Harmonic solution of semiconductor transport equations for microwave and millimetre-wave device modelling

The hydrodynamic transport equations for charges in a semiconductor have been solved for a periodic excitation by means of a harmonic approach, in order to model microwave and millimetre-wave active devices. The solution is based on the expansion of physical variables in a Fourier series in the time domain, and on discretisation in the space domain. A waveform-balance technique in the TD is used to solve the nonlinear equations system. This approach allows for a longer time step with respect to standard TD solutions for most cases of interest, greatly reducing simulation time by at least two orders of magnitude in typical cases. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 36–48, 2004.     

Multistage solid-state power amplifier design by a new alternative synthesis technique

For the first time, the numerical real-frequency technique has been applied to the design of a nonlinear power amplifier. This synthesis technique does not require any transistor model by directly using measured large-signal S-parameters of the power transistor device. The double power-frequency dependence of these S-parameters requires the use of a bidimensional interpolation (spline functions). With the Levenberg–Marquardt optimization and large-signal S-parameters, a specific CAD program optimizes the added-power in order to synthesize the matching networks of the PA. The simulated and measured results of two S-band power amplifiers validate the new synthesis approach. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 87–98, 2004.     

Repair of notched beam under dynamic load using piezoelectric patch

In this paper, the repair of a cracked beam under an external dynamic load employing the electro-mechanical characteristic of piezoelectric material to induce a local moment is presented. Conceptually, an external voltage is applied to actuate a piezoelectric patch bonded on the beam to effect closure of a crack so that the singularity at the crack tip under dynamic load may be decreased. Globally, this has the effect of altering the resonant frequency of the cracked beam towards that of the healthy beam, which is the criterion used for the repair. To demonstrate the repair methodology, a cantilever beam is used as an illustration, where the repair moment coefficient and the voltage required are mathematically derived. The relationship between repair moment coefficient, crack parameters and length of piezoelectric patch is investigated. The difference between the proposed repair criterion and an earlier published criterion for cracked beam under static load is also shown. A numerical example is used to study the effectiveness of the proposed repair methodology and its results are compared with those from 3-D finite element analyses using ABAQUS 6.4 as one means of verification.     

拓宽调速范围的微机PWM变频传动系统

本文对单CPU结构的PWM变频调速系统做了一些探讨。为解决系统中存在的微机计算速度偏低和硬件复杂性问题,较好地处理软件和硬件的配合问题,本文提出了在较少的硬件结构基础上,通过在线设置辅助数据表,实现计算和存贮相结合的PWM方式:在设计中,利用了微机键盘和显示器实现系统管理。为解决电动机低速运行时机械特性变软这一问题,本文提据电动机定子电压和频率的协调控制原则,实现以电动机基波电流和功率因数为反馈信号的协调控制。实验结果表明,所设计的变频调速系统具有较宽的调频范围、较高的电压及频率分辨率,低速带负载能力大为改善,操作灵活方便。     

工频信号相位和幅值测量的新方法

本文提出了一种利用8031单片微机系统测量工频信号的相位和幅值的新方法,此法只需对两个信号进行三次采样后,再经简单的运算,就能得到两个信号的相位差、幅值以及其它许多重要的电量。     

Investigation of rheological properties of TPS modified bitumen

Rheological properties of the virgin bitumen and TPS modified bitumen binders with several percentages of TPS additives were studied.All TPS modified bituminous binders were prepared on a laboratory scale.Dynamic shear rheometer(DSR) strain sweep test was made to measure the linear viscoelasticity areas of various bitumen binders at -20-70 ℃,then temperature sweep test and frequency sweep test were made in the linear viscoelasticity areas.Complex modulus master curves were drawn to analyze and compare various bitumen binders’ rheological properties.Based on the test results,the ideal percentage of TPS additive was brought forward.The results show that TPS modified bitumen binders have more excellent properties at high,medium and low temperatures compared with original bitumen.The dosages of TPS additive are vital to their properties.     

谐振式变换器电路结构分析

本文着重对电压源串联型谐振变换器的理论问题和电路结构作了分析，对电流源并联型谐振变换器也作了概略的介绍。     

干冰膨胀烟丝生产线控制系统设计和优化

以美国进口AIRCO模式膨胀烟丝生产线改造项目为基础,论述了国产新型干冰膨胀烟丝生产线控制系统设计和优化.介绍了干冰膨胀烟丝生产线的基本工艺,控制系统网络结构,实现的主要功能及应用、技术特点.     

考虑随机风影响的隧道通风量计算

现有隧道内通风量计算偏保守,往往需开启更多风机,导致能源浪费严重。本文提出一种考虑随机自然风影响下的隧道内通风量计算方法。将风频引入隧道通风量计算中,指出隧道内风频的两种表示方法,离散型风频分布和韦布尔风频分布,通过最小误差逼近算法计算韦布尔风频分布中的尺度系数A和形状系数K。通过算例可得,进口处考虑随机风比不考虑随机风的通风量多37.8%,说明考虑随机风影响可明显降低风机开启数量。     

基于差频检测技术的高速AD单粒子翻转评估方法研究

本文基于差频检测的原理,提出一种在高频动态输入模式下,对高速高精度模数转换器（AD）的抗单粒子翻转效应进行评估的测试方法,并以一款8位3 GSPS高速AD为测试对象,设计开发了一套高速AD单粒子翻转效应测试系统,对目标器件进行了重离子试验。通过对试验结果的图像和错误数据进行分析,评估参试器件的抗辐照性能参数,为抗辐照高速高精度AD的加固设计提供数据支撑。