It is an object of the present invention to provide an output circuit capable of reducing a consumption current while an output current is suppressed in a case where limitation is placed on an output voltage so as not to fall to a predetermined voltage or less in an output circuit the emitter of which is grounded, the base of which serves as an input node for a control current and the collector of which serves as an output node. Provided are a base current supply section for supplying a base current to the output transistor according to an input signal from the outside, and a base current control section for detecting an inter-terminal voltage between the collector and emitter of the output transistor to control a base current supplied from the base current supply section so as not to cause the inter-terminal voltage to fall to a value lower than a predetermined voltage.

1. Field of the Invention
The present invention relates to an output circuit in semiconductor integrated circuitry, and particularly, to an output circuit having an output transistor the emitter of which is grounded, the base of which serves as an input node for a control current and the collector of which serves as an output node.
2. Description of the Related Art
As a conventional example of an output circuit having an output transistor, there have been available, for example, an output circuit disclosed in JP-A 9-51256 (1997) or an output circuit shown in FIG. 8.
The circuit shown in FIG. 8 includes an output transistor Q1, other transistors Q2 to Q6, a current source I1 and a load X. To be detailed, the transistors Q2 and Q3 are connected between the emitters thereof, the base of the transistor Q2 serves as an input for an input signal VIN, the base of the transistor Q3 serves as an input for a reference voltage V1, and the current source I1 is connected between a power supply voltage VCC and the emitters of the transistors Q2 and Q3 in order to supply a current to the emitters thereof. The collector of the transistor Q4 is connected to the collector of the transistor Q2 and the emitter thereof is grounded, and the collector and base of the transistor Q5 are connected to the collector of the transistor Q3 and the base of the transistor Q4 and the emitter thereof is grounded. The collector of the output transistor Q1 is connected to an output VOUT, the base thereof is connected to a connecting point between the collector of the transistor Q2 and the collector of the transistor Q4 and the emitter thereof is grounded. The collector of the transistor Q6 is connected to the power supply voltage VCC, the base thereof is applied with a reference voltage V2 and the emitter thereof is connected to the output VOUT. The load X is connected between the output VOUT and the power supply voltage VCC.
Then, description will be given of operations in a conventional output circuit shown in FIG. 8. A current of the current source I1 is split into collector currents of the transistors Q2 and Q3 according to a voltage difference between the input signal VIN and a reference voltage V1. The collector current in the transistor Q3 becomes a collector current of the transistor Q4 by the action of a current mirror circuit constituted of the transistors Q4 and Q5. Since the collectors of the transistors Q2 and Q4 are connected to each other, a difference between the collector currents thereof is a base current of the transistor Q1 and a collector current hfe (an h parameter expressing a current amplification factor) times as large as the base current flows through the load X and the power supply voltage VCC drops by an inter-terminal voltage of the load X to obtain a potential at the output VOUT. In a case where the input signal VIN>the reference voltage V1, a collector current of the transistor Q4 is larger than that of the transistor Q2, so that a current is extracted from the base of the output transistor Q1 to reduce a current flowing into the load X and raise a voltage at the output VOUT. To the contrary, in a case where the input signal VIN<the reference voltage V1, a collector current of the transistor Q2 is larger than that of the transistor Q4, so that a base current flows into the base of the transistor Q1, a collector current hfe times as large as the base current flows through the load X to reduce a voltage at the output VOUT. In a case where the voltage at the output VOUT falls to a value lower than a voltage lower than the reference voltage V2 by VBE, the transistor Q6 acts to limit falling of a voltage at the output VOUT so as not to be lower than a voltage lower than the reference voltage V2 by VBE.
In the situation where a collector current of the output transistor Q1 increases, a voltage at the output VOUT falls and limitation is placed on falling of the voltage thereat by the transistor Q6, a current flowing through the collector of the transistor Q6, of a collector current of the output transistor Q1, for the limitation is useless since it does not contribute to a change in output voltage in response to the input signal VIN. Especially, in a case where a sharp change in an instant during which an output transitions is desired and the voltage after the change has only to be retained in value, a current necessary only for a period when an output voltage transitions continues to flow after the change in output voltage, having led to a fault to increase a consumption current.


A status information receiver is communicatively connected to at least one printing device via a network, and adapted to receive status information transmitted from the printing device. The status information is indicative of an operation state of the printing device. An error information detector is adapted to detect whether error information is included in the status information. The error information is indicative of an error occurred in the printing device. A repair information generator is adapted to generate repair information based on the error information. The repair information is indicative of an item in the printing device to be repaired.

The present invention relates to a remote monitoring system and a remote monitoring method, which monitor the operating status of a printer or the like-and detect an anomaly so that an engineer visits a remote location where a client owns a printer for repairing the printer when a failure has arisen in the printer or at the time of maintenance.
In the past, when a failure has arisen in a client's printer, the client makes a telephone call to report the nature of the failure. A call center passes the information on the nature of the failure to a dispatcher of a field service center. The dispatcher makes an arrangement for requesting a customer engineer (CE) to visit the client for repairs. The CE visits the location where the client's printer is placed for repairing the disabled printer. Japanese Patent Publication No. 2003-163778A discloses technique for preparing a report about details of an error and transmitting the report to the call center by facsimile transmission when such a device of the client has become broken down.
However, in the event of occurrence of a failure in the device, such as a printer, it is routine procedure for a person in charge in the call center to actively listen to the client about the status of the failure and make contact with the field service center, which is a department for actually repairing a client's device. Even in the field service center, the dispatcher must designate a CE in charge of the repair and make contact with that CE. As mentioned above, transmittal of information about the nature of the failure is repeated several times from the time the client has made a call until the CE is informed of the failure. For this reason, time is consumed by transmittal of information, and the accuracy of transmittal of information cannot be maintained.
If the status of the failure passed to the call center by the client is uncertain or lacking in explanation, the CE visits the client without ascertaining the true cause of the failure. Reaffirming the nature of the failure while talking with the client entails consumption of much time, or requires a re-visit of the CE to the client or the like. For these reasons, time and manpower are consumed from the time when the device, such as a printer, has broken down until repairing of the device is completed, which in turn adds to service cost.

Remote monitoring system and remote monitoring method


A system for facilitating medical image interpretation includes a processing unit and a display control unit. The processing unit includes a location information module generating a reference location indicator, and a feature marking module generating indication markers. The display control unit is in signal connection with the processing unit and a display device. The display control unit includes an image displaying module controlling the display device to display tissue images, and an auxiliary information displaying module controlling the display device to display, for each of the tissue images displayed by the display device, the reference location indicator and the indication markers together on the tissue image.

In order to diagnose an illness in a patient, a medical professional often has to study, piece by piece, a great number of medical images of computed tomography (CT) or magnetic resonance imaging (MRI) obtained from the patient. However, it may take a great amount of time for the medical professional to study the medical images even though the scope of studying may be narrowed down, based on his/her accumulated experience, to parts of the medical images corresponding to body portions which are more susceptible to the illness. In addition, it may take a great amount of time for the medical professional to locate a lesion to be treated in the patient, to mark the lesion and to measure the size of the lesion, putting an increased burden of workload for the medical professional. Under time pressure, the medical professional would be prone to making mistakes.
Recently, techniques of artificial intelligence (AI) have been applied to facilitate medical image interpretation. However, AI-assisted medical image interpretation software needs to be installed and go through learning in addition to existing image viewer software. Moreover, since the existing image viewer software and the AI-assisted medical image interpretation software are not integrated, the medical professional has to open both software at the same time so as to locate the lesion to be treated by means of comparison, resulting in inconvenience of use.

System for facilitating medical image interpretation


A sparking device, in one aspect, includes first and second electrodes for coupling with corresponding first and second electric potentials. The first electrode includes an elongate member having proximal and distal parts. The second electrode includes a body receiving the proximal part. A first insulation portion electrically insulates the proximal part of the elongate member from the body. The first electrode includes an end member connected with the distal part of the elongate member. The end member includes a first section with a plurality of first electrical contacts offset from a longitudinal axis of the device. The body includes a second section with a plurality of second electrical contacts offset from the longitudinal axis. A plurality of sets of the first and second electrical contacts provide a plurality of gaps for sparking between the first and second electrodes, wherein a difference provided between the first and second electric potentials serves to cause sparking across at least one of the gaps. A second insulation portion is disposed between the longitudinal axis and at least one of the gaps to form a drainage path section, wherein the drainage path section serves to promote avoidance of short-circuiting between the body and the distal part of the elongate member and/or the end member during exposure of the device to precipitation.

