1,720,985 research outputs found
Motion sickness with Earth-horizontal translational and rotational oscillation presented in isolation and in combination
No full textLow-frequency Earth-horizontal translational and rotational oscillations can cause motionsickness in transport. Previous studies have found that motion sickness depends on thefrequency, magnitude, direction and duration of the motion, however, knowledge of themechanisms of motion sickness is far from complete. The concept of sensory conflict – thatmotion sickness arises because of a conflict between sensed and expected sensoryinformation is central to theories of motion sickness, but little is known about how the physicalcharacteristics of motion influence sensed and expected sensory signals. The aim of thisresearch was to advance understanding of the effect on motion sickness of factors which mayinfluence sensed and expected vestibular signals during exposure to low-frequencytranslational and/or rotational oscillation.The first experiment investigated whether motion sickness depends on the phase betweencombined lateral acceleration and roll oscillation at 0.2 Hz. The roll oscillation had one of fourphases relative to the lateral acceleration: 0° delay, 14.5° delay, 29° delay, and 29° advance.Sickness decreased as the delay in the roll motion increased; less sickness occurred with aphase advance than a phase delay, suggesting that motion sickness cannot be predicted fromthe acceleration in the plane of the seat.The second experiment investigated how motion sickness varies between four 60-minuteexposures of 0.1 Hz combined lateral and roll oscillation which involved different combinationsof a high and low magnitude motion: LLLL, HHHH, LHHL and HLHL. The high magnitudemotion produced greater sickness than the low magnitude motion. For the two variable motionconditions, there was no significant difference in accumulated illness ratings when the motionsickness dose values were the same.In the third experiment, 0.2 Hz roll and pitch oscillation were studied at three displacements:±1.83° ±3.66° or ±7.32°. A trend for motion sickness to increase with increasing displacementwas observed; similar sickness was caused by roll and pitch oscillation at each magnitude.In the fourth experiment, subject head displacement was measured during 0.2 Hz fore-and-aftoscillation with and without a backrest at three magnitudes: 0.22, 0.44, and 0.89 ms-2 r.m.s.Illness increased systematically with increasing magnitude of oscillation with a backrest, but lesssystematically without a backrest, suggesting an interaction between the effect of motionmagnitude and the influence of a backrest. There were no significant differences in illness withor without a backrest at any of the magnitudes studied. Between subjects, there was littleevidence to suggest that greater fore-and-aft and pitch displacement of the head wasassociated with an increase in motion sickness.Combined findings from the third and fourth experiments suggest that 0.2 Hz fore-and-aftoscillation causes greater sickness than 0.2 Hz pitch oscillation at each of the three magnitudesstudied (assuming that pitch motion can be represented by the gravitational component, gSin?).A motion sickness model is proposed showing how the factors investigated in this thesis affectthe sensed and expected semi-circular canal signals which are assumed to be involved in thecausation of motion sickness. The model predicts how sensed and expected signals varyaccording to the phase between motions, the magnitude, direction and duration of motion, thetype of motion and the postural support given to subjects. Explanations of how the modelpredicts motion sickness based on the findings of this study and previous studies are discussed
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
Motion sickness from combined lateral and roll oscillation: effect of varying phase relationships
No full textBackground: Previous studies have investigated motion sickness caused by combined lateral and roll oscillation occurring in phase with each other. In tilting trains there can be a phase difference between the two motions.Hypothesis: It was hypothesized that sickness caused by combined lateral and roll oscillation would depend on the phase between the lateral acceleration and the roll displacement.Method: At intervals of at least 1 wk, 20 subjects were seated in a cabin and exposed to four 30-min exposures of combined 0.2 Hz sinusoidal lateral acceleration (± 1.26 ms?2) and 0.2 Hz roll displacement (± 7.32°). The roll oscillation had one of four phases relative to the lateral oscillation: 1) 0° delay (giving 100% compensation of the lateral acceleration); 2) 14.5° delay (75% compensation); 3) 29° delay (50% compensation); and 4) 29° advance (50% compensation). Subjects gave ratings of sickness at 1-min intervals.Results: Sickness was greatest with no delay (100% compensation). Increasing the delay to 14.5° (75% compensation) and to 29° (50% compensation) decreased sickness. Less sickness occurred when the roll displacement led the lateral acceleration by 29° (phase advance) than when the roll displacement followed the lateral acceleration by 29° (phase delay).Conclusions: With combined lateral and roll oscillation, sickness depends on the phase between the two motions. Increasing the delay in the roll motion reduces sickness, but also reduces the compensation. There is less sickness when the roll displacement leads the lateral acceleration than when the roll displacement lags the lateral acceleration
Motion sickness: effect of the magnitude of roll and pitch oscillation
No full textBackground: Rotational oscillation in roll and pitch can cause motion sickness, but it is not known how sickness depends on the magnitude of rotational oscillation or whether there is a difference between the two axes of motion.Hypothesis: It was hypothesized that motion sickness would increase similarly with increasing magnitudes of roll and pitch oscillation.Method: There were 120 subjects (6 groups of 20 subjects) who were exposed to 30 min of 0.2-Hz sinusoidal roll or pitch oscillation at 1 of 3 magnitudes: 1) ± 1.83°; 2) ± 3.66°; or 3) ± 7.32°. Subjects sitting in a closed cabin with their eyes open gave ratings of their illness on a 7-point illness rating scale at 1-min intervals.Results: Over the six conditions, mild nausea was reported by 17.5% of subjects. With both roll oscillation and pitch oscillation, mean illness ratings were least with ± 1.83° of rotational oscillation and greater with ± 3.66° and ± 7.32° of oscillation. At none of the three magnitudes of oscillation was there a significant difference in motion sickness caused by roll and pitch oscillation.Conclusions: With rotational oscillation about an Earth-horizontal axis, there is a trend for motion sickness to increase with increasing motion magnitude. For the conditions investigated, similar motion sickness was caused by roll and pitch oscillation
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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