A grounding contact (1) for inducing noise on a pair of contacts (215) in a high speed, high density electrical connector (2) to ground includes a first section (10) and a second section (11) separated from each other. The first section (10) includes a contact portion (102) for engaging with a daughter board (40) inserted into the connector (2), a fitting portion (104) interferentially engaging with a housing (201) of the connector (2), and a terminal portion (12) to be fitted into a hole of a printed circuit board. The second section (11) includes a contact portion (112) for engaging with the daughter board (40), a fitting portion (114) interferentially engaging with the housing (201) of the connector (2), and a terminal portion (13) for engaging the terminal portion (12) and joining the two sections (10, 11) of the grounding contact (1) together.

1. Field of The Invention
The present invention relates to a grounding contact for a high speed, high density connector, particularly to a grounding contact having contact portions which engage with contact traces on a mated daughter card without scraping the contact traces.
2. The Prior Art
Computers having a high processing speed and occupying a small space are the trend of computer technology development. To meet the trend, high speed and high density connectors are developed, but noise is the main problem affecting such connectors. Therefore, the connectors are equipped with grounding contacts, as disclosed in U.S. Pat. Nos. 5,026,292 and 5,051,099 and Taiwan Patent Application Nos. 79109775 and 80208341.
FIG. 1 of the present application appears as FIG. 3 in U.S. Pat. No. 5,026,292 ('292 patent) with different reference numbers. A grounding contact 3 is formed by stamping (blanking) a metal sheet to have a pair of cantilevered beams 30 each defining a contact portion 301 at a free end thereof. The contact portions 301 are connected to a common bight section 33. A terminal portion 32 extends downward from the bight section 33 to be soldered to a printed circuit board (not shown) for inducing noise received by the contact portions 301 to ground. A pair of projections 31 extend upward from the bight section 33 and engage with an internal wall of a housing of a connector (not shown) to hold the grounding contact 3 in position when the grounding contact 3 is mounted to the connector.
The grounding contact 3 of the '292 patent has been proven to successfully induce noise to ground; however, since the grounding contact 3 is made by blanking a metal sheet, the contact portions 301 thereof are formed with sharp edges which scrape and damage the contact traces on a daughter card when the daughter card is inserted into/withdrawn from the connector. Furthermore, the grounding contact 3 can only be mounted to the connector at a time, which is time consuming and laborious.
Hence, an improved grounding contact for a high speed, high density connector is needed to eliminate the above mentioned defects of current grounding contacts.

Grounding contact for high speed, high density connector


A di-p-tolyldialkylsilane derivative, a photoluminescence polymer formed from the derivative, and methods for preparing the derivative and polymer are provided. The di-p-tolyldialkylsilane derivative is represented by the following formula (1): ##STR1## where R.sub.1 and R.sub.2 are independently selected from the group consisting of phenyl and --(CH.dbd.CH).sub.k R.sub.3 (k is an integer between and inclusive of 0 and 2, and R.sub.3 is hydrogen or alkyl), and X.sup.2 is selected from the group consisting of hydrogen, halogen atom and cyano group. The di-p-tolylalkylsilane derivative of the formula (1) is very useful as a monomer of a functional polymer. The photoluminescence polymer formed from the di-p-tolylalkylsilane derivative of the chemical formula (1) contains a repeating unit having a silicon between the conjugated double bonds, thereby suppressing electron movement of the conjugated double bond. As a result, a range of colors between blue and green, particularly, blue, can be obtained. Also, when the photoluminescence polymer is adopted as a color-developing substance, the threshold voltage characteristics are improved.

1. Field of the Invention
The present invention relates to a di-p-tolyldialkylsilane derivative which is an organic silicon compound useful as a monomer of a functional polymer, a photoluminescence polymer formed therefrom, and methods for forming the di-p-tolyldialkylsilane derivative and the photoluminescence polymer.
2. Description of the Related Art
Recent advances in the information and communications industries have increased the need for high performance display devices. Generally, display devices are classified into luminous types and non-luminous types. Luminous type display devices include cathode ray tubes (CRT), electro-luminescence displays (ELD) and light emitting diodes (LED); non-luminous type display devices include liquid crystal displays (LCD).
As an index of the basic performance of the display device, there are operating voltage, power consumption, luminance, contrast, response time, life span and display color, among others.
The LCD, as one of the non-luminous type display devices, has been most favored recently, due to its light weight and low power consumption. However, characteristics such as response time, contrast and viewing angle properties are unsatisfactory, leaving room for improvement. Meanwhile, the ELD has been focused as a next generation display device which can solve such problems.
The ELD, as one of the luminous type display devices, can be manufactured easily and requires a low driving voltage. In addition, the ELD can be made thin and mass-produced.
A color-developing substance used in the ELD includes an inorganic material and an organic material.
The inorganic material consumes more power, and emits yellow range color, so that an additional complicated process is required to display a full range of colors.
On the other hand, it is anticipated that the organic material can overcome the limitations of the inorganic material. As the organic material, poly(p-phenylenevinylene) (PPV) is known. However, such a compound includes a non-conjugated spacer group such as alkyl and ethylene oxide between photoluminescence groups, so that the threshold voltage is relatively high. When the threshold voltage is high, the photoluminescence polymer can be damaged, and it is difficult to drive the ELD adopting the photoluminescence polymer.

Di-p-tolydialkylsilane derivative and photoluminescene polymer formed therefrom and methods for preparing these compounds


A liquid stabilizing system stabilizes an internal mirror/internal resonator gas discharge laser tube assembly which has a hermetically sealed gas laser tube which includes a gas, a capillary tube, an anode, an anode end assembly, a cathode, a cathode end bell, a cathode end assembly with electrical feed-throughs for the cathode, which are coaxially disposed with a central axis, and laser mirrors, which are sealably mounted to each end of the hermetically sealed gas laser tube. The liquid stabilizing system includes a cylindrical plastic jacket and a cooling liquid. The plastic jacket has a cooling liquid inlet and a cooling liquid outlet and surrounds the hermetically sealed gas laser tube. The cylindrical cooling jacket is sealed to the hermetically sealed laser tube by O-rings which are held in place by plastic retainers. An annulus is formed between the hermetically sealed laser tube and the plastic jacket. The cooling liquid fills the annulus so that the cooling liquid is in intimate contact with all or a large portion of the surface of the hermetically sealed gas laser tube, the thermal conductivity and the specific heat capacity of the cooling liquid being sufficient to prevent misalignment of the laser mirrors under conditions of liquid convection cooling by cooling a substantial portion of the hermetically sealed gas laser tube with minimal asymmetry relative to the central axis.

