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41.
云南省水环境状况及问题分析 总被引:2,自引:0,他引:2
根据2000年云南省主要河流水质监测评价结果,全省评价河段总长9280km中,水质为Ⅰ-Ⅲ类的河长占76.3%,总体上,云南省内各大水系水质良好,但水污染总体上正在加重,从1985-2000年,Ⅰ类河长年均减少2.3%,V类河长年均增长0.6%,废污水直接排入江河是引起污染的重要原因。水环境问题已成为社会经济可持续发展的关键问题,要切实加强水资源的保护,科学地开发利用水土资源,为了有效地改善水环境的质量,污染控制应从源头开始并采取综合治理措施。 相似文献
42.
Critical to restoring the nature conservation value of many river corridors is an understanding of how alluvial landscapes will respond to cessation of river management and land use practices that have previously degraded the environment. This paper analyses changes in valley floor landforms and vegetation patch dynamics, in relation to fluvial disturbance, over a period of almost 100 years following flood embankment abandonment on a wandering gravel‐bed river, namely the River Tummel, Scotland. Such rivers were once typical of many draining upland areas of northern maritime Europe. Prior to abandonment the valley floor landscape was agriculturally dominated and the river for the most part was single thread confined between flood embankments. The pattern of landform change and vegetation patch development over time following a decision in 1903 not to maintain embankments was tracked by geomorphic and land cover mapping utilizing successive sets of aerial photography for the period 1946 to 1994. A historical context for these changes was also feasible because the channel planform in 1900 and earlier channel planform changes dating back to 1753 were known due to the availability of old maps and earlier geomorphic studies. The land cover mapping was validated by comparison of results produced from the interpretation work on the 1994 aerial photographs with the field‐based UK National Vegetation Classification protocol. The findings of the study illustrate that bordering the River Tummel fluvial landforms and vegetation patch mosaics, presumably resembling those that occurred before valley floor land use intensification, evolved in less than 50 years after flood embankment abandonment with a resultant increase in habitat diversity. The change relates primarily to flood‐induced channel planform change and moderate levels of fluvial disturbance. The general significance of this change to plant species diversity on the valley floor of the River Tummel and elsewhere is discussed as is possible implications of the upstream impoundment and scenarios for climatically induced changes in flood frequency and magnitude. The overall outcome is the strong possibility that simple changes in river management and land use practices could result in re‐establishment of the nature conservation value of similar river corridors in Europe over the medium term without active restoration efforts. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
43.
相变换热技术在供暖系统中的开发前景 总被引:3,自引:0,他引:3
介绍相变换热原理、相变暖气片特点以及相变取暖系统的经济性,预示相变换热技术在取暧系统的开发前景。 相似文献
44.
黑河干流中游地区耗水量变化的历史分析 总被引:3,自引:0,他引:3
黑河流域水资源极其匮乏,加之地区上的配置不均衡和中游地区水土资源的过度开发,导致黑河下游出现了严重的生态环境问题,已影响到我国北方广大地区生态环境质量,受到国家的高度重视和全社会的广泛关注。黑河水资源开发利用主要集中在中游地区,该区是全国重要的商品粮、蔬菜和经济作物生产基地之一,耗水量占流域耗水量的85%以上,是黑河的主要耗水区和径流利用区。利用黑河上游控制站莺落峡站和中游控制站正义峡站水文资料,分析了黑河中游耗水量的变化,结果表明:20世纪80年代以前黑河中游耗水量在4.4亿m^3左右,比较稳定;进入20世纪80年代以后,耗水量明显增加,80年代耗水量比70年代以前增加了1.97亿-2.49亿m^3;90年代耗水量又比80年代增加了1.64亿m^3左右;80年代以来流域耗水量呈明显增加的趋势,这是以人类活动影响为主的结果。 相似文献
45.
处在构造边部、低部位的商5-5井,在改注水井排液中发现不含水的高产这种非常规现象,由此引起对地质因素的分析。浅湖相沉积的主体是滩砂微相,它可细分为“滩脊”和“滩侧”,其中“滩脊”砂体的泥质含量低,孔隙度、渗透率都较高,而“滩侧”则泥质含量高,物性差。在从“滩脊”砂体向“滩侧”过渡时,极易形成类似于砂体尖灭的岩性封堵,造成剩余油富集,而“滩脊”不一定就在构造的高部位。陆相沉积的砂体非均质性很强,孔隙度和渗透率在横向上的变化很大,高部位的油层水淹,低部位的油层不一定就高含水,这是因为砂体横向上的非均质性,使同一时间单元沉积的砂体很可能不连通。基于这些分析,地质工作者不妨运用沉积微相的原理在构造的低部位或边部寻找剩余油富集区,商5-5井的现实给了我们很好的启示。 相似文献
46.
