Disk-zoning technique has been widely adopted to increase disks capacities. As a result of disparity of capacities of inner and outer zones, the data transfer rates of the outer zones of a zoned-disk are higher than the inner zones that post a great challenge for zoned-disk based multimedia playback. In this paper, we study the data placement problem of VBR (variable bit rate) videos on zoned-disks. Our objective is to minimize video server buffer size and simultaneously to maximize disk utilization subject to the zone constraints of disk. We introduce the CRT (constant read time) method that allocates each user a constant time period in every service round to retrieve a variable-sized disk block. The CRT method can be formulated as constrained combinatorial problems that its optimum solution can be obtained by employing dynamic programming. Two heuristics are also explored to reduce time and space complexities. According to experiment results, the heuristic algorithms obtain near optimum solutions with shorter computation time.

Using a point matching method, we have numerically analyzed resonance frequencies and unloaded Q factor of whispering gallery modes in a millimeter wave region that are well known as an intrinsic mode of a dielectric disk resonator. We express field distributions of the resonance modes by a summation of spherical waves. Tangential electromagnetic fields inside the disk are matched to those outside the disk at appropriate matching points on a boundary. As the result, a 4N 4N (N; number of matching points) determinant is derived as an eigenvalue equation of the disk resonator. Since elements of the determinant are complex numbers, a complex angular frequency is introduced to make a value of the determinant zero. For a location of the matching points, we also introduce a new technique which is derived from a field expression of the whispering gallery modes. Since an azimuthal angle dependence of the field distributions with a resonance mode number m is presented by the associated Legendre function Pnm(cos θ), we define abscissas θi of the matching points as solutions of Pm+2N-1m (cos θ) = 0. Considering the field symmetry, we also modify the eigenvalue equation to a new eigenvalue equation which is expressed (4N - 2) (4N - 2) determinant. From the results of our numerical analysis, we can find that the resonance frequencies and unloaded Q factor well converge for number of matching points N. A comparison of numerical results and experimental ones, in a millimeter wave band (50 - 100 GHz), shows a good agreement with each other. It is found that our analysis is effective for practical use in the same wave band.

The millimeter wave filter using two whispering-gallery mode dielectric disk resonators is presented in this paper. The coupling coefficients of dual disk resonators and the external Q values of the single resonator excited by a dielectric waveguide are investigated theoretically and experimentally. A 2-stage bandpass filter which is designed at the center frequency of 69.85 GHz with a bandwidth of 500 MHz shows a low-loss property of 1.8 dB insertion loss.

The present paper describes the finite difference time domain (FDTD) analysis of the light-beam diffraction from two- and three-dimensional (2-D and 3-D) magneto-optical (MO) disk structures. First, we show that the proposed new FDTD formulation is valid for MO disk medium and can avoid the divergence of fields encountered during the conventional FDTD calculations. Second, as the application of the present method to more complicated models, the main- and cross-polarized diffracted fields are numerically calculated for 2-D and 3-D four-layered MO disk models. The phase differences between two kinds of polarized components are shown. The results obtained here indicate that the proposed FDTD formulation can be applied to more complicated MO disk structures.

Skew angle effects on the transition noise are analyzed in the longitudinal disk media by micromagnetic simulations at area densities from 14.3 Gb/in2 to 31.5 Gb/in2. The transition noise, including the peak, width and jitter noise, is the dominant noise in ultra-high density disk recording systems. An isotropic medium and an oriented medium, with a fixed grain size of 135 and a coercivity of 2900 Oe, are chosen for the noise analysis. The peak noise is studied by the distribution of the peak magnetization amplitude Mp in each bit. The transition a-parameter is no longer the value as given in the William-Comstock approximation. It is found that the transition noise is highly dependent on both the linear den sity and the skew angle, where the bit length and the grain size are on the same order. In both media, the medium noise increases severely when the skew angle is above 10 degrees.

Medium noise is the dominant noise in ultrahigh density disk recording systems. The peak, width and jitter noise are analyzed by micromagnetic simulations. Four different media, with a fixed grain size of 135 and a coercivity of 2900 Oe, are chosen for medium noise analysis. The linear recording density is increased from 340 KFCI (Kilo flux-changes per inch) to 750 KFCI, while the area density goes up from 14.3 Gb/in2 to 31.5 Gb/in2. The peak-amplitude noise is studied by the distribution of the peak magnetization Mp in each bit. The distribution of Mp develops from a delta-function around the remanence Mr at low densities to a flat distribution at extremely high densities. It is found that the transition a-parameter is no longer proportional to the square root of Mrδ, as given in the William-Comstock approximation. The peak-jitter noise in the read back voltage is analyzed by the percentage of the transition jitter in a bit length.

