解带线性或非线性约束最优化问题的混合三项记忆梯度投影算法

利用Rosen投影矩阵,结合Solodov投影技巧建立求解带线性或非线性不等式约束优化问题的混合三项记忆梯度Rosen投影算法,并证明了算法的收敛性。数值例子表明该算法是有效的。     

梯度法在欧氏距离选址模型中的应用

介绍了物流设施选址目前的方法和模型,重点讨论欧氏距离选址模型的应用,提出了梯度法的求解方法.将梯度法应用于欧氏距离选址模型,并归纳了模型的求解公式.通过实例分析证明梯度法解决欧氏距离选址模型是有效的.     

凸组合投影算法中的组合因子对算法效率的影响

在求解生产生活中各类实际问题的优化模型的算法研究中,投影梯度算法在解决凸约束最优化问题上一直被学者所重视．本文考虑凸组合投影算法求解凸约束最优化问题,在此凸组合投影算法中,由投影梯度法得到的点与上一步迭代点的凸组合得到新的迭代点．此算法不仅利用投影算法得到的点的信息而且也利用了前一步点的信息．进一步,通过数值实验分析凸组合算法的效率及凸组合因子对算法的影响．数值试验结果表明,这种凸组合算法总体比原来投影梯度法更稳定,而且这种凸组合算法在适当的凸组合因子下较投影梯度法收敛更快．     

一个新的谱共轭梯度法

谱共轭梯度法含有两个方向调控参数,是求解无约束优化问题的一类有效方法.本文给出一对参数公式以构建新的谱共轭梯度法,该方法在精确线搜索下与标准FR方法等价,在Wolfe线搜索下具有类似标准DY方法的内在性质.我们证明了采用Wolfe线搜索的新算法在每一次迭代中均产生下降方向,并且具有全局收敛性.数值实验结果表明,新算法数值稳定、有效,适合于求解大规模无约束优化问题.     

Wolfe线搜索下一个新的全局收敛共轭梯度法

共轭梯度法是求解大规模无约束优化问题的有效方法之一,其研究十分活跃.本文给出了一个新的共轭梯度法公式,新公式在精确线搜索下与DY公式等价.基于新公式,采用Wolfe非精确线搜索确定步长,本文设计了一个新的共轭梯度算法,并证明了新算法的下降性和全局收敛性.数值试验结果表明所设计新算法是有效的.     

求解大规模优化的混合共轭梯度法

为了有效求解大规模无约束优化问题,在PRP方法和FR方法的基础上,给出了满足共轭条件的新的混合共轭梯度法.在强Wolfe线性搜索下,证明了此算法的全局收敛性.在特定条件下,新公式与HS公式一致,因此可看作是对HS方法的修正.对7个经典无约束优化问题的数值实验结果表明,所提出的新方法数值稳定.相比已有方法,随着问题规模的增大,所提方法在迭代次数,优化精度及梯度调用次数方面表现出明显优势.     

预处理共轭梯度法求解线性方程组Ax=b

针对共轭梯度法求解线性方程组Ax=b,提出一种预处理思想。基于次思想,首先给出预处理矩阵,然后求解预处理线性方程组,再使用共轭梯度法求解。最后通过几个数值试验,与直接使用共轭梯度法求解线性方程组相比较,本文的方法提高了收敛速度。     

求解非线性等式约束优化问题的共轭梯度投影算法

利用投影矩阵,对求解无约束规划的共轭梯度算法中的参数βk给一限制条件确定βk的取值范围,以保证得到目标函数的共轭梯度投影下降方向,建立了求解非线性等式约束优化问题的共轭梯度投影算法,并证明了算法的收敛性。数值例子表明算法是有效的。     

一类Armijo搜索下的混合HS-PRP共轭梯度法?

为有效求解大规模无约束优化问题,本文基于HS方法和PRP方法,提出了一类新的混合共轭梯度法。该方法在每步迭代中都不依赖于函数的凸性和搜索条件而自行产生充分下降方向。在精确搜索下,本文算法将还原为标准的PRP方法。在适当的条件下,获证了该法在Armijo搜索下,即使求解非凸函数极小化的问题,算法也具有全局收敛性。同时,数值实验表明本文算法可以有效求解优化测试问题。     

一类新的记忆梯度法及其收敛性

本文着重研究求解无约束优化问题的记忆梯度法,利用当前和前面一步迭代点的信息产生下降方向,采用Armijo线性搜索确定步长,得到了一类新的无约束优化算法。新算法在较弱的条件下具有全局收敛性和线性收敛速率,并且不用计算和存储矩阵,适于求解大规模优化问题。数值试验表明算法是有效的。     

供应链中供应商选择问题的研究

针对熵权和灰色关联投影法的各自特点,将两种方法有机地结合起来,建立了基于熵权的供应商选择灰色关联投影评价模型,最后的实例验证了该方法的有效性和可行性,为供应链管理提供了一种新的供应商选择评价方法.     

Thoughts on a methodology to analyse viability of private-sector participation in new infrastructure projects in developing countries

A model has been developed for investment analysis of all types of infrastructure projects: it addresses some of the key issues for developing countries regarding private-sector participation in infrastructure projects. As an illustration, financial analyses of a bulk water supply project and a water distribution project in Sri Lanka are carried out to estimate subsidy percentages required to make the projects viable. To reap maximum benefits from private-sector participation in water supply, the Government should review its policy on water pricing and institute a reasonable increase in tariffs.     

