汽车起动机齿轮拨叉失效分析

分析了引起汽车起动机齿轮拨叉收缩变形及强度低所引起的制品失效原因,采用定型棒对制品进行定型以补偿拨叉的收缩变形;通过改进浇口位置来调整玻璃纤维在制品中的取向,使拨叉受力方向与玻璃纤维取向平行,从而消除了制品因强度低所引起的失效。     

Modification of nylon 66 by electron beam irradiation for improved properties and superior performances

Nylon 66 has been transformed into a material with significantly improved properties like hardness, tensile strength, and flexural modulus by processing it under the optimized dose rate of electron beam in the presence of suitable crosslinkers. Furthermore, percent water absorption of nylon 66 was reduced substantially on irradiation. Thermogravimetric analysis revealed that thermal stability of nylon 66 improved with increasing dose of radiation. Improvement of mechanical and thermal properties and reduction of water absorption of nylon 66 were due to the crosslinking of polyamide molecules made possible by the high energy radiation. Increase of crosslinking with increasing radiation dose was verified by the increase of gel content at higher doses. Differential scanning calorimetry showed that both melting and crystallization temperatures along with percent crystallinity of nylon 66 were decreased with the increasing dose of radiation leading to the development of more amorphous character in this semicrystalline polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

关于尼龙—66纤维化学交联的研究

本文以热分解型过氧化物——过氧化二异丙苯(简称DCP)为引发剂,研究了引发剂浓度、溶胀剂、浸渍时间、浸渍温度对尼龙-66纤维化学交联反应的影响。通过测定交联后纤维溶解性能的变化,确定纤维交联反应的程度:通过对纤维进行红外光谱、X射线广角衍射强度以及强伸度的测定,进一步阐明了化学交联纤维的结构和性能。     

尼龙66原丝物理性能指标测试方法的改进

简述了目前中国神马集团尼龙 6 6浸胶帘子布生产过程中原丝纤度及原丝沸水收缩率指标的测试方法及存在的弊端 .通过对国内外同行业浸胶帘子布生产过程中原丝物理性能测试方法的比较及我公司对比测试 ,对原始数据统计分析后 ,提出了可行的改进意见     

锦纶—66帘子线耐热油剂的研究

根据锦纶—６６帘子线对油剂的要求进行了该油剂的配方设计，调整了平滑剂与乳化剂的比例，合成了理想的耐热油剂，用于原丝和帘子布生产，各项物理性能指标合格，效果良好．     

Leaving home,returning home: Migration as a labor market choice for Alaska Natives

We investigate determinants of the pattern of recent migration of Alaska Natives between rural homelands and urban areas. A review of the literature on moving in the North American North suggests that economic opportunities draw migrants, although such opportunities must be viewed in the context of the mixed subsistence-cash economy prevailing in rural areas of the region. Consequently, we model Native migration as a simultaneous decision with labor market participation in a mixed economy. Estimated equations explaining individual Alaska Native migration choices using the U.S. Census Public Use Microdata Sample (PUMS) are consistent with the model, and also suggest that perceived opportunities differ between women and men.The authors acknowledge financial support from the National Science Foundation, grant OPP-9521459. An earlier version of this paper was presented to the 1998 annual meeting of the Western Regional Science Association     

基于IRC和电热加速老化试验的XLPE电缆绝缘性能研究

为了研究66 kV XLPE电力电缆的绝缘性能,文中采用自主设计的加速老化试验平台,同时对三根样品电缆分别进行两个阶段的电老化、热老化以及电热联合老化.利用等温松弛电流法(IRC)分别对加速老化前后的样品电缆进行试验,分析老化因子的改变,研究电缆的绝缘性能变化.试验结果表明:经过两个阶段的加速老化试验,电老化样品老化因子分别增加3.70%和4.21%,而热老化样品老化因子分别增加4.82%和23.42%,说明电应力和热应力在影响绝缘老化性能中,热应力的“贡献”更大,且温度越高,热应力起到的作用越大;电热联合双应力作用下的样品老化因子分别增加13.04%和37.50%,电热联合作用下老化因子变化远大于单一应力作用的样品老化因子变化,说明电、热两种应力存在某种协同作用,联合作用会加快电缆绝缘劣化.     

Robert Louis Stevenson and the Portrait Photographers

This article is prompted by the remarkable characteristic of nineteenth-century Scotland that circumstances congregate to give an unprecedentedly generous or democratic view of life. Four forms of communication – the statistical accounts, which were followed by the British census records, the boom in publishing, especially in newspapers and journals, and inexpensive communication promoted by the penny post, even the information in street directories and advertisements – all combine with the exploitation of photography to give us insights, which can be disconcertingly specific, acting as occasional spotlights on the landscape. This article is prompted by one particular letter from Robert Louis Stevenson, written when he was a young man, and is followed through two lines of connected thought: the practice of studio photography in Scotland and Stevenson's continuing interest in the photographic portrait.     

Multiple thermosetting of semicrystalline polymers: Polyamide 66 and poly(ethylene terephthalate) fibers

Polyamide 66 fibers were thermoset in a torsion-bending deformation at various temperatures up to 240 °C. Some of the fibers were heat-set at constant length prior to the deformation at presetting temperatures of 150 °C and 200 °C to vary the structural state of the starting material. Fractional recovery was measured after various combinations of temperature and time. It was found that heat setting of PA66 is dominated by time-dependent stress relaxation exhibiting time-temperature equivalence. Increased crystallinity, and/or other molecular rearrangements occurring during presetting, impose additional constraints on molecular mobility, which delay onset of the flow regime and increase the time constant of relaxation at a given temperature. The thermosetting characteristics of PA66 fibers are very similar to those of poly(ethylene terephthalate) fibers. For both polymers, superposing the curves of fractional recovery vs. setting time at different temperatures produce satisfactory master curves, without the need for vertical shifting of the data. Arrhenius plots yield approximate activation energies for the thermosetting flow process of 35-65 kcal/mol in PA66 and 95-115 kcal/mol in PET.     

锦纶66浸胶帘子布胶斑产生原因的探讨

分析了锦纶66浸胶帘子布胶斑产生的原因,讨论了浸胶液质量、干燥区温度、湿度、风速和排风量对胶斑形成的影响。结果表明:锦纶66浸胶帘子布的浸胶液中,间苯二酚与甲醛反应越彻底,胶斑的生成量越少;采用乙烯基吡啶胶乳制成浸胶液,并添加氢氧化钠和氨水,控制其pH值为11.2±0.5,当干燥区温度为(150±1)℃,风速18 m/s,干燥A区相对湿度(24±15)%和排风量140 m3/min,干燥B区相对湿度(18±1)%和排风量25 m3/min,供风机风量为2 200 m3/min,风速为18 m/s,选择棱角形塔顶辊,安装可调式自动清胶器,抑制胶斑形成的效果显著。