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computational modeling of an Earth-Air Heat Exchanger Integrated with Phase Change Materials: A Case Study Performed for the Viamão City, Rio Grande do Sul State, Brazil

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Defect and Diffusion Forum 2023年 427卷 85-94页

作者： Vielma Vivas, Giovanni Antonio Rodrigues, Michel Kepes Alberto, Luiz Rocha, Oliveira Dos Santos, Elizaldo Domingues Silva Brum, Ruth da Isoldi, Liércio André Graduate Program in Computational Modeling Federal University of Rio Grande RS Rio Grande Brazil Graduate Program in Mathematical Modeling Federal University of Pelotas RS Pelotas Brazil

The earth-air heat exchanger (EAHE) is a sustainable option that allows the electrical energy consumption reduction in buildings. The objective of this study is to evaluate the influence of the incorporation of the thermal energy storage principle based on phase change materials (PCM) into the EAHE on its thermal potential. For this, a three-dimensional numerical model of the PCM coupled to the EAHE (EAHE-PCM) was developed based on the effective heat capacity method and adapted to the climatic conditions and soil characteristics of the Viamão city, Rio Grande do Sul State, Brazil. It was found that for a duct diameter and length of 0.11 m and 25.77 m, the incorporation of PCM to EAHE improved by 8.90% and 3.97% in the average annual thermal potential of heating and cooling, respectively. In addition, the average monthly thermal potential increased 19.70% (heating) and 8.48% (cooling), for the months of May and December, respectively, when the PCM was integrated into the system. © 2023 Trans Tech Publications Ltd, Switzerland.

关键词： Phase change materials

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Numerical Analysis of Phase Change Material Parameters on the Behavior of a Ground-Air Heat Exchanger

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Defect and Diffusion Forum 2024年 436卷 103-115页

作者： Vivas, Giovanni Antonio Vielma Rodrigues, Michel Kepes Rocha, Luiz Alberto Oliveira Dos Santos, Elizaldo Domingues Brum, Ruth da Silva Isoldi, Liércio André Graduate Program in Computational Modeling Federal University of Rio Grande RS Rio Grande Brazil Graduate Program in Mathematical Modeling Federal University of Pelotas RS Pelotas Brazil

The ground-air heat exchanger (GAHE) represents an eco-friendly solution for improving temperature conditions and, consequently, lowering the power demand in facilities. The aim of this research is to numerically analyze how the length and position of the phase change material (PCM) affect the behavior of the GAHE. To achieve this, a 3D computational simulation of the PCM integrated with the GAHE was employed, utilizing the equivalent heat capacity approach and tailored to the climate and ground properties of southern Brazil. This GAHE-PCM numerical model was created employing the finite volume method through the ANSYS Fluent program. From the obtained results, it was found that for a PCM length of 20.61 m, the incorporation of this material placed from the duct inlet offered an improvement of 13.37% in the average heating energy performance indicator (EPI) in the month of May, in contrast to the EPI value of 18.04% achieved when the PCM was added from the duct outlet. © 2024 Trans Tech Publications Ltd, All Rights Reserved.

关键词： Ducts

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Four-phase Buck Converter Design and Thermal modeling Using FEA Simulation 14

Four-phase Buck Converter Design and Thermal Modeling Using ...

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14th Seminar on Power Electronics and Control, SEPOC 2022

作者： Eckhardt, Gustavo Lenz, Joao Manoel An Electrical Engineering Undergrad with A Scientific Initiation Scholarship at Unijuí Brazil Unijúi Brazil Mathematical and Computational Modeling Graduate Program Unijúi Brazil Brazil

ISBN: (数字)9781665470896

ISBN: (纸本)9781665470896

Equipment with high efficiency, high power density, reduced size and low cost are in demand in the automotive industry. This work presents a method to design and model a high power-density four-phase DC-DC Buck converter for an automotive application and using the components operating temperature as a design criteria. A parameter sweep is done to select the operating point of the DC-DC converter combined with an iterative method to select part numbers, where preference is given to components that are AEC-Qxxx qualified. The converter is modeled and power losses are computed in SPICE considering the parasitic elements present in the PCB and the dynamic characteristics and non-idealities of the electronic components;thermal modeling is performed using Ansys Icepak. The results indicate that the design meets all electrical and thermal requirements for an automotive application. An efficiency of 95.97% is obtained in a four-phase DC-DC Buck converter that supplies a total of 800 W to 4 loads, in a space of 43.77 cm3, that is, an estimated power density of 18.28 W/cm3. © 2022 IEEE.