1. Field of the Invention
The field of the present invention is internal mirror/internal resonator gas laser tubes.
2. Description of the Prior Art
At present, all internal mirror/internal resonator configurations of gas lasers employ forced or free air convection for dissipation of waste heat from the laser tube. Internal mirror/internal resonator gas lasers employ an envelope forming a gas discharge tube as a resonator support structure where laser mirrors are sealably mounted directly to the ends of the structure and maintained in alignment by the laser tube structure. The internal mirror/internal resonator arrangement has several advantages including simplicity in construction, ruggedness and dependability in operation and ease of maintenance. Historically, however, they have suffered from problems with resonator alignment as a result of thermal distortion of the plasma tube envelope due to operation at elevated temperatures relative to ambient conditions. This is especially true for higher power and/or longer versions of each of these laser types.
Continuous discharge gas lasers in which the gas is from the group consisting of argon, krypton, a mixture of argon and krypton, neon, and helium-cadmium, and helium-neon, are relatively energy inefficient in operation, resulting in the generation of significant waste heat which must be dissipated from the body of the laser tube. Argon, neon, krypton, a mixture of argon and krypton lasers operating in a continuous mode may generate waste heat on the order of fifty to two hundred watts per centimeter of bore length along the positive column or main bore of the laser discharge tube. Helium-cadmium lasers generate waste heat on the order of 4 watts per centimeter and helium-neon lasers about 0.4 watts per centimeter.
In general there are three types of laser tube and resonator configurations for these types of high heat generating gas and metal vapor discharge lasers: internal mirror/internal resonator; internal mirror/external resonator; and external mirror/external resonator types. In internal mirror/internal resonator laser tubes the laser mirrors are sealed onto the ends of the laser tube and therefore are internal to the laser tube. The resonator structure which maintains the laser mirrors in alignment with respect to each other and with respect to the gas discharge capillary of the laser tube is the laser tube structure itself. Therefore the term used to describe this type of resonator construction is internal resonator. In internal mirror/external resonator laser tubes the mirrors are mounted directly to the ends of the laser tube structure and form a hermetic seal. The alignment of these mirrors is however supported and maintained in alignment by an external resonator structure usually made of low thermal expansion materials such as Invar or quartz. Because of the usual difference in thermal expansion coefficient between the laser tube structural materials and the resonator materials the mirrors are normally mechanically isolated from the laser tube using a hermetically sealed bellows which is located between the mirror seals and the main portion of the laser tube. This bellows takes up the differential expansion between the laser tube and the external resonator which occurs due to heating of the laser tube. In external mirror/external resonator laser tube configurations the laser tube is sealed at the ends using windows which are disposed at the Brewster angle. The laser mirrors are external to the laser tube and not part of the hermetic envelope of the laser tube. The laser mirrors are supported in the external resonator in order to maintain alignment.
The choice of laser tube/resonator configuration depends upon the type of laser, its heat dissipation and the performance requirements including output power and optical stability characteristics. Each of the basic types of lasers described above has been available in all three types of tube/resonator configurations depending on the size of the laser. Small lasers for low output power applications normally use the internal mirror/internal resonator type of construction. This type of construction is typical of helium-neon, helium-cadmium, and low power argon-ion lasers. Higher power lasers and/or lasers with better beam pointing or transverse mode stability requirements utilize external resonators whether with internal or external mirrors. External resonators are needed to thermally and mechanically decouple the laser mirrors from the waste heat generated within the laser tube. Because an internal mirror/internal resonator laser tube is operating at elevated temperature compared to ambient, any slight variation in coolant distribution or temperature will cause lateral or axial temperature gradients along the surface of the laser tube. The most problematical temperature gradient in most internal mirror/internal resonator lasers is the lateral temperature gradient, dT, since it directly causes laser mirror rotational misalignments. Steady state temperature gradients which are independent of ambient temperature, input power level, or laser tube operating orientation can normally be compensated for by initial alignment of a laser. These gradients are considered controlled. Random temperature gradients are those which vary with ambient temperature, input power level, laser tube operating orientation or other random parameters. In general this random portion of the temperature gradient is proportional to the laser tube wall temperature. As the tube wall temperature decreases, so does dT. In the limiting case where there is no differential temperature between the tube envelope and ambient, there can be no steady state or transient lateral temperature gradients generated as a result of the cooling. Since thermal misalignment of laser mirrors is due to the magnitude of dT and independent of tube wall temperature, the lowest thermal misalignment will occur at the lowest tube wall temperature above ambient. The random gradients cause constant changes in the differential elongation of the one side of the tube with respect to the other side thereby causing angular rotation of the laser mirrors with respect to each other and with respect to the centerline of the gain capillary. This effect produces wander of the laser beam axis and, in severe cases, variations in the laser output power and mode shape. When a laser tube is subjected to a random lateral temperature gradient, dT, averaged across the length of the laser tube, one side of the laser tube grows a random amount which causes an approximately equal and opposite angular misalignment of the each laser mirror by an amount O.sub.D =aLdT/2D where a is the thermal expansion coefficient of the tube envelope material, L is the spacing between laser mirrors, dT is the random lateral temperature gradient, and D is the laser tube diameter. More elaborate formulations can be generated to describe complex structures where the random gradient varies along the length of the tube and/or the thermal expansion coefficient and/or diameter varies along the length of the tube as a result of the use of several different construction materials and geometry.
U.S. Pat. No. 4,625,317, issued on Nov. 25, 1986 to William P. Kolb and Dale E. Crane, entitled Internal Mirror Laser, teaches a thermal structure and cooling system for an argon-ion laser that is virtually free of thermal asymmetries which includes a laser cathode having a housing constructed of a material of high thermal conductivity and relatively low thermal expansion in conjunction with a cooling structure configuration which readily and uniformly dissipates heat. The support structure is fabricated of copper material of at least a minimal thickness and the cooling fins are disposed in one and two stages of radial fins at specified regions along the support structure forming the discharge tube and enclosed by a tubular thermally conductive band. The use of laser tube construction materials which have a high figure of merit equal to the ratio of thermal conductivity divided by thermal expansion coefficient for the cathode end bell as well as end caps of the laser tube. The high thermal conductivity of the cathode end bell allows circumferential conduction within the end bell and alleviation of random lateral temperature gradients within the cathode end bell.
None of the prior art patents or publications teaches the use of high thermal conductivity, high specific heat capacity liquids in contact with the external surface of the laser tube for the purpose of reducing random lateral and longitudinal temperature gradients in order to stabilize the resonator of an internal mirror/internal resonator laser tube thereby increasing the beam pointing, output power and transverse mode stability and the output power capability of internal mirror/internal resonator laser tubes.
U.S. Pat. No. 5,048,032, entitled Air Cooled RF Induction Excited Ion Laser, issued to John Ekstrand, John P. Goldsborough and David L. Wright on Sep. 10, 1991, teaches an ion laser which includes a resonant cavity and a heat dissipating mechanism. The resonant cavity includes an output coupler and a laser bore and contains an active medium. The heat dissipating mechanism dissipates heat which is associated with the laser bore during excitation of the active medium.
U.S. Pat. No. 5,048,043, entitled Gas Laser, issued to Wolfgang Welsch, Hans Krueger, Klemens Huebner and Rudolf Haeusler on Sep. 10, 1991, teaches a gas laser tube structure. U.S. Pat. No. 5,052,014, entitled Gas Laser Tube with Mask, issued to Masaaki Hiroshima and Yoshio Nakazawa on Sep. 24, 1991, also teaches a gas laser tube structure. U.S. Pat. No. 5,050,184, entitled Method and Apparatus for Stabilizing Laser Mirror Alignment, issued to George A. Nelson on Sep. 17, 1991, teaches an apparatus for stabilizing laser mirror alignment.
U.S. Pat. No. 4,953,176, entitled Angular Optical Cavity Alignment Adjustment Utilizing Variable Distribution Cooling, issued to John P. Ekstrand on Aug. 28, 1990, teaches varying the distribution of heat flow out of the plasma tube or structural element to compensate for any misalignment in response to position of the laser beam which controls misalignment of a laser beam due to bending of a plasma tube for an internal resonator ion laser, or another structural element supporting beam guiding optics. A detector is mounted along the optical path of the laser beam, and generates a position signal indicating drift of the laser beam from a preferred position. A cooling system, thermally connected to the structural material of the plasma tube or the structural element and connected to the detector, conducts heat out of the structural material in a controlled distribution in response to the position signal, so that misalignment of the optics due to thermal bending is minimized.
U.S. Pat. No. 4,987,574 issued on Jan. 22, 1991 to William R. Rowley and Patrick Gill, entitled Helium-Neon Lasers, teaches a stabilized helium-neon laser emits radiation in the ranges of ultra-violet, infra-red and visible other than red in at least two modes. A stabilizing system consists of an alignment heater which bends the laser tubes toward optimum alignment, a coil heater which cyclically varies the tube length and permanent magnets which reduce instability of mode polarizations and to optimize relative intensities of the modes. The transmitted output is stabilized in frequency by control of the laser tube length, with the stabilization signal derived from the steady or varying intensity of intensities of one or both of two orthogonally polarized optical outputs.
Another problem that occurs with lasers operating at high temperatures is that the tube bends and becomes misaligned. U.S. Pat. No. 4,010,363, entitled Laser Alignment System, issued to Karl Gerhard Herngvist on Mar. 1, 1977, teaches a laser alignment system which includes a gas discharge tube for producing the laser beam and a plurality of heaters each of which extends longitudinally along the exterior of the gas discharge tube spaced around the longitudinal axis of the gas discharge tube and which selectively heat the gas discharge tube. The laser alignment system is a rather complicated system which requires the comparison of each of the along the gas discharge tube. Using control circuits selective portions of the gas discharge tube may be heated when the laser becomes misaligned. The system is complex and requires positional misalignment data collection and feedback signals.
Referring again to internal mirror/internal resonator laser tubes, as the length of a laser tube design is increased, the tolerance to angular misalignment of the laser mirrors decreases. However, with increasing tube length, the angular misalignment of the laser mirrors increases due to random lateral temperature gradients induced in the tube by localized variations in the coolant temperature distribution, flow velocity and its distribution, and other factors. At some laser tube length the random deformation becomes greater than the tolerance to deformation and the beam pointing, output power and transverse mode stability degrades to an unacceptable level. Depending on the type of laser and the heat generation required to provide optical output, these lasers have been more or less limited in length and, as a result, laser output power. In addition, the more stringent the requirement on beam pointing, output power or transverse mode stability, the more limited the laser tube length and output power.
The precise length where a tube/resonator design must transition from internal to external resonator depends on many design factors such as the thermal conductivity, thermal expansion coefficient, geometry of the laser tube envelope, and laser mirror configuration, as well as performance factors such as beam pointing, output power and transverse mode stability. Three design parameters can be used to describe the design requirements for a stable internal mirror/internal resonator laser tube: the tolerance angle, .theta..sub.T ; the random thermal deformation angle, .theta..sub.D and the critical tube length, L.sub.C, which is defined as that length where the tolerance angle, .theta..sub.T is equal to the random thermal deformation angle, .theta..sub.D.
U.S. Pat. No. 4,233,568, entitled Laser Tube Mirror Assembly, issued to Randolph W. Hamerdinger and Robert C. McQuilan on Nov. 11, 1980, teaches a laser tube assembly which includes a laser tube and pair of laser mirrors. The laser tube has a hard glass to metal sealed laser resonator which is internal to the plasma tube for use in a helium-cadmium laser. Each laser mirror is sealed to one end of the laser tube. The sealant is able to withstand the relatively high temperatures which are utilized to remove contaminants during fabrication thereof. The sealant is also able to minimize gas permeation therethrough during utilization of the laser tube. U.S. Pat. No. 3,904,986, entitled Gas Laser Tube, issued to Karl Gerhard Hernqvist on Sep. 9, 1975, teaches a gas laser tube which includes an elongated envelope, an active laser medium, an output coupling mirror assembly which is disposed on one end of the elongated envelope and a reflector mirror assembly which is disposed on the other end thereof. U.S. Pat. No. 4,149,779, entitled Internal Laser Mirror Alignment Fixture, issued to Randolph W. Hamerdinger on Apr. 17, 1979, teaches a laser tube mirror alignment fixture.
U.S. Pat. No. 4,224,579, entitled Metal Vapor Laser Discharge Tube, issued to Calvin J. Marlett, Edwin A. Reed, Richard C. Johnson and William F. Hug on Sep. 23, 1980, teaches a metal vapor laser which includes an envelope, a capillary tube, an anode, a cathode and a pair of mirrors. The metal vapor laser discharge tube also includes a reservoir of helium, an evaporator and a condenser. The evaporator is fluidly coupled to the capillary tube adjacent to the anode. An active material is placed in the evaporator. The condenser is fluidly coupled to the capillary tube adjacent to the cathode. The laser discharge tube further includes a heater. The heater is mechanically coupled to the evaporator. The heater applies heat to the active material in the evaporator in order to produce a vapor the positive ions of which the cathode draws to the condenser.
Prior art patents have suggested various techniques to improve heat dissipation efficiency in external mirror/external resonator laser. However, none of these prior art patents relate to the method disclosed here of using liquids to stabilize the performance of internal mirror/internal resonator gas discharge laser tubes.
U.S. Pat. No. 4,715,039, entitled Internal Resonator Water Cooled Ion Laser, issued to Mike F. Miller and Kim M. Gunther on Dec. 22, 1987, teaches a laser which includes a resonator tube, a magnet and a plasma tube. The magnet is concentrically mounted in a spaced relationship within the resonator tube defining between the magnet and the resonator an outer coolant channel. The plasma tube is concentrically mounted in a spaced relationship within the magnet defining between the magnet and the resonator an inner coolant channel. The mirrors are then mounted externally to the plasma tube and are supported by an external resonator structure.
U.S. Pat. No. 4,897,851 issued on Jan. 30, 1990 to David L. Vecht and Shinan-Chur S. Sheng, entitled Water Cooled Laser Housing and Assembly, teaches an external mirror/external resonator which includes a concentrically arranged plasma tube, magnet and resonator tube. The mirrors and associated optics are housed at opposing ends of the resonator tube and are mounted on rods extending from respective ends of the resonator tube. The use of laser tube geometry and tube construction materials stabilizes the beam pointing direction of an external mirror/external resonator argon-ion laser.
U.S. Pat. No. 3,763,442, entitled Ion Laser Plasma Tube Cooling Device and Method, issued to William H. McMahan on Oct. 2, 1973, teaches a device which cools an ion laser plasma tube which is based on the utilization of a thermal conductor which is adapted to become fused to an ion laser plasma tube in such a manner as to efficiently transfer the heat which is generated to a surrounding cooling medium, such as air, while mechanically adjusting to differential thermal expansion and contraction of the ion laser plasma tube.
U.S. Pat. No. 4,081,762, entitled Gas Laser with a Laser Capillary Positioned in a Discharge Tube, issued to Hans Golser and Helmut Kindl on Mar. 28, 1978, teaches an improvement to a gas laser the components of which have substantially equal coefficients of thermal expansion. The gas laser includes a vacuum-tight discharge tube, a laser capillary, an anode, a cathode, electrical discharge generator and two mirrors which form an optical resonator.
U.S. Pat. No. 4,953,172, entitled Gas Laser, issued to Thomas R. Gurski on Aug. 28, 1990, teaches a gas laser with a discharge bore which is defined by a single-bore extruded ceramic discharge tube is disclosed. An outer tube is located over the discharge tube so as to define an annular space therebetween. Caps are located over both ends of the tubes and each cap is provide with at least one gas transport passage so the discharge bore and the annular space are in communication. The annular space is filled with electrically insulating, thermally conducting components such as washers, baffles and ceramic granules. When the laser is in operation the annular space serves as a gas return path so a uniform equilibrium pressure is maintained in the discharge bore. The components in the annular space inhibit the flow of electrical current in the space so all of the current flow is through the discharge bore so as to excite the gas therein. The components in the annular space also provide a thermally conductive path between the discharge tube and the outer tube to diffuse heat away from the discharge bore.
U.S. Pat. No. 4,477,907, entitled Low Power Argon-ion Gas Laser, issued to William H. McMahan on Oct. 16, 1990, teaches a gas laser which achieves low output power by using a plasma guide and mirror configuration which restricts lasing action to a portion of the resonator cavity at relatively high conversion efficiency.
U.S. Pat. No. 4,481,633, entitled Wet-jacket Argon-ion Laser, issued to William H. McMahan on Nov. 6, 1984, teaches a segmented ceramic tube which forms an external mirror/external resonator argon-ion laser discharge tube. The segmented ceramic tube is fluid cooled and constructed to avoid shunting of current through the coolant.
In operation, a laser of the external mirror/external resonator, such as an argon laser, generates considerable heat, which must be removed, at least in applications where stability of laser output is critical. The heat can cause thermal expansion of the resonator structure and can adversely affect the mirror alignment and thus the laser output. Water cooling of the laser is frequently utilized to minimize this problem.

