249 research outputs found
Numerical and experimental study of the flow-by cell for Vanadium Redox Batteries
No full textA mathematical model for vanadium redox batteries (VRBs) is considered. The model has been tuned using experimental data obtained for a single cell with flow-by design. Mass transfer limitations have been determined from experimental data, and a new correlation for mass transfer constant is proposed. Self-discharge of the battery resulting from crossover of vanadium ions through membrane is taken into account by the model as well. It is shown that Fick's law for diffusion describes crossover rather well. The crossover has a large impact on the battery voltage during discharge, but can be neglected during charge due to mutual compensation of diffusion and migration fluxes. Good agreement (with average error less than 7 %) between the experimental and modelled polarization and charge-discharge curves is observed in the whole current density region
Energy efficiency analysis for a kilo-watt class vanadium redox flow battery system
No full textA new methodology for estimation of the key characteristics of commercial scale Vanadium Redox Flow Battery (VRFB) at different operating conditions is proposed. The method is based on a set of simplified correlations that allow estimating VRFB rated power, capacity and operation time directly from the geometry of stack and tank without detailed numerical simulation of the battery. The study is focused on investigation of a kilo-watt class VRFB system (5 kW/15kWh) considering a wide range of current densities (40–100 mA cm−2). The proposed simplified approach is validated considering the most representative cases of battery operation strategies related to slow and fast modes. It demonstrated high accuracy for the estimation of rated power and operation time (average error below 3%) as well as stored energy (average error below 6%) compare to results of detailed numerical simulation. As a result, the proposed methodology can be used as a simple tool for development of proper battery usage protocol (a schedule for battery usage), which could allow avoiding over/underestimation of committed battery energy and power during battery operation. In addition, the obtained results can be also used in order to improve the accuracy of techno-economic studies determining the most economically attractive cases for application of VRFB systems
Zero dimensional dynamic model of vanadium redox flow battery cell incorporating all modes of vanadium ions crossover
No full textA 0-D dynamic mathematical model for a single Vanadium Redox Flow Battery (VRFB) cell is proposed. The model is based on the conservation principles of charge and mass transfer focusing on the precise simulation of crossover with diffusion, migration and convection. The influence of these phenomena on the capacity decay was systematically analyzed, revealing considerable impact of convection component, which dominates under diffusion and migration and mainly responsible for observed capacity loss. The model allows to simulate main characteristics of VRFB systems (such as battery voltage, state of charge, charge/discharge time and capacity decay due to crossover) with high accuracy. The model was validated with experimental data in the wide range of current densities (40–100 mA cm−2), and the results demonstrated good agreement with experiments having an average error within 5% range. In addition, the model requires a modest computational time and power, and, therefore, it can be suitable for application in advanced control-monitoring tools, which are necessary for a long-service life and sustainable operation of VRFB systems
Output feedback control of electrolyte flow rate for Vanadium Redox Flow Batteries
No full textIn this paper, we propose a new strategy for electrolyte flow rate control in Vanadium Redox Flow Batteries. The keystone of our approach is a novel methodology for determination of optimal reference voltage and robust feedback controller design that provides the desired transient and steady state battery performance. In addition, we introduce a hierarchical scheme of the general battery control system that significantly simplifies classification of battery control tasks and gives guidelines for multistage controller design. The research considers a kilo-watt class VRFB system operating in a wide range of loading currents (20–180 A). The proposed control algorithm allows reference trajectory tracking with high accuracy (average error less than 0.0005%), yet providing the required battery performance at twice lower flow rates as compared to the existing solutions, and thus, decreasing pump energy consumption by a factor of 3. As a result, the proposed method can be used for flow rate regulation in practical VRFB systems ensuring their stable and efficient operation under dynamic loading conditions
