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791.
792.
Carol P. Harden Anne Chin Mary R. English Rong Fu Kathleen A. Galvin Andrea K. Gerlak Patricia F. McDowell Dylan E. McNamara Jeffrey M. Peterson N. LeRoy Poff Eugene A. Rosa William D. Solecki Ellen E. Wohl 《Environmental management》2014,53(1):4-13
This article summarizes the primary outcomes of an interdisciplinary workshop in 2010, sponsored by the U.S. National Science Foundation, focused on developing key questions and integrative themes for advancing the science of human–landscape systems. The workshop was a response to a grand challenge identified recently by the U.S. National Research Council (2010a)—“How will Earth’s surface evolve in the “Anthropocene?”—suggesting that new theories and methodological approaches are needed to tackle increasingly complex human–landscape interactions in the new era. A new science of human–landscape systems recognizes the interdependence of hydro-geomorphological, ecological, and human processes and functions. Advances within a range of disciplines spanning the physical, biological, and social sciences are therefore needed to contribute toward interdisciplinary research that lies at the heart of the science. Four integrative research themes were identified—thresholds/tipping points, time scales and time lags, spatial scales and boundaries, and feedback loops—serving as potential focal points around which theory can be built for human–landscape systems. Implementing the integrative themes requires that the research communities: (1) establish common metrics to describe and quantify human, biological, and geomorphological systems; (2) develop new ways to integrate diverse data and methods; and (3) focus on synthesis, generalization, and meta-analyses, as individual case studies continue to accumulate. Challenges to meeting these needs center on effective communication and collaboration across diverse disciplines spanning the natural and social scientific divide. Creating venues and mechanisms for sustained focused interdisciplinary collaborations, such as synthesis centers, becomes extraordinarily important for advancing the science. 相似文献
793.
794.
Fu Zhao William Z. Bernstein Gautam Naik Gary J. Cheng 《Journal of Cleaner Production》2010,18(13):1311-1319
Laser assisted manufacturing processes, when compared with traditional manufacturing processes, have the potential to reduce cost, increase surface resistance to wear and fatigue, extend part/tool life, and expand the range of manufacturable materials. These processes have found niche applications in automotive, aerospace, and defense industries. However, very limited research has been conducted to evaluate and compare the environmental performance of laser assisted processes with traditional methods. This paper conducts case studies on two representative laser based processes, i.e. laser shock peening of 7075-T7351 Aluminum and laser assisted turning of compacted graphite iron. Life cycle assessment is used to benchmark the environmental performance of these two processes to conventional processes, i.e. shot peening and turning, respectively. The life cycle inventory of both the laser based processes and conventional processes are developed using SimaPro 7.1 and the Ecoinvent 2.0 database and life cycle impact assessment is performed using US EPA TRACI. The results of this study show that the environmental performance of the two laser based processes is significantly better than conventional processes. For laser shock peening of aluminum, contribution analysis indicates that this is mainly due to the significant extension of fatigue life of the workpiece being treated. For laser assisted turning of compacted graphite iron, the improved performance is mainly due to the extended tool life since cutting tool manufacturing is an energy intensive process. Development of high-power laser with a lower wavelength (e.g. direct diode system) could eliminate the use of paint in laser assisted turning. This, along with improved wall plug efficiency, makes laser assisted turning even more environmentally benign compared to conventional process. A brief cost analysis suggests that both laser shock peening and laser assisted turning can be economically viable with payback period less than three years for niche applications. 相似文献
795.
796.
Litao Wang Carey Jang Yang Zhang Kai Wang Qiang Zhang David Streets Joshua Fu Yu Lei Jeremy Schreifels Kebin He Jiming Hao Yun-Fat Lam Jerry Lin Nicholas Meskhidze Scott Voorhees Dale Evarts Sharon Phillips 《Atmospheric environment (Oxford, England : 1994)》2010,44(28):3442-3448
Under the 11th Five Year Plan (FYP, 2006–2010) for national environmental protection by the Chinese government, the overarching goal for sulfur dioxide (SO2) controls is to achieve a total national emissions level of SO2 in 2010 10% lower than the level in 2005. A similar nitrogen oxides (NOx) emissions control plan is currently under development and could be enforced during the 12th FYP (2011–2015). In this study, the U.S. Environmental Protection Agency (U.S.EPA)’s Community Multi-Scale Air Quality (Models-3/CMAQ) modeling system was applied to assess the air quality improvement that would result from the targeted SO2 and NOx emission controls in China. Four emission scenarios — the base year 2005, the 2010 Business-As-Usual (BAU) scenario, the 2010 SO2 control scenario, and the 2010 NOx control scenario—were constructed and simulated to assess the air quality change from the national control plan. The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) was applied to generate the meteorological fields for the CMAQ simulations. In this Part I paper, the model performance for the simulated meteorology was evaluated against observations for the base case in terms of temperature, wind speed, wind direction, and precipitation. It is shown that MM5 model gives an overall good performance for these meteorological variables. The generated meteorological fields are acceptable for using in the CMAQ modeling. 相似文献
797.
