SVis: A computational steering visualization environment for surface structure determination

The arrangement of atoms at the surface of a solid accounts for many of its properties: Hardness, chemical activity, corrosion, etc. are dictated by the precise surface structure. Hence, finding it, has a broad range of technical and industrial applications. The ability to solve this problem opens the possibility of designing by computer materials with properties tailored to specific applications. Since the search space grows exponentially with the number of atoms, its solution cannot be achieved for arbitrarily large structures. Presently, a trial and error procedure is used: an expert proposes an structure as a candidate solution and tries a local optimization procedure on it. The solution relaxes to the local minimum in the attractor basin corresponding to the initial point, that might be the one corresponding to the global minimum or not. This procedure is very time consuming and, for reasonably sized surfaces, can take many iterations and much effort from the expert. Here we report on a visualization environment designed to steer this process in an attempt to solve bigger structures and reduce the time needed. The idea is to use an immersive environment to interact with the computation. It has immediate feedback to assess the quality of the proposed structure in order to let the expert explore the space of candidate solutions. The visualization environment is also able to communicate with the de facto local solver used for this problem. The user is then able to send trial structures to the local minimizer and track its progress as they approach the minimum. This allows for simultaneous testing of candidate structures. The system has also proved very useful as an educational tool for the field.

Technical criteria for the desing of foundation slabs and perimetral wall in difficult terrain in Madrid. Spain

This paper explains a procedure for the choice of ballast modules used for the design of direct continuous foundation in karst terrain. The presence of dangerous cavities is introduced in this procedure thereby evaluating risk failure. It also provides pertinent guidelines to direct the geotechnical survey of the terrain.

Technical criteria for the design of foundation slabs and perimetral wall in difficult terrain in south east Madrid, Spain

This paper explains a procedure for the choice of ballast modules used for the design of direct continuous foundation in karst terrain. The presence of dangerous cavities is introduced in this procedure thereby evaluating risk failure. It also provides pertinent guidelines to direct the geotechnical survey of the terrain.

Survey on student motivation and approval of educational environment at Universidad Politécnica de Madrid within the European Higher Education area implementation

A recent study elaborated by Vicerrectorado de Ordenación Académica y Planificación Estratégica of Technical University of Madrid (UPM) defines the satisfaction of the university student body as "the response that the University offers to the expectations and demands of service of the students, considered in a general way ". Besides an indicator of academic and institutional insertion of the student, the assessment of student engagement allows us to adapt the academic offer and the extension services of the University to the real needs of the students. The process of convergence towards the European Higher Education Area (EHEA) raises the need to form in competitions, that is to say, of developing in our students capacities and knowledge beyond the purely theoretical-practical thing. Therefore, the perception and experience of the educational process and environment by the students is an important issue to be addressed to accomplish their expectations and achieve a curriculum accordingly to EHEA expectations. The present study aims to explore the student motivation and approval of the educational environment at the UPM. To this end a total of 97 students enrolled in the undergraduate program of Civil Engineering, Computer Engineering and Agronomic Engineering at UPM were surveyed. The survey consisted of 40 questions divided in three blocks. The first one of 20 questions of personal character in that they were gathering, besides the sex and the age, the degree of fulfilment, implication and dedication with the institution and the academic tasks. In the second block we identify 10 questions related to the perception of the student on the teaching quality, and finally a block of 10 questions regarding the Bologna Process. The students personal motivation was moderately high, with a score of 3.6 (all scores are provided on a 5-point scale), being the most valuable items obtaining a university degree (4,3) and the friendship between students (4,2). Any significant difference was shown between sexes (P=0.23) since the averages for this block of questions were of 3.7±0.3 and 3.5±0.4 for women and men respectively. The students are moderately satisfied with their graduate studies with an average score of 3,2, being the questions that reflect a minor satisfaction the research profile of the teachers (2,8) and the organization of the Schools (2,9). The best valued questions are related to the usefulness and quality of the degrees, with 3,5 and 3,4 respectively, and to the interest of the courses within the degree (3,4). For sexes, the results of this block of questions are similar (3.1±0.3 and 3.2±0.3 for men and women respectively=0.79). Also, there were no differences (P=0.39) between the students who arrange work and studies or do not work (3.1±0.2 and 3.2±0.3 respectively). In conclusion, students at UPM present an acceptable degree of motivation and satisfaction with regard to the studies and services that offer their respective Schools. Both characteristics receive the same value both for men and for women and so much for students who arrange work and studies as for those who devote themselves only to studying. In a significant way, students who are more engaged and are in-class attendants present the major degree of satisfaction.Overall, there is a great lack of information regarding the Bologna Process. In fact to the majority, they would like to know more on what it is, what it means and what changes will involve its implementation.

