Component synthesis vibration suppression method of two component forces for flexible spacecraft

Considering the characteristics of two component forces on component synthesis vibration suppression(CSVS) method, two theorems on two component forces suppressing fractional multiple design frequency are given respectively. Meanwhile, the control force, which is composed by two arbitrary component forces with different initial time, can suppress certain frequencies for secondorder undamped vibration system. Using the above theorems, control moment of jet attitude maneuver on flexible spacecraft is designed on the basis principle of CSVS method. The simulations validate the correctness and effectiveness of the proposed method.     

Molecular Dynamics Simulation for Ultrafine Machining

This article surveys the advances of molecular dynamics (MD) simulation in the research of ultrafine machining and related technologies. Modeling methods, including interatomic potentials and boundary conditions, are addressed. Algorithm strategies for MD simulations are discussed. By applying simulations with Tersoff potential, a case study of the material removal mechanism of the polishing based on coupling vibrations of liquid (PCVL) is presented.     

磁流变对称式气动缸动力机构特性的仿真分析

磁流变气动控制技术是克服传统气动伺服系统缺点、提高定位精度和运动平稳性的一种新技术，是一个崭新而前景广阔的研究领域。该文根据磁流变气动控制技术，构建了一磁流变对称式气动缸动力机构，并建立了该动力机构的数学模型；通过MATLAB仿真语言，对新型动力机构的动、静态性能进行了仿真分析，并和传统气动缸动力机构进行比较。结果表明新型机构较传统机构有更好的动、静态性能。此结论为磁流变技术在气动控制中的应用提供了理论依据。     

Redefining the Diamond Cutting Edge: A Technique that Complements Nano-Metric Surface Generation

Ongoing developments in broadband digital networks and optical devices require mechanical components having nano-metric surface finishes and ultra precision shapes. Such components are processed using the technology of diamond micro-machining in which diamond tools are extensively used. However, these tools are susceptible to chemical attack at high temperatures and induce severe wear, especially when cutting ferrous materials. As a result, these diamond tools need to be redefined (i.e., resharpened) on a regular basis in order to facilitate micro-cutting and to generate nano-metric surface finishes. This paper describes a new way of diamond tool edge re-sharpening and its conditions to achieve both increased accuracy and material removal rate.     

一种喷射泵系统装置和工艺参数的优化匹配方法

以喷射泵系统在给定的工作条件和井底流动压力变化范围内，在满足生产要求的前提下，平均工作效率最高为目标函数，取喷嘴—喉管面积比、地面泵功率和压力、油管尺寸共四个设计变量，从喷射泵复杂的迭代计算过程中确定出气蚀、系统工作性能等限定的十二个约束条件，建立系统优化模型。用约束非线性混合离散优化方法对喷射泵系统装置进行优化匹配。该优化匹配方法可为工程前期系统装置的总体规划和匹配提供理论依据     

提高射流泵效率的研究

效率是射流泵的主要性能指标。文章分析了影响其效率的主要因素，认为面积比是影响射流泵效率的关键所在。通过对大峡水电站排水流泵的正交优化试验，证实了找到最优面积比是提高射流泵效率的有效途径。     

High-Modulus Columns for Liquefaction Mitigation

This paper presents the performance of a shopping complex in Turkey where the soils were improved with jet-grout columns and preload fills and subjected to the 1999 Kocaeli Earthquake (M = 7.4). Under construction at the time of the earthquake, the Carrefour Shopping Center covers an area of 55,000?m2 and is founded on shallow footings, mats, and slabs-on-grade that rest on soft, saturated alluvial sediments consisting of clays, silts, and sands. High-modulus columns constructed by jet grouting were installed at close-to-moderate spacings to reduce anticipated static settlements in the clays and mitigate liquefaction in the sands. The site was subjected to a peak acceleration of approximately 0.2g during the earthquake. Grouting had been completed for about two-thirds of the site when the earthquake struck. Following the event, a field reconnaissance found stark contrast between the performance of the improved and unimproved sections. The jet-grout-treated areas suffered no apparent damage, whereas the unimproved sections of the complex, along with nearby untreated building sites, commonly suffered liquefaction-related settlements of up to 10 cm. This is the only case history known to the authors that documents the field performance of high-modulus columns used in this manner for liquefaction mitigation and direct instrumented measurement of liquefaction-induced settlements.     

采用径向射流冲击与钎焊砂轮解决磨削烧伤的研究

在分析高效磨削烧伤机理的基础上，提出了两项对策：一是采用高压径向射流冲击强化磨削弧区换热，以最大限度地疏导已经产生的积聚在弧区的磨削热；二是采用钎焊超硬磨料砂轮取代传统电镀砂轮，以提高砂轮的锋利度降低磨削比能，减少磨削热的产生。缓进给断续磨削试验结果表明，该两项对策对解决难加工材料磨削烧伤问题效果十分明显，具有广阔的应用前景。     

虚拟轴混联机床研抛模具自由曲面的分片规划

采用虚拟轴混联机床进行模具自由曲面的精加工,为了提高模具自由曲面的研抛精度和效率,论述自由曲面的分片抛光方法。根据计算机图形信息构造特点,将自由曲面划分为一系列曲面信息与工艺特征相同或相似的曲面片族,相似的曲面片族采用相同的工具和相近的工艺参数进行研抛加工。通过理论计算和仿真验证,此方法能够提高研抛效率。     

基于MEMS技术的新型微冷却方式

针对高功率电子器件散热问题,介绍了国际前沿领域电子设备热控制的技术动态．讨论了基于MEMS技术的微冷却器有体积小,散热面积大,消耗功率低,批量制作经济性好等优点。分析了微通道、微喷流和微热管3种基于MEMS技术的新型微冷却方式的传热原理、目前的技术状况及应用前景微通道的采用增加了对流换热面积,提高了对流换热系数;微喷流冷却器中由于高速冷却液的形成,显著提高了换热系数;微热管均热效果极佳。