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1.
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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通过珠三角地区菜农与粮农生产的比较,分析了菜农生产的困境,一定程度上解释了自2010年起频发的菜农自杀现象。分析的菜农生产困境是以后全球经济危机为大环境,国务院出台四万亿投资为背景的,表面上符合"谷贱农伤"的基本规律,实际上是农业资本化以及小农与大市场不对等的必然结果。 相似文献
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Lobert JM Butler JH Montzka SA Geller LS Myers RC Elkins JW 《Science (New York, N.Y.)》1995,267(5200):1002-1005
Surface waters along a cruise track in the East Pacific Ocean were undersaturated in methyl bromide (CH(3)Br) in most areas except for coastal and upwelling regions, with saturation anomalies ranging from + 100 percent in coastal waters to -50 percent in open ocean areas, representing a regionally weighted mean of -16 (-13 to -20) percent. The partial lifetime of atmospheric CH(3)Br with respect to calculated oceanic degradation along this cruise track is 3.0 (2.9 to 3.6) years. The global, mean dry mole fraction of CH3Br in the atmosphere was 9.8 +/- 0.6 parts per trillion, with an interhemispheric ratio of 1.31 +/- 0.08. These data indicate that approximately 8 percent (0.2 parts per trillion) of the observed interhemispheric difference in atmospheric CH3Br could be attributed to an uneven global distribution of oceanic sources and sinks. 相似文献
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《Science (New York, N.Y.)》1984,226(4670):7
As published, figure 2 in the report "Disruption of the terrestrial plant ecosystem at the Cretaceous-Tertiary boundary, western interior" by R. H. Tschudy et al. (7 Sept., p. 1030) contained two errors. The break in the stratigraphic column should have been 3 m, and the iridium concentration should have been in parts per trillion. The correct figure is reproduced below. [see figure in source PDF]. 相似文献
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Foster KL Plastridge RA Bottenheim JW Shepson PB Finlayson-Pitts BJ Spicer CW 《Science (New York, N.Y.)》2001,291(5503):471-474
Bromine atoms are believed to play a central role in the depletion of surface-level ozone in the Arctic at polar sunrise. Br2, BrCl, and HOBr have been hypothesized as bromine atom precursors, and there is evidence for chlorine atom precursors as well, but these species have not been measured directly. We report here measurements of Br2, BrCl, and Cl2 made using atmospheric pressure chemical ionization-mass spectrometry at Alert, Nunavut, Canada. In addition to Br2 at mixing ratios up to approximately 25 parts per trillion, BrCl was found at levels as high as approximately 35 parts per trillion. Molecular chlorine was not observed, implying that BrCl is the dominant source of chlorine atoms during polar sunrise, consistent with recent modeling studies. Similar formation of bromine compounds and tropospheric ozone destruction may also occur at mid-latitudes but may not be as apparent owing to more efficient mixing in the boundary layer. 相似文献
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Orth CJ Gilmore JS Knight JD Pillmore CL Tschudy RH Fassett JE 《Science (New York, N.Y.)》1981,214(4527):1341-1343
An iridium abundance anomaly, with concentrations up to 5000 parts per trillion over a background level of 4 to 20 parts per trillion, has been located in sedimentary rocks laid down under freshwater swamp conditions in the Raton Basin of northeastern New Mexico. The anomaly occurs at the base of a coal bed, at the same stratigraphic position at which several well-known species of Cretaceous-age pollen became extinct. 相似文献
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文化景观遗产研究和实践逐渐步入浙闽遗产保护工作的重要日程。50多年的木拱桥遗产保护历程可以划分为3个阶段,其遗产保护实践的各个阶段都与＂景观＂原意密切相关,可以证明木拱桥文化景观遗产底蕴深厚,文化景观遗产视野下的木拱桥保护工作值得研究。木拱桥文化景观遗产保护工作强调整体性保护,而不是孤立地保护桥的单体。参考世界遗产整体性保护方法,其核心保护目标应该是整体性聚居环境景观的维护和恢复。木拱桥遗产保护不仅需要探索其建构技术,为该技术作为非物质文化遗产的活态传承打下基础;并对留存的古代木拱桥遗产作为历史建筑遗产价值展开充分讨论,认为要在3个层面上分步实施,最终达到保护目标。 相似文献
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Atmospheric dimethyl sulfide (DMS) measurements were made on the Atlantic Coast of the United States at Wallops Island and Cape Henry, Virginia, during June 1975. The very low concentrations, typically less than 30 parts per trillion observed at the Cape Henry site, were thought to result from the smog chemistry associated with the Norfolk metropolitan area. Atmospheric DMS concentrations at the Wallops Island site were much higher, having a geometric mean of 58 parts per trillion and a geometric standard deviation of 2.1. At this site the DMS source strength was estimated to be 6 milligrams of sulfur per square meter per year. Because of wind conditions during this experiment, the DMS source strength is thought to be representative of the DMS source strength of the ocean in the Wallops Island area and is much less than the 130 milligrams of sulfur per square meter per year needed to balance the ocean-atmosphere portion of the global sulfur budget. 相似文献
