An embodiment of a ruggedized interferometer is described that comprises a light source that generates a beam of light; a fixed mirror; a moving mirror that travels along a linear path; a beam splitter that directs a first portion of the beam of light to the fixed mirror and a second portion of the beam of light to the moving mirror, wherein the beam splitter recombines the first portion reflected from the fixed mirror and the second portion reflected from the moving mirror; and a servo control that applies a substantial degree of force to the moving mirror at initiation of a turnaround period, wherein the substantial degree of force is sufficient to redirect the moving mirror traveling at a high velocity to an opposite direction of travel on the linear path.

It is generally appreciated that Fourier Transform Infra Red (FTIR) Spectroscopy techniques provide excellent tools for measuring the concentrations of a large number (e.g. 20+) gasses simultaneously, in real-time. The term "real-time" as used herein typically refers to reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than delaying a report or action. Because of this FTIR has been an important technology for emissions monitoring industries, however there have been challenges to reliably use FTIR for certain portable or industrial applications in environments that produce forces that interfere with FTIR performance. One example of which includes a system to measure emissions of a vehicle in real-time while the vehicle is in motion and subject to forces acting on the instrument that may include vibrations, an aspect change of an instrument relative to gravity (e.g. tilt), change in momentum (e.g. acceleration/deceleration), etc. A specific example of such a system may be referred to as PEMS (portable emissions measurement system) for RDE (Real-Time Driving Emissions).
Those of ordinary skill understand that "interferometer" instruments that utilize FTIR technology typically include what is referred to as a modulator that can be extremely sensitive to vibrations, tilts, and other similar conditions. For example some interferometer embodiments are particularly susceptible to externally applied forces which can result in 1) introduction of aberrations into the data, yielding poor data quality; and/or 2) upset of the control system of the interferometer, causing it to stop scanning temporarily, yielding no data for several seconds. In some cases the externally applied forces could also prevent the instrument from starting to scan from a stopped or off position.
For a continuous measurement system, such as PEMS, it is extremely desirable for the interferometer to produce substantially uninterrupted data (e.g. as few data dropouts as possible) and of substantially equal quality to that which could be obtained in a laboratory environment. One particular type of interferometer, referred to as a "Michelson interferometer" can be configured in a cost effective and compact form desirable for PEMS applications, however Michelson interferometer embodiments typically suffer from issues that result from externally applied forces as described above. For example, a Michelson interferometer works by using a Beamsplitter to reflect and transmit incoming light. One beam path of light reflects off of a stationary mirror, and the other beam path of light reflects off of a moving mirror. These two beams recombine at the Beamsplitter and exit the interferometer. As the moving mirror oscillates back and forth, interference patterns between the two light beams create a modulated signal. This modulated light signal then interacts with a sample, and is finally measured by a detector. In addition, a laser beam of a fixed, known frequency is passed through the interferometer and detected with a separate detector. This laser signal is used to sample the modulated light at a known position spacing (e.g. 1 divided by the frequency of the laser), and the laser signal is also used to control the velocity of the moving mirror through a servo motor. This measured signal in position space is Fourier transformed, resulting in a spectrum in frequency space. Additional description of Michelson interferometers are discussed in "Fourier Transform Infrared Spectroscopy" by Griffiths and de Haseth (Griffiths, Peter R., and James A. De Haseth. Fourier Transform Infrared Spectroscopy. 2nd ed. Hoboken, N.J.: John Wiley & Sons, 2007), which is hereby incorporated by reference herein in its entirety for all purposes.
Those of ordinary skill in the related art appreciate that Michelson interferometer embodiments are very precise instruments and usually incorporate one or more mechanisms to address variations that can occur through physical and/or environmental fluctuations. For example, some embodiments include a dynamic alignment system that tilts the stationary mirror to account for minor misalignments in the interferometer, as well as to account for thermal drift of the interferometer. The dynamic alignment system typically has its own control system separate from the servo motor control system that controls the moving mirror. Both the dynamic alignment and servo motor control systems use the laser signal as the measurement, but in different ways. The moving mirror servo motor control system uses what are referred to as "zero-crossings" of the laser as a measurement of the velocity of the moving mirror. The dynamic alignment system typically uses three separate laser signals separated in the plane of the beam, and uses a control system to lock the phases of the three laser signals in place to some defined phase separation. Minor misalignments in the interferometer normally cause the phase separations of these laser signals to vary throughout the oscillations of the moving mirror. This well-known technique for Michelson Interferometers is described further in standard texts, such as Fourier Transform Infrared Spectroscopy by Griffiths and de Haseth, incorporated by reference above.
However, as described above even with the mechanisms that address physical and/or environmental variations typical Michelson interferometer embodiments do not address significant effects caused by externally applied forces such as, for example, those experienced in portable applications (e.g. for vehicles that include cars, trucks, aviation, etc.) or industrial applications (e.g. power plants or remote emissions monitoring stations with large fans or other devices that cause large vibrations). Further, it is very challenging to develop a Michelson interferometer embodiment that addresses substantial effects caused by externally applied forces in a simple and cost effective manner. For example, those of ordinary skill in the art appreciate that technologies that include what may be referred to as "Quadrature" technologies exist that could address some effects caused by externally applied forces. However, the level of complexity and cost associated with such technologies is prohibitive to portable and industrial applications.
Therefore, there is a need for an improved design of an interferometer that makes it more resistant to externally applied forces in a relatively simple and inexpensive manner.

System and method for an interferometer resistant to externally applied forces

THERMO ELECTRON SCIENTIFIC INSTRUMENTS LLC


This invention is to disclose and claim an open ended light weight molded plastic horseshoe having a core segment of 60% glass fiber reinforced polyurethane plastic molding compound, encapsulated in clear polyurethane having treads and caulks formed on the earth side of the horseshoe. The core segment provides the rigidity for the horseshoe while the encapsulating clear polyurethane provides cushioning and wear properties. The core segment has integrally molded button protrusions on the hoof side surface, the earth side surface, and on the inner and outer edges of the legs.

This invention pertains to horseshoes particularly the method of manufacture of non-metallic light-weight molded plastic horseshoes.
The problems encountered with metal horseshoes are well documented in the literature as noted in the patents cited in the background art noted below.
This invention discloses a method of manufacture of a plastic horseshoe which is light in weight, being about one quarter to one-sixth of the weight of an iron horseshoe, and further this plastic horseshoe is rigid, and formed to the hoof by sizing in manufacture, not flexing of the shoe.
Flexing of the shoe is stated for example in U.S. Pat. No. 4,496,002, where the shoe is fitted to the hoof by cold forming.
Many of the so called horseshoes molded of plastic have a closed heel end or are otherwise described as ring like plates, to prevent outward flexing of the hoof (see U.S. Pat. No. 3,490,536).
The molded plastic horsehoe of this invention is of such rigidity to not require a closed heel, but yet allow spread of the hoof heel, on the shoe hoof surface.
The horseshoe of this invention is mounted on a hoof by conventional nails driven through holes between the treads and at the toe caulk, and the head of the nails bottoming on the core segment.

Plastic molded horseshoe and method of manufacture


A contact structure for a vacuum circuit breaker has an electrically insulating vacuum vessel, fixed and movable contact units sealed in the vacuum vessel and shield members surrounding the fixed and movable contact units in the vacuum vessel. Particles of a metal are applied to at least a part of the inner surface of the vacuum vessel.

