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改革通关利通商 港深繁荣齐共享
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作者 孙启烈 《开放导报》 1996年第4期29-30,共2页
关键词 被访者 汽车专用公路 通过能力 治安问题 沙头角 货车 陆路口岸 排队时间 开放时间 验关人员
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国际儿童环境会议见闻
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作者 刘木廷 《环境教育》 1996年第4期45-47,共3页
国际儿童环境会议见闻刘木廷去年,我有幸率中国代表团,参加联合国在英国召开的第一次国际儿童环境会议。来自五大洲85个国家代表在会上交流了各国环境教育的经验,我从中看到了──各国环境教育的“不等式”会议期间,北美、西欧及... 国际儿童环境会议见闻刘木廷去年,我有幸率中国代表团,参加联合国在英国召开的第一次国际儿童环境会议。来自五大洲85个国家代表在会上交流了各国环境教育的经验,我从中看到了──各国环境教育的“不等式”会议期间,北美、西欧及日本等国家和地区的学生,积极宣传世... 展开更多
关键词 环境教育 环境问题 儿童 中国代表团 中小学环境教育 保护环境 我国环境教育 联合国 验关人员 不等式
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Which Friction Factor Model Is the Best? A Comparative Analysis of Model Selection Criteria
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作者 Ahmed H.Kamel Ali S.Shaqlaih Arslan Rozyyev 《Journal of Energy and Power Engineering》 2018年第3期158-168,共11页
The ongoing research for model choice and selection has generated a plethora of approaches. With such a wealth of methods, it can be difficult for a researcher to know what model selection approach is the proper w... The ongoing research for model choice and selection has generated a plethora of approaches. With such a wealth of methods, it can be difficult for a researcher to know what model selection approach is the proper way to proceed to select the appropriate model for prediction. The authors present an evaluation of various model selection criteria from decision-theoretic perspective using experimental data to define and recommend a criterion to select the best model. In this analysis, six of the most common selection criteria, nineteen friction factor correlations, and eight sets of experimental data are employed. The results show that while the use of the traditional correlation coefficient, R2 is inappropriate, root mean square error, RMSE can be used to rank models, but does not give much insight on their accuracy. Other criteria such as correlation ratio, mean absolute error, and standard deviation are also evaluated. The AIC (Akaike Information Criterion) has shown its superiority to other selection criteria. The authors propose AIC as an alternative to use when fitting experimental data or evaluating existing correlations. Indeed, the AIC method is an information theory based, theoretically sound and stable. The paper presents a detailed discussion of the model selection criteria, their pros and cons, and how they can be utilized to allow proper comparison of different models for the best model to be inferred based on sound mathematical theory. In conclusion, model selection is an interesting problem and an innovative strategy to help alleviate similar challenges faced by the professionals in the oil and gas industry is introduced. 展开更多
关键词 Friction factor information theory model selection turbulent flow straight tubing.
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