基于超磁致伸缩材料的非圆曲面形活塞销孔加工新型机构

To bear more loads for heavy truck pistons, the shape of heavy truck piston pinhole is often designed as noncylinder form. Current methods cannot meet the needs for precision machining on non-cylinder piston pinhole （NCPPH）. A novel mechanism based on giant magnetostrictive materials （GMM） is presented. New models are established for the servo mechanism, GMM, and magnetizing force of the control solenoid to characterize the relationship between the control current of the solenoid and the displacement of the giant magnetostrictive actuator （GMA）. Experiments show that the novel mechanism can meet the needs to perform fine machining on NCPPH effectively.     

Multi-physics coupling field finite element analysis on giant magnetostrictive materials smart component

This study presents a new method to solve the difficult problem of precise machining a non-cylinder pinhole of a piston using embedded giant magnetostrictive material （GMM） in the component. We propose the finite element model of GMM smart component in electric, magnetic, and mechanical fields by step computation to optimize the design of GMM smart component. The proposed model is implemented by using COMSOL multi-physics V3.2a. The effects of the smart component on the deformation and the system resonance frequencies are studied. The results calculated by the model are in excellent agreement （relative errors are below 10%） with the experimental values.     

Chebyshev-Legendre method for discretizing optimal control problems

In this paper, a numerical method for solving the optimal control (OC) problems is presented. The method is enlightened by the Chebyshev-Legendre (CL) method for solving the partial differential equations (PDEs). The Legen-dre expansions are used to approximate both the control and the state functions. The constraints are discretized over the Chebyshev-Gauss-Lobatto (CGL) collocation points. A Legendre technique is used to approximate the integral involved in the performance index. The OC problem is changed into an equivalent nonlinear programming problem which is directly solved. The fast Legendre transform is employed to reduce the computation time. Several further illustrative examples demonstrate the efficiency of the proposed method.     

Research on cubic polynomial acceleration and deceleration control model for high speed NC machining

To satisfy the need of high speed NC （numerical control） machining, an acceleration and deceleration （acc/dec） control model is proposed, and the speed curve is also constructed by the cubic polynomial. The proposed control model provides continuity of acceleration, which avoids the intense vibration in high speed NC machining. Based on the discrete characteristic of the data sampling interpolation, the acc/dec control discrete mathematical model is also set up and the discrete expression of the theoretical deceleration length is obtained furthermore. Aiming at the question of hardly predetermining the deceleration point in acc/dec control before interpolation, the adaptive acc/dec control algorithm is deduced from the expressions of the theoretical deceleration length. The experimental result proves that the acc/dec control model has the characteristic of easy implementation, stable movement and low impact. The model has been applied in multi-axes high speed micro fabrication machining successfully.     

PMAC罗茨鼓风机扭叶转子加工数控系统研究

为实现罗茨鼓风机扭叶转子的专用数控加工,根据三叶扭叶转子的曲面特征,设计了一种新颖的数控铣削的方法,研制了基于PMAC的罗茨鼓风机扭叶转子加工试验台专用数控系统。系统上层控制软件采用模块化设计,并利用V isual Basic6.0开发了相应的人机界面和管理应用功能模块。调试的结果表明,系统软件运行稳定,实现了对了扭叶转子的铣削数控加工。     

Finite particle method for kinematically indeterminate bar assemblies

This study presents a structural analysis algorithm called the finite particle method （FPM） for kinematically indeterminate bar assemblies. Different from the traditional analysis method, FPM is based on the combination of the vector mechanics and numerical calculations. It models the analyzed domain composed of finite particles. Newton＇s second law is adopted to describe the motions of all particles. A convected material flame and explicit time integration for the solution procedure is also adopted in this method. By using the FPM, there is no need to solve any nonlinear equations, to calculate the stiffness matrix or equilibrium matrix, which is very helpful in the analysis of kinematically indeterminate structures. The basic formulations for the space bar are derived, following its solution procedures for bar assemblies. Three numerical examples are analyzed using the FPM. Results obtained from both the straight pretension cable and the suspension cable assembly show that the FPM can produce a more accurate analysis result. The motion simulation of the four-bar space assembly demonstrates the capability of this method in the analysis ofkinematically indeterminate structures.     

高中英语课文的整体教学探索

课文整体教学是完成教学任务的重要手段之一。要顺利完成教学任务,对课文整体教学的理解是基础,设计科学、实效的教学程序是完成课文整体教学的关键所在。按照新的英语课程标准的要求,本文就如何进行课文整体教学,提高学生的英语综合能力进行了探讨。     

酸活化对膨润土比表面积和孔径的影响研究

分别用质量分数为5%、10%、15%、20%、25%和30%的硫酸溶液对黑山膨润土进行酸化改性,用乙二醇乙醚吸附法和氮气吸附法对黑山膨润土及其酸化土的比表面积和孔体积进行分析。结果表明:膨润土酸化改性后,随着硫酸质量分数的增加,外表面积增加不明显,内表面积及总表面积减小;半径大于1nm的孔的体积明显增加,半径小于1nm的孔的体积逐渐减小直至为0。可见,本实验条件下膨润土酸化改性后性质的变化,并不是主要由表面积增加引起的,而是由有效孔(半径>1nm)的大量增加引起的。     

Parallel communication optimization based on least square method for LBM

Efficient communication is important to every parallel algorithm. A parallel communication optimization is introduced into lattice Boltzmann method (LBM). It relies on a simplified communication strategy which is implemented by least square method. After testing the improved algorithm on parallel platform, the experimental results show that compared with normal parallel lattice Boltzmann algorithm, it provides better stability, higher performance while maintaining the same accuracy.     

