 �C, and cut into 2.5-cm steaks. All steaks were cooked to an internal temperature of 71.1 �C before being evaluated for Warner-Bratzler shear force (WBSF), slice shear force (SSF), or being fed to trained sensory panelists. Increasing dose and potency of ?-agonist increased WBSF by 4 to 17% and SSF by 5 to 24% (P 0.05). Probability of steaks failing to meet shear force standards to be certified tender (WBSF 0.05). Steaks from steers fed RH 300 and RH 400 were comparable for all sensory attributes; however, both RH 300 and RH 400 were rated lower for overall tenderness than controls (P 0.05). Results from this study indicated ?-agonists negatively affected beef tenderness and these effects may be more noticeable in steers supplemented with ZH and higher doses of RH. PMID:24166996
Arp, T S; Howard, S T; Woerner, D R; Scanga, J A; McKenna, D R; Kolath, W H; Chapman, P L; Tatum, J D; Belk, K E
...131 0152] Actavis, Inc. a corporation, and Warner Chilott PLC; Analysis of Agreement Containing Consent Orders To Aid Public...from Actavis, Inc. (``Actavis'') and Warner Chilcott plc (``Warner Chilcott'') that is designed to remedy the...
LCSP � Personnel: Lowell Center Fellows: John C. Warner
... Warner President and Chief Technology Officer, Warner Babcock Institute for Green Chemistry, and President, The Beyond Benign Foundation www.WarnerBabcock.Com John received his BS in Chemistry from UMASS Boston, and his PhD in Chemistry from Princeton University. After working at the Polaroid Corporation for nearly a decade, he then served as tenured full professor at UMASS Boston and Lowell (Chemistry and Plastics Engineering).... In 2007 he founded the Warner Babcock Institute for Green Chemistry, LLC (A research organization developing green chemistry technologies) where he serves as President and Chief Technology Officer, and Beyond Benign (a non-profit dedicated to sustainability and green chemistry education). He is one of the founders of the field of Green Chemistry, co-authoring the defining text Green Chemistry: Theory and Practice with Paul ...
This study is a meta-analysis of the effects of the beta-agonists zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RAC) on feedlot performance, carcase characteristics of cattle and Warner Bratzler shear force (WBSF) of muscles. It was conducted to evaluate the effect of the use of these agents on beef production and meat quality and to provide data that would be useful in considerations on the effect of these agents on meat quality in Meat Standards Australia evaluations. We conducted a comprehensive literature search and study assessment using PubMed, Google Scholar, ScienceDirect, Scirus, and CAB and identification of other studies from reference lists in papers and searches. Searches were based on the key words: zilpaterol, zilmax, ractopamine, optaflexx, cattle and beef. Studies from theses obtained were included. Data were extracted from more than 50 comparisons for both agents and analysed using meta-analysis and meta-regression. Both agents markedly increased weight gain, hot carcase weight and longissimus muscle area and increased the efficiency of gain:feed. These effects were particularly large for ZH, however, fat thickness was decreased by ZH, but not RAC. Zilpaterol also markedly increased WBSF by 1.2 standard deviations and more than 0.8 kg, while RAC increased WBSF by 0.43 standard deviations and 0.2 kg. There is evidence in the ZH studies, in particular, of profound re-partitioning of nutrients from fat to protein depots. This work has provided critically needed information on the effects of ZH and RAC on production, efficiency and meat quality. PMID:25548908
Lean, Ian J; Thompson, John M; Dunshea, Frank R
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Full Text Available SciELO Mexico | Language: Spanish Abstract in spanish En este trabajo se describen e ilustran caracter�sticas morfol�gicas de Neochetina eichhorniae (Warner, 1970). Esta especie se ha utilizado para el control biol�gico del lirio acu�tico (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). En el huevo, el aspecto cambiante del corion es dado por el des [...] arrollo embrionario. En la larva se realiz� una descripci�n de la quetotaxia de la c�psula cef�lica y se identificaron tres �nstares larvales con la medici�n de su anchura; tambi�n se revis� la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en t�rax y abdomen, tambi�n se observaron dos tipos de espir�culos; el m�s caracter�stico es el espir�culo abdominal por su posici�n dorsal, que adem�s de ser esclerosado, posee �rganos sensoriales en su �pice. La morfolog�a externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Adem�s se proporciona una descripci�n de las alas, proventr�culo y genitalia, estructuras importantes en la taxonom�a. Las caracter�sticas morfol�gicas de N. eichhorniae encontradas en �ste trabajo pueden ser �tiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926), la cual ha sido liberada en muchos pa�ses. Es el primer trabajo de morfolog�a N. eichhorniae en M�xico. Abstract in english In this study morphological characteristics of Neochetina eichhorniae (Warner, 1970) are described and illustrated. This species has been used for the Biological Control of waterhyacinth (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). In the egg, the changing appearance of the chorion is given b [...] y the embryonic development. Description of larval head capsule chaetotaxy was done. Three larval instars were identified by measuring the head capsule width; microsculpture of the body larva was studied, microspines were evident with different arrangements in thorax and abdomen, two types of spiracles were found; the more distinctive was the dorsal spiracle in the abdomen, which is sclerotized, with sensory organs at its apex. The external morphology of N. eichorniae adult is very similar in both sexes, the main difference among them is the rostrum. Description of the wings, proventriculus and genitalia, important structures in the taxonomy, is provided. The morphological characteristics of N. eichhorniae found in this study can be use to separate from N. bruchi (Hustache) which has been released in many countries. This is the first morphological study of N. eichhorniae in Mexico.
Oscar, Mart�nez-Morales; Edith G., Estrada-Venegas; Armando, Equihua-Mart�nez; Jorge, Valdez-Carrasco.
Ecological investigation of a hazardous waste site, Warner Robins, Georgia
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Landfill No. 4 and the sludge lagoon at Robins Air Force Base, Warner Robins, Georgia, were added to the United States Environmental Protection Agency (EPA) National Priorities List in 1987 because of highpotential for contaminant migration. Warner Robins is located approximately 90 miles southeast of Atlanta. In 1990 CH2M HILL conducted a Remedial Investigation at the base that recommended that further ecological assessment investigations be conducted (CH2M HILL 1990). The subject paper is the result of this recommendation. The ecological study was carried out by the Hazardous Waste Remedial Actions Program (HAZWRAP)Division of Martin Marietta Energy Systems, Inc., working jointly with its subcontractor CDM (CDM 1992a). The primary area of investigation (Zone 1) included the sludge lagoon, Landfill No. 4, the wetland area east of the landfill and west of Hannah Road (including two sewage treatment ponds), and the area between Hannah Road and Horse Creek (Fig. 1). The bottomland forest wetlands of Zone 1 extend from the landfill east to Horse Creek. Surface water and groundwater flow across Zone 1 is generally in an easterly direction toward Horse Creek. Horse Creek is a south-flowing tributary of the Ocmulgee River Floodplain. The objective of the study was to perform a quantitative analysis of ecological risk associated with the ecosystems present in Zone 1. This investigation was unique because the assessment was to be based upon many measurement endpoints resulting in both location-specific data and data that would assess the condition of the overall ecosystem. The study was segregated into five distinct field investigations: hydrology, surface water and sediment, aquatic biology, wetlands ecology, and wildlife biology.
Wade, M. [Oak Ridge National Lab., TN (United States); Billig, P. [Camp Dresser and McKee, Inc., Denver, CO (United States)
The Intensities and High Sensitivity of a Gifted Creative Genius: Sylvia Ashton-Warner
This article explores the inner world of Sylvia Ashton-Warner, a gifted woman whose writing and teaching pedagogy earned her national and international acclaim. However, the acknowledged genius of her work is not explored herein. Rather, the inner world of a creatively gifted adult is examined, with particular reference to Dabrowski's�
White, Sonia
International Nuclear Information System (INIS)
A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)
Histomorphology and Physical Characteristics of Buffalo Meat at Different Sex and Age
The aim of this experiment was to evaluate histology and physical variables of buffalo meat at different sex and ages. Thirty head of buffaloes were used in this experiment. Muscle fiber diameter, fasciculus diameter, thickness of connective tissue, pH, water holding capacity, Warner-Bratzler shear force and cooking loss were measured in this experiment. Analysis of variance of randomized factorial design was used to analyse the data. The differences were analysed by Tukey test. The result sh...
Mahmudah; Nuraini, H.; Winarto, A.; Sumantri, C.
Walter Miles, Pop Warner, B. C. Graves, and the psychology of football.
In 1926-1927, a graduate student, B. C. Graves, working with Stanford University psychologist Walter Miles and legendary football coach Pop Warner, conducted an investigation of variations in signal calling as they affected the charging times of football players. The study was one of two that involved Miles and the ingenious multiple chronograph that he had invented to time the reactions of seven players simultaneously. These studies represented a brief digression in the career of Miles, who certainly was no sport psychologist. They tell of an interesting collaboration between scientist and coaches that produced one of the richest studies in sport psychology in the first half of the twentieth century. PMID:16345007
Baugh, Frank G; Benjamin, Ludy T
Dr. John Atkinson, of the University of the West of England, developed a site for undergraduate students wanting to learn more about soil classification. His site addresses issues such as: shear strength, peak strength, and residual strength testing. Filled with charts, diagrams, statistics, the information is pertinent and easily understood by almost any audience.
Atkinson, John
Shear strain imaging using shear deformations
In this article we investigate the generation of shear strain elastograms induced using a lateral shear deformation. Ultrasound simulation and experimental results demonstrate that the shear strain elastograms obtained under shear deformation exhibit significant differences between bound and unbound inclusions in phantoms, when compared to shear strain images induced upon an axial compression. A theoretical model that estimates the decorrelation between pre- and postdeformation radio frequenc...
Rao, Min; Varghese, Tomy; Madsen, Ernest L.
In the mid-1970s, Women Against Violence Against Women (WAVAW), the first national feminist organization to protest mediated sexual violence against women, pressured the music industry to cease using images of violence against women in its advertising. This article presents a case study of WAVAW's national boycott of Warner Communications, Inc. and documents the activists' successful consumer campaign. The study reveals that media violence was central to feminist organizing efforts, and that WAVAW and related organizations helped establish a climate of concern about violence that motivated scientific research on the relationship between exposure to media violence and subsequent aggression. PMID:18359878
Bronstein, Carolyn
Directory of Open Access Journals (Sweden)
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. Still, even global features of the measurements remain unmatched, and it is inevitable to provide a globally varying source distribution in future.
M. Ern
Directory of Open Access Journals (Sweden)
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. However, even with this optimized set of global launch parameters not all features of the measurements are matched. This indicates that for further improvement spatial and seasonal variations of the launch parameters should be included in GW parameterization schemes.
M. Ern
The aim of this study was to determine the effects of age on chemical composition and tenderness of donkey meat. These characteristics were determined on Longissimus thoracis samples taken from 40 entire donkey males of Martina Franca breed slaughtered at 12 (Group 1, n = 20) and at 18 months (Group 2, n = 20) of age. Tenderness was evalu-ated at two and seven days post slaughter using a Warner-Bratzler shear force device. The chemical composition showed a significant increase in protein cont...
Vincenzetti, S.; Cavallucci, C.; Beghelli, D.; Polidori, P.
A study was conducted to determine the effect of probiotics and thyme essential oil (TEO) as feed additives on the sensory attributes, cooking loss and the texture of broiler chicken meat. Day-old broilers Ross 308� (n = 400) were randomly divided into four groups based on the feed supplement as follows: control, probiotics 0.05%, TEO 0.05% and combination of probiotics and TEO, while the fattening period was 42 days. Warner Bratzler shear force, cooking loss and the following sensory att...
Ebrahim Alfaig; Maria Angelovi?ova; Martin Kral; Ondrej Bu?ko; Maria Walczycka
The recently published Report of theAHAG on the Operation of NHS Research Ethics Committees (the Warner Report) advocates major reforms of the NHS research ethics committees system. The main implications of the proposed changes and their probable effects on the major stakeholders are described.
Epstein, M.; Wingate, D. L.
The formation of adiabatic shear bands is examined with an approximate analytic model. The shear band is viewed as a propagating feature with a well-defined front. The shear band is further partition into a shear-band process zone within which most of the adiabatic heating and shear stress relaxation occurs, followed by a quasi-steady zone within which little dissipation occurs. Although a one-dimensional anlysis of the shear-band dynamics is initially pursued, the analysis is then used to ca...
Grady, D.
Energy Technology Data Exchange (ETDEWEB)
Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.
Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.
Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by $(1-\\kappa)$ where $\\kappa$ is the projected density field. We compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important on smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.
Dodelson, Scott; Shapiro, Charles; White, Martin
We investigate the distortions due to this shear in the microlensing light curves and in the astrometric microlensing centroid shift trajectories. As expected, the light curve deviation increases as the shear increases and the impact parameter decreases. Although the light curve in the presence of a small shear is similar to the simple Paczynski curve with a slightly smaller impact parameter, the detailed difference between the light curve with and without shear reflects the...
Ryu, Yoon-hyun; Park, Myeong-gu
Semiconductor laser shearing interferometer
International Nuclear Information System (INIS)
The application of semiconductor laser on grating shearing interferometry is studied experimentally in the present paper. The method measuring the coherence of semiconductor laser beam by ion etching double frequency grating is proposed. The experimental result of lens aberration with semiconductor laser shearing interferometer is given. Talbot shearing interferometry of semiconductor laser is also described. (author). 2 refs, 9 figs
Directory of Open Access Journals (Sweden)
Full Text Available A study was conducted to determine the effect of probiotics and thyme essential oil (TEO as feed additives on the sensory attributes, cooking loss and the texture of broiler chicken meat. Day-old broilers Ross 308� (n = 400 were randomly divided into four groups based on the feed supplement as follows: control, probiotics 0.05%, TEO 0.05% and combination of probiotics and TEO, while the fattening period was 42 days. Warner Bratzler shear force, cooking loss and the following sensory attributes (colour, odour, taste, texture, meat decomposing and overall acceptability were tested. The obtained results of the Warner Bratzler shear force show that there was significant different (P < 0.05 between control and TEO group and for the cooking loss there was no significant difference between groups. The descriptive sensory analysis results show that the probiotics group results were somewhat similar to that obtained by control while the TEO group and the combination group results were similar. Regarding the sensory analysis we can state that the combination of the probiotics and TEO have a�positive effect on the chicken meat sensory characteristics.
Ebrahim Alfaig
Correlation and Categories of Meat Tenderness Based on Equipment and Panelist Test
Directory of Open Access Journals (Sweden)
Full Text Available The objective of this study was to determine the correlation between Warner-Bratzler shear force (WBSF and cooking loss with sensory local trained panelists rating on beef tenderness, also to determine WBSF range at each tenderness categories (extremely tender, tender, rather tender, rather tough, tough, and extremely tough. Meat from knuckles of Australian Beef Cross (ABX steer were broiled until internal temperature 70, 80 and 90oC to get some WBSF values. Cooking loss was counted as percentages of meat weight losses during cooking. Each WBSF values and cooking loss data were correlated with panelists test scores used linier regression equation. Then, based on that linier regression were estimated WBSF range at each tenderness level. The result indicated that WBSF was positive correlated with panelists test that was indicated with determination coefficient 0.7668 (r2 = 0.7668. Cooking loss was strongly positive correlated with panelists rating tenderness (r2 = 0.8114. The result of meat tenderness range categories: extremely tender 0�3.30 kg/cm2, tender >3.30�5.00 kg/cm2, rather tender >5.00�6.71 kg/cm2, rather tough >6.71�8.42 kg/cm2, tough >8.42-10.12 kg/cm2, extremely tough >10.12 kg/cm2. (Animal Production 10(3: 188-193 (2008 Key Words: Meat tenderness, tenderness categories, panelist test, Warner-Bratzler shear, force, cooking loss
T Suryati
Directory of Open Access Journals (Sweden)
Full Text Available A maciez da carne geralmente � o atributo mais importante para o consumidor. V�rios s�o os fatores que influem sobre esSe aspecto no animal, como por exemplo: gen�tipo, idade, sexo, entre outros. Neste estudo, verificou-se a influ�ncia da idade e do sexo na maciez do m�sculo Longissimus dorsi de ovinos da ra�a Corriedale, atrav�s de m�todos sensoriais e instrumentais. Ap�s o abate, realizou-se a avalia��o visual da textura do m�sculo pela granula��o da superf�cie do mesmo. As amostras foram congeladas por 5 meses. Ap�s a coc��o, foi analisada a maciez da carne pelo equipamento Warner-Bratzler shear medindo a for�a de cisalhamento, e por avalia��o sensorial realizada por uma equipe treinada de julgadores. Resultados obtidos pela avalia��o sensorial e instrumental indicaram que o m�sculo Longissimus dorsi de f�meas e de animais de menor idade foram mais macios.The meat tenderness is the most important atribute to the consumer. Several factors have influence in this aspect, for exemple: genotype, age, sex and others. The objective of this work was to study the influence of age and sex on Longissimus dorsi muscle tenderness of Corriedale lineage lamb, through sensory and instrumental methods. After slaughter Longissimus dorsi, texture was evaluated by granite�s surface method. The samples were frozen for five months. After thawing and cooking, meat tenderness was evaluated by Warner-Bratzler shear and sensory evaluation by a group of trained judges. The results indicated that female and younger animals produced more tender meat.
M�rcia Arocha Gularte
A review is presented on recent progress in shear testing of materials at high and very high strain rates. Some experimental techniques are discussed which allow for materials testing in shear up to 10 6 ls. More detailed informations are provided on experimental techniques based on the Modified Double Shear specimen loaded by direct impact. This technique has been applied so far to test a variety of materials, including construction, armor and inoxidable steels, and also aluminum alloys. The double shear configuration has also been applied to test sheet metals, mostly used in the automotive industry, in a wide range of strain rates. Details of both techniques, including measuring systems and elastic wave propagation in tubes, are discussed. In addition, a new experimental configuration which can be applied for experimental studies of adiabatic shear propagation and high speed machining is discussed. The role of adiabatic heating at different rates of shearing is also discussed, including transition from pure isothermal to pure adiabatic deformation. It appears that the initial impact velocity is an important parameter in development of plastic localization. Finally, a new development is discussed in determination of the Critical Impact Velocity in shear. A comparison is shown between recent experimental findings and a simple analytic estimation. The CIV in shear is a certain mode of adiabatic failure which occurs at relatively high shear velocities of adjacent material layers. Numerical simulations support the existence of the CIV in shear which can be recognized to some extent as a material constant.
Klepaczko, J. R.
We study theoretically the mechanical failure of a simple model of double stranded DNA under an applied shear. Starting from a more microscopic Hamiltonian that describes a sheared DNA, we arrive at a nonlinear generalization of a ladder model of shear unzipping proposed earlier by deGennes [deGennes P. G. C. R. Acad. Sci., Ser. IV; Phys., Astrophys. 2001, 1505]. Using this model and a combination of analytical and numerical methods, we study the DNA "unzipping" transition w...
Chakrabarti, Buddhapriya; Nelson, David R.
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.
Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.
Shear dynamics in cholesterics
We study shear dynamic in cholesteric liquid crystal using a lattice Boltzmann scheme that solves the full, three-dimensional Beris-Edwards equations of hydrodynamics. We show that the coupling between shear and the natural elastic deformation of cholesterics can induce twist in an initially isotropic phase.
Orlandini, Enzo; Marenduzzo, Davide; Yeomans, Julia M.
DEFF Research Database (Denmark)
The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results.
Bay, Niels; Bjerregaard, Henrik
A �coherent and sustained program� of improved radar detection of weather, pilot training, and better communication between pilots and air controllers can greatly reduce the risk of wind shear to airplanes landing or taking off, according to a National Research Council (NRC) committee.Wind shear, characterized by winds rapidly changing direction and speed, has caused several serious accidents in recent years; among the most notable is the July 8, 1982, crash of a Pan American World Airlines jetliner at the New Orleans International Airport, which killed 153 persons. Following the accident, Congress directed the Federal Aviation Administration (FAA) to contract with the NRC to study wind shear.
One or more disc-shaped angular shear plates each include a region thereon having a thickness that varies with a nonlinear function. For the case of two such shear plates, they are positioned in a facing relationship and rotated relative to each other. Light passing through the variable thickness regions in the angular plates is refracted. By properly timing the relative rotation of the plates and by the use of an appropriate polynomial function for the thickness of the shear plate, light passing therethrough can be focused at variable positions.
Ruda, Mitchell C. (Tucson, AZ); Greynolds, Alan W. (Tucson, AZ); Stuhlinger, Tilman W. (Tucson, AZ)
Magnetohydrodynamic Shearing Waves
I consider the nonaxisymmetric linear theory of an isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model appropriate for a thin disk geometry. Linear perturbations in this model can be decomposed in terms of shearing waves (shwaves), which appear spatially as plane waves in a frame comoving with the shear. The time dependence of these waves cannot in general be expressed in terms of a frequency eigenvalue as in a normal mode decomposition, and numerical integration of a set of first-order amplitude equations is required for a complete characterization of their behavior. Their generic time dependence, however, is oscillatory with slowly-varying frequency and amplitude, and one can construct accurate analytic solutions by applying the Wentzel-Kramers-Brillouin method to the full set of amplitude equations. For the bulk of wavenumber space, therefore, the shwaves are well-approximated as modes with time-dependent frequencies and amplitudes. The incompressiv...
Johnson, B M
We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In a...
Onuki, Akira; Furukawa, Akira; Minam, Akihiko
We discuss crack propagation along the interface between two dissimilar materials. The crack edge separates two states of the interface, ``stick'' and ``slip''. In the slip region we assume that the shear stress is proportional to the sliding velocity, i.e. the linear viscous friction law. In this picture the static friction appears as the Griffith threshold for crack propagation. We calculate the crack velocity as a function of the applied shear stress and find that the mai...
Brener, Efim A.; Marchenko, V. I.
Mixing through shear instabilities
In this paper we present the results of numerical simulations of the Kelvin-Helmholtz instability in a stratified shear layer. This shear instability is believed to be responsible for extra mixing in differentially rotating stellar interiors and is the prime candidate to explain the abundance anomalies observed in many rotating stars. All mixing prescriptions currently in use are based on phenomenological and heuristic estimates whose validity is often unclear. Using three-d...
Bru?ggen, M.; Hillebrandt, W.
Hillary Clinton / Judith Warner
K�ige m�juv�imsam naine maailmas - algus EA 22. veebruar 1994. May/4,11,18,25 lk. 22;22;22;21; Jun/1,8,15,22,29 lk. 21; Jul/6,13,20,27 21; Aug/3,10,17,24,31 lk. 21; Sep/7,14,21,28 lk. 21; Oct/5,12,19 lk. 21
Warner, Judith
For highly viscous fluids that slip in parallel sliding plate rheometers, we want to use a slightly converging flow to suppress this wall slip. In this work, we first attack the steady shear flow of a highly viscous Newtonian fluid between two gently converging plates with no slip boundaries using the equation of motion in cylindrical coordinates, which yields no analytical solution. Then we treat the same problem using the lubrication approximation in Cartesian coordinates to yield exact, explicit solutions for dimensionless velocity, pressure and shear stress. This work deepens our understanding of a drag flow through a gently converging slit of arbitrary convergence angle. We also employ the corotational Maxwell model to explore the role of viscoelasticity in this converging shear flow. We then compare these analytical solutions to finite element calculations for both Newtonian and corotational Maxwell cases. A worked example for determining the Newtonian viscosity using a converging shear rheometer is also included. With this work, we provide the framework for exploring other constitutive equations or other boundary conditions in future work. Our results can also be used to design the linear bearings used for the parallel sliding plate rheometer (SPR). This work can also be used to evaluate the error in the shear stress that is caused by bearing misalignment and specify the parallelism tolerance for the linear bearings incorporated into a SPR.
Baek, Hyung M.; Mix, Adam W.; Giacomin, A. Jeffrey
We describe experiments in which we consider the jamming of 2D granular materials under shear. We consider experiments involving both pure and simple shear. The particles making up the material are either disks or ellipses, and in both cases, they are fabricated from a photoelastic material. It is then possible to obtain quantitative data for contact forces, and all other relevant grain-scale information. A key observation from these experiments is that initial states with densities below isotropic jamming can be jammed under applied shear in a range of packing fractions between ?min<=?<=?J, where ?J corresponds to the isotropic (zero shear stress) jamming point. We explore the behaviour of the above systems for ?'s in and near this regime. Specifically, we determine particle contacts and the mean contact number per particle, Z, the number of nearest neighbors, the shear and normal stresses, ? and P, and kinematic properties such as particle rotation and displacement. We find that the states of the system lie on a surface in a space consisting of ?, P, and ?. As time permits, we will explore the affine and non-affine motion of particles.
Zhang, Jie; Ren, Jie; Farhadi, Somayeh; Behringer, Robert
Vacuum skin pack of beef--a consumer friendly alternative.
The aim of this study was to assess how beef quality traits are affected by skin packaging compared with vacuum and high-oxygen modified atmosphere packaging (MAP; 80% O(2) and 20% CO(2)). Both M. longissimus dorsi from 6 young bulls were cut and aged in vacuum for 7 days and then cut into 3.5-cm steaks, thereafter either frozen directly day 7 or stored in skin pack, vacuum pack or MAP for an additional 7 or 14 days and then frozen. Warner-Bratzler shear force, loss and colour were measured and sensory analysis was performed. The results showed no differences in shear force, sensory analysis and total loss between steaks packed in skin pack or vacuum, but skin packed steaks had lower purge loss. MAP steaks had lower sensory scores than the other treatments at days 14 and 21. Raw MAP-steaks were bright red, but showed signs of premature browning when cooked. PMID:21316869
Lagerstedt, �sa; Ahnstr�m, Maria L; Lundstr�m, Kerstin
Aims.Accurate measurement of gravitational shear from images of distant galaxies is one of the most direct ways of studying the distribution of mass in the universe. We describe a new implementation of a technique for measuring shear that is based on the shapelets formalism. Methods: .The shapelets technique describes PSF and observed images in terms of Gauss-Hermite expansions (Gaussians times polynomials). It allows the various operations that a galaxy image undergoes before being registered in a camera (gravitational shear, PSF convolution, pixelation) to be modeled in a single formalism, so that intrinsic ellipticities can be derived in a single modeling step. Results: .The resulting algorithm, and tests of it on idealized data as well as more realistic simulated images from the STEP project, are described. Results are very promising, with attained calibration accuracy better than four percent (1 percent for round PSFs) and PSF ellipticity correction better than a factor of 20. Residual calibration problems are discussed.
Kuijken, K.
Ultrasonic shear wave couplant
Ultrasonically testing of an article at high temperatures is accomplished by the use of a compact layer of a dry ceramic powder as a couplant in a method which involves providing an ultrasonic transducer as a probe capable of transmitting shear waves, coupling the probe to the article through a thin compact layer of a dry ceramic powder, propagating a shear wave from the probe through the ceramic powder and into the article to develop echo signals, and analyzing the echo signals to determine at least one physical characteristic of the article.
Kupperman, David S. (Oak Park, IL); Lanham, Ronald N. (Lockport, IL)
Viewgraphs used in a presentation on wind shear radar simulation are given. Information on a microburst model of radar reflectivity and wind velocity, radar pulse output, the calculation of radar return, microburst power spectrum, and simulation plans are given. A question and answer session is transcribed.
Britt, Charles L.
Shear thickening of cornstarch suspensions
We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. For low rotational rates, we observe shear localization characteristic of yield stress fluids. When the overall shear rate is increased, the width of the sheared region increases. T...
Fall, Abdoulaye; Bertrand, Franc?ois; Ovarlez, Guillaume; Bonn, Daniel
Viscoelastic shear banding in foam
Shear banding is an important feature of flow in complex fluids. Essentially, shear bands refer to the coexistence of flowing and non-flowing regions in driven material. Understanding the possible sources of shear banding has important implications for a wide range of flow applications. In this regard, quasi-two dimensional flow offers a unique opportunity to study competing factors that result in shear bands. One proposal is the competition between intrinsic dissipation and...
Krishan, Kapilanjan; Dennin, Michael
Shear effects in nonhomogeneous turbulence
Motivated by recent experimental and numerical results, a simple unifying picture of intermittency in turbulent shear flows is suggested. Integral Structure Functions (ISF), taking into account explicitly the shear intensity, are introduced on phenomenological grounds. ISF can exhibit a universal scaling behavior, independent of the shear intensity. This picture is in satisfactory agreement with both experimental and numerical data. Possible extension to convective turbulenc...
Toschi, F.; Leveque, E.; Ruiz-chavarria, G.
Energy Technology Data Exchange (ETDEWEB)
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.
Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)
A soft solid is more easily sliced using a combination of normal and shearing deformations rather than diced by squeezing down on it normally with the same knife. To explain why this is so, we experimentally probe the slicing and dicing of a soft agar gel with a wire, and complement this with theory and numerical simulations of cutting of a highly deformable solid. We find that purely normal deformations lead to global deformations of the soft solid, so that the blade has to penetrate deeply into the sample, well beyond the linear regime, to reach the relatively large critical stress to nucleate fracture. In contrast, a slicing motion leads to fracture nucleation with minimal deformation of the bulk and thus a much lower barrier. This transition between global and local deformations in soft solids as a function of the angle of shear explains the mechanics of the paper cut and design of guillotine blades.
Reyssat, E.; Tallinen, T.; Le Merrer, M.; Mahadevan, L.
Plasticity Approach to Shear Design
DEFF Research Database (Denmark)
The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing.
Hoang, Cao Linh; Nielsen, Mogens Peter
We present a time-dependent Ginzburg-Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume {\\it m}. For very small $m$ the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing {\\it m}, accumulation of {\\it m} around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (...
Onuki, A; Minam, A; Onuki, Akira; Furukawa, Akira; Minam, Akihiko
Expanding universes with shear
International Nuclear Information System (INIS)
The classification and the evolution of expanding universes with shear but without rotation and containing dustlike matter are examined taking the cosmological constant into account. We assume the isotropy of the Gaussian curvature in the hypersurface orthogonal to the 4-velocity. Eight types of evolution-curves are found on the parameter diagram constructed by the density parameter and the anisotropy parameter. Monotonic models of the first kind and oscillating models are divided into three of four subclasses by means of the evolutionary characteristics, respectively. (author)
True Shear Parallel Plate Viscometer
This viscometer (which can also be used as a rheometer) is designed for use with liquids over a large temperature range. The device consists of horizontally disposed, similarly sized, parallel plates with a precisely known gap. The lower plate is driven laterally with a motor to apply shear to the liquid in the gap. The upper plate is freely suspended from a double-arm pendulum with a sufficiently long radius to reduce height variations during the swing to negligible levels. A sensitive load cell measures the shear force applied by the liquid to the upper plate. Viscosity is measured by taking the ratio of shear stress to shear rate.
Ethridge, Edwin; Kaukler, William
Failure During Sheared Edge Stretching
Failure during sheared edge stretching of sheet steels is a serious concern, especially in advanced high-strength steel (AHSS) grades. The shearing process produces a shear face and a zone of deformation behind the shear face, which is the shear-affected zone (SAZ). A failure during sheared edge stretching depends on prior deformation in the sheet, the shearing process, and the subsequent strain path in the SAZ during stretching. Data from laboratory hole expansion tests and hole extrusion tests for multiple lots of fourteen grades of steel were analyzed. The forming limit curve (FLC), regression equations, measurement uncertainty calculations, and difference calculations were used in the analyses. From these analyses, an assessment of the primary factors that contribute to the fracture during sheared edge stretching was made. It was found that the forming limit strain with consideration of strain path in the SAZ is a major factor that contributes to the failure of a sheared edge during stretching. Although metallurgical factors are important, they appear to play a somewhat lesser role.
Levy, B. S.; van Tyne, C. J.
Effect of breed on carcass measurements and meat quality characteristics were investigated by using 46 lambs from Turkish Merino, Ramlic, Kivircik, Chios and Imroz breeds. Chios and Imroz carcasses had smaller values for carcass quality characteristics. Breed had no significant effect on pH at 45min and 24h post-mortem, water holding capacity and cooking loss. Kivircik and Imroz lambs had lower Warner Bratzler shear force values than those of Ramlic and Turkish Merino lambs (P<0.01). Meat samples from Kivircik lambs had the highest redness value. Differences among breeds for sensory characteristics, except tenderness were not significant. Tenderness scores given to meat samples of Kivircik lambs were significantly higher (P<0.01) than those of Turkish Merino, Ramlic and Imroz lambs. Indigenous Kivircik breed, which had high carcass quality as those of improved breeds, might be considered for production of better quality meat in Marmara Region of Turkey. PMID:20416578
Ekiz, Bulent; Yilmaz, Alper; Ozcan, Mustafa; Kaptan, Cuneyt; Hanoglu, Hulya; Erdogan, Ismail; Yalcintan, Hulya
Predicting beef tenderness using color and multispectral image texture features.
The objective of this study was to investigate the usefulness of raw meat surface characteristics (texture) in predicting cooked beef tenderness. Color and multispectral texture features, including 4 different wavelengths and 217 image texture features, were extracted from 2 laboratory-based multispectral camera imaging systems. Steaks were segregated into tough and tender classification groups based on Warner-Bratzler shear force. The texture features were submitted to STEPWISE multiple regression and support vector machine (SVM) analyses to establish prediction models for beef tenderness. A subsample (80%) of tender or tough classified steaks were used to train models which were then validated on the remaining (20%) test steaks. For color images, the SVM model correctly identified tender steaks with 100% accurately while the STEPWISE equation identified 94.9% of the tender steaks correctly. For multispectral images, the SVM model predicted 91% and STEPWISE predicted 87% average accuracy of beef tender. PMID:22647652
Sun, X; Chen, K J; Maddock-Carlin, K R; Anderson, V L; Lepper, A N; Schwartz, C A; Keller, W L; Ilse, B R; Magolski, J D; Berg, E P
Comparison of textural atributes of selected meat sausages using instrumental analysis
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Full Text Available Normal 0 21 false false false SK X-NONE X-NONE The aim of the study was to compare textural atributes of selected meat sausages using instrumental analysis. For this purpose, seven different meat sausage samples were treated by instrumental analysis, by the use of Warner-Bratzler probe, �to find differences for two selected textural parameter firmness and work of shear. As expected, various values of mentioned atributes were obtained for different samples tested in fresh stage and after storage under controlled conditions (48 hrs., 30 �C temp., and 60 % R.H. before and after cooking. For statistical evaluation of results, paired T test was used, statistically significant differences were taken at pdoi:10.5219/273
Vladim�r Vietoris
The palatability of tender [Warner-Bratzler shear force values strip loins of 10 different treatments [USDA Prime, High Choice (upper 1/3 Choice), Low Choice (lower 1/3 Choice), Select, Standard, Australian Wagyu, American Wagyu, Holstein Select, Holstein Top Choice (upper 2/3 Choice) and Grass-finished] was evaluated by consumers and a trained flavor panel. In general, tenderness, juiciness, flavor, and overall liking ratings as well as acceptability percentage for each trait, increased with increased fat levels. Moreover, overall liking was highly correlated (P<0.01) with flavor liking (r=0.96) as well as fat percentage (r=0.79). Beef flavor scores were positively associated (P<0.01) with fat-like (r=0.67) and umami (r=0.59) flavors. Fat level was the primary driver of beef flavor acceptability in all samples when no undesirable off-flavors were present. PMID:25299587
Corbin, C H; O'Quinn, T G; Garmyn, A J; Legako, J F; Hunt, M R; Dinh, T T N; Rathmann, R J; Brooks, J C; Miller, M F
The Hypertrophic Marchigiana: physical and biochemical parameters for meat quality evaluation
Directory of Open Access Journals (Sweden)
Full Text Available The aim of this study was to evaluate the meat quality of double muscled Marchigiana young bulls characterized by different genotypes for the hypertrophy: normal and mutated (heterozygous. Calpain and calpastatin activities were determined to verify the state of aging meat on a sample of Longissimus thoracis muscle (XIII thoracic rib taken at slaughtering (0h and after 24 hours (24h. After 14 days of aging, another sample of muscle was taken to evaluate physical and chemical parameters of meat quality. The results showed a better meat quality of mutated animals respect normal animals. Another interesting result was the correlation between the biochemical parameters and some physical parameters, such as WBS (Warner Bratzler Shear Force, CL (Cooking loss. These results showed the relationship between the proteolytic activity of calpain system and meat tenderness.
F. M. Sarti
The aim of the study was to evaluate the influence of cooking conditions (dry air and steam) and final internal temperature (75, 85, 95�C) on the physico-chemical properties of beef infraspinatus (INF) and semimembranosus (SEM) muscles as well as their tenderness and juiciness. Cooking method and temperature influenced moisture, total collagen content in cooked meat and cooking loss, whereas muscle type affected fat, total collagen content and cooking loss. Warner-Bratzler shear force values were affected by cooking method, which also influenced juiciness of roasts. Temperature affected tenderness and juiciness, whereas muscle type influenced juiciness. The most desirable tenderness had INF heated in steam and dry air to 95�C. Processing SEM in dry air to 85 and 95�C lowered the juiciness of the roasts. There were significant correlations between physico-chemical, sensorial and image attributes, however high accuracy of prediction (r(2)>0.8) was achieved only for SEM muscle. PMID:22336137
Modzelewska-Kapitu?a, Monika; D?browska, Ewa; Jankowska, Barbara; Kwiatkowska, Aleksandra; Cierach, Marek
Angus-cross steers (n = 60) were used to assess the effect of forage species [alfalfa (AL; Medicago sativa L.), bermudagrass (BG; Cynodon dactylon), chicory (CH; Cichorium intybus L.), cowpea (CO; Vigna unguiculata L.), and pearl millet (PM; Pennisetum glaucum (L. R Br.)] in replicated 2-ha paddocks for finishing on cattle performance, carcass quality, and meat quality in a 2-yr study. Steers were blocked by BW and assigned randomly to finishing-forage treatments before the start of the experiment. Steers grazing AL and CH had greater (P 1 kg/d). Finishing on legumes (AL and CO) increased dressing percentage, reduced Warner-Bratzler shear force values, and increased consumers preference, whereas finishing on grasses (BG and PM) enhanced anticarcinogenic fatty acid concentrations. PMID:23825343
Schmidt, J R; Miller, M C; Andrae, J G; Ellis, S E; Duckett, S K
Post-slaughter muscle energy metabolism meat colour of South African production systems were compared; steers (n=182) of Nguni, Simmental Brahman crossbreds were reared on pasture until A-, AB-, or B-age, in feedlot until A-AB-age. After exsanguination carcasses were electrically stimulated (400 V for 15 s). M. longissimus dorsi muscle energy samples were taken at 1, 2, 4 and 20 h. Post-mortem samples for meat quality studies were taken at 1, 7 and 14 days post-mortem. Production systems affected muscle glycogen, glucose, glucose-6-P, lactic acid, ATP, creatine-P glycolytic potential (P0.5) water holding capacity, drip loss, and Warner Bratzler shear force. Muscle energy only affected muscle contraction of the A-age-pasture system (shortest sarcomere length of 1.66 ?m vs 1.75 ?m highest WBS of 6 kg vs 5 kg 7 days post-mortem). PMID:23305833
Frylinck, L; Strydom, P E; Webb, E C; du Toit, E
A 2-yr experiment was conducted to compare carcass characteristics and meat palatability attributes of steers ((3/4) British, (1/4) Continental) finished postweaning as calves or yearlings. Calves and yearlings of the same contemporary group were designated to a finishing system at weaning. Calves (n = 73) were finished in the feedlot (191 d) on a high-concentrate diet. Yearlings (n = 84) grazed crop residues after weaning, followed by spring and summer pasture grazing, and concluded with a short finishing period (91 d) in the feedlot. All steers were fed to a constant, fat thickness endpoint of 1 cm. The M. longissimus lumborum steaks from each production system were aged for 7, 14, or 21 d for Warner-Bratzler shear force determination and for 7 or 14 d for in-house sensory panel evaluation. Insoluble, percent soluble, and total collagen were determined. Yearlings produced heavier (P beef with extended aging. PMID:17202391
Brewer, P S; James, J M; Calkins, C R; Rasby, R M; Klopfenstein, T J; Anderson, R V
Hydrodynamic pressure processing (HDP) or shockwave treatment improved tenderness (18% reduction in Warner-Bratzler shear force (WBSF) of beef loin steaks. Endogenous muscle proteolyic activities (cathepsins and peptidases) and protein fragmentation of sarcoplasmic and myofibrillar proteins detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were not influenced by HDP. However, microstructure changes were clearly detected using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). Specifically a disruption of the structure at the muscle fiber bundles and an increased endomysium space were observed. The present paper supports the evidence of physical disruption of the muscle fibers as a cause behind the tenderness improvement. The paper discusses the possible mechanisms responsible for the meat tenderisation induced by HDP treatment. PMID:25117876
Bolumar, Tomas; Bindrich, Utte; Toepfl, Stefan; Toldr�, Fidel; Heinz, Volker
Llama Meat Nutritional Properties
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Full Text Available The aim of this study was to determine the chemical composition of the muscle Longissimus thoracis taken from 20 llama males, reared in the Andean region, slaughtered at an age of 25 months and at a mean final body weight of 74kg. Llama meat showed a low fat (3.51% and cholesterol content (58.16mg/100g, a good protein content (22.42% and an ash content of 3.06%. The Warner-Bratzler shear force values determined in llama meat was 6.56 kg/cm2. This study confirmed that llama meat is healthy and nutritious, and represents a good source of proteins for Andean population.
