Hybrid finite elements for axially loaded elasto-plastic bars

This work reports on the formulation, implementation and validation of hybrid finite elements for elasto-plastic axially loaded bars, under quasi-static conditions. The equations governing the axially loaded bars are defined for both elastic and elastoplastic ranges. Two different hardening models are considered, kinematic and isotropic. The solution of the governing equations involves their discretization in time and space. The discretization in time is made by expanding in Euler series the time variation of the involved quantities and the integration in space is performed using the hybrid finite element method. Independent approximations of the displacement and plastic strain fields are made in the domain of each finite element using Chebyshev polynomials. Unlike conforming displacement finite elements, the bases are hierarchical and not linked in any way to the nodes of the mesh. The hybrid finite element formulation is derived by enforcing the weak form of the governing equations using the Garlerkin method. The computational implementation of the formulation is developed in the Matlab environment. The implementation offers considerable flexibility for the definition of the structure and its loads, the time steps and the finite element mesh. To validate the implementation and assess the convergence properties of the hybrid formulation, a problem with known analytic solution is used. The displacement and stress solution errors are measured and their reduction rates under mesh (h-), basis (p-) and time step (t-) refinements are computed to understand their relative effect on the quality of the solution. A second problem with a higher complexity level is used to illustrate the performance of the formulation when confronted to multiple loading and unloading cycles, that lead to partial and total yielding under traction and compression regimes

Geometric reconstruction and persistence methods

In the present work we reconstruct the homotopy type of an unknown Euclidean subspace from a known sample of data. We carry out such reconstruction through generalized Čech complexes, by choosing radii which are less or equal than the reach of the subspace and by applying the Nerve Lemma. We also approach the reconstruction of a geodesic subspace through its convexity radius and a dense enough sample. Afterwards, we obtain homology and homotopy groups in terms of persistences, together with interleavings and isomorphisms between them. We conclude studying the reconstruction of a particular subspace that has reach equal to zero, where our results cannot be applied.Master's Thesis in MathematicsMAT399MAMN-MA

Survival of the firm and territory.

El objetivo de este trabajo es evaluar el riesgo de mortalidad empresarial. Para ello, en una muestra de más de 11.741 empresas pertenecientes al sector textil-confección se ha estudiado, junto con otros factores, la influencia de la proximidad geográfica (efecto distrito) y la actividad productiva principal (efecto subsector) en la supervivencia de las empresas textiles españolas. Desde un punto de vista teórico-práctico esta industria es especialmente relevante para realizar ese tipo de estudios al menos por dos motivos: 1) porque después de la liberalización del comercio textil se ha visto inmersa en una profunda crisis en las economías más desarrolladas, y 2) porque tiende a agruparse geográficamente en torno a clusters o distritos industriales. Los resultados obtenidos sugieren que el riesgo de mortalidad empresarial se ve reducido por aspectos relativos a la empresa como la antigüedad y el subsector de actividad y, bajo determinadas circunstancias, por la localización en un distrito industrial. PALABRAS CLAVE: mortalidad empresarial, textil, distrito industrial

Quantification of efficiency improvements from integration of battery energy storage systems and renewable energy sources into domestic distribution networks

Due to the increasing use of renewable, non-controllable energy generation systems energy storage systems (ESS) are seen as a necessary part of future power delivery systems. ESS have gained research interest and practical implementation over the past decade and this is expected to continue into the future. This is due to the economic and operational benefits for both network operators and customers, battery energy storage system (BESS) is used as the main focus of this research paper. This paper presents an analytical study of the benefits of deploying distributed BESS in an electrical distribution network (DN). The work explores the optimum location of installing BESS and its impact on the DN performance and possible future investment. This study provides a comparison between bulk energy storage installed at three different locations; medium voltage (MV) side and low voltage (LV) side of the distribution transformer (DT) and distributed energy storage at customers’ feeders. The performance of a typical UK DN is examined under different penetration levels of wind energy generation units and BESS. The results show that the minimum storage size is obtained when BESS is installed next to the DT. However, the power loss is reduced to its minimum when BESS and wind energy are both distributed at load busbars. The study demonstrates that BESS installation has improved the loss of life factor of the distribution transformer

Migratory connectivity and differential patterns of decline in Barn Swallow (Hirundo rustica) in North America: Potential effects of factors on breeding and wintering grounds

