Characterization of light contact in head disk interface with dynamic flying height control

This paper presents an investigation of the light contact in a head disk interface with dynamic flying height control. The touchdown test is conducted for a dynamic flying height control slider and the response is recorded using AE sensor. The bouncing instability and light contacts are observed during thermal actuated touching down process of the slider. The physics-based simulation is conducted to correlate with the experiments, so as to characterize bouncing instability and the factors affecting bouncing instability. The enhanced spectrogram and HHT approaches are used to extract and characterize the non-stationary characteristics of the weak signal of slider response under light contact. It is found that the light contacts are constituted by a series of intermittent transient impact responses with frequency identical to slider??s pitch mode.     

Lubricant bonding, chemical structure, and additive effects on tribological performances at head–disk interfaces

 The lubricant film for head/disk application consists of bonded fraction and unbonded (mobile) fraction. It is well known that the mobile fraction of the lubricant film can replenish the surface sites where the lubricant film was depleted, thus, the surface wear is postponed or alleviated. With a continuous decrease in the head disk spacing, however, too much mobile fraction of lubricant may cause head slider lubricant pick-up, and deteriorate the interface. Two perfluoropolyether (PFPE) lubricants of Z-tetraol and Z-DOL are discussed in this paper. Lubricant Z-tetraol is characteristic of stronger bonding to a carbon overcoat, lower vapor pressure, and higher thermal stability but less mobility than Z-DOL. It is found that, for CSS (contact-start-stop) durability, the interfaces with Z-tetraol show no worse in performance than those with Z-DOL, and less head slider lubricant pick-up on those with Z-tetraol. Based on the above-mentioned, it is possible that the interfaces relying more on the lubricant bonding strength and chemical structure stability are more beneficial to tribological performances than those relying more on the lubricant replenishment. The effects of lubricant additive X1P mixed to Z-tetraol, and Z-DOL, respectively are also studied on tribological performances. Stiction, CSS durability, and head slider lubricant pick-up are discussed among lubricants Z-tetraol, Z-DOL, Z-tetraol/X1P and Z-DOL/X1P. Statistical t-test, F-test, and Weibull analyses are applied to CSS data to differentiate CSS durability performances. Additive X1P is found to enhance CSS durability for both lubricants. Lubricant Z-tetraol/X1P is recommended for the best tribological performances, followed by Z-DOL/X1P, Z-tetraol, and Z-DOL. Received: 7 August 2001/Accepted: 11 December 2001 Authors would like to thank Vidya K. Gubbi, Youmin Liu, and Gunter P. Barth at Seagate, Fremont, CA, for media supplies, lubricant properties, and head slider lubricant pick-up measurements. Authors also thank Gunter P. Bath, Frank Chang, Roger Y. Shih, Hamid R. Saman, Caroline Tjengdrawira and Sam Liang at Seagate for fruitful discussions.     

基于动态调速的定航线飞行冲突探测与解脱

针对同一层空域下的定航线的两架或三架飞行器,提出一种动态调整飞行器飞行速度的方案以避免飞行冲突的发生。当飞行器进入调速区后动态检测各飞行器的位置及相互之间的距离,首先对飞行器和飞行器与航线交叉点之间的距离进行判断,依据判断的结论建立飞行器坐标系,并利用刻画各飞行器间的位置及其变化的一组偏微分方程和优化控制理论对飞行器的速度进行调节。仿真试验结果证明该调速方案是安全的。     

Interactions between nano-spacing flying head sliders and ultra-thin liquid lubricant films with non-uniform distribution in hard disk drives

This paper describes the effect of ultra-thin liquid lubricant films on air bearing dynamics and flyability of less than 10 nm spacing flying head sliders in hard disk drives. In particular, the effect of non-uniform lubricant film distributions on head/disk interface dynamics are studied. The disks with lubricant on one half of disk surface thicker than the other half were used in this study. The dynamics of sliders is monitored using acoustic emission (AE) and the interactions between the slider and disk are investigated experimentally. The disks were also examined with a scanning micro-ellipsometer before and after each test. Complicated slider responses were observed and clarified. In addition, it was found that the periodic lubricant film thickness modulations or non-uniformity caused by the slider-disk contact interactions could be observed. It is suggested that this lubricant film thickness non-uniformity will be one of the technical issues in order to achieve ultra-low head/disk contact interface of less than 10 nm.     

