Identification of contact bouncing vibrations using TFC active slider and adaptive fuzzy control for advanced active slider design

The recent advance of magnetic storage technology includes the active thermal fly-height control (TFC) technique that is able to reduce the clearance between read/write heads and disk surface to be of few nanometers. However, it has been estimated that TFC technique alone cannot provide the even smaller clearances necessary to achieve Tbit/in² recording densities due to the presence of bouncing vibrations and instability. In this work we investigate hybrid active slider technique with both thermal and piezoelectric actuators to achieve extremely high-density recording. The nonlinear system dynamics of thermal actuated slider is established by test-based identification. We propose an adaptive fuzzy control hybrid active slider design in which piezoelectric actuation is added to the existing thermal actuated slider design, so as to fully eliminate the high frequency bouncing vibrations. It can yield more than Tbit/in² recording density with sub-nanometer level clearance, while using the state-of-the-art and matured manufacturing techniques for active piezoelectric slider and TFC slider.     

Visualization of lubricant pickup phenomena by lubricant thickness mapping on slider surface

A slider surface analyzing tester was developed to observe the lubricant thickness distribution on a slider surface by interferometry. We observed three phenomena related to lubricant pickup by the slider. The picked-up lubricant gathered around the boundary of the pad and recess area during the unloading interval, and the gathered lubricant flowed to the trailing edge of the pad after loading on the disk surface. There were two lubricant flows on the pad surface. The first was a circulation flow from the dynamic flying height protrusion area to the leading edge of the pad. The second was a circulation flow from the lubricant pool to the leading edge of the pad. Lubricant dewetting occurred on the slider pad surface when a thick layer of lubricant was adhered to the pad surface.     

Ellipsometric measurement accuracy of ultrathin lubricant thickness on magnetic head slider

The quantitative analysis of lubricant transferred from disk to slider is important in understanding the interaction in head-disk interface and designing a stable head-disk system. When applying ellipsometric technology to determine the lubricant thickness on slider, the measurement accuracy is of concern due to the location-to-location variations of slider optical constants. This paper carried out a systematic and quantitative study on how the variations of slider optical constants affect the measurement accuracy of lubricant thickness. In this study, the distribution of slider optical constant was obtained; a differential method was used to calculate the uncertainty in lubricant thickness and the calculated results were experimentally verified. The results show that for the state-of-art sliders, the uncertainty in lubricant thickness is about 20?% for below 2?nm thicknesses and less than 15?% for around 3?nm thicknesses when measured at 632.8?nm wavelength. The results of this study might be also useful for the other optical instruments used to determine the amount of the transferred lubricant.     

Reduction in lubricant pickup by bias voltage between slider and disk surfaces

We studied the effect of bias voltage between slider and disk surfaces to reduce lubricant pickup by the slider. A perfluoropolyether (PFPE) lubricant film, which is coated on the disk surface, has been considered to be charged to a negative voltage by the airflow on the rotational disk surface. Because the PFPE lubricant film is negatively charged, the lubricant pickup should be reduced by a bias voltage with a negative voltage on the slider surface. We confirmed changes in the lubricant pickup in a lubricant pickup test conducted at different bias voltages. A positive voltage of the slider accelerated the lubricant pickup, whereas a negative voltage reduced it.     

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.     

Experimental study on slider dynamics during touchdown by using thermal flying-height control

To investigate the possibility of further lowering the clearance in head?Cdisk interface systems, slider dynamic behavior during a touchdown sequence with a thermal flying-height control (TFC) function was investigated by using a spinstand-level evaluation utilizing an acoustic emission (AE) sensor and a laser Doppler vibrometer (LDV). Experimental results demonstrated that off-track vibration was easier to excite by head?Cdisk contact at the beginning of head?Cdisk contact. We then confirmed that the amplitude of pitch-mode vibration in the flying-height direction increased and sway-mode vibration in the off-track direction decreased when increasing heater power during the touchdown sequence. Moreover, we found that the peak frequency of pitch-mode vibration shifted to a higher frequency under over-push conditions. Time?Cfrequency domain analysis results showed that the peak shift occurred at several locations during a disk rotation. The mechanism of the peak shift is attributed to the increase in stiffness at the head?Cdisk interface (HDI) due to solid?Csolid contact or mode change occurred in such regions. During the touchdown sequence, the friction force at the HDI continues to increase, even though slider vibration and AE signal decrease when heater power is increased. The friction force at the HDI needs to be decreased to achieve further low-clearance HDI.     

