Dynamic response of a Mindlin elastic rectangular plate under a distributed moving mass

The elastodynamic response of a rectangular Mindlin plate subjected to a distributed moving mass is investigated. The set of governing characteristic partial differential equations that include the effects of shear deformation and rotary inertia is expressed in its dimensionless form. A finite difference algorithm is employed to transform the differential equations into a set of linear algebraic equations. Simply supported edge conditions were used as an illustrative example. The analysis is also valid for other edge conditions. It is found that the maximum shearing forces, bending and twisting moments occur almost the same time. Also, the values of the maximum deflections are higher for Mindlin plates than for non-Mindlin plates.     

流量测量准确性的现场验证及其解决方案

流量计示值准确性的现场验证是交工验收的重要内容。介绍了现场校验法，质量平衡法，热量平衡法，设备能力法等流量测量系统的校验方法以及一些技巧。     

NUMERICAL STUDY ON SORET-EFFECT AND DUFOUR-EFFECT FOR DOUBLE-DIFFUSIVE NATURAL CONVECTION IN POROUS ENCLOSURE

The influences of Soret effect and Dufour effect on the natural convection and heat and mass transfer for a porous enclosure were investigated by means of the penalty finite element method. Numerical results indicate that the Soret and Dufour effects have significant influences on heat and mass transfer in the presence of large temperature gradient and concentration gradient.     

鹰嘴岩隧道软弱破碎岩体的开挖与施工

渫水皂市水利枢纽左岸上坝公路鹰嘴岩隧道围岩主要为Ⅱ、Ⅲ、Ⅳ、Ⅴ类围岩，地质条件复杂，成洞条件差。在隧道施工中，遵循“短进尺，弱爆破、少扰动、早支护”的原则，及时进行监控量测，采取有效的加固措施，取得了良好效果，确保了工程进度与安全。     

A Simple Experimental Technique to Measure Tortuosity in Packed Beds

In this article, a simple and inexpensive experimental technique easy to build in laboratory, for the measurement of tortuosity of a packed bed of inert particles, is described. Experimental values of the tortuosity were obtained with four different packed beds of sand. The experimental results obtained are in good agreement with the theoretical values of tortuosity in a porous media; and the data reported showed the tortuosity to increase with decrease in the void fraction of the packed bed as expected.     

Distinctive Features of Minimization of a Risk Functional in Mass Data Sets

A statistical learning model is considered within the framework of the theory of uniform convergence of frequencies of errors in the case where the convergence is violated as a result of increasing the informativeness of training examples. Drawbacks of nonconstructive refinements of Vapnik-Chervonenkis estimates based on an assumption on the distribution law of violations are shown. A new approach to obtaining constructive estimates for mass data sets is proposed.     

一种中温C/C复合材料抗氧化涂层的制备及其性能

制备了一种工作温度约1 173 K的C/C复合材料抗氧化复合涂层,它由磷酸盐过渡层和陶瓷相阻挡层构成,通过与单一陶瓷相涂层的对比试验研究了它的抗氧化机理。涂覆有该复合涂层的C/C复合材料试样,在空气中1 173 K时氧化10 h的失重率为11.25％,氧化失重率为9.84×10~(-5)g/(cm~2·min),而且其氧化失重率随氧化时间延长而降低;4 h内经过30次从1 173 K至室温急冷急热循环后,失重率为6.38％,涂层基本完好,说明涂层在温度不超过1 173 K时具有良好的抗氧化性和抗热震性。该种涂层适合于中温下C/C复合材料的抗氧化保护。     

热膜式气体质量流量计设计

介绍能够测定空气质量流量,且可自动补偿温度及压力变化对空气流量影响,测量精度高的热膜式气体质量流量计的原理、构造和性能。这种流量计可以满足各种发动机进气流量测量,特别是排放测试的需要。     

大体积承台混凝土施工

阐述了东莞水道特大桥主桥承台大体积混凝土浇筑施工工艺 ,及施工中的注意事项 ,从分层的厚度、表面处理等方面 ,提出了采用泵送混凝土浇筑施工中质量弊病的预防措施     

基于模糊控制的气体流量控制系统

应用热式质量流量计直接测量气体质量流量。高性能AT89S51单片机作为控制器核心，并对控制量采用模糊控制算法。介绍了气体流量控制系统设计方法，给出了硬件原理图和软件主程序流程图。