Simulation of the head-disk interface gap using a hybrid multi-scale method

We present a hybrid multi-scale method that provides a capability to capture the disparate scales associated with modelling flow in micro- and nano-devices. Our model extends the applicability of an internal-flow multi-scale method by providing a framework to couple the internal (small scale) flow regions to the external (large scale) flow regions. We demonstrate the application of both the original methodology and the new hybrid approach to model the flow field in the vicinity of the head-disk interface gap of a hard disk drive enclosure. The internal flow regions within the gap are modelled by an extended internal-flow multi-scale method that utilises a finite-difference scheme for non-uniform grids. Our proposed hybrid multi-scale method is then employed to couple the internal micro-flow region to the flow external to the gap, to capture entrance/exit effects. We also demonstrate the successful application of the method in capturing other localised phenomena (e.g. those due to localised wall heating).     

Hard-particle-induced physical damage and demagnetization in the head-disk interface

Test stand experiments were performed in which 44 μm stainless steel particles and 0.3 μm alumina particles were introduced at the head-disk interface (HDI) of hard disk drives (HDD), and their damage to the HDI was observed and evaluated. An Olympus HDI reliability tester was used to fly the sliders at different radii. Optical microscopy, atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to examine the physical and magnetic conditions of the sliders and the disks after the particle experiments. The results showed that both particle types were able to produce scratches and demagnetization but in very different ways. The alumina particles could become entrapped in the HDI to cause physical damage to both the sliders and disks, whereas the larger stainless steel particles could not get into the HDI. For the alumina particles plastic deformation and high temperatures occur simultaneously to cause demagnetization when a particle-induced scratch is formed. Stainless steel particles can induce high-speed slider/disk contact and physical damage to the slider’s trailing edge through their contributions to flying instability.     

Investigation of thermo-mechanical contact between slider and bit patterned media

Contact between a slider and bit patterned media (BPM) is investigated using finite element analysis. The effect of contact conditions and material properties at the interface between slider and disk on plastic deformation and temperature is studied. In addition, the planarization of bit pattern media on temperature and plastic deformation is investigated for different filler materials. It is found that filler material results in reduction of plastic deformation and temperature.     

Mechanical stability of the interface between a padded slider and magnetic recording disk

Contact state, friction, and meniscus load between a padded slider and a smooth disk are discrete; friction is determined by the number of pads in contact and the meniscus load acting at each pad. By inducing frictional changes through varying sliding direction, we force the slider from one stable state to another and infer which pads are in contact from the corresponding changes in friction. We find the stability of a given contact state is influenced by friction coefficient, pad location, meniscus load, applied mechanical loads and applied moments. A model is proposed to account for these effects.     

Multi-body structural effects on the head-disk interface during operational shocks in hard disk drives

Over the past decades, there has been an increase in the demand for hard disk drives (HDDs) used in mobile computing devices. The work performance of a HDD mainly depends on its ability to withstand external disturbances in such applications. Studies of the HDD’s responses and failures during external shocks can be very beneficial for improving the HDD’s designs. Multi-body operational shock (op-shock) models are developed to study the HDDs’ responses during external shocks. Four models which include different components (a disk, a spindle motor, a base plate, a pivot and a head actuator assembly) are introduced in this study to investigate the effects of various components on the drives’ operating performance. It is found that the models must include certain critical components in order to give results for performance reliability when subjected to operational shocks.     

