Generation of 3rd and 5th harmonics in a thin superconducting film by temperature oscillations and isothermal nonlinear current response

The generation of harmonics of the voltage response is considered when an AC current is applied through a superconducting film above T_c. It is shown that almost at all temperatures the mechanism of the temperature oscillations created by the AC current and the temperature dependence of the resistance dominates over the isothermal nonlinear electric conductivity. Only in a narrow critical region close to T_c the latter is essential for the generation of the harmonics. A detailed investigation of harmonics generation provides an accurate method for measuring the thermal boundary conductance between the film and the insulating substrate. The critical behaviour of the third harmonic will give a new method for the determination of the lifetime of metastable Cooper pairs above T_c. The comparison of the calculated fifth harmonics of the voltage with the experiment is proposed as an important test for the applicability of the employed theoretical models.Comment: 8 pages, LaTeX, submitted to European Journal of Physics

YBCO Transition Edge Sensors Used For Very Low Noise Thermal Control

In electrically substituted radiometers, the ultra low noise control of the temperature is required. In this framework, we present results dedicated to the temperature regulation of copper plates, 3 cm diameter and 1 mm thick, using YBa2Cu3O7-d (YBCO) transition edge sensors (TES). One of the TES was used as the active thermometer of the temperature control unit, whereas the two others measured the plate temperature behavior. Two heating resistors were wound along a spiral pattern, just underneath the copper plate, to minimize the heating delay. The correlation between the two TES was clearly highlighted by applying a small heat perturbation through the second distributed resistor, the path of which closely follows that of the main resistor. Calibrated temperature oscillations of 30 microK rms at 10mHz together with spectral analysis were measured and a temperature resolution in the range of a few microK rms was achieved.Comment: 6 pages, ASC 2002 (Applied Superconductivity Conference), Houston, TX USA (Aout 2002): Oral contribution, to be published in IEEE Trans. Appl. Supercond. June 200

Refining code ownership with synchronous changes

When mining software repositories, two distinct sources of information are usually explored: the history log and snapshots of the system. Results of analyses derived from these two sources are biased by the frequency with which developers commit their changes. We argue that the usage of mainstream SCM (software configuration management) systems influences the way that developers work. For example, since it is tedious to resolve conflicts due to parallel commits, developers tend to minimize conflicts by not contemporarily modifying the same file. This however defeats one of the purposes of such systems. We mine repositories created by our tool Syde, which records changes in a central repository whenever a file is compiled locally in the IDE (integrated development environment) by any developer in a multi-developer project. This new source of information can augment the accuracy of analyses and breaks new ground in terms of how such information can assist developers. We illustrate how the information we mine provides a refined notion of code ownership with respect to the one inferred by SCM system data. We demonstrate our approach on three case studies, including an industrial one. Ownership models suffer from the assumption that developers have a perfect memory. To account for their imperfect memory, we integrate into our ownership measurement a model of memory retention, to simulate the effect of memory loss over time. We evaluate the characteristics of this model for several strengths of memor

Evaluating defect prediction approaches: a benchmark and an extensive comparison

Reliably predicting software defects is one of the holy grails of software engineering. Researchers have devised and implemented a plethora of defect/bug prediction approaches varying in terms of accuracy, complexity and the input data they require. However, the absence of an established benchmark makes it hard, if not impossible, to compare approaches. We present a benchmark for defect prediction, in the form of a publicly available dataset consisting of several software systems, and provide an extensive comparison of well-known bug prediction approaches, together with novel approaches we devised. We evaluate the performance of the approaches using different performance indicators: classification of entities as defect-prone or not, ranking of the entities, with and without taking into account the effort to review an entity. We performed three sets of experiments aimed at (1) comparing the approaches across different systems, (2) testing whether the differences in performance are statistically significant, and (3) investigating the stability of approaches across different learners. Our results indicate that, while some approaches perform better than others in a statistically significant manner, external validity in defect prediction is still an open problem, as generalizing results to different contexts/learners proved to be a partially unsuccessful endeavo

