The present invention, generally speaking, provides a time shift angle demodulator that is of simple construction and has an extended linear range. Range extension is achieved by using the input signals directly, not simply post-processing the S-PFD outputs. In accordance with one embodiment of the invention, a method of measuring the phase or frequency of a periodic input signal uses a periodic reference signal and includes comparing the input signal to the reference signal to obtain a lead signal and a lag signal; changing the count of an up/down counter in dependence on the input signal, the reference signal, the lead signal and the lag signal; and using the lead signal, the lag signal and the count signal to produce a phase or frequency signal. In accordance with another embodiment of the invention, an apparatus for measuring the phase or frequency of a periodic input signal uses a periodic reference signal and includes a comparison circuit for comparing the input signal to the reference signal to obtain a lead signal and a lag signal; a logic circuit, including an up/down counter, responsive to the input signal, the reference signal, the lead signal and the lag signal to change the count of the up/down counter; and circuitry for using the lead signal, the lag signal and the count signal to produce a phase or frequency signal.

1. Field of the Invention
The present invention relates to direct phase and frequency demodulation.
2. State of the Art
Much attention has been focused in recent years on the realization of radio systems using digital logic. Digital logic is less subject to manufacturing variability and is often much simpler and consumes lower power than an equivalent analog structure. In particular, current communications techniques, at least in wireless communications, are based in large part on quadrature modulation and demodulation. Such modulators and demodulators are relatively power-hungry and subject to various inaccuracies and limitations that become apparent as performance is pushed to higher levels.
One proposal for a generally-applicable angle demodulator is described in the dissertation by the present inventor entitled Extended Phase Shift Keying, deposited in the library of the University of California at Davis in August 1998. Of particular interest is the so-called Time-Shift Angle Demodulator (TSAD), described in detail in Section 3.6.2 and Appendix B of the dissertation.
A block diagram of a TSAD 100 is shown in FIG. 1. The TSAD includes two stages, a time difference detector 101 and a pulse combiner/filter 103. The time difference detector measures time between adjacent the rising zero crossings of the two input signals s(t) and r(t). The first of these input signals is the angle modulated signal s(t). The second input signal is an applied reference signal r(t), which is assumed to be matched to the carrier of the angle modulated signal.
The timing information measured by the time difference detector is provided on one of two outputs, a(t) and b(t), at any one time, as a fixed amplitude pulse with width equal to the timing difference of the input signals. The output selected depends on which input signal a rising zero crossing is observed first. If a rising zero crossing of the modulated signal s(t) occurs first, then the measurement output appears on the phase lead output, a(t). If a rising zero crossing of the reference signal r(t) occurs first, then the measurement output appears on the phase lag output, b(t).
The time difference detector may be realized as a sequential phase-frequency detector (S-PFD), as shown in FIG. 2. The pulse combiner/filter may take the form of a differencing circuit followed by a low-pass filter (LPF).
Referring to FIG. 3, an example of operation of the TSAD is shown. The input signal s(t) is assumed to have a frequency 20% lower than that of the reference signal r(t). Initially, the phase of s(t) leads the phase of r(t). The two outputs from the time difference detector, a(t) and b(t), are shown. As the phase of s(t) shifts from leading to lagging the phase of r(t), a transition occurs in which pulses, instead of appearing in the output signal a(t), appear instead in the output signal b(t). The signals a(t) and b(t) are combined to form a difference signal a(t)-b(t), which is low-pass filtered, yielding an output signal v(t) that reflects the linear phase ramp relationship between the two input signals. Because the S-PFD aliases when phase shifts exceed 2π, the S-PFD output "jumps" following the accrual of 2π radian phase shift on the reference signal with respect to the input signal. Corresponding jumps are reflected in the output signal v(t).
The transfer characteristic of the TSAD of FIG. 1 is shown in FIG. 4, showing the output v(t) as a function of the time difference d(t), where Tc represents the period of the reference signal. The transfer characteristic consists of overlapping line segments each having an extent of 2Tc, which corresponds to 4π radians of phase for the reference signal. When the time difference between the input signals becomes greater than 2π or less than −2π, a jump occurs to the next line segment as shown by the arrows in FIG. 4.
In order to increase the usefulness of the TSAD, it is necessary to eliminate the foregoing jumping characteristic, by shifting the line segments of FIG. 4 to form a single continuous line, as illustrated in FIG. 5. Such modification of the transfer relation may be accomplished using a "phase unwrapper," a diagram of which is shown in FIG. 6. The phase unwrapper 610 includes a jump detection unit 611, a counter 613, a multiplier 615 and an adder 617. In operation, when a jump is detected, the appropriate signal offset, expressed as 2πK, is added or subtracted to form a corrected output signal vu.
Referring to FIG. 7, correction may also be achieved using phase scaling. Both the input signals are passed through respective 1/N frequency dividers 701, 703 before being applied to the TSAD of FIG. 1. In order for the input signal to effect a 2π phase shift at the input of the TSAD, there must be a 2πN phase shift at the input to the frequency divider. Thus, with respect to the original signal, the TSAD appears to have had its range extended by a factor of N.
Further simplification of the TSAD, while preserving the transfer relationship of FIG. 5, is desired.


In a computer system having multiple components, a bidirectional scheme which allows bidirectional data communications between components over a single wire without using termination resistors by placing two drivers from two corresponding processor cores on the same wire, and allowing simultaneous data transfer in two directions. This doubles the effective bandwidth per pin without requiring a modification to the clocking scheme of the system. The driver is impedance matched to the line, and used as the termination for the driver on the opposite end of the wire. This reduces the termination power, since no power is consumed when both drivers are in the same state. The bidirectional flow of data creates a ternary encoding, with a relatively simple decoding possible.

Prior art approaches to inter-chip communication utilize unidirectional signal flow on either a point to point interconnect, or a shared bus. For systems in which the electrical length of the interconnect is significant in relation to the edge rate or fundamental frequency of the signals traversing them, and operation at the highest possible speeds is desired, the interconnect medium consists of controlled impedance traces terminated in their characteristic impedance. The goal of these interconnect designs is to obtain the optimum combination of bandwidth, number of wires, power, and cost. The prior art schemes require many wires (e.g., one per signal plus an additional wire for each bidirectional signal) with their corresponding termination resistors in order to achieve the highest possible bandwidth. The termination resistors are used to prevent signal reflection back to the sender, reducing the amount of noise present on the wire.
Current and next generation supercomputers frequently utilize an active backplane with routing components forming a communications mesh. Point-to-point interconnects are used between components on the backplane. FIG. 1 shows a typical prior art approach used in recently developed routers where the links between routers are double terminated; the driver 11 is matched to the impedance of the line Z.sub.0, and the line 13 is parallel terminated using a Thevenin equivalent termination 15. The scheme shown in FIG. 1 is described in detail by E. Reese, et al., "A Phase-Tolerant 3.8GB/s Data-Communication Router for a Multiprocessor Supercomputer Backplane", IEEE Solid-State Circuits Conference, February 1994.
Two goals for future backplanes are to reduce the total number of wires, and remove the termination resistors from the board. One way to reduce the total number of wires is to run the I/O buffers faster than the core circuits of the routing component. For example, with the core of the routing component operating at 200 MHz, reducing the number of pins per port by half would mean that the I/O buffers would need to operate at 400 MHz. This would require two separate clocks for the component, and these clocks would need to be phase locked. Distributing a 400 MHz clock across a system consisting of several thousand processing nodes would not be a simple task. Synthesizing this clock on chip would prove equally challenging.
Another approach would be to increase the information density on the wires by using a form of multi-valued logic, rather than binary. This would be attractive if the latency incurred as a result of encoding and decoding is not excessive, the signal to noise ratio is not degraded, and the gain bandwidth product of the input amplifier is sufficient to handle the smaller swings.
Neither of these approaches addresses the problem of the many on board termination resistors and their associated power consumption. Integration of the terminations on the die forming the integrated circuit would increase the size of the input cell, its corresponding pad capacitance, and the power it consumes. Incorporation of the resistors into the interconnect structure of either the board or the package is a possibility, if there is adequate room in the routing layers, and acceptable resistance tolerances can be achieved, but the power would be unchanged. Termination to a separate supply lowers the power, but the separate supply must be well decoupled in order to maintain a constant termination voltage with respect to the current return path of the driver when many outputs switch simultaneously.

High speed bidirectional signaling scheme


A method for treating a magnet roll including the steps of providing a permanent magnet member having an outer circumferential surface and a plurality of axially extending magnetic poles formed in the outer circumferential surface, slidably surrounding the member with a non-magnetic metal sleeve of hollow cylindrical shape, the sleeve and the member being rotatable relative to each other, blasting a surface of the sleeve with spherical particles of a non-magnetic material having a density in a range of from 3 to 4 g/cm.sup.3 and Mohs' hardness in a range of from 11 to 14 to produce a surface roughness (R.sub.z) in a range of from 0.5 to 8 .mu.m.

