Recent developments in autocollimating telescopes

Developments in autocollimating telescopes since the 1930's are described, including the introduction of photo-electric image detection systems and the more recent use of solid state sources and sensors together with signal processing equipment. Target specifications for the 1980's are for increased total measuring range, setting repeatability and accuracy over the total measuring range. One manufacturer's recent specifications for automatic position sensing autocollimators illustrate the potential for improvement     

车辆智能悬架系统发展趋势研究

对车辆悬架系统的发展历程进行了综合分析,同时对各种悬架系统进行了分析和比较,说明车辆悬架系统研究内容和方法,指出车辆悬架系统的发展方向是智能控制悬架系统,但是其相关关键技术的突破是智能悬架得到广泛应用的前提。     

压电超声微马达的研究新进展

介绍了国内外压电超声微马达的最新研究成果.总结出压电超声马达微型化的通用方法,并指出了压电超声微马达的下一步研究重点.     

Recent developments in analytical electron microscopy

Recent years have seen the way in which the analytical electron microscope has been applied to problems involving thin specimens in metallurgy, mineralogy and many branches of biology. The limits of sensitivity have been explored and its potential usefulness in these fields investigated. Problems concerning the interaction of electrons with the specimen are discussed in relation to the correct choice of operating conditions and specimen preparation. In biological work, frozen sections provide new information about subcellular elemental localization of mobile electrolytes, while analysis of tissue prepared by conventional means is used to detect physiological levels of some naturally occurring elements. Examination of mineral dispersions provides analysis of particles just 10 nm thick, visible only in transmission electron microscopy, and further work with thin metal foils confirms the value of high resolution transmission imaging as a complementary facility to micro-analysis. Work has been done to investigate the possibilities of improving sensitivities both by changing operational parameters and instrumental design, and the value of quantitation in thin specimen analysis explored.     

Recent developments in secondary electron imaging

Some recent experimental and theoretical developments in secondary electron (SE) imaging are reviewed. Coincidence experiments identify inner-shell excitations and single electron valence excitations often as more significant initial events in SE production than the more delocalized process of plasmon generation. Quantitative measurement and interpretation of escape depths in different materials are now becoming possible. Local variations in surface barrier height or work function can be imaged, e.g. at p-n junctions in semiconductors, especially if the effects of external patch fields are overcome.     

车辆半主动悬架联合仿真研究

利用多体动力学软件ADAMS建立了悬架的机械系统模型,运用MATLAB设计了基于模糊算法的半主动悬架控制器,基于ADAMS/View和Matlab/Simulink对半主动悬架进行了联合仿真.仿真结果表明,基于模糊控制的半主动悬架能够很好地降低车身加速度、悬架动挠度及车轮动位移,较大地改善了车辆的行驶平顺性和操纵稳定性.     

汽车半主动悬架的鲁棒控制研究

分析基于电流变阻尼器的半主动悬架系统,建立了1/4车辆状态空间模型,在路面输入是随机白噪声下,应用干扰抑制指标,设计H∞控制器,并且用MATLAB进行了数值仿真,与被动悬架相比,H∞控制下的闭环悬架系统能有效降低车身垂直加速度.     

Recent developments in grinding of advanced materials

This article discusses the recent developments in grinding of advanced materials. Eighty-four journal papers published recently are briefly introduced. The topics are advances in grinding of brittle materials, grinding of silicon, dressing/truing of grinding wheels, grinding fluids, grinding of mirrors and vibration-assisted grinding, measuring/monitoring of grinding, optimization of grinding, modelling and simulation of grinding, and size effect. Ductile mode grinding of brittle materials has been and will continue to be an intensive research area because of its increasing industrial applications and academic demands for fundamental understanding of the ductile mode grinding mechanism. Highly precision manufacturing of silicon substrates faces more and more new challenges. Grinding of silicon continues to be a popular research topic. Using lasers to true and dress grinding wheels has attracted great research interest, because it has significant advantages over mechanical processes. Environmentally friendly grinding fluids are increasingly highly demanded. Vibration-assisted grinding is promising. Monitoring, modelling and optimization of grinding processes help to understand grinding mechanisms and achieve better grinding performance. The size effect is more prominent in grinding than turning and can be used for obtaining a controlled work-hardening surface layer with higher wear resistance and hardness.     

磁控溅射技术进展及应用(上)

近年来磁控溅射技术的应用日趋广泛,在工业生产和科学研究领域发挥巨大作用。随着对具有各种新型功能的薄膜需求的增加,相应的磁控溅射技术也获得进一步的发展。本文将介绍磁控溅射技术的发展,以及闭合磁场非平衡溅射、高速率溅射及自溅射、中频及脉冲溅射等各种新技术及特点,阐述磁控溅射技术在电子、光学、表面功能薄膜、薄膜发光材料等许多方面的应用。     

磁控溅射技术进展及应用(下)

近年来磁控溅射技术的应用日趋广泛,在工业生产和科学研究领域发挥巨大作用。随着对具有各种新型功能的薄膜需求的增加,相应的磁控溅射技术也获得进一步的发展。本文将介绍磁控溅射技术的发展,以及闭合磁场非平衡溅射、高速率溅射及自溅射、中频及脉冲溅射等各种新技术及特点,阐述磁控溅射技术在电子、光学、表面功能薄膜、薄膜发光材料等许多方面的应用。     

