Substituted heterocycles of the general structural formula: ##STR1## are tachykinin receptor antagonists useful in the treatment of inflammatory diseases, pain or migraine, asthma and emesis, and calcium channel blockers useful in the treatment of cardiovascular conditions such as angina, hypertension or ischemia.

Analgesia has historically been achieved in the central nervous system by opiates and analogs which are addictive, and peripherally by cyclooxygenase inhibitors that have gastric side effects. Substance P antagonists may induce analgesia both centrally and peripherally. In addition, substance P antagonists are inhibitory of neurogenic inflammation.
The neuropeptide receptors for substance P (neurokinin-1; NK-1) are widely distributed throughout the mammalian nervous system (especially brain and spinal ganglia), the circulatory system and peripheral tissues (especially the duodenum and jejunum) and are involved in regulating a number of diverse biological processes. This includes sensory perception of olfaction, vision, audition and pain, movement control, gastric motility, vasodilation, salivation, and micturition (B. Pernow, Pharmacol. Rev., 1983, 35, 85-141). The NK-1 and NK-2 receptor subtypes are implicated in synaptic transmission (Laneuville et al., Life Sci., 42: 1295-1305 (1988)).
The receptor for substance P is a member of the superfamily of G protein-coupled receptors. This superfamily is an extremely diverse group of receptors in terms of activating ligands and biological functions. In addition to the tachykinin receptors, this receptor superfamily includes the opsins, the adrenergic receptors, the muscarinic receptors, the dopamine receptors, the serotonin receptors, a thyroid-stimulating hormone receptor, a luteinizing hormone-choriogonadotropic hormone receptor, the product of the oncogene ras, the yeast mating factor receptors, a Dictyostelium cAMP receptor, and receptors for other hormones and neurotransmitters (see A. D. Hershey, et al., J. Biol. Chem., 1991, 226, 4366-4373).
Substance P (also called "SP" herein) is a naturally occurring undecapeptide belonging to the tachykinin family of peptides, the latter being so-named because of their prompt contractile action on extravascular smooth muscle tissue. The tachykinins are distinguished by a conserved carboxyl-terminal sequence Phe-X-Gly-Leu-Met-NH.sub.2. In addition to SP the known mammalian tachykinins include neurokinin A and neurokinin B. The current nonmenclature designates the receptors for SP, neurokinin A, and neurokinin B as NK-1, NK-2, and NK-3, respectively. More specifically, substance P is a neuropeptide that is produced in mammals and possesses a characteristic amino acid sequence (Chang et al., Nature New Biol. 232, 86 (1971); D. F. Veber et al., U.S. Pat. No. 4,680,283).
Substance P is a pharmacologically-active neuropeptide that is produced in mammals and acts as a vasodilator, a depressant, stimulates salivation and produces increased capillary permeability. It is also capable of producing both analgesia and hyperalgesia in animals, depending on dose and pain responsiveness of the animal (see R. C. A. Frederickson et al., Science, 199, 1359 (1978); P. Oehme et al., Science, 208, 305 (1980)) and plays a role in sensory transmission and pain perception (T. M. Jessell, Advan. Biochem. Psychopharmacol. 28, 189 (1981)). For example, substance P is believed to be involved in the neurotransmission of pain sensations Otsuka et al, "Role of Substance P as a Sensory Transmitter in Spinal Cord and Sympathetic Ganglia" in 1982 Substance P in the Nervous System, Ciba Foundation Symposium 91, 13-34 (published by Pitman) and Otsuka and Yanagisawa, "Does Substance P Act as a Pain Transmitter?" TIPS, 8 506-510 (Dec. 1987)!, specifically in the transmission of pain in migraine (see B. E. B. Sandberg et al., Journal of Medicinal Chemistry, 25, 1009 (1982); M. A. Moskowitz, Trends Pharmacol. Sci., 13, 307-311 (1992)), and in arthritis (Levine, et al. Science, 226 547-549 (1984); M. Lotz, et al., Science, 235, 893-895 (1987)). Tachykinins have also been implicated in gastrointestinal (GI) disorders and diseases of the GI tract, such as inflammatory bowel disease see Mantyh et al, Neuroscience, 25 (3), 817-37 (1988) and D. Regoli in "Trends in Cluster Headache" Ed. F. Sicuteri et al., Elsevier Scientific Publishers, Amsterdam, pp. 85-95 (1987)!, and emesis Trends Pharmacol. Sci., 9, 334-341 (1988), F. D. Tatersall, et al., Eur. J. Pharmacol., 250, R5-R6 (1993)!.
It is also hypothesized that there is a neurogenic mechanism for arthritis in which substance P may play a role Kidd et al., "A Neurogenic Mechanism for Symmetric Arthritis" in The Lancet, 11 Nov. 1989 and Gronblad et al., "Neuropeptides in Synovium of Patients with Rheumatoid Arthritis and Osteoarthritis" in J. Rheumatol. 15(12) 1807-10 (1988)!. Therefore, substance P is believed to be involved in the inflammatory response in diseases such as rheumatoid arthritis and osteoarthritis O'Byrne et al., Arthritis and Rheumatism, 33 1023-8 (1990)!.
Evidence for the usefulness of tachykinin receptor antagonists in pain, headache, especially migraine, Alzheimer's disease, multiple sclerosis, attenuation of morphine withdrawal, cardiovascular changes, oedema, such as oedema caused by thermal injury, chronic inflammatory diseases such as rheumatoid arthritis, asthma/bronchial hyperreactivity and other respiratory diseases including allergic rhinitis, inflammatory diseases of the gut including ulcerative colitis and Chrohn's disease, ocular injury and ocular inflammatory diseases, proliferative vitreoretinopathy, irritable bowel syndrome and disorders of bladder function including cystitis and bladder detruser hyperreflexia is reviewed in "Tachykinin Receptors and Tachykinin Receptor Antagonists," C. A. Maggi, R. Patacchini, P. Rovero and A. Giachetti, J. Auton. Pharmacol, 13, 23-93 (1993); see also R. M. Snider, et al., Chem. Ind., 11, 792-794 (1991). Neurokinin-1 receptor antagonists alone or in combination with bradykinin receptor antagonists may also be useful in the prevention and treatment of inflammatory conditions in the lower urinary tract, especially cystitis Giuliani, et al., J. Urology, 150, 1014-1017 (1993)!. Other disease areas where tachykinin antagonists are believed to be useful are allergic conditions Hamelet et al., Can. J. Pharmacol. Physiol., 66, 1361-7 (1988)!, immunoregulation Lotz, et al., Science, 241 1218-21 (1988), Kimball, et al., J. Immunol., 141 (10) 3564-9 (1988); A. Perianin, et al., Biochem. Biophys. Res Commun. 161, 520 (1989)!, post-operative pain and nausea C. Bountra, et al., Eur. J. Pharmacol., 249, R3-R4 (1993), F. D. Tattersall, et al., Neuropharmacology, 33, 259-260 (1994)!, vasodilation, bronchospasm, reflex or neuronal control of the viscera Mantyh et al., PNAS, 85, 3235-9 (1988)! and, possibly by arresting or slowing .beta.-amyloid-mediated neurodegenerative changes Yankner et al., Science, 250, 279-82 (1990)! in senile dementia of the Alzheimer type, Alzheimer's disease and Downs Syndrome. Substance P may also play a role in demyelinating diseases such as multiple sclerosis and amyotrophic lateral sclerosis J. Luber-Narod, et. al., poster C.I.N.P. XVIIIth Congress, 28th Jun.-2nd Jul., 1992!, and in disorders of bladder function such as bladder detrusor hyper-reflexia Lancet, 16th May 1992, 1239!. Antagonists selective for the neurokinin-1 (NK-1) and/or the neurokinin-2 (NK-2) receptor may be useful in the treatment of asthmatic disease (Frossard et al., Life Sci., 49, 1941-1953 (1991); Advenier, et al., Biochem. Biophys. Res. Comm., 184(3), 1418-1424 (1992); P. Barnes, et al., Trends Pharmacol. Sci., 11, 185-189 (1993)). Tachykinin antagonists may also be useful in the treatment of small cell carcinomas, in particular small cell lung cancer (SCLC) Langdon et al., Cancer Research, 52, 4554-7 (1992)!.
It has furthermore been suggested that tachykinin receptor antagonists have utility in the following disorders: depression, dysthymic disorders, chronic obstructive airways disease, hypersensitivity disorders such as poison ivy, vasospastic diseases such as angina and Reynauld's disease, fibrosing and collagen diseases such as scleroderma and eosinophillic fascioliasis, reflex sympathetic dystrophy such as shoulder/hand syndrome, addiction disorders such as alcoholism, stress related somatic disorders, neuropathy, neuralgia, disorder related to immune enhancement or suppression such as systemic lupus erythmatosus (EPO Publication No. 0,436,334), ophthalmic diseases such as conjunctivitis, vernal conjunctivitis, and the like, and cutaneous diseases such as contact dermatitis, atopic dermatitis, urticaria, and other eczematoid dermatitis (EPO Publication No. 0,394,989).
Substance P antagonists may be useful in mediating neurogenic mucus secretion in mammalian airways and hence provide treatment and symptomatic relief in diseases characterized by mucus secretion, in particular, cystic fibrosis S. Ramnarine, et al., abstract presented at 1993 ALA/ATS Int'l Conference, 16-19 May, 1993, published in Am. Rev. of Respiratory Dis., May 1993!.
In the recent past, some attempts have been made to provide peptide-like substances that are antagonists for the receptors of substance P and other tachykinin peptides in order to more effectively treat the various disorders and diseases mentioned above. For example Lowe, Drugs of the Future, 17 (12) 1115-1121 (1992) and EPO Publication Nos. 0,347,802, 0,401,177 and 0,412,452 disclose various peptides as neurokinin A antagonists. Also, PCT Patent Publication WO 93/14113 discloses certain peptides as tachykinin antagonists. In addition, EPO Publication No. 0,336,230 discloses heptapeptides which are substance P antagonists useful in the treatment of asthma. Merck U.S. Pat. No. 4,680,283 also discloses peptidal analogs of substance P. Certain inhibitors of tachykinins have been described in U.S. Pat. No. 4,501,733, by replacing residues in substance P sequence by Trp residues. A further class of tachykinin receptor antagonists, comprising a monomeric or dimeric hexa- or heptapeptide unit in linear or cyclic form, is described in GB-A-2216529. The peptide-like nature of such substances make them too labile from a metabolic point of view to serve as practical therapeutic agents in the treatment of disease. The non-peptidic antagonists of the present invention, on the other hand, do not possess this drawback, as they are expected to be more stable from a metabolic point of view than the previously-discussed agents.
It is known that in the central nervous system baclofen .beta.-(aminoethyl)-4-chlorobenzenepropanoic acid! effectively blocks the excitatory activity of substance P, but because in many areas the excitatory responses to other compounds such as acetylcholine and glutamate are inhibited as well, baclofen is not considered a specific substance P antagonist. Pfizer WIPO patent applications (PCT Publication Nos. WO 90/05525, WO 90/05729, WO 91/18899, WO 92/12151 and WO 92/12152) and publications (Science, 251, 435-437 (1991); Science, 251, 437-439 (1991); J. Med. Chem., 35, 2591-2600 (1992)) disclose 2-arylmethyl-3-substituted amino-quinuclidine derivatives which are disclosed as being useful as substance P antagonists for treating gastrointestinal disorders, central nervous system disorders, inflammatory diseases and pain or migraine. A Glaxo European patent application (EPO Publication No. 0,360,390) discloses various spirolactam-substituted amino acids and peptides which are antagonists or agonists of substance P. A Pfizer WIPO patent application (PCT Publication No. WO 92/06079) discloses fused-ring analogs of nitrogen-containing nonaromatic heterocycles as useful for the treatment of diseases mediated by an excess of substance P. A Pfizer WIPO patent application (PCT Publication No. WO 92/15585 discloses 1-azabicyclo3.2.2!nonan-3-amine derivatives as substance P antagonists. A Pfizer WIPO patent application (PCT Publication No. WO-93/10073) discloses ethylenediamine derivatives as substance P antagonists. PCT Publication No. WO 93/01169 discloses certain aromatic compounds as tachykinin receptor antagonists. A Sanofi publication (Life Sci., 50, PL101-PL106 (1992)) discloses a 4-phenyl piperidine derivative as an antagonist of the neurokinin A (NK2) receptor.
Howson et al. (Biorg. & Med. Chem. Lett., 2 (6), 559-564 (1992)) disclose certain 3-amino and 3-oxy quinuclidine compounds and their binding to substance P receptors. EPO Publication 0,499,313 discloses certain 3-oxy and 3-thio azabicyclic compounds as tachykinin antagonists. U.S. Pat. No. 3,506,673 discloses certain 3-hydroxy quinuclidine compounds as central nervous system stimulants. A Pfizer EPO Patent application (EPO Publication 0,436,334) discloses certain 3-aminopiperidine compounds as substance P antagonists. U.S. Pat. No. 5,064,838 discloses certain 1,4-disubstituted piperidinyl compounds as analgesics. PCT Publication No. WO 92/12128 discloses certain piperidine and pyrrolidine compounds as analgesics. Peyronel, et al. (Biorg & Med. Chem. Lett., 2 (1), 37-40 (1992)) disclose a fused ring pyrrolidine compound as a substance P antagonist. EPO Publication No. 0,360,390 discloses certain spirolactam derivatives as substance P antagonists. U.S. Pat. No. 4,804,661 discloses certain piperazine compounds as analgesics. U.S. Pat. No. 4,943,578 discloses certain piperazine compounds useful in the treatment of pain. PCT Publication No. WO 92/01679 discloses certain 1,4-disubstituted piperazines useful in the treatment of mental disorders in which a dopaminergic deficit is implicated. PCT Publication No. WO 94/00440, EPO Publication No. 0,577,394 and PCT Publication No. WO 95/16679 disclose certain morpholine and thiomorpholine compounds as substance P antagonists.

