Repositorio Institucional UCSC (Univ. Católica de la Santísima Concepción)
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Rationalizing Fe-Modified TiO2 through doping, composite formation, and single-phase structuring for enhanced photocatalysis via inter- and intra-charge transfers
No full textThis study sheds light on how the properties of titanium dioxide (TiO2) are influenced when it is modified with iron (Fe), leading to the formation of Fe-doped-TiO2, Fe2O3-TiO2 composite, and single-phase FeTiO3 systems. The structural formation of the materials, oxidation state, and chemical environments of the elements are analyzed using XRD and XPS techniques. Band structures with UV–visible light driven properties and suitable redox potentials with improved recombination resistance along with an active inter- and intra-charge transfers were observed for Fe2O3-TiO2 and FeTiO3 systems. The photocatalytic efficiency was found to be superior for FeTiO3 system, degrading ~97 and 100 % of phenol, malachite green and rhodamine B dyes in 150 min, respectively along with enhanced recyclability. Interestingly, a competitive S- and Z-scheme was predicted for Fe2O3-TiO2 composite, explaining its photocatalytic mechanism. The scavenger and total organic carbon analyses revealed the radicals driving the photocatalytic reactions and the nature of degradation products, respectively
Variation in the modal response of retrofitted unreinforced masonry walls at different levels of damage
Get PDFThis article presents the results of an experimental campaign conducted on a set of four unreinforced masonry walls at full scale. The purpose of this study is to assess, using non-destructive methods, the impact of retrofitting and damage on the modal response of masonry wall systems. Each wall underwent a sequence of increasing cyclic displacements applied by an actuator at the upper end of the specimen. Modal tests based on vibrations were performed both before and after rehabilitation, as well as during the sequence of increasing displacements. It was demonstrated that frequencies can identify progressive damage when the maximum crack is about to occur, as well as the effect of wall retrofitting when mass contribution is considerable. However, the modal assurance criterion indicator (MAC) fails to properly identify a trend of decreasing correlations as progressive damage increases; instead, it is sensitive to detecting maximum crack and instability conditions. Furthermore, it was determined that the coordinated modal assurance criterion indicator (COMAC) does not identify the damage distribution as expected. However, the cumulative COMAC provides a useful tool for quick visualization and interpretation of COMAC behavior. Finally, a novel damage indicator was tested, MACVF, which improves the trend and successfully identifies the most damage-sensitive mode, especially when the maximum level of damage is reached, giving MAC values below 80%. In addition, frequency variations ranged from 70% to 110% when TRM and WWM retrofitting techniques were applied
An adaptive stabilized finite element method for the Stokes–Darcy coupled problem
No full textFor the Stokes–Darcy coupled problem, which models a fluid that flows from a free medium into a porous medium, we introduce and analyze an adaptive stabilized finite element method using Lagrange equal order element to approximate the velocity and pressure of the fluid. The interface conditions between the free medium and the porous medium are given by mass conservation, the balance of normal forces, and the Beavers–Joseph–Saffman conditions. We prove the well-posedness of the discrete problem and present a convergence analysis with optimal error estimates in natural norms. Next, we introduce and analyze a residual-based a posteriori error estimator for the stabilized scheme. Finally, we present numerical examples to demonstrate the performance and effectiveness of our scheme
Guide for the application of the data augmentation approach on sets of texts in Spanish for sentiment and emotion analysis
Get PDFOver the last ten years, social media has become a crucial data source for businesses and researchers, providing a space where people can express their opinions and emotions. To analyze this data and classify emotions and their polarity in texts, natural language processing (NLP) techniques such as emotion analysis (EA) and sentiment analysis (SA) are employed. However, the effectiveness of these tasks using machine learning (ML) and deep learning (DL) methods depends on large labeled datasets, which are scarce in languages like Spanish. To address this challenge, researchers use data augmentation (DA) techniques to artificially expand small datasets. This study aims to investigate whether DA techniques can improve classification results using ML and DL algorithms for sentiment and emotion analysis of Spanish texts. Various text manipulation techniques were applied, including transformations, paraphrasing (back-translation), and text generation using generative adversarial networks, to small datasets such as song lyrics, social media comments, headlines from national newspapers in Chile, and survey responses from higher education students. The findings show that the Convolutional Neural Network (CNN) classifier achieved the most significant improvement, with an 18% increase using the Generative Adversarial Networks for Sentiment Text (SentiGan) on the Aggressiveness (Seriousness) dataset. Additionally, the same classifier model showed an 11% improvement using the Easy Data Augmentation (EDA) on the Gender-Based Violence dataset. The performance of the Bidirectional Encoder Representations from Transformers (BETO) also improved by 10% on the back-translation augmented version of the October 18 dataset, and by 4% on the EDA augmented version of the Teaching survey dataset. These results suggest that data augmentation techniques enhance performance by transforming text and adapting it to the specific characteristics of the dataset. Through experimentation with various augmentation techniques, this research provides valuable insights into the analysis of subjectivity in Spanish texts and offers guidance for selecting algorithms and techniques based on dataset features
Microbioma y diabetes mellitus tipo 2: La necesidad de conocer la variabilidad poblacional en poblaciones latinoamericanas
