失衡转子的动力响应分析

转子失衡是现场机组转子的常见故障之一.究其故障起因可将转子失衡从理论上划分为力不平衡和力偶不平衡两种类型,而在转子的实际运行过程中,这两种失衡状态往往是相互耦合在一起共同对转子的不平衡响应发挥作用的,此特性无疑给现场转子不平衡响应的识别和诊断工作,以及转子的现场动平衡工作带来了极大的困难.本文基于全息谱技术,通过对失衡转子的工频振动进行再分解,从而在理论上得到了两种失衡状态的动力响应特征.试验结果表明,应用本文提出的识别指标得到的理论计算结果与试验结果完全吻合,识别指标可对两类失衡转子在不同运行工况下的动力响应特征做出准确、可靠的描述.这一研究结果将对现场转子主导失衡故障类型的诊断、故障严重程度的评估及现场转子的动平衡工作产生重要影响.     

New Generalizations of Migdal-Kadanoff Bond-Moving Recursion Procedures and Their Applications

Considering in symmetrical half-length bond operations,we present in this paper two types of newlydeveloped generalizations of the remarkable Migdal-Kadanoff bond-moving renormalization group transformation recursion procedures.The predominance in application of these generalized procedures are illustrated by making use of them to study the critical behavior of the spin-continuous Gaussian model constructed on the typical translational invariant lattices and fractals respectively.Results such as the correlation length critical exponents obtained by these means are found to be in good conformity with the classical results from other previous studies.     

Electroluminescence explored internal behavior of carriers in InGaAsP single-junction solar cell

The internal behaviors of carriers in InGaAsP single-junction solar cell are investigated by using electroluminescence (EL) measurements. Two emission peaks can be observed in current-dependent electroluminescence spectra at low temperatures, and carrier localization exists for both peaks under low excitation. The trends of power index α extracted from excitation-dependent EL spectra at different temperatures imply that there exists a competition between Shockley-Read-Hall recombination and Auger recombination. Auger recombination becomes dominant at high temperatures, which is probably responsible for the lower current density of InGaAsP solar cell. Besides, the anomalous "S-shape" tendency with the temperature of band-edge peak position can be attributed to potential fluctuation and carrier redistribution, demonstrating delocalization, transfer, and redistribution of carriers in the continuum band-edge. Furthermore, the strong reduction of activation energy at high excitations indicates that electrons and holes escaped independently, and the faster-escaping carriers are holes.     

转子系统振动的CSFDB主动控制实验研究

采用可控挤压油膜阻尼器作为主控元件,进行转子系统振动主动控制研究,设计开发了锥形可控挤压油膜阻尼器（Controllable Squeeze Film Damping Bearing,CSFDB).CSFDB的外环轴向位置通过专门设计的电液伺服系统来调节其平淡同的轴向位置对应不同的油膜间隙,使转子系统、CSFDB、电液伺 服系统形成一个闭环控制系统,即主动控制转子系统的振动,本文的实验研究工作内容有,CSFDB-转子系统振动特性实验研究;CSFDB-转子系统加、减速振动特性试验研究;转子系统振动的CSFDB主动控制实验研究。转子模型为一单盘悬臂转子,研究结果表明,CSFDB控制效果明显,所研制的控制仪工作可靠,能满足实时必研究;CSFDB外环位置调节系统设计思路可行,性能可靠避孕药推广应用前景。     

In_(0.53)Ga_(0.47)As/InP雪崩光电二极管响应及电学特性

通过分子束外延生长和开管式Zn扩散方法,制备了低暗电流、宽响应范围的In_(0.53)Ga_(0.47)As/InP雪崩光电二极管.在0.95倍雪崩击穿电压下,器件暗电流小于10nA;-5V偏压下电容密度低至1.43×10~(-8) F/cm~2.在1 310nm红外光照及30V反向偏置电压下,雪崩光电二极管器件的响应范围为50nW~20mW,响应度达到1.13A/W.得到了电荷层掺杂浓度、倍增区厚度结构参数与击穿电压和贯穿电压的关系:随着电荷层电荷密度的增加,器件贯穿电压线性增加,而击穿电压线性降低;电荷层电荷面密度为4.8×10~(12)cm~(-2)时,随着倍增层厚度的增加,贯穿电压线性增加,击穿电压增加.通过对器件结构优化,雪崩光电二极管探测器实现25V的贯穿电压和57V的击穿电压,且具有低暗电流和宽响应范围等特性.     

基于分子束外延生长的1.05 eV InGaAsP的超快光学特性研究

利用分子束外延方法制备了应用于四结光伏电池的1.05 eV InGaAsP薄膜, 并对其超快光学特性进行了研究. 温度和激发功率有关的发光特性表明: InGaAsP材料以自由激子发光为主. 室温下InGaAsP材料的载流子发光弛豫时间达到10.4 ns, 且随激发功率增大而增大. 发光弛豫时间随温度升高呈现S形变化, 在低于50 K时随温度升高而增大, 在50–150 K之间时减小, 而温度高于150 K时再次增大. 基于载流子弛豫动力学, 分析并解释了温度及非辐射复合中心浓度对样品材料载流子发光弛豫时间S形变化的影响.     

Comparison of resonant tunneling diodes grown on freestanding GaN substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy

AlN/GaN resonant tunneling diodes (RTDs) were grown separately on freestanding GaN (FS-GaN) substrates and sapphire substrates by plasma-assisted molecular-beam epitaxy (PA-MBE). Room temperature negative differential resistance (NDR) was obtained under forward bias for the RTDs grown on FS-GaN substrates, with the peak current densities (J_p) of 175-700 kA/cm² and peak-to-valley current ratios (PVCRs) of 1.01-1.21. Two resonant peaks were also observed for some RTDs at room temperature. The effects of two types of substrates on epitaxy quality and device performance of GaN-based RTDs were firstly investigated systematically, showing that lower dislocation densities, flatter surface morphology, and steeper heterogeneous interfaces were the key factors to achieving NDR for RTDs.