Identifying predictors of comfort and discomfort in using hand tools

The aim of the study was to identify predictors of comfort and discomfort in using hand tools. For this purpose, the comfort questionnaire for hand tools (CQH) was developed based on the results of a previous study. In the current study, four screwdrivers were evaluated on comfort (expected comfort at first sight and comfort after short time use) using the CQH and discomfort (local perceived discomfort). The results showed that expected comfort at first sight was predicted by aesthetics. Additionally, functionality and physical interaction, and adverse body effects were the major predictors of overall comfort after short time use. Discomfort was predicted by adverse body effects only. It is concluded that comfort and discomfort in using hand tools have partly the same underlying factors: discomfort feelings also affect the comfort experience.     

Relationships between maximum holding time and ratings of pain and exertion differ for static and dynamic tasks

Ratings of perceived discomfort (0 to 10 scale) have been used to estimate relative maximum holding times (%MHT), particularly for static tasks. A linear 1:10% ratio has been described, where a rating of 5 corresponds to 50%MHT. It is unknown whether this linear ratio is valid for dynamic tasks. Additionally, whether pain or exertion are the primary predictors of discomfort is not clear. Thus, the goal of this study was to investigate both pain and exertion ratings during static (50% maximum; N = 42) and dynamic (75% maximum; N = 34) elbow flexion tasks until failure. Gender, self-reported physical activity, and peak torque were also assessed. Pain and exertion ratings reasonably matched the 1:10% ratio during the static task but not during the dynamic task. Exertion related more strongly to MHT than pain in both tasks. Neither gender nor activity level appeared to influence perceptual ratings, but peak torque explained approximately 20% of the variance in MHT.     

Study and development of morphological analysis guidelines for point cloud management: The “decisional cube”

When talking about reverse engineering, it is necessary to focus on the management of point clouds. Generally speaking, every 3D scanner device codifies simple and complex geometries providing different point cloud densities as an output. Point cloud density is usually more correlated with the technical specifications of the device employed rather than with the morphology of the object acquired. This situation is due to the frequent use of structured grids by a large quantity of devices. In order to solve this problem, we therefore need to integrate the classical structured grid acquisition with a smart selective one, which is able to identify different point cloud densities in accordance with the morphological complexity of the object regions acquired.Currently, we can reach the destination in many different ways. Each of them is able to provide different performances depending on the object morphology and the performances of 3D scanner devices. Unfortunately, there does not yet exist one universal approach able to be employed in all cases. For this reason, the present paper aims to propose a first analysis of the available methodologies and parameters, in order to provide final users with some guidelines for supporting their decisions according to the specific application they are facing. Moreover, the developed guidelines have been illustrated and validated by a series of case studies of the proposed method.     

The effects of lumbar massage on muscle fatigue,muscle oxygenation,low back discomfort,and driver performance during prolonged driving

This paper reviews results of comparisons between novice and expert operators in the supervision of dynamic environments. Firstly, the characteristics of expertise and its operational definitions are discussed. Secondly, the main dimensions of the complexity of these environments are described and the difficulties operators have in coping with complexity are examined. Research work carried out in field studies is then overviewed in order to assess the role of expertise in the three components of process control: monitoring, diagnosis and decision-making and executive control. The discussion stresses the convergent results of various studies. In spite of the diversity of task domains and of novice-expert definitions, results converge on three points: experts are better at producing inference, in anticipating, and have a more functional view of the process. Divergent results on directionality of reasoning, depth of knowledge in relation to performance and synchronization of actions are also discussed. Finally, further research trends are outlined.     

