A contribution to appendage drag extrapolation using computational tools

In this paper, the foundations of the beta method, widely used in todays ship appendage extrapolations, are explored. The present work pretends to validate the Beta Method using experimental and computational tools. The ship used is a rounded bow tugboat with two significant appendages, namely, a midship protective structure for the propulsion system and a stern keel. The experimental and computational data was obtained through Towing Tank trials and a RANSE CFD code, respectively.

Fuel Cells: A Real Option for Unmanned Aerial Vehicles Propulsion

The possibility of implementing fuel cell technology in Unmanned Aerial Vehicle (UAV) propulsion systems is considered. Potential advantages of the Proton Exchange Membrane or Polymer Electrolyte Membrane (PEMFC) and Direct Methanol Fuel Cells (DMFC), their fuels (hydrogen and methanol), and their storage systems are revised from technical and environmental standpoints. Some operating commercial applications are described. Main constraints for these kinds of fuel cells are analyzed in order to elucidate the viability of future developments. Since the low power density is the main problem of fuel cells, hybridization with electric batteries, necessary in most cases, is also explored.

Long Term Performance Study of a Direct Methanol Fuel Cell Fed with Alcohol Blends

The use of alcohol blends in direct alcohol fuel cells may be a more environmentally friendly and less toxic alternative to the use of methanol alone in direct methanol fuel cells. This paper assesses the behaviour of a direct methanol fuel cell fed with aqueous methanol, aqueous ethanol and aqueous methanol/ethanol blends in a long term experimental study followed by modelling of polarization curves. Fuel cell performance is seen to decrease as the ethanol content rises, and subsequent operation with aqueous methanol only partly reverts this loss of performance. It seems that the difference in the oxidation rate of these alcohols may not be the only factor affecting fuel cell performance.

Gromov hyperbolicity of periodic planar graphs

The study of hyperbolic graphs is an interesting topic since the hyperbolicity of a geodesic metric space is equivalent to the hyperbolicity of a graph related to it. The main result in this paper is a very simple characterization of the hyperbolicity of a large class of periodic planar graphs.

Safety and operability of small fishing vessels: study of a series of stability-related accidents

The intact stability of five small Spanish fishing vessels with ages between 3 and 8 years old which sunk in stability related accidents between 2004 and 2007 is compared to the stability of the fishing vessels which were retired from service to build those. The seakeeping performance of both sets of vessels is also compared. The differences found between the results obtained by the two methods have been analyzed. The suitability of seakeeping methods to assess stability performance is discussed.

Lagrangian descriptors: a method for revealing phase space structures of general time dependent dynamical systems

Lagrangian descriptors are a recent technique which reveals geometrical structures in phase space and which are valid for aperiodically time dependent dynamical systems. We discuss a general methodology for constructing them and we discuss a "heuristic argument" that explains why this method is successful. We support this argument by explicit calculations on a benchmark problem. Several other benchmark examples are considered that allow us to assess the performance of Lagrangian descriptors with both finite time Lyapunov exponents (FTLEs) and finite time averages of certain components of the vector field ("time averages"). In all cases Lagrangian descriptors are shown to be both more accurate and computationally efficient than these methods.

Relation of Lagragian structures and drifter dynamics in the Gulf of Mexico

We use a Lagrangian descriptor (the so called function M) which measures the length of particle trajectories on the ocean surface over a given interval of time. With this tool we identify the Lagrangian skeleton of the flow and compare it on three datasets over the Gulf of Mexico during the year 2010. The satellite altimetry data used come from AVISO and simulations from HYCOM GOMl0.04 experiments 30.1 and 31.0. We contrast the Lagrangian structure and transport using the evolution of several surface drifters. We show that the agreement in relevant cases between Lagrangian structures and dynamics of drifters depends on the quality of the data on the studied area.

Lagrangian tools and the assessment of the predictive capacity of geophysical data sets

We examine, with recently developed Lagrangian tools, altimeter data and numerical simulations obtained from the HYCOM model in the Gulf of Mexico. Our data correspond to the months just after the Deepwater Horizon oil spill in the year 2010. Our Lagrangian analysis provides a skeleton that allows the interpretation of transport routes over the ocean surface. The transport routes are further verified by the simultaneous study of the evolution of several drifters launched during those months in the Gulf of Mexico. We find that there exist Lagrangian structures that justify the dynamics of the drifters, although the agreement depends on the quality of the data. We discuss the impact of the Lagrangian tools on the assessment of the predictive capacity of these data sets.

