Gabriel Pinto

Experiences in education innovation: developing tools in support of active learning

The paper focuses on educational projects developed in the ETSII (Escuela Técnica Superior de Ingenieros Industriales) of the Polytechnic University of Madrid during the past few years. These projects were developed as new tools for enhancing the active role of students, for improving practical teaching, especially by means of virtual laboratories and different sets of problems and exercises, and for promoting self-learning. The paper analyses the use of ICT in teaching, with the case of a developed e-learning platform as a tracking system for subjects. The paper concludes by discussing the new educational trends in the Centre, devoted to develop an active role of students by activities such as peer mentoring and laboratory monitors programs, and competitions for achieving multidisciplinary engineering challenges.

Using the Lambert-Beer law for thickness evaluation of photoconductor coatings for recording holograms

Abstract An experimental study on geometrical thickness measurements of photoconductor polymer coatings on thermoplastic polyester film substrate used as commercially available recording holograms is reported. The bases of these measurements which enable the evaluation of both total and coating thicknesses are the interference visible and infrared absorption spectra and the absorbance value of a band caused by the photoconductor coating in the infrared spectrum. A new technique, based on the Lambert-Beer law is proposed in order to obtain the thickness measurement of the coating.

Analysis of the relationship between surface roughness and reflectometrical measurement of polyethylene films

Abstract With the help of mechanical stylus instruments the geometry of polymer film surfaces can be determined directly. The relation between the statistically calculated average roughness, Ra, and the reflectometrical value with incidence angle of light of 60°, R′60, for polyethylene films, can be described by the equation R′ 60 = a + b R a , (where a and b are constants). By using this relationship, the magnitude of reflectometrical value of such materials can be used directly as a quantitative measure of film surface roughness.

Morphology, thermal stability and thermal degradation kinetics of cellulose-modified urea-formaldehyde resin

This article reports a study on the structural characterization and evaluation of thermal degradation kinetics of urea–formaldehyde resin modified with cellulose, known as UFC resin. Structural characterization of UFC undertaken by scanning electron microscopy, Fourier transform infrared and X-ray diffraction analyses reveals that the resin is fairly homogenous, and it constitutes of partly crystalline structure including urea–formaldehyde/cellulose interface morphology different from UFC precursors. Measurement of inherent thermal stability, probing reaction complexity and the thermal degradation kinetic analysis of UFC have been carried out by thermogravimetric/differential thermal analyses (TGA/DTA) under non-isothermal conditions. The integral procedure decomposition temperature elucidates significant thermal stability of UFC. TGA/DTA analyses suggest highly complicated reaction profile for thermal degradation of UFC, comprising various parallel/consecutive reactions. Different differential and integral isoconversional methods have been employed to determine the thermal degradation activation energy of UFC. Substantial variation in activation energy with the advancement of reaction verifies multi-step reaction pathway of UFC. A plausible interpretation of the obtained kinetic parameters of UFC thermal degradation with regard to their physical meanings is given and discussed in this study.

Measuring Properties of Industrial Polymer Films Using Interference Fringes in the Infrared Region

Abstract A study about the interference fringes caused in the infrared region by polymer films and their applications to the evaluation of some properties is reported. Interference fringes, a sinusoidal waveform superimposed on the baseline, arise from reinforcement and destructive interference of various wavelengths of radiation reflected from the internal surfaces of the film when the IR spectrum is carried out. An optical interference method is proposed for measuring the thickness and the refractive index, both within an accuracy better than 1%, and for evaluating the surface texture of polymer films. Each one of these procedures is explained by its application for polypropylene, polystyrene and polyethylene films, respectively, three commercially available industrial films widely used for packing and membranes. These methods can easily be extended to any fair thin film of transparent or weakly absorbing solid materials.

CONSIDERATIONS OF SURFACE STRUCTURE CHARACTERIZATION FOR POLYETHYLENE FILMS BY REFLECTOMETRY

Abstract Several polyethylene film surfaces were examined by the reflectometry technique by using different incidence angles of light. A logarithmic relationship has been found between the measured reflectometrical values using different incident angles.

Kinetics of the thermal degradation mechanisms in urea-formaldehyde cellulose composites filled with zinc particles

This paper reports a study on the structural characterization, thermal stability, and thermal degradation kinetics of urea-formaldehyde cellulose (UFC) composites filled with zinc particles. Structural characterization of UFC/Zn composites carried out by SEM, XRD and FTIR analyses reveals that the composites are fairly homogenous, and the interactions between UFC and zinc in the composites are physical in nature. Afterwards, measurements of inherent thermal stabilities, probing reaction complexity, and thermal degradation kinetics of UFC/Zn composites have been carried out. The integral procedure decompositions temperature elucidates significantly higher thermal stabilities of UFC/Zn composites. Isoconversional kinetic analysis suggests multi-step reaction pathways of UFC/Zn composites in terms of the substantial variations in their activation energies with the reaction advancement. Advanced reaction model determination methodology with the help of an innovative kinetic function F(α, T) reveals that the thermal degradation of UFC goes to completion by following complicated multi-step nucleation/growth mechanisms. A detailed account of the mechanistic information regarding to the thermal degradation processes taking place in UFC/Zn composites is given and discussed in the present study.

Industriall Control of the Filtration in the Beer Manufacturing Process

Abstract In the aim to improve the filtration process in the beer ma nufacture, a study on the beer turbidity have been made using two different techniques: nephelometry and V-UV spectrometry. Even though the former is the most commonly used, we propose the use of V-UV spectrometry since it is possible to follow the performace - of all the filtration line, not only in a punctual way but in a - wide range of wavelenghts. From the results of this work we deduce that V-UV spectrometry offers a better quality of results than nephelometry, being more useful in rutin periodic controls.

SPECTROSCOPIC STUDY ABOUT THE KINETICS OF THE ANTHOCYANIN PIGMENTS EXTRACTION DURING THE MACERATION OF CHERRIES IN LIQUOR

ABSTRACT An experimental study of the effect of temperature on the kinetics of anthocyanin pigments extraction during the maceration of cherries (Prunnus avium) into a hard spirit is reported. The analytical method used was UV-Vis spectrophotometry. The initial extraction rate showed an Arrhenius-type dependency, with an apparent energy activation of 18.7±1.2 kcal/mol. Furthermore, a study about the evolution of the color (from colorless to red-orange) during the soaking process was made by calculating the CIE tristimulus values (X, Y, Z) for illuminant C, until to reach the apparent stabilization of color, what occurs after about two weeks for temperatures of 5°C and 23°C, whereas it happens after about four weeks for the other studied temperature (30°C).

Interference spectra in the visible region of transparent coatings applied to plastic industrial lenses

Abstract The effects of geometry of lenses on the determination of thickness of transparent protective coatings applied to ophtalmic lenses by the interference visible spectra analysis were investigated. The obtained results suggest that, although the thickness of protective coatings is similar (on the order of 3–5 μm), the definition of interference fringes decreases with increasing absolute value of spherical power (measured in diopters); nevertheless, interference visible spectra allow the accurate measurement of thickness of thin transparent layers applied to surface of ophtalmic lenses.