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排序方式: 共有329条查询结果,搜索用时 468 毫秒
311.
目的 研究贫铀合金球对Q235钢靶的侵彻行为,为贫铀合金材料侵彻行为的深入研究以及在战斗部中广泛应用提供支撑。方法 采用Johnson-Cook强度模型和失效模型建立贫铀合金球撞击Q235钢靶的模型,利用Abaqus/explicit模块模拟研究贫铀合金球初速与尺寸对剩余速度、扩孔面积、侵彻深度的影响,并对结果进行分析。结果 通过试验与模拟得到了贫铀合金球的穿靶极限速度,两者结果基本吻合,验证了模型参数的准确性。相同尺寸下,贫铀合金球的剩余速度随初速的增大呈线性增大趋势,穿靶后速度衰减率为14.6%~33.2%。初速为900~1 300 m/s、直径为5~9 mm时,扩孔面积比为1.08~1.286。贫铀合金球的侵彻深度(H)随直径(d)和初速(v)的增大逐渐增大,三者的关系为 。结论 贫铀合金球初速和尺寸是影响侵彻深度的关键因素,但对扩孔直径没有显著影响。 相似文献
312.
Christine Bertram Anna Krätschell Killian O’Brien Warner Brückmann Alexander Proelss Katrin Rehdanz 《Resources Policy》2011,36(4):315-329
Projected increases in demand and thus increasing metal prices have brought the exploration and exploitation of marine mineral resources back into focus. The Atlantis II Deep, located in the central Red Sea between Saudi Arabia and Sudan, is one of the largest marine sulfide deposits known, with high concentrations of metals such as zinc, copper, silver and gold. However, little is known about the economic potential of marine minerals as well as the legal constraints. Our geological assessment shows that the deep is similar in grades and scale to large land-based deposits. Its economic potential is far from negligible. The total present value of possible gross revenues for the four metals zinc, copper, silver and gold ranges from 3.03 to 5.29 billion US$, depending on the assumptions made concerning future price development, mass calculation and discount rate. From a legal perspective, a general duty to cooperate in the exploration and exploitation of non-living resources located in disputed maritime areas is identified in both customary international law and in UNCLOS. It is submitted that a joint development agreement is one means of ensuring compliance with this duty in general and in the case of the Atlantis II Deep in particular. 相似文献
313.
Janis A. Shandro Marcello M. Veiga Jean Shoveller Malcolm Scoble Mieke Koehoorn 《Resources Policy》2011,36(2):178-186
The health of mining communities is becoming a priority for the mining industry, governments, and researchers. This paper describes an exploratory qualitative study into community health issues and mining activities (associated with the mining boom-bust cycle) from the perspective of health and social service providers in the northern Canadian coal mining community of Tumbler Ridge, British Columbia. Health and social service providers report on increases in pregnancies, sexually transmitted infections, and mine related injuries during booming mine activities. During bust times, mental health issues such as depression and anxiety were reported. Overarching community health issues prominent during both boom and bust periods include burdens to health and social services, family stress, violence towards women, and addiction issues. This paper concludes by providing recommendations as to how the industry can enhance community health made by this important stakeholder group. 相似文献
314.
A dichotomous-choice contingent-valuation survey was conducted in the State of Louisiana (USA) to estimate compensating surplus (CS) and equivalent surplus (ES) welfare measures for the prevention of future coastal wetland losses in Louisiana. Valuations were elicited using both willingness to pay (WTP) and willingness to accept compensation (WTA) payment vehicles. Mean CS (WTP) estimates based on a probit model using a Box-Cox specification on income was $825 per household annually, and mean ES (WTA) was estimated at $4444 per household annually. Regression results indicate that the major factors influencing support for land-loss prevention were income (positive, WTP model only), perceived hurricane protection benefits (positive), environmental and recreation protection (positive), distrust of government (negative), age (positive, WTA model only), and race (positive for whites). 相似文献
315.
316.
