Influence of porosity distribution on nonlinear free vibration and transient responses of porous functionally graded skew plates

This article deals with the investigation of the effects of porosity distributions on nonlinear free vibration and transient analysis of porous functionally graded skew (PFGS) plates. The effective material properties of the PFGS plates are obtained from the modified power-law equations in which gradation varies through the thickness of the PFGS plate. A nonlinear finite element (FE) formulation for the overall PFGS plate is derived by adopting first-order shear deformation theory (FSDT) in conjunction with von Karman’s nonlinear strain displacement relations. The governing equations of the PFGS plate are derived using the principle of virtual work. The direct iterative method and Newmark’s integration technique are espoused to solve nonlinear mathematical relations. The influences of the porosity distributions and porosity parameter indices on the nonlinear frequency responses of the PFGS plate for different skew angles are studied in various parameters. The effects of volume fraction grading index and skew angle on the plate’s nonlinear dynamic responses for various porosity distributions are illustrated in detail.     

Critical interfaces in body armour systems

The ballistic performance, and behaviour, of an armour system is governed by two major sets of variables, geometrical and material. Of these, the consistency of performance, especially against small arms ammunition, will depend upon the consistency of the properties of the constituent materials. In a body armour system for example, fibre diameter, areal density of woven fabric, and bulk density of ceramic are examples of critical parameters and monitoring such parameters will form the backbone of associated quality control procedures. What is often overlooked, because it can fall into the User’s domain, are the interfaces that exist between the various products; the carrier, the Soft Armour Insert (SAI), and the one or two hard armour plates (HAP1 and HAP2). This is especially true if the various products are sourced from different suppliers.There are between 30 and 150 individual layers within a typical body armour system, and each of the interfaces between each of those layers will, in some way or another, contribute to the ballistic performance of the system. For example, consider the following interfaces/interlayers: (i) the frictional, sliding, inter-ply surfaces within a soft armour pack, and also between the pack and the carrier, (ii) the air-gaps that may develop within the soft armour pack, (iii) the interconnecting space between the soft armour pack and the hard armour plate, (iv) the nature of the interfaces between adjacent plies of a multiplied backing laminate, even in a highly compressed Ultra High Molecular Weight Polyethylene (UHMWPE) variant, (v) the interlayer between the ceramic and its substrate, within a HAP, and (vi) the geometrical fit between two hard armour plates within a stacked body armour system. This paper will provide a User-friendly overview of all such interfaces and provide unique guidance as to their criticality and influence.     

国防费增长的另一种透视——评《经济增长与国防费规模》

人类迈入新世纪,中国需要思考——面对世界多极化、经济全球化等错综复杂的战略格局,我们将面临怎样的机遇和挑战。国防,作为保卫国家安全稳定的支柱,不能不引起世人的关注;而作为国防建设启动器和调节器的国防费,也必然是各国政府和经济理论界不可回避的课题。正如《经济增长与国防费规模》书中所言:“国防费,作为综合国力形成的直接因素,其研究必须引起理论界的重视;     

对军队企业化工厂调整改革的思考

文章就目前企业化工厂存在的问题进行了分析,阐述了企业化工厂调整改革应遵循的基本原则,并提出相应的对策。     

俄海军面临第五次复兴

第二次世界大战后,苏联经过40多年的发展,形成了一只可以和美国在全球争霸的远洋作战海军。苏联解体后．由于俄罗斯经济长期萧条．俄罗斯海军也面临着前所未有的严峻局面。1989年苏联的造船工业共为其海军制造了78艘潜艇、作战舰艇及勤务舰船,而1995、1996、1997年俄罗斯海军分别只有11、8、6艘新造舰艇服役,到了1999年则只有4艘。     

Mechanical stress and deformation analyses of pressurized cylindrical shells based on a higher-order modeling

In this research, mechanical stress, static strain and deformation analyses of a cylindrical pressure vessel subjected to mechanical loads are presented. The kinematic relations are developed based on higherorder sinusoidal shear deformation theory. Thickness stretching formulation is accounted for more accurate analysis. The total transverse deflection is divided into bending, shear and thickness stretching parts in which the third term is responsible for change of deflection along the thicknes...     

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the fin...     

An energetic nano-fiber composite based on polystyrene and 1,3,5-trinitro-1,3,5-triazinane fabricated via electrospinning technique

Electrospinning is a simple technique used to fabricate polymeric nano-fibrous membranes. These nano-fibers have found a wide range of valuable applications in the biomedical field. However, it has not been utilized with solid high explosives yet. Herein, the electrospinning technique has been used to fabricate polystyrene(PS)/1,3,5-trinitro-1,3,5-triazinane(RDX) composite nanofibers. The governed electrospinning parameters, voltage, distance from the collector, flow rate, mandrel rotating speed...     

在党的阳光下立志成才--兵团实施"西部开发助学工程"综述

西部大开发,科教要先行,人才是关键。2000年8月,一项由中宣部、中央文明办、教育部共同组织实施,旨在为西部地区培养人才的"西部开发助学工程"在西部地区展开。3年来,兵团265名来自贫困家庭的大学生和100名中学生,在党和国家的资助下,正在全国各地重点高等院校和高中"宏志班"勤奋学习,立志成才。一、以高度的责任感,努力做好"西部开发助学工程"的各项工作"西部开发助学工程"资助的学生均是兵团子女,且须是在当年考入全国或省(区、市)属重点高校的品学兼优的本科生,由各师推举候选人,兵团"西部开发助学工程"领导小组确定名单,并在《兵团日报》上予以公示,最终上报中央文明办备案。兵团党委宣传部、兵团文明办、教委,按照中