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Influence of a back restraint on the lateral apparent mass of the seated human body in response to lateral and roll motions
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A comparison of two methods of simulating seat suspension dynamic performance
No full textMany off-road machines are equipped with a suspension seat intended to minimize the vibration exposure of the operator to vertical vibration. The optimization of the isolation characteristics of a suspension seat involves consideration of the dynamic responses of the various components of the seat. Ideally, the seat components would be optimized using a numerical model of the seat. However, seat suspensions are complex with non-linear characteristics that are difficult to model; the development of seat suspensions is therefore currently more empirical than analytical. This paper presents and compares two alternative methods of modelling the non-linear dynamic behaviour of two suspension seats whose dynamic characteristics were measured in the laboratory. A ‘lumped parameter model’, which represented the dynamic responses of individual seat components, was compared with a global ‘Bouc–Wen model’ having a non-linear degree-of-freedom. Predictions of the vibration dose value for a load placed on the seats were compared with laboratory measurements. The normalized r.m.s. errors between the predictions and the measurements were also determined. The median absolute difference between the measured and predicted seat surface vibration dose values over all test conditions for both models was less than 6% of the measured value (with an inter-quartile range less than 20%). Both models were limited by deficiencies in the simulation of top end-stop impacts after the load lifted from the seat surface. The lumped parameter model appears best suited to the development of the overall design of a suspension seat. The Bouc–Wen model can provide a useful simulation of an existing seat and assist the optimization of an individual component in the seat, without measuring the dynamic properties of components in the seat except those of the component being optimized
Evaluation of whole-body vibration exposures in British industry
No full textThis report describes measurements of whole-body vibration on eight excavators and two compact skid-steer loaders. Of the excavators, four were fitted with impact hammers, two with hydraulic crushers, one with a backhoe shovel and one with steel shears.Accelerations were measured on the seat surface and on the floor within the operators’ cabs of the machines in accordance with ISO 2631 (1997). The data have been evaluated in the context of the levels set out in the European Union Physical Agents (Vibration) Directive (2002/44/EC). The report provides predicted daily vibration exposure for each machine. The effects of machine operation and other parameters on the vibration exposures are also considered.This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.<br/
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
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