以山东液化天然气(LNG)项目为例,从环境监理的组织机构体系、管理及技术方法体系、管理程序及体系文件等方面,阐述了Q/SH0569-2013《建设项目环境监理技术规范(试行)》在港口码头及管道运输建设项目环境监理管理体系建立过程中的应用。 相似文献
317.
In recent years, commodity markets show a large amount of volatility and substantial price jumps, indicating an increasing economic scarcity in many cases. As this scarcity makes commodity procurement a critical issue for national economies, industry sectors and manufacturing companies, a number of criticality indices have been presented and utilized in science as well as in practice. These indices are mostly based on an aggregation of different key figures, both qualitative and quantitative. However, the weighting of the different factors is in most cases arbitrary or based on rough estimates. 相似文献
318.
This paper focuses on the creation of a Centre for the recycling of stone materials. The Centre will be able to offer a range of activities amongst which is the improvement of the production chain of the Orosei Marble district in Sardinia, Italy. Several companies operate within the marble producing area, specializing in both quarrying and stone processing. They have formed a Consortium in order to rehabilitate an area of more than 17 ha. The restoration will be carried out through an environmentally sustainable procedure. The area was previously used as a landfill for waste deriving from marble quarrying and processing. At that time unshaped blocks of various sizes (which are unsuitable to block-cutter sawing), waste deriving from both block sawing and slab/strip cutting (such as broken slabs, strips, tiles) and microfine dust from filter presses of water treatment plants were representing an environmental problem. The local administration was struggling to find new areas which could be used for landfills, resulting in an additional cost for the landfill, ultimately affecting the variable production costs. The project involves the building of a venue to be used for temporary storage, treatment of wastes produced by both quarrying and primary processing, in order to make them suitable as secondary raw materials. The project also deals with the catch basin hydrology of the area involved in the project, the building of a multifunctional centre, the landscaping and other environmental features such as vehicle traffic and slopes greening. 相似文献
319.
Studies of the resource curse as it affects African states abound, yet few deal specifically with the experiences of South Africa. The inability of countries to convert natural resource wealth into income and improved development measures remains highly pertinent and is especially apparent in Africa's largest economy. This paper takes a unique approach to study the resource curse by comparing South Africa's political economy with the existing resource curse literature. Using data from international organisations, studies of poverty and qualitative evidence this paper examines South Africa's experience with mineral extraction. It is found that South Africa has experienced many of the symptoms outlined in the resource curse literature including relatively slow GDP growth, gross inequalities, entrenched poverty and the creation of a rentier state. Overall, it is concluded that South Africa has failed to benefit from natural resource wealth and can be classified as a resource cursed state. Not only has mineral wealth failed to benefit much of South Africa's population, sections of society have actually been harmed through the process of mineral extraction. This paper is the first to examine South Africa in light of the current resource curse literature and to conclude that the state far more closely resembles its sub-Saharan African neighbours than its upper-middle income peers. 相似文献
320.
Cutoff grade specifies the available supply of metallic ore from an open pit mine to the multiple processing streams of an open pit mining complex. An optimal cutoff grade strategy maximizes the net present value (NPV) of an open pit mining operation subject to the mining, processing, and marketing/refining capacity constraints. Even though, the quantities of material flowing from the mine to the market are influenced by the expected variation in the available metal content or inherent uncertainty in the supply of ore, the majority of cutoff grade optimization models not only disregard this aspect and may lead to unrealistic cash flows, but also they are limited in application to an open pit mining operation with single processing facility. The model proposed herein determines the optimal cutoff grade policy based on a stochastic framework that accounts for uncertainty in supply of ore to the multiple ore processing streams. An application on a large-scale open pit mining operation develops a unique cutoff grade policy along with a portfolio of mining, processing, and marketing/refining rates. Owing to the geological uncertainty, the approach addresses risk by showing a difference of 14% between the minimum and maximum production rates, cash flows and NPV. 相似文献