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Exact formulation and analysis for the bi-objective insular traveling salesman problem
(MDPI, 2021-11-01) Miranda-Gonzalez, Pablo A.; Maturana-Ross, Javier; Blazquez, Carola A.; Cabrera-Guerrero, Guillermo
This paper aims at studying the Bi-Objective Insular Traveling Salesman Problem (BO-InTSP), which searches for a set of efficient, single visit sequences to collect (or distribute) freight from a set of islands. In this problem, the selection of ports (nodes) to be visited at each island, along with the associated port visit sequence, are optimized simultaneously, while the maritime transportation costs and the ground transportation costs inside the islands are minimized with a bi-objective perspective. This approach is employed since these costs are of a conflictive nature. A previous Approximated Formulation of the BO-InTSP relies on aggregating the actual demand locations within each island in a certain number of centroids for computing the ground transportation costs. Conversely, this paper proposes and develops a novel Exact Formulation for the problem based on the actual demand locations, instead of aggregating the demand inside the islands. Additionally, a systematic evaluation approach is developed to compare the two alternative formulations with different levels of demand aggregation inside the islands, considering the bi-objective nature of the problem. The results reveal that the novel Exact Formulation significantly outperforms the previous aggregated approach in terms of the solutions quality and computational resources. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
A fast-tracking hybrid mppt based on surface-based polynomial fitting and p&o methods for solar pv under partial shaded conditions
(MDPI, 2021-11-01) González-Castaño, Catalina; Restrepo, Carlos; Revelo-Fuelagán, Javier; Lorente-Leyva, Leandro L.; Peluffo-Ordóñez, Diego H.
The efficiency of photovoltaic (PV) systems depends directly on solar irradiation, so drastic variations in solar exposure will undoubtedly move its maximum power point (MPP). Furthermore, the presence of partial shading conditions (PSCs) generates local maximum power points (LMPPs) and one global maximum power point (GMPP) in the P-V characteristic curve. Therefore, a proper maximum power point tracking (MPPT) technique is crucial to increase PV system efficiency. There are classical, intelligent, optimal, and hybrid MPPT techniques; this paper presents a novel hybrid MPPT technique that combines Surface-Based Polynomial Fitting (SPF) and Perturbation and Ob-servation (P&O) for solar PV generation under PSCs. The development of the experimental PV system has two stages: (i) Modeling the PV array with the DC-DC boost converter using a real-time and high-speed simulator (PLECS RT Box), (ii) and implementing the proposed GMPPT algorithm with the double-loop controller of the DC-DC boost converter in a commercial low-priced digital signal controller (DSC). According to the simulation and the experimental results, the suggested hybrid algorithm is effective at tracking the GMPP under both uniform and nonuniform irradiance conditions in six scenarios: (i) system start-up, (ii) uniform irradiance variations, (iii) sharp change of the (PSCs), (iv) multiple peaks in the P-V characteristic, (v) dark cloud passing, and (vi) light cloud passing. Finally, the experimental results—through the standard errors and the mean power tracked and tracking factor scores—proved that the proposed hybrid SPF-P&O MPPT technique reaches the convergence to GMPP faster than benchmark approaches when dealing with PSCs. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Unveiling interdisciplinary horizons: students’ experiences in a first-year calculus course
(Frontiers Media SA, 2023) Armenta, Itzel H.; Dominguez, Angeles
In the realm of higher education, the pursuit of interdisciplinarity aims to foster the exchange and integration of fragmented knowledge, yielding transformative outcomes. Employing a phenomenological method, this study delves into the interdisciplinary experience of twelve students from a first-year undergraduate calculus class. Through the analysis of written questionnaires, focus group sessions, and supplementary qualitative data, a comprehensive understanding of students’ interdisciplinary encounters is unveiled and organized into three main categories: what students think about interdisciplinarity, how they act when being involved in integrations and what external factors are involved in shaping their experience. This paper presents emergent experiential themes, shedding light on both individual and collective experiences, as students navigate and enrich their calculus learning through interdisciplinary connections. Copyright © 2024 Armenta and Dominguez.
