Four-wire current-regulated PWM voltage converter

Shunt active power filters are connected in parallel with the electricity supply network. If the AC mains has a neutral conductor, it is desirable to compensate the mains harmonic currents zero-sequence components. This can be achieved with a four-wire pulsewidth modulation voltage converter connected to the AC mains. In this case, the three-phase and the neutral AC currents must be controlled. A generalization of the space-vector-based current controller in the αβo coordinate system is presented in this paper. With this current controller, all the current harmonic systems of positive, negative, and zero sequence can be injected by the converter and, thus, compensated on the AC mains. The system is also useful to compensate unbalanced currents of fundamental frequency. A useful benefit of this system is that it is possible to control the converter four-wire currents with equal hysteresis errors. Simulation and experimental results are presented     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

Amore Address Mapping with Overlapped Rotating Entries

A memory management unit that supports demand paging is implemented with standard logic and fast-access RAM chips, resulting in much faster address translation that that provided by the standard Motorola MC68451 MMU.     

Correlation of the impact elasticity of cast steels with their coercive force

The character of the correlation of the impact elasticity of cast and subsequently normalized and thermostrengthened steels 08XΓΦЛ and 08XΓTЛ with their coercive force is studied. Such a correlation in the form of a curve characterized by a maximum is observed for both low-carbon and low-alloyed hot-rolled steels.     

Comparison of the Compaction Characterisitics of Selected Food Powders by Vibration, Tapping and Mechanical Compression

The compaction characteristics of selected powders in tapping could be described by either Sone's model or by a single term exponential equation. The Hausner ratio, i.e., the ratio between tapped and loose density, calculated by using these models was found to be a sensitive and useful indictor of the compaction mechanism in different types of tapping tests. The latter, especially where particle attrition was evident, could produce distinctly different compaction patterns. No correlation was found between these powders, Hausner's ratio, and their compressibility in mechanical compaction.     

Runoff and infiltration characteristics of pavement structures--review of an extensive monitoring program.

The stormwater runoff and infiltration performance of permeable pavements has been systematically evaluated within an intensive monitoring program. The primary objective of the investigation was to generate a broad database, which enables the development of an advanced simulation module for urban drainage modelling. Over 160 field and lab scale experiments have been completed and analyzed for surface runoff and infiltration characteristics. The test series include several pavement types under various boundary conditions such as diverse precipitation impacts, varying surface slope and layer construction as well as different stages of surface clogging and several base and subgrade layer characteristics. The results represent a reliable and comprehensive database that allows profound conclusions and substantial recommendations.     

Degradation of retinyl acetate in simple solvent systems

The degradation of vitamin A acetate was studied by u.v. spectrophotometry in three solvent systems: absolute ethanol, ethanol: water (95:5) and hexanes. Three potential degradative factors were investigated: exposure to light, presence of air and temperature. In all systems studied, exposure to light was the major factor. In the ethanol systems, the rate constants calculated for the degradation in the presence or in the absence of oxygen are not significantly different. Analysis of the data by first order kinetic models yielded the best fit in all cases. The activation energy for the degradation reaction in absolute ethanol was found to be 56 ± 8 kJ/mol. The presence of water in ethanol did accelerate the reaction, but the dependence of the rate on the water content is not a simple one.