Future high density magnetic recording requires a nanometer spaced head-slider interface, high track seeking velocity and high spindle speed. Such a combination greatly increases the likelihood of slider-disk and slider-particle-disk impact. Furthermore, the impact can generate high flash temperature and leads to data reliability problems, such as partial or full data erasure. This work report a method to conduct controlled experimental investigations into the possibility of such a data erasure even when the temperature is far below the Curie temperature. Results indicate that the high density magnetic transitions are of high likelihood of being affected by the flash temperature. Investigations also extended to micromagnetic modeling of the flash temperature effect. Results suggest that thermally induced local stress can play important roll in the data erasure process. Modeling results also exhibit that smaller grain size and higher recording density are also of higher likelihood of getting the transitions being affected by the flash temperature.

A systematic continuous data placement scheme on distributed multi-zone disks is developed for video on demand. The proposed scheme makes use of constant read time concept, i. e. , each video stream has the same access time in each service round when serving the request. The developed scheme maximizes not only the averaged data transmitted rate, but also the number of simultaneous accesses. The scheme consists of the following components. First we developed an algorithm that reorganizes the multi-zone disk into several logical zones in the sense that the averaged disk throughput is maximum. Second, a sequential data access method was developed that takes disk loading balance into account. Thus, at each service round, the total amount of data transmitted is a constant. Third, we introduce the idle round technique to reduce the buffer size required at the client site for VBR video stream. As a result, admission control is enforced in an efficient manner. Finally we perform experimental tests to evaluate the performance of the proposed scheme. The results indicate the value of the proposed scheme.

Measurement of the viscosity of liquid using a piezoelectric disk is described. Experiments with a radial expansion mode of a piezoceramic disk were carried out for water-glycerin mixture samples. Resonant resistance has linearity to the square root of the product of density and viscosity of a liquid around 113 kHz.

A standard of Advanced Storage Magneto Optical (AS-MO) having a 6 Gbyte capacity in a 120 mm-diameter single side disk was established by using a magnetically induced superresolution readout method. Transition from in-plane to perpendicular magnetization for exchange-coupled readout layer (GdFeCo) and in-plane magnetization mask layer (GdFe) of the AS-MO disk has been investigated using the noncontinuous model. The readout resolution was sensitive to the thickness of the readout layer. To evaluate readout characteristics of AS-MO disks, the simulation using micro magnetics model was performed and the readout layers were designed. The readout characteristics of the AS-MO disk is improved by making the readout layer thinner.

An integrated slider-suspension system was designed and prototyped. The structure of this system has a full flying air-bearing surface in the leading part with a contamination-resistant feature, and it accommodates a slider with a 5-15 nm head-disk spacing at the trailing part. Performance analysis and simulation were conducted to validate the high performances of the design. Two key issues, the rigid motions (vibrations) and the elastic motions of the slider, were investigated systematically. For the rigid motions, it was found that the natural frequencies of the slider system are dependent on the disk contact stiffness and that the slider vibrations under excitation exhibit various nonlinear resonance. For the elastic motions, the average elastic response of the slider body under the random interaction of the interface was derived and characterized.

A method of evaluating the gas viscous friction force acting on head/disk interface has been developed. In the past, the effect of the gas viscous friction force has been almost negligible, due to its small value compared with the contact friction force. Recently the gas viscous friction force has tended to increase with the decrease in spacing and the increase in relative speed between the slider and the disk, therefore it is becoming necessary to consider its effect on motor load or slider posture. Few experimental studies of the gas viscous friction force, however, have been performed. In this study, the measurement of the gas viscous friction force has been realized by developing a sensitive friction force sensor. Furthermore a method of evaluating the gas viscous and contact friction forces separately has been also established.

The effect of surface roughness is crucial for contact recording and proximity recording. In this paper a probability model is developed for investigation of the influence of surface roughness on flying performance and the contact force of the slider. Simulations are conducted for both the contact recording slider and the proximity recording slider, and the results are well coordinated with the reported experimental results and the self-conducted experimental results. Studies are further extended to the characterization of the roughness of the air bearing surface and the disk surface that may support head/disk spacing between 5 nm and 15 nm.