The present invention relates to a magnet roll used for carrying developer in electrophotography, electrostatic recording, and so on.
Most of magnet rolls used as developing rolls or cleaning rolls in conventional electrophotography or electrostatic recording have such a structure as shown in FIG. 1. In FIG. 1, reference numeral 1 represents a permanent magnet member. The permanent magnet member 1 is formed integrally into a columnar shape, for example, out of sintered powder of magnet material such as hard ferrite, or out of a mixture of ferromagnetic material and binder. A shaft 2 is coaxially fixed in the center of the permanent magnet member 1.
A plurality of axially extending magnetic poles (not-shown) are provided in the outer circumferential surface of the permanent magnet member 1. Next, flanges 3 and 4 are mounted on the shaft 2 at its opposite ends rotatably through bearings 5 and 5. A sleeve 6 formed into a hollow cylindrical shape is fixed to the flanges 3 and 4. The flanges 3 and 4 and the sleeve 6 are made of non-magnetic material such as an aluminum alloy, stainless steel, or the like. Reference numeral 7 represents a sealing member which is fixed between the flange 3 and the shaft 2. The permanent magnet member 1 is usually made to have a diameter in a range of from 15 to 60 mm and a length in a range of from 200 to 350 mm.
According to the above configuration, with the relative rotation between the permanent magnet member 1 and the sleeve 6 (for example, the permanent member 1 is fixed, and the flange 4 is rotated), magnetic developer is absorbed onto the outer circumferential surface of the sleeve 6 to thereby form a magnetic brush to make it possible to perform predetermined working of development, or the like.
In such a magnet roll, it has been known that it is effective to make the surface of the sleeve 6 rough in order to improve the performance of carrying magnetic developer from a developer tank to a development area. As a method of making the surface of the sleeve 6 so rough, there is, for example, a method of giving unshaped sand blasting to the surface of the sleeve 6, as disclosed in U.S. Pat. No. 4,597,661. According to this method, as its superior advantage, it is possible to stir developer by the roughened surface of the sleeve 6 to thereby maintain a proper charged condition, and also stabilize the layer thickness of the developer absorbed on the sleeve 6.
Further, in order to form a good condition of the surface of the sleeve 6 after the above-mentioned blasting, there have been proposed a method using shaped or spherical glass beads as blasting particles (for example, refer to Japanese Patent Unexamined Publication No. Sho-57-116372), a method using unshaped blasting particles together with shaped blasting particles (for example, refer to Japanese Patent Publication No. Hei-2-45189), a method using a mixture of spherical particles and unshaped particles (for example, refer to Japanese Patent Unexamined Publication No. Hei-2-204764), and so on.
Such various proposals have been created to improve the defects in the method using unshaped particles of Al.sub.2 O.sub.3, SiO.sub.2, or the like, in which not only the thickness of a developer layer absorbed and held on the toughened sleeve 6 becomes uneven, but the sleeve 6 is apt to be worn out because of the sharpened shapes of its roughened surface, so that the life of the sleeve 6 becomes short. However, the proposals have problems as follows.
First, in the proposal using glass beads (hereinafter referred to as "FGB"), blasting particles are so brittle as to be easily broken by an impact at the time of collision with the surface of the sleeve 6. Accordingly, there is a problem that the time to maintain predetermined particle size becomes so short that the lifetime is short. In this proposal, therefore, there is a disadvantage that it is necessary to often perform classification of used particles and supply of new particles.
In the proposal using steel balls or stainless steel beads, there is indeed an advantage that they are more durable than the above-mentioned FGB, so that the lifetime thereof is made long comparatively, but the density of material constituting them is so large that it is difficult to control the intensity of spray to the sleeve 6. In the proposal, accordingly, there is a problem that the blasting condition is narrow.
Moreover, in the proposal using steel balls, ferrite particles, or the like, as blasting particles, the balls or particles are constituted by magnetic material so that blasting particles are absorbed onto the surface of the sleeve 6 when blasting is performed in the state where the permanent magnet member 1 is incorporated in the sleeve 6 (usual manner). In this proposal, accordingly, there is a problem that the roughness formed in the surface of the sleeve 6 is apt to be uneven.

Method for treating magnet roll by blasting with nonmagnetic spherical particles


2,5-dialkyl-4-hydroxy-3(2H)-furanones having the formula: ##STR1## are obtained by the aldol condensation, under basic conditions, of a 2,5-dialkyl-dihydro-3(2H)-furanone with an aldehyde, R"CHO, and dehydration of the aldol to the corresponding exocyclic alkene: ##STR2## The alkene is then reacted with ozone in a participating solvent to give the hydroperoxy-hemiacetal which is reduced to the hemiacetal, this then being converted to the desired product by heating under reflux in acidic conditions in an inert atmosphere.

The present invention relates to the preparation of 2,5-dialkyl-4-hydroxy-3(2H)-furanones, and especially, but not exclusively, to the preparation of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, commercially known under the trade name FURANEOL.
FURANEOL is an important aromatic substance found in pineapples (J. O. Rodin et al, J. Food Science (1965) 30, 280). It has a strong, fruity fragrance and is suitable for use in flavouring various food products (U.S. Pat. No. 3,887,589 of the Mar. 6, 1975) on account of its excellent aromatic and organoleptic properties.
According to J. E. Hodge and colleagues (U.S. Pat. No. 2,936,308), FURANEOL can be obtained in small quantities from rhamnose and piperidine acetate; however, rhamnose is very expensive and hence this process is uneconomic. Processes for synthesizing FURANEOL from other starting products are also known. The majority of these are based on the preliminary formation of straight-chain aliphatic derivatives which are then modified to provide appropriate diketogroups, combined with a diol or two halogen atoms, in positions suitable to allow the subsequent cyclyzation into the furanone ring structure to form FURANEOL or its desired homologues (U.S. Pat. No. 3,629,292; Swiss Pat. No. 474,501). Difficulties with these processes, however, are that they involve many expensive operating stages and give rather low yields of the final products.
The object of the present invention is, therefore, to provide a convenient process for the preparation of 2,5-dimethyl-4-hydroxy-3(2H)-furanone and its 2,5-dialkyl homologues.
The present invention is based on the use of 2,5-dimethyl-dihydro-3(2H)-furanone: ##STR3## (C.A. 43, 1949, 5424i; C.A. 47, 1953, 7478c; C.A. 57, 1962, 16526d; C.A. 87, P 117769v; German Pat. No. 2,600,864) as a starting compound for the synthesis of FURANEOL. If the above starting compound could be oxidised, the corresponding diketo-derivative might be obtained and then converted to the enol form, i.e. FURANEOL, according to the general scheme; ##STR4## However, FURANEOL has characteristics typical of reducing agents, that is, it has a considerable tendency to be oxidised (B. Wilhalm et al, Chemistry & Industry (1965) 1629) and the choice of a suitable oxidizing agent for a direct reaction of the above type has been very difficult because of the difficulty in stopping the reaction at the desired stage and avoiding the formation of secondary products by further oxidation or degradation. A rather longer, but more controllable route, has therefore been developed.

Process for the preparation of 2,5-dimethyl-4-hydroxy-3(2H)-furanone and its 2,5-dialkyl homologues

Instituto per la Ricerca Scientifica e Applicata di Technologie Alimentari S.p.A


An evaporator inlet water temperature control system for controlling the inlet water temperature of an evaporator utilized in an inverter driven centrifugal chiller. The system creates the proper chilled water set point at the evaporator outlet needed to maintain the inlet water at its set point for greater efficiency of operation. Control is accomplished by generating an electrical error signal which is a function of an inlet water set point voltage and the actual inlet water temperature. A logic signal is produced as a function of the error signal detected by the circuit and establishes a dead zone band representing a range in which the error signal is acceptable. Output of the control system is passed to the capacity control circuit of an inverter driven centrifugal compressor chiller. When the inlet water temperature reaches its set point during pull-down, the logic output of the circuit sets a flip-flop which enables transmission gates to control changes in the outlet water set point as needed to balance the load of the cooling system.

A. Field of the Invention
This invention relates in general to cooling systems and, in particular, to a capacity control system for regulating chillers.
More specifically, without restriction to the particular use which is shown and described, this invention relates to an evaporator inlet water temperature control system for inverter-driven centrifugal compressor chillers by which evaporator inlet water temperature is controlled by creating the proper evaporator outlet chilled water temperature.
Large capacity air-conditioning systems commonly have employed centrifugal compressors having guide vanes which are adjustable to control the capacity of the compressor for effective and efficient operation. Control of compressor capacity through adjustment of the vanes alone, has proved to be unsatisfactory because of its resultant low efficiency operation of the system. In an effort to overcome such problems, attempts have been made to control not only the position of the pre-rotation vanes, but to regulate the speed of the electric motor driving the compressor for purpose of an energy effective system and to avoid surge.
One highly effective system which relies on vane adjustment and speed control to achieve superior capacity control of a centrifugal compressor chiller, is disclosed in U.S. Pat. No. 4,151,725 to Kountz et al for A Control System for Regulating Large Capacity Rotating Machinery and assigned to the assignee of this invention. In the system disclosed in U.S. Pat. No. 4,151,725, a control system effectively maximizes efficiency without encountering surge problems by monitoring the temperature of the refrigerant in the condenser discharge line, the temperature of the saturated refrigerant leaving the evaporator, the temperature of the chilled water discharged from the evaporator of the chiller, and the inlet guide vane position. Based on the foregoing four parameters and a set point temperature input, the control system described in U.S. Pat. No. 4,151,725 effectively regulates the refrigeration system by regulating the speed of the compressor and adjusting vane position.
The temperature of the chilled water sensed at the outlet from the evaporator in U.S. Pat. No. 4,151,725 is applied to a circuit which also receives a temperature set point signal from a potentiometer or another suitable unit, such as a thermostat in the building space. Thus, a signal is derived representing the difference, if any, between the set point temperature of the thermostat and the like and the instantaneous load. Greater efficiency could be attained in such a refrigeration system, however, if the inlet water being directed to the evaporator on return from the building is constantly monitored and the capacity control system is responsive thereto to maintain a constant or set point temperature at the inlet regardless of the load conditions. Maintenance of the set point inlet temperature of the water to the evaporator in response to actual load conditions would result in significantly improved efficiency and economy of operation since a variable input related directly to the temperature of the water after circulation is applied to the capacity control system.
B. Prior Art Patents
U.S. Pat. No. 4,112,703 to Kountz discloses a refrigeration control system in which a controlled space is maintained at a set point by adjusting the refrigerant temperature at the evaporator outlet in a refrigeration system. In U.S. Pat. No. 3,751,940 to Norbeck, a refrigeration system is disclosed having circuit means for automatically energizing the PRV motor.

