一种定征层状平面结构界面粘接强度的兰姆波方法

置于层状平面结构表面的斜劈超声换能器被用于激发和接收多模兰姆波。文章首先分析了采用多模兰姆波的幅频特性定征界面粘接强度的可行性。基于Ritec-SNAP 超声测量系统,建立了采用兰姆波方法定征层状结构界面粘接强度的实验系统。对于给定的层状平面结构,将粘接层的固化过程用于模拟粘接层界面强度的变化过程。对于不同的粘接层固化时间,实验测得的多模兰姆波幅频曲线明显不同。借助于声——超声技术中的应力波因子,给出了兰姆波应力波因子的定义。实验结果显示,兰姆波应力波因子与间接表示界面粘接强度的固化时间之间存在确定的单调对应关系,表明将多模兰姆波的应力波因子用于定征层状平面结构的界面粘接强度是可行的。     

切尔诺贝利核事故救援对我国核电消防部队建设的启示

介绍了切尔诺贝利核事故消防部队救援的基本情况以及经验和教训,并针对我国目前核电消防的现状,结合切尔诺贝利核事故救援的经验和教训,就我国核电消防安全和队伍建设提出了建议和意见。     

基于混料设计的快硬土壤固化材料配方优化

为探索普通硅酸盐水泥(P·O)、熟石灰(HL)、硅灰(SF)三元混料系统对固化土无侧限抗压强度的影响,综合极端顶点设计和均匀设计思想建立混料回归模型,得出了响应面图形,确定了三元混料系统的最佳配方。在该配方下,固化土7d实际抗压强度可以达到4.75MPa。通过交互作用分析揭示了混料因子间的作用规律:P·O与HL交互作用对固化土7d无侧限抗压强度影响极其显著,P·O与SF交互作用对固化土7d无侧限抗压强度影响显著。对比试验表明,该混料设计方案对提高固化土7d无侧限抗压强度有显著效果,对土壤固化剂配合比优化设计和固化土无侧限抗压强度预测具有指导意义。     

双层隧道边墙位置研究

针对地下快速路的特点和重庆市地形特征,分析了在重庆市地下快速路中使用双层隧道的优越性,并根据双层隧道边墙受力不利原则提出了两种双层隧道新型结构方案。利用计算软件对两种新型结构相对于传统结构的稳定性和边墙二次衬砌受力进行了分析比较,得出边墙位于中隔板中部的双层隧道结构更加适用于城市地下快速路。     

Investigation on the process parameters of TIG-welded aluminum alloy through mechanical and microstructural characterization

Multi-pass TIG welding was conducted on plates (15×300×180 mm3) of aluminum alloy Al-5083 that usually serves as the component material in structural applications such as cryogenics and chemical processing industries. Porosity formation and solidification cracking are the most common defects when TIG welding Al-5083 alloy, which is sensitive to the welding heat input. In the experiment, the heat input was varied from 0.89 kJ/mm to 5 kJ/mm designed by the combination of welding torch travel speed and welding current. Tensile, micro-Vicker hardness and Charpy impact tests were executed to witness the impetus response of heat input on the mechanical properties of the joints. Radiographic inspection was performed to assess the joint's quality and welding defects. The results show that all the specimens displayed inferior mechanical properties as compared to the base alloy. It was established that porosity was progressively abridged by the increase of heat input. The results also clinched that the use of me-dium heat input (1-2 kJ/mm) offered the best mechanical properties by eradicating welding defects, in which only about 18.26% of strength was lost. The yield strength of all the welded specimens remained unaffected indicated no influence of heat input. Partially melted zone (PMZ) width also affected by heat input, which became widened with the increase of heat input. The grain size of PMZ was found to be coarser than the respective grain size in the fusion zone. Charpy impact testing revealed that the absorbed energy by low heat input specimen (welded at high speed) was greater than that of high heat input (welded at low speed) because of low porosity and the formation of equiaxed grains which induce better impact toughness. Cryogenic (-196 C) impact testing was also performed and the results corroborate that impact properties under the cryogenic environment revealed no appreciable change after welding at designated heat input. Finally, Macro and micro fractured surfaces of tensile and impact specimens were analyzed using Stereo and Scanning Electron Microscopy (SEM), which have supported the experimental findings.     

基于多元高斯概率分布的无线局域网定位方法研究

针对无线局域网环境及室内目标定位需求,研究了基于接收信号强度指示的定位技术,提出了一种基于多元高斯概率分布的信号强度模式匹配方法,讨论了定位系统框架。试验结果表明,该方法具有较好的室内定位效果。     

舰船静置爆炸气泡时总纵强度计算方法研究

新型"大气泡能"概念武器在水下爆炸能产生大气泡,对船体总纵强度造成很大影响,有可能使舰体发生纵向折断或倾覆。为研究这种作用,建立了舰船静置爆炸气泡时总纵弯曲强度的理论计算方法。采用静置爆炸气泡的假设,将气泡产生的浮力损失和压力差转化为等效载荷,计算气泡作用后船体的总纵弯矩和剪力并进行强度校核。以某舰艇为例进行计算,结果表明,爆炸气泡作用下船体的剪力和弯矩比静浮状态增大很多,船体发生纵向折断破坏的危险性也随之增大。     

深水环境下潜艇舯部结构撞击强度数值分析

潜艇结构水下碰撞是潜艇的主要事故形式,也是船舶碰撞最为危险的状态之一。文中首先提出潜艇碰撞问题,对碰撞特征进行分析,然后针对某型潜艇舯部典型结构的撞击极限强度特性进行数值计算,结果显示,由于准静压载荷的附连耦合作用,随着静水压力的增加,潜艇舯部耐压壳体结构的防撞能力将大幅下降,而耐压壳体内部平台和舱壁结构将有效提高壳体结构的横向失稳临界应力,改善潜艇结构的径向耐撞能力。     

潜艇结构强度研究的新近进展

本文从结构材料、结构形式、非线性分析、组合壳体和端盖强度以及结构的减振降噪等方面论述了潜艇结构强度研究的新近进展,并指出了今后的研究方向。     

基于深度神经网络的无线覆盖预测算法*

为保证新一代移动无线网络能够根据实时覆盖情况动态地调节小区天线参数,需要实现高效且准确的无线覆盖预测。传统的求解方法通过精确的场强预测来判断天线参数的优劣,虽然精度很高但需要大量的计算资源,无法满足5G和后5G移动网络通过实时覆盖预测进行射频参数动态调整的实际需求。现采用基于深度神经网络的算法对给定天线参数的覆盖效果进行预测,以取代对目标区域的精确场强预测。数值结果表明,该方法能够在保持计算准确性的同时显著减少计算量,为5G动态网络规划提供基础性参考数据。