Abstract: A conductivity sensor configuration which has essentially no external electrical field so that the calibration of the sensor is not affected by the existence of nearby external objects or fouling on the exterior parts of the sensor. Additionally, the sensor is relatively insensitive to electrode fouling or electrode polarization. The sensor includes a tube through which the liquid to be measured flows. An inner electrode plate extends partially along the length of the tube dividing the central portion of the tube into two sections. Two inner electrodes are located on the inner wall, one on each side, and two outer electrodes are located on the inside of the tube opposite the inner electrodes.

Abstract: A dental mirror configured so that it is easier and more comfortable to manipulate than prior art mirrors. The dental mirror includes a handle which is attached to the mirror section with an s-shaped gooseneck so that the handle is offset upwardly. Additionally, grooves on the bottom and a finger rest on top at the distal end of the handle may be provided to further enhance it manipulatability.

Abstract: A dental mirror instrument with a reflecting surface comprising a metallized film or other reflecting material covered by a protective mask with at least one integral removal tab. Individual mirror/mask assemblies are cut from a multi-layer laminate which includes a release layer on the bottom which is adhesively attached to a thin, reflecting film, which is in turn attached to a protective mask layer. The cutting process creates a shaped reflecting surface covered by a protective mask that is congruent with the reflecting surface except for one or more small tabs projecting beyond the reflecting surface which are part of the protective mask and by which the protective mask may be easily removed.

Abstract: An improved amalgam or resin carrier, which has a plunger and lever mechanism similar to the well-known lever-actuated carrier and which has an easily replaceable sleeve or barrel for holding highly filled materials. The barrel may be easily removed for maintenance, cleaning, or replacement. In an alternate configuration, the barrel may be preloaded with a packable composite dental resin, thus allowing quick and easy clinical use. The preloaded barrel may be manufactured in the form of a disposable cartridge, and is especially suitable for use with light-activated materials.

Abstract: A disposable dental mirror and methods of making same. The mirror includes a long, thin, flat blade that provides both a handle and a mirror mount and has a reflective surface applied to one end thereof. The blade is made of a material which need not be sterilizable, such as wood or plastic. In a one embodiment, the reflective surface is made of a metallized film directly applied to one surface of the blade. In an alternate embodiment, a thin, flat piece of a rigid material is located between the blade and the reflective film to ensure flatness of the reflecting surface, thereby reducing distortion.

Abstract: The present invention provides a tool with which a DBA can analyze a VLDB at all levels of data storage, both logical and physical, to analyze performance problems. The invention is particularly applicable to systems in which database files are striped over multiple disk drives. In the present invention, storage of information is monitored at three levels: database files, file system files, and individual disk drives Parameters indicating the activity and performance level of each of the levels of storage are taken at selected intervals and stored. An analysis tool is provided that allows a DBA to select a time window during which the database performance is be assessed. The analysis tool has a map of the logical and physical arrangement of the database being monitored and allows a DBA to move from level to level of both logical and physical structures involved in storing the data while displaying I/O activity in an easily understood manner.

Abstract: An article of manufacture and a method of making same wherein a plurality of mixing wells is formed as a unitary sheet of individual mixing wells arranged in rows and columns. The boundary between each mixing well is scored, perforated, or otherwise made to allow individual pieces to be removed from the sheet. Preferably, the mixing wells may be pressure formed rather than being vacuum formed.

Abstract: A system is provided for reducing power consumption of door and frame heaters of refrigerating devices while maintaining protection against condensation. One or more condensation sensors are attached to the door and are monitored by control circuitry which controls power applied to the door or frame heater. Condensation on the sensor will increase the conductivity of the sensor, which is detected by the control circuitry. When condensation occurs, power is applied to the heater until the condensation is eliminated. The invention includes two different condensation sensor configurations.

Abstract: A new reach-through APD structure which includes a five-layer, double-drift-region, double-junction device, having a p.sup.+ -p-n-p.sup.- -n.sup.+ structure. The middle three layers of the new APD constitute most of the thickness of the device and are fully depleted when the device is biased to its normal operating voltage. In the present invention, only primary carriers generated in the relatively narrow first drift region are subject to the full avalanche gain, resulting in dark current and noise levels much lower than conventional reach-through APD's. The new structure can be used to fabricate integrated arrays of APD's. These arrays are more durable and easily fabricated than are prior art APD's. Additionally, the new array structure does not require segmentation or isolation of the multiplying regions of the different elements of the array, allowing arrays to be made with little or no dead space between elements.