Evaporator inlet water temperature control system


A heat sink assembly includes an electronic device, a heat sink and a clip that compresses the heat sink against the electronic device. A spacer is mounted on the clip to restrain motion of the heat sink relative to the electronic device. A method of securing a heat sink to an electronic device includes compressing the heat sink against the electronic device with a clip, and attaching a spacer to the clip in order to restrain motion.

The present invention relates to a heat sink assembly and a method of assembling a heat sink to an electronic device. The invention particularly relates to a heat sink assembly that includes a clip which compresses a heat sink against an electronic device.
Electronic devices generate heat during operation. Thermal management refers to the ability to keep temperature-sensitive elements in an electronic device within a prescribed operating temperature.
Historically, electronic devices have been cooled by natural convection. The cases or packaging of the devices included strategically located openings (e.g., slots) that allow warm air to escape and cooler air to be drawn in.
The advent of high performance electronic devices, such as processors, now require more innovative thermal management. Each increase in processing speed and power generally carries a xe2x80x9ccostxe2x80x9d of increased heat generation such that natural convection is no longer sufficient to provide proper thermal management.
One common method of cooling electronic devices includes thermally coupling a heat sink to the package of the electronic device. A typical heat sink includes protrusions, such as fins or pins, which project from a body of the heat sink. The protrusions give the heat sink a larger surface area such that the heat sink dissipates a greater amount of thermal energy from the package into the surrounding environment. Heat sinks are fabricated from materials with high thermal conductivity in order to efficiently transfer thermal energy from the electronic device package.
The heat sinks are typically mounted to the electronic devices by using adhesives, screws, and/or bolts. Another common method uses one or more clips to secure a heat sink to an electronic device.
FIGS. 1-5 illustrate a prior art heat sink assembly 10. Heat sink assembly 10 includes a heat sink 20, clip 30 and electronic device 40. Electronic device 40 is mounted to a frame, such as socket 50. Socket 50 is attached to a substrate, such as printed circuit board 51 (see FIGS. 4 and 5). Clip 30 compresses heat sink 20 against electronic device 40 and is typically in the form of a bent wire that includes two legs 32 and an elongated central portion 34 extending between the legs 32. Each leg 32 is substantially perpendicular to central portion 34 and extends from central portion 34 in an opposite direction to the other leg 32.
The central portion 34 of clip 30 extends between protrusions 28 on heat sink 20. Clip 30 is assembled to socket 50 by maneuvering legs 32 under a pair of tabs 52 that are positioned on opposing sides of socket 50. Legs 32 deflect elastically as they are moved under the tabs 52 generating a torque around the central portion 34 of clip 30. The torque compresses the central portion 34 of clip 30 against heat sink 20, which in turn compresses heat sink 20 against electronic device 40. Compressing heat sink 20 against electronic device 40 reduces the thermal resistance between heat sink 20 and electronic device 40.
FIG. 4 illustrates the proper position for heat sink 20 relative to electronic device 40. Heat sink 20 includes a contact surface 21 that should be engaged with electronic device 40 over the entire contact surface 21.
Mechanical shock or vibration during transportation and handling can cause heat sink 20 to shift relative to electronic device 40. FIG. 5 illustrates a case where heat sink 20 has shifted relative to electronic device 40. A portion 22 of the contact surface 21 on heat sink 20 is no longer fully engaged with electronic device 40. This situation is undesirable because anything less than full contact between the contact surface 21 on heat sink 20 and electronic device 40 renders heat sink 20 less effective in conducting thermal energy from electronic device 20.
There is a need for a heat sink assembly and method that securely attaches a heat sink to an electronic device, especially when subjected to mechanical shock or vibration. The clips that are presently used to fasten heat sinks to electronic device packages are unable to adequately secure a heat sink to an electronic device package under such circumstances.


A manufacturing process to produce a laryngeal mask substantially as described in UK Patent GB2205499B consists in a mould which manufactures the inflatable annular ring formation of the device in an inverted form. This allows a more rigid core in the cavity mould or alternatively a dip-moulding process, which in turn, permits greater accuracy in control of wall thickness. An alternative form of the mould eliminates the need to assemble a further component, by incorporating the latter into the same single moulding process. And in a further alternative embodiment, the same single moulding process additionally provides an integrally formed inlet for oesophagus drainage, independent of the larynx-venting function of the mask per se.

This invention relates to an artificial airway device to facilitate lung ventilation in an unconscious patient, and more specifically to such a device designed for placing in the oropharynx of the patient in order to prevent airway obstruction, to permit either spontaneous or controlled ventilation and to prevent the inhalation into the lungs of extraneous matter such as blood.
To maintain the airway of an unconscious patient, and to achieve the three objectives mentioned above, it is normal practice in general anaesthesia to use an endotracheal tube, which is a flexible tube of rubber or plastics, usually with an inflatable cuff around the distal end. Alternatively, an oro- or naso-pharyngeal airway may be used, which is a flexible tube extending from the mouth or nose into the pharynx but not into the larynx, and which, unlike the endotracheal tube, is used in conjunction with a face mask. While preventing obstruction of the airway by the tongue, the oro- or naso-pharyngeal airway cannot conveniently be used for controlled ventilation and does not prevent inhalation of extraneous matter.
The endotracheal tube is introduced through the larynx into the trachea or windpipe, whereupon the cuff is inflated through a small auxiliary tube to seal against the wall of the trachea. Introduction of the endotracheal tube is a skilled operation normally requiring use of a laryngoscope to guide the tube through the larynx, past the vocal cords and into the trachea. There is a risk that the tube or the laryngoscope may cause damage to soft tissues or to the sensitive structures of the larynx. It is not always possible to see the larynx, making intubation difficult or impossible in some patients. There can be a risk of accidental intubation of the oesophagus or of the right or left main bronchus. Placing of the tube in the trachea effectively narrows the interior passage or lumen of the trachea and provides a potential source of damage through infection or pressure while preventing normal upward flow of mucus from the trachea and rendering effective coughing impossible.
My British Patent Specification No. 2111394B describes an artificial airway device comprising a curved or flexible tube and a mask portion carried at one end of the tube. The mask portion has a flexible annular peripheral formation which may be inflatable and which surrounds a hollow interior space or lumen of the mask portion. Said annular peripheral formation of the mask portion is pre-formed with a roughly elliptical shape so as to be capable of conforming to, and of fitting readily within, the actual and potential space behind the larynx, thereby forming a seal around the 3circumference of the laryngeal inlet without having the device penetrate into the interior of the larynx. The tube opens into the lumen of the mask portion to provide the airway, with the axis of the tube at an acute angle to the general plane of the annular peripheral formation and substantially aligned with the major axis of the roughly elliptical shape of the annular peripheral formation of the mask portion. The device thus constitutes a laryngeal mask.
This device has proved successful in use. Insertion of the device has been found to be easy and convenient in the majority of patients. A laryngoscope is not usually required. The mask does not enter the larynx or trachea, so the risk of damage to these structures is avoided and the tracheal lumen is not narrowed, as is the case upon insertion of an endotracheal tube. The risk of accidental entry into the oesophagus or one of the main bronchi is also avoided. Once in place, the laryngeal mask generally permits the lungs to be ventilated by positive pressure. Alternatively, the patient may be permitted to breathe spontaneously.
An improved laryngeal mask is described in my Patent No. GB 2,205,499B, in which there are provided two flexible cross-bars extending across the aperture in the peripheral annular flexible formation. These bars preferably extend substantially parallel with the major axis of the generally elliptical annular formation. As this patent explains, the parallel bars serve to prevent the epiglottis from blocking the airway passage of the mask.
In the existing laryngeal mask, the peripheral seal formation is an inflatable annulus which, when inflated, is a generally elliptical toroid. Its manufacture presents difficulties, in that the process uses a so-called "floating core" within the outer or female part of the mould. This core is supported by a relatively small pin which ultimately defines the bore of the inflation inlet but which must maintain uniform spacing from the adjacent wall surface of the female mould. It is desired that the wall of the moulded annulus be uniformly thin.sup.1, for example, a selected single thickness in the range 0.4 to 1.0 mm, preferably 0.7 mm. In practice, however, injection of liquid rubber into the mould is under high pressure, and the "floating core" support pin is not capable of resisting small displacements which can cause thickness variations in the wall of the moulded product. In consequence, it has been necessary to maintain a relatively thick wall in the peripheral annular formation so that small changes in wall thickness produced by movement of the core during injection will not result in deformity or rupture of the device when air-inflated in the course of use. The difficulty with a relatively thick wall is that the inflatable annulus is less compliant in adapting itself to the contours of the human pharynx and larynx, thus reducing the efficacy of the desired seal to the laryngeal inlet, and/or unduly limiting the pressure which it is possible to use for inflation of the lungs without loss of seal. FNT .sup.1 Thin, for greatest flexibility in establishing the intended peripheral seal to the laryngeal inlet; and uniformly thin, to avoid weak areas that might invite herniation.
A further disadvantage of the existing manufacturing process is that it is highly labor-intensive, since the tubular airway portion of the device to which the peripheral annular formation is attached must be connected via a third part, or back plate. This third part is separately moulded and forms an appropriate shape at one end to fit within the peripheral annular formation and at the other end to receive the tubular airway portion of the device. Finally, the back plate and the cut inner periphery of the inflatable ring must be so adhesively secured as to complete the inflatable integrity of the ring as well as the sealing effectiveness of the back plate to the inflatable ring.

