Technical Note: Method for objective assessment of physical work load at the workplace

This paper presents a method for objective assessment of physical work load at the workplace. The method is based on the DynaPort ADL Monitor. Using accelerometry, this monitor enables the assessment of gross motor activity as it occurs during the activities of daily living (ADL). A case study is conducted to explore the usefulness of the monitor in support of occupational research. The focus is on the cause and reduction of mechanical low back pain (LBP). A patient suffering from mechanical LBP participated in the study. He worked as messenger in contrast with his usual occupation. The patient was examined in both occupations using the monitor. The ADL profiles indicated that the messenger job was more likely to cause LBP than the other occupation of a mechanic.     

Job rotation as a factor in reducing physical workload at a refuse collecting department

The effect of job rotation on the physical workload was investigated for male employees working at a refuse collecting department. Before the introduction of job rotation, an employee worked as a street sweeper, as a refuse collector or as a driver. After the introduction of job rotation, every employee was allowed to alternate between two of the three possible jobs during the day, i.e. refuse collecting/street sweeping, refuse collecting/driving or street sweeping/driving. Two non-rotation groups (i.e. refuse collectors and street sweepers) and two rotation groups (i.e. refuse collectors/street sweepers and street sweepers/drivers) were mutually compared. The physical workload was determined by measuring the perceived load, energetic load and postural load during a full working day. Job rotation resulted in a significant decrease of the perceived load and energetic load and a slight decrease of the postural load. The results indicate that the total amount of work performed by means of job rotation resulted in an overall reduced physical workload of the employees of the refuse collecting department.     

Musculoskeletal symptoms and workload in 12 branches of Dutch agriculture

A postal questionnaire survey was carried out in Dutch agriculture to identify high risk branches with respect to musculoskeletal symptoms and workload. The study population comprised a sample 2580 male employees and employers, with a response rate of 49%. A total of 75% of the employees and 71 % of the employers reported musculoskeletal symptoms during the past 12 months. Low-back pain was most prevalent (one-year prevalence rate of 51% among employees, 47% among employers), followed by symptoms of the neck-shoulder (one-year prevalence rate of 35% among employees, 30% among employers) and knees (one-year prevalence rate of 22% among employees, 17% among employers). There were marked differences between specific branches in the size and nature of musculoskeletal morbidity as well as in self-reported musculoskeletal workload. In particular protective vegetables growing and arboriculture showed both relatively high rates of symptoms and relatively high exposure levels. The results of this study were used to decide which agricultural branches and workload factors should have priority in the ergonomic interventions that followed.     

Activity analysis of English premiership rugby football union refereeing

Little is known about the physiological demands placed on officials during sporting activities. The purpose of this study was to ascertain the movement activities of referees during English Premiership rugby football union matches, and to determine the frequency and duration of these activities. Nine referees who were ranked in the top 20 referees in England were videotaped during a total of 19 matches. During playback of the videotapes, a single observer coded the referees' activities into one of six distinct categories (standing, walking forwards, walking backwards, jogging, running and sprinting) using a computerized video editing system (Observer Video-Pro). The referees were timed over a 20 m distance for the modes of locomotory activity, and the average velocity of the referee for each activity was used to calculate the total distance covered in each mode of activity during matches. The total distance covered during a match was (χ ± SD) 8581 ± 668 m. The mean percentage of total playing time spent in each activity was: standing still, 37.0 ± 11.0%; walking forward, 29.5 ± 7.2%; walking backward, 9.9 ± 3.2%; jogging, 12.8 ± 3.2%; running, 9.8 ± 2.3%; and sprinting, 1.0 ± 0.4%. There were a total of 672 transitions between modes of activity during a match. The results of this study suggest that refereeing top English rugby football union matches is physically demanding. Although the major physiological load is placed on the oxygen transport system, frequent sprint bouts and the associated requirements for acceleration and deceleration impose additional metabolic demands on referees. This information may be used in the design of physical training programmes to optimize performance in referees.     

