Identification of two cracks with different severity in beams and rods from minimal frequency data

It has been known for a long time that the problem of identifying two small cracks in a simply supported beam from the first three natural frequencies can be analytically formulated and solved if the two cracks have equal severity. In this paper we extend this result to the case of cracks with different severity. Each crack is simulated by a rotational elastic spring and the inverse problem is solved in terms of the damage-induced changes in the first four natural frequencies. Closed-form expressions of the damage parameters in terms of the measured frequencies are obtained. The results can be extended to the identification of two cracks in a longitudinally vibrating beam based on a suitable set of natural frequency and antiresonant frequency data. Numerical simulations support the theory, and show that if accurate input data are available and the cracks are not too close, then damage identification leads to satisfactory results

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous seminal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress–strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austenitic steels submitted to impact conditions. Regarding most of the works reported in the literature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008-06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates

A constitutive model for analyzing martensite formation in austenitic steels deforming at high strain rates

This study presents a constitutive model for steels exhibiting SIMT, based on previous seminal works, and the corresponding methodology to estimate their parameters. The model includes temperature effects in the phase transformation kinetics, and in the softening of each solid phase through the use of a homogenization technique. The model was validated with experimental results of dynamic tensile tests on AISI 304 sheet steel specimens, and their predictions correlate well with the experimental evidence in terms of macroscopic stress–strain curves and martensite volume fraction formed at high strain rates. The work shows the value of considering temperature effects in the modeling of metastable austenitic steels submitted to impact conditions. Regarding most of the works reported in the literature on SIMT, modeling of the martensitic transformation at high strain rates is the distinctive feature of the present paper.The researchers of the University Carlos III of Madrid are indebted to the Comunidad Autónoma de Madrid (Project CCG10-UC3M/DPI-5596)) and to the Ministerio de Ciencia e Innovación de España (Project DPI/2008-06408) for the financial support received which allowed conducting part of this work. The authors express their thanks to Mr. Philippe and Mr. Tobisch from the company Zwick for the facilities provided to perform the tensile tests at high strain rates

Compositional representation (CoDa) of the Agenda-setting of the political opinion makers in the main Spanish media groups in the 2015 general election

This article presents an innovative proposal to represent the agenda-setting of the main Spanish media groups (RTVE, Prisa, Vocento, Unidad Editorial, COPE, Atresmedia, Planeta, Godó, Mediaset España and Libertad Digital) in the context of the 2015 Spanish general election. The study uses a quantitative method based on a content analysis of the main Spanish radio and TV programmes with political opinion spaces and the main newspapers linked to these media groups. Furthermore, the compositional methodological approach the CoDa-biplot is used to visualise and emphasise the relative salience of the components under study. The article not only provides a mapping of the agenda of the main media groups in the electoral context, but it also reaches the representation of the effects of priming and the spiral of silence in the proportional study of the issues and senders of the agenda.Este artículo presenta un estudio innovador sobre la representación de la agenda-setting de los principales grupos de medios españoles (RTVE, Prisa, Vocento, Unidad Editorial, COPE, Atresmedia, Planeta, Godó, Mediaset España y Libertad Digital), en el contexto de las Elecciones Generales en España del año 2015. El estudio emplea una metodología cuantitativa con base a un análisis de contenido de los principales programas con espacios de opinión sobre política en la radio y televisión española, así como de los principales periódicos vinculados a estos grupos mediáticos. Asimismo, se emplea la herramienta metodológica composicional del CoDa-biplot, que contribuye a visualizar y enfatizar la relevancia relativa de los componentes en estudio. El artículo proporciona un mapeo de la agenda de los principales grupos de medios en el contexto electoral, al tiempo que alcanza la representación de los efectos del priming y la espiral del silencio en el estudio proporcional de los issues y emisores de la agenda

Studying the benefits of using UML on software maintenance : an evidence-based approach