No full textValidation of the cognitive behavioral social self-efficacy scale in Chilean university students
Get PDFLa Escala Cognitivo-Conductual de Autoeficacia Social fue diseñada para evaluar la autoeficacia social a partir de los dominios cognitivo y comportamental. Esta investigación tuvo como objetivo validar y estimar las propiedades psicométricas de esta escala a través de su aplicación en 824 estudiantes (46.4% mujeres) y (53.4% hombres), entre 17 y 23 años (M=18.71; SD=1.17), que cursaban primer año de sus carreras en una universidad del sur de Chile. Los resultados indicaron un adecuado ajuste del modelo de segundo orden considerando tres dimensiones de autoeficacia social y un factor general. Los coeficientes de consistencia interna para las dimensiones de la escala fueron, ω=.81 (Factor 1: Predictivo), ω=.82 (Factor 2: Cognitivo), ω=.83 (Factor 3: Comportamental) y (Factor General) ω=.87 (Autoeficacia Social). Se concluye que el cuestionario es un instrumento válido y confiable para evaluar este constructo en estudiantes universitarios chilenos
Determinants and impacts of digital entrepreneurship: A pre- and post-COVID-19 perspective
No full textEntrepreneurship and technology have been strongly connected over the last decades. The growth of digital technology and external factors have brought entrepreneurs new opportunities and challenges. The COVID-19 pandemic has reevaluated the relationship between digitalization and innovative business models. Like any entrepreneurial process, entrepreneurs face a complex adaptation process that determines their success or failure. We reviewed 208 articles published in the past decade to identify trends related to the determinants and impacts of digital entrepreneurship pre- and post-COVID-19 pandemic. Our results show trends in the definitions used, the relationship between external and internal factors that enable the exploration of available digital technologies for emerging business models, and the value digital entrepreneurs create for social, economic, and technological developments. Our study proposes a multidimensional framework and discusses challenges and opportunities
Response of wild aquatic insect communities to thermal variation through comparative landscape transcriptomics
No full textFluctuations in temperature are recognized as a potent driver of selection pressure, fostering genomic variations that are crucial for the adaptation and survival of organisms under selection. Notably, water temperature is a pivotal factor influencing aquatic organism persistence. By comprehending how aquatic organisms respond to shifts in water temperature, we can understand their potential physiological adaptations to environmental change in one or multiple species. This, in turn, contributes to the formulation of biologically relevant guidelines for the landscape scale transcriptome profile of organisms in lotic systems. Here, we investigated the distinct responses of seven stream stonefly species, collected from four geographical regions across Japan, to variations in temperature, including atmospheric and water temperatures. We achieved this by assessing the differences in gene expression through RNA‐sequencing within individual species and exploring the patterns of community‐genes among different species. We identified 735 genes that exhibited differential expressions across the temperature gradient. Remarkably, the community displayed expression levels differences of respiration and metabolic genes. Additionally, the diversity in molecular functions appeared to be linked to spatial variation, with water temperature differences potentially contributing to the overall functional diversity of genes. We found 22 community‐genes with consistent expression patterns among species in response to water temperature variations. These genes related to respiration, metabolism and development exhibited a clear gradient providing robust evidence of divergent adaptive responses to water temperature. Our findings underscore the differential adaptation of stonefly species to local environmental conditions, suggesting that shared responses in gene expression may occur across multiple species under similar environmental conditions. This study emphasizes the significance of considering various species when assessing the impacts of environmental changes on aquatic insect communities and understanding potential mechanisms to cope with such changes
Acute effect of different velocity-based training protocols on 2000-meter rowing ergometer performance
No full textThis study aimed to explore the acute effect of 4 velocity-based resistance training (VBT) protocols on 2000-m rowing ergometer (RE2000) time trial, as well as the behavior of the maximal neuromuscular capacities when RE2000 is performed alone or preceded by VBT protocols in the same session. Fifteen male competitive rowers (15–22 years) undertook 5 randomized protocols in separate occasions: (a) RE2000 alone (control condition); (b) VBT against 60% of 1 repetition maximum (1RM) with a velocity loss in the set of 10% followed by RE2000 (VBT60-10 + RE2000); (c) VBT against 60% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT60-30 + RE2000); (d) VBT against 80% 1RM with a velocity loss in the set of 10% followed by RE2000 (VBT80-10 + RE2000); (e) VBT against 80% 1RM with a velocity loss in the set of 30% followed by RE2000 (VBT80-30 + RE2000). The load-velocity relationship (load-axis intercept [L0], velocity-axis intercept [v0], and area under the load-velocity relationship line [Aline]) was used to evaluate the maximal neuromuscular capacities during the prone bench pull exercise before and after each protocol. The time trial was significantly longer for VBT60-30 + RE2000 and VBT80-30 + RE2000 than for RE2000, VBT60-10 + RE2000 and VBT80-10 + RE2000 (all p < 0.001; ES = 0.10–0.15). L0 and Aline were significantly reduced after all protocols (p < 0.001; ES = 0.10–0.13), with Aline reduction more accentuated for VBT60-10 + RE2000, VBT60-30 + RE2000, VBT80-30 + RE2000, and RE2000 (all p = 0.001; ES = 0.11–0.18) than for VBT80-10 + RE2000 (p = 0.065; ES = 0.05). Therefore, VBT protocols with greater velocity loss in the set (30% vs. 10%) negatively affected subsequent rowing ergometer performance, in line with impairment in Aline pulling performance