To devise a heating device of the light irradiation type in which costs can reduced by reducing the number of filament lamps and current source parts without adversely affecting the illuminance distribution with respect to a wafer, in a heating device of the light irradiation type that has a light source part, in which several filament lamps are located parallel to one another, in which at least one of the filament lamps has several filaments which are located along the bulb axis are supplied with power individually to produce light which is irradiated from the light source parts onto an article to be treated, the distance between at least some of the adjacent filament lamps to one another is nonuniform.

1. Field of the Invention
The invention relates to a heating device of the light irradiation type in which a plate-shaped article to be treated, especially a semiconductor wafer, is subjected to rapid heating, holding at a high temperature, and rapid cooling for layer formation, diffusion, annealing or for similar purposes.
2. Description of Related Art
Heat treatment of the light irradiation type in the production of semiconductors, such as layer formation, diffusion, annealing or the like, in carried out in diverse ways. In each of these treatments, a semiconductor wafer (hereinafter also called only a wafer) which is a plate-shaped article to be treated or the like, is heated to a high temperature. If heat treatment of the light irradiation type is used for this heat treatment, the wafer can be quickly heated and its temperature raised in a few seconds to a few dozen seconds to at least 1000° C. When light irradiation is stopped, it can be quickly cooled. However, when a nonuniformity of the temperature distribution occurs in the semiconductor wafer, especially at a temperature of at least 1050° C., a phenomenon called slip occurs in the wafer, i.e., a defect of crystal transition. In this connection, there is the danger that scrap will be formed. Therefore, it is necessary in heat treatment of the wafer using a heating device of the light irradiation type to carry out heating, holding at a high temperature and cooling such that the temperature distribution of the wafer is made uniform. In the case of heating of the wafer for layer formation, to form a layer with a uniform thickness, the wafer must likewise be heated such that the temperature distribution of the wafer is made uniform.
Even if the entire surface of the wafer is irradiated with a uniform irradiance, while in a heating device of the light irradiation type the wafer is kept in the high temperature state, there are cases in which the temperature of the peripheral region of the wafer is low and the temperature distribution of the wafer becomes nonuniform, and in which the above described slip occurs. The reason for the temperature drop of the peripheral wafer region is that heat is radiated from the side of the wafer. The heat radiation from the wafer side causes in the wafer a heat flow, by which a temperature distribution is formed. In order to make the temperature uniform over the entire surface of the wafer, therefore the peripheral region of the wafer must be irradiated with light with a greater irradiance than in the center region of the wafer according to the amount of temperature drop as a result of heat radiation from the wafer side.
On the other hand, as one of the processes for preventing a temperature drop in the peripheral region of the wafer, ordinarily a process was proposed in which auxiliary material with the same heat capacity as the wafer is arranged such that the outer periphery of the wafer is surrounded by it. This auxiliary material is generally called a guard ring.
A case is imagined in which the wafer and guard ring are heated together with uniform light irradiation by the wafer and guard ring being regarded as a one-piece, individual virtual plate body. In this case, no heat radiation arises from the wafer side since the peripheral region of the wafer does not become the peripheral region of the above described virtual plate body. The temperature of the peripheral region of the wafer therefore does not drop. Since the guard ring is arranged such that the outside periphery of the wafer is surrounded by it, it can also act as wafer holding material when it acquires an additional means with which the peripheral edge region of the wafer is held fast. Therefore, there are many cases in which the guard ring is designed to hold the wafer fast. This means that the guard ring is a component designed to equalize the temperature drop which occurs due to heat radiation from the side of the wafer or from its vicinity, and to make the wafer temperature uniform. There are also many cases in which the guard ring is used as a wafer holding material.
However, in fact, it is difficult to produce the guard ring such that it can be considered integral with the wafer, i.e., that the heat capacities are the same. The reasons for this are the following:
1. It is very hard to produce the guard ring from the same material as the wafer. If the guard ring is produced from silicon (Si), which is the same material as the wafer, the heat capacities of the wafer and the guard ring can be made the same. Processing of silicon into a form with which the wafer is held fast is however very difficult. If it is repeatedly exposed to a large temperature difference, it deforms, by which it can no longer be used as a guard ring.
2. A material which can be processed relatively easily and which has a heat capacity with a value somewhat greater than silicon, but close to it, is silicon carbide (SiC) which is generally used for guard rings. However, since the thickness of silicon carbide cannot be made smaller than 1 mm due to processing problems (yield), it is greater than the wafer thickness of 0.7 mm to 0.8 mm.
3. Due to the difference between the specific heat of the above described silicon and the specific heat of the silicon carbide and to the difference between the thicknesses, the heat capacity of the guard ring when heated to a high temperature is roughly 1.5 times greater per unit of area than that of the wafer. In order to eliminate the above described difference between the heat capacities of the wafer and the guard ring, it is therefore necessary to irradiate the guard ring with light with a greater irradiance than the wafer.
The guard ring itself which holds the wafer is, on the other hand, supported in the heat treatment space of the heating device of the light irradiation type by a support which consists of silica glass or a ceramic such as silicon carbide or the like and is located in a metallic chamber as a component of the heat treatment space. The support generally supports the outer peripheral region of the guard ring. Since the support arrangement of the guard ring is made in the above described manner, in the outer peripheral region of the guard ring in addition to heat radiation from the side via the support, heat moves from the guard ring to the metallic chamber. Even if the guard ring is irradiated with light with a uniform irradiance, the temperature therefore drops in the outer peripheral region of the guard ring, causing a temperature distribution in the guard ring.
As was described above, a guard ring of silicon carbide or the like is produced with a smaller thickness. There are therefore cases in which the guard ring is damaged in the case of formation of stresses. If a stress which arises as a result of the temperature distribution in the above described outer peripheral region of the guard ring has exceeded an allowable value, the guard ring is damaged. If the guard ring is irradiated with light under the conditions of irradiance under which there is the possibility of damage of the guard ring by this stress, it is necessary to make the irradiance on the surface of the outer peripheral region of the guard ring greater than the irradiance on the surface at a point outside of the outer peripheral region of the guard ring and to reduce the deviation of the temperature distribution of the guard ring.
This means that both when using a guard ring and also when not using it, the outer peripheral region of the article to be treated (including the single virtual plate body in which the wafer and guard ring are formed integrally with one another) must be irradiated with light with a greater irradiance than the center region of the article to be treated.
FIGS. 1(a) & 1(b) each show an ideal distribution of the irradiance for making the wafer temperature uniform in light irradiation. FIG. 1(a) is a schematic of an ideal irradiance in the case of not using the guard ring. FIG. 1(b) is a schematic of an ideal irradiance in the case of using the guard ring. The x-axis is the distance from the center of the wafer. The central axes in these figures represent the center region of the wafer. The y-axis plots the relative values of the irradiance with which the surfaces of the wafer and the guard ring are irradiated. To simplify understanding, it is assumed that the distribution of the emissivity of the wafer surface is uniform. That is, it is assumed that the temperature of the wafer irradiated with light is proportional to the irradiance on the wafer surface.
As is shown in FIG. 1(a), for an ideal distribution of the irradiance in the case of not using a guard ring, the irradiance on the surface of the center region of the wafer is uniform. Furthermore the irradiance on the surface of the outer peripheral region of the wafer is greater than the irradiance on the surface of the center region of the wafer. This is used to equalize the temperature reduction by heat radiation from the edge face of the wafer.
On the other hand, as is shown in FIG. 1(b), for an ideal distribution of the irradiance in the case of using a guard ring, the irradiance over the entire surface of the wafer is uniform since the guard ring suppresses the effect of heat radiation on the outer peripheral region of the wafer. The irradiance on the surface of the guard ring is greater than the irradiance on the wafer surface. In particular, the irradiance on the surface of the outer peripheral region of the wafer is greater than the irradiance on the surface of the guard ring except for the above described outer peripheral region.
The irradiance on the surface of the guard ring according to FIG. 1(b) is greater than the irradiance on the surface of the outer peripheral region of the wafer according to FIG. 1(a). It is used to equalize the amount by which the heat capacity of the guard ring is greater than the heat capacity of the wafer, as was described above.