关键词： Buck converter

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New Approach for Fault Location in Transmission Lines Using Artificial Neural

SSRN

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SSRN 2022年

作者： Silveira, Eduardo Gonzaga Rocha, Simone Aparecida Cardoso, Rodrigo Tomas Nogueira Research and Graduate Program in Mathematical and Computational Modeling Belo Horizonte Brazil Research and Graduate Program in Electrical Engineering Belo Horizonte Brazil

This paper presents a new algorithm for fault location in transmission lines by using data from measurements of voltages and currents of the two terminals and applying it to artificial neural networks. An electrical circuit is modeled in a transient simulator to generate training and validation files. This method differs from others presented in previous studies because the values of the fault voltages obtained from the line terminals are used instead of using the values of the internal voltages of the sources and their respective Thevenin equivalent impedances. To present the characteristics that distinguish it from other methods, a conventional fault location algorithm based on neural networks is initially described, which demonstrates how the dependence on the parameters of the sources can complicate the application of the artificial neural network in actual cases that occur in electric systems of energy utilities. The new algorithm is then introduced and applied in cases with simulated and real faults. In both situations, low errors are obtained with the proposed model, thereby demonstrating its effectiveness and feasibility for practical application. It should be noted that the neural networks used for the real cases were trained based on simulated faults. © 2022, The Authors. All rights reserved.

关键词： Electric lines

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A quadratic approximation-based local search operator for handling two equality constraints in continuous optimization problems

A quadratic approximation-based local search operator for ha...

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Congress on Evolutionary Computation

作者： Carlos H. Fonseca Elizabeth Fialho Wanner Post-graduate Program in Mathematical and Computational Modeling MG Brasil Department of Computer Engineering MG Brasil

This work presents extensions of the general methodology of employing quadratic approximations of the objective function and constraints for handling non-linear equality constraints in single-objective optimization problems. The methodology does not require any extra function evaluation since the quadratic approximations are constructed using only information that would be already obtained in the course of the optimization algorithms. The methodology is coupled with the Real Biased Genetic Algorithm to tackle non-linear single-objective optimization problems with two equality constraints. The modified algorithm is tested with a set of analytical problems. The results show the modified algorithm finds the constrained optima with enhanced precision and faster convergence. Considering that the new technique does not impose any additional cost to the algorithms, it can be stated that the technique is also suitable for costly black-box problems.

关键词： Optimization Approximation algorithms Linear programming Search problems Genetic algorithms Symmetric matrices Convergence

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Generalized model for solid-on-solid interface growth

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Physical Review E 2015年第5期91卷 052407-052407页

作者： M. F. Richele A. P. F. Atman []Post-Graduate Program in Mathematical and Computational Modeling Federal Center of Technological Education of Minas Gerais Avenida Amazonas 7675 30510-000 Belo Horizonte-MG Brazil

We present a probabilistic cellular automaton (PCA) model to study solid-on-solid interface growth in which the transition rules depend on the local morphology of the profile obtained from the interface representation of the PCA. We show that the model is able to reproduce a wide range of patterns whose critical roughening exponents are associated to different universality classes, including random deposition, Edwards-Wilkinson, and Kardar-Parisi-Zhang. By means of the growth exponent method, we consider a particular set of the model parameters to build the two-dimensional phase diagram corresponding to a planar cut of the higher dimensional parameter space. A strong indication of phase transition between different universality classes can be observed, evincing different regimes of deposition, from layer-by-layer to Volmer-Weber and Stransk-Krastanov-like modes. We expect that this model can be useful to predict the morphological properties of interfaces obtained at different surface deposition problems, since it allows us to simulate several experimental situations by setting the values of the specific transition probabilities in a very simple and direct way.