Method of making an artificial airway device


A load indicator conversion system is disclosed for converting a scale having a mechanical measuring system, such as a conventional portable beam scale, into a scale having an electronic measuring system for providing an electronic display, such as an LCD display, corresponding to the load applied to the mechanical load receiver of the scale, such as the scale platform [104], which is mechanically linked via the beam load rod assembly [110] and an s-hook arrangement [150] to a load cell transducer [1]. A single common temperature sensor is employed adjacent the load cell and the associated electronics to provide information on the variations in temperature to the microprocessor for enabling temperature compensation to take place. The mechanical linkable between the transducer and the existing mechanical load receiving member is accomplished by removing the balance beam [106] and connecting the load cell [1] to the beam load rod [110] which normally mechanically transfers the applied load from the scale platform to [104] the balance beam [106 ].

1. Field of the Invention
The present invention relates generally to electronic measuring systems, and more particularly to load indicator conversion systems for converting a scale having a mechanical measuring system into a scale having an electronic measuring system in which the load applied to the mechanical load receiver is converted into an electronic display.
2. Description of the Prior Art
Mechanical scales in which a load is applied to a mechanical load receiving member, such as a calibrated spring assembly and platform, in order to mechanically control a balance mechanism in order to mechanically provide a weight indication, such as in a conventional portable beam scale, bench scale, or health scale are well known in the art. In addition, electronic systems which measure weight to provide an electronic display based on a load applied to a transducer, such as an analog load cell or a digital load cell, such as disclosed in U.S. Pat. Nos. 3,850,023; 3,665,169; 3,603,298; 4,330,837; 4,143,724; 4,722,406; and 4,137,568 are also well known in the art, as are the use of electronic checkweighers, such as disclosed in U.S. Pat. Nos. 4,321,439; 3,446,299; 3,770,969; and 4,363,408. However, applicants are not aware of any systems which can efficiently, and relatively inexpensively, convert conventional existing mechanical scale into a modern electronic scale so as to provide an electronic display of the magnitude of the load applied to the existing mechanical load receiving member and/or to provide an electronic checkweigher from the existing mechanical scale. This is particularly important in commercial environments where costly mechanical scales are still functional and need not be discarded in order to achieve all of the benefits and advantages desired and needed today in a modern electronic measuring system.
Typically, in prior art electronic scales, a continuous voltage is applied across a load cell arranged in a wheatstone bridge. The voltage across the load cell output is measured, from which the magnitude of the load applied to the load cell is determined. Many of these prior art electronic scales have been battery operated. In early electronic scales of this type, the electrical components and the load cell each used comparatively large amounts of power. With the advent of digital circuitry, the power consumption of the logic components begin to shrink as compared to the load cell and systems were developed to reduce load cell power consumption, such as disclosed in U.S. Pat. No. 4,238,784 which employs an electronic measuring system with a constant dual-frequency pulsed power supply for pulsing the power at the load cell input, thereby utilizing less power than with a continuous D.C. power supply.
However, as noted in the above referred to contemporaneously filed copending patent application, even with such prior art pulsed systems, the zero reading of the transducer tends to drift. This effect is ordinarily caused by temperature changes in the system and by residual voltages in the system during a no pulse cycle. Various techniques have been applied to compensate for drift, such as disclosed in U.S. Pat. No. 4,238,784, however, although satisfactory in some circumstances, such prior art techniques do not enable the pulses to be varied with respect to duty cycle and frequency to thereby further reduce power consumption to lower desired levels.
In order to try to compensate for effects caused by temperature changes in prior art battery operated scales, separate temperature sensors have been employed for separately housed detection and display circuitry, as discussed in the aforementioned copending contemporaneously filed patent application. However, such a prior art arrangement has not only resulted in increased cost, but has also resulted in reduction in correction accuracy.
In the past, when prior art electronic scales were used as checkweighers, they generally incorporated separate display elements to indicate an over/under condition, such as a series of LED's. However, such a prior art arrangement not only adds to the cost of the scale by requiring additional display elements and space on the display face, but the LED's employed also increase the power consumed by the system and further exacerbate the unwanted problem of heat in the casing.
These prior art difficulties with electronic scales, and particularly battery operated electronic scales, having further added to the difficulty in providing an efficient low cost alternative to the previously acceptable mechanical scales which have not as yet outlived their useful life. These disadvantages of the prior art are overcome by the present invention.


A forward feed gear mechanism for a cold pilger rolling mill having at least one forward feed slide, whose advancing movement can be derived from at least one forward feed spindle which is driven in continuous rotation, and an oscillating axial movement can be superimposed on the rotational movement of the forward feed spindle so that the gear mechanism is flexible and adaptable to different settings and provides high acceleration values with a simplified gear unit design. A planetary rolling spindle is provided for generating the axial movement of the forward feed spindles and is coaxially connected with one end of the forward feed spindle so as to be independently rotatable. The housing of the rolling spindle is rigidly arranged in the forward feed gear mechanism housing and the planetary rolling spindle can be driven in rotation in a translatory manner by a separate drive via a spur gear unit stage.

1. Field of the Invention
The invention relates to a forward feed gear mechanism for a cold pilger rolling mill having at least one forward feed carriage or slide, whose feed movement can be derived from at least one forward feed spindle which is driven in continuous rotation. It also being possible to superimpose an oscillating axial movement on the rotational movement of the forward feed spindle.
2. Description of the Prior Art
In cold pilger rolling of pipes, the pipe to be rolled is incrementally rotated and advanced synchronously with the movement of the roll stand. Between these movements, the pipe is generally held securely and does not move. Mechanical gear units which are driven by the roll stand drive are conventionally used to produce the rotating and forward feed movement. Cold pilger rolling mills are also known in which the mechanical gear units are replaced by electric or hydraulic servodrives to produce the stepwise rotational and forward feed movements. These servodrives were moved according to defined settings as a function of the roll stand drive.
A forward feed gear mechanism of the type described above is known e.g. from DE-OS 21 16 604. In this prior art, the rotational movement of the forward feed spindle for the two forward feed slides is derived from the drive of the roll stand. A costly spur gear unit is used for this purpose. A translatory axial movement is superimposed on the continuous rotational movement of the forward feed spindle in that a disk cam gear mechanism causing a reciprocating movement of the forward feed spindle via a system of levers is set in motion by the same drive. When the gear mechanism is adapted in a corresponding manner, the rotational movement of the forward feed spindle and its oscillating axial movement are added or subtracted for advancing or stopping the forward feed slide.
Such mechanical forward feed gear mechanisms are costly and prone to wear and the possibilities for adaptation are limited. Thus, in the past, forward feed gear mechanisms employing separately adjustable electric or hydraulic servodrives were frequently used.
Particularly in electric servodrives for generating forward feed movement, definite restrictions had to be submitted to with respect to the attainable forward feed values. The electric forward feed drives which were used moved the output-drive or power take-off members directly, i.e. the speed at the power take-off was always directly proportional to the speed of the drive motor. Thus, the entire output for generating movement had to be applied by the servodrives so that very narrow limits on forward feed had to be accepted.
Since the advancing or forward feed movement is not reversible, but always progresses in the same direction, the maximum speed range of the servodrives could never be fully utilized. However, the servodrives had to absorb the full load moment. The proportion of motor torque available for acceleration was therefore unnecessarily small so that achievable forward feed values were reduced by external loads (back-rolling forces) conditioned by technical factors relating to the apparatus. Since the spindles engaging with the forward feed slide are rotated in a jerky manner in forward feed servodrives, this rotation requires large acceleration moments which negatively influence the achievable forward feed values.
The gear unit stages between the servomotor and spindle must be designed with a view toward a best possible acceleration. In general, this results in large transmission ratios, i.e. high motor speeds with low spindle speeds. The gear unit stages which are selected in this way automatically condition a lengthy returning movement of the forward feed slide to its initial position even when the servomotor reverses at maximum speed. This represents a significant loss of production time for the operator.

Forward feed gear mechanism for a cold pilger rolling mill


A server device 20 requests a client device 30 to execute one of a plurality of computations having different degrees of difficulty. Client device 30 identifies, based on an amount of computation required for each of said plurality of computations, a computation to be executed and executes the computation. Client device 30, when requesting execution of a given process to server device 20, transmits a result of the computation to server device 20. Server device 20, when the computation result is correct, executes a predetermined process according to a priority based on an amount of the computation.

