Improvement of lubrication and cooling in grinding

The presence of air boundary layer around a grinding wheel impedes the proper entry of cutting fluid into grinding zone and thereby lubrication and cooling are hampered. It leads to the thermal damage to the workpiece and rapid wheel wear. This experimental work is aimed at increasing the lubrication and cooling effects in grinding by a novel method of using scraper board. The experiments are conducted, using the scraper board, to find the critical region where the air pressure is zero. The coolant jet has then impinged into the grinding zone which is maintained within the critical region. The requirement of specific energy, surface texture, and mechanical properties of the ground surface are analyzed and compared with the traditional grinding and the grinding at various positions of scraper board. Results show that the grinding ratio improved by 35.6and 119%, surface roughness decreased by 36 and 54.2%, while the requirement of specific energy is reduced by 50.8 and 57.3% when scraper board is positioned at the critical distance in comparison to the 57.5° position and no scraper board, respectively. The results indicate that the introduction of fluid in the present method can improve the process efficiency and the product quality effectively.     

Cutting force and hole quality analysis in micro-drilling of CFRP

Micro-drilling in carbon fiber reinforced plastic (CFRP) composite material is challenging because this material machining is difficult due to anisotropic, abrasive and non-homogeneous properties and also downscaling of cutting process parameters affect the cutting forces and micro-drilled hole quality extensively. In this work, experimental results based statistical analysis is applied to investigate feed and cutting speed effect on cutting force components and hole quality. Analysis of variance based regression equation is used to predict cutting forces and hole quality and their trend are described by response surface methodology. Results show that roundness error and delamination factor have similar trends to those of radial forces and thrust force, respectively. Non-linear trends of cutting forces and hole quality errors are observed during downscaling of the micro-drill feed value. Optimization results show that cutting forces and hole quality errors are minimum at a feed value which is almost equal to the tool edge radius rather than at the lowest feed value. Therefore, the presented results clearly show the influences of size effects on cutting forces and hole quality parameters in micro-drilling of CFRP composite material.     

钢筋砼连续梁非线性有限元分析

用有限元法对使用荷载下的钢筋砼连续梁做了非线性全过程分析。建立了矩形单元模式,用增量法对连续梁进行非线性分析。编制了计算程序,并对两根连续梁做了对比计算,计算结果与相应的试验结果符合较好。     

煤介质阻挡放电脱硫的影响因素分析

依据介质阻挡放电理论,对原煤进行煤介质阻挡放电脱硫实验。实验结果表明,煤介质阻挡放电脱硫的影响因素与电极结构、介质成分和气隙距离等因素有关,如将介质放到放电间隙中间时脱硫的效果没有将介质直接放在放电极板上的脱硫效果好,加煤的情况下微放电的强度明显大于不加煤的微放电过程强度;脱硫效果呈"U"字型变化,由此推论,在一定的外界条件下,煤介质阻挡放电除硫有一个最佳的施加电压;随着电压的增加,放电脉冲的相位范围逐渐扩展。     

基于网络中心战的导弹部队信息化建设研究

网络中心战作为未来信息化作战的主要样式,已经成为现代战争的主流发展趋势;导弹部队作为未来战争的主要力量,其信息化建设就显得尤为重要;介绍了网络中心战的发展现状,论述了导弹部队在网络中心战中的地位和作用,分析了导弹部队在未来信息化作战的应用使用方法,主要有精确打击、切断信息中枢、突破导弹防御、快速响应及协同作战等;最后,详细分析了导弹部队信息化建设中存在的问题,并指出了进一步研究和建设的重点方向。     

A resonating rheometer using two polymer membranes for measuring liquid viscosity and mass density

A resonating sensor for mechanical liquid properties facilitating measurements at two different modes of operation is presented. One mode is more sensitive to liquid viscosity the other to mass density. A sample liquid is subjected to time-harmonic shear stress induced by two opposed vibrating polymer membranes. These membranes, placed in an external static magnetic field, carry two conductive paths each. The first path is used to actuate the membranes by means of Lorentz forces while the second acts as a pick-up coil providing an induced voltage representing the movement of the membrane. From the resulting frequency response the liquid's viscosity and mass density can be deduced. This double membrane based setup allows examining the test liquid at adjustable frequencies in the low kilohertz range from 500 Hz to 20 kHz by varying the gap between both membranes. The sensor is suitable, e.g., for low cost handheld devices with inline capabilities and disposable sensor elements for measuring Newtonian liquids such as, e.g., oils and aqueous solutions.     