Populations of several Neotropical migratory bird species have experienced declines in the recent decades but long-distance migrant aerial insectivores seem to be declining at greater rates than any other group. The Barn Swallow (Hirundo rustica) is a long-distance migrant and an aerial insectivore whose breeding populations have declined drastically in northern regions of North America but remain stable in certain areas of the southern United States. However, reasons for differential population trends and whether factors on breeding and/or wintering grounds could be causing these declines remain unclear. The main objective of this study was to investigate causes of differential population dynamics experienced by Barn Swallows in North America by 1) studying patterns of migratory connectivity of populations using a three stable isotope approach (δ2H, δ13C and δ15N) and 2) evaluating evidence for factors on breeding and/or wintering grounds causing regional differences in population trends. Tail feathers of Barn Swallow grown on the wintering grounds were collected during breeding season in 2009, 2010 and 2011 across the breeding range of the species. Feathers were examined isotopically (δ2H, δ13C and δ15N) and used to determine the relative strength of migratory connectivity of populations and to identify approximate wintering regions in South America. Long-term mark-recapture data from two breeding colonies in Washington State and Ontario were compared to the Southern Oscillation Index (SOI) for breeding and wintering months as a measure of El Niño Southern Oscillation (ENSO) to study the fundamental effect of large-scale climatic conditions on annual survival rates. Similarly, long-term reproductive parameters (i.e. fledging success, total number of eggs laid, chicks per nest) of breeding individuals in Washington State and Manitoba were used to determine the effects of local weather variation on reproductive performance. Winter-grown feathers grouped according to population sizes were additionally analyzed for costicosterone (CORT) concentrations to test whether declining northern populations have higher exposure to stressors on their wintering grounds in South America. Stable isotope (δ2H, δ13C and δ15N) analyses revealed evidence for a diverse pattern of migratory connectivity among breeding populations. Four isotopically distinct clusters corresponding to different wintering regions were identified and a progressive longitudinal shift in wintering grounds was detected. This study found evidence for a differential effect of ENSO-related weather conditions on inter-annual survivorship of two different breeding populations of Barn Swallows in North America. Annual survivorship of Barn Swallows breeding in Washington State was strongly correlated to ENSO during breeding and wintering months, while no correlation was found for birds breeding in Ontario, potentially due to the geographical variation of the effect of ENSO on weather conditions across North America and South America and the differential degree of migratory connectivity of populations. The length of cold periods (total number of consecutive days (≥ 2 d periods) with maximum daily temperatures lower than 11ºC) was found to have also a strong effect on annual survival rates of birds breeding in Washington State. Analyses of historical weather data showed that declining breeding populations have been exposed to more extensive cold periods than stable populations, suggesting a relationship between length of cold periods in spring and population trends. Annual reproductive performance was significantly affected by environmental conditions early in the breeding season related to ambient temperature, while precipitation variables had little effect. Wintering ground stressors related to CORT seem to have no significant effect on population size changes, since feather-CORT levels from declining populations were similar to those from stable populations. This study has provided a first attempt to identify factors occurring on breeding and/or wintering grounds that could have an effect on population sizes of Barn Swallows in North America. Weather conditions during breeding and wintering months and the degree of migratory connectivity of populations seem to be playing a significant role in the population trends of the species

Assessment of the Effect of Satureja montana and Origanum virens Essential Oils on Aspergillus flavus Growth and Aflatoxin Production at Different Water Activities

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Aflatoxin contamination of foodstuffs poses a serious risk to food security, and it is essential to search for new control methods to prevent these toxins entering the food chain. Several essential oils are able to reduce the growth and mycotoxin biosynthesis of toxigenic species, although their efficiency is strongly influenced by the environmental conditions. In this work, the effectiveness of Satureja montana and Origanum virens essential oils to control Aspergillus flavus growth was evaluated under three water activity levels (0.94, 0.96 and 0.98 aw) using a Bioscreen C, a rapid in vitro spectrophotometric technique. The aflatoxin concentrations at all conditions tested were determined by HPLC-FLD. Aspergillus flavus growth was delayed by both essential oil treatments. However, only S. montana essential oil was able to significantly affect aflatoxin production, although the inhibition percentages widely differed among water activities. The most significant reduction was observed at 0.96 aw, which is coincident with the conditions in which A. flavus reached the highest levels of aflatoxin production. On the contrary, the treatment with S. montana essential oil was not effective in significantly reducing aflatoxin production at 0.94 aw. Therefore, it is important to study the interaction of the new control compounds with environmental factors before their application in food matrices, and in vitro ecophysiological studies are a good option since they provide accurate and rapid results.Peer reviewedFinal Published versio