关键词： CELLULAR automata mathematical models PHASE transformations (Physics) SOLID-solid interfaces PARAMETERS (Statistics) CRYSTAL growth

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Homogenisation for the monodomain model in the presence of microscopic fibrotic structures

arXiv

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arXiv 2020年

作者： Lawson, Brodie A.J. dos Santos, Rodrigo Weber Turner, Ian W. Bueno-Orovio, Alfonso Burrage, Pamela Burrage, Kevin Centre for Data Science Queensland University of Technology QLD Australia ARC Centre of Excellence for Mathematical and Statistical Frontiers Queensland University of Technology QLD Australia Graduate Program on Computational Modeling Universidade de Juiz de Fora Minas Gerais Brazil Department of Computer Science University of Oxford Oxfordshire United Kingdom

MSC Codes 35B27computational models in cardiac electrophysiology are notorious for long runtimes, restricting the numbers of nodes and mesh elements in the numerical discretisations used for their solution. This makes it particularly challenging to incorporate structural heterogeneities on small spatial scales, preventing a full understanding of the critical arrhythmogenic effects of conditions such as cardiac fibrosis. In this work, we explore the technique of homogenisation by volume averaging for the inclusion of non-conductive micro-structures into larger-scale cardiac meshes with minor computational overhead. Importantly, our approach is not restricted to periodic patterns, enabling homogenised models to represent, for example, the intricate patterns of collagen deposition present in different types of fibrosis. We first highlight the importance of appropriate boundary condition choice for the closure problems that define the parameters of homogenised models. Then, we demonstrate the technique’s ability to correctly upscale the effects of fibrotic patterns with a spatial resolution of 10 µm into much larger numerical mesh sizes of 100-250 µm. The homogenised models using these coarser meshes correctly predict critical pro-arrhythmic effects of fibrosis, including slowed conduction, source/sink mismatch, and stabilisation of re-entrant activation patterns. As such, this approach to homogenisation represents a significant step towards whole organ simulations that unravel the effects of microscopic cardiac tissue heterogeneities. © 2020, CC BY.

关键词： Heart

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The Fisher Geometry and Geodesics of the Multivariate Normals, without Differential Geometry

arXiv

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arXiv 2023年

作者： Lawson, Brodie A.J. Burrage, Kevin Mengersen, Kerrie Santos, Rodrigo Weber dos Centre for Data Science Queensland University of Technology Australia School of Mathematical Sciences Queensland University of Technology Australia ARC Centre of Excellence for Plant Success in Nature and Agriculture Australia Department of Computer Science University of Oxford United Kingdom Graduate Program in Computational Modeling Universidade Federal de Juiz de Fora Brazil

Choosing the Fisher information as the metric tensor for a Riemannian manifold provides a powerful yet fundamental way to understand statistical distribution families. Distances along this manifold become a compelling measure of statistical distance, and paths of shorter distance improve sampling techniques that leverage a sequence of distributions in their operation. Unfortunately, even for a distribution as generally tractable as the multivariate normal distribution, this information geometry proves unwieldy enough that closed-form solutions for shortest-distance paths or their lengths remain unavailable outside of limited special cases. In this review we present for general statisticians the most practical aspects of the Fisher geometry for this fundamental distribution family. Rather than a differential geometric treatment, we use an intuitive understanding of the covariance-induced curvature of this manifold to unify the special cases with known closed-form solution and review approximate solutions for the general case. We also use the multivariate normal information geometry to better understand the paths or distances commonly used in statistics (annealing, Wasserstein). Given the unavailability of a general solution, we also discuss the methods used for numerically obtaining geodesics in the space of multivariate normals, identifying remaining challenges and suggesting methodological *** Codes 62B11 (primary), 62-02, 62-08 (secondary) © 2023, CC BY.

