Aplicación de Métodos Meshless al Análisis de Problemas de Autovalores

La presente Tesis Doctoral aborda la aplicación de métodos meshless, o métodos sin malla, a problemas de autovalores, fundamentalmente vibraciones libres y pandeo. En particular, el estudio se centra en aspectos tales como los procedimientos para la resolución numérica del problema de autovalores con estos métodos, el coste computacional y la viabilidad de la utilización de matrices de masa o matrices de rigidez geométrica no consistentes. Además, se acomete en detalle el análisis del error, con el objetivo de determinar sus principales fuentes y obtener claves que permitan la aceleración de la convergencia. Aunque en la actualidad existe una amplia variedad de métodos meshless en apariencia independientes entre sí, se han analizado las diferentes relaciones entre ellos, deduciéndose que el método Element-Free Galerkin Method [Método Galerkin Sin Elementos] (EFGM) es representativo de un amplio grupo de los mismos. Por ello se ha empleado como referencia en este análisis. Muchas de las fuentes de error de un método sin malla provienen de su algoritmo de interpolación o aproximación. En el caso del EFGM ese algoritmo es conocido como Moving Least Squares [Mínimos Cuadrados Móviles] (MLS), caso particular del Generalized Moving Least Squares [Mínimos Cuadrados Móviles Generalizados] (GMLS). La formulación de estos algoritmos indica que la precisión de los mismos se basa en los siguientes factores: orden de la base polinómica p(x), características de la función de peso w(x) y forma y tamaño del soporte de definición de esa función. Se ha analizado la contribución individual de cada factor mediante su reducción a un único parámetro cuantificable, así como las interacciones entre ellos tanto en distribuciones regulares de nodos como en irregulares. El estudio se extiende a una serie de problemas estructurales uni y bidimensionales de referencia, y tiene en cuenta el error no sólo en el cálculo de autovalores (frecuencias propias o carga de pandeo, según el caso), sino también en términos de autovectores. This Doctoral Thesis deals with the application of meshless methods to eigenvalue problems, particularly free vibrations and buckling. The analysis is focused on aspects such as the numerical solving of the problem, computational cost and the feasibility of the use of non-consistent mass or geometric stiffness matrices. Furthermore, the analysis of the error is also considered, with the aim of identifying its main sources and obtaining the key factors that enable a faster convergence of a given problem. Although currently a wide variety of apparently independent meshless methods can be found in the literature, the relationships among them have been analyzed. The outcome of this assessment is that all those methods can be grouped in only a limited amount of categories, and that the Element-Free Galerkin Method (EFGM) is representative of the most important one. Therefore, the EFGM has been selected as a reference for the numerical analyses. Many of the error sources of a meshless method are contributed by its interpolation/approximation algorithm. In the EFGM, such algorithm is known as Moving Least Squares (MLS), a particular case of the Generalized Moving Least Squares (GMLS). The accuracy of the MLS is based on the following factors: order of the polynomial basis p(x), features of the weight function w(x), and shape and size of the support domain of this weight function. The individual contribution of each of these factors, along with the interactions among them, has been studied in both regular and irregular arrangement of nodes, by means of a reduction of each contribution to a one single quantifiable parameter. This assessment is applied to a range of both one- and two-dimensional benchmarking cases, and includes not only the error in terms of eigenvalues (natural frequencies or buckling load), but also of eigenvectors

