Uncertainty propagation using the full second-order approach for probabilistic fatigue crack growth life

Uncertainty propagation of fatigue crack growth life commonly aims to provide the probability distribution of the lifespan needed for probabilistic damage tolerance analysis and for structural integrity assessment. This paper presents a novel methodology for efficiently estimating the parameters of the probability distribution of fatigue lifespan considering the Pearson distribution family. First, the full second-order approach for expected value and variance prediction of probabilistic fatigue crack growth life is extended to predict higher order statistical moments of the underlying distribution. That is, the expected value (first raw moment) and the variance (second central moment) equations are complemented with the probabilistic formulations for the skewness and for the kurtosis (third and fourth central standardized moments, respectively). Then, from these moments, the Pearson distribution type is automatically determined. Finally, the parameters of the particular Pearson distribution type are estimated making the statistical moments of the constructed lifespan distribution match the first four prescribed moments predicted by the probabilistic equations. The validity of the proposed method is verified by a numerical example regarding the fatigue crack growth in a railway axle under random bending loading. It is proven that the probability density function of the lifespan is properly derived by the methodology, without knowing or assuming the output probability distribution beforehand. The methodology presented enables an efficient and an accurate quantification of the lifespan uncertainties via its probabilistic distribution. This probabilistic description of fatigue crack growth life can be subsequently used in reliability studies or in damage tolerance assessment

Propuesta de valores normativos para la clasificación de variables antropométricas en futbolistas profesionales

El objetivo del presente estudio es proponer una clasificación para identificar el % graso ideal a partir de variables antropométricas en futbolistas profesionales. Para lo cual, fueron utilizados 132 futbolistas profesionales a los que se les evaluó la Masa corporal (kg), Estatura (cm) y pliegues cutáneos (mm). Para el análisis estadístico se utilizó la estadística descriptiva de media aritmética (X), desviación estándar (DE), coeficiente de variación (CV) y para clasificar las variables antropométricas se utilizó los percentiles. Los resultados muestran que los valores ideales de % graso de los futbolistas oscila entre 9,0 a 12,6%, (p25 a p75), respectivamente. Finalmente, los parámetros adoptados como puntos de corte podrían ser utilizados como posibles indicadores para diagnosticar futbolistas con riesgo de lesión (pp75), a partir del % graso, masa corporal, e inclusive por la sumatoria de cuatro y seis pliegues cutáneos.The aim of this study is to propose a classification to identify the ideal % fat from anthropometric variables in professional soccer players. To which, using 132 players were professionals who were assessed for body mass (kg) Height (cm) and skinfolds (mm). For statistical analysis, descriptive statistics were used for arithmetic mean (X), standard deviation (SD), coefficient of variation (CV) and to classify the variables used anthropometric percentiles. The results show that the ideal values of % fat of the players ranges from 9.0 to 12.6% (p25 to p75), respectively. Finally, the parameters adopted as cutoff points could be used as indicators to diagnose potential players at risk of injury (p p75) from the % fat, body mass, and even by the sum of four and six skinfolds.Peer Reviewe

Performance evaluation of strategies for integration of elastic and stream traffic

This paper deals with the integration of `stream' traffic and `elastic' traffic in one single network, e.g. an ATM-based or an IP-based network. Here stream traffic refers to traffic with a certain bandwidth guarantee, whereas elastic traffic flows can adapt their rates to the link bandwidth left over by the stream flows. First, models are developed that describe different strategies for sharing link capacities between the stream and elastic flows. Then we give mathematical methods for obtaining performance measures, in particular call blocking probabilities and file transfer delays. Finally, these methods are used for assessing and comparing the efficiency gains achieved by the integration strategies

Estudio del crecimiento de gallinas ponedoras de 18 hasta 60 semanas de edad criadas en jaulas enriquecidas sometidas a diferentes intensidades de iluminación. 2. Tasa de crecimiento

El objetivo del estudio fue comparar la tasa de crecimiento de gallinas ponedoras criadas en jaulas enriquecidas sometidas a diferentes intensidades de iluminación de acuerdo con el esquema factorial 2x3: iluminación del pasillo (lateral y central) versus iluminación del piso (bajo, intermedio y alto) evaluada en el periodo de 18 hasta 60 semanas de edad de acuerdo con el modelo no linear de Gompertz. Las gallinas fueron alojadas en dos bateríasde 3 pisos, con dos filas por piso y cinco jaulas por fila (25 aves/jaula), con un total de 1.50

