Irregularly shaped ice aggregates in optical modeling of convectively generated ice clouds

We propose a model of irregular shaped ice particles for satellite and ground-based cloud remote sensing applications. Microphysical observations have shown that ice particles generated in convective clouds tend to have highly irregular structures as a result of aggregation process. To simulate such complex structures, we used spatial Poisson–Voronoi tessellations. Furthermore, we adopted fractal-like shapes that were consistent with the proposed mass-dimension and area ratio-dimension relationships of measured cirrus particles. Single-scattering properties of the modeled “Voronoi aggregates” at visible wavelengths with size parameters up to 2246 were estimated from numerical calculations using the finite-difference time-domain method and the geometrical-optics integral-equation method. The phase functions for randomly oriented Voronoi aggregates showed features with no halos in the forward-scattering direction and a flat angular dependence in the side-to-backscattering directions. These characteristics and resultant asymmetry factors agreed with those of measured ice particles. Moreover, we confirmed the weak size and shape dependences of these scattering properties for the Voronoi aggregates, as well as high backscattering depolarization ratios and low linear polarizations.     

A miniature charged plate for testing charge accumulation in hard disk drives

A technique for monitoring electrostatic charge accumulation inside a hard disk drive (HDD) is described: a miniature charged plate is built into the top cover of the HDD, connected to a charged plate monitor. Experiments show that the miniature plate technique can be used for detection and measurement of the voltage induced by the charge generated inside the grounded enclosure of a hard drive.     

All-optical phase-change memory in a single gallium nanoparticle

We report on the first demonstration of a quaternary-logical resonatorless optical memory element with information encoded in the structural phase of a single 80 nm gallium nanoparticle. The size of the memory element is comparable with bits in next-generation hard disks, and radically smaller than previously suggested memories exploiting optical resonators. Furthermore, the energy required for switching the nanoparticle is an order of magnitude less than needed in DVD, DVR, or hard disk technologies.     

Soap froths and crystal structures

We propose a physical mechanism to explain the crystal symmetries found in macromolecular and supramolecular micellar materials. We argue that the packing entropy of the hard micellar cores is frustrated by the entropic interaction of their brushlike coronas. The latter interaction is treated as a surface effect between neighboring Voronoi cells. The observed crystal structures correspond to the Kelvin and Weaire-Phelan minimal foams. We show that these structures are stable for reasonable areal entropy densities.     

Molecular Fluids at High Dimensionality

We extend the analysis of orientational first-order phase transitions in anisotropic molecular fluids at high spatial dimensionality to hard-disk fluids, and then to mixture of hard disks and hard spheres. The effect of hard-sphere admixture depends sensitively on the relative sizes of the two geometrical objects, and large spheres completely quench the disk transition. An introductory study is made of spatially ordered states.     

Lyapunov instability of two-dimensional fluids: Hard dumbbells

We generalize Benettin's classical algorithm for the computation of the full Lyapunov spectrum to the case of a two-dimensional fluid composed of linear molecules modeled as hard dumbbells. Each dumbbell, two hard disks of diameter sigma with centers separated by a fixed distance d, may translate and rotate in the plane. We study the mixing between these qualitatively different degrees of freedom and its influence on the full set of Lyapunov exponents. The phase flow consists of smooth streaming interrupted by hard elastic collisions. We apply the exact collision rules for the differential offset vectors in tangent space to the computation of the Lyapunov exponents, and of time-averaged offset-vector projections into various subspaces of the phase space. For the case of a homogeneous mass distribution within a dumbbell we find that for small enough d/sigma, depending on the density, the translational part of the Lyapunov spectrum is decoupled from the rotational part and converges to the spectrum of hard disks. (c) 1998 American Institute of Physics.     

Numerical investigation of airflow inside a 1-in hard disk drive

The increasing application of the hard disk drive in consumer electronic devices has pushed the usage of the small form factor hard drives. At the same time, the data storage industry continues to enhance the capacity and performance of computer hard disk drive. The concerns of track mis-registration caused by various runout still remain with the form factor change. The objective of the current study is to numerically investigate the airflow characteristic inside a 1 in hard disk drive.     

Nonequilibrium phase behavior during the random sequential adsorption of tethered hard disks

We simulate random sequential adsorption of tethered hard disks which undergo limited Monte Carlo surface diffusion to study kinetics and nonequilibrium phase behavior. Tethers allow the disks to move within a specified distance of their original adsorption locations, placing a control on the local entropy of each disk. As the surface coverage increases, systems with sufficiently long tethers form hexatic or crystalline lattices, while short tethers frustrate organization. Lattices form with surprisingly short tether lengths-on the order of one disk diameter.     

Laser-assisted mechanical texturing of magnetic media

Mechanical texturing is the dominant technique for texturing magnetic media and is widely used in current hard disk drive manufacturing processes. This technique possesses the advantages of easy operation and low cost. However, it has an inherent disadvantage since mechanical texturing leads to jagged profiles randomly generated on hard disk surfaces, which precludes its further use in low-fly-height cases. A laser-assisted process working at near-threshold fluences for mechanical texturing was proposed to buff the irregular profiles of mechanical textures formed on Ni-P disk surfaces using a KrF excimer laser (λ=248 nm,τ=23 ns). This process, based on selective melting of the Ni-P surfaces due to inhomogeneous deposition of laser energy, was found to be capable of improving the surface characteristics of mechanically textured Ni-P disks. VSM and XRD analyses demonstrated that magnetic and structural properties of the Ni-P surfaces would not be affected in a detrimental way so as to influence the recording features of the magnetic media after laser buffing. Received: 28 November 2000 / Accepted: 12 December 2000 / Published online: 3 April 2001     