Estabilidad de un buque ultra heavy lift carrier

Se plantea la posible demanda en un futuro del transporte de grandes plataformas petrolíferas semisumergibles de más de 70.000 t de peso, para perforaciones a más de 10.000 pies de profundidad. Estudia la estabilidad de buques Heavy Lift Carrier con mangas atípicas, capaces de transportar estas cargas, y en algunos casos sobresaliendo por sus amuras. Para esto se: 1. Estudia y genera posibles carenas, su compartimentación y lastre para la inmersión o emersión de la cubierta de intemperie, a más de 10 m de profundidad para tomar o dejar la carga, optimizando el proceso. 2. Analiza la estabilidad del buque tanto en inmersión/emersión y navegación, con máximas cargas y con altos centros de gravedad, y establece ábacos de estabilidad límite en función de los parámetros del buque. 3. Plantea la corrección de estabilidad excesiva del buque en condiciones de navegación para evitar las excesivas aceleraciones. Los resultados obtenidos aportan ábacos que permiten, en función de los parámetros carga a transportar (Zg max) - Peso Carga), elegir el buque más adecuado, capaz de efectuar la inmersión, emersión, y navegación, y plantea acciones futuras de investigación. ABSTRACT This work raises the potential demand in the future, to transport large semisubmersible oil rigs over 70,000 tonnes of weight for drilling to 10,000 feet deep. Study vessel stability Heavy Lift Carrier with atypical breadths capable of carrying these burdens, and in some cases standing out for their bows. 1. Examines possible hulls, their partitioning and ballast for immersion or emersion of the weather deck, more than 10 m deep to take –loading (lifting) - or leave (off- loading). 2. Analyzes the stability of the vessel both immersion / emersion and navigation, with maximum loads with high centers of gravity and stability limit states abacus according to the parameters of the ship. 3. Correction raises the stability of the ship over navigation to prevent excessive accelerations. The results allow, in terms of cargo transport parameters (Zg max) - Weight Load), choosing the most suitable vessel capable of carrying out the immersion, emersion, and navigation, and suggests future research activities.

Optimal fits of diffusion constants from single-time data points of Brownian trajectories

Experimental methods based on single particle tracking (SPT) are being increasingly employed in the physical and biological sciences, where nanoscale objects are visualized with high temporal and spatial resolution. SPT can probe interactions between a particle and its environment but the price to be paid is the absence of ensemble averaging and a consequent lack of statistics. Here we address the benchmark question of how to accurately extract the diffusion constant of one single Brownian trajectory. We analyze a class of estimators based on weighted functionals of the square displacement. For a certain choice of the weight function these functionals provide the true ensemble averaged diffusion coefficient, with a precision that increases with the trajectory resolution.

On ergodic least-squares estimators of the generalized diffusion coefficient for fractional Brownian motion

We analyse a class of estimators of the generalized diffusion coefficient for fractional Brownian motion Bt of known Hurst index H, based on weighted functionals of the single time square displacement. We show that for a certain choice of the weight function these functionals possess an ergodic property and thus provide the true, ensemble-averaged, generalized diffusion coefficient to any necessary precision from a single trajectory data, but at expense of a progressively higher experimental resolution. Convergence is fastest around H ? 0.30, a value in the subdiffusive regime.

