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Changes in the shelf macrobenthic community over large temporal and spatial scales in the Bohai Sea, China 总被引:11,自引:0,他引:11
Over the past 20 years, the Bohai Sea has been subjected to a considerable human impact through over-fishing and pollution. Together with the influence of the Yellow River cut-off, the ecosystem experienced a dramatic change. In order to integrate available information to detect any change in macrobenthic community structure and diversity over space and time, data collected during the 1980s and the 1990s from 3 regions of the Bohai Sea (Laizhou Bay, 16 stations, 37–38°N, 119–120.5°E; central Bohai Sea, 25 stations, 38–39°N, 119–121°E; eastern Bohai Bay, 12 stations, 38–39°N, 118.5–119°E) were reanalyzed in a comparative way by means of a variety of statistical techniques. A considerable change in community structure between the 1980s and the 1990s and over the geographical regions at both the species and family level were revealed. After 10 years, there was a considerable increase in abundance of small polychaetes, bivalves and crustaceans but decreased number of echinoderms. Once abundant in Laizhou Bay in the 1980s, a large echinoderm Echinocardium cordatum and a small mussel Musculista senhousia almost disappeared from the surveying area in the 1990s. Coupled with the increased abundance was the increased species richness in general whereas evenness was getting lower in central Bohai Sea and Bohai Bay but increased in Laizhou Bay. K-dominance plot showed the same trend as evenness J′. After 10 years, the macrobenthic diversity in the Bohai Sea as a whole was slightly reduced and a diversity ranking of central Bohai Sea > Laizhou Bay > eastern Bohai Bay over space was also suggested. Sediment granulometry and organic content were the two major agents behind the observed changes. 相似文献
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简要介绍E-2100高级隔热阻尼胶的性能和施工工艺,重点介绍其与聚氨酯发泡作为客车隔热减振材料时的性能对比。 相似文献
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安全电子邮件系统的设计与分析 总被引:5,自引:0,他引:5
分析当前电子邮件在安全方面的隐患,设计一种既能实现端到端的电子邮件安全通信又能在传输层建立安全隧道的电子邮件系统,详细介绍了安全电子邮件系统基于PKI体系实现加密、数字签名、身份认证等部分的设计思路。最后对此系统的安全性加以分析,并与PGP及反垃圾邮件系统进行比较。 相似文献
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在介绍国际上几种典型的产学研结合培养模式基础上,针对我国高等职业技术教学产学研结合的现状,指出了产学研结合中的不足。在此基础上提出了“项目驱动式”培养模式,为产学研结合提供了一条新的路子。同时介绍了在产学研结合具体实施过程中涉及到的“项目驱动式”培养模式的几个关键问题和所取得的成绩。 相似文献
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高职教师课堂教学质量的评价方法研究 总被引:1,自引:0,他引:1
黄会明 《武汉船舶职业技术学院学报》2013,(4):109-112,115
根据高职院校的课堂教学特点,首先构建了具有高职特色的教学质量评价指标体系;然后,利用主成分分析法对评教数据进行数学处理,求得各主成分和综合因子的得分,并对教师的教学质量与师德师表进行量化评价;最后,利用第一、第二主成分的得分聚类图,实现了对教学质量的定性评判。结果表明,主成分分析法提高了教学质量评价的科学性和合理性。 相似文献
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