Bare-tape scaling laws for de-orbit missions in a space debris environment

El entorno espacial actual hay un gran numero de micro-meteoritos y basura espacial generada por el hombre, lo cual plantea un riesgo para la seguridad de las operaciones en el espacio. La situación se agrava continuamente a causa de las colisiones de basura espacial en órbita, y los nuevos lanzamientos de satélites. Una parte significativa de esta basura son satélites muertos, y fragmentos de satélites resultantes de explosiones y colisiones de objetos en órbita. La mitigación de este problema se ha convertido en un tema de preocupación prioritario para todas las instituciones que participan en operaciones espaciales. Entre las soluciones existentes, las amarras electrodinámicas (EDT) proporcionan un eficiente dispositivo para el rápido de-orbitado de los satélites en órbita terrestre baja (LEO), al final de su vida útil. El campo de investigación de las amarras electrodinámicas (EDT) ha sido muy fructífero desde los años 70. Gracias a estudios teóricos, y a misiones para la demostración del funcionamiento de las amarras en órbita, esta tecnología se ha desarrollado muy rápidamente en las últimas décadas. Durante este período de investigación, se han identificado y superado múltiples problemas técnicos de diversa índole. Gran parte del funcionamiento básico del sistema EDT depende de su capacidad de supervivencia ante los micro-meteoritos y la basura espacial. Una amarra puede ser cortada completamente por una partícula cuando ésta tiene un diámetro mínimo. En caso de corte debido al impacto de partículas, una amarra en sí misma, podría ser un riesgo para otros satélites en funcionamiento. Por desgracia, tras varias demostraciones en órbita, no se ha podido concluir que este problema sea importante para el funcionamiento del sistema. En esta tesis, se presenta un análisis teórico de la capacidad de supervivencia de las amarras en el espacio. Este estudio demuestra las ventajas de las amarras de sección rectangular (cinta), en cuanto a la probabilidad de supervivencia durante la misión, frente a las amarras convencionales (cables de sección circular). Debido a su particular geometría (longitud mucho mayor que la sección transversal), una amarra puede tener un riesgo relativamente alto de ser cortado por un único impacto con una partícula de pequeñas dimensiones. Un cálculo analítico de la tasa de impactos fatales para una amarra cilindrica y de tipo cinta de igual longitud y masa, considerando el flujo de partículas de basura espacial del modelo ORDEM2000 de la NASA, muestra mayor probabilidad de supervivencia para las cintas. Dicho análisis ha sido comparado con un cálculo numérico empleando los modelos de flujo el ORDEM2000 y el MASTER2005 de ESA. Además se muestra que, para igual tiempo en órbita, una cinta tiene una probabilidad de supervivencia un orden y medio de magnitud mayor que una amarra cilindrica con igual masa y longitud. Por otra parte, de-orbitar una cinta desde una cierta altitud, es mucho más rápido, debido a su mayor perímetro que le permite capturar más corriente. Este es un factor adicional que incrementa la probabilidad de supervivencia de la cinta, al estar menos tiempo expuesta a los posibles impactos de basura espacial. Por este motivo, se puede afirmar finalmente y en sentido práctico, que la capacidad de supervivencia de la cinta es bastante alta, en comparación con la de la amarra cilindrica. El segundo objetivo de este trabajo, consiste en la elaboración de un modelo analítico, mejorando la aproximación del flujo de ORDEM2000 y MASTER2009, que permite calcular con precisión, la tasa de impacto fatal al año para una cinta en un rango de altitudes e inclinaciones, en lugar de unas condiciones particulares. Se obtiene el numero de corte por un cierto tiempo en función de la geometría de la cinta y propiedades de la órbita. Para las mismas condiciones, el modelo analítico, se compara con los resultados obtenidos del análisis numérico. Este modelo escalable ha sido esencial para la optimización del diseño de la amarra para las misiones de de-orbitado de los satélites, variando la masa del satélite y la altitud inicial de la órbita. El modelo de supervivencia se ha utilizado para construir una función objetivo con el fin de optimizar el diseño de amarras. La función objectivo es el producto del cociente entre la masa de la amarra y la del satélite y el numero de corte por un cierto tiempo. Combinando el modelo de supervivencia con una ecuación dinámica de la amarra donde aparece la fuerza de Lorentz, se elimina el tiempo y se escribe la función objetivo como función de la geometría de la cinta y las propietades de la órbita. Este modelo de optimización, condujo al desarrollo de un software, que esta en proceso de registro por parte de la UPM. La etapa final de este estudio, consiste en la estimación del número de impactos fatales, en una cinta, utilizando por primera vez una ecuación de límite balístico experimental. Esta ecuación ha sido desarollada