The reason for the greater irradiance on the surface of the outer peripheral region of the guard ring than the irradiance on the surface of the guard ring except for the above described outer peripheral region is the suppression of the effect of the temperature drop which occurs in the above described outer peripheral region of the guard ring. Under the conditions of light irradiation under which the guard ring is not damaged as a result of the temperature decrease which occurs in the above described outer peripheral region of the guard ring, i.e., in the case in which the stress which is caused by irradiation is less than or equal to an allowable value, the distribution of the irradiation of the guard ring can also be uniform.
FIG. 2 is a schematic of the arrangement of one example of a prior art heating device of the light irradiation type. FIG. 3 is a schematic of the positional relationships of the filament lamps, the wafer and the guard ring relative to one another for a heating device of the light irradiation type as shown in FIG. 2. In this connection, the heating device of the light irradiation type is viewed from overhead.
As is shown in these drawings, the heating device 100′ of the light irradiation type has a chamber 300′, a silica glass window 4′, a guard ring 5′, a light source part 10′ as the heating means and the like. The chamber 300′ and the silica glass window 4′ form a heat treatment space S2′ in which there is a wafer 6′. The guard ring 5′ is made of a ceramic material, such as silicon carbide or the like. In its inner edge area, the guard ring has a device 50′ which holds the wafer 6′ fast at the outer peripheral region of the wafer 6′. The holding device 50′ for holding the wafer 6′ which is located in the guard ring 5′ is shown, for example, in Japanese patent disclosure document 2000-58471 and corresponding U.S. Pat. No. 6,163,648. The guard ring 5′ is supported in the outer peripheral region 51′ of the guard ring by a support 9′ in the heat treatment space S2′. The lower end of the support 9′ is in contact with the chamber 300′.
The light source part 10′ is made such that several filament lamps 1A′ to 1S′ in the form of a rod-shaped bulb are arranged parallel to one another. For the respective filament lamp 1′, normally there is one filament inside. Because the respective filament in the filament lamps 1A′ to 1S′ receives power supplied by the feed devices 19A-1′, 19B-1′, . . . 19S-1′ which comprise the current source part 7′, radiant energy is emitted. The radiant energy emitted from the filament lamps 1A′ to 1S′ is delivered directly or by a reflector 2′ through the silica glass window 4′ into the heat treatment space S2′, and heats the wafer 6′ and the guard ring 5′ which are located in the heat treatment space S2′.
However, the conventional heating device of the light irradiation type has the following disadvantage.
As was described above, it is necessary to heat the guard ring 5′ with a greater irradiance than the wafer 6′, in order to make the temperature of the wafer 6′ uniform in the heat treatment of the wafer 6′. However, for the heating device 100′ of the light irradiation type, as shown in FIG. 3, the filaments of the filament lamps 1′ to 1Q′ which are arranged with respect to the wafer 6′ are arranged spanning both the wafer 6′ and also the guard ring 5′.
On the other hand, as was described above, there is one filament in each of the respective filament lamps 1A′ to 1S′. The irradiances which are radiated by the filaments to which power was supplied onto the guard ring 5′ and the wafer 6′ are therefore identical to one another. In the case of heating the wafer 6′ with a given temperature, therefore also the guard ring 5′ is heated with the same irradiance as that of the wafer 6′. This means that using a conventional heating device of the light irradiation type, adjustment and heating cannot be achieved such that the irradiance on the surface of the guard ring 5′ is greater than the irradiance on the surface of the wafer 6′.
A process for eliminating the above described disadvantage has been proposed in Japanese patent application 2005-191222 and corresponding commonly-owned, co-pending U.S. Patent Application Publication 2006-0197454 of which the present inventors are co-inventors. FIG. 4 schematically shows the positional relationship between the filament lamps, the wafer constituting the article to be treated, and the guard ring in a heating device of the light irradiation type which was described in this application. In this connection, the heating device of the light irradiation type is viewed from overhead.
This heating device of the light irradiation type, beside the filament lamp formed by the light sources, and besides the current source parts, has the same arrangement as the heating device of the light irradiation type shown in FIG. 2. In the light source part 10′ filament lamps in the form of rod-shaped tubes are arranged parallel to one another such that the distance between the respective central axes is the same. The respective filament lamp proposed in this prior application is characterized in that there are several filaments in the bulb which can be supplied individually. The specific arrangement of the filament lamps is shown in FIG. 13.
In FIG. 4, the filament lamps 1A′, 1B′ . . . 1S′ are arranged in the same manner as in the heating device of the light irradiation type shown in FIG. 2 in the space above the wafer 6′ and the guard ring 5′. The number and length of several filaments which are located in the respective filament lamps 1A′, 1B′, . . . 1S′ are fixed in this connection according to the shape of the wafer 6′ and of the guard ring 5′.
The number of filaments in the respective filament lamps 1A′, 1B′, . . . 1S′ is fixed as follows. In the filament lamps 1F′ and 1N′ which belong to the filament lamp group U1′ which is located in the center region of the light source part 10′, there are five filaments arranged such that there is one filament corresponding to the wafer 6′, two filaments corresponding to the inner peripheral region 52′ of the guard ring and two filaments corresponding to the outer peripheral region 51′ of the guard ring.
Furthermore, in the filament lamps 1C′ to 1E′ and 1O′ to 1Q′ which belong to the filament lamp groups U2′ which are located on the two outer sides of the filament lamp group U1′, three filaments at a time are arranged such that there is one filament corresponding to the inner peripheral region 52′ of the guard ring and two filaments corresponding to the outer peripheral region 51′ of the guard ring.
In the filament lamps 1A′, 1B′, 1R′, 1S′ which belong to the filament lamp groups U3′ which are located on the two outer sides of the filament lamp groups U2′, there is one filament according to the outer peripheral region 51′ of the guard ring.
The length of several filaments for the respective filament lamps 1A′, 1B′, . . . 1S′ is established as follows.
In the filament lamps 1F′ to 1N′ which belong to the filament lamp group U1′, the respective length of the respective filaments 1F-3′ to 1N-3′ which are located over the wafer 6′ is established such that the contour formed by the connection of their ends assumes a shape similar to the outer periphery of the wafer 6′.
Furthermore, the length of the respective filaments 1C-2′ to 1Q-2′ and 1F-4′ to 1N-4′ which are located in the filament lamps 1C′ to 1Q′ which belong to the filament lamp groups U1′, U2′ over the inner peripheral region 52′ of the guard ring is established such that the contour formed by the connection of their ends assumes a shape similar to the outer periphery of the inner peripheral region 52′ of the guard ring and the outer periphery of the wafer 6′.
Furthermore, the length of the respective filaments 1A-1′ to 1S-1′, 1C-3′ to 1E-3′, 1O-3′ to 1Q-3′ and 1F-5′ to 1N-5′ which are located in the filament lamps 1A′ to 1S′ which belong to the filament lamp groups U1′, U2′, U3′ over the outer peripheral region 51′ of the guard ring is established such that the contour formed by the connection of their ends assumes a shape similar to the outer periphery of the outer peripheral region 51′ of the guard ring and the outer periphery of the inner peripheral region 52″ of the guard ring.
The filament lamps 1A′, 1B′, . . . 1S′ shown in FIG. 4 have several filaments which can be supplied individually. The number and length of the above described several filaments are fixed each according to the shape of the wafer 6′, of the inner peripheral region 52′ of the guard ring and the outer peripheral region 51′ of the guard ring.
Therefore, it is possible to fix the radiant energy from the respective filament which is located over the guard ring 5′ to be greater than the radiant energy from the respective filament which is located over the wafer 6′. Furthermore, it is possible to fix the radiant energy from the respective filament which is located over the outer peripheral region 51′ of the guard ring to be greater than the radiant energy from the respective filament which is located over the inner peripheral region 52′ of the guard ring.
This makes it possible to establish a distribution of the illuminance which is near the ideal distribution of the illuminance shown in FIG. 1(b) on the surface of the wafer and the guard ring. Thus, heating of the light irradiation type can be done such that the temperature of the wafer 6′ is made uniform. However, since in the heating device of the light irradiation type shown in FIG. 4 several filaments which are located in the filament lamps 1A′, 1B′, . . . 1S′ are supplied individually, feed devices are required with a number corresponding to the number of filaments which are located in the bulbs of the filament lamps 1A, 1B′, . . . 1S′. When the number of feed devices increases, the current source part becomes larger and costs are increased.
To reduce the costs of the heating device of the light irradiation type, the number of filament lamps which form the light source parts can be easily reduced. However, when simply the number of filament lamps is reduced, the distribution of the irradiance on the irradiation surface becomes nonuniform.
FIGS. 5(a) to 5(c) each schematically show the relation between the number of filament lamps and the distribution of the irradiance on the irradiation surface. It is apparent therefrom that the uniformity of the irradiance distribution on the irradiation surface for a reduced number of filament lamps as shown in FIG. 5(b) compared to FIG. 5(a) is reduced. Especially in the case of heating of the article to be treated which is a silicon wafer at a temperature of at least 1050° C. does the disadvantage of the above described formation of a defect of crystal transition occur when the irradiance for the wafer becomes nonuniform.