Outdoor waste gas, such as landfill gas, can present problems such as foul odor and environmental pollution. Landfill gas is organic waste generated as a landfill decomposes. Typically, this foul-smelling gas consists of fifty-five percent methane, forty-four percent carbon dioxide, and one percent various other constituents, ranging from hydrogen sulfide to complex hydrocarbons. Undesirably, landfill gas may cause severe odor problems when released directly into the atmosphere. Further, methane has been characterized as a "greenhouse" gas, which is believed to significantly contribute to global warming.
Once landfills have reached full capacity, they are generally capped with, among other things, a layer of topsoil to support vegetation and help prevent erosion. A gas vent, gas well, or other gas collection system is typically provided in order to enable the landfill gas generated by the decomposition process to conveniently pass through the cap for release (e.g., in a passive arrangement).
Because landfill gas burns relatively cleanly, the gas emerging from such a vent, etc., may be burned in an effort to eliminate the noxious odor and harmful greenhouse effects. One possibility is to provide a flare to burn the gas as it emerges from the vent. However, disadvantages may result; for instance, it may be difficult to ensure that a flame burns continuously once the flare has been ignited. Several factors may contribute to this difficulty, including variations in the flow rate of the gas as a result of environmental conditions such as temperature and ground water levels. Furthermore, gas flows are commonly subject to variability due to barometric pressure and gas quality changes. Variations in percentage composition of the constituents (e.g., methane and carbon dioxide) of the landfill gas may also alter the gas/air mixture from an optimal ratio suited for maintaining or preserving a continuous flame. Moreover, adverse weather conditions such as wind and/or precipitation (e.g., snow, ice, sleet, hail and/or rain) may tend to extinguish the flame.
Preferably, a flare would be situated near the landfill, to minimize lengths of gas pipes needed. Usually, the flare would be disposed in a remote location, where it would be difficult to monitor the presence of flame, and inconvenient to manually reignite the flare in the event the flame is extinguished. During any time in which the flame is out, gas would disadvantageously be released into the atmosphere, thereby presenting the problem of potentially lengthy periods in which odor and greenhouse effects of the landfill would not be treated.
Various devices may be tried in attempts to address such problems. For instance, vent flares may be provided with electronic ignitors or propane pilot lights. Generally, electronic ignitors include sophisticated technology to monitor the presence of a flame. For example, optical or heat sensors may be employed which activate electronic circuitry upon detecting absence of a flame. A shortcoming of such sophisticated equipment is the relatively large expense in terms of up-front capital expenditure and routine maintenance.
Another approach may employ propane pilot light systems to help ensure that the landfill gas flame burns continuously, by providing a continuously burning pilot light. This type of system has the advantage of being relatively unsophisticated and thus, relatively inexpensive to purchase and simple to maintain. However, a drawback of this approach is that the system requires a separate supply of fuel (i.e., propane) which must be replaced periodically. In addition, the pilot light itself may be extinguished by, for example, wind and/or precipitation, undesirably requiring manual re-lighting.
As an improvement over such previous attempts, an exemplary configuration for a landfill gas vent flare is disclosed in U.S. application Ser. No. 08/559,795 by Hansen (entitled "Self Ignited Landfill Gas Vent Flare and Flarehead," filed Nov. 15, 1995, and assigned to Hansen Family Limited Partnership), which is hereby incorporated herein by reference in its entirety. In one aspect, such a landfill gas vent flare comprises a flarehead and at least one spark initiator. The flarehead is adapted for communication with a landfill gas vent, wherein landfill gas is permitted to flow in a downstream direction from the landfill gas vent to the flarehead. The at least one spark initiator is disposed on the flarehead, and is adapted to generate a continuous series of sparks in the flarehead, wherein the landfill gas flowing in the flarehead is ignited and continuously burned.
However, it remains desirable to provide refinements to the sparking in such a flarehead, for example, through special characteristics which enhance re-ignition over a variety of operating conditions. For instance, should a conventional spark plug be employed, water or ice may short-circuit the plug, or cold weather may shatter the insulation of the plug.
Thus, a need exists for a configuration which advantageously prevents or lessens short-circuiting of a sparking device, such as when snow, ice, sleet, hail and/or rain wets the, for example, hot and/or ground electrodes. A further need exists for formation or shaping of, for instance, the hot and/or ground electrodes, and/or formation or positioning of insulation therebetween, to enhance robustness, dependability, reliability, stability, resiliency and/or durability of such a sparking device. Another need exists for such a sparking device which is economical and/or suited for application(s) such as outdoor waste gas vent flares (e.g., passive landfill gas vent flares).

Sparking device for promoting avoidance of short-circuiting


An oil pumping system to carry oil from an oil sump in a pump housing to an internal oil reservoir in another portion of the pump housing. A top plate is attached to a pump rod and moves in accordance with a reciprocating motion of the pump rod. A bottom plate is below the top plate. A pump mechanism, disposed between the top plate and bottom plate, includes a valve seat that contacts the bottom plate, and an upper portion that contacts the top plate. A first biasing element is configured to urge the valve seat upward away from the bottom plate. A second biasing element is configured to urge the plunger upward away from the valve seat. Upward movement of the pump rod allows oil to flow into the pump mechanism. Downward movement of the pump rod causes the bottom of the valve seat to seal against the bottom plate.

In many conventional types of pumping systems used in a drilling apparatus, controlling and optimizing the performance of a sucker-rod pumping apparatus involves inherent difficulties. One factor which must be taken into account is the stretching of the rod string, which occurs during the upward portion of each pump stroke, and the corresponding contraction of the rod string which occurs during the downward portion of each pump stroke. The rod string, which may be 1000 feet or more long, acts much like an extension spring, which is stretched during the portion of the pump stroke in which the rod string is drawing the fluid upward within the well, and which then contracts back to an essentially un-stretched state as the rod string moves downward during a return portion of the pump stroke. As a result of the rod stretch, an above-ground upward stroke of 32 inches, for a well approximately 1300 feet deep, may only result in a down-hole stroke in the range of 24 to 26 inches, for example. The difference between the magnitude and direction of movement of the pump rod at the top of the well and the corresponding reaction of the rod string and down-hole stroke of the pump involves other complicating factors, including inherent damping within the rod string, fluid damping which occurs during the pump stroke and longitudinal vibrations and natural frequencies of the rod string.
The problems associated with effectively and efficiently operating a sucker-rod pump apparatus are addressed in significantly greater detail in a commonly assigned U.S. Pat. No. 7,168,924 B2, to Beck et al., titled "Rod Pump Control System Including Parameter Estimator", the entire teachings and disclosure of which is incorporated herein by reference thereto. The Beck et al. patent also discloses a rod pump control system, which includes a parameter estimator that determines, from motor data, parameters relating to operation of the rod pump and/or generating a down-hole dynamometer card, without the need for external instrumentation such as down-hole sensors, rod load sensors, flow sensors, acoustic fluid level sensors, etc. In some embodiments disclosed by Beck et al., having a pumping apparatus driven by an electric motor, instantaneous current and voltage, together with pump parameters estimated through the use of a computer model of the sucker-rod pump, are used in determining rod position and load. The rod position and load are used to control the operation of the rod pump to optimize operation of the pump. Beck et al. also discloses a pump-stroke amplifier that is capable of increasing pump stroke without changing the overall pumping speed, or in the alternative, maintaining the well output with decreased overall pumping speed.
The inherent difficulties of operating a sucker-rod pump apparatus may also be compounded by the type of pumping apparatus, such as the typical walking-beam-type apparatus. The problems encountered when using these conventional pumping systems serve as ample evidence of the desirability of providing a new and improved pumping apparatus for use with a sucker-rod pump.
For example, conventional walking beam-type pumping mechanisms must typically be mounted on a heavy concrete foundation, which may be poured in place or pre-cast, located adjacent the well head. Construction of a walking beam pumping mechanism, together with its foundation, typically involves the efforts of several construction workers, over a period which may be a week or more, to prepare the site, lay the foundation, and allow time for the foundation to cure, in addition to the time required for assembling the various components of the walking beam mechanism onto the foundation and operatively connecting the mechanism to the pump rod.
Because of the costs of transporting the apparatus and the concrete or pre-cast foundation to what may be a remote site and the complexity of the site preparation and assembly process, walking beam-type pumping mechanisms are generally only utilized in long-term pumping installations. Further, the large size and massive weight of the walking beam pumping mechanism and its foundation may also problematic when the well is decommissioned. Economic and contractual obligations may require complete removal of the walking beam mechanism and its foundation.
Linear rod pumping systems have been developed to address a number of the above-described problems with conventional pumping systems. Linear rod pumping systems are disclosed in U.S. Pat. Nos. 8,152,492 and 8,641,390 both issued to Beck et al., and both titled "Linear Rod Pump Apparatus and Method", the entire teachings and disclosures of which are incorporated herein by reference thereto.
Embodiments of the present invention represent an advancement over the state of the art in pumping systems. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.


Example vehicle restraints having example anti-rotation features are disclosed herein. In some examples, an actuator in the form of a hydraulic cylinder moves both a vehicle barrier and its brace between stored and activated positions. If the vehicle pushes the barrier from an upper blocking position to an intermediate blocking position, the brace helps support the barrier at the intermediate blocking position to prevent the vehicle from further pushing the barrier to its stored position. To avoid damaging a cover plate or other relatively weak areas of a vehicle's RIG (rear impact guard), some example barriers disclosed herein exert a holding force that is less at the upper blocking position than at the intermediate blocking position.

When loading or unloading a truck parked at a loading dock, it is generally a safe practice to help restrain the truck from accidentally moving too far away from the dock. Some known restraints include a hook-style vehicle restraint that engages what is often referred to in the industry as a truck's ICC bar (Interstate Commerce Commission bar) or RIG (Rear Impact Guard). An ICC bar or RIG comprises a bar or beam that extends horizontally across the rear of a truck, below the truck bed. Its primary purpose is to help prevent an automobile from under-riding the truck in a rear-end collision.
A RIG, however, also provides a convenient structure for a hook-style restraint to reach up in front of the bar to obstruct the bar's movement away from the dock. To release the truck and prepare for the next truck to enter the dock, many restraints descend below the bar to a preparatory position. Although the horizontal bar of a RIG is fairly standardized, the bar's supporting structure can vary significantly. In some cases, the supporting structure can interfere with the operation of the restraint.

Vehicle restraints with anti-rotation features


A method of applying a gray neutrality calibration to a color signal, said method comprising: representing said color signal as a position in a multi dimensional color space, in which each said dimension of said color space represents a respective primary color; defining a gray axis in said multi dimensional color space as a set of coordinates for which a plurality of said primary colors each have a same value as each other; determining a distance between said position representing said color signal and said gray axis; and using said determined distance between said color signal position and said gray axis to apply a gray neutrality correction to said input color signal.

