What has been of terraces? (an analysis linking previous historical terraces projects with a current prototype)

Postprint (published version

Phase-field simulations of viscous fingering in shear-thinning fluids

A phase-field model for the Hele-Shaw flow of non-Newtonian fluids is developed. It extends a previous model for Newtonian fluids to a wide range of shear-dependent fluids. The model is applied to perform simulations of viscous fingering in shear- thinning fluids, and it is found to be capable of describing the complete crossover from the Newtonian regime at low shear rate to the strongly shear-thinning regime at high shear rate. The width selection of a single steady-state finger is studied in detail for a 2-plateaux shear-thinning law (Carreau law) in both its weakly and strongly shear-thinning limits, and the results are related to previous analyses. In the strongly shear-thinning regime a rescaling is found for power-law (Ostwald-de-Waehle) fluids that allows for a direct comparison between simulations and experiments without any adjustable parameters, and good agreement is obtained

Comunicación entre un variador de frecuencia y un autómata programable

Los equipos de control y automatización más usados en la industria, son sin duda el autómata programable y el variador de frecuencia. Entre ellos se puede establece una comunicación para poder compartir datos, y esta se puede hacer de diferentes modo. En este artículo se analizan los métodos más usuales en la industria de comunicar estos dos equipos. Dada la cantidad de equipos y marcas que existen en el mercado y sus posibilidades, se necesitaría de un texto mucho más amplio y completo que el recogido en este artículo. No obstante, se detallan con claridad las formas básicas, para que el lector pueda tener unos conocimientos mínimos que le permitan tomar las decisiones oportunas, tanto en una conexión elemental entre equipos, como la forma de atacar la información mucho más detallada de los fabricantes.Roger Folch, J. (2013). Comunicación entre un variador de frecuencia y un autómata programable. http://hdl.handle.net/10251/3120

Experimental determination of the activity of a 252Cf source

An important research line in nuclear physics nowadays is the study of unstable nuclei. Within this, one area of interest is the study of delayed neutron emission which is of relevance for di erent elds such as astrophysics, nuclear technology and nuclear structure. The study of di erent aspects of decay of exotic nuclei, such as half lives and neutron emission probabilities, provide information about their structure and these measurements are sometimes the only ones that can be performed in nuclei with very low yields. The work presented here aims at measuring the neutron activity of a 252Cf source. The goal is to verify the activity provided by the manufacturer and reduce its quoted uncertainty. The method used to obtain the 252Cf neutron source activity is based on the measurement of the gamma ray spectrum of the ssion products [1]. Once calibrated this source will be used to calibrate a neutron detector designed at UPC that is currently being used to measure delayed neutron emission. However that is beyond the scope of this work. The rst chapter of this document describes the theoretical concepts of delayed neutron emission; it also presents a brief summary about the UPC neutron detector prototype that we aim at calibrating, an overview of di erent types of neutron sources and the calibration method of the detector. The second chapter refers speci cally to the characteristics of 252Cf neutron source calibrated and the experimental setup. Chapters three and four detail the procedure for the determination of the activity of the 252Cf neutron source studied passing through the germanium detector calibration. The last chapter presents the conclusions of the results of this study and improvements to perform in future similar calibrations of this type

Conocimientos y expectativas en la cogeneración de energía eléctrica

Hoy en día existen diferentes industrias con capacidad de generar energía eléctrica, al necesitar en sus procesos la participación de las denominadas energías primarias (fundamentalmente gas natural o derivados del petróleo). Esta característica puede resultar muy atractiva tanto desde el punto de vista económico como desde el punto de vista medioambiental. En este trabajo se analizan de forma básica las condiciones que deben reunir las industrias para poder llevar a cabo esta generación (conocida como ¿cogeneración¿). Se enuncia las dos formas clásicas de cogeneración y se trata de instruir al lector en una tecnología, por la amplitud de este trabajo, solo se pueden enunciar los criterios mínimos de forma que se pueda adquirir una sensibilización para seguir estudiando detenidamente estos temas y en el ámbito que sea más propicio a las necesidades de cada tipo de industria.Roger Folch, J. (2013). Conocimientos y expectativas en la cogeneración de energía eléctrica. http://hdl.handle.net/10251/3122

First measurement of beta-decay half-lives and neutron emission probabilities in several isotopes beyond N = 126

