Advanced control of PWM converter with variable-speed induction generator

This paper describes simple control structures for the vector-controlled stand-alone induction generator (IG) used to operate under variable speeds. Different control principles, indirect vector control and deadbeat current control, are developed for a voltage source pulsewidth-modulation (PWM) converter and the three-phase variable-speed squirrel-cage IG to regulate dc link and generator voltages with the newly designed phase-locked loop circuit. The required reactive power for the variable-speed IG is supplied by means of the PWM converter and a capacitor bank to buildup the voltage of the IG without the need for a battery, to reduce the rating of the PWM converter with the need for only three sensors, and to eliminate the harmonics generated by the PWM converter. These proposed schemes can be used efficiently for variable-speed wind energy conversion systems. The measurements of the IG systems at various speeds and loads are given and show that these systems are capable of good ac and dc voltage regulations.     

Synergy of lysozyme and lanoconazole on the morphology of Candida albicans

Synergism of lysozyme with the imidazole antifungal lanoconazole (LCZ) has been demonstrated in vitro against Candida albicans. To determine the mechanism of the synergistic action, the effects of subinhibitory concentrations of lysozyme (50 microg ml(-1)) and LCZ (1.25 microg ml(-1)), used alone and in combination, on the morphology and ultrastructure of C. albicans cells were studied by fluorescence microscopy using Fungiflora Y, as well as by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In the presence of lysozyme, the separation of apparently mature cells from each other was inhibited, and cells in which cell wall-like material had markedly accumulated in the periplasmic space were frequently observed. Such intracellular ultrastructural changes were not seen in LCZ-treated cells, but normal septal wall biogenesis was inhibited with the resultant formation of long chains of interconnecting cells. When the cultures were treated with the combination of lysozyme and LCZ, intracellular accumulation of cell wall-like materials increased in extent, and the peripheral wall structure was severely damaged. These morphological and ultrastructural findings lead us to the following conclusions: (1) lysozyme and LCZ inhibit the process of cell division in different manners; (2) lysozyme appears to affect cell wall formation more directly and drastically by interrupting the normal assembly and integration of cell wall components; and (3) these effects of lysozyme are noticeably enhanced when combined with LCZ.     

Development of a real-time hand dose monitor for personnel in interventional radiology

Medical procedures denoted as interventional radiology require operation near an X ray beam, which brings high dose exposures to the operators' hands. For the effectual control of their extremity doses, a prototype of a real-time wrist dosemeter has been developed, hand dose monitor (HDM), based on a single silicon detector. Experiments were performed to test its response to diagnostic X rays. The HDM was highly sensitive and showed a linear response down to doses of a few tens of microsieverts. Though dose rate, energy and angular dependence of the response were observed in some extreme conditions, the HDM was proved to be of practical use if it was appropriately calibrated. Since an HDM enables personnel to check their hand doses on a real-time basis, it would enable medical staff to control the exposure themselves.     

Aerosol Generation by a Spray-Drying Technique Under Coulomb Explosion and Rapid Evaporation for the Preparation of Aerosol Particles for Inhalation Tests

In this study, nanosized (<100 nm) aerosol particles with high mass concentrations for inhalation tests were generated by a spray-drying technique with combining Coulomb explosion and rapid evaporation of the droplets. Under typical spray-drying conditions, aerosol particles with average diameter of 50–150 nm were prepared from a suspension of NiO nanoparticles with a primary diameter of 15–30 nm. Under the Coulomb explosion method, the sprayed droplets were charged by being mixed with unipolar ions to break up the droplets, which resulted in the generation of smaller aerosol particles with diameters of 15–30 nm and high number concentrations. Under the rapid evaporation method, the droplets were heated immediately after being sprayed to avoid inertial impaction on the flow path due to shrinkage of the droplet, which increased the mass concentration of the aerosol particles. The combination of the Coulomb explosion and rapid evaporation of droplets resulted in the generation of aerosol particles with sizes less than 100 nm and mass concentrations greater than 1 mg/m³; these values are often necessary for inhalation tests. The aerosols generated under the combined method exhibited good long-term stability for inhalation tests. The techniques developed in this study were also applied to other metal oxide nanoparticle materials and to fibrous multiwalled carbon nanotubes.

