Ingenieria Multidisciplinar
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Mechanical Characterization of a Polymer/Natural Fibers/Bentonite Composite Material with Implementation of a Continuous Damage Model
(MDPI, 2023/02/01) Fernandez Meyli Valin, Rivera Jose Luis Valin, Rodriguez Frank Perez, Losada Henry Figueredo, Abreu Maria Elena Fernandez, Diaz Francisco Rolando Valenzuela, Soto Angel Rodriguez, Alvarez Alexander Alfonso, Quinteros Roberto, Ketterer Cristobal Galleguillos, Garcia del Pino Gilberto
A characterization of composite materials of a polyester matrix reinforced with natural fibers of Cuban henequen and organophilized Cuban bentonite was carried out, the experimental results of which are used to formulate, implement, and validate a scalar damage model. The fibers were added on a weight basis of 15, 20, and 25% as a reinforcing material, and organophilized Cuban bentonite, in amounts of 3, 5, and 7% by weight, was added. Samples containing only polymer and fibers showed the best mechanical performance for 25% of fiber, with increases of 51% in the tensile strength and 169% on the impact resistance. Samples containing polymer and clay showed the best results for 5% of bentonite, with increases of 89% in the tensile strength and 83% on the impact resistance, and samples containing 25% fiber and 5% clay were also prepared and achieved a 98% increase in the tensile strength and 219% in the impact strength. The scalar damage model deals with an internal variable, which corresponds to the damage variable, together with a failure surface that allows identifying the mechanical state of the material dependent on the mechanical stress, obtaining an adequate correlation with the results of the experimental tests.
Analytical Hierarchical Process to Establish the Criteria for Choosing Explosives Suppliers in Small and Medium Mining Companies
(MDPI, 01-09-2023) Ramirez Olivares Edison, Castillo-Vergara Mauricio
Mining plays a pivotal role in economies worldwide, contributing to employment, infrastructure, and the supply of essential raw materials. Chile's global mining powerhouse, particularly in copper production, exemplifies this industry's economic significance. The supplier selection process in the mining industry, a complex and multifaceted task, is explored in detail, specifically focusing on explosives procurement, a critical component for mineral extraction. The paper underscores the importance of informed supplier selection decisions, especially for SMEs, which often need more resources and capabilities for efficient management. To address these challenges, the study proposes applying the Analytic Hierarchical Process (AHP), a multi-criteria decision-making methodology, to identify and prioritize the criteria and sub-criteria pertinent to choosing explosives suppliers. A case study in the Coquimbo Region, Chile, involving SMEs in the mining sector is the empirical foundation for this research. Our research highlights that the foremost criterion for SMEs in the Coquimbo Region's mining sector is relationship with the environment and communities. This reflects the national context of mining community tensions and the rising environmental standards and social expectations, which can profoundly impact mining operations. Quality of products and services is the second most crucial criterion, underscoring SMEs' drive to enhance productivity and efficiency. Contractual compliance follows closely, signifying the integration of SMEs into broader social and environmental sustainability efforts. Conversely, innovation ranks as the least relevant criterion, indicating that SMEs prioritize traditional processes due to limited resources and cost constraints. These insights are valuable for mining supplier company managers, emphasizing the need for sustainability, corporate social responsibility, and management control systems.
Reduced order modeling of parametrized pulsatile blood flows: Hematocrit percentage and heart rate
(PERGAMON-ELSEVIER SCIENCE LTD, 2023/12/01) Farias Catalina, Bayona-Roa Camilo, Castillo Ernesto, Cabrales Roberto C., Reyes Ricardo
This paper numerically evaluates the accuracy and performance of a stabilized finite element Reduced Order Modelling (ROM) approach that is designed to simulate pulsatile blood flows. The method is able to estimate fluid flow parametric solutions of interest in hemodynamics by considering the hematocrit percentage (Hct%) and the heart rate (f(c)) as parameters. The method estimates off-trained parametric scenarios which have not been included in the training data set composing the ROM basis and that can adopt arbitrary values from specific patient conditions. The hematocrit percentages modifies the viscous properties of blood, which are incorporated into the problem physics through a power-law model. The hematocrit percentages are 5 = Hct% = 50, ranging from severe anemia to physiological values. The pulsatile flow condition is modeled via a Womersley function, with f(c)bpm (beats per minute) ranging between 60bpm = f(c) = 120bpm. These frequencies comprise physiological conditions of patients at rest and tachycardia or moderate exercise. Two-and-three-dimensional flows are simulated inside a representative geometry of a carotid artery, where the accuracy is tested by studying the effect of the number of components of the ROM approximating basis and the number of sampling points composing the training data set. The parametric calculation verifies that the proposed approach constitutes a valuable computational tool for simulating complex fluid flow hemodynamics and can be applied to clinical decision-making.
Augmented reality and education in electronics: Relationship between usability, academic performance, and emotions experienced in learning
(WILEY, 01-11-2023) Alvarez-Marin Alejandro, Paredes-Velasco Maximiliano, Velazquez-Iturbide J. Angel, Poblete-Castro Julio C. C.