基于用户界面模型的界面模板

界面模板是一种崭新的界面设计模式，提出了基于界面模型的界面模板概念，在支持界面自动生成的界面开发方法中实现从抽象界面到具体界面的转化。讨论了界面模板的构成与表达、界面模板的分类以及界面模板库体系结构，说明了界面模板的用法。     

修正压力与表面张力计算的两相流 自由界面运动模拟

摘 要：在利用光滑粒子流体幼力学(SPH)方法进行多相流的模拟中,多相流在交界面处由 于密度不连续、粒子界面的压力计算出现误差,出现界面处压力振荡,界面破碎的问题。针对 上述问题,提出了新的压力梯度近似公式和改进的界面处人工斥力公式,使交界面更加清晰、 光滑、无穿透、模拟效果更好。此外,通过给出基于密度权重的色函数计算公式,对大密度比 多相流界面处的表面张力计算公式进行了改进,使得多相流交界面密度过渡更加光滑,模拟效 果更好。最后,通过溃坝、Rayleigh-Taylor 界面不稳定性,非 Boussinesq 锁定交换问题 3 个仿 真实验,得到了不同时刻界面粒子分布图、界面锋面距离等。结果验证了新的压力梯度近似公 式以及界面处人工斥力公式的合理性;通过空气中液滴形成仿真实验,得到了圆形液滴形成的 粒子变化图,结果验证了该改进的表面张力计算方法的有效性。     

Effect of load/unload process on friction/stiction and durability of head-disk interface

 Effect of various operating parameters viz. load/unload speed, disk speed, ramp height, and disk dynamics on load/unload performance, friction/stiction and durability of a head-disk interface (HDI) were studied. Load/unload performance was evaluated using acoustic emission signals and friction force measurements. The load/unload performance was found to be better for higher load/unload durations, lower disk speeds and higher ramp heights. The effect of ramp height was studied for two different slider suspension designs. A slider suspension with `A' type suspension design performed well for higher ramp heights. The slider with `B' suspension design was not affected by a change in ramp height. Disk dynamics studies indicated how strongly HDI can be affected by disk vibrations and supported the effect seen by varying ramp heights. Durability tests revealed that the HDI deteriorated faster for lower ramp heights for a slider with `A' type suspension design than for the slider with `B' type suspension design. Received: 22 February 2002/Accepted: 20 June 2002     

The effect of single- or multiple-layered garments on interface pressure measured at the backpack-shoulder interface

Experiments were aimed at determining whether interface pressure measurements are a true reflection of skin contact pressure when made over different layers of clothing. Interface pressures were recorded at the skin interface and above clothing layers, with 11 participants wearing 10 different clothing combinations. The clothing used was standard issue British military clothing, including body armour (without ballistic plate). Participants wore both single and multiple clothing layers whilst walking on a treadmill carrying a loaded backpack (23.5 kg, British military issue). Results showed no significant differences (p=>0.05) in pressure between different clothing layers either singly, or worn in multiple. In conclusion, the soldier (or leisure user) will gain no or very little relief from applied pressure by wearing garments, even in layers, when carrying a backpack. Also, the findings suggest that interface pressure may adequately be assessed using a sensor placed above the clothing layer(s) rather than at skin surface.     

Touch-down induced contact and friction forces at the dimple/gimbal interface

A dynamic simulation is performed to investigate contact and friction forces at the dimple/gimbal interface. The time history of slider motion, the resultant force as well as the pitch and roll moments acting on the slider are determined. The time-dependent contact and friction forces at the dimple/gimbal interface are obtained. The effect of material properties on contact and friction forces at the dimple/gimbal interface is investigated. Experimental results for touch-down and take-off characteristics are presented.     

基于云模型云滴机制的量子粒子群优化算法

利用云模型云滴的随机性和稳定倾向性的特点,提出了一种云模型云滴机制的量子粒子群优化算法,该算法在量子粒子群优化的基础上,由云模型的X,Y条件发生器产生杂交操作,由基本云发生器产生变异操作,用于求解具有变量边界约束的非线性复杂函数最优化问题。仿真结果表明,该算法具有计算精度较高,搜索速度较快等特点,具有一定的参考和应用价值。     

基于Matlab的接触压力分布测量系统的设计

介绍了一种基于柔性触觉传感器的接触压力分布采集系统和利用Matlab进行系统设计的方法,采集分析系统由柔性触觉传感器阵列、信号处理采集电路和分析软件三部分构成.重点介绍了分析软件对多路传感器数据信号的实时采集、显示、存储,并实现常规文件处理、分布图像绘制等功能的设计.结果表明:系统具有较好的稳定性和分辨率,能够方便地实...     

