William Shepherd

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The plasma crystal experiment PKE–Nefedov, the first basic science experiment on the International Space Station (ISS), was installed in February 2001 by the first permanent crew. It is designed for long-term investigations of complex plasmas under microgravity conditions. ‘Complex plasmas’ contain ions, electrons, neutrals and small solid(More)
Dark matter that was once in thermal equilibrium with the Standard Model is generally prohibited from obtaining all of its mass from the electroweak phase transition. This implies a new scale of physics and mediator particles to facilitate dark matter annihilation. In this work, we focus on dark matter that annihilates through a generic gauge boson portal.(More)
Several configurations of balanced three-phase series <i>RL</i> loads are investigated to consider the feasibility of using thyristor control with integral-cycle triggering. The four-wire star-connected load, with pairs of thyristors in the supply lines and the delta-connection with pairs of thyristors in the load legs, are found to be suitable. Both(More)
Magnitude estimations of the annoyance of 27 individual noise stimuli were made by 24 Ss while viewing television; 8 different spectrum modifications of a basic aircraft noise were introduced at 3 overall intensities. The basic spectrum was that of an untreated commercial jet aircraft takeoff noise; the other 8 were created by removal of one of two amounts(More)
A design method is described for a saturistor which enables the stall current of an induction motor to be restricted to some predetermined value without significant effect on the full-load operation. The design method requires knowledge of the dynamic B¿H loop for the hard magnetic saturistor material. With controlled sinusoidal primary supply voltage and(More)
In June of this year, the FAA sponsored a meeting of representatives of the aviation industry to review problems associated with aging aircraft. While much of this meeting addressed issues of hardware, metal fatigue, and corrosion, there was a discussion of human factors in maintenance. Today's meeting reflects a growing interest in human factors and its(More)
A form of controller/compensator is suggested for the speed control of small induction motors. This controller uses pairs of thyristors in each supply line, incorporated into a resistance/capacitance network. Smooth speed control may be realized over a wide speed range, and the motor current remains substantially sinusoidal. For a small laboratory type(More)