1,720,956 research outputs found
Effect of reclining a seat on the discomfort from vibration and shock on fast boats
No full textPassengers and crew on fast boats can experience high magnitudes of whole-body vibration and mechanical shocks that may present risks to health and cause discomfort. This study investigated the influence of reclining a seat on the discomfort caused by fast-boat motion and whether discomfort can be predicted by overall ride values according to current standards. Subjects judged the discomfort of simulations of a recorded fast boat motion in a seat reclined by 0°, 15°, 30°, 45°, or 60°. Reclining the seat caused no significant change in overall discomfort, suggesting that if a reclined seat can be shown to reduce risks of injury it may be acceptable in respect of comfort. The findings are inconsistent with the predictions of standards and show that revised frequency weightings are required to account for seat pan or seat back inclination.Practitioner Summary: Contrary to predictions of current standards, reclining a seat may not increase discomfort during fast-boat motion. Revised frequency weightings for evaluating the severity of whole-body vibration are required to account for seat pan or seat back inclination
Effect of roll oscillation frequency on motion sickness
No full textBackground: in many environments associated with motion sickness there are low frequency motions in several axes, including roll. Roll motion has often been assumed to be a cause of motion sickness, either alone or in combination with motions in other axes. However, there have been no systematic studies of the effects of roll frequency on sickness. Hypothesis: it was hypothesized that sickness caused by roll oscillation would depend on the frequency of roll. Method: there were 100 male subjects (aged 18 to 26 yr) who participated in a laboratory study. Prior to experiencing motion, all subjects completed a motion sickness history questionnaire giving information on travel and motion sickness experience. The seated subjects were exposed within a closed cabin to 30 min of sinusoidal roll motion at one of five frequencies: 0.025 Hz, 0.05 Hz, 0.10 Hz, 0.20 Hz, or 0.40 Hz. At each frequency, the cabin oscillated through ±8° about a center of rotation located on the seat surface. Ratings of motion sickness were obtained at 1-min intervals. Results: subject illness ratings were positively correlated with their previous motion sickness, although at each frequency the amount of sickness was small. Overall, there was no significant difference in the sickness ratings produced by the five motions. Conclusions: the frequency dependence of motion sickness produced by roll oscillation differs from that associated with vertical and horizontal oscillation. Motion sickness associated with pure roll oscillation of a seat will usually be less than the sickness associated with pure translational oscillation of the seat or the sickness associated with combined translation and rotation
The annoyance caused by simultaneous noise and vibration from railways
No full textA study has been conducted to determine a method of predicting subjective response to simultaneous noise and vibration produced in buildings near railways. The method of magnitude estimation was used by 20 subjects to indicate the annoyance produced by vibration and noise in houses during the passage of six trains. The subjects were exposed to 90 stimuli consisting of 15 paired combinations of four levels of noise and four magnitudes of vibration for each of the six trains. The influence of duration, magnitude, and frequency of vibration and the effect of simultaneous noise were combined to provide a method of predicting the relative annoyance for different combinations of noise and vibration. The resulting relation, which involved the summation of the individual effects of the two stimuli in terms of the vibration dose value and the sound exposure level, was shown to provide a more accurate means of predicting the overall reaction from simultaneous noise and vibration than a method based on either noise or vibration alone. It may also be employed to indicate the relative importance of the two stimuli. The findings suggest that the vibration dose value and the sound exposure level are sufficient to provide useful approximations to subjective reactions to short duration exposures to railway vibration and noise.</p
The frequency dependence of subjective reaction to vertical and horizontal whole-body vibration at low magnitudes
No full textThe assessment of building vibration with respect to human response requires knowledge of the influence of vibration magnitude, frequency, direction, and duration. This article reports an experiment conducted to investigate the effect of three of these factors: frequency, magnitude, and direction. The method of magnitude estimation was employed with a sound reference stimulus (1/3 octave band centered at 1 kHz) so as to determine reaction to vertical (z-axis) and horizontal (y-axis) sinusoidal whole-body vibration. Twenty subjects were exposed to six acceleration magnitudes in the range 0.04-0.4 ms-2 rms at nine frequencies between 4 and 63 Hz. The relation between magnitude estimate rp and acceleration magnitude q> was determined at each frequency in the psychophysical power form tft = k<p”. The value of the exponent n varied from 1.04 to 1.47 for vertical motion and from 0.68 to 1.99 for horizontal motion. For vertical motion, the effect of frequency was not significant; for horizontal motion, the exponent increased with increasing frequency. Vibration frequency weightings were determined to describe subjective response to whole-body vibration at low magnitudes that might occur in buildings. PACS numbers: 43.40.Ng.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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