Evolution of Voronoi/Delaunay Characterized Micro Structure with Transition from Loose to Dense Sphere Packing

Micro structures of equal sphere packing （ranging from loose to dense packing） generated numerically by discrete element method under different vibration conditions are characterized using Voronoi/Delaunay tessellation, which is applied on a wide range of packing densities. The analysis on micro properties such as the total perimeter, surface area, and the face number distribution of each Voronoi polyhedron, and the pore size distribution in each Voronoi/Delaunay subunit is systematically carried out. The results show that with the increasing density of sphere packing, the Voronoi//Delaunay pore size distribution is narrowed. That indicates large pores to be gradually substituted by small uniformed ones during densification. Meanwhile, the distributions of face number, total per/meter, and surface area of Voronoi polyhedra at high packing densities tend to be narrower and higher, which is in good agreement with those in random loose packing.     

高分辨率航拍图像实时记录方法

针对某型高分辨率航空摄像机输出数据流达到每秒200兆字节,常规方法难于实现图像数据实时记录的问题,提出一种自启动多通道混合同步直写SCSI硬盘的方法.通过新设计的状态控制器,优化了SCSI硬盘的记录时序,使多个并行记录通道能根据数据缓存器和硬盘的状态自动产生独立的直写脉冲,以混合同步的方式将数据高速记录到硬盘上.实验结果表明:该方法可使图像数据持续记录速率达到每秒200兆字节,储存容量可达280吉字节,且结构简单、实用.     

Short-time dynamics of the positional order of the two-dimensional hard disk system

We investigate the positional order of the two-dimensional hard disk model with short-time dynamics and equilibrium simulations. The melting density and the critical exponents z and η are determined. Our results rule out a phase transition as predicted by the Kosterlitz–Thouless–Halperin–Nelson–Young theory as well as a first-order transition.     

间歇式高速电视CCD视频图像实时存储系统

针对间歇式高速电视系统中CCD数字图像需要实时无压缩存储的需求,提出一种基于SCSI磁盘阵列的视频图像实时采集存储方案.在磁盘存储速度可行性论证测试的基础上,利用软件技术实现图像数据硬盘实时存储,并将存入硬盘的数据流转换为BMP文件格式加以显示.实验验证了该方案的可行性.     

MELTING OF 2D MONATOMIC SOLIDS-HARD DISK AND SQUARE WELL SYSTEM

Using the Collins model of Liquids the melting of 2D monatomic solids is studied and the melting equation is derived. For the hard disk system our results agree with the computer simulation experiments quite well.For the square well system by means of the LHW theory the triple point and the melting line near the triple point is obtained to establish the phase boundary.     

Air-lubrication of magnetic disk sliders

Steady-state and dynamic flying of a self-acting magnetic disk slider over a hard disk are considered. Some tasks for computations are formulated and the possibilities of developed numerical codes are illustrated. Numerical results of dynamic flying over a disk surface with an obstacle are in agreement with experimental data.     

Future hard disk drive systems

This paper briefly reviews the evolution of today's hard disk drive with the additional intention of orienting the reader to the overall mechanical and electrical architecture. The modern hard disk drive is a miracle of storage capacity and function together with remarkable economy of design. This paper presents a personal view of future customer requirements and the anticipated design evolution of the components. There are critical decisions and great challenges ahead for the key technologies of heads, media, head-disk interface, mechanics, and electronics.     

Topological and statistical properties of a constrained Voronoi tessellation

Voronoi tessellation has been used widely to approximate and model various cellular structures and stochastic patterns appearing in nature. In this work, we present an extended version of the Voronoi tessellation method that partitions the space with certain constraints commonly encountered in either experimental measurements or theoretical models, such as cell volume or size distribution. The new Voronoi method is implemented using an inverse Monte Carlo method. We calculate the topological and statistical properties of tessellated Voronoi cells in several model systems with cell volumes obeying lognormal and bimodal distributions. We also compare the results with those obtained using the conventional Poisson–Voronoi method. We observed systematic changes in the topological properties as well as deviations from some established topological relations as the parameters in the constraint were varied. The application of this constrained Voronoi method in microstructure modelling and characterization in poly- and nano-crystalline materials is briefly discussed.     

二维系统的热力学性质

为了讨论固体和液体的性质,Kawamura曾利用Collins模型,在忽略4-原子和引力势的情况下,研究了二维硬盘系统的相变。本文进一步考虑4-原子和引力势的存在,计算了二维系统的热力学函数,研究了4-原子所占百分数对相变点的影响,讨论了物态方程和定压热容量。 关键词：     

Nonmean-Field Model for Ostwald Ripening of Two-Dimensional Islands

A nonmean-field model for the ripening of two-dimensional islands is presented. In this model, the adatom sea is divided into many small cells that are the polygons of a Voronoi network. The chemical potentials of adatom seas surrounding different islands are different. Strain generated by lattice mismatch is introduced into the model.Computer simulation under periodic boundary conditions is carried out to describe the island ripening in two cases (with and without strain), and demonstrates that small islands may grow faster than large islands, which cannot occur in the mean-field model. The simulated results also show that including strain will slow down the evolution of average island size, and an explanation for this is given.     

iVDR business perspective

This paper describes a perspective for information versatile disk for removable usage (iVDR) business. iVDR is the best bridge media for high-resolution image because of high capacity and high reliability. The first iVDR product was delivered with PMR technology hard disk drives and a copyright protection function for high-definition TV programs. The business opportunity and the new business model are discussed.