A printed grayscale extends at one end from no ink (which shows as white on a white print media) through various shades of gray to full black at the other end of the grayscale.
It is often desirable or necessary to apply a "gray neutrality calibration" correction to a printer device's color space in order to have the printer produce visually neutral grays with some well defined digital inputs, for example equal values of cyan, magenta, and yellow. That is, the values C=M=Y. A common way to achieve this is to apply a 1-dimensional "transfer function" to each of the cyan, magenta and yellow colorants separately. Such transfer functions can be calculated based on the colorimetric or densitometric measurements of a printer's "raw" behavior.
However, an undesirable side effect of using 1-dimensional transfer functions is that they not only affect the gray axis (C=M=Y) but also, the rest of the printer's gamut, i.e. the range of colors, that can be obtained by mixing three or more inks. This can lead to non-linearities, contouring, difficulties in creating color maps, gamut reductions, and other artifacts.
There is a problem in printing grayscale images on an inkjet printer device, using the conventional gray neutrality calibration, that the images do not appear to be gray to the naked eye, and are tinted with a non neutral color, that is the gray looks reddish, brownish, yellowish or greenish. In practice, ensuring a neutral gray color is printed is a non trivial problem, especially when working with a 4 color printer, or a 6 color printer, such as the Hewlett Packard DesignJet 5000 type printer.
Ideally, the gray neutrality calibration should be applied only to the gray axis, but without creating discontinuities elsewhere.

4-dimensional gray neutrality calibration

Hewlett-Packard Development Company, L.P.


An articulated reactor may comprise a generally rectangular member having a longitudinal axis, a transverse axis, an elongate inlet side, and an elongate outlet side. A raised portion extends along a direction that is generally parallel to the longitudinal axis and at least one slot extends from about the elongate outlet side to about the elongate inlet side. The slot forms at least two fingers the raised portions of which are biased against a roller associated with a scanner device when the scanner device is positioned adjacent the articulated reactor.

Imaging devices, such as optical scanners, are well-known in the art and produce machine-readable image data signals that are representative of a scanned object, such as a photograph or a page of printed text. In a typical scanner application, the image data signals produced by an optical scanner may be used by a personal computer to reproduce an image of the scanned object on a suitable display device, such as a CRT or a printer.
A hand-held or portable optical scanner is an optical scanner which is designed to be moved by hand across the object or document being scanned. The hand-held scanner may be connected directly to a separate computer by a data cable. If so, the data signals produced by the hand-held scanner may be transferred to the separate computer "on the fly," i.e., as the image data are collected. Alternatively, the hand-scanner may include an on-board data storage system for storing the image data. The image data may then be downloaded to a separate computer after the scanning operation by any convenient means, such as via a cable or an optical infrared data link.
Hand-held or portable optical scanners are well-known in the art and various components thereof are disclosed in U.S. Pat. No. 5,552,597 of McConica for "Hand-Held Scanner having Adjustable Light Path", U.S. Pat. No. 5,586,212 of McConica, et al., for "Optical Wave Guide for Hand-Held Scanner," U.S. Pat. No. 5,381,020 of Kochis, et al., for "Hand-Held Optical Scanner with Onboard Battery Recharging Assembly," and U.S. Pat. No. 5,306,908 of McConica, et al., for "Manually Operated Hand-Held Optical Scanner with Tactile Speed Control Assembly," all of which are hereby incorporated by reference for all that they disclose.
A typical hand-held optical scanner may include an illumination system and an optical system. The illumination system illuminates the object and the optical system collects light reflected by the illuminated object and focuses a small area of the illuminated object, usually referred to as a "scan region" or "scan line," onto the surface of a photosensitive detector positioned within the scanner. Image data representative of the entire object then may be obtained by sweeping the illuminated scan line across the entire object, usually by moving the hand-held scanner with respect to the object. By way of example, the illumination system may include a light source (e.g., a fluorescent or incandescent lamp or an array of light emitting diodes (LEDs)). The optical system may include a lens and/or mirror assembly to focus the image of the illuminated scan line onto the surface of the detector.
The photosensitive detector used to detect the image light focused thereon by the optical system may be a charge-coupled device (CCD), although other devices may be used. A typical CCD may comprise an array of individual cells or "pixels," each of which collects or builds-up an electrical charge in response to exposure to light. Since the quantity of the accumulated electrical charge in any given cell or pixel is related to the intensity and duration of the light exposure, a CCD may be used to detect light and dark spots on an image focused thereon.
Hand-held optical scanners may be provided with additional utility if they can be made to scan documents without the necessity to move the scanner over the surface of the object being scanned.

Articulated roller reactor for paper feed device


A hydrostatic continuously variable transmission includes a hydraulic pump and a hydraulic motor, supported by a common support shaft, and hydraulically connectable to each other through a hydraulic circuit including an inside passage and an outside passage. A clutch device includes a valve spool, which is slidably disposed in a hollow internal bore formed in the transmission support shaft. The valve spool is operable to make or interrupt fluid communication between the inside passage and the outside passage, according to the movement thereof. A governor mechanism is mounted to a pump casing of the hydraulic pump, and the governor mechanism generates a governor force corresponding to the rotating speed of a clutch cap, by use of centrifugal force generated by the rotation thereof. The valve spool is effectively moved in the hollow internal bore, using the governor force generated from the governor mechanism, to engage or disengage the clutch.

1. Field of the Invention
The present invention relates to a hydrostatic continuously variable transmission including a hydraulic pump and a hydraulic motor connected to each other through a hydraulic closed circuit, and configured so that the capacity of the hydraulic pump or the hydraulic motor is variably controlled, to vary the speed of input rotation of the hydraulic pump and to take out the speed-varied rotation as output rotation of the hydraulic motor. More particularly, the present invention relates to a clutch device for making and interrupting the communication between a high pressure side oil passage and a low pressure side oil passage, constituting the hydraulic closed circuit in the hydrostatic continuously variable transmission.
2. Description of the Background Art
Various types of hydrostatic continuously variable transmissions have been known and put to practical use. One example of a commercial hydraulic continuously variable transmission was sold by Honda and marketed under the trademark "Hondamatic" on the 2001 Honda Fourtrax Foreman Rubicon™ TRX500 ATV.
Another example of a hydrostatic continuously variable transmission is disclosed in Japanese Laid-open Patent No. Hei 6-42446, proposed by the present applicant.
Other examples of known hydrostatic continuously variable transmissions can be found in Japanese Patent No. 2920772 and Japanese Laid-open Patent No. Hei 9-100909. The hydrostatic continuously variable transmission disclosed in these Patent Documents generally includes a swash plate plunger pump, a swash plate plunger motor, and a hydraulic closed circuit for connecting the discharge port and the suction port of the swash plate plunger pump to the suction port and the discharge port of the swash plate plunger motor, respectively. This transmission is configured so that a pump swash plate member is driven by the engine, wherein a pump cylinder and a motor cylinder are connected to each other and disposed on an output shaft, a motor swash plate member is restricted in rotation, and the motor swash plate angle can be variably regulated.
It has been also known that, in the hydrostatic continuously variable transmission configured as above, a clutch valve is provided for making and interrupting fluid communication between a high pressure side oil passage and a low pressure side oil passage constituting the hydraulic closed circuit. The magnitude of transmission of a rotational drive force from the hydraulic pump to the hydraulic motor is controlled using the clutch valve, or a clutch control is conducted for interrupting the transmission of the rotation. For example, in Japanese Laid-open Patent No. Hei 9-100909, an automatic clutch device using such a clutch valve is disclosed.
Meanwhile, the clutch valve provided in the hydrostatic continuously variable transmission has been configured so that its operation is controlled by an actuator, operated by hydraulic pressure generated from a hydraulic governor operated in conjunction with the engine rotation. The known clutch valve has had the problems of a relatively large structure and high cost, due to the need for the hydraulic governor, the actuator and the like.
In view of this, the automatic clutch device described in Japanese Laid-open Patent No. Hei 9-100909 is configured so that the hydraulic pressure in the low pressure side oil passage urges the clutch valve in the opening direction, and the hydraulic governor for increasing a supplied hydraulic pressure supplied to the low pressure side oil passage according a rise in the input rotating speed of the hydraulic pump is connected thereto, to thereby eliminate the need for an exclusive-use actuator, and to provide a simplified structure. However, since the operation of the clutch valve is controlled by the hydraulic pressure using the hydraulic governor, this limits the manufacturer's ability to make the device smaller and compact and to limit the cost. A need still exists for a device which a further simplifies the structure of a clutch for this type of transmission.

Clutch apparatus for a hydrostatic continuously variable transmission and transmission incorporating same


A portable potable water system comprises a tank assembly and system component housing, both mounted on a base structure for ease of transportability. The potable water system includes a circulation system to maintain potability of the water and prevent freezing. A delivery system is provided which supplies the potable water to a user or site. The potable water system components are enclosed in the housing to protect the system from adverse climatic conditions and provide a more secure environment. The system is constructed of components which maintain the potability of the water.

Various apparatus and devices have been proposed to transport liquids or provide a portable source of water or other liquids. In U.S. Pat. Nos. 1,892,519 to Schottgen and 2,437,618 to Schottgen et al, means for transporting liquids are disclosed. In these patents, a tank and liquid dispensing apparatus are mounted on a vehicle for transportation and delivery of liquids such as beer.
U.S. Pat. No. 4,089,446 to Logan, II et al. discloses a portable water supply and dispensing unit which includes a tank and dispensing pump assembly mounted on a pair of wheels. The apparatus is especially adapted for washing of motor vehicles.
However, deficiencies exist in the prior art with respect to providing a potable water system that is portable to service a user in need of a temporary or permanent source of potable water.