Análisis de las pinturas murales de la capilla de los Santos Corporales de Daroca (Zaragoza)

La capilla de los Santos Corporales, ubicada en la Iglesia Colegial de Santa María de Daroca (Zaragoza), alberga una muestra importante de pintura mural medieval de los siglos XIV y XVI. Durante su reciente proceso de restauración, la Unidad de Arqueometría del I.C.M.U.V. ha analizado los pigmentos que inte gran sus pinturas murales. Se han efectuado análisis in situ de fluorescencia de rayos X dispersiva en energía (EDXRF) de una pintura mural que forma parte de un ábside románico del s. XIV, de un relieve que forma parte del retablo relicario cuya policromía data del XVI y de la decoración que se le dio a las bóvedas de las capillas del s. XVI. Adicionalmente se tomaron muestras de pigmentos procedentes de la bóveda del s. XIV que han sido analizadas mediante EDXRF, difracción de ra yos X (XRD) y microscopía electrónica de bamdo (SEM)

Análisis in situ de pintura mural del Monasterio de Santa María de Huerta (Soria)

Se han realizado análisi.s itt situ de fluoreseencia de rayos-X dispersiva en energía (EDXRF) de dos pinturas murales del Monasterio Cisterciense de Santa María de Huerta (Soria). La primera eorresponde al coro y la segunda a la ca pilla de San Benito. Ambas en la iglesia del citado monasterio. Los resultados analíticos nos han permitido identificar y caracterizar los pigmentos que integran las pinturas murales a pesar de estar protegidas por papel paraloid B72

iCanCloud: a flexible and scalable cloud infrastructure simulator

Simulation techniques have become a powerful tool for deciding the best starting conditions on pay-as-you-go scenarios. This is the case of public cloud infrastructures, where a given number and type of virtual machines (in short VMs) are instantiated during a specified time, being this reflected in the final budget. With this in mind, this paper introduces and validates iCanCloud, a novel simulator of cloud infrastructures with remarkable features such as flexibility, scalability, performance and usability. Furthermore, the iCanCloud simulator has been built on the following design principles: (1) it's targeted to conduct large experiments, as opposed to others simulators from literature; (2) it provides a flexible and fully customizable global hypervisor for integrating any cloud brokering policy; (3) it reproduces the instance types provided by a given cloud infrastructure; and finally, (4) it contains a user-friendly GUI for configuring and launching simulations, that goes from a single VM to large cloud computing systems composed of thousands of machines.This research was partially supported by the following projects: Spanish MEC project TESIS (TIN2009-14312-C02-01), and Spanish Ministry of Science and Innovation under the grant TIN2010-16497.Publicad

La evaluación del aprendizaje de estudiantes: validación española del Assessment Experience Questionnaire (AEQ)

El propósito de esta investigación fue traducir al español y analizar las propiedades psicométricas del Assessment Experiences Questionnaire (AEQ) ya que no se dispone de un cuestionario en español que evalúe la experiencia de evaluación del aprendizaje de los estudiantes. Los participantes fueron 329 estudiantes universitarios. Los resultados del análisis de correlaciones y de la regresión lineal múltiple apoyaron la validez predictiva. El análisis factorial confirmatorio confirmó la estructura de nueve factores. Además, la consistencia interna fue aceptable y la correlación test-retest fue moderada. En conclusión, los resultados apoyan preliminarmente el uso de la versión española del AEQ.The aim of this study was the translation of the Assessment Experiences Questionnaire (AEQ) into Spanish, and the analysis of its psychometric proper- ties. We carried out this study because there is no questionnaire in Spanish which evaluates the experience of learning assessment. Participants were 329 university students. Results of the correlation analysis and the multiple linear regression supported the predictive validity of the questionnaire. The confirmatory factor analysis confirmed the nine-factor structure. In addition, internal consistency was acceptable, and the testretest correlation was moderate. In conclusion, the results support the use of the Spanish version of the AEQ as an instrument to assess the students' perception of the experience of learning assessment