Download or read book A Study of Rarefied and Contact Air Bearing Modeling for Hard Disk Drives Using the Direct Simulation Monte Carlo Method written by Weidong Huang and published by . This book was released on 1998 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book American Doctoral Dissertations written by and published by . This book was released on 1998 with total page 784 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1999 with total page 700 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rarefied Gas Dynamics written by Ching Shen and published by Springer Science & Business Media. This book was released on 2006-03-30 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamics is a science engaged in the investigation of the motion of air and other gases and their interaction with bodies, and is one of the most important bases of the aeronautic and astronautic techniques. The continuous improvement of the configurations of the airplanes and the space vehicles aid the constant enhancement of their performances are closely related with the development of the aerodynamics. In the design of new flying vehicles the aerodynamics will play more and more important role. The undertakings of aeronautics and astronautics in our country have gained achievements of world interest, the aerodynamics community has made outstanding contributions for the development of these undertakings and the science of aerodynamics. To promote further the development of the aerodynamics, meet the challenge in the new century, summary the experience, cultivate the professional personnel and to serve better the cause of aeronautics and astronautics and the national economy, the present Series of Modern Aerodynamics is organized and published.

Download or read book Parallel Direct Simulation Monte Carlo DSMC Methods for Modeling Rarefied Gas Dynamics written by Cheng-Chin Su and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Lubrication and Tribology written by Robert W. Bruce and published by CRC Press. This book was released on 2012-07-06 with total page 1173 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the publication of the best-selling first edition, the growing price and environmental cost of energy have increased the significance of tribology. Handbook of Lubrication and Tribology, Volume II: Theory and Design, Second Edition demonstrates how the principles of tribology can address cost savings, energy conservation, and environmental protection. This second edition provides a thorough treatment of established knowledge and practices, along with detailed references for further study. Written by the foremost experts in the field, the book is divided into four sections. The first reviews the basic principles of tribology, wear mechanisms, and modes of lubrication. The second section covers the full range of lubricants/coolants, including mineral oil, synthetic fluids, and water-based fluids. In the third section, the contributors describe many wear- and friction-reducing materials and treatments, which are currently the fastest growing areas of tribology, with announcements of new coatings, better performance, and new vendors being made every month. The final section presents components, equipment, and designs commonly found in tribological systems. It also examines specific industrial areas and their processes. Sponsored by the Society of Tribologists and Lubrication Engineers, this handbook incorporates up-to-date, peer-reviewed information for tackling tribological problems and improving lubricants and tribological systems. The book shows how the proper use of generally accepted tribological practices can save money, conserve energy, and protect the environment.

Download or read book A Study Into Validating a Coupled Method of Characteristics and Direct Simulation Monte Carlo Method Against Empirical Data written by Andrew D. Brown and published by . This book was released on 2020 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The following will outline the methodology and results of validating a coupled Method of Characteristics (MOC) and Direct Simulation Monte Carlo (DSMC) method. This research focused specifically on modeling plume impingement, induced by Reaction Control System (RCS) thrusters that flew on the National Aeronautics and Space Administration’s (NASA’s) space shuttle Discovery. For each simulation, the continuum portion of the RCS thruster was simulated using MOC for solving hyperbolic Partial Differential Equations (PDEs) and computed with the NASA code, Reacting and Multi-phase Program (RAMP). The solution was then implemented as a starting condition into the NASA DSMC code, Direct Simulation and Monte Carlo Analysis Code (DAC). Typically, DSMC models rely on code-to-code validation for fidelity.

