Magnetophonon resonance in the energy relaxation of electrons in a quantum well

The magnetophonon resonance effect in the energy relaxation rate is studied theoretically for a quasi-two-dimensional electron gas in a semiconductor quantum well. An electron-temperature model is adopted to describe the coupled electron-phonon system. The energy relaxation time, derived from the energy relaxation rate, is found to display an oscillatory behavior as the magnetic-field strength changes, and reaches minima when the optical phonon frequency equals integer multiples of the electron cyclotron frequency. The theoretical results are compared with a recent experiment, and a qualitative agreement is found.

X-ray diffraction study of GaAs/InAs/GaAs ultrathin single quantum well

Ultrathin single quantum well (about one monolayer) grown on GaAs(001) substrate with GaAs cap layer has been studied by high resolution x-ray diffractometer on a beamline of the Beijing Synchrotron Radiation Facility. The interference fringes on both sides of the GaAs(004) Bragg peak are asymmetric and a range of weak fringes in the higher angle side of the Bragg peak is observed. The simulated results by using the kinematical diffraction method shows that the weak fringe range appears in the higher angle side when the phase shift introduced by the single quantum well is very slightly smaller than m pi (m:integer), and vice versa. After introducing a reasonable model of single quantum well, the simulated pattern is in good agreement with the experiment. (C) 1996 American Institute of Physics.

A fast-settling frequency-presetting PLL frequency synthesizer with process variation compensation and spur reduction

This paper proposes a fast-settling frequency-presetting PLL frequency synthesizer. A mixed-signal VCO and a digital processor are developed to accurately preset the frequency of VCO and greatly reduce the settling time. An auxiliary tuning loop is introduced in order to reduce reference spur caused by leakage current. The digital processor can automatically compensate presetting frequency variation with process and temperature, and control the operation of the auxiliary tuning loop. A 1.2 GHz integer-N synthesizer with 1 MHz reference input Was implemented in a 0.18μm process. The measured results demonstrate that the typical settling time of the synthesizer is less than 3μs,and the phase noise is -108 dBc/Hz@1MHz.The reference spur is -52 dBc.

基于随机背包的公钥密码

该文构造了一个背包型公钥密码算法。该背包公钥密码具有如下优点:加解密只需要加法和模减法运算,因此加解密速度快;该算法是基于随机背包问题而不是易解背包问题而构造的;证明了在攻击者不掌握私钥信息情况下该密码算法能抵抗直接求解背包问题的攻击,包括低密度攻击和联立丢番图逼近攻击等;证明了攻击者能够恢复私钥信息与攻击者能够分解一个大整数是等价的。分析表明,该算法是一个安全高效的公钥加密算法。

复杂单臂机器人集束型装备调度模型

针对一类存在并行和可重入腔的复杂单臂机器人集束型装备的调度问题,通过对加工腔、机器人、并行和可重入腔中的各个机器人活动进行分析,推导出对应的时序约束关系,建立了问题的混合整数规划模型,从而获得最优的机器人动作序列和最小周期.调度实例表明了模型的可行性和高效性。

任务分配问题的建模与求解

建立了极大极小任务分配问题的混合整数线性规划模型,提出一种矩阵作业解答,并与穷举解及混合整数线性规划解的计算复杂度进行了比较.理论分析和数值试验表明矩阵作业法对两类任务分配问题,极大极小和总体极小任务分配问题,有效地提供最优解.

多目标追逐问题的一种混合整数线性规划解

研究多车辆多目标追逐的路径规划问题。提出两个基于混合整数线性规划(Mixed integer linear programming,MILP)的多目标追逐(Multi-target pursuit,MTP)模型:就近追逐和"一对一"使能追逐。在两个MIP追逐模型中,小车运动的状态方程考虑为具有线性阻尼的质点动力学方程。采用整数变量描述小车与障碍物的相对位置信息,提出"目标膨胀尺寸"的概念来描述对目标的追逐,定义小车的"追逐方向"。采用选取整变量的等高面法求解MILP追逐问题,并给出初始内点整变量的确定方法。最后给出仿真试验1对两个多目标追逐模型进行对比研究,仿真试验2证实了算法的效率。

企业间电子商务风险的综合分析方法

互连网上电子商务的蓬勃发展为企业提供了巨大商机，但风险也是巨大的。同时，网上信息爆炸也需要一种使用的方法对信息进行分析、整理、提取，为下一步的决策提供坚实的基础。本文在总结不同风险分析方法的基础上，提出了一种完整的方法，为网上商务的风险分析和决策提供了一种实用的解决方案。

成批生产计划调度的集成建模与优化

针对多品种批量生产类型,建立了调度约束的生产计划与调度集成优化模型。模型的目标函数是使总调整费用、库存费用及生产费用之和最小,约束函数包括库存平衡约束和生产能力约束,同时考虑了调度约束,即工序顺序约束和工件在单机上的加工能力约束,保证了计划可行性。该模型为两层混合整数规划模型,对其求解综合运用了遗传算法和启发式规则,提出了混合启发式求解算法。最后,针对某机床厂多品种批量生产类型车间进行了实例应用,对车间零件月份作业计划进行分解,得到各工段单元零件周作业计划,确定了零件各周生产批量与投产顺序。