G. Lebboroni
Directory of Open Access Journals (Sweden)
Full Text Available The experiment was performed with thirty-two Altamurana and Trimeticcio lambs slaughtered at 42 and at 70 days of age. Meat organoleptic characteristics were determined on samples of M. Longissimus lumborum and Longissimus thoracis. Colour parameters were not affected by genotype, while L* value and index of yellow decreased (P<0.01 and P<0.05, respectively as age of slaughtering increased. Meat from Altamurana lambs showed lower juiciness (P<0.01 and fatness (P<0.05 than Trimeticcio lambs. No genotype and age of slaughtering effects were found for Warner-Bratzler shear force (WBSF values. Meat from younger lambs was more tender and chewable (P<0.01 but less juicy (P<0.001 and fatty (P<0.05 than meat from lambs slaughterd at 70 days.
A. Girolami
Effect of probiotics and thyme essential oil on the texture of cooked chicken breast meat
Directory of Open Access Journals (Sweden)
Full Text Available Background. Texture is probably the single most critical quality factor associated with the consumers� ultimate satisfaction with a poultry meat product and can be affected by several factors including the type of feed used for chickens fattening. The use of probiotics for meat and carcass quality improvement has been questioned, while the possibility of deposition of essential oils in various muscle tissues can alter the sensory attributes of the chicken�s meat. Material �and methods. Probiotics and thyme essential oil in the percentage of 0.05% were used as feed supplements for Ross 308 broiler chickens, as the broilers were reared in four separated groups based on the feed supplement as follows: control, probiotics, thyme essential oil and combination of probiotics and thyme essential oil group, while the fattening period was 42 days. TA.XT Plus-Texture analyser apparatus was used for determination of the texture profile and Warner Bratzler shear force for the cooked breast meat. Results. Warner Bratzler shear test results showed that the tested feed additives were not affecting the texture of the chicken breast meat, while probiotic appears to have moderately effect on the hardness, cohesiveness, springiness and chewiness attributes of the cooked breast meat compared with the other groups, this effect of probiotics considered as negligible, as the results showed that all the tested groups meat were very tender according to the tenderness scale. Conclusions. According to the obtained results it can be concluded the combination of probiotics and thyme group resulted in the lowest score for the hardness, cohesiveness, springiness and chewiness attributes, while probiotics group scored the highest compared with the control.
Ebrahim Alfaig
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese A maciez da carne geralmente � o atributo mais importante para o consumidor. V�rios s�o os fatores que influem sobre esSe aspecto no animal, como por exemplo: gen�tipo, idade, sexo, entre outros. Neste estudo, verificou-se a influ�ncia da idade e do sexo na maciez do m�sculo Longissimus dorsi de ovi [...] nos da ra�a Corriedale, atrav�s de m�todos sensoriais e instrumentais. Ap�s o abate, realizou-se a avalia��o visual da textura do m�sculo pela granula��o da superf�cie do mesmo. As amostras foram congeladas por 5 meses. Ap�s a coc��o, foi analisada a maciez da carne pelo equipamento Warner-Bratzler shear medindo a for�a de cisalhamento, e por avalia��o sensorial realizada por uma equipe treinada de julgadores. Resultados obtidos pela avalia��o sensorial e instrumental indicaram que o m�sculo Longissimus dorsi de f�meas e de animais de menor idade foram mais macios. Abstract in english The meat tenderness is the most important atribute to the consumer. Several factors have influence in this aspect, for exemple: genotype, age, sex and others. The objective of this work was to study the influence of age and sex on Longissimus dorsi muscle tenderness of Corriedale lineage lamb, throu [...] gh sensory and instrumental methods. After slaughter Longissimus dorsi, texture was evaluated by granite�s surface method. The samples were frozen for five months. After thawing and cooking, meat tenderness was evaluated by Warner-Bratzler shear and sensory evaluation by a group of trained judges. The results indicated that female and younger animals produced more tender meat.
M�rcia Arocha, Gularte; Rosa de Oliveira, Treptow; Juv�ncio Lu�s Fernandes, Pouey; Jos� Carlos, Os�rio.
Shear dynamics of hydration layers
Molecular dynamics (MD) simulations have been performed to investigate the shear dynamics of hydration layers of the thickness of D =0.61-2.44nm confined between two mica surfaces. Emphases are placed on the external shear response and internal relaxation properties of aqueous films. For D =0.92-2.44nm liquid phase, the shear responses are fluidic and similar to those observed in surface force balance experiments [U. Raviv and J. Klein, Science 297, 1540 (2002)]. However, for the bilayer ice (D=0.61nm) [Y. S. Leng and P. T. Cummings, J. Chem. Phys. 124, 74711 (2006)] significant shear enhancement and shear thinning over a wide range of shear rates in MD regime are observed. The rotational relaxation time of water molecules in this bilayer ice is found to be as high as 0.017ms (10-5s). Extrapolating the shear rate to the inverse of this longest relaxation time, we obtain a very high shear viscosity for the bilayer ice, which is also observed quite recently for D ?0.6�0.3nm hydration layers [H. Sakuma et al., Phys. Rev. Lett. 96, 46104 (2006)]. We further investigate the boundary slip of water molecules and hydrated K+ ions and concluded that no-slip boundary condition should hold for aqueous salt solution under extreme confinement between hydrophilic mica surfaces, provided that the confined film is of Newtonian fluid.
Leng, Yongsheng; Cummings, Peter T.
Shear viscosity of magnetic liquids
International Nuclear Information System (INIS)
The shear viscosity of magnetic liquids on the base of kerosene and dodecane was studied. The numeric evaluation of friction coefficient, relaxation times, as well as shear-viscosity coefficient on the base of kerosene and dodecane depending on temperature, density and concentration was conducted.
Folds in ductile shear zones are common structures that have a variety of origins. These can be pre-existing folds that become modified or folds developed during the shearing event. Among the syn-shearing folds, a second subdivision is based on the relative age of the folded surface, which can be pre-existing or newly formed during the shearing event. In each of the three categories final fold geometry and orientation show complex relationships with the kinematic frame. The final fold geometry depends on the vorticity within the shear zone, the rheology and the initial orientation of the folded surface relative to the kinematic framework. It follows that folds are complex structures, difficult to use as kinematic indicators. However, in shear zones where undeformed wall rocks with pre-shear structures are accessible and where kinematics can be well established, folds can provide a valuable natural means to understand the initiation and evolution of structures under non-coaxial regimes. We point to the need of discriminating among different plausible categories, based on the nature of the folded surface and on the inherent structural features of each category.
Carreras, Jordi; Druguet, Elena; Griera, Albert
Shear resistance of beams based on the effective shear depth:
Despite extensive experimental and theoretical studies the shear resistance of beams with longitudinal reinforcement is described by empirical expressions. A reliable empirical formula is derived by Rafla [10]. This formula is based on 442 experimental results. In this report no experiments are described. It is endeavoured to make a new contribution to the theoretical study of shear strength. The model presented in this report is based on the idea that apart from the effective depth of the...
Pruijssers, A. F.
To investigate joint control on hydrology as well as tectonic implications, we conducted a study of joint orientations near the Stony Clove and Warner Creek drainages of the Catskill Mountains, Eastern New York. Specific goals of this research were to determine joint control on stream orientations and groundwater flow, to compare results with previous studies in the area, and to investigate their tectonic significance. Trails, streams, and road cuts were traversed to locate bedrock outcrops whose positions were determined using topographic maps and a handheld GPS unit. Additional outcrops were located using aerial photographs and GIS data. Joint orientations were measured using a standard Brunton pocket transit. The data was analyzed using Orient (Vollmer, 2010), an orientation analysis program, to plot joint and stream orientations on rose diagrams. ArcGIS was used to produce topographic, hill-shade, and stream drainage maps. Over 500 joint orientations at over 100 outcrop stations were collected. The data were plotted on a rose diagrams, and two major joint sets were found, one with a mean strike of 021� and one with a mean strike of 096�. Stream orientations were also plotted on a rose diagram showing an axial mean of 022�, and indicate that the joint set with mean strike of 021 may have a significant control on stream orientations. The hill-shade maps also demonstrate clearly the strong control of jointing on the topography. The data collected in this research expands on previous joint orientation studies of Engelder and Geiser (1980) in the southwestern and central Catskills, and is similar to joint orientations found by Isachsen et al. (1977) in their study of the Panther Mountain circular structure, a possible impact-related feature. The origin of this jointing is thought to be related to Alleghanian (Permian) and possibly Acadian (Devonian) orogenic events.
Haskins, M. N.; Vollmer, F. W.; Rayburn, J. A.; Gurdak, J. J.
Subcritical dynamos in shear flows
Identifying generic physical mechanisms responsible for the generation of magnetic fields and turbulence in differentially rotating flows is fundamental to understand the dynamics of astrophysical objects such as accretion disks and stars. In this paper, we discuss the concept of subcritical dynamo action and its hydrodynamic analogue exemplified by the process of nonlinear transition to turbulence in non-rotating wall-bounded shear flows. To illustrate this idea, we describe some recent results on nonlinear hydrodynamic transition to turbulence and nonlinear dynamo action in rotating shear flows pertaining to the problem of turbulent angular momentum transport in accretion disks. We argue that this concept is very generic and should be applicable to many astrophysical problems involving a shear flow and non-axisymmetric instabilities of shear-induced axisymmetric toroidal velocity or magnetic fields, such as Kelvin-Helmholtz, magnetorotational, Tayler or global magnetoshear instabilities. In the light of sev...
Rincon, F; Proctor, M R E; Cossu, C
Equilibrium Flow Shear and Magnetic Shear Effect on Zonal Flow
International Nuclear Information System (INIS)
Full text: A global transport simulation on ion temperature gradient driven drift wave (ITG) turbulence is performed by using electrostatic gyro-fluid code. The collapse mechanism of internal transport barrier (ITB) is investigated systematically focused on the de-correlation effect of the toroidal mode coupling in qmin region by flow shear which is induced by toroidal momentum source and radial electric field source, and zonal flow (ZF). A heat source is introduced into the model and temporal evolutions of the temperature profile and the ITG turbulence is studied simultaneously in a reversed magnetic shear configuration. In the first case, the off-resonant modes below the qmin region are not taken into account in the simulation, where a internal transport barrier like structure is formed around qmin position. It is found that steady ZF is generated at the edge of rational surfaces of the toroidally coupled ITG modes. The dependence of safety factor profile on the ZF is also studied. Reversed magnetic shear profiles with the same qmin value but different magnetic shear in the core region are examined. For relatively weak magnetic shear cases, the increase of the ZF around qmin region is observed intermittently. Especially, the ZF for the case with the weakest magnetic shear exhibits periodic oscillation. For rather strong magnetic shear case, such intermittent growth of ZF is not observed, in other words, the geod is not observed, in other words, the geodesic acoustic mode (GAM) oscillation is weak. However, the ZF is not so strong to quench the transport completely and the strong barrier formation is not observed for both cases. In the next, the toroidal momentum source and the radial electric field source are introduced into the model independently. The effects of flow shear by these sources on the evolution of the energy propagation in spatial and wave number spaces are examined. It is found that the toroidal flow shear is not so effective for both suppression of ITG mode and toroidal coupling in the radial direction. On the other hand, it is found that E x B flow shear induced by the electric field source locates around qmin region suppresses a meso-scale structure around qmin and contributes to the sustainment of ITB. The effect of off-resonance modes on turbulence suppression will be also discussed, which is now undergoing. (author)
We present results of our cosmic shear survey in progress at the Canada- France-Hawaii Telescope (CFHT). We analysed 1.7 sq. degrees of data, out of which we measured a significant correlation of galaxy shape-orientation over several arcmin scale. We present measurements of the variance of the shear $$ and of the correlation functions $$, $$. The signal is consistent with gravitational lensing by large scale structures predicti...
Waerbeke, L.; Mellier, Y.; Erben, T.; Cuillandre, J. -c; Bernardeau, F.; Maoli, R.; Bertin, E.; Cracken, H. J. Mc; Fevre, O. Le; Fort, B.; Fort, M. Dantel-fort; Jain, B.; Schneider, P.
Shear strength of granular materials
The shear strength properties of granular materials re?ect their inherent force and fabric anisotropy. We analyze the role of fabric and force anisotropies with respect to the critical-state shear strength. Then, a model of accessible geometrical states in terms of particle connectivity and contact anisotropy is presented. This model incorporates in a simple way the fact that, due to steric exclusions, the highest levels of connectivity and anisotropy cannot be reached simultaneously, a pro...
Radjai, Farhang; Aze?ma, Emilien
Fatigue strength of shear connectors
Nowadays steel and concrete composite beams are widely applied in structures mainly subjected to dynamic loads, such as railway and road bridges exposed to traffic loads and industrial crane runways exposed to folk-lift truck loads, the fatigue resistance of these structures must be generally and carefully verified. And normally the shear forces between concrete flange and steel beams are all transferred by different kinds of shear connectors, fatigue failure of composite beam may happen on s...
Xie, En; Valente, Isabel
Noise correlations in shear flows
We consider the effects of a shear on velocity fluctuations in a flow. The shear gives rise to a transient amplification that not only influences the amplitude of perturbations but also their time correlations. We show that, in the presence of white noise, time correlations of transversal velocity components are exponential and that correlations of the longitudinal components are exponential with an algebraic prefactor. Cross correlations between transversal and downstream c...
Eckhardt, B.; Pandit, R.
Shear thickening in highly viscous granular suspensions
We experimentally investigate shear thickening in dense granular suspensions under oscillatory shear. Directly imaging the suspension-air interface, we observe dilation beyond a critical strain ?c and the end of shear thickening as the maximum confining stress is reached and the contact line moves. Analyzing the shear profile, we extract the viscosity contributions due to hydrodynamics ?h , dilation ?c and sedimentation ?g . While ?g governs the shear thinning regime, ?h and ?c together determine the shear thickening behavior. As the suspending liquid's viscosity varies from 10 to 1000 cSt, ?h is found to compete with ?c and soften the discontinuous nature of shear thickening.
Xu, Qin; Majumdar, Sayantan; Brown, Eric; Jaeger, Heinrich M.
The limited growth of vegetated shear layers
In contrast to free shear layers, which grow continuously downstream, shear layers generated by submerged vegetation grow only to a finite thickness. Because these shear layers are characterized by coherent vortex structures and rapid vertical mixing, their thickness controls exchange between the vegetation and the overlying water. Experiments conducted in a laboratory flume show that the growth of these obstructed shear layers is arrested once the production of shear-layer-scale turbulent ki...
Ghisalberti, M.; Nepf, Heidi
Bicontinuous Microemulsions under Steady Shear Flow
Dynamic response of microemulsions to shear deformation on the basis of two-order-parameter time dependent Ginzburg-Landau model is investigated by means of cell dynamical system approach. Time evolution of anisotropic factor and excess shear stress under steady shear flow is studied by changing shear rate and total amount of surfactant. As the surfactant concentration is increased, overshoot peak height of the anisotropic factor increases whereas that of the excess shear stress is almost unc...
Kodama, Hiroya; Komura, Shigeyuki
The catastrophic growth of unstable thermoplastic shear following the transition from homogeneous deformation to heterogeneous localized deformation through distributed shear banding is studied through approximate analytic and computational methods. The calculations provide expressions for shear-band widths, spacing, catastrophic growth times and the rate of stress communication between shear bands. The calculations are applied to heterogeneous shear localization observed in the steady-wave s...
Grady, D.; Kipp, M.
Experimental observation of shear thickening oscillation
We report experimental observation of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. The shear thickening oscillation is caused by the interplay between the fluid dynamics and the shear thickening, and has been predicted theoretically by the present authors using a phenomenological fluid dynamics model for the dilatant fluid, but never been reported experimentally. Using a density-matched sta...
Nagahiro, Shin-ichiro; Nakanishi, Hiizu; Mitarai, Namiko
Shear transfer across cracks in reinforced concrete
International Nuclear Information System (INIS)
An experimental and analytical investigation was conducted to assess the transfer of cyclic shear forces in cracked reinforced concrete by means of the interface shear transfer and dowel action mechanisms. Two test series evaluated the transfer of shear forces by the combination of the interface shear transfer and dowel action mechanisms, and the dowel action mechanism alone. The initial crack width and the reinforcement ratios provided at the shear plane, the number of loading cycles, and the cyclic shear stress intensity were the main variables studied using a test specimen modeled after an idealized section of the cracked structure. The average shear displacement, crack width, and reinforcement strains were measured in each specimen for all load increments. Simplified equations were developed to describe the first loading cycle stiffness exhibited by both the interface shear transfer and dowel action mechanism. A bilinear idealization was proposed for the experimental hysteresis curve of each mechanism together with the corresponding stiffness coefficients. Equations were derived from a nonlinear regression analysis for the splitting failure force for axial or dowel forces, and for their interaction. An equation was also proposed for the ultimate shear stress that can be transferred across a precracked shear plane. The research concluded that shear forces can be efficiently transferred across cracked surfaces by the combined action of the interface shear transfer ad action of the interface shear transfer and dowel action mechanisms. The investigation was motivated by the desire to assess the behavior of the shear transfer mechanism in cracked secondary nuclear containment vessels
FEM Simulation of Incremental Shear
International Nuclear Information System (INIS)
A popular way of producing ultrafine grained metals on a laboratory scale is severe plastic deformation. This paper introduces a new severe plastic deformation process of incremental shear. A finite element method simulation is carried out for various tool geometries and process kinematics. It has been established that for the successful realisation of the process the inner radius of the channel as well as the feeding increment should be approximately 30% of the billet thickness. The angle at which the reciprocating die works the material can be 30 deg. . When compared to equal channel angular pressing, incremental shear shows basic similarities in the mode of material flow and a few technological advantages which make it an attractive alternative to the known severe plastic deformation processes. The most promising characteristic of incremental shear is the possibility of processing very long billets in a continuous way which makes the process more industrially relevant
Shearing the Vacuum Quantum Friction
We consider two perfectly smooth featureless surfaces at T=0, defined only by their respective dielectric functions, separated by a finite distance, and ask the question whether they can experience any friction when sheared parallel to their interface. We find large frictional effects comparable to everyday frictional forces provided that the materials have resistivities of the order of 1 m-Ohm and that the surfaces are in close proximity. The friction depends solely on the reflection coefficients of the surfaces to electromagnetic waves and its detailed behaviour with shear velocity and separation is dictated by the dispersion of the reflectivity with frequency.
Pendry, J B
Noise Correlations in Shear Flows
We consider the effects of a shear on velocity fluctuations in a flow. The shear gives rise to a transient amplification that not only influences the amplitude of perturbations but also their time correlations. We show that, in the presence of white noise, time correlations of transversal velocity components are exponential and that correlations of the longitudinal components are exponential with an algebraic prefactor. Cross correlations between transversal and downstream components are strongly asymmetric and provide a clear indication of non-normal amplification. We suggest experimental tests of our predictions.
Eckhardt, B; Eckhardt, Bruno; Pandit, Rahul
Shear loading of costal cartilage
A series of tests were performed on a single post-mortem human subject at various length scales. First, tabletop tests were performed. Next, the ribs and intercostal muscles were tested with the view to characterize the load transfer between the ribs. Finally, the costal cartilage was tested under shear loading, as it plays an important in the transfer of the load between the ribs and the sternum. This paper reports the results of dynamic shear loading tests performed on three samples of costal cartilage harvested from a single post-mortem human subject, as well as the quantification of the effective Young's modulus estimated from the amount of cartilage calcification.
Subit, Damien
The present work deals with punching shear of flat slabs. I have researched the background of computer program called Sch�ck BOLE�, which is planed for designing additional shear reinforcement (studs) because of punching flat slabs. The equations that the computer uses are based on previous standard prEN 1992-1-1. Since the standard EN 1992-1-1 shortly come out, I have compared the equations that are written in the program with those used in the EN 1992- 1-1. Thus, I have found out no speci...
Lavrenc?ic?, Tomaz?
Unexpected shear strength change in magnetorheological fluids
Smart materials of magnetorheological (MR) fluids could be turned from a liquid state into a solid state, which solidification extent or shear strength often increases monotonically with the applied magnetic field. In this study, the shear stress of a dilute MR fluid decreased with increasing applied magnetic field at a constant shear rate. The dynamic shear stress was significantly higher than the stable counterpart at medium magnetic fields. They are ascribed to the slow particle structure transformation. A higher shear rate and particle volume fraction could reduce the transient time and the shear strength difference.
Tian, Yu; Chen, KaiKai; Shan, Lei; Zhang, Xiangjun; Meng, Yonggang
Experimental observation of shear thickening oscillation
We report experimental observation of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. The shear thickening oscillation is caused by the interplay between the fluid dynamics and the shear thickening, and has been predicted theoretically by the present authors using a phenomenological fluid dynamics model for the dilatant fluid, but never been reported experimentally. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed strong vibrations of the frequency around 20 Hz, which is consistent with our theoretical prediction.
Nagahiro, Shin-ichiro; Mitarai, Namiko
Unexpected shear strength change in magnetorheological fluids
Directory of Open Access Journals (Sweden)
Full Text Available Smart materials of magnetorheological (MR fluids could be turned from a liquid state into a solid state, which solidification extent or shear strength often increases monotonically with the applied magnetic field. In this study, the shear stress of a dilute MR fluid decreased with increasing applied magnetic field at a constant shear rate. The dynamic shear stress was significantly higher than the stable counterpart at medium magnetic fields. They are ascribed to the slow particle structure transformation. A higher shear rate and particle volume fraction could reduce the transient time and the shear strength difference.
Yu Tian
Shear viscosity of an ordering latex suspension
The shear viscosity of a latex which is ordered at rest is studied as a function of the shear rate and volume fraction. At low shear rates and for moderate to high volume fractions, the flow curves show dynamic yield behavior which disappears below a volume fraction of 8%. At high shear rates, the onset to the high shear rate plateau of the viscosity can be observed. A new model for the shear viscosity for lattices at high volume fractions is described. This model is based upon theories for t...
Vorst, B.; Ende, D. Den; Aelmans, N. J. J.; Mellema, J.
The Influence of Shearing Velocity on Shear Behavior of Artificial Joints
In this paper, the effects of shear velocity on the shearing behavior of artificial joints have been studied at different normal stress levels. Here, artificial joints with planar and rough surfaces were prepared with the plaster (simulating soft rock joints) and concrete (medium-hard rock joints) materials. The rough joints had triangular shaped asperities with 10� and 20� inclination angles. Direct shear tests were performed on these joints under various shear velocities in the range of 0.3-30 mm/min. The planar plaster-plaster and planer concrete-concrete joints were sheared at three levels of normal stress under constant normal load boundary condition. Also, the rough plaster-plaster and concrete-concrete joints were sheared at one level of normal stress under constant normal stiffness boundary condition. The results of the shear tests show that the shearing parameters of joints, such as shear strength, shear stiffness and friction angle, are related to the shear velocity. Shear strength of planar and rough plaster-plaster joints were decreased when the shear velocity was increased. Shear strength of concrete joints, except for rough joints with 10� inclination, increased with increasing shear velocity. Regardless of the normal stress level, shear stiffness of both planar plaster-plaster and concrete-concrete joints were decreased when the shear velocity was increased.
Atapour, Hadi; Moosavi, Mahdi
Bolted Structural Joint Sustains Reversing Shear Load
Bolted structural joint satisfies competing requirements to accommodate tolerances yet fits snugly to sustain reversing shear loads. Inner and outer eccentric bushings fit in shear block. Frictional force generated by bolt tension prevents rotation of bushings after assembly.
Mott, J. B.; Medley, D.
Shear modulus estimation with vibrating needle stimulation.
An ultrasonic shear wave imaging technique is being developed for estimating the complex shear modulus of biphasic hydropolymers including soft biological tissues. A needle placed in the medium is vibrated along its axis to generate harmonic shear waves. Doppler pulses synchronously track particle motion to estimate shear wave propagation speed. Velocity estimation is improved by implementing a k-lag phase estimator. Fitting shear-wave speed estimates to the predicted dispersion relation curves obtained from two rheological models, we estimate the elastic and viscous components of the complex shear modulus. The dispersion equation estimated using the standard linear solid-body (Zener) model is compared with that from the Kelvin-Voigt model to estimate moduli in gelatin gels in the 50 to 450 Hz shear wave frequency bandwidth. Both models give comparable estimates that agree with independent shear rheometer measurements obtained at lower strain rates. PMID:20529711
Orescanin, Marko; Insana, Michael
On double shearing in frictional materials
This paper evaluates the mechanical behaviour of yielding frictional geomaterials. The general Double Shearing model describes this behaviour. Non-coaxiality of stress and plastic strain increments for plane strain conditions forms an important part of this model. The model is based on a micro-mechanical and macro-mechanical formulation. The stress-dilatancy theory in the model combines the mechanical behaviour on both scales.It is shown that the general Double Shearing formulation comprises other Double Shearing models. These models differ in the relation between the mobilized friction and dilatancy and in non-coaxiality. In order to describe reversible and irreversible deformations the general Double Shearing model is extended with elasticity.The failure of soil masses is controlled by shear mechanisms. These shear mechanisms are determined by the conditions along the shear band. The shear stress ratio of a shear band depends on the orientation of the stress in the shear band. There is a difference between the peak strength and the residual strength in the shear band. While peak stress depends on strength properties only, the residual strength depends upon the yield conditions and the plastic deformation mechanisms and is generally considerably lower than the maximum strength. It is shown that non-coaxial models give non-unique solutions for the shear stress ratio on the shear band. The Double Shearing model is applied to various failure problems of soils such as the direct simple shear test, the biaxial test, infinite slopes, interfaces and for the calculation of the undrained shear strength. Copyright
Teunissen, J. A. M.
Shear assessment of reinforced concrete slab bridges:
The capacity of reinforced concrete solid slab bridges in shear is assessed by comparing the design beam shear resistance to the design value of the applied shear force due to the permanent actions and live loads. Results from experiments on half-scale continuous slab bridges are used to develop a set of recommendations for the assessment of slab bridges in shear. A method is proposed allowing to take the transverse force redistribution in slabs under concentrated loads into account, as well ...
Lantsoght, E. O. L.; Veen, C.; Walraven, J. C.; Boer, A.
Shear Reinforcements in the Reinforced Concrete Beams
- This study focuses on the use of different types of shear reinforcement in the reinforced concrete beams. Four different types of shear reinforcement are investigated; traditional stirrups, welded swimmer bars, bolted swimmer bars, and u-link bolted swimmer bars. Beam shear strength as well as beam deflection are the main two factors considered in this study. Shear failure in reinforced concrete beams is one of the most undesirable modes of failure due to its rapid progression. This sudden ...
Al-nasra, Moayyad M.
Shear induced crystallization of an amorphous system
The influence of a stationary shear flow on the crystallization in a glassy system is studied by means of molecular dynamics simulations and subsequent cluster analysis. The results reveal two opposite effects of the shear flow on the processes of topological ordering in the system. Shear promotes the formation of separated crystallites and suppresses the appearance of the large clusters. The shear-induced ordering proceeds in two stages, where the first stage is related mai...
Mokshin, Anatolii; Barrat, J. -l
Shear Strength of RC Bridge Deck Cantilevers
An experimental and theoretical investigation of the shear strength of reinforced concrete slabs without shear reinforcement is under way at the Ecole Polytechnique F�d�rale de Lausanne. The first part of the program consists of 6 tests on two large scale bridge deck cantilevers. The specimens are tested under different configurations of concentrated forces simulating traffic loads. The observed failure mode is shear. The second part of the experimental program consists of shear tests on 12...
Vaz Rodrigues, Rui
Refraction of shear zones in granular materials
We study strain localization in slow shear flow focusing on layered granular materials. A heretofore unknown effect is presented here. We show that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirmed by 3D discrete element simulations. We found that shear zones follow Snell's law...
Unger, Tamas
Refraction of shear zones in granular materials
We study strain localization in slow shear flow focusing on layered granular materials. A sofar unknown effect is presented here by showing that shear zones are refracted at material interfaces in analogy with refraction of light beams in optics. This phenomenon can be obtained as a consequence of a recent variational model of shear zones. The predictions of the model are tested and confirmed by 3D discrete element simulations. We found that shear zones follow Snell's law of light refraction.
Unger, T
Recent experimental probes of shear banding
Recent experimental techniques used to investigate shear banding are reviewed. After recalling the rheological signature of shear-banded flows, we summarize the various tools for measuring locally the microstructure and the velocity field under shear. Local velocity measurements using dynamic light scattering and ultrasound are emphasized. A few results are extracted from current works to illustrate open questions and directions for future research.
Manneville, Se?bastien
Modal wavefront reconstruction for radial shearing interferometer with lateral shear.
In a radial shearing interferometer, a portion of the test beam is magnified and used as the reference for the tested wavefront. However, the reference portion is always off center (lateral shear), which complicates the wavefront reconstruction. A modal method for solving this problem is presented here. This method uses orthogonal Zernike polynomials and its matrix formalism to calculate the Zernike coefficient of the wavefront under test. This approach has easier implementation, is better filtering, and has a more adaptive practical situation. The corresponding mathematical formula is deduced, and a computer simulation is also made to verify operation of the algorithm. The result of simulation analysis shows that the proposed method is correct and accurate. PMID:21931435
Gu, Naiting; Huang, Linhai; Yang, Zeping; Luo, Qun; Rao, Changhui
Identification of Shear Band using Elastic Shear Wave Propagation
Directory of Open Access Journals (Sweden)
Full Text Available Localization in soil under high stress level is usually investigated using some indirect measures, e.g., X-ray diffraction method. In the present study, the propagation velocity of shear wave was used to detect localization in sandy soil. Firstly, the general expression to exhibit the stress and density dependencies characteristics under consolidation and triaxial testing conditions of the tested soil was proposed. Adopted the proposed correlation as a reference together with the observed geometry, the shear wave velocity of the localized zone may be assumed. It was found that the density in the localized zone could be much looser than those ever reported in the literature. The void ratio of the localized zone is even larger than the maximum void ratio.
T. Nachiengtai
Shear viscosity and shear thinning in two-dimensional Yukawa liquids
A two-dimensional Yukawa liquid is studied using two different nonequilibrium molecular dynamics simulation methods. Shear viscosity values in the limit of small shear rates are reported for a wide range of Coulomb coupling parameter and screening length. At high shear rates it is demonstrated that this liquid exhibits shear thinning, i.e., the viscosity $\\eta$ diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas will exhibit this effect.
Donk'o, Z; Hartmann, P; Kutasi, K
Signatures of shear thinning-thickening transition in dense athermal shear flows
In non-equilibrium molecular dynamics simulations of dense athermal shear flows, we observe the transition from shear thinning to shear thickening at a crossover shear rate $\\dot\\gamma_c$. Shear thickening occurs when $\\frac{{\\rm d (ln} T_g)}{{\\rm d (ln}\\dot\\gamma)}>2$ with $T_g$ the granular temperature. At the transition, the pair distribution function shows the strongest anisotropy. Meanwhile, the dynamics undergo apparent changes, signified by distinct scaling behaviors ...
Zheng, Wen; Shi, Yu; Xu, Ning
Experimental observation of shear thickening oscillation
DEFF Research Database (Denmark)
We report experimental observations of the shear thickening oscillation, i.e. the spontaneous macroscopic oscillation in the shear flow of severe shear thickening fluid. Using a density-matched starch-water mixture, in the cylindrical shear flow of a few centimeters flow width, we observed that well-marked vibrations of frequency around 20 Hz appear via a Hopf bifurcation upon increasing externally applied shear stress. The parameter range and the frequency of the vibration are consistent with those expected by a simple phenomenological model of the dilatant fluid.
Nagahiro, Shin-ichiro; Nakanishi, Hiizu
Shear instability in nanoporous Si.
Elastic properties of nanoporous Si (np-Si), which is composed of bulk Si containing ordered, nanometer-sized cylindrical pores, are investigated based on first-principles density functional theory calculations. By separately varying the pore size and spacing, it is demonstrated that the elastic stiffness of np-Si under the shear strain perpendicular to the pore axis turns negative when the volume fraction of pores becomes greater than a critical value. The total energy calculations reveal that the negative values in the stiffness originate from the enhanced strain energy, which leads to significant rotation in bonds near the pore surface. Moreover, the high sensitivity of the elastic stiffness to shear induces a structural transformation in np-Si from tetragonal (D2d) to orthorhombic (C2v) phase, which makes it necessary to properly take the effect of external strain due to substrates or electrical leads into account in np-Si-based applications. PMID:25153784
Lee, Joo-Hyoung
Controlled shear/tension fixture
A test fixture for simultaneously testing two material test samples is provided. The fixture provides substantially equal shear and tensile stresses in each test specimens. By gradually applying a load force to the fixture only one of the two specimens fractures. Upon fracture of the one specimen, the fixture and the load train lose contact and the second specimen is preserved in a state of upset just prior to fracture. Particular advantages of the fixture are (1) to control the tensile to shear load on the specimen for understanding the effect of these stresses on the deformation behavior of advanced materials, (2) to control the location of fracture for accessing localized material properties including the variation of the mechanical properties and residual stresses across the thickness of advanced materials, (3) to yield a fractured specimen for strength measurement and an unfractured specimen for examining the microstructure just prior to fracture.
Hsueh, Chun-Hway (Knoxville, TN); Liu, Chain-tsuan (Knoxville, TN); George, Easo P. (Knoxville, TN)
Shear instabilities in granular mixtures
Dynamical instabilities in fluid mechanics are responsible of a variety of important common phenomena, such as waves on the sea surface or Taylor vorteces in Couette flow. In granular media dynamical instabilities has just begun to be discovered. Here we show by means of molecular dynamics simulation the existence of a new dynamical instability of a granular mixture under oscillating horizontal shear, which leads to the formation of a striped pattern where the components are...
Ciamarra, Massimo Pica; Nicodemi, Mario; Coniglio, Antonio
Shearing the Vacuum - Quantum Friction
We consider two perfectly smooth featureless surfaces at T=0, defined only by their respective dielectric functions, separated by a finite distance, and ask the question whether they can experience any friction when sheared parallel to their interface. We find large frictional effects comparable to everyday frictional forces provided that the materials have resistivities of the order of 1 m-Ohm and that the surfaces are in close proximity. The friction depends solely on the ...
Pendry, Jb
Anisotropic diffusion and shear instabilities
We examine the role of anisotropic turbulence on the shear instabilities in a stratified flow. Such turbulence is expected to occur in the radiative interiors of stars, due to their differential rotation and their strong stratification, and the turbulent transport associated with it will be much stronger in the horizontal than in the vertical direction. It will thus weaken the restoring force which is caused by the gradient of mean molecular weight ($\\mu$). We find that the ...
Talon, S.; Zahn, J. -p
Phase Dynamic of Shear Melting
The melting of an ultrathin lubricating film clamped between two atomically smooth solid surfaces that are in relative motion is analyzed. The influence of additive stresses fluctuations, strain and temperature on the process of lubricant melting is investigated taking into account the shear modulus deformation defect. The influence of the system parameters on the phase diagram, where the temperature noise intensity and the temperature of friction surfaces define the areas of dry, liquid and ...
Manko N.N.; Lyashenko I.
Phase Dynamic of Shear Melting
Directory of Open Access Journals (Sweden)
Full Text Available The melting of an ultrathin lubricating film clamped between two atomically smooth solid surfaces that are in relative motion is analyzed. The influence of additive stresses fluctuations, strain and temperature on the process of lubricant melting is investigated taking into account the shear modulus deformation defect. The influence of the system parameters on the phase diagram, where the temperature noise intensity and the temperature of friction surfaces define the areas of dry, liquid and stick-slip friction, is analyzed.
Manko N.N.
We explore the efficacy of network optimisation theory for minimum cut to quantify the evolution of granular fabric and its functionality as a transmission medium in deforming dense granular media. Our focus here is on force transmission in a sheared assembly of polydisperse particles, in a biaxial compression test under constant confining pressure. The granular fabric is examined with respect to the material's force-bearing contact network over that regime when the material has reached its residual strength, and is deforming under a near constant volume in the presence of a fully developed shear band. The structural evolution of the fabric is quantitatively characterized using a representative weighted-directed network that is similarly evolving as the sample deforms. The edges or links, representing the interparticle contacts, are each weighted by the capacity of the contact to transmit force: a scalar that depends solely on the relative motion of the contacting grains. In the large strain failure regime, the minimum cut which represents the bottleneck in force transmission is found to lie in the persistent shear band. This study paves the way for the future analysis of flows and force transmission through an evolving contact network and, in turn, the characterisation of the relationship between the material's contact topology and its capacity to transmit forces through its contact network.
Tordesillas, Antoinette; Cramer, Andrew; Walker, David M.
Nucleation of shear bands in amorphous alloys.
The initiation and propagation of shear bands is an important mode of localized inhomogeneous deformation that occurs in a wide range of materials. In metallic glasses, shear band development is considered to center on a structural heterogeneity, a shear transformation zone that evolves into a rapidly propagating shear band under a shear stress above a threshold. Deformation by shear bands is a nucleation-controlled process, but the initiation process is unclear. Here we use nanoindentation to probe shear band nucleation during loading by measuring the first pop-in event in the load-depth curve which is demonstrated to be associated with shear band formation. We analyze a large number of independent measurements on four different bulk metallic glasses (BMGs) alloys and reveal the operation of a bimodal distribution of the first pop-in loads that are associated with different shear band nucleation sites that operate at different stress levels below the glass transition temperature, Tg. The nucleation kinetics, the nucleation barriers, and the density for each site type have been determined. The discovery of multiple shear band nucleation sites challenges the current view of nucleation at a single type of site and offers opportunities for controlling the ductility of BMG alloys. PMID:24594599
Perepezko, John H; Imhoff, Seth D; Chen, Ming-Wei; Wang, Jun-Qiang; Gonzalez, Sergio
Shear strength of members without transverse reinforcement as function of critical shear crack width
This paper investigates the shear strength of beams and one-way slabs without stirrups based on the opening of a critical shear crack. The shear-carrying mechanisms after the development of this crack are investigated. On this basis, a rational model is developed to estimate the shear strength of members without shear reinforcement. The proposed model is based on an estimate of the crack width in the critical shear region, taking also into account the roughness of the crack and the compressiv...
Muttoni, Aurelio; Ferna?ndez Ruiz, Miguel
Shear instabilities in granular mixtures.
Dynamical instabilities in fluid mechanics are responsible for a variety of important common phenomena, such as waves on the sea surface or Taylor vortices in Couette flow. In granular media dynamical instabilities have just begun to be discovered. Here we show by means of molecular dynamics simulation the existence of a new dynamical instability of a granular mixture under oscillating horizontal shear, which leads to the formation of a striped pattern where the components are segregated. We investigate the properties of such a Kelvin-Helmholtz-like instability and show how it is connected to pattern formation in granular flow and segregation. PMID:15904411
Ciamarra, Massimo Pica; Coniglio, Antonio; Nicodemi, Mario
Mixing in shear thinning fluids
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: English Abstract in english In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. A [...] nalyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.
H., Ameur; M., Bouzit.
Shear strength properties of wet granular materials
We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear...
Richefeu, V; Radja"i, F; Richefeu, Vincent; Youssoufi, Moulay Sa\\"{i}d El; Radja\\"{i}, Farhang
Supercooled Liquids Under Shear: Theory and Simulation
We analyze the behavior of supercooled fluids under shear both theoretically and numerically. Theoretically, we generalize the mode-coupling theory of supercooled fluids to systems under stationary shear flow. Our starting point is the set of generalized fluctuating hydrodynamic equations with a convection term. A nonlinear integro-differential equation for the intermediate scattering function is constructed. This theory is applied to a two-dimensional colloidal suspension. The shear rate dependence of the intermediate scattering function and the shear viscosity is analyzed. We have also performed extensive numerical simulations of a two-dimensional binary liquid with soft-core interactions near, but above, the glass transition temperature. Both theoretical and numerical results show: (i) A drastic reduction of the structural relaxation time and the shear viscosity due to shear. Both the structural relaxation time and the viscosity decrease as $\\dot{\\gamma}^{-\
Miyazaki, K; Yamamoto, R; Miyazaki, Kunimasa; Reichman, David R.; Yamamoto, Ryoichi
The paper presents an artificial neural network technique to predict the shear strength parameters of medium compressibility soil, which influenced by basic properties of soil in unconsolidated undrained conditions. Obviously obtained the undisturbed samples of soil to determination of shear strength parameters is a tedious work. Commercial software�s MATLAB-7 was used for this study. Triaxial shear tests were conducted to obtain these parameters at different water contents and densities. T...
Rajeev Jain; Dr. Pradeep Kumar Jain,; Dr. Sudhir Singh Bhadauria
Shear stress in lattice Boltzmann simulations
A thorough study of shear stress within the lattice Boltzmann method is provided. Via standard multiscale Chapman-Enskog expansion we investigate the dependence of the error in shear stress on grid resolution showing that the shear stress obtained by the lattice Boltzmann method is second order accurate. This convergence, however, is usually spoiled by the boundary conditions. It is also investigated which value of the relaxation parameter minimizes the error. Furthermore, f...
