本文以一道三重积分的竞赛试题为例,对某些三重积分的计算采用截面法,计算简洁,方法灵活.

本文建立了车道被占用后,车辆排队长度的积分方程模型.在具体求解时,将其转化为一阶初值问题,利用显式的Euler格式迭代计算.根据2013年全国大学生数学建模竞赛A题中提供的道路行驶视频[1],采集相关数据后,进行了实际计算,并对模型进行了稳定性检验.得到了如下结论:在车道被占用后,按照“各行其道”的交通行驶规则将比“见缝插针”行驶减少一半的排队时间.

本文首先根据道路实测视频[1],统计出事故发生后每间隔30sec,通过事故横断面的各种车数量,并按一定折算系数转换为标准车当量数,进而得出每30sec内的平均车流量。基于平均车流量散点数据,采用三次样条插值的方法,描绘了从事故发生到事故车撤离期间,事故所处横断面实际通行能力的变化曲线。同时检验了模型对于各时段内统计到的车辆数的稳定性。

The discrepancy between the finite stock of natural resources and infinite demand of human society development is increasingly drastic with the rapid development of economy. The sustainable exploitation and use of resources has caught attention of theorists. The study on the optimal extraction sequence of resources is an important content of sustainable resource exploitation and use. In this study, we make a brief comment on its study content, theoretical advance, study method based on the study actualities, and also make an analysis and forecast of its future trend.

文章建立了关于社会消费品零售总额的一个多元线性回归模型,运用Eviews软件对江苏省15年来的数据进行了分析,得出影响人们消费行为的主要因素为家庭人均可支配收入的结论,并指出大幅增加农民收入是提高社会整体消费水平的关键所在。

The resources security,especially the security of strategic resources is a hot topic of human society in the 21st century.The entry to WTO make China develop fast in economics,but the contradiction between the finity of resources supply capacity and the infinity demand increasingly stands out.Now resources security is the key to guarantee sustainable economical development for China.In this paper,firstly there is a brief introduction to resources security,then,mainly analyzes the situation of petroleum resources,mineral resources and water resources,and points out the characteristic of China resources security.Finally,based on the situation of natural resources in our country,the strategies to guarantee resources security are put forward.

Within the framework of partial equilibrium, this paper discusses the optimal extraction order of several different deposits of an exhaustible resource and concludes that deposits should be exploited in strictly increasing order of costs to maximize the current return.The paper also analyzes the effect of revenues on the extraction order,pointing out that the government could control the extracting order of the resources through collection of resource tax.