基于Abaqus的光学胶动态力学行为分析

黏胶的动态力学性能对终端产品可靠性的影响越来越重要.基于Abaqus的超弹性和黏弹性的本构模型定义光学胶的动态力学参数,用Abaqus/Explicit对静态压缩和落球试验进行仿真分析,通过与实际试验结果的对比验证仿真分析结果.结果表明,在准静态到高应变率的范围内,采用超弹性和黏弹性的本构模型可以准确描述光学胶的动态力学行为.     

基于多相Mumford-Shah模型最小图分割的视乳头杯盘分割*

为了有效地解决血管遮挡、噪声污染、光照不均、对比度小以及个体间差异大等视乳头图像分割中固有 的难题,提出采用基于图论的多相分段常数水平集ＭｕｍｆｏｒｄＳｈａｈ图像分割模型及其相应的图分割最优化方法。实验表明,该方法能够比经典的多相分段常数水平集ＭｕｍｆｏｒｄＳｈａｈ模型更快更精准地分割青光眼病人视乳头图像中的视杯和视盘形态。     

Effects of disk surface roughness on static flying characteristics of air bearing slider by using a combined method of Reynolds equation and rough disk surface

Reynolds equation was modified with adding the surface roughness parameters to analyze the effects of disk surface roughness on the static flying characteristic of an air bearing slider. However, the modification demands the complicated mathematical expressions and related knowledge of physics and mathematics. In this paper, a combined method of Reynolds equation without introducing the roughness parameters and rough disk surface is proposed to investigate the effects of disk surface roughness on the static flying characteristics of an air bearing slider, it is different from those models of modified Reynolds equation introducing the disk surface roughness used by many researchers. More importantly, this method avoids the complicated numerical calculation resulted from the mathematical expressions including the Peklenik parameter \(\gamma\) and roughness R_a. By using an Ω air bearing slider, we investigated the effects of disk surface roughness on the static flying characteristics of this slider, the results show that the Peklenik parameter \(\gamma\) and roughness R_a have a significant influence on the pressure distribution, the load carrying capacity and the location of the pressure centre.     

Static and dynamic flying characteristics of a slider on bit-patterned media (dynamic responses based on frequency domain analysis)

Recording media with grooves, such as discrete track media (DTM) and bit-patterned media (BPM), are considered to be promising media for achieving ultrahigh recording densities. It is thus important to analyze the static and dynamic characteristics of flying head sliders on DTM and BPM using the molecular gas film lubrication equation and the van der Waals (vdW) equation. In this study, we consider BPM with rectangular bits. We express the disk recess as a Fourier series and determine the quasi-static and time-dependent components. We also develop a perturbation method for small groove depths for calculating static slider attitudes and dynamic responses in the frequency domain. The numerical results predict that the grooves will significantly reduce the quasi-static flying height h ₀. They also predict that for a small groove depth h _groove, flying height decrease Δh ₀ almost agree with the value of uniform disk recess obtained by a Fourier series expansion, which also agrees with empirical results. Dynamic slider characteristics obtained by the frequency domain analysis is useful for sliders suffering from excitations of several tens of kHz such as sliders flying at transition between data zone and servo zone, although the dynamic spacing fluctuation by realistic BPM media is negligible.     