Kru?ger, Timm; Varnik, Fathollah; Raabe, Dierk
Derivative moments in stationary homogeneous shear turbulence
A statistically stationary and nearly homogeneous turbulent shear flow is established by an additional volume forcing in combination with stress-free boundary conditions in the shear direction. Both turbulent energy and enstrophy are stationary to a much better approximation than in previous simulations that use remeshing. The temporal fluctuations decrease with increasing Reynolds number. Energy spectra and shear-stress cospectra show that local isotropy is satisfactorily o...
Schumacher, Joerg
Dip of the granular shear stress.
Recent experiments reveal an unexpected dip of the shear stress as the shear rate increases, from the rate-independent regime to Bagnold flow. Employing granular solid hydrodynamics, it is shown that in uniform systems, such dips occur for given pressure or normal stress, but not for given density. If the shear rate is strongly nonuniform, enforcing a constant volume does not prevent the local density to vary, and a stress dip may still occur. PMID:23367937
Krimer, Dmitry O; Mahle, Stefan; Liu, Mario
Large-Scale Cosmic Shear Measurements
We present estimates of the gravitational lensing shear variance obtained from images taken at the CFHT using the UH8K CCD mosaic camera. Six fields were observed for a total of 1 hour each in V and I, resulting in catalogs containing approximately 20,000$ galaxies per field, with properly calibrated and optimally weighted shear estimates. These were averaged in cells of sizes ranging from 1'.875 to 30' to obtain estimates of the cosmic shear variance $$, wit...
Kaiser, Nick; Wilson, Gillian; Luppino, Gerard A.
Developments in Plasticity Approach to Shear
DEFF Research Database (Denmark)
The paper deals with plastic methods applied to shear design of reinforced concrete beams. Emphasis is put on the recently developed crack sliding model applicable to non-shear reinforced and lightly shear reinforced beams and slabs. The model, which is an upper bound plasticity approach, takes into account the mechanism of crack formation followed by crack sliding. Comparisons between the model and test results are carried out. Good agreement has been found over a wide range of cases.
Hoang, Cao Linh; Nielsen, Mogens Peter
Shear wall experiments and design in Japan
International Nuclear Information System (INIS)
This paper summarizes the results of recent survey studies on the available experimental data bases and design codes/standards for reinforced concrete (RC) shear wall structures in Japan. Information related to the seismic design of RC reactor buildings and containment structures was emphasized in the survey. The seismic requirements for concrete structures, particularly those related to shear strength design, are outlined. Detailed descriptions are presented on the development of Japanese shear wall equations, design requirements for containment structures, and ductility requirements
Interface Roughness Parameters and Shear Strength
The interlayer bond strength between binder and wearing course and several possible treatments of enhancing the contact surface roughness and the interlocking are investigated. For this purpose, conventional methods, such as shear tests, but also laser image acquisition of the binder upper surface have been used. The mechanical outcomes of a shear test device and the binder surface roughness parameters, have been compared looking for a relation between the shear performance and the surface...
Andrea, Antonio D.; Cristina Tozzo; Alberto Boschetto; Luana Bottini
Crystallization in a sheared colloidal suspension
We study numerically the crystallization process in a supersaturated suspension of repulsive colloidal particles driven by simple shear flow. The effect of the shear flow on crystallization is two-fold: while it suppresses the initial nucleation, once a large enough critical nucleus has formed its growth is enhanced by the shear flow. Combining both effects implies an optimal strain rate at which the overall crystallization rate has a maximum. To gain insight into the underl...
Lander, Boris; Seifert, Udo; Speck, Thomas
Elastic Turbulence in Shear Banding Wormlike Micelles
We study the dynamics of the Taylor-Couette flow of shear banding wormlike micelles. We focus on the high shear rate branch of the flow curve and show that for sufficiently high Weissenberg numbers, this branch becomes unstable. This instability is strongly sub-critical and is associated with a shear stress jump. We find that this increase of the flow resistance is related to the nucleation of turbulence. The flow pattern shows similarities with the elastic turbulence, so fa...
Fardin, M. A.; Lopez, D.; Croso, J.; Gre?goire, G.; Cardoso, O.; Mckinley, G. H.; Lerouge, S.
Equivalent Strain in Simple Shear Deformations
We show that simple shear and pure shear form two groups of transformations with different properties. The equivalent strain is viewed as an external control parameter of the deformation process at low homologous temperatures. The von Mises strain satisfies group-theoretic properties of both groups, supporting its use for measuring the equivalent strain. The Hencky strain, on the other hand, does not satisfy the simple shear group properties, implying that it is not appropri...
Beygelzimer, Yan
Accurate Shear Measurement with Faint Sources
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of sourc...
Zhang, Jun; Luo, Wentao; Foucaud, Sebastien
Effect of shear stress on soil compaction
This report presents the results from theoretical considerations and practical tests concerning the influence of slip generated shear on the compaction of agricultural soil. The slip mechanics is reviewed and its influence on the stress field below a wheel or track is investigated. It is shown that shear stresses in the interface between wheel and soil have great influence on the magnitude of the major principal stress acting in the upper soil layer. Tests with shear displacement introduced b...
Olsen, Hans Jo?rgen
Can CMB Lensing Help Cosmic Shear Surveys?
Yes! Upcoming galaxy shear surveys have the potential to significantly improve our understanding of dark energy and neutrino mass if lensing systematics can be sufficiently controlled. The cross-correlations between the weak lensing shear, galaxy number counts from a galaxy redshift survey, and the CMB lensing convergence can be used to calibrate the shear multiplicative bias, one of the most challenging systematics in lensing surveys. These cross-correlations can significantly reduce the deleterious effects of the uncertainties in multiplicative bias.
Das, Sudeep; Spergel, David
Long-time tails in sheared fluids
The long-time behaviors of the velocity autocorrelation function $C(t)$ for sheared fluids ^M are investigated theoretically and numerically. It is found the existence of the cross-overs of^M $C(t)$ from $t^{-d/2}$ to $t^{-d}$ ^M in sheared fluids of elastic particles without any thermostat, and from $t^{-d/2}$ to $t^{-(d+2)/2}$ ^M in both sheared fluids of elastic particles with a thermostat and sheared granular fluids,^M where $d$ is the spatial dimension. ^M The validity ...
Otsuki, Michio; Hayakawa, Hisao
Study on magnetorheological shear thickening fluid
In this paper, a magnetic-field-controlled and speed-activated magnetorheological shear thickening fluid (MRSTF) is presented. We fabricated a kind of shear thickening fluid (STF) which was composed of nanosize silica particles suspended in a solvent, ethylene glycol, at high concentrations. Then the micron-size carbonyl iron particles with different volume fractions were added to the STF to fabricate the MRSTF. Their dynamic properties in different shear strain rates and magnetic fields were tested by using a rheometer. The suspension shows an abrupt increase in complex viscosity beyond a critical dynamic shear rate and a magnetic-field-controllable characteristic, as well as being reversible.
Zhang, Xianzhou; Li, Weihua; Gong, X. L.
Study on magnetorheological shear thickening fluid
International Nuclear Information System (INIS)
In this paper, a magnetic-field-controlled and speed-activated magnetorheological shear thickening fluid (MRSTF) is presented. We fabricated a kind of shear thickening fluid (STF) which was composed of nanosize silica particles suspended in a solvent, ethylene glycol, at high concentrations. Then the micron-size carbonyl iron particles with different volume fractions were added to the STF to fabricate the MRSTF. Their dynamic properties in different shear strain rates and magnetic fields were tested by using a rheometer. The suspension shows an abrupt increase in complex viscosity beyond a critical dynamic shear rate and a magnetic-field-controllable characteristic, as well as being reversible
Massive shear wall testing for nuclear industry
International Nuclear Information System (INIS)
Consequences of earthquakes have proven the need to study the shear mechanism of low-rise reinforced concrete shear walls thoroughly. Because of the complexity of reinforced concrete behavior generalized problem solutions are not readily available. Experimental testing remains essential for investigating concrete elements. The contribution deals with cyclic shear testing of thick low-rise reinforced concrete walls. Analysis of the data obtained resulted in the determination of hysteresis characteristics, nonlinear effects for shear, ultimate capacity and damping of the tested specimens. Various strength assessments and comparison to test results is given. The experimental investigation provides valuable results applicable in monitoring and design of structures. (author)
Shear flow generation due to electromagnetic instabilities
International Nuclear Information System (INIS)
Shear flow is the most important ingredient governing nonlinear behaviour of many types of plasma instability. Electromagnetic effects on shear flow generation have been studied for an electromagnetic drift wave called resistive drift-Alfven mode (RDAM) and a global MHD mode called resistive wall mode (RWM). For RDAM it is found that the generated shear flow stabilizes the dominant modes; however, other modes are destabilized. For RWM Maxwell stress due to magnetic fluctuations has a tendency to suppress the poloidal flow near the plasma surface, which gives almost the same saturation level for different initial poloidal flows, since the shear flow stabilization disappears. (author)
Confined Cubic Blue Phases under Shear
We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously b reaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very th in samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direction. Blue phase I responds very differently: its defect network undergoes seemingly chaotic rearrangements under shear, irrespective of system size.
Henrich, O; Marenduzzo, D; Coveney, P V; Cates, M E
Shear banding phenomena in a Laponite suspension
Shear localization in an aqueous clay suspension of Laponite is investigated through dynamic light scattering, which provides access both to the dynamics of the system (homodyne mode) and to the local velocity profile (heterodyne mode). When the shear bands form, a relaxation of the dynamics typical of a gel phase is observed in the unsheared band soon after flow stop, suggesting that an arrested dynamics is present during the shear localization regime. Periodic oscillations of the flow behavior, typical of a stick-slip phenomenon, are also observed when shear localization occurs. Both results are discussed in the light of various theoretical models for soft glassy materials.
Ianni, F; Gentilini, S; Ruocco, G
Shear instability of a gyroid diblock copolymer
DEFF Research Database (Denmark)
The stability of the gyroid phase of diblock copolymers has been studied using combined oscillatory shear and small-angle neutron scattering (SANS) techniques. It is shown that the gyroid phase of polystyrene-polyisoprene (PS-PI) is unstable when exposed to combined large-amplitude and high-frequency shear deformations. The bicontinuous cubic gyroid structure (G) transforms to the hexagonally cylinder phase (HEX). The transition is perfectly reversible, but with a significant difference in time constants. Upon application of shear the G --> HEX transition is instantaneous within experimental resolution, while the HEX --> G relaxation after cessation of shear takes hours. The texture of the shear-induced cylinder phase is shown to be a near ideal monodomain, while the relaxed gyroid phase constitutes a two-dimensional powder with the characteristic 10-spot scattering pattern. The shear-induced destabilization is discussed in relation to analogous observations on shear-induced order-to-order and disorder-to-order transitions observed in related block copolymer systems and in microemulsions. It is discussed whether these phenomena originate in shear-reduced fluctuations or shear-induced dislocations.
Eskimergen, R�ya; Mortensen, Kell
Shear-stress dependence of dinoflagellate bioluminescence.
Fluid flow stimulates bioluminescence in dinoflagellates. However, many aspects of the cellular mechanotransduction are incompletely known. The objective of our study was to formally test the hypothesis that flow-stimulated dinoflagellate bioluminescence is dependent on shear stress, signifying that organisms are responding to the applied fluid force. The dinoflagellate Lingulodinium polyedrum was exposed to steady shear using simple Couette flow in which fluid viscosity was manipulated to alter shear stress. At a constant shear rate, a higher shear stress due to increased viscosity increased both bioluminescence intensity and decay rate, supporting our hypothesis that bioluminescence is shear-stress dependent. Although the flow response of non-marine attached cells is known to be mediated through shear stress, our results indicate that suspended cells such as dinoflagellates also sense and respond to shear stress. Shear-stress dependence of flow-stimulated bioluminescence in dinoflagellates is consistent with mechanical stimulation due to direct predator handling in the context of predator-prey interactions. PMID:17565113
Maldonado, Elisa M; Latz, Michael I
Long-time tails for sheared fluids
International Nuclear Information System (INIS)
The long-time behavior of the velocity autocorrelation function (VACF) for sheared fluids is investigated theoretically and numerically. The existence is found of cross-overs of the VACF from t?d/2 to t?d in sheared fluids of elastic particles without any thermostat, and from t?d/2 to t?(d+2)/2 in both sheared fluids of elastic particles with a thermostat and sheared granular fluids, where d is the spatial dimension. The validity of the predictions has been confirmed by our numerical simulations. (letter)
Statistical Model of Extreme Shear
DEFF Research Database (Denmark)
In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function (PDF) of turbulence driven short-term extreme wind shear events, conditioned on the mean wind speed, for an arbitrary recurrence period. The model is based on an asymptotic expansion, and only a few and easily accessible parameters are needed as input. The model of the extreme PDF is supplemented by a model that, on a statistically consistent basis, describes the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of full-scale measurements recorded with a high sampling rate. The measurements have been extracted from "Database on Wind Characteristics" (http://www.winddata.com/), and they refer to a site characterised by a flat homogeneous terrain. The comparison has been conducted for three different mean wind speeds in the range 15m/s � 19m/s, and model predictions and experimental results are consistent, given the inevitable uncertainties associated with the model as well as with the extreme value data analysis.
Hansen, Kurt Schaldemose; Larsen, Gunner Chr.
Shear wall ultimate drift limits
International Nuclear Information System (INIS)
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated
Shear reinforcement in deep slabs
A considerable amount of data is available in the literature regarding the behavior of normally proportioned slabs, those with span-to-effective-depth (L/d) ratios greater than approximately 8. However, guidance for shear design and response limits of deep slabs (L/d less than 6) used in protective construction is lacking. Thirteen one-way reinforced concrete deep slabs were statically loaded with uniform water pressure to gain a basic understanding of the behavior of deep slabs with reinforcing details typical of protective construction. The post-ultimate behavior of the slabs indicated that a substantial amount of reserve capacity is available in deep slabs with large quantities of principal reinforcement. Based on this series, the recommended response limit for deep slabs having a principal steel ratio near 0.01 and adequate shear reinforcement is approximately 12 deg. For deep slabs with relatively small quantities of principal steel, the response should probably be limited to approximately 8 deg for design purposes.
Woodson, Stanley C.
Shear wall ultimate drift limits
Energy Technology Data Exchange (ETDEWEB)
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated.
Duffey, T.A. [Duffy, (T.A.) Tijeras, NM (United States); Goldman, A. [Goldman, (A.), Sandia, Los Alamos, NM (United States); Farrar, C.R. [Los Alamos National Lab., NM (United States)
A technique for measuring optical beam shear is based on collecting light from the four quadrants of the beam and comparing the optical power collected from each quadrant with that from the other three quadrants. As used here, "shear" signifies lateral displacement of a beam of light from a nominal optical axis. A sensor for implementing this technique consists of a modified focusing lens and a quad-cell photodetector, both centered on the nominal optical axis. The modification of the lens consists in cutting the lens into four sectors (corresponding to the four quadrants) by sawing along two orthogonal diameters, then reassembling the lens following either of two approaches described next. In one approach, the lens is reassembled by gluing the sectors back together. In the simplest variant of this approach, the kerf of the saw matches the spacing of the photodetector cells, so that the focus of each sector crosses the axis of symmetry to fall on the opposite photodetector cell (see figure). In another variant of this approach, the lens sectors are spaced apart to make their individual foci to fall on separate photodetector cells, without crossing the optical axis. In the case of a sufficiently wide beam, the modified lens could be replaced with four independent lenses placed in a square array, each focusing onto an independent photodetector
Martin, Stefan; Szwaykowski, Piotr
Shear strength in one- and two-way slabs according to the critical shear crack theory
Currently, there is no generally-accepted theory giving a physical explanation of the shear strength in one- and two-way slabs. Furthermore, for members without transverse reinforcement, shear strength is estimated in most codes of practice following empirical or semi-empirical approaches. In this paper, the fundamentals of the Critical Shear Crack Theory (CSCT) are introduced. This theory, based on a mechanical model, is shown to provide a unified approach for one- and two-way shear in...
Muttoni, Aurelio; Ferna?ndez Ruiz, Miguel
Shear Behavior Of Reinforced High-Strength Concrete Beams Without Shear Reinforcement
Eighteen rectangular singly reinforced high-strength concrete beams without web reinforcement were tested in combined shear and flexure. The main variables were the longitudinal steel reinforcement ratio and the shear-span to effective depth ratio. The uniaxial compressive strength of concrete was about 93 MPa (13,500 psi). The experimental shear capacities were compared with the shear capacities predicted by different empirical equations presented in literatures. Two empirical equations have...
Wafa, Faisal F.
Evolution of twist-shear and dip-shear in Faring active region NOAA 10930
We study the evolution of magnetic shear angle in a flare productive active region NOAA 10930. The magnetic shear angle is defined as the deviation in the orientation of the observed magnetic field vector with respect to the potential field vector. The shear angle is measured in horizontal as well as vertical plane. The former is computed by taking the difference between the azimuth angles of the observed and potential field and is called the twist-shear, while the latter is...
Gosain, Sanjay; Venkatakrishnan, P.
Two-state shear diagrams for complex fluids in shear flow
The possible ``phase diagrams'' for shear-induced phase transitions between two phases are collected. We consider shear-thickening and shear-thinning fluids, under conditions of both common strain rate and common stress in the two phases, and present the four fundamental shear stress vs. strain-rate curves and discuss their concentration dependence. We outline how to construct more complicated phase diagrams, discuss in which class various experimental systems fall, and sket...
Olmsted, Peter D.
Shear-current effect in a turbulent convection with a large-scale shear
The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force $\\bec{\\cal E}^{(W)} \\propto {\\bf W} {\\bf \\times} {\\bf J}$ and the mean electric current along the original mean magnetic field, where ${\\bf W}$ is the background mean vorticity due to the shear and ${\\bf J}$ is the mean electric current. Th...
Rogachevskii, I.; Kleeorin, N.
Turbulence suppression by E x B shear in JET optimized shear pulses
International Nuclear Information System (INIS)
The authors calculate microinstability growth rates in JET optimized shear plasmas with a comprehensive gyrofluid model, including sheared E x B flows, trapped electrons, and all dominant ion species in realistic magnetic geometry. They find good correlation between E x B shear suppression of microinstabilities and both the formation and collapse of the internal transport barrier
Influence of post-mortem aging in tenderness of chicken breast fillets
Directory of Open Access Journals (Sweden)
Full Text Available In this work, analysis of chicken breast fillets was performed for shear values and sensory evaluation after different times of aging. Aging process was carried out by holding carcasses in covered plastic boxes, in a cold room, at 3 +/- 1masculineC; groups of 5 carcasses were stored and classified according to the period of storage in cold room as 0 (control, 2, 4, 8, 12 and 24 hours. The variation in pH of chicken carcasses during rigor decreased from 6.4 to 5.9. However, during the process of aging, the pH values increased up to 6.2 in the first 12h, probably as the result of proteolysis. The Warner-Bratzler shear values decreased as aging time increases, resulting in a first order kinetic. The carcasses presented a more accentuated decline in shear values in the first two hours of aging. After this period, the curve had a similar performance, achieving values of less than 1 kgf in 4 hours or more, with complete aging being accomplished at 8 hours. The samples with higher period of aging (8, 12 and 24 hours were preferred in sensorial analysis, without significant differences among them.
Santos Helena Caminha
Shear stress in atherosclerotic plaque determination.
Atherosclerosis initiates at predictable focal sites near arterial branches and curves, where blood flow is disturbed and shear stress is complex. Endothelial shear stress is the tangential stress derived from the friction of the flowing blood on the endothelial surface of the arterial wall. It is a key factor in modulating endothelial cell gene expression and vascular development and remodeling. Increasing evidences suggest that shear stress patterns have a strong relationship with atherosclerotic features. Moreover, variations in the local artery geometry during atherogenesis further modify flow shear stress characteristics, which contribute to the rupture site at the plaque upstream. In this study, we summarize the mechanistic evidences that associate shear stress patterns with determined atherosclerotic plaque features. An enhanced understanding of the relationship and pathophysiological function of shear stress patterns in atherosclerotic plaque features is essential, which may provide early prediction of clinical risk and guide individualized treatment strategies. In the current review, we analyzed the function of shear stress on the determination of atherosclerotic lesion and provided an update on the mechanotransduction of shear stress, gene expression regulation, and atherosclerotic plaque development and rupture. PMID:25165867
Li, Xiaohong; Yang, Qin; Wang, Zuo; Wei, Dangheng
Finite element modelling of fabric shear
International Nuclear Information System (INIS)
In this study, a finite element model to predict shear force versus shear angle for woven fabrics is developed. The model is based on the TexGen geometric modelling schema, developed at University of Nottingham and orthotropic constitutive models for yarn behaviour, coupled with a unified displacement-difference periodic boundary condition. A major distinction from prior modelling of fabric shear is that the details of picture frame kinematics are included in the model, which allows the mechanisms of fabric shear to be represented more accurately. Meso- and micro-mechanisms of deformation are modelled to determine their contributions to energy dissipation during shear. The model is evaluated using results obtained for a glass fibre plain woven fabric, and the importance of boundary conditions in the analysis of deformation mechanisms is highlighted. The simulation results show that the simple rotation boundary condition is adequate for predicting shear force at large deformations, with most of the energy being dissipated at higher shear angles due to yarn compaction. For small deformations, a detailed kinematic analysis is needed, enabling the yarn shear and rotation deformation mechanisms to be modelled accurately
Fragility assessment of containment tangential shear failure
International Nuclear Information System (INIS)
This paper presents the fragility assessment of the reinforced concrete containment of the Indian Point-3 reactor with respect to the tangential shear failure. The tangential shear limit state is described in detail. The variations of material strengths such as the concrete compressive strength and reinforcement yield strength are included in the fragility analysis by using the Latin hypercube sampling technique. (orig./HP)
Shear buckling of square perforated plates
The behavior of thin square perforated plates under the action of uniform shear deformation is studied experimentally and analytically using finite element analysis. Elastic Shear buckling strength is established as a function of the diameter of a round, centrally located hole in the plate. Post buckling behavior and the behavior of perforated plates with various ring stiffeners are also studied experimentally.
Grosskurth, J. F., Jr.; White, R. N.; Gallagher, R. H.; Thomas, G. R.
Direct measurement of piezoelectric shear coefficient
Piezoelectric materials exhibit electromechanical coupling which has led to their widespread application for sensors, actuators, and energy harvesters. These materials possess anisotropic behavior with the shear coefficient, and have the largest electromechanical coupling coefficient. However, the shear mode is difficult to measure with existing techniques and thus has not been fully capitalized upon in recent devices. Better understanding of the full shear response with respect to the driving electric field would significantly help the design of optimized piezoelectric shear devices. Here, a simple and low cost direct measurement method based on digital image correlation is developed to characterize the shear response of piezoelectric materials and its nonlinear behavior as a function of external field. The piezoelectric shear coefficient (d15) of a commercial shear plate actuator is investigated in both bipolar and unipolar electric fields. Two different nonlinearities and hysteresis behaviors of the actuators were observed, and the relation between the driving field amplitude and the corresponding d15 coefficient is determined. Moreover, the measured transverse displacement of the plate actuator in simple shear condition is validated through a laser interferometry technique.
Malakooti, Mohammad H.; Sodano, Henry A.
Directory of Open Access Journals (Sweden)
Full Text Available The algebraic proof of the fundamental theorem concerning pure shear, by making use only of the notion of orthogonal projector, is presented. It has been shown that the state of pure shear is the same for all singular symmetric traceless tensors in E3, up to the rotation.
Jari? Jovo P.
Crosswind Shear Gradient Affect on Wake Vortices
Parametric simulations with a Large Eddy Simulation (LES) model are used to explore the influence of crosswind shear on aircraft wake vortices. Previous studies based on field measurements, laboratory experiments, as well as LES, have shown that the vertical gradient of crosswind shear, i.e. the second vertical derivative of the environmental crosswind, can influence wake vortex transport. The presence of nonlinear vertical shear of the crosswind velocity can reduce the descent rate, causing a wake vortex pair to tilt and change in its lateral separation. The LES parametric studies confirm that the vertical gradient of crosswind shear does influence vortex trajectories. The parametric results also show that vortex decay from the effects of shear are complex since the crosswind shear, along with the vertical gradient of crosswind shear, can affect whether the lateral separation between wake vortices is increased or decreased. If the separation is decreased, the vortex linking time is decreased, and a more rapid decay of wake vortex circulation occurs. If the separation is increased, the time to link is increased, and at least one of the vortices of the vortex pair may have a longer life time than in the case without shear. In some cases, the wake vortices may never link.
Proctor, Fred H.; Ahmad, Nashat N.
Plastic deformation: Shearing mountains atom by atom
Energy Technology Data Exchange (ETDEWEB)
Highlights: ? Rocks, wood, ceramics, semiconductors, and metals all deform in the same way, namely by heterogeneous shear banding via hierarchical orthogonal shear modes. ? While the governing principles of deformation are the same for rocks, wood, ceramics, semiconductors, and metals, these materialsdiffer in their microscopic deformation mechanisms and in the width of the shear band, which covers twelve orders of magnitude from angstroms to hundreds of meters. ? Microscopic deformation mechanisms couple to macroscopic deformation mechanisms, i.e. shear banding, through the collective properties of defect groups on the mesoscale. -- Abstract: Conventional wisdom established atomistic defects, dislocations, as agents of plastic deformation. On macroscopic scale, rock, wood, steel, tough ceramics, fiber reinforced composites, and silicon all deform in the same way and produce the same pattern; shear bands. The argumentation presented here, starts on the largest length scale of the problem at hand and leads through a number of hierarchical levels down to the atomistic mechanism. Shear bands develop discontinuously by the motion of a process zone. Locally, i.e. in the process zone, deformation proceeds perpendicularly to the macroscopic shear, in combination with a rotation. The microscopic shear itself may occur again in a discontinuous manner and again orthogonally to the intermediate level and so on at ever smaller scale. Material properties come into play at the highest hierarchical level, i.e. at the smallest length scale where they control the well-known micromechanisms.
M�llner, Peter, E-mail: email@example.com [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States)
Shear flows and shear viscosity in a two-dimensional Yukawa system (dusty plasma).
The shear viscosity of a two-dimensional liquid-state dusty plasma was measured experimentally. A monolayer of highly charged polymer microspheres, with a Yukawa interaction, was suspended in a plasma sheath. Two counterpropagating Ar+ laser beams pushed the particles, causing shear-induced melting of the monolayer and a shear flow in a planar Couette configuration. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order 1 mm(2) s(-1), depending on the monolayer's parameters and shear stress applied. PMID:15524893
Nosenko, V; Goree, J
Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma)
The shear viscosity of a two-dimensional liquid-state dusty plasma was measured experimentally. A monolayer of highly charged polymer microspheres, with a Yukawa interaction, was suspended in a plasma sheath. Two counter-propagating Ar laser beams pushed the particles, causing shear-induced melting of the monolayer and a shear flow in a planar Couette configuration. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order 1 mm^2/s, depending on the monolayer's parameters and shear stress applied.
Nosenko, V
Steel Shear Walls, Behavior, Modeling and Design
In recent years steel shear walls have become one of the more efficient lateral load resisting systems in tall buildings. The basic steel shear wall system consists of a steel plate welded to boundary steel columns and boundary steel beams. In some cases the boundary columns have been concrete-filled steel tubes. Seismic behavior of steel shear wall systems during actual earthquakes and based on laboratory cyclic tests indicates that the systems are quite ductile and can be designed in an economical way to have sufficient stiffness, strength, ductility and energy dissipation capacity to resist seismic effects of strong earthquakes. This paper, after summarizing the past research, presents the results of two tests of an innovative steel shear wall system where the boundary elements are concrete-filled tubes. Then, a review of currently available analytical models of steel shear walls is provided with a discussion of capabilities and limitations of each model. We have observed that the tension only "strip model", forming the basis of the current AISC seismic design provisions for steel shear walls, is not capable of predicting the behavior of steel shear walls with length-to-thickness ratio less than about 600 which is the range most common in buildings. The main reasons for such shortcomings of the AISC seismic design provisions for steel shear walls is that it ignores the compression field in the shear walls, which can be significant in typical shear walls. The AISC method also is not capable of incorporating stresses in the shear wall due to overturning moments. A more rational seismic design procedure for design of shear walls proposed in 2000 by the author is summarized in the paper. The design method, based on procedures used for design of steel plate girders, takes into account both tension and compression stress fields and is applicable to all values of length-to-thickness ratios of steel shear walls. The method is also capable of including the effect of overturning moments and any normal forces that might act on the steel shear wall.
Astaneh-Asl, Abolhassan
Experimental study on the adiabatic shear bands
International Nuclear Information System (INIS)
Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test
Numerical analysis of cross shear plate rolling
DEFF Research Database (Denmark)
The rolling process is widely applied for industrial production of metal plates. In conventional plate rolling the two work rolls are rotating at the same peripheral speed. By introducing a specific difference in the speed of the two work rolls, cross shear rolling is introduced forming a central shear zone between the forward and backward slip zones in the deformation zone thus lowering the rolling load. A numerical analysis of the cross shear rolling process is carried out based on the slab method adopting Wanheim and Bay's general friction model. The pressure distribution along the contact are in the roll gap, the position and the size of the shear zone and the rolling load are calculated. Experimental results are presented verifying the calculations. The numerical analysis facilitates a better understanding of the mechanics in cross shear plate rolling.
Zhang, Wenqi; Bay, Niels
Interface Roughness Parameters and Shear Strength
Directory of Open Access Journals (Sweden)
Full Text Available The interlayer bond strength between binder and wearing course and several possible treatments of enhancing the contact surface roughness and the interlocking are investigated. For this purpose, conventional methods, such as shear tests, but also laser image acquisition of the binder upper surface have been used. The mechanical outcomes of a shear test device and the binder surface roughness parameters, have been compared looking for a relation between the shear performance and the surface characteristics. The comparison between the roughness average and the root mean square of the profile heights with the maximum shear stress shows the achievement of the same strength level for treatments with similar roughness parameters, as proved by the statistical analysis. Furthermore, the comparison between the roughness parameter kurtosis and the maximum height of the profile with the slope of the response curve before the peak and residual shear stress, demonstrates a better locking for more high peaks.
Antonio D'Andrea
Determining Shear Stress Distribution in a Laminate
A "simplified shear solution" method approximates the through-thickness shear stress distribution within a composite laminate based on an extension of laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather, it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply-level stresses can be efficiently determined from global load resultants at a given location in a structure and used to evaluate the margin of safety on a ply-by-ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. The method has been incorporated within the HyperSizer commercial structural sizing software to improve its predictive capability for designing composite structures. The HyperSizer structural sizing software is used extensively by NASA to design composite structures. In the case of through-thickness shear loading on panels, HyperSizer previously included a basic, industry-standard, method for approximating the resulting shear stress distribution in sandwich panels. However, no such method was employed for solid laminate panels. The purpose of the innovation is to provide an approximation of the through-thickness shear stresses in a solid laminate given the through-thickness shear loads (Qx and Qy) on the panel. The method was needed for implementation within the HyperSizer structural sizing software so that the approximated ply-level shear stresses could be utilized in a failure theory to assess the adequacy of a panel design. The simplified shear solution method was developed based on extending and generalizing bi-material beam theory to plate-like structures. It is assumed that the through-thickness shear stresses arise due to local bending of the laminate induced by the through-thickness shear load, and by imposing equilibrium both vertically and horizontally, the through-thickness shear stress distribution can be calculated. The resulting shear stresses integrate to the applied shear load, are continuous at the ply interfaces, and are zero at the laminate-free surfaces. If both Qx and Qy shear loads are present, it is assumed that they act independently and that their effects can be superposed. The calculated shear stresses can be rotated within each ply to the principal material coordinates for use in a ply-level failure criterion. The novelty of the simplified shear solution method is its simplicity and the fact that it does not require solution of a particular boundary value problem. The advantages of the innovation are that an approximation of the though-thickness shear stress distribution can be quickly determined for any solid laminate or solid laminate region within a stiffened panel.
Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.
Boundary Shear Stress around Bridge Piers
Directory of Open Access Journals (Sweden)
Full Text Available This research presents the measurement of boundary shear stress around the base of some elliptical shaped bridge piers using Preston tube technique. The uniform flow was established and a series of measurements having different discharges and channel bed slopes were undertaken. General results are established and then the effects of flow separation on the hydraulic theory are assessed. The Analysis of results shows that behind the bridge piers (horseshoe area; the amount of boundary shear stress reduces dramatically. The figure for the rate of boundary shear stress of nose to end is about ?r = ?n/?e = 3.6. It has a remarkable reduction even in steep slopes. The bed shear stress was found to intensify near the nose of the piers. The distribution of boundary shear stress in both mild and steep channel bed slopes along spanwise direction is presented that may give a valuable perspective of the flow action around piers.
Mirali Mohammadi
Colloidal gels under shear: Strain rate effects
Attractive colloidal particles are trapped in metastable states such as colloidal gels at high attraction strengths and attractive glasses and high volume fractions. Under shear such states flow via a two step yielding process that relates to bond and cluster or cage breaking. We discuss the way the structural properties and related stress response are affected by the shear rate. At low rates colloidal gels yield during start-up shear essentially in a single step, exhibiting a single stress overshoot due to creation of compact flowing clusters. With increasing shear rate a second stress overshoot, linked with further cluster breaking up to individual particles, is becoming more pronounced. We further present the age dependence of the two step yielding and wall slip effects often taking place during rheological experiments of colloidal gels. The latter is related both with the shear rate dependent gel structure as well as the time evolution of the near wall structure.
Koumakis, N.; Ballesta, P.; Besseling, R.; Poon, W. C. K.; Brady, J. F.; Petekidis, G.
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: English Abstract in portuguese Neste trabalho, foram estudados os efeitos de diferentes tempos de matura��o post-mortem sobre os valores de ruptura tecidual (cisalhamento) e avalia��o sensorial de fil�s de peito de frango. O processo de matura��o foi realizado pela manuten��o das carca�as em caixas fechadas de pl�stico e armazena [...] das a 3�1 oC. Grupos de 5 carca�as foram classificados de acordo com o per�odo de armazenagem na c�mara fria como 0 (controle), 2, 4, 8, 12 e 24 horas. Os valores de pH das carca�as durante o per�odo do rigor post-mortem decresceram de 6,4 para 5,9, enquanto que, durante o subseq�ente per�odo de matura��o, os valores voltaram a crescer, atingindo um pH de 6,2 ap�s 12 horas, provavelmente como resultado da prote�lise. Os valores de cisalhamento de Warner-Bratzler decresceram inversamente ao tempo de matura��o, de acordo com uma rea��o cin�tica de primeira ordem, apresentando um decl�nio mais acentuado nos valores de cisalhamento nas primeiras duas horas de matura��o, ap�s o qual o desempenho tendo sido similar para todos os grupos, atingindo valores inferiores a 1kgf em 4 horas ou mais, com a matura��o completa sendo atingida em 8 horas. As amostras com per�odos maiores de matura��o (8, 12 e 24 horas) foram preferidas na an�lise sensorial, sem diferen�as significativas entre elas. Abstract in english In this work, analysis of chicken breast fillets was performed for shear values and sensory evaluation after different times of aging. Aging process was carried out by holding carcasses in covered plastic boxes, in a cold room, at 3 +/- 1�C; groups of 5 carcasses were stored and classified according [...] to the period of storage in cold room as 0 (control), 2, 4, 8, 12 and 24 hours. The variation in pH of chicken carcasses during rigor decreased from 6.4 to 5.9. However, during the process of aging, the pH values increased up to 6.2 in the first 12h, probably as the result of proteolysis. The Warner-Bratzler shear values decreased as aging time increases, resulting in a first order kinetic. The carcasses presented a more accentuated decline in shear values in the first two hours of aging. After this period, the curve had a similar performance, achieving values of less than 1 kgf in 4 hours or more, with complete aging being accomplished at 8 hours. The samples with higher period of aging (8, 12 and 24 hours) were preferred in sensorial analysis, without significant differences among them.
Helena Caminha, Santos; Adriano, Brandelli; Marco Ant�nio Z�chia, Ayub.
Transient dynamics in dense colloidal suspensions under shear: shear rate dependence
International Nuclear Information System (INIS)
A combination of confocal microscopy and rheology experiments, Brownian dynamics (BD) and molecular dynamics (MD) simulations and mode coupling theory (MCT) have been applied in order to investigate the effect of shear rate on the transient dynamics and stress-strain relations in supercooled and glassy systems under shear. Immediately after shear is switched on, the microscopic dynamics display super-diffusion and the macroscopic rheology a stress overshoot, which become more pronounced with increasing shear rate. MCT relates both to negative sections of the generalized shear modulus, which grow with increasing shear rate. When the inverse shear rate becomes much smaller than the structural relaxation time of the quiescent system, relaxation through Brownian motion becomes less important. In this regime, larger stresses are accumulated before the system yields and the transition from localization to flow occurs earlier and more abruptly.
Snell's Law for Shear Zone Refraction in Granular Materials
We present experiments on slow shear flow in a split-bottom linear shear cell, filled with layered granular materials. Shearing through two different materials separated by a flat material boundary is shown to give narrow shear zones, which refract at the material boundary in accordance with Snell's law in optics. The shear zone is the one that minimizes the dissipation rate upon shearing, i.e.a manifestation of the principle of least dissipation. We have prepared the materi...
Knudsen, H. A.; Bergli, J.
Superposition rheology of shear-banding wormlike micelles
Wormlike micelle solutions are submitted to small-amplitude oscillatory shear superimposed to steady shear in the shear banding regime. By imposing a shear oscillation, the interface between high- and low-shear regions oscillates in time. A two-fluid semi-phenomenological model is proposed for superposition rheology in the shear banding regime, which allows us to extract a characteristic velocity for the interface dynamics from experiments involving only a standard rheometer...
Ballesta, P.; Lettinga, M. P.; Manneville, S.
Shear Thickening in a Solution Undergoing Inverse Melting
Abstract Rheological measurements on a solution undergoing inverse melting are presented as a function of temperature and concentration. This solution under shear exhibits the phenomenon of shear thickening, an increase of apparent viscosity with increase in shear rate . In particular a shear thickening transition happens at a critical shear rate which increases with increasing concentration. It defines two different regimes: at low shear rates the fluid shows Newtonian behavi...
Angelini, Roberta; Salvi, Giovanni; Ruocco, Giancarlo
Generalized shear of a soft rectangular block
The problem of the simple shear of a block has been treated in terms of a shear displacement, applied uniformly in a lateral direction and assumed to be a linear function of the height above the base. In this paper, simple shear is generalized: the shear displacement is neither uniform in the lateral direction nor necessarily a linear function of the height. Using second-order isotropic elasticity, the analytical solutions show that the shear displacements are characterized by the product of sine and hyperbolic sine functions of the height and depth variables, respectively. The height dependence of the shear displacement is predicted to be a combination of linear and sinusoidal functions, and is verified against the test data of agar-gelatin cuboidal blocks. If the gravity effect is incorporated, a quadratic dependence on height is additionally predicted. The calculation of stresses reveals the presence of not only negative normal stresses but also sinusoidally varying shear stresses on the lateral planes tending to distort the block about the height direction. These results can be of great importance in tissue/cell mechanics.
Wang, Dong; Wu, M. S.
Directory of Open Access Journals (Sweden)
Full Text Available Through laboratory research performed over the past ten years, many of the critical links between fracture characteristics and hydromechanical and mechanical behaviour have been made for individual fractures. One of the remaining challenges at the laboratory scale is to directly link fracture morphology of shear behaviour with changes in stress and shear direction. A series of laboratory experiments were performed on cement mortar replicas of a granite sample with a natural fracture perpendicular to the axis of the core. Results show that there is a strong relationship between the fracture's geometry and its mechanical behaviour under shear stress and the resulting damage. Image analysis, geostatistical, stereological and directional data techniques are applied in combination to experimental data. The results highlight the role of geometric characteristics of the fracture surfaces (surface roughness, size, shape, locations and orientations of asperities to be damaged in shear behaviour. A notable improvement in shear understanding is that shear behaviour is controlled by the apparent dip in the shear direction of elementary facets forming the fracture.
Philippe Lopez
Convectively driven shear and decreased heat flux
We report on direct numerical simulations of two-dimensional, horizontally periodic Rayleigh-B\\'enard convection, focusing on its ability to drive large-scale horizontal flow that is vertically sheared. For the Prandtl numbers ($Pr$) between 1 and 10 simulated here, this large-scale shear can be induced by raising the Rayleigh number ($Ra$) sufficiently, and we explore the resulting convection for $Ra$ up to $10^{10}$. When present in our simulations, the sheared mean flow accounts for a large fraction of the total kinetic energy, and this fraction tends towards unity as $Ra\\to\\infty$. The shear helps disperse convective structures, and it reduces vertical heat flux; in parameter regimes where one state with large-scale shear and one without are both stable, the Nusselt number of the state with shear is smaller and grows more slowly with $Ra$. When the large-scale shear is present with $Pr\\lesssim2$, the convection undergoes strong global oscillations on long timescales, and heat transport occurs in bursts. N...