Asymmetric transfer in within-subjects experiments on stress interactions

A comparison is made between the results of three similar within-subjects experiments on mild heat paired respectively with the arouser low-frequency noise, and with the depressants 1?mg of l-hyoscine hydrobromide, and the loss of one full night of sleep. The comparison shows that the level of performance in the control condition of a within-subjects experiment may depend upon the nature of the second stress. Bias in the results of the control condition may produce a reliable main effect, or change the sign of a main effect from positive to negative. The direction of transfer between the conditions of a within-subjects experiment may be positive or negative, depending upon the order of presentation of the conditions. The sign of the interaction between two stresses may reverse between the first and second halves of the experiment. The reliable main effects may be quite different from those of a comparable separate-groups design. Thus the transfer bias should always be measured in a within-subjects design. This can be done using separate groups.     

Contact force detection on a minute aperture mounted optical contact slider using an acoustic emission sensor

Advances in the digital network society require both higher density and higher transfer rates in all sorts of storage systems. Especially in optical recording, the trend toward higher density and larger capacity requires novel surface-recording technologies that can drastically diminish head-to-medium spacing, resulting in an improvement in spatial resolution and, finally, a higher recording density. To this end, we have already proposed a novel contact optical head slider that is able to almost cancel the suspension load by generating hydrodynamic pressure, thus realizing a lower net contact force. Evaluating the dynamic contact force is requisite in realizing its stable sliding operation and higher signal readout performance. In this study, a continuous acoustic emission (AE) signal was utilized to detect the dynamic contact force. AE signal modulation was compared with the applied out-of-plane acceleration on a medium generated by a spindle combined piezo-electric actuator. It was clarified that the detected AE modulation amplitude was approximately proportional to the applied acceleration, and that utilizing AE modulation will be a useful method for evaluating dynamic contact force.     

Experiments on manipulator gross motion using self-tuning controller and visual information

A picture of a scene is used to extract information for an adaptive control algorithm. The object of interest is first located by means of a classifier. The position and orientation of the object are determined from a binary picture. The desired path that the gripper of the manipulator is to follow is specified by discrete points, first in the Cartesian and then in the joint coordinate system. The adaptive self-tuning controller is outlined. The controller design is based on a time series difference equation model in which the parameters are estimated on-line. The gains of the controller are tuned so that a quadratic performance criterion is minimized. The performance of the system designed is then tested experimentally, and the results are presented.     

Tribological testing of sliders on discrete track media and verification with numerical predictions

“Flyability” tests were conducted with sliders designed for discrete track recording disks. Laser Doppler vibrometry and acoustic emission were used to characterize the dynamics of the sliders as a function of discrete track parameters. Lubricant depletion was observed depending on the slider nominal flying height. Comparison of experimental results with numerical predictions showed good qualitative agreement.     

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。     

Experiments on estimating egomotion and structure parameters using long monocular image sequences

This paper presents a simple but robust model based approach to estimating the kinematics of a moving camera and the structure of the objects in a stationary environment using long, noisy, monocular image sequences. Both batch and recursive algorithms are presented and the problem due to occlusion is addressed. The approach is based on representing the constant translational velocity and constant angular velocity of the camera motion using nine rectilinear motion parameters, which are 3-D vectors of the position of the rotation center, linear and angular velocities. The structure parameters are 3-D coordinates of the salient feature points in the inertial coordinate system. Due to redundancies in parameterization, the total number of independent parameters to be estimated is 3M+7, whereM is the number of feature points. The image plane coordinates of these feature points in each frame are first detected and matched over the frames. These noisy image coordinates serve as the input to our algorithms. Due to the nonlinear nature of perspective projection, a nonlinear least squares method is formulated for the batch algorithm, and a conjugate gradient method is then applied to find the solution. A recursive method using an Iterated Extended Kalman Filter (IEKF) for incremental estimation of motion and structure is also presented. Since the plant model is simple in our formulation, closed form solutions for the state and covariance transition equations are easily derived. Experimental results for simulated imagery as well as several real image sequences are included.The support of the Advanced Research Projects Agency (ARPA order No. 8459), the U.S. Army Topographic Engineering Center under contract DACA 76-92-C-0009, and the Department of Electrical Engineering at the University of Maryland is gratefully acknowledged.     