Liquid stabilized internal mirror lasers


A method for providing control of surface waves propagating on a surface includes forming a surface treatment on the surface, wherein the surface treatment is configured to achieve a tensor surface admittance distribution matrix on the surface determined according to a modified transformation electromagnetics (tEM) equation.

A jammer can interfere with receivers on the same platform through two pathways: coupling through free-space propagation including multi-path effects and surface wave (SW) coupling or "shin effects", as shown in FIG. 1. Together, these two effects can saturate the receiver by 100+dB, Free-space coupling may be reduced by antenna gain pattern isolation, polarization mismatch, and distance isolation.
In FIG. 1 a transmitting antenna 10, which may be a jammer, transmits a signal. The transmitted signal may travel through free space pathway 12 to a receiving antenna 22. The transmitted signal may also travel to a nearby object 16 through free space pathway 14 and reflect off the nearby object 16 resulting in a multi-path signal 18, which may also travel to the receiving antenna 22. A surface wave signal 20 that travels along surface 19 may also travel to the receiving antenna 22, and if there is a scatterer 24 on the surface, then the scatterer 24 may radiate a surface wave portion 26 into free space and that radiated portion may travel to the receiving antenna 22. The receiving antenna 22 is generally connected by connection 30 to filtering electronics 32, which may attempt to reduce the signal coupling from the transmitting antenna 10 by filtering based on frequency. The filtering electronics 32 is generally connected to a sensitive receiver 34.
SWs 20 that reach the receiving antenna 22 can directly couple into the antenna, as shown by pathways 12 and 18. Additionally, as the surface waves 20 propagate along the surface 19 toward the receiver 22, they may scatter off obstacles or scatterers 24, which may be, for example, seams and rivets in the path, causing radiated interference 26.
Today, magnetic radar absorbing material (MAGRAM) is typically used to reduce the effects of surface wave (SWs) through dissipative loss. While MAGRAM has some advantages, such as wide bandwidth, it is export controlled, expensive, and heavy. Often, its weight makes it unsuitable to place on aircraft wings. MAGRAM is also thick and may have a thickness of 0.5 inch at 15 GHz.
Electromagnetic band-gap materials (EEGs) have also been used in the prior art and suppress surface currents by radiating energy into free space; however, because the radiation is uncontrolled, there may be unintended adverse consequences, especially if the EBG surfaces are in the vicinity of various stores, the wings, pylons, and the fuselage. EBGs can be realized as printed-circuit board structures consisting of patterned metal over a grounded substrate. However, these EBGs often contain vias which add to the fabrication cost and limit their physical flexibility and ability to be conformal to surfaces with complex shapes, such as wings. Typically EBGs do not provide for tailored direction-dependent behavior, polarization control, or beam shaping.
Impedance surfaces have been designed in the past, primarily to control radiation, as described in Reference 1 and 2 listed below, which are incorporated herein by reference. Impedance surfaces have also been used for surface wave guidance to some degree, as described in Reference 3 listed below, which is incorporated herein by reference. However, these references do not describe phase and power profile shaping, polarization control, and absorption. The references also do not address exhibiting a combination of effects such as re-radiation, polarization control, absorption, deliberate guiding, or angle-dependent behavior, in which incident waves from one direction can be re-routed but those from an orthogonal direction are allowed to pass through.
What is needed is to improve the overall isolation between a jammer or other transmitter and a receiver by addressing the surface wave (SW) component of the interference. The embodiments of the present disclosure answer these and other needs.

Metasurfaces for improving co-site isolation for electronic warfare applications


In estimating the relative speed between a vehicle and an objective obstacle, a plurality of objective obstacle data are labeled, and an objective obstacle data preestimated on the basis of the past objective data is compared with an objective obstacle newly provided, thereby judging whether or not there is the same obstacle for every label. With regard to the objective obstacle data decided as being the same, the amount of variation in distance is determined for every label by comparison of the last data and the now data and divided by a sampling time to provide a relative speed. Thus, noise data can be eliminated to reliably provide a relative speed between a subject vehicle and an existent objective obstacle.

