辽东山区人口地域分布研究     

高明辛 《山地学报》1993,(3)

本文在分析了辽东山区土地资源特征和人口特征的基础上,从三个角度讨论了辽东山区的人口垂直分布特征,同时还详细分析了人口布局不合理对山区生态环境和经济的影响。并指出,适度移民、并村并点、整合山村及建设农村小集镇是调整山区人口布局,促进山区经济发展和生态环境恢复的有效途径。  相似文献   

四川紫色水稻土氧化铁的分异     

徐建忠 《山地学报》1993,(4)

以岷江冲积物、黄壤残积物发育成的水稻土为对照,研究了紫色砂岩泥岩母质发育成的紫色水稻土氧化铁的形态及其含量和转化。揭示了紫色水稻土具有无定形铁含量,铁活化度较高,氧化铁的转化作用较弱等独特的发生特性。  相似文献   

普里兹湾及其邻近海域晶磷虾的生态特点研究          下载免费PDF全文

仲学锋  王荣 《极地研究》1993,5(4):32-39

198 9/1 990年和 1 990 /1 991年南极夏季在普里兹湾及其邻近海域进行了拖网调查 ,对这一海域晶磷虾 (Euphausia crystallorophias)幼体和成体的数量分布、发育特点、成体的体长 -频数分布以及体长与体重的关系等进行了研究。晶磷虾的近岸性分布特点非常明显 ,幼体和成体均分布在 1 0 0 0米等深线以浅的水域。在陆架区晶磷虾是优势种 ,其幼体和成体的数量远远高于其他种类的磷虾。幼体密度在 70 - 44 3 6 5个 /1 0 0 0米 3之间 ,平均为 942 8个 /1 0 0 0米 3 ;成体及未成体密度在 1 0 - 2 0 3个 /1 0 0 0米 3 之间 ,平均为 5 7个 /1 0 0 0米 3 。1 990年 1月份幼体发育期组成为 N1 - C3 ,其中C1占优势 ,平均发育期指数在 4.1 2 - 5 .0 7之间 ;2 - 3月份发育期组成为 C1 - F3 ,F1 ,F2占优势 ,平均发育期指数在 6 .98- 7.81之间。1 991年 1月份幼体发育期组成为 N1 - C2 ,平均发育期指数为 2 .71 - 3 .6 3 ,MN占优势。未成体体长在 1 7毫米以下。成体体长在 1 7- 3 7毫米之间 ,主要分布在 2 2 - 3 1毫米体长段。大于 2 8- 3 0毫米的体长段里雌性成体的比例大于雄性成体。雌性成体的体重与体长的关系为 :Log W(毫克 ) =3 .0 1 L og L(毫米 ) - 2 .1 4,(n=2 83 ,r=0 .83 ) ;雄性成体的体重与体长的关系为 :L  相似文献   

Distribution coefficients of210Pb and210Po in laboratory and natural aquatic systems     

K. Wang  R. J. Cornett 《Journal of Paleolimnology》1993,9(2):179-188

We have measured the distribution coefficient (Kd) of²¹⁰Po and²¹⁰Pb in laboratory systems and in natural freshwater systems. In the laboratory systems, an inverse relationship was observed between the particle concentration of sand or lake sediment, and the distribution coefficients of²¹⁰Po and²¹⁰Pb. The slope of the log-linearK _d vs particle concentration relation is consistent with existingK _d-particle concentration theories. These laboratory observations are consistent with similar measurements in two lakes. TheK _d values of Po and Pb for the bottom sediment-pore water system with a high particle concentration were 10 to 100 times lower than those for dilute concentrations of particles suspended in the lake water. TheK _d of²¹⁰Pb in the sediments was >10⁴ so that the diffusive transport of²¹⁰Pb has only a small influence on the interpretation of²¹⁰Pb concentration-depth profiles and the²¹⁰Pb dating of these sediments.This is the second of a series of papers to be published by this journal following the 20^th anniversary of the first application of²¹⁰Pb dating of lake sediments. Dr P. G. Appleby is guest editing.  相似文献   

Sectoral Composition and Spatial Distribution of Department of Defense Services Procurement*     

Jeff R. Crump 《The Professional geographer》1993,45(3):286-296

The purpose of this research is to analyze the composition and distribution of Department of Defense (DOD) services procurement. The results indicate producer services comprise 53% of DOD services outlays. Defense expenditures for services are particularly important in the Washington, D.C., region and in states that either produce weapons or house defense-related R&D facilities. Defense expenditures are providing impetus to service sector growth in Virginia and, simultaneously, are providing the initial stimulus for development of producer services in states such as New Mexico.  相似文献   