Goluskin, David; Flierl, Glenn R; Spiegel, Edward A
Viscoplasticity has been considered to be a dominant element in causing the nucleation of shear instability leading to lithospheric weakening. Here, we propose that a simple contrast in shear moduli may be sufficient for explaining the fast timescale asymmetric shear instability in a bimaterial setting. Not much attention has been paid to heterogeneous elasticity in geodynamical modelling because it is dominant only for short timescales. Up to now, no studies have been made on asymmetric shear instability induced by elastic modulus contrast. Thermal-mechanical numerical simulations based on high-resolution (from 0.4 km � 0.4 km to 0.2 km � 0.4 km meshes) finite-element methods were performed to understand the effects of shear modulus contrast on inducing asymmetric instabilities. Strain-rate and stress-dependent rheology are used with a wide range of activation energy 0-850 kJ mol-1 for all models. Numerical results with enough shear modulus contrast show asymmetric shear instability, which is generated around the interface and then propagates across the interface. Two parts of the lithosphere with different shear moduli (stiff for higher and soft for lower shear modulus lithospheres), which are simply connected to each other without a pre-defined weak zone, were compressed at a constant rate of 2 cm yr-1. Having different shear modulus is justified by chemical heterogeneity of geological minerals and their pressure-temperature dependence. To explore the dynamical effects generated by the contrast in the elastic modulus, the shear modulus of the soft lithosphere is fixed at 32 GPa, whereas that of stiff lithosphere is increased systematically from 32 up to 640 GPa. We also examined the role of activation energy (0-850 kJ mol-1) on the geometrical pattern and the initiation time of asymmetric shear localization. The shear modulus contrast has to be close to two for triggering asymmetric shear instability and is found to be by far a more important controlling factor in causing shear instability than activation energy of the creep law. The instability develops rapidly between 250 000 and 500 000 yr after deformation begins, and thermal weakening in the shear zone is greater, when a stronger shear modulus contrast is prescribed. Our work suggests that initiation of lithosphere-scale asymmetric instability would be faster than previous considerations. Our finding stresses that naturally occurring shear modulus contrast has also important impact on many geological problems related to bimaterial instability.
So, Byung-Dal; Yuen, David A.; Regenauer-Lieb, Klaus; Lee, Sang-Mook
Shear Reinforcements in the Reinforced Concrete Beams
Directory of Open Access Journals (Sweden)
Full Text Available - This study focuses on the use of different types of shear reinforcement in the reinforced concrete beams. Four different types of shear reinforcement are investigated; traditional stirrups, welded swimmer bars, bolted swimmer bars, and u-link bolted swimmer bars. Beam shear strength as well as beam deflection are the main two factors considered in this study. Shear failure in reinforced concrete beams is one of the most undesirable modes of failure due to its rapid progression. This sudden type of failure made it necessary to explore more effective ways to design these beams for shear. The reinforced concrete beams show different behavior at the failure stage in shear compare to the bending, which is considered to be unsafe mode of failure. The diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded or bolted to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Several reinforced concrete beams were carefully prepared and tested in the lab. The results of these tests will be presented and discussed. The deflection of each beam is also measured at incrementally increased applied load.
Moayyad M. Al-Nasra
Shear Excitation of Confined Colloidal Suspensions
We show that geometric confinement dramatically affects the shear-induced configurations of dense mono-disperse colloidal suspensions; a new structure emerges, where layers of particles buckle to stack in a more efficient packing. The volume fraction in the shear zone is controlled by a balance between the viscous stresses and the osmotic pressure of a contacting reservoir of unsheared particles. We present a model that accounts for our observations and helps elucidate the complex interplay between particle packing and shear stress for confined suspensions.
Cohen, I; Weitz, D A; Cohen, Itai; Mason, Thomas G.; Weitz, David A.
Topological defects in gravitational lensing shear fields
International Nuclear Information System (INIS)
Shear fields due to weak gravitational lensing have characteristic coherent patterns. We describe the topological defects in shear fields in terms of the curvature of the surface described by the lensing potential. A simple interpretation of the characteristic defects is given in terms of the the umbilical points of the potential surface produced by ellipsoidal halos. We show simulated lensing shear maps and point out the typical defect configurations. Finally, we show how statistical properties such as the abundance of defects can be expressed in terms of the correlation function of the lensing potential
Shear viscosity of liquid mixtures: Mass dependence
International Nuclear Information System (INIS)
Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model. (author)
Method for shearing spent nuclear fuel assemblies
International Nuclear Information System (INIS)
A method is disclosed for shearing spent nuclear fuel assemblies of the type wherein a plurality of long metal tubes packed with ceramic fuel are supported in a spaced apart relationship within an outer metal shell or shroud which provides structural support to the assembly. Spent nuclear fuel assemblies are first compacted in a stepwise manner between specially designed gag-compactors and then sheared into short segments amenable to chemical processing by shear blades contoured to mate with the compacted surface of the fuel assembly
Shear effects on crystalline structures of poly(L-lactide)
DEFF Research Database (Denmark)
The shearing effects of sheared polymer melts on their finally formed crystalline structures of poly(L-lactide) (PLLA) were investigated by means of small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). The results of WAXD prove that shear has no effects on the crystal structure of PLLA. The SAXS results demonstrate that both of the long period and the thickness of crystalline lamellae increase with rising shear rates when vertical to the shear direction, but remains constant when being parallel to the shear direction. The structural changes for samples prepared with different shear temperature or under the same shear strain but different shear rate were investigated. The mesophase of polymer melts and shearing effects on their pre-ordered phase turned out to be the key factor affecting the crystal structure of PLLA under different shearing conditions.
Xiao, Peitao; Li, Hongfei
Development of short stroke shearing technology for FBR fuel pin
International Nuclear Information System (INIS)
The short stroke shearing tests with simulated fuel pin bundle were carried out in engineering scale. The shearing device was designed to handle the simulated Monju (FBR prototype reactor) type fuel pin bundle. Monju type and Commercial reactor type simulated fuel pins were used for the test. The sheared pin length and the opening ratio of sheared section were measured under several shearing conditions such as the pressure to hold pin bundle, the shearing speed and the filling-ratio of pins in the pin magazine. Both types of fuel pin were able to be sheared accurately at the length of about 10mm, and the opening ratio of sheared section was not significantly reduced. As the results, fundamental data of the short stroke shearing characteristics were obtained and that shearing method was confirmed to be promising with the reliable shearing device. (author)
Wind shear and turbulence simulation
The aviation community is increasing its reliance on flight simulators. This is true both in pilot training and in research and development. In moving research concepts through the development pipeline, there is a sequence of events which take place: analysis, ground based simulation, inflight simulation, and flight testing. Increasing fidelity as progress toward the flight testing arena is accompanied by increasing cost. The question that seems to be posed in relation to the meteorological aspects of flight simulation is, How much fidelity is enough and can it be quantified. As a part of the Langley Simulation Technology Program, there are three principal areas of focus, one being improved simulation of weather hazards. A close liaison with the JAWS project was established because of the Langley Simulation Technology interests regarding reliable simulation of severe convective weather phenomena and their impact on aviation systems. Simulation offers the only feasible approach for examining the utility of new technology and new procedures for coping with severe convective weather phenomena such as wind shear. These simulation concepts are discussed in detail.
Bowles, Roland L.
The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.
Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.; Collier, Craig S.
The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate based on laminated beam theory. The method does not consider the solution of a particular boundary value problem, rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.
Bednarcyk, Brett A.; Aboudi, Jacob; Yarrington, Phillip W.
Effects of transverse shearing flexibility on the postbuckling of plates loaded by inplane shear
This paper presents buckling and postbuckling results for plates loaded by inplane shear. The buckling results have been plotted to show the effects of thickness on the stress coefficient for aluminum plates. Results are given for various length-to-width ratios. Postbuckling results for thin plates with transverse shearing flexibility are compared to results from classical theory. The problems considered are the postbuckling response of plates in shear made of aluminum and of a + or - 45 deg graphite-epoxy laminate. Thus the materials are isotropic and orthotropic, respectively. The plates are considered to be long with side edges simply supported, with various inplane edge conditions, and the plates are subject to a constant shearing displacement along the side edges. Characteristic curves presenting the average shear stress resultant as a function of the applied displacement are given. These curves indicate that change in inplane edge conditions influence plate postbuckling stiffness and that transverse shearing is important in some cases.
Stein, Manuel
The present experiment was carried out to evaluate the effects of electrical stimulation (ES) immediately prescalding (PS), ES immediately postdefeathering (PD), or PS combined with PD (PSPD) on the quality of early deboned (2 h) broiler breast muscles, pectoralis major (fillets), and pectoralis minor (tenders). No stimulation, early-deboned (2 h), and 24-h deboned (24 h) fillets were used for the comparison. The 42-d-old broiler carcasses were electrically stimulated with pulsed current at 200 V for 30 s over a 90-s time interval (total of 1 min over 180 s for PSPD), and breast meat was deboned 2 h postmortem. Quality indicators evaluated were CIE L*, a*, and b* color and pH of the raw fillets and cook yields and Warner-Bratzler (WB) shear force of the fillets and tenders. There were no differences in raw fillet color, pH, and cook yields of both the fillets and tenders between the 3 ES treatments. Effects of different ES treatments on meat WB shear force values varied with breast muscles. For the fillets, the average WB shear force values of both the PS and PSPD samples, which were not different from each other, were significantly lower than those of the PD samples. For the tenders, there were no differences in the average shear force values between the 3 ES treatments. Regardless of ES treatment and breast muscle, early deboned broiler breast meat from ES carcasses required significantly less force to shear than the 2-h control. These results indicate that ES can tenderize early deboned poultry breast muscles; however, the effectiveness of ES tenderization varies with ES treatments for the fillets. The PS treatment is more effective in reducing fillet shear values than PD, and there is no further reduction in shear values with PSPD compared with the PS treatment. PMID:20634531
Zhuang, H; Savage, E M; Lawrence, K
Low-rise shear wall failure modes
International Nuclear Information System (INIS)
A summary of the data that are available concerning the structural response of low-rise shear walls is presented. These data will be used to address two failure modes associated with shear wall structures. First, data concerning the seismic capacity of the shear walls are examined with emphasis on excessive deformations that can cause equipment failure, Second, the data concerning the dynamic properties of shear walls (stiffness and damping) that are necessary for computing the seismic inputs to attached equipment are summarized. This case addresses the failure of equipment when the structure remains functional. The information discussed is used for fragility analysis associated with seismic probabilistic risk analysis (PRA) and for seismic margin assessment
Motifs of Networks from Shear Fractures
Rupture's sequence of shear fractures using a transformation form of aperture patterns to complex networks was studied, and then sub-graphs abundance within the corresponding networks was analyzed. Furthermore, to distinguish the role of contact zones and flow of energy in ruptures tips, the contact strings were constructed. The contacts 'strings were connected by using constrained geometrical distance and amount of net-contact area per string, yields directed networks. For shear rupture, we observed approximately similar trend in sub-graphs distribution which were the results of parallel and transversal aperture profiles (a super-family phenomena). We confirmed the same inherent dynamic of sheared fracture yields the nearly same family of sub-graphs. For directed networks, our results confirmed the role of the feed-forward sub-graphs in flow of energy through the development of shear rupture.
Ghaffari, H O
Shear-flow-enhanced barrier crossing
We consider a single Brownian particle confined in a double well potential (DWP) and investigate its response to a linear shear flow by means of the probability density and current determined via numerical solution of the Fokker-Planck equation. Besides a shear-dependent distortion of the probability distribution, we find that the associated current crossing the potential barrier exhibits a convex dependency on the shear rate when the DWP's minima are far apart. With decreasing distance this functional dependency changes from a convex to concave characteristics accompanied with an increase of the probability current crossing the DWP's barrier. Through the difference map of the particle density distribution it is possible to extract the shear-flow-induced contribution to the particle density driving the barrier-crossing current. This may open the possibility to design specific flow profiles to optimize flow-induced activated transport of nanoparticles.
Kienle, Diego; Bammert, Jochen; Zimmermann, Walter
Shear History Effect on a Phase Transition under Shear of a Salt Free CTAB Solution
We present the results of rheological measurements showing the evolution of shifting Nematic/Isotropic temperature transition under shear. Nematic phase is induced from shear and disappears when temperature rises (always under shear). Successive temperature sweeps on the same solution have a significative effect on the transition temperature showing thus a kind of memory effect. The micellar system studied here is cationic (CTAB) without salt added at concentration of 0.6�M/l which is near b...
Cappelaere, E.; Cressely, R.
Driven torsion pendulum for measuring the complex shear modulus in a steady shear flow
To investigate the viscoelastic behavior of fluid dispersions under steady shear flow conditions, an apparatus for parallel superimposed oscillations has been constructed which consists of a rotating cup containing the liquid under investigation in which a torsional pendulum is immersed. By measuring the resonance frequency and bandwidth of the resonator in both liquid and in air, the frequency and steady-shear-rate-dependent complex shear modulus can be obtained. By exchange of the resonator...
Ende, D. Den; Mellema, J.; Blom, C.
Schematic Mode Coupling Theories for Shear Thinning, Shear Thickening, and Jamming
Mode coupling theory (MCT) appears to explain several, though not all, aspects of the glass transition in colloids (particularly when short-range attractions are present). Developments of MCT, from rational foundations in statistical mechanics, account qualitatively for nonlinear flow behaviour such as the yield stress of a hard-sphere colloidal glass. Such theories so far only predict shear thinning behaviour, whereas in real colloids both shear thinning and shear thickenin...
Cates, Michael E.; Holmes, Colin B.; Fuchs, Matthias; Henrich, Oliver
Shear loading on structures has been recognized as one of the most relevant actions determining structural safety since the 19th century. In the case of reinforced concrete structures, despite the great efforts that have been made through experimental and theoretical research over many years, the nature of the shear failure process of a reinforced concrete beam without shear reinforcement has always, for a substantial part, remained a riddle. The present research work takes a new look at this...
Yang, Y.
Elastic capsules in shear flow: Analytical solutions for constant and time-dependent shear rates
We investigate the dynamics of microcapsules in linear shear flow within a reduced model with two degrees of freedom. In previous work for steady shear flow, the dynamic phases of this model, i.e. swinging, tumbling and intermittent behaviour, have been identified using numerical methods. In this paper, we integrate the equations of motion in the quasi-spherical limit analytically for time-constant and time-dependent shear flow using matched asymptotic expansions. Using this...
Kessler, Steffen; Finken, Reimar; Seifert, Udo
Phenomenology and physical origin of shear-localization and shear-banding in complex fluids
We review and compare the phenomenological aspects and physical origin of shear-localization and shear-banding in various material types, namely emulsions, suspensions, colloids, granular materials and micellar systems. It appears that shear-banding, which must be distinguished from the simple effect of coexisting static-flowing regions in yield stress fluids, occurs in the form of a progressive evolution of the local viscosity towards two significantly different values in t...
Ovarlez, Guillaume; Rodts, Ste?phane; Chateau, Xavier; Coussot, Philippe
Amorphous silicon under mechanical shear deformations: shear velocity and temperature effects
Mechanical shear deformations lead, in some cases, to effects similar to those resulting from ion irradiation. Here we characterize the effects of shear velocity and temperature on amorphous silicon (\\aSi) modelled using classical molecular dynamics simulations based on the empirical Environment Dependent Inter-atomic Potential (EDIP). With increasing shear velocity at low temperature, we find a systematic increase in the internal strain leading to the rapid appearance of st...
Kerrache, Ali; Mousseau, Normand; Lewis, Laurent J.
Athermal analogue of sheared colloidal suspensions
The rheology of Brownian suspensions of hard spheres is investigated numerically beyond the low shear rate Newtonian regime. We test the athermal analogue of these suspensions, built by means of an effective logarithmic repulsive potential originating from vibrational entropic forces. We show that both systems present the same rheology without adjustable parameters. Moreover, all rheological responses display similar Herschel-Bulkley relations once the shear stress and the s...
Trulsson, M.; Bouzid, M.; Kurchan, J.; Clement, E.; Claudin, P.; Andreotti, B.
Rheology of Dense Sheared Granular Liquids
The rheology of dense sheared granular liquids is investigated based on the mode-coupling theory (MCT). This extended MCT includes correlations for the density-current mode as well as the density-density correlation mode, and a self-consistent coupling equation for the energy balance condition. The extended MCT exhibits disappearance of the two-step relaxation of the density-density correlation function, and also successfully reproduces the density dependence of the shear vi...
Suzuki, Koshiro; Hayakawa, Hisao
Shear dispersion in dense granular flows
We formulate and solve a model problem of dispersion of dense granular materials in rapid shear flow down an incline. The effective dispersivity of the depth-averaged concentration of the dispersing powder is shown to vary as the P\\'eclet number squared, as in classical Taylor--Aris dispersion of molecular solutes. An extensions to generic shear profiles is presented, and possible applications to industrial and geological granular flows are noted.
Christov, Ivan C
Adiabatic shearing study by dynamic compression
International Nuclear Information System (INIS)
The adiabatic shearing study was carried out by dynamic compression tests made on a Hopkinson's rod. The deformation rate is around 2x103 s-1; the materials studied are in martensitic steel and a titanium alloy, at ambient temperature and up to 5000C. Microscopic observations show how the break appears, associated with the development of adiabatic shearing bands. The mechanical results are discussed and compared against the theoretical approaches
Shear strength properties of wet granular materials
We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume ...
Richefeu, Vincent; El Youssoufi, Moulay Sai?d; Radjai, Farhang
Shear-induced fragmentation of Laponite suspensions
Simultaneous rheological and velocity profile measurements are performed in a smooth Couette geometry on Laponite suspensions seeded with glass microspheres and undergoing the shear-induced solid-to-fluid (or yielding) transition. Under these slippery boundary conditions, a rich temporal behaviour is uncovered, in which shear localization is observed at short times, that rapidly gives way to a highly heterogeneous flow characterized by intermittent switching from plug-like f...
Gibaud, Thomas; Barentin, Catherine; Taberlet, Nicolas; Manneville, Se?bastien
Supertransient magnetohydrodynamic turbulence in Keplerian shear flows
A subcritical transition to turbulence in magnetized Keplerian shear flows is investigated using a statistical approach. Three-dimensional numerical simulations of the shearing box equations with zero net magnetic flux are employed to determine the transition from decaying to sustained turbulence as a function of the magnetic Reynolds number Rm. The results reveal no clear transition to sustained turbulence as the average lifetime of the transients grows as an exponential function of Rm, in accordance with a type-II supertransient law.
Rempel, Erico L; Proctor, Michael R E
Particle acceleration in astrophysical shear flows
We consider the acceleration of particles due to a velocity shear in relativistic astrophysical flows. The basic physical picture and the formation of power law momentum spectra is discussed for a non-relativistic velocity field using a microscopic approach. We identify possible sites for shear acceleration in relativistic astrophysical jets and analyze their associated acceleration timescales. It is shown in particular that for a mean scattering time $\\tau$ scaling with the...
Rieger, Frank M.; Duffy, Peter
Shear viscosity of degenerate electron matter
We calculate the partial electron shear viscosity $\\eta_{ee}$ limited by electron-electron collisions in a strongly degenerate electron gas taking into account the Landau damping of transverse plasmons. The Landau damping strongly suppresses $\\eta_{ee}$ in the domain of ultrarelativistic degenerate electrons and modifies its %asymptotic temperature behavior. The efficiency of the electron shear viscosity in the cores of white dwarfs and envelopes of neutron stars is analyzed.
Shternin, P. S.
Development of dough under shear flow
Dough mixing involves a combination of different deformation flows, e.g. shear and elongation.The complicated nature of the mixing makes it difficult to understand dough processing on a mechanistic level. Apart from that, a quantitative relation between the type of deformation in the mixing and resulting dough properties is still lacking. This indicates the importance of unraveling the complex process into most relevant deformation patterns such as simple shear and ext...
Peighambardoust, S. H.
Crawling waves, which are interfering shear wave patterns, can be generated in liver tissue over a range of frequencies. Some important biomechanical properties of the liver can be determined by imaging the crawling waves using Doppler techniques and analyzing the patterns. We report that the dispersion of shear wave velocity and attenuation, that is, the frequency dependence of these parameters, are strongly correlated with the degree of steatosis in a mouse liver model, ex vivo. The results...
Barry, Christopher T.; Mills, Bradley; Hah, Zaegyoo; Mooney, Robert A.; Ryan, Charlotte K.; Rubens, Deborah J.; Parker, Kevin J.
Shear Modulus Measurements on Classical Monolayer Systems
The responses to shear of monomolecular films of stearyl alcohol (C18H37OH) and nonadecanoic acid (C18H37COOH) spread on water were studied as a function of density. A static shear modulus appears at a phase transition, previously assigned as the liquid-solid transition. The value of the modulus, however, is several orders of magnitude lower than the Kosterlitz-Thouless prediction.
Abraham, B. M.; Miyano, K.; Xu, S. Q.; Ketterson, J. B.
Shear modulus measurements on classical monolayer systems
International Nuclear Information System (INIS)
The responses to shear of monomolecular films of stearyl alcohol (C18H37OH) and nonadecanoic acid (C18H37COOH) spread on water were studied as a function of density. A static shear modulus appears at a phase transition, previously assigned as the liquid-solid transition. The value of the modulus, however, is several orders of magnitude lower than the Kosterlitz-Thouless prediction
Shear modulus measurements on classical monolayer systems
Energy Technology Data Exchange (ETDEWEB)
The responses to shear of monomolecular films of stearyl alcohol (C/sub 18/H/sub 37/OH) and nonadecanoic acid (C/sub 18/H/sub 37/COOH) spread on water were studied as a function of density. A static shear modulus appears at a phase transition, previously assigned as the liquid-solid transition. The value of the modulus, however, is several orders of magnitude lower than the Kosterlitz-Thouless prediction.
Abraham, B.M.; Miyano, K.; Xu, S.Q.; Ketterson, J.B.
regulation of endothelial phenotype by shear stress
The endothelial monolayer as the innermost lining of blood vessels is directly exposed to the flowing blood. Besides several other biochemical and mechanical factors, wall shear stress modulates the endothelial function. The concrete pattern of shear stress depends on the localization within the vascular network: flow profiles in predilection sites for atherosclerosis differ from those in vessel segments protected from atherosclerosis; sprouting capillaries instead are not perfused at all. Th...
Vorderwu?lbecke, Bernd J.
Critical packing in granular shear bands
Relying on three-dimensional distinct element simulations of axisymmetric triaxial shear tests with spherical grains we demonstrate the existence of a critical volume fraction inside shear bands. This critical state is found to be independent of the initial conditions but dependent on the microscopic friction coefficient. We show that at high friction coefficient the critical packing density converges to a value which can be identified with a \\emph{dynamic random loose packing} limit.
Fazekas, S; Kert�sz, J
The kinetics of hemoglobin S gelation are critical in sickle disease because microvascular obstruction can be avoided if red blood cells pass these vessels during the delay time, before polymerization and gelation occur in sufficient degree to rigidify the cells. Kinetics, including the delay time and the closely related exponential progress rate, are highly sensitive to hemoglobin concentration and degree of deoxygenation. Kinetics are also greatly accelerated by shear, an effect that may contribute to pathogenesis, since red blood cells deform and can undergo shear in vivo. Here we examine the joint dependence of kinetics on shear and hemoglobin concentration. As shear rate increases, the concentration dependence of the exponential progress rate decreases. The large decrease in concentration dependence supports the conclusion that acceleration of gelation by shear is due to breakage and not to enhancement of heterogeneous nucleation. Under shear, new fibers are created by breakage of existing ones, as well as by heterogeneous nucleation. At high shear, the rate of new fiber creation by breakage is very great and dominates that by heterogeneous nucleation. Therefore, if breakage depended only on shear rate and were independent of the concentration of hemoglobin in solution, the concentration dependence of kinetics should vanish. Although it decreases, it does not disappear. The concentration dependence that remains at high shear arises from (1) the direct contribution of fiber growth rate to the exponential progress rate, (2) the dependence of breakage rate on fiber growth rate, and (3) the dependence of solution viscosity on hemoglobin concentration. PMID:8241514
Samuel, R E; Guzman, A E; Briehl, R W
Fan-structure shear rupture mechanism as a source of shear rupture rockbursts
Scientific Electronic Library Online (English)
Full Text Available SciELO South Africa | Language: English Abstract in english This paper proposes the further development of a recently identified shear rupture mechanism (fan mechanism) that elucidates a paradoxical feature of hard rocks - the possibility of shear rupture propagation through a highly confined intact rock mass at shear stresses that can be significantly less [...] than frictional strength. In the fan mechanism, failure is associated with consecutive creation of small slabs (known as 'domino blocks') from the intact rock in the rupture tip, driven by a fan-shaped domino structure representing the rupture head. The fan head combines such unique features as extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Consequently, the failure process caused by the mechanism is inevitably spontaneous and violent. Physical and mathematical models explain unique and paradoxical features of the mechanism, which can be generated in primary ruptures and segmented faults. The fan mechanism provides a novel point of view for understanding the nature of spontaneous failure processes, including shear rupture rockbursts. The process explains, in particular, features of shear rupture rockbursts such as activation at great depths, generation of new shear ruptures in intact rock mass, nucleation of hypocentres at significant distances from the excavation, shear rupture development at low shear stresses, and abnormal rupture violence.
B.G., Tarasov.
Influence of Shear on Rotation Capacity of Reinforced Concrete Members Without Shear Reinforcement
The influence of shear on the rotation capacity of one-way slabs without shear reinforcement is investigated in this paper by means of an experimental study. The experimental program consisted of 11 slab strips 8400 mm (331 in.) long and 450 mm (17.7 in.) thick with a flexural reinforcement ratio of 0.79%. The rotation capacity was investigated for various values of the shear span and for two types of flexural reinforcement (hot-rolled and cold-worked bars). The specimens developed shear fail...
Vaz Rodrigues, Rui; Muttoni, Aurelio; Ferna?ndez Ruiz, Miguel
Shear strength of non-shear reinforced concrete elements : Part 2. T- beams
DEFF Research Database (Denmark)
The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange. The position of the crack in which sliding takes place is determined by the crack sliding model developed by Jin-Ping Zhang. The theoretical calculations are compared with test results reported in the literature. A good agreement has been found.A simplified method to calculate the shear capacity of T-beams is presented.
Hoang, Cao linh
The brittle-viscous-plastic evolution of shear bands in the South Armorican Shear Zone
Shear bands are microscale shear zones that obliquely crosscut an existing anisotropy such as a foliation. The resulting S-C fabrics are characterized by angles lower than 45� and the C plane parallel to shear zone boundaries. The S-C fabrics typically occur in granitoids deformed at greenschist facies conditions in the vicinity of major shear zones. Despite their long recognition, mechanical reasons for localization of deformation into shear bands and their evolution is still poorly understood. In this work we focus on microscale characterization of the shear bands in the South Armorican Shear Zone, where the S-C fabrics were first recognized by Berth� et al. (1979). The initiation of shear bands in the right-lateral South Armorican Shear Zone is associated with the occurrence of microcracks crosscutting the recrystallized quartz aggregates that define the S fabric. In more advanced stages of shear band evolution, newly formed dominant K-feldspar, together with plagioclase, muscovite and chlorite occur in the microcracks, and the shear bands start to widen. K-feldspar replaces quartz by progressively bulging into the grain boundaries of recrystallized quartz grains, leading to disintegration of quartz aggregates and formation of fine-grained multiphase matrix mixture. The late stages of shear band development are marked by interconnection of fine-grained white mica into a band that crosscuts the original shear band matrix. In its extremity, the shear band widening may lead to the formation of ultramylonites. With the increasing proportion of shear band matrix from ~1% to ~12%, the angular relationship between S and C fabrics increases from ~30� to ~40�. The matrix phases within shear bands show differences in chemical composition related to distinct evolutionary stages of shear band formation. The chemical evolution is well documented in K-feldspar, where the albite component is highest in porphyroclasts within S fabric, lower in the newly formed grains within microcracks and nearly absent in matrix grains in the well developed C bands. The chemical variation between primary and secondary new-formed micas was clearly identified by the Mg-Ti-Na content. The microstructural analysis documents a progressive decrease in quartz grain size and increasing interconnectivity of K-feldspar and white mica towards more mature shear bands. The contact-frequency analysis demonstrates that the phase distribution in shear bands tends to evolve from quartz aggregate distribution via randomization to K-feldspar aggregate distribution. The boundary preferred orientation is absent in quartz-quartz contacts either inside of outside the C bands, while it changes from random to parallel to the C band for the K-feldspar and and K-feldspar-quartz boundaries. The lack of crystallographic preferred orientation of the individual phases in the mixed matrix of the C planes suggests a dominant diffusion-assisted grain boundary sliding deformation mechanism. In the later stages of shear band development, the deformation is accommodated by crystal plasticity of white mica in micaceous bands. The crystallographic and microstructural data thus indicate two important switches in deformation mechanisms, from (i) brittle to Newtonian viscous behavior in the initial stages of shear band evolution and from (ii) Newtonian viscous to power law in the later evolutionary stages. The evolution of shear bands in the South Armorican Shear Zone thus document the interplay between deformation mechanisms and chemical reactions in deformed granitoids.
Bukovsk�, Zita; Je?�bek, Petr; Morales, Luiz F. G.; Lexa, Ondrej; Milke, Ralf
Magnetized stratified rotating shear waves
We present a spectral linear analysis in terms of advected Fourier modes to describe the behavior of a fluid submitted to four constraints: shear (with rate S), rotation (with angular velocity ?), stratification, and magnetic field within the linear spectral theory or the shearing box model in astrophysics. As a consequence of the fact that the base flow must be a solution of the Euler-Boussinesq equations, only radial and/or vertical density gradients can be taken into account. Ertel's theorem no longer is valid to show the conservation of potential vorticity, in the presence of the Lorentz force, but a similar theorem can be applied to a potential magnetic induction: The scalar product of the density gradient by the magnetic field is a Lagrangian invariant for an inviscid and nondiffusive fluid. The linear system with a minimal number of solenoidal components, two for both velocity and magnetic disturbance fields, is eventually expressed as a four-component inhomogeneous linear differential system in which the buoyancy scalar is a combination of solenoidal components (variables) and the (constant) potential magnetic induction. We study the stability of such a system for both an infinite streamwise wavelength (k1=0, axisymmetric disturbances) and a finite one (k1?0, nonaxisymmetric disturbances). In the former case (k1=0), we recover and extend previous results characterizing the magnetorotational instability (MRI) for combined effects of radial and vertical magnetic fields and combined effects of radial and vertical density gradients. We derive an expression for the MRI growth rate in terms of the stratification strength, which indicates that purely radial stratification can inhibit the MRI instability, while purely vertical stratification cannot completely suppress the MRI instability. In the case of nonaxisymmetric disturbances (k1?0), we only consider the effect of vertical stratification, and we use Levinson's theorem to demonstrate the stability of the solution at infinite vertical wavelength (k3=0): There is an oscillatory behavior for ?>1+|K2/k1|, where ?=St is a dimensionless time and K2 is the radial component of the wave vector at ?=0. The model is suitable to describe instabilities leading to turbulence by the bypass mechanism that can be relevant for the analysis of magnetized stratified Keplerian disks with a purely azimuthal field. For initial isotropic conditions, the time evolution of the spectral density of total energy (kinetic + magnetic + potential) is considered. At k3=0, the vertical motion is purely oscillatory, and the sum of the vertical (kinetic + magnetic) energy plus the potential energy does not evolve with time and remains equal to its initial value. The horizontal motion can induce a rapid transient growth provided K2/k1?1. This rapid growth is due to the aperiodic velocity vortex mode that behaves like Kh/kh where kh(?)=[k12+(K2-k1?)2]1/2 and Kh=kh(0). After the leading phase (?>K2/k1?1), the horizontal magnetic energy and the horizontal kinetic energy exhibit a similar (oscillatory) behavior yielding a high level of total energy. The contribution to energies coming from the modes k1=0 and k3=0 is addressed by investigating the one-dimensional spectra for an initial Gaussian dense spectrum. For a magnetized Keplerian disk with a purely vertical field, it is found that an important contribution to magnetic and kinetic energies comes from the region near k1=0. The limit at k1=0 of the streamwise one-dimensional spectra of energies, or equivalently, the streamwise two-dimensional (2D) energy, is then computed. The comparison of the ratios of these 2D quantities with their three-dimensional counterparts provided by previous direct numerical simulations shows a quantitative agreement.
Salhi, A.; Lehner, T.; Godeferd, F.; Cambon, C.
Electroviscous effects of simple electrolytes under shear
On the basis of a hydrodynamical model analogous to that in critical fluids, we investigate the influences of shear flow upon the electrostatic contribution to the viscosity of binary electrolyte solutions in the Debye-H\\"{u}ckel approximation. Within the linear-response theory, we reproduce the classical limiting law that the excess viscosity is proportional to the square root of the concentration of the electrolyte. We also extend this result for finite shear. An analytic expression of the anisotropic structure factor of the charge density under shear is obtained, and its deformation at large shear rates is discussed. A non-Newtonian effect caused by deformations of the ionic atmosphere is also elucidated for $\\tau_D\\dot{\\gamma}>1$. This finding concludes that the maximum shear stress that the ionic atmosphere can support is proportional to $\\lambda_D^{-3}$, where $\\dot{\\gamma}$, $\\lambda_D$ and $\\tau_D=\\lambda_D^2/D$ are, respectively, the shear rate, the Debye screening length and the Debye relaxation tim...
Wada, H
Continuous failure state direct shear tests
The paper deals with a new testing procedure aimed at determining the failure envelopes for peak and residual strength in direct shear tests. In a �continuous failure state� direct shear test the specimen is maintained in a state of permanent sliding while the shear and normal stress are being steadily changed. First of all, the specimen is brought to a state of failure in the conventional manner at a chosen constant normal stress. Then under monotonously increasing shear displacement the normal stress is continuously adjusted so that a straight line is produced in the shear stress-displacement plane. Both an increase in the stresses and a decrease is possible. The proper selection of the inclination of the straight line may involve a stress path which corresponds closely to the failure envelope of the specimen. In the case of smooth joint surfaces or in the residual strength state of rough surfaces it is possible to determine exactly the failure envelope with the aid of a single test specimen. The paper also describes a newly developed shear test apparatus suitable for combination with sophisticated servo-controlled loading machines generally available in rock mechanics laboratories.
Tisa, A.; Kov�ri, K.
Strain rate test on RC shear walls
International Nuclear Information System (INIS)
The objective of these tests are to understand the dynamic effect of strain rate on the restoring force characteristics of reinforced concrete shear walls which are the major aseismatic members of reactor buildings. This report consists of the reports of dynamic material test, dynamic shear wall test and the finite element analysis of dynamic shear wall behavior. Twelve shear wall specimens were fabricated for these tests. Loading methods were monotonic horizontal loading and cyclic horizontal loading. The experimental setup is shown. Moreover, the dynamic compressive and tensile tests on mortar cylinders and the dynamic tensile test on reinforcements were performed, using strain rate as the parameter. The results are reported. As to the finite element analysis of shear wall behavior, the outline of the analysis model and the analysis of the statically loaded specimen and the dynamically loaded specimen are described. As for mortar, the compressive strength and tensile strength increased with strain rate. As for shear wall specimens, the cracking stress and ultimate strength increased with horizontal displacement rate. (K.I.)
Bacterial transport suppressed by fluid shear
Bacteria often live in dynamic fluid environments and flow can affect fundamental microbial processes such as nutrient uptake and infection. However, little is known about the consequences of the forces and torques associated with fluid flow on bacteria. Through microfluidic experiments, we show that fluid shear produces strong spatial heterogeneity in suspensions of motile bacteria, characterized by up to 70% cell depletion from low-shear regions due to `trapping� in high-shear regions. Two mathematical models and a scaling analysis accurately capture these observations, including the maximal depletion at mean shear rates of 2.5-10 s-1, and reveal that trapping by shear originates from the competition between the cell alignment with the flow and the stochasticity in the swimming orientation. We show that this shear-induced trapping directly impacts widespread bacterial behaviours, by hampering chemotaxis and promoting surface attachment. These results suggest that the hydrodynamic environment may directly affect bacterial fitness and should be carefully considered in the study of microbial processes.
Rusconi, Roberto; Guasto, Jeffrey S.; Stocker, Roman
Accurate shear measurement with faint sources
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
Zhang, Jun; Luo, Wentao; Foucaud, Sebastien
Evolution of shear zones in granular materials.
The evolution of wide shear zones or shear bands was investigated experimentally and numerically for quasistatic dry granular flows in split bottom shear cells. We compare the behavior of materials consisting of beads, irregular grains, such as sand, and elongated particles. Shearing an initially random sample, the zone width was found to significantly decrease in the first stage of the process. The characteristic shear strain associated with this decrease is about unity and it is systematically increasing with shape anisotropy, i.e., when the grain shape changes from spherical to irregular (e.g., sand) and becomes elongated (pegs). The strongly decreasing tendency of the zone width is followed by a slight increase which is more pronounced for rodlike particles than for grains with smaller shape anisotropy (beads or irregular particles). The evolution of the zone width is connected to shear-induced packing density change and for nonspherical particles it also involves grain reorientation effects. The final zone width is significantly smaller for irregular grains than for spherical beads. PMID:25314435
Szab�, Bal�zs; T�r�k, J�nos; Somfai, Ell�k; Wegner, Sandra; Stannarius, Ralf; B�se, Axel; Rose, Georg; Angenstein, Frank; B�rzs�nyi, Tam�s
Analysis of shear banding in twelve materials
The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.
Batra, R. C.; Kim, C. H.
Scaling properties of turbulence driven shear flow
International Nuclear Information System (INIS)
The characteristics and scaling properties of the turbulence driven shear flow are investigated in a cylindrical laboratory plasma device. For a given plasma pressure, the density fluctuation amplitude and radial particle flux increase with the applied magnetic field. Strong flow shear is found to coexist at high magnetic fields (>700 G) with ?10 kHz drift wave turbulence, but not at low magnetic fields (<700 G). The absolute value of the divergence of the turbulent Reynolds stress at the shear layer is shown to increase with the magnetic field as well. For a fixed magnetic field, the shear flow is found to decrease as the discharge gas pressure is increased. The density fluctuation amplitude and divergence of the turbulent Reynolds stress also decrease with the plasma pressure. For both situations the cross phase between the radial and azimuthal components of the velocity is found to be a key factor to determine variations in the turbulent Reynolds stress at different magnetic fields and discharge pressures. The results show that the generation of the shear flow is related to the development of specific frequency components of the drift wave turbulence for a variety of plasma conditions. The linear stability analysis shows that the observed variation in the turbulence and shear flow with magnetic field is also consistent with a critical gradient behavior.
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Onze provadores selecionados e treinados avaliaram a apar�ncia, aroma, sabor e textura de seis diferentes marcas de figo em calda, comercializadas no mercado brasileiro, utilizando o m�todo de An�lise Descritiva Quantitativa (ADQ) adaptado. As amostras foram testadas utilizando-se blocos incompletos [...] balanceados e os resultados estatisticamente analisados por An�lise de Vari�ncia (ANOVA) e An�lise de Componente Principal (ACP). Figos em calda provenientes de ind�strias distintas mostraram uma grande diferen�a quanto ao perfil sensorial. Dos quinze descriptores desenvolvidos pela equipe sensorial, sucul�ncia e aroma doce foram os mais importantes para discriminar as amostras entre si. As medidas de cor obtidas atrav�s do color�metro de Hunter mostraram boa rela��o com as medidas sensoriais, entretanto, as medidas de textura realizadas pelo aparelho Warner-Bratzler n�o refletiram as varia��es de textura encontradas nas amostras pela equipe sensorial. A metodologia desenvolvida no presente estudo demonstrou ser bastante eficiente na caracteriza��o e discrimina��o de amostras, em fun��o de seus perfis sensoriais. Assim, a presente metodologia pode ser muito �til a laborat�rios de Controle de Qualidade e Desenvolvimento de Novos Produtos nas ind�strias de alimentos. Abstract in english Eleven selected and trained panelists evaluated the appearance, aroma, flavor and texture of six different brands of Brazilian canned figs by adapted Quantitative Descriptive Analysis. A descriptive ballot and reference material illustrating sensory characteristics of the figs were developed. Sample [...] s were tested using a incomplete block design and the results analyzed by Analysis of Variance (ANOVA) and Principal Component Analysis (PCA). The samples sensory profiles showed large differences. From the fifteen descriptors developed by the panel, juiciness and sweet aroma were the most important for discriminating among samples. Instrumental measurements of color, obtained with a Hunter colorimeter, showed good relation with sensory measurements; but the shear force, obtained with a Warner-Bratzler shear instrument, did not related well with sensory measurements of texture. The methodology developed in this study was very efficient for characterizing and discriminating among the samples as a function of their sensory profiles; furthermore, it can be very useful to the Quality Control and Product Development laboratories of food industries.
