Human posture simulation to assess cumulative spinal load due to manual lifting. Part II: accuracy and precision

For assessing a large number of variable manual lifting jobs, posture specification for using the University of Michigan Three Dimensional Static Strength Prediction Program and the revised National Institute for Occupational Safety and Health Lifting Equation may be time-consuming, tedious and subject to human errors. To expedite data analysis with desirable accuracy and precision for the two risk assessment tools, a new data analysis method based on human posture simulation was developed and evaluated. The accuracy and precision of the posture simulation method were evaluated by a repeated measures study design with six postures, three viewing angles and three trial repetitions as experimental factors. The effects of the experimental factors on the average accuracy and precision of the simulation method are reported and discussed. The study results also demonstrated pros and cons of human posture simulation as a means of posture specification for ergonomic risk assessments. The findings about the accuracy and precision of the human posture simulation method for quantifying the risk of musculoskeletal disorders due to manual materials handling may provide researchers with a new way of ergonomic assessments.     

Design and implementation of ergonomic risk assessment feedback system for improved work posture assessment

Ergonomic risk factors which include force, repetition and awkward postures, can result in Work-Related Musculoskeletal Disorders (WMSDs) among workers. Hence, systems that provide real-time feedback to the worker concerning his current ergonomic behaviours are desirable. This paper presents the design and implementation of a human-machine interface posture assessment feedback system whose conceptual model is developed through a model-driven development perspective using the Unified Modeling Language (UML) and interface flow diagrams. The resulting system provides a shop floor with a simple, cost-effective and automatic tool for real-time display of worker's postures. Testing the system on volunteer participants reveals that it is easy to use, achieves real-time posture assessment and provides easy-to-understand feedback to workers. This system may be useful for reducing the rate of occurrence of awkward postures, one of the contributing factors to risk of WMSDs among workers.     

Function-transformation methods for multi-objective optimization

It is useful with multi-objective optimization (MOO) to transform the objective functions such that they all have similar units and orders of magnitude. This article evaluates various transformation methods using simple example problems. Viewing these methods as different means to restrict function values sheds light on how the methods perform. The weighted sum approach for MOO is used to study how well different methods aid in depicting the Pareto optimal set. Whereas using unrestricted weights is well suited for providing a single solution that reflects preferences, it is found that using a convex combination of functions is desirable when generating the Pareto set. In addition, it is shown that some transformation methods are detrimental to the process of generating a diverse spread of points, and criteria are proposed for determining when the methods fail to generate an accurate representation of the Pareto set. Advantages of using a simple normalization–modification are demonstrated.     

Development and Multiobjective Optimization of Improved Cumene Production Processes

Multiobjective optimization (MOO) has been successfully used to improve the process design and operation, by finding trade-offs among conflicting objectives such as energy, capital cost, and profit. In this work, the cumene process design is modified to decrease the raw materials and product losses and to facilitate better energy integration. Here, two slightly different cumene process designs are presented and evaluated. One process design uses a column to vent off the undesired chemicals, whereas the other uses two flash tanks. Additionally, vapor recompression is applied in both the designs to recover energy. Then, MOO of both modified process designs is carried out to examine two trade-offs: total capital cost (TCC) versus material loss and TCC versus utility cost. For this, an Excel-based MOO program is used; it is based on the elitist nondominated sorting genetic algorithm. The cumene process design with column is found to be superior for the first trade-off, whereas the design with two flash tanks is better for the other trade-off. Further, both the designs are compared based on their cumene production capacities; column design is found to be overall superior. Finally, energy requirements of the developed cumene process designs are compared with those reported in recent studies.     

