Reproducibility of subjectively graded voluntary isometric muscle strength in unilateral and simultaneous bilateral exertion

Reproduction error of voluntary isometric muscle strength that was graded subjectively by the subject was investigated under unilateral and bilateral conditions. Six kinds of tasks, i.e. elbow flexion, elbow extension, hand grip, second digit abduction, knee extension and leg extension were employed. It was clear that absolute error (AE) increased with increase of exerted muscle strength in both unilateral and bilateral conditions. Mean of AE in each task was 4-5% of maximal muscle strength in the task in unilateral conditions. Algebraic or constant error (CE) decreased with increase of exerted strength. Demands for smaller strength tended to overshoot and larger ones tended to undershoot. In bilateral conditions when the different levels of strength for each limb were required to be exerted, AE on the weaker side tended to be larger than that in unilateral conditions. Thus a possibility that magnitude of AE might be affected by amount of attention was suggested. The subjectively graded criterion strength for a specific required level, when the strength was expressed as relative to the maximal strength, was almost the same in every task within a subject although it was different between subjects. It is suggested that each subject might have an awareness of relative magnitude of exerted strength.     

A methodology for muscular isometric endurance and fatigue research

The objective of this study was to develop a reliable statistical method of finding a cut-off point between the endurance section and the fatigue section from a single endurance-fatigue curve of force versus time for extended times. Two age groups (20–29, 50–59 years old) with 10 subjects in each group participated in this study. Two muscle groups (biceps and quadriceps) were tested at five levels of % MVC (20, 40, 60, 80 and 100 % MVC). Subjects were instructed to exert a force and reach a designated % MVC level and maintain that level for as long as possible until asked by the experimenter to stop. Each condition was tested for five minutes. The method developed used the sum of squares technique to find the optimal cut-off point on the curve thus, determining the endurance time. The methodology proved to be useful and reliable. The steps involved along with an example are discussed.     

Isokinetic and isometric lifting capacity of Chinese in relation to the physical demand of job

The aim of the study was to formulate normative data for the lifting capacities of a normal Chinese population, in order to establish a basic foundation for further studies and to investigate the relationship between individual attributes including age, gender, height, weight, job physical demand and each type of lifting capacity. Isokinetic and isometric lifting strength at low, waist and shoulder assessment levels were measured using the LIDO Workset II based on a sample of 93 normal Chinese adults (63 men and 30 women) between the ages of 21-51. The 50th percentile score for adult Chinese female's lifting strength was 17.71% lower than the American female while the adult Chinese male's lifting strength was 14.94% lower than the American male. Lifting forces were higher in the 20-40 year age group. The isometric work mode had considerable impact on the lifting capacities, with shoulder level having the highest lifting capacities. The gender and body weight had a significant positive correlation to lifting capacity while job physical demand had a moderate correlation. Age and body heights were weakly correlated to lifting capacity.     

Display-control stereotype strength of left- and right-handers

Many aspects of the performance of left and right handed persons have been reported. It is generally found that (a) Performance of left-handers, when the workplace is set up according to their handedness, is as good as that of right-handers when using their preferred hand. (b) When using the non-preferred hand, left-handers performance is generally superior to that of right-handers, possibly due to their having had to adapt to a right-handed world. There has been little reported research on the difference of stereotype strength or expectancies of device operation for right- and left handers. This paper reports such research using a set of rotational and translational controls with displays in four different locations relative to the operator. It is found that there was no significant effect of handedness of the participant for horizontally-moving displays and left- and right-handers were equivalent in performance. For vertically-moving displays there were effects of handedness through interaction with controls and display location. Some conditions showed non-equivalence of left and right-handedness in stereotype strength.Relevance to industryAbout 10% of people are left-handed, yet live in a world that is largely designed for right-handers. Experiments are reported to show that, for many combinations of control and displays, there is no significant effect of handedness on stereotype strength.     

