高原大地形及海洋热力强迫对东亚及北半球环流和气候变化影响的观测研究     

罗会邦  陈蓉 《气象科学》1995,15(4):17-29

本文总结了“青藏高原大地形及西太平洋暖池势力强迫对东亚及全球气候变化的影响”专题五年来的主要研究工作。其中包括青世故高原东部大气热源的时间演变特征,夏半年高原热源异常对我国降水和北半球环流的影响;西沙海温变化特征及其与我南方降水的关系,北太平洋海温主因子特征及其与华南前汛期降水的变化。  相似文献   

Al—Cu—Li生成的大块准晶结构模型的初探     

陈敬中  路湘豫 《地球科学》1990,15(6):629-634

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使用价值分析优化方法在功能—技术矩阵求解中的应用     

罗庆生  韩宝玲 《武汉大学学报(信息科学版)》1990,(2)

功能—技术矩阵,经众多工作者的努力研究,已渐趋成熟与实用。但如何利用功能—技术矩阵构造在广义现代设计领域中适用的科学模式,解决多学科设计方案的组成与评价问题,还存在薄弱环节。本文利用“使用价值分析优化”的概念,从设计方案技术先进性和经济合理性的协调统一的角度出发,较好地实现了功能—技术矩阵可行优化组合链的组成与评价,弥补了以往的缺陷。  相似文献   

Threshold velocity for wind erosion: the effects of porous fences   总被引：3，自引：0，他引：3  

Zhibao Dong  Guangqiang Qian  Wanyin Luo  Hongtao Wang 《Environmental Geology》2006,51(3):471-475

Porous fence is a kind of artificial windbreak that has many practical applications. The threshold wind velocities at different distances downwind from porous fences were measured and the corresponding characteristics of particle movement observed to assess their shelter effect. It is found that the fence’s porosity is the key factor that determines the resulting shelter effect. The area near a fence can be typically classified into five regions, each with a different mode of particle movement. Dense fences, and especially solid fences, favor the accumulation of sand upwind of the fences. Fences with porosities of 0.3–0.4 produce the maximum threshold wind velocity; those with porosities of 0.3–0.6 (depending on the fence height) provide the maximum effective shelter distance. It is confirmed that the fence porosities of 0.3–0.4 that have been proposed for practical application in previous research are the most effective for abating wind erosion.  相似文献   

Study of stable isotopes for highly deformed aquifers in the Hsinchu-Miaoli area, Taiwan     

Hsueh-Yu Lu  Tsung-Ren Peng  Tsung-Kwei Liu  Chung-Ho Wang  Chih-Chao Huang 《Environmental Geology》2006,50(6):885-898

This study was based on the analysis of isotopic compositions of hydrogen and oxygen in samples from precipitation, groundwater and stream water. In addition, parts of groundwater samples were dated by carbon-14 and tritium. These data are integrated to provide other views of the hydrologic cycle in the Hsinchu-Miaoli groundwater district. The groundwater district is principally composed of Pleistocene and Holocene aquifers. The Pleistocene aquifers are highly deformed by folding and faults into small sub-districts with areas of only tens of square kilometers. These aquifers are exclusively recharged by local precipitation. The Holocene aquifers cover narrow creek valleys, only tens of meters in thickness. The local meteoric water line (LMWL), constructed from rainfall samples in the Hsinchu Science Park, is described by the equation δD=8.02δ¹⁸O+10.16, which agrees with the global meteoric water line. In addition, the precipitation isotopic compositions can be categorized into two distinct end members: typhoon type and monsoon type. The groundwater isotopic compositions are perfectly located on an LMWL and can be considered a mixture of precipitations. Based on the mass balance of isotopic compositions of oxygen and hydrogen, infiltration is more active in the rainy season with depleted isotopic compositions. The amount of infiltration during May–September is roughly estimated to comprise at least 55% of the whole year’s recharge. The isotopic compositions of stream water are expressed by a regression equation: δD=7.61δ¹⁸O+9.62, which is similar to the LMWL. Although precipitation isotopic compositions are depleted during summer time, the isotopic compositions contrarily show an enriched trend in the upstream area. This is explained by the opposite altitude effect on isotopic compositions for typhoon-related precipitations.  相似文献   

