On the use of thermal conductive focusing for solar concentration enhancement

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/We discuss the possibility for solar concentration enhancement via conductive heat transport. Here, we are concerned, as in orthodox approaches, about maximizing the solar concentration to obtain the highest receiver temperature possible, but with one important difference: In the proposed approach, the solar concentration enhancement is attained not by the use of lenses, mirrors, or funnels (i.e., by optical concentration based on radiative transport), but via thermal conduction, what we call thermal conductive focusing. Among the additional advantages of thermal conductive focusing is the capability to concentrate indistinct direct incidence as well as diffusive radiation. Thus, the concept is especially insensitive to cloudy days and particularly attractive in application to environments with important diffusive components of light. Utilizing a simplified geometrical model, an analytical expression for the temperature and concentration gain at the receiver was derived. The particular application for a parabolic solar trough was analysed. Additional research and development is required to explore the possibilities of solar flux enhancement by thermal conductive focusing as well as the optimization of several variables.Peer ReviewedPostprint (author's final draft

On the use of encapsulated phase change materials pebbles and pellets as freeze protection method for low-stature plants/crops

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The use of phase change materials (PCMs) in encapsulated pebbles or pellets as freeze protection method for low-stature plants/crops is proposed and discussed at the conceptual level. Utilizing a simplified geometrical model, it is shown that, for practical applications, small encapsulated-PCM pebbles/pellets of 1-cm sized could provide the necessary heat to prevent the freezing during typical freezing time. Taking into account the balance between the loss of energy on a typical frost night and the latent energy stored in the encapsulated PCMs-pebbles/pellets, the amount of such pebbles/pellets per unit of soil-area was calculated and resulting in the use of less than 2% of the soil-area. The preliminary results at conceptual level are encouraging, however, additional work and R&D is require before its real practical efficacy can be put to test. The choice of the suitable crops, the specific environmental conditions during the freezing time, the manufacture recyclability and environmental impact of the pcm-pebbles/pellets are some of the aspects which must be carefully addressed.Peer ReviewedPostprint (author's final draft

The behavior of radiogenic particles at solidification fronts

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The thermal behavior of insoluble radiogenic particles at the solid-liquid interface of an advancing solidification front and its significance with regard to environmental impact are discussed. It is shown that, unlike classical particles, where the most probable behavior is engulfing by the solidification front, radiogenic particles are more likely to be rejected by the solidification front. Utilizing a simplified physical model, an adaptation of classical theoretical models is performed, where it is shown that, unlike classical particles, for radiogenic particles the mechanism is thermally driven. An analytical expression for the critical velocity of the solidification front for engulfing/rejection to occur is derived. The study could be potentially important to several fields, e.g. in engineering applications where technological processes for the physical removal of radionuclide particles dispersed throughout another substance by inducing solidification could be envisaged, in planetary science where the occurrence of radiogenic concentration could result in the possibility of the eruption of primordial comet/planetoids, or, if specific conditions are suitable, particle ejection may result in an increase in concentration as the front moves, which can translate into the formation of hot spots.Peer ReviewedPostprint (author's final draft

Heat removal system for shutdown in nuclear thermal rockets and advanced concepts

© 2016 by the American Institute of Aeronautics and Astronautics, Inc.It is well-known that a nuclear thermal rocket (NTR) cannot be abruptly shut down. After a power manoeuver, the reactor has contaminated itself with fission products and the decay heat released must be removed by maintaining an adequate flow of hydrogen through its passages. The objective of this work was to derive a first estimate of how much hydrogen will be needed to prevent the core from overheating after shutdown, and, from this, be able to assess the advantages of using a dedicated decay heat removal system to reduce or eliminate the amount of hydrogen needed to prevent the core from overheating after shutdown. Furthermore, the use of such a heat removal system could be needed by certain special nuclear thermal propulsion concepts, such as the fission fragment rocket or the more recently proposed pulsed nuclear thermal rocket, where significant amplification of specific impulse, Isp, as well as thrust can be obtained by the direct use of fission fragments or by pulsing the nuclear core, respectively.Peer ReviewedPostprint (author's final draft

A neutron diode for subcritical multistage multipliers with special reference in tritium breeding

This is a copy of the author 's final draft version of an article published in the Journal of fusion energy. The final publication is available at Springer via http://dx.doi.org/10.1007/s10894-015-0049-7In this paper the interaction between a magnetic field and the neutron spin magnetic moment is explored for use in the design of a neutron diode or valve that allows a neutron flux to pass in one direction, while preventing a neutron flux in the opposite direction. A neutron diode that ensures the unidirectional movement of neutrons could be used in the design of a subcritical multistage neutron multiplier, a device that has thus far not been realised. With a subcritical multistage neutron multiplier, an initial source of neutrons could be multiplied substantially in a very small area. Such a device could have potential applications in tritium breeding in a fusion reactor, in medicine, in space exploration, etc. Utilizing a simplified geometrical model, a first preliminary study is performed to assess the feasibility of this concept.Peer ReviewedPostprint (author's final draft

