基于Petri 网的工程项目多目标协同优化研究

工程项目建设过程需要对项目的进度、质量和成本这三大目标进行集成控制和有效管理。但是,同时实现三大目标的集成控制需要考虑各种约束变量的限制,探讨建立三个目标的相关函数以及进度、质量和成本集成控制机理,并建立多目标协同优化模型,提出工程项目三大目标协同优化的普遍适用性方法。模型结合Petri 网的实时性和动态性,采用粒子群优化算法对模型进行求解,结合实证分析了该模型的可行性和有效性,为工程项目的建设提供决策支持。     

高压燃气管道非稳态流动的特征线法模拟研究

采用特征线法对高压燃气管道非稳态流动的数学模型进行了数值求解,考虑能量方程,对燃气管网非稳态流动进行了理论分析,解决了由于忽略能量方程所带来的计算精度低的问题,编制了用气负荷随时间变化时压力、温度、流量沿管道分布的动态模拟程序,给出了计算实例。模拟数据和实际数据非常接近。     

基于抗风设计的折叠网壳房屋外形优化研究

为改善复杂体型折叠网壳房屋的抗风性能,使其在风荷载作用下具有合理外形,基于计算流体动力学(CFD)的基本理论,运用FLUENT软件进行数值模拟,与风洞试验数据对比验证,探讨与分析轻型折叠网壳房屋的合理数值风洞,包括边界条件、计算域尺寸、网格划分方式、离散格式、求解算法、湍流模型等基本参数和技术的确定。按照《空间网格结构技术规程》(JGJ 7—2010)与野营房屋使用功能要求,以矢跨比、端门倾角、端门高为尺寸参数,设计出28种建筑体型,以0°,30°,45°,60°,90°风向角为分析参数进行140种工况的数值模拟,得出轻型折叠网壳房屋不同体型表面风压分布特性与风荷载体型系数。在此基础上以风压分布最均匀与体型系数标准差最小为优化目标,对轻型折叠网壳房屋进行基于抗风设计的体型优化分析,得到抗风性能良好的合理外形。结果表明,经优化的外形可有效化解房屋表面的不利风压分布,极大提高折叠网壳的抗风性能。     

基于频率最大化目标的六杆四面体网壳截面尺寸优化研究

随着计算机技术的发展,基于有限元优化的拓扑优化算法在工程设计领域得到广泛应用,以提高结构性能和节约材料.在空间结构领域,目前还并未形成系统性的结构优化策略,主要还是依靠工程师的工作经验来进行优化设计.董石麟教授等提出的六杆四面体网壳是一种由相似的四面体模块组成的空间结构,具有重复性和装配性等特点.本文以六杆四面体网壳为分析对象,进行了结构频率最大化的优化设计.根据挑选出的质量参与系数总和超过90%的7阶模态,建立优化函数最大化这7阶模态的频率,以此提高整个结构的动力学性能.优化结果表明,在结构整体减重18.31%的前提下,各阶频率增加了20%到30%,起到了良好的效果.     

关于“钢筋(煤石干石)混凝土网格式加筋土挡土结构强度特性与试验研究”的讨论

自 1968年法国工程师发明了加筋土技术以来 ,加筋土工程因具有多种优势而风靡全世界 ,它被广泛地应用于公路、铁路、港口、市政、民航等大型土木工程。 加筋土是由抗拉强度比较高的加筋材料及填料 (土 )组成 ,加筋材料分为柔性材料和非柔性材料 ,对于柔性筋的加筋土强度 ,一般认为其强度线平行于素土的强度线 ,其粘聚力比素土多一个增量。对于非柔性筋加筋土的强度 ,在文献 [1]中作过介绍 ,在强度表达式的推导过程中 ,其小主应力增量的计算分两步进行 ,第一步假设加筋土相对于不加筋土而言 ,只是粘聚力有提高 ,第二步认为加筋土相对于不加筋土而言 ,只是内摩擦角有提高 ,将两步计算所得小主应力增量取代     

Determination of groundwater sampling frequencies through Bayesian decision theory

Bayesian decision theory is applied to determine an optimum sampling frequency for chlorides in a public water supply well. The well is located approximately one mile downstream of a landfill with an established contaminant plume and has exhibited increasing chloride concentrations. A digital computer program is utilized to solve the optimization problem using Bayes' theorem for continuous probability distributions. The sampling frequency obtained by this method is compared with the frequency used by the authority operating the public water supply well and to the frequencies estimated by other methods that have been recommended for determining sampling frequency. The sampling frequencies obtained using Bayesian decision theory are close to those obtained with other mathematical methods. The results are also similar to the sampling frequency chosen by the operating authority when monitoring the well.     

Additional sampling based on regulation threshold and kriging variance to reduce the probability of false delineation in a contaminated site

Kriging-based delineation when used to determine a cost-effective remediation plan should be based on the spatial distribution of the pollutant. This study proposed an adaptive cluster sampling (ACS) approach based on the regulation threshold and kriging variance for additional sampling to improve the reliability of delineating a heavy-metal contaminated site. A reliability index for reducing the probability of false delineation was used to determine the size and configuration of additional samples. A data set of Ni concentrations in soil was used for illustration. The results showed that the additional sampled observations during ACS were clustered where the Ni concentrations were close to the regulation threshold of 200 mg kg(-1), and were located where the first-phased sampling density was low. Compared with a simple random sampling (SRS), the relative frequency of misclassification over the whole study area (RFMW) using ACS in a 100 replicates simulation was lower when the same sample number of pooled data was used. In addition, the spatial distribution of the local misclassification rate (LMR) showed that the area with a high-valued LMR could be reduced and that the LMR gradients in the region could be lowered by using ACS instead of SRS. The above results suggest that the proposed ACS approach could improve the reliability of kriging-based delineation of heavy-metal contaminated soils.     