Construire son Propre Rapport à l’Autorité Enseignante en s’Engageant dans un Processus d’Autorisation de Soi

Partant des impasses de l’autorité naturelle dans la relation d’enseignement, cet article approfondit la dimension « avoir de l’autorité » qui concerne la part de subjectivité que chaque professeur engage dans cette relation. En se plaçant du point de vue d’un sujet enseignant qui construit son propre rapport à l’autorité en s’engageant dans un processus d’autorisation de soi, l’auteur observe le travail de la subjectivité à l’œuvre dans la relation d’enseignement traversée par la problématique de l’autorité, à travers deux vignettes cliniques. Dans leur prolongement, il situe l’enjeu d’un tel travail, la construction d’une posture professionnelle plus pérenne, adéquate, en convoquant la notion de cadre éducatif qui concerne prioritairement l’ « avoir », à l’articulation de l’histoire personnelle et de la posture professionnelle. Des objets de travail pour la formation se dégagent : le rapport à cette histoire, à soi et aux autres, au savoir ; le retour sur les figures d’enseignants qui habitent le professeur.   Starting from the impasse of natural authority in the educational relationship, this article focuses on the dimension of “having authority”, which concerns the part of subjectivity each teacher engages in the educational relationship. Situating himself from the point of view of a teaching subject who builds her or his relation to authority by engaging in a process of self authorization, the writer of this article observes in two clinical vignettes how subjectivity is at work in the educational relationship as it is linked with the question of authority. Then to situate what is at stake in this subjective process – constructing a more adequate and sustainable professional posture – the article examines the notion of educational framework as it deals primarily with “having” and  how this connects with a teacher’s personal background and professional posture. Questions to address in training are thus the following: the relations to one’s personal story, to oneself, to others and to knowledge; analysing teachers’ figures inspiring trainee teachers.   Partindo dos impasses da autoridade natural da relação docente, esse artigo aprofunda a dimensão “ter autoridade” que concerne à parte subjetiva que cada professor engaja nessa relação. Colocando-se do ponto de vista de um sujeito ensinante que constitui sua própria relação de autoridade se engajando em um processo de autorização de si, o autor observa a função da subjetividade na relação docente atravessada pela problemática da autoridade através de duas vinhetas clínicas. Continuando, ele situa o desafio de tal trabalho, a construção de uma postura profissional mais perene, adequada, convocando a noção de estrutura educacional prioritariamente relacionada ao “ter”, à articulação de história pessoal e da postura profissional. Objetos de trabalho para a formação emergem: a relação com essa história, a si e aos outros, ao saber; o retorno das figuras de ensino que habitam o professor

Élaborer une posture professionnelle singulière pour « avoir » de l’autorité, à travers le cas de Sébastien.: Une approche clinique de l’autorité enseignante

Partindo da pergunta “o que nos faz ter autoridade ou não?”, esta contribuição tem como objetivo entender como Sébastien, professor iniciante do ensino fundamental, está tentando construir essa postura, esse posicionamento profissional que lhe permitiria “ter” autoridade. É a fato de “ter” autoridade que é privilegiado, segundo uma abordagem clínica pautada na sensibilidade psicanalítica. “Ter” autoridade diz respeito à parcela de subjetividade envolvida na relação de ensino. Esta história, que atesta a necessidade deste professor de construir uma relação singular com a autoridade enquanto profissional, em particular devido à influência da figura de um pai que ensina e às primeiras experiências em centros de férias, nos permitirá estender nossa reflexão sobre o lugar do terceiro ao fundar e legitimar a autoridade de ensino. Mostraremos que esse terceiro se refere à problemática do não negociável do lugar geracional e da função institucional – que diz respeito à dimensão estatutária da autoridade de ensino, da ordem da lei antropológica –, bem como à capacidade do professor para definir e manter um enquadre educativo