A method of repairing a bone joint by using a simple and flexible artificial ligament which easily conforms to a patient's anatomy and can be used independently or in combination with an intervertebral graft, implant or prosthesis to return stability to the spine subsequent to a surgical spine procedure, is disclosed. The method includes anchoring the artificial ligament to at least two vertebrae to aid in restoring stability to the compromised joint. The artificial ligament is also disclosed.

The present disclosure relates generally to prosthetic members for joining or repairing bone segments, including artificial ligaments and, more specifically, to an artificial ligament intended for partial or full replacement of the anterior longitudinal ligament of the anterior lumbar, thoracic or cervical spine.
Ligaments extend between adjacent bone structures and serve a primary function of maintaining and providing appropriate stability to the bone structures to maintain the structures in aligned, spaced relation, particularly when subjected to loads in tension or upon torsional movement. Spinal ligaments stabilize and support vertebral bodies during movement of the spine.
During surgical treatment of the spine, a section of a spinal ligament may be resected to provide access to a diseased or damaged intervertebral disc and/or to permit introduction of a fusion implant, bone graft or intervertebral disc prosthesis intended for long term support of the vertebral bodies. The bone graft, fusion implant or intervertebral disc return stability to the spinal column in compression and flexing, however, due to removal of the spinal ligament, the biomechanical characteristics of extension and torsional stability lost by the ligament's removal must be replaced. Current techniques involve the use of metal bone plates which are secured to the vertebral bodies with screw locking mechanisms. Conventional bone plates, however, are rigid and, thus, significantly inhibit spine mobility. Additionally, the screw locking mechanisms utilized with such plates are relatively complicated and provide minimal flexibility with respect to fastener positioning, etc.


The present invention relates to the detection of optical sensors by means of measurement of information relative to the signal intensity and signal modulation phase shift. The proposed method employs the use of CMOS and/or CCD imager and illuminations with different wavelengths. The system is able realize a contactless measurement of a phase shift to curse on a gas concentration an distance.

The present invention relates to the detection of optical sensors by means of measurement of information relative to a signal intensity and a signal modulation phase shift.
The market of inexpensive, smart and disposable intelligent labels, RFID and smart tags is rapidly growing. The most demanding properties to be sensed by such devices are temperature, pressure, moisture, pH, gas concentrations (CO2, CO, NH4, O2, and others) and the concentration of specific chemical ions (ammonia, etc). The basic challenge today consists in bringing on the market a smart solution both on the sensor as on detecting device side. In a most general approach, the sensing element needs to be included into the detection area in such a way that is able to sense the interesting propriety (gas, pH, . . . ) while still able to be remotely activated and interrogated by the distant measurement unit.
One of the future customers of such technology is the packaging industry, where several goods, depending to their nature, need to be packaged under well defined and controlled conditions. Thus, chemical, pharmaceutical and electronic industries are frequently confronted to the problem of exposure to factors like temperature, oxygen or moisture, which excess is leading to the premature degradation of packaged good. The food packaging industry is typically struggling with too high concentration of oxygen and to high temperature.
There are several other applications, where remote, optical evaluation of carbon monoxide, dioxide, ammonia or specific chemical ions is necessary for the general safety or product shelf life reasons. A good example of today's industrial needs is the oxygen sensing for food packaging industry that is currently employing MAP (Modified Atmosphere Packaging) packaging foils to guarantee a constant and low oxygen concentration to the packaged goods. Here, the solution will consist on placing inside such package, or placing it directly on the packaging foil, an oxygen-sensitive element able measure the 02 concentration and communicate this information optically or by RF to the detector unit.
Very strong price pressure, small size requirement and real need of disposable sensors eliminate a variety of "smart tags" communicating remotely with detection or analyzing unit by RF.
The solution of choice in this case consist on disposing inside the package of chemical compound whose light emission properties are directly depending to the oxygen concentration. This can be easily achieved if using one of several possible easily, optically excitable organometallic complexes (transition metal-organic complexes, preferably highly aromatic compounds like porphyrins, etc., for which the oxygen particles are fluorescence quenchers. Thus, the sensing compound or luminescence probe, after its prior excitation by a remote illumination at a specific wavelength, will emit an optical signal (fluorescence) which decay in time is directly informing of temperature and of oxygen concentration. This quencher (here: O2) to signal decay relation is described by the Stern-Volmer relation.
The measurement can relay on the emitted light intensity or on the emission (fluorescence) life time. In the first case, the dependency to the luminescence probe concentration and its purity constitutes a strong disadvantage. The measurement based on fluorescent signal decay, fluorescent modulation phase shift or polarization type and change of emitted light are all not depending to this. Unfortunately, a fluorescence intensity and life time of almost all interesting compounds is not only depending to the concentration of specific fluorescence quenchers but also to temperature.
There is however, a possibility to use another, optically activated compound, the fluorescence intensity or decay time of which is only depending on the temperature. Such compound, just employed as standalone, gives an excellent solution for the disposable and remote temperature sensor, while used along with a quencher-dependent compound, offers internal temperature calibration of the Stern-Volmer relationship linking the quencher concentration, temperature and fluorescence decay. Oregon Green-488 fluorescent dye can be employed for this purpose along with one of several known oxygen-sensitive compounds like Ru(II)[dpp(SO3Na)2]3)Cl2, Ru(II)(dpp), PdTCPPP, PtOEP or other Cr, Mn, or transition metals-organic complexes. An important characteristic of using fluorescence probes is that they are reversible within a very short time period to encompass rapid temperature or atmosphere changes.
Current technology of excitation/analyzing units employs lock-in analyzers, modulated signal generators and photomultipliers. These devices are very complex and have a very large size. Downsizing of such equipment to handheld devices required in several applications is not possible both from a technical and a commercial (high prize) point of view.

Detection and analysis of optical sensing probes

IEE International Electronics & Engineering S.A.


A tie bolt for joining two parts together has a shaft. The shaft in turn has a primary thread for engaging a first part and a secondary thread for engaging a second part, wherein the primary thread and the secondary thread have different pitches. The tie bolt may be used to join together any two parts which are to be locked together to transmit torque.

The present disclosure relates to a tie bolt for engaging two parts, such as two shafts of a gas turbine engine, which tie bolt has two different threads.
Referring to FIG. 1, there is shown an axial load bearing surface 10 of a tie bolt 12 which is used to join together two parts, such as a forward shaft 14 and an aft shaft 16. The axial load bearing surface 10 requires a radial height 18 that limits the minimum bore 20 of another part 22 and also limits the size of a corner fillet 24. Friction of the axial load bearing surface 10 increases the assembly torque required to achieve a desired tensile preload.
The assembly torque advances the tie bolt 12, clamping the forward shaft 14 between the axial load bearing surface 10 and the aft shaft 16 via the primary thread 26.
It may be advantageous if the axial load bearing surface 10 can be eliminated. This may result in a reduction in the radial size of the tie bolt as well as removal of the friction of the axial load bearing surface from the installation torque procedure.


A snowthrower has independent wheel drive trains to allow steering by clutching one drive train while unclutching the other drive train. The clutch in each drive train comprises a plurality of pivotal pawls carried on a drive member with the pawls pivoting in a plane that is substantially perpendicular to the rotational axis of the drive member. The pawls have heads that project through one face of the drive member and tails located on an opposite face of the drive member. The heads of the pawls can engage or disengage notches that are fixed to the driven member to clutch or unclutch the drive and driven members. A shift member axially presses on the tails of the pawls to disengage the heads of the pawls from the driven member. The shift member is selectively moved by an operator using a steering lever on the snowthrower.

Snowthrowers are known having a pair of drive wheels for propelling the snowthrower over the ground. One drive wheel is carried on each side of the snowthrower. Typically, the rotational speed of the drive wheels can be adjusted by the operator using a speed control lever to adjust the ground speed of the snowthrower. In addition, a separate engagement control lever is provided for the operator to selectively engage and disengage the drive wheels. However, once the operator has selected a particular speed for the wheels using the speed control lever and has engaged the wheels using the engagement control lever, the wheels continuously rotate at the same speed.
Many such prior art snowthrowers cannot be steered by the operator other than by pushing or pulling on the handles of the snowthrower while the drive wheels are rotating. For example, to effect a turn to the left, the operator would typically push on the handles to turn the front of the snowthrower to the left. This can be physically demanding for some operators particularly in the snowy conditions in which snowthrowers are used. In addition, the steering provided by such a method typically results in jerky turning motions of the snowthrower to one side or the other. It is thus somewhat difficult to precisely steer the typical snowthrower having a pair of continuously rotating drive wheels.
Some prior art snowthrowers incorporate a steering system that permits the snowthrower to be more easily steered. For example, in some snowthrowers, the drive wheels are driven through a differential. The differential automatically reduces the speed of the drive wheel on the inside of a turn and automatically increases the speed of the drive wheel on the outside of a turn. Thus, while the operator still steers the snowthrower by pushing on the handles, the differential facilitates the turn and allows more precise directional control.
Unfortunately, differentials are relatively expensive and unduly increase the cost of the snowthrower. In addition, when one drive wheel driven by a differential spins or loses traction, the differential automatically transfers torque to the spinning drive wheel from the non-spinning drive wheel. Snowthrowers often operate on icy or snowy surfaces where one drive wheel might hit a patch of ice or snow and lose traction compared to the other drive wheel which retains traction. In this case, the snowthrower loses all traction since the differential transfers all the torque to the spinning drive wheel. As a result, a differential equipped snowthrower is not an effective way in a practical sense to steer a snowthrower.
U.S. Pat. No. 5,018,592 discloses another way to steer a snowthrower. In the 592 patent, each drive wheel is independently driven by a planetary gear transmission. A steering lever provided on each handle is coupled to the planetary gear transmission on the same side of the snowthrower. When the steering lever on one handle is manipulated by the operator, a pawl is removed from engagement with a ring gear to allow the ring gear to rotate and thereby place the planetary gear transmission on that side of the snowthrower into an inoperative, non-driving condition. This effectively unclutches the drive wheel on the inside of the turn to effect a skid type turn, i.e. the drive wheel on the inside of the turn is not powered while the drive wheel on the outside of the turn remains powered.
While the steering system shown in the 592 patent is effective for steering a snowthrower, a planetary gear transmission is relatively complex. In addition to the ring gear, the planetary gear transmission requires a sun gear and a plurality of planet gears between the sun gear and the ring gear. Thus, a durable, simple and less expensive system for steering a snowthrower is desirable.


