几何画板轨迹功能在三维曲面绘制中的应用

探讨了几何画板的绘图功能在空间曲面绘制中的应用,给出通过建立基础网格利用“轨迹”功能绘制曲面网状图和建立三维坐标系利用“追踪”功能绘制曲面的方法。     

Surface settlement caused by twin-parallel shield tunnelling in sandy cobble strata

City metro tunnels are usually constructed as twin-parallel tunnels and their adjacent construction may lead to surface deformation, affecting the surface environment and the safety of the tunnels. Due to its strong dispersion, sandy cobble strata can be easily disturbed by shield tunneling. Based on the project of the Chengdu Metro Line 1, field and model tests were carried out to study the surface settlement caused by shield tunneling in sandy cobble strata by measuring surface settlement curves, ground loss ratios and construction influence zones. The discrete element method (DEM) was used to study the factors affecting the formation of ground arches in sandy cobble strata at the microscopic level. Results show that the shape of the surface settlement curve in sandy cobble strata is different from that in soft soil. The buried depth and clear spacing of the two tunnels had a significant impact on the formation of ground arches.     

Study on the thermal decomposition kinetics of nano-sized calcium carbonate

This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA (thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energyE _a; and that the top-temperature of decompositionT _p decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing bothE _a andT _p to decline sharply with the decrease of the average diameter of nano-particles. Project supported by Guizhou Province Natural Science Foundation of China     

A comparative study of student attitude,learning and teaching practices in Pakistan and Britain

Good teaching is open to change and it involves constantly trying to find out what the effects of instruction are on learning, and modifying that instruction in the light of the evidence. Similarly, the ultimate outcome of instructional practice is effective student learning. Therefore, in this perspective, adequately meeting the varying needs of students is a major challenge for the modern education system in every country. As the title indicates, this paper attempts to explore students’ attitudes to studying and learning in order to help encourage greater engagement with quality learning. The study is based on primary data with regard to postgraduate education and learning in respective British and Pakistani education institutions—i.e. Moray House School of Education (Edinburgh University) and the Institute of Education and Research (University of the Punjab, Lahore). In the context of the collaboration of these two institutions, the paper focuses on the ways and means to enhance the system‐wide capacity for research‐based practice.     

Modeling of contact surface morphology and dust particles by using finite element method

The effect of dust particles on electric contacts and a hazardous size range of hard dust particles using a rigid model were discussed before. As further research, elastic-plastic model of finite element analysis was established in this work, which is closer to real condition. In this work, the behavior of large size and small size particles, and the influence of particles hardness were investigated. The calculating result of small-size particles presents a general hazardous size coefficient for different contact surface morphology; for large-size particles, it presents a hazardous size coefficient for complicated composition of the dust. And the effect of the dust shape is also discussed.     

Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading

INTRODUCTION Fatigue durability has long been important issues in the design of a two-stroke free piston linear engine structure (Torres and Voorwald, 2002; Rahman et al., 2005a; 2005b). Durability assessment is traditionally done in the later part of the product development stage when prototypes are available, and heavily re- lied on in confirming ground durability tests. This process is very time consuming and often results in over-design with weight penalties, which is the major obsta…     

薄带钢连铸技术的发展

主要介绍了国内外薄带钢连铸技术的发展和双辊式薄带连铸的现状，包括连铸机设备结构、工艺参数、浇注钢种以及产品规格、质量等，并分析了影响薄带连铸的几个关键技术。     

纳米粉体表面结构与分散机理研究

从表面物理与表面化学入手分析了纳米粉体的表面结构，由粉体间的相互作用分析对纳米粉团聚与分散机理进行了研究。红外光谱，吸附研究表明：高的比表面积和高的表面能使纳米粉强烈吸附外来物质（如水）反应生成新的表面结构（如R－O－H结构），增加了粉间相互作用力和表面活性是纳米氧化物粉团聚的根本原因。纳米粉表面间化学反应（如－OH基间聚合反应）或生成新的连接物是纳米粉及浆体产生团聚，影响分散性的直接原因。指出了纳米粉体分散的具体途径。     

螺杆、星轮啮合副瞬时接触线分布参数的分析

建立三种不同母面按一次包络形成的螺杆、星轮啮合副的瞬时接触线的数学模型,利用计算机对影响瞬时接触线分布的主要参数进行分析,为瞬时接触线的分布对啮合工作状态的影响的研究提供理论依据。     

Study on the thermal decomposition kinetics of nano-sized calcium carbonate

INTRODUCTIONTherearefewofquantitativethermalanalysis(TA)investigations (Mulokozi,1992 )ofthegoverningrelationsbetweentheparametersofsolidphasereactionkineticsandtheaveragedi ametersofultrafinecalciumcarbonateandtheeffectsoffineparticlesontheirsolidphasere…