Numerical modeling of the electron beam welding and its experimental validation

Electron Beam Welding (EBW) is a highly efficient and precise welding method increasingly used within the manufacturing chain and of growing importance in different industrial environments such as the aeronautical and aerospace sectors. This is because, compared to other welding processes, EBW induces lower distortions and residual stresses due to the lower and more focused heat input along the welding line. This work describes the formulation adopted for the numerical simulation of the EBW process as well as the experimental work carried out to calibrate and validate it. The numerical simulation of EBW involves the interaction of thermal, mechanical and metallurgical phenomena. For this reason, in this work the numerical framework couples the heat transfer process to the stress analysis to maximize accuracy. An in-house multi-physics FE software is used to deal with the numerical simulation. The definition of an ad hoc moving heat source is proposed to simulate the EB power surface distribution and the corresponding absorption within the work-piece thickness. Both heat conduction and heat radiation models are considered to dissipate the heat through the boundaries of the component. The material behavior is characterized by an apropos thermo-elasto-viscoplastic constitutive model. Titanium-alloy Ti6A14V is the target material of this work. From the experimental side, the EB welding machine, the vacuum chamber characteristics and the corresponding operative setting are detailed. Finally, the available facilities to record the temperature evolution at different thermo-couple locations as well as to measure both distortions and residual stresses are described. Numerical results are compared with the experimental evidence.Peer ReviewedPostprint (author's final draft

Enfermedad de Alzheimer y pérdida auditiva

Despite the different epidemiological, neurophysiological and morphological studies published in the literature, it is still not known for sure whether there is a relation between Alzheimer's disease (AD) and peripheral hearing loss. In this work we conduct an auditory study in patients with AD and in volunteer controls in order to investigate this possible relationship. SUBJECTS AND METHODS: The sample studied consisted of 14 patients with a clinical diagnosis of probable AD (age: 79 Y 6 years) and 14 volunteers (age: 76 Y 5 years) who visited the Clinica Universidad de Navarra. After applying a set of thorough criteria to preclude any previous hearing problems, all the participants underwent a subjective hearing assessment by means of pure-tone threshold audiometry and vocal audiometry and an objective auditory assessment using a tympanometry study, stapedial reflex, otoacoustic emissions and brainstem auditory evoked potentials. For the analysis, patients with AD and controls were paired homogenously by sex and age. RESULTS: The main obstacle hindering the study was to recruit the participants, due to the fact that they did not see any direct benefit from the study and it demanded an excessive amount of their time. Pure-tone threshold audiometry showed that patients with AD had a pattern of greater hearing loss for acute frequencies, with statistically significant differences. No significant differences were found in the analysis of the rest of the subjective and objective hearing tests. CONCLUSIONS: The findings of our study both agree and disagree with some earlier works from the literature, which suggests that patients with AD may have their own auditory patter

Título propio de grado UPM: Experto en cooperación para el desarrollo

En el curso 2008/09 se ha puesto en marcha el nuevo título propio de grado UPM “Experto en cooperación para el desarrollo”. Con él se pretende desarrollar la componente formativa del compromiso institucional de la UPM con la Cooperación Universitaria para el Desarrollo. Aglutina iniciativas dispersas que se llevaban a cabo en la UPM, aportando un marco formal común para las tareas docentes en el ámbito de la cooperación para el desarrollo, y establece un nuevo espacio de colaboración entre grupos y profesores comprometidos e interesados en este campo. Están implicados 24 departamentos de 13 escuelas y facultades de la UPM. Se admiten 25 alumnos oficiales de la UPM, en los dos últimos cursos de carrera y han de pasar un proceso de selección. Los títulos propios de grado UPM de Experto complementan el título oficial, pudiendo tener algunas partes en común. Su carga lectiva oscila entre 20 y 120 ECTS. Este título tiene 40 ECTS

Two quasi-optimal solutions for uniform load between two supports

Two frameworks for the title problem are presented, for the half and full plane cases respectively, with semi-analytical layouts. It is shown that both are among the best layouts obtained by several methods, including Simulated Annealing (SA) search and Linear Programming (LP). Respectively, the heights are found to be 0.442 and 0.633 times the span L. The required volume of material is given by V = kwL2/f where w is the load intensity and f the allowable stress, being k respectively equal to 0.985 and 0.758. The corresponding results for the layouts on the basis of the one presented by W. Hemp in 1974 are 0.338L, 0.676L, 1.158wL2/f, and 0.788wL2/f. None of these frameworks meets the conditions of Michell theorem, hence there is not sound proof that they are absolute optima. The meaning of this fact is discussed and two future lines of research are proposed

On the Insurmountable Size of Truss-like Structures

Galileo postulated the existence of an insurmountable size for stone columns bearing a useful load as the size for which the structure is only able to resist its self-weight. Herein a method for the determination of the unsurmountable size for truss-like structures is shown, given the form of these structures and the ratio between the allowable stress and the specific weight of the material (the material structural scope). Three types of bars are considered: straight bars, with solid and hollow rectangular cross-section, and catenary bars with circular cross-section —a limit and theoretical case for estimating a meaningful upper bound of the structural scope—. An approximate rule to estimate the structural efficiency —here named GA rule— is shown, and is compared with numerical solutions using the proposed method

On the layout of a least weight single span structure with uniform load.