Students often find difficult to understand the concepts and working details of electricity because its mechanisms of operation are invisible. The visualization of electricity through an augmented reality (AR) app could assist students in understanding these concepts more intuitively and in improving their academic achievement. Due to the lack of studies on AR apps for electricity education, this study aimed to investigate the effects of an interactive AR app designed for teaching electrical circuits on students. The study investigates its impact on students' academic performance, explores its influence on their emotions, and examines the relationship between the perceived usability of the app and the student's learning outcomes and emotional experiences. The study was conducted in an electromagnetism laboratory with the participation of 28 engineering students. The findings revealed that the students who used the augmented reality application presented a better academic performance than those who participated in the traditional laboratory. Except for the students in the experimental group feeling less shame, there were no discernible variations between the students' feelings in the two groups. Anxiety increases in both groups. The AR application proved to have usability rated as good, but it was not evident that it correlated with academic performance, or the emotions students experienced. Only one relationship was determined between the perceived consistency of the system and hopelessness.
Hyperreduced-order modeling of thermally coupled flows
(ELSEVIER SCIENCE INC, 01-01-2024) Espinoza-Contreras Nicolas, Bayona-Roa Camilo, Castillo Ernesto, Gandara Tomas, Moraga Nelson O.
This article presents a full and reduced-order methodology based on the finite element method that allows the characterization of convective-dominant conjugate heat transfer flows. Reduced-order modeling (ROM) allows the description of several degrees of freedom problems, referred to as full-order modeling (FOM), through a reduced-order surrogate representation based on a Petrov-Galerkin projection onto a reduced subspace. The FOM and ROM problems are stabilized through the Variational Multi-Scale (VMS) method, which ensures stability in dominant convective problems and allows equal interpolation spaces for the pressure, velocity, and temperature. The proposed methodology is validated solving natural heat convection in a differentially heated square cavity, considering air as the working fluid and Rayleigh numbers in the interval 10(4) <= Ra <= 10(8). In this problem, the benefit of using a ROM approximation for the three unknown fields, i.e., velocity, pressure, and temperature, is compared against ROM approximation only in the velocity and pressure fields and a FOM type approximation for temperature. The benefit of using mesh-based hyperreduction and its computational performance and precision are also analyzed. Subsequently, the method simulates a conjugate heat transfer problem that includes natural heat convection, allowing the inclusion of different rheologies between the working fluids. The results verify the precision and speed up of the calculations by more than three hundred times with respect to the time necessary to solve a full-order formulation, emerging it as a great potential tool in the resolution of thermally coupled flows.
The Basis of Aaaalll of Our Program! The Start-Up Chile Playbook as Metagenre
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2023/09/01) Sabaj Omar, Spinuzzi Clay, Varas German, Cabezas Paula, Gerard Valentin
Background: Following previous professional communication research into entrepreneurship, we examine key genres of a specific business accelerator, Start-Up Chile (SUP). Through a triangulated study of interviews, texts, and videos, we examine how the Playbook serves as a regulatory metagenre that represents the SUP experience to the participating firms. We find that aspects of the Playbook's representation are at odds with the other data, divergences that we argue emerge from a broader tension among SUP's stakeholders and goals. Literature review: We review the professional communication literature on entrepreneurship, literature on startups and accelerators, and on writing, activity, and genre research (WAGR). Specifically, we examine WAGR research on metagenres and professional identity formation. Research question: How does this successful international accelerator regularize the learning experience of its exceedingly diverse startups? Specifically, how does SUP regulate the startups' different experiences, reframing the experience of entrepreneurship and teaching these startups to form their professional identity as entrepreneurs? Research methodology: We structured this research as a qualitative case study of SUP. Data included documents, videos, interviews, and social media. We triangulated these data sources to identify points of convergence (in which different data sources supported the same assertions) and divergence (in which data sources contradicted each other). Results: SUP provides the Playbook and Newsletter as metagenres that regulate complex interactions among other genres and events, guiding firms into having roughly equivalent experiences as well as maintaining relationships among volunteers such as mentors. But the Playbook also reframes the experience of entrepreneurship so that it can fit into SUP's program: it reframes the cyclical entrepreneurship process as linear, and it reframes promises of future action as tracking of past actions. In undergoing these experiences, the startups form their professional identity as entrepreneurs. Conclusion: We conclude by discussing implications for accelerators as well as for how professional communication genres and metagenres regulate neophytes' experiences in training programs more broadly.
ALUMINUM RECOVERY FROM MINE TAILINGS, APPLYING INNOVATIVE CHEMICAL AND BIOLOGICAL PROCESSES
(EXECUTIVE BUSINESS SCH-EXEBS, 01-06-2023) Zamarreno-Bastias Ricardo, Espinoza-Barrera Javiera
An investigation was carried out, at the chemical -metallurgical laboratory level, evaluating two methods in the recovery of aluminum, present in an abandoned mining tailing. In order to find a new source of recovery for this element. Aluminum is found in the form of aluminosilicates in the tailings. Two methods were used, a biological process and a chemical one. In the biological one, bioleaching was carried out with cultivated Aspergillus niger fungi, which produces organic acids, which can extract aluminum from the tailings. The chemical method consisted of leaching with two organic acids, citric acid and oxalic acid with the addition of oxidizing agents such as hydrogen peroxide and a strong base. According to the results, the methods that had the highest extraction were chemical, specifically leaching with the mixture of oxalic acid and hydrogen peroxide. In the case of bioleaching, no significant results were obtained in the extraction of aluminum.