Evaluation of ergonomic adjustments of catering carts to reduce external pushing forces

An existing standard catering cart was compared with two prototypes for pushbar and castor design. The first objective of this study was to find out which cart was accompanied with the lowest manually exerted external forces in pushing in a straight way and in pushing a 90 turn. The second objective was to explore effects of the pushbar and castor design of the carts. In the initial and ending phase, the prototypes were accompanied with higher exerted forces compared with the standard catering cart. In pushing straight. the reversed start position of the bigger castors of the prototypes hampered a fluent acceleration and caused higher initial forces. In decelerating, the lower rolling friction of the bigger castors required higher forces to stop the prototypes compared to the standard cart. During the sustained phase, the prototype carts were more favourable. Effects of pushbar and castor design were studied during a turn. The vertical pushbars of the prototypes resulted in lower time-integrated pushing forces. Providing an axis of rotation for turning activities by means of a fixed wheel was proven to be advantageous.     

A New Active Convex Hull Model for Image Regions

This paper presents a new active convex hull model with the following advantages: invariant with respect to the number of pixels to be enveloped; the number of time iterations is invariant, with respect to the image size; time-cheap for large image regions. The model is based on the geometric heat differential equations, derived from parabolic equation, and parameterized by arc length. To prevent the active contour from intruding into concavities and evolve it to the proper convex hull we use a vector field given as a difference between normal and tangent forces. The vector field is also used to segment an image to shells, such that a single region is present in each shell. A penalty function is developed to stop evolvement of those arc segments, whose vectors encountered boundary points of an image region. Based on the model a discrete algorithm is designed and coded by Mathematica 5.2. A condition is developed, with respect to the image size, to guarantee stable convergence of the active contour to the convex hull of the desired region. To validate the advantages and contributions a set of experiments is performed using synthetic, groundwater and medical images of different size and modalities. The paper concludes with a discussion and comparison of the active convex hull model with set of existing convex hull algorithms. Nikolay M. Sirakov received B.S. degree from School of Mathematics and Informatics-Sofia University in 1982, M.S. degree from the same University in the field of Coding Theory in 1983, and Ph.D. degree from Institute of Mechanics-Bulgarian Academy of Sciences in the field of 3D modeling and recognition in 1991. He had research and teaching positions at the Institute of Mechanics (1984–2000—Associate Professor since 1999), International Lab of Artificial Intelligence-Slovak Academy of Sciences (1990), Instituto Superior Technico–CVRM-Portugal (1993, 1998–2000), and Northern Arizona University (2001–2004). Currently Dr. Sirakov is an Assistant Professor of Mathematics and Computer Science at Texas A&M University Commerce. His research interests fall in Active Contours/Surfaces Models to image segmentation and features extraction, 3D reconstruction and visualization, 2D/3D objects matching and classification, Image Processing and Analysis, and Content Based Image Retrieval. He published over seventy papers and was a co-author of two books in the above listed fields.     

Curtain Wall Designs for Wind and Blast: Three Case Studies

Current design for curtain walls subjected to wind, wind-borne debris, and blast contain relatively new structural requirements for the curtain wall designer to address. These new criteria are defined and discussed in application to three case studies of curtain wall systems. The case studies illustrate the impact of these criteria on modern curtain wall designs and offer conclusions regarding the process and impact of designing curtain walls to current standards. It is concluded that projects in hurricane regions require fairly stout deigns and can withstand moderate blast loads. Wind tunnel testing remains a viable option to define design load criteria. Even low-rise building projects in high-velocity wind zones can benefit from wind tunnel modeling due to more precise and often reduced design pressures.     