1. Field of The Invention
The present invention relates to a method for estimating the relative speed between a vehicle and an objective obstacle.
2. Description of The Related Art
A collision preventing system for a vehicle is known, for example, from Japanese Patent Publication No. 4700/86, in which the distance between a subject vehicle and an objective obstacle is measured by a distance measuring unit, and a brake device is operated in accordance with the distance between the subject vehicle and the objective obstacle.
In the above collision system for the vehicle, it is necessary to correctly obtain the relative speed between the subject vehicle and the objective obstacle. However, it is inevitable that noise data are incorporated into objective obstacle data obtained in the distance measuring unit.
In the above prior art collision preventing system for the vehicle, the distance is calculated on the basis of the time between the transmission of a pulse signal and the reception of a first reflection from the objective obstacle in response to the pulse signal and the relative speed is estimated from a variation in such calculated distances. This causes four problems:
First when noises, due to the reflection from a road surface and a matter suspended in the air, are received in a condition in which another vehicle, as an objective obstacle, is travelling ahead of the subject vehicle as shown in FIG. 12A, the noises A and B cannot be distinguished from the signals of the ahead-travelling vehicle, as shown in FIG. 12D. This causes a dispersion in relative speed between the subject vehicle and the ahead-travelling vehicle, as shown in FIG. 12E, notwithstanding that there is actually no variation in relative speed between the subject vehicle and the ahead-travelling vehicle. Therefore, it is impossible to correctly determine the behaviour of the ahead-travelling vehicle, thereby causing misoperation.
Second, when another vehicle has cut in between the ahead-travelling vehicle and the subject vehicle, as shown in FIG. 13A, the distance between the subject vehicle and the ahead-travelling vehicle is measured in a section C, while the distance between the subject vehicle and the cutting-in vehicle is measured in a section D from the middle (see FIG. 13D). In such a transition, the relative speed is disordered, as shown in FIG. 13E and, hence, the behavior of the ahead-travelling vehicle and the subject vehicle cannot be correctly confirmed, causing misoperation.
Third, suppose a condition in which a four-wheel vehicle is travelling ahead of a motorcycle which is in turn, travelling ahead of the subject vehicle, as shown in FIG. 14A, where a higher attention should be directed to the four-wheel vehicle, constituting a dangerous situation for collision. In this condition, the presence of the ahead-travelling four-wheel vehicle cannot be detected until the motorcycle runs away from between the subject vehicle and the ahead-travelling four-wheel vehicle, as shown in FIG. 14C. Hence, when the motorcycle runs past the four-wheel vehicle as a result of a speed reduction of the four-wheel vehicle there is a possibility that the judgement of collision of the vehicle, against the ahead-travelling four-wheel vehicle, is retarded.
Fourth, when the subject vehicle is travelling on a curved road, having corner reflectors E.sub.1 to E.sub.8, such reflectors E.sub.1 to E.sub.8 are sequentially detected, as shown in FIG. 15D. Therefore, not only the behavior of the ahead-travelling vehicle cannot be detected, but also there is the possibility of a misoperation due to the dispersion in relative speed, as shown in FIG. 15E.

Method for estimating relative speed between vehicle and objective obstacle


A feed gas stream containing at least 60% by volume of hydrogen sulphide is burnt in a first combustion region to form water vapor and sulphur dioxide. Oxygen is employed to support combustion is the region. Thermal reaction then takes place in a thermal reaction region between hydrogen sulphide and sulphur dioxide to form sulphur vapor and water vapor. The resulting gas mixture is then cooled and sulphur vapor is extracted in a condenser. The gas mixture then passes into a second combustion region in which a further portion of the hydrogen sulphide is burnt in the presence of oxygen to form further sulphur dioxide and to adjust the mole ratio of hydrogen sulphide to sulphur dioxide to about 2:1. Further reaction between hydrogen sulphide and sulphur dioxide may be conducted in a further thermal reaction region and in catalytic reactors with further sulphur extraction in further condensers. The mole ratio of hydrogen sulphide to oxygen entering the first combustion region per unit time is greater than 2:1 and the mole ratio of hydrogen sulphide to fluid(s) (if any) other than oxygen being introduced into the first combustion region is greater than 3:2 and preferably greater than 4:1. By using substantially pure oxygen to support combustion of the hydrogen sulphide, a relatively large flow rate of feed gas mixture may be handled in a plant of given size.

This invention relates to the treatment of gases. In particular, it relates to the treatment of a gas stream comprising hydrogen sulphide.
Gas streams comprising hydrogen sulphide are typically produced as waste products or by-products from many industrial processes. For example, acid gas streams comprising carbon dioxide and hydrogen sulphide are typically produced during oil refinery operations in which sulphur is removed from crude oil. It is necessary to treat such hydrogen sulphide-containing streams before discharging them to the atmosphere so as to reduce or remove altogether their content of sulphur-containing gases. One well known, widely practised process for treating a gas stream comprising hydrogen sulphide is the Claus process. This process is based on the reaction between hydrogen sulphide and sulphur dioxide to form sulphur vapour and water vapour in accordance with the equation. EQU SO.sub.2 +2H.sub.2 S=2H.sub.2 O+3S
Sulphur exists in the vapour phase in a number of different molecular species such as S.sub.2, S.sub.6 and S.sub.8 according to the temperature.
The first stage of the Claus process is to burn approximately a third of the hydrogen sulphide in the incoming gas stream to form sulphur dioxide and water vapour in accordance with the equation: EQU 2H.sub.2 S+3O.sub.2 =2H.sub.2 O+2SO.sub.2
This combustion reaction takes place in a suitable furnace and normally air is used as the source of oxygen for the purposes of combustion. The furnace is designed such that reaction between the sulphur dioxide and hydrogen sulphide can start in the combustion zone and then continue downstream of the combustion zone. It is however a feature of the Claus reaction that at the temperature that is created by the combustion of hydrogen sulphide, it is not possible to convert more than about 75% of the remaining hydrogen sulphide to sulphur by reaction with sulphur dioxide, and typically between 50 to 70%, of the hydrogen sulphide is so converted. It is however possible to achieve a higher percentage conversion in the presence of a catalyst at a reaction temperature in the order of 200.degree. to 350.degree. C. by reacting the remaining hydrogen sulphide and sulphur dioxide. (At such "catalytic" temperatures, the lower the temperature the higher is the percentage conversion that is achieved). Accordingly, after the gases pass out of the so-called thermal region of the furnace they are cooled to a temperature at which the sulphur that is formed in the furnace condenses. The sulphur is thus recovered. The gases are then reheated to a temperature suitable for the performance of a catalysed reaction between hydrogen sulphide and sulphur dioxide, such temperature typically being in the order of 200.degree. C. A catalytic reaction is then carried out and typically about 60% of the remaining hydrogen sulphide is converted to sulphur. Nonetheless, it is still not possible to achieve 100% conversion as in practice conversions of more than 99.5% can be achieved only at a temperature at which the sulphur vapour condenses and thereby substantially reduces the effectivess of the catalyst. It is therefore typical to perform the catalytic oxidation of hydrogen sulphide with sulphur dioxide in more than one stage with first condensation of sulphur vapour and then re-heating of the hydrogen sulphide bearing gas stream being carried out between each stage. Various means may be employed to effect reheating of the gases prior to each catalytic stage. For example, a small part of the feed gas mixture can be diverted from upstream of the furnace and burnt in in-line burners completely to sulphur dioxide, there being typically one such burner upstream of each catalytic reactor. The hot, sulphur dioxide-containing gases are then mixed with the main gas stream upstream of each respective catalytic reactor so as to effect reheating. Alternatively, a part of the main gas stream can be taken from, say, a waste heat boiler used to cool the main gas stream leaving the furnace and used in the same manner as the gas from the in-line burners. Another alternative is to employ indirect heat exchange with, for example, steam to effect reheating. After two or three such stages, sulphur formed in the most downstream stage is condensed out of the gas stream which is then typically passed to a tail gas clean-up process of a known kind suitable for handling relatively dilute hydrogen sulphide streams (for example the Scot, Beavon or Stretford process), or which is then incinerated.
Many variations on this basic Claus process are possible. Some of these alterations are summarised in the paper "Sulfur Costs vary with Process Selection" by H. Fischer, Hydrocarbon Processing, March 1979, pp125 to 129.
Recently, there has been a trend towards using crude oils of relatively high sulphur contents and also a trend towards stricter environmental standards so far as the discharge to the atmosphere of sulphur-containing gases is concerned, thus requiring an increased number of hydrogen sulphide bearing streams to be treated, and hence more treatment capacity for hydrogen sulphide containing gases. For example, where possible, it is desirable to increase the rate at which a Claus plant of given size is able to produce sulphur. In practice, the ability of such plants to handle an increased throughput of hydrogen sulphide-containing gas is limited. It has been realised that in order to supply the necessary oxygen for combustion, approximately 14 volumes of air are required for each six volumes of hydrogen sulphide in the gas mixture. It has been proposed in for example a paper entitled "Oxygen Use in Claus Sulphur Plants" by M. R. Gray and W. Y. Svrcek, 1981 Gas Conditioning Conference, Oklahoma, 1981 and in a paper entitled "Modifications Jump Sulphur Recovery Plant Capacity", Oil and Gas Journal, August 20th 1984, pp108 to 112, that the capacity of existing Claus processes can be increased by substituting some commercially pure oxygen for air and thereby reducing the proportion of nitrogen in the gas mixture that flows through the process. In practice, however, in many plants, the amount of uprating that can be achieved by this method is limited as there is a tendency for the reduced volume of nitrogen to lead to higher exit temperatures from the furnace that cannot be withstood by the waste heat boiler or heat exchanger associated with the furnace or by the refractory lining of the furnace. Indeed, the more concentrated (in hydrogen sulphide) the gas stream, the less is the possibility of achieving any significant uprating, such possibility often becoming particularly limited for feed gas streams including 80% by volume or more of hydrogen sulphide.
Another proposal for using pure oxygen in the Claus process is set out in U.S. Pat. No. 3,681,024 and its corresponding Canadian patent specification 854094. These patent specifications disclose burning one third of a hydrogen sulphide stream with oxygen of about 95% purity. Plant effluent from a one or two catalytic reactor unit is sent to a water scrubber to reduce the water content of the effluent, and a sufficient amount of the scrubber off-gas is recycled to dilute the oxygen feed so that the furnace temperature is essentially equivalent to that obtained in operation with air. This process is stated to have the advantage of enabling plant size to be reduced. However, existing plants constructed with the intention of using air to support the combustion of the hydrogen sulphide are not readily convertible to perform the process described in U.S. Pat. No. 3,681,024 and this process has not found commercial favour. Moreover, the practice of recycling to the thermal reaction zone a gas mixture that has passed therethrough places a limitation on the amount by which the size of the furnace defining the thermal reaction zone can be reduced, particularly if the incoming hydrogen sulphide stream contains more than, say, 60% by volume of hydrogen sulphide. U.S. Pat. Nos. 3,331,733 and 4,552,747 are other examples of proposals in which gas is recirculated in order to moderate the temperature in the thermal reactor.

