Explorations into the formal structure of drainage basins

Every basin of higher than first order is drained by a channel network composed of two subnetworks. Their basins are separated by a drainage divide line, called the basin divider, which is the primary organizing feature of the main basin. Each basin of magnitude n contains n – 1 subnetworks of higher order, and is therefore organized by a set of n – 1 dividers. The dividers and the basin boundary are interconnected in a graph called the divider network of the basin; in graph-theoretic terms this network forms a tree and has the same magnitude and link numbers as the channel network draining the basin. While the subbasins and subnetworks of a drainage basin form a nesting hierarchy, the corresponding dividers do not; indeed, any two dividers share at most one node in common, and whether they do so is independent of whether the corresponding subbasins are nesting or disjoint. However, the dividers of nesting basins are linked by recursive relationships which permit the derivation of a set of algebraic equations; these equations relate the dividers of a basin to other basin components; for example, their combined length is equal to half the length of all first-order basin boundaries minus the length of the main basin boundary. The second part of the paper explores the dependence of the divider length on other basin parameters. The expected length, as predicted by the assumption of topological randomness, is clearly rejected by the data. An alternative approach (regression) is based on the observed magnitudes of the subbasins separated by each divider, and is reasonably successful in estimating divider length. The last section introduces the concept of the standardized basin defined by a boundary length of unity; the estimated lengths of the basin divider and the basin boundary permit an approximate reconstruction of the idealized basin shape and the location of the divider in it.     

从景观生态学构建城市旅游开发与规划的操作模式

本文尝试建立一个关于旅游开发与规划的应用理论模式,以兼顾理论的抽象性和操作性。模式的构建依据地理空间分析方法,同时借用景观生态学斑、廊、基的概念。文中详细论述了该斑廊基网络结构操作模式的基本特点、变换空间分析方法等运行机制,并以不同城市旅游规划、设计实例说明三大操作块的功能和操作意义。     

线性约束严凸可分规划的对偶梯度法

在[1]及[2]中考虑了原目标函数是强凸的情形,本文考虑更一般的情形,即原目标函数是严凸的,给出了其求解的对偶梯度法;对偶问题可分解成n个一维问题,而一维问题的解可直接得到,从而得到原问题的解,并证明了算法的收敛性。     

山西地震带历史地震序列的统计分析

在工程地震工作中需要知道某地震带或某地区未来100年内的地震活动水平,以便适当选择历史地震的统计时段,从而得到和地震活动水平相适应的不同潜在震源区的各级地震的年平均发生率。 本文利用极值理论、最大熵原理、马尔可夫模型的方法、莫尔纳方法和伯努里模型方法计算了山西地震带未来100年内中强震的年平均发生率、平均重现期大于等于某级地震的个数和发震概率,计算结果表明,山西地震带未来百年内将发生≥6.0级地震3次,发震概率为0.94左右;将发生≥6.5级地震1—2次,发震概率为0.84左右;有可能发生≥7.0级地震,发震概率为0.53左右;发生≥7.5级地震的可能性不大,发震概率为0.32左右;发生≥8.0级地震的可能性很小,发震概率为0.15左右。     

一种新的水面蒸发计算方法

本文应用相似理论,提出一个考虑自由对流和强迫对流相结合的水面蒸发模式,并用实测资料对蒸发模式作了检验。