1,722,643 research outputs found
K. J. Dover (Editeur), E. L. Bowie, Jasper Griffin, M. L. West, Ancient Greek Literature
No full textByl Simon. K. J. Dover (Editeur), E. L. Bowie, Jasper Griffin, M. L. West, Ancient Greek Literature. In: L'antiquité classique, Tome 51, 1982. pp. 340-341
Measurement, evaluation and assessment of human exposures to vibration and their effects on health
No full textVertical vibration of seated subjects: effects of posture, vibration level, and frequency
No full textThe transmissibility of 12 seated subjects to sinusoidal vertical vibration was measured at 12 frequencies in the range of 7 to 75 Hz. Transmissibility, the ratio of seat vibration to vertical head vibration measured on a bite bar, was determined at each of 6 levels of vibration (0.2 to 4.0 m/s2 r.m.s.) in 2 body postures. The postures were defined by the body positions that maximised and minimised the sensation of vibration at the subjects' heads. Measurements of the fore and aft (ax), lateral (ay), and pitch motions of the head were measured on 3 subgroups. Posture had a very large effect on the vibration of the head with an approximate 6:1 difference in the mean vertical head vibration of the subjects between the 2 postures in the range 35 to 50 Hz. In both postures the mean transmissibility of the subjects decreased as frequency increased from 7 to 75 Hz and there were statistically significant reductions in transmissibility with increasing levels of vibration. Some results from individuals are presented to illustrate the large differences between subjects. The reactions of the subjects to the vibration are outlined and some implications of the results are discussed.</p
The evaluation of vehicle vibration and seats
No full textMeasurements of vibration in a variety of road vehicles in common use are compared with the guidance provided in ISO 2631-2974 (E) (Guide for the evaluation of human exposure to vibration). For typical journey durations many of the vibration levels are in excess of the levels corresponding to the 'reduced comfort boundaries' and 'fatigue decreased proficiency boundaries' defined in the ISO Standard. Some of the problems inherent in comparing the measured vibration levels with the Standard are outlined and the need for a revised format for the Standard is discussed. A method of summarising the vibration attenuation of vehicle seats is defined and it is shown that the isolation provided by many of the seats of the 16 vehicles used in the study is poor.</p
A comparison of standardized methods for predicting the hazards of whole-body vibration and repeated shocks
No full textMethods of measuring, evaluating and assessing whole-body vibration and repeated shock are offered in ISO 2631 (1974, 1985), BS 6841 (1987), and ISO 2631 (1997). This paper presents a comparison of guidance on the health effects of vibration and repeated shock given in these standards. International Standard 2631 (1974, 1985) offered a set of exposure limits. British Standard 6841 (1987) defines a measurement and evaluation procedure (based on frequency weightings and the vibration dose value, VDV), gives an action level that can be used to assess vibration severity, and mentions some appropriate actions (consideration of the fitness of exposed persons, design of safety precautions, regular health checks). International Standard 2631 (1997) is unclear in several important areas: which body postures and axes are to be assessed; whether evaluations of multi-axis vibration should be based on the "worst axis" or a combination of the frequency-weighted acceleration in all axes; why a new frequency weighting, Wk, is proposed for vertical vibration when it is almost within the error tolerance of an existing weighting, Wb; why a 1·4 multiplying factor is used to evaluate vibration with respect to health but not with respect to comfort; how to choose between different time-dependencies (overall r.m.s., VDV, running r.m.s., and no time-dependency); allowing use of either the maximum value of a running r.m.s. (i.e., MTVV) or the VDV; allowing different averaging periods when calculating the MTVV; using the crest factor to choose between r.m.s. and either the VDV or MTVV methods; defining two inconsistent criteria for deciding whether to use either the VDV or MTVV methods; giving no guidance on how MTVV values should be assessed; including two very different "health guidance caution zones" (for interpreting r.m.s. and VDV measures); providing ambiguous wording for the health guidance caution zones. Very different conclusions can be reached according to what is measured, how the vibration is evaluated and how it is assessed according to ISO 2631 (1997). However, even though it employs a slightly different frequency weighting for vertical vibration, and a 1·4 multiplying factor for horizontal vibration, ISO 2631 (1997) can be interpreted so as to provide evaluations similar to those made according to BS 6841 (1987). It is concluded that the recently revised International Standard for measuring, evaluating and assessing human exposures to vibration and shock will cause unnecessary confusion.</p
Levels of whole body vibration affecting human vision
No full textA visual task was devised to determine the minimum levels of whole body vibration that affect human vision. This task was the perception of the blur, due to eye motion, of an image of a stationary point source of light and is considered to be as sensitive as any alternative measure of the effects of vibration on visual acuity. Minimum levels of sinusoidal vertical vibration required to produce blur have been determined in a group of 12 subjects seated in a posture that maximized the sensation of vibration at their heads. The effect of vibration frequency (from 7 to 75 Hz) differed between subjects and there was a large individual variability in the levels of both head and seat vibration required to produce blur at any frequency. This intersubject variability has been compared with the potentially large intrasubject variability due to changes in body posture. The experimental results have led to the tentative recommendation of vibration levels below which vibration is not normally expected to reduce visual acuity.</p
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
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