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排序方式: 共有213条查询结果,搜索用时 15 毫秒
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One can say very little about the relative merits of temporary versus permanent salt marsh mosquito control from the Carlson and DeBord study (J. Environ. Econ. Manag. 3, 142–153 (1976)). Their conclusion that temporary control is more cost effective than permanent control is suspect because of their interpretation and use of the data which entered their analyses and because of their interpretation of analytical results. 相似文献
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B. Harms Georg Trier R. Pummerer P. Rohrbach Max Friederichsen 《Die Naturwissenschaften》1918,6(52):771-773
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Max Steenbeck 《Die Naturwissenschaften》1929,17(50):981-982
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Markus Stumm Michael Entezami Karsten Haug Cornelia Blank Max Wüstemann Bernt Schulze Gisela Raabe-Meyer Maja Hempel Markus Schelling Eva Ostermayer Sabine Langer-Freitag Tilo Burkhardt Roland Zimmermann Tina Schleicher Bernd Weil Ulrike Schöck Patricia Smerdka Sebastian Grömminger Yadhu Kumar Wera Hofmann 《黑龙江环境通报》2014,34(2):185-191
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Light duty vehicles, i.e. passenger cars and light trucks, account for approximately half of global transportation energy demand and, thus, a major share of carbon dioxide and other emissions from the transport sector. Energy consumption in the transport sector is expected to grow in the future, especially in developing countries. Cars with alternative powertrains to internal combustion engines (notably battery, hybrid and fuel-cell powertrains), in combination with potentially low carbon electricity or alternative fuels (notably hydrogen and methanol), can reduce energy demand by at least 50%, and carbon dioxide and regulated emissions much further. This article presents a comparative technical and economic assessment of promising future fuel/vehicle combinations. There are several promising technologies but no obvious winners. However, the electric drivetrain is a common denominator in the alternative powertrains and continued cost reductions are important for widespread deployment in future vehicles. Development paths from current fossil fuel based systems to future carbon-neutral supply systems appear to be flexible and a gradual phasing-in of new powertrains and carbon-neutral fluid fuels or electricity is technically possible. Technology development drivers and vehicle manufacturers are found mainly in industrialised countries, but developing countries represent a growing market and may have an increasingly important role in shaping the future. 相似文献
100.
Max Stocker 《Ecological modelling》1983,18(2):121-139
Optimal harvesting strategies for an ungulate population are estimated using stochastic dynamic programming. Data on the Llano Basin white-tailed deer (Odocoileus virginianus) population were used to construct a 2-variable population dynamics model. The model provided the basis for estimating optimal harvesting strategies as a feedback function of the current values of the state variables (prefawning older deer and juveniles). Optimal harvest strategies were insensitive to assumptions about the probability distributions of the stochastic variable (rainfall). The response of the population components to harvesting and the returns obtained from applying optimal strategies were explored through simulation. Mean annual harvest is about 15% of the population. Simplified harvesting strategies based on age-ratios as well as a simplified version based on optimal strategies—but assuming persisting equilibrium juvenile deer density—were compared to optimal strategies through examining values of information. Simplified harvesting strategies lead to a lower harvest over a 50-year simulation period. 相似文献