Abstract: A fast ultrasonic scanner for soft tissue imaging and/or characterization has a transmitter with a divergent beam pattern and an arcuate array of receivers. The propagation delay time of a short acoustic pulse traversing a water bath and immersed specimen depends on the velocity distribution and is detected at each receiver. Digital data is derived from the receiver signals at many angular positions of the scan apparatus and is used to compute a reconstruction of the velocity distribution in the specimen. The instrument provides quantitative measurements of bulk tissue and has application in breast examination and mass screening for breast cancer.

Abstract: A pair of polyphase electrical machines with interconnected rotor windings are mechanically coupled together and driven by a rotating shaft. One stator winding is excited by a fixed carrier frequency, and the output frequency at the other stator winding is proportional to shaft speed. The output signal frequency is not zero at zero shaft speed and is unique for both directions of shaft speed. Brushes, slip rings, and electrical connections to the rotating shaft are not required.

Abstract: A controlled current motor drive system and method for its operation utilizes an open loop technique and simple control circuit additions to modulate the inverter input current at six times motor frequency and reduce sixth harmonic torque pulsations. Conventionally generated current source inverter control signals at six times motor frequency are also used to derive a sixth harmonic ac signal which is fed to the controlled rectifier gating circuit as an additional input.

Abstract: The bond integrity of resin grouted rock bolts or roof bolts anchored within the ceiling in underground mines is tested by inducing broadband vibrations and measuring the resonant frequencies of the axial and transverse vibration modes. Voids in the resin grout or imperfect bonding cause shifts in the resonant frequencies. The tension in expansion nut rock bolts is determined from the resonant frequency of the transverse vibration mode.

Abstract: In force-commutated single phase and polyphase thyristor inverters, a single commutating pulse generator produces commutating impulses for all the commutating thyristors which are individually transformer-coupled to the power circuit to turn off a selected load thyristor. Coasting thyristors to provide zero output voltage levels are also commutated without additional components. The basic commutating pulse generator has one capacitor with provision for recovering trapped energy, and pulse waveshaping and two-level overcurrent capability can be added economically.

Abstract: A plurality of stepper motors are energized one at a time in any order by repeating sets of drive pulses generated by a single motor controller. The actual winding state of each motor is stored in a memory unit. Upon selecting the next motor the controller is cycled until the actual motor winding state and controller winding state compare. The selected motor is then switched and moved by steps to a commanded position while entering new motor winding state data into the memory unit.

Abstract: A ferrite magnetic core includes a one-piece rectangular outer member with aligned circular apertures in which the ends of a cylindrical center member are retained to thus establish a radial air gap. Radial magnetic forces acting on the core members are summed to zero to theoretically eliminate movement and result in low acoustic noise in high operating frequency power inductors and transformers. A magnetic bridge is added to reduce air gap fringing flux outside the core. Other modifications and a "C" core configuration are described.

Abstract: A non-contacting method and apparatus for proximity detection with negligible radiation loss utilizes a microwave junction essentially having propagating waves on one side and evanescent electromagnetic fields on the other. Perturbation of the evanescent fields by an object causes a variation in the reflection coefficient of the propagation mode which is dependent on the distance from the junction to the object. This variation can be detected by measuring the phase shift of the propagating reflected waves relative to a reference.

Abstract: A single phase, high frequency chopper ballast without large magnetic and capacitive components for gaseous discharge lamps such as the Lucalox.sup.R lamp is operated on full wave rectified line voltage. A small auxiliary capacitor stores energy during the peaks of the rectified line voltage when the voltage is high enough to maintain lamp discharge. During the low voltage valley regions the auxiliary capacitor is discharged to supply augmented chopper input voltage or load circuit voltage and provide energy to maintain lamp ionization during the valley regions until the rectified line voltage rises to a usable level.

Abstract: An ac induction motor is supplied with variable frequency and amplitude excitation voltage by a power converter. Precise regulation of torque independent of motor parameter changes is achieved by feedback control loops for maintaining at command values constant airgap flux and also the real component of stator current with respect to airgap voltage as measured by a voltage sensor. The real stator current error controls the slip frequency which adjusts to maintain constant airgap power.

