Economic Filters Applied to Quantitative Mineral Resource Simulations     

Joseph S. Duval 《Natural Resources Research》2003,12(2):121-126

The U.S. Geological Survey has developed a technique that allows mineral resource experts to apply economic filters to estimates of undiscovered mineral resources. This technique builds on previous work that developed quantitative methods for mineral resource assessments. A Monte-Carlo calculation uses mineral deposit models to estimate commodity grades and tonnages of undiscovered deposits. The results then are analyzed using simple estimates of capital expenditures and daily operating costs for a mine and associated mill. The daily operating costs and the value of the ore are used to calculate the net present value of the deposit, which is compared to the capital expenditures to determine whether the deposit is economic. Repetition of these calculations for many deposits produces a table that can be interpreted in terms of the probability of there being deposits that have anet present value exceeding some specified amount. Sample calculations indicate that applying economic filters to simulated mineral resources might change the perception of the results compared to presenting the calculations in terms of the expected mean gross-in-place value of the minerals.  相似文献   

Use of Fuzzy Membership Input Layers to Combine Subjective Geological Knowledge and Empirical Data in a Neural Network Method for Mineral-Potential Mapping   总被引：3，自引：0，他引：3  

Brown  Warick  Groves  David  Gedeon  Tamás 《Natural Resources Research》2003,12(3):183-200

Use of GIS layers, in which the cell values represent fuzzy membership variables, is an effective method of combining subjective geological knowledge with empirical data in a neural network approach to mineral-prospectivity mapping. In this study, multilayer perceptron (MLP), neural networks are used to combine up to 17 regional exploration variables to predict the potential for orogenic gold deposits in the form of prospectivity maps in the Archean Kalgoorlie Terrane of Western Australia. Two types of fuzzy membership layers are used. In the first type of layer, the statistical relationships between known gold deposits and variables in the GIS thematic layer are used to determine fuzzy membership values. For example, GIS layers depicting solid geology and rock-type combinations of categorical data at the nearest lithological boundary for each cell are converted to fuzzy membership layers representing favorable lithologies and favorable lithological boundaries, respectively. This type of fuzzy-membership input is a useful alternative to the 1-of-N coding used for categorical inputs, particularly if there are a large number of classes. Rheological contrast at lithological boundaries is modeled using a second type of fuzzy membership layer, in which the assignment of fuzzy membership value, although based on geological field data, is subjective. The methods used here could be applied to a large range of subjective data (e.g., favorability of tectonic environment, host stratigraphy, or reactivation along major faults) currently used in regional exploration programs, but which normally would not be included as inputs in an empirical neural network approach.  相似文献   

Promoting social justice and conserving montane forest environments: a case study of Nepal's community forestry programme   总被引：1，自引：0，他引：1  

Netra Prasad Timsina 《The Geographical journal》2003,169(3):236-242

This paper analyses participatory forest policy and the ways it has influenced the relationships between people as it relates to the forest resource management. This case study was conducted in the middle hills of Nepal, and information was collected through direct observation, individual interviews, group discussion and secondary information analysis. It substantiates a few examples of how the community forestry programme can be used as a means to promote the participation of the women, the poor and dalit (untouchables) in forest resource management, as well as enhancing social justice and improving the forest resources in their locality. However, it also demonstrates that though the community forestry programme has a positive impact, it faces several constraints and challenges. The local Forest User Group is controlled by a few élites making the poor and disadvantaged vulnerable to further marginalization. The results of the case study strongly indicate that community forestry processes must address the political, economic and social needs of the forest users, and also provide a neutral platform on which the poor can present their cases.  相似文献   

Alpine medicinal plant trade and Himalayan mountain livelihood strategies   总被引：5，自引：0，他引：5  

Carsten Smith Olsen  Helle Overgaard Larsen 《The Geographical journal》2003,169(3):243-254

Commercial alpine medicinal plants are collected from the wild by local rural households throughout the Himalaya and sold in order to increase household incomes. Recent studies indicate that this annual trade amounts to thousands of tonnes of roots, rhizomes, tubers, leaves, etc., worth millions of US dollars. The main market is in India. Based on a national survey, including the most commonly traded species, and a village study this paper investigates the importance of the alpine medicinal plant trade at national and local levels in Nepal. The national survey included standardized open-ended interviews with 232 harvesters, 64 local traders, 66 central wholesalers, 47 regional wholesalers, and 16 production companies. The village survey is based on the daily records of household activities in 15 households in a one-year period. The annual Nepalese alpine and sub-alpine medicinal plant trade is conservatively estimated to vary from 480 to 2500 t with a total harvester value of US$0.8–3.3 million; the average harvester value is estimated at US$66.0 ± 99.0. The trade in 1997/98 amounted to 1600 t with a harvester value of US$2.3 million and an export value equivalent to 2.5% of total export from Nepal. Medicinal plant harvesting was found to constitute an integrated part of local livelihood strategies, contributing from 3 to 44% (average of 12%) of the annual household income. Importance at household level depended on land and animal holdings, and the availability of adult male labour. The validity and reliability of methods and analyses is evaluated, and issues of conservation and management of alpine medicinal plant species under the community forestry scheme are discussed.  相似文献   

