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Compares Wilson's database tape and the IAC "Expanded Academic Index" as explored by librarians in the State University System of Florida. Features addressed include journal coverage; abstracts and full text; subject headings, including consistency versus precision and controlled vocabularies; search software; disk storage requirements; and costs and licensing agreements. (LRW)

Discusses the use of an optical jukebox in a retrieval-intensive application--i.e., for a law firm's litigation support--and examines factors affecting the performance of the jukebox. The imaging system's configuration is explained, document access from workstations is described, and expectations of retrieval times are discussed. (LRW)

Provides an introduction to DOS commands and strategies for the effective organization and use of hard disks. Functions discussed include the creation of directories and subdirectories, enhanced copying, the assignment of disk drives, and backing up the hard disk. (CLB)

This is the third in a series of articles discussing models that can be used to help students visualize the interaction of computer hardware and software. It focuses on a demonstration of how the computer works when the LOGO programing language has been added to memory. (LRW)

Native 2-D low-density parity-check (LDPC) codes provide 2-D burst erasure correction capability and have promising applications in two-dimensional magnetic recording (TDMR) technology. Though carefully constructed rastered 1-D LDPC codes can provide 2-D burst erasure correction, they are not as efficient as 2-D native codes constructed for handling the 2-D span of burst erasures. Our contributions are twofold. First, we propose a new 2-D LDPC code with girth greater than 4 by generating a parity-check tensor through stacking permutation tensors of size $p\times p\times p$ along with the $i,j,k$ -axes. The permutations are achieved through circular shifts on an identity tensor along different coordinate axes in such a way that it provides a burst erasure correction capability of at least $p\times p$. Second, we propose a fast, efficient, and scalable hardware architecture for a parallel 2-D LDPC decoder based on the proposed code construction for data storage applications. Through efficient indexing of the received messages in an RAM, we propose novel routing mechanisms for messages between the check nodes and variable nodes through a set of two barrel shifters, producing shifts along two axes. Through simulations, we show that the performance of the proposed 2-D LDPC codes matches a 1-D QC-LDPC code, with a sharp waterfall drop of three to four orders of magnitude over ~0.3 dB, for random errors over code sizes of ~32 kbits or equivalently ~ $180\times 180 2$ -D arrays. Furthermore, we prove that the proposed native 2-D LDPC codes outperform their 1-D counterparts in terms of 2-D cluster erasure correction ability. For $p=16$ and code arrays of size $48\times 48$ , we implemented the proposed design architecture on a Kintex-7 KC-705 field-programmable gate array (FPGA) kit, achieving a significantly high worst case throughput of 12.52 Gb/s at a clock frequency of 163 MHz. [ABSTRACT FROM AUTHOR]

We propose fast and efficient hardware architectures for a 2-D Bose–Chaudhuri–Hocquenghem (BCH) code of size n × n, with a quasi-cyclic burst error correction capability of t × t, in the frequency domain for data storage applications. A fully parallel encoder with the ability to produce an output every clock cycle was designed. Using conjugate class properties of finite fields, the algorithmic complexity of the encoder was significantly reduced, leading to a reduction in the number of gates by about 94% of the brute-force implementation per 2-D inverse discrete finite field Fourier transform (IDFFFT) point for a 15 × 15, t = 2 2-D BCH code. We also designed a pipelined, low-latency decoder for the above encoder. The algorithmic complexity of various pipeline stages of the decoder was reduced significantly using finite field properties, reducing the space complexity of the entire decoder. For a particular case of n = 15 and t = 2, the architectures were implemented on a Kintex 7 KC-705 field-programmable gate array (FPGA) kit, giving high throughputs of 22.5 and 5.6 Gb/s at 100 MHz for the encoder and decoder, respectively. [ABSTRACT FROM AUTHOR]

The dynamic properties of vertically coupled vortices in two magnetic nanodisks were studied using numerical simulations and analytical calculations. If the core polarizations of the two vortices are parallel, there exist two distinct normal modes with two distinct eigenfrequencies corresponding to the apparent complex motions of two vortices. Conversely, only a degenerate mode with a single eigenfrequency exists when the cores have opposite polarization. We show that the gyration eigenfrequencies can be tuned by changing the coupling strength, i.e., the separation between the disks. The dependence of the normal modes and the eigenfrequencies on the relative vortex-state configuration can be well understood based on the analytic model. [ABSTRACT FROM AUTHOR]

Shingled Magnetic Recording (SMR) Disks are adopted as a high-density, non-volatile media that significantly precedes conventional disks in both the storage capacity and cost. However, inefficient read-modify-writes (RMWs) greatly challenge the management of SMR disks. This article for the first time presents an approach called Tiler to manage SMR disks by dividing the physical space into small autonomous regions (ARs). Each AR can manage its space allocation, address mapping, and cleaning independently. By managing these ARs in a log-structured way, RMWs can be avoided; besides, ARs can also help update data when the adjacent tracks contain no valid data. Tiler is capable of partitioning a large-scale cleaning into self-contained-small-scale cleaning and thus, the data that need to be relocated are limited inside independent ARs, which further minimizes the performance overhead. Our experimental results show that Tiler can shorten the overall system response time by 50.21 percent and reduce the cleaning time by 90.24 percent on average. [ABSTRACT FROM AUTHOR]

