检索结果-南通市图书馆

维普期刊数据库

Statistical Downscaling of Summer Temperature Extremes in Northern China

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2013年第4期30卷 1085-1095页

作者：范丽军 Deliang CHEN 符淙斌严中伟 Key Laboratory of Regional Climate-Environment Research for Temperate East Asia Institute of Atmospheric Physics Chinese Academy of Science Department of Earth Sciences University of Gothenburg

Two approaches of statistical downscaling were applied to indices of temperature extremes based on percentiles of daily maximum and minimum temperature observations at Beijing station in summer during 1960-2008. One was to downscale daily maximum and minimum temperatures by using EOF analysis and stepwise linear regression at first, then to calculate the indices of extremes; the other was to directly downseale the percentile-based indices by using seasonal large-scale temperature and geo-potential height records. The cross-validation results showed that the latter approach has a better performance than the former. Then, the latter approach was applied to 48 meteorological stations in northern China. The cross- validation results for all 48 stations showed close correlation between the percentile-based indices and the seasonal large-scale variables. Finally, future scenarios of indices of temperature extremes in northern China were projected by applying the statistical downsealing to Hadley Centre Coupled Model Version 3 （HadCM3） simulations under the Representative Concentration Pathways 4.5 （RCP 4.5） scenario of the Fifth Coupled Model Inter-comparison Project （CMIP5）. The results showed that the 90th percentile of daily maximum temperatures will increase by about 1.5℃, and the 10th of daily minimum temperatures will increase by about 2℃ during the period 2011- 35 relative to 1980-99.

关键词： indices of temperature extremes percentiles statistical downscaling future scenarios projection. northern China

维普期刊数据库

Convergence of Impact Measures and Impact Bundles

在线全文

学校读者我要写书评

暂无评论

Journal of Data and Information Science 2022年第3期7卷 5-19页

作者： Leo Egghe Hasselt University Campus DiepenbeekDiepenbeek 3590Belgium

Purpose:A new point of view in the study of impact is ***/methodology/approach:Using fundamental theorems in real analysis we study the convergence of well-known impact ***:We show that pointwise convergence is maintained by all well-known impact bundles(such as the h-,g-,and R-bundle)and that theμ-bundle even maintains uniform *** on these results,a classification of impact bundles is *** limitations:As for all impact studies,it is just impossible to study all measures in *** implications:It is proposed to include convergence properties in the study of impact ***/value:This article is the first to present a bundle classification based on convergence properties of impact bundles.

关键词： Pointwise and uniform convergence of impact measures and bundles Second Dini theorem Arzelà’s theorem Bundle classification Generalized h-and g-indices percentiles

维普期刊数据库

在线全文

学校读者我要写书评

暂无评论

American Journal of Computational Mathematics 2016年第1期6卷 17-22页

作者： Pushpalatha Sarla Mallikarjuna Reddy Doodipala Manohar Dingari Department of Engineering Mathematics GITAM University Hyderabad Campus Hyderabad India

The paper focuses on measuring self-similarity using few techniques by an index called Hurst index which is a self-similarity parameter. It has been evident that Internet traffic exhibits self-similarity. Motivated by this fact, real time web users at various centers considered here as traffic and it has been examined by various methods to test the self-similarity. The results from the experiments carried out verify that the traffic examined in the present study is self similar using a new method based on some descriptive measures;for example percentiles have been applied to compute Hurst parameter which gives intensity of the self-similarity. Numerical results and analysis we discussed and presented here play a significant role to improve the services at web centers in the view of quality of service (QOS).

关键词： Long-Range Dependence Self-Similarity Poisson Process percentiles Hurst Parameter

More Erratic and More Extreme: Trends in Precipitation in the State of São Paulo, Brazil

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

American Journal of Climate Change 2023年第1期12卷 140-171页

作者： Lucí Hidalgo Nunes Guilherme Henrique Gabriel Jose A. Marengo Universidade do Estado do Rio de Janeiro (UERJ) Rio de Janeiro Brasil Universidade Estadual de Campinas (UNICAMP) São Paulo Brasil Centro Nacional de Monitoramento e Alertas de Desastres Naturais (CEMADEN) São José dos Campos Brazil