市政排水管网规划和优化设计探讨

分析了市政排水管网规划和优化设计的几个核心问题,把整个排水管网布局的优化问题转变为求网络图的最小费用问题,给出了数学模型的建立与求解步聚,并通过具体工程实例进行了说明,指出该文提出的修正逐步生成法能保证;n-Ⅳ步内获得系统最优布局。     

基于PEST的地下水数值模拟参数优化的应用

本文介绍了参数优化工具PEST的工作流程与基本原理,并建立了一个理想地下水流动模型作为实际观测资料对4个参数进行优化。通过分析优化过程与结果:在参数设置为不同初值的情况下,PEST均能获得与真实值非常接近的优化结果,若初值与真实值越接近,优化迭代次数及调用模型次数越少。通过分析优化过程还发现:参数分区所占比例与参数敏感度有一定的相关性,分区面积越大,该参数敏感度越高;观测资料越丰富,优化结果与真实值越接近,反之优化结果误差较大,这对地下水网布设与优化起到一定的指导作用。     

基于抽样地质统计学的矿渣资源评价

长期以来,对于矿渣的研究主要集中在矿渣堆场重金属对环境影响方面,以及矿渣堆中重金属成分富集、迁移以及污染修复等问题上,而关于矿渣堆中的有用组分资源的评价少有研究。本文在甘肃北部某矿床分布的大量金矿矿渣堆中选取了4#、5#和6#3个矿渣堆为调查对象,基于抽样地质统计学方法,研究其中有用组分金的品位分布特征和规律,并探讨其平均品位误差范围应用其定量分级。将4#和5#矿渣堆资源划分为333级别资源,Au平均品位分别为1.37 g/t和1.28 g/t,6#矿渣资源划分为332资源,金平均品位为1.25 g/t。研究表明抽样统计学方法可以为遗留的大量矿渣堆的资源评价提供科学依据,同时也为绿色矿山评价提供了科学支撑。     

大规模优化及其在上限定理有限元中的应用

通过引进变量将原问题变为标准的内点法问题 ,将原问题的可行域仿射为单位球体区域 ,在仿射后的区域内向目标函数减少最快的方向移动 ,寻求问题的最优解 ,最后进行逆变换 ,将得到的解换回到原可行域。     

小浪底西霞院反调节水库施工控制网优化探讨

根据小浪底西霞院反调节水库施工放样的精度,对其施工控制网进行了优化设计,在此基础上合理选择了控制网的布设方案、观测方案,最终建立了满足要求的施工控制网,从而确保水利枢纽工程的正常施工。     

TBM施工方案优选研究

以某长大隧洞工程的出口段为研究对象,建立了隧洞工程TBM法施工模拟模型,对该工程可行的11个TBM法施工方案进行了模拟与优化研究,以提高施工效率,降低施工费用,缩短施工工期,提高施工组织设计方法的科学性。     

基于大涡模拟的火灾数值模拟网格划分优化方法

摘 要：网格划分是火灾数值模拟的重要环节,对模拟结果的精度以及模拟时间有很大影响。针对火灾数值模拟中的网格划分问题,提出了一种基于大涡模拟的网格划分优化方法。根据大涡模拟的原理,给出了滤波尺度的计算方法,并根据滤波尺度和网格比系数对火场中不同区域的网格尺寸进行优化处理。将优化方法应用于高层建筑火灾的数值模拟,运用FDS软件分别针对优化前网格、优化后网格以及精细网格进行数值模拟,对不同网格划分下的温度、氧气和二氧化碳体积分数进行比对。结果表明：网格优化后,模拟结果与精细网格之间相关系数的均值为0.987,保证了模拟精度;同时,模拟运行时间降低为精细网格的16%,有效提升了火灾模拟的计算效率。     

Locating monitoring wells in groundwater systems using embedded optimization and simulation models

In this paper, a new methodology is proposed for optimally locating monitoring wells in groundwater systems in order to identify an unknown pollution source using monitoring data. The methodology is comprised of two different single and multi-objective optimization models, a Monte Carlo analysis, MODFLOW, MT3D groundwater quantity and quality simulation models and a Probabilistic Support Vector Machine (PSVM). The single-objective optimization model, which uses the results of the Monte Carlo analysis and maximizes the reliability of contamination detection, provides the initial location of monitoring wells. The objective functions of the multi-objective optimization model are minimizing the monitoring cost, i.e. the number of monitoring wells, maximizing the reliability of contamination detection and maximizing the probability of detecting an unknown pollution source. The PSVMs are calibrated and verified using the results of the single-objective optimization model and the Monte Carlo analysis. Then, the PSVMs are linked with the multi-objective optimization model, which maximizes both the reliability of contamination detection and probability of detecting an unknown pollution source. To evaluate the efficiency and applicability of the proposed methodology, it is applied to Tehran Refinery in Iran.