1,720,967 research outputs found
The modelling and design of a mechanism for micro-force measurement
No full textThe null balance method is used for precision force measurement in the precision industry in order to overcome the limitations of the load cell. The performance of any micro-weighing device is determined by the design of the precision mechanism. Such a device should be designed for high reproducibility, large measurement range with high resolution and fast response characteristics. The device consists of a displacement amplification mechanism and a parallel spring. The mechanism proposed here is analysed against the design specifications. The mechanism was designed for a resolution of 0.1 mg, a range of over 100 gf and a settling time of less than 1 s. The results of this design were verified by simulation and by experiment.This work was supported in part by the Brain Korea 21 project
Double force compensation method to enhance the performance of a null balance force sensor
No full textMicroforce measurement is becoming more essential as precision industries such as biomedicine, precision chemistry, semiconductor manufacturing, and so forth develop. A null balance method has been introduced in order to improve on force measurement performances involving a loadcell. The null-balance type force sensor is analyzed and designed for the improvement of measurement performances. The measurement range and the resolution are dependent on the force generation capacity and the various error sources. These characteristics are estimated and verified according to the mechanical sensitivity and the force compensation sensitivity. Two different coil systems are designed and tested experimentally. Double force compensation is proposed in order to obtain a large range and high resolution. The measurement range of the large coil system and the resolution of the small one are fully realized by the double compensation method, After manufacturing, a range over 300 gf and resolution under +/-0.1 mgf were obtained by the double compensation method.This work was supported in part by the Brain Korea 21 Project
Long-stroke tracking actuator for both coarse and fine motion in optical disk drives
No full textIn an optical disk system, the tracking system consists of-a coarse actuator and a fine tracking actuator. This 2-stage actuator requires. many devices in order to obtain both a large stroke and precise movement. The moving parts also have a,heavy mass because of their complicated configuration. As a result, the inertia and friction forces caused by the large mass interfere with fast response and precise movement. This paper describes the design and construction of a one-dimensional tracking actuator that combines a fine tracking actuator with a coarse actuator. The system is designed in the following way: first, a voice coil motor (VCM) is used as the basic drive mechanism for high precision. The permeance method is used to obtain a large driving force for the actuator. The results of this analysis-are verified by simulation and experiment. Second, a focus spring is designed to enhance the stability of the tracking actuator and the sensitivity of the focusing actuator. Third, since friction is the dominant error source the friction force is reduced by a plastic coating, and friction identification is carried out. After the actuator is constructed based on the above design schemes, PD control is applied. The actuator has a resolution under +/-0.1 mum and a stroke over 33 mm. (C) 2003 Elsevier Science Ltd. All rights reserved.This work was supported in part bythe Brain Korea 21 Project
Parallelism error analysis and compensation for micro-force measurement
No full textThe null balance method for micro- and nano-force measurement is widely used in various precision industries. A parallel spring and a lever mechanism are designed and analysed for an electrostatic force balance by the null balance method. Various design parameters are required to obtain high resolution, a large measurement range, and fast response. The corner loading error is one of the most dominant error sources that should be removed. A parallel spring known as the Roberval mechanism, used in the micro-weighing device, can be used for one-axis force measurement since it is very sensitive to the vertical direction force, but insensitive to other force components. However, precise control of parallelism to below a micrometre is required not only to compensate for but also to remove the corner loading error. In this paper, the effects of the parallelism error have been analysed using the Lagrange method and verified by the FEA method. It was found that parallelism control by the proposed precise compensation mechanism enables the simultaneous elimination of and compensation for the corner loading error.This work has been supported by the Korea Research
Council of Public Science and Technology and by the
National Research Laboratory for the Force Measurement and
Evaluation
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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