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Quantitative Evaluation of Sustainable Development and Eco-Environmental Carrying Capacity in Water-Deficient Regions: A Case Study in the Haihe River Basin,China 
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下载免费PDF全文 Quantitative assessment of development sustainability could be a challenge to regional management and planning, especially for areas facing great risks of water shortage. Surface-water decline and groundwater over-pumping have caused serious environmental problems and limited economic development in many regions all around the world. In this paper, a framework for quantitatively evaluating development sustainability was established with water-related eco-environmental carrying capacity (EECC) as the core measure. As a case study, the developed approach was applied to data of the Haihe River Basin, China, during 1998 through 2007. The overall sustainable development degree (SDD) is determined to be 0.39, suggesting that this rate of development is not sustainable. Results of scenario analysis revealed that overshoot, or resource overexploitation, of the Basin's EECC is about 20% for both population and economy. Based on conditions in the study area in 2007, in order to achieve sustainable development, i.e., SDD>0.70 in this study, the EECC could support a population of 108 million and gross domestic product (GDP) of 2.72 trillion CNY. The newly developed approach in quantifying eco-environmental carrying capacity is anticipated to facilitate sustainable development oriented resource management in water-deficient areas. 相似文献
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[目的]研究农业钢拱结构腹板承载力影响因素。[方法]通过有限元方法对径向均布荷载作用下的工形截面钢拱结构进行非线性分析,分析截面几何参数对腹板极限承载力。[结果]结果表明腹板长宽比越大,试件的极限承载力越小,而腹板厚度、翼缘厚度、翼缘宽度越大,试件的极限承载力越大。腹板长宽比和截面尺寸一定时,试件的极限承载力随着圆心角的增大而线性增大。[结论]在实际工程中,适当减小横向加劲肋的间距可有效提高试件极限承载力。建议腹板长宽比上限值为2.0。在建筑尺寸允许下,可将纯弯作用下的钢拱结构的圆心角增大,提高试件截面尺寸的极限承载力。 相似文献
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Olsen PE Kent DV Sues HD Koeberl C Huber H Montanari A Rainforth EC Fowell SJ Szajna MJ Hartline BW 《Science (New York, N.Y.)》2002,296(5571):1305-1307
Analysis of tetrapod footprints and skeletal material from more than 70 localities in eastern North America shows that large theropod dinosaurs appeared less than 10,000 years after the Triassic-Jurassic boundary and less than 30,000 years after the last Triassic taxa, synchronous with a terrestrial mass extinction. This extraordinary turnover is associated with an iridium anomaly (up to 285 parts per trillion, with an average maximum of 141 parts per trillion) and a fern spore spike, suggesting that a bolide impact was the cause. Eastern North American dinosaurian diversity reached a stable maximum less than 100,000 years after the boundary, marking the establishment of dinosaur-dominated communities that prevailed for the next 135 million years. 相似文献
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通过对西北地区实施名优农产品最终加工原产地化模式的必要性与现实可行性的分析,提出了＂名优农产品最终加工原产地化＂产品筛选体系的设计方案,旨在促使西北名优农产品最终加工原产地模式的尽早实施与实践。 相似文献
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Sturges WT Wallington TJ Hurley MD Shine KP Sihra K Engel A Oram DE Penkett SA Mulvaney R Brenninkmeijer CA 《Science (New York, N.Y.)》2000,289(5479):611-613
We detected a compound previously unreported in the atmosphere, trifluoromethyl sulfur pentafluoride (SF(5)CF(3)). Measurements of its infrared absorption cross section show SF(5)CF(3) to have a radiative forcing of 0.57 watt per square meter per parts per billion. This is the largest radiative forcing, on a per molecule basis, of any gas found in the atmosphere to date. Antarctic firn measurements show it to have grown from near zero in the late 1960s to about 0.12 part per trillion in 1999. It is presently growing by about 0.008 part per trillion per year, or 6% per year. Stratospheric profiles of SF(5)CF(3) suggest that it is long-lived in the atmosphere (on the order of 1000 years). 相似文献
16.
