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The recycling of scrap material has been identified as an important strategy in the larger theory of industrial ecology. Industrial ecology argues that the traditional model of industrial activity needs to be transformed into a 'closed loop' industrial ecosystem where used materials (scrap) and by-products would substitute for virgin materials during production processes. The recycling of scrap material forms part of this larger effort to reduce the overall environmental impact of production and consumption. A key, but as yet, unresolved question in this process is the geographic scale (local, regional, national, global) at which loop closing should take place. This preliminary empirical research examines the export and import geography of the seven largest (by weight) US scrap commodities (iron and steel, paper, plastics, aluminium, copper, nickel and zinc) between 1995 and 2005 to ascertain the extent to which US scrap flows overseas and how that might affect our understanding of how material loops can close. Other than an integrated export and import relationship with Canada, the results suggest that there are two distinct circuits of scrap flows in the USA. The USA exports a substantial portion of the recyclable scrap generated each year to rapidly developing countries, while importing smaller quantities of scrap from the EU. With the major exception of exporting higher value iron and steel scrap to China, the US tends to export lower value scrap and import higher value scrap. In part this reflects imbalances in the supply and demand for scrap between the USA and the developing world, the lack of potentially available scrap and the absence of a robust recycling infrastructure in the developing world. Although such scrap circuits are probably not ideal, the use of US scrap in the developing world is both a realistic and preferable alternative in the short to medium term than virgin production. 相似文献
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Marina G. Persova Yuri G. Soloveichik Georgy M. Trigubovich Denis V. Vagin Petr A. Domnikov 《Geophysical Prospecting》2014,62(5):1193-1201
A large closed wire loop is generally used in field experiments for testing airborne electrical exploration equipment. Thus, methods are required for the precise calculation of an electromagnetic response in the presence of a closed wire loop. We develop a fast and precise scheme for calculating the transient response for such a closed loop laid out at the surface of a horizontally layered conductive ground. Our scheme is based on the relationship between the magnetic flux flowing through a closed loop and the current induced in it. The developed scheme is compared with 2D and 3D finite‐element modelling for several positions of an airborne electromagnetic system flying over a closed loop. We also study the coupling effect between the current flowing in the closed loop and the current flowing in the horizontally layered conductive medium. The result shows that for the central position of the transmitter, the difference between axisymmetrical finite‐element modelling and our scheme is less than 1%. Moreover, for the non‐coaxial transmitter–receiver–loop system, the solution obtained by our scheme is in good agreement with full 3D finite‐element modelling, and our total simulation time is substantially lower: 1 minute versus 120 hours. 相似文献
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基于Matlab的控制网平差教学软件与应用 总被引:3,自引:0,他引:3
介绍了基于Matlab的控制网平差软件的功能和特点,并将该软件应用到《控制网平差程序设计》课程的教学过程以及实际工程的数据处理中,取得了良好的效果。 相似文献
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根据反馈地震计的反馈模型推导传递函数,并将其频率特征分解为低频端和高频端两部分。基于反馈模型中低频端频率特性的二阶高通滤波器传递函数,提出低频截止频率扩展的方法,包括降低机械固有角频率ω0、增加摆的质量m、降低灵敏度Sv、增大反馈线圈阻值或减少线径、选用更高电阻率的线圈材料、使用更弱的磁场。通过井下反馈地震计实验,验证了其低频端扩展与理论推导的一致性。 相似文献
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鸳鸯湖矿区位于宁夏回族自治区宁东煤田,该次GPS作业利用3个三等三角点作为起算数据,2个四等三角点作为检核数据,进行网平差及高程拟合。外业数据质量检验结果表明其重复基线及同、异步环闭合差均小于限差,符合规范要求。内业数据处理采用广播星历网基线处理,无约束平差、约束平差基线分量改正绝对值均小于限差值。6个水准点的网平差高程拟合结果证实GPS高程精度优于三角高程。测量成果经宁夏测绘产品质量监督检查站检查,成果精度达到《全球定位系统(GPS)测量规范》(GB/T18314-2001)的有关精度要求。说明鸳鸯湖矿区清水营井田GPS控制网的成果可靠。 相似文献
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IntroductionFBS-3A feedback broadband seismometer is a sensor suitable for digital telemetered seismic network observation, which was developed in a key project among the (Eighth Five-Year Plan( to meet the demand for the development of earthquake and premonitor digital observation experiment system (ZHAO, et al, 1997; ZHUANG, 1995).FBS-3A is quite different from conventional mechanical seismometers because electronic feedback technology is applied to it, as a result the measurement ba… 相似文献
260.
被广泛采用的等价线性黏弹性模型不寻求土体动应力-应变的具体表达式,无法给出能量耗散函数,为深入研究筑坝土石料动力变形机制带来不便。变参数Ramberg-Osgood模型(简称R-O模型)通过变动两个参数以适应土体动模量衰减和阻尼增长,并给出滞回圈的数学表达式。研究中讨论了变参数R-O模型的适应范围,发现该模型不适合描述土体的小应变动力特性,给出了筑坝土石料变参数表达式,绘制了与试验曲线相协调的应力应变滞回圈。可以看出变参数R-O模型能够较好地描述筑坝土石料的动力特性,为进一步研究筑坝土石料的动力耗散与变形机制奠定了基础。 相似文献