The present invention relates to a contact structure for a vacuum circuit breaker used for temporarily interrupting power supplying when an abnormality occurs in power substations, factories and other buildings.
As shown in FIG. 1, a conventional contact structure for a vacuum circuit breaker comprises two electrically insulating cylindrical members 1a-1, 1a-2 which are axially disposed and end plates 2 and 3, provided at outer ends of the cylindrical members 1a-1 and 1a-2, respectively, for forming an evacuated vacuum vessel 1. A fixed contact 4 is connected with a first end portion of an electrically conductive rod 4a having a second end portion which passes through the end plate 2 in an airtight manner. A movable contact 5 is connected with a first end portion of an electrically conductive rod 5a having a second end portion which is movably and hermetically sealed to the end plate 3 through bellows 6. The fixed contact 4 and the conductive rod 4a form a fixed contact unit while the movable contact 5 and the conductive rod 5a form a movable contact unit.
A first end shield member 7-1 is provided for the fixed contact 4. A central shield member 8 is provided in the center of the vacuum vessel 1. A second end shield member 7-2 is provided for the movable contact 5. In other words, the central shield member 8 surrounds the first end portions of the conductive rods 4a and 5a and the contacts 4 and 5. The first end shield member 7-1 surrounds the second end portion of the conductive rod 4a. The second end shield member 7-2 surrounds the second end portion of the conductive rod 5a. These shield members 7-1 and 7-2 play an important role to prevent the vapor of a metal generated between the contacts 4 and 5 on current interruption from being deposited upon the inner wall of the vacuum vessel 1. However, the breakdown voltage is lowered since the electrically insulating cylindrical members 1a-1, 1a-2 are disposed in the vicinity of the end shield members 7-1, 7-2 and the central shield member 8. This is due to a fact that a secondary electron avalanche takes place on the inner surfaces of the insulating cylindrical embers 1a-1 and 1a-2 when a high voltage is applied to the contact structure. A countermeasure against this has been proposed that wherein the insulating cylindrical members 1a-1 and 1a-2 are coated on the inner side thereof with a material having a secondary electron emission efficiency .delta. not greater than 1 such as chromium oxide (Cr.sub.2 O.sub.3). For example, refer to JP-A-60-93721 (laid-open May 25, 1985). A method has been proposed in which the insulating cylindrical members 1a-1 and 1a-2 are coated with films of chromium oxide 1b-1 and 1b-2, respectively only on the inner side thereof facing a gap between the central shield member 8 and the end shield members 7-1 and 7-2. The coating film is 0.1 .mu.m to 5 .mu.m in thickness and the coating is performed by vacuum deposition or sputtering. This enables the electric charges on the inner side of the insulating cylindrical members 1a-1 and 1a-2 to be neutralized for increasing the breakdown voltage and the period of time required for the coating process to be shortened and can provide a contact structure for a vacuum circuit breaker which is economical and has a high blocking voltage and a high capacity.
The resistivity of chromium oxide at room temperatures is in the order of 10.sup.3 .OMEGA.cm. If the insulating cylindrical member is coated with chromium oxide on the inner side facing the gap between the central shield member 8 and the end shield members 7-1 and 7-2 to form a coating layer having a thickness of 0.1 .mu.m to 5 .mu.m, the electric resistance of the coating layer is generally not higher than 10M.OMEGA.. The electrons emitted from the central shield member 8 and the end shield members 7-1 and 7-2, in particular from the end thereof will impinge upon the surface of the chromium oxide layers 1b-1 and 1b-2 to elevate the temperature on the surface thereof. Chromium oxide has negative temperature characteristics in which the resistivity is lowered with an increase of the temperature. The surface temperature of the layers 1b-1 and 1b-2 will be elevated due to collision with electrons when the contact structure is in operation with a voltage applied thereto, and the electric resistance of the chromium layer will be further lowered. If an overvoltage is applied to the contact structure of the vacuum circuit breaker which is kept in operation with a voltage applied thereto for a long period of time, no flashover occurs at an initial stage, but a flashover may occur between the central shield member 8 and the end shield members 7-1 and 7-2 via the chromium oxide layers 1b-1 and 1b-2.
Meanwhile, if coating with chromium oxide is achieved by vacuum deposition or sputtering, a large amount of impurities will be generated inside of an evaporation apparatus or a sputtering apparatus, so that the life time of the apparatus may be shortened. The melting point of chromium oxide is as high as 2320.degree. C. A relatively long period of time is required to perform a coating by vacuum deposition or sputtering. Coating with chromium oxide thus has various problems.

Contact structure for vacuum circuit breaker


This invention relates to an attenuation control system (9) in a switching power conversion system comprising a digital modulator (4), for generating a modulated control signal from a (digital) source signal and a switching power state (6), said attenuation control system comprising: means for digitally attenuating the modulated signal, first gain shifting means (7) for shifting a supply voltage of said power stage between a plurality of predefined voltage levels, said first gain shifting means being arranged to decrease the power stage gain when the attenuation of the modulated signal exceeds a predefined level. This invention also relates to an attenuating method in a switching power conversion system comprising a digital modulator, for generating a modulated control signal from a (digital) source signal, and a switching power stage.

The attenuation control system (i.e. volume control in an audio amplification system) can be a central element of a digital power conversion system.
Most digital controlled power converters are based on a digital modulator that converts a pulse code modulated signals (PCM), received from a source such as a CD-player, to (E.G) pulse width modulated signals (digital PWM modulator). Alternatively the modulator is analog and is preceded by a D/A converter.
The output signal of the digital modulator is fed to a power stage where it is amplified. A typical power converter includes a switching power conversion stage, a filter and a control system.
The digital input of the modulator, i.e. the digital source, can be represented as any given bit frame length, giving a constant dynamic range. An attenuation in the digital domain, as shown in FIG. 1, will compromise the dynamic range of the attenuated digital signal, since the effective bit frame length will be reduced in order to reduce the signal amplitude. Attenuation in the power stage, on the other hand, will not compromise the digital dynamic range.
Noise and distortion contributions in a digital PMA (pulse modulated amplifier) can be caused by inaccuracy of the rising and trailing edges of the pulses in the power stage. An attenuation of the power stage output PWM signal amplitude will retain the dynamic range of the modulated signal, since the noise in the output pulse signals will be equally attenuated.
A general problem in a switching output power stage is the Electro Magnetic Compatibility (EMC), caused by the generally high amplitude of the power stage output PWM signal. In a conventional PMA, the modulation depth is lower at attenuated levels of the digital signal, so that the amplitude of the demodulated signal (i.e. the low pass filtered amplifier output) will be low compared to the amplitude of the power stage output PWM signal. A higher modulation depth combined with lower amplitude of the PWM signal can result in the same modulated signal, but would reduce the EMC problems.
The efficiency of a power stage generally declines when the modulation depth is lowered. This effect is a result of a decreasing ratio between the amplitude of the demodulated, low pass filtered output signal and the amplitude of the power stage output PWM signal. A higher modulation depth combined with lower amplitude of the PWM signal can retain the same modulated signal, but will increase the efficiency and dynamic range.
Therefore, it is desirable to effect attenuation in the power stage, as shown in FIG. 2. A digital amplifier system including attenuation control is described in U.S. Pat. No. 5,898,340. However, this system includes a complex power stage voltage supply, with an output voltage variable in a wide range. A system with a power supply that can change the output voltage continuously within a wide voltage range is very complex and thereby expensive. The mentioned system also includes A/D conversion means in the feedback path from the analog output. This will increase the complexity of the system further.

Attenuation control for digital power converters


A system for identifying specific instances of objects in a three-dimensional (3D) scene, comprising: a camera for capturing an image of multiple objects at a site; at least one processor executable to: use a location and orientation of the camera to create a 3D model of the site including multiple instances of objects expected to be in proximity to the camera, and generate multiple candidate clusters each representing a different projection of the 3D model, detect at least two objects in the image, and determine a spatial configuration for each detected object; and match the detected image objects to one of the multiple candidate cluster using the spatial configurations, associate the detected objects with the expected object instances of the matched cluster, and retrieve information of one of the detected objects that is stored with the associated expected object instance; and a head-wearable display configured to display the information.

The invention relates to the field of three-dimensional object recognition.
Complex industrial settings often have many installations of similar instruments, such that identifying a particular instance of an instrument for servicing, maintenance or repair can prove challenging. Although visual markers, such as barcodes, QR codes, or RFID tags allow uniquely identifying different instruments in such settings, these solutions are often impractical in a large and complex setting due to the significant overhead required to install numerous tags. Moreover, harsh industrial environments can cause these tags to fade or corrode, requiring their regular replacement and maintenance, adding to the cost of implementing such systems.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.

Object instance identification using three-dimensional spatial configuration

International Business Machines Corporation


This invention relates to regeneration of coked catalyst by combustion so that the catalyst can be reused in a hydrocarbon conversion reaction. The completion of coke burn is generally measured with a combination of temperature or change in oxygen concentration. Dropping outlet temperatures require time to wait for increases in inlet temperature to correspondingly move down the regenerator. Faster response times might be expected from increasing oxygen concentration, but a small increase in concentration can lead to a significant increase in peak burn temperature which negatively impacts catalyst life. Controlled peak burning is difficult over the entire bed by merely controlling inlet and outlet oxygen concentrations. The invention accordingly combines a measured lag time for temperature travel with an inlet temperature ramping step to ensure complete coke combustion with high oxygen efficiency, thus providing a rapid regeneration that permits more time for operation at desired reaction conditions.