The effect of hand tools’ handle shape on upper extremity comfort and postural discomfort among hand-woven shoemaking workers

Hand tools are widely used in a large number of occupations. Many workers have to use hand tools to accomplish their duties. This may cause work-related Upper Extremities Musculoskeletal Disorders (UEMSDs). The present study was conducted in Iranian hand-woven shoe industry to (a) investigate the design of hand tools currently used in hand-woven shoemaking operation and (b) design/redesign the tools' handles based on anthropometric tables and ergonomic principles. Based on Iranian workers' anthropometric tables, new handles with different shapes were designed and made for hand tools currently used in hand-woven shoemaking operation (e.g., awl and cloth cutting tool). Hand postures and postural comfort and discomfort were investigated via rating technique using Comfort Questionnaire for Hand Tools (CQH) and upper extremities body map. The results of CQH showed that the handle shape had a significant influence on the hand posture and perceived postural discomfort in the upper extremities. The new ergonomically designed handles were perceived to be more comfortable compared to the traditional ones. Additionally, the new handles improved the hand posture during the operation and reduced the severity of discomfort in the upper extremities compared to the tools with conventional handles. The findings of this study revealed that designing the hand tools’ handles based on ergonomic principles and using anthropometric tables could improve the hand posture, increase comfort, and decrease discomfort in the upper extremities. By this means, reduction in work-related UEMSDs is expected.     

Identification and optimization of key process parameters in noncontact laser scanning for reverse engineering

This Extended Technical Note shows that the final accuracy level of reverse engineered surfaces depends on scanning distance and scanning angle of the laser beam, hence it also depends on the morphology of the scanned objects. On scanning strongly curved objects, such as the ones with free form surfaces, the distance and impact angle of the laser beam are changing continuously during the scanning process. On the basis of these, two critical parameters are specified for the design model, which make it possible to predict these two factors in advance, depending on the morphology of the scanned object. First, a mathematical-statistical design model of the scanning process is generated, which relies on ANOVA (analysis of variance) and DOE (design of experiments). In the next step, a fitness function is optimized by the genetic algorithm (GA) program. This optimization improves the accuracy of the final scanned surfaces, in terms of the minimum standard deviation values of reverse engineered 3D surface model. The proposed approach was confirmed in a case study, which is presented at the end of this Technical Note.     

Effects of shoulder rotation combined with elbow flexion on discomfort and EMG activity of ECRB muscle

Work related MusculoSkeletal Disorders (WMSDs) are injuries or dysfunctions caused by occupational or non occupational tasks involving bad postures, high frequency of exertions or high force levels. In the present study, the effects of shoulder flexion/extension combined with elbow flexion angle on discomfort score were investigated for repetitive gripping task. A laboratory experimental simulation was conducted. Ten male participants volunteered in this study. Four levels of shoulder flexion/extension (−45° extension, 0° neutral, 45° & 90° flexion) with three levels of elbow flexion angle (45°, 90° & 135°) were taken as levels of independent variables. There were 12 combinations available for each participant and the experiment was conducted on the basis of random order of experimental combinations for each participant. Discomfort score on 100 mm visual analogue scale (VAS) and Electromyography (EMG) activity of Extensor Carpi Radialis Brevis (ECRB) muscle were dependent variables for the analyses. The task for the experiment was of 150N ± 5N grip force at a frequency of 15 exertions/minute for five minutes duration. After performing the MANOVA on the recorded data, the results showed that the shoulder flexion/extension and elbow flexion both were highly significant (p < 0.001). Also it was found that −45° shoulder extension combined with 45° elbow flexion angle was the most discomfort posture. The practical relevance of the study is that, in industrial tasks such posture should be avoided to minimize risk of WMSDs.Relevance to industryThe findings in terms of relationship between discomfort/EMG vs. shoulder rotation combined with elbowflexion are important to design Industrial tasks with the reduced risk of WMSDs. Such as, sheet metal cutting, fabrication of sheet metal work, die casting, and drilling operations may require the shoulder movements in extenion/flexion combined with elbowflexion.     