COMPARATIVE ANALYSIS OF QUANTITY TAKE-OFF IN CONCRETE, STEEL BARS AND FORMWORK IN APARTMENT BUILDINGS BASED ON CAD AND BIM METHODOLOGIES
(International Council for Research and Innovation in Building and Construction, 0025) Saavedra,Rodrigo; Melendez,Walter; Garces, Gonzalo
Building Information Modeling (BIM) prepares the quantity take-off (QTO) of the construction elements, helping in the management of the design and construction process and preparing the 3D visualization of the construction phases. BIM increases efficiency and gives users more control over construction-related tasks. Construction industry professionals are aware of the advantages of BIM, but because the software BIM is expensive and requires staff training, BIM is not yet widely used. The present investigation identifies the New Cycle building as a Case Study, in which inconsistencies were detected in the QTO, compared to the real quantities of budgeted materials, so the interested parties decided to implement BIM in the use of QTO as a mechanism of control. The central question addressed was: If BIM had been implemented at the tender stage, could it have provided benefits to the project? To do this, various parameters were evaluated that allowed a comparative analysis to be carried out between the results obtained through the use of the CAD and BIM methodology in the same project. In addition, the work processes associated with both methodologies were studied and the perception of CAD and BIM users in the Architecture, Engineering & Construction (AEC) industry was analyzed through the Delphi method. Using the Analytical Hierarchy Process (AHP) method, it was possible to evaluate and compare the two alternatives, CAD and BIM, in order to determine which of them would have been more effective in satisfying the objectives set in the project, considering various variables, both technical and economical. The study highlights the advantages of BIM over CAD for QTO in construction projects, providing valuable information for informed decision making in future projects. However, BIM adoption faces challenges such as the need for specialized training, industry resistance to change, complex workflows, and investments in software and hardware. To overcome these barriers, it is recommended to implement comprehensive training programs, foster a culture of innovation and collaboration, simplify BIM-QTO workflows, and explore scalable and accessible technological solutions. © 2025 The author(s).
Rapid decline in extratropical Andean snow cover driven by the poleward migration of the Southern Hemisphere westerlies
(Nature Research, 2024-12) Cordero, Raúl R.; Feron, Sarah; Damiani, Alessandro; MacDonell, Shelley; Carrasco, Jorge; Pizarro, Jaime; Karas, Cyrus; Jorquera, Jose; Sepulveda, Edgardo; Cabello, Fernanda; Fernandoy, Francisco; Wang, Chenghao
Seasonal snow in the extratropical Andes is a primary water source for major rivers supplying water for drinking, agriculture, and hydroelectric power in Central Chile. Here, we used estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) to analyze changes in snow cover extent over the period 2001–2022 in a total of 18 watersheds spanning approximately 1,100 km across the Chilean Andes (27–36°S). We found that the annual snow cover extent is receding in the watersheds analyzed at an average pace of approximately 19% per decade. These alarming trends have impacted meltwater runoff, resulting in historically low river streamflows during the dry season. We examined streamflow records dating back to the early 1980s for 10 major rivers within our study area. Further comparisons with large-scale climate modes suggest that the detected decreasing trends in snow cover extent are likely driven by the poleward migration of the westerly winds associated with a positive trend in the Southern Annular Mode (SAM).
How Difficult are Simple Electrical Circuit Conceptions? New Findings
(Eurasian Society of Educational Research, 2023) Quezada-Espinoza, Monica; Dominguez, Angeles; Zavala, Genaro
Research on conceptual understanding is one of the first steps in designing materials to improve learning. Literature reports that students have difficulties analyzing and describing phenomena in electric circuits. This report contributes to students' conceptual difficulties regarding simple electrical circuits by systematically analyzing an open conceptual test answered by 531 first-year engineering students. We found students' reasoning that has not yet been reported in the literature as misconceptions or difficulties. To deepen our understanding of students' difficulties, we chose five students by convenience to interview. We present evidence that there are two main contributions to the taxonomy in this study: the Series Circuit Misconception, which is when students convey that the current through bulbs is the same because they are in series, using that as a mnemonic ignoring any change in the circuit; and the Inverse Parallel Circuit Misconception, that is when students mention that the resistance of the circuit decreases when disconnecting bulbs in parallel, neither are reported in the literature. The results of this study have implications for physics education research in electric circuits and educational practice in the classroom. © 2023 The Author(s).