Morpholine and thiomorpholine tachykinin receptor antagonists


The present invention provides a control apparatus for a plant, which can suppress excessive correction for a spiky disturbance being applied and maintain a good controllability, when controlling the plant, which is a controlled object, with the self-tuning regulator. A detected equivalent ratio KACT is input to a high-pass filter 33, and a high-pass filter output KACTHP is input to a parameter adjusting mechanism 42. The parameter adjusting mechanism 42 calculates a corrected updating vector (KID·dθ(k)) by multiplying an updating component dθ of a model parameter vector by a correction coefficient KID, and adds the corrected updating vector to a preceding value θ(k−1) of the model parameter vector, to thereby calculate a present value θ(k). The correction coefficient KID is changed from “1.0” to a value near “0” upon detection of the spiky response where an absolute value of the high-pass filter output KACTHP increases.

An example of a control apparatus for a plant, which controls an air-fuel ratio of an air-fuel mixture supplied to an internal combustion engine, is described in Japanese Patent Laid-open No. 11-73206. This control apparatus controls the air-fuel ratio using a self-tuning regulator having a parameter adjusting mechanism which functions as an identifier for identifying model parameters of the controlled object model.
In this control apparatus, a self-tuning correction coefficient KSTR is calculated by the self-tuning regulator according to the air-fuel ratio detected by an air-fuel ratio sensor provided in the exhaust system of the engine, and an amount of fuel to be supplied to the engine is controlled with the self-tuning correction coefficient KSTR.
When applying the above conventional control apparatus to a control of the internal combustion engine mounted on a vehicle, a problem that an emission amount of NOx increases upon deceleration of the vehicle caused by a quick return of the depressed accelerator pedal, or upon changing a gear position of a transmission of the vehicle, is confirmed.
When the accelerator pedal is quickly returned, an amount of intake air of the engine quickly decreases, and the fuel adhered to an inner wall of the intake pipe is supplied to the combustion chamber. Accordingly, the air-fuel ratio detected by the air-fuel ratio sensor indicates a spiky change to a richer air-fuel ratio (a change of quickly protruding and returning is hereinafter referred to as a "spike" or a "spiky change"). Therefore, in order to rapidly correct this change in the air-fuel ratio, the self-tuning regulator makes the self-tuning correction coefficient KSTR quickly decrease. As a result, the air-fuel ratio becomes over-lean immediately after the quick return of the accelerator pedal, which makes the emission amount of NOx increase.
FIGS. 14A to 14C respectively show changes in a detected equivalent ratio KACT, the self-tuning correction coefficient KSTR, a target equivalent ratio KCMD, the vehicle speed VP, and the NOx emission amount. The detected equivalent ratio KACT, shown by a thick line in FIG. 14A, is obtained by converting the air-fuel ratio detected by the air-fuel ratio sensor to an equivalent ratio. The target equivalent ratio KCMD, shown by a thin line in FIG. 14A, is obtained by converting a target air-fuel ratio to an equivalent ratio. The self-tuning correction coefficient KSTR is shown by a broken line in FIG. 14A. As shown in FIG. 14B, when a gear change is performed, a rich spike of the detected equivalent ratio KACT is generated, which causes the self-tuning correction coefficient KSTR to quickly change in the lean direction. Accordingly, a lean spike is generated immediately after the rich spike of the detected equivalent ratio KACT. As a result, the NOx emission amount temporarily increases as shown in FIG. 14C.
When applying the PID (proportional, integral, and differential) control to the air-fuel ratio control of the internal combustion engine, the above-described problem does not occur, since the response speed of the PID control is relatively slow. It is considered that the above-described problem is caused since the control by the self-tuning regulator has very high speed response characteristic.


A optical fiber cable wound about an overhead transmission line stretched between supporting poles installed a predetermined distance apart from each other, comprises a tension member, a plurality of plural-core type optical fiber tape-shaped strands arranged on the outside of the tension member, a buffer layer covering outer surface of the arrangement of the plural-core type optical fiber tape-shaped strands, and a sheath covering the outer surface of the buffer layer. The tape-shaped strands each include a plurality of optical fibers arranged side by side, and a covering layer collectively covering the plurality of side by side optical fibers. The particular construction permits the optical fiber cable to house a larger number of optical fibers for a given diameter of the cable while maintaining a high heat resistance and satisfactory mechanical properties.