Catalytic processes for the conversion of hydrocarbons are well known and extensively used. Invariably the catalysts used in these processes become deactivated for one or more reasons. Where the accumulation of coke deposits causes the deactivation, reconditioning of the catalyst to remove coke deposits restores the activity of the catalyst. Coke is normally removed from catalyst by contact of the coke-containing catalyst at high temperature with an oxygen-containing gas to combust and to remove the coke in a regeneration process. These processes can be carried out in-situ within a fixed-bed or the catalyst may be removed from a vessel in which the hydrocarbon conversion takes place and transported to a separate regeneration zone for coke removal. Arrangements for continuously or semi-continuously removing catalyst particles from a reaction zone and for coke removal in a regeneration zone are well known.
In a continuous or semi-continuous regeneration process, coke laden particles are at least periodically added and withdrawn from a bed of catalyst in which the coke is combusted. In those processes having an essentially linear progression of catalyst particles through the bed and a transverse flow of oxidizing gas coke combustion, there are regions of intense burning that extend through portions of the catalyst bed.
In a fixed-bed or batch process, coke laden particles are likewise subjected to a flow of oxidizing gas, but the gas is flowed axially through the bed instead of the particles being flowed through the gas. Similarly, there is a region of intense burning as gas travels down the bed with rising temperature as oxygen in the gas is consumed.
These regions of intense burning are important for complete coke removal, but are also difficult to control in a time efficient manner. Typically coke removal takes a significant amount of time to complete. Any extra time used to ensure complete combustion leads to production losses in an existing regenerator unit with less available reconditioned catalyst, which would otherwise be used for valuable hydrocarbon conversion reactions. Investment losses also occur for oversized equipment built at a larger size than necessary for a new regenerator unit.
For a fixed-bed regeneration process, the completion of coke burn is generally measured with a combination of bed temperature or change in oxygen concentration. Once satisfactory burn criteria have been met, a proof burn is conducted by increasing the regenerator temperature or the oxygen concentration. However, the measurement of the parameters outside the regenerator to set criteria for end of burn require scrutiny in order to avoid regenerator outlet temperature dropping below the peak burn temperature or outlet oxygen concentration increasing, which reflects dropping oxygen utilization. Dropping outlet temperatures require additional lag time to wait for increases in inlet temperature to correspondingly move down the regenerator.
Faster response times can be expected from increasing oxygen concentration, but a small increase in concentration can lead to a significant increase in peak burn temperature. Some beds have low flow areas where oxygen in the effluent can increase, while the low flow area continues to consume all of the available oxygen, thus making controlled peak burning difficult over the entire bed by merely controlling inlet and outlet oxygen concentrations.
Another problem associated with localized regions of intense coke combustion is catalyst deactivation. Exposure of high surface area catalyst to high temperatures for prolonged periods of time will create a more amorphous material having a reduced surface area which in turn lowers the activity of the catalyst until it reaches a level where it is considered deactivated. Deactivation of this type is permanent, thereby rendering the catalyst unusable. When moisture is present—water is a by-product of the coke combustion—the deactivating effects of high temperature exposure are compounded.
The combination of temperature, water vapor, and exposure time determine useful life of the catalyst. The burning of coke in localized portions of a catalyst bed has the deleterious effect of heating gases and generating moisture that pass through downstream portions of the bed and extend the high temperature exposure time of catalyst particles in the bed.
U.S. Pat. No. 3,753,926 discloses a method for regenerating a hydrocarbon conversion catalyst comprising rhenium using two carbon burning steps, where the first step is at a relatively low temperature with a small amount of oxygen and the second step is at a relatively higher temperature and a relatively higher amount of oxygen.
U.S. Pat. No. 4,507,397 discloses a sulfur removal step in a semi-continuous regeneration process prior to carbonaceous deposit oxidation. U.S. Pat. No. 4,810,683 discloses a method for regenerating a platinum containing zeolite. U.S. Pat. No. 5,155,075 discloses a low temperature method for regeneration of a platinum containing zeolite that uses a halogen-free oxygen gas.
U.S. Pat. No. 4,859,643 discloses a method for regenerating coke-contaminated catalyst particles that confines particles in the combustion section of a regenerator zone to a tapered bed configuration, which achieves better utilization of oxygen and minimizes surface area loss of the catalyst. This patent ('643) is hereby incorporated by reference into this patent application.
U.S. Pat. No. 5,001,095 discloses a method for improving a coke combustion process by segregating flue gas from the process into a high moisture content portion that is removed and a low moisture content portion that is recycled to the process.
U.S. Pat. No. 5,151,392 discloses a moving bed regeneration process with separate dispersion and chloriding steps following a coke combustion zone, which allows improved platinum re-dispersion by controlling chloride equilibrium with either oxygen-enriched or oxygen-depleted environments.
U.S. Pat. No. 5,854,162 discloses an offsite regeneration process using a moving bed furnace for a combustion step similar for used hydro-treatment catalysts, and adds a oxy-halogenation step in a sealed rotating furnace that avoids the onset of gas channeling, which improves the homogeneity of catalyst halogenation.
U.S. Pat. No. 5,965,473 discloses a method for reducing chloride emissions from a cyclic regeneration operation while saving operating costs.
U.S. Pat. No. 6,103,652 discloses a staged combustion process and apparatus for regenerating a catalyst in a moving bed that includes at least two separate successive combustion zones.

Regeneration method with efficient oxygen utilization


A diaphragm/spring operated pressure relief valve having a sensing passage of substantially the same flow area as the outlet orifice of the valve whereby failure of either diaphragm results in "fail open" configuration with the addition of a sensing inlet shroud located to capture the total pressure at the inlet and channel it to the sensing chamber to allow the valve to relieve full rated capacity in the event the sensing diaphragm is ruptured.

1. Field of the Invention
The present invention relates to a diaphragm/spring actuated pressure relief valve or back-pressure regulator that is pressure balanced against the outlet pressure for use on tanks where the outlet may be exposed to a pressure or vacuum that can vary in magnitude having improved pressure sensing.
2. Related Art
There are many types of diaphragm/spring actuated pressure relief valves.
The outlet ports of two such commercial valves are unbalanced against outlet pressure, i.e., the opening point of the valves are affected (changed) by the amount of pressure or vacuum on the outlet side due to the valve seat being biased to the outlet pressure. If the diaphragm of either valve ruptures, the spring will keep the valve closed and it will not be able to relieve the full rated capacity of the valve. The most that one of these valves can relieve is the amount that can flow through the small passageway(s) that leads to the diaphragm chamber. In the other valve the maximum relief capacity is whatever can flow through the small threaded port in the spring bonnet, assuming the internal passageways are larger than the spring bonnet port.
A third valve type utilizes a balancing diaphragm to overcome the effects of varying outlet pressure. If the main diaphragm ruptures, the spring will keep the valve closed and it will not be able to relieve the full rated capacity of the main valve. The most that the valve can relieve is the amount that can flow through the relatively small passageways leading to the main diaphragm. Therefore a ruptured main diaphragm can be hazardous and compromise the safety of the system that the valve is intended to protect by not being able to relieve the unwanted pressure build-up.
One of the criteria of determining how well a pressure relief valve performs is the amount of "overpressure" or accumulation required to achieve a certain relieving capacity. "Overpressure" or accumulation is that increment of pressure higher than the set pressure, which is the pressure at which the valve begins to open. Most relief valves that bear the ASME UV stamp, whether they are spring loaded or pilot operated, are rated for capacity at 10% overpressure. Weight loaded tank vents, valves that are closed by a weighted cover over the opening, require a significant overpressure to have meaningful flow for its size. At 10% overpressure weight loaded tank vents do not flow much. Some designs require as much as 50% to over 100% overpressure for significant flow. Prior designs of weight or spring loaded pressure relief valves are not able to open very wide at relatively small overpressures because when the valve opens and relieves, the full tank pressure is not communicated to the sensing chamber or seat due to pressure drops along the sensing path. A smaller more efficient valve can often times be used in place of a larger valve of lower efficiency resulting in savings in cost, weight, and space requirements, with associated benefits.
U.S. Pat. No. 5,845,675 discloses a diaphragm/spring operated pressure relief valve having a sensing passage of substantially the same flow area as the outlet orifice of the valve whereby failure of either diaphragm results in "fail open" configuration. The present diaphragm/spring actuated pressure relief valve uses the same features of U.S. Pat. No. 5,845,675 with the addition of a shrouded sensing inlet located to capture the total pressure at the valve inlet and channel it to the sensing chamber. This arrangement reduces the pressure drop along the sensing path which allows the sensing diaphragm to more accurately sense the tank pressure and lift open the valve seat wider when an increase in tank pressure is sensed, thereby improving the performance of the valve.

Diaphragm actuated pressure relief valve with pressure balanced outlet and fail-safe operation


Mechanism (10) for removably securing a die (22) to the flange (18) of a discharge (14) of a cooker (12) is disclosed including first and second connector rings (30, 56). The first connector ring (30) is rotatably mounted to the flange (18) of the cooker (12) by its securement to C-shaped carrier members (38) rotatably mounted to C-shaped collar members (32) secured to the flange (18). The first connector ring (30) includes a plurality of circumferentially spaced, wedge-shaped teeth (46) extending radially inwardly. The second connector ring (56) is secured to the flange (24) of the die (22) and includes a plurality of circumferentially spaced, wedge-shaped teeth (66) extending radially outward. The second connector ring (56) is axially movable such that the teeth (66) thereof pass axially between the teeth (46) of the first connector ring (30) in an unlocked position. The first connector ring (30) can be rotated by a hydraulic cylinder (52) to a locked position with the teeth (46, 66) of the connector rings (30, 56) axially abutting and camming the flanges (18, 24) of the cooker (12) and the die (22) together to secure the die (22) to the cooker (12).

The present invention generally relates to mechanisms for removably securing a die to the discharge of a cooker and particularly relates to mechanisms for allowing the quick and easy change of a die to the discharge of a cooker.
During the normal operation of a cooker/extruder, it becomes necessary and/or desirable to change the die from which the extrudate passes from the cooker. For example, the die often becomes plugged, requiring it to be replaced with a clean one. Similarly, the die may be replaced with a die extruding extrudates of a differing configuration and/or size. Conventionally, dies were secured to cookers by a plurality of fasteners which were required to be removed and replaced each time the die was desired to be replaced. In addition to being very time consuming, removal and replacement of such fasteners typically required several personnel including mechanics. Further, in addition to personnel costs, the time required to replace the die takes the cooker out of production and loses the steady state conditions for the cooker, with the amount of recovery time to steady state conditions being directly dependent on the time that the cooker is down.
Thus, a need exists for a mechanism that allows for the removable securement of the die to the cooker which does not require the removal and replacement of a plurality of fasteners and which reduces the time and personnel required to replace the die.
It is thus an object of the present invention to provide a novel mechanism for removably securing a die to a cooker.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism which does not require fasteners between the flange of the cooker and the die.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism which reduces the time to replace the die.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism which reduces the personnel required to replace the die.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism resulting in improved product quality due to more frequent die changes.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism resulting in quicker system start-ups such as following down weekends.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism requiring less downtime in replacing dies.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism resulting in increased productivity.
It is further an object of the present invention to provide such a novel cooker die removably securing mechanism having reduced ingredient losses.


Apparatus for controlling and adjusting an arbitrary number of adjustment units for a motor vehicle includes an electro-pneumatic bus to which are connected in arbitrary sequence, both electrically and pneumatically, all the pertinent adjusting units. The electro-pneumatic bus is composed of at least one pneumatic adjustment pressure line and of at least one electric control signal line which may contain several conductors. While reference data from a central control electronics are applied through the electric control signal line of the electro-pneumatic bus, the individual adjusting units are connected through associated valves in the pneumatic system to the pneumatic adjustment pressure line of the electro-pneumatic bus. The adjusting units preferably are designed to be modular control loops. As a result the pneumatically driven adjusting members units not only two positions, but also they may be set and controlled in quasi-analogue manner.

