Trajectory design considering derivative of jerk for head-positioning of disk drive system with mechanical vibration

In this paper, we propose a novel design method of target trajectory for high-speed and high-precision head positioning of a hard disk drive (HDD) system. To realize smooth acceleration and deceleration, the derivative of jerk is considered not to activate any mechanical vibrations. We applied the well-known optimal control theory to fix the initial and terminal conditions. Moreover, we show that various performances can be improved by introducing time-varying weighting coefficients. Some experimental results using a 2.5-in HDD are shown to verify the effectiveness of the proposed method.     

竞走运动员运动训练计划管理系统的设计与开发探究

随着我国经济和科技的快速发展,现代信息化技术的应用已经深入到了社会上的各个领域。在竞走运动员训练计划中建立信息化管理系统是信息化时代发展的必然需求,也是科学化、合理化运动员运动训练计划的制定。使得运动员的运动潜力得到挖掘和激发,使得运动员的竞技水平能够在比赛中得到有效的发挥。     

基于OMAP3530的视频监控客户端设计与实现

本设计基于OMAP3530处理器的开发平台设计视频监控客户端。该客户端通过SIP协议和服务器端通信。视频监控客户端在OMAP3530开发板实现,其ARM端完成客户端呼叫,建立与视频服务器连接,音视频数据流接收、播放和存储等功能,其DSP端完成解码器实时实现。设计重点为客户端oRTP和eXosip库的移植、监控界面的设计和H.264解码器实时实现。     

SiC及其功率器件的激光制孔研究进展

SiC作为第三代半导体材料的典型代表,因具有优异的物化性能,在功率器件领域具有极大的应用前景.文章简要介绍了激光制孔的基本原理,综述了 SiC的长脉冲与超短脉冲激光制孔研究进展,对比了长脉冲与超短脉冲激光的加工特点,分析了不同脉冲宽度下SiC的制孔效果.同时,介绍了 GaN/SiC,AlGaN/GaN/SiC等SiC功率器件的激光制孔研究现状.最后,指出了 SiC及其功率器件激光制孔面临的挑战,并展望了未来的发展方向.     

A Bi‐Lineage Conducive Scaffold for Osteochondral Defect Regeneration

Because cartilage and bone tissues have different lineage‐specific biological properties, it is challenging to fabricate a single type of scaffold that can biologically fulfill the requirements for regeneration of these two lineages simultaneously within osteochondral defects. To overcome this challenge, a lithium‐containing mesoporous bioglass (Li‐MBG) scaffold is developed. The efficacy and mechanism of Li‐MBG for regeneration of osteochondral defects are systematically investigated. Histological and micro‐CT results show that Li‐MBG scaffolds significantly enhance the regeneration of subchondral bone and hyaline cartilage‐like tissues as compared to pure MBG scaffolds, upon implantation in rabbit osteochondral defects for 8 and 16 weeks. Further investigation demonstrates that the released Li+ ions from the Li‐MBG scaffolds may play a key role in stimulating the regeneration of osteochondral defects. The corresponding mechanistic pathways involve Li+ ions enhancing the proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs) through activation of the Wnt signalling pathway, as well as Li+ ions protecting chondrocytes and cartilage tissues from the inflammatory osteoarthritis (OA) environment through activation of autophagy. These findings suggest that the incorporation of Li+ ions into bioactive MBG scaffolds is a viable strategy for fabricating bi‐lineage conducive scaffolds that enhance regeneration of osteochondral defects.     

PID Controller Design for MIMO Processes Using Improved Particle Swarm Optimization

This paper aims at the PID control system design for multivariable input and multivariable output (MIMO) processes. An improved version of a particle swarm optimization (PSO) algorithm is utilized to design PID control gains in MIMO control systems. In addition to the individual best and the global best particles, the velocity updating formula of the developed algorithm includes a new factor, the best particle of each sub-population, to enhance the search capacity. Based on the improved particle swarm optimization (IPSO), a complete design strategy is proposed for MIMO PID control systems. All control gains will be evolved to the optimal values by minimizing the system performance criterion. To show the efficiency of the proposed design method, a multivariable chemical process system with two inputs and two outputs is illustrated. Some experiment results, including different algorithm parameter settings and comparisons with other methods, are given. Numerical simulations indicate that the proposed method is superior to other optimal methods.     

PSO Assisted DD-ESB Beamforming with Robust Capabilities

This paper deals with adaptive array beamforming based on the decision-directed eigenspace-based (DD-ESB) technique with robust capabilities. It has been shown that DD-ESB adaptive beamformer demonstrates the advantages of better output signal-to-interference plus noise ratio performance and less sensitivity to pointing error over conventional ESB beamformers without any specific training bits. In conjugation with particle swam optimization assisted scheme to obtain more correct desired user’s transmitted bits from the output of the ESB, the more correct steering vector of the desired user can be reconstructed for DD-ESB adaptive beamforming in the presence of larger pointing error and relatively low interference-to-noise ratio. Computer simulations are provided to illustrate the effectiveness of the proposed approach.     

Investigation of Sn Whisker Growth in Electroplated Sn and Sn-Ag as a Function of Plating Variables and Storage Conditions

Sn whiskers are becoming a serious reliability issue in Pb-free electronic packaging applications. Among the numerous Sn whisker mitigation strategies, minor alloying additions to Sn have been proven effective. In this study, several commercial Sn and Sn-Ag baths of low-whisker formulations are evaluated to develop optimum mitigation strategies for electroplated Sn and Sn-Ag. The effects of plating variables and storage conditions, including plating thickness and current density, on Sn whisker growth are investigated for matte Sn, matte Sn-Ag, and bright Sn-Ag electroplated on a Si substrate. Two different storage conditions are applied: an ambient condition (30°C, dry air) and a high-temperature/high-humidity condition (55°C, 85% relative humidity). Scanning electron microscopy is employed to record the Sn whisker growth history of each sample up to 4000 h. Transmission electron microscopy, x-ray diffraction, and focused ion beam techniques are used to understand the microstructure, the formation of intermetallic compounds (IMCs), oxidation, the Sn whisker growth mechanism, and other features. In this study, it is found that whiskers are observed only under ambient conditions for both thin and thick samples regardless of the current density variations for matte Sn. However, whiskers are not observed on Sn-Ag-plated surfaces due to the equiaxed grains and fine Ag₃Sn IMCs located at grain boundaries. In addition, Sn whiskers can be suppressed under the high-temperature/high-humidity conditions due to the random growth of IMCs and the formation of thick oxide layers.     

基于短波宽带接收机的并行电离层

提出了一种新的电离层探测方法,不同于传统的串行探测方式,该方法利用短波宽带接收机并结合软件无线电技术,实现了同时对多个电离层信道进行并行探测,大大的缩短了整个短波波段扫频探测的时间,拓宽了电离层探测在一些实时性要求高的场合中的应用.