基于AVR单片机的弓网接触压力检测系统

弓网接触压力作为接触网的重要参数之一,对确保受流质量具有重要意义.针对供电段的实际情况,开发了一套采用AVR作为控制器的接触网弓网压力动态检测系统,实现了弓网压力的检测.设备的使用表明:系统运行稳定,检测效果好、测量数据准确,具有一定的应用前景.     

基于安全性能接口的调度和管理模型研究

以云计算效能提高为目的, 以研究Job调度和资源管理两大决定云计算环境能效的最重要因素为基础, 使用调度和管理对象对作为系统统计信息的参考指标进行采集的方式展开研究。性能代理和服务接口模式(PASI)已经从云环境中采集了原始数据, 通常情况下应用于云的安全技术属于被动防御模式, 如实时动态监控或者深度包检测模式(DPI), 其主要目的是实现动态检测和防御。提出了一个有效的框架以提高云计算中心的综合性能指标, 该架构的建立是基于PASI与DPI相结合的方式, 并且提出了一个基于安全PASI的Job调度和资源管理模型(JDRMSP)。实验结果表明, 该模型有效地提升了云环境的整体运作效能。     

基于混合现实交互界面的下颌运动仿真系统

针对传统医学可视化仿真系统中交互界面和交互技术的缺点,基于视觉跟踪技术采用实物模型设计和实现了一个基于混合现实界面的下颌运动仿真系统。通过对物理界面元素、虚拟界面元素以及交互隐喻的分析,为混合现实环境下的交互技术建立了一个具有通用性的分类体系。物理与虚拟的界面元素之间通过语义映射将用户的操作从物理世界映射到虚拟空间中,从而为用户提供一种更为直观、自然的交互方式。     

基于SPI总线的DSP与音频编解码芯片的接口设计

语音信号处理系统中,DSP与音频编解码芯片存在数据格式与速度不匹配的问题,使接口成为设计的关键。针对该问题提出了一种基于SPI总线的DSP与音频编解码芯片的接口设计方法,介绍了接口的关键组成部分。此方法在FPGA上进行了实现,已应用于SuperV DSP处理器的音频处理系统中。     

基于滑块与矩阵旋转的混沌图像加密算法

针对当前混沌图像加密算法存在的安全缺陷问题,提出了一种基于滑块与矩阵旋转的混沌图像加密算法。在像素位置置乱过程中根据明文图像自身特点,产生与明文图像紧密相关的混沌系统控制参数;旋转图像子矩阵块来打乱整个图像,使所有像素点均匀分布。最后,在像素值替代过程中,利用滑块加密方法,使每一个像素点的加密结果都会影响滑块内的其他若干像素点,从而使加密图像所有像素点的加密结果相互关联,提高了加密图像的安全性。实验仿真结果表明,该加密算法能够有效的抵抗统计特征攻击、差分攻击,具有较高的安全性和良好的加密效果。     

基于BGP路由策略的仿真建模

针对IP网络上存在的“开环路由”问题,给出了相应的BGP路由策略配置。该配置根据BGP的路由决策进程,结合路由图和访问控制列表的使用,来设置相关的路径属性值,从而对出入自治系统的流量加以控制。给出了具体策略的配置步骤,并用OPNET仿真软件建立模型验证了该策略的有效性。     

基于压力模型的柔性物体仿真

现有的方法都不能很好地模拟具有内在体积的柔性物体。针对这种现状,将虚拟气体添加到改进的质点弹簧模型之上。通过内部的气体压力约束及改进的质点弹簧模型的约束实现了对这种柔性物体的模拟。实验表明,该方法真实地模拟了有内在体积的柔性物体,并且具有较强的实时性。