Bilevel Parallel Genetic Algorithms for Optimization of Large Steel Structures

This article is concerned with optimization of very large steel structures subjected to the actual constraints of the American Institute of Steel Construction ASD and LRFD specifications on high-performance multiprocessor machines using biologically inspired genetic algorithms. First, parallel fuzzy genetic algorithms (GAs) are presented for optimization of steel structures using a distributed memory Message Passing Interface (MPI) with two different schemes: the processor farming scheme and the migration scheme. Next, two bilevel parallel GAs are presented for large-scale structural optimization through judicious combination of shared memory data parallel processing using the OpenMP Application Programming Interface (API) and distributed memory message passing parallel processing using MPI. Speedup results are presented for parallel algorithms.     

Unstructured Mesh Computations on Networks of Workstations

Unstructured mesh technology can be used to create highly efficient scientific and engineering application software. Networks of workstations (NOWs) provide cost-effective platforms for the timely solution of large problems in science and engineering. The performance of unstructured mesh computations on NOWs is investigated in this article. Several parallel unstructured mesh algorithms are shown informally to have computation and communication characteristics similar to those of parallel sparse matrix-by-vector multiplication. These characteristics are discussed, and the requirements they place on an interconnection network are described. Experimental data are given to summarize the communication parameters of four different NOW configurations. Finally, extensive empirical results are given to characterize the performance of unstructured mesh computations on the four NOWs.     

Blocked LU Factorization on a Multiprocessor Computer

Abstract: This paper presents implementations of new methods solving LU factorization used in engineering applications. The implementations are done on the Alliant FX/80 mini supercomputer and use Level 3 Basic Linear Algebra Subprograms. Three ways of expressing the LU factorization in terms of blocked algorithms are considered. The performance of the blocked algorithms, using the parallel vector facilities, are compared with a no block algorithm using only subprograms of level I and 2 BLAS.     

In‐Plane Displacement and Strain Image Analysis

Measurements in civil engineering load tests usually require considerable time and complex procedures. Therefore, measurements are usually constrained by the number of sensors resulting in a restricted monitored area. Image processing analysis is an alternative way that enables the measurement of the complete area of interest with a simple and effective setup. In this article photo sequences taken during load displacement tests were captured by a digital camera and processed with image correlation algorithms. Three different image processing algorithms were used with real images taken from tests using specimens of PVC and Plexiglas. The data obtained from the image processing algorithms were also compared with the data from physical sensors. A complete displacement and strain map were obtained. Results show that the accuracy of the measurements obtained by photogrammetry is equivalent to that from the physical sensors but with much less equipment and fewer setup requirements.     

岩石破裂过程分析系统并行计算方法研究

岩石工程灾害与岩石破裂过程失稳密切相关。大型岩石工程破裂过程数值分析需要高效、准确、强大的计算能力支持。一般传统串行计算方法难以满足要求，大规模并行计算是解决这一难题的有效途径。岩石破裂过程分析系统是研究岩石破裂过程的一个重要数值分析工具。代有限元方法和数值计算方法，在消息传递并行环境下，在岩石破裂过程分析系统串行单机版的基础上，结合现利用区域分解和主从编程模式，采用分布存储稀疏线性迭代并行求解方法，在Linux机群上实现应力分析模块中有限元计算的并行处理。通过Windows和Linux协调处理策略，有效地把原有的前后处理功能和机群系统强大的计算能力结合起来，建立岩石破裂过程分析RFPA^3D．Parallel并行分析系统。算例结果表明，并行程序具有很高的加速比和并行效率，能够快速完成三维条件下300万单元的大规模岩石破裂过程分析。应用RFPA^3D-Parallel并行分析系统模拟地壳介质中广泛存在的龟裂现象，再现非均匀介质破坏和裂纹演化过程，从而显示该系统广泛的应用前景。     

Water Distribution System Computer‐Aided Design by Agent Swarm Optimization

Optimal design of water distribution systems (WDSs), including the sizing of components, quality control, reliability, renewal, and rehabilitation strategies, etc., is a complex problem in water engineering that requires robust methods of optimization. Classical methods of optimization are not well suited for analyzing highly dimensional, multimodal, nonlinear problems, especially given inaccurate, noisy, discrete, and complex data. Agent Swarm Optimization (ASO) is a novel paradigm that exploits swarm intelligence and borrows some ideas from multiagent‐based systems. It is aimed at supporting decision‐making processes by solving multiobjective optimization problems. ASO offers robustness through a framework where various population‐based algorithms coexist. The ASO framework is described and used to solve the optimal design of WDS. The approach allows engineers to work in parallel with the computational algorithms to force the recruitment of new searching elements, thus contributing to the solution process with expert‐based proposals.     

