Recent developments in the extrusion of helical gears

With an improved die, a method for manufacturing gears by means of tube extrusion has been developed to a stage where, without noticeable wear of the die, 40,000 workpieces can be manufactured. The paper presents a numerical analysis of the stresses and deflection of the die, offering also a comparison between the modified and the conventional symmetric orifice. Based on the results obtained and using recent work on crack prediction for extrusion dies, the area most prone to rupture is determined. Moreover, a concept for the precorrection of the die is offered to improve the tooth quality of the gears.     

Improving communication energy efficiency in wireless networks powered by Renewable energy sources

Energy efficiency is an important issue in wireless networks where the nodes are powered by batteries. In this work, we analyze the energy consumption in one-transmitter-multiple-receiver communication and develop scheduling schemes to improve energy efficiency at the transmitter. Our focus is on systems powered by a renewable energy source such as solar power. We consider an environment where both energy and time to access the wireless channel and transmit data are limited, and data destined for different receivers have different values and incur different energy costs. We present optimal scheduling algorithms that selectively transmit data at calculated rates so that the throughput or the total transmission value is maximized under given time limits and energy constraints.     

非标准工况下空分设备增产氩的研究与实践

文章对非标准工况下的空分设备增产氩措施进行了研究。以宝钢6#60000m3/h空分设备为例,通过设计型算法和校核型算法,建立了空分设备精馏的数学模型,通过改变数学模型的参数,分析了在非标准工况下精馏塔内的组分浓度分布,并提出了优化后的操作方案和操作参数,实施后提高了空分设备的氩提取率,取得了显著的经济效益。     

高频脉冲电铸Ni-Co纳米复合块体微观结构分析

采用高频脉冲电铸工艺制备出了镍钴纳米复合块体材料，利用场发射扫描电镜、能谱和X射线衍射的方法，重点研究了复合块体沉积层的表面形貌、相结构和结晶取向。结果表明．高频率和润湿剂的添加对沉积层的细化有重要影响，高频脉冲电铸能够获得微观组织致密、均匀的复合块体材料。     

一种新型的节能空调装置--介绍复合末端机组(FC+UWSHP)与空气热源热泵冷/热水机组(ASHP)合并运行的系统

本文所介绍的新型空调系统是一种想法很巧妙的节能空调系统。它由单元式水热源热泵机组(ＵｎｉｔａｒｙＷａｔｅｒＳｏｕｒｃｅＨｅａｔＰｕｍｐ)与风机盘管二者组合而成的末端装置和空气热源热泵冷 /热水机组、蓄热槽等构成。本系统由高砂热学公司开发 ,已完成这方面的实验验证 ,并在东京电力公司的暖通空调技术展示中心展出。经过进一步的技术完善以后 ,可以成为一种有竞争力的空调系统。1　单元式水热源热泵机组 (ＵＷＳＨＰ)的原理单元式水热源热泵是一种房间空调器。可做成窗台下立式和吊顶式 (图 1 )等。它是一种整体型机组 ,制冷机在…     

热重分析对高分子材料中碳酸钙的定量研究

碳酸钙是高分子材料中常用的无机填料，在高温时会同二氧化碳而失重。利用热重分析可准确定出高分子材料中碳酸钙的含量，同时还可测出聚合物，挥发物的含量，热重分析法样品用量小，灵敏度高，所需时间短。     

多时滞Lotka-Volterra互惠系统周期正解的存在性

用重合度理论研究具时滞非自治Lotka-Volterra互惠系统，获得了周期正解的存在性，推广了Gopalsamy及He(1997)的结果。     

针梁台车在大花水水电站引水隧洞混凝土衬砌施工中的改进

大花水水电站引水隧洞由于前期开挖工期略有滞后，为加快施工进度，结合全圆断面的施工特点，大部分引水隧洞采用了全圆针梁穿行式钢模台车进行混凝土衬砌。通过各参建单位对针梁台车的运用和改进，有效地提高了引水隧洞混凝土的衬砌速度，并确保了工程质量。     

铁路站段用交流不间断电源供电系统

结合铁路站段的特点 ,介绍了一种交流不间断电源供电系统 ,能够很好的解决其供电问题。     

聚苯乙烯溴代并接技聚二甲基硅氧烷

聚苯乙烯（PS）在苯溶液中与溴代丁二酰亚胺（NBS）反应，经分离提纯得到了固体溴代聚苯乙烯（PSB）。将所得PSB溶于苯并与低分子量的聚二甲基硅氧烷硅醇锂（PDMSOLi）反应，经分离提纯得到固体的溴代聚苯乙烯接枝聚二甲基硅氧烷（PSB－g-PDMSO),所得PSB-g-PDMSO的结构经^1H-NMR、IR及TEM表征。