关键词： Geometry

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An adapted cardioprotective diet with or without phytosterol and/or krill oil supplement in familial hypercholesterolemia: A pilot study protocol

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Clinical Nutrition Open Science 2024年 54卷 127-139页

作者： de Abreu-Silva, Erlon Oliveira Machado, Rachel Helena Vieira dos Santos, Bianca Rodrigues Kojima, Flávia Soares Santos, Renato Hideo Nakagawa Murizine, Gabriela Souza Homsi, Jordana Rosa Negrelli, Karina Leal Barbante, Letícia Galvão de Barros e Silva, Pedro G.M. de Lima, Andressa Gusmão Tramujas, Lucas Bersch-Ferreira, Ângela Cristine Carvalho, Adriana Bastos de Oliveira, Thaís Martins Izar, Maria Cristina Sampaio, Geni Rodrigues Damasceno, Nágila Raquel Teixeira Rogero, Marcelo Macedo da Silva Torres, Elizabeth Aparecida Ferraz Costa, Rosana Perim de Souza Mota, Luís Gustavo Krey, Julia Pinheiro da Silva, Lucas Ribeiro de Luca, Patrícia Vieira Amaral, Cristiane Kovacs de Oliveira, Patricia Rodrigues da Silva, Renata Alves Moreira, Priscila dos Santos, Elisa Maia de Melo, Rodrigo Morel Vieira Lima, Eduardo Gomes de Luca, André Heck, Thiago Gomes Carvalho, Ana Paula Perillo Ferreira Garofallo, Silvia Bueno Cavalcanti, Alexandre Biasi Marcadenti, Aline Hcor Research Institute SP São Paulo Brazil Division of Health Care Sciences Dresden International University Dresden Germany Department of Education and Research BP - A Beneficência Portuguesa de São Paulo SP São Paulo Brazil Carlos Chagas Filho Biophysics Institute Federal University of Rio de Janeiro RJ Rio de Janeiro Brazil National Institute of Cardiology RJ Rio de Janeiro Brazil Graduate Program in Genetics and Molecular Biology Federal University of Rio Grande do Sul RS Porto Alegre Brazil Paulista School of Medicine Federal University of São Paulo SP São Paulo Brazil Department of Nutrition School of Public Health University of São Paulo SP São Paulo Brazil Hcor Outpatient Nutrition Service SP São Paulo Brazil Hcor Nutrition Service SP São Paulo Brazil Brazilian Association of Familial Hypercholesterolemia SP São Paulo Brazil Dante Pazzanese Institute of Cardiology SP São Paulo Brazil Graduate Program in Cardiovascular Sciences (Professional Master's Degree) National Institute of Cardiology RJ Rio de Janeiro Brazil Graduate Program in Medicine and Health Federal University of Bahia BA Salvador Brazil Hospital Ana Nery BA Salvador Brazil Atherosclerosis Clinical Unit Hospital das Clínicas Heart Institute School of Medicine University of São Paulo SP São Paulo Brazil Dasa Cardiology Unit (Hospital 9 de Julho) SP São Paulo Brazil Clinical Research Center Hospital São José SC Criciúma Brazil Graduate Program in Integral Health Care and Graduate Program in Mathematical and Computational Modeling Regional University of the Northwest of the State of Rio Grande do Sul (UNIJUÍ) RS Ijuí Brazil Health and Nutrition Research Improvement Group /Clinical Hospital Federal University of Goiás GO Goiânia Brazil Feevale University RS Novo Hamburgo Brazil Graduate Program in Health Sciences (Cardiology) Rio Grande do Sul Cardiology Institute/University Foundation of Cardiology RS Porto Alegre Brazil Graduate Program in Epidemiology University

