河流水质模型的逼近方法及误差分析

提出一种平稳河流水质模型简化方法，通过分析存在弥散和忽略弥散作用两种情况下的Streeter-Phelps模型的解,给出了忽略弥散作用的条件和最大误差分析，进而给出多河段模型的一般表达式，数值计算和实际验证结果表明，该方法可给出工程满意的结果。     

基于多核处理器的星空背景弥散效果实现算法

针对空间探测系统仿真中生成星空背景图像不能及时响应的弊端,提出一种利用多核加速生成星空背景图像的算法.阐述星空背景图像产生弥散效果的原理,在二维高斯模型的中心衰减函数基础之上对星空背景弥散效果进行建模仿真,并给出了一种基于多核处理器的并行实现方法.通过对不同恒星数目的星空背景进行仿真,分析了基于多核的并行算法相对于基于单核的串行算法的加速比,得出基于多核处理器的星空背景弥散效果实现算法基本能满足实时性要求.     

视觉属性学习应用研究

视觉属性能够展现人们识别事物时所定义的语义概念,但现有的视觉识别工作往往忽略了属性在分类器设计中能作为中间媒介层的作用.本文给出一种将属性和事物类别同时用于构建分类器的方法.分析了传统多类分类器、直接类别相关模型、间接属性预测模型、直接属性预测模型的特点.在动物和室外场景数据集上的实验证明,利用属性进行分类器学习对于提高传统多目标分类和迁移学习的性能都具有很好的帮助.     

河流水质模型求解的Chebyshev 正交多项式方法

提出一种考虑弥散时Streeter—Phelps一维稳态河流水质模型Chebyshev正交多项式的近似解法．通过对稳态河流水质模型的非线性高阶微分方程式分析，采用Chebyshev正交多项式对各阶微分和弥散系数D进行近似描述，得到稳态河流水质模型的近似表达式．针对近似模型给出了误差指标，并采用最小二乘对近似式中的未知参数进行估计；同时，对算法的总精度进行了讨论．仿真结果表明，该方法的精度高于多种微分方程数值计算方法(如龙格一库塔)，不仅可以提高生化需氧量的计算精度，而且能够大大提高溶解氧浓度计算结果的准确性．     

基于提升方法的短期负荷预测的研究

目前有很多方法可以实现电力负荷预测,但各种方法都有各自的局限性,如何充分利用各种算法,使负荷预测的精确度提高,组合预测方法便应运而生了.然而当前的组合预测方法过于重视算法,而忽略样本.文中给出了一种基于提升方法的电力负荷预测挖掘算法,该方法通过样本权值进行抽样,训练生成模型,并根据模型效率改变样本权值,再次抽样训练生成模型,如此迭代生成多个模型后进行负荷预测.实际应用结果表明该方法比其它方法具有较高的精度.     

基于稀疏编码的弥散微循环模型参数估计神经网络

弥散磁共振成像（Diffusion magnetic resonance imaging, dMRI）是一种重要的无创检测生物组织微观结构的医学成像工具,其中弥散微循环模型（Intravoxel incoherent motion ,IVIM）是已被广泛用于分离组织水扩散和微血管血流运动的弥散磁共振成像模型。求解弥散微循环模型参数的传统方法依赖于从多b值扩散弥散磁共振成像数据（通常≥10个b值）中拟合双指数模型,这需要一个相对较长的采集时间,对于体部弥散微循环模型成像是一个挑战。深度学习方法可以使用q空间数据的一个子集进行弥散磁共振成像模型参数估计,从而加速弥散磁共振成像的采集。然而,常见的基于卷积神经网络的深度学习与生物物理模型无关,因此,网络输出结果缺乏可解释性。本文将稀疏编码与深度学习相结合,提出了一种基于稀疏编码深度学习网络的弥散微循环模型参数估计方法。它利用了深度网络的表达优势,同时结合稀疏化表达的双指数模型来估计胎盘的弥散微循环模型参数,相比于其他算法,本文所拟的算法实现了更高的参数估计准确率和泛化能力。     

一种混合的文本信息检索模型研究

通过对基于统计的信息检索模型和基于本体的信息检索模型进行分析比较,得知这两种模型在某种程度上互补:基于统计的信息检索模型强调关键字的统计信息,然而忽略了关键字之间的语义信息;基于本体的信息检索模型强调关键字之间的语义信息,然而忽略了关键字的统计信息.结合两种信息检索模型各自的优点提出了一种混合的信息检索模型,实验证明该模型在查全率和查准率方面较基于统计的信息检索模型和基于本体的信息检索模型有了一定的改进.     