Heating device of the light irradiation type


Disclosed is a PDP image display method and device for dividing an image of each frame displayed on a PDP corresponding to an input video signal into subfields, each subfield corresponding to a bit that represents one of a plurality of luminance weights, combining luminance weights of the subfields, and displaying gray. The subfields include first and second subfield groups. A number of the subfields included in the second subfield group is greater than a number of the subfields included in the first subfield group. At least one of the subfields, which is used for forming low gray, is included in the second subfield group, and a start point of the second subfield group is varied according to a load ratio of the input video signal.

1. Field of the Invention
The present invention relates to an image display method and device for a plasma display panel (PDP). More specifically, the present invention relates to a PDP image display method and device for reducing flicker and dynamic false contour (DFC) generated when inputting 50 Hz PAL (phase alternating by line) video signals to realize images.
2. Description of the Related Art
A PDP is a display device for restoring image data input as electrical signals by arranging a plurality of discharge cells in a matrix pattern and selectively allowing the discharge cells to emit light.
Gray displaying is needed so that the PDP may operate as a color display device, and a gray realization method for dividing a single field into a plurality of subfields and performing time-division control on the subfields is used to realize the gray display.
Flickers are closely related to the quality of images perceived by humans, as flickers tend to degrade the quality of human visual experience. The flickers are more frequently detected by human eyes as a screen becomes bigger or a frequency lowers.
When images generated using PAL video signals are displayed on a large PDP, both of the above-noted conditions are met, thereby causing a lot of flickers. Therefore, when the PDP is driven at 50 Hz using a minimum incremental arrangement or a minimum decrement arrangement which is a general arrangement of subfields used for the PDP, a lot of flickers are generated.
Since the screen cannot be controlled in the above-noted two conditions that cause flicker, a method for controlling the frequency is used to reduce the flicker.
Korean published application No. 2000-16955 discloses a conventional method for reducing flicker generation by control of the frequency. In order to reduce large screen flickers generated when inputting 50 Hz video signals to drive a PDP, subfields in a single frame are divided into two groups G1 and G2, and the subfields of the groups except the least significant bit (LSB) subfield are established to have the same configuration. In other words, luminance weights are similarly allocated to the subfields of the respective groups, as shown in FIG. 1. The above-described method is much more effective than the conventional subfield arrangement, such as the minimum incremental arrangement or the minimum decrement arrangement.
Referring to FIG. 1, a total interval of a single frame is 20 ms, and the intervals of the respective groups G1 and G2 are fixed as 10 ms. Two suspension intervals are provided, one of which is positioned at the end of the frame, that is, at the end of the second group G2, and the other of which is positioned between the two groups G1 and G2, that is, at the end of the first group G1.
FIG. 2, for example, shows a partial realization of low gray by using a conventional subfield arrangement.
As shown, in the case of displaying low gray such as a low gray of from 0 to 11 by using a conventional subfield arrangement, a time difference between the subfields corresponding to the LSB and the LSB+1 is several ms.
For example, in the case of low gray 3, the lowest subfield SF1 of the first group G1 is turned on, and the lowest subfield SF1 of the second group G2 is turned on. In this instance, the subfield of the first group G1 is a subfield of the LSB, the subfield of the second group G2 is a subfield of the LSB+1, and the time difference between the subfields is 10 ms, a very big difference.
When the subfield arrangement of the Korean published application No. 2000-16955 is used and error diffusion is applied to display low gray, the time difference between the subfields corresponding to the LSB and the LSB+1 is as big as several ms, and a light emission sustain time having the above-noted time difference is short. Therefore, a severe DFC can occur in a boundary of grays when an image sensed by eyes moves.
For example, FIG. 3 shows a concept diagram of a DFC that would be generated when using the disclosure of the above-noted published application, when an image moves in the case where adjacent grays are 4 and 3. As shown in FIG. 3, the DFC occurs at a total of five points when the image moves in the case adjacent grays are 4 and 3, and difference values between the highest gray 4 and a distorted gray from among original grays are respectively 2, 1, 3, 2, and 1.5 depending on the generation points. These difference values show generation intensities of the generated DFC. The distorted gray while moving the image is displayed as color distortion, and it is displayed as color distortion in the DFC pattern.
Since the PDP has high power consumption because of its driving features, an automatic power control (APC) for controlling the power consumption according to a load ratio (or an average signal level (ASL)) of a frame to be displayed is provided. The APC method controls the APC levels according to the load ratio of the input video data, and varies a number of sustain pulses for each APC level to control the power consumption to be below a predetermined level.
Following the APC method, the number of sustain pulses applied to each subfield according to the load ratio is varied. That is, the total number of sustain pulses applied to the respective groups G1 and G2 is varied according to the load ratio, and since each subfield has a number of sustain pulses of as many as luminance weights that the corresponding subfield has, the number of sustain pulses applied to each subfield is also varied.
FIGS. 4A through 4C show positions of the subfields and central positions of light emission for each APC in the conventional PDP subfield structure, FIG. 4A showing a case when the APC is the minimum, FIG. 4B showing a case when the APC is the maximum, and FIG. 4C showing a case when a time of the first group G1 is greater than that of the second group G2.
As shown in FIGS. 4A and 4B, time gaps TIME G1G2 and TIME G2G1 between the central positions of light emission of the groups G1 and G2 are the same when the APC is the minimum and the maximum, and hence, the central positions of light emission of the first and second groups G1 and G2 have periodicity in many gray regions. Therefore, the conventional PDP subfield structure generates fewer flickers.
However, as shown in FIG. 4C, when a subfield occupation time of the first group G1 is longer than that of the second group G2 in the case of forming partial gray irrespective of the APC level, the positions of the top subfields of the first and second groups that are turned on become different. Referring to FIG. 4C, the time gap TIME G1G2 between the light emission centers of the first and second groups G1 and G2 is less than the time gap TIME G2G1 between the light emission centers of the second group G2 and a next frame's first group G1, and as a result, the light emission centers of the groups G1 and G2 lose periodicity, thereby generating flicker.

Image display method and device for plasma display panel


A light-emitting device has a plurality of data lines and a plurality of pixel circuits. Each of the plurality of pixel circuits includes a light-emitting element that has a first electrode and a second electrode and that emits light having an intensity depending on the amount of driving current; a driving transistor that supplies the driving current to the first electrode; a holding transistor that supplies a driving signal supplied via the data lines to the driving transistor; and a connecting line that connects the driving transistor to the holding transistor. The second electrode is formed in a region different from a region in which the data lines are formed such that the second electrode is not opposite to some or all of the data lines.

1. Technical Field
The present invention relates to a light-emitting device using light-emitting elements for emitting light having an intensity depending on the amount of current flowing from an anode to a cathode, such as an organic light-emitting diode element, to an image forming apparatus, and to a display apparatus.
2. Related Art
In recent years, a great deal of attention has been paid to organic electroluminescent elements or organic light-emitting diode (OLED) elements, which are also called light-emitting polymer elements, as next-generation light-emitting devices replacing liquid crystal devices. Since the OLED element is a self-emitting type, a panel using the OLED element has a low dependency on a viewing angle, and moreover, since the OLED element does not require a backlight or reflected light, this element is suitable for a thin display device with low power consumption.
The OLED element is a current driven element that has no voltage retention, like the liquid crystal element, and cannot maintain a light emission state when a supply of a current thereto is disconnected. Accordingly, when the OLED element is driven by an active matrix method, it is common that a driving signal to indicate a gray-scale level of a pixel is supplied to a pixel circuit via a data line, a voltage is written in a gate electrode of a driving transistor by supplying a driving signal to the gate electrode in a write period via a holding transistor in the pixel circuit, the voltage is retained by a gate capacitor and the like, and the driving transistor continues to cause a driving current corresponding to the voltage to flow into the OLED element.
In such a light-emitting device, the OLED element has an anode coupled to the driving transistor, and a cathode opposite to the anode. On the other hand, the cathode is formed opposite to the data line and the holding transistor (for example, see Japanese Unexamined Patent Application Publication No. 2003-316296 (see FIGS. 2 and 3)).
However, when the cathode is opposite to the data line, a stray capacitance is produced between the cathode and the data line. The stray capacitance acts as a capacitive load from the point of view of a driving circuit for driving the data line. Accordingly, if the driving circuit has low driving capability, there is a problem in that it is difficult to write a voltage signal into the data line at high speed, and the brightness of the OLED element is lowered. On the other hand, even if a driving circuit having high driving capability is used a high load still needs to be driven and therefore, there is a problem in that power consumption is increased. In addition, since the stray capacitance is increased when the holding transistor is opposite to the cathode of the OLED element, there is the same problem as in the data line. Particularly, when an operation state of the driving transistor is controlled by supplying a driving signal having a preset pulse width to the driving transistor and the brightness of the OLED element is controlled by the preset pulse width, there arises a problem in that the driving signal having the preset pulse width is deteriorated due to the capacitive load, and thus, the desired brightness may not be obtained.
More particularly, when the light-emitting device is applied to a head unit of an image forming apparatus, since the OLED element is required to have high brightness because of sensitivity of a photoreceptor, there arises a significant problem of lack of write due to the stray capacitance. In addition, if the write period in a large display panel is short, there is also a significant problem of lack of write due to the stray capacitance.

Light-emitting device, image forming apparatus, and display apparatus


Torquable tubular member for use in a flexible elongate device comprising an elongate tubular body having a cylindrical wall and a longitudinal axis extending longitudinally of the cylindrical wall. The cylindrical wall has formed therein a plurality of spaced-apart slots spaced longitudinally of the longitudinal axis. At least certain of the slots have a first portion which extends generally radially of the tubular body and a second portion which extends generally longitudinally of the tubular body.

This invention relates to a torquable catheter and a torque tube for use therewith.
In the past, steerable catheters have heretofore been provided to facilitate maneuvering in blood vessels. However, in the past with such devices it has been difficult to achieve a substantially one to one ratio of movement for the proximal and distal extremities of the catheter. There is therefore a need for a new and improved catheter which can achieve such a one-to-one ratio and torquable tubular member for use therewith.


An electrode mounting structure of a surface treatment apparatus in which a metal electrode is disposed so as to oppose to an inner-peripheral surface of a cylinder, the electrode and the cylinder are energized in a state where treatment liquid is interposed between the electrode and the cylinder inner-peripheral surface so as to perform pre-plating or plating to the cylinder inner-peripheral surface, and the metal electrode is detachably attached to a metal electrode holder member. The structure includes a resin coupler having a threaded portion engaged with a threaded portion formed on the electrode holder member.

