共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Patrick O'Sullivan 《Geographical analysis》1995,27(2):176-181
An entropy-maximizing model of the geographic deployment of power by states is derived from a minimal set of assumptions about the system's operation. The outcome is a production-constrained gravity model. This is manipulated to yield the general expression for the boundary between the spheres of influence of competing powers. Even in this simplest of forms, the model provides a logically consistent theoretical framework with which to view the outcomes of major geopolitical changes. The elaboration and disaggregation of the model to tackle finer adjustments would not be difficult. 相似文献
11.
Intuition suggests that firms that can apply price discrimination make higher profits than firms that are restricted in their pricing policy. In this paper, we show that, in general, this is not the case. In the framework of a two-dimensional spatial model with elastic demand à la Lösch, we further investigate the interplay of transport costs, competition, and price policy. One of our results is that under realistic specifications of parameters each firm gains a monopolistic area in the center of its market that has the same shape as the entire market, but with a convexly or concavely distorted separating line, depending on the extension of the market. 相似文献
12.
2004年7月,全国党报社长、总编辑研讨会在满洲里召开,会议安排了去俄罗斯赤塔市采访观光。三天的赤塔之行,让人感受最深的是俄罗斯民族对大自然的呵护和亲近。呵护自然由满洲里至赤塔480公里的旅程,可谓是地广人稀。沿途所见的30余个市镇村落,千户以上不过二三,多是百余户、几十户。彼此隔着几十或是十几公里的茫茫荒野林海,大多没有人烟、牛羊、耕地。由于人烟稀少,即便是公路两侧的荒草,也十分茂盛,厚厚的,一层盖着一层,将地面遮掩得严严实实;在林区,路边的原始树木也比比皆是。在拥有丰富自然资源的同时,是俄罗斯人对大自然的倍加珍惜与… 相似文献
13.
In the past decade Tobler has provided an innovative cartographic presentation of migration flows. The central theme of this research has been to utilize detailed migration data to reveal the underlying structures of migration flows. Even though the analyses are not explanatory models of migration exchanges, the application of these techniques to migration flows over time and across different spatial scales provides a visual generalization of often extremely complex flows. The application of his techniques at two spatial scales for the Netherlands illustrates both the strengths and weaknesses of migration force fields for the analysis of migration. 相似文献
14.
我国水田考古始于20世纪90年代初.根据目前出土的史前时期的十多处200多块水田遗迹进行总结,史前水田以小型和不规则形的平底浅坑式田块为主,都具有较为完善的灌溉体系.根据湖南澧县城头山、浙江余姚施岙和余杭茅山遗址发现的水田中的田埂形态分析,我国以方便灌溉为首要目的 的畦田萌芽于距今6000年左右,以生土田埂界隔地下田面为标志;成熟于良渚文化中晚期,以人工田埂规划地面田为标志.畦田是水稻种植过程中的一大发明,之后的水田仍然延续着内部作畦的方法,并对后世北方地区的灌溉农业产生了深远的影响. 相似文献
15.
16.
17.
Robert Haining 《Geographical analysis》1977,9(2):107-129
The problems of model specification in one- and two-dimensional stationary random fields are considered, with particular reference to the class of spatial autoregressions. The role of the autocorrelation function is discussed and it is shown to have a valuable exploratory use, especially in identifying directional bias in random fields. It is recommended that this analysis be supplemented by a likelihood-ratio test, which permits more precise tests of hypotheses about the form of the underlying model. 相似文献
18.
<正>对朋友讲,我要去门源看海,大家笑我是痴人说梦,门源地处青海省,是不折不扣的内陆地区,在这里怎么可能看到浩瀚的、波涛汹涌的海呢?可当我说那里有门源人在50万亩黑土地上,用一望无际的油菜花,编织成青海最大的、恢宏壮观的花海,大家才恍然大悟。我曾两次身入门源,都用不同的故事,装满了自己的行囊。第一次是2008年的7月初,车出西宁不久,本是晴空万里的天气,突然就阴云密布,下起小雨来。一路上,云雾遮山绕谷,雨水中的景致,皆是望不透的绿,咫尺之内,便觉万里之遥。 相似文献
19.
20.
Benjamin W. Fortson IV 《Indo-Iranian Journal》1996,39(1):41-54
An earlier version of this paper was presented at the American Oriental Society's 203rd Meeting (Chapel Hill, April 1993), and I am grateful for comments from the participants there, especially William Malandra. Mark Hale, Stanley Insler, Stephanie Jamison, P. Oktor Skjærvø, and Calvert Watkins all deserve special thanks for contributing much time and advice. The research for this paper was made possible by a grant from the National Science Foundation. 相似文献