Determinant factors to discriminate the body weight loss in overweight people

Introduction. Most studies have described how the weight loss is when different treatments are compared (1-3), while others have also compared the weight loss by sex (4), or have taken into account psychosocial (5) and lifestyle (6, 7) variables. However, no studies have examined the interaction of different variables and the importance of them in the weight loss. Objective. Create a model to discriminate the range of weight loss, determining the importance of each variable. Methods. 89 overweight people (BMI: 25-29.9 kg?m-2), aged from 18 to 50 years, participated in the study. Four types of treatments were randomly assigned: strength training (S), endurance training (E), strength and endurance training (SE), and control group (C). All participants followed a 25% calorie restriction diet. Two multivariate discriminant models including the variables age, sex, height, daily energy expenditure (EE), type of treatment (T), caloric restriction (CR), initial body weight (BW), initial fat mass (FM), initial muscle mass (MM) and initial bone mineral density (BMD) were performed having into account two groups: the first and fourth quartile of the % of weight loss in the first model; the groups above and below the mean of the % of weight loss in the second model. The discriminant models were built using the inclusion method in SPSS allowing us to find a function that could predict the body weight loss range that an overweight person could achieve in a 6 months weight loss intervention.Results. The first discriminant analysis predicted that a combination of the studied variables would discriminate between the two ranges of body weight loss with 81.4% of correct classification. The discriminant function obtained was (Wilks? Lambda=0.475, p=0.003): Discriminant score=-18.266-(0.060xage)- (1.282xsex[0=female;1=male])+(14.701xheight)+(0.002xEE)- (0.006xT[1=S;2=E;3=SE;4=C])-(0.047xCR)- (0.558xBW)+(0.475xFM)+(0.398xMM)+(3.499xBMD) The second discriminant model obtained would discriminate between the two groups of body weight loss with 74.4% of correct classification. The discriminant function obtained was (Wilks? Lambda=0.725, p=0.005): Discriminant score=-5.021-(0.052xage)- (0.543xsex[0=female;1=male])+(3.530xheight)+(0.001xEE)- (0.493xT[1=S;2=E;3=SE;4=C])+(0.003xCR)- (0.365xBW)+(0.368xFM)+(0.296xMM)+(4.034xBMD) Conclusion. The first developed model could predict the percentage of weight loss in the following way: if the discriminant score is close to 1.051, the range of weight loss will be from 7.44 to -4.64% and if it is close to - 1.003, the range will be from -11.03 to -25,00% of the initial body weight. With the second model if the discriminant score is close to 0.623 the body weight loss will be above -7.93% and if it is close to -0.595 will be below - 7.93% of the initial body weight. References. 1. Brochu M, et al. Resistance training does not contribute to improving the metabolic profile after a 6-month weight loss program in overweight and obese postmenopausal women. J Clin Endocrinol Metab. 2009 Sep;94(9):3226-33. 2. Del Corral P, et al. Effect of dietary adherence with or without exercise on weight loss: a mechanistic approach to a global problem. J Clin Endocrinol Metab. 2009 May;94(5):1602-7. 3. Larson-Meyer DE, et al. Caloric Restriction with or without Exercise: The Fitness vs. Fatness Debate. Med Sci Sports Exerc. 2010;42(1):152-9. 4. Hagan RD, et al. The effects of aerobic conditioning and/or caloric restriction in overweight men and women. Medicine & Science in Sports & Exercise. 1986;18(1):87-94. 5. Teixeira PJ, et al. Mediators of weight loss and weight loss maintenance in middle-aged women. Obesity (Silver Spring). 2010 Apr;18(4):725-35. 6. Bautista-Castano I, et al. Variables predictive of adherence to diet and physical activity recommendations in the treatment of obesity and overweight, in a group of Spanish subjects. Int J Obes Relat Metab Disord. 2004 May;28(5):697-705.

Preference intensity in MCDM when an additive utility function represents DM preferences

We propose a new method for ranking alternatives in multicriteria decision-making problems when there is imprecision concerning the alternative performances, component utility functions and weights. We assume decision maker?s preferences are represented by an additive multiattribute utility function, in which weights can be modeled by independent normal variables, fuzzy numbers, value intervals or by an ordinal relation. The approaches are based on dominance measures or exploring the weight space in order to describe which ratings would make each alternative the preferred one. On the one hand, the approaches based on dominance measures compute the minimum utility difference among pairs of alternatives. Then, they compute a measure by which to rank the alternatives. On the other hand, the approaches based on exploring the weight space compute confidence factors describing the reliability of the analysis. These methods are compared using Monte Carlo simulation.

