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排序方式: 共有179条查询结果,搜索用时 15 毫秒
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Ladder handling by telecommunications technicians represents an indispensable part of their daily work, but may generate musculoskeletal injury risk. These workers have a high prevalence of shoulder and back injuries, motivating research to quantify postures and loading using different ladders during common handling tasks. Twenty-five participants completed carry, raise (against a wall or free standing), and simulated removal from a van roof tasks using three ladders (8.5m 2-piece wood; 8.5m 2-piece fibreglass, 9.2m 3-piece wood). Data collection included kinematics and kinetics during these ladder handling tasks, as well as perceived discomfort, perceived exertion and post-collection ladder and task preferences. Significant effects depended on task and ladder. Dominant arm (the arm completing the primary action) elevation was higher while extending the ladder (114.7 ± 3.4°) than the carry task (53.5 ± 3.5°) (p < 0.05). Joint moments in the dominant shoulder and trunk were highest for the 2-piece wood ladder (59.0 ± 2.2 Nm and 254.8 ± 8.8 Nm) averaged across all tasks. Joint forces were increased when using the 2-piece wood ladder compared to the 3-piece wood ladder (p < 0.05), while the greatest discomfort in the shoulders occurred using the 2-piece wood ladder in the carry task. Many tasks approached or exceeded strength capability of a 50th percentile male's predicted strength. While no ladder universally mitigated physical demands while lowering perceptual difficulty, construction differences yielded trends toward preferring the 2-piece fibreglass or 3-piece wood ladders over the 2-piece wood ladder. This work has direct relevance to workplaces with ladder handling and provides recommendations for ladder selection and strength requirements across tasks. 相似文献
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一个图的全染色被称为点可区别的即对任意两个不同点的相关联元素及其本身所构成的色集合不同。其中所用的最少颜色数称为G的点可区别全色数。本文定义了一种排序方法:三角排序。利用该排序的结果证明了当n≡5(mod8)和C4n-1/2+2〈m≤C4n/2+2时,梯图Lm≌Pm×P2的点可区别全色数为n。 相似文献
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以Visual C 6.0作为开发工具,介绍了软PLC控制系统的软、硬件结构,详细叙述了其具体实施方案,并给出实际运用,验证了它的正确性. 相似文献
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Wen-Ruey Chang Yueng-Hsiang Huang Chien-Chi Chang Christopher Brunette Nils Fallentin 《Ergonomics》2016,59(8):1100-1108
Ladder inclined angle is a critical factor that could lead to a slip at the base of portable straight ladders, a major cause of falls from heights. Despite several methods established to help workers achieve the recommended 75.5° angle for ladder set-up, it remains unclear if these methods are used in practice. This study explored ladder set-up behaviours in a field environment. Professional installers of a company in the cable and other pay TV industry were observed for ladder set-up at their worksites. The results showed that the actual angles of 265 ladder set-ups by 67 participants averaged 67.3° with a standard deviation of 3.22°. Although all the participants had training on recommended ladder set-up methods, only 3 out of 67 participants applied these methods in their daily work and even they failed to achieve the desired 75.5° angle. Therefore, ladder set-up remains problematic in real-world situations.
Practitioner Summary: Professional installers of a cable company were observed for portable straight ladder set-up at their worksites. The ladder inclined angle averaged 67.3° with a standard deviation of 3.22°, while the recommended angle is 75.5°. Only a few participants used the methods that they learned during training in their daily work. 相似文献
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《Ergonomics》2012,55(3):221-234
Portable ladders are one of the most ancient tools conceived by man. They remain ubiquitous and indispensable even today. It is interesting to note that there is little difference between the makeshift portable ladders used throughout history and some still used today. The design of portable ladders seems to have simply evolved, rather than been subject to formal design process, including ergonomic criteria. An analysis of 277 fatalities associated with ladders was conducted to describe the pattern of ladder fatalities and identify and assess ergonomic design controls. All ladder fatalities analysed were found to contain multiple human, equipment (ladder) and environmental causative factors. It is hypothesized that significant gains with regard to reducing future fatalities can be achieved by applying ergonomic design principles to ladders to accommodate predictable and undesirable human behaviour. Without effective future change, the only prediction that can be made is that the pattern of ladder fatalities will simply continue. 相似文献
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