Experiments on semantic interoperability of agent reputation models using the SOARI architecture

In the last decades, we have experienced a rapid increase in the number of available online e-services. Agent-based computing has been advocated as a natural computational model to automate the interaction with those services, thus enabling the formation of multiagent systems. In these latter, agents may use trust and reputation as the main control mechanism and they usually exchange such information in order to accelerate reputation evaluation. However, due to the semantic heterogeneity of the different reputation models, agents interaction about reputation has to deal with interoperability issues. Therefore, this paper presents some experiments using SOARI, an architecture that enables the semantic interoperability among agents that have heterogeneous reputation models. Such experiments were conducted using two reputation testbeds and three agent reputation models in order to analyze the accuracy of the agents reputation evaluation in the presence of a more expressive communication apparatus, as well as the effect of the heterogeneity among reputation models on this accuracy.     

Experiments on the evaluation of functional ranges using a random interval arithmetic

A software tool using standard and special interval arithmetic operations together with an idea which is developed in the discrete stochastic arithmetic (DSA) approach for round-off error evaluation is proposed in this paper for a statistical computation of functional ranges. The CESTAC method is a Monte Carlo method which uses DSA and provides the accuracy on any computed result with a high probability. On the other hand, interval computation gives a guaranteed interval containing the result but this interval may be in some cases useless because much too wide. Here it is proposed to combine both approaches to obtain a smaller but only highly probable interval containing the range of a rational function for given interval data. Various numerical experiments are given.     

Experiments on six commercial TCP implementations using a software fault injection tool

TCP, the de facto standard transport protocol in today's operating systems, is a very robust protocol that adapts to various network characteristics, packet loss, link congestion, and even significant differences in vendor implementations. This paper describes a set of experiments performed on six different vendor TCP implementations using ORCHESTRA, a tool for testing and fault injection of communication protocols. These experiments uncovered violations of the TCP protocol specification, and illustrated differences in the philosophies of various vendors in their implementations of TCP. The paper summarizes several lessons learned about the TCP implementations through these experiments. © 1997 John Wiley & Sons, Ltd.     

Effect of thermal pole tip protrusion and disk roughness on slider disk contacts

Ultra-high areal density for hard disk drives requires a stable head disk interface at a flying height lower than 8 nm. At such a low flying height, small flying height variations may cause slider/disk contacts. Slider/disk contacts can also occur when a write-current is applied to the write coil since the flying height between slider and disk can be affected by the thermal expansion of the pole tip. In this paper, we investigate the vibration characteristics of sliders during thermally induced contacts using laser Doppler vibrometry. We perform a parametric study of contact events using disks with different surface roughness and lubricant thicknesses, and analyze the slider motion statistically. For a given write current, we observe that the slider vibrations increase with disk roughness and lubricant thickness.     

Activity recognition using eye-gaze movements and traditional interactions

The need for intelligent HCI has been reinforced by the increasing numbers of human-centered applications in our daily life. However, in order to respond adequately, intelligent applications must first interpret users’ actions. Identifying the context in which users’ interactions occur is an important step toward automatic interpretation of behavior. In order to address a part of this context-sensing problem, we propose a generic and application-independent framework for activity recognition of users interacting with a computer interface. Our approach uses Layered Hidden Markov Models (LHMM) and is based on eye-gaze movements along with keyboard and mouse interactions. The main contribution of the proposed framework is the ability to relate users’ interactions to a task model in variant applications and for different monitoring purposes. Experimental results from two user studies show that our activity recognition technique is able to achieve good predictive accuracy with a relatively small amount of training data.     

Magnetic source impact on nanofluid heat transfer using CVFEM

Influence of variable magnetic field on Fe₃O₄–H₂O heat transfer in a cavity with circular hot cylinder is investigated. Innovative numerical method is chosen, namely CVFEM. The effects of radiation parameter, Rayleigh and Hartmann numbers on hydrothermal characteristics are presented. Results indicated that Lorentz forces cause the nanofluid motion to decrease and augment the thermal boundary layer thickness. Temperature gradient augments with augmentation of radiation parameter, Rayleigh number, but it reduces with augmentation of Lorentz forces.