Double combustion oxygen enhanced sulfur recovery process


A system on chip (SOC) system includes functional modules, including a first and second functional module. The first and second functional module are configured to send, to an aggregation module and in a standardized message format, first and second status information associated with the first and second functional module according to a first and second set of one or more reporting rules, respectively. The aggregation module aggregates the first status information in the standardized message format and the second status information in the standardized message format and insert a timestamp to obtain a timestamped and aggregated message stream. The timestamped and aggregated message stream is stored and enables a visualization system to analyze the first functional module and the second functional module.

Unexpected behaviors in embedded and/or system on chip (SOC) systems are notoriously difficult to debug given the real-time nature and the complexity of such systems. Debugging techniques that work with other types of systems (such as invasive debug probes added at key locations in non-real-time systems, "brute force" debug in simple systems, and the addition of probes at easily accessed points in distributed systems) are not easily portable and/or feasible with some embedded and/or SOC systems. New techniques that provide better tools and/or techniques for analyzing, debugging, and/or monitoring such systems would be desirable.

Collection of runtime information for debug and analysis


A method is provided for fabricating an EEPROM (EEPROM (electrically erasable and programmable read-only memory) device, which can help improve the quality of the tunneling oxide layer in the EEPROM device for reliable operation of the EEPROM device. This method is characterized in that the portion of the tungsten silicide (WSi) layer that is directly laid above the tunneling oxide layer is removed, while still allowing all the other part of the tungsten silicide layer to remain unaltered. As a result, in the subsequent heat-treatment process, the degradation in the quality of the tunneling oxide layer that occurs in the prior art due to the forming of a trapping center therein can be prevented. The tunneling oxide layer is thus more assured in quality, allowing the resultant EEPROM to operate reliably with high performance.

1. Field of the Invention
This invention relates to semiconductor fabrication technologies, and more particularly, to a method for fabricating an EEPROM (electrically erasable and programmable read-only memory) device with improved quality for the tunneling oxide layers therein.
2. Description of Related Art
An EEPROM (electrically erasable and programmable read-only memory, also abbreviated as E.sup.2 PROM) is a semiconductor, nonvolatile, programmable read-only memory device whose contents can be electrically erased and then selectively rewritten without having to remove it from its host circuit board. Due to the erasable and programmable feature, the EEPROM is more versatile in utilization than other types of ROMs. In the EEPROM device, the data erasure and rewrite operation can be carried out one bit at a time. A conventional single-polysilicon EEPROM device is illustratively depicted in the following with reference to FIGS. 1A-1C.
FIG. 1A shows the first step, in which a semiconductor substrate 10 is prepared. A field oxide layer 11 is then formed in a selected area. A first oxide layer 12 is subsequently formed over the entire top surface of the substrate 10 and the field oxide layer 11. The first oxide layer 12 is then selectively removed so as to form a tunneling window 13, exposing a selected area on the substrate 10. Next, a second oxide layer 14 is formed over the entire top surface of the wafer, including the entire first oxide layer 12 and filling the tunneling window 13. The part of the second oxide layer 14 that is laid in the tunneling window 13, as indicated by the reference numeral 14b, serves as a tunneling oxide layer; all the other parts of the second oxide layer 14 and its underlying first oxide layer 12 serve in combination as a gate oxide layer, here collectively indicated by the reference numeral 14a.
FIG. 1B shows the subsequent step, in which a polysilicon layer 15 and a tungsten silicide (WSi) layer 16 are successively formed over the entire top surface of the wafer through, for example, two respective chemical-vapor deposition (CVD) processes. The polysilicon layer 15 and the WSi layer 16 are then selectively removed, allowing the remaining portions of these two layers 15 and 16 that are laid over the tunneling oxide layer 14b on one side of the field oxide layer 11 to serve as a floating gate 17, while the remaining portions of the same over the gate oxide layer 14a on the other side of the field oxide layer 11 serve as a gate 18.
FIG. 1C shows the subsequent step, in which a high-voltage ion-implantation (HVI) process is performed on the wafer with the field oxide layer 11, the floating gate 17, and the gate 18 serving as a mask. A heat-treatment process is then performed on the wafer. Through these two processes, impurity ions are implanted and driven into the unmasked portions of the substrate 10 to form a pair of source/drain regions 19 in the substrate 10 on both sides of the gate 18.
In the foregoing method, the floating gate 17 is formed from a combination of the WSi layer 16 and the underlying polysilicon layer 15. Since the WSi layer 16 is customarily formed through CVD process, remnant fluorine (F) or chlorine (Cl) atoms can be left in the WSi layer 16. A bad consequence of this can occur when the WSi layer 16 is heated in the subsequent heat-treatment process used to drive ions into the source/drain regions, because stress can occur in the heated WSi and the remnant fluorine or chlorine atoms in the WSi layer 16 can be diffused into the tunneling oxide layer 14b. This turns the tunneling oxide layer 14b into a trapping center. During operation of the EEPROM device, the electric charges caught in the trapping center cause uneven and inconsistent electric fields in the tunneling oxide layer 14b, which easily causes breakdown in the tunneling oxide layer 14b. The reliability of the resultant EEPROM device is thus degraded.

Method of fabricating an electrically erasable and programmable read-only memory (EEPROM) with improved quality for the tunneling oxide layer therein


Methods and apparatus for software threads to access both shared and unshared data in a single software unit. Prior to a thread executing a set of computer language instructions in a collection of software units, it creates a copy of the respective location data segment of the collection of software units. Thereafter, prior to the thread accessing a software unit in the collection of software units that has an associated set of shared data, the thread sets a pointer in its location data segment copy to the equivalent value in the location data segment of the collection of software units. The thread will thereafter access the set of data associated with the software unit when it executes the respective software unit.