Abstract: An active quench circuit for interrupting the current flow in an avalanche photodiode (APD) operating in Geiger mode and for resetting the APD. The invention increases the speed of quenching and reduces the time required to bring the APD voltage back to its operating voltage above the breakdown voltage. The circuit includes a small inductor which isolates the reset circuit from the APD during the initial discharge and which provides a current pulse into the APD immediately after the end of the quenching operation to recharge the diode. The reset circuit also includes a diode assembly that increases the speed of the avalanche current pulse and that prevents the circuit from oscillating or latching under certain operating conditions. The circuit presents a low impedance to the APD during during reset, and is much less sensitive to the APD capacitance than prior art circuits.

Abstract: A method of measuring induction motor parameters so that the speed and torque control of an induction motor controller may be optimized. While the motor is stopped, a test signal made up of a current pulse of a known amplitude is applied to one or more windings of the motor stator for a selected period of time, after which the current pulse is turned off. After a short delay, the instanteous voltage across the stator windings is measured, and also an integration of the stator voltage is started which continues long enough so that the stator voltage decays to substantially zero. The measured voltage and integrated voltage are respectively proportional to the rotor resistance and the motor magnetizing inductance.

Abstract: A two-stage band-pass amplifier filter circuit which uses a bi-quad amplifier in each stage, the bi-quad amplifier being connected between an AC feedback amplifier in the signal transmission path and ground. The bi-quad amplifiers each provide a variable impedance and effectively operate as series-resonant circuits such that, during closed loop operation, the overall amplifier-filter circuit has a high gain at or near resonance and a very low gain off-resonance and has a phase shift of 0.degree. at resonance and .+-.90.degree. substantially off-resonance. The bi-quad amplifiers are connected to the feedback resistance of the signal path amplifier via a coupling resistance, the signal path amplifier feedback resistance being greater than the coupling resistance, normally by a factor as high as 20 to 1, so that the bi-quad amplifier is thereby prevented from overloading during operation.

Abstract: An analog-to-digital converter for performing extremely accurate measurements of AC voltages. In the conversion process, the most significant bits are determined using a precision ratio transformer having multiple, binary-weighted windings which are selectively connected in series during a first interval to provide an approximation to the input voltage to be measured via a successive approximation conversion technique. The digital value so determined is clocked into a bi-directional counter. The transformer output signal at the end of the first interval is subtracted from the input signal to give an AC residue signal which represents the round-off error from the successive approximation conversion performed during the first interval. The residue signal is synchronously detected and applied to a dual slope type of converter during a second interval, the digital output thereof being accumulated in the counter.

Abstract: A fume hood controller system in which the sash position is monitored by a transducer which provides a signal indicative of the area of the hood opening. A variable speed controller responsive to the sash position signal to provides a fan speed which varies as a function of the sash opening. An optional circuit monitors the power drawn by the motor and compares the actual power drawn by the motor with the expected power for the present sash position. If the actual power falls below the threshold, an alarm signal is generated indicating a reduced air flow in the fume hood. Additionally, motor overload may be detected by comparing the motor speed control signal with the actual motor speed. An alternate embodiment is shown in which the present invention may be used to control a single blower which exhausts a plurality of fume hoods while maintaining a substantially constant face velocity in each hood.

Abstract: The present invention generates a motor slip frequency value and two current magnitude values representing quadrature components of the motor stator current to be generated. Closed-loop control of the motor operation is provided by feeding back a signal representative of the motor shaft speed or position calculate the torque required from the motor. The feedback signal is separated into high and low frequency components. Additional circuitry changes the value in response to detected variations in the high frequency components of the feedback signal. The addition of this circuitry causes the motor control circuit to no longer represent the inverse of the motor transfer function network.

Abstract: A transducerless brushless permanent magnet motor in which a signal induced by the rotor in an unexcited winding is used to sense the rotor position. The sensed voltage, induced in the winding by the rotor, is integrated to provide a representation of the magnetic flux coupling the rotor and winding. Before start-up, both the rotor position and the integrator are initialized to align the circuit representation of the flux with the actual flux.In an additional embodiment of the invention, a self-initialization circuit is provided to automatically preset the rotor and flux integrator to pre-determined and corresponding values.

Abstract: The invention includes a low-drag cycle having an elongated frame extending between a smaller front wheel and a larger rear wheel. A cyclist assumes a recumbant position over the frame facing down. A cycle is steered by means of the front wheel, while the cyclist powers the cycle by means of a pedal arrangement driving the larger rear wheel. A streamlined, pod-shaped body which is symmetrical about an axis parallel to the direction of travel achieves a very low coefficient of drag and maximizes laminar flow to further reduce drag. The cycle wheels are contained within two streamlined fairings which extend from the streamlined cycle body to near the ground, the area between wheels being left open to increase the lateral stability of the cycle and to allow the rider to straddle the frame so that both feet may be placed on the ground while starting or stopping the cycle.