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491.
城市机动车尾气污染控制的综合对策体系研究 总被引:3,自引:0,他引:3
在综述城市机动车尾气污染的已有对策基础上,阐述了包括规划层次、管理层次、工程层次和车辆层次在内的综合对策体系,并就国内不同阶段所侧重的对策层次进行了探讨。 相似文献
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A three‐dimensional hydrodynamic model was applied to Lake Paldang, South Korea. The lake has three inflows, of which Kyoungan Stream has the smallest flow rate and poorest water quality. Since all drinking water intake stations are located near the confluence of Kyoungan Stream within the lake, this contaminated tributary may have a significant impact on the quality of drinking water sources. The optimum drinking water intake location was determined from the applied model. The model was calibrated and verified using the data measured under different hydrological conditions. The model results were in reasonable agreement with the field measurements in both calibration and verification. The circulation and spreading patterns of the incoming flows in the lake, as well as their composition ratios to the drinking water intakes were determined from the model, and three alternative intake locations were proposed. The simulation results suggested that the horizontal and vertical relocations of the intake aqueduct could significantly decrease the composition ratio of the contaminated water. From this study, it was concluded that the three‐dimensional hydrodynamic model could successfully simulate the temporal and spatial mixing patterns of incoming flows and become a useful tool in determining the optimum water intake location in Lake Paldang. 相似文献
493.
A. Alexiou P. Kostarakis V. N. Christofilakis T. Zervos A. A. Alexandridis K. Dangakis C. Soras V. V. Petrović B. M. Kolundžija A. R. Dordević 《The Environmentalist》2005,25(2-4):215-221
Summary The performance of a cellular phone commercial helical antenna at 900~MHz band, both in free space and in the presence of
a human head phantom was studied. Numerical simulation of the phone model for the latter case has been performed giving 3D
radiation diagrams. The effect of the phantom head on radiation diagrams is presented. The relative amount of the EM power
absorbed in the head was obtained for several distances of the phone. Measurements were carried out in a RF anechoic chamber
using standard horn antennas and a calibrated measuring system. Absolute radiation patterns of the antenna gain were obtained
in the three principal planes. Significant reduction of the absorbed power could be achieved just by moving the phone 1 cm
away from the head. 相似文献
494.
Modeling the Influence of Dynamic Zoning of Forest Harvesting on Ecological Succession in a Northern Hardwoods Landscape 总被引:2,自引:0,他引:2
Dynamic zoning (systematic alteration in the spatial and temporal allocation of even-aged forest management practices) has been proposed as a means to change the spatial pattern of timber harvest across a landscape to maximize forest interior habitat while holding timber harvest levels constant. Simulation studies have established that dynamic zoning strategies produce larger tracts of interior, closed canopy forest, thus increasing the value of these landscapes for interior-dependent wildlife. We used the simulation model LANDIS to examine how the implementation of a dynamic zoning strategy would change trajectories of ecological succession in the Great Divide Ranger District of the Chequamegon–Nicolet National Forest in northern Wisconsin over 500 years. The components of dynamic zoning strategies (number of zones in a scenario and the length of the hiatus between successive entries into zones) and their interaction had highly significant impacts on patterns of forest succession. Dynamic zoning scenarios with more zones and shorter hiatus lengths increased the average amount of the forest dominated by early successional aspen (Populus sp.). Dynamic zoning scenarios with two zones produced more late successional mature northern hardwoods than scenarios with four zones. Dynamic zoning scenarios with very short (30 years) or very long (120 years) hiatus lengths resulted in more late successional mature northern hardwoods than scenarios with intermediate hiatus lengths (60 and 90 years). However, none of the dynamic scenarios produced as much late successional mature northern hardwoods as the static alternative. Furthermore, the amounts of all habitat types in all dynamic zoning scenarios fluctuated greatly in time and space relative to static alternatives, which could negatively impact wildlife species that require a stable amount of habitat above some minimum critical threshold. Indeed, implementing dynamic zoning scenarios of different designs would have both positive and negative effects on wildlife species and for other objectives of forest management. 相似文献
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高艳玲 《中国环境管理干部学院学报》2003,13(3):30-32
生态城市是可持续发展理念在城市建设过程中的具体体现,是一个全新的概念。本文首先介绍了生态城市的定义、特点和生态城市的主要建设模式,从而提出了建设生态城市的对策。 相似文献
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从安全生产管理体制到安全生产运行机制 总被引:7,自引:4,他引:7
“企业负责 ,行业管理 ,国家监察 ,群众监督”的安全生产宏观管理体制的确定 ,对我国安全生产工作起到了积极的促进作用。但是 ,随着我国改革开放的不断深入和市场经济体制的建立 ,该管理体制的概念和内容已不能适应当前形势发展的需要。为此 ,笔者建议使用“安全生产运行机制”的概念代替“安全生产管理体制”的概念 ,并提出我国应该建立和完善“国家监督 ,部门负责 ,企业自律 ,职工维权 ,中介服务”的安全生产运行新机制。 相似文献