Methods and an apparatus are provided for providing handoff information to a candidate mobile node initially served on a first carrier. The candidate mobile node may inform a wireless-communication network that hard-handoff criteria are met for the first carrier. The network may identify a plurality of neighboring mobile nodes served on a second carrier and within a threshold distance of the candidate. The network may receive a measurement of forward-link signal quality of the second carrier from each neighboring mobile node. Using the received forward-link-signal-quality measurements, the network may estimate the forward-link signal quality of the second carrier at the location of the candidate mobile node. If that estimated forward-link signal quality exceeds a signal-quality threshold, the network may provide hard-handoff information about the second carrier to the candidate mobile node.

Many people use mobile nodes, such as cell phones and personal digital assistants (PDAs), to communicate with and through wireless-communication networks. These mobile nodes and networks typically communicate over a radio-frequency (RF) air interface according to a wireless protocol such as Code Division Multiple Access (CDMA), perhaps in conformance with one or more industry specifications such as IS-95, IS-856, and IS-2000. Other protocols may be used as well, such as iDEN, TDMA, AMPS, GSM, GPRS, UMTS, EDGE, WiMAX (e.g., IEEE 802.16), LTE, microwave, satellite, MMDS, Wi-Fi (e.g., IEEE 802.11), and others now known or later developed.
In a typical wireless-communication network, a plurality of base stations are included, each of which defines one or more wireless coverage areas. A mobile node positioned in one of these wireless coverage areas can communicate over the RF air interface with the base station, which may provide the mobile node access to one or more circuit-switched, packet-switched, and/or other transport networks.
Mobile nodes and base stations conduct communication sessions (e.g. voice calls and data sessions) over frequencies known as carriers. A base station may provide service in a given wireless coverage area on one or more carriers. The communication from the wireless-communication network to a given mobile node are said to occur on a forward link, while those from a given mobile node to the wireless-communication network are said to occur on a reverse link. A typical mobile node periodically measures the strength of the carrier to determine a signal strength of the forward link.
A mobile node may travel between wireless coverage areas; for example, the mobile node may begin a wireless communication session in a first wireless coverage area and subsequently leave the first wireless coverage area. While the mobile node is being served in the first wireless coverage area, the mobile node may be served on a first carrier. As the mobile node leaves the first wireless coverage area, the mobile node may determine that the signal strength of the first carrier is relatively low.
Upon determining the signal strength of the first carrier is relatively low, the mobile node may request that the wireless-communication network perform a "handoff"; that is, a transfer of service between from the first carrier to a second carrier during a communication session. In particular, a "hard handoff" involves transferring the mobile node from the first carrier before establishing service on the second carrier while maintaining the communication session. In contrast, a "soft handoff" transfers the mobile node from the first carrier after establishing service on the second carrier while maintaining the communication session. After the handoff is performed, the mobile node is served on the second carrier.

Method and apparatus for intelligent mobile-assisted hard handoff


A system and methods for sanitation of ice storage equipment. An ozone generator provides a sanitizing agent comprised of a mixture of ambient air and ozone. The sanitizing agent is circulated through an ice storage bin. The sanitizing agent cleanses interior surfaces of the ice storage bin and also cleanses surfaces of an ice dispenser that dispenses ice from the ice storage bin.

A self-contained ice machine with dispenser provides a convenient source of ice (and typically water) for dispensing into cups or serving containers. These machines are commonly used in healthcare facilities to serve ice and water to patients.
Sanitation of the ice producing evaporator, ice storage bin, and dispensing mechanism typically requires manual application of a sanitizing solution to these components. Since all of the ice must be emptied from the bin and partial disassembly of the machine is required to access the interior of the bin, the frequency of sanitation is often on the order of weeks or months. Microorganisms can be introduced into the storage bin through gaps in the joints of the bin, the dispensing outlet, and through the ice produced by the evaporator, causing loss of sanitation during the periods between sanitizing.
Thus, there is a need for a system and method of cleaning an ice storage and dispenser equipment without disassembly.

Sanitation system and method for ice storage and dispensing equipment


A burner assembly for an oven appliance is provided. The burner assembly includes a gas burner and a flame spreader. The flame spreader defines a slot or a series of apertures that is substantially parallel to the gas burner. The slot or series of apertures can decrease a thickness of a boundary layer positioned adjacent the flame spreader or increase a velocity or a temperature or both of the boundary layer.

Oven appliances generally include a cabinet that defines a cooking chamber for receipt of food items for cooking. Heating elements are positioned within the cooking chamber to provide heat to food items located therein. The heating elements can include a bake heating element positioned at a bottom of the cooking chamber and/or a broil heating element positioned at a top of the cooking chamber. The heating elements can be gas burners that burn a combustible gas within the cooking chamber in order to provide heat to food items located therein.
In oven appliances with gas burners, a flame spreader is generally mounted above the gas burners in order to facilitate uniform heat distribution within the cooking chamber. In particular, the flame spreader can increase in temperature during operation of the oven appliance and provide a significant source of radiative heat to food items within the cooking chamber. Heated gases generated by the gas burners can provide the heat needed to increase the temperature of the flame spreader. However, a boundary layer of relatively cool air positioned adjacent the flame spreader can hinder convective heat transfer between the gas burner's heated gases and the flame spreader.
The thickness of the boundary layer and the velocity and temperature profiles of the boundary layer can affect convective heat transfer between the gas burner's heated gases and the flame spreader. In general, a relatively thinner boundary layer and a relatively high speed boundary layer can facilitate increased convective heat transfer. Also, facilitating direct contact between the gas burner's heated gases and the flame spreader can improve heat transfer therebetween.
Accordingly, a flame spreader with features for decreasing a thickness of a boundary layer positioned adjacent the flame spreader would be useful. In addition, a flame spreader with features for increasing a velocity or a temperature or both of a boundary layer positioned adjacent the flame spreader would be useful.


The present invention provides antibody-based arrays for detecting the activation state and/or total amount of a plurality of signal transduction molecules in rare circulating cells and methods of use thereof for facilitating cancer prognosis and diagnosis and the design of personalized, targeted therapies.

Tumor cells are often found in the blood of patients with various early stages of cancer as "micrometastases" (disseminated tumor cells), and are also found in metastatic cancers. The number of tumor cells in blood depends on the stage and type of the tumor. Tumors are extremely heterogeneous. As a result, a biopsy from a single site might not represent the heterogeneity in a tumor population. Biopsies are typically obtained on primary tumors; however, most metastatic tumors are not biopsied, making molecular analysis of tumor samples even more difficult.
During tumor metastasis, the most aggressive tumor cells leave the primary tumor and travel through the blood and lymphatic system to reach a distant location. Thus, circulating tumor cells from blood represent the most aggressive and homogenous population of tumor cells. The number of metastatic tumor cells in blood can vary from one to several thousand cells per milliliter of blood. Accordingly, specific and sensitive methods are needed to detect these cells for diagnostic and prognostic purposes. The present invention satisfies this need and provides related advantages as well.

This patent is subject to a terminal disclaimer.

Antibody-based arrays for detecting multiple signal transducers in rare circulating cells


A resid hydrotreating process hydrotreats a resid bottoms fraction from the reduction of crude oil. The hydrotreated bottoms fraction is then subjected to deep vacuum reduction and in some cases deasphalted by solvent extraction to produce an oil suitable for use as a catalytic cracking feedstock and a resins fraction suitable for solvating resid in a hydrotreating process.

