A System and Method for Gas Recognition by Analysis of Bispectrum Functions is based on the Higher-Order Spectral analysis of time series measurements of resistance fluctuations in Metal Oxide Semiconductor (MOS) gas sensors, such as Taguchi-type sensors. A two-dimensional contour plot module of the bispectrum function is treated as a pattern. These patterns include information about the analyte(s) whereby characteristics of the gas can be identified.

The System and Method for Gas Recognition by Analysis of Bispectrum Functions generally relates to chemical analyte detection and identification, and more particularly, to a system and method of chemical analyte detection and identification by analysis of resistance fluctuations of a Metal Oxide Semiconductor (MOS) gas sensor.
Homeland defense, including anti-terrorist efforts require highly selective, sensitive, and reliable detection of harmful agents. Intensive research has resulted in the use of chemical and biological sensor elements for the development of systems known as electronic noses (for gas and odor sensing) and electronic tongues (for fluid sensing).
One way of gas sensing is based on Metal Oxide Semiconductor (MOS) gas sensors. These devices generally operate by measuring the change in resistance between electrode pairs as a result of the interaction between the surface of the metal-oxide semiconductor and the ambient gas. As gas molecules are adsorbed and desorbed by the MOS sensor, the resistance of the sensor changes. Traditionally, only the DC (average) resistance is measured. The DC resistance is a single value that cannot be used as a pattern for recognition of different gases.
More recently, the power spectral density of fluctuations in the resistance of the MOS sensor have been measured. This power spectral density can be used to generate a pattern to identify different gases by giving information about power of the stochastic component at different frequencies. However, the power spectral density looses information about the phase relationships of the resistance fluctuations.
Therefore, it can be appreciated that a sensitive and reliable method of MOS sensor analysis that preserves phase relationships of resistance fluctuations is needed.

System and method for gas recognition by analysis of bispectrum functions

The United States of America as represented by the Secretary of the Navy


A method and apparatus for controlling the flow of a fiber suspension having a direction of flow and a consistency from 5-25% including a treatment chamber having an axis extending in the direction of flow of the fiber suspension, a suspension inlet and a suspension outlet opposite the suspension inlet, the suspension inlet and outlet having the same diameter and an axis in alignment with the axis of said treatment chamber;. a fluidizing rotor within the chamber for fluidizing the fiber suspension, the fluidizing rotor having an axis of rotation transverse to the axis of the treatment chamber; and PA1 a throttling arrangement disposed between the rotor and the suspension outlet for throttling the suspension flow.

Medium and high consistency pulp (consistency 8-30%) forms a very stiff material; it can be so stiff that one can stand with ordinary shoes on the pulp and not sink into the pulp. The reason for it is that fiber with the length of a few millimeters form a strong-three dimensional fiber network. The fibers are rather rigid and when they rest on each other they form a strong structure.
High consistency pulp is still generally pumped by a displacement pump or a screw pump. This was up till now the only way to pump high consistency pulp. When the pulp is pumped by such pumps, no control valve is used in the discharge side. There are two reasons for that. Firstly, high consistency pulp is stiff and the pumps produce a pulsating pressure. If there is a throttling in the discharge side, it produces strong pressure pulses in the pipe system, which can break structures. Secondly, a displacement pump works even though if there is no pulp in the suction side or so little pulp that it would only partly fill the compartments of the pump. The pump can work so that it pumps forward everything that comes from the suction side to the compartments.
High consistency pulp can, however, be changed momentarily into a flowing state by the breaking fiber network by bringing shear forces to the suspension. This is called fluidization of high consistency pulp. Normally fluidization is effected by some kind of powerful rotor. For example, in a high consistency pump the rotor effects the fluidization in the suction duct of the pump. Fluidization is a reversible process, and as soon as the rotor is stopped or the pulp is no longer in the range of the rotor, the fiber network is formed again and the suspension becomes again a substantially solid material.
Lately, a new type of high consistency pump has become accepted in the mills, cf., e.g. U.S. Pat. No. 4,435,122. This new kind of pump is a centrifugal pump, in which high consistency pulp is fluidized, in other words changed into a flowing state just before the pulp reaches the range of the pump impeller. With this technique in pumping high consistency pulp it is usually necessary to assemble a control valve in the discharge side of the pump according to FIG. 1 in order to ensure that there is always pulp in the suction side of the pump or that the amount of the pulp to be pumped is correct. Reason for this is the fact that a centrifugal pump always has to have its inlet opening filled with pulp and thus its operation is most often controlled in such a way that the pulp level in the vessel prior to the pump is maintained substantially constant by means of throttling the discharge of the pump.
If the capacity of a pump is adjusted by a control valve according to FIG. 1, the head of the pump is considerably lowered in the control valve because of the rigid character of the pulp. In controlling the flow of high consistency pulp the resistance i.e. pressure drop is often several bars even with the best valves known.
Often in pulp mills a pulp pump is followed by yet another device, namely a mixer for mixing chemicals into the pump, for example, in bleaching. The mixing may be effected either in a separate mixer or in a high consistency pump. When chemicals are mixed in a medium/high consistency pump, they are added either before the pump or at the outer rim of the impeller. If this is done, a separate mixer is not necessary, but the same device may serve both as a mixer and a pump. However, if the chemicals are in the form of gases they cannot be added before the pump as centrifugal pumps pumping medium or high consistency pulp are usually provided with means for separating gas from pulp whereby the chemicals would be the first gases to be separated.
Often a pump cannot be used as a mixer for several reasons. Such may be, for example, material problems or the fact that the amount or the quality of the chemicals in such that the chemicals cannot be added into the pump. Hereby one has to use a separate mixer according to FIG. 2. There are cases in which part of the chemicals may be fed to the pump and the rest to the mixer or all chemicals to the mixer depending on the situation.
A mixer being used in connection with medium or high consistency pulps consists of a substantially cylindrical casing with an axial inlet opening and an axial outlet opening and protrusions on the inner surface, of an axially rotating rotor which has protrusions on the outer surface, and of a feed duct for chemicals which opens to a substantially annular mixing zone between the rotor and the casing. Said mixer, although very practical and reliable, is, however, rather complicated to manufacture of special material. This kind of a mixer has still a severe drawback relating to its operation. After being efficiently mixed with the chemicals and having started to rotate in the mixing zone due to the rotation of the rotor the pulp leaves the annular mixing zone in a direction coaxial with the rotor whereby the rotational movement of the pulp continues and the pulp tends to form a rotating annulus on the wall of the flow channel. Also the pressure in the pulp decreases rapidly as the flow area of the pulp suddenly increases. The result of these two factors is that the gases, i.e. most often the chemicals, tend to separate in the middle of the flow starting to form gas bubbles. Thus the mixing of the chemicals with the pulp is not as efficient and even as could be expected.
As one can note from the foregoing there are several different devices utilized in connection with the pulp pump, namely the pump itself, the control valve and a chemical mixer. A purpose of the present invention is to combine these devices in such a way that the result would be most economical in the point of view of both the manufacturer of the devices and their users.
It would, of course, be possible to combine all of the above mentioned three devices together, but there is one factor which makes it practically impossible. As explained above, the chemicals may be mixed within the pump, wherefore the pump perhaps should be manufactured of a more durable material, but not always. However, when pumping medium or high consistency pulps the control valve should be arranged so close to the pump impeller that the fluidized pulp would not have time to reverse back into plug flow by forming a fiber network. It is to be noted at this stage that the discharge duct of a centrifugal pump is always tangential in order not to resist the flow out of the pump. On one hand, this kind of tangential arrangement would be impossible in case high consistency pulps were to be pumped, as the distance from the impeller blades maintaining the fluidized state at a sufficient level to the throttling arrangement arranged in a tangential discharge duct would be long enough for allowing the pulp to form fiber network, whereby an ordinary valve would either cause a high pressure loss or be entirely clogged. On the other hand, the discharge duct could be arranged substantially radially, whereby the above defined distance would be minimized, but the sharp turn in the volute flow from circumferential to radial would bring about a considerable drop in pressure substantially equalling the drop in an ordinary valve.

Method and apparatus for improving the control and treatment of fiber suspension flow


A nonpolymeric silsesquioxane is provided wherein at least one silicon atom of the silsesquioxane is directly or indirectly bound to an acid-cleavable substituent RCL. The silsesquioxane has a glass transition temperature Tg of greater than 50° C., and the RCL substituent can be cleaved from the silsesquioxane at a temperature below Tg, generally at least 5° C. below Tg. The remainder of the silicon atoms within the silsesquioxane structure may be bound to additional acid-cleavable groups, acid-inert polar groups RP, and/or acid-inert nonpolar groups RNP. The nonpolymeric silsesquioxane can be a polyhedral silsesquioxane optionally having one to three open vertices, such that the polyhedron appears to be a “partial cage” structure, or a macromer of two to four such polyhedral silsesquioxanes. Photoresist compositions containing the novel nonpolymeric silsesquioxanes are also provided, as is a method for using the compositions in preparing a patterned substrate.

