1,721,017 research outputs found
Imputation techniques for the reconstruction of missing interconnected data from higher Educational Institutions
Full text linkEducational Institutions data constitute the basis for several important analyses on the educational systems; however they often contain not negligible shares of missing values, for several reasons. We consider in this work the relevant case of the European Tertiary Education Register (ETER), describing the Educational Institutions of Europe. The presence of missing values prevents the full exploitation of this database, since several types of analyses that could be performed are currently impracticable. The imputation of artificial data, reconstructed with the aim of being statistically equivalent to the (unknown) missing data, would allow to overcome these problems. A main complication in the imputation of this type of data is given by the correlations that exist among all the variables. We propose several imputation techniques designed to deal with the different types of missing values appearing in these interconnected data. We use these techniques to impute the database. Moreover, we evaluate the accuracy of the proposed approach by artificially introducing missing data, by imputing them, and by comparing imputed and original values. Results show that the information reconstruction does not introduce statistically significant changes in the data and that the imputed values are close enough to the original values
Optimization methods for the imputation of missing values in Educational Institutions Data
Full text linkThe imputation of missing values in the detail data of Educational Institutions is a difficult task. These data contain multivariate time series, which cannot be satisfactory imputed by many existing imputation techniques. Moreover, almost all the data of an Institution are interconnected: the number of graduates is not independent from the number of students, the expenditure is not independent from the staff, etc. In other words, each imputed value has an impact on the whole set of data of the institution. Therefore, imputation techniques for this specific case should be designed very carefully. We describe here the methods and the codes of the imputation methodology developed to impute the various patterns of missing values which appear in similar interconnected data. In particular, a first part of the proposed methodology, called ``trend smoothing imputation'', is designed to impute missing values in time series by respecting the trend and the other features of an Institution. The second part of the proposed methodology, called ``donor imputation'', is designed to impute larger chunks of missing data by using values taken form similar Institutions in order to respect again their size and trend. • Trend smoothing imputation can handle missing subsequences in time series, and is given by a weighted combination of: (a) weighed average of the other available values of the sequence, and (b) linear regression. • Donor imputation can handle full sequence missing in time series. It imputes the Recipient Institution using the values taken from a similar institution, called Donor, selected using optimization criteria. • The values imputed by our techniques should respect the trend, the size and the ratios of each Institution
Continuities and discontinuities at the Oscurusciuto rock shelter (Ginosa, Taranto). The last Neanderthals in Southern Italy
No full textThe Oscurusciuto rock shelter, located in the Ginosa ravine (Taranto, Apulia), is a very important site for the understanding of Neandertal subsistence and settlement strategies in Southern Italy. The deposit, about 6 m thick and with a base of 60 m2 , is made up of several levels Middle Palaeolithic in age (fig. 1). The series so far investigated (between SU 1 and SU 15) ranges between 42,724±716 cal BP (Beta 181165 AMS) (SU 1) and 55 ± 2 kyrs (40Ar/39Ar) (SU 14 – tephra identified as the Mount Epomeo Ischia green tuff; Allen et alii 2000). Such a chronological interval is crucial in European prehistory as it falls upon the period of disappearance of Homo neanderthalensis and of the dispersal of the first groups of Anatomically Modern Humans. Excavations and studies on the Oscurusciuto Shelter are being led by the Unità di Ricerca di Preistoria e Antropologia of the Dipartimento di Scienze Fisiche, della Terra e dell’Ambiente of the University of Siena (Boscato, Ronchitelli 2008; Villa et alii 2009; Boscato et alii 2011; Ronchitelli et alii 2011; Spagnolo et alii 2015). The study comprises: taxonomic and taphonomic investigations on faunal remains, analysis of lithic production through a technological and techno-functional approach, micromorphological analyses of hearths and assessment of the spatial meaning of these features. The aim of this work is to individuate, from a diachronic point of view, the continuities and discontinuities inside the lithic techno-complexes, the site space management and the mobility patterns within the territory. Such objectives are reached by a multidisciplinary approach. The different datasets which have been gathered are statistically elaborated within a GIS platform in order to determine the modalities of space management. The different datasets which have been gathered are statistically elaborated within a GIS platform in order to determine the modalities of space management. The application of the RMU method (lithic raw material units), on technological and spatial bases, allows the recognition of single activities (Marciani 2013; Spagnolo 2013; Spagnolo et alii 2015). This research comprises the integrated study of the lower section of the series so far investigated in the Shelter: SU 15, SU 14, SU 13 and SU 11. These stratigraphic units are particularly interesting for the reconstruction of Neandertal behaviour, given that each of them shows peculiarities in terms of structural elements, spatial management, type of occupation and lithic production systems. SU 15 is a living floor in which a phase of abandonment is recorded and is sealed by the deposition of the SU 14 tephra. This surface is characterized by stone alignments which define two possible structures. SU 14 (fig. 2) is an almost sterile layer about 60 cm thick, made of volcanic ashes. Traces of a short frequentation can be seen only few centimetres under the top of the layer. SU 13 is a short palimpsest which represents the first stable re-colonization of the site after the environmental impact created by volcanic ash deposition. In this layer, 10 aligned hearths were found which divide up the site into areas devoted to different activities. The overlying SU 11 is a palimpsest about 30 cm thick, characterized by the superimposition of tens of hearths. The results of these studies will bring important and useful advances in research on the behavioural and settlement features of Neandertals, particularly at this time when there are many Italian and international projects which face these questions by means of different and innovative approaches
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
Climbing the time to see Neanderthal behaviour’s continuity and discontinuity: SU 11 of the Oscurusciuto Rockshelter (Ginosa, Southern Italy)
Full text linkThe Oscurusciuto Rockshelter (Ginosa, Southern Italy) is a perfect sample-site for the reconstruction of multiple aspects of the last Neanderthals life. Different settlement strategies are attested in the excavated portion of the stratigraphic sequence, dated between ~ 55 and 43 ka BP. As a first goal, the reconstruction of the site spatial organization across the palimpsest SU 11 was achieved by a high-temporal-resolution approach (assisted by sedimentological analysis), integrating lithic technology, zooarchaeology and spatial analysis (by means of the GIS technology). As a second goal, a diachronic perspective was adopted by comparing results from SU 11 with the previously studied evidence from the underlying SU 13. Results were processed at a diachronic scale, highlighting similarities and differences related both to the type of activities carried out at the site and to their spatial management. This allowed us to recognize discontinuities and, especially, continuities of settlement dynamics, which can be related to phenomena of cultural transmission hinting to a “memory of places”. Such results stimulate the debate not only on the necessity to study Middle Palaeolithic contexts at different temporal scales but also on the necessity to develop more refined multidisciplinary analytical protocols. The study of settlement dynamics at high-resolution scales allows to take advantage of the potentialities of contextual analysis i.e. the integration of results from different disciplines and data from the whole range of archaeological evidence in order to reconstruct solid behavioural models
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
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