Max Bill: variaciones sobre la búsqueda de la belleza

Max Bill es un artista lógico. Quince variaciones sobre el mismo tema 1938, podría ser el epítome de la lógica de Bill: la obra como resultado de la aplicación de leyes distintas sobre una estructura de orden. La gran diversidad formal de la obra de Max Bill –entre sus diseños de objetos, su tipografía, su pintura, su escultura o su arquitectura no parece haber líneas formales evidentes- se debe a que, para él, cada tarea es diferente y depende de medios y leyes propios. Una diversidad que podría ser erróneamente interpretada como un tipo de eclecticismo. Su conferencia en el Werkbund suizo de 1948 “belleza de la función, belleza como función”, se aleja del discurso funcionalista al proponer la belleza como una igual al resto de funciones. Cada obra ha de satisfacer la finalidad para la que ha sido construida y cumplir todas las funciones que en ella intervienen pero, además, ha de ser bella. La particularidad de Bill estriba en que, reconociéndose a sí mismo como un artista lógico, incluye la belleza como una más de las funciones a cumplir por cualquier objeto. Su famoso aforismo en relación a la configuración del entorno, desde la cuchara a la ciudad, incluiría la arquitectura en el ámbito de los objetos que han de cumplir esta nueva función. La búsqueda de la belleza será una constante en su obra. No una belleza generalizable y determinada a priori, sino una belleza entendida como predicado singular, individualizada para cada tarea. De este modo, podemos analizar, alternativamente, la belleza lógica de sus construcciones geométricas y la belleza simbólica de sus monumentos; la belleza del espacio sin fin en las superficies de una sola cara y la belleza prefabricada en sus más austeras realizaciones; la belleza elemental de sus esculturas y la belleza corriente con que sus arquitecturas se integran en la ciudad. Podemos plantearnos la posibilidad de una belleza de la estructura y entender simultáneamente la belleza cruda de su obra maestra, los edificios de la Escuela de Ulm. La búsqueda de la belleza nos ayudará a entender que, en la obra de Bill, la razón intuitiva -como modo de conocimiento- toma mayor importancia de la que parece. La forma como suma de todas las funciones en unidad armónica, será el resultado de un adecuado equilibrio entre razón lógica y razón intuitiva. ABSTRACT Max Bill is a logical artist. We could consider “Fitfteen variations on the same theme”, 1938, as the Bill’s logic epitome: the work as a result of the application of different tectonic laws on the order structure. The variety of the form in Bill’s work –his designed objects, his typography, his painting, his sculpture, or his architecture do not seem to have, between them, a direct line connecting the form- is due to the fact that, for him, each task is different and it depends on the own means and tectonic laws. A kind of diversity that could be misinterpreted like certain type of eclecticism. His lecture at the Suisse Werkbund (1948) “beauty from function and as function” is far from the functionalist speech, when proposing beauty as an equal to the rest of functions. In his own words, each work has to satisfy the purpose it was built for and fulfill all functions, and furthermore it has to be beautiful. Seeing himself as a logical artist, Bill however introduces beauty as one more of the functions that any object has to fulfill. His famous aphorism related to the environment management, from the spoon to the city, would include architecture as one more of the objects that have to satisfy this new function. The pursuit of beauty is a constant in his work. It won’t be a general beauty determined in advance, but a singular predicate, individualized for each task. That way, we can analyze, alternatively, the logical beauty of his geometric constructions and the symbolical beauty of his monuments; the beauty of the endless space in the single-sided surfaces and the prefabricated beauty in his most stricts constructions; the elemental beauty of his sculptures and the ordinary beauty with which some of his architectures are integrated in the city. We can also try the possibility of a beauty from the structure and understand, at the same time, the raw beauty of his architectural masterpiece, the buildings of the Ulm School of Design. The pursuit of beauty in Bill’s work will help us to understand that intuitive reason, as a way of knowledge, takes more importance than it seems. Form, as the harmonious expression of the sum of all functions, will be the result of an appropriate balance between logical and intuitive reason.

Fast-Twitch Glycolytic Skeletal Muscle Is Predisposed to Age-Induced Impairments in Mitochondrial Function

funcion mitocondrial en fibras rápidas

The C57Bl/6 mouse serves as a suitable model of human skeletal muscle mitochondrial function

Función mitocondrial en ratas

Two near-optimal layouts for trusslike bridge structures bearing uniform weight between supports

Although the primary objective on designing a structure is to support the external loads, the achievement of an optimal layout that reduces all costs associated with the structure is an aspect of increasing interest. The problem of finding the optimal layout for bridgelike structures subjected to a uniform load is considered. The problem is formulated following a theory on economy of frame structures, using the stress volume as the objective function and including the selection of appropriate values for statically indeterminate reactions. It is solved in a function space of finite dimension instead of using a general variational approach, obtaining near-optimal solutions. The results obtained with this profitable strategy are very close to the best layouts known to date, with differences of less than 2% for the stress volume, but with a simpler layout that can be recognized in some real bridges. This strategy could be a guide to preliminary design of bridges subject to a wide class of costs.