Long-lived particle phenomenology in one-loop neutrino mass models with dark matter
(Springer Science and Business Media Deutschland GmbH, 0025-02) Arbeláez, Carolina; Cottin, Giovanna; Helo, Juan Carlos; Hirsch, Martin; de Melo, Téssio B.
Neutrino masses and dark matter (DM) might have a common origin. The scotogenic model can be considered the proto-type model realizing this idea, but many other variants exist. In this paper we explore the phenomemology of a particular DM neutrino mass model, containing a triplet scalar. We calculate the relic density and check for constraints from direct detection experiments. The parameter space of the model, allowed by these constraints, contains typically a long-lived or quasi-stable doubly charged scalar, that can be searched for at the LHC. We reinterpret existing searches to derive limits on the masses of the scalars of the model and estimate future sensitivities in the high-luminosity phase of the LHC. The searches we discuss can serve to constrain also many other 1-loop neutrino mass models. © The Author(s) 2025.
Environmental assessment of formal and informal waste treatment of liquid crystal display (LCD) monitors
(Elsevier B.V., 2025-01-25) Labra Cataldo, Nicolás; Gallego-Schmid, Alejandro; Muñoz, Edmundo; McLachlan, Carly
In Santiago, Chile, 315,000 liquid crystal display (LCD) monitors are discarded annually. Of this amount, the formal sector of refurbishment and recycling manages only 5 %, creating the conditions for the emergence of informal management systems. This study provides the first comprehensive environmental and circularity assessment of monitor treatment across multiple impact categories, identifying trade-offs associated with formal and informal operations. For this, a life cycle assessment approach is utilised at both the product-level and the municipal management systems level, addressing the processes from the collection of the monitor to its end-of-life. At the product-level, two formal and two informal routes for managing an LCD monitor were evaluated. The results reveal that formal treatment companies have the best environmental performance in all the midpoint categories of ReCiPe, achieving benefits 42,000 times greater than formal disposal for marine eutrophication, and 25 % better than informal flea market traders across all categories. The analysis of management processes attributes most environmental benefits to refurbishment, representing between 76 % and 99 % of the magnitude of the assessed environmental impacts. A sensitivity analysis shows that the environmental performance of an informal trader surpasses that of a formal treatment company when both offer the same expected lifespan for a refurbished monitor and maintain their respective refurbishment rates offered. The municipal-level analysis was carried out through the evaluation of three scenarios. The results indicate that the scenario in which the informal sector cooperates with the formal sector and exclusively dedicates to collecting monitors exhibits superior environmental performance, averaging environmental benefits that are ten times greater than the current scenario and achieving valorisation rates of 22 %, the highest among the evaluated scenarios. The results of this research contribute to the discussion on formalisation and the promotion of the circular economy in the Global South.
Applying Machine Learning Sampling Techniques to Address Data Imbalance in a Chilean COVID-19 Symptoms and Comorbidities Dataset
(Multidisciplinary Digital Publishing Institute (MDPI), 0025-02) Ormeño-Arriagada, Pablo; Márquez, Gastón; Araya, David; Rimassa, Carla; Taramasco, Carla
Reliably detecting COVID-19 is critical for diagnosis and disease control. However, imbalanced data in medical datasets pose significant challenges for machine learning models, leading to bias and poor generalization. The dataset obtained from the EPIVIGILA system and the Chilean Epidemiological Surveillance Process contains information on over 6,000,000 patients, but, like many current datasets, it suffers from class imbalance. To address this issue, we applied various machine learning algorithms, both with and without sampling methods, and compared them using different classification and diagnostic metrics such as precision, sensitivity, specificity, likelihood ratio positive, and diagnostic odds ratio. Our results showed that applying sampling methods to this dataset improved the metric values and contributed to models with better generalization. Effectively managing imbalanced data is crucial for reliable COVID-19 diagnosis. This study enhances the understanding of how machine learning techniques can improve diagnostic reliability and contribute to better patient outcomes. © 2024 by the authors.
Can climate knowledge enable Warragamba Dam, Sydney, Australia to be used to manage flood risk?