1. Technical Field
The present invention relates to a technique for causing a server device to execute a process in response to a request from a client device and a server device.
2. Background Information
In recent years, a variety of communication services which utilize the Internet have come into use. One example of a communication protocol which is used for sending and receiving data over the Internet is TCP (Transmission Control Protocol). TCP is a connection-type communication protocol which enables highly reliable data communication to be carried out over the Internet. Under TCP, a data transmitting device (hereinafter, "server device") and a data receiving device (hereinafter, "client device") exchange connection data (hereinafter, "connection identifier") prior to transmission of content data. The exchanged connection identifier is used to specify a communication path (hereinafter, "connection") to thereby establish a connection for transmission of content data. Examples of connection identifiers include: a communication address assigned to a server device or a client device; data indicating a communication port (e.g. a communication port number) used by the devices for respectively transmitting and receiving data; or an initial value of a sequence number. Under TCP, a connection is established using a procedure referred to as a "3-way handshake". A general description of this procedure follows.
FIG. 10 provides an overview of a 3-way handshake executed by a server device 40A and a client device 50A. Each of the devices is capable of communicating under TCP. It is assumed for the purposes of this explanation that a user who wishes to obtain content data from server device 40A performs a predetermined operation such as inputting data (e.g., URL) representing a communication address of server device 40A and a communication protocol to be used for acquiring the desired content data. Client device 50A first transmits to server device 40A a SYN message 200, as shown in FIG. 10. SYN message 200 is used for requesting establishment of a connection when data is to be transmitted from server device 40A to client device 50A (hereinafter, "downlink connection"); and the message includes a connection identifier for the downlink connection.
Server device 40A, upon receiving SYN message 200, allocates a computer resource (hereinafter, "resource") for establishing a connection with the source of the SYN message 200, client device 50A. Specifically, server device 40A writes, in a memory device such as RAM (Random Access Memory), and data (e.g., a connection identifier of the downlink connection mentioned above) for identifying a correspondent device (i.e., client device 50A). Server device 40A then transmits to client device 50A a SYN/ACK message 210 indicating receipt of SYN message 200, and also transmits a request for establishing a connection in the reverse direction (hereinafter, "uplink connection"). The uplink connection is used when data is transferred from client device 50A to server device 40A; and the SYN/ACK message 210 includes a connection identifier for the uplink connection. Server device 40A retransmits SYN/ACK message 210 by referring to stored data in the memory device in a case that a message acknowledging a receipt of SYN/ACK message 210 (hereinafter, "ACK") is not received within a predetermined time since the transmission of the message 210.
Client device 50A, upon receiving SYN/ACK message 210, reads the connection identifier in the SYN/ACK message 210 and establishes a connection (i.e., the uplink connection) in accordance with the connection identifier. Client device 50A then transmits to server device 40A an ACK 220 indicating receipt of the SYN/ACK message 210. ACK 220 includes a connection identifier for the downlink connection. Upon receiving ACK 220, server device 40A establishes the uplink connection identified by the connection identifier included in ACK 220, deletes data identifying the correspondent device from the memory device, and awaits receipt of a message transmitted through the downlink connection from the client device 50A, such as a request for transmitting data (e.g., a message containing a HTTP GET method).
It is to be noted that since resources of server device 40A, such as a capacity of a memory device, are limited, a number of connection identifiers (i.e., data indicating a correspondent device with which a connection is about to be established) which can be stored in the memory device is also accordingly limited. Thus, a number of ACKs 220 from client devices 50A for which server device 40A can wait is limited to a number of connection identifiers which can be retained at the server. It is this limitation that makes a server vulnerable to abuse. Namely, a denial of service attack can be launched against the server by a malicious client device by sending from the device a large number of SYN messages 200 to the server for queuing, thereby exhausting the resources of the server. Such an attack is referred to as a "SYN Flood Attack."
When a SYN Flood Attack is launched, a malicious client device which is the source of the attack continuously transmits a large number of SYN messages 200 to server device 40A. When the server sends or attempts to send responsive SYN/ACK messages 210 no ACK 220 is forthcoming from the client device. The server therefore retains for a set time period data identifying a correspondent device, assuming that a connection between the correspondent device is not yet established, and awaits an ACK 220. When a SYN Flood Attack is attempted, a number of connection identifiers queued at the server soon reaches an upper limit. As a result, the server device is no longer able to accept connection requests from client devices; and communication services cannot be provided.
Various methods have been proposed for dealing with SYN Flood Attacks. They include a client puzzle protocol disclosed in Ari Juels and John Brainard (RSA Labs), "Client Puzzles: A Cryptographic Defense Against Connection Depletion Attacks", and a client puzzle auction disclosed in XiaoFeng Wang, Michael K. Reiter, "Defending Against Denial-of-Service Attack with Puzzle Auctions", Proceedings of the 2003 IEEE Symposium on Security and Privacy, 2003. In the following, description will be given of these techniques with reference to the attached figures.
FIG. 11 is a diagram providing an overview of a client puzzle protocol. In the figure, a server device 40B and a client device 50B are communication devices which establish a connection according to the client puzzle protocol. Server device 40B differs from server device 40A of FIG. 10 in that the device 40B does not store data showing a source of SYN message 100 upon reception, and that the device 40B transmits, upon receiving SYN message 100, transmits a message (a RST/ACK message 101 of FIG. 11) requesting execution of a predetermined computation and a reply including a result of the computation. RST/ACK message 101 includes data representing the predetermined computation (hereinafter, "client puzzle").
Client device 50B, upon receiving RST/ACK message 101, performs a computation designated by the client puzzle contained in RST/ACK message 101, and transmits to server device 40B a SYN message 102 after writing a computation result in the message. In the following, execution of a computation designated by a client puzzle will be referred to as "to solve a client puzzle," and a computation result as "a solution of a client puzzle." When server device 40B receives SYN message 102, it determines whether the solution contained in SYN message 102 is correct; and the device 40B establishes a connection between client device 50B in accordance with a procedure that is the same as that employed in a 3-way handshake method, only when the solution is determined to be correct.
Thus, server device 40B transmits a client puzzle to client device 50B which has requested establishment of a connection, and does not establish a connection until the correct solution of the client puzzle is returned from client device 50B. A client device attempting a SYN Flood Attack on server 40B by transmitting a large number of SYN messages can no longer continue the attack unless it submits to server device 40B a correct solution to a client puzzle returned from the server as a response to each SYN message. To continue a SYN Flood Attack on server 40B, a client device has to solve a number of client puzzles, which means that the client device must have large resources available for computation. Consequently, the client device becomes incapable of continuing to transmit SYN messages. Thus, according to the client puzzle protocol, a SYN Flood Attack can be effectively handled.
A crucial factor in implementing the client puzzle protocol is that an amount of computation designated by a client puzzle is appropriately tuned ("an amount of computation" will be hereinafter referred to as "client puzzle difficulty"). In a case that client puzzle difficulty is set too low, i.e., the computation amount is too small, it is possible for a client device to obtain a solution for a client puzzle by using relatively few resources; and as a consequence, a SYN Flood Attack cannot be defended against. Conversely, when client puzzle difficulty is too high, i.e., a computation amount is too large, it would take time even for a legitimate client device not attempting a SYN Flood Attack to solve a client puzzle; as a result, such a client device will have difficulty in utilizing a communication service provided by a server device.
In reality, however, it is not readily possible to tune an appropriate level of client puzzle difficulty suited for each client device in an existing communication system. Generally, there is used in an existing communication system a mixture of various client devices with different degrees of capability, such as personal computers and PDA (Personal Digital Assistance)s, but an appropriate level of client puzzle difficulty depends on the capability of each client device. The client puzzle auction proposed by Wang, et. al has provided, as its object, a solution for such a problem existing in the client puzzle protocol. Description is now given of the client puzzle auction.
FIG. 12 is a diagram for describing an overview of the client puzzle auction. A server device 40C and a client device 50C are communication devices which establish a connection according to the client puzzle auction. Client device 50C of FIG. 12 is adapted to transmit either one of first data or second data when transmitting a SYN message 102 (102a or 102b) containing an obtained solution of a client puzzle, the first data being a request for transmission for a client puzzle with higher difficulty and the second data being a request for not transmitting any more difficult client puzzle.
Server device 40C, when the first data is included in SYN message 102 received from client device 50C, generates a client puzzle with higher difficulty and transmits a RST/ACK message 101b containing the generated client puzzle. In a case where SYN message 102 received from client device 50C includes the second data, server device 40C initiates establishment of a connection according to a conventional 3-way handshake.
According to the client puzzle auction, server device 40C of FIG. 12, when it receives SYN messages 102 from a plurality of client devices, gives a higher priority to SYN message 102 including a solution for a client puzzle with higher level of difficulty when handling a request and establishes a connection preferentially with a client device which is the source of such a SYN message 102. Since generally large resources are consumed for solving a client puzzle with high level of difficulty, transmission frequency of connection open requests will be reduced. A higher priority is given as a compensation for a client device which has accepted a higher process burden and which is rendered capable of transmitting connection establishment requests less frequently. In other words, client server 50C must accept commitment of large resources if it wishes to have a connection open request it transmits to be handled by server device 40C with higher priority.
As described above, since committing large resources is an obstacle for a client device to perform a SYN Flood Attack, the client puzzle auction enables effective defense against a SYN Flood Attack. Further, since each client device 50C is enabled to receive a client puzzle suited for its own process capability and solve the puzzle, the above described problem existing in the client puzzle protocol is also solved. Thus, according to the client puzzle auction, a client device is enabled to shoulder a burden depending on its process capability, and a connection is established according to a priority corresponding to a burden each client device has accepted.
Nevertheless, when the client puzzle auction is used, a number of messages exchanged between a server device and a client device (hereinafter, "communication traffic") is increased when compared with the conventional 3-way handshake and the client puzzle protocol, as obvious from what is shown in FIGS. 10, 11, and 12. Such an increase of communication traffic between a server device and a client device is not welcome, since it potentially becomes a factor for causing congestion in a communication network through which communication between the two devices is performed.