CFRP钢管混凝土核心轴压短柱静力性能研究

目的为了解CFRP钢管混凝土核心轴压短柱的各组成部分协同工作，内力重分布．应力-应变关系以及承载力简化计算等问题．方法以试验研究为基础，对研究对象进行理论分析．结果试件在受力过程中存在内力重分布现象：在加载初期，钢管以承受纵向压力为主；在加载后期，钢管和CFRP筒以承受环向拉力为主，给出了此类构件的应力-应变关系曲线以及承载力计算表达式、结论在达到最大承载力之前。钢管。主筋和外围混凝土能够保持协同工作；根据CFRP筒约束效应系数的不同，可以将应力-应变关系曲线划分为若干阶段；计算值与实测值吻合良好且偏于安全．     

Suction Stress Characteristic Curve for Unsaturated Soil

The concept of the suction stress characteristic curve (SSCC) for unsaturated soil is presented. Particle-scale equilibrium analyses are employed to distinguish three types of interparticle forces: (1) active forces transmitted through the soil grains; (2) active forces at or near interparticle contacts; and (3) passive, or counterbalancing, forces at or near interparticle contacts. It is proposed that the second type of force, which includes physicochemical forces, cementation forces, surface tension forces, and the force arising from negative pore-water pressure, may be conceptually combined into a macroscopic stress called suction stress. Suction stress characteristically depends on degree of saturation, water content, or matric suction through the SSCC, thus paralleling well-established concepts of the soil–water characteristic curve and hydraulic conductivity function for unsaturated soils. The existence and behavior of the SSCC are experimentally validated by considering unsaturated shear strength data for a variety of soil types in the literature. Its characteristic nature and a methodology for its determination are demonstrated. The experimental evidence shows that both Mohr–Coulomb failure and critical state failure can be well represented by the SSCC concept. The SSCC provides a potentially simple and practical way to describe the state of stress in unsaturated soil.     

管道推力对汽轮机安全运行影响的试验研究

在诱发机组振动的潜在因素中 ,与汽轮机相连接的蒸汽及油系统管道由于运行中高温热变形引起的对本体的推力是其中的重要方面。该文提出了研究管道推力对电站汽轮机安全运行影响的综合试验研究方法 ,并在现场机组故障诊断中得到了应用。图 2参 4     

确定柔性机器人主动控制力的一种新算法

提出一种计算柔性机器人铰上主动控制力的程式化方法，在已知柔性机器人铰上运动学规律的前提下求产生这种规律的主劝控制规律通常需先通过求解系统动力学正总是俐到部件变形规律，然后通过动力学逆问题得到。本文在不破坏原方程程式化的形式的前提下将原动力学方程转化为另一种等价的程式化形式将上述两个过程合并在一起求解，减化了计算步骤，并提高了计算效率。     

框架剪力墙结构考虑剪力墙剪切变形时的内力和位移

本文用沿高度方向连续化的方法，建立了考虑剪力墙剪切变形时框架剪力墙结构在水平荷载作用下共同工作时的平衡微分方程。推导了多种荷载情况下结构内力和位移的计算公式。同时，进一步分析了剪切变形对框架剪力墙结构内力和位移的影响。     

企业经济效益量化分析与控制技术

针对目前国有企业存在的问题，在理论上对经济系统的机理和机理与效益之间的关系进行了深入分析，从生产力与生产关系的深层次上指出了国有企业经济效益下降的原因，并从技术上提出了政府对国有企业调控职能的实现方法。     

On the numerical implementation of variational arbitrary Lagrangian–Eulerian (VALE) formulations

This paper is concerned with the implementation of variational arbitrary Lagrangian–Eulerian formulations, also known as variational r‐adaption methods. These methods seek to minimize the energy function with respect to the finite‐element mesh over the reference configuration of the body. We propose a solution strategy based on a viscous regularization of the configurational forces. This procedure eliminates the ill‐posedness of the problem without changing its solutions, i.e. the minimizers of the regularized problems are also minimizers of the original functional. We also develop strategies for optimizing the triangulation, or mesh connectivity, and for allowing nodes to migrate in and out of the boundary of the domain. Selected numerical examples demonstrate the robustness of the solution procedures and their ability to produce highly anisotropic mesh refinement in regions of high energy density. Copyright © 2006 John Wiley & Sons, Ltd.