共查询到20条相似文献，搜索用时 281 毫秒
1.
投影仿真是CT仿真研究的基础。本文基于二分法原理,研究了一种CT投影快速仿真方法,并对仿真过程进行了优化。针对由凸物体组成的待扫描体,可实现任意轨迹的扫描,投影仿真精度可无限逼近于解析投影精度。数值仿真实验验证了本文方法的有效性。 相似文献
2.
Billie F. SpencerJr Chia-Ming Chang Thomas M. Frankie Daniel A. Kuchma Pedro F. Silva Adel E. Abdelnaby 《地震工程与工程振动(英文版)》2014,13(1):63-77
Hybrid simulation has been shown to be a cost-effective approach for assessing the seismic performance of structures. In hybrid simulation, critical parts of a structure are physically tested, while the remaining portions of the system are concurrently simulated computationally, typically using a finite element model. This combination is realized through a numerical time-integration scheme, which allows for investigation of full system-level responses of a structure in a cost-effective manner. However, conducting hybrid simulation of complex structures within large-scale testing facilities presents significant challenges. For example, the chosen modeling scheme may create numerical inaccuracies or even result in unstable simulations; the displacement and force capacity of the experimental system can be exceeded; and a hybrid test may be terminated due to poor communication between modules (e.g., loading controllers, data acquisition systems, simulation coordinator). These problems can cause the simulation to stop suddenly, and in some cases can even result in damage to the experimental specimens; the end result can be failure of the entire experiment. This study proposes a phased approach to hybrid simulation that can validate all of the hybrid simulation components and ensure the integrity large-scale hybrid simulation. In this approach, a series of hybrid simulations employing numerical components and small-scale experimental components are examined to establish this preparedness for the large-scale experiment. This validation program is incorporated into an existing, mature hybrid simulation framework, which is currently utilized in the Multi-Axial Full-Scale Sub-Structuring Testing and Simulation (MUST-SIM) facility of the George E. Brown Network for Earthquake Engineering Simulation (NEES) equipment site at the University of Illinois at Urbana-Champaign. A hybrid simulation of a four-span curved bridge is presented as an example, in which three piers are experimentally controlled in a total of 18 degrees of freedom (DOFs). This simulation illustrates the effectiveness of the phased approach presented in this paper. 相似文献
3.
本文简要介绍基于飞行时间（TOF）技术的正电子发射断层扫描成像（PET）的基本原理以及用于TOF-PET探测器模拟常用的Geant4,GATE,DETECT2000等模拟工具包,回顾近年来相关研究,对基于Monte Carlo方法的各种TOF-PET模拟,对影响LSO/LYSO晶体TOF-PET时间分辨的各项因素的模拟进行综述,并对未来TOF-PET模拟发展提出展望。 相似文献
4.
5.
无单元Galerkin法采用滑动最小二乘法拟合场函数,只需节点无需单元,具有前处理简单、精度高、解高次连续等优点,被用于求解探地雷达(GPR)正问题.本文从Maxwell方程出发,推导了GPR正演需满足的波动方程;详细介绍了滑动最小二乘法形函数的构造方法.针对EFGM不满足插值条件导致强加边界条件的处理变复杂的特性,采用罚因子法对强加边界条件进行了处理;同时为了消除EFGM进行GPR正演模拟时来自截断边界处的超强反射,采用透射边界条件把GPR波在截断边界处的反射波透射出去,进而压制了来自截断边界处的反射波.然后,编制了EFGM的GPR正演模拟Matlab程序,应用该程序对典型GPR地电模型进行了正演模拟,并把该正演剖面图与基于线性插值FEM正演剖面图进行了对比,结果表明了EFGM用于GPR正演计算的正确性及有效性,并且在相同节点数条件下,EFGM比矩形剖分的FEM的精度要高,更有利于指导雷达剖面的数据解译. 相似文献
6.
