El papel del péndulo en la construcción del paradigma newtoniano

This paper shows the important role of one of the most common instruments, the pendulum, in the construction of the newtonian paradigm. From the analysis of some interesting applications carried out by the greatest scientists of that time, we conclude that the appropriate use of the pendulum in the classroom can be an easy way to introduce historical and epistemological evolution of basic physical concepts

Transferencia inter-dominios en resolución de problemas : una propuesta instruccional basada en el proceso de «traducción algebraica»

Understanding a science and math word problem means constructing mental representations at different levels of abstraction. Secondary students have dificulties solving algebraic word problems due to the transition from the concrete representation to the mathematic representation. In order to facilitate the «algebraic translation» of the problems, we adapt a «rule to put a problem into equations» by Puig (1998) and insert it in an experimental methodology devoted to improving the inter-domain transfer in science. Results show the power of the instructional methodology to overcome most of the students’ dificulties, no matters their average academic performance.Comprender un problema con enunciado en ciencias y matemáticas implica construir representaciones mentales en diferentes niveles de abstracción. Las dificultades que los estudiantes de secundaria tienen a la hora de resolver problemas algebraicos con enunciado parecen originarse en la transición entre la representación concreta y la representación matemática de los problemas. Para facilitar este proceso llamado «traducción algebraica del problema», se adapta una «regla para poner un problema en ecuaciones» propuesta por Puig (1998) y se integra en una metodología experimental en la que se busca mejorar la transferencia inter-dominios en ciencias. Los resultados muestran la potencia de la propuesta para superar gran parte de los obstáculos que los estudiantes de estos niveles tienen, con independencia de su rendimiento académico global

ZnO growth by MOCVD: numerical study

EnIII−V compound device fabrication is facing today challenging issues typically related to high volume manufacturing such as process reliability, process consistency, cost−reduction. Each step of the overall device manufacturing process must be carefully analysed and replicated to obtain reproducible device structures. Purifiers are commonly used in MOVPE processes and are becoming standard equipment in both research and production environments. In most cases implementation of gas purification strategies is enabling to achieve ultimate product purity and process reproducibility by defect and contamination control. In addition, an appropriate gas purification strategy is effective in high value component/chemicals protection (e.g. high purity MO sources), and as an assurance against line contamination due to human error or component failure. Purifier operating conditions can vary noticeably and a knowledge of which parameters can affect ultimate gas purity should be of interest to MOVPE operators to master gas distribution line contamination issues. Expertise on such parameters and their effect is essential to obtain a reliable product and sub−ppb contamination control throughout the purifier's lifetime and not only in spot demonstrations

Bandgap and effective mass of epitaxial cadmium oxide

The bandgap and band-edge effective mass of single crystal cadmium oxide, epitaxially grown by metal-organic vapor-phase epitaxy, are determined from infrared reflectivity, ultraviolet/visible absorption, and Hall effect measurements. Analysis and simulation of the optical data, including effects of band nonparabolicity, Moss-Burstein band filling and bandgap renormalization, reveal room temperature bandgap and band-edge effective mass values of 2.16±0.02 eV and 0.21±0.01m0 respectively