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排序方式: 共有392条查询结果,搜索用时 15 毫秒
1.
This research focuses on the spatial economics of geothermal district energy (DE) systems that distribute hot fluids through a pipeline network to multiple thermal customers. We argue here that DE is held back by uncertainty about its economic feasibility when implemented in real places. DE works best with high urban densities, but in the US the best geothermal resources are in the less-populated west. Economic geography theory suggests that the optimal size of a DE firm's service area should depend on the trade-off between the economies of scale inherent in a large service area and the greater network development costs and heat loss involved in serving a large area. The HEATMAP© software program developed by Washington State University was used to study the feasibility of numerous scenarios for a proposed DE system in Mammoth Lakes, California. Results indicate that the core area of the town is large enough, dense enough, and in close enough proximity to the resource for profitable DE development. Proposed ski village developments would increase the thermal load density and significantly enhance its ability to remain competitive with other fuels, even in pessimistic sensitivity analyses regarding geothermal heat input costs, public participation, and retro-fitting costs. 相似文献
2.
介绍了美国DIPPR、德国DETHERM和日本NIST的组织情况和编篡工作,从此得到启示,以求加速我国化工物性数据编篡工作的发展。 相似文献
3.
思想库在当今社会有着非常重要的作用 ,为政府、企业团体等提供关于重大问题的决策咨询 ,是现代社会不可或缺的机构。研究型大学是一个国家高层次人才聚集的地方 ,有着丰富的信息资料和学术氛围的优势。美国的许多研究型大学都建设有思想库 ,并有着重要影响 ,而我国研究型大学中思想库的建设相对滞后。本文对美国研究型大学中思想库研究的特点进行分析 ,以期对我国的研究型大学建立思想库提供参考。 相似文献
4.
依据英国金属网公布的2003年、2004年、2005年第1季度美国钽铌原料和制品进口统计数据.评述了美国钽铌市场的状况,着重关注了中国向美国出口钽铌的情况。 相似文献
5.
Biwei Deng Rong Xu Kejie Zhao Yongfeng Lu Sabyasachi Ganguli Gary J. Cheng 《Materials Today》2018,21(5):467-474
Manufacturing ultralight and mechanical reliable materials has been a long-time challenge. Ceramic-based mechanical metamaterials provide significant opportunities to reverse their brittle nature and unstable mechanical properties and have great potential as strong, ultralight, and ultrastiff materials. However, the failure of ceramics nanolattice and degradation of strength/modulus with decreasing density are caused by buckling of the struts and failure of the nodes within the nanolattices, especially during cyclic loading. Here, we explore a new class of 3D ceramic-based metamaterials with a high strength–density ratio, stiffness, recoverability, cyclability, and optimal scaling factor. Deformation mode of the fabricated nanolattices has been engineered through the unique material design and architecture tailoring. Bending-dominated hollow nanolattice (B-H-Lattice) structure is employed to take advantages of its flexibility, while a few nanometers of carbonized mussel-inspired bio-polymer (C-PDA) is coherently deposited on ceramics’ nanolayer to enable non-buckling struts and bendable nodes during deformation, resulting in reliable mechanical properties and outperforming the current bending-dominated lattices (B-Lattices) and carbon-based cellulose materials. Meanwhile, the structure has comparable stiffness to stretching-dominated lattices (S-Lattices) while with better cyclability and reliability. The B-H-Lattices exhibit high specific stiffness (>106?Pa·kg?1·m?3), low-density (~30?kg/m3), buckling-free recovery at 55% strain, and stable cyclic loading behavior under up to 15% strain. As one of the B-Lattices, the modulus scaling factor reaches 1.27, which is lowest among current B-Lattices. This study suggests that non-buckling behavior and reliable nodes are the key factors that contribute to the outstanding mechanical performance of nanolattice materials. A new concept of engineering the internal deformation behavior of mechanical metamaterial is provided to optimize their mechanical properties in real service conditions. 相似文献
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7.
This literature survey is for heat transfer to supercritical water flowing in channels. The objectives are to assess the work that was done and to understand the specifics of heat transfer at these conditions. Our exhaustive literature search, which included over 450 papers, showed that the majority of experimental data were obtained in vertical tubes, some data in horizontal tubes and just a few in other flow geometries including bundles. In general, the experiments showed that there are three heat transfer modes in fluids at supercritical pressures: (1) normal heat transfer, (2) deteriorated heat transfer with lower values of the heat transfer coefficient (HTC) and hence higher values of wall temperature within some part of a test section compared to those of normal heat transfer and (3) improved heat transfer with higher values of the HTC and hence lower values of wall temperature within some part of a test section compared to those of normal heat transfer. The deteriorated heat transfer usually appears at high heat fluxes and lower mass fluxes. Also, a peak in HTC near the critical and pseudo-critical points was recorded. Due to the limited number of publications that are devoted to heat transfer in bundles cooled with water at supercritical pressures, more work is definitely needed to provide the additional information for design purposes. 相似文献
8.
我国新一轮电力体制改革要求还原电力商品属性、建立市场化机制,但具体如何实施还在争论或讨论中。目前美国的电力市场运转良好,其电力体制改革的经验和方法值得我们借鉴。本文介绍美国电力市场的缘起,分析能量管理系统(EMS)在美国电力市场发展和电力市场管理系统中的作用,讨论电力市场的基本原理以及美国电力市场的形成和实现方法,为我国电力市场的发展和实现提供参考。 相似文献
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10.
Zhenling Liu 《Energy Sources, Part B: Economics, Planning, and Policy》2018,13(3):169-172
The most important characteristics and limitations of solar energy were reviewed in this study. The analysis of different aspects indicated that the most important global challenges of solar energy development were climatic challenges, technical constraints, and unwillingness to make investments. After describing current conditions and predicting the future of solar energy, this study analyzed the policies formulated by developed countries to develop this from of energy. Accordingly, China has gotten ahead of other countries in this industry due to the technological production of solar panels and governmental supports. Finally, the economic estimation of solar energy was presented by dealing with the economic barriers to this form of energy in developed countries. According to the significant growth in the reduction of solar energy electricity production cost, this source of energy can be used as a major source in the future. It was then recommended to use a hybrid of solar energy with other sources such as wind to reduce the costs. 相似文献