1. Field of the Invention
The present invention relates to an electrode mounting structure of a surface treatment apparatus for pre-plating or plating a surface of an object to be treated of an object, especially, a cylinder inner-peripheral surface of a cylinder of an engine.
2. Description of the Related Art
In a surface treatment apparatus for pre-plating or plating a cylinder inner-peripheral surface of a cylinder, it is necessary to periodically perform maintenance for an electrode to clean it or to renew masking thereof. Because of this reason, the electrode can be attached to or detached from an electrode holder member.
In an electrode mounting structure of a conventional surface treatment apparatus disclosed in Japanese Patent Application Laid-open No. 7-305198 (Patent Publication 1), as shown in FIG. 7, an electrode 101 and an electrode holder member 102 are formed with threaded portions 103 and 104, respectively, so as to be engaged with each other. Furthermore, Japanese Patent Application Laid-open No. 2006-2204 (Patent Publication 2) discloses a structure shown in FIG. 8 in which a bolt 105 penetrating an electrode holder member 102 is screw-engaged with a threaded portion 106 of an electrode 101, and the electrode 101 is mounted on an electrode holder member 102. In FIGS. 7 and 8, cylinders 100 are objects to be treated.
According to the electrode mounting structures described in the Patent Publications 1 and 2, however, since materials of the threaded portions (threaded portions 103 and 104 or bolt 105 and the threaded portion 106) are both composed of metals, a spark may be caused at the threaded portions, and adhesion may be caused at this threaded portion. Therefore, it becomes difficult to detach the electrode 101, and the maintenance performance of the electrode 101 becomes deteriorated.
This tendency appears seriously for a circulating plating apparatus in which circulation liquid is circulated between the electrode 101 and a cylinder inner-peripheral surface of the cylinder 100 because density of current flowing through the electrode 101 and the cylinder 100 is greater than that of an immersion-type plating apparatus.

Electrode mounting structure of surface treatment apparatus


It is desired to provide technology that enables automatic measurement of the size of a subject with a reduced number of frames of images required, relaxed restrictions on the coverage and light projection, and no limitation on the shape of the subject. Provided is an information processing device including: a depth information acquiring unit configured to acquire depth information; a data conversion unit configured to convert the depth information into three-dimensional data; a subject extraction unit configured to extract a subject area where a subject is present on the basis of the three-dimensional data; and a size measurement unit configured to measure a size of the subject on the basis of the subject area, in which the size measurement unit detects six planes circumscribing the subject area and measures the size of the subject on the basis of the six planes.

In recent years, there has been technology for measuring the size of a subject. For example, technology is disclosed in which the size of a subject is measured on the basis of specified positions when a rectangular parallelepiped subject is captured by a camera and displayed on the screen, and a user specifies these positions of a total of four points on the screen including a vertex of three sides of the rectangular parallelepiped subject converging at the vertex and the other ends of the three sides on the opposite side to the vertex (for example, see Patent Document 1).
Also disclosed is technology related to a size measuring device including: a light projecting unit configured to project a light pattern having a geometric shape onto the vicinity of a vertex where three sides of a rectangular parallelepiped subject converge; two cameras configured to capture the light pattern reflected by the subject; and a measuring unit configured to measure the size of the subject on the basis of parallax information obtained from images captured by the respective two cameras (for example, see Patent Document 2). It is premised that such a size measuring device includes an active stereo camera including a light projecting unit configured to project a geometrical light pattern and two cameras.
Furthermore, also disclosed is technology related to a measuring device including: an image acquiring unit configured to periodically acquire a distance image; a shape data generating unit configured to generate shape data for each distance image on the basis of distance images of a plurality of frames; an estimation unit configured to estimate the position and the angle for each of the distance images on the basis of the distance images of the plurality of frames; a detection unit configured to detect a subject on the basis of the shape data, the position, and the angle; and a measurement unit configured to measure the size of the detected subject (for example, see Patent Document 3).

Information processing device, information processing method, and individual imaging device for measurement of a size of a subject

SONY SEMICONDUCTOR SOLUTIONS CORPORATION


Disclosed is a dual wafer stage switching system for a lithography machine. The system comprises a base stage (30), a wafer stage (16.1) running at a pre-processing workstation, and a wafer stage (16.2) running at an exposure workstation. A rotating motor (41) is mounted under the base stage (30) for rotating the two wafer stages after the wafer stages have completed pre-processing and exposure operations in order to complete position switch of the wafer stages, wherein the base stage (30) is kept stationary during the switch. The present invention avoids rotation of a large inertia base stage and has low requirement for motor power, while eliminating a guide rail docking device and an auxiliary device and greatly simplifying system configuration. The system is easy and convenient to operate and easy to control.

In manufacturing process of an integrated circuit (IC) chip, it is one of the most important processes to expose and transfer a design pattern of a chip onto a photoresist on the wafer surface, which is performed with an apparatus called lithography machine (exposure machine). The resolution and exposure efficiency of the lithography machine has a significant impact on the characteristic line width (i.e., the resolution) and production rate of the IC chip. And, as a critical system of the lithography machine, the motion precision and process rate of the wafer ultra-precision motion positioning system (hereinafter abbreviated as wafer stage), can largely determine the resolution and exposure efficiency of the lithography machine.
FIG. 1 illustrates the main principle of a step-and-scan projection lithography machine. Deep ultra-violet light from a light source 45 transmits through a mask 47 and lens 49 and projects a certain portion of the pattern of the mask onto a specific chip of the wafer 50, wherein the motions of the mask and the wafer are in opposite directions and are synchronized according to a specific speed ratio, and finally, the whole pattern on the mask is transferred onto the corresponding chip of the wafer.
The main function of the wafer stage motion positioning system is to move, with the wafer held thereon, in the exposure process at a preset speed and in a preset direction in order to allow precise transfer of the mask pattern onto various parts of the wafer. Due to the small line width of the chip (presently, the minimum line width has reached 45 nm), in order to guarantee the precision and resolution of the lithography, the wafer stage is required to have a very high moving and positioning accuracy; since the productivity of the lithography is determined largely by the motion speed of the wafer stage, for improvement of productivity, there is an increasing demand for improving the motion speed of the wafer stage.
FIG. 2 is a structural schematic diagram of a wafer support platform of a lithography machine in the related art. The wafer support platform 16 includes a coarse motion module 18 and a fine motion module 20. Each of the coarse motion module 18 and the fine motion module 20 has a stationary part, a movable part and a driving part. A stationary part 8 of the coarse motion module 18 is connected to a base stage 30. The movable part of the coarse motion module 18 is movable relative to the stationary part. A stationary part 12 of the fine motion module 20 is connected to the movable part 10 of the coarse motion module 18. A movable part 14 of the fine motion module 20 is movable relative to the stationary part 12. The wafer support platform 16 is configured to support a wafer W, and the wafer W is not a part of the wafer support platform. Herein, the "stationary part" is a concept defined with respect to the movable part, and the "stationary part" itself can also be movable. It is well known that the driving motor for the coarse motion module may be a linear motor, etc., and the driving motor for the fine motion module may be a planar motor, a voice coil motor, etc.

Dual wafer stage switching system for a lithography machine


Methods for reducing read disturb using NAND strings with poly-silicon channels and p-type doped source lines are described. During a boosted read operation for a selected memory cell transistor in a NAND string, a back-gate bias or bit line voltage may be applied to a bit line connected to the NAND string and a source line voltage greater than the bit line voltage may be applied to a source line connected to the NAND string; with these bias conditions, electrons may be injected from the bit line and annihilated in the source line during the read operation. To avoid leakage currents through NAND strings in non-selected memory blocks, the threshold voltages of source-side select gate transistors of the NAND strings may be set to a negative threshold voltage that has an absolute voltage value greater than the source line voltage applied during the read operation.

Semiconductor memory is widely used in various electronic devices such as cellular telephones, digital cameras, personal digital assistants, medical electronics, mobile computing devices, and non-mobile computing devices. Semiconductor memory may comprise non-volatile memory or volatile memory. A non-volatile memory allows information to be stored and retained even when the non-volatile memory is not connected to a source of power (e.g., a battery). Examples of non-volatile memory include flash memory (e.g., NAND-type and NOR-type flash memory) and Electrically Erasable Programmable Read-Only Memory (EEPROM).
Both flash memory and EEPROM utilize floating-gate transistors. For each floating-gate transistor, a floating gate is positioned above and insulated from a channel region of the floating-gate transistor. The channel region is positioned between source and drain regions of the floating-gate transistor. A control gate is positioned above and insulated from the floating gate. The threshold voltage of the floating-gate transistor may be controlled by setting the amount of charge stored on the floating gate. The amount of charge on the floating gate is typically controlled using Fowler-Nordheim (F-N) tunneling or hot-electron injection. The ability to adjust the threshold voltage allows a floating-gate transistor to act as a non-volatile storage element or memory cell. In some cases, more than one data bit per memory cell (i.e., a multi-level or multi-state memory cell) may be provided by programming and reading multiple threshold voltages or threshold voltage ranges.
NAND flash memory structures typically arrange multiple floating-gate transistors in series with and between two select gates. The floating-gate transistors in series and the select gates (e.g., the source-side select gate and the drain-side select gate) may be referred to as a NAND string. In recent years, NAND flash memory has been scaled in order to reduce cost per bit. However, as process geometries shrink, many design and process challenges are presented. These challenges include increased neighboring word line interference, reduced data retention, and increased leakage currents.

Boosting read scheme with back-gate bias


A slurry mixer comprises a container assembly and pressurized air delivery system for mixing gravitationally separable heavy particulate of target slurry. The container assembly essentially comprises an inferior container portion, a superior container portion, a vertical container diameter, and accumulator plates, which plates are spatially located in superior adjacency to the inferior container portion orthogonal to the vertical container diameter. The air delivery system delivers compressed air to a gas outlet cooperable with the accumulator plates for outletting gas into the container assembly. The accumulator plate feature functions to plate-shape the outlet gas into a substantially planar initial bubble shape. The initially planar bubble shape is upwardly directed toward the superior tank portion in radial adjacency to the vertical container diameter. The outlet gas displaces slurry components via dynamic matter-displacing bubble action, and the initially planar bubble shape maximizes the matter-displacing effectiveness of the bubble action for mixing the slurry.