Server device, client device, and process execution method


An apparatus comprising an outer casing with a base, at least one side wall, and a top, within which are located a drum, typically with a curved side wall and first and second end walls, an agitator and a liquid retainer. The liquid retainer and a side wall having aligned ports through which an end portion of the drum may reversibly travel between a first retracted position and a second extended position. The travel of the drum out of the side wall to the extended position allows access to at least one aperture in the curved side wall of the drum.

This invention relates to laundry, apparatus, and in particular laundry apparatus that are loaded and unloaded in a substantially horizontal direction.
Laundry apparatus that is loaded and unloaded in a substantially horizontal direction is often called xe2x80x9cfront loadingxe2x80x9d. Most typically this apparatus is one of or a combination of a washing machine, tumble dryer and/or spin dryer.
Conventional front loading laundry apparatus have a hinged door located on a substantially vertical face of the apparatus. This has the benefit that it allows the apparatus to be placed under a solid surface such as a work top in a kitchen or the like. The problem with front loading apparatus is that use of such a machine requires the user to bend down when loading and unloading the apparatus; the laundry is then either pushed into or pulled out of the apparatus. This combination of bending and pushing/pulling can be painful and difficult for people with back problems, the infirm or the elderly.
In EP-A-0050395 an apparatus for handling laundry is proposed. That apparatus is an industrial sized washing machine which is filled and emptied by way of pneumatically driven drawers which contain the items to be laundered, and which are extended from the casing of the apparatus. Each drawer includes a compartment that is substantially half a cylinder (when cut in a plane passing through the longitudinal axis of the cylinder); the two compartments face each other so as to form a cylinder, the compartments are divided one from the other by internal walls so that two different washes can be performed at the same time. This apparatus allows the vertical loading and unloading of the laundry. The apparatus disclosed in EP-A-0050395 is not, however, suitable for adaptation to a domestic scale, is complicated in construction and operation, and because of its two chamber construction impractical in use as, to balance the drum, both drawers have to be equally loaded. This is not always possible in a domestic situation.
According to the present invention there is provided a laundry apparatus. The laundry apparatus comprises an outer casing with a base, at least one side wall and a top within which are located a receptacle for items to be laundered, a means for agitation of said items, a liquid or fluid retention means at least partially surrounding said receptacle, and control means. In the apparatus, the receptacle is a drum with a curved side wall and first and second end walls, the liquid retention means and a side wall are provided with aligned ports through which an end portion of the drum may reversibly travel between a first withdrawn position and a second extended position, the distance of travel of the end of the drum out of the side wall to the extended position being sufficient to allow access to at least one aperture in the curved side wall of the drum, said aperture is configured and dimensioned to allow insertion and removal of the items to be laundered, and the direction of travel of the drum is substantially parallel to the longitudinal axis of the drum.
The drum may be substantially cylindrical, or of a substantially frustoconical shape. If the drum is substantially frustoconical, it is preferred that the wider end of the drum travels out of the casing when the drum moves to the extended position.
The advantage of the present invention is that because of its configuration, when the aperture in the drum is in such a position to allow insertion and removal of items to be laundered from the drum, the insertion and removal can be done in a substantially vertical direction. This involves much less bending and twisting for the user than earlier known front loading machines. The apparatus of the present invention is suitable for either domestic or industrial (e.g. with greater loads than encountered domestically) use.
In a particularly preferred embodiment of the present invention, the drum and/or the aligned ports are configured so that the end portion of the drum can only travel through the aligned ports when the drum has a predetermined orientation relative to the outer casing. It is preferred that this feature allows the drum only to be able to pass through the aligned ports when the aperture through the curved side wall of the drum is substantially in the nearest or furthest portion of the drum from the top of the casing (at the highest or lowest part of the drum when the apparatus is positioned for use). This allows either convenient filling of the drum (when the aperture is in the portion of the drum nearest the top of the casing) or convenient emptying of the drum (when the aperture is in the portion of the drum most distant from the top of the casing). This embodiment is particularly beneficial to people with back problems or the elderly and infirm because it requires very much less agility on the part of the user. In particular when the laundry is being emptied from the drum, gravity will perform the majority of the work and require little intervention, if any, from the user.
The liquid retaining means, the drum of the drum actuation means may be provided with indexing means to cause the drum to be correctly orientated to pass through the port at the completion of laundering the items that were to be laundered.
It is preferred that at least one aperture in the drum is provided with reversible aperture closure means, said closure means being actuated by movement of the drum between the withdrawn and extended positions. The closure means preferably causes the aperture to be opened when the drum moves into the extended position, and closed when the drum moves into the withdrawn position.
It is preferred that a portion of at least one of the walls of the drum is adapted to allow the passage of liquid through that portion of the wall. Preferably, that portion of the wall is formed from netting, wire mesh, perforated metal sheet or metal sheet provided with one or more apertures. Most preferably the holes, apertures or perforations through which the liquid may flow are so dimensioned that the items to be laundered cannot fit through said holes, apertures or perforations.
The drum may be formed of walls of one or more layers. The composition of each of the layers may be different.
The ability of liquid so flow into and out of the drum allows for washing or draining of the items to be laundered. When the apparatus is being used for washing the items to be laundered, the liquid retention means holds the liquid that is used for washing said items, with said items being immersed in said liquid whilst within the drum. The drum may be rotated to agitate the items to be laundered. The general construction of laundry apparatus incorporating an inner drum within which the items to be laundered are retained, and a liquid retaining means within which the liquid to wash those items is kept is a standard construction and will not be further described herein. laundered.
It is most preferred that the drum is supported within the liquid retaining means by one or more drum support means. The drum support means preferably allow the drum to move both in the direction of the longitudinal axis of the drum, and to move so as to agitate the items to be laundered. In one embodiment, the or each of said drum support means is preferably a support bar substantially parallel to the central axis of the drum. The or each support bar is preferably engaged with either the curved side wall of the drum or the peripheral edge of the first and second end walls of the drum.
It is particularly preferred that the support bars are either telescopic or engaged with the drum in such a fashion that movement of the drum from its withdrawn to extended position is possible.
Most preferably the support bars are three in number, and located at 120xc2x0 spacing about the periphery of the drum, with this configuration of support bars, the drum is preferably provided with one aperture spaced evenly between two support bars, and the end of the drum may only pass through the aligned ports when the aperture is in the portion of the drum that is vertically upwards when the apparatus is orientated for use.
The drum can be supported in other fashions from that described above. For example, the drum supported by engagement of the first or second end wall of the drum with drum support means.
A further advantage of the present invention is that, unlike currently known front loading machine, the contents of the drum, can be easily viewed by a user. This enables the drum to be efficiently filled and, once the laundry has been done, completely emptied.
The liquid retention means and side wall of the casing are provided with means to close the aligned ports, especially when the apparatus is in use. Said means preferably form a water-tight seal with the edges defining the ports.
In a preferred embodiment of the present invention the movement of the end of the drum through the aligned ports occurs simultaneously with the port closure means disengaging from the edges that define the aperture and moving away from the port.
In a most preferred embodiment, the drum and the port closure means are all supported on two or more support bars that are orientated in a direction substantially perpendicular to the face of the casing. In this embodiment, the port closure means retains its orientation relative to the drum when the drum is in the extended position.
In one embodiment of the present invention there is further provided a reversibly extending drip tray that extends beneath the drum and between the casing of the apparatus and the port closure means when the drum is in its extended position. Said drip tray can, when the drum is in its retracted position and the port closure means in a position to closure the port, be stored in a concertina fashion; other storage configurations for the drip tray are also possible.
In an alternative, the port closure means may be hinged to the outer casing of the laundry apparatus. The hinging can be arranged so that the closure means preferably swings around either a vertical axis or around a substantially horizontal axis when the apparatus is installed. Where the port closure means swings around a substantially horizontal axis, the port closure means can, if the hinges are situated at the lower portion of the port (when the apparatus is installed), act as a drip tray.


A multi-mode mobile station is able to wirelessly communicate with a wireless wide area network (WWAN) and with a wireless local area network (WLAN). The WLAN includes a “virtual” visitor location register (VVLR) for storing information about multi-mode mobile stations being served by the WLAN. The VVLR communicates with a home location register (HLR) in the WWAN in order to facilitate roaming between the WWAN and WLAN by the multi-mode mobile station.

1. Field of the Invention
The present invention relates to telecommunications and, more particularly, to a "virtual" visitor location register for a wireless local area network.
2. Description of Related Art
A traditional enterprise telephone network includes a number of landline extension telephones (either analog or digital) connected to a private branch exchange (PBX). The PBX, in turn, is connected to the public switched telephone network (PSTN), e.g., via a primary rate interface or a basic rate interface. Increasingly, however, more diverse types of communication devices are being used in enterprise networks. For example, the PBX may be connected via a local area network (LAN) to packet-based communication devices, such as voice-over-packet (VoP) telephones or audio-equipped personal computers. In addition, the PBX may be an "JP-PBX" communicatively coupled to a packet-switched network, such as the Internet, instead of or in addition to the PSTN.
The PBX may also be part of a wireless local area network (WLAN) that includes one or more wireless access points for communicating with mobile stations over air interfaces. Such mobile stations may include wireless telephones, wirelessly-equipped personal digital assistants (PDAs), wirelessly-equipped laptop computers, and/or other wireless communication devices. The air interface communications may conform to a WLAN specification, such as IEEE 802.11b, Bluetooth, HomeRF, or HiperLAN. Alternatively, or additionally, the air interface communication may occur in a cordless telephone format, in a Multichannel Multipoint Distribution Service (MMDS) format, or in some other format. Some of these mobile stations may also be able to communicate with a wireless wide area network (WWAN), using an air interface format such as CDMA or GSM. Thus, when a multi-mode mobile station is within the wireless coverage area of the WLAN, it may use the WLAN for communication, and when the multi-mode mobile station is within the wireless coverage of the WWAN, it may use the WWAN for communication.
WWAN signaling protocols, such as IS-41, typically support roaming between areas served by different serving systems. For example, each serving system in a WWAN may include a visitor location register (VLR) that communicates with a home location register (HLR) for mobility management and other purposes. Now, with the interest in multi-mode mobile stations that may be in communication with either a WWAN or a WLAN at any given time, there is a need to provide additional systems and methods for mobility management in order to facilitate roaming between the WWAN and WLAN. For example, it is desirable to be able to reach a multi-mode mobile station by dialing the same directory number, regardless of whether the multi-mode mobile station is in communication with the WWAN or with the WLAN.

