压电材料智能力矩控制器对具有不确定参数升船结构顶部厂房地震反应的鲁棒控制   总被引：1，自引：0，他引：1  

瞿伟廉  李学安等 《地震工程与工程振动》2001,21(2):145-151

文中建立了压电材料智能力矩控制器对具有不确定参数升船结构顶部厂房地震反应鲁棒控制的设计计算方法，并对中国某升船结构的等效结构体系进行了仿真分析。计算结果表明，智能力矩控制器能有效地减小顶部厂房的鞭梢效应。在考虑顶部厂房因端部山墙引起的侧移刚度不确定性的条件下，智能力矩鲁棒控制器的控制效果和稳定性要优于常规的主动控制器。  相似文献   

Development of the collision ratio to infer the time at which to begin a collision avoidance of a ship     

《Applied Ocean Research》2016

A prior study attempted to solve the intrinsic problem of a critical collision condition including the slower ship’s dilemma by considering the maneuverability of the own ship and the International Regulations for Preventing Collisions at Sea (COLREGs). The collision ratio proposed in the previous study provided insight into the solution of the intrinsic problem, but it was not suitable as an index to determine the time at which to begin the maneuver to avoid the collision.This paper develops a collision ratio as an index that can be used to determine the time at which to begin the collision avoidance maneuver. The collision ratio is calculated by considering the maneuverability of the own ship, the COLREGs, and three virtual intrusion domains (VIDs). The validity of the inferred collision ratio is then assessed according to the dynamic characteristics of the own ship and the basic knowledge of the collision avoidance algorithm. The results indicate that the proposed collision ratio is suitable for use as a new index to determine the time at which to begin the collision avoidance maneuver.  相似文献   

基于MapGIS K9三维数字校园虚拟系统的设计与实现     

魏超  贾勇帅  王贵群  刘欣 《测绘与空间地理信息》2016,(8):80-83

近年来,数字校园继数字地球、数字城市之后成为各高校研究的热点,三维数字校园虚拟系统构建平台多样、方法多元,却鲜有基于国内自主产权的MapGIS K9数字校园系统。因此,本文以某农业大学(南校区)为研究对象,对三维数字校园虚拟系统进行设计与实现。利用南方CASS、3DS Max、MapGIS K9及其他相关软件,通过资料收集整理、地理信息测量采集、建立1:500校园数字地形图、建立属性数据库、三维建模、多平台融合、交互式设计等一系列步骤,实现了某农业大学(南校区)三维数字校园虚拟系统的三维可视化和信息查询、测距、校园导航、自由路径游览、漫游视频录制的交互式功能,可以有效进行校园建筑属性信息查询与部分管理。  相似文献   

浅谈基于ERDAS的三维GIS系统实现     

甘翠 《测绘与空间地理信息》2017,40(7)

主要研究利用三维空间数据、DOM及DEM创建三维虚拟场景。将ERDAS IMAGINE的Virtual GIS模块与第三方建模软件相结合,解决了模型导入ERDAS Virtual GIS Viewer中贴图丢失的问题,实现了立体模型的仿真构建和三维GIS系统的动态管理。同时,对模拟雾气分析、空间视域分析和洪水淹没分析等方面的应用进行了研究,使该系统更具应用价值。  相似文献   

基于多种边界层方案的天津PM_2.5集合预报试验          下载免费PDF全文

蔡子颖  姚青  韩素芹  郝天依  刘敬乐 《应用气象学报》2017,28(5):611-620

基于大气化学模式WRF/Chem采用4种边界层方案（YSU,BL,MYJ和MYN3）模拟2015年全年天津地区细颗粒物质量浓度演变趋势,分析不同边界层方案对天津地区PM_2.5质量浓度模拟和预报的影响,并构建多种边界层方案的集合预报产品,以期提高天津地区PM_2.5质量浓度预报效果。结果表明:大气化学模式的4种边界层方案在空气质量模拟中均有较好的适用性,PM_2.5模拟值与观测值相关系数达到0.76左右,晴空和大风天气BL方案表现较优,阴天和小风天气YSU和MYJ方案表现优于其他两种方案,综合所有过程没有任何单一方案具有显著优势。基于上述原因,该文开展多种边界层方案的天津空气质量集合预报试验,经过对2015年全年模拟值分析,多边界层方案和多气溶胶机制扰动的集合预报可以减小PM_2.5质量浓度预报的相对误差和均方根误差,降低重污染天气预报的漏报率,提升空气质量等级预报能力,在计算资源得到保证的基础上,是一种可以提升数值模式PM_2.5质量浓度预报能力的有效手段。  相似文献   

Forced vibration analysis of an offshore tower carrying an eccentric tip mass with rotary inertia due to support excitation     

