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1.
汪槱生 《变流技术与电力牵引》2006,(2):1-3
从技术改造、循环经济、防污治污、政策支持、综合利用、可再生能源等方面推进能源资源节约,这既是缓解能源资源供求矛盾的重大举措,也是从源头上减少污染、改善生态环境的重要途径. 相似文献
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针对强风区铁路风沙流灾害防治工程,开展最大输沙量和强风携沙风荷载2个最关键工程计算问题的研究。结合现场踏勘资料与测试数据,分析风向、风力和持续时间3个影响因素对最大输沙量矢量合成与计算的控制影响,基于优势强风流理论,归纳给出信风型、季风型和对流型3种典型工程风型的输沙量计算方法,并且为准确采集沙样数据,专门设计出能随主风向自动转动的野外自动风导向积沙仪。基于现场测试数据,根据相似准则与量纲和谐原理,推导强风区携沙风单位体积沙砾颗粒流体平均飞跃速度计算公式,用于强风区携沙风冲击荷载计算,计算结果符合工程实际,满足工程计算要求。 相似文献
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秦志高 《南通航运职业技术学院学报》2007,6(4):77-80
文章通过对船舶运输过程中石油污染来源的分析,结合行业特点,阐述了针对油污染的预防措施,同时从航运业角度提出了含油废水的处理和船舶溢油的处理方法。 相似文献
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通过对伊朗城市轨道交通工程市场的分析和评估,结合中伊两国经贸合作发展和我国企业的优势,提出对伊朗城市轨道交通工程的市场开拓策略。 相似文献
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研究共享自动驾驶汽车(SAV)与普通汽车共存背景下,SAV公司如何根据运营目标优化经营策略并影响通勤者出行方式选择. 假设高速公路上存在一定数量的独驾通勤者,无车通勤者在SAV和地铁之间进行权衡. 分析固定需求和弹性需求下,SAV公司追求系统总成本最小或系统净收益最大和利润最大时的最优经营策略,即SAV票价和容量,进而得到均衡时模式划分情况,SAV最优发车数,系统总成本或系统净收益,以及公司利润等指标. 算例对均衡结果进一步验证发现,SAV公司垄断经营会收取较高的票价,提供容量较小的车型. 在系统最优情形下,SAV公司无法获得正利润,需要政府补贴运营. 相似文献
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随着大连机动车保有量快速增长,城区规模不断扩大,主城区内停车问题逐渐凸显,且呈现出区域差别化的特点.在总结其他城市经验的基础上,结合大连城市发展现状及规划,划定停车分区,提出各分区停车设施供给策略,为大连城市未来停车系统的发展提供参考. 相似文献
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C.A. Bost C. Cott F. Bailleul Y. Cherel J.B. Charrassin C. Guinet D.G. Ainley H. Weimerskirch 《Journal of Marine Systems》2009,78(3):363
During the last 30 years, at-sea studies of seabirds and marine mammals in the oceans south of the Subtropical Front have described an association with major frontal areas. More recently, the advancement in microtechnology has allowed the tracking of individuals and investigations into how these marine predators actually use the frontal zones. In this review, we examine 1) the relative importance to apex predators of the different frontal zones in terms of spatial distribution and carbon flux; 2) the processes that determine their preferential use; and 3) how the mesoscale dynamics of frontal structures drive at-sea foraging strategies of these predators. We review published results from southern waters and place them in a broader context with respect to what has been learned about the importance of fronts in oceans farther north.Some fronts constitute important boundaries for seabird communities in southern waters. At a mesoscale the maximum values of seabird diversity and abundance correspond to the location of the main fronts. At-sea surveys show a strong curvilinear correlation between seabird abundance and sea surface temperatures. High mean species richness and diversity for whales and seabirds are consistently associated with the southern water mass boundary of the Antarctic Circumpolar Current, the Subtropical Front and the Subantarctic Front; in the case of the Polar Front mean seabird densities are more variable. At small-scales, variation in seabird occurrence has been directly related to the processes at fronts in a limited number of cases. A significant positive relation was found between some plankton feeding species and frontal temperature gradient–phytoplankton variables.Telemetric studies have revealed that several apex predators (penguins, albatrosses, seals) perform long, directed foraging trips either to the Subtropical front or Polar Front, depending on locality. Seabirds with low flight costs, such as albatrosses, are able to reach fronts at long distances from colonies, showing variable foraging strategies as a function of the distances involved. Diving birds such as King penguins, that travel at a higher cost and lower speed, rely on the predictable spatial distribution of mesopelagic fish found close to the Polar Front. They may use the currents associated with eddies as oceanographic cues in the active search for frontal zones. Once in these areas they dive preferentially in and below the depth of the thermocline where catches per unit effort are high. Elephant seals concentrate foraging activity principally inside or at the boundary of cyclonic eddies. These mesoscale features appear to offer exceptional productivity favourable for foraging by various diving top predators.The connection between biophysical parameters at fronts and predators is likely to be made through biological enhancement. Top predators appear to forage at locations where prey are advected by physical processes and others where prey are produced locally. Long-term research on at-sea distributions and demographic parameters of top predators are essential to assess the consequences of potential shift in front distributions in relation to global warming. Such environmental changes would add to the impact of fish extraction by the industrial fisheries on the southern food webs. 相似文献