1. Field of the Invention
The disclosed invention generally relates to an apparatus for mixing slurries such as coal tar and asphalt based sealers. More particularly, the disclosed invention relates to an apparatus and associated method for mixing slurries by way of air-pulse agitation.
2. Brief Description of the Prior Art
Conventional methods and systems for mixing slurries such as coal tar and asphalt based sealers have incorporated mechanical mixing implements such as paddles. Less conventional methods include air or bubble-action agitation of the slurry mixture. While paddle-type slurry mixers may well function to properly mix a slurry into a uniform mixture, the machinery is often costly, complicated, and requires a great deal of maintenance. Air-based slurry mixing systems fare no better than their paddle mixing counterparts in terms of cost, complexity and inherent need for high levels of maintenance and care. Those systems that have been simplified in design so as to overcome the cost and complexity-related difficulties attendant to such designs often prove ineffectual for properly mixing the slurries. Some of the more pertinent art relating to paddle-type mixers, air-type mixers and the like is briefly set forth hereinafter.
U.S. Pat. No. 3,953,003 ('003 patent), which issued to Mahig, discloses a Tank Provided with Pneumatic Mixing Pipe. The '003 patent teaches a container adapted to thoroughly mix fluid material, especially suspensions, comprising a tank provided with a vertical mixing pipe, a vertical air lifting pipe, a gas collecting chamber located at the upper end of the mixing pipe, and a connecting pipe affixed at one end to the collecting chamber and communicating therewith and affixed at its other end to the bottom of the air lifting pipe and communicating therewith.
U.S. Pat. No. 4,298,287 ('287 patent), which issued to McCarter, III et al., discloses a Center Draft Asphaltic Concrete Drum Mixer. The '287 patent teaches a continuous drum mix asphalt plant wherein dust is exhausted from an intermediate zone of the drum mixer between its drying and mixing zones. The dust is exhausted radially through openings into a collection housing, which communicates with a dust collector and exhaust blower. An end housing at the discharge end of the drum communicates with the same dust collector and blower. Dampers are provided to control the relative proportion of air exhausted from the drum through the respective housings. Aggregate deflectors on the interior wall of the drum at the intermediate zone allow air and dust to flow while inhibiting the flow of aggregate. The collection housing surrounding the intermediate zone is of a size such as to produce a reduction in the velocity of the air as it passes out of the drum. Consequently, it serves as a knock-out box for the collection of larger particles which are carried out of the drum, but which settle out of the air stream as a result of the velocity decrease. These collected particles are reintroduced into the drum by scoops on the exterior of the drum. These scoops are also used for the introduction of recycled asphaltic concrete.
U.S. Pat. No. 4,895,451 ('451 patent), which issued to Hockett, discloses a Mixing Device. The '451 patent teaches an improved mixing device for mixing an abrasive such as sand with a flowing fluid such as compressed air. The improved mixing device comprises a body member having a major internal channel being defined along a major axis. The major internal channel extends between a major input and a major output of the major internal channel. The body member includes a minor internal channel defined along a minor axis and extending from a minor input to an intersection with a portion of the major internal channel located between the major input and the major output of the major internal channel. The flowing fluid is directed into the major input whereas the abrasive is directed into the minor input for enabling the abrasive to mix with the flowing fluid within the major internal channel and to discharge from the major output. The minor internal channel is established at an acute angle relative to the major internal channel and extends generally toward the major input of the major internal channel for enabling abrasive erosion of the body member to be distributed over a region of the body member during prolonged use of the mixing device.
U.S. Pat. No. 4,941,599 ('599 patent), which issued to Reinertz et al., discloses a Method and Apparatus for Thoroughly Mixing a Suspension Containing a Fluid and Solid Matter Constituents. The '599 patent teaches an apparatus and a method for thoroughly mixing a suspension containing a fluid and solid matter constituents and spraying the thoroughly mixed suspension onto a surface. The apparatus includes a pressure and seal tight container enclosed on all sides for accommodating the suspension therein. The container has a top region and has a base region whereat the solid matter constituents tend to collect to form a sediment. A cylinder and a piston generate a charge of air under pressure which is conducted through a passage into the base region of the container to break up the sediment and thoroughly mix the solid matter constituents in the fluid as the air under pressure rises through the suspension to collect at the top region of the container where it imparts pressure to the suspension. A nozzle unit mounted on the container vents the container to permit the air under pressure to entrain the thoroughly mixed suspension to form a spray. With the invention, the suspension is always thoroughly mixed for each pumping operation and during the spraying operation so that a loss of function because of blockage of the spray system is prevented.
U.S. Pat. No. 5,002,426 ('426 patent), which issued to Brown et al., discloses a Paddle Mixer for Asphalt Pavers. The '426 patent teaches a revolving paddle mixer for re-mixing a hot asphalt mix deposited in the hopper of a road paving machine. The mixer takes the form of a plurality of paddles angularly positioned relative to each other and mounted on a revolving shaft adjacent to the conveyor for transporting the asphalt mix material to the rotating auger. The resultant re-mixture is more uniform and dense so that a smooth pavement is laid on the roadway.
U.S. Pat. No. 5,009,508 ('508 patent), which issued to Wojdylo, discloses an Apparatus for Mixing Concrete. The '508 patent teaches an abstract for mixing concrete which includes a tank having at least a portion thereof which permits the inside of the tank to be visually observed from the outside of the tank. An inlet is disposed in the top of the tank for inserting concrete ingredients. An outlet is disposed in the bottom of the tank for permitting the mixed concrete to be withdrawn from a chamber inside the tank. The tank includes seals for selectively sealing all openings into the chamber of the tank and an opening is provided for introducing air under pressure into a lower portion of the tank for the purpose of being able to mix the concrete using such air pressure.
U.S. Pat. No. 5,380,082 ('082 patent), which issued to Milstead, discloses an Asphalt Drum Mixer with Curved Scoop-like Mixing Tips. The '082 patent teaches an asphalt drum mixer comprising a rotating drum within a fixed sleeve which defines an annular chamber, and mixing tips mounted on the drum and in the annular chamber. The mixing tips pass through the hot mix asphalt lying in the bottom of the annular chamber and mix and shear the hot mix asphalt and increase its residence time in the drum mixer. In one preferred embodiment, the mixing tips may comprise curved scoop-like elements which lift the hot mix asphalt higher than conventional paddles and greatly increase residence time of the mix in the drum over conventional paddles. The quality of the mix is thus greatly improved. In another preferred embodiment the mixing tips may comprise curved scoop-like elements having slots which greatly increase sheering of the hot mix asphalt, thereby further improving the quality of the mix.
U.S. Pat. No. 5,586,731 ('731 patent), which issued to Glaze et al., discloses a Compost Mixing and Aerating Apparatus. The '731 patent teaches an improved composting apparatus particularly suited for use with straw-like materials. The composting apparatus includes a counter-rotating drum and paddle assembly which generates a plurality of air streams in which the composting material is entrained. The air streams rotate in a vortex like pattern within a chamber to mix and aerate the composting material. The composting apparatus is configurable for being driven sideways through fence gates and the like, and has an additional configuration for being towed without requiring a trailer.
U.S. Pat. No. 5,676,716 ('716 patent), which issued to Gohara et al., discloses an Apparatus for Mixing a Tank and Improving Air/Liquid Contact in an Oxidized System. The '716 patent teaches an apparatus to mix a slurry mixture with an oxidization air within a reaction tank of a wet scrubber spray tower of a flue gas desulfurization system for a furnace. The apparatus improves the contact between forced oxidization air and slurry mixture within the reaction tank. U.S. Pat. No. 5,824,141 ('141 patent), which also issued to Gohara et al., discloses an apparatus to mix a slurry mixture with an oxidization air within a reaction tank of a wet scrubber spray tower of a flue gas desulfurization system for a furnace. The apparatus improves the contact between forced oxidization air and slurry mixture within the reaction tank.
From a consideration of the foregoing disclosures, it may be seen that the prior art discloses complex paddle-type mixers (e.g. the '426 and '082 patents); complex air-type mixers (e.g. the '003, '451, and '599 patents), and simplistic air-type slurry mixers (e.g. the '508 patent). Coal tar sealers, asphalt based sealers, and similar other slurry type mixtures (such as concrete) having heavy (or gravitationally separable) particulate mixed with aggregate are generally easier to blend with air agitation than by conventional paddle agitation. The prior art thus perceives a need for a simplified air-based slurry mixing apparatus and/or methodology, which apparatus and associated method may well function to provide a homogenous slurry mixture at minimized cost and maintenance.


Thiazolinone substituted quinoline derivatives where the quinoline ring is substituted at the 2 position which derivatives demonstrates CDK1 antiproliferative activity and are useful as anti-cancer agents.