The patterning of radiation sensitive polymeric films with high energy radiation such as photons, electrons, or ion beams is the principle means of defining high resolution circuitry found in semiconductor devices. The radiation sensitive films, often referred to as photoresists regardless of the radiation source, generally consist of multicomponent formulations that are coated onto a desired substrate such as a silicon wafer. The radiation is most commonly ultraviolet light at wavelengths of 436, 365, 257, 248, 193 or 157 nanometers (nm), or a beam of electrons or ions, or 'soft' x-ray radiation, also referred to as extreme ultraviolet (EUV) or x-rays. The radiation is exposed pattern wise and induces a chemical transformation to occur that renders the solubility of the exposed regions of the films different from that of the unexposed areas when the films are treated with an appropriate developer, usually a dilute, basic aqueous solution, such as aqueous tetramethylammonium hydroxide (TMAH).
Typical photoresists contain a polymeric component and are generally comprised of a polymeric matrix, a radiation sensitive component, a casting solvent, and other performance enhancing additives. The highest performing photoresists in terms of sensitivity to radiation and resolution capability are "chemically amplified" photoresists, allowing high resolution, high contrast and high sensitivity that are not generally provided by other photoresists. Chemically amplified photoresists are based on a catalytic mechanism that allows a relatively large number of chemical events such as, for example, deprotection reactions in the case of positive photoresists or crosslinking reactions in the case of negative tone photoresists, to be brought about by the application of a relatively low dose of radiation that induces formation of the catalyst, often a strong acid.
The absorbance characteristics of the polymeric matrix also impacts the suitability of a given photoresist for exposure with particular radiation sources. The choice of a polymer must be carefully considered when designing a material for lithographic applications, particularly where such polymers are to provide a relatively transparent matrix for radiation-sensitive compounds such as photoacid generators (PAGs). Absorbance characteristics are important because the wavelength of radiation used in optical lithography is directly proportional to the ultimate resolution attainable with a photoresist. The desire for higher resolution has therefore led to to the use of shorter and shorter radiation wavelengths. For example, the phenolic polymers used for 248 nm imaging, namely derivatives of poly(4-hydroxystyrene)(PHS), are unsuitable for use with 193 nm radiation as the opacity of these PHS materials at 193 nm does not allow for sufficient radiation to create an appropriate image profile throughout the photoresist film thickness. As a result, the selection of particular materials is necessary for each wavelength of optical radiation used.
The dissolution characteristics of photoresist materials in a developer are also important considerations. The semiconductor industry has largely supported the use of TMAH as a developer for photoresists. PHS materials, e.g., tend to dissolve very uniformly in TMAH without swelling. Additionally, the rate at which the polymeric films dissolve can be tuned, for example, by the use of protecting groups and dissolution inhibitors in positive tone photoresists, and by effective crosslinking and other functionalization in negative tone photoresists. Uniform dissolution has been a difficult property to incorporate into new photoresist materials, however, especially those designed specifically for 193 nm imaging. The current polymer resists for 193 nm imaging, such as acrylic acid derivatives, cyclic olefins and alternating cyclic olefin-maleic anhydride-based materials, generally fall into this category of nonlinear dissolution. In fact, these materials often exhibit significant swelling during the initial stages of development, making the development of photoresists based on these materials difficult.
Alternative materials based on fluoroalcohols have been previously proposed as a means of providing aqueous base solubility. See, e.g., Ito et al. (2001), "Polymer Design for 157 nm Chemcially Amplified Resists," Proc. SPIE 4345:273–284; Kunz et al. (2001), "Experimental VUV Absorbance Study of Fluorine-Functionalized Polystyrenes," Proc. SPIE 4345:285–295; and Bae et. al. (2001), "Rejuvination of 248 mn Resist Backbones for 157 nm Lithography," J. Photopolym. Sci. Tech. 14:613–620. Examples of such materials include norbornene hexafluoroalcohol, styrene hexafluoroalcohol and cyclohexyldodecylfluoro-alcohol-based polymers. While each of these platforms provides base-soluble materials, each has disadvantages for commercial high resolution photoresist applications. For example, the norbornene hexafluoroalcohol monomer requires special polymerization conditions, such as ring-opening polymerization, transition metal catalyzed addition polymerization, or alternating free-radical polymerization with a comonomer such as maleic anhydride. Thus, this monomer does not accommodate a large number of suitable comonomers—a desirable property which allows for a large degree of variation in composition, and thereby, materials properties. As well, the styrene hexafluoroalcohol-based polymers are not suitable for imaging with 193 nm radiation due to their opacity at this wavelength, as with other styrenic materials such as PHS. The cyclohexyldodecylfluoroalcohol acrylates also suffer from their high degree of synthetic complexity and high manufacturing expense.
Other photoresists based upon silsesquioxane polymers have also been developed. For example, in commonly assigned U.S. patent application Ser. No. 10/079,289, entitled "Substantially Transparent Aqueous Base Soluble Polymer System for Use in 157 nm Resist Applications," novel fluorocarbinol- and/or fluoroacid-functionalized silsesquioxane polymers suitable for use in lithographic photoresist compositions are described. Photoresists containing silsesquioxane polymers have also been previously described in U.S. Pat. No. 6,087,064 to Lin et al., U.S. Pat. No. 5,385,804 to Premlatha et al., U.S. Pat. No. 5,338,818 to Brunsvold et al., and U.S. Pat. No. 5,399,462 to Sachdev et al., which disclose the use of aryl or benzyl substituted polysilsesquioxanes in photoresists.
Despite the widespread use of polymeric photoresist materials, as the need for higher resolutions and minimum feature sizes increases, certain characteristics of polymeric resist materials may result in non-uniform pattern features. For example, the non-linear dissolution rates of some polymers, as well as the distribution of polymer chain lengths and chain entanglements, may lead to non-uniform feature dimensions and line edge roughness at very small feature sizes. In turn, such pattern variations may induce fluctuations in threshold voltages and line resistances, thereby degrading circuit performance.
In principle, the use of nonpolymeric materials as photoresists represents a potentially useful approach for avoiding the problems associated with polymeric materials. Since resists derived from single molecules would not contain mixtures of polymer chains of varying lengths, the dissolution characteristics and properties should be uniform. In addition, higher resolutions and decreased line edge roughness may be possible since single molecules have much smaller sizes than polymers and would not suffer from molecular chain entanglement.
Although few examples of nonpolymeric resist materials have been reported to date, the use of certain nonpolymeric materials has been disclosed. In U.S. Pat. No., 6,197,473 to Kihara et al., for example, the use of calixarenes, i.e., cyclic phenolic resins, is disclosed. Photoresists based on calixarenes have also been previously described in, e.g., Ochiai et al. (1997), "High Resolution EB Lithography on Organic resists: Molecular Size Effect," J. Photopolymer Sci. and Tech. 10(4):641–646; and Fujita et al. (1996), "Nanometer-Scale resolution of Calixarene Negative Resist in Electron Beam Lithography," J. Vac. Sci. Techol., B14(6):4272–4276.
In U.S. Pat. No. 6,632,582 to Kishimura et al., a siloxane compound is disclosed in which certain substituents may be attached to the silicon atoms, such as an alkyl compound, an ester compound, an ether compound, a sulfone compound, a sulfonyl compound and an aromatic compound. The use of such compounds as resist materials, however, appears to be compromised by the low glass transition temperatures (Tg) of the materials such that the post-exposure bake temperatures would exceed the Tg.
Although improvements in photoresist technology and materials have been made, an ongoing need exists for new photoresist materials and compositions that can provide desirable characteristics for high resolution photoresist applications.

Molecular photoresists containing nonpolymeric silsesquioxanes

International Business Machines Corporation


A light receiving optical system includes: a relay optical system for converging light to be measured which has been converged on an image plane of an objective optical system. The light receiving optical system has a relay optical system with a relay lens operable to be selectively switched between first and a second conjugate positions, and a first and a second light flux limiting aperture members selectively switched between the first and the second conjugate positions. The relay optical system selectively forms, on the image plane of the objective optical system, an enlarged image and a reduced image of a view angle defining aperture in the case where the relay lens is selectively switched between the first and the second conjugate positions to define an incident light flux through the view angle defining aperture by a first and a second light flux limiting apertures, respectively.

