Optimal control and energy storage for DC electric train systems using evolutionary algorithms

Railway Engineering Science - Electrified railways are becoming a popular transport medium and these consume a large amount of electrical energy. Environmental concerns demand reduction in energy...     

Reanalysis of solidus points and Te chemical potential for Te-rich CdTe(s)

The author’s previously published partial pressures of tellurium over tellurium-rich CdTe are reanalyzed to yield new solidus points as well as temperatures and partial pressures for compositions within the homogeneity range. Although the results are qualitatively the same as before, they are more satisfactory in that some thermodynamic inconsistencies have been removed. The composition range of the CdTe phase extends slightly beyond the equal atom fraction,X _Te=0.5, to a Te-rich composition of (X _Te−0.5)=(1 to 7)×10⁻⁵. The data are in fair agreement with that obtained from total pressure measurements at generally higher compositions. Since both types of measurement are near the limits of attainable accuracy, their agreement would seem to confirm the essential correctness of both.     

Computer generation of phase diagrams and the associated free energy curves for a binary system

An interactive computer program is introduced in order to make a simultaneous graphical presentation of phase boundaries and their corresponding free energy curves. The program, which uses a graphics display terminal, is a useful tool in teaching thermodynamic concepts involved in phase diagrams, especially for undergraduate students.     

An Active Feedback System for Stabilizing Visual Images

In normal vision, eye movements cause the image to move on the retina. Special apparatus can stabilize the image on the retina so it cannot move, and vision fades away. Previous methods for stabilizing the image were either optical systems or complex computer-controlled feedback systems. A simpler feedback system is presented which detects eye motion and rotates a mirror through which the target is viewed, to exactly compensate for eye motion. Unlike previous optical systems, this new system has no lenses in either the viewing or the image-forming path to limit the spatial resolution.     

A Multi-Channel Pulse-Coded Multiplexing and Demodulating Telemetry System

A multiplexing, demodulating, and recording telemetry system designed to process multiple pulse-coded temperature channels is described. The system provides complete control of recording and multiplexing sequences and timing, and gives a single analog signal in response to each sample of pulse-coded data. It identifies all channels and indicates to a computer when a new data sample is to be processed. The system is self-calibrating to maintain accuracy over extended data collection periods, and is inexpensive.     

Methods for the determination of cyclopropenoid fatty acids. VII. The dilution-HBr-titration technique as a general method

The stepwise HBr titration method for the cyclopropenoid analysis of cottonseed oils is subject to serious inaccuracies when applied to samples containing higher cyclopropenoid concentrations, particularly if they contain appreciable amounts of alumina-adsorbable materials. A modification of the method is described which eliminates these sources of error. Its validity has been established by the analysis of a wide range of synthetic compositions including compositions containing massive amounts of interfering HBr-reactive substances and other alumina-adsorbable materials. The method with further modification can be used to analyze glycerides with the same high degree of accuracy. Presented at the AOCS Meeting in Houston, April 1965. So. Utiliz. Res. Dev. Div., ARS, USDA.     

Thermal Conductivity/Diffusivity of Silicon Carbide Whisker Reinforced Mullite

The thermal conductivity and diffusivity of silicon carbide whisker reinforced mullite was shown to increase with whisker content. This effect was much greater for vapor-liquid-solid (VLS) whiskers than for rice-hull (RH) whiskers. This suggests that the thermal conductivity for the VLS whiskers was significantly higher than for the RH whiskers. Due to preferred orientation of the whiskers, thermal conductivity and diffusivity of the composite samples exhibited significant anisotropy.     

Some mechanical properties of an epoxy resin system cured with multiple crosslinking agents

Arbitrary cure times and glass transition temperatures are reported for an epoxy resin cocrosslinked by various weight fractions of hexamethylenediamine (HMDA) and m-phenylenediamine (m-PLDA). The glass transition temperatures of the epoxy resin systems studied yielded an excellent fit to an empirical equation developed by Dyvik for copolymers. The cure time parameters were found to be a linear function of the weight fractions of each crosslinking agent present. The mechanical properties of the epoxy resins were measured by an in situ dynamic modulus technique which employed the use of a resin-coated metallic substrate.     

Hydrolytic degradation of ionically cross-linked polyphosphazene microspheres

The hydrolytic degradation of gel microspheres based on calcium cross-linked phosphazene polyelectrolytes, poly[di(carboxylatophenoxy)phosphazene] (PCPP) and poly[(carboxylatophenoxy) (glycinato)phosphazene] (PCGPP), was investigated. These microspheres are of importance as carriers in protein and cell encapsulation. Both PCPP and PCGPP ionotropic polyphosphazene hydrogels are degradable in an aqueous environment (pH 7.4, 37°C). The degradation rates can be increased by incorporation of hydrolysis sensitive glycinato groups as the pendant structures in the polymer (PCGPP). Hydrolysis of these polymer hydrogels led to low molecular weight (<1,000 Da) products. The erosion and molecular weight profiles varied also according to the molecular weight of the polyphosphazene constituting the gel beads. Another approach to affect the degradation rates consists of coating microspheres with poly-L -lysine. Ionotropic polyphosphazene hydrogels have potential as biodegradable devices for controlled drug delivery systems. © 1994 John Wiley & Sons, Inc.     

Mechanism of carbon nanotube growth from camphor and camphor analogs by chemical vapor deposition

Single walled nanotubes have been synthesized by chemical vapor deposition from camphor, camphor analogs (camphorquinone, norcamphor, norbornane, camphene, fenchone), and various other precursors (menthone, 2-decanone, benzene, methane). The high temperature conditions (865 °C) and Fe/Mo alumina catalyst used in the syntheses are archetypal conditions for the production of single walled carbon nanotubes. It has been shown that the mechanism of tube growth is unlikely to depend upon the production of reactive five- and six-member rings, as has been previously suggested. The results suggest that the presence of oxygen in the precursor does not significantly improve the quality of tubes by etching amorphous carbon: it is suggested that the control of the flux of the precursor to the catalyst is more important in the production of high quality tubes. There is, however, evidence for different distributions of tube diameter being produced from different precursors.