The invention relates to apparatus for controlling adjustment units and, in particular for controlling several such adjustment units.
In particular the invention concerns apparatus for controlling adjusting members and setting adjustment units in motor vehicles. Illustratively such adjustment units are flaps, sliders or valves of for many diverse kinds, illustratively car air conditioners, locks of all sorts, for instance a central locking system, or adjustment mechanisms such as headlight beam controls or seat adjustments.
Adjustment units of this sort are typically controlled and operated either pneumatically or electrically in motor vehicles.
Electric-motor driven apparatus for control and adjustment require an expensive set of components and tend to drain the electric power supply of the motor vehicle.
Pneumatically controlling and adjusting apparatus are more economical than those driven by electric motors and operate quietly and reliably. Additionally, pneumatic systems do not drain the motor vehicle power supply. However, the complex pneumatic line system entails substantial assembly work, and as a rule such apparatus can assume only two positions of the adjusting members.
The state of this art also includes a known locking system combining electric and pneumatic control-and-adjustment wherein the individual adjusting members are each fitted with electrically driven pumps which upon actuation generate the required adjustment pressure to the adjusting members. While such a design may save the assembly labor required for the pneumatic line system, it does not reduce costs or operational noise.
In the light of this state of the art, it is the object of the present invention to create an apparatus for controlling and adjusting at least one and preferably several adjusting members, particularly for motor vehicles, said apparatus being compact and demanding only little assembly work and making possible also intermediate positions using pneumatic drive means.


There is disclosed a high density test probe assembly, and method of fabricating it. The probe assembly has a multitude of wire-like probe elements whose exposed tips are spaced on centers X and Y to match the centers of closely spaced surface pads of a VLSI circuit. Interconnections to and from the probe elements (for connection to external test equipment) are provided by a multi-layer arrangement of insulating and conducting layers within the body of the probe assembly. The tips of the probe elements are canted relative to vertical so that when the probe assembly is pushed down into mating position onto a VLSI circuit, the probe elements uniformly deflect laterally in one direction only and give a "wiping" action in contacting surface pads of the VLSI circuit together with a desired normal contact force. The method of fabricating the probe assembly includes forcing all of the probe elements through staggered vias in the multilayer arrangement. This step simultaneously makes desired electrical interconnections to the probe elements, precisely aligns and captivates the probe elements, and bends (cants) their ends so that they deflect uniformly in one direction only when the probe assembly is mated with a VLSI circuit.

In the past decade the density per unit area of electronic devices, such as very large scale integrated (VLSI) circuits, has greatly increased. By some estimates this increase in density has been on the order of 10,000 times what it was earlier. The space or area available with a VLSI circuit in which to make the large number of necessary connections to and from it and other circuitry is becoming almost vanishingly small measured by previous standards. As a result, there is now a difficult problem in providing easily mateable connections to and from the VLSI circuits when they are being tested, which connections are also small enough to fit the minute spaces available, and which are reliable and easily manufacturable.
In the present inventor Walsh's U.S. Pat. No. 4,554,506, which has an assignee in common with the present patent application, there is disclosed a modular probe assembly for use in testing VLSI circuits. This probe assembly utilizes a large number of relatively very long thin wire contact "beams" mounted in holes on close centers around the sides of plastic guide elements. These guide elements are stacked together vertically into an assembly. The holes in the guide elements are intentionally not aligned vertically in order to "bow" or pre-buckle each of the contact beams. This pre-buckling helps control the force of each contact beam when its end contacts and wipes against a surface pad on a VLSI circuit. The contact beams are permitted to flex dynamically near their lengthwise mid-points when the beams are pressed into contact with the surface pads of the VLSI circuit. In actual practice, because of the relatively large degree of dynamic flexing of the contact beams and in order to insure that they do not touch each other and cause electrical short-circuits, the beams were made of thin, pre-insulated wires. By way of example, the wires were about 4 mils in diameter with about one mil of insulation (such as polyimide). It has been found however that occasionally some of the insulation on the wires in the vicinity of their ends rubs off and comes between the ends and the contact pads on a VSLI circuit under test. This causes erratic electrical results and necessitated careful and regular cleaning of the contact beams.
As VLSI circuits have become even more dense, it has become desirable to provide contact "beams" or elements of a probe assembly throughout an area rather than merely around the periphery of the test probe assembly. But this in turn leads to the problem of making individual electrical connections from other circuitry (e.g., test equipment) to each of the densely packed contact elements of the probe assembly. By way of example, there may be a density of 10,000 or more surface pads per square inch of area of a VLSI circuit with the corresponding need to space the contact elements of a probe assembly on 10 mil or closer centers in both the "X" and "Y" directions. It is desirable to provide an effective and economical solution to this need.

International Business Machines Corporation


There is provided an image processing apparatus for approximating the contour of a character or the like by a set of function curves or straight lines, thereby compressing the image data by contour decision information. This apparatus comprises: a designating section to designate a curve portion of a contour line; a section to obtain slopes and coordinates of the curve portion at the initial and terminative points thereof or of each interval which is obtained by dividing the curve portion designated by the designating section; a section to determine a dividing point in the interval or on the curve portion; a section to obtain the coordinates of the dividing point; an approximating section to approximate the curve portion on the basis of the slopes of the curve portion and on the basis of the coordinates of the initial and terminative points and the dividing point; and a coder to encode the codes corresponding to the coordinates of a plurality of special points on the approximated curve into the coded data of the curve or interval. The approximating section performs the curve approximation by using a Bezier cubic curve and stores as the contour data of four special points on the Bezier cubic curve. Thus, the contour of image data can be approximated at a high speed and the image data can be easily compressed.

1. Field of the Invention
The present invention relates to a compressing system of image data including characters and the like and, more particularly, to an image processing apparatus in which a contour of a character or the like is approximated by a set of functional curves or straight lines and the image data is compressed by the contour decision information.
2. Related Background Art
It is well known that an amount of dot data which is obtained by dividing image data of a character or the like into dots is extremely large. Therefore, in order to compress such a large quantity of data and then store or transmit the compressed data, various kinds of data compressing methods have been proposed. The shape of character or the like is detected as a contour and the contour decision information is stored, thereby compressing the data amount. For example, there are known: a straight line approximating method disclosed in Japanese Patent Laid-Open Applications Nos. 149522/1979 and 79154/1980; an n-degree curve approximating method disclosed in Japanese Patent Laid-open Nos. 39963/1982, 134745/1983, and 75976/1985; and the like.
However, according to the former straight line approximating method, smoothness of the contour is not assured. On the other hand, according to the latter n-degree curve approximating method, although smoothness of a curve is ensured, it is complicated to convert the functional equations to the curve, so that it takes a long time to generate the curve. Therefore, this method has the drawback that it cannot be practically used in a high speed display device such as CRT or laser beam printer in terms of the processing speed. To solve this drawback, there is known a method using a Bezier cubic curve which can generate a curve at a high speed. However, according to this method, since a method of forming an approximation to a given curve has not been established yet, there is a problem in that the approximation is difficult.

Image processing apparatus capable of efficient coding of complex shape information


This invention is generally directed toward a method for producing metallocene catalyst systems. Specifically, the method involves removing solid impurities from a solution of activated metallocene wherein activation has the effect of solubilizing the metallocene but not the impurities. The resulting catalyst system is higher in activity and produces polymer having excellent particle morphology with little or no reactor fouling.

Metallocene catalyst systems are extensivily used in a variety of polymerization systems. Typically, these systems include two components, the metallocene component and activator component. A problem associated with metallocene catalyst systems is the presence of impurities which detrimentally effect catalyst performance and polymer particle morphology. Among the most common impurities associated with the metallocene component are metal salts which are either formed or remain unreacted during the metallocene synthesis. The detrimental effect of these impurities is generally not recognized.
Removing these impurities or preventing their formation during metallocene synthesis presents a number of difficulties such as reduced yield of metallocenes, use of large volumes of solvent, and an overall increase in expense. For example, U.S. Pat. No. 5,302,733 describes a lengthy synthesis involving filtration, extraction, separation, evaporation, and/or recrystallization steps to isolate racemic metallocene isomers of interest. The metallocene compound recovered is reported as being substantially free of alkali metal salt by-product. Removing metal salts and other contaminants after metallocene compound synthesis would be difficult because many metallocene compounds along with the impurities typically associated with such compounds are sparingly soluble or less in hydrocarbon solvents thus making purification impractical. Therefore, there exists a need for a simple post synthesis method of purification which enhances polymerization performance and is cost effective.

Method for preparing metallocene catalyst systems


A temperature compensating outdoor wall padding apparatus in one embodiment incorporates a stretch fabric into the edges of a vinyl cover to provide a tension on the vinyl cover minimizing the possibility of wrinkling of the vinyl cover due to a change in temperature. In another embodiment, the temperature compensating outdoor wall padding apparatus may employ a resilient cover, stretchable in 4 directions and pre-tensioned to provide tension on the resilient cover minimizing the possibility of wrinkling of the resilient cover due to a change in temperature. Methods for forming the same are also disclosed.