基于坐姿分析的座椅舒适度测试与评价

人们的很多生产生活活动是在坐姿下完成的,因此研究坐姿舒适度有很重要的意义。坐姿舒适度在座椅的设计中扮演着越来越重要的角色,而对座椅舒适度的研究也逐渐偏重对坐姿舒适度的评价。人性化座椅的设计必须满足舒适度高的要求,以达到人体舒适坐姿的需求。针对坐姿舒适度评价,采用经典的光学动作捕捉技术和问卷调查相结合的方法对坐姿舒适度进行科学评价。实验选用美国Motion Analysis光学动作捕捉系统,设置11个Eagle数字捕捉镜头,用EVaRT软件获取了40名志愿者人体关键点在空间中的点位数据,采用PCA主成分分析提取特征点的方法提取关键点,用MATLAB软件自主编程对关键点数据进行处理和计算,比较测试者坐在2种不同座椅上的关节角度和力矩数据差异。统计结果表明,志愿者采用不同的姿势坐在不同的座椅上时,躯干、大腿、膝盖部位的角度和力矩数据差异较为明显。结合人机工程理论,利用这些数据差异对坐姿进行分析,为座椅设计提供理论依据。这种人机工程学理论分析评价和问卷调查相结合的方法,为座椅的舒适度评价提供了有效的依据。     

肌肉骨骼疾患风险评估方法趋势研究

目的肌肉骨骼疾患是与工作姿势有关的主要职业病,不仅影响工人的健康,而且对经济造成巨大的损失。而不良的工作姿势是引发肌肉骨骼疾患的主要原因。因此评估工作姿势所造成的肌肉骨骼疾患并采取科学的纠正措施逐渐成为相应领域研究的热点问题。基于现有对肌肉骨骼疾患风险评估方法的研究现状和未来趋势进行分析与展望。方法通过对肌肉骨骼疾患、人因风险评估、人体姿态识别等核心概念的相关文献进行梳理和归纳,论述了肌肉骨骼疾患风险评估的主要方法,并重点分析了图像识别技术在肌肉骨骼疾患风险评估中的应用,结合人体骨架与神经网络算法模型对作业姿势进行识别,探讨了人工智能环境下,基于图像识别的评估方法中待解决的难点问题,对未来可能发展趋势进行预测。结论将肌肉骨骼风险评估方法总结为三大类,并分析其在现场评估应用过程中的优缺点;结合图像识别技术的发展,对肌肉骨骼风险评估提出了展望,即智能化自动化评估、多评估方法融合、多通道特征识别。     

Multi-objective engineering design using preferences

System design is a complex task when design parameters have to satisy a number of specifications and objectives which often conflict with those of others. This challenging problem is called multi-objective optimization (MOO). The most common approximation consists in optimizing a single cost index with a weighted sum of objectives. However, once weights are chosen the solution does not guarantee the best compromise among specifications, because there is an infinite number of solutions. A new approach can be stated, based on the designer's experience regarding the required specifications and the associated problems. This valuable information can be translated into preferences for design objectives, and will lead the search process to the best solution in terms of these preferences. This article presents a new method, which enumerates these a priori objective preferences. As a result, a single objective is built automatically and no weight selection need be performed. Problems occuring because of the multimodal nature of the generated single cost index are managed with genetic algorithms (GAs).     

Constructing an optimal facility layout to maximize adjacency as a function of common boundary length

An effective facility layout implies that departments with high flow are laid adjacent. However, in the case of a very narrow boundary length between the neighbouring departments, the adjacency would actually be useless. In traditional layout design methods, a score is generally assigned independent of the department’s boundary length. This may result in a layout design with a restricted material flow. This article proposes a new concept of adjacency in which the department pairs are laid adjacent with a wider path. To apply this concept, a shop with unequal rectangular departments is contemplated and a mathematical programming model with the objective of maximizing the sum of the adjacency degrees is proposed. A computational experiment is conducted to demonstrate the efficiency of the layout design. It is demonstrated that the new concept provides a more efficient and a more realistic layout design.     