1. Field of the Invention
The present invention relates to a light receiving optical system to be incorporated in a spectral device such as a spectrophotometer, and more particularly to a light receiving optical system operable to switch a view angle, and a spectrophotometer incorporated with the light receiving optical system.
2. Description of the Related Art
FIG. 7 is a diagram showing an example of a conventional light receiving optical system to be incorporated in a spectral device such as a spectrophotometer. The light receiving optical system 900 shown in FIG. 7 has an aperture plate (hereinafter, called as a "view angle switching aperture plate") 902 for view angle switching control. The view angle switching aperture plate 902 is formed with an aperture 902a having a radius Ra for providing a view angle of 1°, and an aperture 902b having a radius Rb for providing a view angle of 0.1° with respect to an image plane of the objective lens 901. Immediately after a light flux 903a incident onto the objective lens 901 is converged i.e. condensed while passing through the aperature 902a or 902b, the light flux 903a is incident onto a conversion fiber 904 through an incident end 904a.
The view angle θ is given by: 2*a tan(Ra/F1) or 2*a tan(Rb/F1), where F1 is a distance between the objective lens 901 and the view angle switching aperture plate 902, Ra is a radius of the aperture 902a, Rb is a radius of the aperture 902b, and the symbol "*" indicates multiplication. The conversion fiber 904 has the incident end 904a of a circular shape in cross section at one end thereof, and a slit-shaped exit end 904b at the other end thereof, (see FIG. 4 to be described later). The exit end 904b serves as an incident slit of a polychromator 905. In this arrangement, a light flux incident through the circular incident end 904a is allowed to be efficiently incident onto a diffraction optical system (not shown) in the polychromator 905 with a predetermined slit width.
The view angle θ is switched by moving e.g. sliding the view angle switching aperture plate 902 to such a position that one of the apertures 902a and 902b is aligned in front of the incident end 904a. The incident site i.e. the incident position of incident light (i.e. the light flux 903a converged by the objective lens 901) onto the incident end 904a may be displaced due to a reproduction error with respect to the aperture position in the switching operation. This may displace the exit position of exit light 903c through the exit end 904b, thereby impairing measurement reproducibility.
On the other hand, an aperture 906a of an aperture stop 906 disposed near the objective lens 901 is adapted to regulate the incident light flux i.e. the incident light amount with respect to the aperture 902a or the aperture 902b of the view angle switching aperture plate 902 to define a possible incident angle of incident light. The possible incident angle is substantially maintained after propagation of the light flux through the conversion fiber 904, and is substantially equal to an exit angle i.e. a divergent angle ω of the exit light 903c. Preferably, the exit angle ω is substantially coincident with a possible incident angle with respect to a concave diffraction grating (not shown) in order to sufficiently utilize the performance of the concave diffraction grating in the diffraction optical system of the polychromator 905. The aperture diameter of the aperture stop 906 is defined to realize the above arrangement. The effective brightness of the whole optical system is substantially determined based on the effective area of the exit aperture i.e. the exit end 904b, in other words, based on the radius Ra of the aperture 902a, the radius Rb of the aperture 902b, and the exit angle ω. In the case where the aperture 902b for providing the view angle of 0.1° is aligned in front of the incident end 904a of the polychromator 905, the amount of light to be incident onto the polychromator 905 is merely one-hundredth of the amount of light to be incident onto the polychromator 905 in the case where the aperture 902a for providing the view angle of 1° is aligned in front of the incident end 904a of the polychromator 905, unconditionally i.e. irrespective of the performance of the objective lens 901.
In a light receiving optical system 920 disclosed in e.g. Japanese Unexamined Patent Publication No. 2001-264166 (D1), as shown in FIG. 8, a relay lens 923 is arranged between a view angle switching aperture plate 921 and an incident end 922a of a conversion fiber 922. The relay lens 923 is arranged at such a position that a focal point thereof is aligned with the center of an aperture 921a or an aperture 921b of the view angle switching aperture plate 921 to form an image 922c through the incident end 922a of the conversion fiber 922 immediately behind an objective lens 924. The image 922c serves as an aperture stop image for regulating a light flux to be incident onto a polychromator 925. Similarly to the arrangement example shown in FIG. 7, the conversion fiber 922 has a slit-shaped exit end 922b serving as an incident slit of the polychromator 925. Also, similarly to the arrangement example shown in FIG. 7, switching of the view angle .theta. is performed by moving the aperture plate 921 to such a position that one of the aperture 921a and the aperture 921b is aligned in front of the incident end 922a. In the example shown in FIG. 8, however, there is no likelihood that the incident site of a light flux 926a onto the incident end 922a may be displaced resulting from a position error of the aperture 921a or the aperture 921b to be used in the switching operation, because the light flux 926a passing through the aperture 921a or the aperture 921b is incident onto the entirety of the incident end 922a, irrespective of the aperture position of the aperture 921a and the aperture 921b.
However, since the angle distribution of incident light i.e. the light flux 926a with respect to the incident end 922a is changed resulting from the position error, transmission efficiency of the conversion fiber 922 is changed accordingly. Also, the angle distribution of exit light 926c is changed resulting from a change in angle distribution of the incident light. As a result, the diffraction efficiency i.e. the reflection efficiency of the concave diffraction grating is changed, which may impair measurement reproducibility. Assuming that the aperture 921a is operable to provide a view angle of 1.degree., and the aperture 921b is operable to provide a view angle of 0.1°, similarly to the arrangement example shown in FIG. 7, the amount of incident light to be incident onto the polychromator 925 in the case where the aperture 921b is aligned in front of the incident end 922b of the polychromator 925 is unconditionally one-hundredth of the amount of light to be incident onto the polychromator 925 in the case where the aperture 921a is aligned in front of the incident end 922b of the polychromator 925.

Light receiving optical system, and spectrophotometer incorporated with the same


Powder composed of particles of a rapidly solidified dispersion strengthened aluminum base alloy is compacted into billet form. The billet is vacuum autoclaved at a temperature ranging from 350.degree. C. to the alloy's incipient melting temperature and formed into a substantially fully dense wrought product. Gas content of the alloy is decreased and powder degassing steps are eliminated. The dispersion strengthened aluminum wrought product is produced in an economical and efficient manner.

1. Field of the Invention
The present invention relates to dispersion strengthened aluminum-base alloys, and more particularly to a method for reducing the gas content of an extruded, forged or rolled aluminum powder metallurgy product.
2. Description of the Prior Art
In recent years the aerospace industry has searched for high temperature aluminum alloys to replace titanium and existing aluminum alloys in applications requiring operating temperatures approaching 350.degree. C. While high strength at ambient and elevated temperatures is a primary requirement, certain design applications mandate that candidate alloys also exhibit, in combination, ductility, toughness, fatigue and corrosion resistance, as well as lower density than the materials currently being used.
One of the major restrictions to the widespread utilization of high temperature aluminum alloys is their inability to be welded or brazed. The application of standard welding and brazing practices to these high performance aluminum alloys results in the formation of excessive porosity in the weld and heat affected zone of the joint due to the outgassing of the alloy during the joining cycle and the coalescence of the gases to form porosity. The excessive gas porosity, is caused in part by the presence of hydrogen, as hydroxide or water, in the base metal. Also the slow cooling of the welded area may favor the formation of coarse, brittle intermetallics which will severely reduce the joint strength and ductility when compared to the base metal. Finally, any treatment given to these alloys to improve their weldability must be cost effective.
The hydrogen content may be reduced by heat treatment of the high temperature aluminum alloy in vacuum at high temperature. However, the heat treatment is limited by the reduction of the base metal strength as the heat treating time and temperature increases. Previous disclosures have shown that the weld porosity in powder metallurgy aluminum alloys (Al-10Fe-5Ce) can be virtually eliminated by a combination of preweld vacuum heat treatment, i.e. 750.degree. F. for 24 hrs. in vacuum, and direct current electrode negative welding, with only a minor decrease in base metal tensile strength, the welds exhibit a brittle behavior due to brittle phases formed near the weld interface. These welds are restricted to non-structural applications. (Gas Tungsten Arc Welding of Al-10Fe-5Ce, Guinn Metzger, report No. AFWAL-TR-87-4037, AFWAL/MLLS, Wright-Patterson AFB, Ohio 45433, February 1987).
To date, the majority of aluminum base alloys being considered for elevated temperature applications are produced by rapid solidification. Such processes typically produce homogeneous materials, and permit control of chemical composition by providing for incorporation of strengthening dispersoids into the alloy at sizes and volume fractions unattainable by conventional ingot metallurgy. Processes for producing chemical compositions of aluminum base alloys for elevated temperature applications have been described in U.S. Pat. No. 2,963,780 to Lyle et al., U.S. Pat. No. 2,967,351 to Roberts et al., U.S. Pat. No. 3,462,248 to Roberts et al., U.S. Pat. No. 4,379,719 to Hildeman et al., U.S. Pat. No. 4,347,076 to Ray et al., U.S. Pat. No. 4,647,321 to Adam et al. and U.S. Pat. No. 4,729,790 to Skinner et al. The alloys taught by Lyle et al., Roberts et al. and Hildeman et al. were produced by atomizing liquid metals into finely divided droplets by high velocity gas streams. The droplets were cooled by convective cooling at a rate of approximately 10.sup.4 .degree. C./sec. Alternatively, the alloys taught by Adam et al., Ray et al. and Skinner et al. were produced by ejecting and solidifying a liquid metal stream onto a rapidly moving substrate. The produced ribbon is cooled by conductive cooling at rates in the range of 10.sup.5 to 10.sup.7 .degree. C./sec. In general, the cooling rates achievable by both atomization and melt spinning greatly reduce the size of intermetallic dispersoids formed during the solidification. Furthermore, engineering alloys containing substantially higher quantities of transition elements are able to be produced by rapid solidification with mechanical properties superior to those previously produced by conventional solidification processes.
The need remains in the art for a process for reducing the gas contents of rapidly solidified, dispersion strengthened aluminum base alloys while retaining useful mechanical properties after welding or brazing.