Background and aims: A healthy diet is one of the pillars of familial hypercholesterolemia (FH) treatment. However, the best dietary pattern and indication for specific supplementation have not been established. Our aim is to conduct a pilot study to assess the effect of an adapted cardioprotective diet with or without phytosterol and/or krill oil supplement in participants with a probable or definitive diagnosis of FH, treated with moderate/high potency statins. Methods: A national, multicenter, factorial, and parallel placebo-controlled randomized clinical trial with a superiority design and 1:1:1:1 allocation rate will be conducted. The participants will undergo whole exome sequencing and be allocated into four treatment groups: 1) a cardioprotective diet adapted for FH (DICA-FH) + phytosterol placebo + krill oil placebo;2) DICA-FH + phytosterol 2 g/day + krill oil placebo;3) DICA-FH + phytosterol placebo + krill oil 2 g/day;or 4) DICA-FH + phytosterol 2 g/day + krill oil 2 g/day. The primary outcomes will be low-density lipoprotein (LDL)-cholesterol and lipoprotein (a) levels and adherence to treatment after a 120-day follow-up. LDL- and high-density lipoprotein (HDL)-cholesterol subclasses, untargeted lipidomics analysis, adverse events, and protocol implementation components will also be assessed. Results: A total of 58 participants were enrolled between May–August 2023. After the end of the follow-up period, the efficacy and feasibility results of this pilot study will form the basis of the design of a large-scale randomized clinical trial. Conclusions: This study's overall goal is to recommend dietary treatment strategies in the context of FH. © 2024 The Author(s)

关键词： Diet Fatty acids Healthy Hypercholesterolemia Omega-3 Phytosterols

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Considering discrepancy when calibrating a mechanistic electrophysiology model

arXiv

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arXiv 2020年

作者： Lei, Chon Lok Ghosh, Sanmitra Whittaker, Dominic G. Aboelkassem, Yasser Beattie, Kylie A. Cantwell, Chris D. Delhaas, Tammo Houston, Charles Novaes, Gustavo Montes Panfilov, Alexander V. Pathmanathan, Pras Riabiz, Marina Weber dos Santos, Rodrigo Worden, Keith Mirams, Gary R. Wilkinson, Richard D. Computational Biology & Health Informatics Dept. of Computer Science University of Oxford United Kingdom MRC Biostatistics Unit University of Cambridge United Kingdom Centre for Mathematical Medicine & Biology School of Mathematical Sciences University of Nottingham United Kingdom Department of Bioengineering University of California San Diego United States Systems Modeling and Translational Biology GlaxoSmithKline R&D Stevenage United Kingdom ElectroCardioMaths Programme Centre for Cardiac Engineering Imperial College London United Kingdom CARIM School for Cardiovascular Diseases Maastricht University Netherlands Graduate Program in Computational Modeling Universidade Federal de Juiz de Fora Brazil Department of Physics and Astronomy Ghent University Belgium Laboratory of Computational Biology and Medicine Ural Federal University Ekaterinburg Russia U.S. Food and Drug Administration Center for Devices and Radiological Health Office of Science and Engineering Laboratories United States Department of Biomedical Engineering King’s College London Alan Turing Institute United Kingdom Dynamics Research Group Department of Mechanical Engineering University of Sheffield United Kingdom School of Mathematics and Statistics University of Sheffield United Kingdom

Uncertainty quantification (UQ) is a vital step in using mathematical models and simulations to take decisions. The field of cardiac simulation has begun to explore and adopt UQ methods to characterise uncertainty in model inputs and how that propagates through to outputs or predictions. In this perspective piece we draw attention to an important and under-addressed source of uncertainty in our predictions — that of uncertainty in the model structure or the equations themselves. The difference between imperfect models and reality is termed model discrepancy, and we are often uncertain as to the size and consequences of this discrepancy. Here we provide two examples of the consequences of discrepancy when calibrating models at the ion channel and action potential scales. Furthermore, we attempt to account for this discrepancy when calibrating and validating an ion channel model using different methods, based on modelling the discrepancy using Gaussian processes (GPs) and autoregressive-moving-average (ARMA) models, then highlight the advantages and shortcomings of each approach. Finally, suggestions and lines of enquiry for future work are provided. Copyright © 2020, The Authors. All rights reserved.

关键词： Uncertainty analysis

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