Determination of the just noticeable difference (JND) in trunk posture perception

The purpose of this study was to assess the ability of subjects to detect a visual difference between trunk postures. Three groups of participants, ranging from novices to experts, were required to make perceptual discriminations between two trunk postures from a series of image pairs on a computer screen. Images were presented for flexion and lateral bending motions from three different reference postures in both ascending and descending directions. Overall, direction played the largest role, interacting with all other variables. Subjects were most sensitive to changes in the ascending direction, where differences were detected at an average of 2°. In the descending direction, subjects detected differences at an average of 7° between postures. These data have implications for the usability and design of posture matching-based biomechanical software interfaces and the accuracy of peak and cumulative load estimates from models that utilize such interfaces to acquire segment posture inputs.     

The Effect of Jar Holding Posture on Finger Force and Torque during a Jar‐Opening Task for Young Females

Many young females have difficulty opening jars. Although previous studies have attempted to clarify the body posture effect during such a task, the experiments therein focused on a single digit or actions with unnatural finger positions and were further restricted to upper extremity postures. A further study is required to investigate the fingers’ coordination, as well as each subject's natural and self‐selected upper extremity posture and finger grasp location when opening a jar. This study focused on the forces and coordination of the right hand fingers during a jar opening movement under both vertical and free‐way opening postures. A jar simulator was set up to record the forces applied by finger groups (the thumb, the index–middle finger group, and the ring–little finger group) of the right hand. A self‐selected finger position and free‐arm posture of each subject were allowed. Results show that the force vectors of the finger groups were all in the counterclockwise direction for both postures. The total force and overall torque of the right hand decreased in the vertical opening posture. The thumb produced greater tangential and resultant forces in the vertical opening posture. Despite normal forces being 1.82–3.54 times the tangential forces for both postures, no difference was found for the normal force to tangential force ratio for each finger group between the two opening postures. The index–middle finger group had similar torque contributions for both postures. The torque contribution of the thumb increased (26% and 21% for vertical and free‐way posture, respectively), while the ring–little finger group torque contribution decreased (35% and 42% for vertical and free‐way posture, respectively) in the vertical opening posture. As such, the free‐way opening posture is the better strategy for young females to open a jar. Copyright © 2013 John Wiley & Sons, Ltd.     

磁流变阻尼器MNS模型参数不确定性分析

磁流变阻尼器（Magneto-Rheological damper）因其优异的性能,在地震和风荷载下的结构振动控制中有广阔的应用。采用磁流变阻尼器进行结构控制时,建立相对精确的非线性模型是设计控制策略重要因素之一,也是保证对其进行数值分析时具有较高可信度的关键因素之一。从传统优化方法获得的确定性模型参数无法考虑由于磁流变阻尼器的现象学模型（phenomenological model）内在的不确定性,从而可能导致阻尼器模型出现不准确的预测。使用马尔可夫链蒙特卡洛方法,该研究对磁流变阻尼器的Maxwell Nonlinear Slider（MNS）模型的不确定性分析,并通过与现有200 kN足尺磁流变阻尼器试验结果,证明了概率模型能够更好地预测磁流变阻尼器在预定的正弦曲线位移和实时混合模拟的位移响应下的输出力和能量耗散,从而为进一步分析结构在磁流变阻尼器控制下的响应预测提供了更为有效的工具。     

Evaluation of turbo and hydro‐generator torques due to electromechanical interaction

Abstract

The computer prediction of turbogenerator behaviour following fault or disturbance conditions has become an important feature in the assessment of machine system design, pre‐commissioning test appraisals, system operational procedures, machine monitoring strategy and post‐event damage diagnoses. In this paper computer methods are described to assess the comparative severity of various electrical faults and disturbances, the effect of specific operational practices together with the prediction of peak torsional transient behaviour. This paper is supported by realistic examples simulating the transient behaviour of a number of generational units.     