Method for producing aluminum powder alloy products having lower gas contents


The present invention provides a through-hole structure for connecting a connector to a printed circuit board, the through-hole structure comprising a signal through-hole having a conductive layer therein for supplying a signal to the printed circuit board, power through-holes having a conductive layer therein for supplying power to the printed circuit board, and dielectric constant adjusting portions formed among the signal through-hole and the power through-holes. Moreover, the present invention provides a printed circuit board having the above-described through-hole structure formed therein.

The present invention relates to a printed circuit board, more specifically to a through-hole structure positioned in the printed circuit board for connecting a high-frequency connector to the printed circuit board.
In some cases, a connector is mounted directly onto a printed circuit board for various purposes such as signal input from an external device and as power supply to the printed circuit board. In such a case, as the frequency of the signal from the external device becomes higher, a problem of impedance mismatch may occur. Such impedance mismatch lowers integrity of the signal, or in some cases, makes it impossible for the signal to transmit. Accordingly, it is necessary that any impedance mismatch between a connection portion of the printed circuit board and the connector, particularly at high-frequency, be substantially eliminated.
Heretofore, impedance matching has been performed by providing through-hole conductors around a signal through hole, where the through-hole conductors are extending parallel to the signal through hole side walls. Since the through-hole conductors are arranged in the vicinity of a signal path and the distance between the through holes can be small, electrostatic capacitance in the signal path exists. Such existence of electrostatic capacitance in the signal path directly results in an increase of stray capacitance. When a high-frequency connector is connected to the connector portion of the printed circuit board to supply the signal thereto, through-hole conductors arranged around a signal through-hole become less effective at controlling impedance mismatching. Moreover, demand for high density packaging on the printed circuit board has increased more and more in recent years. Therefore, in many cases, a power supply circuit conductor is also provided in the vicinity of the through hole for transmitting a high-frequency signal therethrough. A through-hole structure and a printed circuit board, which are capable of adjusting the impedance in the connection portion of the board having a high-frequency connector connected thereto, have been required.
It is believed that a through-hole structure in a connection portion of a printed circuit board, which does not increase stray capacitance due to the increase of the electrostatic capacitance in the signal path, and is capable of readily and effectively adjusting the impedance in the connection portion of the printed circuit board when a high-frequency connector is utilized to transmit a high-frequency signal therethrough, would represent a significant advancement in the art.
Accordingly, it is the object of this invention to provide a new and unique through-hole structure.
Another object of this invention is to provide a through-hole structure as part of a connection portion of a printed circuit board.
The invention significantly reduces interference and noise in the connection portion of a printed circuit board when the connection portion is connected to a high frequency connector.
According to one aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a second through-hole positioned in the connector portion of the dielectric substrate relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the through-hole structure, and at least one dielectric constant adjusting portion positioned in the connector portion of the dielectric substrate relative to the first and second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to another aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a second through-hole positioned in the connector portion of the dielectric substrate relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the through-hole structure, and at least one dielectric constant adjusting portion positioned in the connector portion of the dielectric substrate between the first and second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to yet another aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a second through-hole positioned in the connector portion of the dielectric substrate relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the through-hole structure, and at least one dielectric constant adjusting through-hole positioned in the connector portion of the dielectric substrate relative to the first and second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to still yet another aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a second through-hole positioned in the connector portion of the dielectric substrate relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the through-hole structure, and at least one dielectric constant adjusting through-hole positioned in the connector portion of the dielectric substrate between the first and second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to another aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a plurality of second through-holes positioned in the connector portion of the dielectric substrate relative to the first through-hole, each of the plurality of second through-holes including the conductive layer therein for supplying electrical power to the through-hole structure, and a plurality of dielectric constant adjusting portions centrosymmetrically positioned around the first though hole in the connector portion of the dielectric substrate relative to the plurality of the second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to yet another aspect of the invention, there is provided a through-hole structure comprising a dielectric substrate having a connector portion therein, the connector portion having a dielectric constant, a first through-hole positioned in the connector portion of the dielectric substrate, the first through-hole including a conductive layer therein for supplying a signal to the through-hole structure, a plurality of second through-holes positioned in the connector portion of the dielectric substrate relative to the first through-hole, each the plurality of second through-holes including the conductive layer therein for supplying electrical power to the through-hole structure, and a plurality of dielectric constant adjusting portions asymmetrically positioned around the first though hole in the connector portion of the dielectric substrate relative to the plurality of the second through-holes to adjust the dielectric constant of the connector portion of the dielectric substrate.
According to still yet another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a second through-hole positioned in the through-hole structure relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the printed circuit board, and at least one dielectric constant adjusting portion positioned in the through-hole structure relative to the first and second through-holes to substantially prevent impedance mismatch between the printed circuit board and the connector.
According to another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a second through-hole positioned in the through-hole structure relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the printed circuit board, and at least one dielectric constant adjusting portion positioned in the through-hole structure between the first and second through-holes to substantially prevent impedance mismatch between the printed circuit board and connector.
According to yet another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a second through-hole positioned in the through-hole structure relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the printed circuit board, and at least one dielectric constant adjusting through-hole positioned in the through-hole structure relative to the first and second through-holes to substantially prevent impedance mismatch between the printed circuit board and the connector.
According to still yet another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a second through-hole positioned in the through-hole structure relative to the first through-hole, the second through-hole including the conductive layer therein for supplying electrical power to the printed circuit board, and at least one dielectric constant adjusting through-hole positioned in the through-hole structure between the first and second through-holes to substantially prevent impedance mismatch between the printed circuit board and the connector.
According to another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a plurality of second through-holes positioned in the through-hole structure relative to the first through-hole, each of the plurality of second through-holes including the conductive layer therein for supplying electrical power to the printed circuit board, and a plurality of dielectric constant adjusting portions centrosymmetrically positioned around the first through-hole in the through-hole structure relative to the plurality of second through-holes to substantially prevent impedance mismatch between the printed circuit board and the connector.
According to yet another aspect of the invention, there is provided a printed circuit board comprising a dielectric substrate having a connector portion therein, a through-hole structure in the connector portion for connecting a connector to the printed circuit board, a first through-hole positioned in the through-hole structure, the first through-hole including a conductive layer therein for supplying a signal to the printed circuit board, a plurality of second through-holes positioned in the through-hole structure relative to the first through-hole, each of the plurality of second through-holes including the conductive layer therein for supplying electrical power to the printed circuit board, and a plurality of dielectric constant adjusting portions asymmetrically positioned around the first through-hole in the through-hole structure relative to the plurality of second through-holes to substantially prevent impedance mismatch between the printed circuit board and the connector.

Through-hole structure and printed circuit board including the through-hole structure

International Business Machines Corporation


A method of compressing color source image data includes forming a quantization table with a "supra-threshold" term. This method includes a step of selecting a set of target images, where each target image includes one or more image elements such as text. These image elements are then analyzed to identify those that are more important for visual quality. These "supra-threshold" terms are then selected that gives a larger weight to the quantization table elements that correspond to important image elements and a smaller weight to the table elements that correspond to less important image elements. This process selectively weights the characteristics of each DCT basis vectors. By giving larger weights to the table elements that correspond to the "up-downness" of the image, i.e., the vertical attributes of the image elements, and the "left-rightness" of the image, i.e., the horizontal attributes of the image elements, and smaller weights to the table elements corresponding to the "criss-crossedness" of the image, i.e., the diagonal attributes of the image elements, the visual quality of an image that includes text can be preserved while significantly increasing the compression ratio.