Tereza C.A., ALMEIDA; Mar�lia I.S., FOLEGATTI; Maria Teresa A., FREIRE; M�rcia S., MADEIRA; Fernando T., SILVA; Maria Aparecida A.P. da, SILVA.
Directory of Open Access Journals (Sweden)
Full Text Available Onze provadores selecionados e treinados avaliaram a apar�ncia, aroma, sabor e textura de seis diferentes marcas de figo em calda, comercializadas no mercado brasileiro, utilizando o m�todo de An�lise Descritiva Quantitativa (ADQ adaptado. As amostras foram testadas utilizando-se blocos incompletos balanceados e os resultados estatisticamente analisados por An�lise de Vari�ncia (ANOVA e An�lise de Componente Principal (ACP. Figos em calda provenientes de ind�strias distintas mostraram uma grande diferen�a quanto ao perfil sensorial. Dos quinze descriptores desenvolvidos pela equipe sensorial, sucul�ncia e aroma doce foram os mais importantes para discriminar as amostras entre si. As medidas de cor obtidas atrav�s do color�metro de Hunter mostraram boa rela��o com as medidas sensoriais, entretanto, as medidas de textura realizadas pelo aparelho Warner-Bratzler n�o refletiram as varia��es de textura encontradas nas amostras pela equipe sensorial. A metodologia desenvolvida no presente estudo demonstrou ser bastante eficiente na caracteriza��o e discrimina��o de amostras, em fun��o de seus perfis sensoriais. Assim, a presente metodologia pode ser muito �til a laborat�rios de Controle de Qualidade e Desenvolvimento de Novos Produtos nas ind�strias de alimentos.Eleven selected and trained panelists evaluated the appearance, aroma, flavor and texture of six different brands of Brazilian canned figs by adapted Quantitative Descriptive Analysis. A descriptive ballot and reference material illustrating sensory characteristics of the figs were developed. Samples were tested using a incomplete block design and the results analyzed by Analysis of Variance (ANOVA and Principal Component Analysis (PCA. The samples sensory profiles showed large differences. From the fifteen descriptors developed by the panel, juiciness and sweet aroma were the most important for discriminating among samples. Instrumental measurements of color, obtained with a Hunter colorimeter, showed good relation with sensory measurements; but the shear force, obtained with a Warner-Bratzler shear instrument, did not related well with sensory measurements of texture. The methodology developed in this study was very efficient for characterizing and discriminating among the samples as a function of their sensory profiles; furthermore, it can be very useful to the Quality Control and Product Development laboratories of food industries.
Tereza C.A. ALMEIDA
Tempo de cozimento e textura de ra�zes de mandioca / Cooking time and texture of cassava roots
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste trabalho foi avaliar a adequa��o de medidas instrumentais de textura como �ndice de qualidade de ra�zes da mandioca de mesa e sua correla��o com o tempo de cozimento. Quinze ra�zes de mandioca foram colhidas no 11.� m�s de cultivo na regi�o noroeste fluminense. Peda�os de ra�zes for [...] am cozidos em �gua, sendo o tempo de cozimento determinado, em triplicata, quando se observou pouca resist�ncia � penetra��o do garfo. A resist�ncia ao corte foi realizada nas polpas cruas e cozidas, em cinco a nove repeti��es, operando o textur�metro TA. XT Plus Texture Analyser com probe Warner-Bratzler Blade HDP/BSW, velocidades de pr�-teste de 0,2 cm/s, de p�s-teste e de teste de 0,5 cm/s, e dist�ncia de 5 cm. Os dados foram analisados por ANOVA e teste de m�dia Tukey (tempo de cozimento); GLM, LSMEANS e PDIFF (resist�ncia ao corte) e an�lise de correla��o de Pearson (p Abstract in english The objective of this work was to evaluate the adequacy of instrumental texture analyses as a quality index for cassava roots for direct consumption, and the correlation with cooking time. Fifteen cassava roots were harvested in the eleventh month of growth in the northwest of the State of Rio de Ja [...] neiro. Pieces of roots were boiled in water and the cooking time determined in triplicate, to the point where there was little resistance to penetration by a fork. The shear strength was determined in the raw and cooked pulps with five to nine replicates, using the texturometer TA-XT Plus Texture Analyser with the Warner-Bratzler Blade HDP / BSW probe, a pre-test speed of 0.2 cm/s, post-test and test speed of 0.5 cm/s and distance of 5 cm. The data were analyzed by ANOVA and Tukey (cooking time), GLM, LSMEANS and PDIFF (shear resistance) and Pearson's correlation analysis (p
Simone Vilela, Talma; Selma Bergara, Almeida; Rozana Moreira Pereira, Lima; Henrique Duarte, Vieira; Pedro Amorim, Bebert.
The effect of the fattening diet, slaughter weight and sex on meat quality was studied in a total of 156 hybrid rabbits. After weaning, rabbits were divided into three groups of 52 animals each (50% male and 50% female), that were allocated for three weeks to one of three commercial diets containing low (14.28%, A), medium (18.04%, B) and high (20.48%, C) fibre content with decreasing energy levels. Animals were slaughtered at 2.0 and 2.3kg after the consumption of a common pre-slaughter non-medicated concentrate and pH, colour, water-holding capacity (WHC), Warner-Bratzler shear test and sensory analysis were all measured. Meat from animals fed with low fibre and high energy was the least luminous. Rabbits slaughtered at 2.0kg showed more yellowness than at 2.3kg at 0min. In both traits, these differences did not prevail after 15min of blooming. Globally, meat from males was more coloured than that of the females, both at 0 and 15min of blooming. No significant differences were found for pH, WHC or shear test for the individual effects. In the sensory analysis, rabbit and grass odours were more intense at 2.0kg than at 2.3kg of slaughter weight. PMID:20416607
Carrilho, M C; Campo, M M; Olleta, J L; Beltr�n, J A; L�pez, M
The extent of proteolysis is independent of sarcomere length in lamb longissimus and psoas major.
The objective of this experiment was to determine the effect of sarcomere length on postmortem proteolysis and meat tenderness. Eighteen Dorset market-weight sheep were slaughtered conventionally. The longissimus thoracis et lumborum and psoas major from each carcass were either left intact on the carcass (control), which was chilled at 0 degrees C, or excised from the carcass and chilled in an ice slurry (0 degrees C). At 24 h, control muscles were excised, and all muscles were cut into sections and assigned to 1 or 10 d of postmortem storage at 2 degrees C. Sarcomere length was shorter (P raw longissimus; 1.45 vs 3.03 microm, raw psoas major). Sarcomere length was not affected (P > .05) by aging time. Western blot analysis of troponin-T and desmin indicated no effect (P > .05) of the shortened treatment compared to the control on the extent of proteolysis. Regardless of aging time or treatment, troponin-T was more degraded (P Warner-Bratzler shear force was greater (P shear force declined more in longissimus than in psoas major during aging. We conclude that sarcomere length did not affect the extent of proteolysis. However, sarcomere length may have an indirect effect on tenderization during aging due to its effect on initial tenderness. PMID:10492451
Wheeler, T L; Koohmaraie, M
Shear-enhanced compaction in viscoplastic rocks
The phenomenon of mutual influence of compaction and shear deformation was repeatedly reported in the literature over the past years. Dilatancy and shear-enhanced compaction of porous rocks were experimentally observed during both rate-independent and rate-dependent inelastic deformation. Plastic pore collapse was preceding the onset of dilatancy and shear-enhanced compaction. Effective bulk viscosity is commonly used to describe compaction driven fluid flow in porous rocks. Experimental data suggest that bulk viscosity of a fluid saturated rock might be a function of both the effective pressure and the shear stress. Dilatancy and shear-enhanced compaction can alter the transport properties of rocks through their influence on permeability and compaction length scale. Recent investigations show that shear stresses in deep mantle rocks can be responsible for spontaneous development of localized melt-rich bands and segregation of small amounts of melt from the solid rock matrix through shear channeling instability. Usually it is assumed that effective viscosity is a function of porosity only. Thus coupling between compaction and shear deformation is ignored. Spherical model which considers a hollow sphere subjected to homogeneous tractions on the outer boundary as a representative elementary volume succeeded in predicting the volumetric compaction behavior of porous rocks and metals to a hydrostatic pressure in a wide range of porosities. Following the success of this simple model we propose a cylindrical model of void compaction and decompaction due to the non-hydrostatic load. The infinite viscoplastic layer with a cylindrical hole is considered as a representative volume element. The remote boundary of the volume is subjected to a homogeneous non-hydrostatic load such that plane strain conditions are fulfilled through the volume. At some critical values of remote stresses plastic zone develops around the hole. The dependence of the effective bulk viscosity on the properties of individual components as well as on the stress state is examined. We show that bulk viscosity is a function of porosity, effective pressure and shear stress. Decreasing porosity tends to increase bulk viscosity whereas increasing shear stress and increasing effective pressure reduce it.
Yarushina, V. M.; Podladchikov, Y. Y.
Effects of shear stress on the microalgae Chaetoceros muelleri
The effect of shear stress on the viability of Chaetoceros muelleri was studied using a combination of a rheometer and dedicated shearing devices. Different levels of shear stress were applied by varying the shear rates and the medium viscosities. It was possible to quantify the effect of shear stress over a wide range, whilst preserving laminar flow conditions through the use of a thickening agent. The threshold value at which the viability of algae was negatively influenced was between 1 an...
Michels, M. H. A.; Goot, A. J.; Norsker, N. H.; Wijffels, R. H.
Problem of punching shear in slabs on culumns
Existing technical solutions enabling sufficient punching resistance failure of flot slabs were analyzed. The reasons that ultimately lead to punching shear and the consequences of shear punching were examined as well. The main causes of punching shear are the condensed shear stresses in the part of the slab that is in contact with the columns. Symbols used at punching shear and an overlook of elements with appropriate reinforcement calculation were presented. The control exten...
Bartol, Joz?e
Shear deformations of slender reinforced concrete walls under seismic loading
Experimental results gained from quasi-static cyclic tests on 34 slender structural reinforced concrete walls available in the literature are used to examine the shear deformations for displacement demands in the inelastic range. Based on these results the distribution of shear strains within the walls and the variation of shear deformations with top displacements is discussed. It is shown that for shear walls whose shear transfer mechanism is not deteriorating significantly the ratio of shea...
Beyer, Katrin; Dazio, Alessandro; Priestley, Nigel
Shear strength behavior of human trabecular bone.
The shear strength of human trabecular bone may influence overall bone strength under fall loading conditions and failure at bone-implant interfaces. Here, we sought to compare shear and compressive yield strengths of human trabecular bone and elucidate the underlying failure mechanisms. We analyzed 54 specimens (5-mm cubes), all aligned with the main trabecular orientation and spanning four anatomic sites, 44 different cadavers, and a wide range of bone volume fraction (0.06-0.38). Micro-CT-based non-linear finite element analysis was used to assess the compressive and shear strengths and the spatial distribution of yielded tissue; the tissue-level constitutive model allowed for kinematic non-linearity and yielding with strength asymmetry. We found that the computed values of both the shear and compressive strengths depended on bone volume fraction via power law relations having an exponent of 1.7 (R(2)=0.95 shear; R(2)=0.97 compression). The ratio of shear to compressive strengths (mean�SD, 0.44�0.16) did not depend on bone volume fraction (p=0.24) but did depend on microarchitecture, most notably the intra-trabecular standard deviation in trabecular spacing (R(2)=0.23, pshear, the main tissue-level failure mode was tensile yield of the obliquely oriented trabeculae. By contrast, for compression, specimens having low bone volume fraction failed primarily by large-deformation-related tensile yield of horizontal trabeculae and those having high bone volume failed primarily by compressive yield of vertical trabeculae. We conclude that human trabecular bone is generally much weaker in shear than compression at the apparent level, reflecting different failure mechanisms at the tissue level. PMID:22884967
Sanyal, Arnav; Gupta, Atul; Bayraktar, Harun H; Kwon, Ronald Y; Keaveny, Tony M
Functional and morphological responses of endothelial cells (ECs) to fluid shear stress are thought to be mediated by several mechanosensitive molecules. However, how the force due to fluid shear stress applied to the apical surface of ECs is transmitted to the mechanosensors is poorly understood. In the present paper, we performed an analysis of an intracellular mechanical field by observation of the deformation behaviors of living ECs exposed to shear stress with a novel experimental method. Lateral images of human umbilical vein ECs before and after the onset of flow were obtained by confocal microscopy, and image correlation and finite element analysis were performed for quantitative analyses of subcellular strain due to shear stress. The shear strain of the cells changed from 1.06+/-1.09% (mean+/-SD) to 4.67+/-1.79% as the magnitude of the shear stress increased from 2 to 10 Pa. The nuclei of ECs also exhibited shear deformation, which was similar to that observed in cytoplasm, suggesting that nuclei transmit forces from apical to intracellular components, as well as cytoskeletons. The obtained strain-stress relation resulted in a mean shear modulus of 213 Pa for adherent ECs. These results provide a mechanical perspective on the investigation of flow-sensing mechanisms of ECs. PMID:20175996
Ueki, Yosuke; Sakamoto, Naoya; Sato, Masaaki
Shear-current effect in a turbulent convection with a large-scale shear.
The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force epsilon (W) proportional to W x J and the mean electric current along the original mean magnetic field, where W is the background mean vorticity due to the shear and J is the mean electric current. This results in a large-scale dynamo even in a nonrotating and nonhelical homogeneous sheared turbulent convection, whereby the alpha effect vanishes. It is found that turbulent convection promotes the shear-current dynamo instability, i.e., the heat flux causes positive contribution to the shear-current effect. However, there is no dynamo action due to the shear-current effect for small hydrodynamic and magnetic Reynolds numbers even in a turbulent convection, if the spatial scaling for the turbulent correlation time is tau(k) proportionalto to k-2, where k is the small-scale wave number. PMID:17500991
Rogachevskii, Igor; Kleeorin, Nathan
Repeated buckling of composite shear panels
Failures in service of aerospace structures and research at the Technion Aircraft Structures Laboratory have revealed that repeatedly buckled stiffened shear panels might be susceptible to premature fatigue failures. Extensive experimental and analytical studies have been performed at Technion on repeated buckling, far in excess of initial buckling, for both metal and composite shear panels with focus on the influence of the surrounding structure. The core of the experimental investigation consisted of repeated buckling and postbuckling tests on Wagner beams in a three-point loading system under realistic test conditions. The effects of varying sizes of stiffeners, of the magnitude of initial buckling loads, of the panel aspect ratio and of the cyclic shearing force, V sub cyc, were studied. The cyclic to critical shear buckling ratios, (V sub cyc/V sub cr) were on the high side, as needed for efficient panel design, yet all within possible flight envelopes. The experiments were supplemented by analytical and numerical analyses. For the metal shear panels the test and numerical results were synthesized into prediction formulas, which relate the life of the metal shear panels to two cyclic load parameters. The composite shear panels studied were hybrid beams with graphite/epoxy webs bonded to aluminum alloy frames. The test results demonstrated that composite panels were less fatigue sensitive than comparable metal ones, and that repeated buckling, even when causing extensive damage, did not reduce the residual strength by more than 20 percent. All the composite panels sustained the specified fatigue life of 250,000 cycles. The effect of local unstiffened holes on the durability of repeatedly buckled shear panels was studied for one series of the metal panels. Tests on 2024 T3 aluminum panels with relatively small unstiffened holes in the center of the panels demonstrated premature fatigue failure, compared to panels without holes. Preliminary tests on two graphite epoxy shear panels with small holes in the center showed no similar fatigue life degradation and no shift in failure mode. Further tests on the effect of holes are in progress.
Singer, Josef; Weller, Tanchum
Microstructural Evolution in Adiabatic Shear Localization
Shear bands were generated under prescribed and controlled conditions in stainless steel( Fe-18Hat-shaped specimens, deformed in a Hopkinson bar were used, yielding strain rates of approximately 104s-1 and shear strains that could be varied between 1 and 100.Specimens recovered from the collapse of thick-walled cylinders were also investigated. Microstructural characterization was performed by electron backscattered diffraction (EBSD) with orientation imaging microscopy(OIM), and transmission electron microscopy (TEM). The shear-band thickness was approximately 8 �m. This low-stacking fault energy alloy deforms, at the imposed strain rates (outside of the shear band), by planar dislocations and stacking fault packets, twinning, and occasional martensitic phase transformations at twin-twin intersections. EBSD reveals gradual lattice rotations of the grains approaching the core of the band. A [110] fiber texture (with the [110] direction perpendicular to both shear direction and shear plane normal) develops both within the shear band and in the adjacent grains. The formation of this texture, under an imposed global simple shear, suggests that rotations take place concurrently with the shearing deformation. This can be explained by compatibility requirements between neighboring deforming regions.EBSD could not reveal the deformation features at large strains because their scale was beklow thwe resolution of this technique.Transmission electron microscopy reveals a number of features that are interpreted in terms of the mechanisms of deformation and recovery/recrystallization postulated. They include the observation of grains with sizes in the nanocrystalline domain. The microstructural changes are described by an evolutionary model, leading from the initial grain size of 15 �m to the final submicronic (sub)grain size. Calculations are performed on the rotations of grain boundaries by grain-boundary diffusion, which is 3 orders of magnitude higher than bulk diffusion at the deformation temperatures. They indicate that the microstructural reorganization can take place within the deformation times of a few milliseconds. Research supported by US Army Research Office MURI Program under Contract DAAH04-96-1-0376 and the Department of Energy Grant DEFG0300SF2202.
Meyers, M. A.; Perez-Prado, M. T.; McNelley, T. R.; Xue, Q.; Xu, Y.
Stochastic parametric resonance in shear flows
Directory of Open Access Journals (Sweden)
Full Text Available Time-periodic shear flows can give rise to Parametric Instability (PI, as in the case of the Mathieu equation (Stoker, 1950; Nayfeh and Mook, 1995. This mechanism results from a resonance between the oscillatory basic state and waves that are superimposed on it. Farrell and Ioannou�(1996a, b explain that PI occurs because the snap-shots of the velocity profile are subject to transient growth. If the flows were purely steady the transient growth would subside and not have any long lasting effect. However, the coupling between transient growth and the time variation of the basic state create PI. Mathematically, transient growth, and therefore PI, are due to the nonorthogonal eigenspace in the linearized system. Poulin et al.�(2003 studied a time-periodic barotropic shear flow that exhibited PI, and thereby produced mixing at the interface between Potential Vorticity (PV fronts. The instability led to the formation of vortices that were stretched. A later study of an oscillatory current in the Cape Cod Bay illustrated that PI can occur in realistic shear flows (Poulin and Flierl, 2005. These studies assumed that the basic state was periodic with a constant frequency and amplitude. In this work we study a shear flow similar to that found in Poulin et al. (2003, but now where the magnitude of vorticity is a stochastic variable. We determine that in the case of stochastic shear flows the transient growth of perturbations of the snapshots of the basic state still generate PI.
F. J. Poulin
Review article: Cosmology with cosmic shear observations
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...
Kilbinger, Martin
Shear-enhanced adhesion of Pseudomonas aeruginosa
Bacterial adhesion is the first step in the development of surface-associated communities known as biofilms, which are the cause of many problems in medical devices and industrial water systems. However the underlying mechanisms of initial bacterial attachment are not fully understood. We have investigated the effects of hydrodynamics on the probability of adsorption and detachment of Pseudomonas aeruginosa strain PA14 on model surfaces under flow, in straight microfluidic channels, and measured the distribution of bacteria residence time as a function of the shear rate. Our main discovery is a counter-intuitive enhanced adhesion as the shear stress is increased over a wide range of shear rates. In order to identify the origin of this phenomenon, we have performed experiments with several mutant strains. Our results show that shear-enhanced adhesion is not regulated by primary surface organelles, and that this process is not specific to a certain type of surface, but rather appears a general feature of the adhesive behavior of P. aeruginosa. These results suggest that shear-induced adhesion could be a very widespread strategy in nature.
Lecuyer, Sigolene; Rusconi, Roberto; Shen, Yi; Forsyth, Alison; Stone, Howard
Turbulent transport in reversed magnetic shear plasma
International Nuclear Information System (INIS)
The turbulent transport of particles and ion heat in reversed magnetic shear plasma are investigated. A dispersion relation for the electrostatic drift wave driven by ion temperature gradient, electron temperature gradient, magnetic field gradient, and trapped electrons is derived within the framework of two-fluid theory and in sheared coordinate system. Correspondingly the turbulent particle and ion thermal diffusivities in quasi-linear approximation are obtained. The present model self-consistently includes five factors: the magnetic shear and the sheared velocity, and the three ways of coupling between them. It is found that the five factors presented in the turbulent transport coefficients as well as the dispersion relation can produce turbulent particle- and heat-pinch, i.e., turbulent diffusivity of particles and that of ion heat in the negative magnetic shear region are smaller than zero. Hence the particle and ion heat diffusivities reduce significantly in that region. The numerical results for the particle and ion heat diffusivity are in good agreement with the experimental results
Pressure-shear experiments on granular materials.
Energy Technology Data Exchange (ETDEWEB)
Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.
Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)
Particle Distribution in Suspension Shear Flow
An earlier proposed constitutive relation for normal stresses originated by random particle fluctuations is used to describe a joint effect of thermal and shear-induced fluctuations on concentrational distributions in suspension flow. Averaged products of components of the fluctuation velocity are evaluated on a basis of the rational mechanics approach combined with a simple kinematic consideration. The equation of momentum conservation of the dispersed phase of a suspension closed with this constitutive relation is applied to unidirectional shear flow in the gravity field and to rotational Couette flow. Coupling of the thermal and shear-induced fluctuations results in that the ability of shear flow to suspend particles has a minimum at a certain particle size, all other things being equal. The developed model provides also for a reasonable explanation of particle distributions observed in Couette flow. The approach based on the consideration of momentum balance for the dispersed phase is proved to lead to an effective equation of convective diffusion of the suspended particles. Coefficients of mutual diffusion due to both thermal and shear-induced fluctuations are drastically different from corresponding self-diffusivities as regards both their scaling and their concentrational dependence.
Buyevich, Yu A.; Webbon, Bruce W. (Technical Monitor)
Dynamic Modes of Red Blood Cells in Oscillatory Shear Flow
The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle $\\theta$, and phase angle $\\phi$ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. i) tank-treading (TT): $\\phi$ rotates while the shape and $\\theta$ oscillate. ii) tumbling (TB): $\\theta$ rotates while the shape and $\\phi$ oscillate. iii) intermediate motion: both $\\phi$ and $\\theta$ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation beco...
Noguchi, Hiroshi
High-shear-rate capillary viscometer for inkjet inks
International Nuclear Information System (INIS)
A capillary viscometer developed to measure the apparent shear viscosity of inkjet inks at high apparent shear rates encountered during inkjet printing is described. By using the Weissenberg-Rabinowitsch equation, true shear viscosity versus true shear rate is obtained. The device is comprised of a constant-flow generator, a static pressure monitoring device, a high precision submillimeter capillary die, and a high stiffness flow path. The system, which is calibrated using standard Newtonian low-viscosity silicone oil, can be easily operated and maintained. Results for measurement of the shear-rate-dependent viscosity of carbon-black pigmented water-based inkjet inks at shear rates up to 2x105 s-1 are discussed. The Cross model was found to closely fit the experimental data. Inkjet ink samples with similar low-shear-rate viscosities exhibited significantly different shear viscosities at high shear rates depending on particle loading.
Exponential Shear Flow of Linear, Entangled Polymeric Liquids
DEFF Research Database (Denmark)
A previously proposed reptation model is used to interpret exponential shear flow data taken on an entangled polystyrenesolution. Both shear and normal stress measurements are made during exponential shear using mechanical means. The model iscapable of explaining all trends seen in the data, and suggests a novel analysis of the data. This analysis demonstrates thatexponential shearing flow is no more capable of stretching polymer chains than is inception of steady shear at comparableinstantaneous shear rates. In fact, all exponential shear flow stresses measured are bounded quantitatively by stressmeasurements taken during inception of steady shear. Information taken from the model about chain stretching suggests thatnormal stress measurements are strong indications of stretching, whereas shear stress measurements are indicative of bothchain stretching and segment orientation.
Neergaard, Jesper; Park, Kyungho
Shear rupture under constant normal stiffness boundary conditions
A grain based Distinct Element Method and its embedded Grain Based Method are used to simulate the fracturing processes leading to shear rupture zone creation in a calibrated massive (non-jointed) brittle rock specimen deformed in direct shear under constant normal stiffness boundary conditions. Under these boundary conditions, shear rupture zone creation relative to the shear stress versus applied horizontal displacement (load-displacement) curve occurs pre-peak, before the maximum peak shear strength is reached. This is found to be the result of a normal stress feedback process caused by the imposed shear displacement which couples increases in normal stress, due to rupture zone dilation, with shear stress, producing a complex normal-shear stress-path that reaches and then follows the rock's yield (strength) envelope. While the yield envelope is followed, the shear strength increases further and shear stress oscillations (repeated stress drops followed by re-strengthening periods) in the load-displacement curves occur due to fracture creation as the rupture zone geometry smoothens. Once the maximum peak strength is reached (after a series of shear stress oscillations) the largest stress drops occur as the ultimate or residual shear strength is approached. The simulation results provide insight into the fracturing process during rupture zone creation and improve the understanding of the shear stress versus applied horizontal displacement response, as well as the stick-slip behaviour of shear rupture zones that are being created under constant normal stiffness boundary conditions.
Bewick, R. P.; Kaiser, P. K.; Bawden, W. F.
Shear stress in lattice Boltzmann simulations.
A thorough study of shear stress within the lattice Boltzmann method is provided. Via standard multiscale Chapman-Enskog expansion we investigate the dependence of the error in shear stress on grid resolution showing that the shear stress obtained by the lattice Boltzmann method is second-order accurate. This convergence, however, is usually spoiled by the boundary conditions. It is also investigated which value of the relaxation parameter minimizes the error. Furthermore, for simulations using velocity boundary conditions, an artificial mass increase is often observed. This is a consequence of the compressibility of the lattice Boltzmann fluid. We investigate this issue and derive an analytic expression for the time dependence of the fluid density in terms of the Reynolds number, Mach number, and a geometric factor for the case of a Poiseuille flow through a rectangular channel in three dimensions. Comparison of the analytic expression with results of lattice Boltzmann simulations shows excellent agreement. PMID:19518377
Kr�ger, Timm; Varnik, Fathollah; Raabe, Dierk
Viscoelastic Phase Separation in Shear Flow
We investigate viscoelastic phase separation in polymer solutions under shear numerically using a time-dependent Ginzburg-Landau model. The gross variables in our model are the polymer volume fraction and a conformation tensor. The latter represents chain deformations and relaxes slowly on the rheological time giving rise to a large viscoelastic stress. The polymer and the solvent obey two-fluid dynamics in which the viscoelastic stress acts asymmetrically on the polymer and, as a result, the stress and the diffusion are dynamically coupled. Above the coexistence curve and for shear rates larger than a crossover value, phase separation is induced incompletely and the solution behaves chaotically. Below the coexistence curve, sharp interfaces appear with increasing the quench depth and the solvent regions act as a lubricant. In these cases the composition heterogeneity causes more enhanced viscoelastic heterogeneity such that the macroscopic stress is decreased at fixed shear rate. We find steady two-phase sta...
Imaeda, T; Onuki, A; Imaeda, Tatsuhiro; Furukawa, Akira; Onuki, Akira
Streamline curvature in supersonic shear layers
Results of an experimental investigation in which a curved shear layer was generated between supersonic flow from a rectangular converging/diverging nozzle and the freestream in a series of open channels with varying radii of curvature are reported. The shear layers exhibit unsteady large-scale activity at supersonic pressure ratios, indicating increased mixing efficiency. This effect contrasts with supersonic flow in a straight channel, for which no large-scale vortical structure development occurs. Curvature must exceed a minimum level before it begins to affect the dynamics of the supersonic shear layer appreciably. The curved channel flows are compared with reference flows consisting of a free jet, a straight channel, and wall jets without sidewalls on a flat and a curved plate.
Kibens, V.
Bacterial motility and chemotaxis in shear
Bacteria often exhibit directed motility (``taxis'') in response to gradients of dissolved resources, like nutrients or oxygen. While we have a detailed understanding of chemotaxis in quiescent environments, it has been largely overlooked how this behavior is affected by fluid flow, despite the ubiquity of flow in bacterial habitats. Here we present experiments on aerotaxis (attraction to dissolved oxygen) of Bacillus subtilis in controlled shear flows. Using novel microfluidic devices we expose bacterial suspensions to steady oxygen gradients, with independent control over shear rates. From single-cell trajectories and the spatial distribution of bacteria, we show that the cell rotation induced by shear reduces the aerotactic performance, demonstrating that hydrodynamic conditions affect bacterial fitness.
Rusconi, Roberto; Guasto, Jeffrey S.; Son, Kwangmin; Stocker, Roman
Shear viscosity of a hot pion gas
International Nuclear Information System (INIS)
The shear viscosity of an interacting pion gas is studied using the Kubo formalism as a microscopic description of thermal systems close to global equilibrium. We implement the skeleton expansion in order to approximate the retarded correlator of the viscous part of the energy-momentum tensor. After exploring this in g?4 theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity ? is determined by the spectral width, or equivalently, the mean free path of pions in the heat bath. We derive a new analytical result for the mean free path which is well conditioned for numerical evaluation and discuss the temperature and pion-mass dependence of the mean free path and the shear viscosity. The ratio ?/s of the interacting pion gas exceeds the lower bound 1/4? from AdS/CFT correspondence. (orig.)
Bounds on Surface Stress Driven Shear Flow
The background method is adapted to derive rigorous limits on surface speeds and bulk energy dissipation for shear stress driven flow in two and three dimensional channels. By-products of the analysis are nonlinear energy stability results for plane Couette flow with a shear stress boundary condition: when the applied stress is gauged by a dimensionless Grashoff number $Gr$, the critical $Gr$ for energy stability is 139.5 in two dimensions, and 51.73 in three dimensions. We derive upper bounds on the friction (a.k.a. dissipation) coefficient $C_f = \\tau/\\bar{u}^2$, where $\\tau$ is the applied shear stress and $\\bar{u}$ is the mean velocity of the fluid at the surface, for flows at higher $Gr$ including developed turbulence: $C_f le 1/32$ in two dimensions and $C_f \\le 1/8$ in three dimensions. This analysis rigorously justifies previously computed numerical estimates.
Hagstrom, George I
Shear hell holes and anisotropic universes
International Nuclear Information System (INIS)
If the early universe was highly anisotropic, primordial black holes may have formed prolifically (despite previous claims to the contrary) even if the initial density fluctuations were small. However, the holes would initially be endowed with an immense amount of shear, so it is not obvious that they would evolve into the conventional type of stationary black hole envisaged by the ''no hair'' theorem. If they do settle down to stationary state, it may only be on a considerable time scale;and in principle there might exist soliton-type solutions which represent holes with shear which persists indefinitely. Such 'shear hell holes,' termed here, could have even more dramatic properties than the usual stationary holes: in particular,they might be prolific generators of gravitational radiation and they could be associated with interesting quantum effects. (author)
Shear banding in soft glassy materials
Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic �glassy� features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.
Fielding, S. M.
Universal Anisotropy in Force Networks under Shear
Scaling properties of patterns formed by large contact forces are studied as a function of the applied shear stress, in two-dimensional static packings generated from the force network ensemble. An anisotropic finite-size-scaling analysis shows that the applied shear does not affect the universal scaling properties of these patterns, but simply induces different length scales in the principal directions of the macroscopic stress tensor. The ratio of these length scales quantifies the anisotropy of the force networks, and is found not to depend on the details of the underlying contact network, in contrast with other properties such as the yield stress.
Ostojic, S; Nienhuis, B; Ostojic, Srdjan; Vlugt, Thijs J. H.; Nienhuis, Bernard
Anomalous distribution functions in sheared suspensions
We investigate velocity probability distribution functions (PDF) of sheared hard-sphere suspensions. As observed in our Stokes flow simulations and explained by our single-particle theory, these PDFs can show pronounced deviations from a Maxwell-Boltzmann distribution. The PDFs are symmetric around zero velocity and show a Gaussian core and exponential tails over more than six orders of magnitude of probability. Following the excellent agreement of our theory and simulation data, we demonstrate that the distribution functions scale with the shear rate, the particle volume concentration, as well as the fluid viscosity.
Harting, J.; Herrmann, H. J.; Ben-Naim, E.
Stability Criteria of 3D Inviscid Shears
The classical plane Couette flow, plane Poiseuille flow, and pipe Poiseuille flow share some universal 3D steady coherent structure in the form of "streak-roll-critical layer". As the Reynolds number approaches infinity, the steady coherent structure approaches a 3D limiting shear of the form ($U(y,z), 0, 0$) in velocity variables. All such 3D shears are steady states of the 3D Euler equations. This raises the importance of investigating the stability of such inviscid 3D she...
Li, Y. Charles
Halo abundances and shear in void models
DEFF Research Database (Denmark)
We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all times and radii, but it also gives interesting clues about the impact of the background shear on the growth of perturbations. Our results give hints about the possibility of constraining the background shear via cluster number counts, which could then give rise to strong constraints on general inhomogeneous models, of any scale.
Alonso, David; Garc�a-Bellido, Juan
Seismic behaviour of concrete shear walls
International Nuclear Information System (INIS)
Concrete shear walls have an important contribution to building stiffness. So, it is necessary to know their behaviour under seismic loads. The ultimate behaviour of shear walls under dynamic loadings has been studied. The study includes: - A description of the non linear global model based on cyclic static tests. - Non linear time history calculations for various forcing functions. The comparison of linear and non linear results have shown important margins related to the ductility when the bandwidth of the forcing function is narrow and centred on the wall natural frequency
Velocity Profiles in Slowly Sheared Bubble Rafts
Measurements of average velocity profiles in a bubble raft subjected to slow, steady-shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for three-dimensional foams and emulsions [Coussot {\\it et al,}, Phys. Rev. Lett. {\\bf 88}, 218301 (2002)]. For sufficiently slow shear, the flow is generated by nonlinear topological rearrangements. We report on the connection between this short-time motion of the bubbles and the long-time averages. We find that a smooth, average velocity is reached after averaging over only a relatively few number of rearrangement events.
Lauridsen, J; Dennin, M; Lauridsen, John; Chanan, Greg; Dennin, Michael
Universal anisotropy in force networks under shear
Scaling properties of patterns formed by large contact forces are studied as a function of the applied shear stress, in two-dimensional static packings generated from the force network ensemble. An anisotropic finite-size-scaling analysis shows that the applied shear does not affect the universal scaling properties of these patterns, but simply induces different length scales in the principal directions of the macroscopic stress tensor. The ratio of these length scales quantifies the anisotropy of the force networks, and is found not to depend on the details of the underlying contact network, in contrast with other properties such as the yield stress.
Ostojic, Srdjan; Vlugt, Thijs J. H.; Nienhuis, Bernard
Gyrokinetic study of the edge shear layer
International Nuclear Information System (INIS)
The delta-f gyrokinetic model originally formulated for core turbulence is extended to treat medium-amplitude electromagnetic turbulence expected in the transcollisional edge regions of modern tokamaks. Both electrons and ions, and the field polarization equations, are followed. The effect on the turbulence of an externally applied E x B velocity shear and alternatively an initial E x B vorticity profile to which the turbulence can back-react are studied. Imposed shear reduces the short wavelength component but increases the long wavelengths. The localized vorticity layer has a more general suppressive effect
Shear unzipping of double stranded DNA
We propose a simple nonlinear scaler displacement model to calculate the distribution of effect created by a shear stress on a double stranded DNA (dsDNA) molecule and the value of shear force $F_c$ which is required to separate the two strands of a molecule. It is shown that as long as the force pulls entire strand in the direction of its application the value of $F_c$ depends linearly on the length; the deviation from linear behaviour takes place when part of a strand move...
Prakash, Shikha; Singh, Yashwant
The global wall shear stress measurement technique using shear-sensitive liquid crystal (SSLC) is extended to wind tunnel measurements. Simple and common everyday equipment is used in the measurement; in particular a tungsten-halogen light bulb provides illumination and a saturation of SSLC coating color change with time is found. Spatial wall shear stress distributions of several typical flows are obtained using this technique, including wall-jet flow, vortex flow generated by a delta wing and junction flow behind a thin cylinder, although the magnitudes are not fully calibrated. The results demonstrate that SSLC technique can be extended to wind tunnel measurements with no complicated facilities used.
Zhao, Ji-Song; Scholz, Peter; Gu, Liang-Xian
Computer simulation of three dimensional shearing of granular materials: Formation of shear bands
We used computer simulations to study spontaneous strain localization in granular materials, as a result of symmetry breaking non-homogeneous deformations. Axisymmetric triaxial shear tests were simulated by means of standard three-dimensional Distinct Element Method (DEM) with spherical grains. Carefully prepared dense specimens were compressed between two platens and, in order to mimic the experimental conditions, stress controlled, (initially) axisymmetric boundary conditions were constructed. Strain localization gave rise to visible shear bands, previously found experimentally under similar conditions by several groups, and different morphologies could be reproduced. We examined the stress-strain relation during the process and found good agreement with experiments. Formation mechanism of shear bands is discussed.
Fazekas, S; Kert�sz, J; Wolf, D E
Using an approximation scheme within the convective diffusion (two-body Smoluchowski) equation framework, we unveil the shear-driven aggregation mechanism at the origin of structure formation in sheared colloidal systems. The theory, verified against numerics and experiments, explains the induction time followed by explosive (irreversible) rise of viscosity observed in charge-stabilized colloidal and protein systems under steady shear. The Arrhenius-type equation with shear derived here, extending Kramers� theory in the presence of shear, clearly demonstrates the important role of shear drive in activated-rate processes as they are encountered in soft condensed matter.
Zaccone, Alessio; Wu, Hua; Gentili, Daniele; Morbidelli, Massimo
Mode coupling theory for sheared granular liquids
Sheared granular liquids are studied by the mode coupling theory. It is shown that, in contrast to thermostatted systems, current correlations play an essential role in the dynamics. The theory predicts that the plateau of the density time-correlator disappears for most situations, while it appears in the elastic limit. The result is compatible with molecular dynamics simulations.
Suzuki, Koshiro; Hayakawa, Hisao
Modeling of Turbulent Free Shear Flows
The modeling of turbulent free shear flows is crucial to the simulation of many aerospace applications, yet often receives less attention than the modeling of wall boundary layers. Thus, while turbulence model development in general has proceeded very slowly in the past twenty years, progress for free shear flows has been even more so. This paper highlights some of the fundamental issues in modeling free shear flows for propulsion applications, presents a review of past modeling efforts, and identifies areas where further research is needed. Among the topics discussed are differences between planar and axisymmetric flows, development versus self-similar regions, the effect of compressibility and the evolution of compressibility corrections, the effect of temperature on jets, and the significance of turbulent Prandtl and Schmidt numbers for reacting shear flows. Large eddy simulation greatly reduces the amount of empiricism in the physical modeling, but is sensitive to a number of numerical issues. This paper includes an overview of the importance of numerical scheme, mesh resolution, boundary treatment, sub-grid modeling, and filtering in conducting a successful simulation.
Yoder, Dennis A.; DeBonis, James R.; Georgiadis, Nicolas J.
A cutter mounting tool for shears
International Nuclear Information System (INIS)
The tool is aimed for cutters with a block shape and sharp edges, to be mounted on a blade holder through pressure or locking screws, at the bottom of specific recessions, ensuring a good alignment of the cutting edges. The tool has been especially designed for maintenance robot manipulation of nuclear fuel pin sawing shears. 3 refs., 7 figs
Shears band in near spherical 138Ce
International Nuclear Information System (INIS)
In recent years, rotational like sequences of strongly enhanced magnetic dipole (M1) transitions have been observed in spherical or near-spherical nuclei with very small deformation and low quadrupole collectivity. Thus the measured values of B(M1) from the lifetime of the levels of such bands can give clear evidence of the presence of shears mechanism
Mixing of shear Alfven wave packets
The general problem of the enhanced dissipation of shear-Alfven waves and, in particular, their "phase mixing", resulting from their propagation in inhomogeneous background magnetic fields, is considered from a different view point. It is shown that the dissipative mechanism proceeds essentially as the accelerated diffusion of a passively advected tracer, i.e. its "mixing" by inhomogeneous flows. Therefore, standard "phase mixing" corresponds to the effect of an "Alfvenic" shear flow while enhanced dissipation at a magnetic X-point corresponds to mixing by an "Alfvenic" strain flow. An eikonal formulation of the problem is adopted which means that the evolution of the global wave perturbation is supposed to result from the dynamics of a superposition of wave packets. Since shear-Alfven wave packets experience continuous shearing/straining while advected by the Alfvenic flow $\\mathbf{V}_{A}$, their mixing process is also equivalent to a cascade of wave energy in $k$-space. This gradual creation of smaller scal...
