Performance evaluation of dynamically linearized and kinematically redundant planar manipulators

The objective of this research is to investigate the feasibility of a theoretical development which could lead to advanced manipulator concepts offering fast dynamic and control features. Specifically, the application of “dynamic linearization” to a kinematically redundant planar manipulator is studied. In comparing such a manipulator with a standard non-linear, non-redundant design it is shown that in addition to the expected merits in linearity, dexterity, and computational simplicity, savings in actuator energy consumption can also be realized using a relative simple trajectory optimization scheme.     

Phase separation studies in RIM polyurethanes catalyst and hard segment crystallinity effects

Polyurethanes were prepared from pure 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BDO) or 1,2-ethane diol (EDO) and α,ω-hydroxyl poly(propylene oxide) (PPO) by reaction injection moulding (RIM). Hard segment (MDI + BDO or EDO) level was 45–50 wt%. The PPO had about 20% ethylene oxide copolymerized in at the chain ends to provide 80% primary OH end groups. M_n was varied from 2000 to 4000. Dibutyl tin dilaurate catalyst and mould temperature were varied. Dynamic mechanical, wide-angle X-ray, differential scanning calorimeter, molecular weight and tensile elongation measurements were made on the RIM polyurethanes. At low reaction rates (low catalyst or temperature) highly crystalline, well phase separated but low molecular weight polymers were produced. At high catalyst or temperature levels more poorly phase separated but high molecular weight, tough polymers resulted. Higher M_n PPO gave better phase separation and EDO gave higher melting temperatures. Preventing hard segment crystallinity by substituting asymmetric MDI or glycols resulted in phase compatibility.     

Removing cesium radionuclides from sodium-potassium coolant

Translated from Atomnaya Énergiya, Vol. 66, No. 1., pp. 22–24, January, 1989.     

Analysis of performance of fuel elements of the BOR-60 reactor with vibrocompacted uranium-plutonium oxide fuel

Translated from Atomnaya Énergiya, Vol. 66, No. 5, pp. 299–302, May 1989.     

Long distance fiber-optic transmission of C-band microwave signals to and from a satellite antenna

We demonstrate here the use of high-speed semiconductor lasers and detectors with low loss optical fiber for the transmission of the 500-MHz C-band microwave signal spectrum to and from a satellite antenna. The optical system has low attenuation and large band, width, so the microwave signals can be transmitted directly at the microwave frequency (4 or 6 GHz) over 20 km of fiber without regeneration or qualization. The optical system introduces ≈ 1 dB or less of degradation for both low spectral density QPSK signals and high spectral density FM video signals present in typical satellite transmission systems. For the video signals, the signal to noise after AM conversion was reduced from 56 to 55 dB. The microwave drive level to the laser must be significantly larger (typically > -10 dBm) than the intensity noise of the laser, yet small enough (typically < 10 dBm) to reduce the intermodulation distortion signals to an acceptable level. The laser bias current must be several times threshold so that the resonance frequency is beyond the frequency band of interest (4-6 GHz in this case). A flat modulation response is then obtained, and the intensity noise and intermodulation levels are low.     

A Device for Measurements of Dielectric Characteristics of Liquid Crystalline Materials, Solid Substances, and Their Melts

The device developed allows one to measure the dielectric characteristics of solid substances and their melts at frequencies of 20–20000 Hz and in a wide temperature range of 20–250°C. The measured temperature dependencies of the dielectric permittivities of several molecular and liquid crystals (stilbene, diphenyl, naphthalene, cholesterylpelargonate, and 8OCB) are presented.