Cumulative impacts of aggregate extraction on seabed macro-invertebrate communities in an area off the east coast of the United Kingdom     

Keith Cooper  Sin Boyd  John Aldridge  Hubert Rees 《Journal of Sea Research》2007,57(4):288-302

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空间目标的聚合模型   总被引：2，自引：0，他引：2  

李霖 《测绘学报》1997,26(4):337-343

本文定义了集合元素的聚合算子，简述其特性，以此聚合算子为基础，提出了空间目标的聚合模型。根据ＧＩＳ空间目标的属性，分析了聚合算子的表现形式。由此模型的特点可以得出：聚合模型适合于ＧＩＳ层次数据的组织，它能减少数据的冗余和维护数据的一致性。经概念及含义的比较，指出了面向对象的模型方法很适合此聚合模型的实施。  相似文献   

Relationships between texture and mechanical properties of hybrid rocks from the Jaala–Iitti complex, southeastern Finland     

M. Risnen 《Engineering Geology》2004,74(3-4):197-211

The relationships between petrographical and mechanical properties of rock aggregate raw materials from the hybridised, subvolcanic Jaala–Iitti complex, southeastern Finland, were investigated. Petrography was quantified from polished thin sections with a polarising microscope to determine the modal composition and grain size distribution, and resistance to fragmentation and abrasion were determined. Abundance of fine-grained minerals (especially of hornblende), fine grain size-dominated grain size distribution, uniform spatial dispersion of hornblende crystals, and intense micrographic intergrowth texture with interlocking grain boundaries were found to have the greatest positive influence on the mechanical properties. The results showed the potentiality of hybridised rocks as raw materials for high quality aggregates that can resist fragmentation and abrasion.  相似文献   

A GIS Analysis to Evaluate Areas Suitable for Crushed Stone Aggregate Quarries in New England,USA     

Robinson  Gilpin R.  Kapo  Katherine E.  Raines  Gary L. 《Natural Resources Research》2004,13(3):143-159

Aggregate is a low unit-value mineral commodity. Costs to move aggregate from the mine site to the point of use is a large fraction of the resource cost to users. Production sites for aggregate occur where suitable source materials exist and where transportation and market conditions are favorable. The increasing demand for aggregate and the difficulty of developing and permitting new sites and of renewal of permits on existing sites of aggregate production indicates that aggregate will be supplied from sources yet to be developed or delineated in many areas. Site development and permitting for aggregate production is difficult because many land management plans and zoning actions fail to anticipate prospective source areas for aggregate in a way that is consistent with both the source rock quality and the transportation and socioeconomic factors that define the economic viability of the industry. Spatial analysis provides a method to integrate both geology and economic (transportation and marketplace) parameters in a regional model. Weights of evidence (WofE) analysis has been used to measure the spatial correlation of geologic map, transportation network, and population data with current production sites for crushed stone aggregate in the New England region of the northeastern United States. Weighted logistic regression (WLR) is used with the WofE results to rank areas in terms of their relative suitability for production of crushed stone. Spatial analysis indicates that 85% of the 106 crushed stone aggregate quarries in New England are sited within 1.6 km (1 mile) of either a principal highway or rail line in the region. Seventy-eight percent of crushed stone aggregate quarries are sited in census tracts with population densities exceeding 100 people/mile². These relations illustrate the importance of proximity to both transportation corridors and developing areas where aggregate is predominately used. Only one active crushed stone quarry is located in a census tract with a population density less than 15 people/mile², reflecting the lack of sufficient market demand in many rural areas to develop an operation there. However, since 1990, almost all new quarries have been developed in census tracts with population densities less than 200 people/mile², indicating the difficulty of permitting new quarry sites in highly populated areas. Crushed stone aggregate is produced predominately from three hard rock types that are distributed widely in New England; 28% of sites use granitic rock, 25% use carbonate rocks, and 25% use mafic rock types that are categorized as trap rock by the aggregate industry. The other crushed stone aggregate sources include a variety of fine-grained metamorphic rock types. Carbonate rocks and Jurassic basalt (the primary trap rock source) are the most prevalent source rocks on an area-weighted basis. Spatial analysis can be used on a regional scale to rank areas by their relative suitabilityfor crushed stone aggregate production based on geology, transportation, and population parameters. The results of this regional analysis can identify areas for more detailed evaluation. As transportation or population features change, the model can be revised easily to reflect these changes.  相似文献   

Effect of organic matter on splash detachment and the processes involved     

E. I. Ekwue 《地球表面变化过程与地形》1990,15(2):175-181

The influence of organic matter on splash detachment was investigated using soils with grass and peat treatments. The relationship between organic matter and aggregate stability to water disruption was positive for soils with grass treatment while it was negative for those with peat treatment. Organic matter from both treatments, however, reduced splash detachment by rainfall. Soils with grass did this by increasing aggregate stability while peat acted as a mulch on the soil surface. This implies that though organic matter always reduces splash detachment, different processes may be involved, depending on the form of the organic material. Because of the different processes involved, both negative and positive relationships between splash detachment and aggregate stability as reported in literature were obtained for the soils with grass and peat respectively.  相似文献   