Non-rigid isometric ICP: A practical registration method for the analysis and compensation of form errors in production engineering

The unprecedented success of the iterative closest point (ICP) method for registration in geometry processing and related fields can be attributed to its efficiency, robustness, and wide spectrum of applications. Its use is however quite limited as soon as the objects to be registered arise from each other by a transformation significantly different from a Euclidean motion. We present a novel variant of ICP, tailored for the specific needs of production engineering, which registers a triangle mesh with a second surface model of arbitrary digital representation. Our method inherits most of ICP’s practical advantages but is capable of detecting medium-strength bendings i.e. isometric deformations. Initially, the algorithm assigns to all vertices in the source their closest point on the target mesh and then iteratively establishes isometry, a process which, very similar to ICP, requires intermediate re-projections. A NURBS-based technique for applying the resulting deformation to arbitrary instances of the source geometry, other than the very mesh used for correspondence estimation, is described before we present numerical results on synthetic and real data to underline the viability of our approach in comparison with others.     

Effect of display location on control-display stereotype strength for translational and rotational controls with linear displays

Experiments were designed to investigate the effects of control type and display location, relative to the operator, on the strength of control/display stereotypes. The Worringham and Beringer Visual Field principle and an extension of this principle for rotary controls (Hoffmann E.R., and Chan A.H.S. 2013). “The Worringham and Beringer ‘Visual Field’ Principle for Rotary Controls. Ergonomics.” 56 (10): 1620–1624) indicated that, for a number of different control types (rotary and lever) on different planes, there should be no significant effect of the display location relative to the seated operator. Past data were surveyed and stereotype strengths listed. Experiments filled gaps where data are not available. Six different control types and seven display locations were used, as in the Frame of Reference Transformation Tool (FORT) model of Wickens et al. (Wickens, C.D., Keller, J.W., and Small, R.L. (2010). “Left. No, Right! Development of the Frame of Reference Transformation Tool (FORT).” Proceedings of the Human Factors and Ergonomics Society 54th Annual Meeting September 2010, 54: 1022–1026). Control/display arrangements with high stereotype strengths were evaluated yielding data for designers of complex control/display arrangements where the control and display are in different planes and for where the operator is moving. It was found possible to predict display/control arrangements with high stereotype strength, based on past data.

Practitioner Summary: Controls and displays in complex arrangements need to have high compatibility. These experiments provide arrangements for six different controls (rotary and translational) and seven different display locations relative to the operator.     

程序配电器减振器等效模拟及动强度分析

为优化橡胶减振器与程序配电器的性能参数匹配,提高程序配电器的安全性和可靠性,在Patran中采用等效模拟的方法进行某橡胶减振器结构的有限元建模,分析连接螺栓的动态强度特性,并通过试验进行特性验证.结果证明所采用的建模方法和仿真技术可行.     

The effect of vibration exposure during haul truck operation on grip strength,touch sensation,and balance

Falls from mobile equipment are reported at surface mine quarry operations each year in considerable numbers. Research shows that a preponderance of falls occur while getting on/off mobile equipment. Contributing factors to the risk of falls include the usage of ladders, exiting onto a slippery surface, and foot or hand slippage. Balance issues may also contribute to fall risks for mobile equipment operators who are exposed to whole-body vibration (WBV). For this reason, the National Institute for Occupational Safety and Health, Office of Mine Safety and Health Research conducted a study at four participating mine sites with seven haul truck operators. The purpose was to ascertain whether WBV and hand-arm vibration (HAV) exposures for quarry haul truck operators were linked to short-term decreases in performance in relation to postural stability, touch sensation threshold, and grip strength that are of crucial importance when getting on/off the trucks. WBV measures of frequency-weighted RMS accelerations (wRMS) and vibration dose value (VDV), when compared to the ISO/ANSI standards, were mostly below levels identified for the Health Guidance Caution Zone (HGCZ), although there were instances where the levels were within and above the specified Exposure Action Value. Comparably, all mean HAV levels, when compared to the ISO/ANSI standards, were below the HGCZ. For the existing conditions and equipment, no significant correlation could be identified between the WBV, HAV, postural stability, touch sensation threshold, and grip strength measures taken during this study.     