Beghini et al (Struct Multidisc Optim doi:10.1007/s00158-013-1030-6, 2013) have published a very interesting paper arriving to practically the same nearly optimal solutions for the so named “bridge prob- lem” that the Writers published a year before, but using an alternative and remarkable approach to the problem. In spite of this general agreement, the Writers think that some details of the paper can be improved and there are results that can be given a clear and mean- ingful interpretation thanks to an old and practically unknown theorem on optimal slenderness

Genetic variants of innate immune receptors and infections after liver transplantation.

Infection is the leading cause of complication after liver transplantation, causing morbidity and mortality in the first months after surgery. Allograft rejection is mediated through adaptive immunological responses, and thus immunosuppressive therapy is necessary after transplantation. In this setting, the presence of genetic variants of innate immunity receptors may increase the risk of post-transplant infection, in comparison with patients carrying wild-type alleles. Numerous studies have investigated the role of genetic variants of innate immune receptors and the risk of complication after liver transplantation, but their results are discordant. Toll-like receptors and mannose-binding lectin are arguably the most important studied molecules; however, many other receptors could increase the risk of infection after transplantation. In this article, we review the published studies analyzing the impact of genetic variants in the innate immune system on the development of infectious complications after liver transplantation

Producción científica nacional e internacional en drogas de diseño (1988-1997)

Rafael Aleixandre Benavent: [email protected]ón: El conocimiento de las fuentes de información científica es imprescindible para el abordaje del problema del consumo de drogas de diseño. El objetivo de este trabajo es analizar la producción científica nacional e internacional sobre esta conducta, a partir del análisis bibliométrico de las publicaciones. Material y método: La producción científica sobre drogas de diseño se ha obtenido de las bases de datos IME, MEDLINE, ISOC y teseo durante el período 1988-1997. También se revisaron las referencias bibliográficas de los artículos recuperados en la base de datos IME. Los artículos obtenidos se distribuyeron por años, tipo documental, revista de publicación y temática, instituciones y países de procedencia, idiomas y temas tratados. Resultados: En las revistas españolas se publicaron 34 artículos y en las extranjeras 2.181. Los principales aspectos tratados se refieren a la toxicidad, concepto y clasificación y actividad farmacológica de las drogas de diseño. Las áreas temáticas más productivas son la neuropsiquiatría, la farmacología y la medicina general e interna. Conclusiones: El análisis muestra que existen escasos estudios experimentales y epidemiológicos publicados en España. Las revistas son de drogodependencias, temática general, neuropsiquiatría y farmacología, lo que pone de relieve la multidisciplinariedad de esta conducta adictiva. Predominan los estudios sobre la 1-metil-4-fenil-1,2,3,6-tetrahidropiridina y los análogos y derivados de la MDMA.Introduction: The knowledge of the scientific information sources is essential to approach the problem of the design drugs consumption. The objective of this work is directed to analyse the national and international scientific production about such behaviour, starting from the analysis bibliometric of the publications. Material and method: The scientific production on design drugs is being obtained from the data base IME, MEDLINE, ISOC and teseo during the 1988/1997 begin_of_the_skype_highlighting              1988/1997      end_of_the_skype_highlighting begin_of_the_skype_highlighting              1988/1997      end_of_the_skype_highlighting period. It has been done checking the bibliographic references of the articles recovered from the data base IME. The articles obtained have been separated by year, documentation type, journals thematic, institutions, country of origin, language and subject-matter. Results: In the spanish journals there has been published 34 articles and 2.181 in foreing journals. The main aspects treated make reference to toxicity, concept, classification and pharmacological activity of the design drugs. The thematic areas more productive are neuropsychiatry, pharmacological and general and internal medicine. Conclusions: The analysis points out that its does exist minimal experimental and epidemiological studies published in Spain. The journals more productives are specialised in drug addiction, general thematic, neuropsychiatry and pharmacological, what underlines the multidisciplinary of this addictive behaviour. The studies of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and of analogues and derived of MDMA predominate

Formulación estabilizada de elementos finitos triangulares y tetraédricos para problemas de incompresibilidad en grandes deformaciones

Se presenta una formulación en multiescalas del método de elementos finitos capaz de estabilizar el comportamiento de elementos mixtos en problemas de elasticidad y de plasticidad incompresibles en grandes deformaciones. Esta formulación se fundamenta en el concepto de las sub-escalas ortogonales (OSGS) y se aplica a elementos triangulares y tetraédricos mixtos, con interpolaciones de desplazamientos y presión continuas. La formulación permite eludir la condición de estabilidad de Babu˘ska-Brezzi, y ofrece como principal ventaja la posibilidad de utilizar interpolaciones lineales en elementos mixtos triangulares y tetraédricos, muy convenientes en aplicaciones de interés práctico debido a su versatilidad para la generación de mallas sobre configuraciones geométricas complejas. Se explican tanto las consideraciones empleadas en el planteamiento, como los principales aspectos de implementación. Una de las contribuciones más relevantes de esta formulación es la eficacia y originalidad de la aproximación propuesta para el parámetro de estabilizaci ón. Finalmente, mediante ejemplos de simulación se muestra el buen comportamiento de los elementos obtenidos en comparación con elementos estándar y Q1P0.Peer Reviewe