Abstract: A current source power converter for an electric motor is comprised by a combined controlled rectifier and chopper which is coupled to a controlled-current inverter by a dc reactor. In the motoring mode the combined rectifier and chopper functions as a phase controlled rectifier to control the current magnitude. In the dynamic braking mode a line switch is opened and a braking resistor placed across the rectifier output, and the combined rectifier and chopper is operated as a chopper to control the average voltage across the braking resistor and thus the current magnitude during braking.

Abstract: A three phase bridge inverter supplies rectangular wave currents to an inductive load and to capacitors connected in wye across the load for wave shaping as well as filtering and power factor correction. A commutating capacitor connected to the midpoint of the wye-connected capacitors is controlled by two auxiliary thyristors. The commutating capacitor voltage is sensed and an incoming thyristor is not fired until the voltage rises to a level sufficient to commutate the next thyristor in sequence. This commutation is independent of load inductance.

Abstract: An electrical connector for applications where reliability and safety are needed uses transformer couplings made in two separable sections. Upon clamping together the surrounding metal housing halves, each inductively coupled pair of transformer windings is enclosed by the associated cup-type ferrite magnetic core to minimize undesired interference and result in good magnetic coupling.

Abstract: Improved stable four-quadrant operation of an induction motor supplied with variable amplitude and frequency stator line current by a motor controller with a constant current source converter is achieved by using several feedback control loops to control the slip frequency as well as the stator line current amplitude and frequency. Speed feedback is employed with optional control of rotor speed. Motor performance is optimized by indirectly regulating air gap flux to its rated value by controlling slip frequency as a function of sensed stator current. Thus, torque is approximately linear with stator current.

Abstract: A broadband Impatt diode amplifier for microstrip includes a two-section quarter wavelength impedance transformer. Since the width of one transformer section exceeds a half wavelength, spurious mode resonance is suppressed using a longitudinal slot with an absorbing resistor or by offsetting the transformer sections. A compact configuration combines the power of two microwave diodes over a broad frequency range.

Abstract: A cut-off tubular housing has flat surfaces for mounting multiple solid state microwave oscillators using microstrip circuitry, each exciting a wire-like resonant coupler wound on a central dielectric support tube for receiving a frankfurter or other material body. The couplers are longitudinally spaced and angularly staggered so that energy coupled to different regions of the body is absorbed by the material to thereby isolate couplers and hence sources even at close spacings. In a rectangular configuration, a non-resonant box has a planar array of serpentine or spiral resonant couplers with adjacent couplers oriented orthogonally to minimize coupling.

Abstract: A cut off conductive enclosure tube supports a plurality of wire-like energy coupling elements partially wrapped about a centrally located dielectric support tube for receiving a frankfurter or other material body. Each coupling element is excited by an independent low power source of microwave energy, the energy coupled to different regions of the body being absorbed thereby to provide isolation between coupling elements and sources. Continuous processing operations are possible, and a rectangular configuration and industrial heating applications are described.

Abstract: A motor control circuit and method for regulating the torque of an ac induction motor operated at a variable frequency utilizes as a controlled variable the modified in-phase component of stator current which is compensated for the voltage drop across the stator resistance. Both positive and negative torque are approximately linear assuming the slip frequency is changed linearly, and only the per phase line current and voltage are sensed. A traction application is described.

Abstract: A single phase controlled capacitive filter with a smaller, more efficiently used filter capacitor than conventional capacitive filters is connected between rectifier terminals and supplies voltage to an active load producing dc output voltage. The charge and discharge intervals of the filter capacitor are controlled by gate controlled thyristors or other devices such that discharge occurs when the instantaneous rectified line voltage falls below the dc output voltage. The filter capacitor during discharge is placed in series with the load or can remain in parallel with the load in a simpler arrangement.

Abstract: Variable frequency sine waves are converted to constant amplitude cosine waves using the relationship cos .omega.t = .sqroot.1-sin.sup.2 .omega.t. The converter has an almost instantaneous response characteristic and is suitable for a wide frequency range. An application is cosine timing waves for phase controlled converters and cycloconverters.