The field of this invention pertains to computer systems, and more particularly, is directed to multi-threaded processing in a computer system.
A typical computer system is comprised of a collection of software, accessible by a variety of executing threads; i.e. applications.
As shown in FIG. 2, software code may be organized into software libraries 101. A software library 101 is a collection of software packages 103. A software package 103 is a collection of related procedures 105 and/or functions 107, collectively termed routines, stored together in the computer system for continued use as a unit. Software packages 103 provide a method of encapsulating and storing related procedures 105 and functions 107 together as a unit.
Procedures 105 and functions 107 each consist of a set of computer language statements functionally grouped together as an executable unit to perform a specific task. Procedures 105 and functions 107 are essentially equivalent constructs, except that functions 107 return a single value to the caller, while procedures 105 do not return any value. Procedures 105 and functions 107 may be called explicitly by applications or user stations of a computer system.
A typical multi-context/shared data architecture for a computer system, as depicted in FIG. 3, has a plurality of software packages in a software library 201. Each software package has a related context associated with it. A context in this multi-context/shared data architecture is a collection of data required by the routines of a software package to execute properly. Thus, the software package 202 is associated with the context 203, the software package 204 is associated with the context 205 and the software package 206 is associated with the context 207.
The data in each context in the software library 201 is designated, i.e., designed to be, shared, or global, or exposed, data. Thus, threads executing the software library, either consecutively or concurrently, access the same data in a context when they call the same routines of a software package.
Threads are lightweight processes that exist within a larger process. In a multi-context/shared data architecture, threads share the same software code and related data, but have their own individual program counters, machine registers and stacks. A process is a mechanism that can execute a series of steps; some systems refer to processes as xe2x80x9cjobsxe2x80x9d or xe2x80x9ctasksxe2x80x9d.
For example, if there are two threads 304 and 306, as depicted in FIG. 4A, executing consecutively, and both call the same procedure 305 in the software package 302, then both threads 304 and 306 share data in the context 303. However, because the two threads 304 and 306 execute consecutively, i.e., one after the other, there are no data access contention issues. As one thread executes before the other, the first thread to execute finishes accessing the shared data in the context 303 before the second thread begins to execute. Executing consecutively, threads 304 and 306 will not access the same data at the same time.
Yet, if the same two threads 304 and 306 execute concurrently, and both threads 304 and 306 call the same procedure 305 in the software package 302, the situation raises data access contention concerns. This is because both threads 304 and 306 may potentially attempt to access the same data in the context 303 at essentially the same time.
In such a situation, one thread may change the value of a data item that a second thread is relying on to have an original, unchanged value. This can result in faulty processing by the second thread. Thus, when two or more threads may potentially access the same data at the same time, a mutual exclusivity mechanism, i.e., a mutex, is generally required to manage access to the shared data in the context 303.
A mutex may be a semaphore 312. When a first thread 304 calls 308 a procedure 305 in a software package 302, thereby accessing data in the related context 303, the semaphore 312 associated with context 303 is set. When a second thread 306 thereafter calls 310 the procedure 305 in the software package 302, involving access to the data in the related context 303, the second thread 306 first checks the context 303 associated semaphore 312. As semaphore 312 has been set by the first thread 304, the second thread 306 must wait to gain access to data in the context 303.
When the first thread 304 exits from the procedure 305 in the software package 302, it no longer requires access to the data in the related context 303. Thus, the semaphore 312 is reset to indicate that the data in the context 303 is not being accessed. Sometime thereafter, when the second thread 306 checks the semaphore 312 and discovers that it indicates that the data in the context 303 is not being accessed, then the semaphore 312 is once again set, and the second thread 306 continues its processing, executing the procedure 305.
As with the first thread 304, when the second thread 306 exits the procedure 305 in the software package 302, it no longer requires access to the data in the related context 303. Thus, the semaphore 312 is once more reset to indicate that the data in the context 303 is not being accessed.
A package that uses shared data and relies on a mutex to protect the data from access contentions is referred to as a thread-safe package. An advantage of a thread-safe package is that threads may share the same data. Another advantage of a thread-safe package is that it conserves memory space. The same data is used by each thread calling a particular routine in a specific software package. Thus, in computer systems where memory space and/or allocation are at a premium, thread-safe packages are favored.
A disadvantage of thread-safe packages is that their use can affect the processing time of concurrently executing threads. For example, if there are ten threads executing concurrently and they all call a routine in the same software package at essentially the same time, then nine threads will thereafter have to wait for the first thread to gain access to the data in the related context to exit the associated routine. Thereafter, eight threads will have to wait for the second thread to gain access to the data in the related context to exit the associated routine, and so on. The tenth thread to gain access to the respective data, thereby continuing its processing, may be forced to wait a relatively long time to do so. In time critical processing threads, this wait may fail to meet established system performance requirements.
In an alternative multi-context/unshared data architecture, an example of which is depicted in FIG. 4B, the data in each context is designated unshared, or private, or local. With this architecture, threads executing either consecutively or concurrently create a copy of the context for each software package that they access via a routine call. The software packages in a multi-context/unshared data architecture do not rely on a mutex to protect data from concurrent access. Thus, these packages may be referred to as non thread-safe packages.
Non thread-safe packages, rather than using mutexes for data protection, rely on the accessing threads to first make a copy of the package""s context, and thereafter execute the respective routines using the context copy.
For example, if two threads 404 and 406 execute consecutively, and both threads call the same procedure 405 in the software package 402, then both threads will need to access the data in the related context 403. As the software package 402 is non thread-safe, meaning its related data in the context 403 is not to be shared, when a first thread 404 calls 408 procedure 405 in the software package 402, a copy 412 of the context 403 is created for this first thread""s use. Likewise, when a second thread 406 calls 410 procedure 405, a copy 414 of the context 403 is created for this second thread""s use.
The processing is similar if both threads 404 and 406 execute concurrently. When the first thread 404 calls 408 procedure 405 in the software package 402, a copy 412 of the context 403 is created for this first thread""s use. When the second thread 406 calls 410 procedure 405, a copy 414 of the context 403 is created for this second thread""s use.
An advantage of a non thread-safe package is that, when more than one thread concurrently calls one of its routines, thread processing may be expected to be quicker than if the package was thread-safe, and, therefore, used a mutex to control access to its shared data. For example, as shown in FIG. 4B, the second thread 406 does not have to wait for the first thread 404 to execute the procedure 405 before it may execute the procedure 405. Because each thread 404 and 406 in this system uses its own copy of the context 403, coordination and control of the data access between these threads is not required.
However, a disadvantage of a non thread-safe package is that it does not allow for the sharing of data, which may be a requirement or a desired feature of the system. Further, the use of a non thread-safe package can entail significantly more memory than the use of an equivalent thread-safe package. For each thread that executes, i.e., runs, in a multi-thread/unshared data system, a copy of the context for each package accessed must be created. For example, if there are ten threads executing, and they all call a routine in the same software package, and the related context is one megabyte in size, than an additional ten megabytes of memory must be available for creating the context copies. For systems in which the memory space is small, or, for whatever reason, is at a premium, the multi-context/unshared data architecture can prove unworkable.
An additional problem with either architecture, i.e., multi-context/shared data or multi-context/unshared data, is that a thread calling a particular routine in a software package must be cognizant of the individual software package""s associated context. Further, the thread, if it calls several routines from a variety of software packages, must keep track of which context is associated with which software package. This can add to the data management requirements, thereby increasing the overall complexity of a thread""s processing.
For example, in a multi-context/shared design system, a thread calling a routine in a first software package must be able to identify the first software package""s associated context, and distinguish it from the contexts associated with other software packages, in order to correctly manage the mutex for the first software package. Additionally, each context may have a different access mechanism, requiring a thread to keep track of and use different access mechanisms to different contexts. In a computer system using multi-context/unshared data, a thread calling a routine in a first software package must be able to identify the first software package""s associated context, and distinguish it from the contexts associated with other software packages, in order to create a copy of the correct context. Too, in a computer system using multi-context unshared data, a thread may have to access the individual contexts of various software packages differently, in order to create the respective copies thereof.
It would, therefore, be advantageous to provide a simple, single, uniform interface for threads to use to access the various data segments of a software library, or any collection of software units and their related data.
Further, it would be advantageous to provide a mechanism whereby threads can access both shared and unshared data in the same software unit, e.g., a software package. This would provide flexibility both in handling memory allocation issues and time processing concerns in a computer system. A more optimum computer system for handling multi-thread processing would thereby be created.
The invention provides a computer system with a single, common interface to the data segments of a collection of software units. The invention further provides apparatus and methods for allowing threads to access both shared and unshared data in a single software unit.
In an embodiment, a collection of software units is comprised of units that are associated with data segments of shared data, i.e., thread-safe software units, and units that are associated with data segments of unshared data, i.e., non thread-safe software units. A collection of location variables, generally stored in a location data segment, is associated with the collection of software units. Each location variable is associated with an address for a data segment for a software unit.
Each time a thread is to execute software in the collection of software units it creates a version of the respective location data segment. If the thread will thereafter access a software unit that has associated shared data, the thread sets a pointer in its location data segment version to the equivalent value in the respective location data segment. In this manner, the thread will access the associated data segment of the software unit when it accesses the software unit.
If the thread will access a software unit that has associated unshared data, the thread creates a copy of the respective unshared data segment. The thread then sets a pointer in its location data segment version to point to the address of the unshared data segment copy. In this manner, the thread will access its copy of the unshared data segment when it accesses the respective software unit.
Thus, a general object of the invention is to provide a flexible multi-thread environment in which each thread can access data segments associated with a collection of software units via a single interface. A further general object of the invention is to allow threads to access both shared and unshared data in the same collection of software units. Other and further objects, features, aspects and advantages of the invention will become better understood with the following detailed description of the accompanying drawings.

Methods and apparatus for multi-thread processing utilizing a single-context architecture

Abstract: Also, prior to the thread accessing a software unit in the collection of software units that has an associated set of unshared data, the thread creates a copy of the set of unshared data. The thread thereafter sets a pointer in its location data segment copy to the start address in memory of the local copy of the unshared data set. The thread will thereafter access the local set of unshared data when it executes the respective software unit.


This invention relates to binary blends of cellulose esters and aliphatic-aromatic copolyesters, cellulose esters and aliphatic polyesters as well as ternary blends of cellulose esters and/or aliphatic polyesters and/or aliphatic-aromatic copolyesters and/or polymeric compounds as well as fibers, molded objects, and films prepared therefrom.