Maximizing the yield of highly-valued petroleum products from crude oil requires that refiners convert relatively high-boiling materials such as petroleum residue, better known as resid, to more valuable, lower boiling products. One method for converting resid to more valuable products involves hydrotreating the resid and fractionating the products using a resid hydrotreating unit, or RHU.
Refiners often fractionate hydrotreated resid by atmospheric and/or vacuum distillation. The distillation tower bottoms produced in these units are known as RHU bottoms, hydrotreated resid bottoms fractions or RHU resid. Unlike most lower-boiling hydrotreated materials removed by distillation, RHU bottoms require additional processing to remove materials that foul or poison downstream processing units.
Non-reactive carbonaceous solids are one particularly undesirable component of RHU bottoms. These generally non-reactive solids are known to foul process piping, vessels and valves as they precipitate from RHU bottoms.
RHU bottoms also contain relatively high concentrations of RAMS and of metals such as vanadium and nickel. These metals are particularly undesirable RHU bottom components because they are known to poison various catalysts used in downstream processing equipment such as fluidized catalytic cracking units.
Efficient processing of RHU bottoms preferably requires fractionating the bottoms and reducing the concentration of RAMS carbon, metals and heteroatoms such as nitrogen and sulfur in the lighter bottoms fractions. This permits the lighter, higher quality fractions to be recycled for reprocessing, used as process solvents or diluents or catalytically upgraded to more valuable products. Our U.S. Pat. Nos. 4,940,529; 5,013,427; 5,124,025; 5,124,026 and 5,124,027 disclose several processes for using and upgrading RHU bottoms. Each of these patents is hereby incorporated by reference.
In our processes, two or more solvent extraction steps typically separate the RHU bottoms into two or more fractions generally characterized as asphaltenes, resins and oils. These processes typically fractionate hydrotreated RHU bottoms using a solvent extraction process which processes the bottoms through a series of near-supercritical and supercritical separators operating at a generally constant pressure and successively higher temperatures. In a typical three-stage unit, an asphaltene phase is separated from resins, oils and solvents in a first separator. A second separator separates resins from the deasphalted phase removed from the first separator, and a third separator removes solvent from an oil/solvent phase removed from the second separator.
The relatively heavy asphaltene fraction typically contains high levels of metals and RAMS carbon and can be coked or used as solid fuel. The resin fraction can be recycled to the RHU hydrotreating reactor for mixing with virgin resid feedstock, and the relatively light oil fraction can be catalytically cracked in a fluidized catalytic cracking unit (FCCU) or treated in a catalytic feed hydrotreating unit (CFHU).
While our processes provide a variety of improved methods for separating and using fractions from heavy feedstocks such as RHU bottoms, refiners desire additional processes which simultaneously can maximize the yield of the relatively light oil fraction and minimize the metal, heteroatom and RAMS carbon concentrations in the oil fraction.
It is known that solvent selection can alter the quality and yield of deasphalted oil (DAO) produced in a solvent extraction unit (SEU). Generally, when an SEU employs a relatively high molecular weight solvent, asphaltene yields are reduced and DAO yields maximized. Unfortunately, DAO produced in this manner contains relatively higher levels of RAMS carbon and metals. Conversely, lower molecular weight solvents often yield more asphaltenes and less of a higher quality DAO.
Examples 1 and 2 summarized in Tables 1 and 2 below illustrate SEU solvent selection effects. In Example 1, a three-stage solvent extraction unit employing n-butane solvent separated a hydrotreated resid into asphaltene, resin and oil fractions. The solvent to feed ratio was approximately 8:1 by volume, with the deasphalting, resin/oil and solvent recovery separators operating at about 660 psi and 291, 310 and 350 degrees Fahrenheit, respectively. In Example 2, n-pentane solvent extraction was conducted in an identical solvent extraction unit having three separators operating at about 550 psi and 363, 393 and 450 degrees Fahrenheit. Comparing Examples 1 and 2 illustrates that while the higher molecular weight pentane solvent doubled DAO yields, use of this solvent also increased the heteroatom and RAMS carbon concentration of the DAO.
TABLE 1 ______________________________________ Resid Oils Resins Asphaltenes ______________________________________ Wt % 100 17 20 63 N, wt % 0.92 0.4 0.5 1.4 S, wt % 2.78 1.42 1.88 3.24 Ramsbottom Carbon, 41 6 11 62 wt % Ni, ppm 70 1 2 131 V, ppm 140 <2 <2 284 ______________________________________
TABLE 2 ______________________________________ Resid Oils Resins Asphaltenes ______________________________________ Wt % 100 34 23 43 N, wt % 0.92 0.53 0.98 -- S, wt % 2.78 1.80 2.22 2.99 Ramsbottom Carbon, 41 11 23 70 wt % Ni, ppm 70 1 4 192 V, ppm 140 <2 2 329 ______________________________________
Other examples of solvent selection effects can be found in the paper entitled "How Solvent Selection Effects Extraction Performance", presented in March, 1986 at the National Petroleum Refiners Association Annual Meeting, Paper No. AM-86-36. The examples presented in that paper as well as Examples 1 and 2 above suggest that an improved deasphalting process requires more than solvent optimization if oil yield and quality are to be simultaneous maximized.
Other workers in the field of solvent extraction have attempted to improve solvent extraction processes generally by increasing the number of solvent extraction steps or by recycling various process streams within the solvent extraction unit. For example, U.S. Pat. No. 4,305,814 discloses the use of up to five individual separation steps to further differentiate the components of a hydrocarbonaceous feedstock, while U.S. Pat. Nos. 4,239,616 and 4,290,880 seek to improve SEU performance by recycling a portion of the asphaltene or resin fraction through the same or subsequent separation zones.
While the SEU modifications discussed above may improve SEU performance in some cases, the modified processes are complex, not easily changed as operational requirements vary, or seem unlikely to produce significant improvements in DAO quality without decreasing DAO yields and/or increasing asphaltene yields. Therefore, refiners continue to desire a resid hydrotreating process which includes a deasphalting process capable of minimizing RHU bottoms asphaltene production while at the same time providing an oil fraction having relatively low concentrations of RAMS carbon, metals and/or heteroatoms.

Resid hydrotreating using solvent extraction and deep vacuum reduction


Memory cells and methods for programming and erasing a memory cell by utilizing a buried select line are described. A voltage potential may be generated between a source-drain region and the buried select line region of the memory cell to store charge in a storage region between the source-drain and buried select line regions. The generated voltage potential causes electrons to either tunnel towards the buried storage region to store electrical charge or away from the buried storage region to discharge electrical charge.

Flash memory and other non-volatile memories are structured to have an array of memory cells arranged in rows and columns. Each memory cell comprises a floating gate transistor, and similar to the field-effect transistor, has a control gate, a source region and a drain region. The source region is separated from the drain region by a channel region, but unlike the field-effect transistor, a floating gate typically made of doped polysilicon is disposed over the channel region and electrically isolated from the channel region by a thin insulating layer of gate oxide. The control gate is then formed over the floating gate, and separated by another layer of insulator. Therefore, the floating gate is insulated from the channel, the control gate and all other components of the flash memory cell, thus "floating."
The flash memory cell can be programmed to store charge representing data, erase the stored charge to prepare for another program operation, or read the data in the programmed memory cell. The flash memory cell is programmed by storing charge on the floating gate, which thereafter remains on the gate for an indefinite period. Charge is stored on the floating gate by applying appropriate voltages to the control gate and the drain region or the source region. An electrical charge may be stored in the floating gate by a number of different ways. For example, programming can be performed by channel hot-electron injection (CHE), where a sufficiently large positive bias is applied to the control gate while the source is grounded to attract electrons through the gate oxide and into the floating gate region. The voltage applied to the control gate, called the programming voltage, determines the amount of charge to store on the floating gate. Before programming, the flash memory cell is generally erased by removing any charge trapped in the floating gate. An erase voltage is applied to the control gate to generate a gate voltage having a polarity opposite to that used in the programming operation. For example, in a process called drain-Fowler-Nordheim (FN) tunneling, a relatively large negative bias is applied on the control gate and a positive bias is applied to the drain region to cause the electrons to tunnel towards the drain through the gate oxide and deplete any charge from the floating gate.
After a memory cell has been programmed, the flash memory cell may be read by applying a positive control gate to source voltage, called read voltage. The amount of charge stored on the flash memory cell determines the magnitude of the threshold voltage that must be applied to the control gate to allow the flash memory cell to conduct current between the source and the drain. The source is coupled to ground, and a suitable positive voltage is applied to the drain, which is used as the output terminal of the cell. As negative charge is added to the floating gate, the threshold voltage of the flash memory cell increases. During a read operation, the read voltage applied to the control gate must be large enough to render the cell conductive if no charge is stored on the floating gate, but not large enough to render the cell conductive if charge is stored on the floating gate. Therefore, if the floating gate of the flash memory cell is charged, the drain will remain at the positive voltage and output a "1" value. If the floating gate of the flash memory cell is not charged, the cell will ground the drain and output a "0" value.
Two types of flash memory array architectures are the "NAND" and "NOR" architectures, so called for the logical form in which the basic flash memory cell configuration for each is arranged. FIG. 1 illustrates a typical NOR flash memory array 10 of conventional design. The array 10 includes memory cells 18 arranged in rows and columns. The drains of the memory cells 18 of a single column are coupled to each other in series by a common bitline 20 (BL-1 to BL-3), and the gates of the memory cells 18 of a single row are coupled to each other by a common select line 30 (WL-1 to WL-3). The sources of the memory cells 18 in the array are additionally coupled to an array source 40.
The read operation is performed on a row-by-row basis, where the read voltage is applied to a selected select line 30, thereby applying the read voltage to the control gates of all the memory cells in that row. The array source 40 is coupled to ground and the bitline 20 for each column is precharged to a supply voltage VCC, such that if the gate to source voltage of each memory cell 18 of the selected row is greater than the threshold voltage, the channel region of the memory cell 18 will become conductive. However, since charge must be transported through the gate oxide during programming and erase operations, memory cell 18 will get some incremental damage over time, eventually making it difficult to properly distinguish between a "1" and a "0". This limits the number of program/erase cycles to typically 1 million.
FIG. 2 is a block diagram illustrating the formation of a prior art metal oxide semiconductor flash memory cell 200 having a floating gate 212. The flash memory cell 200 includes a control gate 230 formed over the floating gate 212. Both the control gate 230 and the floating gate 212 are deposited using a standard polysilicon layer, except the floating gate 212 is encapsulated by a dielectric material (not shown). The control gate 230 is connected to the select line 30 of FIG. 1, and is separated from the floating gate 212 by an insulator 232 of appropriate material and thickness. A thin layer of gate oxide 233 separates the floating gate 212 from the silicon surface of a channel region 225, which is formed by doping commercially available silicon material. The channel region 225 separates a source region 214 and a drain region 216, which are also formed by appropriately doping the silicon layer, and may be either p-type or n-type depending on the transistor-type of the memory cell 200. The source and drain regions 214, 216 are isolated from the source and drain regions of adjacent memory cells by shallow trenches 220, that are formed by depositing one of several types of dielectric material known in the art.
As the control gate 230 is subjected to high voltage levels during every program and erase operation (either by CHE or FN tunneling), the silicon surface of the memory cell 200 body and the gate oxide layers 233 between the gates 212, 230 are incrementally damaged due to hot electrons that are induced by the higher voltage levels. Charges may be trapped at the silicon-oxide interface and within the gate oxide layers 233. As the electrons become heated by the high energy fields, their kinetic energy increases, causing the electrons to bombard the silicon-oxide interface, and become trapped. Consequently, the damage to the oxide layers 233 and silicon surface gradually changes the properties of the memory cell 200 so much that the memory cell's 200 threshold voltage may be modified. The damaged interface and the oxide layers 233 may also cause charge to leak from the control gate 230, the floating gate 212 or the channel region 225 due to one or more of the oxide layers 233 deteriorating due to trapped electrons. The read voltage level applied to the control gate 230 may become insufficient to carry out a proper read operation as the properties of the memory cell 200 are altered. Eventually, it becomes difficult to distinguish the different threshold voltage levels of the memory cell 200 during a read operation. Additionally, the type of gate oxide and the thickness of the gate oxide layer are limited to certain materials, known in the art, that must achieve the particularized threshold voltage while withstanding the damage to the control gate 230 in order to meet industry standard program/erase cycles during the life of the cell.
There is, therefore, a need to, for example, avoid damaging effects of the higher voltage levels on the control gate.