The study assessed changes in rainfall variability and the frequency of extreme events (very wet and very dry) in the state of S?o Paulo, Brazil, for a 40-year period that divided into two sub-groups: 1973-1992 (P1) and 1993-2012 (P2). Data of 79 rain gauge stations were selected to represent the different climatic and geomorphological domains of the state. The annual pattern was evaluated through the scale and the shape parameters of the gamma distribution and the 95th and the 5th percentiles thresholds, the latter also employed to evaluate the seasonal spatial patterns (rainy season, Oct.-Mar. and sub-humid to dry season, Apr.-Sep.). Results showed that the average precipitation was similar in P1 and P2, but S?o Paulo evolved to a pattern of increased irregularity in the rainfall distribution, with a rise of approximately 10% in the number of extremes between 1973 and 2012, especially in the very dry occurrences, and in the north and west of the state, which are the least rainy regions. Moreover, while 55% of the evaluated rain gauges recorded more extreme wet episodes in P2, 76% registered more dry extreme episodes in the same period. Some very dry or very wet events recorded after the 40-year period evaluated were discussed in terms of the associated weather patterns and their impacts on society and attested to the validity of the results found in the quantitative assessment. The qualitative analysis indicates that if the trends of more irregular distribution of rain and increase in extreme events persist, as pointed out by the gamma and percentile analyses, they would continue to bring serious effects on the natural and social systems in the state, which is the most populous and has the strongest and most diversified economy in Brazil.

关键词： Rainfall Extremes São Paulo Gamma Distribution percentiles Impacts

Use of Pearson’s Chi-Square for Testing Equality of Percentile Profiles across Multiple Populations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Statistics 2015年第5期5卷 412-420页

作者： William D. Johnson Robbie A. Beyl Jeffrey H. Burton Callie M. Johnson Jacob E. Romer Lei Zhang Department of Biostatistics Pennington Biomedical Research Center Louisiana State University Baton Rouge USA Office of Health Data and Research Mississippi State Department of Health Jackson USA

In large sample studies where distributions may be skewed and not readily transformed to symmetry, it may be of greater interest to compare different distributions in terms of percentiles rather than means. For example, it may be more informative to compare two or more populations with respect to their within population distributions by testing the hypothesis that their corresponding respective 10th, 50th, and 90th percentiles are equal. As a generalization of the median test, the proposed test statistic is asymptotically distributed as Chi-square with degrees of freedom dependent upon the number of percentiles tested and constraints of the null hypothesis. Results from simulation studies are used to validate the nominal 0.05 significance level under the null hypothesis, and asymptotic power properties that are suitable for testing equality of percentile profiles against selected profile discrepancies for a variety of underlying distributions. A pragmatic example is provided to illustrate the comparison of the percentile profiles for four body mass index distributions.

关键词： Asymptotic Chi-Square Test Equality of percentiles Large Sample Test Median Test Nonparametric Methods

Conditional Quantile Polynomial Distributed Lag Model with an Application to Rubber Price Returns

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Physical Science and Application 2015年第2期5卷 108-115页

作者： Kwadwo Agyei Nyantakyi Ghana Institute of Management and Public Administration (GIMPA) Greenhill College Business School Box AH 50 AchimotaAccra Ghana

Impacts of returns on assets are not instantaneously felt, since there is lag period. In this paper we consider the problem of developing a model for the conditional QPDL （quantile polynomial distributed lag） and investigate the influences of the conditioning variables on the location, scale and shape parameters of the QPDL model. As an economic application, we consider the production of rubber and its price returns ofSri Lanka. From the analysis we observed that the QPDL model applications were better estimators than the PDL （Polynomial Distributed Lag） models.

关键词： Asset returns percentiles parameter estimators production.

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

体育系科新生分类录取方法的探讨

江西师范大学学报(自然科学版) 1988年第2期 128-134页

作者：舒晓山九江师专体育系

几年来,体育系科新生录取的文化“分数线”和体育“分数线”的划定,方法简单,缺乏科学性,违背了招生文件精神,一定程度上影响了新生质量.本文根据招生文件精神,分别作出考生文化、体育成绩频数分布表,采取百分位数法划定其等级,进而制... 详细信息

几年来,体育系科新生录取的文化“分数线”和体育“分数线”的划定,方法简单,缺乏科学性,违背了招生文件精神,一定程度上影响了新生质量.本文根据招生文件精神,分别作出考生文化、体育成绩频数分布表,采取百分位数法划定其等级,进而制定分类录取参考表.1985年按上述方法录取的新生文化成绩平均为403.4分,体育成绩平均为82.6分,比按“分数线”录取的新生的文化成绩平均提高39.9分.

关键词： the classification of enrollment percentiles a deviding marks marks for general knowledge marks for professional knowledge