This article compares the role of policy instruments in stimulating long-term technological change in Danish and Norwegian wind industry. It concludes that although predictability has periodically been low, Denmark's broad portfolio of policies and measures has been well adapted to the different stages in the development of its wind industry. This has contributed to a high degree of innovation, successful establishment in niche markets, high degree of diffusion and establishment of domestic and international mass markets, and—in recent years—an increasingly successful replacement of senescent technology with new. The motivation of Norway's wind energy policies and measures—at least up until the late 1990s—has been to increase power supply rather than to stimulate industrial development and technological change. Policies and measures have been weaker than in Denmark; have been less stable over time; and stimulated the demand side much less. They have not sufficiently covered the wind industry's perceived needs on different stages in the development of new technology, and have not sufficiently stimulated continuous improvement, learning and new product development (dynamic efficiency) in industry. This has been part of the reason why there has been only a limited extent of innovation and diffusion of wind technology in Norway. 相似文献
47.
A series of polyurethane microcapsules containing a phase change material (PCM) of n‐octadecane was successfully synthesized by an interfacial polymerization in aqueous styrene‐maleic anhydride (SMA) dispersion with diethylene triamine (DETA) as a chain extender reacting with toluene‐2,4‐diisocyanate (TDI). The average diameter of microPCMs is in the range of 5–10 μm under the stirring speed of 3000–4000 rpm. Optical and SEM morphologies of microPCMs had ensured that the shell was regularly fabricated with the influence of SMA. FTIR results confirmed that the shell material was polyurethane and the SMA chains associated on core material reacted with TDI forming a part of shell material. The shell thickness was decreasing in the range of 0.31–0.55 μm with the molar ratio of DETA/TDI from 0.84 to 1.35 and the weight of core material increasing from 40 to 80% (wt %). By controlling the weight ratio of PCM as 40, 50, 60, 70, and 80% in microPCMs, it was found using DSC that the Tm and Tc of microPCMs were in the range of 29.8–31.0oC and 21.1–22.0°C and an obvious phase change had been achieved nearly the same temperature range of that of PCM. The results from release curves of microPCM samples prepared by 1.4, 1.7, and 2.0 g of SMA indicated the release properties were affected by the amount of the dispersant, which attributed to the emulsion effect and shell polymerization structure. The above results suggest that the shell structure of microPCMs can be controlled and the properties of microPCMs determined by shell will perform proper practical usage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4996–5006, 2006 相似文献
48.
X. Liang X. Wang J. Zhuang Y. Chen D. Wang Y. Li 《Advanced functional materials》2006,16(14):1805-1813
Uniform magnetite, hematite, and goethite nanocrystals were prepared through an attractive method based on an oleic acid/alcohol/water system. By adjusting the synthetic parameters (base concentration, alcohol content, categories of alcohols, etc.), the controlled synthesis of uniform magnetite, hematite, and goethite nanocrystals can be easily achieved. Detailed investigations on the effect of the experimental parameters on the morphology of the final products and the phase transitions among the magnetite, hematite, and goethite phases were carried out. Finally, a method of doping other metal ions into magnetite was developed and the magnetic properties of magnetite doped with different metal elements were studied. 相似文献
49.
D. Twigger M. Byard S. Draper R. Driver R. Hartley S. Hennessy C. Mallen R. Mohamed‡ C. O'Malley§ T. O'Shea‡ E. Scanlon‡ 《Journal of Computer Assisted Learning》1991,7(2):144-155
Abstract This paper outlines the work of the Conceptual Change in Science project, funded as part of the ESRC InTER programme. The aims of this research project are to clarify and describe the process of change in learners' conceptual understandings of natural phenomena. The domain of reasoning selected for study is that of mechanics. Computer software which may be useful in exploring and developing pupils' reasoning and promoting conceptual change in this domain is being developed and evaluated. The group that is carrying out the research is based at the Universities of Leeds, Glasgow and the Open University. 相似文献
50.