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381.
This paper focuses on the diversity of engine technologies for low emission vehicles (LEVs) that are developed by car manufacturers in order to substitute for the conventional internal combustion engine vehicle (ICEV). Our purpose is to analyse the competition between the various technologies for LEVs as well as the innovative strategy of car manufacturers. We first propose to define and to represent these technological trajectories in order to compare their performances and to identify their strengths and weaknesses. The technological bottlenecks, the barriers to the adoption of these alternative engine technologies as well as the features of this technological competition are underlined. We then use a patent data analysis to study the patent portfolios of the main car manufacturers in these technologies over the period [1990–2005]. The dynamics of patent applications by car manufacturers gives insight on the competition among technologies and on the strategy of firms. This analysis emphasises the progressive diversification of firms' patent portfolios over the whole set of engine technologies and the differentiated strategic positioning of car manufacturers according to countries. 相似文献
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南京市处于长江流域下游,是我国重要的农业生产基地,也是全国经济发达地区之一。它既有近郊的蔬菜生产,又有远郊的粮食作物种植,农田生态类型与农、牧、副的复合生态类型多种多样,而且其生产潜力很大。本文对南京市郊生态系统的建设进行分析研究,并着重探讨生态系统建设模式及土地合理利用,为建立合理的南京市郊区农业生态系统提供依据。 相似文献
385.
当前“低碳经济”、“低碳生活”等理念在众多媒介有大量的表述和宣传报道。但抽样调查显示,实际上广大公众对于“低碳”的认知却颇有一些不甚清晰明了。概念的模糊性及不确定性,势必影响并阻碍我们积极倡导和实践推进生态文明建设,努力实现清洁发展、安全发展、绿色发展及可持续发展。 相似文献
386.
矿物包裹体研究表明,武义萤石矿床是含矿地热水活动的产物。其形成温度为130°±27℃,压力为47.23-426.96×10~5帕。属于低温浅成热液矿床。冷渗流大气降水在深处受地热影响加热活化,发生水—岩化学反应和物质交换,导致含矿地热水的形成。它在构造作用和热力及压力梯度驱动下回返上升,于地表—近地表裂隙带与大气降水混合,温压骤降,加以冷的含CO_2和O_2的大气降水界入,使成矿物质自溶液中沉淀析出。 相似文献
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Xi Yang Ping Xie Yunzhen Yu Hong Shen Xuwei Deng Zhimei Ma Peili Wang Min Tao Yuan Niu 《环境科学学报(英文版)》2015
We conducted an experiment to study the interaction effects of Microcystis aeruginosa and Pseudomonas pseudoalcaligenes on off-flavors in an algae/bacteria co-culture system at three temperatures (24, 28 and 32°C). Gas chromatography–mass spectrometry was applied to measure off-flavor compounds dimethyl sulfide (DMS), dimethyl trisulfide (DMTS), 2-methylisoborneol, geosmin (GEO) and β-cyclocitral. During the lag phase of co-cultured M. aeruginosa (first 15 days), P. pseudoalcaligenes significantly increased the production of DMS, DMTS and β-cyclocitral at all three temperatures. In the exponential phase of co-cultured M. aeruginosa (after 15 days), M. aeruginosa became the main factor on off-flavors in the co-culture system, and β-cyclocitral turned to the highest off-flavor compound. These results also indicated that DMS, DMTS and β-cyclocitral were the main off-flavor compounds in our M. aeruginosa/P. pseudoalcaligenes co-culture system. Univariate analysis was applied to investigate the effects of M. aeruginosa and P. pseudoalcaligenes on the production of off-flavors. The results demonstrated that both M. aeruginosa and P. pseudoalcaligenes could increase the production of DMS and DMTS, while β-cyclocitral was mainly determined by M. aeruginosa. Our results also provide some insights into understanding the relationship between cyanobacteria and heterotrophic bacteria. 相似文献
389.
An activation process for developing the surface and porous structure of palygorskite/carbon(PG/C) nanocomposite using ZnC l2 as activating agent was investigated. The obtained activated PG/C was characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy(FTIR), field-emission scanning electron microscopy(SEM), and Brunauer–Emmett–Teller analysis(BET) techniques. The effects of activation conditions were examined,including activation temperature and impregnation ratio. With increased temperature and impregnation ratio, the collapse of the palygorskite crystal structure was found to accelerate and the carbon coated on the surface underwent further carbonization. XRD and SEM data confirmed that the palygorskite structure was destroyed and the carbon structure was developed during activation. The presence of the characteristic absorption peaks of C_C and C–H vibrations in the FTIR spectra suggested the occurrence of aromatization. The BET surface area improved by more than 11-fold(1201 m2/g for activated PG/C vs. 106 m2/g for PG/C) after activation, and the material appeared to be mainly microporous. The maximum adsorption capacity of methylene blue onto the activated PG/C reached 351 mg/g. The activated PG/C demonstrated better compressive strength than activated carbon without palygorskite clay. 相似文献
390.
Hongli Wang Qian Wang Jianmin Chen Changhong Chen Cheng Huang Liping Qiao Shengrong Lou Jun Lu 《环境科学学报(英文版)》2015,(1):290-297
The characteristic ratios of volatile organic compounds(VOCs) to i-pentane, the indicator of vehicular emissions, were employed to apportion the vehicular and non-vehicular contributions to reactive species in urban Shanghai. Two kinds of tunnel experiments, one tunnel with more than 90% light duty gasoline vehicles and the other with more than 60% light duty diesel vehicles, were carried out to study the characteristic ratios of vehicle-related emissions from December 2009 to January 2010. Based on the experiments, the characteristic ratios of C6–C8aromatics to i-pentane of vehicular emissions were 0.53 ± 0.08(benzene), 0.70 ± 0.12(toluene),0.41 ± 0.09(m,p-xylenes), 0.16 ± 0.04(o-xylene), 0.023 ± 0.011(styrene), and 0.15 ± 0.02(ethylbenzene), respectively. The source apportionment results showed that around 23.3% of C6–C8 aromatics in urban Shanghai were from vehicular emissions, which meant that the non-vehicular emissions had more importance. These findings suggested that emission control of non-vehicular sources, i.e. industrial emissions, should also receive attention in addition to the control of vehicle-related emissions in Shanghai. The chemical removal of VOCs during the transport from emissions to the receptor site had a large impact on the apportionment results. Generally, the overestimation of vehicular contributions would occur when the VOC reaction rate constant with OH radicals(k OH) was larger than that of the vehicular indicator, while for species with smaller k OH than the vehicular indicator, the vehicular contribution would be underestimated by the method of characteristic ratios. 相似文献