THE VOICE AND THE SONG FRO A GLOBAL AND INTERDISCIPLINARY APPROACH INPRIMARY EDUCATION

Through the voice and song we can find the right tools to work in an interdisciplinary, globalized and changing learning environment. This approach is about creating new strategies for working with different competencies required in the acquisition of knowledge, promoting active and collaborative methodologies and in consideration of diversity. During this process students involved Teacher Education and teachers from different knowledge areas of the Faculty of Education at the University of Zaragoza (Spain). The song will apply its power to stimulate emotions, develop sensitivity, memory and imagination. Our principal objective is to use the voice and the song as an interdisciplinary tool for students taking a Master Degree in Primary Education (6-12 years) in the acquisition of different competencies. The results take into consideration the potential lack of a musical background that students may have, an emphasis has been placed on the selection of the material used and the change in attitude of participants during the process, in assessing the experience positively

Propiedades psicométricas del inventario de violencia en las relaciones de noviazgo en adolescentes del distrito La Esperanza

El presente estudio tuvo como objetivo general determinar las propiedades psicométricas del Inventario de Violencia en las Relaciones de Noviazgo en adolescentes del distrito La Esperanza. El tipo de investigación es tecnológico y diseño descriptivo simple. La muestra la constituyeron 644 estudiantes de cuarto y quinto grado del nivel de educación secundaria de cinco Instituciones Educativas del distrito de La Esperanza, varones y mujeres, con edades entre 15 y 17 años, con registro de matrícula vigente en el año escolar 2019. Los resultados obtenidos muestran que, al estimar la validez de constructo del instrumento, mediante el método Ítem – test, los treinta y cinco items de las dos sub-escalas: Violencia Cometida y Violencia Sufrida, que componen el instrumento, presentan índices de correlación que oscilan entre .204 y .421; y entre .207 y .397, respectivamente. Asimismo, los resultados del análisis factorial confirmatorio, obtenidos mediante el método de máxima verosimilitud y bajo el supuesto de 5 factores relacionados, evidenciaron un p-valor estadísticamente significativo (p =.000) e índices de ajuste satisfactorios en ambas subescalas. La confiabilidad del instrumento se estimó, mediante el método de consistencia interna, alcanzando los siguientes índices Omega que oscilan entre .784 y .837, en la subescala Violencia Cometida; y entre. 774 y .849, en la subescala Violencia Sufrida, evidenciando así, una confiabilidad muy buena.The purpose of this study was to determine the psychometric properties of the Inventory of Violence in Dating Relationships in adolescents in the La Esperanza district. The type of research is technological and simple descriptive design. The sample was made up of 644 fourth and fifth grade students from the secondary education level of five Educational Institutions in the district of La Esperanza, men and women, aged between 15 and 17, with registration in force in the 2019 school year. The results obtained show that, when estimating the construct validity of the instrument, by means of the Item - test method, the thirty-five of the two subscales: Committed Violence and Suffered Violence, which make up the instrument, correlation indexes ranging between .204 and .421; and between .207 and .397, respectively. Likewise, the results of the confirmatory factor analysis, obtained through the maximum likelihood method and under the assumption of 5 related factors, showed a statistically significant p-value (p = .000) and satisfactory adjustment rates in both subscales. The reliability of the instrument was estimated, using the internal consistency method, reaching the following Omega indices ranging between .784 and .837, in the Violence Committed subscale; and between. 774 and .849, in the Suffering Violence subscale, thus demonstrating very good reliability.Tesi

Riboflavin-sensitized photooxidation of Ceftriaxone and Cefotaxime: kinetic study and effect on Staphylococcus aureus

Trace amounts of the widely used β-lactam antibiotics (Atbs) in waste water may cause adverse effects on the ecosystems and contribute to the proliferation of antibiotic-resistant bacteria. On these grounds, kinetic and mechanistic aspects of photosensitized degradation of Ceftriaxone (Cft) and Cefotaxime (Ctx), have been studied in pure water by stationary and time-resolved techniques. Additionally, possible implications of these photoprocesses on the antimicrobial activity of the Atbs have also been investigated. Photoirradiation of aqueous solutions of Cft and Ctx produces the degradation of both Atbs in the presence of Riboflavin (vitamin B2), a well known pigment dissolved in natural aquatic systems. The process occurs through Type I and Type II mechanisms, with effective prevalence of the former. The participation of O2−, OH and O2(1Δg) is supported by experiments of oxygen consumption carried out in the presence of specific scavengers for such reactive oxygen species. Microbiological assays exhibit a parallelism between the rate of Cft and Ctx photodegradation and the loss of their bactericidal capacity on Staphylococcus aureus strains. Results contribute to both understanding kinetic and mechanism aspects of the degradation and predicting on natural decay of Atbs waste water-contaminants.Fil: Reynoso, Eugenia. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Spesia, Mariana Belen. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia, Norman Andino. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Biasutti, Maria Alicia. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Criado, Susana Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin