共查询到20条相似文献,搜索用时 15 毫秒
1.
Perry H 《Science (New York, N.Y.)》1983,222(4622):377-384
Historical trends in U.S. coal production, transportation and utilization and their causes are analyzed. The changing structure of the coal industry and its possible future direction, as it is driven by the effects of the oil embargo and world oil prices, are examined. National policies in the United States to increase coal use from indigenous sources in order to diversify and increase reliability of supply raise questions as to availability of coal supply and potential markets. Possible constraints on U.S. coal production, transportation, and utilization are appraised and it is concluded that increased coal consumption is "demand constrained." The causes and potential means of removal of these limitations are examined. 相似文献
2.
能源问题已成为制约一个国家经济发展的重要因素之一,我国已成为继美国之后的全球第二大能源消费国。当前我国能源的供需矛盾主要表现为煤炭供大于求,油气资源严重不足,对国际市场的依赖程度随国民经济的增长而加剧,但当前我国各项能源发展战略措施尚不能从根本上解决中国未来能源领域内存在的问题。 相似文献
3.
The future adequacy of freshwater resources is difficult to assess, owing to a complex and rapidly changing geography of water supply and use. Numerical experiments combining climate model outputs, water budgets, and socioeconomic information along digitized river networks demonstrate that (i) a large proportion of the world's population is currently experiencing water stress and (ii) rising water demands greatly outweigh greenhouse warming in defining the state of global water systems to 2025. Consideration of direct human impacts on global water supply remains a poorly articulated but potentially important facet of the larger global change question. 相似文献
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为研究农业种植结构对水能利用的影响,以实现粮食增产、农民增收、农业节水节能的协调发展,对石家庄各县(市)2002年、2007年、2012年的农业种植结构以及农业用水和用能量的变化情况进行分析。结果表明:(1)石家庄市农业耗水大县主要集中在东部及东南部;西部及西南部的县(市)耗水量较少,同时农业能耗量呈现出与水耗量变化的相对一致性,这主要受西部地区地形所限,可耕地面积少,农业种植结构中除夏玉米、冬小麦外,谷子等低耗水的传统农作物仍较多,经济作物种植面积远小于东部县市;(2)2002~2012年石家庄各县(市)农业水能利用量变化表现出一定差异:其中,藁城、辛集、赞皇、平山、行唐、赵县、深泽、元氏、新乐和鹿泉10个县(市)呈现出水能变化的一致性;其余7县(市)及市区仍存在着水能变化不一致的现象。这主要是由各地的自然条件及其对农业种植结构的调整造成的。 相似文献
6.
中国是严重缺水的国家,水资源供需矛盾十分突出。雨水是地下水的最重要补给源,也是解决水资源供需矛盾的重要途径之一。本研究中,通过借鉴美国雨水涵养与初雨水净化的成熟经验,设计了中国雨水涵养利用与初雨水净化系统,对屋面、绿地、道路、硬覆盖的排水与雨水涵养以及涵养水的利用、初雨水的净化等进行了研究。该系统在涵养雨水的同时,解决了初雨水净化的问题,与非涵养的普通雨水排水系统相比,管道长度短,管径小,节省了系统造价,是中国雨水利用的创新体系。 相似文献
7.
Energy and the u.s. Economy: a biophysical perspective 总被引:1,自引:0,他引:1
A series of hypotheses is presented about the relation of national energy use to national economic activity (both time series and cross-sectional) which offer a different perspective from standard economics for the assessment of historical and current economic events. The analysis incorporates nearly 100 years of time series data and 3 years of cross-sectional data on 87 sectors of the United States economy. Gross national product, labor productivity, and price levels are all correlated closely with various aspects of energy use, and these correlations are improved when corrections are made for energy quality. A large portion of the apparent increase in U.S. energy efficiency has been due to our ability to expand the relative use of high-quality fuels such as petroleum and electricity, and also to relative shifts in fuel use between sectors of the economy. The concept of energy return on investment is introduced as a major driving force in our economy, and data are provided which show a marked decline in energy return on investment for all our principal fuels in recent decades. Future economic growth will depend largely on the net energy yield of alternative fuel sources, and some standard economic models may need to be modified to account for the biophysical constraints on human economic activity. 相似文献
8.