This invention relates to data compression using the JPEG compression standard for continuous-tone still images, both grayscale and color.
A committee known as "JPEG" which stands for "Joint Photographic Experts Group," has established a standard for compressing continuous-tone still images, both grayscale and color. This standard represents a compromise between reproducible image quality and compression rate. To achieve acceptable compression rates, which refers to the ratio of the uncompressed image to the compressed image, the JPEG standard adopted a lossy compression technique. The lossy compression technique was required given the inordinate amount of data needed to represent a color image, on the order of 10 megabytes for a 200 dots per inch (DPI) 8.5".times.11" image. By carefully implementing the JPEG standard, however, the loss in the image can be confined to imperceptible areas of the image, which produces a perceptually lossless uncompressed image. The achievable compression rates using this technique are in the range of 10:1 to 50:1.
FIG. 1 shows a block diagram of a typical implementation of the JPEG compression standard. The block diagram will be referred to as a compression engine. The compression engine 10 operates on source image data, which represents a source image in a given color space such as CIELAB. The source image data has a certain resolution, which is determined by how the image was captured. Each individual datum of the source image data represents an image pixel. The pixel further has a resolution which is determined by the number of bits used to represent the image pixel.
The source image data is typically formatted as a raster stream of data. The compression technique, however, requires the data to be represented in blocks. These block represent a two-dimensional portion of the source image data. The JPEG standard uses 8.times.8 blocks of data. Therefore, a raster-to-block translation unit 12 translates the raster source image data into 8.times.8 blocks of source image data. The source image data is also shifted from unsigned integers to signed integers to put them into the proper format for the next stage in the compression process. These 8.times.8 blocks are then forwarded to a discrete cosine transformer 16 via bus 14.
The discrete cosine transformer 16 converts the source image data into transformed image data using the discrete cosine transform (DCT). The DCT, as is known in the art of image processing, decomposes the 8.times.8 block of source image data into 64 DCT elements or coefficients, each of which corresponds to a respective DCT basis vector. These basis vectors are unique 2-dimensional (2D) "spatial waveforms," which are the fundamental units in the DCT space. These basis vectors can be intuitively thought to represent unique images, wherein any source image can be decomposed into a weighted sum of these unique images. The discrete cosine transformer uses the forward discrete cosine (DCT) function as shown below, hence the name. ##EQU1## where: C(k), C(l)=1/.sqroot.2for k, l=0; and C(k), C(l)=1 otherwise
The output of the transformer 16 is an 8.times.8 block of DCT elements or coefficients, corresponding to the DCT basis vectors. This block of transformed image data is then forwarded to a quantizer 20 over a bus 18. The quantizer 20 quantizes the 64DCT elements using a 64-element quantization table 24, which must be specified as an input to the compression engine 10. Each element of the quantization table is an integer value from one to 255, which specifies the stepsize of the quantizer for the corresponding DCT coefficient. The purpose of quantization is to achieve the maximum amount of compression by representing DCT coefficients with no greater precision than is necessary to achieve the desired image quality. Quantization is a many-to-one mapping and, therefore, is fundamentally lossy. As mentioned above, quantization tables have been designed which limit the lossiness to imperceptible aspects of the image so that the reproduced image is not perceptually different from the source image.
The quantizer 20 performs a simple division operation between each DCT coefficient and the corresponding quantization table element. The lossiness occurs because the quantizer 20 disregards any fractional remainder. Thus, the quantization function can be represented as shown in Equation 2 below. ##EQU2## where Y(k,l) represents the (k,l)th DCT element and Q(k,l) represents the corresponding quantization table element.
To reconstruct the source image, this step is reversed, with the quantization table element being multiplied by the corresponding quantized DCT coefficient, but in so doing the fractional part is not restored. Thus, this information is lost forever. Because of the potential impact on the image quality of the quantization step, considerable effort has gone into designing the quantization tables. These efforts are described further below following a discussion of the final step in the JPEG compression technique.
The final step of the JPEG standard is an entropy encoding, which is performed by an entropy encoder 28. The entropy encoder 28 is coupled to the quantizer 20 via a bus 22 for receiving the quantized image data therefrom. The entropy encoder achieves additional lossless compression by encoding the quantized DCT coefficients more compactly based on their statistical characteristics. The JPEG standard specifies two entropy coding methods: Huffman coding and arithmetic coding. The compression engine of FIG. 1. assumes Huffman coding is used. Huffman encoding, as is known in the art, uses one or more sets of Huffman code tables 30. These tables may be predefined or computed specifically for a given image. Huffman encoding is a well known encoding technique that produces high levels of lossless compression. Accordingly, the operation of the entropy encoder 28 is not further described.
Referring now to FIG. 2, a typical JPEG compressed file is shown generally at 34. The compressed file includes a JPEG header 36, the quantization (Q) tables 38 and the Huffman (H) tables 40 used in the compression process, and the compressed image data 42 itself. From this compressed file 34 a perceptually indistinguishable version of the original source image can be extracted when an appropriate Q table is used. This extraction process is described below with reference to FIG. 3.
A JPEG decompression engine 43 is shown in FIG. 3. The decompression engine essentially operates in reverse of the compression engine 10. The decompression engine receives the compressed image data at a header extraction unit 44, which extracts the H tables, Q tables, and compressed image data according to the information contained in the header. The H tables are then stored in H tables 46 while the Q tables are stored in Q tables 48. The compressed image data is then sent to an entropy decoder 50 over a bus 52. The Entropy Decoder decodes the Huffman encoded compressed image data using the H tables 46. The output of the entropy decoder 50 are the quantized DCT elements.
The quantized DCT elements are then transmitted to an inverse quantizer 54 over a bus 56. The inverse quantizer multiplies the quantized DCT elements by the corresponding quantization table elements found in Q tables 48. As described above, this inverse quantization step does not yield the original source image data because the quantization step truncated or discarded the fractional remainder before transmission of the compressed image data.
The inverse quantized DCT elements are then passed to an inverse discrete cosine transformer (IDCT) 57 via bus 59, which transforms the data back into the time domain using the inverse discrete cosine transform. The inverse transformed data is then transferred to block-to-raster translator 58 over a bus 60 where the blocks of DCT elements are translated into a raster string of decompressed source image data.
From the decompressed source image data, a facsimile of the original source image can be reconstructed The reconstructed source image, however, is not an exact replication of the original source image.
As described above, the quantization step produces some lossiness in the process of compressing the data. By carefully designing the quantization tables, however, the prior art methods have constrained the loss to visually imperceptible portions of the image. These methods, and their shortcomings, are described below.
The JPEG standard includes two examples of quantization tables, one for luminance channels and one for chrominance channels. See International Organization for standardization: "Information technology--digital compression encoding of continuous--tones still images--part 1: Requirements and Guidelines, " ISO/IEC IS10918-1, Oct. 20, 1992. These tables are known as the K.1 and K2 tables, respectively. These tables have been designed based on the perceptually lossless compression of color images represented in the YUV color space.
These tables result in visually pleasing images, but yield a rather low compression ratio for certain applications. The compression ratio can be varied by setting a so-called Q-factor or scaling factor, which is essentially a uniform multiplicative parameter that is applied to each of the elements in the quantization tables. The larger the Q-factor the larger the achievable compression rate. Even if the original tables are carefully designed to be perceptually lossless, however, a large Q-factor will introduce artifacts in the reconstructed image, such as blockiness in areas of constant color or ringing in text -scale characters. Some of these artifacts can be effectively cancelled by post-processing of the reconstructed image by passing it through a tone reproduction curve correction stage, or by segmenting the image and processing the text separately. However, such methods easily introduce new artifacts. Therefore, these methods are not ideal.
As a result of the inadequacy of the Q-factor approach, additional design methods for JPEG discrete quantization tables have been proposed. These methods can be categorized as either perceptual, which means based on the human visual system (HVS) or based on information theory criteria. These methods are also designated as being based on the removal of subjective or statistical redundancy, respectively.
These methods form the Q table from two separate terms: a threshold term, chosen depending on the particular method selected, and a bit-rate term, chosen based on the desired compression ratio. This is shown graphically in FIG. 4.
The flowchart in FIG. 4 shows a basic three-step process of forming a Q-table according to prior art methods. First, a so-called threshold term is selected in step 64. The term is referred to as "threshold" because it relates to the HVS thresholds, below which the quantization is perceptually lossless. Second, a bit-rate term is selected in step 66. This is essentially the Q-factor described above. The bit-rate term can be thought of as a normalization factor that allows the control of the bitrate of the compressed image. This factor is important for applications having a limited channel bandwidth (e.g., FAX) or with limited storage space (e.g., digital cameras). Finally, the Q-table is formed in step 68 using both of these terms. Typically, this step just involves dividing a threshold term by a corresponding bit-rate term. Each of these steps is described further below.
Referring now to FIG. 5, a flowchart showing the two methods, statistical and subjective, for determining the threshold term is shown. Both methods begin by selecting a set of typical images in step 70. This set is chosen to represent the desired image characteristics so that the Q-table is optimized for these images. Next, the particular method is chosen. If a statistical or information theoretical method is chosen, steps 74 and 76 are executed, while if a perceptual or subjective method is desired, steps 78 and 80 are instead executed.
In the statistical or information theoretical method, the threshold term is chosen based on the energy within an 8.times.8 block of DCT transformed image data. The energy is typically represented by the variance of the DCT elements across the entire image. The quantization levels are then allocated in abundance to the DCT basis vectors having larger variances. Conversely, those quantization levels having a smaller variance have fewer quantization levels. The problem with these methods is that they do not take into account the HVS and, as a result, the generated solutions may produce reconstructed images of poor visual quality. Some have tried to attenuate this result by combining the statistical method with multi-level error diffusion. In this refined method, the error made in the quantization is diffused to an adjacent DCT element. These refined methods, however, are more computationally intensive and do not fully restore the visual quality of the image.
In the subjective or perceptual methods, an error or difference between the compressed and uncompressed image is adjusted to the threshold of detectability of the human visual system (HVS). This is accomplished in the two steps 78 and 80 shown in FIG. 5. In the first step 78, a difference is computed between the original and compressed images. This difference is used in step 80 to allocate the bandwidth so that the difference image is below the detection threshold. The detection threshold is established using psychophysical experiments. The process of establishing the threshold using the psychophysical experiments further comprises two steps. In the first step, the perceptual color space is used to develop a detection model for a specific class of features by performing the psychophysical experiments. In the second step, this model is applied to predict the visibility thresholds for the quantization errors. The threshold terms are then chosen so that the errors are just below the threshold level.
This subjective or perceptual method, as well as others such as the "contrast masking" method proposed by Robert J. Safranek, "JPEG compliant encoder utilizing perceptually based quantization," Human Vision, Visual Processing, and Digital Display V1913, 117-126, SPIE, 1993, address the task of perceptually lossless compression. For many applications, e.g., color facsimile, the generated solutions are too conservative in that the achievable compression rate is too low. For color facsimile applications, this low compression ratio produces unacceptable transmission times. Furthermore, the images used in the psychophysical experiments to characterize the HVS are sine wave gratings. While these sine wave gratings adequately represent pictorial images, used indiscriminately such targets do not predict well the perception of text. Consequently, these perceptual methods do not effectively control artifacts in text such as ringing around characters.
Hybrid forms of these statistical and subjective methods described above have been proposed which try to take the best of both methods. Although a frequency component might have a high variance, it might not be very significant for contributing information to the HVS. Therefore, for a given image, the image quality can be improved by reallocating the transmission bandwith to perceptually important information while attenuating information not perceptible. Alternatively, for a given perceptual quality, the number of bits required to encode a pixel can be reduced.
An example of such a hybrid method can be found in David L. McLaren and D. Thong Nguyen, "Removal of Subjective Redundancy from DCT-coded Images," IEE Proceedings-I, 138, 5, 345-350, 1991. The McLaren and Nguyen method, instead of using a uniform Q-factor, separates the coefficient thresholding from the quantization stages. By considering the coefficient energy distribution and the contrast sensitivity curve of the HVS, the method harshly thresholds the DCT coefficients, obtaining substantially better bit rates without perceptually degrading the images. This method, however, was designed using video images. One characteristic of video images is the substantial cross-talk in the transducers, which "smoothens" the images. For instance, text in video images is typically large so that this problem can be reduced. In color facsimile communication, there is much less cross talk because hard edges are desirable. Moreover, color scanners typically have problems of sensor misalignment and images are often half-toned, which introduces interference patterns. These artifacts, typical for color facsimile, can adversely bias the statistical analysis of coefficient energy as taught in McLaren and Nguyen.
In another hybrid method proposed by K. R. Rao and his co-workers, (see, e.g., Bowonkoon Chitprasert and K. R. Rao, "Human Visual Weighted Progressive Image Transmission," IEEE Transactions on Communications, COM-38,7,1040-1044, 1990) a perceptual model is used for classification of the data to establish a transmission hierarchy. In a first step, a Q table is generated based on estimates of energy in each 8.times.8 block. In a second step, a modulation transfer function (MTF) is empirically determined for the HVS and the MTF is multiplied by the DCT coefficients at the corresponding frequencies. For progressive transmission, the resulting weighted coefficient sub-blocks are sorted according to their AC energy into classes. As in the McLaren and Nguyen method, however, the work of Rao, et al., focuses on pictorial images at low resolution for either television or low resolution computer video displays. Color facsimile communication takes place at higher resolutions and most of the time contains text. Accordingly, these methods are not particularly well suited for color facsimile data.
A third hybrid method has been proposed by Siegel that has some resemblance to Safranek's method. See U.S. Pat. No. 5,063,608 entitled, "Adaptive Zonal Coder," issued to Shepard L. Siegal. In Siegel's method, just before the entropy encoder, each block is scanned and a running block activity measure, such as the running sum of squares or absolute values, is computed. If there are sufficient low frequency terms, according to Siegel the higher frequency terms are of less importance and, due to the nature of human visual response, may be omitted without perceived image degradation. This method, however, is computationally intensive and thus may make a hardware implementation impractical. Moreover, Siegel's method may not be well suited for typical color facsimile data which typically includes a combination of text and graphics.
Accordingly, a need remains for a method for selecting JPEG quantization tables which is particularly adapted to color facsimile applications.