Billie F.Spencer Jr. Chia-Ming Chang Thomas M.Frankie Daniel A.Kuchma Pedro F.Silva Adel E.Abdelnaby 《地震工程与工程振动(英文版)》2014,(Z1)
Hybrid simulation has been shown to be a cost-effective approach for assessing the seismic performance of structures. In hybrid simulation,critical parts of a structure are physically tested,while the remaining portions of the system are concurrently simulated computationally,typically using a finite element model. This combination is realized through a numerical time-integration scheme,which allows for investigation of full system-level responses of a structure in a cost-effective manner. However,conducting hybrid simulation of complex structures within large-scale testing facilities presents significant challenges. For example,the chosen modeling scheme may create numerical inaccuracies or even result in unstable simulations; the displacement and force capacity of the experimental system can be exceeded; and a hybrid test may be terminated due to poor communication between modules(e.g.,loading controllers,data acquisition systems,simulation coordinator). These problems can cause the simulation to stop suddenly,and in some cases can even result in damage to the experimental specimens; the end result can be failure of the entire experiment. This study proposes a phased approach to hybrid simulation that can validate all of the hybrid simulation components and ensure the integrity largescale hybrid simulation. In this approach,a series of hybrid simulations employing numerical components and small-scale experimental components are examined to establish this preparedness for the large-scale experiment. This validation program is incorporated into an existing,mature hybrid simulation framework,which is currently utilized in the Multi-Axial Full-Scale Sub-Structuring Testing and Simulation(MUST-SIM) facility of the George E. Brown Network for Earthquake Engineering Simulation(NEES) equipment site at the University of Illinois at Urbana-Champaign. A hybrid simulation of a four-span curved bridge is presented as an example,in which three piers are experimentally controlled in a total of 18 degrees of freedom(DOFs). This simulation illustrates the effectiveness of the phased approach presented in this paper. 相似文献
7.
磁线圈对地磁场的物理模拟及对地磁导航研究的意义 总被引：1，自引：0，他引：1
利用磁线圈对地球基本磁场开展动态模拟,将地磁场随空间的变化转化为在实验室中随时间的变化,能够为地磁导航系统的匹配试验提供物理仿真的地磁场环境。本项研究依照虚拟仪器技术思路,对磁线圈、恒流电源、磁通门磁力仪(或Overhauser磁力仪)和工控机进行数字化连接,并采用LabVIEW编程进行驱动控制,通过自动调节线圈绕组中的电流大小来实现对磁场的物理模拟并进行实时监测,尝试组建了地磁场动态模拟系统,并分别开展了对地磁场总强度和三分量信号的动态模拟实验。模拟系统可以实现天然地磁场和人工编制两种动态信号的输出模拟,且拟合效果良好。地磁场动态模拟系统的初步建立为今后地磁匹配试验等研究提供了仿真磁场环境。 相似文献
8.
波动方程有限差分法是一种使用广泛的地震波数值模拟方法.但是有限差分法本身固有存在着数值频散问题,会降低地震波场模拟的精度与分辨率.为了克服常规有限差分算子的数值频散,本文针对VTI介质地震波数值模拟问题,构造了频率-空间域qP波波动方程高精度有限差分优化算子,根据最优化理论中高斯-牛顿法确定了高精度有限差分算子的优化系数.利用常规差分算子和高精度优化差分算子对归一化相速度的频散关系精度进行了对比分析,并对均匀各向同性介质和均匀VTI介质中的qP波地震波场进行了有限差分数值模拟,通过频散关系精度分析和波场数值模拟结果表明：有限差分优化算子具有较高的波场数值模拟精度,有效压制了传统有限差分算子数值模拟中的数值频散现象,提高了有限差分算子精度,为VTI介质频率-空间域qP波正演模拟奠定了基础. 相似文献
9.