Outdoor stadium wall padding has been a fixture since the 1970's, protecting athletes at all levels from dangerous impacts with solid wood and/or concrete walls. The padding is typically constructed of 3 materials, a ¾-inch plywood backer board, a 3-inch polyurethane foam padding adhered to the board, and a laminated or coated UV resistant vinyl cover. This construction provides an appropriate level of safety and durability while addressing the aesthetics required by both college and professional teams. In today's era of nationally televised day and night games, it is important that the aesthetics are maintained regardless of weather/temperature or time of day.
During the cool spring and fall evenings found in the Northeast and Midwest and other geographic areas, temperatures can drop downwards 30 degrees Fahrenheit to 40 degrees Fahrenheit in a few hours. This significant variation in temperature forces the padding to contract, with the padding reacting quicker than the vinyl covering, creating a wrinkling or sagging effect in the vinyl. This wrinkling condition is temporary at best, with recovery occurring during the next warming cycle.
There is a need for further wall padding for outdoor stadiums, and more particularly to temperature compensating outdoor wall padding.

Temperature compensating outdoor wall padding apparatus and method for forming the same


A method of producing an array of photovoltaic cells responsive to incident radiation by forming heterojunction-forming material layers over a transparent substrate panel having a transparent electrically conductive coating and thereafter removing selected portions of the materials to form a plurality of cells on a common substrate. The cells are then electrically interconnected by depositing electrically conducting materials over substantially the entire panel and removing only those portions of the deposited materials required to form series electrical connections.

The search for alternate energy sources in the United States and throughout the world is progressing at an ever increasing rate as the available supplies of energy are being consumed. There are many alternate sources of energy which might be tapped but for technological and/or cost considerations. Solar energy is one source which is being extensively examined due to its abundance and to an apparent absence of environmentally deleterious side effects.
The technology and theory for producing basic photovoltaic cells which generate electrical energy in response to solar input is generally well known. The main technical problems which are currently under investigation deal with reducing this basic technology to a practice which is applicable to the production of such photovoltaic cells at a cost which is competitive with that required to construct and operate present day power generating facilities utilizing such energy sources as oil, coal, or nuclear fission. To accomplish this goal, it is apparent that electrical generating stations utilizing photovoltaic cells must be fabricated using mass production techniques wherein large areas, measured in terms of square miles, can be literally covered with such mass-produced photovoltaic cells. In accordance with the present invention, large area photovoltaic panels will be formed using production-type techniques and will thereafter be formed into an array of series connected photovoltaic cells in a process suited to mass production and in a size to generate commercial quantities of electrical energy.


A semiconductor device and manufacturing method thereof attaining higher capacitor capacitance and lower power consumption are provided. On an interlayer oxide film which is a BPTEOS film containing an impurity, an interlayer oxide film which is a TEOS film not containing any impurity is formed. Openings of approximately inverted frusto-conical shape of approximately the same size are formed in interlayer oxide films, respectively, providing a contact hole of such a shape that includes two inverted frusto-cones continued in the vertical direction as a whole is provided. Along the inner wall surface of the contact hole, a storage electrode, a dielectric film and a cell plate electrode constituting a capacitor are formed successively.

1. Field of the Invention
The present invention relates to a semiconductor device and manufacturing method thereof. More specifically, the present invention relates to a semiconductor device having a capacitor and a contact plug in an MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a DRAM (Dynamic Random Access Memory) or the like, and to a manufacturing method thereof.
2. Description of the Background Art
As the technique of manufacturing semiconductors and especially the technique of miniature processing have been developed, degree of integration and capacity of DRAMs for MOS transistors have been increased. As the degree of integration increases, the area occupied by a semiconductor element per 1 bit has been decreased. Therefore, the area of a capacitor storing information (charges) decreases, and hence charges stored therein decreases. As a result, the capacitor has come to be very sensitive to slight electrical influence, so that there have been problems of erroneous calling of information where charges are erroneously injected to the capacitor or charges are erroneously ejected from the capacitor, as well as the problem of soft error in which the contents of the memory is destroyed by .alpha. ray or the like. Further, as the semiconductor device has been reduced in size, contact area between a transistor and an interconnection or a contact area of a contact plug connecting interconnections with each other is reduced, so that contact resistance at the content portion is increased. This means that excessive voltage is required in a highly miniaturized semiconductor devices and that power consumption increases.
In order to address one of the aforementioned problems, that is, reduction of capacitor capacitance resulting from miniaturization of the semiconductor devices, various methods have been proposed to increase area of occupation in a capacitor using a polycrystalline silicon film or the like for the storage electrode. According to one of the proposed methods, the storage electrode is formed in a cylindrical shape, so as to increase contact area in a direction vertical to the main surface of the semiconductor substrate.
The structure of a conventional cylindrical capacitor and manufacturing method thereof will be described with reference to FIGS. 22 to 28. First, on a P type silicon substrate 102, an isolating oxide film 105a is formed, resulting in separate element forming regions. On the element forming region formed separately by isolating oxide film 105a, a gate oxide film 104c and a gate electrode 104 (word line) of a two-layered structure including a high melting point metal silicide film 104a and a polycrystalline silicon film 104b are formed. Thereafter, using gate electrode 104 as a mask, source/drain regions 103, which are n.sup.- diffusion layers, are formed by impurity implantation. In this manner, an MOSFET, that is, an MOS field effect transistor is formed. Thereafter, to cover gate electrode 104 and isolating oxide film 105a, an interlayer oxide film 105b is deposited on semiconductor substrate 102. Thereafter, a contact hole 106a is formed to be connected to source/drain region 103. Thereafter, a contact plug is filled in contact hole 106a, and etched to a prescribed shape. Thus, a bit line 106 connected to the MOS field effect transistor is formed as shown in FIG. 22. Then, an interlayer oxide film 105c is deposited on interlayer oxide film 105b, and a contact hole 107a for forming a plug establishing electrical connection between source/drain region 103 and a storage electrode of the capacitor is formed. Thereafter, a conductive material is filled in contact hole 107a, so that a contact plug 107 is formed. Thereafter, an interlayer oxide film 105j is deposited on interlayer oxide film 105c and contact plug 107. On interlayer oxide film 105j, a prescribed mask is formed, and thereafter, a contact hole 150 in which a capacitor is to be formed, is formed by etching as shown in FIG. 24. Thereafter, a polycrystalline silicon film, which is to be storage electrodes 108a and 108b, is formed in contact hole 150. Thereafter, a capacitor dielectric film 101 is formed to cover an upper surface of interlayer oxide film 105j and surfaces of storage electrodes 108a and 108b. Thereafter, a film which is to be a cell plate electrode 109, is deposited to cover capacitor dielectric film 101, and in this manner, the capacitor is completed.
As the two-dimensional area of semiconductor substrate 102 occupied by the semiconductor device decreases, the capacitor formed through the above described steps has come to be formed extending considerably large in the vertical direction with respect to semiconductor substrate 102. In other words, contact hole 105 in which the capacitor is formed is large in the vertical direction with respect to the main surface of semiconductor substrate 102.
Therefore, generally, contact hole 150 in which storage electrode 109 is formed has an upper portion of interlayer oxide film 105j etched by larger amount than the lower portion through dry etching as can be seen from FIG. 25, and therefore the contact hole come to have an inverted frusto-conical shape with inclined sidewalls, of which opening diameter gradually increases from the lower portion to the upper portion of interlayer oxide film 105j. Therefore, when a two-dimensionally small contact hole 150 is to be formed, the lower portion of contact hole 150 come to have too small an opening diameter relative to the upper portion. As a result, at the lower portion of contact hole 150, the conductive material for forming the film to be the storage electrode 109 may not be sufficiently filled but clogged.
If the conductive material for forming the film to be cell plate electrode 109 is not properly filled in the lower portion of contact hole 150, surface area of that portion which functions as an electrode of cell plate electrode 109 reduces, resulting in reduced electrostatic capacitance of the capacitor. Even when the conductive material for forming the film to be cell plate electrode 109 is properly filled, cell plate electrode 109 becomes very thin at the lower portion of contact hole 105, and therefore it becomes difficult to store sufficient charges. Thus the function of the cell plate electrode cannot be ensured.
Further, the higher the height of the capacitor from the main surface of semiconductor substrate 102, contact hole 150 come to have the higher aspect ratio.
Here, as the sidewalls of contact hole 150 are inclined, the opening diameter is small at the lower portion of contact hole 150, and further, a phenomenon referred to as bowing, where the opening diameter at the upper portion of contact hole 150 come to be smaller than the middle portion of contact hole 150, is observed. When the phenomenon of bowing occurs in contact hole 150, a material 170 formed along contact hole 150 provided in interlayer oxide film 105k cannot be properly filled, resulting in undesirable void inside the material 170.
Further, problems experienced in contact plug 107 will be described with reference to FIGS. 27 and 28. FIG. 27 is a cross section taken along the line B--B of FIG. 23. As can be seen from FIG. 27, contact plug 107 is required of a small opening diameter at an upper portion of contact hole 107a, considering short-circuit with bit line 106. Therefore, when the contact hole is formed in the frusto-conical shape in a two dimensionally small semiconductor device as described above, the opening diameter at the lower portion becomes considerably small. Accordingly, the contact resistance at the contact between the lower surface of conductive contact plug filled in contact hole 107a and source/drain region 103 is high. Further, as can be seen from FIG. 28, when the opening diameter of contact hole 107a is enlarged by wet etching to reduce contact resistance to provide contact hole 107b, there will be an increased possibility of short-circuit between bit line 106 and the contact plug formed along contact hole 107b.