We have studied vortex core switching in a Permalloy disk with a cavity defect using micromagnetic simulation and analytical calculation methods. It is demonstrated that the existence of a cavity that can attract and pin the vortex core in the nanodisk plays an important role in controlling the reversal of the vortex core by coherent excitation. The diagram of the vortex core switching with different cavity radii is presented based on the calculation of the effective potential energy. It is shown that there are three cases that are dependent on the distance between the cavity and the disk centers. For a smaller distance, the reversal cannot occur without applying a second sufficiently strong field pulse with the direction opposite to the orientation of the first pulse, and the amplitude of the second field pulse that can release and reverse the polarity of the vortex core increases with increasing of the radius of the cavity. Then, for a critical distance range, the vortex core can be released from the cavity and reverse automatically. When the distance is large enough the vortex core cannot be attracted and pinned by the cavity, the reversal cannot be controlled by the cavity. [ABSTRACT FROM AUTHOR]

Many search algorithms are limited by the amount of memory available. Magnetic disk storage is over two orders of magnitude cheaper than semiconductor memory, and individual disks can hold up to a terabyte. We augment memory with magnetic disks to perform brute-force and heuristic searches that are orders of magnitude larger than any previous such searches. The main difficulty is detecting duplicate nodes, which is normally done with a hash table. Due to long disk latencies, however, randomly accessed hash tables are infeasible on disk, and are replaced by a mechanism we call delayed duplicate detection. In contrast to previous work, we perform delayed duplicate detection without sorting, which runs in time linear in the number of nodes in practice. Using this technique, we performed the first complete breadth-first searches of the 2×7, 3×5, 4×4, and 2×8 sliding-tile Puzzles, verifying the radius of the 4×4 puzzle and determining the radius of the others. We also performed the first complete breadth-first searches of the four-peg Towers of Hanoi problem with up to 22 discs, discovering a surprising anomaly regarding the radii of these problems. In addition, we performed the first heuristic searches of the four-peg Towers of Hanoi problem with up to 31 discs, verifying a conjectured optimal solution length to these problems. We also performed partial breadth-first searches of Rubik's Cube to depth ten in the face-turn metric, and depth eleven in the quarter-turn metric, confirming previous results. [ABSTRACT FROM AUTHOR]

A model is presented that accounts for the observation of periodic lubricant ripples formed when a slider is flying on-track over a lubricated disk surface. It is shown that lubricant flow modulation from the air shear stress due to the low flying slider acting as a spring is responsible for the observed corrugation, as repeated flying over the same track enhances the effect. This is somewhat moderated by the relaxation of the lubricant perturbation, by surface diffusion. Depending on the relative magnitude of the shear and diffusion processes, the system can find itself into regions of stability where small perturbations decay away, or regions of instability where they increase exponentially. Instability is enhanced for lower fly height and higher disk rotational frequency, making it a challenge for future growth in disk drive performance and areal density. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Laser-induced structural decompositions of hydrogenated amorphous carbon films deposited by dc-magnetron sputtering on magnetic hard disks were studied using a microbeam Ar[sup +] laser (514.5 nm). The laser had varying powers between 3.0 and 0.3 mW at a focused circular spot of 2.5 µm diameter, corresponding to approximate fluence rates between 6 × 10[sup 4] to 6 × 10[sup 3] J cm[sup -2] s[sup -1]. The effect of laser power on decomposition rate could be expressed by an exponential equation. Based on the relationship between laser power and temperature, relative apparent activation energies for film decompositions were obtained and found to decrease with the increase of film hydrogen content and the elapse time of laser irradiation. All the films irradiated with laser powers between 0.75 and 0.3 mW followed the apparent first-order reaction. The reaction order tended to increase at higher laser powers and hydrogen content in the films. [ABSTRACT FROM AUTHOR]

Studies the surface roughness of a computer disk using atomic force microscopy (AFM) and light scattering. Anisotropic rough surfaces and experimental techniques; AFM measurements; Light scattering measurements.

The continuous reduction of head–disk spacing has made the use of supersmooth media a necessity in gaining ultrahigh magnetic recording areal density. To overcome the stiction barrier associated with supersmooth disks without compromising the head flyability requirement, texture features can be transferred from the disk surface to the slider surface, creating a new type of head–disk interface, the padded slider interface. The tribology of a padded slider interface is in many ways different from that of the traditional head–disk interface with texture on the disk only. In this article, various unique tribological aspects of the padded slider interface are discussed in detail. Both theoretical modeling results and experimental data are presented to elucidate the stiction, friction, and wear behaviors of this novel head–disk interface. It is shown that the padded slider technology offers a viable alternative to the ramp load technology as a head–disk interface solution for the ultrahigh areal density. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Focuses on a study of interface reactions between the magnetic layer and the protective carbon coating, and the influence of these interactions on magnetic properties of rigid disk media for magnetic data storage. Background of the study; Experimental details; Results of the study.