基于Pi-演算的扩展有向图工作流模型及验证

为了加强工作流模型对业务流程的描述能力,提出了一种扩展有向图工作流模型及其验证方法.针对基于有向图工作流模型的不足,提出了扩展有向图工作流模型,并给出了该模型的定义和图形符号描述.在用Pi-演算准确描述扩展有向图工作流模型的基础上,给出了用Pi-演算分析和验证扩展有向图工作流模型正确性的方法.最后,结合实验对扩展有向图工作流模型及验证方法进行了仔细分析,实验结果表明了该工作流模型及验证方法的有效性和正确性.     

考虑热电耦合效应的缓冲器插入功耗优化

为了改善芯片的功耗和温度特性,提出了一种缓冲器插入功耗优化方法.该方法基于延时、功耗和温度三者之间的热电耦合效应,给出了相应的延时、功耗和热模型;通过在允许的范围内牺牲部分延时来优化功耗,并在优化过程兼顾温度对延时和功耗的影响以及互连电感效应对延时的影响,利用Matlab软件求得最佳优化结果.采用该方法针对65 nm和45 nm工艺节点的缓冲器插入进行分析和验证的结果表明了其有效性.文中同时指出忽略互连电感效应会低估芯片的优化稳态功耗和温度.     

不完备信息系统中基于集对相似度的粗集模型

讨论了已有粗集扩充模型处理不完备信息的局限,分析了空值相等与确定值相等在概率上的明显差异.依据集对分析理论,提出了集对相似度和相似度容差关系,进而给出一种基于集对相似度的粗集拓展模型.该模型的方法是:通过引入差异度系数体现空值相等与确定值相等之间的差别,利用相似度容差关系及差异度系数确定数据对象的邻域,再利用该邻域得到上下近似集,同时在求上近似时忽略空值的差异性,在求下近似时强调空值的差异性.实验表明,该模型在相同阈值参数的情况下,结果更加合理,精度更高.     

Review of urban storm water models

This paper reviews models for simulating storm water quantity and quality in an urban environment. This has been achieved by examining a number of storm water models in current use. The important features of twelve models, which represent a wide range of capabilities and spatial and temporal resolution have been described. Specific topics covered are: identifying important urban water quality parameters; the classification of modelling approaches; modelling approaches used to estimate water quantity and quality. These include statistical, empirical, hydraulic and hydrological models. Water resources management and planning tools, that are included in some urban storm water models, such as economic analysis, optimisation and risk analysis are also discussed. Features of twelve storm water models have been summarised. These models have been chosen because they demonstrate how components that are important in managing urban storm water have been incorporated in a modelling framework. These models have been categorised in terms of their functionality, accessibility, water quantity and quality components included in the model and their temporal and spatial scale. The information in this paper provides planners and managers with an overview of modelling approaches that have been used to simulate storm water quantity and quality. In particular, it provides managers with an appreciation of the limitations and assumptions made in various modelling approaches. This review will also benefit modellers by providing a comprehensive summary of approaches and capabilities of a number of storm water models in current use. Potential urban storm water research opportunities have also been identified.     

Application of mesh-adaptation for pollutant transport by water flow

An adaptive finite volume method is proposed for the numerical solution of pollutant transport by water flows. The shallow water equations with eddy viscosity, bottom friction forces and wind shear stresses are used for modelling the water flow whereas, a transport-diffusion equation is used for modelling the advection and dispersion of pollutant concentration. The adaptive finite volume method uses simple centred-type discretization for the source terms, can handle complex topography using unstructured grids and satisfies the conservation property. The adaptation criteria are based on monitoring the pollutant concentration in the computational domain during its dispersion process. The emphasis in this paper is on the application of the proposed method for numerical simulation of pollution dispersion in the Strait of Gibraltar. Results are presented using different tidal conditions and wind-induced flow fields in the Strait.     

Application of mesh-adaptation for pollutant transport by water flow

An adaptive finite volume method is proposed for the numerical solution of pollutant transport by water flows. The shallow water equations with eddy viscosity, bottom friction forces and wind shear stresses are used for modelling the water flow whereas, a transport-diffusion equation is used for modelling the advection and dispersion of pollutant concentration. The adaptive finite volume method uses simple centred-type discretization for the source terms, can handle complex topography using unstructured grids and satisfies the conservation property. The adaptation criteria are based on monitoring the pollutant concentration in the computational domain during its dispersion process. The emphasis in this paper is on the application of the proposed method for numerical simulation of pollution dispersion in the Strait of Gibraltar. Results are presented using different tidal conditions and wind-induced flow fields in the Strait.     