(Institute of Physics, 0023-12) Devanand, Anjana; Pitman, Andy J; Carvajal, Guido; Khan, Stuart J
Dams that serve a dual purpose of water supply and flood mitigation operate to maintain a defined full supply level of water that balances the two conflicting requirements. To optimize the use of available storage space, the full supply level may be adjusted to reflect changing risks of future water shortages and future flood inflows based on known seasonal variations and current observations. The Warragamba Dam in eastern Australia is located upstream of the populated Hawkesbury-Nepean valley which has one of the largest flood exposures in the country. However, the operating protocol of the reservoir does not include provisions to reduce the full supply level of the dam for flood mitigation. Large scale climate indicators that are known to influence the hydroclimate of this region may potentially contain useful information to inform the dual use of this reservoir, but their utility for this purpose has not been studied. Here we explore whether current observations of large-scale climate along with antecedent catchment conditions can be used to estimate the probability of large inflows into the reservoir in the next 3- and 6 months, to aid flood management. We find that the predictors have a substantial influence on the probability of large inflows. The probability differences during opposite predictor phases vary by season and range from 30% to 70%. Our results indicate that considering current climate information to inform dual use of the Warragamba dam has merit. © 2023 The Author(s). Published by IOP Publishing Ltd.
Analysis and comparison of students' conceptual understanding of symmetry arguments in Gauss's and Ampere's laws
(American Physical Society, 2023-01) Campos, Esmeralda; Hernandez, Eder; Barniol, Pablo; Zavala, Genaro
Identifying students' difficulties in understanding Gauss's and Ampere's laws is important for developing educational strategies that promote an expertlike understanding of the field concept and Maxwell's equations of electromagnetic phenomena. This study aims to analyze and compare students' understanding of symmetry when applying Gauss's and Ampere's laws to calculate the electric or magnetic field. We conducted a study to analyze how students reason regarding the symmetry conditions necessary to apply Gauss's or Ampere's laws to calculate the electric or magnetic field in three inverse problems. We applied two open-ended questionnaires with parallel surface features, one for Gauss's law and the other for Ampere's law, to 322 engineering students. The three inverse problems present different scenarios with the common characteristic that there is no sufficient symmetry to solve the electric or magnetic field from its corresponding equation. We analyzed students' answers with a phenomenographic approach, focusing on students' answers to a yes or no question and their reasoning. The main findings of the study are the descriptive categories of understanding and the comparison of the categories between contexts (outcome space). The correct reasoning is identifying the necessary symmetry to apply Gauss's or Ampere's law. The other categories refer to the surface features of each scenario to explain students' answers, applying Gauss's or Ampere's law in an oversimplified way and thinking that it would be possible but more complicated in these scenarios. The descriptive categories are related to some of the difficulties previously reported in the literature with standard problems involving Gauss's and Ampere's laws. However, inverse problems elicited variations in the types of reasoning related to the surface features of the scenarios and their parallel representations. The comparative analysis between the electricity and magnetism contexts allowed for identifying that analyzing currents can be more challenging for students than analyzing point charges. This study's findings can guide introductory and intermediate electricity and magnetism instructors to redirect their approach to Gauss's and Ampere's laws by introducing the analysis of inverse problems. © 2023 authors. Published by the American Physical Society.
Mesalazine solubility in supercritical carbon dioxide with and without cosolvent and modeling
(Nature Research, 0025-12) Sajadian, Seyed Ali; Esfandiari, Nadia; Rojas, Adrián; Hemmati, Salar; Jouyban, Abolghasem; Aguila, Gonzalo; Garlapati, Chandrasekhar
In this study, the solubility of mesalazine in supercritical carbon dioxide with and without cosolvent was carried out for the first time at different temperatures and pressure values ranging from 308 to 338 K and 12 to 30 MPa, respectively. The determined experimental molar solubilities of mesalazine in supercritical carbon dioxide were in the range of 4.41 × 10–5 to 9.97 × 10–5 (308 K), 3.9 × 10–5 to 13.1 × 10–5 (318 K), 3.4 × 10–5 to 16 × 10–5 (328 K) and 3.3 × 10–5 to 18.4 × 10–5 (338 K). Meanwhile, the determined experimental molar solubilities in supercritical carbon dioxide using 2% dimethyl sulfoxide as cosolvent were in the range of 28.22 × 10–5 to 36.2 × 10–5 (308 K), 26.07 × 10–5 to 51.41 × 10–5 (318 K), 25.02 × 10–5 to 69.07 × 10–5 (328 K) and 25.86 × 10–5 to 82.6 × 10–5 (338 K). A novel association model was employed to simulate the solubility data of the binary and ternary systems. Various semiempirical correlations were utilized to calculate the solubility of mesalazine in supercritical carbon dioxide. The new association model was deemed the most superior model, achieving an average absolute relative deviation value of 4.13% without a cosolvent, and 3.36% when a cosolvent was included. © The Author(s) 2025.