A Review.of: “Man and Motor Cars: An Ergonomic Study.” By S. Black. (Seeker and Warburg, 1966.) [Pp. 373.] 63s

This study was concerned with examining driver patterns for three different sized vehicles (small cars, family cars, trucks and buses) through an intersection controlled by a traffic signal. Observations were made morning, noon and afternoon, when there was precipitation and no precipitation. Records were also kept as to whether the drivers wore alone or with passengers and whether the drivers were males or fomales. Results were found showing that family car drivers were the most cautious and that small ear, truck and bus drivers were approximately similar to each other, being less cautious. Drivers with passengers were more cautious and did not violate the law by passing a red light as frequently as did drivers without passengers. Approximately similar driving patterns were found for males and fomales. Different driving patterns were obtained for the three-sized vehicles during morning, noon and afternoon, when there was precipitation and no precipitation.     

无线传感器网络中多重覆盖算法的研究

在无线传感网器络中的硬件资源普遍受限的情况下,形成优秀的覆盖控制策略己成为无线传感器网络研究领域的热点课题。本文提出了一种能量有效的多重物理覆盖算法,在保障覆盖与连通性的前提下,以能量、覆盖度为衡量指标,采用调度机制实现节点轮换活跃与休眠,有效地提高网络生存时间。仿真实验结果表明,与目前典型算法相比,提出的算法在网络生存时间、能量消耗与消亡节点数上具有显著的优势。     

气井稳定携液之我见

业内对于临界携液流量的认识一直都存在着分歧。以Turner、李闽为代表的液滴携液理论观点认为"当气体流速达到一定数值后,液相分散成小液滴被携带走";而以李颖川等为代表的气液两相管流实验模拟者则认为"在气井生产过程中雾状流很难出现,气井生产基本上是以段塞流为主,液滴模型无法解释气井实际排液情况"。为了还原低压低产气井实际生产状态,基于弗劳德相似准数,以流速相似原理模拟低压、低产井实际生产情况,并开展了相应的实验研究。结果表明:①低压、低产气井实际上存在"上雾+下段塞"混合流动状态;②上部雾状流携液满足液滴模型计算结果,当气相流速高于临界携液流速则上部可连续带液,否则会导致积液段液量缓慢增加;③下部表现为段塞流,当气相流速高于1.95 m/s,则表现为连续流动,气井基本无积液,当气相流速低于0.195 m/s,则表现为难以流动,气井不产液,面临水淹。实验所得结果与气井实际生产情况相当吻合,可以为气井有效开采提供技术支撑。     

A study on physical and mechanical properties for soft to firm clays in Yangon area – Properties of clays deposit at the sedimentary basins in Myanmar

Recently, a great deal of foreign investment has been entered into construction of the social infrastructure of Myanmar. Many construction projects are therefore on-going, and these are especially planned in the Yangon area. While these construction booms are increasing, existing studies on the geotechnical problems in the Yangon area such as problematic soils like soft clays are limited at present. Information on soil properties has also not been shared and has been confined to individual projects. In this paper, the boring and laboratory tests carried out in the Yangon area are selected and focused upon among the tests carried out in Myanmar. Laboratory test results for clay deposits in the Yangon area are analyzed and the differences in soil properties between different sedimentary basins and sub-areas divided by the Tertiary sediment ridge that runs from north to south at the center of Yangon are clarified together with a comparison to the clays found in other countries, which have been previously investigated.     

长沙市区岩土体工程地质特征

在收集大量勘察资料的基础上，结合勘察工程实践，对长沙市区岩土体地质特征及工程性能进行了系统地归纳总结，并提出了该地区岩土体主要物理力学性质指标经验值。     

高反膜的计算机模拟及对实践的指导意义

本文利用计算机对多层介质高反膜反射谱的模拟发现,当构成高反膜系的高、低两种折射率材料的光学厚度不一致时,反射带两侧的第一个谷值的大小将不同,据此作者认为在高反膜镀制时可根据反射带两侧第一个谷值大小情况来调节高反膜中单层膜厚度,实验结果证明了模拟结果的正确性,同时也确证了作者提出的这种方法是可行的。