1. Field of the Invention
The present invention relates to an optical fiber cable wound about an overhead transmission line for transmitting power of high voltage, said optical fiber cable being used for optical communication or the like.
2. Description of the Related Art
An optical fiber is not electrically affected by a power line such as a transmission line. Based on this property, an optical fiber cable B wound about an overhead transmission line A installed in advance has been developed as shown in FIG. 1 to permit communication between, for example, a power station and a substation.
The optical fiber cable B wound about the overhead transmission line A is required to meet the conditions described below. First of all, the optical fiber cable is heated by the heat generated from the overhead transmission line itself. In, particularly, the summer season, the overhead transmission line is heated to temperatures exceeding 100.degree. C. in some cases, with the result that the optical fiber cable is also heated to about 100.degree. C. If an accident occurs by short-circuiting in the overhead transmission line, the optical fiber cable is momentarily heated to about 300.degree. C. Naturally, the optical fiber cable wound about the overhead transmission line is required to exhibit a high heat resistance, i.e., resistance to about 300.degree. C.
It should also be noted that an overhead transmission line is stretched between supporting poles installed a predetermined distance apart from each other and, thus, receives a very high wind pressure. Naturally, it is important for the optical fiber cable wound about the overhead transmission line to have an outer diameter as small as possible. To be more specific, the outer diameter of the optical fiber cable should be at most about 5 mm.
A conventional optical fiber cable constructed to meet the two requirements described above has a cross section as shown in FIG. 3. It is seen that a plurality of single-core type optical fiber strands 16, each having a covering, are arranged about the outer surface of a tension member 1, made of, for example, FRP (Fiber Reinforced Plastic). Further, the optical fiber strands 16 are covered with a fluoroplastic sheath (protective layer) 17. FIG. 2 shows the construction of the single-core type optical fiber strand 16. Specifically, the strand 16 comprises an optical fiber 13 consisting of a core 11 and a clad 12 each formed of silica glass, a buffer layer 14 made of, for example, a silicone resin and positioned to cover the optical fiber 13, and an outermost layer 15 made of, for example, a fluoroplastic and positioned to cover the buffer layer 14.
In the conventional optical fiber cable described above, the outermost layer 15 of the single-core type optical fiber strand 16 is made of a fluoroplastic. Since the fluoroplastic outermost layer 15 is hard and permits sufficiently protecting the optical fiber 13, it is unnecessary to provide a buffer layer made of, for example, a silicone resin to cover the outer surface of the tension member 1. However, in the case of preparing an optical fiber cable having an outer diameter of about 5 mm by using the single-core type optical fiber strands 16, only about 12 strands can be incorporated in the optical fiber cable. An optical fiber cable having only about 12 single-core type optical fiber strands incorporated therein is incapable of handling an increase in data expected in the future. In other words, the optical fiber cable is incapable of transmitting a large amount of optical signals.
For enabling the optical fiber cable to be capable of transmitting a large amount of optical signals, it is certainly possible to incorporate a larger number of the single-core type optical fiber strands 16 by diminishing the outer diameter of each of the strands 16. As a matter of fact, the outer diameter of the strand 16 can be diminished by decreasing the thickness of the outermost layer 15 of the strand 16. It is also possible to diminish the outer diameter of the optical fiber cable by decreasing the thickness of the protective layer 17 to permit the cable of a predetermined thickness to include a larger number of the single-core type optical fiber strands 16. If the thickness of the outermost layer 15 or the protective layer 17 is decreased, however, the optical fiber cable fails to exhibit a sufficient heat resistance and satisfactory mechanical properties such as tensile strength and so on.

Optical fiber cable wound about overhead power transmission line


An apparatus and method are disclosed for continuously producing a stress free sheet of dough. The dry ingredients are measured and mixed on a continuous basis and the liquid ingredients are injected into the stream of dry ingredients. The ingredients are then transferred to a temperature controlled kneading chamber which generates a continuous stream of dough. The dough stream is discharged from the kneading chamber without benefit of rollers or stress inducing apparatus through a discharge conduit of predetermined flow resistance. The resulting stress free continuous stream of dough has a well developed and undamaged gluten network producing a high quality dough product.

This invention relates to an apparatus and method for commercially producing sheets of dough and more particularly, for producing "stress free" sheets of dough. "Stress free" dough is dough which has not had the gluten of the dough fractured or damaged in the sheeting process.
The current practice for commercially producing sheets of dough by a batch method generally involves measuring the required dry ingredients (i.e., flour, sugar, yeast, etc.) and mixing them with the appropriately measured liquid ingredients (i.e., water, oil, etc.). The resulting dough paste created by mixing of these ingredients is then kneaded until the desired dough mass containing the gluten network is formed. The dough mass is then typically transferred to a retention hopper or bin and commingled with previously prepared batches of dough from which the dough mass is extruded by a combination of peripherally ribbed oppositely rotating discharge rollers which force the dough mass through an extrusion die or restricted opening to form a continuous stream of dough. In the course of forcing the dough through the extrusion die, the discharge rollers forcefully pull small portions of the dough from the large dough mass in the retention bin and push it through the die or restricted opening to form the continuous stream of extruded dough. Once extruded, the stream of dough can be shaped, rolled, or cut to the desired specifications depending on the ultimate dough product (i.e., croissant, bread loaf, bun, pizza crust, etc.).
As the dough is kneaded or worked during the kneading process, the gluten network is generated in the dough. The gluten network is a highly elastic and cohesive gel structure which is generally indicative of the quality of the dough. The more developed and undamaged the gluten network remains in the dough, the higher the quality of the resulting dough product. Gluten in the dough is damaged or destroyed as a result of high stresses or shear forces applied to the dough. Therefore, the less stress imparted to the dough or the more "stress free" the dough remains during the formation of a dough stream, the higher the quality of the resulting dough product.
In the practice of the above described commercial process for producing a continuous sheet of dough, peripherally ribbed discharge rollers which pull the dough from the retention bin and force it into the extrusion die exert a significant shear or tearing force on the dough. These shear forces greatly damage and destroy the gluten network. Additionally, the mechanical work energy of the discharge rollers applied to the dough in the course of shearing it from the dough mass and forcing it through the extrusion die, increases the temperature of the dough by as much as 5.degree. F. This temperature increase further damages the dough.
In addition to the damage to the dough mass imparted by the shear stress and the increase in temperature of the dough, the compression forces applied to the dough by the discharge rollers further damage the dough. The resulting stream of compressed dough emerging from the extrusion die is difficult to shape and form because of these compression forces. The damaged dough can be partially restored if passed through a series of rollers and shapers, but this corrective measure is much more timely and costly than if the dough had never been compressed and the gluten network damaged in the first place. An additional corrective measure common in the industry to rehabilitate compressed dough and the damaged gluten network thereof is to leave the dough to rest for as much as two hours after extrusion from the retention bin. Once again, this practice serves to only partially regenerate the gluten and is inherently time consuming and a further complicating requirement to produce a continuous sheet of quality stress free dough. The dough which has been rehabilitated is still of a lesser quality and resistant to shaping than "stress free" dough.
There are prior patents directed to methods and apparatus for producing a continuous stream of stress free dough. U.S. Pat. No. 5,091,202, for example, discloses a dough hopper with a pair of vertically mounted conveyors and a pair of discharge rollers positioned below an opening in the bottom of the hopper. The continuous stream of dough is produced according to the disclosure of this patent by pulling the dough out of the hopper opening and sandwiching it between the conveyors and then the discharge rollers. The dough is flattened and narrowed to achieve a stream of dough by controlling the cross-sectional area between the conveyors and between the rollers and regulating their respective rotational velocities. However, the gluten is still damaged with such a method due to the compressive forces between the conveyors and rollers and the work energy converted to heat energy when applied to the dough by the conveyor and roller rotation.
Similarly, U.S. Pat. No. 4,276,317 discloses a method for producing a strip of dough by means of a plurality of opposing pairs of discharge rollers positioned below a dough hopper. The rollers form the strip of dough by reducing the spacing between each successive pair of discharge rollers thereby flattening the dough as it passes between the rollers. The resulting dough stream generated by the practice of this patent is also not truly stress free due to the compressive forces and the temperature rise experienced by the dough according to the practice of this patent.
Another method for producing a continuous stream of "stress free" dough is disclosed in U.S. Pat. No. 4,904,491 in which the dough is severed into portions by cutter blades at the bottom of a dough hopper. The blades section the dough into individual portions which are weighed and placed on a conveyor to occupy a space proportional to its mass. The speed of the conveyor is controlled to correspond to the mess of each portion of dough and each successive portion is positioned to overlap the previous portion, thereby forming a continuous stream of dough when rolled and shaped appropriately. Although gluten damaging excessive pressures are reduced, the involved steps of weighing each portion of dough and regulating the conveyor to overlap each portion complicate the dough stream production. In addition, cutting the dough into individual portions severs the gluten network formed in the dough thereby requiring reformation of the gluten network when the dough is ultimately formed into a stream.
The so called "stress free" systems described in the above identified patents are all based on a batch process where the dough is mixed and kneaded in a batch mixer. Batch sizes can vary from as little as 100 pounds to as much as 2,000 pounds per batch.
In the time frame of starting and finishing the use of the batch, time lapses of up to 20 minutes are common. The dough structure changes due to continuing moisture absorption, development of yeast and relaxation of gluten during this time frame. This results in changes of quality from beginning to end of batch, as well as changes of consistency and workability of the dough.
This inconsistency requires specialized, automated sheeting systems to produce a more consistent finished product. The invention of this application mixes and kneads the dough continuously which results in consistent dough throughout the process since each dough particle has the same mix time, knead time and rest time.
The system of this invention makes it possible to use lower amounts of yeast, since lapse times between mixing and finishing the final product can be as little as two minutes, which results in very little to no yeast development. This is a big advantage, particularly for frozen dough products.

Method for producing a stress free continuous dough stream


A modular rail and post fence system. The fence system includes a plurality of rail assemblies with each rail assembly formed from a pair of panels. Each panel has a pair of sidewalls joined together at an angle to form an angled edge wherein the pair of panels are joined together to form a rail assembly. A plurality of elongated posts are also provided. Each elongated post has at least one longitudinal recess with a pair of opposed protrusions extending into the longitudinal recess. At least one pair of notches in the pair of opposed protrusions is provided whereby the angled edges of each rail assembly are received in one pair of notches of the elongated posts. The entire system may be fabricated, assembled, and installed without fasteners.