The simulation of a continuously deforming lateral boundary in problems involving the shallow water equations

A finite-difference method is given for the treatment of a continuously deforming lateral fluid boundary in computer simulations of systems involving the shallow water equations. The technique is described in the context of a numerical storm surge model for the east coast of India. Using a forcing wind-stress distribution representative of the 1977 Andhra cyclone, a comparison is made between simulations using models both with and without inland intrusion of water along the coast of Andhra Pradesh.     

基于SWMM模型的城市暴雨洪水模拟与分析

为了进行城市暴雨洪水模拟分析,以湖北省恩施市中心城区为研究区域,在河流水系分布和洪水来源分析的基础上,提出洪水分析计算方案,构建一、二维耦合SWMM模型计算典型频率(10,20,50,100年一遇)河道洪水演进和漫堤淹没过程,获得较为准确的洪水淹没范围、水深、淹没历时和洪峰到达时间等信息,并结合GIS进行洪水影响评价。结果表明,清江干流主要河段基本满足20年一遇的防洪标准,清江干流和龙洞河部分河段现状防洪能力较低。SWMM模型是一种成熟的城市雨洪径流模型,适宜于城市暴雨洪水模拟与分析应用。     

Improved storm water management through irrigation rescheduling for city parks

In this work, a modeling and scheduling approach for an integrated storm water management and irrigation problem is presented. The primary objective is to simultaneously ensure that the green space is irrigated appropriately and the level of the storm water pond is maintained adequately. It is proposed to use closed-loop irrigation scheduling to achieve the objective. A steady-state model is developed to calculate the soil water storage for different irrigation amounts. To handle the uncertainty, real-time feedback from the pond is used to re-evaluate the scheduling optimization problem every week. Simulation results show that the proposed closed-loop scheduling gives much improved control performance.     

Effects of submersion depth on wave uplift force acting on Biloxi Bay Bridge decks during Hurricane Katrina

A large portion of the Biloxi Bay Bridge was submerged and destroyed by surface waves and storm surge associated with Hurricane Katrina in 2005. In this paper, the time history of wave forces exerted on the Biloxi Bay Bridge during Hurricane Katrina was investigated by a wave-loading model. The Volume of Fluid (VOF) method was adopted in the model to track the variations of water surface levels. In order to obtain wave parameters and storm-surge elevation at the bridge site during Hurricane Katrina, a storm surge model and a wave propagation model were coupled to hindcast the hydrodynamic conditions. Outputs of the coupled wave-surge models were imported to the wave-loading model to simulate the dynamic wave forces acting on the bridge deck. In order to evaluate the maximum uplift wave force, five different bridge deck elevations submerged at different water depths were investigated. The processes of wave-bridge interaction were simulated by the wave-loading model. The wave profiles, velocity field in the vicinity of the bridge, and dynamic wave forces on the decks were analyzed. Results indicate that the uplift force on the submerged bridge deck span exceeded its own weight under the extreme wave and storm surge conditions during Hurricane Katrina. Moreover, the numerical simulations suggest that the maximum uplift wave force occurred when the storm surge water level reached the top of the bridge deck.     

基于雷达基数据的风暴单体跟踪与预报

多普勒雷达基数据对风暴单体的跟踪及预报具有十分重要的意义.针对雷达监测预报的原理和特点,建设性地提出了一种跟踪和预报方法.根据“体扫间隔,特征相似,近距离优先”三个匹配准则来匹配两时刻的风暴单体,再利用加权最小二乘法对风暴单体在下一时刻的位置进行预报.通过对天津市2005～2011年间74个天气过程的实验和评估,结果表明:该方法的可预报单体数更多,单体平均预报误差更小,能够更好地实现风暴单体的跟踪及预报.     

实用微型涡喷发动机控制系统的设计

介绍了国产某型涡喷发动机控制律的设计过程,从对发动机的数学建模入手,通过系统辨识得出其模型参数,采用差量式PID算法,使用Matlab/Simulink模块进行控制参数的调试,最后将控制律用Keil C编程;并在发动机上进行参数的最终调节;实现了发动机转速的稳定控制;该设计方法对于其他控制对象的PID控制律的设计可供参考;实际应用表明,该系统工作性能稳定、可靠.