Method for selecting JPEG quantization tables for low bandwidth applications


An X-ray examination apparatus includes an X-ray source (1) for irradiating an object (2) by means of an X-ray beam (3) in order to form an X-ray image. An optical image is derived from the X-ray image by means of an X-ray detector (4). The optical image is picked up by means of an image pick-up apparatus (5). The image pick-up apparatus (5) includes a plurality of image sensors (6, 7) for deriving separate electronic sub-image signals from the optical image. The image pick-up apparatus also includes a subtraction unit (8) for subtracting the electronic sub-image signals from one another. The image pick-up apparatus (5) also includes a control circuit (9) which is arranged to make integration periods of individual image sensors (7, 8) commence at instants which are spaced a waiting period apart. The difference signal represents changes in the X-ray image or, when the X-ray energy is changed during the waiting period, differences in X-ray absorption due to energy-dependency.

1. Field of the Invention
The invention relates to an X-ray examination apparatus, including an X-ray detector for deriving an optical image from an X-ray image, an image pick-up apparatus for picking up the optical image, which image pick-up apparatus includes a plurality of image sensors for deriving separate electronic sub-image signals from the optical image, and a subtraction unit for deriving a difference signal from the electronic sub-image signals.
2. Description of the Related Art
An X-ray examination apparatus of this kind is known from German Patent DE 11 23 410.
The known X-ray examination apparatus includes two television cameras which simultaneously pick up the optical image. One of the television cameras is set out-of-focus so that it picks up only coarse structures in the optical image. The other television camera is accurately focused so that it accurately picks up coarse structures as well as fine details in the optical image. Each of the television cameras delivers a video signal, one video signal representing the coarse structures and the small details whereas the other video signal represents the coarse structures only. The video signals are subtracted from one another and the resultant difference signal is applied to a monitor. The difference signal thus represents mainly the small details and these details are displayed with high contrast on the monitor. Therefore, the known X-ray examination apparatus is suitable for high-contrast reproduction of image information relating to smalls in the X-ray image. Because the video signals relate to different components of simultaneous image information, the known X-ray examination apparatus is not suitable for forming a difference image representing changes in the optical image. Changes occur, for example when a contrast medium is injected into a patient to be examined.

X-ray examination apparatus including a subtraction unit


A method for operating a multi-cylinder internal combustion engine includes varying the opening or closing of engine valves including intake or exhaust valves, in fluid communication with each of the cylinders of the engine. The method further includes generating a signal indicative of engine valve status in response to monitoring an acceleration parameter of the engine. An engine includes a computer configured to determine a performance status of intake or exhaust valves of the engine responsive to monitoring an engine acceleration parameter such as crankshaft acceleration. The computer is configured via fault detection and cylinder trimming routines to adjust valve performance based on a nominal crankshaft acceleration for the engine.

Variably timed intake and exhaust valves are used in a variety of engines, notably compression ignition internal combustion engines. Conventional engine systems utilize a rotating cam configured to control opening and/or closing of engine valves at desired times during an engine cycle. Variable valves provide some flexibility in opening or closing timing in such engine systems via actuators configured to control valve position separately from cam rotation. By varying the opening or closing timing of engine valves, operating strategies are enabled which can provide enhanced control over cylinder conditions during an engine cycle, enabling operating strategies to reduce emissions or facilitate engine braking, for example. As is well known in the art, however, these systems do not always consistently perform precisely as desired, and the performance characteristics of variable valves can vary under certain conditions.
One known application for variable valves relates to selectively holding open intake valves. In a typical engine cycle, a rotating cam opens an intake valve during an intake stroke in a particular cylinder, then permits the valve to return to a closed position approximately when the corresponding piston reaches a bottom dead center position and begins a compression phase. Variable intake valve actuation may be used to keep a particular intake valve in an open position past the point at which cam rotation would ordinarily allow the intake valve to close.
It is common for variable valves to be hydraulically actuated, via an intake valve actuator separate from the engine cam. In such a design, as an intake valve moves toward an open position under the influence of a rotating cam, hydraulic fluid is permitted to flow into a control cavity. A separate control valve may be then used to block fluid draining from the cavity, such that the intake valve actuator is hydraulically locked and inhibits closing of the intake valve. The intake valve may be held in an open position until such time as the control valve is adjusted to permit draining of fluid and consequent returning of the intake valve to a closed position. As alluded to above, however, certain performance characteristics such as the specific timing of variably actuated valve closing can depart from an optimal timing. Variations in timing can degrade overall engine performance, and emissions quality, and can render certain operating schemes unachievable.
One method of diagnosing problems in a variable valve engine relies upon the use of a pressure sensor coupled with a common rail that supplies actuation fluid to the intake valve actuator. Operation of variable valve actuators in an engine has been shown to be associated with certain changes in pressure in a common rail. Thus, an electronic controller may be coupled with the pressure sensor and configured to log changes in common rail pressure which correspond with expected changes from variable valve actuator operation. While such systems have performed relatively well over the years, they add expense and complexity to an engine system, and can suffer from reliability and warranty issues.
Another approach to monitoring certain aspects of engine performance and operation is known from United States Patent Application Publication No. 2005/0257604 to Zavarehi et. al. ("Zavarehi"). Zavarehi is directed to a method and system for determining engine cylinder power level deviations via an analysis of crankshaft speed fluctuations. To detect these power level deviations, the engine is operated at a steady state low idle condition, and engine speed data collected over a plurality of engine cycles. An averaged, filtered data set is compared to expected engine speed data. Substantial deviations from the expected speed data may indicate power level deviation in a particular cylinder. While Zavarehi provides an approach suitable for evaluating certain aspects of engine operation, other strategies concerned with variable valve performance are desirable.
The present disclosure is directed to one or more of the problems or shortcomings set forth above.