1. Field of the Invention
The present invention relates to a modular rail and post fence system that may be constructed and assembled without any fasteners. In particular, the present invention is directed to a modular rail and post fence system which may be roll formed from conventional flat metal pieces and may be shipped in component parts for storage and may be distributed and shipped to locations in the field for assembly.
2. Prior Art
Various types of rail fencing systems have been proposed in the past. In a typical system, a plurality of posts and a plurality of rails are manufactured and then shipped to distribution or sales points. The individual components are then shipped to the installation location where the posts are installed and the rails are attached to the posts by fasteners. Decreasing the costs associated with shipping and storage is desirable.
In an effort to provide modular fence systems and to ease installation, various types of connection mechanisms have been proposed in the past.
Arnd (U.S. Pat. No. 3,338,602) discloses a pair of tubular shaped pieces 1 and 2 having a square cross section which are joined together. Connecting member 3 with a flexible projection 4 joins the tubular pieces together.
Murdock (U.S. Pat. No. 3,608,938) discloses a fence system with tubular rails 36. Connectors 41 extending from fence post 12 are received in the open ends of rails 36.
Jenkins (U.S. Pat. No. 4,468,067) discloses a display ease with rail horizontal member 24 which is pinned to post frame member 14 by a hook member 60 received in open end 62 of rail 24.
Bisch (U.S. Pat. No. 5,873,564) in FIGS. 17 through 19, discloses a metal fence with a rail 204 which is held to a frame by elastic, spring-like pin 210.
Wittig et al. (U.S. Pat. No. 6,042,296) discloses a variety of panel fasteners. FIG. 11 discloses a fastener 500 with legs 513a and b to lock an adjoining panel. Ends 530a and b include camming surfaces 580a and b and locking surfaces 582a and b.
Waimsley (U.S. Pat. No. 6,631,887) in FIG. 6, discloses a rail 66 with side edges turned inward.
A number of proposals in the past have suggested eliminating conventional fasteners to secure rails to posts, for example, Schall et al. (U.S. Pat. No. 6,375,166). There nevertheless remains a need to produce a rail and post fence system that eliminates the need for any fasteners, either in manufacturing or assembling.
There have also been known snap lock joint connections for metal panels, such as button punch or Pittsburgh lock connections.
It would also be desirable to be able to ship the rails and posts and components thereof in nested fashion to reduce shipping space and shipping costs.
Accordingly, it is a principal object and purpose of the present invention to provide a modular rail and post fence system which may be constructed, assembled, and installed without use of any fasteners.
It is a further object and purpose of the present invention to provide a modular rail and post fence system wherein the individual components may be nested together for savings on shipping, transportation and storage.
It is a further object and purpose of the present invention to provide a modular rail and post fence system wherein the individual components may be roll formed from flat sheets of metal.


A cutting tool is provided and includes a plurality of cutting inserts located in respective insert pockets. The cutting inserts each include a top cutting plane with at least one cutting edge and a bottom support plane. The top cutting plane includes an engagement portion for mating with a respective engagement portion located in the respective insert pocket. A clamping wedge clamps the cutting insert against the respective insert pocket. A shear resistance created between the engagement portions of the cutting insert and the respective insert pocket during operation of the tool is greater than a centrifugal force created during operation of the cutting tool. In an exemplary embodiment, the engagement portions are shown as a plurality of serrations. The cutting tool is particularly useful in high speed milling operations.

Cutting tools used for machining work pieces of metal, such as steel, aluminum, titanium, etc., typically include a tool holder for mounting removable cutting inserts. During operation of the cutting tool, a centrifugal force Fz is generated. In high speed milling operations, centrifugal force Fz becomes significant due to its relationship with spindle speed (growing in power 2 proportional to spindle speed) in accordance with the equation Fz=M*W2*R, where M is the mass of the insert, W is the speed of rotation, and R is distance between the rotational center of the tool and the position of the insert's center of mass. The cutting tool system becomes unbalanced when the centrifugal force Fz exceeds a clamping force.
With reference to FIG. 20, the relationship of cutting speed on cutting force is shown. As illustrated in FIG. 20, an increase in cutting speed typically supports a reduction of the cutting force. In particular, the hardness and strength of the workpiece material is decreased due to increased temperature in the cutting zone at high speeds. At the same time, centrifugal force applied to the insert Fz is growing dramatically (square to RPM). There is a point where the centrifugal force becomes larger than the amplitude of the cutting force. For high speed machining, the centrifugal force will be typically larger than cutting force. High speed machining typically has RPMs in excess of 10,000. However, most traditional designs of inserts and clamping mechanisms are designed for low centrifugal force and may fail during high speed machining.
At high cutting speeds, centrifugal forces applied to the cutting element significantly exceed cutting forces. If the clamping system fails, kinetic energy accumulated during rotation will be released in accordance with EK=(½)MV2 wherein M is the mass of the object and V is the linear velocity at the moment of failure. Because of the above-noted relationship, one of most important factors and requirement at high speeds is safety of the rotating tool.
Cutting tools have been designed with an open pocket for location of a cutting insert. A disadvantage with this particular design is that high centrifugal force is applied to the clamping screw, which is already pre-stressed during clamping. When the screw fails, the insert is "free to fly" to release significant kinetic energy.
There are known designs of milling cutters which utilize inserts with serrations on a bottom surface or surface opposed to the cutting plane of the insert, as shown, for example, in U.S. Pat. Nos. 5,924,826, 5,810,518, and 6,921,234. A disadvantage of these systems is vulnerability of the cutter body for collisions and breakage of the inserts. Because serrations are provided on the insert bottom to support insert load, and being extended to the maximum, damage occurred is usually very severe and repair is very difficult. Another disadvantage of these designs is the absence of axial adjustment mechanism, which would allow precision positioning of the inserts without costly grinding in assembly.
Finally, as discussed above, a single screw is used for securing the insert in the open pocket. If the screw fails, the entire insert will be released from the pocket. There is no additional features or redundancy that further prevents the insert from being released during operation should the screw fail. Therefore, there is a need in the art for a cutting tool where the clamping screw is not subjected to the cutting load, and does not take significant centrifugal load. In addition, there is a need in the art for redundant securing features in high speed applications.
While the serrations provided on the bottom surface can absorb a significant portion of centrifugal force, they can not absorb 100% of the centrifugal force. Due to the angular nature of the serration's cross section, there still is a portion of centrifugal force, which has "lifting" power. When cutter rotation speed is increasing, a portion of centrifugal force reflected through serrations to the clamping screw is growing also. At some point, the centrifugal force will cause the insert to lift and make the cutting tool fail. Another disadvantage of this type of cutting tool is that if the insert uses two cutting edges, the second edge will experience premature wear by hitting chips generated during the cut. Also, ongoing chips contact elements of any adjustment mechanism, which further creates premature wear.
For cutting tools having a carbide tip, the ability to stay retained in the insert becomes even more crucial. Because carbide is twice as dense as steel, it will be subjected to a larger centrifugal load. Due to its weight, it is more likely to fly out of the pocket. In addition, the carbide tip takes a majority of the cutting load, and could become separated from the body. For applications using carbide tips, it is important that should a failure occur, that only a small portion of the carbide tip be released, causing a smaller likelihood of damage.
Accordingly, there is a need in the art for an improved milling cutter for high speed milling operations. In addition, there is a need in the art for an insert that is more resistant to wear and failure. Finally there is a need in the art for redundant securing features in high speed applications, particularly those using heavier materials such as carbide.

Cutting tool with adjustable indexable cutting insert


A steering apparatus for vehicle comprises a steering shaft including a first portion connected to a steering member and a second portion connected to steerable wheels; a transmission ratio variable mechanism capable of varying a transmission ratio as a ratio of a steered angle of the steerable wheels to a steering angle of the steering member; and a reaction-force compensation motor for compensating a steering reaction force of the steering member caused by the operation of the transmission ratio variable mechanism. The transmission ratio variable mechanism includes a differential mechanism for differentially rotatably interconnecting the first and second portions; and a differential-mechanism motor for driving the differential mechanism. Both an axis of a rotary shaft of the differential-mechanism motor and an axis of a rotary shaft of the reaction-force compensation motor are aligned with an axis of the steering shaft.

1. Field of the Invention
The present invention relates to a steering apparatus for vehicle adapted to vary a ratio of a steered angle of steerable wheels to a steering angle of a steering member.
2. Description of Related Arts
The above steering apparatus for vehicle is shown in the following documents 1 to 3.
Document 1: Japanese Unexamined Patent Publication No. 2002-240729
Document 2: Japanese Unexamined Patent Publication No. 2004-224085
Document 3: Japanese Unexamined Patent Publication No. 2005-343205
The above document 3 discloses an arrangement comprising: a first shaft connected with a steering wheel; a second shaft connected to vehicle wheels; and a planet gear mechanism for rotation-transmittably interconnecting the first and second shafts. The planet gear mechanism comprises: a first sun gear fixed to the first shaft; a second sun gear fixed to the second shaft; a plurality of pinions disposed around the first and second shafts; and a carrier enclosing the pinions. The rotation of the steering wheel is transmitted to the first shaft, the first sun gear, the pinions, the second sun gear and the second shaft in this order and is finally transmitted to the vehicle wheels.
A transmission ratio of the planet gear mechanism (a ratio of the number of revolution of the second sun gear to the number of revolutions of the first sun gear) may be varied by a first motor driving the carrier into rotation. An output from the first motor is transmitted to the carrier via a small gear connected with an output shaft of the first motor, and a toothed portion formed on an outer periphery of the carrier and meshed with the small gear. Thus the number of revolutions of the carrier is varied.
In a case where the transmission ratio is varied in the aforementioned manner, speed shifting is carried out between the first and second shafts. As a result, a relation between the steering angle and the reaction force from the vehicle wheels is varied from that in a state prior to the change of transmission ratio. The characteristic of the reaction force varies irrespective of the intent of a driver, and a driver has an uncomfortable steering feeling. In order to eliminate this uncomfortable steering feeling, an arrangement is made such that a second motor is provided and an output from the second motor is transmitted to the first shaft via a reduction mechanism including a small gear and a large gear. Thus the variations of the characteristic of the reaction force are prevented.
In the case of the document 3, however, the first and second motors oppose to each other with the steering shaft interposed therebetween. The housings of these motors are protruded radially of the steering shaft so that the system is increased in size.
In view of the foregoing, the invention has an object to provide a steering apparatus for vehicle achieving size reduction.


There are provided an ASE correction unit which corrects control errors regarding either or both of the gain and the output level of the optical amplifier, which control errors are generated due to the ASE, and an ASE correction controller which controls the correction of the control errors by these ASE correction unit based on a predetermined time constant. Accordingly, the ASE correction errors of the optical amplifier, which performs the ASE correction are suppressed, and stabilization of the output signal light level and the optical amplification gain at the time of changes of the wavelength number can be attained.