Numerical modelling of flow and transport in rough fractures

Simulation of flow and transport through rough walled rock fractures is investigated using the latticeBoltzmann method （LBM） and random walk （RW）, respectively. The numerical implementation isdeveloped and validated on general purpose graphic processing units （GPGPUs）. Both the LBM and RWmethod are well suited to parallel implementation on GPGPUs because they require only next-neighbourcommunication and thus can reduce expenses. The LBM model is an order of magnitude faster onGPGPUs than published results for LBM simulations run on modern CPUs. The fluid model is verified forparallel plate flow, backward facing step and single fracture flow; and the RWmodel is verified for pointsourcediffusion, Taylor-Aris dispersion and breakthrough behaviour in a single fracture. Both algorithmsplace limitations on the discrete displacement of fluid or particle transport per time step to minimise thenumerical error that must be considered during implementation.
2014 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.     

岩石破裂过程分析系统中的应力并行求解

岩石破裂过程分析和一些相关的岩石工程计算问题迫切需要高效、准确、强大的计算能力的支持，用来解决普通微机已经无法满足的大规模计算需求。在岩石破裂过程分析系统单机版的基础上，结合现代有限元方法，利用超大规模并行计算技术，实现了应力分析模块中有限元计算的并行处理。计算实例表明，并行有限元程序具有很高的加速比，在机群上能够快速完成三维条件下近千万个自由度的应力分析求解，为实现岩石破坏过程分析系统的大规模科学计算提供一定的参考价值。     

基于松弛变量的不等式约束三维电阻率并行反演方法研究

 三维电阻率反演存在多解性问题,且求解耗时较长,制约着电阻率法探测的实际应用。针对该问题,提出在反演方程中施加不等式约束、设计并行算法的解决思路。在传统的常规光滑约束反演基础上,引入松弛变量,将携带有地下介质电阻率变化范围上下限值信息的不等式约束施加到反演方程。利用原始对偶内点法原理,构造新的目标函数,可将模型电阻率值限定在不等式约束范围内并直接在约束规定的可行域内进行寻优,从理论上可压制反演的多解性。同时,设计偏导数矩阵求解并行算法和Cholesky分解并行算法,可使反演速度提高50%以上。综上形成了基于松弛变量的不等式约束三维电阻率并行反演方法,并开展相应的数值反演试验与工程应用验证。结果表明上述反演方法充分利用不等式约束的先验信息,在去除反演成像的假异常、压制反演的多解性、改善反演准确性和计算效率等方面有明显效果。     

一种改进的用于裂缝图像分割的Otsu方法

裂缝是隧道衬砌最常见的病害之一,基于近几年快速发展的工程检测系统与图像处理算法的研究,提出了一种CCD相机的衬砌裂缝快速检测系统采集裂缝图像。在提取裂缝特征之前,需要将裂缝区域与图像背景分离。采用Otsu法进行分割处理,然而传统的Otsu方法对裂缝区域过小的图像易产生欠分割;对背景不单一或光照度不均匀的裂缝图像易造成过分割的情况。根据Ostu方法分割特点对该方法进行改进,以达到更好的裂缝图像分割效果,从而为实现隧道裂缝的快速检测埋下基础。     

地下工程并行优化反演分析及算例验证

 通过重构非线性惯性权重函数和引入“加速因子”,对传统粒子群优化算法的收敛性进行改进。同时基于消息传递平台对算法进行主从式并行改进,编程实现基于普通计算机机群系统分布式存储并行模式的大型地下工程并行优化反演分析。算例分析表明,改进的粒子群优化算法其收敛性能得到显著改善,并行改进策略可显著加快反演速度和提高计算效率。探讨围岩松动损伤劣化、监测数据可靠性、并行粒度和负载均衡等并行优化反演分析中所面临的主要问题及其对计算精度和效率的影响,并提出有效解决方案,为大型地下工程的参数反演和动态优化设计提供一种新思路。     

Parallel-Vector Algorithm for Optimization of Large Steel Structures on a Shared-Memory Machine

An efficient parallel-vector algorithm is presented for optimization of large-space steel structures subjected to realistic code-specified constraints and multiple-loading conditions. The algorithm has been used for minimum-weight design of several high-rise building structures, including an 81-story building structure with 9245 members. It is shown that both parallel processing and vectorization performance improve with the increase in size of the structure. For the largest 81-story structure, speedups of 6.58 and 17.8 are achieved due to parallel processing (using eight processors) and vectorization, respectively. When vectorization is combined with parallel processing, a high speedup of 99.2 is achieved.     

