Dynamic pushing on three frictional surfaces: maximum acceptable forces,cardiopulmonary and calf muscle metabolic responses in healthy men

Pushing is an important materials handling activity in many occupations; however, pushing-related physiological investigations are still in infancy. The purpose was to evaluate maximum acceptable forces and physiological responses while pushing on: treadmill (TREAD); plywood floor (PLY); and Teflon floor (TEF). Acceptable forces, cardiopulmonary and calf muscle oxygenation and blood volume responses were collected simultaneously while 12 men (age 39 ± 13 years; height 178 ± 6 cm; and body mass 91.5 ± 16 kg) pushed for 2 h on each surface at their psychophysical workload. Participants selected higher forces on the PLY, resulting in higher pulmonary oxygen uptake compared to that of TEF (by ～9%) and TREAD (by ～18%). Pushing on the TEF demonstrated 50–56% lower blood volume changes and 1.5–1.8 times more oxygenation-force ratio than that for other surfaces. It is concluded that, to avoid a potential slip, participants were conservative in selecting acceptable forces to push on the slippery TEF. Part of this compensatory strategy on the TEF resulted in less muscle activity and, therefore, less demand for oxygen delivery to the calf muscle than for other surfaces. The present findings of significant force- and physiological-related differences in treadmill vs. high inertia pushcart clearly demonstrate that pushing experiments are essential to evaluate functional abilities of the workers.     

A Modeling and Rendering Method for Snow by Using Metaballs

The display of natural scenes such as mountains, trees, the earth as viewed from space, the sea, and waves have been attempted. Here a method to realistically display snow is proposed. In order to achieve this, two important elements have to be considered, namely the shape and shading model of snow, based on the physical phenomenon. In this paper, a method for displaying snow fallen onto objects, including curved surfaces and snow scattered by objects, such as skis, is proposed. Snow should be treated as particles with a density distribution since it consists of water particles, ice particles, and air molecules. In order to express the material property of snow, the phase functions of the particles must be taken into account, and it is well-known that the color of snow is white because of the multiple scattering of light. This paper describes a calculation method for light scattering due to snow particles taking into account both multiple scattering and sky light, and the modeling of snow.     

A method for integrating ergonomics analysis into maintainability design in a virtual environment

Designers must consider human factors/ergonomics when making decisions from the perspective of maintainability. As an important aspect of maintainability, maintenance space should be made adequate at the design stage to achieve a convenient maintenance process. A maintenance space evaluation method that considers ergonomics is proposed in this study. By comparing free swept volumes and constrained swept volumes in a virtual environment, maintenance space could be evaluated quantitatively and objectively. The results of the evaluation are obtained by combining the principles of ergonomics and maintainability. These results can help designers improve product design such that it fits ergonomics and maintainability requirements. A case study is introduced at the end of this paper to demonstrate the feasibility of the proposed method in efficiently evaluating the maintenance space based on the layout design of the product components in the design stage.Relevant to industryFor a large number of disasters caused by human errors in current industry, the result of this study contributes a guide to fully consider human factors in maintainability design through virtual environment and is beneficial to designers and engineers of industrial application fields.     

Ergonomic Analysis of Mobile Cart–Assisted Stocking Activities Using Electromyography

Workers in grocery stores are exposed to numerous musculoskeletal risks that can be reduced using assistive devices while performing stocking tasks. A regional grocery store has recently deployed a mobile cart without comprehension of its ergonomic impact on workers, which this article investigates using normalized electromyography data (%MVC). This article studies not only ergonomic impact based on %MVC values but also work performance represented by a muscle force metric (MFM). The results from this study showed highest muscle groups in %MVC and MFM were the erector spinae and triceps. Interestingly, muscle activations on erector spinae were reduced when mobile cart is used. %MVC and MFM distribution for value‐added‐ and non‐value‐added subtasks were slightly different, with larger differences observed for non‐value‐added tasks. Video recordings revealed higher work performance when the mobile cart is used. In future research, the number of participants will be increased to further validate the results from this study.     