A Geodesign Method of Human-Energy-Water Interactive Systems for Urban Infrastructure Design: 10KM2 Near-Zero District Project in Shanghai

The grand challenges of climate change demand a new paradigm of urban design that takes the performance of urban systems into account, such as energy and water efficiency. Traditional urban design methods focus on the form-making process and lack performance dimensions. Geodesign is an emerging approach that emphasizes the links between systems thinking, digital technology, and geographic context. This paper presents the research results of the first phase of a larger research collaboration and proposes an extended geodesign method for a district-scale urban design to integrate systems of renewable energy production, energy consumption, and storm water management, as well as a measurement of human experiences in cities. The method incorporates geographic information system (GIS), parametric modeling techniques, and multidisciplinary design optimization (MDO) tools that enable collaborative design decision-making. The method is tested and refined in a test case with the objective of designing a near-zero-energy urban district. Our final method has three characteristics. ① Integrated geodesign and parametric design: It uses a parametric design approach to generate focal-scale district prototypes by means of a custom procedural algorithm, and applies geodesign to evaluate the performances of design proposals. ② A focus on design flow: It elaborates how to define problems, what information is selected, and what criteria are used in making design decisions. ③ Multi-objective optimization: The test case produces indicators from performance modeling and derives principles through a multi-objective computational experiment to inform how the design can be improved. This paper concludes with issues and next steps in modeling urban design and infrastructure systems based on MDO tools.     

Maximum Gauge Pressure in Dangerous Goods Packagings Under Normal Conditions of Carriage – Comparison of Direct Measurement and Calculation

The objective of this work was to determine the maximum gauge pressure in the vapour phase above the liquid in different design types of dangerous goods packagings under normal conditions of carriage. The design types investigated were steel and plastic packagings with a volume of approximately 6 l. Two different methods were applied. In method 1, the pressure inside the packaging filled with a certain filling substance (dichloromethane) was directly measured under simulated conditions of carriage (degree of filling: 90%; filling temperature: 15°C; temperature during storage: 31°C). The maximum measured gauge pressures were between 89 mbar for a light plastic jerrican and 336 mbar for a steel drum. In method 2, the gauge pressure was calculated. The consideration of a rigid packaging combined with the assumption of a vapour pressure of zero during filling and sealing can serve as a worst case scenario. The calculated gauge pressure is approximately 1061 mbar. This procedure leads to the highest safety factor and does not require any experimental investigations. For a more realistic approximation of the gauge pressure of a non‐rigid packaging, a packaging‐specific function of relative expansion can be used, which is determined by a hydraulic pressure test. The calculated values ranged from 105 to 347 mbar. Method 2 provides conservative results. No hazardous filling substance is needed, and it allows a prediction of gauge pressure for other temperatures, substances and filling degrees. Therefore, this method could serve as alternative to UN Model Regulations 6.1.5.5.4 (a). Copyright © 2014 John Wiley & Sons, Ltd.     

Optimizing multi-response surface problems: How to use multi-objective optimization techniques

A common problem encountered in product or process design is the selection of optimal parameter levels that involves the simultaneous consideration of multiple response characteristics, called a multi-response surface problem. Notwithstanding the importance of multi-response surface problems in practice, the development of an optimization scheme has received little attention. In this paper, we note that Multi-Response surface Optimization (MRO) can be viewed as a Multi-Objective Optimization (MOO) and that various techniques developed in MOO can be successfully utilized to deal with MRO problems. We also show that some of the existing desirability function approaches can, in fact, be characterized as special forms of MOO. We then demonstrate some MOO principles and methods in order to illustrate how these approaches can be employed to obtain more desirable solutions to MRO problems.     

Software Defect Prediction Based on Stacked Contractive Autoencoder and Multi-Objective Optimization

