1,720,991 research outputs found
Three-axis lever actuator with flexure hinges for an optical disk system
No full textA three-axis lever actuator with a flexure hinge has been designed and fabricated. This actuator is driven by electromagnetic force based on a coil-magnet system and can be used as a high precision actuator and, especially as a pickup head actuator in optical disks. High precision and low sensitivity to external vibration are the major advantages of this lever actuator. An analysis model was found and compared to the finite element method. Dynamic characteristics of the three-axis lever actuator were measured. The results are in very close agreement to those predicted by the model and finite element analysis. (C) 2002 American Institute of Physics
Reduction of seek time of tracking actuator with pulsed excitation in optical disk
No full textTime consumption during the track seek is an important factor which indicates the ability of an optical disk system. In a two-stage tracking actuator, latency time exists before the laser beam follows the destination track because of the vibration of the fine actuator. Modified velocity profiles and control techniques for the actuator have been proposed to reduce the latency time. When a fine actuator is locked to the coarse actuator, another latency time caused by the disk eccentricity cannot be reduced. It becomes possible to forecast the eccentricity as the rotation type of the optical disk changes to constant angular velocity (CAV). Thus the latency time can be reduced by excitation of the fine actuator with the same velocity of the track when the coarse actuator stops. Pulsed excitation is used for the excitation. This method is applied to a compact disk read-only memory (CD-ROM)
Beam rotation actuator based on dove prism in the optical storage media
No full textA beam rotation actuator, which can be utilized to improve the data transfer rate for optical disk systems, has been developed. The newly developed beam rotation actuator with high-resolution and fast response was assembled for micro positioning of an optical storage media. The beam rotation actuator is utilized to put multi-beam spots on more than one track on an optical disk simultaneously in addition to tracing multi-beam spots on tracks in a radial direction. Multi-beam spots turn on an optical axis by rotating dove prism in the optical path at the end of a cantilever arm. The beam rotation actuator is made of bimorph peizoelectric material. The dove prism is responsible for both high-resolution movement as well as multi-beam spot rotation. The dynamic equation of the beam rotation actuator is derived theoretically. The actuator is designed on the grounds of an analytical equation. It is shown that the beam rotation actuator has a natural frequency of 54 Hz or more, and the actuator has high-resolution. The application performance of the beam rotation actuator is verified as the feedback control is applied. (C) 2000 Published by Elsevier Science Ltd
Multifaceted and nanobored particle arrays sculpted using colloidal lithography
No full textA novel method of fabricating multifaceted and nanobored particle arrays via colloidal lithography using colloidal-crystal layers as masks for anisotropic reactive-ion etching (RIF) is reported. The shape of the sculpted particles is dependent on the crystal orientation relative to the etchant flow, the number of colloidal layers, the RIF conditions, and the matrix (or mask) structure. in colloidal lithography. Arrays of non-spherical particles with sculpted shapes, which to date could not otherwise be produced, are fabricated using a tilted anisotropic RIF process and the layer-by-layer growth of a colloidal mask. These nonspheric spherical particles and their ordered arrays can be used for antireflection surfaces, biosensors, and nanopatterning masks, as well as non-spherical building blocks for novel colloidal crystals. In addition, polymeric particles with patterned holes of controlled depths obtained by the present method can be applied to the fabrication of functional composite particles.Center for Nanoscale Mechatronics and Manufacturing of the 21st Century Frontier Research Program (M102KN010002-05K1401-00214).
National R&D Project for Nano Science and Technology of the Ministry of Commerce, Industry and Energy
BK21 program
CUPSERC
from Wiley InterScience or from the author
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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