Bian, Nicolas
Shear generated turbulence in the natural environment
Shear generated turbulence is an important source of mixing in both the ocean and atmosphere. Often because of sampling difficulties we are limited to deriving statistical relationships between the turbulence activity and the larger scale properties of the fluid flow. The Western Equatorial Pacific proves to be an ideal natural laboratory to study shear generated turbulence. Here turbulent production is dominated by the shear associated with relatively long lived flow structures in the form of high vertical mode inertia-gravity waves and flow instabilities. With enough vertical resolution we can directly measure the characteristics of these flow features. We find a strong relationship between the vertical shear and stratification and the turbulent dissipation and implied vertical diffusion coefficient. In addition there is a strong indication from the our observations that the vertical mixing length scale is inversely proportional to the buoyancy frequency as found in numerical DNS and LES studies. The dataset is also an excellent test for parameterization schemes. We find with suitable modification that one such scheme is able to capture a good deal of the vertical variation of turbulent activity as well as variations between different sampling periods.
Richards, Kelvin
Shear behavior of bovine scleral tissue.
Ocular tissue properties have been widely studied in tension and compression for humans and a variety of animals. However, direct shear testing of the tissues of the sclera appear to be absent from the literature even though modeling, analyses, and anatomical studies have indicated that shear may play a role in the etiology of primary open angle glaucoma (POAG). In this work, the mechanical behavior of bovine scleral tissue in shear has been studied in both out-of-plane and in-plane modes of deformation. Stress-strain and relaxation tests were conducted on tissue specimens at controlled temperature and hydration focusing on trends related to specimen location and orientation. There was generally found to be no significant effect of specimen orientation and angular location in the globe on shear stiffness in both modes. The in-plane response, which is the primary load carrying mode, was found to be substantially stiffer than the out-of-plane mode. Also, within the in-plane studies, tissue further from the optic nerve was stiffer than the near tissue. The viscosity coefficient of the tissue varied insignificantly with distance from the optic nerve, but overall was much higher in-plane than out-of-plane. PMID:24805965
Argento, Alan; Kim, Wonsuk; Rozsa, Frank W; DeBolt, Kori L; Zikanova, Sophia; Richards, Julia R
Shear modulus property characterization of nanorods.
We demonstrate an innovative technique for the direct measurement on the shear modulus of an individual nanorod. This measurement is based on atomic force microscopy (AFM) and microfabrication techniques. A nanorod is first aligned along the edge of a small trench in a silicon substrate, and then one end of the nanorod is fixed on the substrate. When an AFM tip scans over the nanorod in contact mode, the nanorod will be twisted by the comprehensive action from the force of the AFM tip, confinement from the trench edge and the fixing end. The shear deformation and the corresponding force that caused the deformation can be retrieved from topography and lateral force image, respectively. By small-angle approximation, the shear modulus of the ZnO NR, which has a radius of 166 nm and a length of 4 ?m, is measured to be 8.1 � 1.9 GPa. This method can be applied directly to characterize the shear modulus of any nanowire/nanorod that possesses a polygon cross section. PMID:23205561
Jiang, Chengming; Lu, Wenqiang; Song, Jinhui
Turbulent transport in tokamak plasmas with rotational shear.
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E�B shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the E�B shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity. PMID:21635042
Barnes, M; Parra, F I; Highcock, E G; Schekochihin, A A; Cowley, S C; Roach, C M
49 CFR 230.28 - Higher shearing strength of rivets.
...DEPARTMENT OF TRANSPORTATION STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Strength of Materials � 230.28 Higher shearing strength of rivets. A higher shearing strength may be used for rivets when...
49 CFR 230.27 - Maximum shearing strength of rivets.
...DEPARTMENT OF TRANSPORTATION STEAM LOCOMOTIVE INSPECTION AND MAINTENANCE STANDARDS Boilers and Appurtenances Strength of Materials � 230.27 Maximum shearing strength of rivets. The maximum shearing strength of rivets per square...
Interfacial Shear Strength Evaluation of Jute/Poly(Lactic Acid)
In order to evaluate the interfacial shear strength between fiber bundle and matrix of jute/poly(lactic acid) (PLA), a fiber bundle pull-out test method is proposed. Shear stress distribution was calculated based on the parabolic shear-lag analysis. Fiber bundle pull-out tests were conducted to evaluate the effects of molding condition on the interfacial shear strength. The interfacial shear strength increased with increasing molding temperature up to 185�C. Then gradual decrease in the interfacial shear strength with molding temperature was observed. Similar tendency was also observed in the effect of molding time, whereas the interfacial shear strength decreased with increasing molding pressure. Comparing the result of the tensile tests in the previous study, interfacial shear strength has corelations with tensile strength.
Kobayashi, Satoshi; Yamamoto, Tatsuro; Nakai, Asami
Scientific Electronic Library Online (English)
Full Text Available SciELO Mexico | Language: English Abstract in spanish La suavidad de la carne bovina es un rasgo importante para la satisfacci�n del consumidor y es la principal caracter�stica asociada a su palatabilidad, por lo que es importante evaluar su variabilidad en diferentes razas bovinas. Un experimento fue dise�ado para evaluar la Fuerza de Corte de Warner- [...] Bratzler (FCWB) de carne del ojo de la costilla de bovinos Brangus rojos y su aceptabilidad. La suavidad de la carne fue evaluada mediante la FCWB; adem�s, se realiz� una evaluaci�n de preferencia de consumo para estimar cuantitativamente la suavidad, jugosidad, sabor, t�rmino y aceptaci�n general de los cortes evaluados. La media de la FCWB fue 5.03 kg � 0.93 kg, lo que te�ricamente representa una carne dura. En la distribuci�n de las muestras se registraron 21 % y 11 % de cortes, respectivamente, de carne moderadamente suave y suave. La condici�n de los animales (toros o novillos) no fue significativa para la FCWB (p > 0.5). Todas las caracter�sticas evaluadas en la evaluaci�n hed�nica tuvieron alrededor de 6 puntos de un total de 8 (8 era mejor). La suavidad, jugosidad y sabor mostraron una correlaci�n alta y significativa (p Abstract in english Beef tenderness is an important trait in consumer satisfaction and has been considered as the main trait for palatability, for which reason it is important to evaluate its variability in different cattle breeds. An experiment was designed to evaluate the Warner Bratzler Shear Force (WBSF) of Red Bra [...] ngus cattle rib eye steaks and consumer acceptance. The tenderness of beef rib eye steaks was evaluated by the WBSF. A consumer preference evaluation test was carried out to quantitatively estimate tenderness, juiciness, flavor, doneness and general acceptance of the evaluated steaks. Mean WBSF was 5.03 kg � 0.93 kg, theoretically indicating a tough beef. The distribution of the samples showed 21 % and 11 % of moderately tender and tender beef cuts, respectively. Cattle condition (bulls and steers) was not significant for the WBSF (p > 0.5). All the traits evaluated in the hedonic evaluation had approximately 6 points of a total of 8 (8 was best). Tenderness, juiciness and flavor presented a high and significant correlation (p
Gaspar Manuel, Parra-Bracamonte; Ana Mar�a, Sifuentes-Rinc�n; Williams, Arellano-Vera; Juan Gabriel, Maga�a-Monforte; Jos� Alberto, Ram�rez-De Le�n; Gonzalo, Vel�zquez.
High strength semi-active energy absorbers using shear- and mixedmode operation at high shear rates
This body of research expands the design space of semi-active energy absorbers for shock isolation and crash safety by investigating and characterizing magnetorheological fluids (MRFs) at high shear rates ( > 25,000 1/s) under shear and mixed-mode operation. Magnetorheological energy absorbers (MREAs) work well as adaptive isolators due to their ability to quickly and controllably adjust to changes in system mass or impact speed while providing fail-safe operation. However, typical linear stroking MREAs using pressure-driven flows have been shown to exhibit reduced controllability as impact speed (shear rate) increases. The objective of this work is to develop MREAs that improve controllability at high shear rates by using pure shear and mixed shear-squeeze modes of operation, and to present the fundamental theory and models of MR fluids under these conditions. A proof of concept instrument verified that the MR effect persists in shear mode devices at shear rates corresponding to low speed impacts. This instrument, a concentric cylinder Searle cell magnetorheometer, was then used to characterize three commercially available MRFs across a wide range of shear rates, applied magnetic fields, and temperatures. Characterization results are presented both as flow curves according to established practice, and as an alternate nondimensionalized analysis based on Mason number. The Mason number plots show that, with appropriate correction coefficients for operating temperature, the varied flow curve data can be collapsed to a single master curve. This work represents the first shear mode characterization of MRFs at shear rates over 10 times greater than available with commercial rheometers, as well as the first validation of Mason number analysis to high shear rate flows in MRFs. Using the results from the magnetorheometer, a full scale rotary vane MREA was developed as part of the Lightweight Magnetorheological Energy Absorber System (LMEAS) for an SH-60 Seahawk helicopter crew seat. Characterization tests were carried out on the LMEAS using a 40 vol% MRF used in the previous magnetorheometer tests. These were analyzed using both flow curves and apparent viscosity vs. Mason number diagrams. The nondimensionalized Mason number analysis resulted in data for all conditions of temperature, fluid composition, and shear rate, to collapse onto a single characteristic or master curve. Significantly, the temperature corrected Mason number results from both the bench top magnetorheometer and full scale rotary vane MREA collapse to the same master curve. This enhances the ability of designers of MRFs and MREAs to safely and effectively apply characterization data collected in low shear rate, controlled temperature environments to operational environments that may be completely different. Finally, the Searle cell magnetorheometer was modified with an enforced eccentricity to work in both squeeze and shear modes simultaneously to achieve so called squeeze strengthening of the working MRF, thereby increasing the apparent yield stress and the specific energy absorption. By squeezing the active MR fluid, particles undergo compression-assisted aggregation into stronger, more robust columns which resist shear better than single chains. A hybrid model describing the squeeze strengthening behavior is developed, and recommendations are made for using squeeze strengthening to improve practical MREA devices.
Becnel, Andrew C.
Collision statistics in sheared inelastic hard spheres.
The dynamics of sheared inelastic-hard-sphere systems is studied using nonequilibrium molecular-dynamics simulations and direct simulation Monte Carlo. In the molecular-dynamics simulations Lees-Edwards boundary conditions are used to impose the shear. The dimensions of the simulation box are chosen to ensure that the systems are homogeneous and that the shear is applied uniformly. Various system properties are monitored, including the one-particle velocity distribution, granular temperature, stress tensor, collision rates, and time between collisions. The one-particle velocity distribution is found to agree reasonably well with an anisotropic Gaussian distribution, with only a slight overpopulation of the high-velocity tails. The velocity distribution is strongly anisotropic, especially at lower densities and lower values of the coefficient of restitution, with the largest variance in the direction of shear. The density dependence of the compressibility factor of the sheared inelastic-hard-sphere system is quite similar to that of elastic-hard-sphere fluids. As the systems become more inelastic, the glancing collisions begin to dominate over more direct, head-on collisions. Examination of the distribution of the times between collisions indicates that the collisions experienced by the particles are strongly correlated in the highly inelastic systems. A comparison of the simulation data is made with direct Monte Carlo simulation of the Enskog equation. Results of the kinetic model of Montanero [J. Fluid Mech. 389, 391 (1999)] based on the Enskog equation are also included. In general, good agreement is found for high-density, weakly inelastic systems. PMID:19518225
Bannerman, Marcus N; Green, Thomas E; Grassia, Paul; Lue, Leo
Spurious Shear in Weak Lensing with LSST
Energy Technology Data Exchange (ETDEWEB)
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
Nonlinear stability of relativistic sheared planar jets
The linear and non-linear stability of sheared, relativistic planar jets is studied by means of linear stability analysis and numerical hydrodynamical simulations. Our results extend the previous Kelvin-Hemlholtz stability studies for relativistic, planar jets in the vortex sheet approximation performed by Perucho et al. (2004a, A&A, 427, 415; 2004b, A&A, 427, 431) by including a shear layer between the jet and the external medium and more general perturbations. The models considered span a wide range of Lorentz factors (2.5-20) and internal energies (0.08 c^2-60 c^2) and are classified into three classes according to the main characteristics of their long-term, non-linear evolution. We observe a clear separation of these three groups in a relativistic Mach-number Lorentz-factor plane. Jets with a low Lorentz factor and small relativistic Mach number are disrupted after saturation. Those with a large Lorentz factor and large relativistic Mach number are the stablest, due to the appearance of short wavelength resonant modes which generate local mixing and heating in the shear layer around a fast, unmixed core, giving a plausible solution for the problem of the long-term stability of relativistic jets. A third group is present between them, including jets with intermediate values of Lorentz factor and relativistic Mach number, which are disrupted by a slow process of mixing favored by an efficient and continuous conversion of kinetic into internal energy. In the long term, all the models develop a distinct transversal structure (shear/transition layers) as a consequence of KH perturbation growth, depending on the class they belong to. The properties of these shear layers are analyzed in connection with the parameters of the original jet models.
Perucho, M.; Mart�, J. M.; Hanasz, M.
Assessing the strength of existing structures has become a major issue for structural engineers. Such analyses are often performed after changes of use of the structure or due to new design codes requirements. This is particularly relevant with respect to the shear strength of post-tensioned concrete bridges. Such structures were often designed in the past with fairly low amounts of shear reinforcement and do not comply with current code requirements in terms of amount of transverse reinforce...
Rupf, Michael; Ferna?ndez Ruiz, Miguel; Muttoni, Aurelio
Local Stress Relaxation and Shear-banding in a Dry Foam under Shear
We have developed a realistic simulation of 2D dry foams under quasi-static shear. After a short transient, a shear-banding instability is observed. These results are compared with measurements obtained on real 2D (confined) foams. The numerical model allows us to exhibit the mechanical response of the material to a single plastication event. From the analysis of this elastic propagator, we propose a scenario for the onset and stability of the flow localization process in fo...
Kabla, Alexandre; Debregeas, Georges
Rate dependent shear bands in a shear transformation zone model of amorphous solids
We use Shear Transformation Zone (STZ) theory to develop a deformation map for amorphous solids as a function of the imposed shear rate and initial material preparation. The STZ formulation incorporates recent simulation results [Haxton and Liu, PRL 99 195701 (2007)] showing that the steady state effective temperature is rate dependent. The resulting model predicts a wide range of deformation behavior as a function of the initial conditions, including homogeneous deformation...
Manning, M. L.; Daub, E. G.; Langer, J. S.; Carlson, J. M.
Turbulent transport across shear layers in magnetically confined plasmas
Energy Technology Data Exchange (ETDEWEB)
Shear layers modify the turbulence in diverse ways and do not only suppress it. A spatial-temporal investigation of gyrofluid simulations in comparison with experiments allows to identify further details of the transport process across shear layers. Blobs in and outside a shear layer merge, thereby exchange particles and heat and subsequently break up. Via this mechanism particles and heat are transported radially across shear layers. Turbulence spreading is the immanent mechanism behind this process.
Nold, B.; Ramisch, M. [Institut f�r Grenzfl�chenverfahrenstechnik und Plasmatechnologie, Universit�t Stuttgart, D-70569 Stuttgart (Germany); Manz, P.; Birkenmeier, G. [Physik-Department E28, Technische Universit�t M�nchen, James-Franck-Str.1, D-85748 Garching (Germany); Max-Planck-Institut f�r Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Ribeiro, T. T.; M�ller, H. W.; Scott, B. D. [Max-Planck-Institut f�r Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Fuchert, G. [IJL, Universit� de Lorraine, CNRS (UMR 7198), BP 40239 Vandoeuvre-l�s-Nancy (France); Stroth, U. [Max-Planck-Institut f�r Plasmaphysik, Boltzmannstr. 2, D-85748 Garching (Germany); Physik-Department E28, Technische Universit�t M�nchen, James-Franck-Str.1, D-85748 Garching (Germany)
Effects of test conditions on shear behaviour of composite soil
Test conditions, such as shearing rate and normal stress, have been long recognised as influencing the measured shear strength of clays and sands. However, their influence on composite soils, which have a wide range of particle sizes, has attracted much less attention from researchers. In this study, a total of 35 direct shear tests at different shearing rates under different normal stresses were conducted on specimens prepared by mixing different proportions of kaolin and glass beads. The ch...
Xiang, X.; Li, Y.; Chan, Ls; Yeung, At
Hysteresis and Lubrication in Shear Thickening of Cornstarch Suspensions
Aqueous and brine suspensions of corn starch show striking discontinuous shear thickening. We have found that a suspension shear-thickened throughout may remain in the jammed thickened state as the strain rate is reduced, but an unjamming front may propagate from any unjammed regions. Transient shear thickening is observed at strain rates below the thickening threshold, and above it the stress fluctuates. The jammed shear-thickened state may persist to low strain rates, with...
Chu, Clarence E.; Groman, Joel A.; Sieber, Hannah L.; Miller, James G.; Okamoto, Ruth J.; Katz, Jonathan I.
Turbulent transport in tokamak plasmas with rotational shear
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E�B shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcati...
Barnes, M.; Parra, Fi; Highcock, Eg; Schekochihin, Aa; Cowley, Sc; Roach, Cm
Chaotic Dynamics in Shear-thickening Surfactant Solutions
We report the observation of dynamical behaviour in dilute, aqueous solutions of a surfactant CTAT (cetyl trimethylammonium p-toluenesulphonate), below the overlap concentration c$^{\\star}$. At these concentrations, CTAT forms cylindrical micelles and shows a pronounced shear thickening transition above a concentration-dependent critical shear rate $\\dot\\gamma_{c}$. An analysis of the time-series of the stress relaxations at controlled shear rates in the shear-thickening reg...
Bandyopadhyay, Ranjini; Sood, A. K.
Interface shear and pressure characteristics of wheelchair seat cushions
Pressure ulcer incidence rates have remained constant despite advances in support surface technology. Interface shear stress is recognized as a risk factor for pressure ulcer development and is the focus of many shear reduction technologies incorporated into wheelchair cushions; however, shear reduction has not been quantified in the literature. We evaluated 21 commercial wheelchair seat cushions using a new methodology developed to quantify interface shear stress, interface pressure, and hor...
Akins, Jonathan S.; Patricia E Karg, Ms; David M Brienza, Phd
Shear strength of rock joints based on quantified surface description
One of the primary objectives of this work is to better understand the frictional behavior of joints under shear loads, including the creation of damage zones. Discontinuities have an important influence on the deformational behavior of rock systems. The choice of a general criterion to determine the shear strength of rough rock joints is a general problem that has been investigated for many years. Numerous shear models have been proposed in the last decades to relate shear-strength to measur...
Grasselli, Giovanni
Band crossing in Shears band of $^{108}$Cd
The level lifetimes have been measured for a Shears band of $^{108}$Cd which exhibits bandcrossing. The observed level energies and B(M1) rates have been successfully described by a semi-classical geometric model based on shear mechanism. In this geometric model, the bandcrossing in Shears band has been described as the reopening of the angle between the blades of a shear.
Roy, Santosh; Datta, Pradip; Pal, S.; Chattopadhyay, S.; Bhattacharya, S.; Goswami, A.; Jain, H. C.; Joshi, P. K.; Bhowmik, R. K.; Kumar, R.; Muralithar, S.; Singh, R. P.; Madhavan, N.; Rao, P. V. Madhusudhana
Shear strengthening of RC beams with high performance jacket
The possibility of strengthening RC elements for increasing the bearing capacity under shear actions is an important issue in the retrofitting field. In RC existing structures, made in the �60s and �70s, the shear reinforcement is often not sufficient to satisfy the prescription of current codes. Hence, in the xc0020retrofitting of these structures it is often necessary to increase the shear bearing capacity. A possible use of low thickness high performance jackets for shear strengthen...
Mostosi, Serena; Riva, Paolo; Maringoni, S.; Meda, Alberto
Punching shear strength of reinforced concrete slabs without transverse reinforcement
A mechanical explanation of the phenomenon of punching shear in slabs without transverse reinforcement is presented on the basis of the opening of a critical shear crack. It leads to the formulation of a new failure criterion for punching shear based on the rotation of a slab. This criterion correctly describes punching shear failures observed in experimental testing, even in slabs with low reinforcement ratios. Its application requires the knowledge of the load-rotation relationship of the s...
Muttoni, Aurelio
Shear Capacity of Concrete Beams under Sustained Loading:
Long-term tests on large-scale concrete beams without shear reinforcement, which are tested for more than two years under sustained loading close to the ultimate shear capacity (load ratio ranging from 87% to 95%) under climate controlled condition, show that sustained loading has no significant effect on the shear capacity. Although many flexural and shear cracks develop, the beams carry the load for a long time. The tests show that crack formation takes place only within some days after the...
Sarkhosh, R.; Walraven, J. C.; Den Uijl, J. A.; Braam, C. R.
Shear Reinforcement Requirements for High-Strength Concrete Bridge Girders
A research program was conducted on the shear strength of high-strength concrete members. The objective was to evaluate the shear behavior and strength of concrete bridge members with compressive strengths in the range of 10 000 to 15 000 psi. The goal was to determine if the current minimum amount of shear reinforcement together with maximum spacing limits in the 2004 AASHTO LRFD Specifications, and the upper limit on the nominal shear strength were applicable to concrete compressive strengt...
Ramirez, J. A.; Aguilar, Gerardo
A bilateral shear layer between two parallel Couette flows
We consider a shear layer of a kind not previously studied to our knowledge. Contrary to the classical free shear layer, the width of the shear zone does not vary in the streamwise direction but rather exhibits a lateral variation. Based on some simplifying assumptions, an analytic solution has been derived for the new shear layer. These assumptions have been justified by a comparison with numerical solutions of the full Navier-Stokes equations, which accord with the analyti...
Narasimhamurthy, Vagesh D.; Ellingsen, Simen A?; Andersson, Helge I.
Dynamic pore-pressure fluctuations in rapidly shearing granular materials.
Results from two types of experiments show that intergranular pore pressures fluctuated dynamically during rapid, steady shear deformation of water-saturated granular materials. During some fluctuations, the pore water locally supported all normal and shear stresses, while grain-contact stresses transiently fell to zero. Fluctuations also propagated outward from the shear zone; this process modifies grain-contact stresses in adjacent areas and potentially instigates shear-zone growth. PMID:17748707
Iverson, R M; Lahusen, R G
We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.
L�pez-Barr�n, Carlos R.; Gurnon, A. Kate; Eberle, Aaron P. R.; Porcar, Lionel; Wagner, Norman J.
Fluid Effects on Shear Waves in Finely Layered Porous Media
International Nuclear Information System (INIS)
Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity
Fluid Effects on Shear Waves in FInely Layered Porous Media
Energy Technology Data Exchange (ETDEWEB)
Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity.
Berryman, J G
49 CFR 178.338-12 - Shear section.
...2010-10-01 2010-10-01 false Shear section. 178.338-12 Section 178...Vehicle Transportation � 178.338-12 Shear section. Unless the valve is located...of liquid or vapor, must incorporate a shear section or breakage groove adjacent...
Directory of Open Access Journals (Sweden)
Full Text Available Square-plate twist (SPT tests were conducted to measure the shear modulus and shear strength using the method, which was a modification of the International Organization for Standardization (ISO 15310 standardized method. In the SPT test, the length/thickness ratio varied. In addition, asymmetric four-point bending (AFPB tests were conducted, and the shear modulus and shear strength obtained were compared with those obtained by the SPT tests. The shear modulus was obtained effectively by the SPT test when the specimen was thin enough. Although the shear strength was evaluated as higher than that obtained by the AFPB tests, it might be regarded as an apparent value of shear strength when the range of length/thickness is limited. To obtain the actual shear strength by the SPT test, some modification of the equation is required.
Hiroshi Yoshihara
International Nuclear Information System (INIS)
The shear strength of NSC (Normal Strength Concrete) has been extensively researched. However, very little data is available on the shear strength of HSC beams for fc > 6000 psi (40MPa). In this research, 35 beams with five values of longitudinal steel and seven values of shear span to depth (aid) ratio have been tested to study the effect of longitudinal steel and shear span to depth ratio. The results have been compared with the provisions of ACI 318-06 as well. The results have shown that shear failure is anticipated when the longitudinal steel ratio for p > 1 %. The shear strength of HSC normally increases with the increase of longitudinal steel and decreases with the increase in shear span to depth ratio, as exhibited in normal strength, but the failure is more sudden and brittle. The ACI 318 provisions for shear strength of beams are normally good predictors but for a/d >5. (author)
This dissertation introduces the MODES "method of detecting simple-shear," which is specifically designed for extracting the amount and preferred orientation of simple-shear from the deformation-gradient and velocity-gradient tensors. Because simple-shear is diagnostic of shear zones and faults, and the Global Positioning System (GPS) is used in tectonic studies to determine the deformation-gradient or velocity-gradient tensor, this study provides improvements and extensions to existing analy...
Griffiths, Jake
Shear capacity of high-strength concrete beams with their point of inflection within the shear span
The shear strength of concrete does not increase in proportion with the concrete grade. Thus, when high-strength concrete is used in place of normal-strength concrete, the shear capacity of the structure could become critical. In the study presented, the effect of concrete strength on the shear capacity of concrete beams was investigated. As previous research on normal-strength concrete beams has shown that the presence of an inflection point within the shear span can significantly influence ...
Islam, Ms; Pam, Hj; Kwan, Akh
We carried out pointwise local velocity measurements on 40mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system sho...
Herle, Vishweshwara; Manneville, Se?bastien; Fischer, Peter
Controlling dump combustor flows using countercurrent shear
Countercurrent shear flow control is being established as an effective technique for enhancing turbulence and mixing in various turbulent flows. The basic features of the countercurrent shear layer, including the high levels of turbulence and large turbulent structures, suggest that the technique has vast potential for enhancing combustion. With this as motivation, a novel countercurrent dump combustor was designed and tested under cold flow conditions to study the potential benefits of using counterflow for controlling combustion flows. The countercurrent dump combustor is a suction based system which induces a suction counterflow through a variable height gap at the sudden expansion dump plane. The control technique performed well, as peak turbulence levels, cross-stream averaged turbulent kinetic energy, and cross-stream momentum diffusion increased with applied suction. The countercurrent dump combustor operates via two mechanisms: enhanced global recirculation and near field control of the separated shear layer. In general, the enhanced recirculation is a modulation of the natural recirculation bubble which exists with the confined separated flow, and is predominantly sensitive to the suction mass flow rate. The near field dynamics of the separated shear layer is modulated through the development of a countercurrent shear layer near the separation point, and is governed by the velocity ratio near the dump plane. The use of counterflow also produces larger structures, which alleviates the high strain rates caused by the increased turbulent energy. This result will allow for increased burning rates without the detrimental effects of strain induced flame stretch. This is a significant advantage over the conventional dump combustor. The turbulence is also highly three-dimensional with counterflow, which will allow for control of thermo-acoustic instabilities through disruption of spanwise coherence. The observations of the cold flow study of the countercurrent dump combustor suggest that there will be multiple benefits for using countercurrent shear control in reacting flows. Future studies will be conducted on the countercurrent dump combustor under conditions of premixed combustion. Expected benefits include enhanced combustion, increased volumetric heat release, and reduced thermo-acoustic instabilities.
Forliti, David John
Inherent Rheology of a Granular Fluid in Uniform Shear Flow
In contrast to normal fluids, a granular fluid under shear supports a steady state with uniform temperature and density since the collisional cooling can compensate locally for viscous heating. It is shown that the hydrodynamic description of this steady state is inherently non-Newtonian. Differing degrees of inelasticity sample the complete nonlinear dependence of the shear viscosity on the shear rate. As a consequence, the Newtonian shear viscosity cannot be determined from experiments or simulation of uniform shear flow. The relationship to the Chapman-Enskog method to derive hydrodynamics is clarified using an exactly solvable kinetic model.
Santos, A; Dufty, J W
Origin of strain localization in sheared amorphous solids
A two dimensional amorphous material is modeled as an assembly of mesoscopic elemental pieces coupled together to form an elastically coherent structure. Plasticity is introduced as the existence of different minima in the energy landscape of the elemental constituents. Adding structural relaxation, it is shown that the model predicts homogeneous deformation at large shear rates, shear bands when the shear rate is reduced, and stick-slip-like motion at the shear bands for the lowest shear rates. Increase of dynamical yield stress with sample age is also observed.
Jagla, E A
Flows induced by flat surfaces sheared in their own plane
International Nuclear Information System (INIS)
Exact steady solutions of the Navier�Stokes equations for fluid flow induced by flat plates executing uniform or nonuniform shearing motion in their own plane are reported. In several cases uniform transpiration through the plate is required for existence of solutions. Solutions combining plate shear with plate stretching are also given. It is shown that hyperbolic shearing motion can give rise to damped oscillatory fluid motion above the plate while simple and spatially periodic shearing motions do not. This is interpreted as waves traveling on vertically attenuated vortex lines set up in the fluid when the hyperbolic shear is sufficiently strong. (paper)
A shear-flow instability relevant to advanced tokamak operation
International Nuclear Information System (INIS)
An ideal magnetohydrodynamic instability which is driven by sheared flow and which may be relevant to reversed-shear advanced tokamak operation is described. If there is flow shear at the qmin surface, relatively weak velocity shear can driven this instability, with a time scale of the flow. The flows may be significantly slower than the ambient poloidal Alfven velocity, and no inflection point is needed. Thus the time scale of the instability may be significantly longer than that of the poloidal Alfven transit time, and it might account for disruption of reversed-shear discharges recently observed in JT-60U. (author)
Shear zones in granular media: 3D Contact Dynamics simulation
Shear zone formation is investigated in slow 3D shear flows. We simulate the linear version of the split-bottom shear cell. It is shown that the same type of wide shear zones is achieved in the presence as well as in the absence of gravity. We investigate the relaxation of the material towards a stationary flow and analyze the stress and the velocity fields. We provide the functional form of the widening of the shear zone inside the bulk. We discuss the growth of the region ...
Ries, Alexander; Unger, Tamas; Wolf, Dietrich E.
Shear banding during cyclic deformation of sub-microcrystalline nickel
International Nuclear Information System (INIS)
Sub-microcrystalline nickel produced by pulsed electrodeposition was investigated during cyclic deformation at high plastic strain amplitude. After a certain number of loading cycles the specimen developed a 'macro' shear band at 45o with respect to the tensile axis, which acted as a crack initiator. Electron backscatter diffraction revealed that the shear band consists of relaxed grains elongated along the shear plane, showing a typical shear texture. The shear band texture was reproduced with the viscoplastic self-consistent polycrystal model using {1 1 1} slip systems.
Cosmic shear full nulling: sorting out dynamics, geometry and systematics
An explicit full nulling scheme for cosmic shear observations is presented. It makes possible the construction of shear maps from extended source distributions for which the lens distance distribution is restricted to a definite interval. Such a construction allows us to build totally independent shear maps, at all scales, that can be taken advantage of to constrain background cosmological parameters and systematics using the full statistical power of cosmic shear observations. Another advantage of such construction is that, as the lens redshift distribution can be made arbitrarily narrow, scale mixing due to projection effects can be limited allowing controlled predictions on the large-scale shear power spectrum from perturbation theory calculations.
Bernardeau, Francis; Nishimichi, Takahiro; Taruya, Atsushi
Velocity profiles in shear-banding wormlike micelles
Using Dynamic Light Scattering in heterodyne mode, we measure velocity profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to exhibit both shear-banding and stress plateau behavior. Our data provide evidence for the simplest shear-banding scenario, according to which the effective viscosity drop in the system is due to the nucleation and growth of a highly sheared band in the gap, whose thickness linearly increases with the imposed shear rate. We discuss various details of the velocity profiles in all the regions of the flow curve and emphasize on the complex, non-Newtonian nature of the flow in the highly sheared band.
Salmon, J B; Manneville, S; Molino, F; Salmon, Jean-Baptiste; Colin, Annie; Manneville, Sebastien; Molino, Francois
Fiber optic plantar pressure/shear sensor
A full-scale foot pressure/shear sensor that has been developed to help diagnose the cause of ulcer formation in diabetic patients is presented. The design involves a tactile sensor array using intersecting optical fibers embedded in soft elastomer. The basic configuration incorporates a mesh that is comprised of two sets of parallel optical fiber plane; the planes are configured so the parallel rows of fiber of the top and bottom planes are perpendicular to each other. Threedimensional information is determined by measuring the loss of light from each of the waveguide to map the overall pressure distribution and the shifting of the layers relative to each other. In this paper we will present the latest development on the fiber optic plantar pressure/shear sensor which can measure normal force up from 19.09 kPa to 1000 kPa.
Soetanto, William; Nguyen, Ngoc T.; Wang, Wei-Chih
Drop impact of shear thickening liquids
The impact of drops of concentrated non-Brownian suspensions (cornstarch and polystyrene spheres) onto a solid surface is investigated experimentally. The spreading dynamics and maxi- mal deformation of the droplet of such shear thickening liquids are found to be markedly different from the impact of Newtonian drops. A particularly striking observation is that the maximal de- formation is independent of the drop velocity and that the deformation suddenly stops during the impact phase. Both observations are due to the shear-thickening rheology of the suspensions, as is theoretically explained from a balance between the kinetic energy and the viscously-dissipated en- ergy, from which we establish a scaling relation between drop maximal deformation and rheological parameters of concentrated suspensions.
Boyer, Francois; Dijksman, J Frits; Lohse, Detlef
Search for shears mechanism in 142Sm
International Nuclear Information System (INIS)
Generation of angular momentum in weakly deformed nuclei by shears mechanism is a well known phenomenon in nuclear structure physics. During the last two decades, rotational-like bands consisting of dipole transitions have been observed systematically near the spherical region and interpreted as Magnetic Rotor. In this mechanism the total angular momentum along the band is generated by the gradual alignment of the two angular momentum blades and the shears arrangement of the high j orbital give rise to a large transverse magnetic dipole moment. In the present INGA experiments at TIFR, the level structure of 141,142Sm is studied in order to look for the possible observation of magnetic and anti magnetic rotational bands by measuring the life time of the excited states using DSAM technique
Shear-Induced Mixing in Polymer Blends
The effect of shear flow on phase separation in critical polymer blends is reviewed. For a low-molecular-weight blend, the response is in good agreement with the theoretical predictions of Onuki and Kawasaki. The break-up of large-scale critical fluctuations by the flow leads to a drop in the temperature Tc at which phase separation begins. For a high-molecular-weight blend, the data suggest that the mode-coupling contribution to the decay rate of composition fluctuations is significant in both the miscible and immiscible phases. No shear-induced shift in Tc is apparent at any temperature in the one-phase region away from the equilibrium critical point, consistent with mean-field statics.
Hobbie, Erik K.; Nakatani, Alan I.; Han, Charles C.
Shear coalescence studies of compatibilized polymer blends
The suppression or retardation of droplet coalescence during shear flow has become one way to assess the effectiveness of compatibilization in polymer blends. Such studies have typically been performed on immiscible blends to which pre-made block copolymer is added as a compatibilizing agent. In this work, we explore immiscible blends that have been compatibilized using solid-state shear pulverization. Recent research in the Torkelson lab at Northwestern has demonstrated that chain scission and recombination during pulverization can lead to in situ formation of block copolymers. In this work, we study immiscible blends of polystyrene and polypropylene. Chain scission during pulverization of individual homopolymers leads to reductions in viscosity and elasticity. We compare the coalescence behavior in blends that have been co-pulverized to those which have been simply physically mixed.
Brinker, Kristin; Burghardt, Wesley
Shear bond strengths of new enamel etchants.
Many dental adhesive systems now rely on simultaneous etching of enamel and dentin. Instead of the traditional 35-40% phosphoric acid, new etchants (including 10% maleic acid, 10% phosphoric acid, and oxalic acid/aluminum nitrate) are used. This in vitro study determined the shear bond strengths of resin composite to enamel which was etched with these agents according to manufacturers' instructions. The control etchant, 35% phosphoric acid, gave a mean bond strength of 24.5 MPa. 10% maleic acid and 10% phosphoric acid had significantly lower shear bond strengths (13.2 MPa). Gluma 1 & 2 Conditioner (oxalic acid/aluminum nitrate) had a mean bond strength of 6.3 MPa, which was significantly less than the other etchants. Bond strengths for each etchant were not affected by the type of unfilled resin used. PMID:8240781
Swift, E J; Cloe, B C
Shear and Compression Viscoelasticity in Polymer Monolayers
Poly-vinlyacetate (PVAc) forms very stable and reproducible monolayers on the surface of water, a model system to understand polymer physics on two dimensions. A recently introduced technique is applied here to to study viscoelasticity of PVAc monolayers. The method is based on measurement of surface tension in two orthogonal directions during anisotropic deformation. Compression and shear moduli are explored over a very large concentration range, highlighting a series of four different regimes. At low concentration the polymers are in a dilute gas. Above the overlap concentration $\\Gamma^\\ast$ there is a fluid semi-dilute region, where the monolayer properties are described by scaling laws. At a threshold concentration $\\Gamma^{\\ast\\ast}$, a decrease in the gradient of pressure with concentration is observed, and we argue that there is still a large fraction of free area on the surface. Compressing further, we then identify close packing as the point where the pressure gradient rises sharply and a shear modu...
Ferenczi, T A M; Ferenczi, Toby A. M.; Cicuta, Pietro
Shear Viscosity in a CFL Quark Star
We compute the shear viscosity in the color-flavor locked (CFL) phase of dense quark matter at low temperature T. Then the contributions of mesons, quarks and gluons to the transport coefficients are Boltzmann suppressed. CFL quark matter displays superfluid properties, and transport phenomena in such cold regime are dominated by phonon-phonon scattering. We study phonons within thermal field theory and compute the mean free path associated to their most relevant collision processes. While the mean free path relevant for shear viscosity usually concerns large-angle collisions, small-angle processes turn out to be more efficient for transport phenomena in the CFL matter. We find the same T-dependence for the phonon damping rate and mean free path as for that of superfluid He4. Our results are relevant for the study of rotational properties of compact stars, and correct wrong estimates existing in the literature.
Manuel, C; Llanes-Estrada, F J; Manuel, Cristina; Dobado, Antonio; Llanes-Estrada, Felipe J.
Direct measurement of shear properties of microfibers
As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar� 119, were also characterized with this system and were found to have G = 16.5 � 2.1 and 2.42 � 0.32 GPa, respectively.
Behlow, H.; Saini, D.; Oliveira, L.; Durham, L.; Simpson, J.; Serkiz, S. M.; Skove, M. J.; Rao, A. M.
Static inelastic analysis of RC shear walls
A macro-model of a reinforced concrete (RC) shear wall is developed for static inelastic analysis. The model is composed of RC column elements and RC membrane elements. The column elements are used to model the boundary zone and the membrane elements are used to model the wall panel. Various types of constitutive relationships of concrete could be adopted for the two kinds of elements. To perform analysis, the wall is divided into layers along its height. Two adjacent layers are connected with a rigid beam. There are only three unknown displacement components for each layer. A method called single degree of freedom compensation is adopted to solve the peak value of the capacity curve. The post-peak stage analysis is performed using a forced iteration approach. The macro-model developed in the study and the complete process analysis methodology are verified by the experimental and static inelastic analytical results of four RC shear wall specimens.
Chen, Qin; Qian, Jiaru
Turbulent Shear Layers in Supersonic Flow
A good understanding of turbulent compressible flows is essential to the design and operation of high-speed vehicles. Such flows occur, for example, in the external flow over the surfaces of supersonic aircraft, and in the internal flow through the engines. Our ability to predict the aerodynamic lift, drag, propulsion and maneuverability of high-speed vehicles is crucially dependent on our knowledge of turbulent shear layers, and our understanding of their behavior in the presence of shock waves and regions of changing pressure. Turbulent Shear Layers in Supersonic Flow provides a comprehensive introduction to the field, and helps provide a basis for future work in this area. Wherever possible we use the available experimental work, and the results from numerical simulations to illustrate and develop a physical understanding of turbulent compressible flows.
Smits, Alexander J
Stochastically driven instability in rotating shear flows
Origin of hydrodynamic turbulence in rotating shear flows is investigated. The particular emphasis is the flows whose angular velocity decreases but specific angular momentum increases with increasing radial coordinate. Such flows are Rayleigh stable, but must be turbulent in order to explain observed data. Such a mismatch between the linear theory and observations/experiments is more severe when any hydromagnetic/magnetohydrodynamic instability and then the corresponding turbulence therein is ruled out. The present work explores the effect of stochastic noise on such hydrodynamic flows. We essentially concentrate on a small section of such a flow which is nothing but a plane shear flow supplemented by the Coriolis effect. This also mimics a small section of an astrophysical accretion disk. It is found that such stochastically driven flows exhibit large temporal and spatial correlations of perturbation velocities, and hence large energy dissipations of perturbation, which presumably generate instability. A ra...
Mukhopadhyay, Banibrata
Undulatory swimming in shear-thinning fluids
The swimming behaviour of microorganisms can be strongly influenced by the rheology of their fluid environment. In this manuscript, we experimentally investigate the effects of shear-thinning viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer's kinematic data (including propulsion speed) and velocity fields. We find that shear-thinning viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode's speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation, and an increase in fluid velocity near the nematode's tail, compared to Newtonian fluids of similar effective viscosity. These findings are in good agreement with recent theoretical and numerical results.