Research and Realization of High-Power Medium-Voltage Active Rectifier Concepts for Future Hybrid-Electric Aircraft Generation
(Institute of Electrical and Electronics Engineers Inc., 2021-12) Trentin, Andrew; Sala, Giacomo; Tarisciotti, Luca; Galassini, Alessandro; Degano, Michele; Connor, Peter H.; Golovanov, Dmitry; Gerada, David; Xu, Zeyuan; La Rocca, Antonino; Eastwick, Carol N.; Pickering, Stephen J.; Wheeler, Patrick; Clare, Jon C.; Gerada, Chris
In this article, we describe the research and development of a 3 kV active rectifier for a 4 MW aerospace generator drive system demonstrator. The converter is fed by a multiphase high-speed/high-frequency permanent magnet generator. The main aim of the work is to demonstrate for the first time the feasibility of an MW-class generator system meeting future hybrid-electric propulsion requirements. A concept with multiple and isolated three-phase systems feeding different power buses is proposed to meet the availability requirements. Multiple converters (one for each three-phase system) are connected in series and/or in parallel to achieve the rated power and dc-link voltage. This article describes the key design concepts and the development and testing of the converter to meet the challenging application requirements. Reduced power tests are carried out on a full-scale 4 MW converter prototype, validating the proposed design. The work represents a step forward in terms of voltage, power, and output frequency with respect to the state-of-the-art. © 1982-2012 IEEE.
Mesalazine solubility in supercritical carbon dioxide with and without cosolvent and modeling
(Nature Research, 0025-12) Sajadian, Seyed Ali; Esfandiari, Nadia; Rojas, Adrián; Hemmati, Salar; Jouyban, Abolghasem; Aguila, Gonzalo; Garlapati, Chandrasekhar
In this study, the solubility of mesalazine in supercritical carbon dioxide with and without cosolvent was carried out for the first time at different temperatures and pressure values ranging from 308 to 338 K and 12 to 30 MPa, respectively. The determined experimental molar solubilities of mesalazine in supercritical carbon dioxide were in the range of 4.41 × 10–5 to 9.97 × 10–5 (308 K), 3.9 × 10–5 to 13.1 × 10–5 (318 K), 3.4 × 10–5 to 16 × 10–5 (328 K) and 3.3 × 10–5 to 18.4 × 10–5 (338 K). Meanwhile, the determined experimental molar solubilities in supercritical carbon dioxide using 2% dimethyl sulfoxide as cosolvent were in the range of 28.22 × 10–5 to 36.2 × 10–5 (308 K), 26.07 × 10–5 to 51.41 × 10–5 (318 K), 25.02 × 10–5 to 69.07 × 10–5 (328 K) and 25.86 × 10–5 to 82.6 × 10–5 (338 K). A novel association model was employed to simulate the solubility data of the binary and ternary systems. Various semiempirical correlations were utilized to calculate the solubility of mesalazine in supercritical carbon dioxide. The new association model was deemed the most superior model, achieving an average absolute relative deviation value of 4.13% without a cosolvent, and 3.36% when a cosolvent was included. © The Author(s) 2025.