(1) Field of the Invention
The present invention relates to a control device and a control method of an optical amplifier, and more particularly to a control device and a control method of an optical amplifier suitably applicable to a constant output control and a constant-gain control of an optical amplifier.
(2) Description of Related Art
Today, a wavelength division-multiplexing (WDM) device, which increases a transmission capacity by inputting into one transmission line (optical fiber) a plurality of optical signals with different wavelengths, has been widespread. Moreover, in an optical ring network, as an optical transmission device (optical node), which enables the increase and decrease of an arbitrary wavelength regarding a multiplexed WDM light in the middle of the transmission line, an OADM (Optical Add-Drop Multiplex) device has also been put to practical use.
In the WDM optical-communications system described here, there is a need to control the output signal light power per one wave to be constant by controlling the amplification gain to be constant in the optical amplifier even when the wavelength number of the WDM light changes. For this reason, an optical amplifier is needed that responds at high-speed to the increase and decrease of the wavelength. In controlling optical amplifiers today, this high-speed response control is generally executed by an automatic gain control (AGC).
Moreover, under the conditions that optical amplifiers are coupled in multi-stages like a long-distance WDM optical communications system, if there occurs a change in the transmission line loss due to the temperature, or aging and the like of the transmission fibers, the transmission fibers would incur a deterioration of the transmission quality if only AGC would be used. Then, in order to absorb input fluctuations (input dynamic range) per one wave and obtain a constant signal output level (power), there is a need to execute ALC (Automatic Level Control) in addition to AGC, combined with it.
In FIG. 9, a configuration of the conventional optical amplifier, which uses such AGC combined with ALC, is shown. The optical amplifier shown in FIG. 9 is constituted as an in-line amplifier of a two-stage amplification configuration, and is comprised of: as an optical circuit section, erbium-doped optical fibers (EDF) 100a and 100b which are optical amplification media; a variable optical attenuator (VOA) 101 for adjusting the optical level (the amount of loss) provided between such EDF 100a and 100b: beam splitters (BS) 102a and 102b, photo-diodes (PD) 103 and 104, which constitute a monitoring circuit of the input/output light level of EDF 100a in the pre-stage; an excitation light source (LD) 105 and a WDM coupler (wavelength coupler) 106 which constitute an excitation light circuit for EDF 100a; BS 107a as well as 107b and PD 108 as well as 109 which constitute a monitoring circuit of the input/output light level of EDF 100b arranged in the post-stage; and an excitation light source (LD) 110 and an WDM coupler 111 which constitute an excitation light circuit for EDF 100b.
Moreover, as a control circuit section (an electric circuit section), there are also provided an AGC circuit 121 for EDF 100a of the pre-stage, an AGC circuit 122 for EDF 100b in the post-stage, and an ALC circuit 123 which controls the amount of attenuation of VOA 101 as well as ASE correction circuits (adder) 124 and 125.
In the optical amplifier (EDFA) using such EDF, a total sum of the gain by each of EDF 100a and 100b and the loss in VOA 101 makes the gain (a total EDF gain) as the whole optical amplifier, and the total EDF gain can be changed by changing the gain of EDF 100a and 100b, or the amount of loss in VOA 101.
Specifically, in the above-described optical amplifier, a WDM light inputted from a signal input terminal is amplified in EDF 100a, and after the output level thereof (namely, an input level to EDF 100b in the post-stage) being adjusted in VOA 101, is then amplified again in EDF 100b and outputted. Then, at this time, a part of the input/output light in each of EDF 100a and 100b is branched out in BS 102a as well as 102b, and BS 107a as well as 107b, respectively, and the input/output light power of each of EDF 100a and 100b is monitored in PD 103 as well as 104, and in PD 108 as well as 109, respectively. Namely, each of PD 103, 104, 108 and 109 inputs an electric signal (a voltage value) corresponding to the input light quantity into corresponding AGC circuits 121 and 122, respectively.
In the AGC section (AGC circuits 121 and 122), an AGC is carried out including the power fluctuation of an input signal light. Namely, the output power (an excitation light power) of LDs 105 and 110 is controlled based on the input voltage value from each of PDs 103, 104, 108 and 109, such that the total EDF gain is kept at a predetermined constant value (such that the ratio of the input light level of EDF 100a in the pre-stage and the output light level of EDF 100b in the post-stage may be constant).
On the other hand, in the ALC circuit 123, in order to absorb the input fluctuation per one wave (input dynamic range) and obtain a constant output signal light level, the total EDF gain is changed in the direction of suppressing the power fluctuation of the input signal light by adjusting the amount of loss in VOA 101, based on the monitoring value of PD 109 (that is, the output light level of EDF 100b in the post-stage).
Accordingly, when the input light power fluctuates at a speed sufficiently slower than the speed of the response (time constant) of the ALC circuit 123, it is possible to completely suppress a fluctuation of the input light power within the input dynamic range and control the total EDF gain to a predetermined value.
Incidentally, as described in the following Patent Document 1, a time constant of the AGC is set sufficiently short with respect to the response time (length of time from a time of the excitation light power having changed until the gains of EDF 100a and 100b being adjusted to the desired values corresponding to the changes thereof; usually several milli seconds) of EDFs 100a and 100b, so as to sufficiently cope with the wavelength number fluctuation (the increase and decrease of the wavelength) of the input signal light, as described above. On the other hand, the time constant of the ALC is set, for example, so as to be longer (such as 10 or more times and the like) than the time required for a supervisory control signal to be transmitted to each optical node through OSC (Optical Supervisory Channel).
Incidentally, in the optical amplifier using EDF, ASE (Amplified Spontaneous Emission), which becomes a noise component along with the amplification of the input light, is generated as described in the paragraphs 0053 and 0054 of the Patent Document 1. For this reason, on the assumption that the input light power (the total power) for the optical amplifier is designated by "Pin", the input light power per one wave to the optical amplifier by "Pin_ch", the output light power (the total power) by "Pout", the signal gain by "G", the ASE output generated in its own stage by "Pase", and the wavelength number by "m", the gain set by the AGC is expressed by the following equation (1), and an error due to the ASE will be generated in association with the signal gain G which is a desired gain. And, this error depends on the multiplexing number of the wavelength of the WDM light.
                                                                        AGC                                                                                gain                            =                                                Pout                  /                  Pin                                =                                                      (                                                                  G                        ×                        Pin                                            +                      Pase                                        )                                    /                  Pin                                                                                =                              G                +                                  Pase                  /                                      (                                          m                      ×                      Pin_ch                                        )                                                                                (        1        )
Therefore, it is apparent that the AGC gain has only to be increased in association with the signal gain G only by the amount of Pase/(m×Pin_ch). Then, in the conventional optical amplifier shown in FIG. 9, the ASE correction value (=Pase/G) is reflected on the input information (the monitoring value of the input light power of EDF 100a and 100b) to the AGC section (AGC circuits 121 and 122) by means of the adders 124 and 125. In addition, in some cases the ASE correction value is reflected on the monitoring value of the output light power of EDFs 100a and 100b (refer to FIG. 11 of the Patent Document 1). Moreover, as described in the paragraph 0058 of the Patent Document 1, as for also the ALC the ASE correction value is also reflected. In addition, the details of such ASE correction are described, for example, in the paragraphs 0055 and 0056 of the Patent Document 1.
[Patent Document 1]
Japanese Patent Laid-Open (Kokai) 2003-174421.
Incidentally, since the above-described "ASE correction value" is significantly dependent on the input light power per one wave, the "ASE correction value" always needs to be changed at the time of ALC in which the input light level per one wave is likely to fluctuate. The control value thereof is set based on the input light power per one wave level (Pin_ch), and is, therefore, the value which originally is not subjected to any change by the fluctuation of the wavelength number.
However, in the event that a fluctuation of the wavelength number has occurred during the ALC, it is assumed, until the correct wavelength number information can be obtained by the OSC or the like, that there is no changes in the wavelength number, with the result that changes of the input light power due to the fluctuation of the wavelength number are interpreted as changes in the input light level per one wave. As a consequence, an error would occur in the ASE correction value, and in configurations like the optical amplifier described above based on FIG. 9 or the technologies of the Patent Document 1, in which the ASE correction value is reflected on the desired control value of the total EDF gain or on the desired control value of VOA 101, an error would occur also in this desired control value.
Namely, in the control information (the gain of the whole optical amplifier, each EDF gain, ASE correction values, and the like) by which a desired value is set from the input light level per one wave, a control error would occur. As a result, the control value (the amount of attenuation) of VOA 101, which should originally be constant even at the time of the increase and decrease of the wavelength number, will change, and the transmission quality of the main signal light (WDM light) will degrade due to the influence of the gain deviation, and the like.
Moreover, in the device in which optical amplifiers are coupled in multi-stages, the ASE correction value generated in its own stage is notified by the OSC or the like to an optical amplifier arranged in the post-stage, and is used as the control information in this optical amplifier, however, when a fluctuation of the wavelength number occurs in the state of ALC, an accurate ASE correction value which should be generated in its own stage can not be calculated, therefore, a control using the ASE correction value at the time of the increase and decrease of the wavelength number cannot be carried out in the subsequent optical amplifier.

Control device and control method of optical amplifier


A wave pool having multiple wave breaking zones extending across the pool floor, wherein different wave breaking formations with different wave characteristics can be generated within each zone, using the same wave energy derived from the same original wave, wherein surfers with different abilities can surf in different locations within the same pool. Specific features are provided that enable breaker waves to be properly managed and controlled such that intermediate/advanced surfers can surf in one zone and beginner surfers can surf in another zone. Included are special dividers to prevent surfers from crossing from one zone to the next, while at the same time, allowing wave energy to pass through. An attenuating means is provided to help reduce the choppiness of the waves. Unique exit areas are provided along the sidewalls to enable surfers to exit from the wave pool at various locations, such as directly from the zones, so that surfers don't have to surf or traverse all the way to the shallow end to exit the pool.

