Thursday, August 11. 2022
Two-level approach for numerical modeling of blood flow in the liver lobule
A.V. Grigorev1, P.N. Vabishchevich2
Department of Compututational Technologies, Institute of Mathematics and Informatics, M.K. Ammosova North-Eastern Federal University,
Yakutsk, Russia
Received 7 December, 2020
Abstract: A two-level approach is considered for numerical modeling of the blood flow in the liver-lobule system in this work. Within the framework of this approach it is proposed to apply a double continua model to describe the flow of blood at each of the two levels. The proposed two-level model can be scaled to typical cases of blood flow in biological structures containing lobules. The numerical implementation is based on the use of the finite element method over space and finite-difference approximations over time. The results of simulations of blood flow in the liver-lobule system are presented that carried out in combined three-dimensional and two-dimensional computational meshes.
c 2022 European Society of Computational Methods in Sciences and Engineering
Keywords: Two-level approach, Double porosity model, Blood flow in liver, Finite element method, Biomedical modeling
Mathematics Subject Classification: 92-10 Biology and other natural sciences: Mathematical modeling or simulation for problems pertaining to biology
PACS: 87.85.Tu Biomedical engineering: modeling of biomedical systems
Tuesday, June 21. 2022
Winfried Auzingera, Katrina N. Burdeosd, Merlin Fallahpourc, Othmar Kochb, Renier G. Mendozad, Ewa B. Weinmullera
aInstitute of Analysis and Scientific Computing, TU Wien, Wiedner Hauptstrasse 8-10/E101, A-1040 Wien, Austria
bWolfgang Pauli Institute, Oskar Morgenstern-Platz 1, A-1090 Wien, Austria
cDepartment of Mathematics and Computer Science, University of Basel, Spiegelgasse 1, 4051 Basel, Switzerland
dInstitute of Mathematics, University of the Philippines Diliman, Quezon City,Philippines, 1101
Abstract: The Matlab package bvpsuite 2.0 is a numerical collocation code for the approximation of solutions of a broad range of boundary value problems in ordinary differential equations. In this article, its newly implemented pathfollowing module with automated step-length control is presented. Two versions using the pseudo-arclength continuation method, allowing pathfollowing beyond turning points, were developed, both taking advantage of the existing features of bvpsuite 2.0 such as error estimation and mesh adaptation. The firrst version is based on the Gauss-Newton method. The second version is now contained in the package bvpsuite 2.0 and uses its built-in iterative method, the Fast Frozen Newton method. Their operating principles are presented and their performance is compared by means of the computation of some pathfollowing problems. Furthermore, the results of computations with bvpsuite 2.0 for a problem with path bifurcations are presented.
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Monday, February 14. 2022
Andrii Chugaia, Svitlana Alyokhina a,b, and Andrii Zhuravkab
a Institute for Mechanical Engineering Problems of the National Academy of Sciences of Ukraine, 2/10
Pozharskogo st., Kharkiv 61046, Ukraine, e-mail: alyokhina@ipmach.kharkov.ua
b Kharkiv National University of Radioelectronics, 14 Nauky ave., Kharkiv 61166, Ukraine
The paper is concerned to the development of an approach which allow us for solving the layout problem of container with spent nuclear fuel on the storage site to apply methods of geometric design. An exact mathematical model of optimal layout problem of spent nuclear fuel containers in the storage site is constructed. Due to phi-function technique the mathematical model is constructed as a non-linear mathematical programing problem. The features of the mathematical model are presented. It is shown that the feasible solution region can be presented as a union of subregion. Each of the subregion is described by systems of inequalities which the left parts are continuous functions. On the bases of features the solution approach is proposed.
Keywords: mathematical modeling, phi-function, NP-hard problem, spent nuclear fuel, layout problems, nuclear safety
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Sunday, January 30. 2022
F. Iavernaro3
Dipartimento di Matematica, Universita di Bari, I-70125 Bari, Italy
D. Trigiante
Dipartimento di Energetica, Universita di Firenze, I-50134 Firenze, Italy
Received 11 March, 2009; accepted in revised form 23 April, 2009
Dedicated to John Butcher on the occasion of his 75th birthday
Abstract: We define a class of arbitrary high order symmetric one-step methods that, when applied to Hamiltonian systems, are capable of precisely conserving the Hamiltonian function when this is a polynomial, whatever the initial condition and the stepsize h used.
The key idea to devise such methods is the use of the so called discrete line integral, the discrete counterpart of the line integral in conservative vector fields. This approach naturally suggests a formulation of such methods in terms of block Boundary Value Methods, although they can be recast as Runge-Kutta methods, if preferred.
