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The ruggedness of a superjunction metal–oxide semiconductor field-effect transistor (MOSFET) under unclamped inductive switching conditions is improved by optimizing the avalanche current path. Inserting a P-island with relatively high doping concentration into the P-column, the avalanche breakdown point is localized. In addition, a trench type P+ contact is designed to shorten the current path. As a consequence, the avalanche current path is located away from the N+ source/P-body junction and the activation of the parasitic transistor can be effectively avoided. To verify the proposed structural mechanism, a two-dimensional (2D) numerical simulation is performed to describe its static and on-state avalanche behaviours, and a method of mixed-mode device and circuit simulation is used to predict its performances under realistic unclamped inductive switching. Simulation shows that the proposed structure can endure a remarkably higher avalanche energy compared with a conventional superjunction MOSFET. 相似文献
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受海面强风和海-气相互作用影响,表面声道普遍存在于冬季海洋环境中,是一种天然有利于声传播的波导.但是海面波浪使得海表形成粗糙界面,会严重破坏这种优良性能.本文利用南海北部海区的一次冬季声传播实验数据,研究表面声道声传播特性.研究表明,海底底质对表面声道内声传播的影响较弱,当海面风较小时,涌浪造成的影响为主要原因.实验数据显示,考虑涌浪后的粗糙海面给70km远处带来了10dB的传播损失增长.因此在考察南海北部海区冬季声场特性时,不仅要考虑海面风浪的影响,更需要考虑周围海域传来的涌浪的影响.研究涌浪存在时的声传播特性对提升声纳设备在海况较差时的使用性能具有重要意义. 相似文献
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提出了一种利用Doppler-warping变换的水下对空运动声源的线谱探测方法。该方法首先利用Doppler-warping变换线性化目标线谱的多普勒相位,再提取线性化后的目标线谱点,结合波束形成算法实现对目标的探测。仿真和海试数据处理结果表明,与直接提取目标线谱实现探测的方法相比,所提出方法有以下几个优势:(1)将目标线谱多普勒相位线性化,线谱跟踪更为稳定连续;(2)将目标线谱频带展宽的能量重新集中到原频率附近,在低信噪比环境下能更好地提取目标线谱;(3)将干扰线谱瞬时频率非线性化,能更好地实现干扰线谱的分离。海试数据处理结果表明,实现了对远至16.8 km处空中运动目标的水下有效探测,探测能力与抗干扰能力明显增强。 相似文献
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研究了结晶紫-H2O体系浮选分离A u(SCN)4-的行为及与一些金属离子分离的条件。结果表明,在水溶液中,Au(Ⅲ)与结晶紫(CV)和硫氰酸铵形成不溶于水的三元缔合物A u(SCN)4-.CV+,此三元缔合物沉淀浮于水相上层形成界面清晰的液-固两相。当溶液中结晶紫和硫氰酸铵的浓度分别为7.0×1-0 4m ol/L和5.0×1-0 3mol/L时,Au(Ⅲ)可与R h(Ⅲ)、G a(Ⅲ)、Mn(Ⅱ)、A l(Ⅲ)、Ni(Ⅱ)、Cd(Ⅱ)、F e(Ⅱ)、Mg(Ⅱ)和Sn(Ⅳ)离子分离。该方法具有简便、快速和不污染环境等特点,在微量金的分离和富集分析中有一定的实用价值。 相似文献
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由于空气、海水介质声阻抗差异巨大,空中声源辐射的噪声透射入水的能量损失很大,加之水中声源目标的干扰,从水下探测空中声源相对困难。海试数据分析表明,空中高速运动声源噪声透射入水后信号较弱,在频繁存在干扰的水下声场环境中,常规宽带波束形成方法难以生效.针对空中声源普遍存在线谱的特点,首先利用线谱识别、提取与跟踪以及线谱加密技术对水下水平阵接收信号进行线谱分析,再通过剔除强干扰目标的线谱,成功分离出包含空中声源的线谱信号,实现对空中运动声源的探测,最远距离达16.8 km。通过理论和实验数据分析,验证了探测结果的正确性. 相似文献
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Direct Monte Carlo simulations are employed to investigate the granular pressures in granular materials with a power-law particle size distribution. Specifically, smooth circular discs of uniform material density are engaged in a two-dimensional rectangular box, colliding inelastically with each other and driven by a homogeneous heat bath at zero gravity. The resulting pressures are found to decrease as the widths of particle size distribution are increased. Moreover, the granular pressures in power-law systems are found to be unequally distributed among the various sizes of particles, with large particles possessing more pressure than their smaller counterparts. The width-dependent nature of the total pressures is induced by the more dispersion of smaller particles in the system as the particle size distribution is widened. 相似文献
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静电陀螺仪的稳速控制所需的转速信号是从包含多种信息的光电传感器输出中提取的,因此准确地提取转速信号是稳速控制的前提。文中分析了采用平面反射式光电传感器读取信息的静电陀螺的转速提取机理,讨论了自适应相干模板法滤除窄带干扰的原理,并将其应用到静电陀螺的转速信号提取中,在DSP(数字信号处理器)上得到实现。在某静电陀螺实验中得到了实时的转速信息,取代了原有的模拟系统,为数字化的稳速系统提供了可靠的参数。 相似文献
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