Systems, methods and devices for a memory having a buried select line


A cassette housing assembly of a tape recorder is provided including a cassette housing having an upper surface portion, side surface portions, and a lower surface portion having a fixed stopper formed at one side thereof. The housing forms a space for receiving a cassette. A mobile stopper is installed on the lower surface of the upper surface portion of the cassette housing member to be capable of moving along the lower surface. A spring is coupled to one side of the lower surface of the upper surface portion of the cassette housing member and to one side of the mobile stopper to bias the mobile stopper. The cassette housing assembly minimizes damages to the cassette housing assembly due to incorrect insertion of the cassette can be prevented and a user can easily recognize mis-insertion of the cassette.

1. Field of the Invention
The present invention relates to a cassette housing assembly of a tape recorder, and more particularly, to a cassette housing assembly of a tape recorder having an apparatus for preventing an incorrect insertion of a cassette in the cassette housing by being upside down.
2. Description of the Related Art
A tape recorder is for recording/reproducing audio or video information on/from a magnetic tape. In the tape recorder, a cassette housing assembly is provided to load a cassette onto a deck. When a cassette is inserted into a cassette housing assembly and a switch is turned on, the driving of the cassette housing assembly begins and the cassette is placed at a loading position on the deck.
FIG. 1 shows a deck of a tape recorder, more particularly, an 8 mm camcorder.
Referring to the drawing, a deck 10 includes a chassis assembly 11, a cassette housing assembly 12, a head drum assembly 13, and a loading mechanism 15. On the chassis assembly 11, installed are a reel disk assembly for running the magnetic tape of the cassette (not shown) by being inserted in a spool of the cassette and a head drum assembly 13 including a magnetic head (not shown). A space for receiving the cassette is formed in the cassette housing assembly 12. The cassette housing assembly 12 has an upper surface portion 12a, side surface portions 12b and 12b', and a lower surface portion 12c. The loading mechanism 15 is installed between the side surface portion 12b' of the cassette housing assembly 12 and the chassis assembly 11. The cassette housing assembly 12 is lowered by the loading mechanism 15 to a level of the chassis assembly 11 to load the cassette, or is lifted to unload the same.
In the cassette housing assembly of the tape recorder structured as above, an apparatus for preventing an incorrect insertion of a cassette is provided. A incorrect-insertion preventing function is usually performed by a stopper (not shown) which is installed at one side of the lower surface of the cassette housing assembly. For instance, when a cassette (not shown) is inserted in a normal state, the stopper is positioned in a groove provided between the leading portion of a main unit of the cassette and a cassette lid thereof. Next, when loading of the cassette begins, the cassette lid (not shown) is opened by a lid contact portion (not shown) formed on a side surface of the chassis, thus exposing a magnetic tape. When the cassette is incorrectly inserted, the stopper is not positioned into the groove and thus the cassette lid is not opened. As a result, the cassette can be correctly maintained in the cassette housing assembly.
FIG. 2 shows a cassette housing assembly according to the conventional technology. Referring to the drawing, the cassette housing assembly 22 includes an upper surface portion 22a, side surface portions 22b and 22b' respectively formed to the left and right sides of the upper surface portion 22a, and a lower surface portion 22c. A cassette is inserted in a direction indicated by arrow "C" into a space formed by the upper surface, side surface and lower surface portions 22a, 22b and 22b', and 22c. A fixed stopper 25 is installed at one side of the lower surface portion 22c. The fixed stopper 25 vertically protrudes from the plane of lower surface portion 22c.
FIGS. 3A to 3C are side views of the cassette housing assembly in which a cassette is inserted, viewing from a direction indicated by arrow "A" in FIG. 2.
Referring to FIG. 3A, a conventional cassette 38 has a main unit 38a, an outer lid 36 rotatably installed at a leading portion 38b of the main unit 38a, and an inner lid 37 rotatably installed with respect to the outer lid 36. The cassette 38 is inserted in a direction indicated by arrow "C" into a space defined by an upper surface portion 22a, side surface portions 22b and 22b', and a lower surface portion 22c of the cassette housing assembly 22. A groove (not shown) is provided between the leading portion 38b of the main unit 38a and the outer lid 36, as described in the above. Therefore, when a cassette is correctly inserted, the fixed stopper 25 shown in FIG. 2 is positioned in the groove and thus insertion of the cassette 38 into the cassette housing assembly 22 is not hindered.
FIG. 3B shows a state in which the cassette housing assembly is lowered to a level of the chassis assembly 11 (see FIG. 1). The cassette housing assembly 22 is lowered by the operation of the loading mechanism 15 (see FIG. 1). Here, the outer lid 36 and the inner lid 37 open by contacting a lid contact portion (not shown) formed at one side of the chassis assembly 11. Reference numeral 31 indicates a protrusion formed on the upper surface portion 22a of the cassette housing assembly 22. The inner lid 37 contacts the protrusion 31 as it rotates and moves backward.
FIG. 3C shows a state in which a cassette is inserted upside down. When the cassette is inserted upside down into the cassette housing assembly 22, the fixed stopper 25 is not positioned in the groove (not shown) provided between the cassette leading portion 38b and the cassette outer lid 36. Accordingly, as shown in the drawing, the cassette 38 slides along the upper surface of the fixed stopper 25. That is, since the main unit 38a of the cassette 38 is inserted into a restricted space of the cassette housing assembly 22 defined by the protrusion 31 and the fixed stopper 25, correct insertion of the cassette in the cassette housing assembly 22 cannot be performed. Also, a user determines whether the cassette is correctly inserted by examining a state of insertion thereof.
However, the above conventional apparatus for preventing an incorrect insertion of a cassette has the following disadvantages.
When a user incorrectly inserts the cassette 38 into the cassette housing assembly 22 even though the insertion of the cassette 38 may be prevented by the fixed stopper 25, the cassette almost enters in the cassette housing assembly 22 because there is an enough space inside the cassette housing assembly 22 for allowing the cassette to slide. In doing so, the surface of the cassette 38 may be scratched by the fixed stopper 25 and also the cassette can contact the other mechanisms or elements in the deck 10 and damage the same. Also, since a user usually determines whether the cassette is correctly inserted in the deck by checking the distance that the cassette is inserted into the deck, a misjudgment on whether the cassette has been correctly inserted may occur.

Cassette housing having cassette stoppers to prevent mis-insertion


An NMR sample tube is offered which can be spun at high speed stably. The NMR sample tube is adapted for use in solid-state NMR spectroscopy and includes a tubular member, spacers, and cover bodies. The spacers are disposed inside the tubular member. Each spacer has first and second surfaces located on opposite sides. The first surfaces of the spacers define a space filled up with a sample. The tubular member has openings which are closed off by the cover bodies.