Prospect of modeling industrial scale flow batteries – From experimental data to accurate overpotential identification
No full textA vast literature exists on modelling of small-scale single-cell experiments for flow batteries, but very few reports have been published on large stacks, consisting of tens of cells, each with an active area of hundred square centimeters. In this report, a large set of measurements taken on a kW-class vanadium test facility is used to develop an accurate ad-hoc physical model. Experimental data consist of polarization curves at a broad range of states of charge and electrolyte flow rates, as well as electrochemical impedance spectra. The model is capable to decouple three sources of voltage losses: activation, ohmic, and concentration overpotentials. In addition, a new numerical approach for identifying the main parameters of electrochemical kinetics and mass-transport has been proposed. To the best of our knowledge, this is the first time when a model for voltage losses analyses was developed and fitted to a data from large-scale flow battery, being validated with a sensitivity analysis study. Investigations showed that activation losses have a sophisticated nature in combination with mass-transport limitations and play an important role in a wide range of loading current densities. As a result, they must be included in a reliable model able to reflect a non-linear voltage behavior of large stacks. This work also highlights that, in the investigated case, activation losses are likely to be attributed to the positive electrode rather than to the negative one. The obtained results could facilitate the development of advanced simulation and design of large-scale flow battery stacks
The Youth of the 21st Century: Education, Science, Innovations
No full textThe Youth of the 21st Century: Education, Science, Innovations : Proceedings of IV International Conference for Students, Postgraduates and Young Scientists, Vitebsk, December 6, 2017 / [editional board: I. M. Prishchepa [and others]] ; Ministry of Educational Establishment, "Vitebsk State P. M. Masherov University". - Vitebsk : Vitebsk State P. M. Masherov University, 2017. - 213 р. : ill., tab. - Bibliogr. at the end of art. - ISBN 978-985-517-642-9.-The collection of articles includes the Conference proceedings submitted by the authors at the International Conference for Students, Postgraduates and Young Scientists "The Youth of the 21st Century: Education, Science, Innovations" and dedicated to solving current scientifiс problems in natural sciences, teсhnical sciences and humanities. Articles may be used by scientists, teachers, postgraduates, undergraduates and students of higher educational establishments
History Department Faculty Gains Four Members
No full textNews release announcing Mr. Tong-Chin Rhee, Sister Mary Evelyn Jegen, Mr. Bruce M. Taylor, and Mr. Jules J. Pugach will join the faculty of the University of Dayton\u27s history department
Homology and cohomology groups of commutative Banach algebras and analytic polydiscs
No full textIn this paper we deduce the existence of analytic structure in a neighbourhood of a maximal ideal M in the spectrum of a commutative Banach algebra, A, from homological assumptions. We assume properties of certain of the cohomology groups Hn(A, A/M), rather than the stronger conditions on the homological dimension of the maximal ideal the first author has considered in previous papers. The conclusion is correspondingly weaker: in the previous work one deduces the existence of a Gel\u27fand neighbourhood with analytic structure, here we deduce only the existence of a metric neighbourhood with analytic structure. The main method is to consider products of certain co-cycles to deduce facts about the symmetric second cohomology, which is known to be related to the deformation theory of algebras. \ua9 Glasgow Mathematical Journal Trust 2000
Клініко-лабораторна характеристика вітамін D-дефіцитного рахіту у дітей раннього віку при ожирінні = Clinical-laboratory characteristics of vitamin D-deficient rickets in infants with obesity
No full textТokarchuk N. I., Pugach M. М., Chekotun Т. V., Starinetz L. S., Savicka T. V., Lagoda V. V. Клініко-лабораторна характеристика вітамін D-дефіцитного рахіту у дітей раннього віку при ожирінні = Clinical-laboratory characteristics of vitamin D-deficient rickets in infants with obesity. Journal of Education, Health and Sport. 2015;5(11):111-116. ISSN 2391-8306. DOI http://dx.doi.org/10.5281/zenodo.33536
http://ojs.ukw.edu.pl/index.php/johs/article/view/2015%3B5%2811%29%3A111-116
https://pbn.nauka.gov.pl/works/667735
Formerly Journal of Health Sciences. ISSN 1429-9623 / 2300-665X. Archives 2011–2014 http://journal.rsw.edu.pl/index.php/JHS/issue/archive
Deklaracja.