Advanced object-oriented methods and concepts for simulations of multi-body systems

A common way to simulate the motion and behaviour of a complex system is to approximate it with a multi-body system based on particles, and to evaluate the particle interactions over time. Normally, the calculations require such a large amount of computer power that methods have been developed to decrease computation time by taking advantage of new computer architectures. These methods have been in use since the early 1980s, but there is still a lack of concepts supporting the application of these methods, to build highly efficient simulation systems with reusable entities. In this paper we describe a new approach for the development of flexible, efficient methods and techniques to control multi-body systems. The major goal of our concept is the integration of advanced modern simulation techniques such as particle-based modelling and simulated annealing, and efficient data structures such as octrees and the Greengard algorithm. We introduce high-level concepts represented by agents, environments, and controllers based on and supported by the object-oriented paradigm. We demonstrate the flexibility of our new simuation system for applications related to environmental research and air quality control.     

一种基于充要强度的优化规则发现方法

提出了一种基于信息系统的优化规则的提取方法,主要目的是提取信息系统中具有一定充要性的优化规则。首先,提出了充要强度并讨论了它的性质。其次,由于搜索空间的巨大和遗传算法的全局优化的特性,设计了使用遗传算法进行优化规则搜索的方法。最后,通过实验说明方法的有效性。     

Dependence of grip strength on shoulder position and its implications for ergonomics practice

Grip strength (GS) variability due to positional changes in the upper extremity joints is of importance while designing workstations and work methods. This study was conducted to analyze the GS variations due to positional changes at shoulder joint when some important variables were under control. The GSs of dominant and nondominant hands were measured in eight shoulder (0°, 45°, 90°, and 135° of flexion and abduction) and standard test positions (STP). One hundred and thirteen subjects 20–30 years old completed the study. At the dominant side, no significant difference was observed in the pairwise comparisons between STP and the others. Maximum and minimum GSs were obtained in 0° abduction and 45° flexion and abduction, respectively. At the nondominant side, GSs were significantly lower (p < 0.001) in the corresponding test positions and demonstrated more variability. The findings of this study can contribute to the available knowledge to guide occupational ergonomists in their practices.     

Function identification for the intrinsic strength and elastic properties of granitic rocks via genetic programming (GP)

Symbolic Regression (SR) analysis, employing a genetic programming (GP) approach, was used to analyse laboratory strength and elasticity modulus data for some granitic rocks from selected regions in Turkey. Total porosity (n), sonic velocity (vp), point load index (Is) and Schmidt Hammer values (SH) for test specimens were used to develop relations between these index tests and uniaxial compressive strength (σ_c), tensile strength (σ_t) and elasticity modulus (E). Three GP models were developed. Each GP model was run more than 50 times to optimise the GP functions. Results from the GP functions were compared with the measured data set and it was found that simple functions may not be adequate in explaining strength relations with index properties. The results also indicated that GP is a potential tool for identifying the key and optimal variables (terminals) for building functions for predicting the elasticity modulus and the strength of granitic rocks.     

Integrated neural and robotic simulations. Simulation of cerebellar neurobiological substrate for an object-oriented dynamic model abstraction process

Experimental studies of the Central Nervous System (CNS) at multiple organization levels aim at understanding how information is represented and processed by the brain’s neurobiological substrate. The information processed within different neural subsystems is neurocomputed using distributed and dynamic patterns of neural activity. These emerging patterns can be hardly understood by merely taking into account individual cell activities. Studying how these patterns are elicited in the CNS under specific behavioral tasks has become a groundbreaking research topic in system neuroscience. This methodology of synthetic behavioral experimentation is also motivated by the concept of embodied neuroscience, according to which the primary goal of the CNS is to solve/facilitate the body–environment interaction.With the aim to bridge the gap between system neuroscience and biological control, this paper presents how the CNS neural structures can be connected/integrated within a body agent; in particular, an efficient neural simulator based on EDLUT (Ros et al., 2006) has been integrated within a simulated robotic environment to facilitate the implementation of object manipulating closed loop experiments (action–perception loop). This kind of experiment allows the study of the neural abstraction process of dynamic models that occurs within our neural structures when manipulating objects.The neural simulator, communication interfaces, and a robot platform have been efficiently integrated enabling real time simulations. The cerebellum is thought to play a crucial role in human-body interaction with a primary function related to motor control which makes it the perfect candidate to start building an embodied nervous system as illustrated in the simulations performed in this work.     