It is well known that cellulose esters are important as commercial plastics and as fibers. In general, cellulose esters are used in plastic applications where hard but clear plastics are required. For example, cellulose esters are used in tool handles, eyeglass frames, toys, toothbrush handles, and the like. All of these applications require a combination of high melting and glass transition temperatures as well as high modulus and good tensile strength. Formulations based on cellulose esters which provide plastic films with low modulus but good tensile strength while maintaining sufficient melting and glass transition temperatures (Tg) to allow thermal processing are generally unknown. Formulations based on cellulose esters which allow thermal extrusion of fibers are also generally unknown.
Because of the high melt temperatures and low melt stability of many of the cellulose esters, plasticizers such as dioctyl adipate or triphenylphosphate are often added to the cellulose ester to lower the melt temperatures during melt processing of the polymer. Although this technique is effective, addition of a monomeric plasticizer often creates secondary problems related to volatile or extractable plasticizers such as dye drip during melt extrusion or long-term dimensional stability (creep) in an object made from the cellulose ester.
The most basic requirement for polymer-polymer miscibility is that the free energy of mixing be negative (.DELTA.G<0). Although on the surface it would seem that polymer-polymer miscibility would be common, in reality there are only a few known miscible binary blends and even fewer known miscible ternary blend systems (Brannock, G. R.; Paul, D. R., Macromolecules, 23, 5240-5250 (1990)). The discovery of miscible binary or ternary blends is very uncommon.
The classical experimental techniques for determining polymer blend miscibility involve the determination of the optical clarity of a film made from the blend, measurement of the appropriate mechanical properties, and measurement of the glass transition temperature by an appropriate thermal analysis technique such as dynamic mechanical thermal analysis (DMTA) or differential scanning calorimetry (DSC). If a blend is miscible, films made from the blend will generally be clear. Likewise, mechanical properties of a blend, such as tensile strength or tangent modulus, are often intermediate between those of the blend components. Furthermore, a miscible amorphous blend will show a single Tg intermediate between that of the component homopolymers while an immiscible or partially miscible blend will show multiple Tg's. In the case of a completely immiscible blend, the Tg's will be those of the homopolymers. For partially miscible blends, the Tg's will be intermediate values corresponding to partially miscible phases rich in one of the components. The variation in binary blend Tg can be modeled by the Fox-Flory equation, Tg.sub.12 =Tg.sub.1 (W.sub.1)+Tg.sub.2 (W.sub.2, where Tg.sub.12 is the Tg of the blend, Tg.sub.1 and Tg.sub.2 are the Tg's of homopolymers, and W.sub.1 and W.sub.2 are the weight percent of each component in the blend. Since the Fox equation does not take into account specific interaction between the blend components the Gordon-Taylor equation, Tg.sub.2 =Tg.sub.1 +kW.sub.2 (Tg.sub.2 -Tg.sub.12)/W.sub.1 ! where k is a constant, is often preferred in blend analysis. For a homogenous, well mixed system, a plot of Tg.sub.12 versus W.sub.2 (Tg.sub.2 -Tg.sub.12)/W.sub.1 will yield a straight line the slope of which is equal to k and the ordinate intercept will be equal to Tg.sub.1. The constant k is often taken as a measure of secondary interactions between the blend components. When k is equal to one, the Gordon-Taylor equation reduces to a simple weight average of the component Tg's.
Miscible blends of cellulose esters and other polymers are generally unknown. The most notable exceptions include the work disclosed by Koleske, et al. (U.S. Pat. No. 3,781,381 (1973)), Bogan and Combs (U.S. Pat. No. 3,668,157 (1972)), Waniczek et al., (U.S. Pat. No. 4,506,045 (1985)), and Wingler et al. (U.S. Pat. No. 4,533,397 (1985)). Koleske et al. reported that blends, formed by solution casting of polycaprolactone and cellulose ester mixtures, are miscible. Later work by Hubbell and Cooper (J. Appl. Polym. Sci., 1977, 21, 3035) demonstrated that cellulose acetate butyrate/polycaprolactone blends are in fact immiscible. Bogan and Combs have reported that block copolymers of polyether-polyesters form miscible blends with some cellulose esters. Critical to the invention of Bogan and Combs was the use of an elastomeric block copolymer; they report that the corresponding homopolymeric elastomers were incompatible with cellulose esters. Waniczek et al., have disclosed that polyester carbonates and polyether carbonates copolymers form miscible blends with many cellulose esters and are useful as thermoplastic resins. Wingler et al. report that contact lenses can be prepared from blends consisting of (A) 97-70% by weight of one or more cellulose esters and (B) 3-30% by weight of an aliphatic polymeric compound having ester moieties, carbonate moieties, or both ester and carbonate moieties in the same polymer chain. The invention of Wingler et al. is limited to aliphatic polymeric compounds; no reference is made to random copolymers consisting of aliphatic diacids, aromatic diacids, and suitable diols or polyols. The invention of Wingler is further limited to cellulose mixed esters having a weight per cent hydroxyl of 1.2% to 1.95% (DS.sub.OH =0.11-0.19 where "DS" or "DS/AGU" refers to the number of substituents per anhydroglucose unit where the maximum DS/AGU is three). The invention of Wingler et al. is also limited to binary miscible blends and by the composition range of the blends (3-30% aliphatic polymeric compound). No reference is made to blends containing an immiscible component where the immiscible component is useful for enhancing properties such as water vapor transmission rates or biodegradability. Immiscible blends of cellulose esters and aromatic polyesters have also been disclosed by Pollock et al. (U.S. Pat. No. 4,770,931 (1988)) which are useful in applications such as paper substitutes.
One time use, disposable items are common. Examples of such disposable articles include items such as infant diapers, incontinence briefs, sanitary napkins, tampons, bed liners, bedpans, bandages, food bags, agricultural compost sheets, and the like. Examples of other disposable items include razor blade handles, toothbrush handles, disposable syringes, fishing lines, fishing nets, packaging, cups, clamshells, and the like. For disposable items, environmental non-persistence is desirable.
Disposable articles are typified by disposable diapers. A disposable diaper typically has a thin, flexible polyethylene film cover, an absorbent filler as the middle layer, and a porous inner liner which is typically nonwoven polypropylene. The diaper construction also requires tabs or tape for fastening the diaper (typically polypropylene) as well as various elastomers and adhesives. Although the absorbent filler is usually biodegradable or easily dispersed in an aqueous environment, currently neither the outer or inner liner nor the other parts such as the tabs or adhesives will degrade from microbial action. Consequently, disposable absorbent materials such as diapers accumulate in landfills and place enormous pressure on waste systems. Other disposable articles such as plastic bags or plastic compost sheets suffer from similar problems.
Numerous studies have demonstrated that cellulose or cellulose derivatives with a low degree of substitution, i.e., less than one, are biodegradable. Cellulose is degraded in the environment by both anaerobic or aerobic microorganisms. Typical endproducts of this microbial degradation include cell biomass, methane(anaerobic only), carbon dioxide, water, and other fermentation products. The ultimate endproducts will depend upon the type of environment as well as the type of microbial population that is present. However, it has been reported that cellulose esters with a DS greater than about one are completely resistant to attack by microorganisms. For example, Stutzenberger and Kahler (J. Appl. Bacteriology, 66, 225 (1986)) have reported that cellulose acetate is extremely recalcitrant to attack by Thermomonospora curvata.
Polyhydroxyalkanoates (PHA), such as polyhydroxybutyrate (PHB), polycaprolactone (PCL), or copolymers of polyhydroxybutyrate and polyhydroxyvalerate (PHBV), have been known for at least twenty years. With the exception of polycaprolactone, they are generally prepared biologically and have been reported to be biodegradable (M. Kunioka et al., Appl. Microbiol. Biotechnol., 30, 569 (1989)).
Polyesters prepared from aliphatic diacids or the corresponding carboxylic ester of lower alcohols and diols have also been reported to be biodegradable. For example, Fields and Rodriguez ("Proceedings of the Third International Biodegradation Symposium", J. M. Sharpley and A. M. Kaplan, Eds., Applied Science, Barking, England, 1976, p. 775) prepared polyesters from C2-C12 diacids coupled with C4-C12 diols and found that many were biodegradable.
Aliphatic polyesters have been used in very few applications mainly because of their low melting points and low glass transition temperatures (generally less than 65.degree. C. and -30.degree. C., respectively). At room temperature, the physical form of many of the aliphatic polyesters is as a thick, viscous liquid. Therefore, aliphatic polyesters are not expected to be generally useful.
On the other hand, aromatic polyesters, such as poly(ethylene terephthalate), poly(cyclohexanedimethanol terephthalate), and poly(ethylene terephthalate-co-isophthalate), have proven to be very useful materials. Aromatic polyesters, however, are generally very resistant to biodegradation (J. E. Potts in "Kirk-Othmer Encyclopedia of Chemical Technology", Suppl. Vol, Wiley-Interscience, New York, 1984, pp. 626-668). Block copolyesters containing both aliphatic and aromatic structures have been prepared and have been shown to be biodegradable. Examples of aliphatic-aromatic block copolyester-ethers include the work of Reed and Gilding (Polymer, 22, 499 (1981)) using poly(ethylene terephthalate)/poly(ethylene oxide) where these block copolymers were studied and found to be biodegradable in vitro. Tokiwa and Suzuki have investigated block copolyesters such as those derived from poly-(caprolactone) and poly(butylene terephthalate) and found them to be degraded by a lipase (J. Appl. Polym. Sci., 26, 441-448 (1981)). Presumably, the biodegradation is dependent upon the aliphatic blocks of the copolyesters; the blocks consisting of aromatic polyester are still resistant to biodegradation. Random aliphatic-aromatic copolyesters have not been investigated in this regard.
While random copolyesters with low levels of aliphatic diacids are known (e.g., Droscher and Horlbeck, Ange. Makromol. Chemie, 128, 203-213(1984)), copolyesters with high levels (>30%) of aliphatic dicarboxylic components are generally unknown. Copolyesters with as much as 40% aliphatic dicarboxylic acid components have been disclosed in adhesive applications; however, these copolyesters adhesives contain at least two dialcohol components in order to achieve the desired adhesive properties (Cox, A., Meyer, M. F., U.S. Pat. No. 4,966,959 (1990)).
There are many references to the preparation of films from polymers such as polyhydroxybutyrate (PHB). Production of films from PHB generally involves solvent casting principally because PHB polymers tend to remain sticky or tacky for a substantial time after the temperature has dropped below the melting point of the PHB. To circumvent this problem, Martini et al. (U.S. Pat. Nos. 4,826,493 and 4,880,592) teach the practice of co-extruding PHB with a thermoplastic that is non-tacky. Such thermoplastics remain as a permanent layer on the PHB film or may be a sacrificial film which is removed following extrusion.
PHB has also been reported to be useful in the preparation of disposable articles. Potts (U.S. Pat. Nos. 4,372,311 and 4,503,098) has disclosed that water soluble polymers such as poly(ethylene oxide) may be coated with biodegradable water insoluble polymers such as PHB. In these inventions, the PHB layer, which is distinct from the water soluble layer, degrades exposing the water soluble layer which will then disperse in an aqueous environment.
There have been other reports of the preparation of a biodegradable barrier film for use in disposable articles. Comerford et al. (U.S. Pat. No. 3,952,347) have disclosed that finely divided biodegradable materials such as cellulose, starch, carbohydrates, and natural gums may be dispersed in a matrix of nonbiodegradable film forming materials which are resistant to solubility in water. Wielicki (U.S. Pat. No. 3,602,225) teaches the use of barrier films made of plasticized regenerated cellulose films. Comerford (U.S. Pat. No. 3,683,917) teaches the use of a cellulosic material coated with a water repellent material.
There exists in the market place the need for thermoplastics which are useful in molding, fiber, and film applications. For these applications, it is desirable that the thermoplastic blend be processable at a low melt temperature and have a high glass transition temperature. These thermoplastics should not contain volatile or extractable plasticizers. Moreover, there is a need in the marketplace for a biodegradable material for use in disposable articles such as diapers, razors, and the like. As an example, unlike films prepared from polymers such as PHB, the material should be amenable to both solvent casting and melt extrusion. In melt extruding this material, coextrusion with other thermoplastics should not be a requirement. The barrier properties of this new biodegradable material should be adequate so that coating with a water insoluble polymer is not required. The new material should disperse completely in the environment and not require coating with a water soluble polymer. The mechanical properties of the material should be such that films of low modulus but of high tensile strength can be prepared.

