汽车荷载作用下桥梁冲击系数影响规律研究

以三跨连续箱梁桥为研究对象,建立了桥梁模型和车辆模型从而组成车桥耦合动力模型,并对车辆荷载作用下桥梁结构的冲击系数进行研究分析。研究表明:增加横向车道数可以使桥梁的冲击系数增大,纵向距离越大桥梁冲击系数越小;车辆在制动状态下的桥梁冲击系数明显大于车辆匀速状态时的冲击系数,并且车辆在桥梁中跨前半部分制动时,动力冲击系数要大于后半跨;车辆在跳车冲击作用下,桥梁跨中冲击系数明显增大,且在跨中跳车时,桥梁动力冲击系数为最大。     

NaCl质量分数对中相微乳液相行为及增溶性能的影响

中相微乳液相行为及增溶能力主要受油、无机盐、表面活性剂及助表面活性剂组分的影响,本实验在油水体积比1∶1与1∶2两种不同条件下,使用石油磺酸盐加乳化剂质量配比为4∶1总质量分数为0.3%,并以总质量分数为0.2%和0.4%作为对照组,利用Winsor相图盐度扫描法探究了中相微乳液相态特征的变化,并评价其增溶性能。结果表明：在油水体积比1∶1条件下所形成的中相微乳液远大于油水比1∶2条件下形成的;随着表面活性剂质量分数的增加,形成中相微乳液所需Na Cl质量分数越低,“盐宽”范围变大且中相微乳液体积增加。随着Na Cl质量分数的增加,表面活性剂的亲油性逐渐增强,增溶参数增加。     

冬青树叶表面的红外光谱特征

用红外衰减全反射技术(ATR)研究了各生长期和不同环境中冬青树叶表面的红外光谱特征.当用黑色塑料袋套在冬青枝条上48 h后,树叶表面的水分有所增加,其它成分变化甚微.当用透明塑料袋套在枝条上48 h后,树叶表面酯类物质的特征峰1 730、1 682 cm-1增加,且峰强度相当.当冬青叶片与甲苯气体接触48 h后,叶片反面酯类物质的特征峰(1 730、1 168、1 039 cm-1)有所减少.同样,叶片正面的酯类物质(1 730、1 168、1 039 cm-1)也有所减少.扫描电镜能谱也证实了叶片反面酯类物质确有减少.     

线型双酚A酚醛树脂的合成

对线型双酚A酚醛树脂的合成工艺及催化剂浓度、种类、反应时间、醛酚比等影响因素进行了研究。结果表明,随着反应物醛酚比的增大,产物中残留的BPA量呈下降趋势,软化点先上升后下降,在1.2左右出现峰值;随反应时间延长,产物的软化点升高,分子质量增大,残留BPA量减少,分子质量分散性增加;催化剂用量增大,分子质量增大,软化点增高,残留BPA含量降低。合理的催化剂用量为m(BPA)∶m(催化剂)=100∶20。以合成的BPAN代替双氰胺(D ICY)作环氧树脂EB454A80的固化剂,在相同的固化工艺条件下,固化物的Tg提高近12℃。     

产品基因调控网络的设计知识析出新模式

为从产品基因调控网络(Gene Regulatory Network,GRN)中析出更为完善、系统的设计知识,基于社会网络分析理论(Social Network Analysis,SNA)构建了一种新的产品GRN设计知识析出模式.提出节点中心性的3种独立分析维度和中心度综合指数,并依此完善节点类型的特征描述与设计规则;...     