Thursday, January 13. 2022
FAZEL HADADIFARD, SATBIR MALHI, AND ZHENGYI XIAO
Abstract. In this paper, a class of finite difference numerical techniques is presented to solve the second-order linear inhomogeneous damped wave equation. The consistency, stability, and convergences of these numerical schemes are discussed. The results obtained are compared to the exact solution, ordinary explicit, implicit finite difference methods, and the fourth-order compact method (FOCM). The general idea of these methods is developed by using C0-semigroups operator theory. We also showed that the stability region for the explicit finite difference scheme depends on the damping coefficient.
c 2022 European Society of Computational Methods in Sciences and Engineering
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Monday, March 8. 2021
Beny Neta ∗
Naval Postgraduate School
Department of Applied Mathematics
Monterey, CA 93943
e-mail: bneta@nps.edu, Tel: 1-831-656-2235, Fax: 1-831-656-2355
Received 01/02/2020, Revised 10/12/2020, Accepted 02/03/2021
Abstract: A new trigonometrically-fitted method of order 12 is developed and compared to an existing P-stable method of the same order. Our method fit exactly the sine and cosines functions sin(rωx), cos(rωx), r = 1,2 and monomials up to degree 9. Our method is tested on several linear and nonlinear examples to demonstrate its accuracy and sensitivity to perturbation in the known frequency. We also show where it is preferable to use the trigonometrically-fitted method. Our method shows its efficiency in solving a nonlinear equation both in terms of global accuracy and CPU run time.
c 2021 European Society of Computational Methods in Sciences and Engineering
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Monday, February 1. 2021
S.A. Khuri1, I. Louhichi, A. Sayfy
Department of Mathematics and Statistics, American University of Sharjah - UAE
Received 14 January, 2019; accepted in revised form 26 January, 2021
Abstract: In this article, we study a fixed point iteration scheme that involves the Green’s function for the numerical solution of a larger class of fourth order boundary value problems (BVPs). The scheme enjoys important features such as its high accuracy, reliability, and fast convergence. We analyze and prove convergence of the iterative procedure using the contraction principle. Several numerical examples of fourth order boundary value problems are used to test the proposed method. The numerical results clarify very good agreement with the exact solution and superiority of this approach when compared with other numerical results that exist in the literature. Furthermore, the method requires less CPU time than other techniques.
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Saturday, December 12. 2020
Research of Integrated Passive Methods of Heat Dissipation Intensification to Improve the Efficiency of Gas-Dynamic Temperature Stratification
Е.V. Tsvetova, V.N. Kovalnogov, R.V. Fedorov
Department of Heat and Power Engineering, Ulyanovsk State Technical University, Severny Venets str. 32, Ulyanovsk, 432027, Russia
© European Society of Computational Methods in Sciences and Engineering
Keywords: numerical simulation, gas-dynamic temperature stratification, dispersion flow, heat transfer
coefficient, developed surfaces
Mathematics Subject Classification: 65R20 Numerical methods for integral equations
Received: 04/09/2020, Revised: 20/10/2020, Accepted: 05/12/2020
Abstract: A possibility was analyzed to increase the efficiency of the gas-dynamic temperature stratification process through the use of complex passive methods of heat transfer intensification: developed surfaces - longitudinal fins on the heat transfer surface in the subsonic flow path; additives to the gas flow of the disperse phase with a twisting flow.
PACS: 02.60.Cb Numerical simulation; solution of equations
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Saturday, December 12. 2020
Numerical Simulation and Investigation of the Influence of the Characteristics of the Building Envelope on Energy Efficiency and Energy Saving Potential
Yu.E. Chamchiyan, V.N. Kovalnogov, R.V. Fedorov
Department of Heat and Power Engineering, Ulyanovsk State Technical University, Severny Venets str. 32, Ulyanovsk, 432027, Russia
Received: 03/09/2020, Revised: 15/10/2020, Accepted: 08/12/2020
Abstract: The heat engineering characteristics of external enclosing structures and their influence on the microclimate of the building are analyzed. Potential spheres in the field of providing microclimate for energy saving are considered. The potential for savings in the implementation of automated regulation of microclimate systems is presented.
© European Society of Computational Methods in Sciences and Engineering
Keywords: numerical simulation, numerical methods, energy efficiency, energy saving, microclimate.
