Inefficiency persistence and heterogeneity in Colombian electricity distribution utilities

The electricity reform in Colombia has exhibited gains in terms of reliability but its effects on firms efficiency and service quality have not been clear. Previous studies evaluating the performance of distribution companies after the reform have not found evidence of improvements, although large differences in efficiency have been found among firms. This suggests high inefficiency persistence and heterogeneity in the Colombian distribution sector. In this paper, we propose an extension of dynamic stochastic frontier models that accounts for unobserved heterogeneity in the inefficiency persistence and in the technology. The model incorporates total expenses, service quality and energy losses in an efficiency analysis of Colombian distributors over fifteen years after the reform. We identify the presence of high inefficiency persistence in the sector, and important differences between firms. In particular, rural companies and firms with small customers present low persistence and evidence the largest gains in efficiency during the period. However, increases in efficiency are only manifested during the last five years when the main improvements in service quality and energy losses are presented. Overall, inefficiency persistence, customer density and consumption density are found to be important criteria to be considered for regulatory purposes

Inefficiency persistence and heterogeneity in Colombian electricity distribution utilities

The electricity reform in Colombia has exhibited gains in terms of reliability but its effects on firms efficiency and service quality have not been clear. Previous studies evaluating the performance of distribution companies after the reform have not found evidence of improvements, although large differences in efficiency have been found among firms. This suggests high inefficiency persistence and heterogeneity in the Colombian distribution sector. In this paper, we propose an extension of dynamic stochastic frontier models that accounts for unobserved heterogeneity in the inefficiency persistence and in the technology. The model incorporates total expenses, service quality and energy losses in an efficiency analysis of Colombian distributors over fifteen years after the reform. We identify the presence of high inefficiency persistence in the sector, and important differences between firms. In particular, rural companies and firms with small customers present low persistence and evidence the largest gains in efficiency during the period. However, increases in efficiency are only manifested during the last five years when the main improvements in service quality and energy losses are presented. Overall, inefficiency persistence, customer density and consumption density are found to be important criteria to be considered for regulatory purposes

Bayesian estimation of inefficiency heterogeneity in stochastic frontier models

Estimation of the one sided error component in stochastic frontier models may erroneously attribute firm characteristics to inefficiency if heterogeneity is unaccounted for. However, unobserved inefficiency heterogeneity has been little explored. In this work, we propose to capture it through a random parameter which may affect the location, scale, or both parameters of a truncated normal inefficiency distribution using a Bayesian approach. Our findings using two real data sets, suggest that the inclusion of a random parameter in the inefficiency distribution is able to capture latent heterogeneity and can be used to validate the suitability of observed covariates to distinguish heterogeneity from inefficiency. Relevant effects are also found on separating and shrinking individual posterior efficiency distributions when heterogeneity affects the location and scale parameters of the one-sided error distribution, and consequently affecting the estimated mean efficiency scores and rankings. In particular, including heterogeneity simultaneously in both parameters of the inefficiency distribution in models that satisfy the scaling property leads to a decrease in the uncertainty around the mean scores and less overlapping of the posterior efficiency distributions, which provides both more reliable efficiency scores and rankings

Entropy and temperature of black holes in a gravity's rainbow

The linear relation between the entropy and area of a black hole can be derived from the Heisenberg principle, the energy-momentum dispersion relation of special relativity, and general considerations about black holes. There exist results in quantum gravity and related contexts suggesting the modification of the usual dispersion relation and uncertainty principle. One of these contexts is the gravity's rainbow formalism. We analyze the consequences of such a modification for black hole thermodynamics from the perspective of two distinct rainbow realizations built from doubly special relativity. One is the proposal of Magueijo and Smolin and the other is based on a canonical implementation of doubly special relativity put forward recently by the authors. In these scenarios, we obtain modified expressions for the entropy and temperature of black holes. We show that, for a family of doubly special relativity theories satisfying certain properties, the temperature can vanish in the limit of zero black hole mass. For the Magueijo and Smolin proposal, this is only possible for some restricted class of models with bounded energy and unbounded momentum. With the proposal of a canonical implementation, on the other hand, the temperature may vanish for more general theories; in particular, the momentum may also be bounded, with bounded or unbounded energy. This opens new possibilities for the outcome of black hole evaporation in the framework of a gravity's rainbow.Comment: 11 pages, 2 new references added, version accepted for publication in Physical Review

Variación anual de la concentración de aeropolen de Compositae en la atmósfera de Córdoba