Asymptotic values of quasiregular maps

Suslin analytic sets characterize the sets of asymptotic values of entire holomorphic functions. By a theorem of Ahlfors, the set of asymptotic values is finite for a function with finite order of growth. Quasiregular maps are a natural generalization of holomorphic functions to dimensions n ≥ 3 and, in fact, many of the properties of holomorphic functions have counterparts for quasiregular maps. It is shown that analytic sets also characterize the sets of asymptotic values of quasiregular maps in Rn, even for those with finite order of growth. Our construction is based on Drasin's quasiregular sine function

Quasi-isometries and isoperimetric inequalities

We consider the stability of isoperimetric inequalities under quasi-isometries between Riemann surfaces. Kanai observed that quasi-isometries preserve isoperimetric inequalities on complete Riemannian manifolds with finite geometry: positive injectivity radius and Ricci curvature bounded from below (see [2]). In [1], it is shown that the linear isoperimetric inequality is a quasi-isometric invariant for planar Riemann surfaces (genus zero surfaces) with vanishing injectivity radius. Moreover, it is proved that non-linear isoperimetric inequalities can only hold for Riemann surfaces with positive injectivity radius, and hence, by Kanai's observation, preserved by quasi-isometries. In this talk we present an overview on isoperimetric inequalities and give some of the ideas of the proofs of the results cited above.

Docencia no presencial como alternativa a la clase magistral en los primeros cursos de ingeniería

La implantación de los nuevos grados en la Universidad Politécnica de Madrid ha supuesto la reducción del número de créditos destinados a las asignaturas básicas. En las titulaciones anteriores se dedicaban numerosas horas prácticas de matemáticas a la resolución de problemas en el aula por parte de los alumnos, con el apoyo de profesores y materiales. Estas tutorías colectivas tienen difícil encaje en nuestras nuevas titulaciones, dado que las asignaturas de matemáticas no sólo se han reducido en número de créditos, sino que también se ha reducido el número de horas presenciales de trabajo de los alumnos para facilitar su aprendizaje autónomo. Nuestro objetivo es, pues, conciliar una disminución de las horas presenciales con el aprendizaje autónomo, manteniendo las clases participativas de titulaciones anteriores. Para ello, hemos recurrido a nuestra experiencia previa de la enseñanza no presencial: los Cursos Masivos Online en Abierto (MOOC). En ellos, la clase magistral se desmenuza en vídeos y presentaciones cortas, de unos pocos minutos de duración, las llamadas píldoras educativas, al final de las cuales el alumno tiene que responder a unas pocas preguntas que muestren que ha captado las ideas que se desea transmitir.

Clase magistral y docencia no presencial en matemáticas en los primeros cursos de los grados de ingeniería

En esta comunicación se analizan los problemas detectados en la docencia de asignaturas de matemática aplicada en primeros cursos de los nuevos grados en ingeniería y se propone una iniciativa piloto en curso tendente a solventarlos., basada en el aprendizaje mixto y el uso de píldoras educativas, al estilo de los MOOC.

A CAD development strategy for the next years

This paper suggests a new strategy to develop CAD applications taking into account some of the most interesting proposals which have recently appeared in the technology development arena. Programming languages, operating systems, user devices, software architecture, user interfaces and user experience are among the elements which are considered for a new development framework. This strategy considers the organizational and architectural aspects of the CAD application together with the development framework. The architectural and organizational aspects are based on the programmed design concept, which can be implemented by means of a three-level software architecture. These levels are the conceptual level based on a declarative language, the mathematical level based on the geometric formulation of the product model and the visual level based on the polyhedral representation of the model as required by the graphic card. The development framework which has been considered is Windows 8. This operating system offers three development environments, one for web pplications (HTML5 + CSS3 + JavaScript), and other for native applications C/C++) and of course yet another for .NET applications (C#, VB, F#, etc.). The use rinterface and user experience for non-web application is described ith XAML (a well known declarative XML language) and the 3D API for games and design applications is DirectX. Additionally, Windows 8 facilitates the use of hybrid solutions, in which native and managed code can interoperate easily. Some of the most remarkable advantages of this strategy are the possibility of targeting both desktop and touch screen devices with the same development framework, the usage of several programming paradigms to apply the most appropriate language to each domain and the multilevel segmentation of developers and designers to facilitate the implementation of an open network of collaborators.

