交通系统智能决策的算法研究

遗传算法是近年来迅速发展起来的一种全新的随机搜索与优化算法，但由于其自身固有的缺陷，通常优化过程的收敛速度较慢，局部搜索能力不足，而且算法稳定性较差。而蚁群算法广泛应用在旅行商问题计算中，目前是较好的求解最短路由问题的算法之一。就其自身来说有很多优点，如正反馈性、鲁棒性和智能性，但是在寻优过程中容易陷入局部最佳的缺点。针对上述情况，将遗产算法与蚁群算法相结合，用于实际交通系统寻找最优路径的问题中，并定义了目标函数，以路径可靠性和路径长度为优化目标，寻找最合适的救灾路线。最后通过实际计算结果的对比验证，说明了该方法的有效性。     

三峡茅坪溪沥青混凝土心墙堆石坝位移反演分析与安全预测

本文研究了基于综合应用人工神经网络和演化算法的位移反演分析方法,并将此方法应用于三峡茅坪溪沥青混凝土心墙堆石坝的变形反演分析中。以茅坪溪一期工程原型观测成果为依据,反演出能够正确反映坝体变形特性的邓肯-张EB模型参数,从而预测了施工期末和蓄水期末该坝的变形特性,并基于总应力法研究了心墙水力劈裂破坏发生的可能性,为茅坪溪堆石坝运行期的安全生产提供依据。研究结果表明,茅坪溪心墙堆石坝不会发生水力劈裂破坏,该坝蓄水后虽然水压上升,但心墙仍是安全的。     

考虑火场环境实时作用下的人群疏散仿真研究

在现行的性能化防火设计中,通常将火灾发展与人员疏散两个过程分开考虑,从而忽略了火场环境对人员疏散过程的实时作用。该方法与实际情况有很大差异。笔者借助火灾模拟程序CFAST和人员疏散仿真软件buildingEXODUS,以某地铁车站为例,进行了火场环境实时作用下的人群疏散仿真研究。结果表明,火场环境会降低人群的判断和活动能力,延长疏散时间并产生其他的不利后果。因此,在防火设计中考虑火场环境对人群疏散的实时影响是十分必要的。     

数字隐写技术及发展趋势

笔者通过强调数字隐写算法和隐写分析算法间的矛盾统一,介绍数字隐写算法的发展历程和趋势以及国内外的研究现状。重点介绍具有代表性的空域LSB隐写算法和频域JPEG图像隐写算法。通过基本算法、对基本算法的分析方法、基本算法改进措施的顺序,介绍算法的发展历程,分析算法的性能。对当前实验研究的进展和数字隐写技术存在的问题进行说明,并提出一些建设性意见,对隐写技术的发展前景和方向进行展望,指出数字隐写技术会成为密码术的重要补充,在信息安全传输方面发挥巨大的作用。     

人员位置固定的公共场所分区疏散研究

通过将分区疏散转化为分配问题(Allocation Problem),并采用启发式的A*优化算法,对人员位置固定的公共场所分区疏散进行研究。进一步利用基于元胞自动机模型的大型公共场所人员疏散行为模拟仿真系统,在充分考虑公共场所中每个人员的状态、人员之间以及人员与周围环境的相互作用的前提下,对疏散分区的效果进行模拟;通过与未分区的模拟结果相比较,可以认为,分区疏散有助于人员快速疏散,大大缩短整体避难时间,而且基于移动路径搜索的分区更加切合实际。     

可靠性分配理论在系统安全目标实现中的应用

在系统安全理论中,确定各基本事件的可靠度以实现所给定的系统安全目标值问题一直没有得到很好解决。笔者将可靠性分配理论与故障树分析方法相结合,提出了2个层次可靠度分配法:最小割集之间采取可靠度再分配法,对构成最小割集的各个基本事件之间采取等分配法。从而建立系统中各单元可靠度再分配量化模型。为便于应用,通过实例,详述系统各单元可靠性分配的计算过程。研究表明,运用该模型可准确、简便地计算出各单元的可靠度,使系统在给定的目标值条件下达到系统的安全性优化。     

LEAST COST SOLUTIONS TO THE PROBLEM OF EFFLUENT ABATEMENT IN URBAN SYSTEMS1

ABSTRACT: There is a significant misallocation of resources in the construction and operation of municipal sewage treatment systems in North America. Central to this misallocation is the inadequate evaluation of alternative treatment technologies, alternative distributions of responsibility for waste treatment, and alternative mechanisms for inducing compliance with treatment system requirements. Perverse incentives in the current institutional structure limit the scope of alternatives examined by decisionmakers. Determination of the least cost solution to the problem of urban effluent abatement requires mathematical modeling for the delineation of optimal treatment strategies on a system wide basis. The adoption of modern methods of systems analysis can identify significant opportunities for the reduction of economic waste in the treatment of municipal sewage.     

UNIT HYDROGRAPHS – A COMPARATIVE STUDY1

ABSTRACT. Unit hydrographs derived by using two methods, linear programming and least squares, are compared. Test data comprise rainfall and runoff information from four storms over the North Branch Potomac River near Cumberland, Maryland. The mathematical bases of these methods for unit-hydrograph derivation are explained. The linear programming method minimizes the sum of absolute deviations, and the least squares method minimizes the sum of the squares of deviations. Computer subroutines are readily available for application of these methods. The unit hydrographs derived with the two methods are practically the same for storms 2 and 3, but differ somewhat for storms 1 and 4. However, the reconstituted direct surface runoff hydrographs are similar to those observed with the exception of the hydrograph for storm 4 which had a relatively more non-uniform rainfall excess of a considerably larger duration.     

A CODED ALGORITHM FOR CAPACITY EXPANSION OF A WATER QUALITY MANAGEMENT SYSTEM1

ABSTRACT: This paper describes a mathematical model, an algorithm and a computer program that were specially developed to study the problem of a water quality management system undergoing a rapidly increasing environmental stress. The model output will determine the locations, sizes and the timing of construction of new treatment plants plus an overall treatment plant operating policy so that environmental standards are maintained at a minimum cost. The model, as formulated, is a 0-1 mixed integer programming problem which is solved by decomposing it into a capital budgeting problem (solved by Little's branch and bound algorithm) and an operational policy problem (solved by linear programming). The coded algorithm (in FORTRAN 10) has been tested with a semi-realistic example.     

ESTIMATION OF PRE- AND POST-DEVELOPMENT NONPOINT WATER QUALITY LOADINGS1

ABSTRACT: A simple procedure for estimating pre- and post-development water quality loadings from residential communities is discussed. The procedure deals with: (a) gathering basic water quality loading numbers observed by others at several watersheds with various land uses; (b) obtaining the breakdown of proposed land uses at various phases of the community development; and (c) estimating pre- and post-development water quality loading numbers by taking the weighted average of the basic loading numbers in terms of areal coverages of different land uses at various phases of development. Results of this simplified procedure have been verified indirectly by comparing them with the estimates derived independently through a more fundamental but time-consuming approach. The procedure was used to evaluate the anticipated water quality impact of two future residential communities in South Florida by analyzing four water quality parameters: Suspended Soils (SS), Total Nitrogen (TN), Total Phosphorus (TP), and Biochemical Oxygen Demand (BOD₅). Although computation of loading numbers with mixed land uses is not an exact science at the present time, the recommended approach appears to be the best available technique to analyze quantitatively the water quality-quantity-land use interactions.