La familia Composirae corwi tU)'C un grupo CU)'OS representantes son cntomófilas, por ello las concentraciones deted adas en la atmósfera han sido bajas. El muestreo se llevó a cabo en Córdoba durante los años 1982. 1983 y 1984 mediante un mucstrcador BURKARD sporc-trap colccado a unos 15m de altura. Se han reconocido un total de 7 tí pos morfológico!> de granos de polen pertenecientes a esta ramilia: tipo Aruflemis,Artemisia, Clutaurea, tipo fleliam! tuJ, Iipo Taraxawm, Srneáo yXa11lhium. Las mayorcscantidadm. tic granos de polen de· teClados pertenecen al tipo l!t !illntlzus, considerados como alergcnos por algunos autores. Sus altas conccnt.radoncs en el aire, en la época de. rccolc.cción del girasol, hace que posiblemente tenga alguna importanci<~ e~~ las polinosis cslivalu. Se han detectado granos de polen. de procedencia lejana, deArtemi.fia, planta con polen ahamenlc alcrgógcno, por tanto pueda ser causa de polioosis de verano en aquellas zonils de !a pro\'incia donde es abundanlcThc Composírae bclong 10 a broad systcmatic group allhough, duc to rhe cntomophylous charactcr of thc spccics, the pollcn conccnltations of lhc samplcs in thc atmosphcrc in thc city of Córdob3 were not beco vcry high. Sampling of poli en grains was e<1rricd out for thrcc ycars (1982, 1983 and 1984) by n1eans ola Burkard sporc- trap samplcr locatcd about t5 m abovc ground leve!. Scvcn morphologica1 typcs of rollen grain~ wcrc recognizcd: AnOzemir, Artemisia, Ccntaurcu typc, Helianrhus typ::, Toraxocum, Su:r:cio and Xanrhium rypc~. Thc largeSI annual amounts of poUeo glilins U::tcclcd wcrc of Hefiamlms typ:, considcrcd allcrgcnic by many authors. Thc higl1er lc-.·els in thc a.ir (ounU duriog tbc. harvcsling scason of sunflowcrs may be rc.spansible for summcr pollinoscs. Arlt misia pollcn g.rains dcvcloping far from thc sampling point wcrc dctcctc:d. Thcsc !.pccics are probably responsible for parl of summcr polli noses duc lo their higb aJlergenic polcntial, at lcast in thc arcas whcrc this plant is abundan!

Graphic Classes in the Worldwide Classroom: A Comparison of Two MOOC Experiences

Graphics are present in the day-to-day professional practice of architects and engineers, not only to receive and transmit information, but also to design and create. Students who are accepted on university courses have varied curriculum vitae, and some may initially lack skills. Consequently, engineering schools have developed a Massive Open Online Course (MOOC) entitled “The Language of Engineering” (ELI), which reviews basic geometry concepts and develops spatial intelligence, among others. The Barcelona School of Architecture has produced “From reality to design. From design to augmented reality” (RA), which covers topics including traditional architectural representation and the latest techniques. The goal of this study was to explain and analyse the main characteristics and learning strategies of these two MOOC (strengths, weaknesses and opportunities for improvement). The results show that although strategies vary depending on the subjects, the contents and exercises should be practical and adapted to students (interests, level, time availability and aesthetics), always considering motivation as a key point (gamification). These topics have been found to have a considerable influence on the success of a MOOC. Therefore, the conclusions should be considered in subsequent versions of these courses and other MOOCs.Postprint (author's final draft

The discrimination capabilities of Micromegas detectors at low energy

The latest generation of Micromegas detectors show a good energy resolution, spatial resolution and low threshold, which make them idoneous in low energy applications. Two micromegas detectors have been built for dark matter experiments: CAST, which uses a dipole magnet to convert axion into detectable x-ray photons, and MIMAC, which aims to reconstruct the tracks of low energy nuclear recoils in a mixture of CF4 and CHF3. These readouts have been respectively built with the microbulk and bulk techniques, which show different gain, electron transmission and energy resolutions. The detectors and the operation conditions will be described in detail as well as their discrimination capabilities for low energy photons will be discussed.Comment: To be published in the proceedings of the TIPP2011 conference (Physics Procedia

Gaseous time projection chambers for rare event detection: Results from the T-REX project. II. Dark matter

As part of the T-REX project, a number of R&D and prototyping activities have been carried out during the last years to explore the applicability of Micromegas-read gaseous TPCs in rare event searches like double beta decay (DBD), axion research and low-mass WIMP searches. While in the companion paper we focus on DBD, in this paper we focus on the results regarding the search for dark matter candidates, both axions and WIMPs. Small ultra-low background Micromegas detectors are used to image the x-ray signal expected in axion helioscopes like CAST at CERN. Background levels as low as $0.8\times 10^{-6}$ c keV$^{-1}$cm$^{-2}$s$^{-1}$ have already been achieved in CAST while values down to $\sim10^{-7}$ c keV$^{-1}$cm$^{-2}$s$^{-1}$ have been obtained in a test bench placed underground in the Laboratorio Subterr\'aneo de Canfranc. Prospects to consolidate and further reduce these values down to $\sim10^{-8}$ c keV$^{-1}$cm$^{-2}$s$^{-1}$will be described. Such detectors, placed at the focal point of x-ray telescopes in the future IAXO experiment, would allow for 10$^5$ better signal-to-noise ratio than CAST, and search for solar axions with $g_{a\gamma}$ down to few 10$^{12}$ GeV$^{-1}$, well into unexplored axion parameter space. In addition, a scaled-up version of these TPCs, properly shielded and placed underground, can be competitive in the search for low-mass WIMPs. The TREX-DM prototype, with $\sim$0.300 kg of Ar at 10 bar, or alternatively $\sim$0.160 kg of Ne at 10 bar, and energy threshold well below 1 keV, has been built to test this concept. We will describe the main technical solutions developed, as well as the results from the commissioning phase on surface. The anticipated sensitivity of this technique might reach $\sim10^{-44}$ cm$^2$ for low mass ($<10$ GeV) WIMPs, well beyond current experimental limits in this mass range.Comment: Published in JCAP. New version with erratum incorporated (new figure 14