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Ecosystem effects of fishing in kelp forest communities 总被引:6,自引:0,他引:6
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九龙江流域水葫芦打捞去除水体营养盐模型研究 总被引:1,自引:0,他引:1
水葫芦被收获时,水体中的营养盐也将包含在植物组织中而被去除.本研究首先通过野外实验和参考国内外有关文献,建立了九龙江流域水葫芦生长数学模型和持续生产模型,确定了模型的各有关参数:水葫芦生长容量K值为25.6 kg/m2、最大生长速率rmax为0.12d-1;水体中氮和磷的半饱和系数hN和hP值分别为0.2和0.03;水葫芦最低生长温度(mθin)为7℃,最适水温(oθpt)为30℃,最高生长温度(θmax)为40℃.随后采用所建立的模型计算了研究区水葫芦打捞的营养盐去除效果,研究区面积6 000m2的水体实施水葫芦打捞策略后,1a所能收获的水葫芦最大产量为9.18×105kg,去除的TP为214.4kg,TN为966.6kg. 相似文献
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The working group Mathematical Geology of the Freie Universität Berlin was formed in 1971. We review quantitative methods used by the working group since 1983 to treat mineral exploration problems. The methods applied vary from elementary statistical analysis of multivariate exploration data to optimal strategies for selecting favorable targets, and from multiobjective decision-making for additional drill hole locations to expert systems in exploration.The methods applied are directly related to the level of information at each stage of the exploration process. Special emphasis was placed on the relationship between and evaluation of subjective and objective data. Case studies illustrating the various methods are presented for different kinds of mineral deposits and exploration environments. 相似文献
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对2001~2002年度玉林荔枝生产周期的农业气象条件进行诊断分析,得出2002年获得大丰收的主要原因是,秋梢抽生期雨水正常,秋梢抽生既及时又健壮;冬季在寒冷和干旱的双重作用下,花芽发育比较完全;春季气候温暖,雨量适中,雨日偏少,风和日丽,非常有利于荔枝的孕蕾和开花授粉;幼果期和膨大期气象条件也很正常。 相似文献
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The paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of buildings based on the use of shape memory alloys (SMA) in place of conventional steel or rubber devices. To get some generality in the results, different resisting reinforced concrete plane frames were analysed, either protected or not. ‘New’ and ‘existing’ buildings were considered depending on whether seismic provisions are adopted in the building design or not. Base isolation and energy dissipation were equally addressed for both conventional and innovative SMA‐based devices. Fragility analyses were performed using specific damage measures to account for comparisons among different damage types; the results were then used to estimate quantitatively the effectiveness of the various protection systems. More specifically, the assessment involved a direct comparison of the damage reduction provided by each protection system with respect to the severe degradation experienced by the corresponding non‐protected frame. Structural damage, non‐structural damage and damage to contents were used on purpose and included in a subsequent phase of cost analysis to evaluate the expected gains also in terms of economic benefits and life loss prevention. The results indicate that base isolation, when applicable, provides higher degrees of safety than energy dissipation does; moreover, the use of SMA‐based devices generally brings about better performances, also in consideration of the reduced functional and maintenance requirements. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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In this paper, the results of a survey conducted in the Cukurova region of Turkey are presented. The aim of this research is to identify groups of farmers who differ in their risk sources and risk management strategies. The respondents to the survey were divided into three risk attitude groups, risk averse, risk seeking and risk neutral. Factor analysis has been conducted on information obtained from 112 farmers in 2000. From the findings of the research, risk sources were labelled as environmental, price, catastrophe, input costs, production and technological, political, finance, personal, marketing, health and social security. The dimensions of risk strategies were named as diversification, off-farm income, marketing, planning, financing and security. 相似文献
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阐述了非开挖技术在上海的发展轨迹、应用现状和战略思考,并以翔实和权威的资料论证了有关论点,对全国非开挖技术发展有关情况也有概括性的介绍 相似文献