Semiconductor device and manufacturing method thereof


An electronic printing apparatus employs digitally controlled toner conveyors and writing head to print monocomponent toners on plain paper in a single pass. Integrated circuits and thin film transistors convert high level image information into toner controlling pulses. Pixel intensity is programmed by associating a counted number of packets of toner with each level of pixel depth.

In electrophotography, the development process of attracting charged toner particles to a latent image on a photoreceptor surface is known. In the early 1980s Canon introduced a monocomponent development system based on insulating toner, magnetic transport, and a non-contact development referred to as jumping development. The toner particles jumped across the gap between a donor roll and a photoconductive drum using large (1200 V peak-peak) AC fields superimposed across the development zone, T. Takahashi et al, Photogr. Sci. Eng. 26, 254 (1982).
Subsequently, Toshiba also developed a noncontact jumping development method described in U.S. Pat. No. 4,836,135 issued to Kohyama et al, Developing Apparatus Having One-Component Developing Agent. In addition, Toshiba developed a toner charging apparatus similar to that used in the preferred embodiment of the present invention, see Hosoya et al, IEEE-IAS Annu. Conf. Proc. (1985) p 1495.
The present invention relates to toner transport methods involving jumping or rolling of packets of toner from one electrode to another. As examples, the electrodes may be on a surface comprising a toner conveyor or on a surface comprising a writing head. The present invention thus has broad applicability to toner transport and imaging.
In an electrostatic printing device, toner particles are moved by a force qE, the product of the particle charge and the local electric field. If the electric field is too large, air breakdown will occur. The field value at which breakdown occurs is quite strongly dependent on the gap between electrodes. The maximum usable field while avoiding field emission is around 70 volts per micron when the electrode gap is around 5 microns. (See R. M. Schaffert, Electrophotography, 2nd edition, p 518 for a graph entitled Modified Paschen Curve.) To create a fast printing device it is advantageous to use the highest possible electric fields, because higher fields will accelerate the particles to higher velocities. Properly directed, higher particle velocities will translate into faster printing machines. If control electrodes are used to move the toner, then the optimum gap between the electrodes is around 5.mu.. Fortunately, modern photolithographic techniques are available to create conductive patterns approaching 5.mu. line width and space on large substrates, including rigid and flexible media.
Existing electrophotographic processes have treated toner as a continuous medium which is imaged in bulk. By contrast, the apparatus of the current invention controls and directs individual toner particles or toner packets for an extremely high degree of control over the printed image. This microscopic level of control would normally be expected to result in a very slow printing process. However, high speed is made possible and practical by the application of large scale integrated circuits (ICs) and active thin film transistor circuits (TFTs) that convert high level image information into toner controlling voltages. An example of the speed advantage in the preferred printing embodiment is that 2400 pixels are imaged in parallel to produce a new pixel line which spans the width of a page. A digital processor is provided for each pixel to be printed. As will be described, the digital processor converts 24 bit pixel words into serial bit streams that independently control the amount of toner delivered at each pixel site on the paper. Thus process complexity has been shifted from electromechanical to electronic. By virtue of the logic power and speed available in ICs and TFTs, the twin goals of high performance and low manufacturing cost can be simultaneously realized.
The preferred toner in the current invention is monocomponent, non-magnetic, and non-conducting. It has a mean diameter of around 5.mu. which matches the optimum electrode width and spacing of 5.mu., and avoids the effects of van der Waals forces which can dominate the qE force at smaller toner diameters. Preferably, the toner formulation results in resilient particles which do not fracture on collision; thus avoiding toner fragments or "fines" at very small sizes. In addition, the preferred toner shape is spherical rather than irregular; this enables rolling transport mechanisms for particles moving on a surface.
The author's co-pending applications, Ser. No. 07/658,397 filed Feb. 20, 1991 and Ser. No. 07/842,004 filed Feb. 25 1992 are incorporated herein by reference. They describe digital imaging methods based on moving packets of toner from electrode to electrode. The present invention includes rolling of spheridized toner particles to achieve toner transport with less energy applied. The present invention also includes the use of TFTs in the preferred embodiment for cost effective implementations of the writing head.

Electrostatic printing apparatus and method


A desynchronizer (20) for desynchronizing data stored within synchronous payload envelopes of a synchronous communication protocol such as SONET (Synchronous Optical Network), provides for smoothing the periodically discontinuous clock signal associated with that data after the synchronous communication protocol overhead has been removed. The desynchronizer accommodates for shifts in the position of the payload envelope and hence, the data within the synchronous communication frame as well as adjustments within the data itself due to asynchronous bit stuff information. The desynchronizer utilizes a leak filter (26) having a linear branch (54) and an integrator branch (56), both branches having adjustable factors (61, 63, 65, 88, 90, 91, 93, 95, 100, 102, 105) regarding their operation, wherein the adjustable factors are selected depending upon threshold values (86, 87, 89, 62) which in turn are based upon the difference between the average write address and read address for the associated elastic store (22) within which the incoming data removed from the synchronous communication system frame is temporarily stored. The leak filter (26) forms part of a phase locked loop which in turn adjusts the read clock frequency (46) in a manner which minimizes overflow or underflow of the elastic store while simultaneously minimizing the rate of change of the read clock rate so as to limit jitter. A fault recovery apparatus forms part of the desynchronizer for enabling fastlock high gain factors (67, 97, 107) to quickly adjust the read clock when elastic store overflow or underflow occurs. The gain factors associated with both the linear branch and integrator branch are provisionable (118, 120) as well as elastic store size and thresholds resulting in a desynchronizer which can be modified to meet the particular jitter requirements of a particular synchronous communication system. A calculation engine (82) performs iterative calculations to generate the leak filter output value using a reduced number of logic gates for ASIC implementation.

As discussed generally in Digital Telephony, Second Edition (John Bellamy, John Wiley & Sons, Inc.) at Chapter 7, the problems associated with network synchronization control and management include maintaining a smooth payload clock at a network node. As noted there, a number of factors are associated with the problem of variations in the clock signal as received downstream from the original sender, including clock instability, noise and interference, effective changes in the length of the transmission medium, changes in the velocity of propagation, doppler shifts, irregular timing information, etc., all of which affect the received clock downstream from the sending source. Typically, elastic stores have been used in the recovery of clock information with using phase locked loops in association with a variable control oscillator to adjust the read signal associated with the data stored in the elastic store for transmission further downstream.
In addition, since the adoption of synchronous optical network standards, such as SONET and the CCITT counterpart known as Synchronous Digital Hierarchy (SDH), standard ways for formatting digital signals, such as DS-1, DS-1C, DS-2, DS-3 and CCITT counterparts, within a synchronous payload envelope (SPE, called a virtual container --VC-- by CCITT) have existed. The SONET and the SDH standards provide for movement of the SPE within the SONET or SDH defined frame. Movement of the payload effectively means a change in the rate at which the digital signal is being written at a node of the synchronous network. Desynchronizers attempt to smooth this rate as read from the node so that the extracted digital signal has a payload clock frequency as constant as possible, thereby minimizing this rate of change, otherwise known as jitter.
As the payload is removed from the synchronous frame containing line and section overhead, the resulting periodically discontinuous payload clock signal must be smoothed to a periodically continuous clock signal associated with the resynchronized payload output data. An elastic store provides straightforward means for accomplishing this result. The payload data as removed from the synchronous frame is thus written into the elastic store at the periodically discontinuous ram. This discontinuous rate, as averaged over many synchronous frames, is then used to read data from the elastic store at the digital signal's periodically continuous rate. The pointer mechanism comprises a set (pointer word is actually in 2 bytes) of information which is used to define the start of the next SONET synchronous payload envelope (SPE) in order to allow the envelope to move within the SONET frame. When there is a pointer adjustment, the amount of data within the SPE for the current SONET frame changes by one byte. However, it is not desirable to make an instantaneous adjustment in the elastic store read clock to reflect this change. Rather, it is desirous that the read clock rate gradually increase or decrease to accommodate the pointer adjustment so as to minimize output jitter and to bring the read clock frequency back to average write clock frequency. The slower the adjustment is made to the read clock frequency, the less output jitter (rate of change of the read clock) is generated.
Ideally if the payload (digital signal) did not move within the synchronous frame and if asynchronous stuff bits were not required within the payload itself, no jitter would be seen on the elastic store read clock. However, both payload movement within the synchronous frame, known as pointer movement, and asynchronous stuff bits to accommodate data rate fluctuation within the payload itself, do occur.
A listing of prior art documents which are directed to the problems associated with desynchronizers, including SONET desynchronizers is presented in Table 1.
TABLE 1 ______________________________________ REFERENCES ______________________________________ 1. T1.105-1991 "Digital Hierarchy - Optical Interface Rates and Formats Specification (SONET), Section 7 Synchronization 2. T1X1.6/88-028 "Analysis of Jitter & Wander Associated with Pointer Adjustments," British Telecom. (2a) T1X1.6/88-029 "A Possible Design for a Desynchronizer Accommodating Pointer Adjustments," British Telecom. 3. T1X1.6/89-029 "Results of Simulations of a Possible Desynchronizer Design," British Telecom. 4. T1X1.6/88-026 "A Synchronous Desynchronizer." Bellcore Signals," Bellcore. 5. T1X1.6/88-041 "Pointer Spreading Desynchronizer," Northern Telecom. (5a) T1X1.3/92-071 "Jitter Accumulation Results in SONET Islands for Milli-Hertz NE Clock Bandwidths," Alcatel. (5b) T1X1.3/92-072 "DS3 Payload Output Jitter Proposal," Alcatel. (5c) T1X1.3/92-017 "Additional SONET Islands Jitter Simulation Results," Alcatel. (5d) T1X1.3/92-006 "Initial Draft of SONET Jitter Standard," Tellabs. 6. "Short Term Stability Specification of SONET Timing Reference Signals," Bellcore. 7. T1 LB280 "A Technical Report on the Effects of SONET on Payload Output Jitter, T1X1.3 8. T1X1.6/90-005 "STS-1 and OC-N Jitter Proposal," Alcatel 9 "Design and Performance Verification of a SONET-TO-DS3 Desynchronizer", Hamlin, Jr., TranSwitch Corp., Shelton, Connecticut, published before February 25, 1992. 10. U.S. Pat. No. 4,996,698 - Nelson - February 26, 1991 11. U.S. Pat. No. 5,052,025 - Duff et al - September 24, 1991 ______________________________________
The problem addressed in prior art devices is thus to smooth the receive clock of the digital signals contained within the SPE, such as a DS-3 signal or a DS-1 signal so as to minimize output jitter while simultaneously inhibiting elastic store overflow or underflow.
Prior art techniques associated with SONET to DS-3 desynchronizers typically cause output phase transitions in the one unit interval (UI) range (one bit), which at the DS-3 rate corresponds to 22 nanoseconds (ns) (1/44.736 mb/sec). Such large phase steps can cause high levels of jitter on the recovered clock since they are only filtered with relatively high bandwidth phase lock loops (PLL's). Various manufacturers have devices which cause such levels of jitter, as noted in Table 1.
In the technique disclosed in U.S. Pat. No. 4,996,698, the pointer changes are smoothed using a high-pass filter and summing the output of this filter with the periodically discontinuous payload clock and then applying this summed signal to a type 2 low-pass filter using a phase locked loop synchronizing technique.
U.S. Pat. No. 5,052,025 discloses an adaptive bit leaking arrangement in conjunction with a digital phase locked loop and synchronizing elastic store to achieve improved jitter performance. An estimate of a bit leaking interval is adaptively obtained based on the intervals between a sequence of consecutive pointer adjustments in the received signal.
Although these prior art techniques have been able to reduce output jitter associated with pointer adjustments, recent SONET/asynchronous jitter studies such as the Alcatel T1X1.3 contributions to T1X 1.3/92-017, -041 have shown that peak jitter levels of 0.2 -0.25 (UI) unit interval per pointer, or lower are required to limit pointer generated jitter to reasonable allocation levels. At the present time it has been found that the filtering algorithm used in a DS-1 rate desynchronizer as disclosed in applicant's copending application Ser. No. 771,037, is not readily adaptable to a DS-3 rate. This is due to the fact that a high frequency over sampling clock must be used which is not practicable at the present time for a DS-3 rate. The present invention overcomes such problems associated with the prior art while providing improved fault recovery and programmability of the desynchronizer parameters. It also uses an iterative calculation engine which is able to calculate the bit leaking value on a repetitive basis while dramatically reducing the number of gates necessary to implement the circuitry as an ASIC.