Cyclin-dependent kinases (CDKs) are serine-threonine protein kinases that play critical roles in regulating the transitions between different phases of the cell-cycle, such as the progression from a quiescent stage in G1 (the gap between mitosis and the onset of DNA replication for a new round of cell division) to S (the period of active DNA synthesis), or the progression from G2 to M phase, in which active mitosis and cell-division occurs. (See, e.g., the articles compiled in Science, 274:1643–1677 (1996); and Ann. Rev. Cell Dev. Biol., 13:261–291 (1997)). CDK complexes are formed through association of a regulatory cyclin subunit (e.g., cyclin A, B1, B2, D1, D2, D3 and E) and a catalytic kinase subunit (e.g., CDK1, CDK2, CDK4, CDK5 and CDK6). As the name implies, the CDKs display an absolute dependence on the cyclin subunit in order to phosphorylate their target substrates, and different kinase/cyclin pairs function to regulate progression through specific phases of the cell-cycle.
As seen above, these protein kinases are a class of proteins (enzymes) that regulate a variety of cellular functions. This is accomplished by the phosphorylation of specific amino acids on protein substrates resulting in conformational alteration of the substrate protein. The conformational change modulates the activity of the substrate or its ability to interact with other binding partners. The enzyme activity of the protein kinase refers to the rate at which the kinase adds phosphate groups to a substrate. It can be measured, for example, by determining the amount of a substrate that is converted to a product as a function of time. Phosphorylation of a substrate occurs at the active-site of a protein kinase.
In view of the above properties, these kinases play an important part in the propagation of growth factor signal transduction that leads to cellular proliferation, differentiation and migration. Fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) have been recognized as important mediators of tumor promoted angiogenesis. VEGF activates endothelial cells by signaling through two high affinity receptors, one of which is the kinase insert domain-containing receptor (KDR). (See, Hennequin L. F. et. al., J. Med. Chem. 45(6):1300 (2002). FGF activates endothelial cells by signaling through the FGF receptor (FGFR). Solid tumors depend upon the formation of new blood vessels (angiogenesis) to grow. Accordingly, inhibitors of the receptors FGFR and KDR that interfere with the growth signal transduction, and thus slow down or prevent angiogenesis, are useful agents in the prevention and treatment of solid tumors. (See, Klohs W. E. et. al., Current Opinion in Biotechnology, 10:544 (1999).
Because CDKs such as CDK1 serve as general activators of cell division, inhibitors of CDK1 can be used as antiproliferative agents. These inhibitors can be used for developing therapeutic intervention in suppressing deregulated cell cycle progression.


A speed-difference-dependent hydraulic, consisting of a stationary rotating gear housing (27) with a housing (25) which forms a reservoir for operating fluid, a hydrostatic displacement machine (35), a drive shaft (30), a friction coupling (36) and a piston (5) to have an impact on the friction coupling (36), by which pressure is created in a pressure chamber (4) when there is a differential speed between the gear housing (27) and the drive shaft (30). In order to achieve quick regulation and adaptation of the characteristics, a first and second opening (9, 10) are connected by means of a first and second rotating insertion (13, 14), and a first and second regulating control valve (15, 16) are connected with the reservoir (8), by which the first and the second control valves (15, 16) are formed as regulating throttle valves, so that independent of the direction of the differential speed, it can be controlled on the respective supply side as well as on the discharge side of the displacement machine.

1. Field of Invention
The invention relates to a speed-difference-dependent hydraulic coupling, consisting of a rotating gear housing which is stationary, a housing which forms a reservoir for operating fluid, a hydrostatic displacement machine in the gear housing, a drive shaft, and a friction coupling to connect the drive shaft with the gear housing and a piston to have an impact on the friction coupling, by which pressure is created in a pressure chamber when there is a differential speed between the gear housing and the drive shaft, which influences an impact on the friction coupling, and by which the hydrostatic displacement machine is provided with a first and second opening for the supply and discharge of operating medium and a third and fourth opening for connection with the pressure chamber.
2. Description of the Prior Art
These type of couplings are being applied in various configurations in the motive power line of motor vehicles to directly transfer a torque or to block a connected differential power transmission to drive the wheels of an axle or for distribution of the starting torque between two axles. The hydrostatic displacement machine consists, for example, of an internal rotor and an external rotor. However, hydrostatic displacement machines of other types of construction can also be used. In any case when there is a differential speed, two parts (e.g. drive housing and output shaft) perform a relative motion and create an impacting pressure on the pistons of the friction coupling.
This type of coupling is renowned, for example, from U.S. Pat. No. 5,536,215. In this case, a valve of a bimetallic laminar will be provided between the pressure chamber and a space with lesser pressure, i.e. the coupling area. This valve shall compensate viscosity changes of the operating fluids, which depend on the temperature. Other regulating devices will not be provided.
As disclosed in U.S. Pat. No. 4,727,966 (hereinafter xe2x80x9c""966xe2x80x9d), another such coupling in a slightly different arrangement is renowned. In this type of coupling, discharge openings with restrictors will be provided between the third and fourth openings and the pressure chamber. These discharge openings enable different set pressures for the two possible directions of the differential speed, i.e. a difference between the driving and delayed operations, or forwards and reverse speeds.
Furthermore, as shown in FIG. 7 of the ""966 reference, regulating devices are already provided, i.e. more discharge valves, the set pressure of which can be regulated. The adjusting signal for this will be determined by a control device of different operating sizes. The control devices are installed in the rotating part. Thus, the adjusting signals, in this case hydraulic, must be fed to them by a rotating entry. The pressure on the suction side of the displacement machine will not be influenced. All of this and in addition the impact of the centrifugal force on the regulating devices makes a delicately sensitive, exact and quick regulation impossible.
In German Patent Document Number DE 198 54 867 A, another similar coupling is renowned in another arrangement, by which the pressure chamber itself, rather than the displacement machine, is connected by a rotating entry with a control valve equipped with a rigid housing for pressure modulation on the pressure side. In this way only an imperfect control is possible. Therefore, in order to tow the motor vehicle, the displacement machine must be made completely pressureless, which necessitates a valve on the suction side. Furthermore, the valve arrangement requires the coupling unit to be constructed in such a way that it has a number of other disadvantages.
The aim of this invention is to further develop a coupling which is of a kind that ensures a delicately sensitive, exact and quick regulation and adaptation of the characteristic with at least expense as possible.
The above aim of the invention is achieved in that the streams of the first and second openings, respectively, are connected to the reservoir by a first and second rotating entry and a first and second valve with rigid housings, and that the first and second valves are formed as regulating throttle valves, so that independent of the direction of the differential speed, there will be a control action on the supply as well as on the discharge side of the displacement machine.
Therefore, control valves will be provided at the shortest way to and from the displacement machine on the pressure and suction sides, which have direct impact on the coupling with very little delay in all driving conditions possible. Since these are controllable throttle valves, i.e. arranged in the main stream, it is possible to control over the entire regulating range in a delicately sensitive and exact manner.
There are also the following advantages of the arranged control valves in rigid housings; simple connection with the control device, no disturbing influences of the centrifugal force, no restrictions of the size and good access. Furthermore, due to these advantages, the supply and discharge of the operating medium is possible on the side of the displacement machine, so that the rotating insertions could be provided relatively simple at small diameters. The additional costs for the rotary transmission is made competitive due to the omission of the necessary non-return valves without both control valves in the same line.
In one embodiment of this invention, the first and the second valve forms a common control valve. Apart from the reduction in costs in this connection, improvement of the reliability without any loss in the function capability in the driving operation is also achieved. During this, the first and second valves could be controlled by proportional valves or by a stepping motor.
In a further embodiment of this invention, a double-acting non-return valve will be provided between the third and fourth openings and the pressure chamber. Due to the fact that one side is always open at this valve, the pressure chamber above this valve and the regulating valve can be made pressureless very quickly, which is of an advantage especially when braking (ABS, ESP). Furthermore, the valve can be installed in the wall between the displacement machine and the pressure chamber which especially saves space. Acceptable transition from one type of operation to the other is ensured by the fact that there is only one valve with one circuit element (preferably with a ball).
An advantage of this invention is that the common control valve is formed by a movable adjusting piston in a sleeve. The sleeve is connected to the streams of the reservoir on both sides and has a first and second lateral control opening. The pressure side of the displacement machine is connected with the first control opening and the suction side of the displacement machine is connected with the second control opening.
During operation, the adjusting pistons close the first and the second control openings in its two end positions and more or less close the two control openings in the two intermediate positions in countercurrent. Due to this, the rate of opening and closing of both valves is achieved with less construction costs. Space efficiency and accessibility are further improved if the sleeves of the control valve have a plane arrangement transversal to the revolution axis of the coupling in the area of the rotating insertions.
Another advantage of this invention is that the double-acting non-return valve consists of a tangential bore in a plane arrangement transversal to the revolution axis of the coupling and a locking device therein between the displacement machine and the pressure chamber. Both ends of the tangential bore are connected to the third and fourth openings of the displacement machine and its center point to the pressure chamber. In this way the valve is not influenced by the centrifugal force in case of minimal space requirement.

Speed-difference-dependent hydraulic coupling with control valves

Steyr-Daimler-Puch Fahrzeugtechnik AG and Co. KG


One aspect of the present invention includes a cover assembly for a floor box supporting at least one receptacle mounted therein. The assembly comprises at least one cover plate, at least one lid and a lock. The cover plate for at least partially covering the floor box includes at least one lock receiving channel. The at least one lid is pivotally secured to the cover plate for movement between a closed position covering the receptacle and an open position permitting access to the receptacle. The lock retains the lid in the closed position. Also, the lock is disposed at least partially within the channel and moveable between a locking position for retaining the lid in the closed position and at least one release position wherein the lid is not retained by the lock.

