伏安特性实验中电压表的改进应用

改进了传统电压表的面板设计,使电压表不仅能测两端的电压,还能测量自身的电流.于是在测量元件的伏安特性实验中,使用该电压表可以不考虑被测器件电阻的大小,均采用电流表外接的接线方式,即让电压表分流.再利用电压表的电流测量功能,测出自身分流电流的大小,从而可以准确得出被测器件的电流与两端的电压.     

High-Current Multi-Finger Mesa InGaAs/InP DHBTs

Characteristics of single- and multi-finger mesa InGaAs/InP double heterojunction bipolar transistors （DHBTs） are compared. The current gain decreases with the increasing number nf of the emitter fingers due to the mutual thermal interaction between the fingers. The Kirk current can be as high as 150mA for four-finger DHBT. No degradation of the peak of the current gain cutoff frequency ft is found for multi-finger DHBTs. The peak of the maximum oscillation frequency fmax decreases with an increase of nf due to the increasing parasitic resistance of the base. The results are very helpful for applications of the common-base DHBTs in power amplifiers operating at very high frequencies.     

肖特基结的制备与势垒测量

采用磁控溅射方法在Nb07％-SrTiO3基片上制作Au薄膜接触,并在氧气气氛下750℃退火30 min,在室温环境下测量电流电压和电容电压等特性曲线,观测整流特性,根据相应实验数据采用饱和电流法、电容C-2与反偏电压V成线性关系计算肖特基势垒的大小.     

利用高压热处理技术提高Bi-2223/Ag高温超导带材临界电流

提高临界电流密度(Jc)对促进Bi-2223/Ag高温超导带材的应用有着重要意义.在常压热处理条件下所制备的带材中存在大量的裂纹、孔洞和第二相颗粒等,这些因素都会对带材的超导连接性能产生破坏作用.我们成功建立了一套可用氧气氛的热等静压设备,工作气压和温度可同时达到15MPa和850°C.通过引入裂纹愈合热处理过程,我们成功对带材进行了高压热处理,所得样品中第二相颗粒和裂纹数量大幅度降低,77K、自场下的临界电流相比常压热处理样品提高了20%左右.     

Numeral eddy current sensor modelling based on genetic neural network

This paper presents a method used to the numeral eddy current sensor modelling based on the genetic neural network to settle its nonlinear problem. The principle and algorithms of genetic neural network are introduced. In this method, the nonlinear model parameters of the numeral eddy current sensor are optimized by genetic neural network （GNN） according to measurement data. So the method remains both the global searching ability of genetic algorithm and the good local searching ability of neural network. The nonlinear model has the advantages of strong robustness, on-line modelling and high precision. The maximum nonlinearity error can be reduced to 0.037% by using GNN. However, the maximum nonlinearity error is 0.075% using the least square method.     

Current--voltage characteristics of an individual helical CdS nanowire rope

This paper studies the electronic transport in an individual helically twisted CdS nanowire rope, on which platinum microleads are attached by focused-ion beam deposition. The current-voltage （I - V） characteristics are nonlinear from 300 down to 60 K. Some step-like structures in the I - V curves and oscillation peaks in the differential conductance （dI/dV - V） curves have been observed even at room temperature. It proposes that the observed behaviour can be attributed to Coulomb-blockade transport in the one-dimensional CdS nanowires with diameters of 6-10 nm.     

SQUID结合涡旋电流法用于铍材残余应力检测的可行性

涡旋电流法是材料无损检测常用方法之一，近年国际上多个研究小组对用于金属材料内残余应力检测开展了研究，涡旋电流法被认为是无损检测确定材料内残余应力的潜在方案。文中从实验和电磁场数值模拟两方面对此问题开展研究。     

测量脉冲大电流的四光路光学电流传感器技术

 在传统光学电流传感器技术的基础上，提出了一种四光路光学电流传感器，其通过四路输出信号可准确确定偏转角，使电流的测量范围不受正弦函数的单调性的限制，从而提高了电流的测量范围。配合四光路结构，提出了新的反正切函数数据处理方法，其不存在角度不灵敏区、可纠正原始数据的缺陷，从而提高了测量精度。实测了充电电压为4.5 kV、电容为50 μF和导线有效穿过磁光探头14次的快开快门的总短路电流，其峰值达85 kA，与理论值87 kA能较好地吻合，从而证明了四光路光学电流传感器可有效地测量脉冲大电流。     

MOSFET调制器的实验研究

 介绍了MOSFET调制器的基本原理，并对其并联分流和感应叠加两种开关结构进行了实验研究。基于可编辑逻辑器件设计了其触发电路，驱动电路采用高速MOSFET对管组成的推挽输出形式，加快了MOSFET的开关速度。利用Pspice软件对开关上有无剩余电流电路(RCD)两种情况进行仿真，结果表明，加装RCD电路可以有效吸收MOSFET在关断瞬间产生的反峰电压。实验中，电流波形用Pearson线圈测量，用3个MOSFET并联作开关，当电容充电电压为450 V，负载为30 Ω时，脉冲电流13 A，前沿20 ns，平顶约80 ns；用3个单元调制器感应叠加，当电容充电电压为450 A，负载为30 Ω时，脉冲电流强度为40 A，前沿25 ns，平顶约70 ns。     

新型高功率径向强流速调管振荡器

 提出了一种新结构的高功率径向强流速调管振荡器,该器件利用折叠式同轴谐振腔的微波场与接近空间电荷限制电流的径向电子束强烈相互作用产生高功率微波。首先对这种器件的实现机理进行了初步的分析，提出了有间隙电压情况时的径向同轴间隙的空间电荷限制电流1维近似估计模型。分析表明：对于电子束直流接近但小于直流空间限制电流的径向速调管，当有调制间隙电压时，空间限制电流要小于无调制间隙电压情况下的直流空间限制电流，径向强流电子束电流接近和超过空间电荷限制电流时会出现强烈的调制。然后用PIC程序对其特性进行了粒子模拟，在二极管输入电压500 kV、电子束电流为30 kA条件下，最终得到了峰值功率6 GW、频率1.3 GHz的微波输出。