高端磁盘阵列马尔科夫过程可靠性模型研究

介绍了基于马尔科夫过程的磁盘阵列典型模型,分析了典型模型中存在的不足。依照海量存储系统中磁盘阵列工作的特点,结合蒙特卡罗方法,引入新的状态和参数,对基于马尔科夫过程的磁盘阵列可靠性计算模型进行改进,使可靠性数值更接近实际情况。     

An event-based model for continuous media data on heterogeneous disk servers

Over the last few years, there has been intense work on the problem of retrieval of continuous media (CM) data from disk. However, no single unified framework exists within which such retrieval problems can be studied. In this paper, we first propose a formal model for CM data retrieval from heterogeneous disk servers. This model can be used to characterize CM data retrieval problems independently of how data is laid out on disk, and what objectives (e.g., minimize client delay, maximize buffer utilization, etc.) the system manager is interested in. We then show how using this formal model, we can neatly define what it means to optimally handle events that occur in movie-on-demand (MOD) systems. Examples of such events include new clients entering the system, old clients leaving the system, continuing clients doing pause, rewind and fast-forward operations. Multiple events may occur simultaneously and we show how such events trigger state transitions in the system. We then develop an algorithm called the QuickSOL algorithm that handles events occurring in MOD systems. This algorithm works in two phases: in the first phase, it quickly finds a way of handling as many of the events occurring at time t as possible. In the second phase, it optimizes the solution found in the first phase. The advantage is that the algorithm can be interrupted anytime after the first phase is completed. We report on experiments showing that QuickSOL works well in practice.     

A graphical editor and process visualization system for man-machine interfaces of dynamic systems

The process visualization system of a manmachine interface is presented. It allows human operator(s) to interact with a dynamic technical system, here a thermal power plant. Also, a graphical editor for designing dynamic pictures of the process visualization system is explained. Both new systems have a common architecture and are based on the computer graphics standard PHIGS-2D with extensions for handling non-graphical and graphical information. The hierarchical information structures are manipulated with lists and pointers in a dynamic visual database. The two menu-driven interfaces for designers and for operators are described with their multi-window display layouts. The software of both systems is highly portable to different hardware and to other application domains.     

The dimensional effects of windowing on crosstalk for high speed hard disk drive interconnects

As the areal density rapidly changes, the signal reflection increases. In order to avoid the reflection between a magnetic recording head and a read/write driver on hard disk drive interconnects (HDDIs), the windowing technique is used to keep low insertion loss and it causes the higher crosstalk between lines. In this work, the crosstalk on idealized HDDI with windowing is investigated. The crosstalk represented by the scattering parameters calculated by using the full wave simulation software based on finite integral technique. From the results, the improvement of insertion loss and transmission bandwidth (?3 dB bandwidth) can be found when the window percentage is increased. For the 90% windowed structure, these are improved as 4.27 dB at 1 GHz and 4.53 GHz comparing with the conventional structure, respectively. Besides, the crosstalk increases with the increasing of window percentage. However, it can be suppressed up to 5.68 dB in a range of 0.24–1 GHz when the window percentage is 90%. Furthermore, the 90% of windowed structure with 8 mm window pitch possess the lowest crosstalk about 30.22 dB in a range of 0.32–6.4 GHz. In addition, the placing position of windows in a reference plane with a half of the rest length at both ends should be avoided because it increases both crosstalk and insertion loss. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:217–222, 2014.     

运动声阵列跟踪系统坐标模型研究

为了研究运动声阵列跟踪系统的非线性及坐标模型之间的耦合问题,设计了三维运动声阵列的结构模型,分析了声阵列跟踪系统的状态参数;建立了运动声阵列系统的坐标模型,讨论了坐标模型之间的转换关系,确定了输出声阵列观测信息的坐标模型;以目标在匀加速及匀速转弯状态下,建立了运动声阵列笛卡尔坐标模型,分析了模型的非线性因素;基于状态空间的变换方法,建立了运动声阵列的修正极坐标模型,为进一步研究运动声阵列跟踪系统的跟踪算法奠定了理论基础。     

A novel method based on realistic head model for EEG denoising

It is necessary to remove the noise in EEG before further EEG analysis and processing. For EEG is deeply masked in the noise background, it is very difficult to denoise EEG effectively. Proposed in this paper is a novel realistic head model based sparse decomposition algorithm to denoise EEG, which is an iterative procedure combining the subject's physiology of EEG generation into the denoising procedure. In this algorithm, the lead field overcomplete dictionary is numerically calculated according to the realistic head model firstly, and then the instantaneous EEG spatial potential is decomposed into one sparse combination of atoms in the lead field matrix by matching pursuit, and the sparse combination of atoms is to be regarded as the denoised EEG signal. The realistic head based sparse decomposition was tested by the simulated noisy potential and a real EEG recording collected in an oddball stimulus experiment, the results consistently confirmed the new method removed the uncorrelated noise in EEG effectively.     