Magnetic properties of loess deposits on the northeastern Qinghai-Tibetan Plateau: palaeoclimatic implications for the Late Pleistocene   总被引：1，自引：0，他引：1  

Xiaoyong Wang  Huayu Lu  Huifang Xu  Chenglong Deng  Tianhu Chen  Xianyan Wang 《Geophysical Journal International》2006,167(3):1138-1147

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Global positioning system: A field guide for the social sciences – John Spencer, Erian G. Frizzelle, Philip H. Page and John B. Vogler     

X. X. Lu 《Singapore journal of tropical geography》2006,27(1):104-106

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GIS-based flood hazard mapping at different administrative scales: A case study in Gangetic West Bengal, India   总被引：4，自引：0，他引：4  

Joy Sanyal  X.X. Lu 《Singapore journal of tropical geography》2006,27(2):207-220

This paper addresses the need for an efficient and cost-effective methodology for preparing flood hazard maps in data poor countries, particularly those under a monsoon regime where floods pose a recurrent danger. Taking Gangetic West Bengal, India, as an example and using available historical data from government agencies, the study compiled a regional map indicating hazard prone subregional areas for further detailed investigation, thereby isolating actual high risk localities. Using a GIS (Geographical Information System), a composite hazard index was devised incorporating variables of flood frequency, population density, transportation networks, access to potable water, and availability of high ground and maximum risk zones were mapped accordingly. A digital elevation model derived from high resolution imagery available in the public domain was used to calculate elevated areas suitable for temporary shelter during a flood. Selecting administrative units of analysis at the lowest possible scales – rural development blocks (regional) and revenue villages (subregional) – also ensures that hazard mapping is prepared in line with the existing rural planning and administrative authorities responsible for remedial intervention.  相似文献   

桂北地区早石炭世杜内期的长身贝类的发现及其生物古地理意义     

王海涛  孙元林  陆济璞 《古地理学报》2006,8(4):439-550

在广西北部兴安县高尚镇金子山剖面下石炭统鹿寨组底部，新发现了长身贝类腕足化石，包括1新种、1个相似种、6个未定种和2个属种未定类型。这些长身贝类以Productellidae和Productidae科的分子为主，另有少量Echinoconchidae和Monticuliferidae科的分子。这些长身贝类全部属于生活在静水环境中的薄壳类型，无一与华南同期地层中已知类型相同。它们之间的差异可能反映了不同沉积环境条件对腕足动物群属种的控制。在鹿寨组底部发现的长身贝类以及近年在桂林南边村和黔南睦化剖面腕足动物群的发现显示出华南台缘斜坡―盆地相区杜内阶中的腕足动物群具有极高的属种分异度，不但有大量见于世界其他地方同期动物群中的分子，也包含有不少原本认为只在维宪阶或更高层位出现的类型或全新的类型，说明华南台缘斜坡―盆地相区不但与世界其他地区的腕足动物群之间存在密切的生物地理区系联系，而且华南台缘斜坡―盆地相区是杜内期腕足动物起源和辐射演化的重要策源地之一。许多属种可能是在这里起源，并迁移扩散到其他地方。  相似文献   

我国煤炭资源开发利用中某些问题的探讨   总被引：3，自引：0，他引：3  

罗景一  牛建英 《中国煤田地质》2006,18(3):6-10

针对我国煤炭资源开发利用中存在的诸如煤炭资源的低效率应用、无序开采、生态环境恶化等问题，指出了我国煤炭资源管理法规中存在的问题，提出了加强煤炭资源开发管理、构建煤炭循环经济体系、加大安全投入、加强煤炭矿区环境的治理和保护、健全有偿使用资源法规制度等对策。  相似文献