Specyfika i zawartość merytoryczna czasopisma nie ulega zmianie.
Zgodnie z informacją MNiSW z dnia 2 czerwca 2014 r., że w roku 2014 nie będzie przeprowadzana ocena czasopism naukowych; czasopismo o zmienionym tytule otrzymuje tyle samo punktów co na wykazie czasopism naukowych z dnia 31 grudnia 2014 r.
The journal has had 5 points in Ministry of Science and Higher Education of Poland parametric evaluation. Part B item 1089. (31.12.2014).
© The Author (s) 2015;
This article is published with open access at Licensee Open Journal Systems of Kazimierz Wielki University in Bydgoszcz, Poland and Radom University in Radom, Poland
Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium,
provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License
(http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited.
This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial
use, distribution and reproduction in any medium, provided the work is properly cited.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Received: 05.09.2015. Revised 05.10.2015. Accepted: 30.10.2015.
КЛІНІКО-ЛАБОРАТОРНА ХАРАКТЕРИСТИКА ВІТАМІН D-ДЕФІЦИТНОГО РАХІТУ У ДІТЕЙ РАННЬОГО ВІКУ ПРИ ОЖИРІННІ
CLINICAL-LABORATORY CHARACTERISTICS OF VITAMIN D-DEFICIENT RICKETS IN INFANTS WITH OBESITY
Н.І. Токарчук¹, М.М. Пугач¹, Т.В. Чекотун¹, Л.С. Старинець², Т.В. Савицька², В.В. Лагода²
N. I. Тokarchuk¹, M. М. Pugach¹, Т. V. Chekotun¹, L. S. Starinetz², T. V. Savicka², V. V. Lagoda²
¹Вінницький національний медичний університет ім. М. І. Пирогова, Україна
²Вінницька обласна дитяча клінічна лікарня, Україна
¹N.I. Pirogov Vinnitsa National Medical University, Ukraine
²Regional Children's Hospital Vinnitsa, Ukraine
Abstract
The study involved 120 infants suffering from vitamin D-deficient rickets which were divided into subgroups based on physical development indicators. We conducted a clinical examination of children anamnesis, and determined serum concentrations of 25 (OH) D. While studying in what way vitamin D-deficient rickets severity in infants depends of physical development indicators, we found increase in severity of rachitic process according to increasing values of body weight. Thus, the largest proportion of medium severity cases of vitamin D-deficient rickets was determined in children who were obese. In infants with rickets, the lowest vitamin D status was registered against the background of obesity. This aspect is possibly predetermined by the influence of endogenous pathogenic factors in the state of obesity due to the deposit of vitamin D in adipose tissue.
Key words: vitamin D-deficient rickets, obesity, infants, hydroxyvitamin D.
Резюме
У дослідженні прийняли участь 120 дітей першого року життя, хворі на вітамін D-дефіцитний рахіт, і були розподілені на підгрупи залежно від показників фізичного розвитку. Нами проведено клініко-анамнестичне обстеження дітей та визначення в сироватці крові концентрації 25(OH)D. При вивченні залежності ступеня тяжкості вітамін D-дефіцитного рахіту у дітей першого року життя від показників фізичного розвитку, нами виявлено зростання тяжкості рахітичного процесу відповідно до збільшення значень маси тіла. Так, найбільша питома вага випадків середнього ступеня важкості вітамін D-дефіцитного рахіту констатована у дітей, які мали ожиріння. У дітей першого року життя, хворих на рахіт, найнижчий статус вітаміну D було зареєстровано на тлі ожиріння. Даний аспект, можливо, обумовлений впливом патогенетичних ендогенних факторів при ожирінні за рахунок депонування вітаміну D в жировій тканині.
Ключові слова: вітамін D-дефіцитний рахіт, ожиріння, діти раннього віку, гідроксивітамін D
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