汽车悬架优化过程的Pareto最优解

针对悬架优化过程目标函数相互冲突的问题,建立了四自由度半车模型,并施加随机路面激励,在此基础上研究了悬架多目标优化(MOP)。采用Matlab软件m文件与Simulink相结合的方法对悬架刚度、阻尼参数进行了数值模拟,分析了刚度或阻尼变化时悬架动行程与车身加速度之间的变化关系,并提出了一种通过数值模拟求解两目标函数优化下Pareto最优解的方法。研究结果表明,该方法可以有效地获得悬架动行程及车身加速度两目标函数下的优化解。     

Recent developments in precision radial grating manufacture

It was approximately two years ago that the Cranfield Unit for Precision Engineering (CUPE) established its own in-house facility for the manufacture of master radial gratings¹. This has been strengthened following the recent purchase of master radial and linear grating generating equipment from the National Engineering Laboratory, East Kilbride, and the transfer of technical knowledge to make the system operable. As a result CUPE is now is possession of two operable grating manufacturing facilities - a resist system (CUPE) and photographic emulsion system (ex-NEL).     

汽车非线性悬架最优控制的研究

建立了车辆两自由度非线性动力学模型及包含悬架刚度立方非线性的运动微分方程,运用Runge-Kutta方法求出了被动悬架与半主动悬架系统对水泥路面、搓板路面、卵石路、鱼鳞坑路4种路谱的响应,采用模拟计算法得出车身竖直振动加速度的均方根值,并将被动悬架与半主动悬架系统的响应进行比较,在振动舒适度改进的同时,悬架弹簧的变形量增大,因此应该合理选择系统参数为汽车的动态设计提供了理论依据.     

基于汽车悬架的多目标优化方法的研究

为了解决汽车悬架的平顺性和操稳性相互耦合的问题,根据万向集团提供的W1车型的相关数据,利用多体动力学仿真软件Adams/car对海马W1车型进行了整车建模,并对该车型进行了平顺性和操稳性仿真.根据国标的评价指标对海马W1车型进行了评价,从而得到汽车平顺性和操稳性的初始性能水平.利用多学科优化软件iSight-FD和多体...     

履带车辆悬挂系统稳定性分析

履带车辆悬挂系统不仅直接影响到车辆的平顺性和舒适性,而且对履带车辆的稳定性能和行进间射击精度有着重要的影响。基于履带车辆建立了路面模型和车辆悬挂系统的二自由度动力学模型,采用Simulink对悬挂系统动力学模型进行仿真计算,并通过改变悬挂的阻尼刚度和弹簧刚度来分析其对车辆稳定性和车辆射击精度的影响,为悬挂系统的设计提供基础。     

车辆悬架K&C特性分析

汽车作为一种交通工具已经融入到了大多数人的生活当中,悬架系统是现代汽车的重要组成部分。一个具有良好综合性能的悬架系统,对提高汽车的平顺性和操纵稳定性有着重要的意义。建立了整车动力学模型,在此基础上对七自由度整车模型进行简化,得到1/4悬架动力学模型。对影响汽车平顺性的主要参数K&C进行了理论分析,并在该理论分析的基础上采用分段方法描述了悬架K&C非线性特性表达式,从而为研究车辆整体性能和进一步了解悬架非线性特性的时域性提供思路。     

Identification techniques applied to a passive elasto-magnetic suspension

The paper presents an experimental passive elasto-magnetic suspension based on rare-earth permanent magnets, characterized by negligible dependence on mass of its natural frequency.The nonlinear behaviour of this system, equipped with a traditional linear elastic spring coupled to a magnetic spring, is analysed in time domain, for non-zero initial conditions, and in frequency domain, by applying sweep excitations to the test rig base. The dynamics of the system is very complex in dependence of the magnetic contribution, showing both hardening behaviour in the elasto-magnetic setup, and softening motion amplitude dependent behaviour in the purely magnetic case. Hence it is necessary to adopt nonlinear identification techniques, such as non-parametric restoring force mapping method and direct parametric estimation technique, in order to identify the system parameters in the different configurations.Finally, it is discussed the ability of identified versus analytical models in reproducing the nonlinear dependency of frequency on motion amplitude and the presence of jump phenomena.     

磁流变互联悬架的馈能特性及动力学性能分析

针对兼顾汽车行驶平顺性和馈能特性的需求,提出了一种新型磁流变互联悬架模型.先构建磁流变减振器力学与馈能的理论模型,并通过Simulink软件搭建磁流变减振器模型和磁流变互联悬架模型,分析影响馈能特性的主要参数;基于整车仿真模型,以30 km/h车速和一段C级路面为激励输入,对磁流变互联悬架与传统液压互联悬架进行对比仿真,分析互联悬架在实际路面激励下馈能特性和汽车行驶平顺性的变化规律.结果表明:磁流变互联悬架的减振效果更好;在满足车辆行驶平顺性需求的前提下,具有有效回收互联悬架振动能量和提高抗俯仰侧倾的能力.     

Recent developments in the tribology of artificial joints

A history of the tribological development of artificial joints compares how these are lubricated with the mechanisms involved in human joints. It is concluded that while healthy human joints are lubricated by fluid film action, all current artificial joints at best are lubricated by mixed lubrication and hence wear is taking place throughout the life of the prosthesis. A new concept in artificial joints is described. Soft elastic layers simulate articular cartilage and if selected carefully can develop full fluid film lubrication with consequential low friction and minimal wear.