Some effects of menu characteristics and user personality on performance with menu-driven interfaces

User performance with menu-based systems was studied. Three experiments concerning the effects of menu structure, menu breadth, menu system depth, several support facilities and user personality characteristics on user performance, measured in terms of search time and accuracy, are reported. The main findings are that performance is affected by menu structure, the depth of the menu system, the presence of escape facilities, the structure of the alternatives within the menu, some methods of informative support and certain personality characteristics. Some expensive support facilities are found to have no effect. The results are discussed in relation to problems of menu interface design.     

To model objects in information systems and user interfaces: implications for object-oriented methods

Abstract. A general way of contrasting the object-oriented to the function-oriented approach, called 'object-order' and 'function-order', is proposed in this paper. In addition, when modelling information systems, there is a third principle of ordering, 'subject-order'. Object and function-order are used to define the two approaches to modelling information systems and in human-computer interaction, in ways that are compatible to the corresponding distinction in programming. The conditions for selecting either of the two approaches are, however, not discussed here.
By means of an object-ordered method, e.g. Jackson System Development (JSD), an object-ordered model is produced, and the user interface that can be derived from the model is object-ordered too. However, other guidelines in JSD support subject-order. A function-ordered interface can be derived from the subject-ordered model. A computer system designed by means of an object-organized method may therefore obtain an interface that is partially object-ordered and partially function-ordered. Other object-oriented methods give guidelines for designing function-oriented interfaces without relating these guidelines to the model.
The system designer may benefit from having three principles of ordering when modelling a system. However, a user may be confused by an interface that sometimes gives preference to objects, sometimes to functions.     

Psychologically inspired anticipation and dynamic response for impacts to the head and upper body

We present a psychology-inspired approach for generating a character' s anticipation of and response to an impending head or upper body impact. Protective anticipatory movement is built upon several actions that have been identified in the psychology literature as response mechanisms in monkeys and in humans. These actions are parameterized by a model of the approaching object (the threat) and are defined as procedural rules. We present a hybrid forward and inverse kinematic blending technique to guide the character to the pose that results from these rules while maintaining properties of a balanced posture as well as characteristics of the behavior just prior to the interaction. In our case, these characteristics are determined by a motion capture sequence. We combine our anticipation model with a physically-based dynamic response to produce animations where a character anticipates an impact before collision and reacts to the contact, physically, after the collision. We present a variety of examples including threats that vary in approach direction, size and speed.     

基于云模型的虚拟人摇头动作不确定性控制*

以虚拟人摇头表达否定性信息为例,设计了最大摇头角否定云、摇头次数否定云和摇头速度否定云。分别运用正向云生成算法产生云滴,获得摇头动作序列的最大摇头角度、摇头次数和摇头速度。三个控制参数均以各自的期望值为中心正态分布。仿真实验表明,所提出的基于云模型的虚拟人摇头控制算法能够产生呈规律性差异的摇头动作序列控制曲线。给出了三类云模型数字特征的建议值。     

基于动态P模型的GMM-FBG电流传感器磁滞建模

针对现有GMM-FBG电流传感器的磁滞非线性问题,在经典Preisach模型的基础上提出了一种改进的Preisach磁滞模型,给出了改进后的Preisach模型密度函数和模型分析方程,对频率依赖的模型参数进行辨识,提高了模型对动态磁滞曲线的预测精度;并运用改进后的模型对GMM-FBG电流传感器进行磁滞建模及实验验证。实验结果表明该模型能够较好的预测GMM-FBG工频电流传感器的磁滞非线性,模型的预测误差在3.6%以内,传感系统电流测量灵敏度可达到0.069 nm/A。