Jong-Shyong Wu  Chin-Tzu Chen 《Ocean Engineering》2007,34(8-9):1235-1244

Dynamic responses of structures due to earthquake excitation are the important problems in engineering, thus, the information concerned is plenty. However, most of the literature is relating to the discrete methods, particularly to the finite element method (FEM), and the one relating to the method combining both the “continuous” and “discrete” models is rare. The objective of this paper is to provide some information in this respect. First, the analytical solution for the natural frequencies and normal mode shapes of a “continuous” tower, without contacting water (or “dry” tower), carrying an eccentric tip mass possessing rotary inertia is determined. Next, the partial differential equation of motion for the forced vibration of the tower, contacting water (or “wet” tower), subjected to support excitation is transformed into a matrix equation by using the last natural frequencies and normal modes shape of the freely vibrating dry tower. Finally, the numerical integration method is used to solve the matrix equation to yield the seismic response of the wet tower. In theory, the mode superposition method is correct only if the total number of modes considered approaches infinity, however, numerical results of this paper reveal that superposition of only the lowest six modes will yield excellent results to be very close to the corresponding ones obtained from the conventional FEM. For this reason, the CPU time required by the presented approach is less than 5% of that required by the conventional FEM.  相似文献   

对水产资源评估的两种世代分析方法比较     

刘群  曾晓起 《中国海洋大学学报(自然科学版)》1995,(4)

本文采取常用的种群评估方法，应用模拟数据比较研究了两种世代分析方法（ＶＰＡ）（Ｇｕｌｌａｎｄ（１９６５）ＶＰＡ方法和分离ＶＰＡ方法（ＰｏｐｅａｎｄＳｈｅｐｈｅｒｄ１９８２））。指出：在没有应用捕捞努力量调谐最近捕劳死亡率时，分离ＶＰＡ和ＧｕｌｌａｎｄＶＰＡ都不能正确反映实况；当使用调谐方法后，两种方法的结果都有所改善；对三组初始捕捞死亡率，Ｇｕｌｌａｎｄ方法给出相同结果；相反分离ＶＰＡ对不同初始值作出不同答案，但是在初始值接近真值时，分离ＶＰＡ的计算值较Ｇｕｌｌａｎｄ方法为好。  相似文献   

GPU ray casting method for visualizing 3D pipelines in a virtual globe     

Zhaocong Wu  Jie Shao  Guohui Deng 《International Journal of Digital Earth》2019,12(4):428-441

Pipelines are an important part of urban infrastructure development. As part of a virtual globe (VG), the high-efficiency and high-quality visualization of 3D large-scale and high-density urban pipelines is of great importance. This paper proposes a GPU-based pipeline ray casting method for the visualization of urban-scale pipelines in the framework of a VG. The method involves the initial partitioning of the pipeline data into tiles, based on the relationship between the pipeline layer scale and the discrete global grid system (DGGSs). The pipeline centerline in each tile is then segmented and encoded, and a coarser pipeline bounding volume is subsequently constructed using a geometry shader. Finally, the fine 3D pipeline is rendered using a pixel shader. The results of the experimental implementation of the proposed method show that it satisfies the requirements for the multiscale visualization of pipelines in a VG. Moreover, compared with the traditional polygon-based method, the method facilitates a 20% increase in rendering frame rate for the same pixel level accuracy display effect. It also enables the visualization of the thickness of the 3D pipeline without any obvious effect on the rendering efficiency.  相似文献   

开放段长城敌台接闪器的设置     

宋平健  李京校  李如箭  逯曦  钱慕晖 《气象科技》2015,43(4):754-758

在开放段长城的敌台上设置接闪器,既要考虑其型式和保护范围,还应充分考虑到设置接闪器对敌台墙体的扰动及对长城整体风貌的影响。本文提出了对长城敌台的直击雷保护,宜采用接闪杆和接闪带的组合型式作接闪器。在执行对长城最小干预的文物保护原则基础上,根据长城的防雷类别,运用滚球法保护原理,针对可登临敌台游人的保护,提出了接闪杆应设置在敌台垛墙4个外角处、高度宜控制在45 m以下,指出采用接闪杆保护游人仍存在一定的局限性;明确了设置在不可登临敌台上接闪杆的高度不宜超过1 m。探讨了减少接闪杆数量的可能性,结论为：当接闪杆少于4支时其高度将显著增加,对长城本体的扰动及风貌影响明显,不宜采用。提出了对游人可能接触到的接闪杆金属部位应采取防接触电压的保护措施。  相似文献   

基于三维的地质灾害遥感解译标志管理系统设计与实现   总被引：1，自引：0，他引：1  

乌云其其格  马维峰  张时忠  唐湘丹  刘文婷 《国土资源遥感》2012,(2):148-151

总结了滑坡、泥石流地质灾害解译标志的内容和特点,建立了解译标志的数据模型和数据库,并对地质灾害的解译标志信息进行编码,研制了基于Virtual Globe三维环境的地质灾害解译标志管理系统.该系统对有效存储管理地质灾害解译标志,提高地质灾害遥感解译的工作效率具有重要价值.  相似文献