Wave pools have become extremely popular around the world. They generally comprise a wave generator located on one end and a sloped floor with a shoreline having a beach on the opposite end, wherein waves are formed by the generator that travel along the surface of the body of water until they break along the shoreline and spill onto the beach.
Wave pools of this type help create waves similar to those that exist in nature, but the predominant use of these wave pools has been to provide waves for those who desire to bob up-and-down in the deep end, and wade in the shallow breaking-wave part of the pool. Although attempts have been made in the past to create an enhanced wave pool with larger and more powerful waves suitable for surfing, the problem has been that these pools are predicated on historic wave pool designs, and when surfers attempt to ride these waves toward the shoreline, they are carried forward and across the body of water, toward the shallow end, which increases the risk of injury that can result from deep water surfers transitioning to shallower water and colliding into waders, etc.
An additional problem faced by conventional wave pools used for surfing is the economic value of such pools which is often diminished by the relatively low throughput they provide, i.e., the number of surfers who can enjoy riding the waves at any given time within the same pool. Also, enlarging pool size and the power of wave generators can be cost prohibitive.
What is needed, therefore, is a wave pool design having specific features that enable breaker waves to be properly managed and controlled such that intermediate/advanced surfing areas can be separated from beginner surfing areas, and wherein exit areas are provided intermittently across the wave pool to enable surfers to exit properly without interfering with the progress of the waves and without the surfer having to travel all the way to shore.

Method and apparatus for managing and controlling breaker waves in a wave pool


For a fuel injected combustion engine a fuel pressure regulator having a rapidly and accurately regulated output pressure over a wide range of flow rates by bypassing and returning to a fuel tank a portion of the input fuel from a fuel pump through a bypass valve actuated by a flexible diaphragm. The diaphragm is responsive to the pressure of the input fuel on one side of the diaphragm and a vacuum on the other side of the diaphragm having a magnitude which is varied as a function of the flow rate of the fuel bypassed through the valve and returned to the fuel tank. Preferably, this vacuum is produced by a venturi or orifice through which the bypass fuel flows. Applying this vacuum to the diaphragm opposes the bias of a spring acting on the diaphragm and provides an output fuel pressure to the engine over a wide range of flow rates which is essentially constant relative to the atmosphere or, if desired, an output fuel pressure having a positive slope which increases with increasing flow rate of the output fuel supplied to the engine.

In many engines with fuel injection systems, it is desirable to supply liquid fuel to the injector or injectors at a pressure which is either constant relative to atmospheric pressure or varies so that it is constant relative to the pressure drop across the injectors when open which is a function of the intake manifold pressure of the combustion air. Both the combustion air pressure and the flow of fuel supplied to the engine varies with engine speed, load and other operating conditions.
Previously, a variety of fuel pressure regulators have been developed one of which is shown in U.S. Pat. No. 5,579,739. This regulator has a generally flat, flexible diaphragm disposed between two chambers and subjected to manifold pressure on one side and pressurized liquid fuel on the other side. In use, this regulator does not achieve or maintain a uniform and constant differential fuel pressure across the injectors. Rather, the differential fuel pressure varies with the rate of fuel flow and drops as fuel consumption increases. This inconsistent pressure differential across the fuel injectors adversely affects the performance of the engine. Additionally, this regulator does not compensate for dynamic pressure losses in the fuel system between the regulator and the injectors.


A method for manufacturing a cantilever structure of a probe card is disclosed. In accordance with the method of the present invention, a first sacrificial wafer is used as a mold to form a cantilever structure having various shapes, a microscopic pitch and a high aspect ratio. In accordance with the method of the present invention, a probe tip may be formed by using a second sacrificial substrate and a bonding.

1. Field of the Invention
The present invention relates to a method for manufacturing a cantilever structure of a probe card, and more particularly to a method for manufacturing a cantilever structure of a probe card wherein a silicon wafer is used as a mold to form a cantilever structure having various shapes, a microscopic pitch and a high aspect ratio.
2. Description of the Related Art
Generally, one or more dies are formed on a wafer. A wafer-level test should be carried out to find out that the one or more dies are not defective. The wafer-level test is carried out using a probe card having a plurality of cantilever structure having a probe beam, a tip and a bump. The cantilever structures contact a plurality of pads formed on the wafer, and relays a test signal from a tester to the plurality of pads to carry out the test.
As a size of a semiconductor device is reduced, a pitch of the pads is also reduced. Therefore, a distance between the probe tips for carrying out the test by contacting the pads is also drastically reduced. In addition, a number of the probe tips are drastically increased in order to test a large number of dies per test.
Therefore, a need for a probe card including a cantilever structure having various pitched and shapes is increasing.

Method for manufacturing cantilever structure of probe card


A portable steel drum assembly for use in a marching band includes a first steel drum having a defined playing surface including a first set of predefined indentations defining a first set of notes and a second steel drum having a defined playing surface including a second set of predefined indentations defining a second set of notes. The first and second steel drums each have a diameter less than twenty-two inches providing the steel drum assembly with sufficient lightweightness and compactness enabling a musician to perform the steel drum assembly while carrying the steel drum assembly. A steel drum carrier including a harness and a steel drum mount enables a musician to carry the first and second steel drums.

This invention relates to a percussion instrument used by marching bands, and more particularly to a lightweight portable steel drum assembly for being played by marching bands while marching.
The steel drum is a musical instrument which is generally crafted from discarded 55-gallon drums or barrels. The creation of the steel drum as a musical instrument is credited as originating from Ellie Mannette in 1946. To transform the discarded drum into a musical instrument, the 55-gallon barrel is first cut to a particular height such that one end of the barrel remains intact and the other end opens into the interior of the drum. The enclosed end of the barrel is deformed into the barrel's interior forming a concave surface. Indentations are formed in the concave surface and are of particular shapes and sizes for producing specific notes when struck by a musical hammer or mallet.
There are several types of steel drums which include a soprano, a double tenor, double second, and a triple guitar. These drums each have a different set of indentations for producing various tones and musical voices. The indentations are located around the internal periphery of the concave surface and also around the center of the concave surface in a discrete pattern for producing the separate notes. For instance, the soprano drum has a skirt which is approximately five to five and a half inches in length and contains twenty-nine discrete indentations for producing a range of notes including two complete octaves and part of a third.
Steel drums are used in orchestral settings and in marching bands. However, due to the heaviness and bulkiness of the steel drums, the steel drums are mounted on stands and remain stationary. A typical steel drum weighs fifteen to eighteen pounds. Thus a two piece ensemble weighs over thirty pounds. The stationary placement of the steel drums limits the participation of the musician involved with the marching band. Unlike the other musicians, the steel drum musicians are forced to remain on the sideline while the other members of the marching band perform in the flamboyant on field musical production.
Furthermore, since no steel drum has heretofore been designed for being played while the musician is marching, no portable mounting mechanism has been provided enabling a marching band member to play a steel drum while marching on the field.
Accordingly, it is an object of the present invention to provide a steel drum which is light weight and portable for playing by a marching band member while marching on the field;
Also, it is an object of the present invention to provide a portable light weight steel drum assembly which includes a sufficient range of notes for providing a musically viable instrument;
Furthermore, it is an object of the present invention to provide a portable light weight steel drum assembly with a particular layout of notes which enables the steel drum assembly to be easily played without requiring an awkward hand maneuver;
Additionally, it is an object of the present invention to provide a mounting mechanism enabling a musician to carry the light weight portable steel drum assembly in a playing position while marching on a field in a marching band.


The invention relates to a monolithic porous material based on amorphous silica or activated alumina or on one of their mixtures, the material comprising substantially rectilinear capillary ducts that lie parallel to one another, and being intended to be used as packing in a chromatography column, characterised in that:                the ducts have, relative to one another, a substantially uniform cross section;        the cross-section of each duct is uniform over its entire length;        the ducts pass right through the material;        the volume of micropores smaller than 0.3 nm is smaller than 50% of the total porous volume of the material.