Including modelling as part of software development appears to have various benefits. Why then is it that not all companies use software modelling? One of the main reasons is that it requires up-front investments. From an economic point of view, any type of investment must be justified in terms of how much payback there will be at a later stage. This being the case, in the context of software projects, investment in modelling should be justified by benefits, such as improved productivity and improved product quality, which can be seen later during software development or maintenance. When such benefits are not tangible or foreseeable, modelling becomes a practice without clear added value for the system being developed. The problem, therefore, is how we can investigate and prove whether or not modelling, or some specific characteristics of modelling, provide any benefits during software development and maintenance. As long as this question remains unanswered, it will be difficult to motivate and justify modelling activities in real software projects. This thesis therefore contributes to partially answering these open questions by focusing the empirical research on the benefits of using UML modelling during software maintenance.Algorithms and the Foundations of Software technolog

Unique determination of a single crack in a uniform simply supported beam in bending vibration

In this paper we consider one of the basic inverse problems in damage detection based on natural frequency data, namely the identification of a single open crack in a uniform simply supported beam from measurement of the first and the second natural frequency. It is commonly accepted in the literature that the knowledge of this set of spectral data allows for the unique determination of the severity and the position (up to symmetry) of the damage. However, in spite of the fact that many numerical evidences are in support of this property, the result is rigorously proved only when the severity of the crack is small. In this paper we definitely show, by means of an original constructive method, that the above result holds true for any level of crack severity. (C) 2016 Elsevier Ltd. All rights reserved

Combine use of Selected Schizosaccharomyces pombe and Lachancea thermotolerans Yeast Strains as an Alternative to the Traditional Malolactic Fermentation in Red Wine Production

Most red wines commercialized in the market use the malolactic fermentationprocess in order to ensure stability from a microbiological point of view. In this secondfermentation, malic acid is converted into L-lactic acid under controlled setups. Howeverthis process is not free from possible collateral effects that on some occasions produceoff-flavors, wine quality loss and human health problems. In warm viticulture regions suchas the south of Spain, the risk of suffering a deviation during the malolactic fermentationprocess increases due to the high must pH. This contributes to produce wines with highvolatile acidity and biogenic amine values. This manuscript develops a new red winemakingmethodology that consists of combining the use of two non-Saccharomyces yeast strains asan alternative to the traditional malolactic fermentation. In this method, malic acid is totallyconsumed by Schizosaccharomyces pombe, thus achieving the microbiological stabilizationobjective, while Lachancea thermotolerans produces lactic acid in order not to reduce andeven increase the acidity of wines produced from low acidity musts. This technique reducesthe risks inherent to the malolactic fermentation process when performed in warm regions.The result is more fruity wines that contain less acetic acid and biogenic amines than thetraditional controls that have undergone the classical malolactic fermentation

The coupon collector urn model with unequal probabilities in ecology and evolution

International audienceThe sequential sampling of populations with unequal probabilities and with replacement in a closed population is a recurrent problem in ecology and evolution. Examples range from biodiversity sampling, epidemiology to the estimation of signal repertoire in animal communication. Many of these ques- tions can be reformulated as urn problems, often as special cases of the coupon collector problem, most simply expressed as the number of coupons that must be collected to have a complete set. We aimed to apply the coupon collector model in a comprehensive manner to one example—hosts (balls) being searched (draws) and parasitized (ball colour change) by parasitic wasps— to evaluate the influence of differences in sampling probabilities between items on collection speed. Based on the model of a complete multinomial process over time, we define the distribution, distribution function, expectation and variance of the number of hosts parasitized after a given time, as well as the inverse problem, estimating the sampling effort. We develop the relationship between the risk distribution on the set of hosts and the speed of parasitization and propose a more elegant proof of the weak stochastic dominance among speeds of parasitization, using the concept of Schur convexity and the ‘Robin Hood transfer’ numerical operation. Numerical examples are provided and a conjecture about strong dominance—an ordering characteristic of random variables—is proposed. The speed at which new items are discovered is a function of the entire shape of the sampling probability distribution. The sole comparison of values of variances is not sufficient to compare speeds associated with different distributions, as generally assumed in ecological studies