爆炸载荷下加筋板的动力学性能分析

为提升军舰、潜艇和航空母舰外板的抗爆炸载荷冲击能力,采用Abaqus分析爆炸载荷下材料阻尼、应变率、加筋板的几何构型及加强筋的几何参数对结构动力学性能的影响.结果表明：加筋板相对于平板具有优异的抗爆炸载荷冲击能力;材料的阻尼及应变率对结构动力学性能影响较大;双十字加筋板相对于其他几何构型的加筋板具有更优良的抗爆炸载荷冲击的能力;矩形加强筋截面高宽比对加筋板动力学性能影响较明显,在结构设计中应该根据需求进行合理选择.     

抗冲击性能要求下一种新型夹心板的设计研究

防护板在舰船上的应用非常广泛,它对于提高舰船抵抗水下爆炸冲击波载荷性能、抗碰撞冲击性能等都具有重要作用.文中利用薄壁圆管的吸能特性设计了离散型和紧密型圆管夹心板,使用大型非线性有限元软件MSC.Dytran建立水域、炸药及防护板的三维有限元模型,并进行水下爆炸数值仿真计算,从板的吸能能力、加速度响应、变形量三个方面分析了两种夹心板和普通平板在水下爆炸载荷作用下的抗冲击性能,仿真计算结果表明离散型夹心板的抗爆性能优于紧密型夹心板和普通平板.     

水下爆炸作用下轻型鱼雷冲击响应数值仿真

轻型鱼雷受水下爆炸作用的冲击响应对鱼雷设计具有重要意义;利用ABAQUS软件验证了材料动态失效对圆桶结构水下爆炸数值仿真的影响,并对美制MK44型鱼雷受深水炸弹攻击下的冲击响应进行仿真计算,给出了两种失效准则下的安全距离和破坏模式;结果表明,考虑材料动态失效时应使用水为主耦合面的公式进行计算,结构变形响应取决于加筋方式;研究可为可对轻型鱼雷的设计和考核提供参考。     

典型舰船水下爆炸冲击环境仿真

利用冲击谱描述方法,对舰船在水下爆炸载荷作用下的冲击环境进行了数值模拟和分析. 利用MSC Dytran软件计算在爆炸载荷作用下舰船各测点的加速度,用加速度计算得到冲击谱,并总结出爆炸参数和冲击谱的关系. 通过分析表明冲击谱的谱值由船底外板到最上层甲板呈衰减的趋势;各测点加速度谱值随爆炸距离的增加近似呈指数衰减;各测点的加速度谱值随炸药量的增加近似呈抛物线增加.     

水下刚性壁装药爆炸气泡简化模型和数值仿真

为预测沉底装药水下爆炸产生气泡的最大半径和脉动周期,建立了水下刚性壁上的装药爆炸产生气泡的动力学模型.从Bernoulli方程和能量守恒两个角度推导出描述半球形气泡径向运动的流体动力学方程,通过能量法确定了方程的初始条件.对方程数值求解得到第一脉动周期内气泡半径和径向运动速度随时间变化的曲线.利用ANSYS-AUTODYN软件的高精度Euler-Godunov求解器和计算结果映射技术,建立了水下刚性壁上装药爆炸产生气泡运动的数值仿真模型.计算得到了气泡膨胀、收缩、上浮和脉动压力时程曲线及其几何形状变化规律.理论模型与仿真计算得到的气泡半径、脉动周期和径向运动速度均吻合,说明该理论模型满足工程所需精度要求.     

受剪复合材料加筋平板筋条剥离分析

为研究筋条-蒙皮界面强度对复合材料加筋平板剪切承载能力的影响,采用基于接触属性定义的粘聚区模型分析蒙皮-筋条界面损伤的萌生和扩展,采用基于二维Hashin准则的渐进损伤模型计算复合材料层板失效.仿真结果与试验吻合较好,验证基于接触属性定义的粘聚区模型用于整体复合材料加筋板筋条剥离分析的工程实用性.计算结果表明:为充分发挥复合材料加筋板的承载潜力,筋条-蒙皮界面应具有较高的强度.     

金属加筋板压缩稳定性分析的随机缺陷法

为使金属加筋板稳定性分析更加真实可靠,在分析中引入随机的初始几何缺陷,采用一致缺陷法通过ANSYS对金属加筋板进行压缩稳定性有限元分析,总结一致缺陷法的优缺点,进而提出一种考虑加筋板初始几何缺陷的随机缺陷法并进行试验.结果表明:一致缺陷法对非线性变形分析有一定的引导作用,使非线性变形朝着特征值屈曲模态的方向发展;随机缺陷法将结构的初始缺陷看作是随机的,缺陷大小和分布无法预测,更能反映加筋板真实的工作性能.编写加筋板自动建模程序和随机缺陷自动分析程序,从而大大提高分析效率,使随机缺陷法用于设计成为可能.     

圆柱壳在水下爆炸载荷作用下的动力仿真分析

圆柱壳是船舶、潜艇和海洋工程结构物的重要组成部分,研究其在水下爆炸载荷作用下的响应对提高结构物的使用周期有着重要的作用.利用LS-DYNA动力有限元程序对张效慈等人做的深水爆炸水动压力场对潜体结构的动态响应试验进行数值模拟.分析了不同材料圆柱壳和不同参数复合材料圆柱壳在水下爆炸载荷作用下的抗冲击性.计算结果表明,复合材料比钢、铜、铝合金金属材料的抗冲击性好,弹性模量小的复合材料的抗冲击性好.方法可以简单快速的计算圆柱壳的抗冲击性,为舰船的设计提供参考.     

基于ANSYS/LS-DYNA的加筋板入水冲击仿真

采用ANSYS/LS-DYNA有限元分析软件数值模拟入水冲击问题,重点研究平板类结构体入水冲击数值仿真和冲击荷载作用下的结构动力响应;首先采用ANSYS前处理器建立平板和十字加筋板入水冲击数值模型,然后通过LS-DYNA求解器数值计算入水冲击的动力响应,并分析比较了各个模型计算得到的位移、等效应力、压力等变量变化,最后得出以下结论,加筋板具有吸收更多人水冲击能量的作用,且耐撞性更强,结构更偏于安全.     

水下爆炸冲击波数据记录仪的设计与实现

本文从水下爆炸冲击波的概念出发,介绍了水下爆炸冲击波的特征,应用爆炸气泡运动理论确定了波形参数。然后根据水下冲击波的特征,分析了水下爆炸冲击波数据记录仪的测试原理,介绍了两种模拟实际水下爆炸冲击波信号的测试方法。再通过简易的水下爆炸试验,得到了冲击波的压力-时间历史曲线及其参数并与理论值作了比较。最后通过直线拟合和误差分析进一步证明了文中提出的水下爆炸冲击波测试方法是一套科学的、有效的冲击波压力测试方法。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。