Using implementation science to develop and deploy an oncology electronic health record
(Elsevier Ltd, 2025-01) Taramasco, Carla; Noel, Rene; Márquez, Gastón; Robles, Diego
The management of oncology clinical processes involves the efficient management of data using electronic clinical records to effectively monitor and treat oncology patients. As the process of treating and monitoring cancer patients involves multiple stakeholders with differing perspectives, the implementation and deployment of oncology clinical registries represent a significant challenge. In this study, we address this complexity by employing a technique that helps translate implementation strategies into requirement identification methods, which are subsequently disseminated throughout the implementation and deployment phases of health information systems. We applied this technique to develop an electronic health record for the national cancer plan in Chile. The findings indicate that six implementation strategies are essential to addressing stakeholder needs, as well as three requirement identification techniques to describe the underlying problem. Furthermore, a study conducted with 27 stakeholders revealed that the perception of the oncology electronic clinical record has considerable acceptance in three critical functionalities related to the clinical process of oncology patient management. The use of implementation science strategies provides an alternative approach to understanding the underlying problem that stakeholders face when they require healthcare technologies.
Adaptation and combination of two scales to measure dispositional gratitude in health sciences faculty: a psychometric analysi
(BioMed Central Ltd, 2024-02) Beltran-Sanchez, Jesus Alfonso; Valle de la O, Adrian; Nava-Manzo, Josue Omar; Dominguez, Angeles
Background: The study of gratitude has been a trending subject in psychology and emerging in health sciences education. For the past several years, interest has been aroused through various published contributions that still lack scientific support, so it is necessary to have instruments that obtain valid and reliable data about it. Gratitude has proven to be sensitive to different cultures. This research aims to determine the psychometric properties using a combined scale to measure dispositional gratitude in health sciences faculty. Method: A quantitative study was conducted with a non-experimental trans-sectional design with a correlational scope, with a sample of 216 professors of health sciences in a northeastern Mexico private university divided into subsamples for an Exploratory Factor Analysis (n = 113) and a Confirmatory Factor Analysis (n = 103). The Gratitude Questionnaire, Work Questionnaire and Brief Interactive Optimism-Garcia was applied to 110 women, 104 men and 2 who prefer not to specify their gender. Results: The result was a unifactorial measurement model composed of 10 items with evidence of construct validity (χ2 = 59.83, df = 20, p < 0.001, χ2/df = 59.83/20 = 2.99, SRMR = 0.11, GFI = 0.96; NFI = 0.93, RFI = 0.91, AGFI = 0.93), PRATIO = 0.78, PNFI = 0.73; concurrent validity with interactive optimism (r = 0.45, p < 0.001); convergent validity (AVE = 0.42); and reliability (α = 0.88; ω = 0.88). Conclusions: This model measures dispositional gratitude in health sciences Mexican faculty and contributes a vital instrument to advance future educational innovations involving this construct. The validation of the one-factor model with convergent reliability and validity suggests that the total scale score serves as an adequate measure of gratitude. Finally, it represents a valuable contribution to the teaching of health sciences since it generates healthy environments with prosocial attitudes that facilitate flourishing in personal and academic life, and in the future, health professionals with humanism as their standard
Mathematics classroom explanation: a literature review
(HISIN (History of Information Systems), 0025-01) Valdes, Gabriel
Research on explanation in the teaching of mathematics at the secondary education level is crucial for improving understanding and the effective learning of mathematical concepts. This study focuses on analyzing empirical research that has addressed the explanation in the teaching of mathematics at the secondary level, published in the last five years in journals indexed in the Web of Science. Methodology: A systematic analysis is carried out, following the PRISMA methodology to ensure a systematic and reproducible analysis. Results: The findings highlight that research at the primary and secondary educational levels on mathematical explanation is scarce. Studies with teaching innovations predominate. Discussions: The need for ongoing training for teachers is discussed, emphasizing the importance of clear explanations tailored to the needs of the students to facilitate deep and enduring learning, as well as the practical implications of the study. Conclusions: This study underscores the opportunity to expand research in this field to enrich pedagogical practices and improve the teaching of mathematics at fundamental educational levels. © 2025, HISIN (History of Information Systems). All rights reserved.
