Numerical and experimental study of submerged supple nets: Applications to fish farms

Our aim is to investigate the behavior of submerged supple nets. This work generates many problems owing to the discontinuous and highly flexible nature of the nets. Only the action of external forces can bring an infinitely flexible structure like a net into a definite shape. When considering supple nets immersed in a fluid, these external forces themselves depend on the net geometry. A numerical method to solve this fluid-structure coupling problem is proposed, and is applied to fish farms. In order to validate the calculation model of the hydrodynamic forces on the mesh sides, we measured the hydrodynamic forces on a plane panel of netting spread across a transverse current. We thus proved that the Landweber model modified according to the Richtmeyer formula as regards friction gives good results. The calculated shape of the fixed net cage is qualitatively in accordance with flume tank observations. We have adapted the algorithm to the study of the dynamic behavior of floating fish farms.     

Evaluation,prioritization and selection of transportation investment projects in New York City

Over the last decade, a large number of high capital cost transportation projects have been proposed for the New York City Region. Many have resulted from addressing evolving capacity needs, changes in regional demographics and economics, meeting the improvements necessitated by operating century old subway systems and recognizing the impact of moving freight in a dense region. But the catalyst for bringing all of these projects to the attention of the public and all regional agencies was the tragedy of September 11, 2001. While these projects entail massive investments ($50–$60 billion), little analytical work has been carried out to measure the transportation and economic costs and benefits they entail and to categorize them accordingly. Competition among agencies to secure adequate resources to implement any of the desired projects makes such analysis necessary; yet there still remain political, vested economic interests and agency rivalry barriers to achieving this important planning objective. This paper reports the methodological approach taken by these authors for consistent and transparent project evaluation and then presents results from the ranking and prioritizing methodology. The policy underpinnings and implications of the analysis are discussed in a subsequent paper and thus only briefly touched upon here in the concluding section.     

数据网微机管理数据库的建立与统计处理

本文简要介绍了数据网管理数据库的建立、数据统计方法及实现的具体功能。文中将数据网的描绘分解为多个链结，建立关系型数据库记录每个链结，由此实现对网络描述，并进一步生成网络图和资源分配图。     

分层递阶智能控制任务转换模型的研究现状

分析了分层递阶智能控制任务转换模型的研究现状，较为详细地讨论了国际上在这一领域的最新研究成果－Ｐｅｔｒｉ网任务转换模型。     

应用MSS图象对成昆铁路北段水系、植被与泥石流分布规律的判释

水系为泥石流发育之环境及其运动之通道;植被的发育程度又与生态平衡及山体稳定密切相关。水系及植被的分布和发育情况与泥石流的分布和发育情况存在着一定的规律性,本文通过对成昆铁路北段的卫片判释,仅就这一宏观规律加以阐述与探讨。     

基于UML状态图和基本Petri网生成测试用例

结合UML状态图和Petri网提出了一种生成测试用例的方法。将UML状态图转换成对应的EN-系统模型，利用EN-系统的性质检测并排除UML状态图中的不可达状态和事件的冲突和冲撞；再应用与合理的UML状态图对应的EN-系统生成可达状态图，利用可达状态图生成测试用例。该方法一方面可以很好地实现并行子状态的嵌套问题，避免了将并行的UML子状态展平成EFSM时引起的状态爆炸问题；另一方面，由于测试用例的覆盖标准是基于可达状态图的基路径、事件和可达状态覆盖，所以还很好地解决了对系统的不同测试要求和状态的可达性问题。     

浅埋大跨径箱涵暗挖顶推施工技术

介绍在重交通量、浅覆盖、多管线等复杂条件下,大跨径箱涵暗挖顶推施工方法和技术措施。     

超大跨度斜拉桥活载几何非线性分析

进入超大跨度范围后,斜拉桥几何非线性问题更加突出。以主跨为1 088m的苏通大桥为研究对象,采用线性理论、线性二阶理论和非线性理论,分析几何非线性对超大跨度斜拉桥活载效应的影响。研究表明,即使对超过1 000m的公路斜拉桥,采用线性二阶理论(即只需考虑斜拉索弹性模量折减和恒载几何刚度矩阵的影响)计算活载效应完全可以满足工程要求。     

基于BP神经网络的某挖掘机故障诊断知识库设计

针对传统知识库存在知识获取困难、表达复杂、推理容易产生组合爆炸等缺陷,提出了一种基于神经网络的知识库建构方法,建立了某型挖掘机的神经网络知识库。研究了BP网络的结构及训练算法,阐明了知识库的实现过程,并以液压泵故障诊断为例,证明了神经网络知识库具有知识获取简单、表达清晰、推理逻辑性强等特性。     

基于减隔震设计的大跨度连续梁桥抗震性能评价

基于高烈度区的某大跨度连续梁桥(89m+170m+89m),采用非线性时程分析法进行结构动力特性及抗震性能分析。全桥均采用三维梁单元建立空间模型,对于双曲面球形减隔震支座的滞回耗能特性和自恢复功能,活动支座的摩擦耗能以及固定销剪断后的效应进行了模拟,同时模拟了阻尼器的阻尼耗能作用。研究结果表明:采用双曲面球形减隔震支座及桥台处纵向阻尼器后,结构的反应得到了很好的控制,确保了高烈度区结构的抗震安全性。