冲击载荷作用下某型越野车保险杠的试验和数值模拟

采用落锤冲击试验机对某型越野车保险杠进行抗冲击动态力学实验,测得了保险杠的冲击力时程曲线和保险杠的跨中最终位移,并采用有限元软件ABAQUS对保险杠进行数值模拟。落锤冲击实验与数值模拟结果表明:保险杠的冲击力初始峰值、冲击力的持续时间和残余的塑性变形与冲击速度呈正相关;在冲击载荷作用下,保险杠发生了不同程度的塑性变形,展现出了良好的抗冲击性能和吸能特性。     

薄金属圆板在圆锥头弹体正冲击下的破裂模式

在临界破裂速度下(圆板产生破裂的最小速度),对四种不同材料的薄金属圆板在具有不同圆锥半角的圆锥头子弹正冲击下的破裂模式进行了实验研究。发现,随着圆锥半角的增加,板的破裂模式分别有刺透型、花瓣型和剪切型。并且,对一种材料的板,存在一个临界转换半圆锥角,当ψ>ψ cc时,板为剪切型破坏,当ψ<ψ 时,子弹在冲击点处形成小孔。     

基于AD694测控直流何服电动机实时数据采集系统设计

介绍以8031单片机为系统控制核心的转换控制器的硬件及软件设计问题,利用电流型ADC具有抗干扰能力强.量化噪声小、分辨率高,线性度好,转换速度较高的特性,提出了采用高精度AD694控制电机速度和数据采集的解决方案.     

基于AD694测控直流伺服电动机实时数据采集系统设计

介绍以8031单片机为系统控制核心的转换控制器的硬件及软件设计问题,利用电流型ADC具有抗干扰能力强、量化噪声小、分辨率高、线性度好、转换速度较高的特性,提出了采用高精度AD694控制电机速度和数据采集的解决方案.     

冷库门运行速度控制装置开发与应用

工业冷库门运行速度的大小对于冷库门的使用性能具有很大的影响。本文针对冷库门运行过程中速度控制的方法进行研究,提出了通过采用变频控制技术实现对冷库门的速度进行控制。通过试装测试,结果表明采用基于变频控制技术的控制装置可以实现对冷库门速度的有效控制,冷库门可以快速的开、关,并减少对冷库门框的冲击。     

镀锌钢带恒速卷绕的计算机控制

提出了采用计算机控制实现镀锌钢带以恒定速度卷绕的技术方法。要达到整个卷绕过程中线速度恒定,须以正确的算法计算逐字减少Ｄ／Ａ转换控制字的时间间隔。     

信息时代外语教学模式展望

人类进入信息时代，计算机技术和网络技术的迅速发展对固有的外语教学模式形成了巨大的冲击。本文介绍了新技术条件下外语教学中已呈现出、并将被广泛采用的几种主要教学模式，同时对丰富的网络资源支持下，外语教学的优势及教师在新的教学模式中面临的角色转换等内容进行了阐述。     

新常态下国企青年员工思想引领的对策思考

进入以速度变化、结构优化、动力转换为特征的经济发展新常态以来,国有企业发展面临新的挑战。在此背景下,作为国有企业可持续发展的有生力量,青年员工的思想状态也在受到深刻的影响和冲击,青年员工的思想引领工作面临新的问题。如何有效做好青年员工群体的思想引领工作,已成为国有企业全面深化改革进程中一项亟需解决的重要课题。     

高速光纤通信中信号接收器的设计与实现

本文首先介绍了应用于高速光纤通信中信号接收的几种电路结构,并对其进行分析与总结,提出了采用光电转换的等效电路模型。然后对光电接收转换电路进行改进,提出了一种前馈式的信号接收器总体设计方案,并对该方案的性能进行分析,重点是信息传输的速度和误码率,详细介绍了前馈式的信号放大原理与实现方法。     

知识经济条件下对传统会计假设再认识

会计假设是构成财务会计与报告的基础,假设表明财务会计的环境特征,通过对知识经济条件下传统会计假设受到的冲击进行分析、探讨与研究,从空间、时间、速度、数量四个方面赋予了会计假设新的解释。     

五孔探针在气流速度测量中的应用

气速是工程和实验研究所关注的重要参数之一,在化工领域内对流体速度进行准确测量对实验结果至关重要.本文对五孔探针在气速测量相关方法中的应用进行说明,尤其是对在高速测量中五孔探针的使用进行详细的研究.对五孔探针在Ma＞0.3的高速气流速度测量中的应用进行了研究,探讨了五孔探针在高速气流中的标定和测量方法,设计加工了锥形五孔...     

Finite element analysis of dynamic response and structure borne noise of gearbox

A dynamic finite element method combined with finite element mixed formula for contact problem is used to analyze the dynamic characteristics of gear system. Considering the stiffness excitation, error excitation and meshing shock excitation, the dynamic finite element model is established for the entire gear system which includes gears, shafts, bearings and gearbox housing. By the software of I-DEAS, the natural frequency, normal mode, dynamic time-domain response, frequency-domain response and one-third octave velocity grade structure borne noise of gear system are studied by the method of theoretical modal analysis and dynamic response analysis. The maximum values of vibration and structure borne noise are occurred at the mesh frequency of output grade gearing.     