Incremental phase smoothing desynchronizer and calculation apparatus


Continuous process for manufacturing an oxirane, according to which an olefin is reacted at a temperature above 35xc2x0 C. and for a period of more than 48 hours, with a peroxide compound in the presence of a zeolite-based catalyst and in the presence of a metal salt, in which the catalyst undergoes no regeneration treatment and in which the rate of deactivation of the catalyst, expressed as being a percentage of the conversion of the peroxide compound lost per gram of oxirane produced per gram of zeolite determined after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide function per gram of zeolite, is less than or equal to 0.15%.

This application is a 371 of PCT/EP99/08703 dated Nov. 11, 1999.
The invention relates to a continuous process for the manufacture of an oxirane by reaction between an olefin and a peroxide compound in the presence of a zeolite-based catalyst. The invention relates more particularly to a process for manufacturing 1,2-epoxypropane (or propylene oxide) by reaction between propylene and hydrogen peroxide.
It is known practice to manufacture propylene oxide by epoxidation of propylene using hydrogen peroxide and in the presence of a catalyst of TS-1 type, as described, for example, in patent application EP 0,230,949. This known process has the drawback of leading, under certain conditions, to poor selectivities and a deactivation of the catalyst.
Patent application EP 0,712,852 describes the use of a metal salt for this reaction, but these reaction conditions require a periodic or very frequent regeneration of the catalyst.
The invention is directed towards overcoming this drawback by providing a continuous process for manufacturing an oxirane, which exhibits high selectivity while at the same time producing only minimal deactivation of the catalyst.
The invention consequently relates to a continuous process for manufacturing an oxirane by reaction, at a temperature above 35xc2x0 C. and for a period of more than 48 hours, of an olefin with a peroxide compound in the presence of a zeolite-based catalyst and in the presence of a salt, in which the catalyst undergoes no regeneration treatment and in which the rate of deactivation of the catalyst, expressed as being a percentage of the conversion of the peroxide compound lost per gram of oxirane produced per gram of zeolite determined after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide function per gram of zeolite, remains less than or equal to 0.15%.
One of the essential features of the invention lies in the addition of a salt. The reason for this is that it has been found that the presence of a salt in the epoxidation reaction medium limits the side reactions which give rise to the formation of unwanted by-products. The addition of a salt thus makes it possible to increase the selectivity.
Another particular feature of the invention lies in a minimal deactivation of the catalyst after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide (xe2x80x94OOH) function per gram of zeolite. More particularly, the rate of deactivation of the catalyst is expressed as being a percentage of conversion of the peroxide compound lost per gram of oxirane produced per gram of zeolite determined after establishing the reaction conditions, i.e. after the consumption of 2.5 mol of peroxide function per gram of zeolite. The rate of deactivation of the catalyst is less than or equal to 0.15%. Advantageously, this rate of deactivation is less than or equal to 0.1%. The rate of deactivation is preferably less than or equal to 0.05%.
Yet another essential feature of the process of the invention lies in the temperature at which the olefin reacts with the peroxide compound in the presence of the catalyst and the metal salt. The reason for this is that the Applicant has found that a temperature above 35xc2x0 C. makes it possible to overcome the gradual deactivation of the catalyst and that the presence of a metal salt makes it possible to carry out the reaction at a substantially higher temperature without, however, any appreciable reduction in the reaction selectivity being observed. It is advantageous to carry out the reaction at a temperature above or equal to 40xc2x0 C. and preferably above or equal to 45xc2x0 C. A temperature above or equal to 50xc2x0 C. is most particularly preferred. However, the reaction temperature is generally below 100xc2x0 C. and preferably below 80xc2x0 C.
The salt used in the process according to the invention can be a metal salt or an ammonium salt. Generally, the metal is chosen from alkali metals and alkaline-earth metals. The alkali metals most usually used are lithium, sodium, potassium and caesium. The alkaline-earth metals which can be used in the context of the present invention are mainly magnesium, calcium, strontium and barium.
The metal salts used are mainly halides, oxides, hydroxides, carbonates, sulphates, phosphates and organic acid salts such as acetates. The halides are generally fluorides, chlorides, bromides and iodides. A preference is shown for chlorides.
The salt used in the process according to the present invention is preferably an alkali metal halide and advantageously sodium chloride.
The amount of metal salt used in the present process is expressed as the content of ammonium or metal ions from the salt relative to the amount of catalyst expressed in millimol (mmol) of metal or of ammonium per gram of zeolite. Generally, the salt is introduced such that its content in the reaction medium is greater than or equal to 10xe2x88x924 mmol/g of zeolite and less than or equal to 10 mmol/g of zeolite. Advantageously, the metal salt content is greater than or equal to 10xe2x88x923 mmol/g of zeolite and less than or equal to 1 mmol/g of zeolite. A preference is shown for a content of greater than or equal to 10xe2x88x922 mmol/g of zeolite and less than or equal to 0.5 mmol/g of zeolite.
The catalysts used in the process according to the invention contain a zeolite, i.e. a solid containing silica which has a microporous crystalline structure. The zeolite is advantageously free of aluminium. It preferably contains titanium.
The zeolite which can be used in the process according to the invention can have a crystal structure of ZSM-5, ZSM-11 or MCM-41 type or of beta-zeolite type. Zeolites of ZSM-5 type are suitable for use. Those with an infrared adsorption band at about 950-960 cmxe2x88x921 are preferred.
The zeolites which are particularly suitable are titanium silicalites. Those corresponding to the formula xTiO2(1xe2x88x92x)SiO2 in which x is from 0.0001 to 0.5, preferably from 0.001 to 0.05, give high-quality performance. Materials of this type, known under the name TS-1 and having a crystal structure of ZSM-5 type, give particularly favourable results.
Advantageously, the catalyst is in the form of spherical particles obtained by dispersing a sol containing zeolite crystals with a compound capable of forming a gel in the zone of a reactor containing a reaction gas such that the sol becomes fragmented into grains of sol at the reaction zone inlet. The grains of sol flow in the reaction zone along a curvilinear trajectory and, in doing so, the grains of sol solidify to a gel and can be collected.
The catalyst particles generally have an average diameter of greater than or equal to 0.01 mm and less than or equal to 5 mm, a specific surface of greater than or equal to 1 m2/g and less than or equal to 900 m2/g (determined according to the nitrogen adsorption method), an apparent density of between 0.1 and 1.0 g/ml, a pore volume of between 0.25 and 2.5 ml/g and a pore diameter distribution with a maximum of between 15 and 2000 xc3x85.
In one particular embodiment of the process according to the invention, the reaction is carried out continuously in a reactor in the liquid phase in the presence of a solvent, and a gaseous compound is introduced continuously into the reactor at a flow rate which is sufficient to entrain some of the oxirane produced, which is collected with the gaseous compound at the place at which this gaseous compound leaves the reactor. This specific embodiment can be advantageous since it has been observed that the oxirane reacts in the epoxidation reaction medium with the water which accompanies the peroxide compound and/or the solvent to form by-products, thereby reducing the selectivity of the epoxidation reaction. By introducing a gaseous compound into the reaction medium at a flow rate which is sufficient to entrain the oxirane produced and remove it from the reactor at the same time as the gaseous compound, the contact time between the oxirane produced and the epoxidation reaction medium is reduced. This thus avoids the formation of by-products and increases the selectivity of the epoxidation.
The function of the gaseous compound is to entrain the oxirane produced out of the reaction medium in order to prevent the oxirane from remaining in contact with the reaction medium for too long and thus to prevent the formation of side by-products. In other words, the gaseous compound makes it possible to remove the oxirane produced from the reaction medium by stripping.
The gaseous compound used in the specific embodiment of the process according to the invention can be any compound which is in gaseous form under the epoxidation conditions and which has no negative influence on the epoxidation reaction. It can be chosen from inert gases such as nitrogen.
Generally, in the specific embodiment of the process according to the invention, the olefin is introduced into the reactor in gaseous form and in a large excess such that the gaseous olefin can act, partially or completely, as the gaseous compound, i.e. such that it can entrain the oxirane produced and remove it from the reactor.
Advantageously, the gaseous compound is introduced into the reactor at a flow rate such that it makes it possible not only to entrain at least some of the oxirane produced but also to circulate the liquid phase in the reactor, in particular when this reactor is of loop type.
Generally, the gaseous compound is introduced into the reactor at a flow rate such that the ratio of the molar flow rate of the gaseous compound to the molar feed flow rate of the peroxide compound is at least 5, in particular at least 8, values of at least being common. The ratio of these molar flow rates is generally less than or equal to 50, in particular less than or equal to 30, values less than or equal to 20 being common.
Any type of reactor can be used in the process according to the invention, in particular a reactor of loop type. A fixed-bed reactor may also be suitable. Reactors of bubble-siphon loop type, in which the circulation of the liquid and optionally also of the catalyst is obtained by bubbling a gas into one of the arms, is particularly suitable. An example of such a reactor is represented schematically in FIG. 1. The gaseous compound (preferably the olefin) is introduced into the bottom of the reaction zone 1 via the pipe 2. The other reagents (peroxide compound, solvent, catalyst, one or more optional additives) are introduced into the reactor via the pipes 3 and 4. The liquid phase circulates in the reactor in the direction of the arrows. The gaseous compound rises in the reaction zone 1 and thus entrains the oxirane produced therein. A mixture of the gaseous compound and oxirane produced leaves the reactor via the pipe 5. The liquid phase leaving from the top of the reaction zone 1 is recycled into the bottom of the reaction zone via a heat exchanger 6. The liquid phase, which is depleted in oxirane by virtue of stripping, overflows via the pipework 7. A reactor comprising 2 concentric zones can also be used in the process according to the invention, the central zone providing the function of zone 1 of the reactor represented schematically in FIG. 1, and. the peripheral zone providing the function of the zone 6 of the reactor represented schematically in FIG. 1.
In the process according to the invention, it may moreover prove advantageous to maintain the pH of the liquid phase during the reaction between the olefin and the peroxide compound at a value of at least 4.8, in particular at least 5. The pH is advantageously less than or equal to 6.5, in particular less than or equal to 6. Good results are obtained when the pH is from 4.8 to 6.5, preferably from 5 to 6. The pH of the liquid phase during the epoxidation reaction can be controlled by adding a base. This base can be chosen from water-soluble bases. They may be strong bases. They may also be weak bases.
The peroxide compounds which can be used in the process according to the invention are peroxide compounds containing one or more peroxide (xe2x80x94OOH) functions which can release active oxygen and which are capable of carrying out an epoxidation. Hydrogen peroxide and peroxide compounds which can produce hydrogen peroxide under the epoxidation reaction conditions are suitable for use. Hydrogen peroxide is preferred.
Generally, the molar ratio between the amount of olefin used and the amount of peroxide compound used is greater than or equal to 0.1 and less than or equal to 100. Advantageously, this ratio is greater than or equal to 1 and less than or equal to 50. Preferably, this ratio is greater than or equal to 5 and less than or equal to 25.
In the process according to the invention, when it is carried out continuously, the peroxide compound is generally used in an amount of at least 0.005 mol per hour and per gram of zeolite, in particular at least 0.01 mol per hour and per gram of zeolite. The amount of peroxide compound is usually less than or equal to 2.5 mol per hour and per gram of zeolite and in particular less than or equal to 1 mol per hour and per gram of zeolite. A preference is shown for an amount of peroxide compound of greater than or equal to 0.03 mol per hour and per gram of zeolite and less than or equal to 0.25 mol per hour and per gram of zeolite.
In the process according to the invention, the peroxide compound is advantageously used in the form of an aqueous solution. In general, the aqueous solution contains at least 10% by weight of peroxide compound, in particular at least 20% by weight. It usually contains not more 70% by weight of peroxide compound, in particular 50% by weight.
The oxirane which can be prepared by the process according to the invention is an organic compound comprising a group corresponding to the general formula:
The oxirane generally contains from 2 to 20 carbon atoms, preferably from 3 to 10 carbon atoms. An oxirane which can advantageously be prepared by the process according to the invention is 1,2-epoxypropane.
Olefins which are suitable in the process according to the invention generally contain from 2 to 20 carbon atoms and preferably from 3 to 10 carbon atoms. Propylene is preferred.
The solvents which can be used in the process according to the invention may be aliphatic organic derivatives containing from 1 to 4 carbon atoms. Methanol may be mentioned by way of example.


