A quantitative assessment of the effects of passive upper extremity exoskeletons on expert cardiovascular sonographers’ muscle activity and posture while performing transthoracic echocardiograms (TTE)

During scanning, sonographers often assume significant awkward postures which may lead to musculoskeletal pain and disability. Two exoskeletons were tested as an ergonomic intervention by sonographers during transthoracic echocardiograms (TTE). Four sonographers each performed TTEs using right- and left-handed scanning techniques, with and without two different passive upper extremity exoskeletons in two two-by-two experimental designs. Posture, muscle activity, and subjective discomfort scores were recorded. Of the two exoskeletons tested, the updated FLEX® design significantly reduced 10th percentile upper trapezius muscle activity during left hand scanning, while the AIRFRAME® did not impact muscle activity across all the muscles of interest. Furthermore, there was a slight decrease in the self-reported discomfort levels in their wrist and hands associated with performing TTE when wearing Exos1 compared to baseline. However, participants experienced issues with comfort, limitations on their range of motion (ROM), and interference with tasks with both exoskeletons. Collectively, the results indicate that the tested exoskeleton designs provide minimal benefit for reducing upper extremity muscle workload during TTE ultrasonography tasks.     

Long-duration assessment of upper arm posture and motion and their association with perceived symptoms among bakery workers

Awkward shoulder postures have been suggested to be a cause of shoulder discomfort among bakery workers. This study aimed at long-duration assessment of upper arms posture and motion and their association with perceived symptoms among bakery workers. Among workers in three types of bread systems, fifty-seven bakers were randomly selected. The self-reported rates for the perceived severity and frequency of shoulder discomfort were collected through questionnaires. Working postures and movements of the shoulders during work were continuously recorded with inclinometry measurements for three hours. Percentage of time spent with the upper arm right elevated more than 60° was significantly correlated with the perceived discomfort rate in the right shoulder for all bakery workers (r = 0.48 to 0.63, p ≤ 0.05). A significant correlation was found between angular velocity with the perceived discomfort intensity for right upper arm.(r = 0.60 to 0.87, ≤0.005) of all workers in the three baking systems. Physical exposure in bakers was characterized by significantly more awkward postures and the percentage of time spent with the upper arms elevated more than 60°. The current findings can facilitate more informed decisions with respect to both engineering (e.g.ergonomic workstation and tool design) and administration (e.g. work organization) control strategies.     

Dual-Rotation Speed Friction Stir Welding: Experimentation and Modeling

Implementing differential rotation speeds of pin and shoulder in the friction stir welding process is considered. Experimental investigations were carried out using a newly designed and fabricated apparatus for dual-rotation speed friction stir welding. Metallographic studies demonstrated that appropriate selection of separate pin and the shoulder rotation speeds not only results in defect-free joints, but also affects the weld zone by controlling the heat input delivered. An energy model for predicting maximum temperature was extended to the dual-rotation speed friction stir process. The model was verified using the previous experimental results reported in the literature.     

基于上臂关节角度和肌电信号的二自由度假肢控制方法

肌电信号的采集易受到空气湿度和皮肤表面汗液等多种随机因素的干扰,使采集到的肌电信号极不稳定.为了应对此问题,市售的肌电假肢普遍采用基于开关量的控制方法,但是开关量对多自由度假肢的控制依赖于顺序动作切换,这使得假肢的实际使用过程比较繁琐.利用肢体运动学信息的假肢控制方法常见于下肢假肢,这是因为上肢的运动受抓取物体的形状和位置等因素变化,其肢体运动的规律性较差.本文提出一种利用上臂关节角度和肌电信号的控制方法,利用人体在抓握时肩关节的运动模式区分使用者对不同形状物体的抓握,并将此方法应用在二自由度假肢的控制中.通过与开关量控制的假肢在日常物品抓握实验中的对比,表明本文所提出方法在稳定性和使用效率方面都优于开关量控制的方式.     

翻领成型器交接曲线研究的现状与进展

介绍了翻领成型交换曲线研究的现状与进展,还分析了交接曲线的不同函数表达式的计算特点。     

Integrating a hip belt with body armour reduces the magnitude and changes the location of shoulder pressure and perceived discomfort in soldiers*

Soldiers carry heavy loads that may cause general discomfort, shoulder pain and injury. This study assessed if new body armour designs that incorporated a hip belt reduced shoulder pressures and improved comfort. Twenty-one Australian soldiers completed treadmill walking trials wearing six different body armours with two different loads (15 and 30 kg). Contact pressures applied to the shoulders were measured using pressure pads, and qualitative assessment of comfort and usability were acquired from questionnaires administered after walking trials. Walking with hip belt compared to no hip belt armour resulted in decreased mean and maximum shoulder pressures (p < 0.005), and 30% fewer participants experiencing shoulder discomfort (p < 0.005) in best designs, although hip discomfort did increase. Laterally concentrated shoulder pressures were associated with 1.34-times greater likelihood of discomfort (p = 0.026). Results indicate body armour and backpack designs should integrate a hip belt and distribute load closer to shoulder midline to reduce load carriage discomfort and, potentially, injury risk.