Mapping and geochemical characterization of the Toarcian organic matter in the Mediterranean Tethys and Middle East     

Franois Baudin  Jean-Paul Herbin  Mireille Vandenbroucke 《Organic Geochemistry》1990,16(4-6)

Organic matter from Toarcian outcrops and boreholes in several basins around the Mediterranean Sea and Middle East has been studied. Rock-Eval pyrolysis, elemental analyses of kerogens and gas chromatography of chloroform extracts within these different basins have been used to determine the amount, petroleum potential and type of the organic matter. The results have been used to compile a mapping of the organic matter for the Toarcian stage, which shows heterogeneities in the distribution and type of organic matter:

1. (1) Marine organic matter (type II) occurs in different environments of deposition. Whereas high contents (>5% total organic carbon) correspond to thick deposits within the West European realm (Great Britain, North Sea, Paris Basin and Germany), the organic matter is less abundant in the Mediterranean area where lower concentrations (1–2% TOC), preserved in Lower Toarcian thin levels, are limited only to restricted basins (northern Italy, Greece).

2. (2) The predominance of continental organic matter (type III) along the northern margin of the Tethys corresponds to a deltaic environment.

3. (3) There is a predominance of altered organic matter within the carbonated platforms around the Mediterranean Tethys.

These results, supplemented with the data issuing from the literature, add a geochemical dimension to the paleogeography of the Tethys.  相似文献   

有限元法在中国南海及邻域区域稳定性研究中的应用   总被引：2，自引：1，他引：2  

詹文欢  丘学林 《大地构造与成矿学》1990,14(2):165-170

本文运用有限元法对南海及邻域现代构造应力场进行了初步的计算,结果表明:应力差(△a)的数值呈现有规律的分布,根据△a值的大小可以把本区划分为四个活动区:它们分别是烈活动区(△a>500bar)、强活动区(250bar<△a<500bar)、中活动区(12Sbar<△a<250bar)、弱活动区(△a<125bar)。其中南海北部及华南沿海地区属中活动区,这种环境对工程建设较为有利。  相似文献   

Assessment of reliability in water distribution networks using entropy based measures   总被引：2，自引：0，他引：2  

K. Awumah  I. Goulter  S. K. Bhatt 《Stochastic Environmental Research and Risk Assessment (SERRA)》1990,4(4):309-320

Entropy based expressions for measurement of reliability and redundancy have recently been reported. These measures approach assessment of the reliability of the distribution network from the intrinsic redundancy of the network layout. The paper extends earlier work on entropy functions by including a more explicit statement of the alternate paths available in the network and by recognizing that under certain circumstances, e.g., failure of some part of the network work, an outflow link from a node under normal working condition may become an inflow link to the same node. The measures are assessed by comparison with parameters measuring Nodal Pair Reliability and percentage of flow supplied at adequate pressure for a range of networks and link failure conditions in this networks. The entropy measures are shown to reflect changes in the network reliability, as measured by these two comparative parameters, very well.  相似文献   

On the distribution of flood volume in partial duration series analysis of flood phenomena     

V. Choulakian  N. El-Jabi  J. Moussi 《Stochastic Hydrology and Hydraulics》1990,4(3):217-226

A methodology based on the theory of stochastic processes is applied to the analysis of floods. The approach will be based on some results of the theory of extreme values over a threshold. In this paper, we focus on the estimation of the distribution of the flood volume in partial duration series analysis of flood phenomena, by using a bivariate exponential distribution of discharge exceedances and durations over a base level.  相似文献   

新疆喀拉通克铜镍硫化矿区二、三号矿床特征及成因     

张纯仪 《矿物岩石》1990,10(1):79-87

喀拉通克铜镍硫化矿区二、三号矿床的两个岩体为隐伏的中－基性岩体，受北西向断裂的控制，侵位于石炭统南明水组上段之下部地层中，为岩浆熔离型铜镍硫化矿床。矿物成分以磁黄铁矿、镍黄铁矿、黄铜矿为主。有用元素除铜、镍外，尚伴生有金、银、铂、色、钴、硫可综合利用。它国内外同类型矿床相比，具有成岩、成矿时代新，岩体基性程度低、铜大于镍等特点，因而又具有新的地质找矿意义。  相似文献