逆向工程中UML活动图的呈现技术研究

在获取动态信息的基础上,研究了UML活动图的呈现技术,给出在Rose中呈现活动图的算法,论述了表示进程创建关系的Fork类型动态信息和表示进程同步关系的Wait类型动态信息的呈现和基于对象流的进程间通信关系呈现。最后,通过实际的系统验证了该算法的有效性。     

An ergonomic comparison of pneumatic and electrical pistol grip hand tools

The purpose of this study was to compare the ergonomic demands associated with air and DC pistol grip hand tool use. Seven channels of EMG data were collected from 15 male and 15 female subjects to estimate the muscular demands on the forearms, biceps, shoulders and neck. An accelerometer was also used to estimate the torque reaction transmitted to the hand. Subjects performed drilling with five pistol grip tools obtained from two tool suppliers. This resulted in two air tools, one non-transducerized electric (DC_NT) and two transducerized electric (DC_T) tools. Three types of joints were simulated: (1) , (2) and (3) . Subjects were asked to drill five joints to completion within a period, and to repeat this five times for each condition (25 joints per condition). Results of a three factor repeated measures ANOVA indicated that, in comparison to air tools, pistol grip DC tools do not pose an additional risk of musculoskeletal injury to the upper limbs. In fact, the data suggest that the use of pistol grip DC tools will reduce the demands on the forearms during horizontal drilling.

Relevance to industry

Powered hand tools can potentially cause upper limb injuries due to the postures, repetitions, and forces associated with their use. However, while DC tools have engineering advantages (loop monitoring of the tool, and increased quality control) the ability to implement ergonomic strategies also appears to reduce the muscle demands associated with tool use.     

Choice of handle characteristics for pistol grip power tools

The optimal surface material and cross-section of power tool handles are not sufficiently described in ergonomic literature. The objective of the present study was to increase knowledge in these matters. The handle of four similar drilling machines were covered with rubber with different hardness. The preferences and forearm muscle electric activity (12 male and 12 female subjects) as well as the vibration level (6 male subjects) when using these drilling machines were assessed. The results showed that foam rubber on the handle is a more preferable covering material compared to harder rubber and it does not increase the muscular activity. Foam rubber on the handle may also to some extent attenuate vibrations.

Furthermore preferred width and thickness of handles for drilling machines were evaluated by letting 12 male and 12 female subjects perform three tasks: (a) choosing handle width (free choice) and ranking handle thickness (3 alternatives), (b) ranking handle width (3 alternatives), (c) making a handle out of hand putty (free choice). The subjects hand size (hand length, functional grip diameter and hand volume) were also measured and compared to their preferences. The results showed that the most commonly used handle cross-section size (50×35 mm) is an acceptable compromise in terms of preferences. The measured hand size measures had low correlation with preferred handle width/circumference.

Relevance to industry

Information concerning the design of handles for power tools is essential for tool designers.     

Estimation of hand force in ergonomic job evaluations

The aims of the present study were: (1) to collect normative data of pinch and power grip strength with a newer digital dynamometer; (2) to study the ability of hand grip force matching using a hand dynamometer where the validity and reliability issues were studied; and (3) to study the relationship between hand grip force matching and muscle activities of three forearm and hand muscles. This study consisted of two experiments. One hundred and twenty subjects volunteered in the first experiment, where hand grip strength and hand force estimation data were collected. The second experiment had 14 volunteers, where muscle activities of the hand and forearm were collected during the tests of hand grip strength and hand force matching estimations. Results showed that the power grip and pinch grip strengths collected with a newer digital dynamometer were comparable to similar studies using older equipment. At the group level, the force matching method was largely accurate and consistent. Instructions to the subjects about force matching estimation were important to the accuracy and consistency of the estimated forces. Estimation in force matching might depend on perceptions of several major muscle activities.     

