Compensation for magnetizing inrush currents in transformers using a PWM inverter

When a transformer is connected to a circuit, under certain conditions, magnetizing inrush currents may be about ten times the full load current of the transformer. The currents contain a large amount of harmonic components and cause some relays to trip out. In this paper, the magnetizing inrush currents are compensated using a PWM inverter. The magnetizing inrush currents are detected and the PWM inverter generates compensating currents for the inrush currents. Hysteresis current controllers are used for fast response. The validity of this compensation is investigated by the simulation results. In addition, hardware implementation for the compensator is accomplished to verify the simulation results. Moreover, for the compensator, the relation between the compensating characteristics, the maximum switching frequency, and the coupling reactor is discussed based on the simulation results. Finally, characteristics of two current controllers (hysteresis band current controller and ramp‐comparison controller) are compared and it is shown that the hysteresis band current controller is more suitable for the compensator. The PSCAD/EMTDC electromagnetic transient simulator is used for the simulations. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(2): 53–64, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10023     

Photodynamic effect of polyethylene glycol-modified fullerene on tumor

Fullerence (C60) efficiently generates singlet oxygen when irradiated with light, and thus should have a photodynamic effect on tumors, if it is accumulated in the tumor tissue. To explore tumor targeting of C60, we chemically modified the water-insoluble C60 with polyethylene glycol (PEG), not only to make it soluble in water, but also to enlarge its molecular size. When injected intravenously into mice carrying a tumor mass in the back subcutis, the C60-PEG conjugate exhibited higher accumulation and more prolonged retention in the tumor tissue than in normal tissue. The conjugate was excreted without being accumulated in any specific organ. Following intravenous injection of C60-PEG conjugate or Photofrin to tumor-bearing mice, coupled with exposure of the tumor site to visible light, the volume increase of the tumor mass was suppressed and the C60 conjugate exhibited a stronger suppressive effect than Photofrin. Histological examination revealed that conjugate injection plus light irradiation strongly induced tumor necrosis without any damage to the overlying normal skin. The antitumor effect of the conjugate increased with increasing irradiation power and C60 dose, and cures were achieved by treatment with a dose of 424 micrograms/kg at an irradiation power of 107 J/cm2. These findings indicate that PEG-modified C60 is a candidate agent for photodynamic tumor therapy.     

Duplication and partial evaluation

This paper presents a general implementation framework for reflective languages. It allows us to systematically build reflective languages which have the following favorable properties: (1) user programs are allowed to access and change (parts of) metalevel interpreters, (2) reflective facilities are available at every level, (hence there exists conceptually an infinite tower of interpreters), and (3) the interpreter runs as efficiently as the conventional (directly implemented) metacircular interpreter when reflection is not used. Our scheme is divided into three stages. First, we define interpreters which give the operational semantics of each level, and conceptually construct the infinite tower of these interpreters. They are thenduplicated to obtain directly executed interpreters, while introducing double interpretation to maintain redefinability of interpreters. Finally, partial evaluation is employed to collapse the double interpretation into single interpretation. We illustrate our scheme by implementing a particular reflective language calledBlack in Scheme, but it is general enough to be applied to other reflective languages. The paper gives the complete Scheme implementation of Black and demonstrates some examples. We also show how a system with the delta abstraction introduced by Blond can be constructed in our framework.     

Antitumor effect and mechanism of a novel multifunctional nucleoside, 3''-ethynylnucleoside, on human cancers

Entomologic and virologic factors were investigated to determine whether gray-headed flying foxes (Pteropus poliocephalus) from Indooroopilly Island, Brisbane, Australia could be vertebrate hosts of Ross River (RR) virus. Aedes funereus was the most abundant mosquito species with 6,300-38,700 females per light trap night in the flying fox camp containing gray-headed, black (P. alecto), and little red (P. scapulatus) flying foxes. Sixteen Ae. funereus blood meals from this collection were analyzed by hemoglobin electrophoresis and were found to be from P. alecto. From pledget feeding with RR virus, the infectious dose required to infect 50% of wild caught Ae. funereus was log10 4.2 50% tissue culture infectious doses per mosquito, with a transmission rate to mice of 17% at 9-10 days post infection. Experimental infection of 10 juvenile P. poliocephalus produced viremias of low titer in five animals, with a duration of 1-4 days and a mean of two days. Three percent of colonized Ae. vigilax that fed on the 10 animals during this period became infected. One of the five viremic flying foxes and two of the five aviremic animals produced a detectable immune response by either neutralization or hemagglutination-inhibition tests. Based on the low to moderate vector competence of Ae. funereus for RR virus, and evidence that P. poliocephalus is a poor vertebrate host of RR virus, it is unlikely that RR virus transmission would be maintained between these two species, but it could be maintained by other more competent vector/host pairs.     

Minimum Potential of Charged Insulator to Cause Incendiary Discharges

Incendiary discharges can occur when a grounded metal sphere approaches a charged insulator, but there are few studies on its electrostatic potential causing ignition. The aim of this research is to determine the minimum potential required for ignition of flammable gases and vapors mixed with air. Discharges between a charged plastic film and grounded metal spheres are experimentally investigated, and an equation for estimating the discharge energy is presented. Then the minimum potential to produce the incendiary discharge is considered from this equation and compared with the experiments. It becomes clear that the minimum potential is determined by the diameter of the grounded metal sphere, the potential of the charged plastic film, and its apparent capacitance. The results obtained with hydrogen-air and propane-air mixture are reported.     

Organic EL materials based on styryl and amine derivatives

Excellent organic electroluminescent materials are needed in order to obtain color EL devices with high performance. We have succeeded in realizing bright and efficient devices with long lifetime in various color regions, based on styryl and amine derivatives.     

Unusual responses to light and darkness of ocular melatonin in European sea bass

Regulation by light and darkness of melatonin rhythms in the plasma and eye of the European sea bass (Dicentrarchus labrax) was studied. During light-dark cycles, plasma and ocular melatonin exhibited day-night changes with higher levels at mid-dark and at mid-light, respectively. Circulating melatonin levels were low in constant light but high in constant darkness (DD); ocular melatonin levels showed the reverse pattern. Plasma melatonin exhibited circadian rhythm for 1 cycle but the rhythm was no longer apparent on day 2. There was no circadian rhythm in ocular melatonin. Acute light exposure in DD decreased plasma melatonin but increased ocular melatonin. These results suggest that circulating melatonin may be used as a signal for darkness but ocular melatonin is used as a signal for the light phase.     

Effect of Pt and Ba content on NO x Storage and Reduction Over Pt/Ba/Al2O3

Effects of Pt and Ba content of Pt/Ba/Al₂O₃ on NO _x storage reduction (NSR) catalyst were investigated by means of kinetic analysis of surface nitrates using in situ FT/IR. Turnover frequencies of both storage and reduction of nitrate were significantly enhanced at higher Ba content, while those were higher at lower Pt content below 0.2 wt%.     

Microcomputer Control for Sensorless Brushless Motor

The microcomputer control of a brushless motor without a shaft position sensor is studied. A method which permits the determination of the permanent magnet rotor position by the back electromotive force (EMF) induced in the stator windings and the starting technique which uses the motor as a synchronous motor at standstill are explained. The motor voltage is chopped by commutator transistors to change the motor speed. The control system consists of a 4-b single-chip microcomputer and two quad-comparators.