扁挤压筒型腔有限元应力分析及形线优化

本文对８５０ｘ３２０ｍｍ扁挤压筒内套进行了有限元分析计算，运用优化设计理论对扁挤压筒型腔进行计算机辅助形状优化设计，确定了使应力集中系数降为最小的最优形线，为延长扁挤压筒使用寿命提供了一条有效途径。     

光纤用户环路的现状和关键技术

本文简单介绍了光纤用户环路的结构,详细描述了美国、日本、英国和德国等通信发达国家在光纤用户环路方面的研究现状,并指出了光纤用户环路的关键技术。     

水下沉井黏土层爆破参数优化选择研究

杨泗港长江大桥沉井基底持力层为坚硬黏土层,施工中通过爆破辅助开挖实现沉井下沉。为确保黏土层能够顺利破坏和刃脚结构不发生损伤,需采用合理的爆破参数。对此,从爆破参数设计出发,应用ANSYS/LS-DYNA数值模拟软件,对不同爆破参数下黏土层和刃脚结构的应力变化和破坏效果进行了分析,并结合相应的动态破坏判据进行判断。最终确定合理的临空面高度、装药量分别为2 m和4.5~6 kg。施工过程中刃脚下临空面高度控制在2 m左右,装药量取4.5 kg,黏土层爆破效果和刃脚保护程度均达到了要求。最终经过3次循环爆破,1号塔沉井下沉到指定位置。     

Microstructure and mechanical properties of Mg–6Sn and Mg–6Zn alloys prepared by different processing techniques: a comparative study

The microstructure and mechanical properties of Mg–6Sn and Mg–6Zn are investigated and compared in cast/heat treated, rolled and extruded conditions. Compared to the heat treated alloys, the grain size of both alloys decreases while the volume fraction of precipitates increases by rolling and extrusion in Mg–6Sn alloy at 350 ºC due to dynamic recrystallization and dynamic precipitation of intermetallic phases. Zinc has a stronger grain refining effect than tin in the heat treated alloys while the opposite effect is found in the rolled and extruded alloys. For the heat treated alloys the Mg–6Sn the strength reached 158.7 MPa with elongation 5.2% while Mg–6Zn exhibited a higher strength of 183.7 MPa and 8.4% elongation. In rolled condition the strength of Mg–6Sn reached 224 MPa with 1.6% elongation while Mg–6Zn exhibited a lower strength of 124 MPa and a lower ductility of 0.5% elongation due to susceptibility to hot shortness. Extrusion of Mg–6Sn alloy resulted in the maximum attained strength of 281 MPa and an elongation of 6.1% while Mg–6Zn cracked during extrusion due to hot shortness. The results obtained are discussed with respect to microstructure evolution in both alloys.     

路侧停车区域非机动车冲突概率分布

为揭示路侧停车对非机动车骑行行为的影响机理,结合现场调查数据开展了路侧停车区域非机动车与机动车之间严重性冲突判别、非机动车避险行为及严重性冲突概率分布模型研究.提出以非完全制动距离作为非机严重性冲突判别指标,获得研究路段非机严重性冲突及避险行为数据,得出减速是最主要的避险方式;构建了非机严重性冲突的泊松概率分布模型,提出了以正态分布为基础的骑行安全性判定模型及临界值计算标准,并以调查路段进行了安全性评估.     

胎面挤出膨胀与收缩的研究

在总结前人对挤出膨胀和收缩研究的基础上，对胎面挤出膨胀比和收缩率进行了一些理论分析和计算。根据解析式推导出膨胀比的简化计算公式：F(B)＝ClFl(γ／θ） C2F2(t) C3。收缩变形分为弹性形变恢复产生的内在收缩量和热收缩量两部分，内在收缩量与膨胀比计算公式相同，热收缩量通过公式△L＝L(σ0)β(θ0—θ1)计算。     

路缘石对汽车碰撞中央分隔带护栏的影响分析

通过在ADMAS中建立多自由度三维汽车模型、护栏模型等，模拟汽车与护栏碰撞的过程，并对比了有、无路缘石条件下的仿真结果，发现路缘石的存在对汽车碰撞影响很大。     

首都国际机场新航站楼结构设计及施工

首都国际机场新航站楼工程建设规模大，工期紧，根据建筑设计和功能需要，采用了多种薄壁钢屋架，并推广应用建设部十项新技术。采用无粘结预应力混凝土及超长间距伸缩缩短设计方案，基础底板设置滑动层等技术措施，对加快工程进度，提高工程质量，降低工程造价发挥了很大作用。     

Simulation of a photovoltaic/thermal heat pump system having a modified collector/evaporator

A new photovoltaic/thermal heat pump (PV/T-HP) system having a modified collector/evaporator (C/E) has been developed and numerically studied. Multi-port flat extruded aluminum tubes were used in the modified C/E, as compared to round copper tubes used in a conventional C/E. Simulation results suggested that a better operating performance can be achieved for a PV/T-HP system having such a modified C/E. In addition, using the meteorological data in both Nanjing and Hong Kong, China, the simulation results showed that this new PV/T-HP system could efficiently generate electricity and thermal energy simultaneously in both cities all-year-round. Furthermore, improved operation by using variable speed compressor has been designed and discussed.     

Use of soybean isolate in coated foods: simulation study employing glass balls and substantiation with extruded products

Simulation studies on coating using glass balls as ideal solid and soy flour isolate dispersions of different concentrations (10–25%) and at different temperatures (20–50 °C) were conducted. A few coating parameters such as total uptake of dispersion, solid uptake, dimensionless uptake (DU) and uptake per unit area were determined. Further, the study was extended by using corn‐soy extrudates in place of glass balls while using soy flour isolate dispersion of same concentrations and maintained temperature ranges. Rheological characteristics of the dispersions like flow behaviour index, consistency index, apparent viscosity and yield stress were determined to relate them with coating behaviour. The dispersions behaved like a non‐Newtonian shear‐thinning fluid and exhibited yield stress between 0.75 and 1.72 Pa. An increase in concentration of solids in the dispersion increased yield stress, consistency index and apparent viscosity while the flow behaviour index decreased from 0.67 and 0.39. Inter‐relationships between various rheological and coating characteristics were determined; simulation studies on coating by employing glass balls can provide a good interrelation of |r| ≥ 0.88–0.99 that is comparable with |r| ≥ 0.69–0.99 (P ≤ 0.01) obtained with actual experimentation using corn‐soy extrudates.