Download or read book Tribological Study of Contact Interfaces in Hard Disk Drives written by Youyi Fu and published by . This book was released on 2016 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: To achieve an areal density of 1 terabits per square inch (1.55 gigabits/mm2) in hard disk drives, the size of magnetic grains in hard disks has been reduced to approximately 7 nm and the spacing between the magnetic head and the disk has been minimized to 1 to 2 nm. At a spacing on the order of 1 to 2 nm between the head and the disk, it is likely that contacts between the magnetic head and the disk occur during reading and writing, causing erasure of data or even failure of the head/disk interface. Wear particles can be generated as a consequence of contacts between slider and disk, and if particles enter the head/disk interface, catastrophic failure of the head/disk interface can occur. To reduce the generation of wear particles and avoid failure of the head/disk interface, it is important to investigate how the tribological performance of all contact interfaces in hard disk drives can be improved. In this dissertation, the tribological performance of the most important contact interfaces in a hard disk drive are investigated with a focus on the generation of wear particles and lubricant migration. First, fretting wear is investigated to study the effect of a diamond-like carbon (DLC) overcoat on wear of the dimple/gimbal interface. A numerical simulation model based on finite element analysis was developed to explain the experimental results. Then, lubricant migration on the air bearing surface and its effect on the head medium spacing (HMS) was investigated as a function of temperature, slider position, and "parking time" of the slider on the ramp. Thereafter, the thermal response of a thermal sensor during contact with asperities on the disk surface was analyzed. The effects of experimental and environmental conditions on the resistance change of the sensor were studied. Finally, experimental and numerical investigations were performed to analyze contact between the suspension lift tab and the ramp in hard disk drives. The voice coil motor current was used to characterize the change of the friction force and the generation of wear debris at the lift tab/ramp interface during load/unload testing. Numerical simulations were performed to analyze how to reduce contact stress between the lift-tab and the ramp. The results of this dissertation will be helpful in improving the tribological performance of hard disk drives.

Download or read book Rare Event Simulation using Monte Carlo Methods written by Gerardo Rubino and published by John Wiley & Sons. This book was released on 2009-03-18 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a probabilistic model, a rare event is an event with a very small probability of occurrence. The forecasting of rare events is a formidable task but is important in many areas. For instance a catastrophic failure in a transport system or in a nuclear power plant, the failure of an information processing system in a bank, or in the communication network of a group of banks, leading to financial losses. Being able to evaluate the probability of rare events is therefore a critical issue. Monte Carlo Methods, the simulation of corresponding models, are used to analyze rare events. This book sets out to present the mathematical tools available for the efficient simulation of rare events. Importance sampling and splitting are presented along with an exposition of how to apply these tools to a variety of fields ranging from performance and dependability evaluation of complex systems, typically in computer science or in telecommunications, to chemical reaction analysis in biology or particle transport in physics. Graduate students, researchers and practitioners who wish to learn and apply rare event simulation techniques will find this book beneficial.

Download or read book Numerical and Experimental Investigation of the Load unload Behavior of Subambient Pressure Hard Disk Drive Sliders written by Stefan Weissner and published by . This book was released on 2001 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Parallel Direct Simulation Monte Carlo DSMC Methods for Modeling Rarefied Reactive and Non reactive Hypersonic Flow written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Investigation of Operational Shocks and Vibrations in Mobile Hard Disk Drives written by Rahul Rai and published by . This book was released on 2011 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last decade, there has been a continuous increase in the demand of hard disk drives (HDDs) for the mobile applications. In such devices, HDDs are often subjected to mechanical shocks and vibrations. Such external disturbances can degrade the read/write (R/W) performance of mobile drives and in extreme cases it can even cause the loss of stored magnetic information. Hence the ability of the head-disk interface (HDI) to withstand such excitation becomes critical in determining the reliability of a mobile disk drive. This dissertation presents a simulation method to accurately model the response of a mobile HDD to external disturbances which can aid the design process. A numerical investigation was conducted on a 2.5 inch form factor laptop drive to understand the dynamics of the HDI during dynamic events such as operational shocks. A detailed model for the mobile disk drive was developed which includes a spinning disk, a fluid dynamic bearing (FDB) based spindle motor, a base plate and an actuator. The behavior of the HDI subjected to various disturbances was determined by solving a fluid-structure interaction problem in which a spinning disk and a head (slider) were coupled through an air bearing. Case studies were conducted to determine the effect of parameters like shock pulse width, HDD orientation, parking ramp contact and FDB dynamic coefficients on the performance of a HDD during the excitation. It was observed that the proximity of the pulse to the HDD component's natural frequencies has an adverse effect on the shock resistance of the HDI. Furthermore, the orientation of the HDD during the shock can also affect the stability of the HDI. In the case of planar excitations, the FDB dynamics becomes critical in determining the slider's vibration amplitude. This knowledge about the HDI failure mechanism and its vibration characteristics can be helpful in designing a mobile HDD with a better shock performance.