Multiphoton resonance ionization has been combined with energetic ion bombardment to examine dopant concentrations ofindium on the surface of silicon. The results yield a linear relation between the indium concentration and the known bulk values and a detection limit of 9 parts per trillion, at a mass resolution exceeding 160. This measurement, which surpasses the limits of any previous surface analysis by a factor of 100, has been made possible with an experimental configuration that optimizes sampling and detection efficiency while reducing background noise to virtually zero. During the analysis, submonolayer quantities of the surface are removed, so that as few as 180 surface atoms may be counted. 相似文献
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竹集成材与常见建筑结构材力学性能比较 总被引：2，自引：0，他引：2
对竹集成材和竹指接集成材的物理力学性能进行了试验研究，并与几种常用的建筑结构木材（如落叶松Larix gmeinl，水曲柳Fraxinus mandshurica，杉木cunninghamia lanceolata），毛竹Phyllostachys pubescens及多孔砖砌体、混凝土物理力学性能相比。结果表明：竹集成材的抗拉强度和抗压强度较高，抗剪强度表现良好的塑性性能，是一种综合力学性能很好的建筑结构材料，其产品不仅可在梁、板、柱等常见建筑结构中使用，也适于工字梁、桁架等复杂结构用材；竹指接集成材受指接的影响，其抗拉强度、抗压强度和抗剪强度低于竹集成材，但已能满足一般承重类的结构材料使用。 相似文献
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兴安落叶松目测等级锯材抗拉强度的宽度尺寸效应 总被引：2，自引：0，他引：2
以兴安落叶松锯材作为研究对象,研究了不同目测等级下锯材试材宽度与其顺纹抗拉强度之间的依存性。选取3种宽度尺寸的目测等级锯材,分成高、低目测等级组,按照相同的测试跨度测试锯材顺纹抗拉强度,并利用斜率法和形状参数法估计高、低目测等级试材顺纹抗拉强度5%分位值的宽度尺寸效应。结果表明：1）落叶松锯材宽度增加,其顺纹抗拉强度下... 相似文献
19.
A number of features have been identified as absorption lines of hydrogen cyanide in infrared spectra of stratospheric absorption obtained from a high-altitude aircraft. Column amounts of stratospheric hydrogen cyanide have been derived from spectra recorded on eight flights. The average vertical column amount above 12 kilometers is 7.1 +/- 0.8 x 10(14) molecules per square centimeter, corresponding to an average mixing ratio of 170 parts per trillion by volume. 相似文献
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陈思亮 《信阳农业高等专科学校学报》2009,19(4):9-11
现阶段,我国存在大量的隐名出资现象,但《公司法》对其却没有任何规定。关于隐名出资人与显名股东的法律地位问题,理论及实务界并未形成共识。隐名出资的类型很多,对其纠纷的处理也不尽相同。问题的最终解决有赖于股权信托制度的建立。 相似文献