The close contact between two phases such as a gas and a liquid to promote their chemical or physical interaction is an important operation in chemical engineering.
To promote interface phenomena on the contact surface between these two phases, it is endeavoured to increase this contact surface as much as possible, and to increase the effects of mixing in the vicinity thereof.
For such purpose, beds of fine solid particles are frequently used through which a fluid passes and with which they interact.
These beds, called particle beds or packings, offer large exchange surfaces on account of the small size of their constituent particles, and on account of the large divided status of the fluid passing through them.
These phenomena promote the speedy accomplishing of material transfer processes, chemical reactions or any other diffusion-related phenomena.
Their applications particularly cover the fields of both analytical and preparative liquid and gas chromatography.
Chromatography is a particular technique, which has its own advantages and constraints and is thereby different from other related techniques, such as adsorption and heterogeneous catalysis, by applying solid packings and fluids.
In adsorption, it is sought to retain a compound of a fluid effluent on the surface of which it is adsorbed via an isotherm, or on which it reacts. It is sought to purify the fluid. Large specific surface areas are needed. High-capacity beds are necessary. The efficiency of the packing is not critical (number of theoretical plates) and the use of beds of granules with a diameter from 1 to 2 mm is preferred. Indeed the efficiency only has negligible influence on the dimensioning of the bed to the extent that it only acts on the stiffness of the percolation front which is good as soon as about 20 theoretical plates are attained. The adsorbent then needs to be regenerated by a combination of means, temperature, chemical reaction, which removes the adsorbed or combined impurities. The operation is therefore sequential but the cycle times are numbered in days or in weeks. The mass of the bed is dimensioned. The pressure drops are low.
In catalysis, it is sought to carry out a chemical reaction on the surface of the solid. It is desired that the reagents remain for an optimal time in contact with the solid. There again, this is a question of adsorption forces and chemical reactions. One is interested in the dwelling time criteria. Reasoning with a number of theoretical plates is inoperative. The regularity of the packing is one factor among others and is secondary before catalytic selectivity. It is not sought to separate the molecules. The pressure drops are low.
In chromatography, several components present in a fluid load sequentially admitted according to a short time interval counted in minutes are separated by propagating it from one entry point to an exit point of a solid column under the effect of an eluting fluid. The obtained separation may be achieved by a very wide variety of forces which start competing with the driving effect of the eluent, sharing, adsorption, steric interactions, ionic interactions, etc. . . . This method provides high resolving power, each component behaving differently. To enhance this resolving power, the column has to have a great number of theoretical plates, for example 1,000. This also means that the diffusion resistances should be minimized, and therefore that the diffusion distances should be short, and that the column has to be long. These combined factors have the result that chromatography is a technique which requires excellent regularity of the flow and therefore of the packing, and a small characteristic dimension of the latter, leading to pressure drops which rapidly become critical with particulate solids. These are the problems which have to be solved in chromatography.
On the other hand, preparative chromatography practically and simply feasible is one of the essential unsolved problems of chemical engineering.
In the prior art, for this purpose, devices with discontinuous columns of great diameter and so-called simulated mobile bed devices are essentially used. In this first case, the fine particle beds require working with high pressure drops making the device complex and costly. In the second case, a displacement of a solid packing is simulated by sequencing it in a train of individual fixed beds of small lengths, individual beds at the limits of which are moved the feeding point and the points for drawing off the products. These devices have moderate efficiency and are de facto essentially discontinuous in their management.
In the literature, packings for chromatography have been proposed, consisting of a large number of jointed capillary channels operating in parallel (Express gas chromatography on multicapillary columns and its potential, V. N Sidelnikov et al., Catalysis in Industry 2012, Vol. 2, N° 3, pp 206, 216). These different capillaries operate independently of each other since their walls are solid and non-porous. In particular, their diameters and their filling level by the stationary phase are always slightly different from each other. This operating independence causes a strong loss of efficiency because of the different rates of flow of the eluent fluid in capillaries of variable diameter. Because of this defect, these devices have not been developed significantly
U.S. Pat. No. 5,332,480 of Datta and Beardsley describes an electrophoresis technique on individual annularly positioned and rotary capillaries. However this arrangement only has the purpose of easily cooling the capillaries which are positioned far from each other for allowing circulation of a coolant fluid at their periphery. The productivity of the apparatus is very low. Indeed, the capillaries have to be far away from each other in order to be cooled, are relatively only very few, and the fraction of the free section for the passing of the process fluid becomes very small. The capillaries do not include any stationary phase indispensable for obtaining chromatographic separation. Such a device cannot be used in chromatography. It will be further noted that the optimum diameter of the claimed capillaries is comprised between 100 and 250 micrometres and is not adapted for high productivity in the liquid phase chromatography for which a smaller diameter will be preferred. This point actually illustrates the fundamental structural difference between an electrophoresis method based on an applied external electric field for which the diameter of the capillary is not critical for the efficiency of the separation, and partition chromatography for which the efficiency closely depends on the diffusive distances between stationary and mobile phases. There is no obvious equivalence between both methods.
U.S. Pat. No. 4,657,742 to Beaver P. proposes an alternative to these particle packings comprising a tube packed with aligned fibres which may be porous and hollow. One disadvantage of this packing is that the eluting fluid flows both inside and outside the hollow fibres in the voids left between their stacking. Since the eluting fluid flows at two very different rates inside the hollow fibres and on periphery thereof in the interstices separating the fibres of circular section, there is resulting loss of efficacy. Another disadvantage of this device is that the walls of the hollow fibres must be sufficiently thick so that they can be handled and packed withstanding the mechanical stresses induced by the stacking thereof. This means that the diffusional balancing between adjacent fibres is slow, and the packing is little efficient. Another disadvantage of this device is that it is difficult to apply to bundles of fibres of large diameter since the chemical stability of the packing would be difficult to ensure.
U.S. Pat. No. 4,957,620 to Cussler E. describes the use of bundles of hollow polymer fibres for use as chromatographic column. The assembly suffers from the same disadvantages as above: the thickness of the wall of the fibres must be higher than that of the central channel in order to impart sufficient mechanical strength to these fibres allowing the handling and assembly thereof. As a result, transfers of material by diffusion between the material of the walls and eluting fluent are slow. The eluting fluid flows at two very different rates inside the hollow fibres and on the periphery thereof. Here again the stabilization of large diameter packing is difficult owing to the lack of strong bonds between adjacent fibbers.
U.S. Pat. No. 4,818,264 describes the use of bundles of capillary columns in glass or silica to perform multicapillary gas chromatography. This system has the serious drawback that the capillaries behave independently of each other. On this account, it is difficult to obtain identical behaviour of the different channels and careful, scrupulous attention must be given to the manufacture of channels that are all identical.
Patent application US 2005/0139536 to Belov Y. P. describes a chromatographic column whose channels are coated with different thicknesses of stationary phase so as to offset hydrodynamic inequalities between the different channels. This work exemplifies the difficulty in obtaining good performance levels with a multicapillary column formed of individualized channels which do not communicate by diffusion.
The publications by Nishihara H. «Ordered macroporous silica by ice templating», Chemistry of Materials, 28 Feb. 2005, pages 683-689 and Mukai S. R. «Formation of monolithic silica gel microhoneycomb (SMH's) using pseudo steady state growth of microstructural ice crystals »Chemical Communications, 4 Mar. 2004, pages 874-875 describe a potential pathway for forming multicapillary structures in silica. The documents refer to a method of manufacturing microstructures of ordered porous silica, of honeycomb shape and 3.6 to 40 pm in diameter. The method comprises causing directional growth of ice crystals in low-cohesion silica gels and evaporating a solvent by freeze-drying.
However, the described method only functions with silica gels having low cohesion i.e. with low silica concentration. The structures obtained are therefore very lightweight, namely having a density of the order of 0.12 g/cm3 according to the authors of these publications. The relative volume of the capillaries is high. As such, they will not perform well in liquid chromatography for which a dense packing is sought having strong retention capacity. In addition, packing that is so lightweight is mechanically fragile.
Additionally, examination of all the photographs in the two articles shows that the diameters of the channels differ by a factor of about 10, and that these channel diameters fluctuate to a large extent and are irregular over their length. These channels have most variable environment and morphology, their cross-section possibly being square, pentagonal, hexagonal, etc. These irregularities mean that such packing is inefficient for high performance analytical chromatography for which perfect homogeneity of the packing is required.
Finally, the packings described in these articles are obtained over a restricted range of diameters, from 3.6 to 42 μm. Yet, the range extending below 2 μm is of particular interest for application in high pressure liquid chromatography (HPLC), and the range extending above 50 μm is of particular interest for application to gas chromatography.
U.S. Pat. No. 6,210,570 to Holloway R. describes monolithic packing in porous silica for chromatography. Said packing is formed of more or less spherical pores forming tortuous passages through the packing. These passages are tortuous and a fluid passing them encounters numerous obstacles, the pores and the solid being randomly distributed in space within the packing. This forms a major difference with a flow through an empty capillary tube in which the fluid does not encounter any microscopic obstacle over an optimal rectilinear pathway. They display a lower pressure drop than a particle packing but higher than that of a capillary having the same separation efficacy for a given analysis, and have intermediate separation impedance between the two. They have the advantage of allowing a macroscopically uniform flow of the eluting fluid through the packing on account of their monolithic structure, unlike the case with the stack of capillary tubes described in patent U.S. Pat. No. 4,657,742.
The following publications: N, Ishizuka, Designing monolithic double pore silica for high speed liquid chromatography, Journal of Chromatography A, 797 (1998), 133-137, K Nakanishi, Phase separation in silica sol-gel system containing polyacrylic acid, Journal of non crystalline Solids 139 (1992, 1-13 and 14-24, K. Nakanishi, Phase separation in Gelling Silica-Organic Polymer Solution: Systems Containing Poly(sodium styrenesulphonate), J. Am. Ceram. Soc. 74 (10) 2518-2530-30 (1991) deal with the same subject matter as the Holloway patent. The aim is to obtain a monolithic packing in silica comprising two families of pores, one of interconnected macropores in which a liquid is able to flow relatively freely and the other a family of mesopores or micropores creating a specific surface area and hence activity for the exchange of material.
Patent PCT WO01/47637 of Faber et al. describes a y (gamma) alumina and zeolite monolith intended for catalysis. Application to chromatography is not mentioned. The method for manufacturing this monolith comprises sintering at 850° C. where boehmite becomes gamma alumina, thereby losing its chromatographic properties. Further this monolith has a channel diameter of more than 1 mm.
US patent application 2006/0090649 of Wei Liu presents a ceramic monolith intended for applications as a mineral membrane and not in chromatography. The only known means for preparing these monoliths in the state of the art involves high temperature sintering which makes the material lose its chromatographic properties. The claimed diameter for the channels is greater than 0.5 mm.
Patent PCT WO 95/28279 of Purushottam et al. presents a monolith for which the base material is active coal (carbon activated honeycomb, in the title). Indeed it is clearly mentioned on page 17 line 11 and 12 that the structure consists of a carbon continuum or backbone. A third-party mineral solid body may be added into the carbon, but the latter has a too small volume or is of a shape such that it does not form a monolith or the base of the latter. The described method does not give the possibility of obtaining a monolith (literally «a single stone») based on an aluminosilicate. In particular, this is not a sol gel method. French patent No. 2 957 276 does not mention the proportion of micropores with a diameter of less than 0.3 nm present in the packing. Now these pores decrease the capacity of the packing for a chromatographic application. They cause a highly significant decrease in the diffusion flow between the adjacent channels, thereby being detrimental to the efficiency of a chromatographic column using them. This patent does not mention combinations of alumina and silica.
U.S. Pat. No. 5,234,594 presents a filter consisting of contiguous rectilinear channels in a glass matrix. However this matrix is not porous. This is solid glass. According to the present invention, the material separating the channels has to be pores so that the behavioral differences between the adjacent channels are balanced by diffusion and more chromatographic efficiency is obtained. This porous nature of the wall of the channels unambiguously emerges from the drawings 1 and 2 and from the wording of claim 1.
U.S. Pat. No. No. 5,864,743 of Tuchinsky et al. describes a method for making multi-capillary packings in alumina characterised in that a powdery alumina layer immersed in a binder around an element formed by powdery carbon immersed in another binder is assembled, in that such elements are joined in a bundle, in that they are extruded once or twice, in that the binders are removed, in that the carbon is burnt and in that high temperature sintering of the thereby shaped alumina is caused. In order that this be practically possible, sintering should be carried out at a temperature not very far from the material's melting point or of the order of the latter, i.e. 2,050° C. for alumina, or of the order of its boiling point, 3,000° C. for alumina. This means in practice that the obtained alumina will have undergone deep dehydration and an allotropic transformation after having been subject to the temperature required for sintering, and it will be alpha alumina with low specific surface area, and not activated alumina with a high specific surface area, the only interesting one for uses in adsorption or for chromatography. The porosity, the specific surface area and the porous volume will have been extensively decreased regardless of the sintering temperature. Such packings are only of marginal interest for chemical engineering. On the other hand, the extrusion steps are extremely detrimental to the quality and regularity of the final product. The peripheral fibres of the extruded bundle will be subject to stresses, shearings and deformations extremely different from those located in its centre, and their morphology will be thereby affected. This will be all the more critical since the binders will have non-Newtonian behaviour. Finally the actual sintering is a highly penalizing operation dimensionally, particularly for parts of large dimensions. During sintering, significant shrinkages and changes in dimensions occur, which are difficult to control, which are the major causes of irregularities and defects in the final packing.
However, the large majority of separations are still conducted on particle beds, which are easier to manufacture.
There is therefore a need for a product having advantages in terms of reliability and ease of manufacture of particle packing, allowing the uniform microscopic and macroscopic flow of eluting fluid in the bed, whilst maintaining the advantages of capillary columns.