Supported by the recent advancement of experimental test methods, numerical simulation, and high‐speed communication networks, it is possible to distribute geographically the testing of structural systems using hybrid experimental–computational simulation. One of the barriers for this advanced testing is the lack of flexible software for hybrid simulation using heterogeneous experimental equipment. To address this need, an object‐oriented software framework is designed, developed, implemented, and demonstrated for distributed experimental–computational simulation of structural systems. The software computes the imposed displacements for a range of test methods and co‐ordinates the control of local and distributed configurations of experimental equipment. The object‐oriented design of the software promotes the sharing of modules for experimental equipment, test set‐ups, simulation models, and test methods. The communication model for distributed hybrid testing is similar to that used for parallel computing to solve structural simulation problems. As a demonstration, a distributed pseudodynamic test was conducted using a client–server approach, in which the server program controlled the test equipment in Japan and the client program performed the computational simulation in the United States. The distributed hybrid simulation showed that the software framework is flexible and reliable. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
10.
The paper proposes a high-level conceptual and technological approach to manage the ensemble-based simulation, taking into account changing states of both simulated system and system of models. The approach includes systematization of ensemble-based modeling and simulation techniques, analysis of simulation results, quality assessments, and detailed analysis of ensemble management procedures using classification operators. The technological basis for such an approach includes ensemble-based simulation techniques using domain-specific software combined within a composite application; data science approaches for analysis of available datasets (simulation data, observations, situation assessments, etc.). Within this work, a set of case studies is addressed to examine the opportunities provided by the developed approach considering ensemble-based simulation of storm surges for flood prediction in St. Petersburg, Russia as an example. 相似文献
11.
应用小波伽略金方法,对Maxwell方程进行离散化,导出了DB2-MRTD算法的探地雷达3D差分公式、数值稳定性条件.在此基础上,开发了探地雷达MRTD(multi-resolution time domain)法正演模拟程序,该程序极大地提高了运算速度,改善了三维探地雷达正演方法,并利用该自制程序,对三角形金属体模型进行了正演模拟,得到了其相应的正演合成三维剖视图及切片图,通过对这些模拟结果进行分析,可以加深对三维雷达反射特征的认识,提高探地雷达探测的可靠性、准确度,同时也说明时域多分辨率法在探地雷达三维正演模拟中的有效性. 相似文献
12.
当前的地震模拟系统存在用户指令传达不及时、系统反馈不准确的问题,针对这些问题,提出一种改进的地震模拟系统人机交互设计方法,构建地震模拟系统的整体交互流程。通过设计4×4按键电路、LCD接口电路,完成键盘与显示器之间的数据传输、用户指令的传递;同时引入虚拟现实技术设计人机交互的脚本、代码。实验结果表明,所设计的地震模拟系统人机交互模式的稳定性高达98.9%,准确率高达99.6%,能够有效实现地震模拟的人机交互。 相似文献
13.
为了使地震波正演数值模拟系统适合于不同尺度情况下的数值计算,提出了不同尺度数值模拟均需满足的4个共性条件和2个调节机理(即稳定和频散调节机理).认为空间尺度的变化与主频成反比,与时间步长成正比,在保证数值计算过程稳定和较高数值模拟前提下,根据尺度调节机理可以合理地选择波场模拟参数,实现不同尺度快速稳定、高精度的波场正演... 相似文献
14.
Masayoshi Nakashima 《地震工程与结构动力学》2020,49(10):949-962
This historical note reports on the early days of the development of an experimental method called “hybrid simulation.” As background, the seeds of this concept, initiated in the early 1970s by Japanese researchers, are presented first, followed by initial efforts (regarded as Stage I) to realize the concept of hybrid simulation and its first applications to explore the seismic performance of structures. The initial research in this now-seminal field of earthquake engineering began in the early 1970s by Koichi Takanashi and his coworkers at the Institute of Industrial Science, the University of Tokyo. Their highly notable efforts in laying the groundwork for hybrid simulation occurred in the mid-1970s through the early 1980s by Takanashi (for steel structures) and Tsuneo Okada (for RC structures). These two men and their coworkers first applied hybrid simulation to explore the seismic behavior, performance, and design of various types of building structures. In Stage I, this method was called “the on-line computer-controlled test” or “pseudo dynamic test” because the unique feature of the method was the combined test and simulation and the intentional slow loading in the test. Extension of the scope and application of hybrid simulation occurred largely between the early 1980s and the early 1990s (regarded as Stage II) in conjunction with the United States–Japan joint research project. A few notable efforts made around that period are touched upon briefly, including error propagation and suppression in multi-degree-of-freedom hybrid simulation, application of the substructure methodology to hybrid simulation, and real-time hybrid simulation. 相似文献
15.