Application of wearable sensors for human gait analysis using fuzzy computational algorithm

The authors have developed and tested a wearable inertial sensor system for the acquisition of gait features. The sensors were placed on anatomical segments of the lower limb: foot, shank, thigh, and hip, and the motion data were then captured in conjunction with 3D ground reaction forces (GRFs). The method of relational matrix was applied to develop a rule-based system, an intelligent fuzzy computational algorithm. The rule-based system provides a feature matrix model representing the strength of association or interaction amongst the elements of the gait functions (limb-segments accelerations and GRFs) throughout the gait cycle. A comparison between the reference rule-based data and an input test data was evaluated using a fuzzy similarity algorithm. This system was tested and evaluated using two subject groups: 10 healthy subjects were recruited to establish the reference fuzzy rule-base, and 4 relapsing remitting multiple sclerosis subjects were used as an input test data; and the grade of similarity between them was evaluated. This similarity provides a quantitative assessment of mobility state of the impaired subject. This algorithmic tool may be helpful to the clinician in the identification of pathological gait impairments, prescribe treatment, and assess the improvements in response to therapeutic intervention.     

基于GA和FEM的夹具布局和变夹紧力优化设计

通过夹具布局和夹紧力大小的优化可以提高薄壁件加工精度．建立了夹具布局和变夹紧力分层优化模型．首先,以工件加工变形最小化和变形最均匀化为目标函数,对夹具布局进行优化设计;其次,基于优化的夹具布局对变夹紧力进行设计．采用有限元法计算工件的加工变形,加工变形求解时综合考虑了接触力、摩擦力、切削力、夹紧力和切屑的影响．采用遗传算法求解优化模型,获得优化的夹具布局和变夹紧力．通过实例分析,验证了分层优化设计方法可以进一步减小工件加工变形,提高加工变形均匀度．     

Slippage control in soft finger grasping and manipulation

Handling objects with robotic soft fingers without considering the odds of slippage are not realistic. Grasping and manipulation algorithms have to be tested under such conditions for evaluating their robustness. In this paper, a dynamic analysis of rigid object manipulation with slippage control is studied using a two-link finger with soft hemispherical tip. Dependency on contact forces applied by a soft finger while grasping a rigid object is examined experimentally. A power-law model combined with a linear viscous damper is used to model the elastic behavior and damping effect of the soft tip, respectively. In order to obtain precise dynamic equations governing the system, two second-order differential equations with variable coefficients have been designed to describe the different possible states of the contact forces accordingly. A controller is designed based on the rigid fingertip model using the concept of feedback linearization for each phase of the system dynamics. Numerical simulations are used to evaluate the performance of the controller. The results reveal that the designed controller shows acceptable performance for both soft and rigid finger manipulation in reducing and canceling slippage. Furthermore, simulations indicate that the applied force in the soft finger manipulation is considerably less than the rigid “one.”.     

计算机生成兵力研究进展

计算机生成兵力（ＣＱＦ－Ｃｏｍｐｕｔｅｒ Ｇｅｎｅｒａｔｅｄ Ｆｏｒｃｅｓ）是分布交互仿真中的关键技术之一。该文详细地介绍了国内外ＣＧＦ研究与的现状,并在综合分析的基础上,对ＣＧＦ领域的研究方向及我国ＣＧＦ研究中注意的问题提出了自己的看法。