Combination of non-classical pseudospectral and direct methods for the solution of brachistochrone problem

In this paper, we propose a combination of non-classical pseudospectral and direct methods to find the solution of brachistochrone problem. The method converts the optimal control problem of brachistochrone, into a sequence of quadratic programming problems. To this end, the quasilinearization method is used to replace the nonlinear optimal control problem into a sequence of constrained linear-quadratic optimal control problems; then each of the state variables is approximated by a weighted interpolation function based on the non-classical orthogonal polynomials. The method gives the information of the quadratic programming problems explicitly (the Hessian and the gradient of the cost function). Using this method, the solution of the brachistochrone problem is compared with those in the literature.     

带有时限的多点应急系统库存策略优化研究

主要研究有时限约束的应急供应系统的库存服务水平问题。考虑随机需求下的包含一个中央供应点和多个不同地方供应点的二级系统,当缺货发生时,基于就近原则的转运模式建立了有时限约束的地方供应点库存策略优化模型,在此基础上分析了随机转运和不转运两种模式对模型的影响,最后采用粒子群算法对模型进行求解和分析。结果表明:在有时限约束时,就近原则模式下的库存策略具有较高的服务水平,并且时限约束越紧,其优势越显著。     

关于IV-(∈,∈Ⅴq)模糊格蕴涵子代数

运用区间值模糊集的思想对IV-(∈,∈Ⅴq)-模糊格蕴涵子代数概念作进一步研究。给出了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的若干新的性质与刻画;获得了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的象与原象成为IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的条件;讨论了IV-(∈,∈Ⅴq)-模糊格蕴涵子代数的直积特征。     

Electro-oxidation of dimethyl ether on Pt/C and PtMe/C catalysts in sulfuric acid

The electro-oxidation of dimethyl ether (DME) on PtMe/Cs (Me = Ru, Sn, Mo, Cr, Ni, Co, and W) and Pt/C electro-catalysts were investigated in an aqueous half-cell, and compared to the methanol oxidation. The addition of a second metal enhanced the tolerance of Pt to the poisonous species during the DME oxidation reaction (DOR). The PtRu/C electro-catalyst showed the best electro-catalytic activity and the highest tolerance to the poisonous species in the low over-potential range (<0.55 V, 50 °C) among the binary electro-catalysts and the Pt/C, but at the higher potential (>ca. 0.55 V, 50 °C), the Pt/C behaved better than PtRu/C. The apparent activation energy for the DOR decreased in the order: PtRu/C (57 kJ mol⁻¹) > Pt₃Sn/C (48 kJ mol⁻¹) ≈ Pt/C (46 kJ mol⁻¹). On the other hand, the activation energy for the MOR showed a different turn, decreased in the following order: Pt/C (43 kJ mol⁻¹) > Pt₃Sn/C (35 kJ mol⁻¹) ≈ PtRu/C (34 kJ mol⁻¹). The temperature dependence of the DOR was greater than that of the oxidation of methanol (MOR) on the PtRu/C.     

WTO法在中国国内的法律适用问题

从条约法的角度,通过对条约法在国内适用的理论与实践分析,结合WTO法的一些特性,并参考其他WTO成员方的作法,对WTO法在中国国内的适用问题提出了几点建议.     

An Observing Method for Flux and Speed with Direct Torque Control

An observing method for stator flux and rotor flux is presented. Based on the proposed flux observing method, a novel speed estimator has been designed. At last, the speed estimator combined with the flux observing is applied in the direct torque control system without speed sensor. The simulation results show that these methods can improve the accuracy of speed observing and the low speed performance of direct torque control system, and strengthen the robustness of system.     

基准离焦偏差控制技术

一种新的采用基准离焦信号的针孔调焦方案,用于激光直写的自动对焦子系统。通过在离焦曲线上提取参考离焦信号,建立基准离焦判据,它能容易地区分前离焦或后离焦,有效地克服了原有针孔调焦方案难于根据离焦信号来分辨离焦方向的弱点。借助微处理器和模拟电路实现了这一方案,并因此获得了均匀的1靘线宽的线条。     

关于改善外商投资软环境的思考

在日益激烈的竞争中 ,要进一步提高利用外资的质量和水平 ,关键是要搞好投资环境建设 ,尤其是要着力改善外商投资的软环境。本文从外商投资软环境的内涵出发 ,在分析改善外商投资软环境的背景基础上 ,提出了完善外商投资软环境的策略和具体做法     

直驱式电液位置系统PID控制的研究

针对直驱式电液位置系统的特点，使用PID控制改善系统的特性。经过对比分析，采用不完全微分PID控制策略。通过仿真在不同负载下系统对阶跃和斜坡信号的响应，分析结果得出：采用PID控制方法后带载系统响应时间、稳态误差变小，系统刚度增大，减小了负载带来的影响，能够达到控制的需要。     

感应电机无速度传感器直接转矩控制的智能优化设计

在一些特定作业环境中,需要对电机转速进行精确调控.为了改善直接转矩控制系统低速时常规PI调节器带来的转速脉动,设计了基于模糊神经网络的新型PI调节器,改进后的转速调节器具有快速自整定、微超调的特性.针对MARS转速观测器低速时的不稳定性,设计了基于人工神经网络的模型参考自适应速度观测器,改进后的转速观测器具有良好的动、静态特性.仿真结果表明:智能优化设计使得直接转矩控制系统的控制效果明显提高,且有更好的鲁棒性和自适应性.