Basic Characteristics of Squarewave Irwerter Circuit with Series R-L Load

In this paper, the steady state operations of the squarewave inverter circuit with a series R-L load are discussed. The circuit consists of transistors and feedback diodes. The basic equation is derived from its equivalent circuit. Solving the basic equation with steady state conditions, the instaneous value of the load current i is derived. The period t(2) for which the current flows from the supply to the load and the period t(l) for which the current feedbacks through diodes from the load to the supply are calculated from (i), and the ratio of t(l) to t(2) is illustrated using power factor of fundamental wave, pf, as a variable. The ratios of transistor mean current I(tr), diode mean current I(D), supply mean current I(s) to the load current I are illustrated using pf as a variable, too. In result, each current ratios to I is shown in simple expressione. The load current can be calculated simply using the coefficient reading off the figure. In addition, it becomes clear from the figure that the load current is scarcely influenced by the harmonic voltage in less than 0.8 of pf. The ratio t(2)/(t(1)+t(2)) calculated in squarewave voltage, shows the limit of pulse width control whose out put voltage is the squarewave

A Driving Method of a Spuare Waveform Inverter Circuit Using Power Transistors

In recent years, the development of a high power transistor element is proceeding. A high power inverter circuit using power transistors are finding a good number of applications in induction heating and melting. Turn off time of power transistors occupies 5-lOμs of switching characteristics. A driving method to give base inputs for a half period is widely used for a inverter circuit. But this method has the following defects, the short-circuit current flows through two transistors because the other pair transistors turn on before one pair transistors turn off. So the switching loss is increased, the maximum output and the efficiency are decreased. In this paper, a driving method to give base inputs for the less period as compared with a half period is discussed. Using this method, the foregoing defects is lost and the driving frequency is able to become higher. In addition, it become clear that the square waveform output is given using this method in the case of R-L load

Individual Variations in Inorganic Arsenic Metabolism Associated with AS3MT Genetic Polymorphisms

Individual variations in inorganic arsenic metabolism may influence the toxic effects. Arsenic (+3 oxidation state) methyltransferase (AS3MT) that can catalyze the transfer of a methyl group from S-adenosyl-l-methionine (AdoMet) to trivalent arsenical, may play a role in arsenic metabolism in humans. Since the genetic polymorphisms of AS3MT gene may be associated with the susceptibility to inorganic arsenic toxicity, relationships of several single nucleotide polymorphisms (SNPs) in AS3MT with inorganic arsenic metabolism have been investigated. Here, we summarize our recent findings and other previous studies on the inorganic arsenic metabolism and AS3MT genetic polymorphisms in humans. Results of genotype dependent differences in arsenic metabolism for most of SNPs in AS3MT were Inconsistent throughout the studies. Nevertheless, two SNPs, AS3MT 12390 (rs3740393) and 14458 (rs11191439) were consistently related to arsenic methylation regardless of the populations examined for the analysis. Thus, these SNPs may be useful indicators to predict the arsenic metabolism via methylation pathways

POLLUTION BY PERSISTENT TOXIC SUBSTANCES IN VIETNAM : A REVIEW OF TWO DECADE MONITORING STUDIES

Joint Research on Environmental Science and Technology for the Eart

Arsenic contamination in groundwater and residents from Ha Nam and Ha Tay Provinces of Red River Delta, Vietnam

Joint Research on Environmental Science and Technology for the Eart

Trace element and stable isotope analyses of deep sea fish from the Sulu sea, Philippines

Thirty-five deep sea fishes belonging to 22 species and one unidentified specimen obtained from the Sulu Sea, located in the southwestern area of the Philippines were analyzed in the late 2002, for 23 trace elements using ICP-MS, HGAAS and CV-AAS. Predominant accumulation of strontium (Sr) was observed in all the samples. This stems from the fact that the whole body of fish was homogenized since Sr is known to accumulate in bones and hard tissues. Mercury concentrations in all the 36 samples were below the detection limit. Cadmium concentrations were generally below 1ìg/g dry weight (dw) except in Pterygotrigla spp. (4.29 ìg/g dw) and Sternoptyx pseudodiaphana (2.89 ìg/g dw). Concentrations of Pb were predominantly low with about 90% of the specimens having less than 1 ìg/g dw. In general, concentrations of Sr, Zn, Cu, Se and Cd appeared to increase with increasing depth of occurrence of the species.Manganese, Tl, Pb, Bi, In, Cs and As showed significant positive correlation (p < 0.05) with d15N, suggesting that these elements were biomagnified. To our knowledge, this is the first study reporting Tl biomagnification in fish. Rubidium and Cs showed significant positive correlation with d13C, implying that Rb and Cs would originate from offshore waters as oceanic plankton has high d13C. Comparing results from this study to the dietary standards and guidelines for Hg, Pb, Cu and Zn in fish and shellfish of the Ministry of Agriculture, Fisheries and Food of the United Kingdom,these levels were not high to warrant concern if they were to be consumed by humans. However, 16.7% of the fish samples had high Cr levels when compared with the Hong Kong’s safe limit of 4 ìg/g dw for Cr in sea food. This constitutes a health risk to humans, as Cr is potentially toxic

Contamination by arsenic and other trace elements in drinking water and residents in Vietnam

Joint Research on Environmental Science and Technology for the Eart

CONTAMINATION BY ARSENIC AND LEAD IN RESIDENTS FROM VIETNAM

Joint Research on Environmental Science and Technology for the Eart