一种基于改进帧差法的运动目标检测

针对视频中的运动目标离摄像头较近时由于形状的变化而导致目标边界测定不准确的问题,在帧间差分法的基础上,提出了一个求精运动目标边界的算法。先用得到边界值计算目标中心点,再对视频中的运动目标进行运动距离和速度的检测,并在Matlab中进行仿真。实验结果表明,该算法对帧差法的结果进行求精后,得到的运动目标的状态值更接近于实际情况,改进的算法更适合于视频中运动目标形状变化较大的情况下进行运动目标状态的检测。     

Wind-induced response analysis of a wind turbine tower including the blade-tower coupling effect

To analyze wind-induced response characteristics of a wind turbine tower more accurately, the blade-tower coupling effect was investigated. The mean wind velocity of the rotating blades and tower was simulated according to wind shear effects, and the fluctuating wind velocity time series of the wind turbine were simulated by a harmony superposition method. A dynamic finite element method （FEM） was used to calculate the wind-induced response of the blades and tower. Wind-induced responses of the tower were calculated in two cases （one included the blade-tower coupling effect, and the other only added the mass of blades and the hub at the top of the tower）, and then the maximal displacements at the top of the tower of the tow cases were compared with each other. As a result of the influence of the blade-tower coupling effect and the total base shear of the blades, the maximal displacement of the first case increased nearly by 300% compared to the second case. To obtain more precise analysis, the blade-tower coupling effect and the total base shear of the blades should be considered simultaneously in the design of wind turbine towers.     

码垛机器人的CP轨迹规划

对于码垛机器人,轨迹规划的核心是控制曲线的选取和其算法的实现,其轨迹规划是有的束非线性形的复杂问题,本文根据求得的逆运动学解,用ＭＡＴＬＡＢ软件对轨迹规划进行编程,得出了关节变量的运动曲线,为以后的伺服控制提供了依据。     

激光涂层在多冲碰撞载荷下的变形与失效研究

In applying impact loads with multishocks to perform shock experiments for laser cladded cobalt-base and nickel-base alloy coats on the surface of mild carbon steel or austenitic stainless steel, it is found that, under an impact force that is 11%-43% of the static yield limit of the material, micro-plastic deformation is generated both in the coat and upper part of the base. Repeated trials will cause cumulated macro-plastic deformation. After a total of 250,000 impacts, relative deformation rates of 2.2% and 8.9% result in the coat and base, respectively. Moreover, there is a rigidification phenomenon both in the coat and upper part of the base. When the coat covers the entire base, under impact loads with multishocks, the final stress is less than that when the base is only partly covered, and the life is longer.There is intense deformative rigidification and material floating effect on the lower part of the edge of the covering coat. Meanwhile, cracks are likely to occur and spread in this part.     

基于速度图解法的辛普森式行星齿轮机构传动方案分析

利用速度图解法绘制3个等速点的线速度矢量,以直观了解机构中各元件的转动状态,并总结了利用速度图解法分析辛普森式行星齿轮机构的原则;利用相似三角形原理计算各传动方案的传动比,通过对速度图解法与解析法传动比的比较分析,验证了该方法和过程的正确性.     

砂土地震液化的不确定性判别法综述

通过对不同自由场地液化势估计的方法和公式进行总结和比较 ,发现剪切波速比其它波的波速更能反映地基岩土层的工作性能 ,现已为全国地基勘察规范所采用     

神经生长因子对大鼠脑缺血再灌注后HIF-1α及HSP70表达的影响

采用大鼠大脑中动脉（MCAO）模型,肌肉内注射神经生长因子（NGF）,经过免疫组化和HE染色检测Sprague—Dawley（SD）大鼠脑缺血再灌注后HIF-1α（缺血诱导因子）及HSP70（热休克蛋白70）表达的变化及神经生长因子的影响。结果表明,肌肉注射神经生长因子对脑缺血再灌注有明显的保护作用,HIF—1α及HSP70表达增加可能是其机制之一。     

High velocity flow simulation using lattice Boltzmann method with no-free-parameter dissipation scheme

A finite difference lattice Boltzmann method of second-order accuracy in time is developed based on non-oscillatory scheme with no-free-parameter dissipation (NND) difference scheme in this paper. The NND lattice Boltzmann method is used to simulate high-speed flows by constructing a new equilibrium distribution function of the lattice Boltzmann method.Compared with a variation of lattice Boltzmann method developed by Qu, et al., the present method can capture shock waves and handle oscillations of high velocity flows accurately in larger time steps and in shorter computing time. Numerical results indicate the correctness and capability of simulating shock wave interactions of the NND lattice Boltzmann method.