The effect of cushion of air on vibration transmitted to vehicle drivers based on standard

زمینه و هدف: ارتعاش تمام بدن (WBV) از دلایل اصلی اختلالات اسکلتی عضلانی رانندگان است. یک روش برای کاهش ارتعاش استفاده از وسیله عایق می باشد. در این تحقیق، جهت کاهش میزان ارتعاش از یک تشکچه هوا استفاده شده و با اندازه گیری ارتعاش منتقله به رانندگان قبل و بعد از استفاده از تشکچه، اثربخشی آن در کنترل ارتعاش مورد بررسی قرار گرفت. روش بررسی: این مطالعه، مداخله ای و بر روی 95 نفر از رانندگان شرکت واحد اتوبوسرانی انجام شد. پارامترهای ارتعاش در سه محور ورود ارتعاش به بدن، در دو مرحله قبل و بعد از قرار دادن تشکچه بر روی صندلی راننده توسط دستگاه ارتعاش سنج اندازه گیری و با استفاده از آزمون آماری t زوجی مقایسه شدند. یافته ها: مقایسه مقادیر ارتعاش قبل و بعد از استفاده تشکچه نشان داد که ماکزیمم فشار (Pmax) در محورهای X،Y به ترتیب(m/s2) 2921/0 و (m/s2) 3081/0 کاهش (05/0

Designing and validation a visual fatigue questionnaire for video display terminals operators

Background: Along with the rapid growth of technology its related tools such as computer, monitors and video display terminals (VDTs) grow as well. Based on the studies, the most common complaint reported is of the VDT users. Methods: This study attempts to design a proper tool to assess the visual fatigue of the VDT users. First draft of the questionnaire was prepared after a thorough study on the books, papers and similar questionnaires. The validity and reliability of the questionnaire was confirmed using the content validity index (CVI) beside that of the Cronbach's Coefficient Alpha. Then, a cross-sectional study was carried out on 248 of the VDT users in different professions. A theoretical model with four categories of symptoms of visual fatigue was derived from the previous studies and questionnaires. Having used the AMOS16 software, the construct validity of the questionnaire was evaluated using the confirmatory factor analysis. The correlation co-efficiency of the internal domains was calculated using the SPSS 11.5 software. To assess the quality check index and determining the visual fatigue levels, visual fatigue of the VDT users was measured by the questionnaire and visual fatigue meter (VFM) device. Cut-off points were identified by receiver operating characteristic curves. Results: CVI and reliability co-efficiency were both equal to 0.75. Model fit indices including root mean of squared error approximation, goodness of fit index and adjusted goodness of fit index were obtained 0.026, 0.96 and 0.92 respectfully. The correlation between the results measured with the questionnaire and VFM-90.1 device was-0.87. Cut-off points of the questionnaire were 0.65, 2.36 and 3.88. The confirmed questionnaire consists of four main areas: Eye strain (4 questions), visual impairment (5 questions) and the surface impairment of the eye (3 questions) and the out of eye problems (3 questions). Conclusions: The visual fatigue questionnaire contains 15 questions and has a very remarkable validity and reliability. Usingthis questionnaire and its findings, one will be able to identify, assess and finally prevent the effective factors of VDT users' visual fatigue