Gagnon, David A; Arratia, Paulo E
Fragility assessment of containment tangential shear failure
Energy Technology Data Exchange (ETDEWEB)
This paper presents a fragility analysis method for concrete containments with respect to tangential shear limit state. The tangential shear limit state for reinforced concrete containments is described in detail. In addition, a Latin hypercube sampling technique is employed to include the variations of material strengths into the fragility analysis. The fragility curve for an actual reinforced concrete containment in the US is generated to illustrate the fragility analysis method. The structures and components used in nuclear power plants are conservatively designed; as a result, the limit state probability is extremely small and sensitive to various assumptions. Thus, the proposed fragility assessment techniques should be able to predict a reliable lower tail region of the fragility curve. In addition, it should be verifiable. However, it is recognized that a rigorous fragility analysis for structures and components is extremely complicated. Thus, a simplified but yet realistic fragility analysis method is needed for practical purposes. (author).
Hwang, H.H.M. (Memphis State Univ., TN (USA)); Pepper, S.E. (Brookhaven National Lab., Upton, NY (USA)); Chokshi, N.C. (Nuclear Regulatory Commission, Washington, DC (USA). Office of Nuclear Regulatory Research)
Mixing control in a plane shear layer
An investigation of mixing processes in a plane shear layer by a direct numerical simulation with a high-order numerical technique, the isoparametric spectral element method, is presented. The computational domain includes a region with the splitter plate that allows to start the flow as a laminar (Blasius) boundary layers with different velocities and concentrations, merging in the shear layer and undergoing transition to highly-unsteady structures with intensive mixing. The augmentation of mixing as a function of a downstream location, the intensity and type of vortical structures in the layer is investigated by an introduction of disturbance at the high-velocity inflow. The character of the dynamic mixing is displayed along with time averaged profiles and statistical characteristics.
Korczak, K. Z.; Wessel, R. A.
Shear-bulk coupling in nonconformal hydrodynamics
We compute the temporal evolution of the pressure anisotropy and bulk pressure of a massive gas using second-order viscous hydrodynamics and anisotropic hydrodynamics. We then compare our results with an exact solution of the Boltzmann equation for a massive gas in the relaxation time approximation. We demonstrate that, within second-order viscous hydrodynamics, the inclusion of the full set of kinetic coefficients, particularly the shear-bulk couplings, is necessary to properly describe the time evolution of the bulk pressure. We also compare the results of second-order hydrodynamics with those obtained using the anisotropic hydrodynamics approach. We find that anisotropic hydrodynamics and second-order viscous hydrodynamics including the shear-bulk couplings are both able to reproduce the exact evolution with comparable accuracy.
Denicol, Gabriel S; Ryblewski, Radoslaw; Strickland, Michael
Shear-bulk coupling in nonconformal hydrodynamics
We compute the temporal evolution of the pressure anisotropy and bulk pressure of a massive gas using second-order viscous hydrodynamics and anisotropic hydrodynamics. We then compare our results with an exact solution of the Boltzmann equation for a massive gas in the relaxation time approximation. We demonstrate that, within second-order viscous hydrodynamics, the inclusion of the full set of kinetic coefficients, particularly the shear-bulk couplings, is necessary to properly describe the time evolution of the bulk pressure. We also compare the results of second-order hydrodynamics with those obtained using the anisotropic hydrodynamics approach. We find that anisotropic hydrodynamics and second-order viscous hydrodynamics including the shear-bulk couplings are both able to reproduce the exact evolution with comparable accuracy.
Denicol, Gabriel S.; Florkowski, Wojciech; Ryblewski, Radoslaw; Strickland, Michael
Shear instabilities in shallow-water magnetohydrodynamics
Within the framework of shallow-water magnetohydrodynamics, we investigate the linear instability of horizontal shear flows, influenced by an aligned magnetic field and stratification. Various classical instability results, such as H{\\o}iland's growth rate bound and Howard's semi-circle theorem, are extended to this shallow-water system for quite general profiles. Two specific piecewise-constant velocity profiles, the vortex sheet and the rectangular jet, are studied analytically and asymptotically; it is found that the magnetic field and stratification (as measured by the Froude number) are generally both stabilising, but weak instabilities can be found at arbitrarily large Froude number. Numerical solutions are computed for corresponding smooth velocity profiles, the hyperbolic-tangent shear layer and the Bickley jet, for a uniform background field. A generalisation of the long-wave asymptotic analysis of Drazin & Howard (1962) is employed in order to understand the instability characteristics for both ...
Mak, Julian; Hughes, D W
Direct measurement of shear properties of microfibers.
As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar(�) 119, were also characterized with this system and were found to have G = 16.5 � 2.1 and 2.42 � 0.32 GPa, respectively. PMID:25273783
Behlow, H; Saini, D; Oliveira, L; Durham, L; Simpson, J; Serkiz, S M; Skove, M J; Rao, A M
Brownian forces in sheared granular matter
The response of granular matter to a slow applied shear is erratic and intermittent, the so called "stick-slip" motion. In this state, observable quantities can display power law statistics in common with many other phenomena ranging from solid-on-solid friction to earthquakes, suggesting analogies between such different phenomena. Here we present results from a series of experiments on a granular medium sheared in a Couette geometry and show that their statistical properties can be computed in a quantitative way from the assumption that the resultant from the set of forces acting in the system performs a Brownian motion. The same assumption has been utilised, with success, to describe other phenomena, such as the Barkhausen effect in ferromagnets, and so the scheme suggests itself as a more general description of a wider class of driven instabilities.
Baldassarri, A; Petri, A; Zapperi, S; Pontuale, G; Pietronero, L; Baldassarri, Andrea; Dalton, Fergal; Petri, Alberto; Zapperi, Stefano; Pontuale, Giorgio; Pietronero, Luciano
Linear Inviscid Damping for Monotone Shear Flows
In this article we prove linear stability, inviscid damping and scattering of the 2D Euler equations around regular, strictly monotone shear flows $(U(y),0)$ in a periodic channel under Sobolev perturbations. We treat the settings of an infinite channel, $\\mathbb{T} \\times \\mathbb{R}$, as well as a finite channel, $\\mathbb{T} \\times [0,1]$, with impermeable boundary. We first prove inviscid damping with optimal algebraic rates for strictly monotone shear flows under the assumption of controlling the regularity of the scattered vorticity. Subsequently, we establish linear stability of the scattering equation in Sobolev spaces under perturbations which are of not too large wave-length with respect to $x$, depending on $U''$.
Zillinger, Christian
Shear and rotation in Chaplygin cosmology
We study the effect of shear and rotation on results previously obtained dealing with the application of the spherical collapse model (SCM) to generalized Chaplygin gas (gCg) dominated universes. The system is composed of baryons and gCg and the collapse is studied for different values of the parameter $\\alpha$ of the gCg. We show that the joint effect of shear and rotation is that of slowing down the collapse with respect to the simple SCM. This result is of utmost importance for the so-called unified dark matter models, since the described slow down in the growth of density perturbation can solve one of the main problems of the quoted models, namely the instability described in previous papers [e.g., H. B. Sandvik {\\it et al.}, Phys. Rev. D {\\bf 69}, 123524 (2004)] at the linear perturbation level.
Del Popolo, A; Maydanyuk, S P; Lima, J A S; Jesus, J F; 10.1103/PhysRevD.87.043527
Shear unzipping of double stranded DNA
We propose a simple nonlinear scaler displacement model to calculate the distribution of effect created by a shear stress on a double stranded DNA (dsDNA) molecule and the value of shear force $F_c$ which is required to separate the two strands of a molecule. It is shown that as long as the force pulls entire strand in the direction of its application the value of $F_c$ depends linearly on the length; the deviation from linear behaviour takes place when part of a strand moves in opposite direction under the influence of force acting on the other strand. The calculated values of $F_c$ as a function of length of dsDNA molecules are in very good agreement with the experimental values of Hatch et al (Phys. Rev. E $\\bf 78$, 011920 (2008)).
Prakash, Shikha
Shear unzipping of double-stranded DNA.
We use a simple nonlinear scaler displacement model to calculate the distribution of effects created by a shear stress on a double-stranded DNA (dsDNA) molecule and the value of shear force F(c) that is required to separate the two strands of a molecule at a given temperature. It is shown that for molecules of base pairs fewer than than 21, the entire single strand moves in the direction of applied force, whereas for molecules having base pairs more than 21, part of the strand moves in the opposite direction under the influence of force acting on the other strand. This result as well as the calculated values of F(c) as a function of length of dsDNA molecules are in very good agreement with the experimental values of Hatch et al. [Phys. Rev. E 78, 011920 (2008)]. PMID:22060401
Prakash, Shikha; Singh, Yashwant
The shear mode of multilayer graphene
The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43?cm-1 in bulk graphite to ~31?cm-1 in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions.
Tan, P. H.; Han, W. P.; Zhao, W. J.; Wu, Z. H.; Chang, K.; Wang, H.; Wang, Y. F.; Bonini, N.; Marzari, N.; Pugno, N.; Savini, G.; Lombardo, A.; Ferrari, A. C.
Shear viscosity, cavitation and hydrodynamics at LHC
International Nuclear Information System (INIS)
We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.
The objectives of this study were to 1) compare four models for breeding value prediction using genomic or pedigree information and 2) evaluate the impact of fixed effects that account for family structure. Comparisons were made in a Nellore-Angus population comprising F2, F3 and half-siblings to embryo transfer F2 calves with records for overall temperament at weaning (TEMP; n = 769) and Warner-Bratzler shear force (WBSF; n = 387). After quality control, there were 34,913 whole genome SNP markers remaining. Bayesian methods employed were BayesB (?? = 0.995 or 0.997 for WBSF or TEMP, respectively) and BayesC (? = 0 and ??), where ?? is the ideal proportion of markers not included. Direct genomic values (DGV) from single trait Bayesian analyses were compared to conventional pedigree-based animal model breeding values. Numerically, BayesC procedures (using ??) had the highest accuracy of all models for WBSF and TEMP (??g? = 0.843 and 0.923, respectively), but BayesB had the least bias (regression of performance on prediction closest to 1, ??y,x = 2.886 and 1.755, respectively). Accounting for family structure decreased accuracy and increased bias in prediction of DGV indicating a detrimental impact when used in these prediction methods that simultaneously fit many markers. PMID:25505837
Hulsman Hanna, Lauren L; Garrick, Dorian J; Gill, Clare A; Herring, Andy D; Sanders, James O; Riley, David G
Effect of bleeding method and low voltage electrical stimulation on meat quality of ostriches
Scientific Electronic Library Online (English)
Full Text Available SciELO South Africa | Language: English Abstract in english The effect on ostrich muscle quality of an additional thoracic stick (TS) to the normal ventral throat slit to bleed ostriches after electrical stunning was evaluated. The additional TS had no negative or positive effect on the drip loss, cooking loss, colour or pH and temperature readings of the fi [...] llet (Muscularis iliofibularis), big drum (M. gastrocnemius, pars interna) and inside loin (M. iliotibialis cranialis). None the less, personal observations would recommend the use of TS due to ethical considerations. An early post mortem low voltage electrical stimulation (ES) of the carcasses also had no influence on the cooking loss, drip loss and colour of these muscles. Electrical stimulation did result in a lower pH45 in both the fillet and big drum muscles. However, after 24 h the pH of the muscles did not differ. Electrical stimulation also caused elevated initial muscle temperatures, although this effect was only temporary due to the efficient cooling mechanism used in the abattoir. Electrical stimulation also had no effect on the Warner Bratzler shear force values in the fillet. It can be concluded that low voltage ES has no advantage pertaining to physical quality characteristics of importance in an ostrich abattoir.
L.C., Hoffman; S.W.P., Cloete; S.J., van Schalkwyk; S.St.C., Botha.
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: English Abstract in portuguese A composi��o qu�mica percentual aproximada do cupim m. Rhomboideus (RB) derivado de Nelore (Bos indicus) de 24 meses de idade mostrou ser um m�sculo diferenciado. H� uma maior fra��o de material lip�dico em RB chegando a ser 14 vezes proporcionalmente maior em compara��o ao m. Longissimus dorsi (LD) [...] (p Abstract in english The proximate chemical composition of hump, known in Brazil as cupim, Rhomboideus m. (RB), of Nelore (Bos indicus) aged 24 months revealed it to be a unique beef muscle. It presents a lipid fraction 14-fold as high as that of Longissimus dorsi m. (LD) taken from the same animal (p[...] value reported so far. This was unequivocally observed by the histological evaluation. Proportionally more protein fraction and conversely less moisture were also observed in RB. Analysis of collagen and its crosslinking with hydroxylysylpyridinium (HP) showed there to be 22.9% more collagen and 14-fold as much HP in RB as in LD. Contrary to the expectations, the tenderness of fresh samples evaluated by Warner Bratzler shear force measurements led to values of 8.05 and 5.81 kgf for LD and RB, respectively (p
Mayka Reghiany, Pedr�o; Fernanda, Lassance; Nilson Evelazio de, Souza; Makoto, Matsushita; Paulo, Telles; Massami, Shimokomaki.
Postmortem aging of carcasses obtained from Angus-Hereford (n = 8) and 5/8 Brahman crossbred (n = 8) heifers was investigated to determine the cause of variation in meat tenderness. Raw longissimus muscle (LM) myofibril fragmentation index was lower and cooked LM Warner-Bratzler shear force was greater for the 5/8 Brahman crossbreds (P less than .05). The activities of calcium-dependent protease (CDP) -I and -II were not affected (P greater than .05) by breed; however, CDP inhibitor activity was higher (P less than .05) in the 5/8 Brahman carcasses. The activities of cathepsins B and B + L were not affected by breed or postmortem storage time (0, 1, 3, 7 or 14 d). Hereford-Angus carcasses were fatter opposite the 12th rib and had higher USDA yield grades and marbling scores (P less than .05). Hereford-Angus crossbreds had less dark, coarse band formation around the exterior of the LM and lighter, finer-textured lean (P less than .05). Cooking loss (%) and cooking rate (g/min) were not affected by breed or postmortem aging (P greater than .05). The increased toughness in the 5/8 Brahman carcasses may be due to increased CDP inhibitor activity. PMID:2005010
Shackelford, S D; Koohmaraie, M; Miller, M F; Crouse, J D; Reagan, J O
The objectives of this study were to 1) compare four models for breeding value prediction using genomic or pedigree information and 2) evaluate the impact of fixed effects that account for family structure. Comparisons were made in a Nellore-Angus population comprising F2, F3 and half-siblings to embryo transfer F2 calves with records for overall temperament at weaning (TEMP; n = 769) and Warner-Bratzler shear force (WBSF; n = 387). After quality control, there were 34,913 whole genome SNP markers remaining. Bayesian methods employed were BayesB (?? = 0.995 or 0.997 for WBSF or TEMP, respectively) and BayesC (? = 0 and ??), where ?? is the ideal proportion of markers not included. Direct genomic values (DGV) from single trait Bayesian analyses were compared to conventional pedigree-based animal model breeding values. Numerically, BayesC procedures (using ??) had the highest accuracy of all models for WBSF and TEMP (??g? = 0.843 and 0.923, respectively), but BayesB had the least bias (regression of performance on prediction closest to 1, ??y,x = 2.886 and 1.755, respectively). Accounting for family structure decreased accuracy and increased bias in prediction of DGV indicating a detrimental impact when used in these prediction methods that simultaneously fit many markers. PMID:25505837
Hulsman Hanna, Lauren L.; Garrick, Dorian J.; Gill, Clare A.; Herring, Andy D.; Sanders, James O.; Riley, David G.
Scientific Electronic Library Online (English)
Full Text Available SciELO Brazil | Language: English Abstract in english The objectives of this study were to 1) compare four models for breeding value prediction using genomic or pedigree information and 2) evaluate the impact of fixed effects that account for family structure. Comparisons were made in a Nellore-Angus population comprising F2, F3 and half-siblings to em [...] bryo transfer F2 calves with records for overall temperament at weaning (TEMP; n = 769) and Warner-Bratzler shear force (WBSF; n = 387). After quality control, there were 34,913 whole genome SNP markers remaining. Bayesian methods employed were BayesB ( ? = 0.995 or 0.997 for WBSF or TEMP, respectively) and BayesC (? = 0 and ?), where ? is the ideal proportion of markers not included. Direct genomic values (DGV) from single trait Bayesian analyses were compared to conventional pedigree-based animal model breeding values. Numerically, BayesC procedures (using ?) had the highest accuracy of all models for WBSF and TEMP ( ?gg = 0.843 and 0.923, respectively), but BayesB had the least bias (regression of performance on prediction closest to 1, ?y,x = 2.886 and 1.755, respectively). Accounting for family structure decreased accuracy and increased bias in prediction of DGV indicating a detrimental impact when used in these prediction methods that simultaneously fit many markers.
Lauren L. Hulsman, Hanna; Dorian J., Garrick; Clare A., Gill; Andy D., Herring; James O., Sanders; David G., Riley.
Histomorphology and Physical Characteristics of Buffalo Meat at Different Sex and Age
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Full Text Available The aim of this experiment was to evaluate histology and physical variables of buffalo meat at different sex and ages. Thirty head of buffaloes were used in this experiment. Muscle fiber diameter, fasciculus diameter, thickness of connective tissue, pH, water holding capacity, Warner-Bratzler shear force and cooking loss were measured in this experiment. Analysis of variance of randomized factorial design was used to analyse the data. The differences were analysed by Tukey test. The result showed that muscle fiber diameter was influenced by ages. The difference muscle fiber diameter among ages indicated that 8-12 mo and 1.5 yr old have smaller diameter compared to three year old (P<0.05, but there was no differences between two, three and four years old. The fasciculus diameter, thickness of connective tissue, tenderness, pH value, water holding capacity, and cooking lost indicated no significant found in all stage of age and sex of samples. Meat qualities of buffaloes were not affected by age (2-4 yr and sex.
Carcasses from Hanwoo steers (n?=?15) and cows (n?=?15) were classified into three groups: group 1 (G1), the carcasses had 10% to group 2 (G2), the carcasses had 13% to group 3(G3), the carcasses had 17% to group on quality traits and Warner-Bratzler shear force (WBSF) of Psoas major (PM), Longissimus thoracis (LT), Longissimus lumborum (LL), Longus colli (LC), Supraspinatus (SS), Latissimus dorsi (LAD), Semimembranosus (SM), Quadriceps femoris (QF), Biceps femoris (BF) and Semitendinosus (ST) muscles. Our results showed that pH values of LT, LL, LC, BF and QF muscles were lower in steers than in cows (P?PM, LD and QF muscles in G1, and QF muscle in G3; however, with additional ageing, the gender effect was observed for most of the muscles. Most muscles showed ageing responses; however, the rates of ageing response significantly varied depending on gender and carcass groups. The muscles of G1 and G2 had generally higher tenderization potentials than those of G3. Furthermore, most muscles in G3 had generally lower WBSF values than in G1 and G2. These results clearly indicate that ageing has a significant effect on quality and WBSF of beef muscles, and the classification by loin IMF level may be useful for prediction of the tenderness of other muscles. PMID:25491951
Park, Beom Young; Seong, Pil Nam; Ba, Hoa Van; Park, Kyoung Mi; Cho, Soo Hyun; Moon, Sung Sil; Kang, Geun Ho
In this study, 10 young steers received no beta agonist (C), 50 animals all received zilpaterol hydrochloride (Z), with 1 group receiving Z while the other 4 groups received Z and vitamin D(3) at the following levels (IU/animal /day) and durations before slaughter: 7 million for 3 days (3D7M) or 6 days (6D7M), 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). LD samples were vacuum-aged 14 days post mortem, and repacked in high-oxygen modified atmosphere (70% O(2)/30% CO(2)) for a further 7 days. Parameters included Warner Bratzler shear force (WBSF), myofibril fragment length, thiobarbituric acid reactive substances, free thiol levels, muscle fat, and instrumental colour parameters. When allowing for a conversion period of vitamin D(3) to its active metabolites, supplementing the zilpaterol treated steers with a high dosage of vitamin D(3) (6D7M7N) resulted in improved colour stability, higher stability towards protein oxidation and lower stability towards lipid oxidation. PMID:21723673
Hansen, Stine; Frylinck, Lorinda; Strydom, Phillip E
In this study, 20 young steers received no beta-agonist (C), 100 animals all received zilpaterol hydrochloride (Z), with 1 group only receiving Z while the other 4 groups received zilpaterol and vitamin D3 at the following levels (IU/animal/day) and durations before slaughter: 7 million for 3 days (3D7M); 7 million for 6 days (6D7M); 7 million for 6 days with 7 days no supplementation (6D7M7N) and 1 million for 9 days (9D1M). Left carcass sides were electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner-Bratzler shear force (WBSF), myofibril filament length, sarcomere length and calpastatin and calpain enzyme activity. Both ES and prolonged aging reduced WBSF (P<0.001). 6D7M, 6D7M7N and Z remained significantly tougher than C (P<0.001), while 3D7M and 9D1M improved WBSF under NES conditions. ES is more effective to alleviate beta-agonist induced toughness than high vitamin D3 supplements. PMID:21658849
Strydom, P E; Hope-Jones, M; Frylinck, L; Webb, E C
Cattle breeds indigenous to Africa (Sanga) compare favourably to Bos indicus breeds with regard to adaptation to harsh environments. This study compared the meat quality of three Sanga breeds (Nguni, Tuli and Drakensberger), a Sanga-related breed (Bonsmara) and a B. indicus breed (Brahman) and supported these results with biochemical and histological measurements on the M. longissimus lumborum. Twelve young grain-fed steers of each breed were slaughtered and carcasses were electrically stimulated. All Sanga (and related) breeds, with the exception of the Tuli, had lower Warner-Bratzler shear force (SF) values at 2 and 21 days post mortem compared with the BR (P < 0.05). Measurements related to the calcium-dependent protease system and myofibrillar fragmentation explained the bulk of the variation among breeds, whereas variation in fibre type, sarcomere length and connective tissue properties gave less convincing support. With the exception of the Tuli, Sanga and Sanga-related breeds produced more tender (according to SF) meat than BR, mainly due to favourable calpain-to-calpastatin ratios. Small differences in colour, drip loss and cooking properties were found among breeds (P < 0.05). PMID:22445415
Strydom, P E; Frylinck, L; Smith, M F
Relationship between pre-slaughter stress responsiveness and beef quality in three cattle breeds.
The relationship between stress responsiveness and beef quality of 40 Nguni, 30 Bonsmara and 30 Angus steers was determined. The L(?) values, pHu, cooking loss (CL) and Warner-Bratzler shear force (WBSF) were determined. Catecholamine levels were determined from urine samples collected at slaughter. Bonsmara steers had the highest (P<0.05) levels of catecholamines with respective epinephrine, norepinephrine and dopamine concentrations of 10.8, 9.7 and 14.8nmol/mmol. Nguni steers had the lowest (P<0.05) levels of catecholamines, with respective catecholamine concentrations of 5.1, 4.3 and 4.0nmol/mmol. In the Nguni steers, there were significant (P<0.05) correlations between catecholamines and L(?) and between dopamine and tenderness in meat aged for two days (WBSF2). In the Bonsmara, dopamine was correlated (P<0.05) pHu, WBSF2 and CL. No significant correlations were found in the Angus. Therefore the relationship between stress responsiveness and certain beef quality traits may not be similar in different breeds. PMID:20416575
Muchenje, V; Dzama, K; Chimonyo, M; Strydom, P E; Raats, J G
The current study compared meat quality of Nguni, Bonsmara and Angus steers raised on natural pasture. Fifteen seven-month-old weaners of each breed were kept at the University of Fort Hare Farm for 12 months till slaughter. Monthly weights of the steers were recorded. Carcasses were electrically stimulated. The m. longissimus thoracis et lumborum was sampled for the measurement of meat colour, pH, drip loss, sarcomere length, myofibrillar fragmentation length and Warner Bratzler (WB) shear force. The Nguni had the highest (P<0.05) average daily gain. Bonsmara and Angus steers had higher (P<0.05) carcass weight and dressing percentage than the Nguni steers. Meat quality characteristics were similar among all the breeds except that Nguni meat was darker (L(?)) (P<0.05) than meat from the other two breeds. The respective L(?) values for Nguni, Bonsmara and Angus steers were 36.5, 38.6 and 39.9. There were significant (P<0.05) correlations among some meat quality traits. There were significant (P<0.05) correlations between WB values of meat aged for 2 and 21 days in Nguni and Bonsmara, but not in Angus. Meat quality from Nguni compares favourably with that from established breeds, when raised on natural pasture. PMID:22062594
Muchenje, V; Dzama, K; Chimonyo, M; Raats, J G; Strydom, P E
Beta agonists used as growth enhancers are known to affect the aging potential of beef muscle negatively. On the other hand, procedures like electrical stimulation could accelerate rigor and the aging process. In this study, 20 out of 40 young steers received no beta agonist (C), the remaining twenty steers received a beta agonist (zilpaterol hydrochloride) (Z) for the 30 days prior to slaughter followed by 4 days withdrawal. After slaughter carcasses were split, the left side electrically stimulated (ES) and the right side not stimulated (NES). Samples were aged for 3 or 14 days post mortem. Parameters included Warner Bratzler shear force (WBSF), myofibril filament length (MFL), sarcomere length and calpastatin and calpain enzyme activity. Zilpaterol resulted in increased (P<0.001) WBSF mainly due to an increased (P<0.001) calpastatin activity. ES improved tenderness (P<0.001) in general by early onset of rigor triggering the activity of calpains. ES also reduced the calpastatin activity (P<0.001), which partially countered the effect of high calpastatin activity on the aging potential of Z loins. ES can therefore be implemented to improve meat tenderness in zilpaterol supplemented steers, although steers without zilpaterol will still have an advantage in final tenderness. PMID:20619545
Hope-Jones, M; Strydom, P E; Frylinck, L; Webb, E C
Canada B4 beef carcasses are penalized because the longissimus thoracis (LT) at the grade site (12-13th ribs) is darker than the color threshold for normal bright cherry-red beef. Previous studies have shown that not all B4 carcasses have pH>6.0; therefore, the relationship between LT pH and meat quality was investigated by collecting thirty half-carcasses comprised of the following: ten Canada AA (AA, control), ten B4 with LT pH>6.0 (CL, classic), and ten B4 with LT pH<6.0 (AT, atypical). LT from CL carcasses had the lowest mean lactate level, lowest glucidic potential and highest mean pH value. LT muscle from CL and AT carcasses was dark and had decreased purge, drip loss and cooking loss. Warner-Bratzler shear force values and sensory panel results showed that AT beef was toughest (P<0.0001), substantiating economic penalty. Causal mechanisms for AT carcasses may be inconsistent with traditional DFD theory because of close to normal final muscle pH. PMID:25173716
Holdstock, J; Aalhus, J L; Uttaro, B A; L�pez-Campos, O; Larsen, I L; Bruce, H L
The objective of this study was to evaluate the meat quality and shelf life of steaks from steers fed dried distillers grains with solubles (DDGS) or dried corn gluten feed (CGF) compared with soybean meal with corn (SBM) as a protein supplement from weaning to slaughter. Angus cross steers (n = 81; BW = 306 � 26.1 kg) were randomly assigned to pens (n = 9) and fed a stocker diet of corn silage (75% of DM) with DDGS, CGF, or SBM and ground ear corn. After 84 d of stockering, 12 steers (BW = 397 � 15.3 kg) were randomly selected from each treatment and finished using the same protein supplement at 25% of DM for 100 d. Carcass data were collected (24 h) and the longissimus lumborum was fabricated into steaks at 48 h postmortem. Steaks were assigned to proximate analysis, Warner-Bratzler shear force (7-, 14-, or 21-d aging), and retail display (1, 3, 6, or 9 d). Protein source did not affect carcass yield, quality, or longissimus lumborum composition (P > 0.05). After 7 d of aging, DDGS and CGF steaks were more tender (P 0.05) among diets except SBM steaks were more red (P 0.05) the rate of lipid oxidation. Total SFA concentrations were similar (P > 0.05) among treatments; however, total MUFA were less (P weaning until slaughter while maintaining meat quality when compared with steers fed soybean meal as a protein supplement. PMID:21642492
Segers, J R; Stewart, R L; Lents, C A; Pringle, T D; Froetschel, M A; Lowe, B K; McKeith, R O; Stelzleni, A M
Effects of the dark-cutting condition were examined on commercially slaughtered beef carcass sides that were classified into groups exhibiting 1/3, 1/2, and full degrees of the dark-cutting (DEGDC) condition, as evaluated by a USDA-Agricultural Marketing Service grader (n = 20 per group). Twenty-nine muscles of each carcass side were evaluated to determine the ultimate pH and color (L*, a*, and b*). Fourteen beef muscles (biceps femoris, deep pectoral, chuck complexus, gluteus medius, infraspinatus, latissimus dorsi, psoas major, longissimus thoracis, longissimus lumborum, semimembranosus, semitendinosus, triceps brachii long head, tensor fasciae latae, and vastus lateralis) were evaluated using Warner-Bratzler Shear force (WBSF) and a trained sensory panel. The muscle x DEGDC interaction was significant for ultimate pH, L*, a*, and b* values (P sensory panel scores (P > 0.05), but differences were detected among muscles (P sensory scores or WBSF between DEGDC classes suggested equal sensory expectations for muscles from dark-cutting carcasses. PMID:18344305
Bass, P D; Scanga, J A; Chapman, P L; Smith, G C; Tatum, J D; Belk, K E
Scientific Electronic Library Online (English)
Full Text Available SciELO South Africa | Language: English Abstract in english Fifteen young Holstein Friesian bulls (18 mo of age) were divided into three groups of five. All groups were fed a diet consisting of 60% concentrate and 40% roughage. The control (C) group received a mixture of dry meadow hay, dry lucerne and wheat straw as roughage. The second and third treatment [...] groups were fed a similar mixture of roughage partially substituting wheat straw with wet sugar beet pulp (SBP) at levels of 4% and 8% on a dry matter (DM) basis, respectively. Dry matter intake and feed efficiency ratio (kg DM intake/kg weight gain) of the C group were significantly higher than those of the 4% SBP and 8% SBP groups. Slaughter and carcass traits indicated that there were no significant differences between dietary treatments. The inclusion of 8% SBP significantly improved panel ratings for tenderness, juiciness, beef flavour intensity and general acceptance, as well as number of chews before swallowing and the Warner Bratzler Shear value. Proximate analysis of the meat did not demonstrate differences between meat from the bulls fed C and the SBP diets. It was concluded that wheat straw could be replaced by 8% SBP in the finishing diet for young Holstein Friesian bulls in order to improve feed efficiency and sensory quality characteristics of their meat.
S., Y& #252; ksel; M., Yanar; L., Turgut; A., & #214; zl& #252; t& #252; rk; S., Kopuzlu; E., Sezgin.
Muscles (n=9) from beef rounds (n=40) were subjected to one of the four tenderization strategies: control, blade tenderization, enzymatic tenderization or salt/phosphate injection. Treated muscles were aged, cut into steaks, cooked using one of the two cooking methods (dry-heat or moist-heat), and Warner-Bratzler shear (WBS) force values were determined. For dry-heat cookery, injection with a salt and phosphate solution resulted in the lowest WBS values, however, WBS values for blade tenderization and enzymatic tenderization were comparable in the M. adductor, M. vastus lateralis, M. rectus femoris, and M. semimembranosus (cranial and caudal aspects). The M. gluteobiceps (cranial and caudal aspects, and ischiatic head) and M. semitendinosus showed little improvement in WBS values with any of the tenderization treatments. For moist-heat cookery, only the M. rectus femoris and M. semimembranosus, caudal aspect, showed significant decreases in WBS values, and those improvements were only associated with salt and phosphate injection and enzymatic tenderization. Within each cooking method and tenderization treatment, the M. rectus femoris, M. semimembranosus, cranial aspect had the lowest WBS values, whereas the M. gluteobiceps, ischiatic head and M. semimembranosus typically had the highest WBS values. All tenderization strategies increased the frequency of muscles being rated as "very tender" (WBS<31.4 N) and "tender" (31.4 N Kolle, B K; McKenna, D R; Savell, J W 2004-09-01
Examining the initial stages of shear localization in amorphous metals
International Nuclear Information System (INIS)
A mesoscale simulation by shear transformation zone (STZ) dynamics is used to analyze the initial stages of shear localization in amorphous metals, of which many details remain unresolved due to the difficulty in accessing the appropriate time- and length-scales. Examination of a constant strain-rate tensile test of a model amorphous metal reveals four different stages in the microscopic processes that lead to formation of a shear band. These stages are identified as: (i) STZ clustering, where potential nucleation sites form as STZ activations cluster in space; (ii) growth following nucleation, where a nascent shear band exhibits a propagating front that defines the shear band path; (iii) relaxation thickening, where the shear band thickens and relaxes the system down to the flow stress; and (iv) flow thickening, where the shear band exhibits prolonged thickening at the flow stress. The results are consistent with the literature but suggest that a shear band is defined by a front that propagates very quickly with negligible accumulated strain. This propagating front likely occurs below the resolution of current methods that only observe simultaneous slip in a shear band where significant strain can be accumulated at much slower rates. Analysis of a thermodynamic model also suggests a specific critical stress that is required to nucleate a shear band, after which the shear band is allowed to grow unconstrained
Nonequilibrium shear viscosity computations with Langevin dynamics
We study the mathematical properties of a nonequilibrium Langevin dynamics which can be used to estimate the shear viscosity of a system. More precisely, we prove a linear response result which allows to relate averages over the nonequilibrium stationary state of the system to equilibrium canonical expectations. We then write a local conservation law for the average longitudinal velocity of the fluid, and show how, under some closure approximation, the viscosity can be extra...
Joubaud, Remi; Stoltz, Gabriel
Dynamical compressibility of dense granular shear flows
It has been conjectured by Bagnold [1] that an assembly of hard non-deformable spheres could behave as a compressible medium when slowly sheared, as the average density of such a system effectively depends on the confining pressure. Here we use discrete element simulations to show the existence of transverse and sagittal waves associated to this dynamical compressibility. For this purpose, we study the resonance of these waves in a linear Couette cell and compare the results...
Trulsson, Martin; Bouzid, Mehdi; Claudin, Philippe; Andreotti, Bruno
An implementation of Bayesian lensing shear measurement
The Bayesian gravitational shear estimation algorithm developed by Bernstein & Armstrong can potentially be used to overcome multiplicative noise bias and recover shear using very low signal-to-noise ratio (S/N) galaxy images. In that work, the authors confirmed that the method is nearly unbiased in a simplified demonstration, but no test was performed on images with realistic pixel noise. Here, I present a full implementation for fitting models to galaxy images, including the effects of a point spread function (PSF) and pixelization. I tested the implementation using simulated galaxy images modelled as S�rsic profiles with n = 1 (exponential) and n = 4 (De Vaucouleurs'), convolved with a PSF and a flat pixel response function. I used a round Gaussian model for the PSF to avoid potential PSF-fitting errors. I simulated galaxies with mean observed, post-PSF full width at half-maximum equal to approximately 1.2 times that of the PSF, with lognormal scatter. I also drew fluxes from a lognormal distribution. I produced independent simulations, each with pixel noise tuned to produce different mean S/N ranging from 10-1000. I applied a constant shear to all images. I fitted the simulated images to a model with the true S�rsic index to avoid modelling biases. I recovered the input shear with fractional error ?g/g < 2 � 10-3 in all cases. In these controlled conditions, and in the absence of other multiplicative errors, this implementation is sufficiently unbiased for current surveys and approaches the requirements for planned surveys.
Sheldon, Erin S.
A Simple Model for Sheared Granular Layers
We phenomenologically investigate stick-slip motion of sheared granular layers. Our phenomenology is constructed in the context of nucleation-and-growth of the fluidized area which is triggered by collapsing of stress chains. Based on this picture, we give a simple friction model by introducing the degree of the fluidization. It is found that the present model can successfully reproduce major features of the experimental results reported by Nasuno {\\it et al.} (Phys. Rev. E ...
Furukawa, Akira; Hayakawa, Hisao
Surface Shear and Persistent Wave Groups
We investigate the interaction of waves with surface flows by considering the full set of conserved quantities, subtle but important surface elevation changes induced by wave packets and by directly considering the necessary forces to prevent packet spreading in the deep water limit. Narrow surface shear flows are shown to exert strong localizing and stabilizing forces on wavepackets to maintain their strength and amplify their intensity even in the linear regime. Subtle pac...
Chafin, Clifford
Fractures of the olecranon for shear
International Nuclear Information System (INIS)
In spite of the fact that the metaphysiaries fractures of the olecranon are relatively rare, when complex lesions are presented that involve shear mechanisms it is necessary to consider the possibility of open reduction. The case of a 5 year-old patient is presented with elbow luxo-fracture with an apparent of the epiphysis slip, type 1 of Salter of the radial dome
Shear modulus of neutron star crust
Shear modulus of solid neutron star crust is calculated by thermodynamic perturbation theory taking into account ion motion. At given density the crust is modelled as a body-centered cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temper...
Baiko, D. A.
Shear adhesion strength of aligned electrospun nanofibers.
Inspiration from nature such as insects' foot hairs motivates scientists to fabricate nanoscale cylindrical solids that allow tens of millions of contact points per unit area with material substrates. In this paper, we present a simple yet robust method for fabricating directionally sensitive shear adhesive laminates. By using aligned electrospun nylon-6, we create dry adhesives, as a succession of our previous work on measuring adhesion energies between two single free-standing electrospun polymer fibers in cross-cylinder geometry, randomly oriented membranes and substrate, and peel forces between aligned fibers and substrate. The synthetic aligned cylindrical solids in this study are electrically insulating and show a maximal Mode II shear adhesion strength of 27 N/cm(2) on a glass slide. This measured value, for the purpose of comparison, is 270% of that reported from gecko feet. The Mode II shear adhesion strength, based on a commonly known "dead-weight" test, is 97-fold greater than the Mode I (normal) adhesion strength of the same. The data indicate a strong shear binding on and easy normal lifting off. Anisotropic adhesion (Mode II/Mode I) is pronounced. The size and surface boundary effects, crystallinity, and bending stiffness of fibers are used to understand these electrospun nanofibers, which vastly differ from otherwise known adhesive technologies. The anisotropic strength distribution is attributed to a decreasing fiber diameter and an optimized laminate thickness, which, in turn, influences the bending stiffness and solid-state "wettability" of points of contact between nanofibers and surface asperities. PMID:25105533
Najem, Johnny F; Wong, Shing-Chung; Ji, Guang
Optimisation and control of shear flows
Transition to turbulence and flow control are studied by means of numerical simulations for different simple shear flows. Linear and non-linear optimisation methods using the Lagrange multiplier technique are employed. In the linear framework as objective function the standard disturbance kinetic energy is chosen and the constraints involve the linearised Navier�Stokes equations. We consider both the optimal initial condition leading to the largest disturbance energy growth at finite times ...
Monokrousos, Antonios
A wall-shear stress predictive model
International Nuclear Information System (INIS)
Following the approach of Marusic et al. (2010b), here we develop a predictive model for the fluctuating wall-shear stress, where the only required input is large-scale information of the streamwise velocity at a location in the outer, logarithmic region of the flow. The model consists of two components, incorporating a superposition and modulation effect of outer region motions that interact with the flow field in the viscous sublayer. The model is seen to capture Reynolds number trends reliably.
Shear testing of stack bonded masonry
Stack bonded masonry is scarcely used in practice, except for aesthetic reasons. Nevertheless, a regular array of units allows to place reinforcement in the joints, which can be of major importance for masonry shell roofs, as proposed by Eladio Dieste. In order to contribute to the knowledge of the behavior of stack bonded masonry under shear loading, which seems not to have been addressed before, an experimental research program using the triplet test was carried out. The specime...
Lourenc?o, Paulo B.; Barros, Joaquim A. O.; Oliveira, Juliana T.
Shear flow pumping in open microfluidic systems
We propose to drive open microfluidic systems by shear in a covering fluid layer, e.g., oil covering water-filled chemical channels. The advantages as compared to other means of pumping are simpler forcing and prevention of evaporation of volatile components. We calculate the expected throughput for straight channels and show that devices can be built with off-the-shelf technology. Molecular dynamics simulations suggest that this concept is scalable down to the nanoscale.
Rauscher, M; Koplik, J; Rauscher, Markus; Koplik, Joel
Shear rheological characterization of motor oils
Measurements of high pressure viscosity, traction coefficient, and EHD film thickness were performed on twelve commercial automotive engine oils, a reference oil, two unformulated base oils and two unformated base oil and polymer blends. An effective high shear rate inlet viscosity was calculated from film thickness and pressure viscosity coefficient. The difference between measured and effective viscosity is a function of the polymer type and concentration. Traction measurements did not discriminate mileage formulated oils from those not so designated.
Bair, Scott; Winer, Ward O.
Multiphase gas transport in a shear zone
In the post-operational phase of a Low/Intermediate-Low radioactive waste repository, gas will be generated in the caverns due to anaerobic corrosion of metals, and also chemical and microbial degradation of organic substances. Previous investigations on gas migration have indicated that discrete water conducting features (e.g. shear zones) are mainly responsible for gas transport from the caverns through the geosphere. Two phase flow processes occur in these water conducting features; the c...
