1,721,354 research outputs found
Climate change and its ecological and socioeconomic impact: evidence from China's historical document for Qing dynasty
No full textClimate change is currently of great concern by scientist and public. However, the ecological and socio-economic effects of long-term climate change remains largely unknown. To study on the long-term climate change, and its impacts on the environmental conditions, ecological and socio-economic consequences, the long time series of climate related events from historical records are needed to fill the gap of the instrumental data. In this study, a unique data source -- "The compendium of Chinese Meteorological records of the Last 3,000 years (Zhang 2004) which contains invaluable information about climate related events recorded in the China's historical documents were digitized for the last Dynasty. Pearson correlation test was conducted to test the relationship between crop harvest and climate events in case study one. The results revealed that climate conditions affected past agriculture harvest in China. Besides direct effect of cooling on the land carrying capacity, periodic ecological stresses such as drought events can significantly reduce the agricultural yield. The issue of stationarity of variables is the great concern in this study. Local variations both in temporal and spatial scale analysis were considered in the following case studies. Second case study applied continuous wavelet analysis for analyzing the local variation in temporal scale. The result revealed that the periodicity of fluctuations of locusts, temperature and drought series are consistently at around 100 year's band. The consistent associations between locust and temperature, temperature and drought, locust and drought at same frequency and time space indicted the possible casual interlinks of temperature-drought-locust plague. The finding suggests that drought events driven by long term variation of temperature change explains locust dynamics better than floods. The last case study used Geographically Weighted Regression methods for analyzing spatially varying relationships between determinate variable--famine and explanatory variables such as floods, droughts, poor harvest and locust outbreaks. The results implicated that all variables have significant effects on famine occurrence in last Dynasty of China. Among the explanatory variables, drought shows strongest effect on famine. The results also suggested that there are significant spatial variations across the study area. Therefore, it's important to consider the local regression methods for analyzing the relationships between famine and other climate conditions.Ph.D.Includes abstractVitaIncludes bibliographical referencesby Yufei Wan
径向剪切干涉波面重构的数值模拟分析
No full textIn order to acquire the original wavefront information in radial shearing interferometry, wavefront reconstruction is necessary, the iterative algorism for wavefront reconstruction was deduced in this paper, based on which an numerical simulation using Matlab with different iteration number and shearing ratio was conducted. The simulation comes to the following conclusion: Properly selection of the shearing ratio can simplify the computational complexity. Compared with the small distortion wavefront reconstruction, more but appropriate iteration number in large distortion wavefront reconstruction is needed. Preferred shearing ratios for different measured wavefront PV values are summarized as follows: a. if WPV>10λ, beta>0.7; b. if 6&lambda
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Polarization-insensitive subwavelength grating reflector based on a semiconductor-insulatormetal structure
No full textDispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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