近、现代黄河三角洲地貌形态反演   总被引：5，自引：0，他引：5  

刘庆生  刘高焕  励惠国 《地理与地理信息科学》2003,19(2):93-96

1855年黄河改夺大清河河道后于山东利津县东北入海。至今黄河尾癌河道历经10次大的改道变迁，塑造了近、现代黄河三角洲，形成了7个主要的亚三洲堆积体。该文利用黄河尾癌河道改道资料，近、现代河口流路变迁图，近、现代黄河三角洲体系图以及1985－1986年的水文工程地质钻孔资料，在研究黄河三角洲沉积模式的基础上，对工程地质钻孔数据进行沉积层序分析，将今论古，反推近、现代黄河三角洲沉积地貌，研究结果近似展示了近、现代黄河三角洲二维平面的发育演变和其时其地的地貌形态。  相似文献   

城市基准地价评估的容积率内涵及其修正系数的确定--以石家庄市为例   总被引：6，自引：1，他引：6  

葛京凤  黄志英  梁彦庆 《地理与地理信息科学》2003,19(3):98-100,108

基淮地价评估是当前城市地价评估的主要形式。容积率既反映了土地的利用状况，同时也是影响地价的主要因素之一。该文阐述了容积率内涵，分析容积率与地价、环境的关系，探讨合理容积率的确定，以石家庄市为例，探索容积率修正系数确定的正确途径，避免在容积率概念、修正系数等问题上产生混淆。  相似文献   

东莞城市化过程中若干问题研究   总被引：10，自引：3，他引：10  

黄靖 《地理与地理信息科学》2003,19(5):73-76

改革开放以来，东莞市积极吸纳海外资本与技术，通过“三来一补”企业的快速发展，带动了非农产业和小城镇的迅速发展。然而，受我国分散的工业化和农村城市化政策体制的影响，在快速城市化过程中也暴露出很多值得关注的问题。该文基于实地考察与问卷访谈，重点分析了土地利用效率低、外来人口集中以及基础设施建设与城市经济发展不相协调等问题，并提出协调城市化发展的对策。  相似文献   

京、津、冀区域群发性强沙尘暴分析   总被引：1，自引：2，他引：1  

刘学锋  安月改  田国强 《地理与地理信息科学》2003,19(6):74-76

利用1954—2002年82个站的气象观测资料，探讨京、津、冀区域群发性强沙尘暴的认定标准，构建较完整的群发性强沙尘暴序列，并分析该地区群发性强沙尘暴的时空分布特征和气候变化趋势。近50a京、津、冀区域共出现了39例群发性强沙尘暴，河北省的冀西北高原区和石家庄、保定、衡水、沧州四市交接处饶阳一带是京、津、冀区域强沙尘暴天气的多发区。多发季节为3—5月，占全年总数的76．9％，其中4月份最多，占全年总数的51．3％。群发性强沙尘暴年代际变化呈现总体减少趋势，其发生次数、覆盖面积均是以20世纪90年代为最低值．  相似文献   

两湖平原农业洪害特征与减灾技术措施   总被引：1，自引：0，他引：1  

陶建平  张安录  李翠霞 《地域研究与开发》2003,22(2):75-78

两湖平原是我国农业水资源最丰富的地区之一，河湖水系四通八达，农业生产条件优越。由于人类不适当的经济活动，大规模围湖垦殖破坏了两湖平原自然生态环境，洪涝频繁发生，农业损失严重。两湖平原必须实施综合性的农业减灾技术措施：长江上中游地区实施退耕还林、全面启动天然林保护工程，保持水土；两湖地区实行退田还湖，提高湖泊分蓄洪能力；应用GPS、GIS技术预警，有效调度洪水；调整湖区农业结构，发展避洪农业。  相似文献   

水土流失评价数据库建立中的数据标准化研究--以中国潜在水土流失评价数据库为例   总被引：2，自引：0，他引：2  

马晓微  杨勤科  刘宝元 《地域研究与开发》2003,22(3):14-17,35

在水土流失评价数据库的建立研究中，涉及到数据的标准化问题。该研究以中国潜在水土流失评价数据库建立过程中的数据标准化研究为例，探讨建立适合水土流失评价数据标准化的方法。研究包括了水土流失数据标准化建设中的评价数据库的设计、数据的标准化。其中，数据的标准化包括数据的收集与分析、数据的录入、投影变换、其它格式向ARC/INFO格式的转换、补充编制专题文档等。  相似文献