高斯混合模型在错误隐藏技术中的应用

把高斯混合模型(GMM)用于视频流的错误隐藏技术中,并对此进行了分析、论证、研究。GMM依据邻近的时域和空域的信息,用最小均方差来估计丢失像素的区域;如部分视频数据丢失,根据丢失视频数据邻近的时-空域信息通过GMM做一个最小均方差估计;如丢失宏块周围的时域信息也随之丢失,则采用反复迭代估计的方法来解决。和现有的基于时-空域的错误隐藏方法相比,基于GMM的错误隐藏方法提高了PSNR,且对于大范围内的丢包率都是有效的。仿真实验也证实了基于GMM的错误隐藏方法能较好地提高和改善视频的主客观质量。     

Optimal distributed resource allocation in a wireless sensor network for control systems

INTRODUCTION With the rapid development of wireless com-munication technology, the combination of wireless communication and control systems becomes a new trend of networked control systems. Among the kinds of wireless technologies, wireless sensor network (WSN) has attracted a lot of interest and visibility due to its huge application space. WSN is a kind of wire-less ad-hoc network which connects embedded sen-sors, actuators, and processors and in which each node consists of a wireles…     

混联式混合动力客车逻辑控制策略研究

混合动力客车的控制策略决定整车的性能。分析某混联式混合动力客车的组成结构和基于逻辑控制的控制策略,建立相应的混联式混合动力客车仿真模型及其控制器,通过AVL/CRUISE和MATLAB/Simulink联合仿真分析,获得该车在中国典型城市公交工况下的动力性和百公里油耗。仿真结果表明,各主要部件能按照控制规则实现状态的合理切换,基于逻辑控制的控制策略能满足整车性能指标要求。     

镗孔时发生让刀现象分析及解决方法

通过镗孔时让刀现象的原因分析,探索消除让刀有效方法。结果表明,镗孔时让刀的原因有镗杆受力产生的弯曲弹性挠变和简谐运动;镗杆与导向套的精度及配合间隙产生圆周滑动和单摆运动;镗床导轨进给方向与主轴轴线不平行产生爬行和偏摆运动三个方面。可以从提高镗杆的刚度和螺旋下刀加工方式;采用回转式镗套前后双导向支承;改善润滑条件和改进机床设计方法加以解决。     

鼠洞对铁路轨枕的危害研究及治理

在考虑轨道稳定性的过程中,要考虑鼠洞对轨枕的危害性.鼠洞会使轨枕底与道碴之间存在空隙,列车运行时鼠洞会使轨枕产生附加动力.对轨枕进行了动力学计算和强度校核,当鼠洞严重时,轨枕不能满足动力学强度条件.本文就鼠洞对轨枕的危害性进行了研究,介绍了大瑶山隧道治理鼠洞的实验,该实验效果较好,提出了治理鼠洞的基本方法,本文的研究结果为改进鼠洞对轨枕的危害提供了一定的科学依据,具有一定的指导意义和应用价值.     

Neural network method for solving elastoplastic finite element problems

INTRODUCTION An Artificial Neural Network (ANN) is an in-formation-processing paradigm that is inspired by the way biological nervous systems, such as the brain, process information. It is composed of a large number of highly interconnected processing elements (neu-rons) working in unison to solve specific problems. In recent years, neural network has been widely applied in the field of engineering construction as a large dimensional nonlinear dynamic system, because of its support for …     

电力GIS系统中电力设施图形表达

在电力GIS系统项目实施过程中存在着诸如地理信息与电力信息结合不紧密、数据量过大致使系统效率降低等问题。引发这些问题的根源在于电力GIS系统中图形数据的表达和组织上存在某种矛盾。本文主要探讨了电力GIS系统中电力设施图形表达上的2大难点问题,即电力线路与开关型电力设备(如杆上开关)的图形表达问题,并针对电力拓扑关系的表达提出了图形拓扑法和拓扑表法2种实现方式。     

A current-differential-based method for improving dynamic characteristics of electromagnetic actuators

This paper presents a new control strategy based on current differential feedback to accelerate the dynamic response of electromagnetic actuators, instead of traditional closed-loop control based on displacement feedback. The method mainly includes a differentiator, proportioner and signal synthesizer. Analysis and simulation on the step characteristics of an electromagnetic actuator were discussed, and all the results show that the approach can improve the actuator＇s step response greatly. Finally, the control method is applied to a real gravure system which verifies the control performance.     

加强教学过程控制的研究和实践

本文尝试运用全面质量管理的理论原则和方法,加强对教学过程控制,增强教学管理的及时性、针对性和准确性,从而达到提高教学质量的目的。     

基于CN时域有限差分方法对手征电磁介质的研究

利用CN时域有限差分方法对无限大手征电磁介质中平面波的传播进行仿真计算．与其他算法比较发现．CN时域有限差分法在计算结果的精度和计算量上有一定优势．     

基于预测控制的直接转矩控制系统的研究

针对异步电动机直接转矩控制（DTC）系统在低速时由于开关频率不稳定而引起转矩脉动较大的缺点，提出了一种预测控制方法。该方法根据转矩和定子磁链的误差来确定应该施加的参考电压矢量，最后利用空间矢量脉宽调制（SVPWM）方法来合成该矢量，这样即保证了逆变器的开关频率恒定，从而大大降低转矩脉动。仿真结果表明，在低速下定子磁链轨迹近似为圆，转矩脉动不明显。