Error assessment in structural transient dynamics

This paper presents in a unified framework the most representative state-of-the-art techniques on a posteriori error assessment for second order hyperbolic problems, i.e., structural transient dynamics. For the sake of presentation, the error estimates are grouped in four types: recovery-based estimates, the dual weighted residual method, the constitutive relation error method and error estimates for timeline-dependent quantities of interest. All these methodologies give a comprehensive overview on the available error assessment techniques in structural dynamics, both for energy-like and goal-oriented estimates

Goal-oriented space-time adaptivity for transient dynamics using a modal description of the adjoint solution

This article presents a space-time adaptive strategy for transient elastodynamics. The method aims at computing an optimal space-time discretization such that the computed solution has an error in the quantity of interest below a user-defined tolerance. The methodology is based on a goal-oriented error estimate that requires accounting for an auxiliary adjoint problem. The major novelty of this paper is using modal analysis to obtain a proper approximation of the adjoint solution. The idea of using a modal-based description was introduced in a previous work for error estimation purposes. Here this approach is used for the first time in the context of adaptivity. With respect to the standard direct time-integration methods, the modal solution of the adjoint problem is highly competitive in terms of computational effort and memory requirements. The performance of the proposed strategy is tested in two numerical examples. The two examples are selected to be representative of different wave propagation phenomena, one being a 2D bulky continuum and the second a 2D domain representing a structural frame

Online structural damage classification methodology for offshore wind turbine foundations using data stream analysis

Structural health monitoring (SHM) of wind turbines is crucial to improve maintenance and extend their lifespan. This study develops an online data analysis methodology using data stream analysis to classify damage in the links of an offshore wind turbine foundation. The methodology is validated using a laboratory-scaled jacket-type wind turbine foundation structure. 2460 measurements of the healthy structure were acquired, and a 5mm crack was applied to four different links to determine the four unhealthy classes. 820 measurements were taken for each of the unhealthy structures, resulting in a dataset with 5740 instances. As this is an imbalanced multiclass classification problem, a random sampler approach was used to treat the data. The only data obtained was from eight triaxial accelerometers distributed throughout the structure. Three different tree-based stream data classifiers were compared: Hoeffding Tree classifier, Extremely Fast Decision Tree classifier, and Hoeffding Adaptive Tree classifier. Each classification model underwent a tuning parameter procedure, and high values of the receiving operating characteristic area under the curve (ROC AUC) metric were achieved as a result. It is important to note that stream learning differs from batch learning.Peer ReviewedPostprint (published version

Crosstalk characterization of fabrics elaborated with conductive yarns

The electrical characterization of crosstalk of fabrics elaborated with conductive yarns is investigated. The impact of the source, victim and ground traces location is reported. The experimental results show that the crosstalk in fabrics is higher in comparison with other conductive media. Nevertheless, the results show that the standard strategies to reduce the coupling between lines can be used on fabrics. Doing this, fabrics elaborated with conductive yarns can be used as a conductive media for digital buses, which can help to improve the integration of electronic devices in textile.Peer ReviewedPostprint (author's final draft

Entorn interactiu i semipresencial per a l'aprenentatge de les matemàtiques aplicades a l'enginyeria industrial

El projecte sorgeix davant la constatació del baix rendiment acadèmic i falta de motivació i estudi en les assignatures de matemàtiques de part dels estudiants de les enginyeries tècniques. Davant d’aquest fet, es va plantejar posar en marxa una experiència pilot durant les classes de pràctiques de laboratori dels estudiants de fase selectiva. Es va crear tota una sèrie de material –llibres electrònics, tutorials, aplicacions i gràfics interactius– que permetien a l’alumne treballar dins d’un entorn d’autoaprenentatge que els motivava a fer i autocorregir els exercicis proposats. La proposta del projecte ha estat, doncs, la creació d’un entorn tecnològic –pàgina web i eines d’aprenentatge— que ajudi a la consecució dels següents objectius: (1) la motivació de l’estudiant respecte al l’aprenentatge de les ciències matemàtiques (2) l’establiment d’un marc de treball atractiu, interactiu i semipresencial a través de les noves tecnologies (3) foment del treball cooperatiu. La part interactiva i semipresencial s’allotja en una pàgina web. Mitjançant el programa de càlcul simbòlic MAPLE, que facilita la creació i disseny de MAPLETS, eines interactives que permeten interacció amb l’usuari, independència de plataformes i integració a la web. La innovació del projecte rau en l’ús d’aquest marc de treball recentment desenvolupat, amb gran potencialitat simbòlica (i per tant didàctica) i de càlcul. En definitiva, el que es proposa és un recorregut guiat cap a la maduresa de l’estudiant en tot allò que representa el seu procés d’aprenentatge, amb el suport d’eines telemàtiques i la vinculació de l’aprenentatge (conceptual i procedimental) amb els continguts de la seva titulació

Short communication: Recombinant mammary serum amyloid A3 as a potential strategy for preventing intramammary infections in dairy cows at dryoff

Mammary serum amyloid A3 (M-SAA3) has shown potential in stimulating innate immunity during intramammary infections, at calving and at dryoff. In this study, we produced recombinant caprine M-SAA3 to test its ability to reduce intramammary infections with Staphylococcus aureus, Streptococcus uberis, Streptococcus dysgalactiae, and Escherichia coli, which are all common mastitis-producing pathogens. Recombinant production of M-SAA3 (followed by lipopolysaccharide removal to avoid lipopolysaccharide-nonspecific stimulation of the immune system) was successfully achieved. Mammary serum amyloid A3 stimulated the expression of IL-8 in a dose-dependent manner in primary mammary cultures. Although a direct killing effect on Staph. aureus by M-SAA3 was not detected, this acute phase protein was able to reduce Staph. aureus, Strep. uberis, and Strep. dysgalactiae infections by up to 50% and induced a reduction in E. coli counts of 67%. In general, the best concentration of caprine M-SAA3 for inhibiting infections was the lowest concentration tested (10 μg/mL), although higher concentrations (up to 160 μg/mL) increased its antimicrobial potential against some pathogens.info:eu-repo/semantics/acceptedVersio

Matrius i sistemes

2008/200

Sistemes d’autoaprenentage i d’autoavaluació dins la plataforma Atenea

La ràpida evolució dels Learning Management Systems (LMS) i la introducció en la nostra Universitat de Moodle han permès l'estandardització de la producció dels materials d'ensenyament. L'avaluació automàtica dels estudiants és un dels aspectes clau en la introducció de noves formes d'estudi semipresencial. Aquestes activitats tenen efectes en l'avaluació de l'assignatura i en l'autonomia dels estudiants. Això sintonitza amb les directrius del nou Espai Europeu d'Educació Superior. Aquest treball explica una experiència de primera mà: reemplaçar les llistes estàtiques de problemes per un conjunt d'exercicis aleatoris on s'avalua la resposta automàticament (mitjançant Wiris Quizzes), cobrint el 100% del contingut de les matèries.Peer Reviewe

Bases concursos closques i fractals

2010/201

Use of wiris quizzes in an online calculus course

Calculus courses often present a large number of difficulties to undergraduate students of scientific studies, especially in engineering degrees. These difficulties are sometimes related to teaching and assessment strategies. In this paper, a teaching innovation experience is presented within the framework of the Universitat Oberta de Catalunya. This teaching experience is focused on a continuous assessment through a systematic use of the so-called WIRIS quizzes. Academic outcomes are very positive from both quantitative and qualitative viewpoints.Peer ReviewedPostprint (author's final draft