工程测绘系统的研究

工程测绘系统的研究可以概括为外业测量的傻瓜化、内业数据处理的自动化、成果报表的标准化。由工程测量数据采集子系统、工程测量数据处理子系统以及工程测量数据管理子系统三个子系统构成的工程测绘系统是上海市测绘院针对工程测绘领域进行的一次技术革新。本文首先介绍了工程测绘系统的研发背景与研究内容,随后结合三个子系统分步阐述了工程测绘系统所涉及的一系列关键技术,最后对系统特色与应用情况进行了介绍。完善的数据采集子系统,全方位的内业数据处理子系统,基于局域网的数据管理子系统,可以有效摒弃工程测绘外业与内业之间的二次操作带来的质量控制隐患,推进工程测量体系化、标准化生产流程,实现简便、适用、高效的工程测量数据的采集、处理和管理。     

Nonlinear Transient Dynamic Analysis on Parallel Processors

Abstract: Two approaches for parallel implementation of nonlinear transient dynamic analysis algorithms have been presented in this paper. One is based on geometric decomposition, and the other one is processor-farm approach. Both shared memory (Magnum IV) and transputer-based message-passing systems have been chosen for implementation of the proposed parallel algorithms for dynamic analysis. Multithread concepts have been employed on transputer networks to optimize the code by overlapping communications with computations. Numerical studies indicate that explicit transient dynamic analysis can be implemented effectively employing geometric decomposition technique both on shared and message-passing systems.     

Vision‐Based Natural Frequency Identification Using Laser Speckle Imaging and Parallel Computing

This study focuses on the identification of the natural frequencies of structures through the analysis of the speckle pattern that a laser creates and a camera records. The laser pointer spreads its light over a target area on the structure and creates the speckle pattern. The ambient vibrations affect the pattern and a camera records the changes. The stream of images is fed into a graphics processing unit (GPU). The developed parallel code includes different algorithms: the speckle contrast image (SCI), the speckle flow imaging (SFI), and an innovative application of k‐means clustering that uses the geometrical centroid of each cluster as virtual sensors. The tracking of the centroid in time domain through the images creates a vibration signal. The signals from different clusters are processed together to extract the natural frequencies of the structure. This study applies the proposed method to different sample structures both in laboratory and in the field to demonstrate how the obtained signals are reliable and easy to handle. The GPU technology enhances the performance of the entire method and allows the achievement of real‐time processing. All these features create an inexpensive, portable, and efficient tool to inspect any structure or its components.     

工程岩体三维构模中钻孔数据处理方法

钻探、物探等工程地质勘察数据是揭示工程岩体空间状态的原始数据,其大量原始数据的处理是工程岩体三维构模中存在的主要困难之一。从三维构模的角度出发,将工程岩体按几何特征抽象为连续性岩体、断裂岩体、倒转褶皱岩体和侵入岩体4种结构单元类型。由于钻孔数据是描述工程岩体的重要原始数据,且具有多尺度性的特点,以钻孔数据为例,提出原始数据的纵向概化准则、横向概化准则和纵横向协调准则的处理方法,解决工程岩体多尺度显示问题。根据地质学的地质数据解释方法,结合岩层层状分布的特点,提出工程岩体三维构模中急需的钻孔数据处理方法:原始数据纵向概化准则和原始数据层处理概化方法。利用层处理方法对实测钻孔数据进行概化处理,确定工程岩体所对应的结构单元类型,进而建立组合结构工程岩体三维模型,验证了所提出的钻孔数据处理方法的可行性。     

Parallelization of the Evolution Strategy for Discrete Structural Optimization Problems

The parallelization of a modified multimembered evolution strategy for solving structural optimization problems with discrete variables is described. Evolution strategies imitate biologic evolution and combine the concept of artificial survival of the fittest with evolutionary operators to form a robust search mechanism. An important characteristic of evolution strategies that differs from other conventional optimization algorithms is that instead of a single design point, the evolution strategies work simultaneously with a population of design points in the space of variables. This allows for an implementation in a parallel computing environment. In this paper two ways for the parallel implementation of evolution strategies, and their realization in two parallel computing environments are presented.     

遗传算法与网格结构杆件优化下料

遗传算法是一种基于生物学进化原理的全新搜索策略,它已广泛应用于社会科学、计算机科学和工程技术等诸多领域,并取得了一定的成果。将遗传算法应用于网格结构杆件下料优化,经过工程实例分析表明．该方法简单易行,且效果明显。     

注浆加固技术在城镇道路路基处理中的应用

在城镇道路施工中常遇到路基沉降问题,其处理方法也多种多样。具体工程中采用的施工技术必须根据工程的现场实际来确定,本人结合工程实例,就注浆加固处理技术的应用加以阐述,以供有关工程技术人员借鉴。