Peter Harborth Roland Fuß Kai Münnich Heinz Flessa Klaus Fricke 《Waste management (New York, N.Y.)》2013,33(10):2099-2107
Mechanical biological treatment (MBT) is an effective technique, which removes organic carbon from municipal solid waste (MSW) prior to deposition. Thereby, methane (CH4) production in the landfill is strongly mitigated. However, direct measurements of greenhouse gas emissions from full-scale MBT landfills have not been conducted so far. Thus, CH4 and nitrous oxide (N2O) emissions from a German MBT landfill in operation as well as their concentrations in the landfill gas (LFG) were measured. High N2O emissions of 20–200 g CO2 eq. m?2 h?1 magnitude (up to 428 mg N m?2 h?1) were observed within 20 m of the working face. CH4 emissions were highest at the landfill zone located at a distance of 30–40 m from the working face, where they reached about 10 g CO2 eq. m?2 h?1. The MBT material in this area has been deposited several weeks earlier. Maximum LFG concentration for N2O was 24.000 ppmv in material below the emission hotspot. At a depth of 50 cm from the landfill surface a strong negative correlation between N2O and CH4 concentrations was observed. From this and from the distribution pattern of extractable ammonium, nitrite, and nitrate it has been concluded that strong N2O production is associated with nitrification activity and the occurrence of nitrite and nitrate, which is initiated by oxygen input during waste deposition. Therefore, CH4 mitigation measures, which often employ aeration, could result in a net increase of GHG emissions due to increased N2O emissions, especially at MBT landfills. 相似文献
798.
垂直流人工湿地水力学特点对污水净化效果的影响 总被引:56,自引:0,他引:56
通过在污水中加入示踪剂,研究了人工湿地的水力学特点及其对污水净化效果的影响规律.结果表明,影响水力学各特点的主要原因是湿地植物根系所造成的物理学和生物学上的效应.水力学各特点与污水净化效果之间存在着密切关系:出水快、出水量大的系统具有较好的净化效果;除无植物系统外,停留时间较长的系统有较好的净化效果;容水体积大的系统净化效果也较好;水力负荷则主要通过影响其他各水力学特点而影响净化效果.结果表明,对水力学特点的优化将极大地促进污水净化效果的提高. 相似文献
799.
中庭火灾烟流相似模型 总被引:3,自引:0,他引:3
将燃烧着的火焰视为具有一定发热量的热源、不计辐射传热的影响 ,建立中庭火灾烟气流动控制微分方程组 ,并导出模型实验相似准则 ;提出模型与原型局部相似的模型律 ;忽略围护结构热相似 ,建立 1/ 8模型试验台 ;开展中庭火灾烟流填充过程模型实验 ,模型实验与原型实验结果吻合。研究表明 :理论模型律是合理的 ,采用小比例的相似模型实验 ,研究中庭火灾烟流的发展是可行的 相似文献
800.
Urban Emergency Response System (UERS) is a modernization symbol of a city. With acceleration of urbanization process and constant expansion of city size in China, China cities must respond to various emergencies timely and effectively to satisfy urban residents’ needs for public security. In recent years, many China cities made trials and efforts in setting up and improving the UERS. At the same time, the China government began to build Emergency Response Systems (ERS) in some cities to deal with various possible emergencies. In this paper, using Petri net (PN), we study the performance of China typical UERS and establish its PN model for performance analysis. Based on the Markov chain (MC) of the model, the performance of China typical UERS is analyzed. Results from our simulation are in conformity with practical operation of China current UERS. 相似文献