This patent is subject to a terminal disclaimer.

Multi-capillary monolith made from amorphous silica and/or activated alumina


An apparatus for floatation and propulsion of a user on a body of water, with the user in a standing position, includes two pontoons, a mechanical connection of the pontoons and a propulsion system responsive to vertical articulation of the pontoons.

When people use devices to stand on the water, they usually either use the movement of the water (i.e. surfing), the wind (i.e. windsurfing or kite surfing) or their arms (i.e. standup paddleboarding) to propel them. Less commonly, people have used the forward and backward sliding movement of pontoons to provide motion.
The forward and backwards sliding of pontoons has drawbacks of stability and efficiency. It requires the user to move his or her legs forward and backwards at the same time as balancing as waves come from all directions.

Angular velocity-controlled pontoon propulsion system


A method for operating a renewable energy power plant comprising a plurality of renewable energy generators. The method comprises: identifying a predetermined condition of the renewable energy power plant, of the grid, or of the connection between the renewable energy power plant and the grid, the predetermined condition indicating a weak grid interconnection between the renewable energy power plant and the grid; and controlling each renewable energy generator in an adaptive active power mode in response to recovery of the grid from a voltage deviation. The adaptive active power mode comprises: determining a thermal capacity of a chopper resistor of the renewable energy generator; calculating, based upon the determined thermal capacity, a limit level of rate of change of active power output that may be implemented by the renewable energy generator; and operating the renewable energy generator to output active power at the calculated rate of change limit level.

It is important for renewable energy power plants, such as wind power plants, to provide reliable and high quality power. In particular, it is important to reduce oscillations and fluctuations in active power output, reactive power output, and/or voltage output from the power plant. This is because oscillations in any of these outputs may cause instability of power networks to which the power plant connects.
For example, the interconnection between a remote power plant and a power network may, under certain situations, be described as being a 'weak grid interconnection'. In other words, the power plant is connected to a power network that is considered to be a 'weak grid' at the point of interconnection. This means that small changes in reactive/active power exchange between the plant and the network may result in large voltage oscillations. Weak grids are typically identified by measuring a short-circuit ratio of the grid, and comparing it to a threshold value, usually three, where a weak grid has a short-circuit ratio of less than 3. The problems posed by weak grid interconnections and conventional solutions to reduce unwanted oscillations caused by them are discussed in patent application nos. WO 2016/062316 and EP 2463979.
A particular challenge faced where weak grid interconnections exist is fault recovery. After a fault has occurred on the power network, where the voltage level of the network deviated from normal operational levels, network operators expect the power plant to support the recovery of voltage back to its pre-fault levels by supplying sustained active power. However, during a fault, active power falls, and so must be ramped back up to pre-fault levels after the grid recovers from the fault, but, as noted above, small changes in active power exchange cause instability in weak grid interconnections.
WO 2016/062316 and EP 2463979 propose solving the problem of instability following grid fault recovery by slowly ramping the active power using predetermined ramp rates. However, while there is a need to ramp active power back to pre-fault levels as slowly as possible, using a predetermined ramp rate may not always be the best approach for certain situations.
Therefore, there exists a need for a solution that takes into account all factors concerning fault recovery in weak grid interconnected renewable energy power plants and thereby mitigates at least some of the above-mentioned problems.

Adaptive active power control in renewable energy power plants


A memory device includes an array of memory cells arranged as a plurality of rows and columns, each row being coupled to an associated read word line, and each column forming at least one column group, where the memory cells of each column group are coupled to an associated read bit line. Each column has an active mode of operation where a read operation may be performed on an activated memory cell within that column group, and a non-active mode of operation where the read operation is not performable. Precharge circuitry is used, for each column group, to precharge the associated read bit line to a first voltage level prior to the read operation. Each memory cell includes coupling circuitry connected between the associated read bit line and a reference line associated with the column group containing that memory cell.

1. Field of the Invention
The present invention relates to a memory device comprising an array of memory cells, and to a method of controlling leakage current within such a memory device.
2. Description of the Prior Art
When developing memory devices, significant development effort is expended in seeking to improve the performance, and/or reduce the power consumption, associated with write and read operations. For example, the articles "A Step-Down Boosted-Wordline Scheme for 1-V Battery-Operated Fast SRAMs", by H Morimura et al, IEEE Journal of Solid-State Circuits, Volume 33, No. 8, August 1998, Pages 1220 to 1227, "PVT-and-Aging Adaptive Wordline Boosting for 8T SRAM Power Reduction" by A Raychowdhury et al, ISSCC 2010, Session 19, High-Performance Embedded Memory, 19.6, Pages 352 to 354, and "Low Power SRAM with Boost Driver Generating Pulsed Word Line Voltage for Sub-1V Operation" by M Iijima et al, Journal of Computers, Volume 3, No. 5, May 2008, Pages 34 to 40, describe various techniques for boosting a word line voltage for either performance or power reduction reasons.
The article "A 45 nm Dual-Port SRAM with Write and Read Capability Enhancement at Low Voltage" by D Wang et al, IEEE 2007, Pages 211 to 214 describes write and read enhancement mechanisms which boost the ground line to a negative potential. As another approach for improving performance, the article "An 8T Sub-Threshold SRAM Cell Utilising Reverse Short Channel Effect for Write Margin and Read Performance Improvement" by T Hyoung Kim et al, IEEE 2007 Custom Integrated Circuits Conference (CICC), Pages 241 to 244, describes improving write margin and read performance of 8T sub-threshold SRAMs by using long channel devices to utilise the pronounced reverse short channel effect. The article "8T Single-Ended Sub-Threshold SRAM with Cross-Point Data-Aware Write Operation" by Yi Chiu et al, IEEE 2011, pages 169 to 174, describes a 8T SRAM cell suitable for low power and low voltage operation, the cell having a structure which maintains disturbance free read operation, whilst improving the write-ability of the cell in order to improve the minimum voltage at which write operations can be performed.
Whilst articles such as those mentioned above are concerned with improving performance and/or reducing power consumption of the memory device, another issue is becoming more and more significant, this issue being the amount of leakage current observed within the memory device.
As process geometries shrink in modern data processing systems, the variability in the operating characteristics of the individual circuit elements increases. Considering as an example a memory device consisting of an array of memory cells, it will be understood that each memory cell will typically consist of a number of electronic components such as transistors, and the variability in those individual components significantly increases as process geometries shrink. Furthermore, there is an increasing desire to operate data processing systems at lower and lower supply voltages, but as the supply voltage decreases, reliability issues due to the variations in the individual components become more prominent.
One reliability concern arises from the fact that leakage current can increase within the individual memory cells as the process geometries shrink. There are various potential leakage current paths within a memory device, but one area of concern is leakage current arising through components connected to a bit line within the memory device.
An array of memory cells will typically be arranged as a plurality of rows and columns, each row of memory cells being coupled to at least one associated word line (in some implementations there will be separate word lines for write operations and read operations), and each column of memory cells forming at least one column group. One or more bit lines will typically be associated with each column group (again some implementations will provide separate write bit lines and read bit lines), and each memory cell in the column group will have components coupled to such bit lines.
When the memory cells in one or more columns are not being accessed, there will continue to be various components coupled to the bit lines, and these can give rise to leakage paths through which leakage current occurs, increasing the power consumption of the device.
Considering as an example a single-ended memory cell, such a memory cell uses a single read bit line coupled via coupling circuitry to an internal node of the memory cell to allow the data value stored in that memory cell to be read during a read operation. The single read bit line is precharged to a first voltage level (typically the supply voltage Vdd) prior to a read operation, and then if a memory cell coupled to that read bit line is addressed during a read operation (by an asserted read word line signal on the read word line to which that memory cell is coupled), the voltage on the bit line will either stay at the first voltage level, or will discharge towards a second voltage level (typically a ground potential), depending on the value stored within the memory cell.
When the memory cells of a column group are not being subjected to a read operation, all of the memory cells within a column group will still be coupled to the read bit line via their associated coupling circuitry, and this can give rise to significant leakage current.
Accordingly, it would be desirable to provide an improved technique for reducing such leakage current within a memory device, without compromising performance of the memory device.

Memory device and method of controlling leakage current within such a memory device