Download or read book Dynamics and Stability of Thermal Flying height Control Sliders in Hard Disk Drives written by Jinglin Zheng and published by . This book was released on 2012 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a recent development to further reduce the flying height of a magnetic head in hard disk drives (HDDs) to nanometers, thermal flying-height (TFC) control technology is now widely applied in the HDD industry because it enables consistent read/write spacing, increased storage density and improved HDD reliability. The fast development of TFC technology presents new challenges to head designers because of the complicated structure of a TFC head, the thermo-mechanical-coupling effects and tribology issues arising at nanometer read/write spacing. A steady-state TFC solver dedicated to obtaining the steady-state flying attitude of a TFC slider is developed in this thesis. This solver uses a finite volume based solver (CML static solver) to solve the generalized Reynolds equation and obtain the pressure and spacing fields in the air bearing and a commercial coupled-field solver (ANSYS) to obtain the stress and strain fields due to internal heating. An iterative procedure is adopted to consider the cooling effect of the air bearing on the heater-induced protrusion. Accuracy of the solver is verified by drive-level magnetic tests on several combinations of air bearing and heater designs. TFC sliders' performances under different ambient conditions are investigated based on the TFC solver. It is found that the thermal actuation efficiency of a TFC slider increases with altitude because of the weakened cooling and reduced air bearing stiffness at the transducer area at a higher altitude. In addition, a TFC slider maintains a more consistent read/write spacing at different humidity levels, compared with a non-TFC slider, because the thermal actuation is able to compensate part of the pressure loss caused by water condensation. A TFC slider's flying height in air-helium mixtures is shown to be a highly nonlinear function of the fraction of helium in the gas mixture due to the combined effects of the gas mean free path, viscosity and heat conductivity. These results provide general guidelines for heater and ABS designers to reduce a TFC slider's sensitivity to ambient conditions and improve HDD reliability. A touchdown numerical model for predicting TFC sliders' dynamics at touchdown and over-pushed conditions is developed and implemented based on the CML dynamic simulator. It extends the solution of the time-varying generalized Reynolds equation to near-contact and contact conditions using a statistical multi-asperity approach. Various interfacial forces are considered by use and further development of a sub-boundary lubrication model to capture important tribological effects occurring at touchdown. This model is able to predict a TFC slider's unstable dynamics at the beginning of touchdown, which has been discovered in many related experimental studies. The effects of different head-disk interface factors are investigated using this numerical model. It is found that the suspension is actively involved in the TFC slider's bouncing vibrations and has a significant influence on the excited second air bearing pitch mode. It is also shown that adhesion force serves as an essential factor in exciting the second air bearing mode whereas other interfacial forces only affect details of the slider's bouncing behaviors. By changing the interfacial properties, namely, the interface roughness and lubricant thickness, the variation of interfacial forces with spacing reduction differs, which leads to very different touchdown patterns. With a rougher interface profile the slider smoothly transfers from a flying stage to a sliding stage. With a smoother interface profile the slider experiences a flying-bouncing-sliding transition. With the smoothest interface the slider goes through a flying-bouncing-surfing-sliding transition. The touchdown behaviors predicted by the numerical simulator are correlated with experiments conducted on industry-provided head parts with the same ABS and suspension design. Similar touchdown stages and excited modes are also discovered in the experiments. Though experiments showed a slider spectrum with richer frequency components, the modes missed from the numerical simulations are recovered by conducting a harmonic analysis on a full HGA model with air bearing included. The different touchdown dynamic patterns predicted here result in significant differences in the successful touchdown detection, which is very important for realizing reliable read/write operations, and therefore this work provides guidelines for head disk interface (HDI) optimization. The general approach proposed here is also applicable to studies on the effects of other important HDI factors, such as air bearing geometric features, heater-induced protrusion profiles, and suspension design parameters, and on the slider's touchdown dynamics behaviors, which will assist in obtaining solutions to performance and reliability issues in current hard disk drives.

Download or read book Monte Carlo Methods in Statistical Physics written by Kurt Binder and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 425 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the seven years since this volume first appeared. there has been an enormous expansion of the range of problems to which Monte Carlo computer simulation methods have been applied. This fact has already led to the addition of a companion volume ("Applications of the Monte Carlo Method in Statistical Physics", Topics in Current Physics. Vol . 36), edited in 1984, to this book. But the field continues to develop further; rapid progress is being made with respect to the implementation of Monte Carlo algorithms, the construction of special-purpose computers dedicated to exe cute Monte Carlo programs, and new methods to analyze the "data" generated by these programs. Brief descriptions of these and other developments, together with numerous addi tional references, are included in a new chapter , "Recent Trends in Monte Carlo Simulations" , which has been written for this second edition. Typographical correc tions have been made and fuller references given where appropriate, but otherwise the layout and contents of the other chapters are left unchanged. Thus this book, together with its companion volume mentioned above, gives a fairly complete and up to-date review of the field. It is hoped that the reduced price of this paperback edition will make it accessible to a wide range of scientists and students in the fields to which it is relevant: theoretical phYSics and physical chemistry , con densed-matter physics and materials science, computational physics and applied mathematics, etc.