Aliphatic-aromatic copolyesters and cellulose ester/polymer blends


A dog is disclosed for mounting on a shuttle assembly of a bale ejector system of a square baler. The dog has two pointed ends and at least one mounting feature that permits the dog to be pivotably mounted on the shuttle assembly. The dog is symmetrical so as to be selectively capable of being mounted on the shuttle assembly in each of two orientations in order to extend the service life of the dog.

WO96/29195 discloses a square baler which, instead of using the compacting plunger to unload tied bales from the bale case, comprises an auxiliary ejector system to enable the operator to off-load completed bales. The ejector system comprises a shuttle assembly housed within hollow rails of the bale case. The shuttle assembly consists of a frame that is reciprocated in the direction of movement of the compacting plunger and has dogs projecting upwards from it to engage in the underside of the bales. The dogs grip the bale only during the forward stroke of the shuttle assembly, that is to say when it is moving towards the discharge outlet of the bale case, and slip relative to the underside of the bale during the return stroke. In this way, the reciprocation of the shuttle assembly incrementally advances the bales towards the discharge outlet.
The ejector mechanism of WO96/29195 is controllable to enable the operator to select whether to discharge only the last bale in the bale case (the one nearest the discharge outlet) or both the last bale and the one before it. To achieve this, the dogs are arranged on the shuttle in a longitudinally extending series and at least some of the dogs are controllable by the operator using a selector assembly so that the controlled dogs may be positioned either to extend into the bale case or to be retracted from it.
Apart from the complexity resulting from the need to control dogs individually, the ejector system of WO96/29195 suffers from the disadvantage that the operator needs first to inspect the position of the bales in the bale case in order to decide on which of the dogs to activate.
To avoid these disadvantages, the Applicants' earlier patent application number EP 08154199.7 discloses a square baler having a bale case within which crop is compacted by means of a plunger, a discharge outlet at one end of the bale case and an ejector system for advancing bales towards the discharge outlet independently of the movement of the compacting plunger. The ejector system comprises a shuttle assembly mounted in a wall of the bale case for reciprocation parallel to the direction of movement of the bales in the bale case, and at least one dog mounted on the shuttle assembly to engage in the last bale in the bale case positioned nearest the discharge outlet and to advance the bale incrementally out of the discharge outlet in response to reciprocation of the shuttle assembly. A second shuttle assembly is mounted in a wall of the bale case for reciprocation independently of the first shuttle assembly, the second shuttle assembly having at least one dog mounted thereon to engage in the next-to-last bale in the bale case.
In one embodiment, the second shuttle assembly has a series of dogs staggered over its entire length and is capable of advancing bales as far as the discharge outlet of the bale case. In this case, reciprocation of the second shuttle assembly on its own will suffice to advance both the last bale and the next-to-last bale to the discharge outlet.
In an alternative embodiment, the second shuttle assembly is designed to move the next-to-last bale only as far as a position where it will be taken up by the first shuttle assembly. In this case, both shuttles need to be reciprocated to discharge the next-to-last bale in the bale case.
Without regard to the exact positions of the completed bales in the bale case, the operator may thus elect to discharge only the last bale by operating the first of the shuttle assemblies or to discharge both the last and next-to-last bale by reciprocating the second shuttle assembly either on its own or in conjunction with the first shuttle assembly.
An important advantage of EP 08154199.7 is that the dogs do not need to be controlled, i.e. selectively enabled and disabled. Each dog is instead pivotably mounted on the shuttle assembly and designed to act in a manner analogous to the pawl of a pawl and ratchet. Thus, each dog will pivot into an extended gripping position during the forward movements of the shuttle to advance the bale towards the discharge outlet and will retract during reverse movements of the shuttle assembly to slip relative to the bale.
When using pivotable dogs, they may be biased into their extended position by gravity or by means of a spring. EP 08154199.7 also teaches that the dogs may be designed to protrude slightly into the bale case when retracted so that they will be raised automatically into their extended position as they grip into a bale.
The present invention seeks to improve on the design of the dogs used in the reciprocating ejector assemblies such as for example known from EP 08154199.7.
Each dog in EP 08154199.7 comprises a generally triangular plate that is pivoted in such a manner that its own weight rotates it into a retracted rest position in which its side lies nearly level with the floor of the bale case. The small part of the dog that projects above the floor digs into the bale when the shuttle assembly is moved towards the discharge outlet of the baler and the resistance that it encounters rotates the dog into its raised position. The bale is now gripped and moves with the shuttle assembly. During the movement of the shuttle away in the opposite direction, the dog returns to the rest position in which it is retracted and no long grips the bale. Two stops are provided against which the dog rests in its retracted and extended position, respectively.

Dog for an ejector system of a square baler


A flotation device useable as a life-preserver and a water toy, the device including a casing formed of water-impermeable synthetic plastic film material shaped to define a pocket for receiving a conventional pillow having a compressible filler. The pocket is provided with a closable inlet which when closed, hermetically seals the pillow-stuffed casing to provide a compressible yet buoyant life-preserver. The casing may be die cut to assume the contours of a humanoid or animal-like figure whereby the floatation device then functions as a water toy.

1. Field of Invention
This invention relates generally to flotation devices useable in swimming pools, lakes and in other bodies of water suitable for bathers and swimmers, and more particularly to a flotation device created by a conventional pillow stuffed into the pocket of a synthetic plastic film casing.
2. Status of Prior Art
A life-preserver is a flotation device adopted to keep its user afloat in water. While many flotation devices are formed of inflatable rubber or plastic film material, these have the disadvantage of being rendered useless should the inflatable be punctured, or should its air inlet valve become defective. Moreover, with a conventional mouth-inflatable flotation device, it takes a fairly long time and some effort to inflate the device.
Hence a preferred form of flotation device or life-preserver is one whose buoyancy depends on a fibrous stuffing, such as kapok. Kapok is a silk cotton used for stuffing cushions and pillows as well as life-preservers. The advantage of a kapok-stuffed buoyancy device is that its buoyancy will not be impaired should the device be punctured. However a kapok-stuffed life-preserver, unlike one that is inflatable, cannot be deflated and stored in a flat, compact state.
The concern of the present invention is with the needs of families with children that travel by car either on a vacation trip or for any other reason. In the course of such travel, there are stopovers at motels and other accommodations having swimming facilities, such as a pool or a nearby lake. It is customary when a family makes use of a pool or lake to provide at least one flotation device that members of the family, when necessary, can hold onto or play with as a water toy.
In widespread use are inflatable flotation devices fabricated of synthetic plastic film material molded or die cut to resemble an animal-like or humanoid figure. A buoyant inflatable device of this type functions not only as a water toy, but also as a life-preserver. The advantage of such inflatable flotation devices is that they may be deflated and flattened out when not in use and then folded into a compact form. Thus a traveling family can store folded flotation devices in the trunk of the family vehicle. However as previously noted, inflatable flotation devices cease to be effective should there be a loss of air due to a puncture or tear in the plastic, or because of a defective valve.
And while kapok-filled flotation devices provide a high measure of protection in water, such devices cannot be deflated and reduced in size. In a family vehicle on a vacation trip in which the trunk of the car is crowded with articles of clothing and many other items the family needs to take along, little room is available for large flotation devices.
Since in a flotation device in accordance with the invention, use is made of a conventional pillow, of prior art interest in the 1987 Spector U.S. Pat. No. 4,670,924 entitled "Transformable Pillow." This patent discloses a dual-function pillow which is transformable into a figurative form or character. In its normal mode, the pillow serves as a comfortable head rest, while in its transformed mode it functions as a plaything. The pillow which has a soft and compressible body includes a rectangular bag or outer case whose face has applied thereto a two-dimensional figure or character. The bag or case is provided with one or more transversely-placed draw strings which when tightened then act to constrict the pillow and to thereby impart contours thereto to define a main head portion and at least one secondary portion to create a three-dimensional form.