This invention related generally to floor box covers and more particularly to those covers employing one or more pivotally secured lids that cover the one or more receptacles mounted within the floor box.
Floor box covers with individual pivotal lids are quite well known in the art. Some examples of this can be found in U.S. Pat. No. 5,064,969, U.S. Pat. No. 6,114,623 and U.S. Pat. No. 6,790,084. As shown therein, a screwdriver or other tool is inserted into a notch located generally opposite the hinge and is used to pry the lid upwards thereby exposing one electrical socket underneath. They may or may not be latched or wedged in the closed position and hence it may not take much effort to raise them.
An improvement on this basic design is shown in U.S. Pat. No. 4,443,654, U.S. Pat. No. 5,422,434 and U.S. Pat. No. 6,179,634. In each of these patents the lid is even more securely restrained in the closed position should such be required, for example, to exert pressure on a gasket. This mechanical restraint takes the form of a screw head that has been modified so as to have a straight or flat edge. The screw is rotated to align the flat edge with the edge of the lid thereby enabling the lid to open. When the lid is to be locked closed, the screw is again rotated so that its round circumference now overlaps the edge of the lid thereby preventing the lid from opening. Obviously, such a design requires the use of a tool to rotate the screw as needed.
A different approach is shown in U.S. Pat. No. 4,770,643, U.S. Pat. No. 6,018,126 and U.S. Pat. No. 6,854,226. Each of these covers incorporates a sliding door that blocks the user from connecting a plug to the covered electrical fixture. To expose the fixture, the door must be slid back so that the prong openings in the door align with the prong openings in the fixture. These designs to not use pivotal lids as in the earlier examples.
U.S. Pat. No. 6,552,262 improves upon the above design in that it incorporates a pivotal lid along with a sliding door, both of which must be activated if the user is to access the covered fixture. Other versions of floor box covers are shown in U.S. Pat. No. 6,265,662 and U.S. Pat. No. 6,417,450. They rely upon either a bendable rod or a locking hook arrangement to retain a lid in place.
There is therefore a need for an improved floor box cover with a new means of latching or securing pivotal lids in the closed position as well as easily enabling their release. The lid(s) of such an improved cover should be useable without the need for tools or other implements that may be required to pry the lid upwards. Additionally, such a cover should have a latching mechanism that can operate multiple lids rather than there being a single mechanism for a single lid as previously taught. Further, a mechanism should be provided that, except for the immediate operation of releasing the lid, returns back to its normal position while the fixture is in use. Further still, a mechanism should be provided that can be easily closed and locked in that position by pressing down upon the lid, such as with a foot. Hence, there should be no need for the user to manipulate the device by hand to close and lock the lid as previously required. Additionally, the cover should be designed such that if the lid is inadvertently left in the open position, it will automatically become locked by simply stepping on the cover. These and many objects and advantages of this invention will become apparent upon further review and investigation.

Electrical floor box cover with slide locks


An apparatus comprises a main pole being configured to be operable to display at least one flag. At least one illumination source is disposed in a longitudinal length of the main pole. The illumination source is configured to at least illuminate a facing surface of the displayed flag. A switch mechanism is configured to be operable for activating and deactivating the illumination source.

The following background information may present examples of specific aspects of the prior art (e.g., without limitation, approaches, facts, or common wisdom) that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. It is believed that many individuals may wish to display a flag, banner or pennant on their vehicles or other items to show support for an activity, group, or person such as, but not limited to, a sports team, a school, a hobby, a child, a political candidate, etc. Furthermore, some of these individuals may wish to interchange multiple flags of different shapes, sizes, and designs on a single mounting device. In addition, one can expect that it may be desirable for some flags to be lit for improved visibility.
The following is an example of a specific aspect in the prior art that, while expected to be helpful to further educate the reader as to additional aspects of the prior art, is not to be construed as limiting the present invention, or any embodiments thereof, to anything stated or implied therein or inferred thereupon. By way of educational background, another aspect of the prior art generally useful to be aware of is that there are some currently available flag mounting systems that generally provide non-changeable, non-detachable vehicle or non-vehicle flag mounting systems where flags are typically interchanged along with entire pole assemblies so that consumers may need to buy multiple flags with attached pole systems to support multiple groups, people or objects.
In view of the foregoing, it is clear that these traditional techniques are not perfect and leave room for more optimal approaches.
Unless otherwise indicated illustrations in the figures are not necessarily drawn to scale.

Apparatus for displaying and illuminating a flag


The present invention is characterized in that oxides of Y, Ba and Cu having a superconductive substance-forming composition are melted, the melt is rapidly cooled and solidified, the obtained sheet is heated at a temperature of 1000.degree. to 1350.degree. C. to produce a partially melted state thereof, and the sheet is gradually cooled at a rate lower than 200.degree. C./hr, whereby a texture in which grains of the RE.sub.2 BaCuO.sub.5 phase having a diameter smaller than 20 .mu.m are dispersed in the REBa.sub.2 Cu.sub.3 O.sub.7-y phase is obtained.

Current research into the utilization of oxide superconductive materials is directed to the sintering process (see Jap. J. Appl. Phys., Vol. 26, No. 5, 1987, pages L624 through L626). According to this process, starting powders (RE, i.e., a rare earth element including Y and oxides or carbonates of Ba and Cu) are mixed at a predetermined composition of REBa.sub.2 Cu.sub.3 O.sub.7, the mixture is calcined to form a calcined powder having a structure of REBa.sub.2 Cu.sub.3 O.sub.7-y, and this calcined powder is then molded and sintered to obtain a superconductive material. As an application of this process, there can be mentioned research by Toshiba into the forming of a wire by packing the calcined powder into a metal cover or the like (Jap. J. Appl. Phys., Vol. 26, No. 5, 1987, pages L865 and L866). Moreover, a process has been attempted in which the calcined powder is molded into a plate and the plate is sintered to obtain a shielding material. These trials, however, have not been practically utilized because the critical current density of the sintered body is low.
The process in which the starting material is heat-melted at a high temperature and gradually cooled is not used for the preparation of a superconductive material, although used for the growth of a single crystal. In this case, in general, the starting powder containing a considerable excess of Cu or CuBa is grown in an alumina crucible. As a typical instance there can be mentioned research by NTT (Jap. J. Appl. Phys., Vol. 26, No. 5, 1987, pages L851 through L853).
In currently available superconductive materials such as sintered bodies, only current densities of several thousand A/cm.sup.2 are obtained at a temperature of 77 K. and an external magnetic field He of O T (Tesla), and thus they cannot be put to practical use. For a practical utilization, the current density must be increased to about 10.sup.4 A/cm.sup.2 at a temperature of 77 K. and an He of several T.
An object of the present invention is to improve the characteristics by using a melting process different from the conventional process for the production of a superconductive material, and to make it possible to practically utilize a superconductive material of the YBa.sub.2 Cu.sub.3 O.sub.7-y phase (hereinafter referred to as "123 phase").
The main problems to be solved to enable a practical utilization are as follows.
1) Improvement of the current density (Jc) in a zero magnetic field and a magnetic field.
2) Improvement of the shapeability into a wire, a coil, a plate and the like.
3) Improvement of the mechanical strength.
In a sintered body obtained according to the conventional sintering process, since the particle size is as fine as several microns to several hundred microns, many grain boundaries exist in the interior of the sintered body: These grain boundaries have a weak superconductivity, and a large superconductive current in particles is restricted and reduced at the grain boundaries. Accordingly, in the sintered body, the Jc is small, and is greatly reduced to scores of A/cm.sup.2 in a magnetic field. Furthermore, processing of the sintered body after the sintering and bonding of sintered bodies, is very difficult, and moreover, the sintered body is defective in that it is inherently brittle.

YBa.sub.2 Cu.sub.3 O.sub.7-y type oxide superconductive material containing dispersed Y.sub.2 BaCuO.sub.5 phase and having high critical current density


A head assembly 52,152 for a pulverized coal nozzle includes a turning vane 54 or a curved vane 154 disposed within a pipe elbow. The vanes 54,154 are angled relative to the inlet port and the outlet port of the pipe elbow to redirect a stream of air and pulverized solid fuel particles from the inlet port 60,160 toward the outlet port 62,162. The coal rope-breaking vane 56 is pivotable about an axis to adjust an angle of the vanes relative to a stream of air and pulverized solid fuel particles from the inlet port 60,160. An adjustment bar 66 may connect to the vanes 56 and extend outward through the pipe elbow to allow the vanes 56 to be adjusted while the pulverized solid fuel particles flow through the head assembly 52. The pipe elbow may further include inspection ports 68,168 and a removable cover 70,170. The vanes may be attached to the removable cover 70,170 thus allowing them to be easily removed and replaced.