Variable valve performance detection strategy for internal combustion engine


The instant device serves to pierce and irrigate fluid filled tubing. It consists of an upper jaw and a lower jaw mounted on locking pliers. The upper jaw consists of an upper jaw mounting plate fastened to the upper jaw of the locking pliers and a piercing pin unit, along with a replaceable hollow press fit piercing pin held within such unit which piercing pin unit is held in the upper jaw mounting plate after the unit's insertion through a metallic washer locking cushion. The device's lower jaw consists of a lower jaw tube cradle component mounting plate fastened to the lower jaw of the locking pliers and further consists of a tube cradle component with eight cylindrically shaped notches for receipt of any one of six different sizes of cylindrically shaped tubing. The tube cradle component is held to the lower jaw tube cradle component mounting plate by way of a threaded retaining shoulder bolt. The tube cradle component is amenable to being so held from either of its ends and it can be rotated through 360 degrees and further held fast in any one of eight positions so that one of the eight cylindrically shaped receiving notches is aligned with the tip of the replaceable hollow press fit piercing pin by way of a springloaded detent screw that is insertable into a tapped hole in the lower jaw tube cradle component mounting plate and that further fits into any one of eight detent screw holes, four in the front face of the tube cradle component and four in its posterior face. A piece of tubing held in the receiving notch of desired diameter positioned in alignment with the tip of the press fit piercing pin, by way of appropriate rotation of the tube cradle component and then a fastening of the appropriate face of the tube cradle adjacent the front face of the lower jaw tube cradle component mounting plate, is pierced by the piercing pin protruding through a replaceable rubber sealing gasket affixed into a counterbore in the base of the upper jaw mounting plate.

1. Field of the Invention
The instant invention relates in some respect to those various tools and devices as serve to crimp, perforate, pierce and/or irrigate pipes, canisters, tubing and the like.
2. Possible Prior Art
Some art that may perhaps relate in some way to the instant invention would perhaps be the those items to be found in i.e., classes/subclasses: 30/363, 62/77; 529; 531, 72/409, 81/418-426.5, 222/83.5, 89, to wit:
______________________________________ Inventor Invention Patent No. Date ______________________________________ 1. Diggs Irrigation Apparatus 4,017,958 4/19/77 2. E. Granberg Combined Rivet 3,156,087 11/10/64 Punch and Spinner 3. T. W. Brooks Dispensing Device 3,147,887 9/8/64 4. M. Kamla Perforating Device 3,296,696 1/10/67 for Deflating Cans 5. S. A. Motches Replaceable Die 2,838,970 6/17/58 Et Al Nest Crimping Tool 6. Rodgers Tool for Attaching 4,697,483 10/6/87 and Detaching Spring Clip from Shaft 7. J. A. Cashion Pivoted Tool 3,336,825 8/22/67 Having a Wedge- Shaped Jaw Portion for Engaging a Tie Rod Sleeve 8. Lowther Mechanic's Tubing 4,982,631 1/8/91 Plug 9. Villazon Hand Tool 4,041,740 8/16/77 10. Robertson et al. Refrigerant 4,852,769 8/1/89 Charging Tool ______________________________________

Tube piercing and fluid irrigation device


Metal gate stacks and integrated methods of forming metal gate stacks are disclosed. Some embodiments comprise NbN as a PMOS work function material at a thickness in a range of greater than or equal to 5 Å to less than or equal to 50 Å. The PMOS work function material comprising NbN has an effective work function of greater than or equal to 4.75 eV. Some embodiments comprise HfO2 as a high-κ metal oxide layer. Some embodiments provide improved PMOS bandedge performance evidenced by improved flatband voltage. Some embodiments exclude transition metal niobium nitride materials as work function materials.

Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors, and resistors on a single chip. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
As device dimensions have shrunk, device geometries and materials have experienced difficulty maintaining switching speeds without incurring failures. Several new technologies have emerged that allow chip designers to continue shrinking device dimensions. Control of the dimensions of device structure is a key challenge for present and future technology generations.
Microelectronic devices are fabricated on a semiconductor substrate as integrated circuits in which various conductive layers are interconnected with one another to permit electronic signals to propagate within the device. An example of such a device is a complementary metal-oxide-semiconductor (CMOS) field effect transistor (FET) or MOSFET. A gate electrode is part of an integrated circuit. For example, a MOSFET comprises a gate structure disposed between source and drain regions that are formed in the semiconductor substrate. The gate structure or stack generally comprises a gate electrode and a gate dielectric. The gate electrode is disposed over the gate dielectric to control a flow of charge carriers in a channel region that is formed between drain and source regions beneath the gate dielectric.
Current PMOS high-κ metal gate stacks include TiN as high-κ capping layer followed by TiN as a PMOS work function material. Some new PMOS work function materials advantageously show more PMOS bandedge Vfb performance, yet also demonstrate an equivalent oxide thickness (EOT) penalty.
Accordingly, there is a need for materials with more bandedge flatband voltage (Vfb) performance than TiN. Further, there is a need for these devices to have a minimal EOT penalty.


A thermoelectric generator apparatus of a vehicle may include a high temperature member, through which exhaust gas passes, a low temperature member, which maintains a temperature lower than a temperature of the high temperature member, and which includes a first coolant pipe holder supporting one of coolant pipes, a heat transfer plate which extends from the first pipe holder and may be located opposite to a corresponding high-temperature member, and a second coolant pipe holder formed on the other side of the heat transfer plate and supporting another of the coolant pipes, and a thermoelectric module disposed between the high temperature member and the low temperature member.

1. Field of the Invention
The present invention relates to a thermoelectric generator of vehicle, and more particularly, to a thermoelectric generator of vehicle, which uses the heat of the exhaust gas of an automobile to generate electricity.
2. Description of Related Art
A thermoelectric element is an element, which uses a thermoelectric phenomenon, in which thermal energy is converted to electric energy by converting the temperature difference between the two ends of an element into electricity, or in which electric energy is converted to thermal energy by having electricity run through an element and by causing the temperature difference in the two ends. Such thermoelectric element is used in a small scale cooling, heating or generating device.
When a thermoelectric element is used in a small scale generating device, it is called a thermoelectric generation device or a thermoelectric generator. This device is mainly used in a power supply unit of a wireless communication device, of a spaceship and of a nuclear-powered submarine as well as in a thermoelectric generator installed in an exhaust system of a vehicle.
FIG. 1 is a cross-sectional view illustrating a thermoelectric generator of a vehicle.
As illustrated, a thermoelectric generator installed in an exhaust system of a vehicle 10 comprises; a hexagonal exhaust heat recovering device 40, which high-temperature exhaust gas passes through; a cooling device 30, which is installed outside of the exhaust heat recovering device 40 and inside of which coolant passes through; and the multitude of thermoelectric modules 20, which are in contact with the exterior of the exhaust heat recovering device 40 and with the interior of the cooling device 30 to generate electricity using the temperature difference between the two ends.
Inside the exhaust heat recovering device 40, high-temperature exhaust gas runs and it conveys thermal energy to the thermoelectric modules 20. Inside the cooling device 30 is formed a cooling pipe, which increases the temperature difference between the interior of the thermoelectric modules 20 in contact with the exhaust heat recovering device 40 and the exterior of the thermoelectric modules 20 in contact with the cooling device 30. As the temperature difference between the interior and the exterior of the thermoelectric module increases 20, the efficiency of the thermoelectric generator installed in the exhaust system of a vehicle increases.
In order to generate lots of electricity in a thermoelectric generator, i.e. to increase the thermoelectric generation efficiency, thermal energy of the exhaust gas must be conveyed to the thermoelectric modules efficiently. However, in the traditional thermoelectric generator of a vehicle, thermal energy of the exhaust gas is not conveyed to the high temperature member sufficiently, so the recovery rate of the thermal energy of the exhaust gas drops and hence, the thermoelectric efficiency of a thermoelectric generator drops.
Also, in the traditional thermoelectric generator of a vehicle, although a cooling device 30 occupies a great area, the heat-exchange area is small, and therefore, the heat conveyance rate is low compared to the size, and the efficiency of thermoelectric generation is low.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.


The current invention relates to the use of tetrabenzylthiuram disulfide/urea curative package for thermosetting rubber elastomers in an environmentally sound method of eliminating undesirable nitrosamines. The unique curative package synergistically increases the cure rate and physical properties of the elastomeric compound while reducing the amount of accelerator needed for vulcanization.