Parameterization for reconstruction of 3D freeform objects from laser-scanned data based on a PDE method

Published online: 19 July 2001     

Assessing the physical loading of wearable computers

Wearable computers enable workers to interact with computer equipment in situations where previously they were unable. Attaching a computer to the body though has an unknown physical effect. This paper reports a methodology for addressing this, by assessing postural effects and the effect of added weight. Using the example of arm-mounted computers (AMCs), the paper shows that adopting a posture to interact with an AMC generates fatiguing levels of stress and a load of 0.54 kg results in increased level of stress and increased rate of fatigue. The paper shows that, due to poor postures adopted when wearing and interacting with computers and the weight of the device attached to the body, one possible outcome for prolonged exposure is the development of musculoskeletal disorders.     

An electromyography study in three high risk poultry processing jobs

This paper presents the results of a muscle load study of poultry processing operators performing three different jobs: basket packing, cutting/packing and trimming. Eighteen operators participated in this study. Surface electromyography (EMG) was recorded from bilateral upper trapezius, right forearm flexor and extensor muscles during the job performance. Results showed high muscle loads of the forearm flexor and extensor muscles for the operators conducting all three jobs. The static loading for both trapezius muscles was low (<1% MVC). However, the peak load could be up to 24% MVC on the upper trapezius muscles in some individuals. The job of cutter/packer had significantly higher trapezius loads, while trimmer operators had significantly higher peak forearm flexor and median extensor loads than the other jobs. Lack of ergonomic consideration of workstation designs may be one of the reasons causing the high trapezius loads for some of the cutting/packing operators and basket packers. Repetitive pinching operations and the frequent use of knives in cutting may be a major contributing factors causing high forearm muscle loads. An efficient knife sharpening program or alternative cutting methods (mechanical knives or scissors), modified processing procedures in order to reduce the pinching effort, and properly adjusted workstation may be able to improve the muscle loading conditions for the high risk poultry processing jobs.

Relevance to industry

Detailed quantitative information on the muscle loading of poultry processing operators provides insight to the risk factors causing musculoskeletal disorders and may be used to help evaluate ergonomic intervention measures for reducing these risk factors.     

A Review of:“Safety in Manual Materials Handling.” By COLIN G. DRURY. (Cincinnati: US Dept. of Health,Education & Welfare, 1978.) [Pp. viii+ 209.]

The extension force against resistance was recorded in 23 postures for 12 subjects to find explanations for the decrease in back strength in asymmetric postures. A reduction in muscle force in asymmetric postures was found up to 40%, but was strongly dependent on the plane in which asymmetry occurred, and on the posture to which it referred. A quantitative relationship between the forces exerted in different asymmetric postures is discussed, as a basis for formulating universal ergonomic guidelines for optimal working postures. The reduction in force in different asymmetric postures can be explained by length of the muscle, the activation of the muscle, and the moment angle of the muscle.     

IA-64逆向工程中谓词消除技术研究

IA-64体系结构支持判断执行,提高指令级并行性,但是编译器为了充分利用该特性而做的优化将程序代码进行深度重构,对逆向工程来说很难从优化后的可执行代码中恢复原程序逻辑。该文提出了消除谓词的反优化技术,提高了可执行代码逆向工程的质量。     

基于形态学和小波变换的心电信号去噪算法

在处理心电信号采集过程中混入的基线漂移、工频干扰及肌电干扰等噪声的过程中,小波变换取得了广泛的应用。针对小波算法的缺陷及不足,提出了一种基于数学形态学和小波阈值的混合算法。该算法利用非线性形态学滤波器滤除基线漂移,将获得的含高频噪声心电信号通过小波阈值算法进行处理,最后获得无噪声的ECG（心电）信号。采用MIT/BIH Arrhythmia Database中的数据对算法进行了验证,实现了三种主要干扰的滤除,本算法效果良好,为后续特征点的识别奠定了基础。     

Applying knowledge to reverse engineering problems

This paper summarizes a series of recent research results made at Edinburgh University based on projects that apply domain knowledge of standard shapes and relation ships to solve or improve reverse engineering problems. The problems considered are how to enforce known relationships when data fitting, how to extract features even in very noisy data, how to get better shape parameter estimates and how to infer data about unseen features.