Systems and methods for transcoding a transport stream or a video stream. A video stream includes a quantization matrix and a quantization scale that define how DCT frequency coefficients are quantized. A transport stream is transcoded by updating the quantization matrix and/or the quantization scale such that a new set of DCT frequency coefficients may be generated. Typically the quantization scale and/or the quantization matrix are updated such that the DCT frequency coefficients are more coarsely quantized such that their encoding consumes fewer bits. The quantization matrix can be updated such that select frequency coefficients are affected. Transcoding can operate at any level of the video stream, such as the frame level, the slice level, or the macroblock level. The bit rate of the video stream can therefore be adjusted or altered according to a current quantization level and a current bit rate.

1. The Field of the Invention
The present invention relates to systems, methods, and computer program products for transcoding transport or video streams. More particularly, the present invention relates to systems, methods, and computer program products for reducing a bit rate of a video or transport stream by generating a new set of discrete cosine transform (DCT) frequency coefficients.
2. Description of the Related Art
Digital video signals have several significant advantages over their analog counterparts. They can be transmitted over long distances and stored without degradation. They can be encrypted and otherwise processed for purposes such as security and unnecessary or redundant information can be removed from the digital video signals. One cost, however, of digital signals is related to the bandwidth that they consume. More specifically, uncompressed digital or video signals can consume significant bandwidth. This is particularly a problem in situations where multiple digital signals are being broadcast or where the digital signal is being transmitted over a medium such as the Internet, which has limited bandwidth in many circumstances.
This problem has been partially solved through the use of compression. One compression scheme is defined by the Moving Pictures Expert Group (MPEG). The bit stream defined by MPEG is the output of an encoding process that is designed to significantly compress the video picture information. As the MPEG standard only defines the syntax of the resulting bit stream, the standard is flexible enough to be used in a variety of different situations, such as satellite broadcast services, cable television, interactive television services, and the Internet.
The MPEG encoding process generally occurs as follows. A video signal is sampled and quantized to define color and luminance components for each pixel of the digital video. Values representing the color and luminance components are stored in structures known as macroblocks. The color and luminance values stored in the macroblocks are converted to frequency values using a discrete cosine transform (DCT). The transform coefficients obtained from the DCT represent different frequencies in the brightness and the color of the picture.
The MPEG encoding process takes advantage of the fact that human visual system is insensitive to high frequencies in color and luminance changes, and quantizes the transform coefficients to represent the color and luminance information by smaller or more coarsely scaled values. The quantized DCT transform coefficients are then encoded using run level (RLC) and variable length coding (VLC) techniques, which further compress the video stream. The MPEG standard also provides additional compression through motion compensation techniques.
However, even compressed video or MPEG streams may still have a bit rate that is unsatisfactorily high for certain applications, and therefore there is a need to further compress the video stream or reduce the bit rate of the stream. One solution to this problem is to transcode the MPEG stream by completely decoding the MPEG stream and then re-encoding the MPEG stream at a higher compression ratio to reduce the bit rate to an acceptable level. However, transcoding an MPEG stream in this fashion is often computationally expensive because of the need to perform an inverse quantization and an inverse DCT to recreate an approximation of the original data prior to re-encoding the data in accordance with a desired bit rate. Transcoding a video stream is even more complex when motion estimation and compensation are performed.
As previously stated however, transcoding a video stream is often necessary because the bit rate of the incoming video stream may be higher than the available bandwidth or the bit rate of the incoming MPEG stream may be higher than the optimal bit rate for storage of the video stream on a storage medium such as a hard disk drive. In view of these and other problems presented by video streams, minimally complex systems and methods are needed for transcoding a video stream.

Non-compensated transcoding of a video stream