The current invention relates to the use of tetrabenzylthiuram disulfide/urea curative package for curing elastomers in an environmentally safe method of eliminating undesirable nitrosamines. The unique curative package synergistically increases the cure rate of the tetrabenzylthiuram disulfide accelerator while reducing the amount of accelerator needed for vulcanization.
Vulcanization may be defined as a reaction in the presence of heat where a chemical additive reacts with an elastomer to change it from a plastic, tacky solid to a thermoset, fixed solid with improved strength and elasticity, and increased hardness. The vulcanization reaction is one in which the polymeric rubber molecules are cross-linked by the vulcanizing agent to form a network of macromolecules having less mobility and which have the desired physical properties of a usable rubber product. The type of crosslinking (or vulcanizing) agent will vary with the type of rubber used and the properties desired.
The most commonly used vulcanizing agent is sulfur, as it enters into reactions with the majority of the unsaturated rubbers to produce vulcanizates. Sulfur, in the presence of heat, reacts with adjoining olefinic bonds in the polymeric backbone chains or in pendant chains of two elastomeric molecules to form cross-links between the molecular chains.
Vulcanization, as originally known, required long hours and elevated temperatures. Progress was made in speeding the process and improving the properties of the vulcanized product by using accelerators. Reduction in the time required for vulcanization is generally accomplished by changes in the amounts and types of accelerators used.
An accelerator can be defined as a material which, when added to rubber, will materially reduce the time and temperature necessary to effect vulcanization of rubber with sulfur. Organic accelerators are divided into certain chemical groups, and can be classified as either primary or secondary accelerators based on the compound' activity in elastomeric compounds.
Thiazoles and sulfenamides are known to yield a classical curemeter vulcanization curve with adequate scorch time and are known as primary accelerators. Thiurams, dithiocarbamates, aldehyde amines and guanidines are classified as secondary accelerators. It is usual practice for primary and secondary accelerators to be used in combination.
Activators are compounds which render accelerators more potent. Examples of commonly used activators include zinc oxide used with stearic acid and zinc salts of lauric and related fatty acids used with thiazoles, thiurams, and dithiocarbamates. Other examples of activators include the action of guanidines or aldehydeamines with the thiazoles and the action of aromatic amines with xanthogen disulfides.
The compounds which are the subject of this invention include an improvement to the class of accelerators known as thiuram disulfides. Thiuram disulfides constitute a major class of accelerator which are intermediate in activity between the dithiocarbamates and thiazoles. They are less heat sensitive than the former and are readily processable under standard manufacturing conditions.
Thiuram disulfide accelerators are fast, strong, non-discoloring, and give vulcanized stocks having high tensile strengths, low set and high resilience. They function well in the presence of carbon blacks, acidic fillers, or softeners.
Two of the thiuram disulfides in common use are tetramethylthiuram disulfide(TMTDS) and tetraethylthiuram disulfide(TETDS). These accelerators may be used either as primary or secondary accelerators and are especially useful as secondary accelerators with thiazoles as primary accelerators. Recent concerns over certain nitrosamines has created an incentive to minimize their presence in the workplace. Nitrosamines are formed during vulcanization when the amines generated directly or indirectly from these accelerators combine with nitrogen oxides present in the atmosphere. It is postulated, given the basic structure of the thiuram disulfide accelerators, that decomposition and subsequent reaction with nitrogen oxides present in air (NOx) form nitrosamines of the general formula O.dbd.N--NR2, where R is the tetra substituted moiety on the thiuram disulfide.
The challenge is to retain the advantages of the thiuram disulfide accelerators while eliminating the generation of certain undesirable N-nitrosamines. The accelerator of this invention, known as tetrabenzyl thiuram disulfide, meets that challenge only when combined with urea and sulfur in a unique curative package. Toxicologic studies of this experimental accelerator have shown that dibenzyl nitrosamine (DBNA) that may be formed during a vulcanization side reaction as indicated above is non-carcinogenic, is present in very small amounts, and that an increase in its concentration following vulcanization is not observed. This accelerator, tetrabenzylthiuram disulfide (TBTDS) which can be made by, for example, the process given in U.S. Pat. No. 4,459,424, example 37, and by a general process for the preparation of thiuram disulfides contained therein and in U.S. Pat. No. 4,468,526 has been found to have some processing drawbacks and is not a direct replacement for the commonly used tetraalkyl thiuram disulfides described above. When tetramethyl thiuram disulfide is replaced on a part-to-part basis by TBTDS in rubber compounds, some of the physical properties of the cured elastomers are not as satisfactory as those obtained with tetramethyl thiuram disulfide.
An object of this invention is to reduce the time for curing tetrabenzylthiuram disulfide while imparting excellent physical properties to the cured elastomer. A still further object of this invention is to provide a process for curing elastomers which will not generate any potentially dangerous nitrosamines into the workplace.

Tetrabenzylthiuram disulfide/urea cured elastomeric composition


The invention provides a muffler for an internal combustion engine having excellent durability (resistance to scattering) even when being exposed to a high-temperature exhaust gas and capable of maintaining a high sound absorption coefficient over a long period. Such a muffler comprises a metal tube provided with a plurality of small holes, an inorganic fiber sound-absorbing material arranged on the outer periphery thereof and a metal shell covering the outside of the sound-absorbing material, in which a scattering prevention member is disposed between the metal tube and the sound-absorbing material. The sound-absorbing material is a laminated structure of crystalline alumna fiber mat and glass fiber mat. As the scattering prevention member, there is used a stainless woven wire cloth, a woven fabric made from inorganic fiber and a metal roll.

A sound-damping treatment for noise component included in an exhaust gas is carried out by disposing a muffler in a halfway of an exhaust tube.
As the muffler, there are known various structures, among which an adequate structure is used in accordance with conditions such as a displacement of an engine and the like. As the muffler for damping noise component of high frequency among various noise components included in the exhaust gas, there is well-known a structure that an inorganic fiber sound absorbing material is disposed around a metal tube (inner tube) provided with a plurality of small holes and then covered with a metal shell.
In such a muffler, glass fibers having a low heat resistance and the like are usually used as the inorganic fiber sound absorbing material. Recently, the rise of exhaust gas temperature becomes conspicuous with the advancement of engine performances, and hence the glass fibers are fused and shrunk by heat of the exhaust gas to form beads. On the other hand, pressure shock accompanied with the passage of the high-temperature exhaust gas concentrates in the small holes of the metal tube and hence the metal tube vibrates or the passing exhaust gas pulsates. Thus, the bead-shaped glass fiber is put through the small holes into the inside of the metal tube and scattered to the outside together with the exhaust gas. Therefore, this muffler has a problem that the sound damping effect is considerably degraded.
In order to solve the above problem, a muffler 1 as shown in FIG. 1 has been proposed in JP-U-61-59819 and JP-Y-6-19785. In the muffler 1, a metal cushioning material 6 such as stainless wool is interposed between a metal tube 3 provided with a plurality of small holes 2 and a sound absorbing material 5 covered with a metal shell 4 and made from glass fibers.
Since the muffler 1 is to damp noise components, however, the metal cushioning material 6 is rendered into an interconnecting cell structure and does not thermally protect the glass fiber sound absorbing material 5. Further, the metal cushioning material is softened by heat of the exhaust gas, so that the effect as a cushioning material is very low. As a result, the conventional muffler 1 has a drawback that it is difficult to damp noise components over a long period.
And also, there is disclosed a method of improving the heat resistance by using silica-alumina ceramic fiber or general-purpose crystalline alumina fiber as the inorganic fiber sound absorbing material. However, the silica-alumina ceramic fiber contains about 50 wt % of granulated substance called as shot, so that there is caused a problem that the shot is moved inside the sound absorbing material by vibration to form spaces in the sound absorbing material. On the other hand, the general-purpose crystalline alumina fiber is a refractory heat-insulating material usually used as a thermal insulant for a high-temperature ceramic furnace of about 1400.degree. C. and has an average fiber size of 2.7-3.2 .mu.m, which is finer than an average fiber size of the conventional glass fiber of about 9 .mu.m, and a high true specific gravity. For this end, the pressure drop becomes higher and particularly there is caused a problem that sound absorption coefficient at a high frequency side is considerably low.
On the contrary, there is a method of increasing a filling density of the general-purpose crystalline alumina fiber. However, as the filling density increases, mass as a sound absorbing layer becomes higher and noise hardly enters into the sound absorbing layer and hence there is caused a problem that the sound absorption coefficient as a whole lowers.
In general, the muffler has a structure that both ends of the metal shell having a diameter larger than that of the metal tube are size-reduced to approximately an outer diameter of the metal tube and fixed to an outer periphery of the metal tube at each opening portion of the metal shell through welding and the sound absorbing material is filled in a space defined between the metal tube and the metal shell. In such a structure, the metal tube is compressed to cause buckling due to the difference in thermal expansion between the metal tube exposed to the high-temperature exhaust gas and the metal shell exposed to air, or the weld portion between the metal tube and the metal shell is peeled off to cause the leakage of the exhaust gas and hence there is a problem that sound radiating the exhaust gas becomes large.
In order to solve the above problems, there is known a structure that the welding between the metal tube and the metal shell is carried out at either an opening portion at both ends of the metal shell, while a mesh-shaped stainless gasket is previously attached to the other opening portion of the metal shell and interposed between the metal tube and the metal shell, whereby the influence of the thermal expansion difference between the metal tube and the metal shell is eliminated to prevent the leakage of the exhaust gas to thereby control volume of radiating sound. However, the gasket should be previously fixed to the metal shell by spot welding or the like, so that the number of assembling steps increases and also the cost increases.