Modeling of MOS-side carrier injection in trench-gate IGBTs

A compact trench-gate IGBT model that captures MOS-side carrier injection is developed. The model retains the simplicity of a one-dimensional solution to the ambipolar diffusion equation, but at the same time captures MOS-side carrier injection and its effects on steady-state carrier distribution in the drift region and on switching waveforms. © 2007 IEEE.

Improving the performance of a valveless pulse combustor using unsteady fuel injection

This paper describes an experimental investigation into the effect of unsteady fuel injection on the performance of a valveless pulse combustor. Two fuel systems were used. The first delivered a steady flow of ethylene through choked nozzles, and the second delivered ethylene in discrete pulses using high-frequency fuel injectors. Both fuel systems injected directly into the combustion chamber. The high-frequency fuel injectors were phase locked to the unsteady pressure measured on the inlet pipe. The phase and opening pulse width of the injectors and the time-averaged fuel mass flow rate through the injectors were independently varied. For a given fuel mass flow rate, it is shown that the maximum pressure amplitude occurs when fuel is injected during flow reversal in the inlet pipe, i.e. flow direction is out of the combustor. The optimal fuel injection pulse width is shown to be approximately 2/9th of the cycle. It should, however, be noted that this is the shortest time in which the injectors can reliably be fully opened and closed. It is shown that by using unsteady fuel injection the mass flow rate of fuel needed to achieve a given amplitude of unsteady pressure can be reduced by up to 65% when compared with the steady fuel injection case. At low fuel mass flow rates unsteady fuel injection is shown to raise the efficiency of the combustor by a factor of 7 decreasing to a factor of 2 at high fuel mass flow rates. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

The influence of injection conditions and soil types on soil improvement by microbial functions

Research has begun on Microbial Carbonate Precipitation (MCP), which shows promise as a soil improvement method because of its low carbon dioxide emission compared to cement stabilized agents. MCP produces calcium carbonate from carbonates and calcium in soil voids through ureolysis by "Bacillus Pasteurii". This study focuses on how the amount of calcium carbonate precipitation is affected by the injection conditions of the microorganism and nutrient salt, such as the number of injections and the soil type. Experiments were conducted to simulate soil improvement by bio-grouting soil in a syringe. The results indicate that the amount of precipitation is affected by injection conditions and soil type, suggesting that, in order for soil improvement by MCP to be effective, it is necessary to set injection conditions that are in accordance with the soil conditions. © 2011 ASCE.

Complete genomic sequences for hepatitis C virus subtypes 6e and 6g isolated from Chinese patients with injection drug use and HIV-1 co-infection

In one of our recent studies, two HCV genotype 6 variants were identified in patients from Hong Kong and Guangxi in southern China, with injection drug use and HIV-1 co-infection. We report the complete genomic sequences for these two variants: GX004 and

High prevalence of HIV-1 and hepatitis C virus coinfection among injection drug users in the southeastern region of Yunnan, China

The southeastern region of Yunnan province is a key site for drug trafficking and HIV-1 infection spread from the west of Yunnan and Laos to southeastern China. To investigate the prevalence of HIV-1 infection and hepatitis C virus (HCV) coinfection among injection drug users (IDUs) in southeastern Yunnan, three cohorts of 285 addicts, including 242 IDUs and 43 oral drug users, living in the cities of Gejiu and Kaiyuan and the county of Yanshan were studied. HIV-1 and HCV infections were detected by enzyme-linked immunosorbent assay and/or polymerase chain reaction. Data on the age, sex, risk behavior, drug use history, employment, ethnic background, and marriage status were obtained by interview. The overall prevalence of HIV-1 infection was 71.9%. The rate of HCV coinfection among 138 HIV-1-infected IDUs was 99.3%. Most HIV-infected IDUs were 20 to 35 years old (86.7%) and were ethnic Han (75.9%), suggesting that the epidemic in Yunnan is no longer confined to non-Han ethnic minorities, HIV prevalence in female IDUs (81.2%) was significantly higher than in male IDUs (68.2%) (p <.05). The prevalence of HIV infection reached 68.4% after 1 year of injection drug use. Needle/syringe sharing is the major high risk factor for the spread of HIV-1 and HCV infections. Large-scale educational campaigns are urgently needed to reduce the spread of HIV and HCV infection in these regions.