Practitioner Summary: Soldiers carry heavy loads that increase their risk of discomfort and injury. New body armour designs are thought to ease this burden by transferring the load to the hips. This study demonstrated that designs incorporating a hip belt reduced shoulder pressure and shoulder discomfort compared to the current armour design.     

六自由度肩关节康复机器人设计与仿真

针对肩关节运动损伤康复训练问题,通过分析肩关节的运动方式,设计一种外骨骼肩关节康复机器人。对机器人的整体样机机械结构进行简单建模设计,并解决了肩关节旋转中心瞬时可变性的问题;通过D-H法推导出机器人运动学方程,并通过MATLAB验证了运动学方程的正确性。利用ADAMS软件中建立的虚拟样机模型,对机器人进行运动学和动力学的仿真,得到各关节角速度与时间的关系和各关节的驱动力矩曲线。最后通过蒙特卡洛法,计算出机器人末端运动的位置云图,得到机器人末端的运动范围。仿真分析验证了机器人结构的可行性和运动学方程的正确性,可以实现康复目的。     

发动机风扇叶片凸肩工作面挤压应力研究

针对风扇叶片凸肩结构工作面挤压应力分布情况,建立了风扇叶片凸肩工作面接触有限元计算模型,分析了工作状态下叶片凸肩工作面挤压应力分布和变形情况。通过对实际工作后的风扇叶片凸肩工作面进行了检测,有限元仿真分析结果与实际工作面检测结果一致。研究了凸肩工作面挤压应力分布原因,并发现凸肩工作面的挤压应力分布和变形主要由初始紧度和工作载荷决定。该挤压应力的研究将为风扇叶片凸肩工作面的结构设计与制造提供参考依据。     

Investigating the influence of curbs on single-vehicle crash injury severity utilizing zero-inflated ordered probit models

The severity of traffic-related injuries has been studied by many researchers in recent decades. However, previous research has seldom accounted for the effects of curbed outside shoulders on traffic-related injury severity. This study applies the zero-inflated ordered probit (ZIOP) model to evaluate the influences of curbed outside shoulders, speed limit change, as well as other traditional factors on the injury severity of single-vehicle crashes. Crash data from 2003 to 2007 in the Illinois Highway Safety Database were employed in this study.     

Biomechanical aspects of work-related musculoskeletal disorders

This article provides a review of the biomechanics literature on the low back and upper extremities. Biomechanics is the study of forces acting on and generated within the body and of the effects of these forces on the tissues, fluids, or materials used for diagnosis, treatment, or research purposes. The discussion begins with an overview of basic concepts and methods. This is followed by the two literature reviews. The study selection criteria are presented at the beginning of each review. The two bodies of literature differ in maturity; the research on the low back is more substantial. The number of studies reviewed is 196 for the low back and 109 for the upper extremities. While there are certainly individual factors that put a person at risk for back pain, overall, this body of literature indicates that back pain can be related to excessive mechanical loading of the spine that can be expected in the workplace. The literature also indicates that appropriate reduction of work exposure can decrease the risk of low back disorder. Hence, it is clear, from a biomechanical perspective, that exposure to excessive amounts of physical loading can increase the risk of low back disorder. The literature also reveals that there are strong relationships between physical loads in the workplace and biomechanical loading, internal tolerances, and pain, impairment, and disability associated with the upper limb. Although many of these relationships are complex, the associations are clear. The biomechanical literature has identified relationships between physical work attributes and external loads for force, posture, vibration and temperature. Research has also demonstrated relationships between external loading and biomechanical loading (i.e. internal loads or physiologic responses). Relationships between external loading and internal tolerances (i.e. mechanical strain or fatigue) have also been demonstrated. Finally, relationships have been shown between external loading and upper limb pain, discomfort, impairment or disability. Although the relationships exist, the picture is far from complete. Individual studies have, for the most part, not fully considered the characteristic properties of physical work and external loading (i.e. magnitude, repetition or duration). Few studies have considered multiple physical stress factors or their interactions. The existence of these interactive relationships supports the load-tolerance model presented in this paper.