Melting heat transfer with radiative effects and homogeneous–heterogeneous reaction in thermally stratified stagnation flow embedded in porous medium

The present article deals with thermally stratified stagnation-point flow saturated in porous medium on surface of variable thickness along with more convincing and reliable surface condition termed as melting heat transfer.Homogeneous–heterogeneous reaction and radiative effects have been further taken into account to reconnoiterproperties of heat transfer.Melting heat transfer and phenomenon of homogeneous–heterogeneous reaction have engrossed widespread utilization in purification of metals,welding process,electroslag melting,biochemical systems,catalysis and several industrial developments.Suitable transformations are utilized to attain a scheme of ordinary differential equations possessing exceedingly nonlinear nature.Homotopic process is employed to develop convergent solutions of the resulting problem.Discussion regarding velocity,thermal field and concentration distribution for several involved parameters is pivotal part.Graphical behaviors of skin friction coefficient and Nusselt number are also portrayed.Concentration of the reactants is found to depreciate as a result of strength of both heterogeneous and homogeneous reaction parameters.With existence of melting phenomenon,declining attitude of fluid temperature is observed for higher radiation parameter.

Note on characteristics of homogeneous-heterogeneous reaction in flow of Jeffrey fluid

This letter describes the characteristics of homogeneous-heterogeneous re- action in the boundary layer flow of a Jeffrey fluid due to an impermeable horizontal stretching sheet. An analysis is carried out through the similar values of reactant and auto catalyst diffusion coefficients. Heat released by the reaction is not accounted. The exact solution for the flow of the Jeffrey fluid is constructed. The series solution for the concentration equation is derived. The velocity and concentration fields reflecting the impact of interesting parameters are plotted and examined.

摩擦搅拌焊新工艺发展与应用

介绍了摩擦搅拌焊新工艺的现状、特点、优缺点。

异质板材连接成形技术的研究现状

异质板材连接是装备制造及交通运输等多个领域实现轻量化的有效途径之一,但因材质属性方面存在明显差异,使用传统连接方法时存在着一定的技术瓶颈。对TIG焊、激光焊等为代表的焊接方法和机械连接方法的工艺特点及研究现状进行了详细评述,重点介绍了各工艺在异质板材连接领域所起的优势作用及发展潜力,并结合行业发展及使用需求对异质板材连接工艺的发展进行了展望,进而为异质板材连接新工艺的研究及开发提供技术参考。

银行表外业务、货币政策传导与银行风险承担

从理论和实证两个层面检验了表外业务对银行风险承担影响的双重效应,即表外业务发展提高了银行风险承担水平(直接效应)以及表外业务通过强化货币政策银行风险承担渠道提高银行风险承担水平(间接效应)。理论分析表明,表外业务高复杂性、高杠杆率、低透明度和流动性期限错配风险直接提高了银行风险承担水平;表外业务对利益搜寻效应的强化和对央行沟通和反应函数的改变则强化了货币政策银行风险承担渠道。利用25家上市商业银行2009~2016年的面板数据,在采用两步法规避货币政策与表外业务的内生性影响的前提下,本文实证检验发现:表外业务与银行风险承担水平正相关,并且表外业务确实强化了货币政策银行风险承担渠道,提高了商业银行的风险承担水平。进一步,本文探讨了表外业务对银行风险承担影响的异质性,与股份制商业银行相比,系统重要性商业银行的响应更为稳健与审慎。本文的研究为理解货币政策银行风险承担渠道的影响因素提供了一个新的重要视角,对防范表外业务风险具有重要的借鉴意义。

地面拉锚式钢板桩内力计算的弹性曲线法

文章根据静力平衡条件按弹性曲线法和等值梁法相结合的原理,使在非均质土的计算中无需将各层土加权平均换算成均质土而直接分层计算,给出了计算地面拉锚式钢板桩支护结构土压力及其内力的分析方法,并在一实际工程中运用了该方法,取得了良好的效果。

非平面齿PDC钻头研制与应用

长庆油田刘家沟组地层具有岩石致密、砂泥岩互换频繁、研磨性强、可钻性差、石英含量高的特点,常规PDC钻头在此类地层破岩效果不佳,钻头进尺和钻头寿命得不到有效保障。为此,公司自主设计并制造了一种新型PDC钻头——非平面齿PDC钻头,并开展了室内模拟实验和现场入井试验。通过现场应用表明,该新型钻头能突破均质性差和研磨性强地层PDC钻头的应用禁区,在机械钻速和钻头进尺方面,其使用性能能比肩国外优质钻头,具有较高的推广应用前景。

基于Kriging模型的钢铝异质板料无铆钉铆接结构工艺参数优化

针对钢铝异质板料无铆钉铆接成形接头力学性能差的问题,对铆接过程的结构工艺参数优化开展研究。以提高接头的最大抗拉力和抗剪力为目标,首先,建立了无铆钉铆接成形过程数值仿真模型,通过对比接头截面关键尺寸,验证了数值模型的可靠性;其次,对主要结构工艺参数进行拉丁超立方抽样试验,获取代表性样本点集及其数值仿真结果;随后,利用Kriging模型对接头的颈厚值和自锁值进行预测,预测相对误差小于10%,验证了Kriging模型的预测能力;最后,将Kriging模型与遗传算法相结合,进行结构工艺参数的多目标优化,采用优化后的结构工艺参数进行试验,无铆钉铆接接头的最大抗拉力提高了9.4%,最大抗剪切力提高了26.4%,验证了优化结果的有效性。