Download or read book Numerical Investigation of the Effects of Operational Shock and Disk Surface Pattern on the Dynamics of Head Disk Interface in Hard Disk Drives written by Liping Li and published by . This book was released on 2013 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates the effects of shock and the disk surface pattern on the head disk interface (HDI) response in hard disk drives (HDDs). A new local adaptive mesh method is proposed at the end to improve the accuracy and efficiency of the algorithm to simulate the sliders' steady flying attitudes. Over the past decades, there has been an increase in the demand of HDDs used in portable devices. In such applications, the work performance of a HDD mainly depends on its ability to withstand external disturbances. Studies of the HDD's responses and failures during external shocks can be very beneficial for improving the HDD's design. A multi-body operational shock (op-shock) model is developed for this purpose in this thesis. The Guyan reduction method is used to model all the components considered in the op-shock model (a disk, a spindle motor, a base plate, a pivot and a head actuator assembly (HAA)). A fluid dynamic bearing (FDB), between the rotating and stationary units in the spindle motor, is simplified as a spring-dashpot system to save computation efforts. The same simplification is applied to a ball bearing (BB) system between the rotating and stationary units in the actuator pivot. Then the reduced models for all the components are assembled to obtain a complete multi-body op-shock model. Four models which include different components are introduced in this thesis to investigate various components' effects on the HDD's operating performance. The HDDs' failure mechanisms are also studied. It is found that different components influence the HDI responses in different ways. The ramp load/unload (LUL) technology has been proved to be a better alternative to the contact start-stop (CSS) approach due to the advantages of increasing areal density and greater durability. However, the application of the LUL ramps in the HDDs increases the possibility of collisions between the disk and the ramps since the ramps sit closely to the disk's outer radius. Therefore, it is important to study the ramp effects on the HDD's response during a shock. A reduced model of a deformable ramp is developed and implemented to the multi-body op-shock model. Numerical analyses using three ramp models (no-ramp model, rigid ramp model and deformable ramp model) are carried out to study the HDD's failure dependence on different ramp models. Bit patterned media (BPM) recording is one of the promising techniques for future disk drives in order to increase the areal density above 4 Tbit/in2. In patterned media, an individual recorded bit is stored in a distinct magnetic island. Thus, the BPM can change the topography of the disk surface and has an effect on the flying characteristics of the air bearing sliders. Proper designs of sliders and disks in the HDDs are required in order to achieve a stable work performance. So a simulator to model a slider's flying condition over a BPM disk is particularly important. Three methods (the averaging method, the Homogenization method and the Taylor expansion Homogenization methods) are implemented to simulate a slider's flying attitude, and finally an economical accurate method is chosen (the Taylor expansion Homogenization method) to investigate the slider's dynamics on partially planarized patterned media. In modern HDDs, the requirement of small and steady head disk spacing leads to more complicated air bearing surface designs. Thus it is challenging for an air bearing simulator to accurately capture the pressure under a slider's surface. A new local adaptive grid-generating algorithm is developed and is used to simulate the sliders' steady flying attitude. Local finer meshes (mesh's dimension decreases to half) are created on the nodes of the current grids, which have pressure gradients or geometry gradients larger than a pre-defined tolerance. Two sliders are used to demonstrate the applicability of this method. It is found that this new local adaptive grid-generating method improves the stability and efficiency of the simulation scheme.

Download or read book Direct Simulation Monte Carlo Modeling of Silicon Thin Film Deposition Using Supersonic Beams written by Gang Chen and published by . This book was released on 1998 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Guide to Monte Carlo Simulations in Statistical Physics written by David P. Landau and published by Cambridge University Press. This book was released on 2000-08-17 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes all aspects of Monte Carlo simulation of complex physical systems encountered in condensed-matter physics and statistical mechanics, as well as in related fields, such as polymer science and lattice gauge theory. The authors give a succinct overview of simple sampling methods and develop the importance sampling method. In addition they introduce quantum Monte Carlo methods, aspects of simulations of growth phenomena and other systems far from equilibrium, and the Monte Carlo Renormalization Group approach to critical phenomena. The book includes many applications, examples, and current references, and exercises to help the reader.