基于物理机制的随机地震动场中供水管网抗震功能反应分析

城市供水管网是生命线工程的重要组成部分,由于受到工程场地地震动随机性的影响,其系统结构响应和服务功能也应呈现显著的随机性。传统的埋地管线地震反应分析既不能考虑管网拓扑结构的影响,也难以反映随机地震动的作用,同时,管线的结构响应未能落实到系统的功能性评价之上。为了解决上述三个难题,该文在工程场地地震动随机场物理模型的基础之上,通过引入埋地管网地震反应分析模型,结合概率密度演化方法,实现了具有非线性特性的埋地管网的随机地震反应分析;进而,结合管网流体的瞬变流分析理论,实现了城市供水管网的动态抗震功能反应分析,为供水管网的抗震功能可靠度研究奠定了基础。     

发电机螺栓松动故障特征检测方法及试验研究

提出一种通过提取时域指标特征和运用主成分分析法(PCA)诊断螺栓松动故障的方法,将原始数据进行经验模式分解(EMD)后计算相应IMF的5个无量纲因子;利用主成分分析法(PCA)对数据向量进行降维和残基空间投影处理,计算数据样本的预测误差,在智能供水系统试验台架上开展螺栓松动故障诊断试验,试验结果表明,所建立PCA模型能...     

Case investigation in safety and reliability of a family heat supply system

Corrosion investigation and reliability analysis of a family heat supply system has been carried out. Results indicate that the smoke emission steel pipe mainly suffers the corrosion at high temperature, and the corrosion components in the heat supply system undergo the atmospheric corrosion attack in indoor environment. Besides, safety and reliability related corrosion factors include water temperature, water oxygen concentration, pH value, carbon dioxide content, and chloride and sulfate ion in water have been discussed. It is concluded that the make‐up water quality is crucial to the safety and reliability of the heat supply system.     

Radial Distribution of the Position of the Arc in a Plasmatron

The radial-distribution function of the position of the arc in a plasmatron of an axial scheme with gas-vortex stabilization has been determined from the results of standard measurements of the radial pulsations of the projection of the arc. A model allowing explanation of the displacement of the distribution maximum from the axis of the discharge chamber with increase in the current has been proposed. Based on this model, the condition for the discharge-channel radius with which gas-vortex stabilization is efficient has been obtained.     

ASRWM: an arid/semiarid region water management model

Water shortage resulting from both natural conditions and human activities has been proved to be a bottleneck that chokes development in arid and semiarid regions. Systems analysis provides an effective way of clarifying conflicts between water supply and demand. In this study, an arid/semiarid region water management (ASRWM) model is developed for sound planning of a water resources system. The proposed model is founded on interval-fuzzy multiobjective programing (IFMOP) for effectively reflecting complexities of the study system and expediently facilitating solution of the model. Member-ship functions for modeling objectives and constraints are formulated to reflect uncertainties in different system components and their interrelationships. To evaluate the applicability of the proposed model, a case study for the Luopu County in northwestern China has been undertaken. The modeling outputs generated through scenario analyses are based on in-depth examination of several sensitive issues including farming, horticulture, stockbreeding, spring water allocation, pasture expansion, and land exploitation. The obtained results lead to two alternatives that provide an useful basis for formulating desired policies of sustainable development in the region. Through the case study, the proposed model is proved to have reasonable computational requirements and to be applicable to large-scale practical planning problems.     

Performance of an automotive air conditioning system with the variation of state-of-charge of the storage battery

In an automotive air conditioning system (AACS), the evaporator blower and the condenser fan are powered by a DC power supply containing a storage battery. The unique mutual interaction between the battery and the AACS, when the battery is isolated from the external power supply, has been investigated experimentally. As the prime movers draw power, the charge level of the battery falls and in turn the speed of the prime movers drops continuously. This deteriorates the performance of the condenser and the evaporator. Besides, a Matlab/Simulink based model has been developed to study the characteristics of the said electromechanical system during the charging and discharging cycles of the battery. Steady state performance of the system has also been studied at different battery voltage to supplement the dynamic data. The study reveals the typical deterioration of the cooling capacity and the COP of the system during the gradual derating of the supply voltage.     

Issues of water supply and contemporary urban society: the case of Greater Amman, Jordan

Over the last two decades, Jordan has suffered a chronic water crisis, and is the tenth most water-scarce nation on Earth. Such water stress has been well illustrated in the case of Greater Amman, the capital, which has grown dramatically from a population of around 2000 in the 1920s, to 2.17 million today. One of the distinctive characteristics of the water supply regime of Greater Amman is that since 1987 it has been based on a system of rationing, with households receiving water once a week for various durations. Amman is highly polarized socio-economically, and by means of household surveys, both quantitative and qualitative, conducted in high- and low-income divisions of the city, a detailed empirical evaluation of the storage and use of water, the strategies used by households to manage water and overall satisfaction with water supply issues is provided in this paper, looking specifically at issues of social equity. The analysis demonstrates the social and economic costs of water rationing and consequent management to be high, as well as emphasizing that issues of water quality are of central importance to all consumers regardless of their socio-economic status within the city.     

软X射线光刻机对准系统中的图象预处理方法

在图象处理系统中,处理速度是很重要的技术指标。本文介绍了一种采用求和投影法进行的预处理方法,在处理速度方面得到了很大的提高,取得了比较理想的效果．