Turner JA 《Science (New York, N.Y.)》2004,305(5686):972-974
Identifying and building a sustainable energy system are perhaps two of the most critical issues that today's society must address. Replacing our current energy carrier mix with a sustainable fuel is one of the key pieces in that system. Hydrogen as an energy carrier, primarily derived from water, can address issues of sustainability, environmental emissions, and energy security. Issues relating to hydrogen production pathways are addressed here. Future energy systems require money and energy to build. Given that the United States has a finite supply of both, hard decisions must be made about the path forward, and this path must be followed with a sustained and focused effort. 相似文献
9.
中国高粱产业发展特征及趋势分析 总被引:1,自引:0,他引:1
高粱是我国重要的杂粮作物。近年来,中美贸易中高粱交易量剧烈波动,高粱供需形势发生显著变化,高粱产业发展备受关注。从中国高粱的生产特征、贸易特征、消费特征等方面入手,对1960-2018年国内高粱产业发展趋势及发展现状进行分析。研究发现,中国高粱从主要粮食作物转变为小杂粮,近年来种植面积略有提高;国内高粱消费主要用于酿酒和饲料,虽然中国是世界第三大高粱消费国,但人均消费水平并不高;目前,中国作为世界第一大高粱进口国,进口量受饲料高粱需求影响猛增猛减,出口量极小且相对稳定。未来,中国高粱的发展规模将保持相对稳定,新的增长空间主要取决于旱作粮食作物的发展和消费途径的拓展。 相似文献
10.
高粱是我国重要的杂粮作物。近年来,中美贸易中高粱交易量剧烈波动,高粱供需形势发生显著变化,高粱产业发展备受关注。从中国高粱的生产特征、贸易特征、消费特征等方面入手,对1960—2018年国内高粱产业发展趋势及发展现状进行分析。研究发现,中国高粱从主要粮食作物转变为小杂粮,近年来种植面积略有提高;国内高粱消费主要用于酿酒和饲料,虽然中国是世界第三大高粱消费国,但人均消费水平并不高;目前,中国作为世界第一大高粱进口国,进口量受饲料高粱需求影响猛增猛减,出口量极小且相对稳定。未来,中国高粱的发展规模将保持相对稳定,新的增长空间主要取决于旱作粮食作物的发展和消费途径的拓展。 相似文献
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The global spread of malaria in a future, warmer world 总被引:1,自引:0,他引:1
The frequent warnings that global climate change will allow falciparum malaria to spread into northern latitudes, including Europe and large parts of the United States, are based on biological transmission models driven principally by temperature. These models were assessed for their value in predicting present, and therefore future, malaria distribution. In an alternative statistical approach, the recorded present-day global distribution of falciparum malaria was used to establish the current multivariate climatic constraints. These results were applied to future climate scenarios to predict future distributions, which showed remarkably few changes, even under the most extreme scenarios. 相似文献
12.
R D Gerard 《Science (New York, N.Y.)》1966,153(738):870-871
Estimates of the water budget of Long Island Sound suggest that it could become the largest reservoir in the United States, with a freshwater surplus equal to 12 times the present needs of New York City. The engineering aspects of this undertaking are within the scope of present technology. The dam structures required to isolate this area from the sea could serve as important highway links in place of highway-bridge projects presently under study. 相似文献
13.
Barnett TP Pierce DW Hidalgo HG Bonfils C Santer BD Das T Bala G Wood AW Nozawa T Mirin AA Cayan DR Dettinger MD 《Science (New York, N.Y.)》2008,319(5866):1080-1083
Observations have shown that the hydrological cycle of the western United States changed significantly over the last half of the 20th century. We present a regional, multivariable climate change detection and attribution study, using a high-resolution hydrologic model forced by global climate models, focusing on the changes that have already affected this primarily arid region with a large and growing population. The results show that up to 60% of the climate-related trends of river flow, winter air temperature, and snow pack between 1950 and 1999 are human-induced. These results are robust to perturbation of study variates and methods. They portend, in conjunction with previous work, a coming crisis in water supply for the western United States. 相似文献
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Geologic reasons indicate that the dominant position of the Middle East as a source of conventional petroleum will not be changed by new discoveries elsewhere. The share of world crude oil production coming from the Middle East could increase, within 10 to 20 years, to exceed 50 percent, under even modest increases in world consumption. Nonconventional resources of oil exist in large quantities, but because of their low production rates they can at best only mitigate extant trends. Increased production of natural gas outside the United States, however, offers an opportunity for geographically diversified energy supplies in the near future. 相似文献
15.
