排序方式: 共有8条查询结果,搜索用时 531 毫秒
1
1.
2.
用波长1064nm,触发光能为0.5mJ的激光脉冲触发电极间隙为4mm的半绝缘(SI)GaAs光电导开关,当偏置电压达到4kV时,开关并未引发自持放电,而是进入非线性(lock-on)工作模式,即开关处于光控预击穿状态。分析认为:通过激子的产生和离解激子效应贡献了光电导;碰撞电离、雪崩倍增、激子效应补充了因外界光源撤出后所需的载流子浓度和能量。在上述因素的相互作用下,SI-GaAs 光电导开关并没有引发自持放电而是处于光控预击穿状态,丝状电流特性影响着开关的损伤程度。 相似文献
3.
A 4 mm gap semi-insulating(SI) GaAs photoconductive switch(PCSS) was triggered by a pulse laser with a wavelength of 1064 nm and a pulse energy of 0.5 mJ.In the experiment,when the bias field was 4 kV, the switch did not induce self-maintained discharge but worked in nonlinear(lock-on) mode.The phenomenon is analyzed as follows:an exciton effect contributes to photoconduction in the generation and dissociation of excitons. Collision ionization,avalanche multiplication and the exciton effect can supply carrier concentration and energy when an outside light source was removed.Under the combined influence of these factors,the SI-GaAs PCSS develops into self-maintained discharge rather than just in the light-controlled prebreakdown status.The characteristics of the filament affect the degree of damage to the switch. 相似文献
4.
5.
Experiments with the limited space-charge accumulation(LSA) mode of oscillation in a large gap semiinsulating (SI) GaAs photoconductive semiconductor switch(PCSS) are discussed.It has been observed that growth and drift of a photo-activated charge domain(PACD) are quenched only when the bias voltage is more than twice the threshold voltage.The original negative resistance characteristics are directly utilized in the LSA mode;during LSA operation the spatial average of the electric field varies over a large portion of the negative differential mobility region of the velocity-electric field characteristic.The work efficiency of an SI GaAs PCSS is remarkably enhanced by electric field excursions into the positive resistance region when the total electric field is only below the threshold part of the time.The LSA mode can only operate in the certain conditions that satisfy the quenching of the accumulation layer and the smaller initial domain voltage. 相似文献
6.
为解决齿轮箱机脚结构噪声超标问题,利用LMS VituralLab软件从动力学仿真、模态、传递路径和模态贡献度几个方面对该机组进行了振动分析和噪声预估。首先,对齿轮系进行动力学仿真,得到轴承动态力。然后,采用基于模态叠加法的强迫振动响应分析方法,计算得到齿轮箱机脚位置的结构噪声。最后,针对超标现象,对齿轮箱进行传递函数与模态贡献度分析,提出结构优化方案。根据模态振型可锁定振动最敏感位置,并在此处采取增加肋板的方式。优化后的振动仿真结果及声学边界元法计算出辐射声场的声压分布表明:传递函数和模态贡献度有明显改善,齿轮箱机脚振动较优化前减小了3.2 dB,辐射声场的声压级可以满足指标要求。该仿真分析与结构优化方法可有效指导实际工程机组的优化设计。 相似文献
7.
8.
为研究不同浓度酒精水混合蒸气流经板式换热器时压降的变化,在实验压力为110 kPa时,在板式换热器中进行了酒精和水混合蒸气凝结换热实验,酒精的气相质量浓度分别为0、1%、2%、5%、10%和20%,蒸气的质量流量为6~12 kg/h,在实验中测量了板式换热器进出口的压降,并进行了可视化观察。结果表明:各浓度的混合蒸气压降都随流量的增大而增大,压降与出口蒸气干度几乎呈线性关系,摩擦因子随出口干度增大而呈指数形式的递减;当流量不变时,压降随浓度的增大而增大,浓度越大流量越小,所对应的摩擦因子也越小;纯水蒸汽凝结时依然呈现出膜状凝结,而混合蒸气由于凝结时存在Marangoni效应,出现了非膜状凝结的形态;对实验数据以等效Re和Bo为自变量,以摩擦因子为因变量进行了拟合,拟合公式的平均误差为24.5%。 相似文献
1