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- Burström, Lage, 1954-, et al.
(författare)
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Acute effects of vibration on thermal perception thresholds
- 2006
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Ingår i: Diagnosis of injuries caused by hand-transmitted vibration - 2nd International workshop, Göteborg, 2006. - : Springer Science and Business Media LLC.
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Konferensbidrag (refereegranskat)abstract
- Objective This study focuses on the acute effects of vibration and how vibrations influence the measures of the thermal perception thresholds during different vibration magnitudes, frequencies, and durations.Methods The fingers of ten healthy subjects, five males and five females, were exposed to vibration under 16 conditions with a combination of different frequency, intensity and exposure time. The vibration frequency was 31.5 and 125 Hz and exposure lasted between 2 and 16 min. The energy-equivalent frequency weighted acceleration, according to ISO 5349-1, for the experimental time of 16 min was 2.5 or 5.0 m/s(2) (r.m.s.), corresponding to a 8-h equivalent acceleration, A(8) of 0.46 and 0.92 m/s(2), respectively. A measure of the thermal perception of cold and warmth was conducted before the different exposures to vibration. Immediately after the vibration exposure the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures at every minute for a maximum of 10 min. If the subject's thermal thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min.Results For all experimental conditions and 30 s after exposure, the mean changes of the thresholds compared with the pre-test were found to be 0.05 and -0.67C for the warmth and cold thresholds, respectively. The effect of the vibration exposure was only significant on the cold threshold and only for the first minute after exposure when the threshold was decreased. The warmth threshold was not significantly affected at all. The frequency and the exposure time of the vibration stimuli had no significant influence on the perception thresholds for the sensation of cold or warmth. Increased equivalent frequency weighted acceleration resulted in a significant decrease of the subjects' cold threshold, not the warmth. The thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency weighted acceleration or the unweighted acceleration.Conclusion When testing for the thermotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained the previous praxis of 2 h avoidance of vibration exposure before assessment is recommended.
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| 3. |
- Knez, Igor, et al.
(författare)
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Influences of culture and environmental attitude on thermal, emotional and perceptual evaluations of a public square
- 2006
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Ingår i: International Journal of Biometeorology. - : Springer Science and Business Media LLC. - 0020-7128 .- 1432-1254. ; 50:5, s. 258-268
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Tidskriftsartikel (refereegranskat)abstract
- The main objective of the present quasi-experimental study was to examine the influence of culture (Swedish vs Japanese) and environmental attitude (urban vs open-air person) on participants' thermal, emotional and perceptual assessments of a square, within the PET (physiological equivalent temperature) comfortable interval of 18-23 degrees C. It was predicted that persons living in different cultures with different environmental attitudes would psychologically evaluate a square differently despite similar thermal conditions. Consistent with this prediction, Japanese participants estimated the current weather as warmer than did Swedish participants and, consistent with this, they felt less thermally comfortable on the site, although participants in both countries perceived similar comfortable thermal outdoor conditions according to the PET index. Compared to the Japanese, the Swedes estimated both the current weather and the site as windier and colder, indicating a consistency in weather assessment on calm-windy and warm-cold scales in participants in both cultures. Furthermore, Swedish participants felt more glad and calm on the site and, in line with their character (more glad than gloomy), they estimated the square as more beautiful and pleasant than did Japanese participants. All this indicates that thermal, emotional and perceptual assessments of a physical place may be intertwined with psychological schema-based and socio-cultural processes, rather than fixed by general thermal indices developed in line with physiological heat balance models. In consequence, this implies that thermal comfort indices may not be applicable in different cultural/climate zones without modifications, and that they may not be appropriate if we do not take into account the psychological processes involved in environmental assessment.
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| 4. |
- Neumann, W. P., et al.
(författare)
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Production system design elements influencing productivity and ergonomics - A case study of parallel and serial flow strategies
- 2006
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Ingår i: International Journal of Operations & Production Management. - : Emerald. - 0144-3577 .- 1758-6593. ; 26:8, s. 904-923
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - The purpose of this paper is to investigate a strategic change from parallel cell-based assembly (old) to serial-line assembly (new) in a Swedish company with special reference to how production system design elements affect both productivity and ergonomics. Design/methodology/approach - Multiple methods, including records and video analysis, questionnaires, interviews, biomechanical modelling, and flow simulation were applied. Findings - The new system, unlike the old, showed the emergence of system and balance losses as well as vulnerability to disturbances and difficulty handling all product variants. Nevertheless, the new system as realised partially overcame productivity barriers in the operation and management of the old system. The new system had impaired ergonomics due to decreased physical variation and increased repetitiveness with cycle times that were 6 per cent of previous thus increasing repetitiveness, and significantly reducing perceived influence over work. Workstations' uneven exposure to physical tasks such as nut running created a potential problem for workload management. The adoption of teamwork in the new system contributed to significantly increased co-worker support - an ergonomic benefit. Practical implications - Design decisions made early in the development process affect both ergonomics and productivity in the resulting system. While the time pattern of physical loading appeared to be controlled by flow and work organisation elements, the amplitude of loading was determined more by workstation layout. Psychosocial conditions appear to be affected by a combination of system elements including layout, flow, and work organisation elements. Strategic use of parallelisation elements in assembly, perhaps in hybrid forms from configurations observed here, appears to be a viable design option for improved performance by reducing the fragility and ergonomic problems of assembly lines. Originality/value - The interacting design elements examined here pose potential "levers" of control by which productivity and ergonomics could be jointly optimised for improved total system performance.
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