University large lectures in MICASE: a systemic functional analysis

Se analizan las estrategias y la estructura discursiva de las conferencias del corpus MICASE (El corpus de inglés académico oral de la Universidad de Michigan) desde una perspectiva dual: el enfoque sistémico-funcional y el estudio de Young sobre conferencias. Los resultados demuestran que las conferencias son un género complejo que no solo incluye el contenido ideacional sino diversas evaluaciones de los profesores sobre los temas tratados. Los profesores usan fuentes académicas, convenciones formales y un estilo idiosincrático. También muestran su punto de vista mediante el uso de marcadores modales y adverbios que varían en función de las distintos tipos de conferencia (Biología/ Ciencias de la Salud, Arte y Humanidades, Ciencias Sociales/ Educación).

Fishing effort control regulations influence on stability, safety and operability of small fishing vessels: study of a series of stability related accidents occurred in Spain between 2004 and 2007

Entre los años 2004 y 2007 se hundieron por problemas de estabilidad cinco pesqueros españoles de pequeña eslora, de características parecidas, de relativamente poca edad, que habían sido construidos en un intervalo de pocos años. La mayoría de los tripulantes de esos pesqueros fallecieron o desaparecieron en esos accidentes. Este conjunto de accidentes tuvo bastante repercusión social y mediática. Entre ingenieros navales y marinos del sector de la pesca se relacionó estos accidentes con los condicionantes a los diseños de los pesqueros impuestos por la normativa de control de esfuerzo pesquero. Los accidentes fueron investigados y publicados sus correspondientes informes; en ellos no se exploró esta supuesta relación. Esta tesis pretende investigar la relación entre esos accidentes y los cambios de la normativa de esfuerzo pesquero. En la introducción se expone la normativa de control de esfuerzo pesquero analizada, se presentan datos sobre la estructura de la flota pesquera en España y su accidentalidad, y se detallan los criterios de estabilidad manejados durante el trabajo, explicando su relación con la seguridad de los pesqueros. Seguidamente se realiza un análisis estadístico de la siniestralidad en el sector de la pesca para establecer si el conjunto de accidentes estudiados supone una anomalía, o si por el contrario el conjunto de estos accidentes no es relevante desde el punto de vista estadístico. Se analiza la siniestralidad a partir de diversas bases de datos de buques pesqueros en España y se concluye que el conjunto de accidentes estudiados supone una anomalía estadística, ya que la probabilidad de ocurrencia de los cinco sucesos es muy baja considerando la frecuencia estimada de pérdidas de buques por estabilidad en el subsector de la flota pesquera en el que se encuadran los cinco buques perdidos. A continuación el trabajo se centra en la comparación de los buques accidentados con los buques pesqueros dados de baja para construir aquellos, según exige la normativa de control de esfuerzo pesquero; a estos últimos buques nos referiremos como “predecesores” de los buques accidentados. Se comparan las dimensiones principales de cada buque y de su predecesor, resultando que los buques accidentados comparten características de diseño comunes que son sensiblemente diferentes en los buques predecesores, y enlazando dichas características de diseño con los requisitos de la nueva normativa de control del esfuerzo pesquero bajo la que se construyeron estos barcos. Ello permite establecer una relación entre los accidentes y el mencionado cambio normativo. A continuación se compara el margen con que se cumplían los criterios reglamentarios de estabilidad entre los buques accidentados y los predecesores, encontrándose que en cuatro de los cinco casos los predecesores cumplían los criterios de estabilidad con mayor holgura que los buques accidentados. Los resultados obtenidos en este punto permiten establecer una relación entre el cambio de normativa de esfuerzo pesquero y la estabilidad de los buques. Los cinco buques accidentados cumplían con los criterios reglamentarios de estabilidad en vigor, lo que cuestiona la relación entre esos criterios y la seguridad. Por ello se extiende la comparativa entre pesqueros a dos nuevos campos relacionados con la estabilidad y la seguridad delos buques: • Movimientos a bordo (operatividad del buque), y • Criterios de estabilidad en condiciones meteorológicas adversas El estudio de la operatividad muestra que los buques accidentados tenían, en general, una mayor operatividad que sus predecesores, contrariamente a lo que sucedía con el cumplimiento de los criterios reglamentarios de estabilidad. Por último, se comprueba el desempeño de los diez buques en dos criterios específicos de estabilidad en caso de mal tiempo: el criterio IMO de viento y balance intenso, y un criterio de estabilidad de nueva generación, incluyendo la contribución original del autor de considerar agua en cubierta. Las tendencias observadas en estas dos comparativas son opuestas, lo que permite cuestionar la validez del último criterio sin un control exhaustivo de los parámetros de su formulación, poniendo de manifiesto la necesidad de más investigaciones sobre ese criterio antes de su adopción para uso regulatorio. El conjunto de estos resultados permite obtener una serie de conclusiones en la comparativa entre ambos conjuntos de buques pesqueros. Si bien los resultados de este trabajo no muestran que la