Field of the Invention
The present invention relates to an NMR sample tube and NMR spectrometer.
Description of Related Art
An NMR (nuclear magnetic resonance) spectrometer is an analytical instrument for detecting a signal arising from atomic nuclei having spin magnetic moments by applying a static magnetic field to the nuclei to induce the spin magnetic moments for producing a Larmor precession and irradiating the nuclei with RF waves having the same frequency as the precession to bring the nuclei into resonance.
Samples to be investigated by NMR include two types: solution samples and solid samples. Among them, many solution samples give quite sharp NMR spectra and, therefore, it is widespread to perform molecular structural analysis of chemical substances from the obtained high-resolution NMR spectra.
On the other hand, in an NMR spectrum of a sample in solid phase, interactions (such as dipolar interactions) which would be nullified by rotational Brownian motion in a solution manifest themselves directly and so the spectral linewidth broadens extremely, thus obscuring chemical shift terms. Therefore, in an NMR spectrum, it is impossible to isolate the signal peaks arising from various portions of a molecule under investigation. As a result, it has been thought that solid-state NMR spectroscopy is unsuited for molecular structural analysis.
MAS (magic angle spinning) has attracted attention as a method of overcoming this undesirable phenomenon and giving rise to sharp solid-state NMR spectra. In particular, anisotropic interactions are removed and chemical shift terms can be extracted by tilting the sample tube at the magic angle of 54.7° to the static magnetic field and spinning the tube at high speed.
For example, JP-A-2011-227036 discloses an NMR spectrometer equipped with a sample spinner having a gas bearing that supplies gas into between a sample tube and a sample tube-holding mechanism to keep the sample tube afloat. The gas bearing permits the sample tube to be spun at high speed about an axis tilted at 54.7° to the static magnetic field.
In such an NMR spectrometer, it is generally required that the sample tube be spun at high speeds of several kilohertz to tens of kilohertz within the static magnetic field in order to perform good NMR spectroscopy of solid samples employing MAS.
To implement the MAS method, a solid sample placed within a static magnetic field must be spun at high speed. However, it is not easy to obtain rotational speeds of kilohertz to tens of kilohertz which are regarded as needed spinning speed. Accordingly, gas bearing techniques have been heretofore adopted to obtain such rotational speeds, and various methods have been proposed.
FIG. 11 shows a conventional high-speed spinner for solid-state NMR spectroscopy. The spinner includes a cylindrical stator 11 that surrounds a rotor 12 with a slight spacing therebetween. A solid sample is sealed in the rotor 12. The bottom of the cylindrical stator 11 is covered by a thrust stator 13. A thrust rotor 14 is mounted at the bottom of the rotor 12 in an opposite relation to the thrust stator 13 to maintain the position of the rotor 12 taken in the thrust direction. A turbine 16 is mounted in an upper part of the rotor 12 to impart a rotating force to the rotor 12 by gas jets ejected from turbine nozzles 15 formed in the stator 11. The rotor 12, thrust rotor 14, and turbine 16 together constitute a rotor-turbine assembly that spins at high speed.
FIG. 12 is a cross section of a conventional high-speed spinner for solid-state NMR spectroscopy, the cross section being taken along line bb of FIG. 11. As is obvious from FIG. 12, a thin layer of gas is formed between the stator 11 and the rotor 12 by continuously supplying gas from plural gas feeding holes 911 formed in the stator 11 toward the interior of the stator 11. This results in a journal gas bearing. That is, the frictional resistance between the stator 11 and the rotor 12 is reduced to a minimum. Consequently, the rotor-turbine assembly can be spun inside the stator 11 at high speed.
FIG. 13 is a cross section of the conventional high-speed spinner for solid-state NMR spectroscopy, the cross section being taken along line cc of FIG. 11. As is obvious from FIG. 13, gas jets ejected from the turbine nozzles 15 formed eccentrically relative to the stator 11 act on the blades of the turbine 16, imparting a rotating force on the rotor-turbine assembly. The gas jets acting on the turbine 16 change in orientation and form gas streams 17 shown in FIG. 11, the streams 17 being discharged out of the high-speed spinner.
Development of a high-speed spinner using such a hydrostatic bearing was commenced by Doty (U.S. Pat. No. 4,456,882). Then, Bartuska et al. (U.S. Pat. No. 4,511,841) have proposed a high-speed spinner using a combination of a hydrostatic bearing and a hydrodynamic bearing. Doty et al. (U.S. Pat. No. 5,508,615) have attempted to make improvements in the hydrostatic bearing.
It has been found that when the above-described high-speed spinner is used and the spinning rate of the sample tube is raised, if the natural vibration frequency of the sample tube comes into coincidence with the spinning speed, synchronous vibrations occur. This phenomenon is observed when a rotor-turbine assembly supported by a gas bearing is spun at high speed. Generally, the phenomenon is caused by an imbalance in the rotor-turbine assembly. If the imbalance is large, the sample tube may come into contact with the gas bearing at the resonant point that is a natural vibration frequency at which synchronous vibrations take place, thus causing seizure or damage. This makes it impossible to raise the spinning speed. This will be described in further detail below.
The resonant point of synchronous vibrations is given as follows.
In cylindrical mode, the resonant point is given by
      N    1    =            1              2                π                                (                  k          M                )                    1        2
In conical mode, the resonant point is given by
      N    2    =            1              2                π                                (                              2                        k                                                                                J              2                                                          I              t                        -                          I              0                                      )                    1        2            where M is the mass of a rotor-turbine assembly supported by one radial bearing, k is the bearing rigidity per radial bearing, It is the inertial moment about the center of gravity of the rotor-turbine assembly, I0 is the polar inertial moment about the central line of the rotor-turbine assembly, and J is a half of the center-to-center distance of two radial bearings.
FIG. 14 is a graph showing the rotational characteristics of a rotor-turbine assembly supported by a gas bearing. The horizontal axis indicates the spinning rate of the rotor-turbine assembly. The vertical axis indicates the amplitude of swings of the rotor-turbine assembly. As shown in FIG. 14, in order to spin the rotor-turbine assembly at high speed, the two resonant points given by the above-described equations must be exceeded. It is necessary to reduce the imbalance in the rotor-turbine assembly to permit it to be spun at high speeds beyond the resonant points.
Therefore, in order to spin the sample tube at high speed in an NMR instrument, the sample tube is required to be filled up with a sample such that the imbalance in the filled sample tube is reduced. However, solid samples filling the sample tube may assume various states such as powdered state, pasty state, and rubber-like state. Also, solid samples assume various forms such as particulate form, filmy form, and block form. For these reasons, it is difficult to fill up a sample tube with a sample with a small amount of imbalance. It has been difficult to spin a sample tube at high speed stably.


Depolarizing system for polarized light formed of a birefringence crystal wedge which receives the beam of polarized light at a first surface and outputs spatially depolarized light from its output surface. The wedge may include small steps on one of the surfaces or special orientations to depolarize the light. The wedge may be substantially triangular in shape so that the surface decreases from one side to the other.

This invention pertains generally to polarization control in fiber optic and free-space optical systems. Specifically the present invention relates to an optic apparatus for depolarizing polarized light in optical fibers and in free space.
Many components in advanced fiber optic communication (T. Okoshi, xe2x80x9cRecent Advances in Coherent Optical Fiber Communication Systems,xe2x80x9d J. Lightwave Technology, Vol. LT-5, No. 1, pp. 44-52, 1987) and sensing systems, such as interferometers and electro-optic modulators, are polarization sensitive. In order for these polarization sensitive devices to function properly, an input light""s polarization state is precisely aligned with a particular axis of the devices. Unfortunately, the polarization state of light propagating in a length of standard circular fiber varies along the fiber due to random birefringnece induced by thermal stress, mechanical stress, and irregularities of the fiber core (I. P. Kaminov, xe2x80x9cPolarization in Optical Fibers,xe2x80x9d IEEEE J. Quantum Electronics, Vol. QE-17, No. 1, pp. 1-22, 1981). Thus typically, a standard optic fiber outputs elliptically polarized light with varying degrees of ellipticity, and with the major elliptical axis at an arbitrary angle relative to a reference orientation.
One prior art method of solving the polarization problem utilizes polarization controllers. Polarization controllers, including tri-plate controllers, fiber tri-loop controllers, and the Yao controller (see Photonics Spectra, April issue, pp. xxx, 1998), typically convert an arbitrary polarization state into a desired polarization state. However, such polarization controllers cannot accommodate rapid polarization fluctuations in the fiber and therefore are unsuitable in systems where the polarization state fluctuates due to time dependent thermal or mechanical stresses on the fiber, or due to polarization fluctuations of the laser light itself.
Another method of solving the polarization fluctuation problem is to depolarize polarized light. One prior art m method of depolarizing light utilizes an electro-optic modulator to rapidly modulate the polarization state. However, the electro-optic modulator output is not truly depolarized. The output of the electro-optic modulator depolarizer only appears depolarized to an observer or detector having a response slower than the modulation speed. Another disadvantage of the electro-optic modulator depolarizer is high cost. Typical electro-optic modulator systems utilize a high frequency microwave signal source and an expensive electro-optic modulator. A third disadvantage of such an electro-optic depolarizer is the high loss, resulting from coupling between optical fibers and the waveguide in the electro-optical modulator.
A second prior art method for depolarizing light uses a recirculating fiber loop which includes a 2xc3x972 fiber coupler with two input ports, 1 and 2, and two output ports, 3 and 4. (xe2x80x9cTunable single mode fiber depolarizerxe2x80x9d by P. Shen, J. C, Palais, and C. Lin, Electronics Letters, Vol. 33, No. 12, pp. 1077-1078). The output port 4 is connected with input port 2 to form a recirculating loop. A first polarization controller is placed at input port 1 and a second polarization controller is placed inside the loop. The loop length is much larger than the coherence length of the input light so that the recirculating beams do not interfere with one another. Due to the incoherent addition of the recirculating beams, the output at port 3 is the superposition of different polarization states with different intensities. Depolarization occurs by averaging over the many different polarization states of the recirculating beams. The degree of polarization at output port 3 depends on the input state of polarization, the coupling ratio of the coupler, and the birefringnece of the fiber loop. By properly adjusting the two polarization controllers, polarized light entering input port 1 exits output port 3 unpolarized.
One disadvantage of using a recirculating fiber loop is that the time coherence of the depolarized beam is degraded and therefore may not be suitable for coherent communication systems. In addition, interference noise may arise when the loop length is not sufficiently longer than the coherence length of the input beam. Furthermore, device performance depends strongly on the input signal""s coherence length and thus the recirculating fiber loop is not suitable for systems where diversified signal sources are present. Finally, the device may be very bulky due to the long loop length (as long as a few km for DFB lasers).
Due to the disadvantages of prior art methods of depolarizing light described above, improved method of depolarizing light is needed.
The present invention relates to a method and apparatus of depolarizing or randomizing polarization states of an optical beam. One embodiment of the invention uses a wedged birefringent crystal with its wedge formed by many small steps. Another embodiment of the invention contains many randomly oriented birefringent crystal chips. Different parts of the optical beam passing through the apparatus experience different retardations and exit with different polarization states, resulting a spatially depolarized light beam. Focusing the spatially depolarized beam into an optical fiber results in a depolarized guided wave.

Devices for depolarizing polarized light