Abstract A device for headspace sorptive extraction (HSSE) combined with gas chromatography separation and mass spectrometry detection (GC–MS) is presented. The gadget is based on a simple magnetic disk that permits the stir bar to be placed at the top of the sample vial. The complete surface of the coated stir bar is exposed to the headspace atmosphere, and the movement of the bar caused by the magnetic stirrer in the liquid sample facilitates the sorption process. The final consequence is increased sensitivity and repeatability when compared with a glass-made comercial device for the same purpose. Successful determination of ten chlorobenzenes in waters testifies the good performance of the new device. Graphical abstract fx1 Highlights • A homemade device to facilitate headspace sorptive extraction is presented. • The device is cheap, simple and can be adapted to common sample vials. • The determination of chlorobenzenes is a test to check its practical usefulness. [ABSTRACT FROM AUTHOR]

Highlights • Formation and dynamics of edge solitons in confined notch structure. • Notch induced fast vortex polarity switching. Abstract Magnetic vortices are characterized by the sense of in-plane magnetization chirality and by the polarity of the vortex core. Searching for efficient ways to control the vortex polarity and chirality is of highly fundamental and practical significance towards high speed and high density non-volatile memory applications. Here we report a novel vortex core (VC) switching process in a notched disk, driven by a pulse field. Micromagnetic simulations demonstrate that the dynamics of edge solitons around the notch play a critical role in the switching process, that leads to a sub-nanosecond VC fast switching. The switching diagram as a function of the field strength and duration was presented to indicate the operational range. Further studies on the VC switching under an out-of-plane bias field demonstrate that such switching is deterministic and robust against magnetic environment. Finally, by applying a resonant alternative field, a periodic VC switching is observed with much reduced switching field. The presented results indicate the potential of notched disks for VC based memory applications. [ABSTRACT FROM AUTHOR]

Abstract Disk springs have been widely used in machine tools, aerospace vehicles, and automobiles. Pioneering work by Almen -Laszlo has inspired a deeper understanding of the nonlinear behavior over the last eight decades. There is a need for extending the analysis for stepped section disk springs. In this paper, we report the effect of the stepped section on the force-deflection and variable stiffness characteristics. A simplified method for predicting load deflection of the stepped disk spring has been developed incorporating the geometric non-linearity. Extending the work of Almen-Laszlo, Curti, and Rosa, we present a theoretical analysis that predicts the force deflection characteristic as function of the geometric parameter and the theoretical model is verified using finite element results. Highlights • Methodology to enhance energy absorption in disk spring by addition of stepped section has been presented. • Theoretical formulation available in the paper helps designer to choose the section parameters for optimum energy storage. • Results of theoretical formulation are verified by FE results. • Results from the present paper has been compared with the previous published work. [ABSTRACT FROM AUTHOR]

Recent advances in hard disk drive mechanics, specifically the successful introduction of helium-filled enclosures, have enabled significant increases in drive capacity. The track mis-registration characteristics of helium-filled enclosures are significantly improved compared with air-filled enclosures. We discuss how these changes in mechanical capability alter the factors limiting areal density for future products and discuss how further improvements in capacity will be realized. [ABSTRACT FROM AUTHOR]

Deals with a study which described the physical and magnetic characteristics of rigid single layer perpendicular recording media. Comparison between the desired physical and magnetic parameters for perpendicular media with those for longitudinal media; Impact of the differences on production techniques; Production considerations.

Provides information on a study which discussed the characteristics of a magnetic disk drive with 10 gigabit per square inch density. Requirements for high track density; Use of flyheads and longitudinal recording; Servos and actuators.

Provides information on a study which described a range of possible partial-response maximum-likelihood detection schemes for the signal processing of magnetic disk recording systems. Methods; Results and discussion; Conclusion.

Deals with the magnetic media for 10 gigabyte per square inch hard disk storage. Recording format and magnetic requirements; Status of media development as of April 1996; Discussion of media structure preparation approach.

Presents information on a study that examined the production of carbon dioxide from the sliding interface of a carbon-coated thin-film magnetic recording disk. Methodology of the study; Results and discussion on the study.

Presents a study which addressed the topographic effect of surface roughness of a rotating magnetic disk on the flying height of a slider. Effect of the surface roughness of a magnetic disk on the instability of the air bearing; Approach used in examining fluctuations in flying height induced by disk topography; Details on the dynamics of a slider attached to a cantilever suspension; Characteristics of surface roughness and stochasticity.

Presents a study which analyzed the behavior of liquid lubricant films on the disk surfaces in magnetic recording using the concepts of disjoining and capillary pressure. Schematic representation of a particulate disk drives; Details on the disjoining pressure; Distribution of liquid lubricant; Types of pressure gradients or forces to drive the lubricant flow.

Presents a study which addressed the depletion of thin liquid films due to the combined effect of centrifugation, surface roughness, and air shear. Uses of magnetic disk systems; Construction of the surface asperities; Mathematical model of viscous flow.