aprobación de la nueva normativa de esfuerzo pesquero haya significado una merma general de seguridad en sectores enteros de la flota pesquera, sí se concluye que permitió que algunos diseños de buques pesqueros, posiblemente en busca de la mayor eficiencia compatible con dicha normativa, quedaran con una estabilidad precaria, poniendo de manifiesto que la relación entre seguridad y criterios de estabilidad no es unívoca, y la necesidad de que éstos evolucionen y se adapten a los nuevos diseños de buques pesqueros para continuar garantizando su seguridad. También se concluye que la estabilidad es un aspecto transversal del diseño de los buques, por lo que cualquier reforma normativa que afecte al diseño de los pesqueros o su forma de operar debería estar sujeta a evaluación por parte de las autoridades responsables de la seguridad marítima con carácter previo a su aprobación. ABSTRACT Between 2004 and 2007 five small Spanish fishing vessels sank in stability related accidents. These vessels had similar characteristics, had relatively short age, and had been built in a period of a few years. Most crewmembers of these five vessels died or disappeared in those accidents. This set of accidents had significant social and media impact. Among naval architects and seamen of the fishing sector these accidents were related to the design constraints imposed by the fishing control effort regulations. The accidents were investigated and the official reports issued; this alleged relationship was not explored. This thesis aims to investigate the relationship between those accidents and changes in fishing effort control regulations. In the introduction, the fishing effort control regulation is exposed, data of the Spanish fishing fleet structure and its accident rates are presented, and stability criteria dealt with in this work are explained, detailing its relationship with fishing vessel safety. A statistical analysis of the accident rates in the fishing sector in Spain is performed afterwards. The objective is determining whether the set of accidents studied constitute an anomaly or, on the contrary, they are not statistically relevant. Fishing vessels accident rates is analyzed from several fishing vessel databases in Spain. It is concluded that the set of studied accidents is statistically relevant, as the probability of occurrence of the five happenings is extremely low, considering the loss rates in the subsector of the Spanish fishing fleet where the studied vessels are fitted within. From this point the thesis focuses in comparing the vessels lost and the vessels that were decommissioned to build them as required by the fishing effort control regulation; these vessels will be referred to as “predecessors” of the sunk vessels. The main dimensions between each lost vessel and her predecessor are compared, leading to the conclusion that the lost vessels share design characteristics which are sensibly different from the predecessors, and linking these design characteristics with the requirements imposed by the new fishing control effort regulations. This allows establishing a relationship between the accidents and this regulation change. Then the margin in fulfilling the regulatory stability criteria among the vessels is compared, resulting, in four of the five cases, that predecessors meet the stability criteria with greater clearance than the sunk vessels. The results obtained at this point would establish a relationship between the change of fishing effort control regulation and the stability of vessels. The five lost vessels complied with the stability criteria in force, so the relation between these criteria and safety is put in question. Consequently, the comparison among vessels is extended to other fields related to safety and stability: • Motions onboard (operability), and • Specific stability criteria in rough weather The operability study shows that the lost vessels had in general greater operability than their predecessors, just the opposite as when comparing stability criteria. Finally, performance under specific rough weather stability criteria is checked. The criteria studied are the IMO Weather Criterion, and one of the 2nd generation stability criteria under development by IMO considering in this last case the presence of water on deck, which is an original contribution by the author. The observed trends in these two cases are opposite, allowing to put into question the last criterion validity without an exhaustive control of its formulation parameters; indicating that further research might be necessary before using it for regulatory purposes. The analysis of this set of results leads to some conclusions when comparing both groups of fishing vessels. While the results obtained are not conclusive in the sense that the entry into force of a new fishing effort control in 1998 caused a generalized safety reduction in whole sectors of the Spanish fishing fleet, it can be concluded that it opened the door for some vessel designs resulting with precarious stability. This evidences that the relation between safety and stability criteria is not univocal, so stability criteria needs to evolve for adapting to new fishing vessels designs so their safety is still guaranteed. It is also concluded that stability is a transversal aspect to ship design and operability, implying that any legislative reform affecting ship design or operating modes should be subjected to assessing by the authorities responsible for marine safety before being adopted.