电流辅助对铆钉压铆过程及连接性能的影响

钛合金铆钉在塑性成型过程中存在变形抗力大、变形不均匀等问题。在铆接过程中引入电流辅助铆接技术可有效提升钛合金铆钉的铆接质量,其原理为通过在铆接过程中施加电流,改善金属铆钉塑性,提高铆钉的可加工性。以TA2M航空用铆钉为研究对象,研究了6种电流密度水平下铆钉的温升过程与成型效果,并开展拉伸试验与疲劳试验研究铆接件的力学性能。研究发现,通电会在较短时间内产生显著的焦耳热效应,这对难变形的钛合金铆钉来说是一种有效的热软化手段;通电带来的铆钉软化效应极大降低了加工难度,改善了镦头的成型效果;当通以电流密度为26 A/mm²的电流时,压铆力降低了24.69%,且镦头直径增大了6.80%,高度降低了14.04%,更加接近标准所要求的尺寸;电流辅助铆接技术对钛合金板连接件静态拉伸强度的影响不显著,但可有效提升连接件的疲劳寿命。     

Phase Equilibrium Characteristics of CO2 and Ionic Liquids with [FAP]-Anion Used for Absorption-Compression Refrigeration Working Pairs

The study of the phase equilibrium characteristics of CO₂-ionic liquids(ILs)as new absorption-compression type refrigeration working pairs is of great importance.Three kinds of ILs,i.e.,[emim][FAP],[bmim][FAP]and[hmim][FAP],were chosen as potential absorbents.The solubility of CO₂in these ILs was measured experimentally within 0 to 5.0 MPa at temperatures of 293.15 K to 333.15 K,and the effects of temperature,pressure,IL anion and cation structure and stirring action on CO₂solubility were also discussed and analyzed.The results showed that the longer alkyl chains in an identical IL family,the alkyl fluoride group in IL anions and the stirring action by a magnetic stirrer had positive effects on the solubility of CO₂.In the three ILs,[hmim][FAP]possessed the best performance for CO₂absorption;the solubility of CO₂reached 0.7641 at a pressure of 5 MPa and temperature of 293.15 K,the maximum solubility measured in this work.The CO₂-[hmim][FAP]binary mixture is recommended as a potentially applicable working pair for CO₂absorption-compression refrigeration systems.     

Numerical Simulation Study on Cooling Characteristics of a New Type of Film Hole

A new type of film cooling hole with micro groove structure is presented in this paper.Based on the finite volume method and the Realizable k-εmodel,the film cooling process of the hole in a flat plate structure is simulated.The surface temperature distribution and film cooling effect of different film cooling holes were analyzed.The effects of micro-groove structure on wall attachment and cooling efficiency of jet were discussed.The results show that under the same conditions,the transverse coverage width and overall protective area of the new micro-groove holes are larger than those of the ordinary cylindrical holes and special-shaped holes.Compared with ordinary holes,the new micro-groove holes can better form the film covering on the surface and enhance the overall film cooling efficiency of the wall.For example,when the blowing ratio M=1.5,the effective coverage ratio of micro-groove holes is 1.5 times the dustpan holes and is 8 times the traditional cylindrical holes.It provides reference data and experience rules for the optimization and selection of advanced cooling structure of high performance aero-gas engine hot-end components.     

Experimental Investigation of Heat Transfer in Microchannel with Inlet Cavitation Structure

Heat transfer of R134 a through the microchannel with an inlet reentrant cavitation structure was investigated for high flux thermal management of electronic devices.The cavitating flow patterns,pressure,and heat transfer characteristics were studied in the range of effective heat fluxes from 0 to 138.4 W/cm2 with mass flow velocities from 2.12 to 5.23 m/s.A stable and ideal starting point of two phase flow and heat transfer was commendably provided by the inlet cavitation orifice.There existed an axis deviation liquid jet after the micro-orifice.The refrigeration vapor was generated from the cavitation structure but liquidized at the downstream of the channel.The wall temperature along flow orientation presented an opposite trend under the test states with or without heat input.The cavitation structure can significantly suppress the flow oscillation in microchannels and the outlet pressure fluctuation reduced about 72%compared with the fluctuation at the entrance.The heat transfer coefficient had been distinctly impacted by heat flux at lower heat input and then maintained the value nearly constant of 11.0 W/(cm²·K)with the critical heat flux of 88.4 W/cm2.     

Numerical Investigations of Film Cooling Characteristics of Interrupted Slot and Trench Holes on a Vane Endwall

This paper describes film cooling characteristics of the novel combined configuration employing interrupted slot and trench holes on a vane endwall.Interrupted ...