A linear mass spectrometer by induced Hall potential for electromagnetic isotopic separation working at high pressures

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In this paper a novel alternative for bulk electromagnetic separation working at high pressures is proposed. It is shown that if a self-induced Hall potential is stimulated in the boundaries, the system will be able to take advantage of the collisions process, boosting the isotopic separation and resulting in a linear-spectrometer with a higher spatial separation per unit length than a traditional calutron. Although originally the concept was devised for the production of medical isotopes where the minority isotope to be separated is produced by neutron capture and is the heavier isotope, if the Hall potential is replaced by an external electrical field, the concept is equally applicable for situations where the minority isotope is the lighter one, as for example in the enrichment of uranium. Additional R&D is required to explore further the possibilities of this concept and to identify optimal values for several of the system design variables.Peer ReviewedPostprint (author's final draft

MOMENTOS DE LOS LÍMITES GEOMÉTRICOS Y SU APLICACIÓN AL CONTROL DE CALIDAD AUTOMATIZADO EN LA INDUSTRIA

In this research the performance of the Chen's Improved (Boundary) Moments is carefully compared to that of the traditional (Massive) Moments. To achieve this investigation, the pattern recognition power of the former is thoroughly assessed against that of the latter. The boundary moments are evaluated by two methods, in the first by edge-tracing, in the second method the edge pixels are considered as though they are met when sweeping the image space. It is concluded that the computation of the Boundary Moments by sweeping the image space associates minimum computational complexity to a high enough object classification efficiency, thus they may be used in lieu of the traditional moments.En esta investigación se lleva a cabo una detallada comparación de la performance de los Momentos Mejorados (de Borde), de C.C. Chen, con los Momentos Masivos tradicionales, para ejecutar este examen, el poder de reconocimiento de objetos de los primeros es cuidadosamente comparado con aquella de los últimos. Los Momentos de Borde son evaluados usando dos métodos, en el primero, mediante Trazado de Bordes, y en el segundo, mediante Barrido de Imagen. Se concluye que el cálculo de los Momentos de Borde mediante Barrido de Imagen, asocia una Complejidad Computacional mínima a una suficientemente alta eficiencia en la clasificación de objetos, pudiendo entonces ser usados en lugar de los Momentos Tradicionales

Fusión controlada de imágenes

A Virtual Lab to experiment on controlled fusion of two digital images has been developed. The resulting image has user pre-defined percentages of each contributing image. With the aim on improving the quality of the resulting image in the fusion, the Virtual Lab has been enabled with the option of selecting a color to be ignored during the fusion process, in this way this color is not fussioned. Successful experiments have been executed fusing three images using the same algorithm.Se ha desarrollado un laboratorio virtual para experimentar la fusión controlada de dos imágenes digitales. La imagen resultante posee porcentajes predefinidos de cada imagen participante. Con la finalidad de mejorar la calidad de la imagen resultante de la fusión, el laboratorio virtual incluye la opción de ignorar un color durante la fusión, lo que hace que este color no experimente fusión alguna. Se han realizado experimentos exitosos fusionando tres imágenes con el mismo algoritmo

Rotura de maquinaria: Una explicación a partir de la Teoría del Caos

An attempt to explain the process of machinery breakdown by means of Chaos Theory is presented. Machines carry out repetitive tasks that may be mathematically modelled as combinations of forced oscillatory motions; consequently these are perfect candidates to eventually evolve towards chaos. The exposition is made having as a model the route to chaos in the damped and forced non-linear oscillator.Se expone una tentativa para explicar el proceso de las fallas en maquinarias, basada en la teoría del caos. Las máquinas realizan tareas repetitivas que podrían ser modeladas matemáticamente como combinaciones de movimientos oscilatorios forzados; en consecuencia éstas son perfectas candidatas a eventualmente evolucionar hacia el caos. Se hace la exposición teniendo como modelo, la ruta hacia el caos seguida por un oscilador no lineal amortiguado y forzado

Laboratorio Virtual para la detección automatizada de siluetas en imágenes fusionadas

En algunas aplicaciones asociadas a la visualización de imágenes, por ojo humano o mediante visión automatizada por computadora, es necesario poder visualizar exclusivamente las siluetas de los elementos que aparecen en las imágenes, ya sea para emitir un diagnostico o para continuar con otros algoritmos de procesamiento digital de imágenes. En este documento se reporta el desarrollo de un Laboratorio Virtual, esto es, un módulo de software interactivo e integrado para llevar a cabo extracción de bordes, basada en histogramas, de imágenes fusionadas. El modulo incluye la generación automática de un umbral heurístico de binarizacion en la etapa previa a la extracción de siluetas, una característica que conduce a la eventual automatización de todo el proceso