水资源紧缺对北京市GDP增长造成的不利影响分析

采用水资源模糊定价模型探讨了北京市痧资源紧缺对国内生产总值（GDP）增长带来的不利因素，结果表明：水资源紧缺使北京市GDP增长产生较大的损失，1981－1995年GDP损失量达128．14亿元，平均年损失率为1．72％，并且这种损失还逐年递增。     

抗差LM算法求解遥感影像严格物理模型

Levenberg-Marquardt(LM)算法是一种求解非线性模型的数值算法,已成功地应用于最小二乘曲线拟合和非线性最优化中.LM算法能克服Hessian矩阵病态对解的影响,但是不能抵抗输入样本中粗差的干扰.为消除粗差对求解模型的影响,将等价权思想应用于LM算法中,对LM算法中的样本添加权重,得到抗差LM算法.通过其在Landsat5和SPOT5几何校正模型中应用,验证了该算法具有良好的抗差性,可以解决遥感图像校正模型解算过程中粗差的影响问题.     

关于农村地区支付结算服务环境的调查与思考

在对山西北部地区农村支付服务环境进行全面考察的基础上,对其存在的问题进行了分析研究,并就如何促进农村支付结算业务发展提出了对策和建议。     

税收筹划在企业中的应用

介绍了税收筹划的概念和我国税收筹划的现状,分析了税收筹划产生和发展的原因,阐述了税收筹划在企业中的应用,推出了若干应注意的问题.     

鞍山市2000年第三产业国民生产总值预测

鞍山市第三产业国民生产总值按近10年的趋势发展,到2000年可能达到37亿元;根据近11年相关指标数据,运用逐步回归法,按鞍山市国民经济和社会发展十年规划目标预测,第三产业国民生产总值在本世纪末应达到40.9亿元。     

A differential equation model of North American cinematic box-office dynamics

A new mathematical model is presented for the box-office dynamicsof a motion picture released in North America. Though previouswork on this problem has usually involved probabilistic methods,the new model for describing cumulative box-office gross usesa continuous-time, differential-equation approach. This model,which consists of a system of three nonlinear, coupled, ordinarydifferential equations, incorporates the effects of marketingand advertising expenses, audience reaction, critical reviews,and previous box-office behavior, among other factors. Analyticalasymptotic results are presented for various parameter regimes.In the general case, the model must be solved numerically. Numericalsimulations are tested against actual revenue data from severalrecent movies to analyse the model's accuracy. An algorithmfor practical usage of the model is presented.     

工业供水效益计算中工业效益值的计算方法问题

本文主要论述了工业供水效益计算中工业效益值的合理选定问题,从各方面分析比较了目前计算工业效益值的几种方法.文中认为,各种计算方法的特点和作用不同,用途也不同;在计算工业效益值时,应采用工业净产值的计算方法,这在水利经济理论和实践上是较为合理的、适当的、可行的.     

New results for the Directed Profitable Rural Postman Problem

We study a generalization of the Directed Rural Postman Problem where not all arcs requiring a service have to be visited provided that a penalty cost is paid if a service arc is not crossed. The problem, known as Directed Profitable Rural Postman Problem, looks for a tour visiting the selected set of service arcs while minimizing both traveling and penalty costs. We add different valid inequalities to a known mathematical formulation of the problem and develop a branch-and-cut algorithm that introduces connectivity constraints both in a “lazy” and in a standard way. We also propose a matheuristic followed by an improvement heuristic (final refinement). The matheuristic exploits information provided by a problem relaxation to select promising service arcs used to solve optimally Directed Rural Postman problems. The ex-post refinement tries to improve the solution provided by the matheuristic using a branch-and-cut algorithm. The method gets a quick convergence through the introduction of connectivity cuts that are not guaranteed to be valid inequalities, and thus may exclude integer feasible solutions.     

Team Orienteering Problem with Decreasing Profits

Team Orienteering with Decreasing Profits (DP-TOP) extends the classical Team Orienteering problem (TOP) by considering the profit of each client as a decreasing function of time. It consists of maximizing the sum of collected profit by a fixed number K of vehicles, visiting each client at most once. In this work, we present lower bounds based on a Dantzig-Wolfe decomposition and column generation as well as upper bounds obtained by an evolutionary local search approach (ELS).     

流体力学中的总流伯努利方程

文章从宏观上分析流体的平衡和运动规律,着重阐述流体力学中理想流体和压强的概念以及静止流体内压强的分布规律.文章介绍了流体的定常运动及流线、流量和总流的概念,给出了连续性方程,并在此基础上推导了理想流体定常运动的总流伯努利方程.结合工程实际问题,文章还介绍了实际流体的定常流动的总流伯努利方程.