有限变形理论能量释放率增率形式

基于有限变形理论中的能量原理和变分原理,考虑以有裂纹的瞬时位形为参考,建立增量变形引起的裂纹扩展方程能够更真实的描述裂纹尖端的扩展机制,在含有裂纹物体的瞬时变形的基础上,推导了裂纹体的能量释放率和增率的形式,提出了裂纹扩展判据.该判据反映了单位时间内裂纹扩展单位面积可以提供的能量与单位时间内裂纹扩展单位面积所需要的能量...     

聚己内酯二醇型水性聚氨酯分散液的合成和性能

聚己内酯二醇(PCL)是由己内酯开环聚合而成的性能优良独特的聚酯,由于结构的独特性,它可作为原料用于合成高性能的聚氨酯弹性体、胶粘剂、涂料等。本工作以Solvay公司CAPA系列的PCL为基础原料,合成了水性聚氨酯分散液,研究了其相应的胶体性能、力学性能以及热力学性能。研究发现,虽然引发剂在PCL中只占3.0％-4.5％,却对聚氨酯性能的影响较大,PCL的相对分子质量、软硬段比及扩链剂种类等对水性聚氨酯的性能也有影响。     

环境行为学视角下建成环境与儿童出行 影响机制研究

儿童依赖建成环境,并通过基本的出行行为满足其 自身发展的各项必要需求,其中儿童独立出行水平和出行方式 至关重要。随着中国城镇化持续推进,大城市边缘的小城镇在 迅速发展的同时,其建成环境也给儿童出行带来了一定安全隐 患,儿童出行安全问题值得关注。从环境行为学视角,结合既 往文献将儿童出行的影响因素归纳整理成个体、环境和其他因 素,随后对长沙市岳麓区莲花镇第五实验小学1 509名6~12 岁儿童及其家长展开实证调查和数据统计分析。结果显示： 儿童和家长对环境的安全感知会对儿童的出行决策产生较大 影响,机动车交通量及速度、交叉路口、道路复杂程度、步 道和自行车道及其基础设施设置、自然水体等是主要的显著 影响因素。据此,从空间布局、道路设计、交通设施配置和 社会环境方面提出了提升儿童出行安全水平的小城镇规划策 略建议。     

全球弹性纤维工业的前景

2007年早期开始，弹性纤维在许多方面已明显发出了下滑趋势信号，目前的全球金融危机可能加剧了这个问题。即使新的投资者相信他们可以替代现有的供应商，但也有必要研究严重的中期需求和供应的趋势，关注这种趋势同样不可回避全球经济形势中的当前问题，这样可使弹性纤维从当前状态更快地得到恢复。     

PREDICTING DRYING BEHAVIOR OF SPAGHETTI IN A CONTINUOUS INDUSTRIAL DRYER WITH THE MODELS DETERMINED IN A LAB SCALE BATCH SYSTEM

In the first stage of this study experimental data were obtained by using a lab scale batch type dryer, operating under various constant temperature/constant relative humidity combinations; then a mathematical model was determined for the effective diffusivity of moisture in spaghetti. In the second stage of the study the model obtained in the lab scale batch type dryer was used to calculate the moisture content of the spaghetti leaving continuous industrial scale dryer, and its success was tested by comparing with the experimentally determined moisture content of the product. The model was not found successful and corrected. Mathematical models based on experimental data obtained in a bench-top laboratory dryer underestimated the apparent equilibrium moisture content and over estimated the effective diffusivity of water in spaghetti in industrial scale continuous drying equipment. The structural differences in the product, extrapolation of the data beyond the range of the original experiments, variations in mode (batch versus continuous), surface-to-volume ratios, flow patterns, and geometry associated with each drying system were anticipated as the cause of the scale up problem.     

Structural and Molecular Orbital Studies of Si-Phenyl Silaanthracenes

The Si-phenyl derivatives of 1-, 2-, 9- silaanthracenes have been subjected to theoretical analysis with density functional theory (B3LYP/6-31G(d)) to obtain their molecular orbital properties. 2-silaanthracene has been found to be thermodynamically the most stable derivative among the trio. Moreover, the effects of the position of the Si substitution and phenyl attachment on the aromaticity of the parent anthracene have been investigated by NICS calculations at ring centers. The structures have been found to be less aromatic with respect to their unsubstituted counterparts.     

Automatic filters prevent nozzle blockages on cooling water system

In the steel industry continuous casting is a way of melting down recycled material to produce new rolled steel products for reuse across a wide variety of different industries. The process needs a reliable water cooling system to ensure that the steel is kept at precisely the right temperature. Water spray wands are used to deliver this water but they can become blocked and threaten the continuous operation of a factory. To avoid this scenario, Avesta Polarit has fitted a Boll automatic self-cleaning filter on the water feed line at its factory in Sheffield, UK, so that no particulates can block the water sprays and bring production to a halt. The new installation provides filtration performance down to 250 microns.