Building an Open Social Learning Community Around a DSpace Repository on Statistics

4th International Conference on Open RepositoriesThis presentation was part of the session : Conference PostersIn this paper we describe a project which aims to build an open social learning community around a learning object repository (LOR) based on DSpace containing learning resources about Statistics. We combine the preservation capabilities of DSpace with the facilities of a tagging mechanism such as Delicious. On top of this ensemble we intend to build a new browsing interface for improving users' learning experience when using the LOR. We also intend to gather and analyze usage data in order to better understand the real learning process in virtual learning environments.Spanish Government Grant under Refs. TIN2006-15107-C06 and EA2008-015

A Metafrontier Analysis of Technical Efficiency of Selected European Agricultures

Farm Management,

A Metafrontier Analysis of Technical Efficiency of Selected European Agricultures

Technical efficiency refers to the situation where it is impossible for a firm to produce, with the given know-how, (1) a larger output from the same inputs or (2) the same output with less of one or more inputs without increasing the amount of other inputs. In practice, the interest is on the relative position in terms of efficiency of a particular firm with respect to others. Therefore, technical efficiency is characterised by the relationship between observed production and some ideal or potential production (Greene, 1993). Although the beginning of the efficiency work can be traced to the 1950s (Farrell, 1957), there have been a growing interest on its use in benchmarking performance, predominantly as a means of identifying best practice and improving the efficiency of resource use within the agricultural industry (e.g., Defra 2004, SAC 2009). This paper deals with the estimation of technical efficiency for the agricultural sectors in several European countries and moreover, it aims to compare the efficiency amongst them using a metafrontier analysis. The use of this type of analysis is justified because a frontier, which represents the best available technology within a particular region/country cannot be strictly compared across other regions/countries, unless they operate under the same production set. The metafrontier analysis has been developed in a number of studies (Battese and Rao, 2002; Nkamleu et al., 2006; Chen and Song, 2006; O‟Donnell et al., 2008.) The metafrontier analysis in this paper, which uses data from the Farm Accountancy data Network (FADN), was focused on four farm types: two specialised farming types (i.e., specialist cereals, oilseed and protein crops and specialist dairying) and two more mixed farming sets (i.e., general field cropping and mixed farms), and was applied to a total of 11 countries namely Belgium, Denmark, France, Germany, Hungary, Ireland, Italy, Netherlands, Poland, Spain and the UK. For most of the countries the information was available from 1995 until 2007, excepting Hungary and Poland, for which it was available only since 2004. Also note that not all the farm types were available for all the countries. The structure of the paper is as follows: it starts presenting an overview of the metafrontier analysis used to compare technical efficiency amongst the European countries. It is followed by the empirical work, which comprises a description of the data used, the estimation and discussion of the results. Finally we present conclusions.Research and Development/Tech Change/Emerging Technologies,

Anomalous temperature dependence of the band-gap in Black Phosphorus

Black Phosphorus (BP) has gained renewed attention due to its singular anisotropic electronic and optical properties that might be exploited for a wide range of technological applications. In this respect, the thermal properties are particularly important both to predict its room temperature operation and to determine its thermoelectric potential. From this point of view, one of the most spectacular and poorly understood phenomena is, indeed, the BP temperature-induced band-gap opening: when temperature is increased the fundamental band-gap increases instead of decreasing. This anomalous thermal dependence has also been observed, recently, in its monolayer counterpart. In this work, based on \textit{ab-initio} calculations, we present an explanation for this long known, and yet not fully explained, effect. We show that it arises from a combination of harmonic and lattice thermal expansion contributions, which are, in fact, highly interwined. We clearly narrow down the mechanisms that cause this gap opening by identifying the peculiar atomic vibrations that drive the anomaly. The final picture we give explains both the BP anomalous band-gap opening and the frequency increase with increasing volume (tension effect).Comment: Published in Nano Letter