para cintas, y permite representar los efectos tanto de la velocidad de impacto como el ángulo de impacto. Los resultados obtenidos demuestran que la cinta es altamente resistente a los impactos de basura espacial, y para una cinta con una sección transversal definida, el número de impactos críticos debidos a partículas no rastreables es significativamente menor. ABSTRACT The current space environment, consisting of man-made debris and tiny meteoroids, poses a risk to safe operations in space, and the situation is continuously deteriorating due to in-orbit debris collisions and to new satellite launches. Among these debris a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Mitigation of space debris has become an issue of first concern for all the institutions involved in space operations. Bare electrodynamic tethers (EDT) can provide an efficient mechanism for rapid de-orbiting of defunct satellites from low Earth orbit (LEO) at end of life. The research on EDT has been a fruitful field since the 70’s. Thanks to both theoretical studies and in orbit demonstration missions, this technology has been developed very fast in the following decades. During this period, several technical issues were identified and overcome. The core functionality of EDT system greatly depends on their survivability to the micrometeoroids and orbital debris, and a tether can become itself a kind of debris for other operating satellites in case of cutoff due to particle impact; however, this very issue is still inconclusive and conflicting after having a number of space demonstrations. A tether can be completely cut by debris having some minimal diameter. This thesis presents a theoretical analysis of the survivability of tethers in space. The study demonstrates the advantages of tape tethers over conventional round wires particularly on the survivability during the mission. Because of its particular geometry (length very much larger than cross-sectional dimensions), a tether may have a relatively high risk of being severed by the single impact of small debris. As a first approach to the problem, survival probability has been compared for a round and a tape tether of equal mass and length. The rates of fatal impact of orbital debris on round and tape tether, evaluated with an analytical approximation to debris flux modeled by NASA’s ORDEM2000, shows much higher survival probability for tapes. A comparative numerical analysis using debris flux model ORDEM2000 and ESA’s MASTER2005 shows good agreement with the analytical result. It also shows that, for a given time in orbit, a tape has a probability of survival of about one and a half orders of magnitude higher than a round tether of equal mass and length. Because de-orbiting from a given altitude is much faster for the tape due to its larger perimeter, its probability of survival in a practical sense is quite high. As the next step, an analytical model derived in this work allows to calculate accurately the fatal impact rate per year for a tape tether. The model uses power laws for debris-size ranges, in both ORDEM2000 and MASTER2009 debris flux models, to calculate tape tether survivability at different LEO altitudes. The analytical model, which depends on tape dimensions (width, thickness) and orbital parameters (inclinations, altitudes) is then compared with fully numerical results for different orbit inclinations, altitudes and tape width for both ORDEM2000 and MASTER2009 flux data. This scalable model not only estimates the fatal impact count but has proved essential in optimizing tether design for satellite de-orbit missions varying satellite mass and initial orbital altitude and inclination. Within the frame of this dissertation, a simple analysis has been finally presented, showing the scalable property of tape tether, thanks to the survivability model developed, that allows analyze and compare de-orbit performance for a large range of satellite mass and orbit properties. The work explicitly shows the product of tether-to-satellite mass-ratio and fatal impact count as a function of tether geometry and orbital parameters. Combining the tether dynamic equation involving Lorentz drag with space debris impact survivability model, eliminates time from the expression. Hence the product, is independent of tether de-orbit history and just depends on mission constraints and tether length, width and thickness. This optimization model finally led to the development of a friendly software tool named BETsMA, currently in process of registration by UPM. For the final step, an estimation of fatal impact rate on a tape tether has been done, using for the first time an experimental ballistic limit equation that was derived for tapes and accounts for the effects of both the impact velocity and impact angle. It is shown that tape tethers are highly resistant to space debris impacts and considering a tape tether with a defined cross section, the number of critical events due to impact with non-trackable debris is always significantly low.