A head-disk spacing tester that includes the effect of lubricant will be necessary if the slider-disk interaction is to be considered. The interaction and interaction induced spacing variation can be quantitatively characterized by optical method and by replacing the functional disk media with a glass disk covered with a carbon layer and a lubricant layer of the same materials and the same layer thickness as the functional disk media. This paper reports a tester configuration based on that concept. Experimental investigations into the nanometer spaced head-disk interface with such a setup are presented also. Results indicate that the lubricant plays an important role in slider-disk interaction and the vibration of the slider-disk interface. Two types of interface vibration were noticed: contact vibration and bouncing vibration. For the bouncing case, the natural frequency of air-bearing and its fold frequencies will be excited and air-bearing plays more important role in the determination of the slider vibration, comparing with the contact-vibration case.

Generating conditions of the optical feedback noise in self-pulsing lasers were experimentally examined. The noise charcteristics were determined by changing the operating power, the feedback distance and the feedback ratio for several types of self-pulsing lasers. The idea of the effective modulation index was introduced to evaluate the generating conditions in an uniform manner based on the mode competition theory. Validity of the idea was experimentally confirmed for generation of noise.

Recent attractive high-speed networks require network file servers with high-speed read performance to deliver huge multimedia files, like voice or movie files. This paper proposes new design and implementation techniques that yield high-speed file servers based on UNIX. The techniques are request reduction, in which contiguous blocks on UNIX file system (UFS) are gathered for reducing the number of command requests from the file system to the device driver, and a direct access method for cutting through the buffer cache mechanism. A file server prototype based on a general-purpose personal computer (PC) is constructed and its performance is evaluated. The preliminary results show that the prototype achieves high-speed file read performance in excess of 100 Mbytes/s even on an OpenBSD PC-UNIX system with 3 RAID controllers and 9 hard drives in RAID level 0 configuration.

A novel method is proposed to calculate the distributed coupling of dual-modes in a circular resonator. New theoretical expressions are devised to accumulate the infinitesimal coupling between orthogonal modes and their validity is justified by the FD-TD analysis and experiments. The distributed coupling concept of a circular disk resonator is applied to a square disk resonator to calculate its resonant frequency. We have fabricated two types of low-profile dual-mode square dielectric disk resonator BPF, using high dielectric constant material (εr = 93) having a dimension of 5 mm 5 mm 1 mm. The filter characteristics are explained by the transmission line circuit model.

The disk allocation problem examined in this paper is finding a method to distribute a Binary Cartesian Product File on multiple disks to maximize parallel disk I/O accesses for partial match retrieval. This problem is known to be NP-hard, and heuristic approaches have been applied to obtain suboptimal solutions. Recently, efficient methods such as Binary Disk Modulo (BDM) and Error Correcting Code (ECC) methods have been proposed along with the restrictions that the number of disks in which files are stored should be a power of 2. In this paper, a new Disk Allocation method based on Genetic Algorithm (DAGA) is proposed. The DAGA does not place restrictions on the number of disks to be applied and it can allocate the disks adaptively by taking into account the data access patterns. Using the schema theory, it is proven that the DAGA can realize a near-optimal solution with high probability. Comparing the quality of solution derived by the DAGA with the General Disk Modulo (GDM), BDM, and ECC methods through the simulation, shows that 1) the DAGA is superior to the GDM method in all the cases and 2) with the restrictions being placed on the number of disks, the average response time of the DAGA is always less than that of the BDM method and greater than that of the ECC method in the absence of data skew and 3) when data skew is considered, the DAGA performs better than or equal to both BDM and ECC methods, even when restrictions on the number of disks are enforced.

This paper gives an overview of research activities on high performance databases in Japan. It focuses on parallel algorithms for relational databases and data mining, parallel approaches for object-oriented databases, and parallel disk systems. Studies surveyed in this paper are carried out mainly by database researchers in Japanese universities under the Grant-in-Aid for Scientific Research (1996-1998).

This paper implements some new techniques to analyze the light beam scattering from a magneto-optical (MO) disk using the three-dimensional finite-difference time-domain (FDTD) method. The anisotropic FDTD update equations are implemented to calculate the propagation of a coherent monochromatic light in the MO material. An anisotropic absorbing boundary condition based on Berenger's perfectly matched layer (PML) concept is also developed. The Gaussian incident light beam is introduced into FDTD computation region exactly by using equivalent electric and magnetic currents. The scattering pattern of light beam from the MO disk is computed and in part compared with that obtained by using the boundary element method. The scattering patterns by the circular recording bit of different radius are calculated to indicate the optimum radius of the recording bit.