Enrique Andrés Coleoni

Simulation of x-ray spectra generated by electron impact on solids

A simulation algorithm that generates x-ray emission spectra of samples irradiated with kilovolt electron beams was developed. The algorithm is based on a Monte Carlo package which performs simulations of both electron and photon transport for arbitrary materials and geometries. The code uses semi-empirical ionization cross-sections obtained from an optical data model and a simple model to describe the angular distribution of bremsstrahlung photons. The simulation efficiency is optimized by the use of a variance reduction technique. The reliability of the simulation code was analyzed by comparing the results with electron probe measurements for different specimens and measurement conditions, including thin films and oblique incidence. In general, there was good agreement between the simulation results and experiences. Copyright

UN FENÓMENO, DOS TEORÍAS: UNA ELECCIÓN PARA LA RESOLUCIÓN DE PROBLEMAS EN FÍSICA

The present work is a) a comparative analysis of two theoretical approaches for cognition in Physics Problem Solving, and b) a discussion of the extent to which both of these approaches are able to account for protocols of students solving problems. One of the approaches is grounded on the classical expert-novice difference studies. The other one is a theoretical framework based on a mani- fold and context-sensitive view of cognition. The analysis addresses two key aspects of problem solving: the nature of the knowledge involved and the processes that takes place. The result of this analysis points out the limitations and the benefits of these approaches in order to understand why students do what they do when solving problems.

Diferenciando grados de sofisticación epistémica durante la resolución de un problema de electrostática

Resumen: El presente es un estudio en el cual se analizan las producciones de tres estudiantes de un curso universitario introductorio mientras resuelven un problema de electrostatica. El objeto de estudio son las epistemologias personales, las cuales sirven a los estudiantes, y a los sujetos en general, para gestionar el propio conocimiento y posicionarse de maneras particulares frente a este durante tareas cognitivas como la resolucion de problemas. Se presenta un aporte de caracter teorico en relacion al constructo de sofisticacion epistemica. Se proveen elementos que permiten graduarla y tomarla como un indicador de la experticia de los sujetos en el plano epistemico. La importancia de los resultados radica en la posibilidad de visibilizar mas la dimension epistemica en el aprendizaje de la fisica. Palabras clave: Ensenanza de la fisica. Ensenanza superior. Epistemologia personal. Resolucion de pro -blemas. Electrostatica. Abstract: The present paper presents a case study in which an analysis is carried out on the production of three introductory physics students while solving an electrostatic problem at college level. The objects under study are students’ personal epistemologies, which enable them, and everyone, to deal with their own knowledge in different ways when confronted to cognitive activities such as problem solving. The contribution of this paper is theoretical, and is related to the construct of epistemic sophistication. Our analysis provides elements that allow for a grading of sophistication as an indicator of subjects’ epistemic expertise. Results are important in their potential value to better understand the epistemic dimension in the learning of Physics. Keywords: Physics teaching. Higher education. Personal epistemology. Problem solving. Electrostatics.