Jo?dar, Jorge
Formation of a sheared flow Z pinch
The ZaP Flow Z-Pinch project is experimentally studying the effect of sheared flows on Z-pinch stability. It has been shown theoretically that when dVz/dr exceeds 0.1kVA the kink (m =1) mode is stabilized. [U. Shumlak and C. W. Hartman, Phys. Rev. Lett. 75, 3285 (1995).] Z pinches with an embedded axial flow are formed in ZaP with a coaxial accelerator coupled with a 1m assembly region. Long-lived, quiescent Z pinches are generated throughout the first half cycle of the current. During the initial plasma acceleration phase, the axial motion of the current sheet is consistent with snowplow models. Magnetic probes in the assembly region measure the azimuthal modes of the magnetic field. The amplitude of the m =1 mode is proportional to the radial displacement of the Z-pinch plasma current. The magnetic mode levels show a quiescent period which is over 2000 times the growth time of a static Z pinch. The axial velocity is measured along 20 chords through the plasma and deconvolved to provide a radial profile. Using data from multiple pulses, the time evolution of the velocity profile is measured during formation, throughout the quiescent period, and into the transition to instability. The evolution shows that a sheared plasma flow develops as the Z pinch forms. Throughout the quiescent period, the flow shear is greater than the theoretically required threshold for stability. As the flow shear decreases, the magnetic mode fluctuations increase. The coaxial accelerator provides plasma throughout the quiescent period and may explain the evolution of the velocity profile and the sustainment of the flow Z pinch.
Golingo, R. P.; Shumlak, U.; Nelson, B. A.
Shear friction capacity of recycled concretes
The aim of this research was to determine the behavior of recycled concrete in response to the phenomenon of shear transfer. To perform it, a conventional control concrete and a concrete with 50% recycled coarse aggregate were designed. An additional goal was to shed light on how this behavior is modified with a pozzolanic addition, silica fume. Therefore, two types of concrete were designed, a conventional and a recycled concrete, both made with 8% of silica fume. In conclusion, a...
Eiras, J.; Carro, D.; Marti?nez, F.; Gonza?lez Fonteboa, B.
Formation of a sheared flow Z pinch
International Nuclear Information System (INIS)
The ZaP Flow Z-Pinch project is experimentally studying the effect of sheared flows on Z-pinch stability. It has been shown theoretically that when dVz/dr exceeds 0.1kVA the kink (m=1) mode is stabilized. [U. Shumlak and C. W. Hartman, Phys. Rev. Lett. 75, 3285 (1995).] Z pinches with an embedded axial flow are formed in ZaP with a coaxial accelerator coupled with a 1 m assembly region. Long-lived, quiescent Z pinches are generated throughout the first half cycle of the current. During the initial plasma acceleration phase, the axial motion of the current sheet is consistent with snowplow models. Magnetic probes in the assembly region measure the azimuthal modes of the magnetic field. The amplitude of the m=1 mode is proportional to the radial displacement of the Z-pinch plasma current. The magnetic mode levels show a quiescent period which is over 2000 times the growth time of a static Z pinch. The axial velocity is measured along 20 chords through the plasma and deconvolved to provide a radial profile. Using data from multiple pulses, the time evolution of the velocity profile is measured during formation, throughout the quiescent period, and into the transition to instability. The evolution shows that a sheared plasma flow develops as the Z pinch forms. Throughout the quiescent period, the flow shear is greater than the theoretically required threshold for stability. As the flow shear decreases, the magnetic mode fluctuations increase. The coagnetic mode fluctuations increase. The coaxial accelerator provides plasma throughout the quiescent period and may explain the evolution of the velocity profile and the sustainment of the flow Z pinch
Surface shear rheology of saponin adsorption layers.
Saponins are a wide class of natural surfactants, with molecules containing a rigid hydrophobic group (triterpenoid or steroid), connected via glycoside bonds to hydrophilic oligosaccharide chains. These surfactants are very good foam stabiliziers and emulsifiers, and show a range of nontrivial biological activities. The molecular mechanisms behind these unusual properties are unknown, and, therefore, the saponins have attracted significant research interest in recent years. In our previous study (Stanimirova et al. Langmuir 2011, 27, 12486-12498), we showed that the triterpenoid saponins extracted from Quillaja saponaria plant (Quillaja saponins) formed adsorption layers with unusually high surface dilatational elasticity, 280 � 30 mN/m. In this Article, we study the shear rheological properties of the adsorption layers of Quillaja saponins. In addition, we study the surface shear rheological properties of Yucca saponins, which are of steroid type. The experimental results show that the adsorption layers of Yucca saponins exhibit purely viscous rheological response, even at the lowest shear stress applied, whereas the adsorption layers of Quillaja saponins behave like a viscoelastic two-dimensional body. For Quillaja saponins, a single master curve describes the data for the viscoelastic creep compliance versus deformation time, up to a certain critical value of the applied shear stress. Above this value, the layer compliance increases, and the adsorption layers eventually transform into viscous ones. The experimental creep-recovery curves for the viscoelastic layers are fitted very well by compound Voigt rheological model. The obtained results are discussed from the viewpoint of the layer structure and the possible molecular mechanisms, governing the rheological response of the saponin adsorption layers. PMID:22830458
Golemanov, Konstantin; Tcholakova, Slavka; Denkov, Nikolai; Pelan, Edward; Stoyanov, Simeon D
Shear sensing based on a microstrip patch antenna
International Nuclear Information System (INIS)
A microstrip patch antenna sensor was studied for shear sensing with a targeted application of measuring plantar shear distribution on a diabetic foot. The antenna shear sensor consists of three components, namely an antenna patch, a soft foam substrate and a slotted ground plane. The resonant frequency of the antenna sensor is sensitive to the overlapping length between the slot in the ground plane and the antenna patch. A shear force applied along the direction of the slot deforms the foam substrate and causes a change in the overlapping length, which can be detected from the antenna frequency shift. The antenna shear sensor was designed based on simulated antenna frequency response and validated by experiments. Experimental results indicated that the antenna sensor exhibits high sensitivity to shear deformation and responds to the applied shear loads with excellent linearity and repeatability. (paper)
Effect of Magnetic Shear on Magneto-Rayleigh-Taylor Instability
Because of diffusion of the azimuthal magnetic field into a cylindrical liner which encloses a plasma that is embedded in an axial magnetic field [1], the magnetic field within the liner may exhibit a strong magnetic shear, offering the interesting possibility of shear stabilization of the magneto-Rayleigh-Taylor instability (MRT). Here, we use the ideal MHD model to study this effect of magnetic shear in a finite slab. It is found that magnetic shear reduces the MRT growth rate in general. However, the feedthrough factor is virtually independent of magnetic shear. The limiting cases of zero magnetic shear and infinite magnetic shear are consistent with the generalized analytic model [2]. [4pt] [1] S. A. Slutz et al., Phys. Plasmas 17, 056303 (2010). [0pt] [2] Y. Y. Lau et al., Phys. Rev. E. 83, 066405 (2011); M. R. Weis et al., in this conference.
Zhang, Peng; Lau, Y. Y.; Rittersdorf, I. M.; Weis, M. R.; Gilgenbach, R. M.; Slutz, S. A.; Sinars, D. B.; Herrmann, M. C.; Cuneo, M. E.
Effects of shear stress on the microalgae Chaetoceros muelleri.
The effect of shear stress on the viability of Chaetoceros muelleri was studied using a combination of a rheometer and dedicated shearing devices. Different levels of shear stress were applied by varying the shear rates and the medium viscosities. It was possible to quantify the effect of shear stress over a wide range, whilst preserving laminar flow conditions through the use of a thickening agent. The threshold value at which the viability of algae was negatively influenced was between 1 and 1.3 Pa. Beyond the threshold value the viability decreased suddenly to values between 52 and 66%. The effect of shear stress was almost time independent compared to normal microalgae cultivation times. The main shear stress effect was obtained within 1 min, with a secondary effect of up to 8 min. PMID:20191365
Michels, Michiel H A; van der Goot, Atze J; Norsker, Niels-Henrik; Wijffels, Ren� H
Shear strength of oil palm shell foamed concrete beams
International Nuclear Information System (INIS)
Four reinforced oil palm shell foamed concrete (OPSFC) beams were fabricated, and their shear behaviour was tested. The OPSFC has a target density of approximately 1600 kg/m3 and a 28-day compressive strength of about 20 MPa. Two beams were cast with shear reinforcements while the other two were cast without such reinforcements. For comparison, four reinforced normal weight concrete (NWC) beams were also cast. The beams that contained shear links failed in flexure mode, while those without links failed in shear mode. The experimental results indicated that the shear capacities of OPSFC beams without shear links are higher than those of the NWC beams and exhibit more flexural and shear cracks.
Horizontal Shear Wave Imaging of Large Optics
Energy Technology Data Exchange (ETDEWEB)
When complete the National Ignition Facility (NIF) will be the world's largest and most energetic laser and will be capable of achieving for the first time fusion ignition in the laboratory. Detecting optics features within the laser beamlines and sizing them at diameters of 0.1 mm to 10 mm allows timely decisions concerning refurbishment and will help with the routine operation of the system. Horizontally polarized shear waves at 10 MHz were shown to accurately detect, locate, and size features created by laser operations from 0.5 mm to 8 mm by placing sensors at the edge of the optic. The shear wave technique utilizes highly directed beams. The outer edge of an optic can be covered with shear wave transducers on four sides. Each transducer sends a pulse into the optic and any damage reflects the pulse back to the transmitter. The transducers are multiplexed, and the collected time waveforms are enveloped and replicated across the width of the element. Multiplying the data sets from four directions produces a map of reflected amplitude to the fourth power, which images the surface of the optic. Surface area can be measured directly from the image, and maximum depth was shown to be correlated to maximum amplitude of the reflected waveform.
Quarry, M J
Spurious Shear in Weak Lensing with LSST
The Large Synoptic Survey Telescope (LSST) is one of the most powerful ground-based weak lensing survey telescopes in the upcoming decade. The complete 10-year survey will image $\\sim$ 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to $r\\sim27.5$, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of \\textit{additive} systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing ana...
Chang, C; Jernigan, J G; Peterson, J R; AlSayyad, Y; Ahmad, Z; Bankert, J; Bard, D; Connolly, A; Gibson, R R; Gilmore, K; Grace, E; Hannel, M; Hodge, M A; Jee, M J; Jones, L; Krughoff, S; Lorenz, S; Marshall, P J; Marshall, S; Meert, A; Nagarajan, S; Peng, E; Rasmussen, A P; Shmakova, M; Sylvestre, N; Todd, N; Young, M
Singular eigenfunctions for shearing fluids I
International Nuclear Information System (INIS)
The authors construct singular eigenfunctions corresponding to the continuous spectrum of eigenvalues for shear flow in a channel. These modes are irregular as a result of a singularity in the eigenvalue problem at the critical layer of each mode. They consider flows with monotonic shear, so there is only a single critical layer for each mode. They then solve the initial-value problem to establish that these continuum modes, together with any discrete, growing/decaying pairs of modes, comprise a complete basis. They also view the problem within the framework of Hamiltonian theory. In that context, the singular solutions can be viewed as the kernel of an integral, canonical transformation that allows us to write the fluid system, an infinite-dimensional Hamiltonian system, in action-angle form. This yields an expression for the energy in terms of the continuum modes and provides a means for attaching a characteristic signature (sign) to the energy associate with each eigenfunction. They follow on to consider shear-flow stability within the Hamiltonian framework. Next, the authors show the equivalence of integral superpositions of the singular eigenfunctions with the solution derived with Laplace transform techniques. In the long-time limit, such superpositions have decaying integral averages across the channel, revealing phase mixing or continuum damping. Under some conditions, this decay is exponential and is then the fluid analogue of Landau damping. Finally, the authors discuss the energetics of continuum damping
Behaviour of voids in a shear field
DEFF Research Database (Denmark)
When voids are present in a ductile material subject to a shear dominated stress state under low stress triaxiality the voids collapse to micro-cracks, which subsequently rotate and elongate in the shear field. In the present plane strain analyses for cylindrical voids a surface load normal to a plane connecting the ends of the micro-crack is used as an approximate representation of contact stresses during frictionless sliding. In a previous study of the same problem the author applied hydrostatic pressure inside the nearly closed micro-crack to approximate contact conditions. The transverse surface loads used in the present analyses avoid the tendency to unrealistically elongate the voids. It is found that even though the model applied here gives significantly later occurrence of a maximum overall shear stress than that found by using hydrostatic pressure, the present model does predict a maximum in all the cases analyzed and thus illustrates the micro-mechanism leading to failure of the material by localization of plastic flow.
Tvergaard, Viggo
Density-shear instability in electron MHD
We discuss a novel instability in inertia-less electron magneto-hydrodynamics (EMHD), which arises from a combination of electron velocity shear and electron density gradients. The unstable modes have a lengthscale longer than the transverse density scale, and a growth-rate of the order of the inverse Hall timescale. We suggest that this density-shear instability may be of importance in magnetic reconnection regions on scales smaller than the ion skin depth, and in neutron star crusts. We demonstrate that the so-called Hall drift instability, previously argued to be relevant in neutron star crusts, is a resistive tearing instability rather than an instability of the Hall term itself. We argue that the density-shear instability is of greater significance in neutron stars than the tearing instability, because it generally has a faster growth-rate and is less sensitive to geometry and boundary conditions. We prove that, for uniform electron density, EMHD is "at least as stable" as regular, incompressible MHD, in...
Wood, Toby S; Lyutikov, Maxim
Shear modulus of neutron star crust
Shear modulus of solid neutron star crust is calculated by thermodynamic perturbation theory taking into account ion motion. At given density the crust is modelled as a body-centered cubic Coulomb crystal of fully ionized atomic nuclei of one type with the uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative $\\propto T$ contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behavior is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for li...
Baiko, D A
Turbulent shear control with oscillatory bubble injection
Energy Technology Data Exchange (ETDEWEB)
It is known that injecting bubbles into shear flow can reduce the frictional drag. This method has advantages in comparison to others in simplicity of installation and also in environment. The amount of drag reduction by bubbles depends on the void fraction provided in the boundary layer. It means, however, that certain power must be consumed to generate bubbles in water, worsening the total power-saving performance. We propose oscillatory bubble injection technique to improve the performance in this study. In order to prove this idea of new type of drag reduction, velocity vector field and shear stress profile in a horizontal channel flow are measured by ultrasonic velocity profiler (UVP) and shear stress transducer, respectively. We measure the gas-liquid interface from the UVP signal, as well. This compound measurement with different principles leads to deeper understanding of bubble-originated drag reduction phenomena, in particular for unsteady process of boundary layer alternation. At these experiments, the results have demonstrated that the intermittency promotes the drag reduction more than normal continuous injection for the same void fraction supplied.
Park, Hyun Jin; Oishi, Yoshihiko; Tasaka, Yuji; Murai, Yuichi; Takeda, Yasushi, E-mail: firstname.lastname@example.com [Hokkaido University, Sapporo (Japan)
High-shear-rate optical rheometer
We have developed a parallel-plate rheometer in a magnetic-disk drive configuration constructed of optically transparent materials and operating with a very small gap for measurements at very high shear rates. The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating. Both disk and slider have been made of optically transparent material to allow optical measurements simultaneously with the rheological measurements. In the present mode, the apparatus is set up for simultaneous rheometery and birefringence measurements on a thin film of polymer lubricant. Rheology and birefringence measurements were made on a perfluoropolyether lubricant over a range of strain rate from 103 s-1 to greater than 106 s-1 with 800 nm, 400 nm, and 200 nm film thicknesses.
Mriziq, K. S.; Dai, H. J.; Dadmun, M. D.; Jellison, G. E.; Cochran, H. D.
Shear Systematics in LSST Simulated Images
The Large Synoptic Survey Telescope (LSST) is a large-aperture, wide-field, ground-based telescope designed to provide a complete survey of 20,000 square degrees of sky in six optical bands every few nights. Over ten years of operation, it will measure the magnitudes, colors, and shapes of several billion galaxies. As such, LSST will probe cosmic shear down to levels far beyond those accessible with current surveys. The unprecedented statistical power of LSST will impose new requirements on the control of weak lensing systematics. Various noise sources become important in this context, associated with counting statistics, atmospheric effects, and wavefront errors introduced by the telescope and camera systems. We are studying these various noise components and their impact on shear measurements using simulated LSST images produced by a prototype high fidelity photon-by-photon Monte Carlo code. The code includes the most significant physical effects associated with photon propagation through the atmosphere, reflection off of the three mirror surfaces of the telescope, and propagation through the elements of the camera and on into the detector. We report on preliminary results from this program, including plots of residual shear error correlation functions due to errors in the object shape estimation for realistic LSST operating conditions.
Chang, Chihway; Kahn, S. M.; Jernigan, G.; Peterson, J. R.; Rasmussen, A. P.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Nagarajan, S.; Pizagno, J.; Shmakova, M.; Sylvestre, N.; Todd, N.; Young, M.
Fibre-reinforced plastic composites - Determination of the in-plane shear stress/shear strain response, including the in-plane shear modulus and strength, by the plus or minus 45 degree tension test method
International Organization for Standardization. Geneva
Distribution functions of a simple fluid under shear. II. High shear rates
International Nuclear Information System (INIS)
The distortion of structure of a simple, inverse 12 soft-sphere fluid undergoing plane Couette flow is studied by nonequilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) with a high-shear-rate version of the nonequilibrium (NE) potential obtained recently from the NE distribution function theory of Gan and Eu [Phys. Rev. A 45, 3670; 46, 6344 (1992)]. The theory suggests a NE potential under which the equilibrium structure of the fluid is that of a NE fluid, and also suggests a corresponding Ornstein-Zernike equation with its closure relations. As in the low-shear-rate case [Yu. V. Kalyuzhnyi, S. T. Cui, P. T. Cummings, and H. D. Cochran, Phys. Rev. E 60, 1716 (1999)] the agreement between EMD and the modified hypernetted chain version of the theory is good. Although the high-shear-rate version of the NE potential improves the agreement between NEMD and EMD results (in comparison with the low-shear-rate version), its predictions are still unsatisfactory. With the high-shear-rate NE potential, EMD gives qualitatively correct predictions only for the shift of the position of the first maximum of the NE distribution function. The corresponding changes in the magnitude of the first maximum predicted by EMD have an opposite direction in comparison with those predicted by NEMD. It is concluded that the NE potential used is not very successful, and more accurate models for the potential are needed
Shear strength and permeability evolution during shear-holding in single rock fracture
International Nuclear Information System (INIS)
This paper presents direct shear test results for single jointed granite and mortar specimens to investigate effects of long-term load holding on mechanical and hydrological properties of rock joints. From the test results, it was confirmed that shear strength increased and permeability decreased for mortar specimens through three days load holding. For granite specimens, however, significant change was not confirmed on mechanical and hydrological properties through up to twenty days load holding due to smallness of confining pressure compared with the strength of granite and shortness of load holding. Relationship between the time of shear holding (th) and the growth of shear strength during shear holding (??) was examined for mortar specimens. When tn was shorter than 106sec, ?? increased in proportional to the logarithm of th as Dieterich's log-linear model, which explains the time-dependency of ?? as increase of contact area of fracture surface due to asperity creep. When th was about 106sec, however, ?? was larger than the value predicted by the Dieterich's log-linear model. This result implies growth of adhesion driven by chemical action at contact area of fracture surface such as pressure solution and precipitation. (author)
Finite element analysis for the shear strength appearing in in situ rock shear tests
International Nuclear Information System (INIS)
The mechanisms of the strength which appeared in in situ rock shear tests were examined with a finite element analysis in this paper. A set of plaster model laboratory tests simulating the in situ rock shear tests was analyzed. The plaster models were expressed initially with constant strain triangles (CSTs). Then, the displacement was imposed gradually, and each CST was replaced with a triangular element containing an embedded interface at the point when the stress in each CST reached the failure criterion of the material. The cracking patterns and the deformation obtained from the computation resembled those in the laboratory tests. The cracking pattern under each normal stress deviated from that under different conditions; and therefore, the stress path and the shear strength appeared differently under the various normal stress conditions. The relationship between the apparent shear strength and the failure criterion of the material also changed depending on the normal stress. The shear strength measured in the model tests appeared to be lower than the material strength in the lower and in the higher normal stress ranges. Such differences were thought to occur due to the influence of the stress distributions, which were not assumed, but were caused by several different cracking patterns.
The influence of ante-mortem treatment on relationship between pH and tenderness of beef.
Longissimus lumborum et thoracis muscles from 150 cattle comprising Czech Pied breed bulls and cows were used to investigate the relationship between pH value and beef tenderness as influenced by housing before slaughter and by the hanging mode of carcasses. The pH value was measured in the loin at the end of the slaughter-line (pH(0)) and after cooling of carcasses (pH(24),pH(48)). The texture of raw meat was measured 72h post-mortem by the Warner-Bratzler shear method; the shear force was related to pH. Curvilinear relationships with coefficients of correlation r=0.64 (Pshear force and the pH value 24h p.m. were found with maximal shear force (the most tough meat) in the range of pH(24) from 6.2 to 6.4. Lower correlations (r=0.72 and r=0.54) between pH(24) and meat tenderness were found in the case of cows individually housed and housed in groups, respectively. No significant relationships were found between texture and pH measured at the end of the slaughter-line (r=0.59 for bulls and r=0.65 for cows) and 48h post-mortem (r=0.64 for bulls and r=0.50 for cows). The mode of housing of cattle before slaughter influenced the properties of beef significantly. Meat of bulls housed in groups before slaughter was less tender (the shear force was higher) than meat of bulls individually housed. It could be explained by higher depletion of glycogen before slaughter and thus insufficient pH decline. Generally, the meat of cows was more tender than of bulls irrespective of housing. No significant differences were found between the left and right halves of carcasses. Thus the mode of hanging had no influence on beef tenderness. PMID:22063610
Jelen�kov�, Jarmila; Pipek, Petr; Staruch, Ladislav
International Nuclear Information System (INIS)
Analytical solution of transverse shear strain vibration of a tube caused by internal gaseous detonation near the second critical speed (shear group velocity) is not reported in the literature. It is performed based on a steady state model and first order shear deformation theories (model I and II) in this paper, and the results are verified through comparison with the finite element results reported in the literature. There are no known experimental ways of directly measuring dynamic transverse shear strain and only theoretical results and numerical data are available. The finite element method is very time consuming compared with the analytical solution. It is shown in this paper that the resonance phenomenon of the transverse shear strain vibration near the second critical speed can be predicted by steady state model and first order shear deformation theories. The first order shear deformation theory (model II) has a good agreement with finite element results in prediction of dynamic amplification factors and critical speeds.
Displacements at shear crack in beams with shear reinforcement under static and fatigue loadings
Energy Technology Data Exchange (ETDEWEB)
The fatigue tests of rectangular reinforced concrete beams with vertical or inclined plain and/or deformed stirrups different in bond characteristics, reinforcement ratio and diameter were conducted under static and repeated loadings. Opening and shearing displacements along shear cracks as well as stirrup strains and concrete deformations along stirrups were measured. The effects of the bond characteristics, reinforcement ratio and diameter of the stirrup on stirrup slip and crack displacement in the direction of the stirrup were revealed. The method for predicting the opening displacement of shear cracks under static and repeated loadings was proposed in consideration of the angle, bond characteristics and diameter of the stirrup as well as a concrete strength and the amount and number of repeated loadings. The predicted crack displacements agreed with the experimental results and previously reported data. 13 refs., 12 figs., 2 tabs.
Hassan, H. (The University of Tokyo, Tokyo (Japan)); Ueda, T. (Hokkaido Universtiy, Sapporo (Japan)); Farghaly, S.
Shear strength of non-shear reinforced concrete elements : Part 3. Prestressed hollow-core slabs
DEFF Research Database (Denmark)
The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone.Due to the fact that the anchorage of the reinforcement takes place by bond, a rotation failure, which is induced by a crack formed at the support with subsequent slip of the reinforcement, is also considered. This failure mode is likely to occur in cases with a high prestressing force combined with a short shear span.The theoretical calculations are compared with test results from the literature. A good agreement has been found.
Hoang, Cao linh
Property of Alfven eigenmode in JT-60U reversed shear and weak shear discharges
International Nuclear Information System (INIS)
This paper reports activity of Alfven eigenmode (AE) in the JT-60U reversed shear (RS) and weak shear (WS) plasmas. The AEs with a rapid frequency sweeping and then saturation of frequency as qmin decreases has been observed in low-?h RS discharges with Negative-ion-based NBI (NNBI) or ICRH. We introduce the new type of AE which we call reversed-shear-induced Alfven Eigenmode (RSAE) near qmin. This puzzling frequency change can be explained by considering the properties of RSAE and their transition to toroidal Alfven Eigenmodes (TAEs). We verify the existence of RSAEs and their transition to TAEs from magnetic fluctuations and measured q-profile in JT-60U plasmas. The AE amplitude is maximum during this transition, e.g., ?2.4 min min transition range of n = 1 AE to avoid substantial fast ion loss by large amplitude AEs in RS plasmas. (author)
Property of Alfven eigenmode in JT-60U reversed shear and weak shear discharges
International Nuclear Information System (INIS)
This paper reports activity of Alfven Eigenmode (AE) in the JT-60U reversed shear (RS) and weak shear (WS) plasmas. The AEs with a rapid frequency sweeping and then saturation of frequency as qmin decreases has been observed in low- ?h RS discharges with Negative-ion-based NBI (NNBI) or ICRH. We introduce the new type of AE which we call reversed-shear-induced Alfven Eigenmode (RSAE) near qmin. This puzzling frequency change can be explained by considering the properties of RSAE and their transition to toroidal Alfven Eigenmodes (TAEs). We verify the existence of RSAEs and their transition to TAEs from magnetic fluctuations and measured q-profile in JT-60U plasmas. The AE amplitude is maximum during this transition, e.g., ?2.4 min min transition range of n = 1 AE to avoid substantial fast ion loss by large amplitude AEs in RS plasmas. (author)
Wall-Shear Stress Distribution in Turbulent Duct Flow
The wall-shear stress sensor MPS^3 based on flexible micro-pillars has been used to experimentally assess the two-dimensional wall-shear stress distribution in turbulent duct flow at moderate Reynolds number. A sensor array covering an area of 90x125 viscous length-scales along the streamwise and spanwise direction, respectively and 1-D sensor-lines spanning 125 viscous length-scales have been applied. The results evidence the co-existence of low- and high-shear regions representing ``foot-prints'' of near-wall coherent structures. Applying Taylor's hypothesis allows to crudely assess the streamwise length-scales of the near-wall flow field. Especially the low-shear regions attain streamwise dimensions of approximately 1,000 viscous length-scales. These low-shear regions resemble long meandering bands locally interrupted and deflected by regions of high-shear stress. A qualitative comparison evidences the structures detected in the present study to be similar to wall-shear stress distributions reported in the literature and to structures found in higher regions of the boundary layer. The results allow assessing statistics of the streamwise and spanwise wall-shear stress distribution, such as convection velocities of wall-shear stress fluctuations, two-point-, and auto-correlations. Geometric properties of the streak-like wall-shear stress distributions will also be discussed.
Gro�e, Sebastian; Schr�der, Wolfgang
Non-Newtonian viscosity of atomic fluids in shear and shear-free flows
International Nuclear Information System (INIS)
Simple shear and various simple shear-free flows with constant traceless velocity gradient are simulated at the microscopic level for an atomic fluid at a single state point. The dependence of the viscosity upon the strain rate is obtained for each specific flow and analyzed on the basis of the retarded motion expansion of the nonequilibrium pressure tensor. Within the investigated range of strain rate, the pressure and the internal energy follow a linear behavior in terms of the second scalar invariant of the strain-rate tensor which, as expected by symmetry, is common to all flows
Evolution of thermal ion transport barriers in reversed shear/optimised shear plasmas
International Nuclear Information System (INIS)
The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)
Evolution of thermal ion transport barriers in reversed shear/ optimised shear plasmas
International Nuclear Information System (INIS)
The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)
Shear strength of non-shear reinforced concrete elements : Part 1-Statically indeterminate beams
DEFF Research Database (Denmark)
The report deals with the shear strength of statically indeterminate reinforced concrete beams without shear reinforcement. Solutions for a number of beams with different load and support conditions have been derived by means of the crack sliding model developed by Jin- Ping Zhang.This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete.Proposals have been made on how the derived standard solutions may be applied to more complicated cases, such as continuous beams, beams with combined loading, prestressed beams and beams with different reinforcement area at top and bottom.
Hoang, Cao linh
Shear Wave Seismic Interferometry for Lithospheric Imaging
Green's function retrieval by seismic interferometry (SI) exists in a variety of forms. A common theme uniting many of the approaches of SI centers on the ability to create new seismic traces by cross correlating a received signal recorded at two separate locations. The sum of this operation for multiple sources results in the creation of a new signal such that one of the recording locations acts as a virtual source to the other. This presentation focuses on the use of teleseismic earthquake events to create a virtual shear wave source for imaging lithospheric features. Events are selected at long offsets for primarily two reasons: namely, (a) at large offsets the incoming wavefront approximates a plane wave due to spread of the wavefront in relation to the comparatively finite seismic array, and (b) the large distances act as a natural temporal filter to separate the incident P and S arrivals. Furthermore, using shear wave energy as an imaging source benefits from a variety of properties including a lower propagation velocity and the possibility for separate treatment of the shear vertical and shear horizontal fields. Prior to selecting a field dataset, a series of 1D earth forward modeling experiments with 2D elastic propagation were conducted. Initial modeling results indicate that SP converted energy maps primarily to the vertical component with little presence on the radial component. This suggests that decomposition techniques may be unnecessary as preprocessing for field data, but remains an option should field data dictate its use. Sufficient illumination by unique ray parameter sampling is essential for clearly resolving subsurface features through SI; however, initial decimation studies indicate that while clarity is reduced proportional to reduction of available ray parameters, it is still possible to identify strong reflectors even with relatively poor sampling. A challenge encountered by using earthquake events as an imaging source is the complexity of the source time function (STF). The heterogeneous subsurface near the source locations gives rise to complications of the incident field that need to be mitigated for successful SI application. The frequency and phase spectrum of such events is influenced by the event depth, ghost reflections, near surface complexity, earth's intrinsic attenuation of high frequency content, and travel distance. Numerical experiments indicate that correcting the received signal via whitening, or deconvolution, and bandpass filtering will be required to limit the impact of the STF on data quality. Finally, a field dataset is selected from southern Mexico with over 100 earthquake events that meet our criteria for magnitude and location. By azimuthally limiting a window around the relatively linear orientation of the seismometer array, earthquakes that vary in offset correspond to sampling of unique ray parameters. In earthquakes with sufficient shear energy, the S, SS, ScS, and SKS phases can be treated as separate events with individual ray parameters. Both of these techniques help to improve the overall illumination of the subsurface with better sampling. By using shear wave SI as a preprocessing technique, we hope to produce an image of the unique subduction setting beneath the seismometer array that offers new interpretable value to the region.
Frank, J.; Ruigrok, E. N.; Wapenaar, C. A.
Results of shear studies with 241-AY-101 sludge
International Nuclear Information System (INIS)
The Department of Energy's Tanks Focus Area (TFA) authorized a project to study the effect of shear on the settling properties of high-level waste sludge to support retrieval programs. A series of settling studies was conducted on a composite sample of tank 241-AY-101 (AY-101) material. Comparisons were made with duplicate samples that were sheared with a tissue homogenizer and allowed to settle. Aliquots of sheared and unsheared settled solids were submitted for chemical and radiological analyses. There are five major conclusions from the study that apply to AY-101 sludge: (1) Sludge settling rates are detectably decreased after shearing of particles by means of a tissue homogenizer. A significant decrease in the settling rates was measured after 2 minutes of shearing. A smaller additional decrease in the settling rates was observed after an additional 10 minutes of shearing. (2) Sodium and Cesium appear to be present in both the liquid and solid phases of the composite sample. (3) The shearing of the solids does not appear to significantly change the distribution of the radionuclides, (241Am, 90Sr, Total Alpha, or other radionuclides), within the solids. (4) The mean particle diameter decreases after shearing with the tissue homogenizer and affects the settling rate in proportion to the square of the particle diameter. (5) The sonication of the unsheared particles produces a similar particle size reduction to that of shearing with a tissue homoion to that of shearing with a tissue homogenizer. It is difficult to quantitatively compare the shear produced by a mixer pump installed in a double-shell tank with that produced by the tissue homogenizer in the laboratory. On a qualitative basis, the mixing pump would be expected to have less mechanical and more hydraulic shearing effect than the tissue homogenizer. Since the particle size distribution studies indicate that (for the AY-101 solids) the breaking up of particle aggregates is the main means of particle size reduction, then the hydraulic shearing of the mixing pump may well produce similar shearing effects as the tissue homogenizer. (Mechanical shear represents the shear caused by direct contact between a particle and a metal surface; hydraulic shear is caused by the particle moving between fluids traveling at different speeds.)
Microstructural and crystal fabric evolution during shear zone formation
The microstructures and crystal fabrics associated with the development of an amphibolite facies quartzo-feldspathic mylonitic shear zone (Torridon, NW Scotland) have been investigated using SEM electron channelling. Our results illustrate a variety of microstructures and fabrics which attest to a complex shear zone deformation history. Microstructural variation is particularly pronounced at low shear strains: significant intragranular deformation occurs via a domino-faulting style process, whilst mechanical incompatibilities between individual grains result in characteristic grain boundary deformation accommodation microstructures. A sudden reduction in grain size defines the transition to medium shear strains, but many of the boundaries inherited from the original and low shear strain regions can still be recognized and define distinctive bands oriented at low angles to the shear zone margin. Grains within these bands have somewhat steeper preferred dimensional orientations. These domains persist into the high shear strain mylonitic region, where they are oriented subparallel to the shear zone margin and consist of sub-20 ?m grains. The microstructures suggest that the principal deformation mechanism was intracrystalline plasticity (with contributions from grain size reduction via dynamic recrystallization, grain boundary migration and grain boundary sliding). Crystal fabrics measured from the shear zone vary with position depending on the shear strain involved, and are consistent with the operation of several crystal slip systems (e.g. prism, basal, rhomb and acute rhomb planes) in a consistent direction (probably parallel to a and/or m). They also reveal the presence of Dauphine twinning and suggest that this may be a significant process in quartz deformation. A single crystal fabric evolution path linking the shear zone margin fabric with the mylonitic fabric was not observed. Rather, the mylonitic fabric reflects the instantaneous fabric which developed at a particular location for a particular shear strain and original parental grain orientation. The mature shear zone therefore consists of a series of deformed original grains stacked on top of each other in a manner which preserves original grain boundaries and intragranular features which develop during shear zone evolution. The stability of some microstructures to higher shear strains, the exploitation of others at lower shear strains, and a continuously evolving crystal fabric, mean that the strain gradient observed across many shear zones is unlikely to be equivalent to a time gradient.
Lloyd, G. E.; Law, R. D.; Mainprice, D.; Wheeler, J.
Shear-Alfven Waves in Gyrokinetic Plasmas
International Nuclear Information System (INIS)
It is found that the thermal fluctuation level of the shear-Alfven waves in a gyrokinetic plasma decreases with plasma b(* cs2/uA2), where cs is the ion acoustic speed and uA is the Alfven velocity. This unique thermodynamic property based on the fluctuation-dissipation theorem is verified in this paper using a new gyrokinetic particle simulation scheme, which splits the particle distribution function into the equilibrium part as well as the adiabatic and nonadiabatic parts
Propagation of waves in shear flows
The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside
Fabrikant, A L
Reliability assessment of containment tangential shear failure
Energy Technology Data Exchange (ETDEWEB)
This report presents the latest developments of the reliability analysis method for concrete containments. In specific, the tangential shear limit state for reinforced concrete containments is described in detail. Also, the flexure limit state has been modified such that the strain of tensile reinforcement is limited. Furthermore, the variations of material strength such as concrete compressive strength and reinforcement yield strength are included in the reliability analysis by using the Latin hypercube sampling technique. Then, the reliability analysis results and fragility curves for two containments are presented.
Pepper, S.; Hwang, H.; Pires, J.
A Simple Model for Sheared Granular Layers
We phenomenologically investigate stick-slip motion of sheared granular layers. Our phenomenology is constructed in the context of nucleation-and-growth of the fluidized area which is triggered by collapsing of stress chains. Based on this picture, we give a simple friction model by introducing the degree of the fluidization. It is found that the present model can successfully reproduce major features of the experimental results reported by Nasuno {\\it et al.} (Phys. Rev. E {\\bf 58}, 2161 (1998)) with quantitatively good agreement.
Furukawa, A; Furukawa, Akira; Hayakawa, Hisao
Interface instability in shear banding flow
We report on the spatio-temporal dynamics of the interface in shear-banding flow of a wormlike micellar system (cetyltrimethylammonium bromide and sodium nitrate in water) during a start-up experiment. Using the scattering properties of the induced structures, we demonstrate the existence of an instability of the interface between bands along the vorticity direction. Different regimes of spatio-temporal dynamics of the interface are indentified along the stress plateau. We build a model based on the flow symetry which qualitatively describes the observed patterns.
Lerouge, S; Decruppe, J P
Stochastic parametric resonance in shear flows
Time-periodic shear flows can give rise to Parametric Instability (PI), as in the case of the Mathieu equation (Stoker, 1950; Nayfeh and Mook, 1995). This mechanism results from a resonance between the oscillatory basic state and waves that are superimposed on it. Farrell and Ioannou�(1996a, b) explain that PI occurs because the snap-shots of the velocity profile are subject to transient growth. If the flows were purely steady the transient growth would subside and not have any long l...
Poulin, F. J.; Scott, M.
Microalga propels along vorticity direction in a shear flow
Using high-speed digital holographic microscopy and microfluidics, we discover that, when encountering fluid flow shear above a threshold, unicellular green alga Dunaliella primolecta migrates unambiguously in the cross-stream direction that is normal to the plane of shear and coincides with the local fluid flow vorticity. The flow shear drives motile microalgae to collectively migrate in a thin two-dimensional horizontal plane and consequently alters the spatial distribution of microalgal cells within a given suspension. This shear-induced algal migration differs substantially from periodic rotational motion of passive ellipsoids, known as Jeffery orbits, as well as gyrotaxis by bottom-heavy swimming microalgae in a shear flow due to the subtle interplay between torques generated by gravity and viscous shear. Our findings could facilitate mechanistic solutions for modeling planktonic thin layers and sustainable cultivation of microalgae for human nutrition and bioenergy feedstock.
Chengala, Anwar; Hondzo, Miki; Sheng, Jian
Assessment of susceptibility of rape stems to shearing
Directory of Open Access Journals (Sweden)
Full Text Available In the present study, the authors used a dynamic shearing and densitometric method for the asses- sment of susceptibility of stems of winter rape, vars Mar, Bolko, Leo, Ceres and Libravo to shearing. They determi- ned dynamic shearing energy per a unit of the stem cross section area, in the natural state as well as after the removed of parenchyma, density and DOD parameter, indicating the amount of X-ray energy absorbed by the stems. It was found that susceptibility of rape stems to shearing depends on their structure. A strict correlation was shown to exist between the dynamic shearing energy and the amount of X-ray radiation energy absorbed by the stem. Moreover, in study showed that the application of the X-ray method greatly enhanced the possibility to determine of the suscep- tibility of rape stems to shearing.
Vielikanov L.
Shear banding deformation in Cu/Ta nano-multilayers
International Nuclear Information System (INIS)
Highlights: ? Formation of shear bands in Cu/Ta multilayers is layer thickness dependent. ? Unique layer-morphology with prevalent mismatched laminate structure was observed. ? A new physical mechanism that dominates shear band formation is suggested. - Abstract: Nanoscale Cu/Ta multilayers with individual layer thickness ranging from 3 to 70 nm were deformed under nanoindentation at room temperature. Shear bands can be observed only when individual layer thickness is reduced to 9 nm or below, indicating formation of shear bands in the Cu/Ta multilayers is layer thickness dependent. By observing the cross sectional transmission electron microscope images of the indentation fabricated through focused ion beam technique, shear banding deformation causing a unique layer-morphology with prevalent mismatched laminate structure has been reported for the first time. By capturing and analyzing a series of typical indentation-induced deformed microstructures, a new physical mechanism of shear banding behavior in metallic nano-multilayers is suggested.
Resonant Low Frequency Interlayer Shear Modes in Folded Graphene Layers
Naturally or artificially stacking extra layers on single layer graphene (SLG) forms few-layer graphene (FLG), which has attracted tremendous attention owing to its exceptional properties inherited from SLG and new features generated by introducing extra freedom. In FLG, shear modes play a critical role in understanding its distinctive properties. Unfortunately, energies of shear modes are so close to excitation lasers to be fully blocked by a Rayleigh rejecter. This greatly hinders investigations of shear modes in FLG. Here, we demonstrate dramatically enhanced shear modes in properly folded FLG. Benefiting from the extremely strong signals, for the first time, enhancement mechanism, vibrational symmetry, anharmonicity and electron-phonon coupling (EPC) of shear modes are uncovered through studies of two-dimensional (2D) Raman mapping, polarization- and temperature-dependent Raman spectroscopy. This work complements Raman studies of graphene layers, and paves an efficient way to exploit low frequency shear m...
Cong, Chunxiao

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