Virtual visitor location register for a wireless local area network


A waveguide structure includes a substrate, a waveguide film, and an overlay material in contact with the waveguide film. The overlay material may also contact the substrate or the film may be disposed between the overlay and the substrate. The overlay material has a higher refractive index than the waveguide so that the ratio of the effective refractive indexes is substantially constant for all propagating modes supported by the waveguide.

The use of multimode slab waveguides where overlay devices are used to perform geometrical optics on the propagating light is restricted because device operation is mode dependent. When multiple modes are excited within a waveguide, beam steering or focusing properties can vary significantly. This is a major concern where there is an optical axis along which there are additional devices having dimensions about the size of the beam, which typically occurs.
There are, however, several advantages of using waveguides supporting multiple modes. Often a thin-film preparation technique, required for some materials and their associated characteristics, will limit the thinness of resulting films and so result in the appearance of multiple propagation modes. These methods might include: flame hydrolysis of silicon dioxide doped films, dip-coating from sol-gel solutions or indiffusion of dopants into existing waveguides or substrates. It is desirable to have a waveguide structure that can operate with a thicker thin-film and take advantage of the benefits of thicker waveguide layers. Two of the benefits of using thicker waveguide layers are lower propagation losses and more efficient end-fire coupling of light from a fiber, laser diode, or microscope objective.


A hearing device comprises a receiver, an input buffer and a sample processor, the receiver being adapted to receive samples of a digital audio signal and feed received samples as a digital input signal to the input buffer, the sample processor being adapted to process the buffered samples to provide samples of a digital output signal such that the digital output signal is a sample-rate converted representation of the digital input signal with a predetermined target sample rate. The hearing device further comprises a latency controller adapted to estimate the quality of reception of the digital audio signal and to control the processing of the buffered samples in dependence on the estimated quality of reception.

Hearing devices that perform digital signal processing of digital audio signals received from another device are known in the art. Such hearing devices may be designed so that the processing rate, i.e. the rate with which the signal processing requires input samples, equals the input rate, i.e. the rate with which audio signal samples are received. However, various factors, such as production tolerances, variations in the clock frequencies of the transmitting and receiving devices and errors in the transmission, may cause the input rate to at least temporarily deviate from the processing rate. At the same time it is often desired to keep the processing rate constant over time. In such cases, the input signal is preferably pre-processed to ensure that the signal processing receives the required samples at the processing rate.
A known and rather simple solution is to provide the hearing device with an input buffer into which the received samples are written on arrival and from which the respective oldest unread sample is read by the signal processing when it requires a new sample. When a buffer under-run occurs, i.e. when the buffer is empty when a read operation is due, then the last sample read is repeated as input to the signal processing. When a buffer over-run occurs, i.e. when the buffer is full when a write operation is due, then the sample to be written is discarded (skipped). This simple form of sample-rate conversion, in the following referred to as skip-and-repeat, has the disadvantage that the skipping and repeating of samples causes clearly audible artefacts in the processed signal. It is further only successfully applicable when the input rate and the processing rate are close to each other.
It is further known to upsample the input signal to provide samples at a resampling rate which is an integer multiple—defined as the upsampling factor—of the input rate. The skip-and-repeat procedure is performed on the upsampled signal, and thus at the resampling rate, to provide a sample rate equalling an integer multiple of the processing rate. The resulting signal is subsequently downsampled to the processing rate by an integer downsampling factor. This upsampled skip-and-repeat method also causes artefacts in the processed signal, but they are less audible than those caused by the simple skip- and repeat method described above. Furthermore, by selecting different up- and downsampling factors this method may be used to perform sample-rate conversion when the input rate and the processing rate are not close to each other.
In the present context, the conversion ratio is defined as the ratio of the processing rate to the input rate. The range of conversion-ratio variations with which a device has to cope may differ between different systems and scenarios. If the range of variations is large and/or if variations occur fast, then a more sophisticated control of the skipping and repeating in the upsampled skip-and-repeat method is required to avoid that multiple skip operations or multiple repeat operations occur immediately after each other, which could otherwise significantly reduce the quality of the processed signal. The upsampled skip-and-repeat method is more sensitive to such variations than the simple method because in the upsampled method a single missing input sample may cause several consecutive repetitions of an upsampled signal sample. Where the input signal is received in packets each comprising multiple signal samples, the content of entire packets may be lost due to transmission errors. The loss of packets, and the well known and widely implemented retransmission of lost packets to avoid gaps in the processed audio signal, both worsen these problems.
In the above mentioned skip-and-repeat methods, multiple skip operations or multiple repeat operations occurring immediately after each other are mainly caused by the fact that the decision to increase or decrease the conversion ratio is taken on the basis of information regarding a single sample and that the decision is immediately carried out, namely by skipping or repeating the respective sample. Therefore, alternative methods have been developed in the art, which provide a slower working control of the conversion ratio.
One such known alternative method comprises performing sample-rate conversion with a piecewise constant conversion ratio, e.g. by upsampling and downsampling as described above, however without skipping and repeating upsampled samples. The received input samples are buffered, and the conversion ratio is increased when the buffer level, i.e. the number of buffered samples, sinks below a predetermined lower threshold, and conversely decreased when the buffer level grows above a predetermined upper threshold. The thresholds are preferably selected so that their difference is smaller than the total buffer size and they thus provide room both below the lower threshold and above the upper threshold. This extra room is used to allow for overshoot of the control algorithm. The buffer size, the buffer thresholds and the step sizes with which the conversion ratio is respectively increased and decreased are chosen such that they together allow the method to adapt to expected variations in the input rate without risking actual buffer under-runs or over-runs. The method also works when one of the upsampling and the downsampling factor equals unity.
Signal processing generally requires resources, such as logic circuits, memory space, computation time or power, each of which is typically a limited resource in hearing devices—and even more so in battery-powered hearing devices. It is therefore desirable to implement sample-rate conversion in hearing devices using methods that are particularly efficient. In most sample-rate conversion methods, and particular in such methods comprising upsampling and subsequent downsampling of the resampled signal, filtering is required to avoid aliasing artefacts in the processed signal. This filtering adds significantly to the complexity and the resource consumption of the sample-rate conversion, and the design of the filters is therefore of high importance in hearing devices. Upsampling followed by—or integral with—filtering to remove aliased frequencies is in the art generally referred to as interpolation. In the following, the term upsampling should be interpreted to cover both upsampling without such filtering and interpolation.
An efficient known method for sample-rate conversion comprises the use of so-called polyphase filters in the upsampling and in the downsampling steps. Each received input sample is fed in parallel to a set of digital filters, which each represents a specific phase of an interpolation filter to be applied. The outputs of the phase filters in the set are cyclically sampled at the resampling rate, one cycle for each input sample, and the thus resampled samples are cyclically fed to individual digital filters in a second set. Each filter in the second set represents a specific phase of a downsampling filter to be applied, and the outputs of these phase filters are added at the processing rate, thus providing a sample-rate-converted signal at the processing rate. The interpolation filter is typically configured to suppress frequencies above half the input rate, and the downsampling filter is typically configured to suppress frequencies above half the processing rate. The interpolation filter and the downsampling filter thus suppress aliasing artefacts in the processed signal. The sum of the lengths of the phase filters in a set is equal to or slightly larger than the length of the respective interpolation or downsampling filter.
In [1], chapter 10.5.3, "Time-Variant Filter Structures", the authors disclose how sample-rate conversion using polyphase filters may be implemented in a particularly efficient manner. In the disclosed method, the interpolation filter and the downsampling filter are combined in a single filter configured such that it suppresses frequencies above half the minimum of the input rate and the processing rate. The method allows the computation of the sample-rate converted signal to be performed basically by buffering the received input samples and at the processing rate computing a scalar product of a subset of the buffered samples and a subset of filter coefficients of the filter. The actual subsets to be used are selected dynamically from respectively the input buffer and a set of filter coefficients, using respective indices that are dynamically updated for each output sample to be computed.
The above described methods based on polyphase filters, may obviously be used in combination with the above described method wherein a piecewise constant conversion ratio is changed when the buffer level exceeds predetermined buffer thresholds. The conversion ratio may be changed by changing the upsampling factor and/or the downsampling factor. Since, however, the lengths and the coefficients of the phase filters depend on the up- and downsampling factors, the lengths and the coefficients of the phase filters must either be recomputed or be read from a repository of pre-stored filter configurations each time the conversion ratio changes. This obviously requires computation time and/or storage space in addition to the resources required for the conversion itself.
Furthermore, changing the conversion ratio based on predetermined buffer thresholds as described above causes the latency, i.e. the time delay from an input sample is received until the corresponding output sample is delivered to the signal processing, to vary with time and, at least to some extent, unpredictably. Also, in the known methods and devices, the buffer thresholds are chosen in advance and such that adaptation is possible when the input rate variations are within a range expected at the time of implementing the method or manufacturing the device. If the variations are larger than expected, the sample-rate conversion may not function properly, and if the variations are smaller than expected, the latency will be longer than needed. However, in hearing devices a consistent and short latency is often important, particularly when a hearing-device user is able to see the source of the sound he or she is listening to, e.g. when the user listens to the sound of a video or a TV broadcast.
Also, in hearing devices wherein retransmission of lost packets is implemented, the size of the input buffer and the value of the lower buffer threshold are typically selected to allow for a predetermined number of consecutive retransmissions of the same lost packet before a buffer under-run occurs. This, however, causes the latency to be larger than needed during time periods without retransmission.