Phenomenographic analysis and comparison of students' conceptual understanding of electric and magnetic fields and the principle of superposition
(American Physical Society, 2021-12) Campos, Esmeralda; Hernandez, Eder; Barniol, Pablo; Zavala, Genaro
There are studies of students' understanding of the concept of the electric field, the magnetic field, and the use of the superposition principle that have contributed to the creation of both educational strategies and assessment tools. However, the difficulties of these two concepts have not been compared comprehensively. Therefore, this study aims to compare students' conceptual understanding of electric and magnetic fields in questions regarding the field created by one source and the field produced by a system of two sources. We focus our study on students' explanations about the magnitude and direction of the field and their application of the superposition principle in both contexts (electric and magnetic). We conducted this study with 322 engineering students in a Mexican university. We designed two versions of an open-ended questionnaire, one with the context of electricity and the other with magnetism. We created the questions using the parallelism between electricity and magnetism and used schematic representations with similar surface features to represent this parallelism. Analyzing the data through a phenomenographic approach, the students' drawings and explanations gave insight into their understanding of the concept of field and the superposition principle application in the context of electricity and magnetism. We found that students have similar categories of understanding the concept of the electric and the magnetic field. In both contexts, there is an evident relationship between applying the principle of superposition and understanding the concept of field. We found that there is a greater tendency that a student correctly applies the superposition principle if that student has a robust representation of the field. We found evidence that students consistently merge two different representations (vector plots and field lines) in electricity and magnetism. We named this category of representation "hybrid vectors and field lines."We also found that some students who draw hybrid representations of the field can still apply the superposition principle correctly. However, some conceptual understanding difficulties are dependent on the context: the known difficulty of confusion between forces and fields is more attached to the electricity context. The confusion between electricity and magnetism concepts is more relevant in the magnetism context. As in other literature, we found more evidence that the correct answer in multiple-choice questions may lead students who have mild difficulties (such as memorization and creating a hybrid representation) to choose a correct answer. We recommend that teachers and researchers of electricity and magnetism acknowledge the relationship between the conceptual understanding of the field and applying the superposition principle. We suggest that instructors be attentive to how they approach using representations of electric and magnetic fields. © 2021 authors. Published by the American Physical Society.
Development of computational approaches with a fragment-based drug design strategy: In silico hsp90 inhibitors discovery
(MDPI, 2021-12-02) León, Roberto; Soto-Delgado, Jorge; Montero, Elizabeth; Vargas, Matías
A semi-exhaustive approach and a heuristic search algorithm use a fragment-based drug design (FBDD) strategy for designing new inhibitors in an in silico process. A deconstruction reconstruction process uses a set of known Hsp90 ligands for generating new ones. The deconstruction process consists of cutting off a known ligand in fragments. The reconstruction process consists of coupling fragments to develop a new set of ligands. For evaluating the approaches, we compare the binding energy of the new ligands with the known ligands. © 2021 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 (https:// creativecommons.org/licenses/by/ 4.0/).
Distributed Control Scheme for Clusters of Power Quality Compensators in Grid-Tied AC Microgrids
(Multidisciplinary Digital Publishing Institute (MDPI), 2023-11) Martínez-Gómez, Manuel; Burgos-Mellado, Claudio; Morales-Paredes, Helmo Kelis; Gómez, Juan Sebastián; Verma, Anant Kumar; Bonaldo, Jakson Paulo
Modern electrical systems are required to provide increasing standards of power quality, so converters in microgrids need to cooperate to accomplish the requirements efficiently in terms of costs and energy. Currently, power quality compensators (PQCs) are deployed individually, with no capacity to support distant nodes. Motivated by this, this paper proposes a consensus-based scheme, augmented by the conservative power theory (CPT), for controlling clusters of PQCs aiming to improve the imbalance, harmonics and the power factor at multiple nodes of a grid-tied AC microgrid. The CPT calculates the current components that need to be compensated at the point of common coupling (PCC) and local nodes; then, compensations are implemented by using each grid-following converter’s remaining volt-ampere capacity, converting them in PQCs and improving the system’s efficiency. The proposal yields the non-active power balancing among PQCs compounding a cluster. Constraints of cumulative non-active contribution and maximum disposable power are included in each controller. Also, grid-support components are calculated locally based on shared information from the PCC. Extensive simulations show a seamless compensation (even with time delays) of unbalanced and harmonics current (below 20% each) at selected buses, with control convergences of 0.5–1.5 [s] within clusters and 1.0–3.0 [s] for multi-cluster cooperation. © 2023 by the authors.

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