1,720,963 research outputs found
Comparison of SVM and boosted regression trees for the delineation of lacustrine sediments using multispectral ASTER data and topographic indices in the lake Manyara Basin
No full textThe lower member of the so called Manyara Beds is a distinct lacustrine sedimentary layer which indicates, with an elevation of more than 140 m above today's lake level, a high stand of the paleolake Manyara in the Monduli District in northern Tanzania. The Manyara Beds are rich in Pleistocene vertebrate fossils. In this study we focus on the delineation of this specific stratigraphic layer in order to yield new insights into paleontological settings, landscape evolution and to plan paleontological fieldwork. We compare the performance of a support vector classifier with a linear as well as a Gaussian kernel, with boosted regressiontree approaches to identify the lithostratigraphic layers of the Manyara Beds. For the identification of the lacustrine sediments, multispectral informationof ASTER satellite imagery and topographic indices derived from a digital elevation model were utilized as input feature sets. Acceptable classification accuracies were obtained with all methods. Thus, the Manyara Beds can be delineated and new sites with paleolake sediments were detected. The highest overall accuracy with 92% was provided by the support vector machine approach with a linear kernel for a binary classification problem. For a multi-class classification problem with three target classes the support vector classifier achieved 80% accuracy with a linear, as well as a Gaussian kernel. © 2015 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany
Use of Remote Sensing data, terrain analysis and stochastic modeling to predict current and future flood risk in a small Mediterranean catchment (T. Teiro, Italy)
No full textThe Delineation of Paleo-Shorelines in the Lake Manyara Basin Using TerraSAR-X Data
Full text linkThe purpose of this paper is to describe the delineation of paleo-shorelines using high resolution microwave images and digital image processing tools, and with that to contribute to the understanding of the complex landscape evolution of the Lake Manyara Basin. The surroundings of Lake Manyara are the focus of several paleo-archeological investigations, since the location is close to Olduvai Gorge, where paleo-anthropological findings can be traced back to homo habilis. In the catchment of Lake Manyara two hominin-bearing sites (0.78 to 0.63 Ma), lots of vertebrate fossils and hand axes from different periods were found. Understanding the development and extent of the lake is crucial for understanding the regional paleo-environment of the Quaternary. Morphological structures of shorelines and terraces east of Lake Manyara were identified from TerraSAR-X StripMap images. By applying a Canny edge detector, linear features were extracted and revised for different image acquisitions using a contextual approach. Those features match literature and field references. A digital elevation model of the region was used to map the most distinct paleo-shorelines according to their elevation
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
Dispelling 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
Assessment of flash floods in a small Mediterranean catchment using terrain analysis and remotely sensed data: A case study in the Torrente Teiro, Liguria, Italy
No full textMediterranean catchments are particularly sensitive to temperature oscillations, rainfall intensity and human activities. Especially intensive precipitation events, changing land-use and thin soil layer trigger surface runoff generation and hence, soil erosion, sediment transport, flooding and related damages.
In this study, we propose a methodology using remotely sensed data, terrain analysis and stochastic modeling to characterize the soil hydrological and physical components of the Teiro catchment. Particularly, we focus on the triggering land-cover and soil information that can be derived with multispectral remote sensing techniques. To study the hydrological dynamics of the Teiro catchment we applied the Soil Conservation Service Curve Number method implemented in a GIS system for different precipitation events related to various return periods. The input data was calculated based on multispectral indices describing the heterogeneity of soils and vegetation. The discharges obtained show reasonable values that have been validated with mapped flooded areas of the 4th October 2011 flood event. This event corresponds roughly to a 10 years return period. However, it is striking that a 50 years return period event was calculated to yield the double amount of discharge and thus, implies a major hazard for the local populatio
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