Density and viscosity of linear perfluoropolyethers under high pressures

New experimental data on the density and viscosity of linear, unbranched perfluoropolyethers are presented at temperatures from 273 to 333 K and pressures up to 180 MPa. The measurements were carried out by a high-pressure burrette apparatus and a falling-cylinder viscometer. The uncertainties of the measurements are estimated to be less than 0.09% for the specific volume and 2.5% for the viscosity. The P-V data at each temperature are correlated satisfactorily by the Tait equation. The viscosity data are also analyzed and correlated with pressure or molar volume by several empirical and theoretical equations.     

基于体绘制法的头部CT图像的三维重建

介绍了体绘制法重建医学三维图像的方法,基于真实CT图像数据,使用MATLAB的图像处理工具箱重建了头部的三维图像.     

向下鼓气泡进入水或磁性液体的数值模拟与实验验证

应用数值与实验的方法分析了气泡向下鼓入水和磁性液体的过程,通过数学模型应用PLIC-VOF方法仿真重现了气泡的形成与破裂机理,通过数值模拟获得了气泡的形状与生长周期,用CCD摄像头完成实验测量,实验与模拟达到了数值上的吻合。     

作物可视化中的碰撞检测及响应研究

将碰撞检测与响应技术引入作物可视化生长模拟,针对以NUR13S曲面表示的作物叶片,提出了一种基于曲 面分割技术及混合层次包围盒实现作物叶片间碰撞检测的方法。首先采用节点插入技术分割叶片曲面,然后为分割 后的叶片曲面建立轴向包围盒(AAI313)与固定方向凸包(FDH)的混合层次包围盒树:根节点采用AA1313包围盒,以快 速排除不可能相交的叶片;其它层节点采用FDH包围盒,以保证精确地判定距离较近的叶片间碰撞状态。在此基础 上,根据作物叶片形态变化规律,提出了较合理、有效的冲突响应机制。实例分析表明,所建立的算法可有效地应用于 作物叶片碰撞的模拟实现。     

A framework with modified fast FCM for brain MR images segmentation

Intensity inhomogeneity, noise and partial volume (PV) effect render a challenging task for segmentation of brain magnetic resonance (MR) images. Most of the current MR image segmentation methods focus on only one or two of the effects listed above. In this paper, a framework with modified fast fuzzy c-means for brain MR images segmentation is proposed to take all these effects into account simultaneously and improve the accuracy of image segmentations. Firstly, we propose a new automated method to determine the initial values of the centroids. Secondly, an adaptive method to incorporate the local spatial continuity is proposed to overcome the noise effectively and prevent the edge from blurring. The intensity inhomogeneity is estimated by a linear combination of a set of basis functions. Meanwhile, a regularization term is added to reduce the iteration steps and accelerate the algorithm. The weights of the regularization terms are all automatically computed to avoid the manually tuned parameter. Synthetic and real MR images are used to test the proposed framework. Improved performance of the proposed algorithm is observed where the intensity inhomogeneity, noise and PV effect are commonly encountered. The experimental results show that the proposed method has stronger anti-noise property and higher segmentation precision than other reported FCM-based techniques.     

Large area forest stem volume mapping in the boreal zone using synergy of ERS-1/2 tandem coherence and MODIS vegetation continuous fields

ERS-1/2 tandem coherence was reported to have high potential for the mapping of boreal forest stem volume (e.g. Santoro et al., 2002, 2007a; Wagner et al., 2003; Askne & Santoro, 2005). Large-scale application of the data for forest stem volume mapping, however, is hindered by the variability of coherence with meteorological and environmental acquisition conditions. The traditional way of stem volume retrieval is based on the training of models, relating coherence to stem volume, with the aid of forest inventory data which is generally available for a few small test sites but not for large areas. In this paper a new approach is presented that allows model training using the MODIS Vegetation Continuous Fields canopy cover product (Hansen et al., 2003) without further need for ground data. A comparison of the new approach with the traditional regression-based and ground-data dependent model training is presented in this paper for a multi-seasonal ERS-1/2 tandem dataset covering several well known Central Siberian forest sites. As a test scenario for large-area application, the approach was applied to a multi-seasonal ERS-1/2 tandem dataset of 223 ERS-1 and ERS-2 image pairs covering Northeast China (~ 1.5 million km²) to map four stem volume classes (0-20, 20-50, 50-80, and > 80 m³/ha).