Software defect prediction plays an important role in software quality assurance. However, the performance of the prediction model is susceptible to the irrelevant and redundant features. In addition, previous studies mostly regard software defect prediction as a single objective optimization problem, and multi-objective software defect prediction has not been thoroughly investigated. For the above two reasons, we propose the following solutions in this paper: (1) we leverage an advanced deep neural network—Stacked Contractive AutoEncoder (SCAE) to extract the robust deep semantic features from the original defect features, which has stronger discrimination capacity for different classes (defective or non-defective). (2) we propose a novel multi-objective defect prediction model named SMONGE that utilizes the Multi-Objective NSGAII algorithm to optimize the advanced neural network—Extreme learning machine (ELM) based on state-of-the-art Pareto optimal solutions according to the features extracted by SCAE. We mainly consider two objectives. One objective is to maximize the performance of ELM, which refers to the benefit of the SMONGE model. Another objective is to minimize the output weight norm of ELM, which is related to the cost of the SMONGE model. We compare the SCAE with six state-of-the-art feature extraction methods and compare the SMONGE model with multiple baseline models that contain four classic defect predictors and the MONGE model without SCAE across 20 open source software projects. The experimental results verify that the superiority of SCAE and SMONGE on seven evaluation metrics.     

二氧化铀粉末运输容器假想跌落事故下的安全设计与试验验证

目的 设计易裂变二氧化铀粉末运输容器,证明容器在最危险姿态下,可以满足9 m跌落的核临界、屏蔽安全和放射性物质包容相关设计准则。方法 设计外柔内刚的三层密封容器,内外壳之间填充聚氨酯减振吸能材料,建模分析容器多种姿态下的结构与功能材料动态响应,确定最危险跌落姿态。针对最危险工况开展实际跌落测试试验,证明容器在假想事故下的安全性。结果 容器在最危险跌落工况下,聚氨酯材料减振吸能效果与设计计算相符,中子吸收板、中子慢化板等功能材料位置和缺损量符合要求。二氧化铀粉末的密封性得以保障。结论 以有限元分析为基础的容器仿真分析与样机试验结果匹配度较高,试验样机通过了相关跌落试验,证明了容器在危险姿态下的9 m跌落安全性能。     

基于OWAS方法的选煤厂工人肌肉骨骼损伤分析

探讨选煤厂拣矸作业中危险姿势对工人肌肉骨骼损伤的影响。通过问卷调查和工作姿势分析系统（OWAS）对工人不良作业姿势重复出现的比例以及身体损伤状况进行评估与分析。结果显示工人背部和颈部出现不良作业姿势的比例、危害和损伤程度较高。这与疲劳自觉症状调查和OWAS系统分析所得出的结果基本一致。采取恰当的轮岗方式,增加座椅以及防护装备可有效降低工人肌肉骨骼的损伤程度,同时会更好的提高工作表现并减少工伤事故的发生。     

矿物质粉体对砂浆及混凝土Cl-渗透性的影响

研究了不同水胶比、不同矿物质粉体掺量的砂浆和混凝土，经标准养护至56天、90天时的导电量。在相同水胶比和相同矿物质粉体掺量下，混凝土的导电量远低于砂浆的导电量。含矿物质粉体的砂浆及混凝土的导电量均低于基准砂浆及混凝土的导电量。导电量随水胶比的降低而降低，也随龄期的增长而降低。     

SIMULTANEOUS DESIGN/CONTROL OPTIMIZATION OF SYMMETRIC CROSS-PLY LAMINATES OF HYBRID CONSTRUCTION

Optimal level of hybridization and optimal closed-loop and open-loop control functions are determined for a symmetric, cross-ply laminate of hybrid construction. The objectives of the optimization problem are to maximize the fundamental frequency (design objective) and to minimize the dynamic response to external disturbances (control objective) with minimum expenditure of control energy. The design/control problem is formulated as a multiobjective optimization problem by employing a performance index which combines the design and control objectives in a weighted sum. The control energy is limited by taking a quadratic functional of the control force as a penalty term in this performance index. The plate is constructed as a sandwich hybrid laminate with outer layers of a high-stiffness material. Hybridization refers to the relative amounts of high and low stiffness fibers. Comparative numerical results are given for hybrid and non-hybrid laminates which indicate that although the hybrid laminate quantities generally fall in between those of the high and low-stiffness ones, this is not always the case. This is especially true for the optimal design variable. Both the closed-loop and the open-loop controls are observed to be effective in damping out the excessive vibrations. Moreover, it is found that optimally designed laminates have a reduced dynamic response as compared to non-optimal ones.