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排序方式: 共有140条查询结果,搜索用时 906 毫秒
41.
42.
T. M. Pradeep Vinayakaprasanna N. Hegde N. Pushpa Ambuj Tripathi K. Asokan 《辐射效应与固体损伤》2013,168(9-10):859-872
ABSTRACTThe pre- and post-irradiation effects on the DC electrical characteristics of 100?MeV Phosphorous (P7+) and 80?MeV Nitrogen (N6+) ion-irradiated NPN transistors were studied in the dose range from 600?krad (Si) to 100?Mrad (Si). The different electrical characteristics, such as Gummel characteristics, excess base current (ΔIB?=?IB-Post?–?IB-Pre), current gain (hFE), damage constant (K) and output characteristics, were measured in situ after ion irradiation. The considerable increase in the base current (IB) at lower VBE and slight decrease in the collector current (IC) at higher VBE were observed after ion irradiation. The C–V measurements revealed that the doping concentration (Nd) was found decreased, while the built-in potential (Vbi) increased after irradiation. The ion-irradiated results are compared with 60Co gamma-irradiated results in the same dose range. The SRIM simulation was performed to understand the range of ions and energy loss in the transistor structure. The SRIM simulation showed that 100?MeV P7+ and 80?MeV N6+ ions can easily pass through the active region of transistors by creating ionization and displacement damages in the device structure. The irradiation results showed that ions induce more degradation in the electrical characteristics when compared to 60Co gamma radiation at the same dose range. 相似文献
43.
Kaining Shi Russell LowKen-Pin Hwang Shanglian BaoJingfei Ma 《Magnetic resonance imaging》2011,29(2):293-299
The fast spin echo (FSE) triple-echo Dixon (FTED) sequence uses bipolar triple-echo readout during each echo-spacing period of FSE to collect all the images necessary for Dixon water and fat separation in a single scan. In comparison to other FSE implementations of the Dixon technique, the triple echo readout used in FTED incurs minimal deadtime in the pulse sequence design and thus greatly enhances the overall scan efficiency. A potential drawback of FTED is that the time dependence of the gradient moment along the frequency encode direction becomes more complicated than in FSE and flow compensation based on the gradient moment (GM) nulling is difficult to achieve. In this work, the first order GM along the frequency encode direction of FTED was examined and two different methods to minimize the GM were proposed. The first method nulls the GM at all the locations of the refocusing radiofrequency pulses so that the Carr-Purcell Meiboom-Gill condition is always maintained. The second method minimizes the GM of the spin echo component of the FSE signal at the echo locations. The efficacy of both methods in reducing the first order GM and flow-related artefacts was demonstrated both in phantom and in images in vivo. 相似文献
44.
A series of carbazole/quinoxaline hybrids have been synthesized by classic Ullmann and Pd/Cu-catalyzed Sonogashira coupling reaction. Their photophysical, thermal, and electrochemical properties were investigated. The introduction of electron rich carbazole and electron deficient quinoxaline on to the 1,3,5-benzene center leads to a twisted structure with good glass forming property and imparts a bipolar character. The triplet energies in the range of 2.34-2.53 eV indicate them as potential host materials in phosphorescent OLEDs. 相似文献
45.
《偏微分方程通讯》2013,38(5-6):1005-1022
Abstract The combined semi-classical and quasineutral limit in the bipolar defocusing nonlinear Schrödinger–Poisson system in the whole space is proven. The electron and current densities, defined by the solution of the Schrödinger–Poisson system, converge to the solution of the compressible Euler equation with nonlinear pressure. The corresponding Wigner function of the Schrödinger–Poisson system converges to a solution of a nonlinear Vlasov equation. The proof of these results is based on estimates of a modulated energy functional and on the Wigner measure method. 相似文献
46.
We consider the initial value problem for multi-dimensional bipolar compressible Navier-Stokes-Poisson equations, and show
the global existence and uniqueness of the strong solution in hybrid Besov spaces with the initial data close to an equilibrium
state. 相似文献
47.
为了稳定可靠地触发CO2激光器旋转火花开关,设计了一套高压脉冲触发系统并且提出了一种新型的绝缘栅双极晶体管(IGBT)驱动与保护方法。根据CO2激光器中旋转火花开关的触发结构,应用复杂可编程逻辑器件(CPLD)芯片EPM3512开发了可以输出100~500 Hz重频脉冲信号以及单次脉冲信号的触发信号源;应用光耦HCPL-3120设计了具有过流、过压保护功能兼有电磁兼容(EMC)设计的IGBT驱动电路;对高压脉冲变压器进行建模并通过PSPICE软件仿真;搭建了实验平台,进行了联机性能测试。实验结果表明:在500 Hz的重复频率下,高压脉冲触发系统可连续稳定地输出高于38 kV的高压重频脉冲,基本满足CO2激光器的旋转火花开关稳定可靠触发的要求。 相似文献
48.
Edwin Vera Jacqueline Sandeaux Françoise Persin Gérald Pourcelly Manuel Dornier Jenny Ruales 《Journal of membrane science》2009
Electrodialysis (ED) using two-stack configurations with homopolar or bipolar membranes was investigated for deacidification of tropical fruit juices (passion fruit, mulberry, naranjilla). The objective was to develop a mathematical treatment for ED to predict the behavior of a fruit juice at industrial scale from ED performances at laboratory scale. From parameters such as current efficiency, electric resistance of the anion exchange membrane, and coefficients of variation with temperature determined in a laboratory-scale stack, modeling was applied to a pilot-scale stack that has a total effective membrane area 70 times larger. If no fouling took place, and except for conductivity at pH higher than 3.8, the differences between the experimental and simulated values for pH, titrable acidity, voltage, and energy consumption were inferior to 7%, 16%, 20%, and 15%, respectively, for all the fruit juices and operating conditions. Moreover, the average electrical charge of citric acid species transferred was 2.16 for all fruit juices, indicating that the current transport was mainly due to the ionic species issued from the secondary dissociation of the citric acid. 相似文献
49.
50.
《佛山科学技术学院》2014,6(4):505-522
In this paper, we discuss some properties of the self complement and self weak complement bipolar fuzzy graphs, and get a sufficient condition for a bipolar fuzzy graph to be the self weak complement bipolar fuzzy graph. Also we investigate relations between operations union, join, and complement on bipolar fuzzy graphs. 相似文献