Abstract: A continuous process for the production of poly(trimethylene terephthalate) is disclosed. According to the process, a liquid feed mixture comprising bis-3-hydroxypropyl terephthalate and/or low molecular weight polyesters of 1,3-propanediol and terephthalic acid, the liquid feed mixture having a mole ratio of propylene groups to terephthalate groups of 1.1 to 2.2 is fed to a prepolymerizer. Bis-3-hydroxypropyl terephthalate and the low molecular weight polyesters are continuously polymerized to form a poly(trimethylene terephthalate) prepolymer and a first stream of gaseous by-products. Poly(trimethylene terephthalate) prepolymer having a relative viscosity of at least about 5 is continuously withdrawn from the prepolymerizer and continuously fed to a final polymerizer, where it is continuously polymerized to form a higher molecular weight poly(trimethylene terephthalate) and a second stream of gaseous by-products.

Abstract: Variable beamwidth antenna systems for use on spacecraft that is capable of changing their beamwidths while the spacecraft in on orbit. The variable beamwidth antenna systems include a main reflector, a subreflector, a feed horn, a main reflector displacement mechanism and a feed horn (or subreflector) displacement mechanism. For broaden the beamwidth, the RF feed horn and the subreflector are moved close together by proper distance. The main reflector is moved away from the subreflector along a line through centers of their respective surface by a distance given by a predetermined equation. Another embodiment of the present invention provides for a zoom contour beam antenna system that radiates a contour beam and whose beam is variable or zoomable.

Abstract: A Gregorian reflector antenna system optimized for an elliptical antenna aperture. The Gregorian reflector antenna system comprises a main reflector, a subreflector, and a feed horn for illuminating the subreflector. The subreflector illuminates the main reflector with an elliptically shaped feed cone of energy. The subreflector has a surface defined by the equation x 2 a 2 + y 2 b 2 + z 2 c 2 = 1 , where x, y, and z are three axes of the Cartesian coordinate system.

Abstract: Variable beamwidth antenna systems for use on spacecraft that is capable of changing their beamwidths while the spacecraft in on orbit. The variable beamwidth antenna systems include a main reflector, a subreflector, a feed horn, a main reflector displacement mechanism and a feed horn (or subreflector) displacement mechanism. For broaden the beamwidth, the RF feed horn and the subreflector are moved close together by proper distance. The main reflector is moved away from the subreflector along a line through centers of their respective surface by a distance given by a predetermined equation.

Abstract: Improved active multiple beam antennas that comprise an amplifier array or grid amplifier having substantially identical amplifiers. A feed array having a plurality of antenna elements provides RF energy. A microwave lens is disposed adjacent to the feed array that weakly focuses the RF energy from the feed array. The amplifier array or grid amplifier is disposed opposite the microwave lens from the feed array. The feed array illuminates the amplifier array or grid amplifier via the microwave lens. The weakly focused RF signals are amplified without changing their respective directions of propagation, which forms powerful multiple beams in the far field.

Abstract: A screwdriver handle includes a main body having an end releasably engaged with a screwdriver tip. The main body includes two opposite lateral sides each having a compartment defined therein. Two pivotal covers are pivotally connected to the main body to cover the compartments, respectively. Each pivotal cover includes a holder plate formed on an inner side thereof and having a number of holes for holding screwdriver tips and a number of semi-circle recesses for holding sockets. When a push pin is pushed, two hooks of the pivotal covers are disengaged with two latches of an engaging member that is moved by the push pin such that the pivotal covers pivot outwardly under the action of two elastic members.

Abstract: A power converter which transfers energy from an output circuit coupled to a secondary winding of a power transformer to an input circuit coupled to a primary winding of the power transformer in order to reduce the power loss and electromagnetic interference (EMI) originating from a primary switch. The reciprocating action of the converter is accomplished by placing the series switched path of a secondary switch in parallel with a diode in the output circuit. A control circuit is coupled to the primary switch and the secondary switch which allows the inherent capacitance of each switch to discharge before turning on the respective switch, thereby reducing the EMI and power losses occurring at these switches. The control circuit includes feedback and feedforward voltage control of the switching duty cycle. The control circuit varies the energy transferred from the output circuit to the input circuit according to changes in the accumulated charge on the primary switch.