Copyright 2014 American Association for Aerosol Research     

The relation between activated carbon adsorption and water quality indexes

In order to estimate the adsorbability by activated carbon of organic compounds dissolved in aqueous solutions, the contribution of individual atoms to the adsorption process is calculated. The contribution of carbon, bromine and chlorine atoms is positive, that of oxygen atoms is negative, that of hydrogen atoms is very small and that of nitrogen atoms is influenced by the kind of functional group in which they are contained. The dominant factors governing adsorption are the numbers of carbon and oxygen atoms in a molecule. The activated carbon's effectiveness for adsorption of organic compounds dissolved in solutions can be predicted from such water quality indexes as total organic carbon, total organic nitrogen, total organic halogen an total oxygen demand.     

Toward Mega-pixel Neutron Imager Using Current-Biased Kinetic Inductance Detectors of Nb Nanowires with ^{10}B Converter

We present not the results but the idea of a superconducting nanowire detector with \(^{10}\) B conversion layer for sensing a single neutron. We use \(^{7}\) Li ion and \(^{4}\) He ion emitted as two independent heat sources, which appear in opposite direction associated with nuclear reaction \(^{10}\) B(n, \(^{4}\) He) \(^{7}\) Li. We probe a change in the kinetic inductance \(L_\mathrm{k}\) coming from inertia of the Cooper pairs. Our detector is different from a conventional kinetic inductance detector (KID), but is named as a current-biased KID. We use two sets of Nb nanowires with superconducting readout taps to monitor the local signal. In between the X meander and the Y meander, we inserted a \(^{10}\) B layer acting as a conversion layer from neutrons to charged particles. We plan to fabricate a mega-pixel neutron imager by coupling 10 bit linear position-sensitive arrays along the X and Y directions with the single flux quantum readout circuits.     

Combined convection heat transfer in a channel with two ribs attached to one wall

Two-dimensional calculations were performed for combined convection heat transfer in a channel with two ribs attached to one wall, following a previous study on the forced convection case without buoyancy. The flow is heated from the surfaces of both ribs and the present study dealt with the two cases of buoyancy-assisted flow and buoyancy-opposing flow. The effect of Reynolds number, Re_L, and modified Richardson number, Ri^*, was examined keeping the space between ribs, σ, and blockage ratio, τ, constant (σ = 3.0, τ = 0.5). Increasing the magnitude of buoyancy, unsteady flows predicted by the present calculations are stabilized in both cases. Serious deterioration of Nusselt number on the second rib suddenly occurs in a certain range of Ri^* due to the flow stabilization. This is because flow unsteadiness plays an important role for heat transfer enhancement as was described in a previous study. However, in buoyancy-assisted flow, a similar deterioration of Nusselt number also appears on the second rib even if flow remains steady. This is caused by the disappearance of a strong rotating flow which exists in the cavity between both ribs and keeps the fluid in the cavity cooler. © 1999 Scripta Technica, Heat Trans Asian Res, 28(5): 379–394, 1999     

Quarter-micrometer SPI (Self-aligned Pocket Implantation) MOSFET'sand its application for low supply voltage operation

A novel SPI (Self-aligned Pocket Implantation) technology has been presented, which improves short channel characteristics without increasing junction capacitance. This technology features a localized pocket implantation using gate electrode and TiSi₂ film as self-aligned masks. An epi substrate is used to decrease the surface impurity concentration in the well while maintaining high latch-up immunity. The SPI and the gate to drain overlapped structure such as LATID (Large-Angle-Tilt Implanted Drain) technology allow use of the ultra low impurity concentration in the channel region, resulting in higher saturation drain current at the same gate over-drive compared to conventional device. The carrier velocity reaches 8×10⁶ cm/sec and subthreshold slope is less than 75 mV/dec, which can be explained by low impurity concentration in the channel and in the substrate. The small gate depletion layer capacitance of SPI MOSFET was estimated by C-V measurement, and it can explain high performance such as small subthreshold slope. On the other hand, the problem and the possibility of low supply voltage operation have been discussed, and it has been proposed that small subthreshold slope is prerequisite for low power device operated at low supply voltage. In addition, the drain junction capacitance of SPI is decreased by 65% for N-MOSFET's, and 69% for P-MOSFET's both compared with conventional devices. This technology yields an unloaded CMOS inverter of 48 psec delay time at the supply voltage of 1.5 V