An interaction effect between young children's field dependence-independence and order of learning with glass-box and black-box simulations: Evidence for the malleability of cognitive style in computer-supported learning

A counterbalanced measures design was used to examine whether the order of learning with a glass-box simulation about the life cycle of butterflies, and, a black-box simulation about the life of bees, differentially affected field-dependent and field-independent children's performance on two related knowledge tests. The children aged from 5 to 6.5 years old were classified into a field type based on their Children's Embedded Figures Test scores. Subsequently, they were assigned into Group A and Group B. Group A learned first with the glass-box simulation followed by the black-box simulation, while Group B used the tools in the reverse order. A statistically significant interaction effect was found between field type and order of learning with the simulations on the butterfly post-test performance, showing that learning first with the black-box simulation facilitated field-dependent children's subsequent learning with the glass-box simulation. The results tap on the issue about whether field dependence-independence is a cognitive ability or cognitive style, and the issue of the malleability of cognitive styles as well. Implications and future research directions are discussed.     

嵌入式虚拟协同开发环境的设计与实现

为了提高嵌入式系统的开发效率和设计可靠性、提供在获得硬件原型之前的虚拟集成验证手段,本文引入了软硬件协同验证的概念,提出了一种新的基于网络的嵌入式虚拟协同开发环境实现方法,通过采用松耦合布局的指令集仿真器和逻辑仿真器来构建虚拟集成验证环境,并在此基础上优化逻辑仿真,分离和抑制不必要的逻辑仿真周期,有效地提高了协同验证仿真性能.     

支持实体数控铣削仿真验证的Cuboid-Array模型的研究

研究了Z-Buffer,Dexel和Ray-representation建模思想和方法,提出Cuboid-array的实体近似建模方法．采用基于设计模型的实体数控仿真验证技术,以Cuboid-array表示干涉元素集合体,提出基于B-rep和Cuboid-array的双体建模的近似实体数控仿真验证技术．给出了基于Cuboid-array的数控仿真验证算法,研制了基于双体建模和双体显示的数控仿真验证实验系统,实现了面向过程和结果的实体数控仿真的集成、面向实体数控仿真和实体数控验证的集成,并给出了实验用例．     

A Visibility Sphere Marching algorithm of constructing polyhedral models for haptic sculpting and product prototyping

This paper presents a Visibility Sphere Marching algorithm of constructing polyhedral models from Dexel volume models for haptic virtual sculpting. Dexel volume models are used as the in-process models representation during interactive modification in a haptic virtual sculpting system. The stock material represented in a Dexel volume model is sculpted into a designed model using a developed haptic sculpting system. The sculpted Dexel volume models are converted to polyhedral surface models in STL format by the proposed visibility sphere marching algorithm. The conversion turns out to be an interesting and challenging problem. The proposed visibility sphere marching algorithm consists of three sub-algorithms: (i) roof and floor covering, (ii) wall-building, and (iii) hole-filling algorithms. The polyhedral surface models converted from the Dexel volume models can then be input to and processed by available computer-aided manufacturing (CAM) or rapid prototyping systems. The presented technique can be used in virtual sculpting, CAD/CAM, numerically controlled machining verification and rapid prototyping.     

Parallelization and scalability of a spectral element channel flow solver for incompressible Navier–Stokes equations

Direct numerical simulation (DNS) of turbulent flows is widely recognized to demand fine spatial meshes, small timesteps, and very long runtimes to properly resolve the flow field. To overcome these limitations, most DNS is performed on supercomputing machines. With the rapid development of terascale (and, eventually, petascale) computing on thousands of processors, it has become imperative to consider the development of DNS algorithms and parallelization methods that are capable of fully exploiting these massively parallel machines. A highly parallelizable algorithm for the simulation of turbulent channel flow that allows for efficient scaling on several thousand processors is presented. A model that accurately predicts the performance of the algorithm is developed and compared with experimental data. The results demonstrate that the proposed numerical algorithm is capable of scaling well on petascale computing machines and thus will allow for the development and analysis of high Reynolds number channel flows. Copyright © 2007 John Wiley & Sons, Ltd.     

FPGA与DDR2 SDRAM互联的信号完整性分析

论述了Virtex-5和DDR2?SDRAM在互联中的信号完整性问题,利用前仿和后仿的措施分析和验证了它们在不同互联拓扑结构下的信号完整性。通过原型机的测试,验证了该理论在高速电路设计中的应用有效性。