Method for operating a hearing device and hearing device


A method for removing a polyp from inside a patient, comprises the steps of inserting an endoscopic insertion member into a patient, ejecting a cauterization loop from the insertion member, and maneuvering the insertion member and the cauterization loop from outside the patient to place the cauterization loop over a polyp inside the patient. A web member is ejected also from the endoscopic insertion member and is opened from a collapsed configuration to a substantially cup shaped opened configuration having a concave inner surface. The endoscope insertion member and the opened web member are maniipulated from outside the patient to juxtapose the concave inner surface of the web with the polyp, whereupon suction is applied to the web member to form a negative pressure zone between the web member and the polyp, thereby attaching the web member to the polyp in a vacuum seal. Then electrical current is conducted to the cauterization loop to sever the polyp from the patient. The web entrains the severed polyp for removal from the patient.

This invention relates to an endoscopic procedure for retrieving objects such as polyps from inside patients. This invention also relates to an associated endoscopic instrument assembly.
In a conventional polyp retrieval operation, an endoscope is inserted into an internal cavity of a patient, e.g., into the colon, and is used to visually identify and locate the polyp in the internal cavity. Upon the identification of the polyp or other growth which is to be removed, a wire extending through a tube in the biopsy channel of the endoscope is slid in the distal direction so that a cauterization loop connected to the wire is ejected from the distal end of the tube and the endoscope. The loop and the endoscope are manipulated from outside of the patient to pass the loop over the polyp or growth. The wire is then withdrawn in the proximal direction to tighten the loop around a base region or neck of the polyp. Once the loop is in contact with the base region of the polyp, an electrical current is conducted through the loop via the wire. Generally, as the loop is closed about the base region of the polyp, electrical current is transmitted through the narrowed organic tissues and thereby generates therein heat sufficiently great to cut and cauterize.
Once a polyp is severed by such a snare cauterization technique, it frequently becomes difficult to capture the polyp and retrieve it from the patient. Sometimes the cauterization loop is used in an effort to ensnare the polyp. Other capture techniques involve the use of forceps or the application of suction. In using forceps, the snare cauterization tube is removed from the biopsy channel of the endoscope and replaced with the forceps. In using suction, a vacuum is applied via a suction channel of the endoscope.
No matter which specific technique is used, the polyp frequently escapes from the capturing instrumentality and falls away into the colon (or other cavity). Especially in cases where the polyp is large, the effort and time expended in retrieving the severed polyp may rival or even exceed the effort and time required to locate and sever the polyp. In extreme cases, the endoscope must be removed without the polyp and the patient given an enema in an attempt to flush out the polyp from the colon.
Furthermore, there are numerous cases where a severed polyp is never recovered. Sometimes, the polyp is masserated during the retrieval attempt. In all such cases, the pathologist is unable to determine whether the polyp contains carcinoma in situ (localized) or infiltrative carcinoma (spread). The patient must then undergo a colon ressection, sometimes unnecessarily.
In any event, the manipulations necessary to remove a severed polyp generally increase the trauma to the patient, the expense of the surgery and the hospitalization time. There is now a long-felt need to improve the snare cauterization technique to facilitate the capture and retrieval of severed polyps.
U.S. Pat. Nos. 5,201,740 and 5,190,542 to Nakao and Wilk disclose a cauterization loop with an attached capture pocket. Such a snare assembly represents a significant advance in the art and evidently solves all of the problems inherent in polyp retrieval. However, it appears that there is some rooom in the industry for an alternative method for snare retrieval.

Polyp retrieval method and associated instrument assembly


There is provided a process for the production of a sintered article which comprises steps of. shaping a raw material powder comprising silicon nitride, PA1 thermally treating a shaped article in a non-oxidizing atmosphere at a temperature of 1300.degree. to 1650.degree. C. for at least 2 hours to form .beta.-silicon nitride of not less than 85% calculated from X-ray diffraction patterns and to increase a relative density of the article to not less than 80%, preferably to 80 to 85 %, and PA1 sintering the thermally treated article at a temperature of 1700.degree. to 2000.degree. C.

1. Field of the Invention
The present invention relates to a process for the production of a sintered silicon nitride made article having a high strength.
2. Description of the Related Art
Generally, strength of a ceramic material depends on, for example, a porosity ratio, a particle size and a surface condition of a crystal. Such factors affect strength of a sintered article made of silicon nitride which is one of important ceramic materials used for structural members.
In order to increase the strength of a Si.sub.3 N.sub.4 based sintered article, sintering aids and sintering processes have been developed. For example, Am. Ceram. Soc. Bull., 52, 560, (1973) reports that a bending strength of up to 100 Kg/mm.sup.2 with the use of a hot press sintering, and Preprint for the 1981 Annual Conference of the Ceramic Association of Japan, 178 (1981) reports that the same strength as above with the use of a low pressure sintering. In each case, the strength is increased by extremely reducing the porosity.
Japanese Patent Kokoku Publication Nos. 21091/1974 and 38448/1973 describe a process for the production of the silicon nitride made sintered article based on Si.sub.3 N.sub.4 --Y.sub.2 O.sub.3 --Al.sub.2 O.sub.3 in which Y.sub.2 O.sub.3 is used as a main sintering aid.
As described in these Publications, it may be contemplated thought that the strength and toughness of the ceramic material are increased since Si.sub.3 N.sub.4 in a .beta.-crystal lattice is present in a fibrous structure and dispersed in a matrix phase. Namely, the lattice of .beta.-crystal is a hexagonal one, and an anisotropical crystal growth along C axis is effectively used. A fibrous particle of .beta.-Si.sub.3 N.sub.4 crystal may grow to more than ten and few microns along a longitudinal axis as described in Japanese Patent Kokoku Publication No. 38448/1973 and J. Ceram. Ass. Jpn., 94, 96 (1986).
Since the growth of the fibrous structure is required in the prior arts as described above, abnormal growth of the crystal particles and generation of pores in relation to such growth may arise. Thus, this growth is not necessarily effective to increase the strength of the ceramic material.
In addition, in the case where the hot press sintering is used in order to form the fibrous structure as described in Japanese Patent Kokoku Publication No. 21091/1974 or where a raw material of the .beta.-crystal of Si.sub.3 N.sub.4 which has been thermally treated for the fibrous structure growth is added, the increase of the strength cannot be expected.

Process for production of sintered silicon nitride made article


An operation circuit based on a floating-point representation system includes a first bypass line with respect to a shifter, and a second bypass line with respect to a two's complementer. When values of the exponent parts of two input operands are identical to each other, the mantissa part of one of the input operands bypasses the shifter, and is supplied to an ALU. In the other case, the mantissa of one of the input operands passes through the shifter, and is always supplied to the ALU. The mantissa of the other input operand is directly supplied to the ALU. When the values of the exponent parts are identical to each other, an output of the ALU passes through the two's complementer and is output as a final operation result. In other cases, the output of the ALU is directly supplied as the final operation result. The sign of the final operation result is determined by a sign discriminator.

The present invention generally relates to an operation circuit based on a floating-point representation.
Generally, the fixed-point representation system is not, capable of representing an extremely large number, because of the narrow span of numbers which can be represented by the fixed-point representation system. Additionally, in most cases, the fixed-point representation system handles only an integer. For these reasons, it is required to provide another representation system for representing real numbers, as is necessary for operation for use in science and technology. From this viewpoint, a floating-point representation system has been proposed, in which two numbers called an exponent and a mantissa are combined.
A general floating-point number is represented as follows: EQU -1).sup.s .multidot.m.multidot.R.sup.e ( 1)
where `R` is the radix and `s` denotes the sign. When the sign is positive, s=0, and on the other hand, when the sign is negative, s=1. Further, `m` and `e` are the mantissa and the exponent, respectively. The floating-point representation system is constructed by combining the representation of formula (1) and the fixed-point representation. It is noted that the effective length of the digits depends on the length of the mantissa. For this reason, when it is desired to represent numbers with high precision, a representation system is employed such that an increased length of the mantissa part is used.
The floating-point operation can provide a wide dynamic range and high precision, compared with integer operation. Particularly, the recent trend exhibits the requirement of high-speed operation capable of satisfying requirements for a variety of high-level operations.
A conventional floating-point operation circuit for processing two input operands includes selectors, an exponent part comparator, a shifter, an arithmetic and logic unit (hereafter simply referred to as an ALU), and a complementer. The input operands pass through the exponent part comparator, the shifter, the ALU and the complementer without exception. However, it is noted that there are some cases where some operands are not required to be passed through all the parts. Particularly, an amount of delay occurring in the shifter and the complementer is about same as that for the ALU. From this viewpoint, there exists a delay in signal processing in the conventional floating-point operation circuit. Such a delay prevents high-speed floating-point operation.

Operation circuit based on floating-point representation with selective bypass for increasing processing speed