In this work beta-decay half-lives and neutron-emission probability values have been experimentally determined for first time in several nuclei beyond the neutron-shell closure at N=126. To this aim the accelerator complex at the GSI center for heavy ion research (Germany), in combination with the FRS fragment separator, were employed. The beta-decay detection system consisted of a charged particle detector named SIMBA, which served to detect both ion and beta-particles, surrounded by an array of He-3 based neutron counters named BELEN. The half-life values of eighteen isotopes of Au, Hg, Tl, Pb and Bi were determined, as well as the neutron-branching ratios (or upper limits) for seven nuclei. A comparison of the present results with previous half-life measurements in this mass-region shows a generally good agreement, thus reflecting the systematic validity of the decay data available in this region. Compared to theoretical models, our results show a reasonable agreement for half of the analyzed isotopes, and large discrepancies of up to a factor of 10 for the other half. The measured neutron-branching ratios represent the first set of experimental data available in this mass-region for several isotopes. Owing to the absence of previous experimental results, the values reported here can be only compared with theoretical predictions. In summary, a fair compatibility is found between FRDM+QRPA calculations, which however are underestimating by a factor of 5 the neutron-branching ratio of Tl-215, which is the most exotic nucleus measured in this work.En aquest treball s'han determinat, experimentalment i per primera vegada, vides mitjanes i valors de probabilitat d'emissió de neutrons de diversos nuclis amb més de 126 neutrons. Per tal d'obtenir les dades es va realitzar un experiment a les instal·lacions del centre d’investigació d'ions pesats GSI a (Alemanya), combinat amb el separador de fragments FRS. El sistema de detecció d'ions i desintegracions beta va consistir d'un detector de partícules carregades anomenat SIMBA, que estava envoltat per una matriu de comptadors proporcionals d’'He-3 que conformen el detector de neutrons BELEN. En total s'han determinat valors de vida mitjana de divuit isòtops d'or, mercuri, tal·li, plom i bismut, així com també la probabilitat d'emissió de neutrons (o llindars superiors) de set d'ells. Comparant els resultats amb les mesures de vides mitjanes anteriors en aquesta regió de nuclis s'observa un bon acord, reflectint la validesa de la sistemàtica de les dades existents. D’'altra banda, fent la comparació amb els models teòrics, els resultats mostren un acord raonable per la meitat dels isòtops analitzats, i grans discrepàncies, de fins a un factor 10, per l'altra meitat. Pel que fa a les probabilitats d'emissió de neutrons mesurades, essent la primera mesura experimental a la regió per a diversos nuclis, no és possible comparar amb altres els valors obtinguts. La única comparació que es pot avaluar és amb les prediccions teòriques. En resum, els resultats són compatibles amb el model FRDM + QRPA, no obstant s'observen discrepàncies considerables en alguns isòtops de fins a un factor 5, com és el cas del valor obtingut per Tl-215, que correspon al nucli més exòtic del qual s'’ha determinat la probabilitat d’'emissió de neutrons

Quantitative Phase Field Model of Alloy Solidification

We present a detailed derivation and thin interface analysis of a phase-field model that can accurately simulate microstructural pattern formation for low-speed directional solidification of a dilute binary alloy. This advance with respect to previous phase-field models is achieved by the addition of a phenomenological "antitrapping" solute current in the mass conservation relation [A. Karma, Phys. Rev. Lett 87, 115701 (2001)]. This antitrapping current counterbalances the physical, albeit artificially large, solute trapping effect generated when a mesoscopic interface thickness is used to simulate the interface evolution on experimental length and time scales. Furthermore, it provides additional freedom in the model to suppress other spurious effects that scale with this thickness when the diffusivity is unequal in solid and liquid [R. F. Almgren, SIAM J. Appl. Math 59, 2086 (1999)], which include surface diffusion and a curvature correction to the Stefan condition. This freedom can also be exploited to make the kinetic undercooling of the interface arbitrarily small even for mesoscopic values of both the interface thickness and the phase-field relaxation time, as for the solidification of pure melts [A. Karma and W.-J. Rappel, Phys. Rev. E 53, R3017 (1996)]. The performance of the model is demonstrated by calculating accurately for the first time within a phase-field approach the Mullins-Sekerka stability spectrum of a planar interface and nonlinear cellular shapes for realistic alloy parameters and growth conditions.Comment: 51 pages RevTeX, 5 figures; expanded introduction and discussion; one table and one reference added; various small correction

Communicative methodology: Contributions to social impact assessment in psychological research

Recent advancements in the social impact assessment of science have shown the diverse methodologies being developed to monitor and evaluate the improvements for society as a result of research. These assessment methods include indicators to gather both quantitative and qualitative evidence of the social impact of science achieved in the short, medium, and long terms. In psychology, the impact of research has been mainly analyzed in relation to scientific publications in journals, but less is known about the methods for the social impact assessment of psychological research. Impact assessment in the domains of educational psychology and organizational psychology presents synergies with bottom-up approaches that include the voices of citizens and stakeholders in their analyses. Along these lines, the communicative methodology (CM) emerges as a methodology useful for the communicative evaluation of the social impact of research. Although the CM has widely demonstrated social impact in the social sciences, less is known about how it has been used and the impact achieved in psychological research. This article unpacks how to achieve social impact in psychology through the CM. In particular, it focuses on the theoretical underpinnings of the CM, the postulates linked to psychological research and some key actions for the implementation of the CM in relation to the design of Advisory Committees, working groups, and plenary meetings in research. Furthermore, it shows how the CM has been implemented in illustrative cases in psychological research. The article finishes with a conclusion and recommendations to further explore the ways in which the CM enables the social impact of research in psychology