An Aggregate Constraint Method for Inequality-constrained Least Squares Problems   总被引：3，自引：0，他引：3  

Junhuan Peng  Hongping Zhang  Suli Shong  Chunxi Guo 《Journal of Geodesy》2006,79(12):705-713

The inequality-constrained least squares (ICLS) problem can be solved by the simplex algorithm of quadratic programming. The ICLS problem may also be reformulated as a Bayesian problem and solved by using the Bayesian principle. This paper proposes using the aggregate constraint method of non-linear programming to solve the ICLS problem by converting many inequality constraints into one equality constraint, which is a basic augmented Lagrangean algorithm for deriving the solution to equality-constrained non-linear programming problems. Since the new approach finds the active constraints, we can derive the approximate algorithm-dependent statistical properties of the solution. As a result, some conclusions about the superiority of the estimator can be approximately made. Two simulated examples are given to show how to compute the approximate statistical properties and to show that the reasonable inequality constraints can improve the results of geodetic network with an ill-conditioned normal matrix.  相似文献   

The introduction of neural network system and its applications in rock engineering   总被引：3，自引：0，他引：3  

Yi Huang  Stefan Wnstedt 《Engineering Geology》1998,49(3-4):253-260

The neural network system has been developing very fast recently. It has been widely used in many industries such as automation, nuclear power plant, chemical industry, etc. Neural network systems have a great advantage in dealing with problems in which many factors influence the process and result, and the understanding of this process is poor, and there are experimental data or field data. In rock engineering, many problems are of this nature. In this paper, a brief introduction to neural network systems is given. Problems such as what is a neural network, how it works and what kind of advantages it has are discussed. After this, several applications in rock engineering, made by us, are presented. Case 1 is ore boundary delineation. In this case, the rock are divided into three classes, i.e.: (1) waste rock; (2) semi-ore; and (3) ore for mining purposes. The neural network system built can judge whether it is ore, semi-ore or waste rock along the borehole according its corresponding geophysical logging data, such as gamma-ray, gamma-gamma, neutron and resistivity. Case 2 is aggregate quality prediction. In this case, the quality parameters: (1) impact value; (2) abrasion value I; and (3) abrasion value II are predicted by using a neural network system based on density, point load, content of quarts and content of brittle minerals. Case 3 is rock indentation depth prediction. In this case, the rock indentation depth under indentation load is predicted by the established neural network system based on the indentation load on rock, indenter type and rock mechanical properties, such as uniaxial compressive strength, Young's modulus. Poisson's ratio, critical energy release rate and density. In all these cases, the neural network systems have been applied successfully. The testing results are satisfactory and better than the existing techniques.  相似文献   

岩石圈流变实验研究的进展   总被引：2，自引：2，他引：0  

杨恒  白武明 《地球物理学进展》2000,15(2):79-89

岩石高温高压变形实验是了解地球内部物质流动特性的最直接的手段 .本文概述了近年来岩石流变实验研究的一些成果 ,重点总结了水和部分熔融对上地幔顶部橄榄石流变行为的影响 ,以及地壳多相岩石流变实验研究的一些成果 .  相似文献   

The use of low-grade and unsound crushed rock aggregates in Ghana for construction     

D. O. K. Kuma 《Geotechnical and Geological Engineering》1995,13(4):217-225

Summary Ghana and many developing countries have relied heavily, in the past, on hard granites and granitic gneisses for the production of rock aggregates and rock products for civil engineering works including the construction of roads and buildings. Experience in Ghana has shown however, that the quantity of crushed rock aggregates produced from hard rocks have proved insufficient for the needs of the country. This situation has called for engineering geological studies into the use of rock types and rock formations previously designated as low grade and unsound for the production of aggregates. The major objective of this study was to review the occurrences of non-conventional hard rocks and gravels such as quartzites, silicified sandstones, metagreywackes, dolomitic limestones and quartz gravels. This was followed by the application of appropriate standard specification tests to establish criteria for the selection and recommendation for the use of low grade and unsound rocks and gravels for various civil engineering projects in Ghana and other developing countries, especially those of the subregion with similar geological formations.  相似文献   

Sediment transport mechanisms and selective removal of soil particles under unsteady-state conditions in a sheet erosion system     

Elham Sirjani  Majid Mahmoodabadi  Artemi Cerda 《国际泥沙研究》2022,37(2):151-161

Selective removal of particles and nutrients by water erosion is a key factor in soil erosion studies.Most agricultural soils are located on gentle slopes where fertility is high;however,until now,the main attention on sediment transport mechanisms was paid to high-slope gradients,where soil erosion is intense,but soils are less productive.Despite the importance of sediment size distribution(SSD) and transport mechanisms under unsteady-state conditions,few studies have been done on this issue.Hi...  相似文献