Zilberman D Schmitz A Casterline G Lichtenberg E Siebert JB 《Science (New York, N.Y.)》1991,253(5019):518-522
Pesticides enhance agricultural productivity, but the environmental and health side effects of their use justify government regulation, a subject of continuing societal debate. Bans on pesticide use are the principal regulatory device used in the United States. The economic impacts of such bans depend on the availability of substitutes, supply and trade conditions, and research and development. Without substitutes, pesticide bans result in reduced production levels and higher prices, a substantial loss of discretionary income to consumers, and a redistribution of income among agricultural producers. Most food safety concerns can be addressed by establishing standards and markets for pesticide-differentiated products, but worker safety and clean water concerns will require direct controls. Pesticide-use fees are shown to be more efficient than outright pesticide bans as a mechanism to obtain environmental goals. 相似文献
16.
【目的】为了改善城乡的生态环境和能源供应,研究北京城郊农村家庭的生活能源消费情况和影响因素。【方法】运用描述统计方法分析了调研数据。【结果】电力、煤炭和燃气等商品能源为主要消费对象,煤炭占到生活能源消费的50%以上;秸秆和薪柴等生物质能源的消费量大大减少;太阳能、沼气等新型能源的消费较少。当收入水平和能源获取条件变得更好时,城郊农村家庭就会更多消费便捷和清洁的能源。【结论】城郊农村家庭生活能源消费的这一趋势,对生态环境和能源供应造成新的压力。政府应通过制定政策鼓励能源的清洁化使用,鼓励开发太阳能、无污染生物质能源等可再生能源。 相似文献
17.
晋西黄土残塬沟壑区水分变化及其利用效率研究 总被引:6,自引:0,他引:6
通过定位观测 ,分析了晋西黄土残塬沟壑区土壤水分动态、土壤供水与耗水关系及林木水分利用效率。结果表明 :由于严重的水土流失及坡向的影响 ,水分分布极为不均 ,不同部位水分变化规律的总趋势是 :沟底 >沟坡下部 >塬面 >塬坡 >沟坡中上部 ;幼林地土壤水分消耗大于供给 ,水分供需矛盾突出 ,雨季水分供给充足 ,土壤贮水增加 ;不同坡向水分亏损大小顺序为 :阳坡 >半阳坡 >阴坡 ;从水分利用效率看 ,由于幼林地水分供应不足 ,林木生长不同程度受到限制 ,林木水分利用效率较低 相似文献
18.
We described three uses of energy for which greater efficiency is feasible: transportation, space heating, and air conditioning. Shifts to less energy-intensive transportation modes could substantially reduce energy consumption; the magnitude of such savings would, of course, depend on the extent of such shifts and possible load factor changes. The hypothetical transportation scenario described here results in a 22 percent savings in energy for transportation in 1970, a savings of 2800 trillion Btu. To the homeowner, increasing the amount of building insulation and, in some cases, adding storm windows would reduce energy consumption and provide monetary savings. If all homes in 1970 had the "economic optimum" amount of insulation, energy consumption for residential heating would have been 42 percent less than if the homes were insulated to meet the pre-1971 FHA standards, a savings of 3100 trillion Btu. Increased utilization of energy-efficient air conditioners and of building insulation would provide significant energy savings and help to reduce peak power demands during the summer. A 67 percent increase in energy efficiency for room air conditioners would have saved 15.8 billion kilowatt-hours in 1970. In conclusion, it is possible-from an engineering point of view-to effect considerable energy savings in the United States. Increases in the efficiency of energy use would provide desired end results with smaller energy inputs. Such measures will not reduce the level of energy consumption, but they could slow energy growth rates. 相似文献
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AAAS Committee on Arid Lands 《Science (New York, N.Y.)》1972,175(4022):667-669
We conclude, then, that large-scale importation of irrigation water into water-deficient areas in the United States should not be undertaken simply because it is technically feasible, the water and land are available, and water deficits now or in the foreseeable future can be documented. Rather, we believe that if there is a compelling reason for large-scale water importation, it is to prevent massive social and economic disruption in an established irrigated area. 相似文献