多次透射公式（MTF）物理概念简单,便于在计算机上实现时空解藕的高精度波动数值模拟。然而,MTF与其它局部人工边界条件类似,存在数值模拟失稳问题,如高频振荡便是可能出现的失稳现象。本文在分析MTF高频振荡失稳机理的基础上,提出了在波动有限元数值模拟中消除MTF高频振荡失稳的一种措施,即在整个有限元数值模拟区内施加与应变速率成正比的较小粘性阻尼;同时,讨论了这一稳定措施的有效性及其对数值计算精度的影响,并通过数值试验检验了这一稳定措施的可行性。结果表明,消除高频振荡失稳的措施行之有效,且只对波动有限元数值模拟中无意义的高频分量具有抑制作用,而对有意义的较低频段内的波动有限元数值模拟精度影响较小。 相似文献
16.
数字合成X射线体层成像技术能利用有限角度下的投影数据重建物体任意断层的图像.在数宁合成X射线体层成像重建算法研究中,模拟投影数据是重要的步骤,本文提出了一种基于GPU光线投射算法的数字合成X射线体层成像投影数据模拟方法.比较传统CPU模拟手段,GPU模拟方法计算速率快,且基于硬件支持的三线性插值能够得到更加接近实际的投... 相似文献
17.
脉动风场模拟技术的研究与进展 总被引：5，自引：0，他引：5
通过对脉动风场模拟技术近20年来国内外研究成果的总结,阐述了脉动风场模拟研究的发展历程。首先简要介绍了近地风场的特性和脉动风场模拟技术的研究现状,然后从脉动风场模拟技术的研究方法出发,分别介绍了谐波合成法、线性滤波法和小波方法在风场模拟技术中的研究发展现状和所面临的问题,最后对风场模拟技术的未来趋势进行了展望。 相似文献
18.
—The Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) is used to investigate the mutual response of a tropical squall line and the ocean. Simulated squall line compares well with the observations, and consists of counterrotating vortices, and has a bow shape bulge toward the leading edge. In addition to these features, which are also shown in the previous numerical simulations, the unique results from the coupled simulation indicate that the air–sea interaction processes within the squall line are important. They affect both the atmosphere and the ocean locally. Simulated upper ocean displays significant response to the squall line with upwelling and baroclinicity. Depth of the ocean mixed layer in the coupled simulation becomes modified due to feedback processes. Ocean temperature acts as a destabilizing factor, and the salinity as a stabilizing factor. Surface turbulent fluxes from the coupled simulation are about 10% less than that of the uncoupled simulation. The SST in the coupled simulation decreases by about 0.21°C. Predicted squall line in the coupled simulation is weaker as compared to the uncoupled simulation. This is reflected in terms of differences in surface fluxes, cloud water, rain water and vertical velocities between the two simulations. 相似文献
19.
20.
-- We have simulated a rupture transition from quasi-static growth to dynamic propagation using the boundary integral equation method. In order to make a physically reasonable model of earthquake cycle, we have to evaluate the dynamic rupture propagation in the context of quasi-static simulation. We used a snapshot of the stress distribution just before the earthquake in the quasi-static simulation. The resultant stress will be fed back to the quasi-static simulation. Since the quasi-static simulation used the slip-and time-dependent constitutive relation, the friction law itself evolves with time. Thus, we used the slip-weakening constitutive relation for dynamic rupture propagation consistent with that used for the quasi-static simulation. We modeled a San Andreas type strike-slip fault, in which two different size asperities existed. 相似文献