The present invention relates to pulverized solid fuel (pulverized coal) delivery systems and, more particularly, to a fuel head assembly for use in a pulverized coal delivery system.
FIG. 1 depicts an example of a pulverized solid fuel-fired steam generator 10, which is shown to include a combustion chamber 14 within which the combustion of pulverized solid fuel (e.g., pulverized coal) and air is initiated. Hot gases that are produced from combustion of the pulverized coal and air rise upwardly in the steam generator 10 and give up heat to fluid passing through tubes (not shown) that in conventional fashion line the walls of the steam generator 10. The steam generated in the steam generator 10 may be made to flow to a turbine (not shown), such as used in a turbine/generator set (not shown), or for any other purpose.
The steam generator 10 may include one or more windboxes 20, which may be positioned in the corners or the sides of the steam generator 10. Each windbox 20 is provided with a plurality of air compartments 15 through which air supplied from a suitable source (e.g., a fan) is injected into the combustion chamber 14 of the steam generator 10. Also disposed in each windbox 20 is a plurality of fuel compartments 12, through which pulverized coal is injected into the combustion chamber 14 of the steam generator 10.
The pulverized coal is supplied to the fuel compartments 12 by a pulverized coal supply means 22, which includes a pulverizer 24 in fluid communication with the fuel compartments 12 via a plurality of pulverized solid fuel ducts 26. The pulverizer 24 is operatively connected to an air source (e.g., a fan), whereby the air stream generated by the air source transports the pulverized coal from the pulverizer 24, through the solid fuel ducts 26, through the fuel compartments 12, and into the combustion chamber 14.
FIG. 2 depicts a cross-sectional, elevation view of a conventional pulverized coal nozzle assembly 34 disposed within a fuel compartment 12. While only one fuel compartment 12 is shown, it will be appreciated that each fuel compartment 12 of FIG. 1 may include a nozzle assembly 34. The nozzle assembly 34 includes a nozzle tip 36, which protrudes into the combustion chamber 14, a fuel feed pipe 38, which extends through the fuel compartment 12 and a head assembly 40 by which the nozzle assembly 38 is coupled to the solid fuel duct 26. Typically, the head assembly 40 comprises an elbow that connects the substantially vertical solid fuel duct 26 with the substantially horizontal fuel feed pipe 38.
The nozzle tip 36 may have a double shell configuration, comprising an outer shell 39 and an inner shell 42. The inner shell 42 is coaxially disposed within the outer shell 39 to provide an annular space 44 between the inner and outer shells 42, 39. The inner shell 42 is connected to the fuel feed pipe 38 for feeding a stream of pulverized coal entrained in air through the fuel feed pipe 38 and the inner shell 42 into the combustion chamber 14 (FIG. 1). The annular space 44 feeds a stream of secondary air into the combustion chamber 14, which helps to cool the nozzle tip 36. While the nozzle tip 36 is shown as being separate and pivotable relative to the fuel feed pipe 38, it will be appreciated that the end of the fuel feed pipe 38 may instead be shaped to form a stationary nozzle tip.
Historically, pulverized coal boiler systems have had difficulty achieving uniform distribution of pulverized coal and transport air across the fuel duct 26 and nozzle assembly 34. Maldistribution is associated with the transport in a two phase flow system of a pulverized solid (e.g., coal) and gas (e.g., air). At each turn in the fuel duct 26, separation between the phases occurs. Finally, when the piping transitions from the vertical fuel duct 26 to horizontal nozzle assembly 34, a narrow, concentrated stream of coal, known as a "coal rope", has been established in certain portions of the cross section of the fuel feed pipe 38.
Each nozzle assembly 34 will have a different coal rope concentration and location depending on the upstream routing of the fuel duct 26 and other factors such as air and coal flow rates. This coal roping promotes localized erosion that accelerates wear and reduces component life. Coal roping also decreases the fuel/air mixing efficiency and, thus, decreases the efficiency of fuel combustion.
The coal ropes cause erosion where they contact the walls. They follow the airflow currents. In FIG. 2, the currents may cause the ropes to erode the walls of the fuel feed pipe 38. The fuel feed pipes 38 are located inside of the fuel compartments 12. These typically pass through the windbox. Therefore, it is very difficult to replace parts within the fuel feed pipe 38.
Other parts, such as the head assembly 40 are exposed and easier to access and maintain.
In the past, improving pulverized coal distribution through the horizontal nozzle assembly 34 was done with a device known as a coal rope breaker, which are typically mechanical devices disposed in the fuel feed pipe 38. For example, U.S. Pat. No. 6,105,516 describes multiple, transversely extending rib segments protruding into the fuel feed pipe portion of the nozzle, U.S. Pat. No. 5,526,758 describes a distribution half-cone mounted within a burner nozzle, and U.S. Pat. No. 5,588,380 describes a conical diffuser with angled support legs disposed along the coal nozzle axis. Another known method for breaking up coal ropes includes placing an orifice within the fuel feed pipe 38.
Experience and computer modeling has indicated that these coal rope breaking devices have had some success in redistributing the air, but little impact on the pulverized coal distribution within the nozzle. Furthermore, these coal rope-breaking devices add unwanted pressure drop to the pulverized coal delivery system. This pressure drop could have the potential of reducing or limiting the pulverizer system delivery capacity.
Thus, there is a need for a device that is easy to service and maintain that improves pulverized coal distribution through the burner nozzle assembly to eliminate or reduce the formation of coal ropes and the problems associated with coal ropes, while reducing the amount of unwanted pressure drop in the pulverized coal delivery system.

Coal rope distributor with replaceable wear components


In a network coupling redundant controllers to a control system, an electronic device is provided. The device comprises a first interface coupled to the control system addressed using a unique medium access control (MAC) address, a second interface coupled to a first redundant controller, and a third interface coupled to a second redundant controller. The device receives a first message via the first interface and transmits the first message via the second interface and via the third interface. The device receives a second message via the second interface and transmits the second message via the first interface. The device receives a third message via the third interface and transmits the third message via the first interface.

Process control systems may be implemented to automatically control industrial processes based on pre-defined logic and/or rules. Industrial processes may be carried out by motors, valves, heaters, pumps, and the like, which may be referred to as process devices or field devices, in manufacturing plants, refineries, food processing plants, and other plants. The process control systems may monitor parameters and/or properties of on-going processes by receiving outputs from sensors coupled to the processes, for example temperature sensors, pressure sensors, motion sensors, weight sensors, density sensors, flow rate sensors, and other sensors. Automated control devices, for example controllers, may adjust and control process devices based on the sensed parameters and properties based on pre-defined logic and/or command inputs from, for example, a human machine interface. To provide for higher reliability and/or safety, controllers may be deployed redundantly, such that a failure of one controller may be compensated for by another controller, for example by the other controller assuming responsibility for controlling the subject process.


Improved techniques for transmission and display of video data are described. A point of sale terminal includes a processor, memory and software executed by the processor to create frames of data and to analyze the frames of data to create differential data defining differences between preceding and succeeding frames of data. The differential data can be applied to the preceding frames to construct the succeeding frames. At least one frame is transmitted to an external video interface using an external connection such as a universal serial bus port. Differential data is also transmitted to the external video interface. The differential data is applied to the frame which has been transmitted in order to create succeeding frames. The frames of video data are displayed using a display connected to the video interface.

Visual displays of one kind or another have been present in point of sale terminals for many years. The steadily increasing sophistication of electronics used in point of sale terminals has increased the amount of visual information which may displayed. Retailer awareness of the ability of point of sale terminals to display large amounts of information has tended to increase the amount of information which retailers desire to display.
Modern point of sale terminal hardware and software can easily generate enough visual information to be displayed on multiple displays. For example, a terminal might have two displays, one displaying the details of the transaction and another displaying promotional messages. One point of constraint which tends to inhibit the use of multiple displays is that prior art terminals typically employ one of two techniques in order to drive multiple displays. One such technique is the use of multiple video cards, one video card for each display. This approach adds expense because an additional video card is added for each added display. In addition, each video card requires an expansion slot, making the slot unavailable for other uses. Another commonly used technique is the use of special video adapter cards which are designed to drive two or more displays. These cards tend to be expensive.
Modern point of sale terminals are typically built using computers such as personal computers. Personal computers typically provide one or more data output ports that may include serial ports, wireless interfaces and ports, universal serial bus ports and the like. The data output ports allow the computers to transmit data to and receive data from other devices. For example, the universal serial bus port is widely used and allows connection to a wide variety of different devices. However, version 1.1 of the universal serial bus port in particular does not provide sufficient bandwidth for acceptable driving of a display using typical prior art video technology which is cost effective from a customer point of view.
The use of additional hardware, or specialized, expensive hardware to enable a terminal to drive two or more displays limits the appeal of the terminal because retailers who need only a single display will not wish to pay for the added capability provided by a terminal that can drive two or more displays. However, it will be recognized that even retailers presently needing only one display may greatly desire the flexibility of adding one or more additional displays in the future if that flexibility is achieved at little or no additional cost for the initial purchase of the terminal. Furthermore, the retail business is a highly competitive and cost conscious so that even retailers wanting two or more displays will want them at the lowest possible cost. There exists, therefore, a need for techniques which allow a terminal to be optionally configured to drive two or more displays without a need to build additional hardware into the terminal, and which allow the terminal to transmit video data to two or more displays using standard output ports commonly included in computers used in point of sale terminals.

Methods and apparatus for improved display of visual data for point of sale terminals


A server computer identifies a cached document and its associated cache update history in response to a request or in anticipation of a request from a client computer. The server computer analyzes the document's cache update history to determine if the cached document is de facto fresh. If the cached document is de facto fresh, the server computer then transmits the cached document to the client computer. Independently, the server computer also fetches an instance of the document from another source like a web host and updates the document's cache update history using the fetched instance of the document.

To access a document (e.g., a webpage) on the Internet, a user must download the document from a document source to a client computer using a software application such as a web browser. A document source is typically a web host (sometimes called a web server) but can be a proxy server that prefetches the document from the web host. Upon receipt of a document request from a client, the proxy server first checks if the requested document has been prefetched and stored in its own cache. If not, the proxy server then fetches the requested document from the web host. Even if the requested document is found in the proxy server's cache, it may not be servable to the client if its content is no longer fresh. The freshness of a document's content is usually determined by an expiration timestamp value set by the content provider. If the current time is post the expiration timestamp, the document's content is deemed stale, and if the current time is prior to the expiration timestamp, the document's content is deemed current or not stale.
However, a document's expiration timestamp is not always an accurate prediction of the document content's freshness. For various reasons, there is often no content change to a document even a long time after its associated expiration timestamp is passed. As a result, a proxy server could waste resources downloading documents having identical contents as the ones currently in the proxy server's cache. Moreover, refreshing a document who content has not in fact changes may unnecessarily delay the rendering of the document by a requesting client.
In view of the foregoing, there is a need for new methods of determining the freshness of a cached document more accurately and thereby improving the performance of the proxy server as well as users' web browsing experience.

Systems and methods for cache optimization