Mathematics Subject Classification: 65R20 Numerical methods for integral equations
PACS: 02.60.Cb Numerical simulation; solution of equations
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Saturday, December 12. 2020
Influence of the Air Swirling Speed on the Processes of Joint Combustion of the Fuel-Air Mixture in the Active Combustion Zone of Power Plants
R.V. Fedorov, A.V. Chukalin, V.N. Kovalnogov, U.J. Mizher, M.M. Zamaleev
Department of Heat and Power Engineering,
Ulyanovsk State Technical University, Severny Venets str. 32, Ulyanovsk, 432027, Russia
Received: 01/09/2020, Revised: 15/10/2020, Accepted: 07/12/2020
Abstract: The search for new solutions in the field of energy, preventing negative impact on the environment, is one of the priority tasks for modern society. It is natural gas that has a stable position in the demand of the UES of Russia for fossil fuel. One of the promising areas is the use of biogas as a source of thermal energy for power plants. It has been established that the main difference between biogas and natural gas, which affects the density, calorific value, and speed of flame propagation, is caused by the presence of more than 30% carbon dioxide in its composition. Combined combustion of natural gas and biogas, subject to good mixing due to the tangentially swirling apparatus of the fuel-air mixture, can increase the stability of biogas combustion, reduce the maximum adiabatic temperature in the zone of active combustion of power boilers of TPPs, which in turn will lead to a decrease in the content of NOx, CO2 in products combustion. For the combustion of biogas at the power plants in operation at TPPs of the UES of Russia, it is important to carry out, on the basis of the theoretical data obtained on the effective combustion modes of fuels, the technical re-equipment of the burners. The paper presents a turbulence model k – ε RNG, which makes it possible to simulate the combustion of natural gas and biogas during tangential swirling of the air-fuel mixture. The qualitative characteristics of biogas, the quantitative content of NOx, CO2 in the combustion products, the temperature distribution in the zone of active combustion of fuel combinations - natural gas, biogas, natural gas / biogas is presented.
© European Society of Computational Methods in Sciences and Engineering
Keywords: Numerical simulation, modeling, biogas, co-combustion, efficiency, emission reduction
Mathematics Subject Classification: 65R20 Numerical methods for integral equations
PACS: 02.60.Cb Numerical simulation; solution of equations
Tuesday, December 8. 2020
Effectiveness of the Probabilistic Assessment to Analyse of the Tall Building Safety using FE Method
J. Kralik, J. Kralik, jr. and P. Rosko
Faculty of Civil Engineering, Slovak University of Technology in Bratislava, 810 05 Bratislava, Slovakia
and
Centre of Mechanics and Structural Dynamics 1010 Vienna University of Technology Vienna, Austria
Received 01/03/2020, Revised 21/07/2020, Accepted 30/10/2020
Abstract: This paper describes some experiences from the deterministic and probabilistic analysis of building structure reliability and safety. There are presented the methods and requirements of Eurocode EN 1990, standard ISO 2394 and JCSS. On the example of the probability analysis of the reliability of the tall buildings is demonstrated the affectivity of the probability design of structures using FE Method.
© European Society of Computational Methods in Sciences and Engineering
Keywords: Extreme environment effect, earthquake, nonlinearity, probability, sensitivity, RSM, ANSYS
Mathematics Subject Classification: 00A69, 49Mxx
Tuesday, December 8. 2020
Probabilistic Assessment to Analyze of Steel Hall Collapse due to Extreme Wind Impact
J. Kralik and J. Kralik, jr.
Department of Structural Mechanics,
Faculty of Civil Engineering,
Slovak University of Technology in Bratislava,
810 05 Bratislava, Slovakia
Received 28/02/2020, Revised 21/07/2020, Accepted 28/10/2020 Abstract: Engineering structures are designed to resist all expected loadings without failure. However, structural failures do happen occasionally, mainly due to inadequate design and construction, especially for extreme loads. The main aim of this contribution is to find out the maximum load carrying capacity of the steel frame. Account is taken of nonlinear material behavior and geometry of member, in combination of the stability analysis.
© European Society of Computational Methods in Sciences and Engineering
Keywords: Extreme wind, nonlinearity, probability, sensitivity, NPP, RSM, FEM, ANSYS
Mathematics Subject Classification: 00A69, 49Mxx
Tuesday, November 17. 2020
Numerical Analysis of the One-Dimensional Nonlinear Boundary Value Problem that Modeling an Electrostatic NEMS by Two-Sided Approximations Method
O. Konchakovska, M. Sidorov
Department of Applied Mathematics, Faculty of Information and Analytical Technologies and Managment,
Kharkiv National University of Radio Electronics,
61166, Kharkiv, Ukraine
Received 17 May, 2020; accepted in revised form 10 November, 2020
Abstract: The problem of numerical analysis of a nanoelectromechanical system, whose mathematical model is the first boundary value problem for a nonlinear one-dimensional elliptic equation, has been considered. An algorithm for obtaining two-sided approximations to a unique positive solution of the problem has been constructed using the method of successive approximations. The work of the proposed method is demonstrated by a series of computational experiments.
c⃝ 2020 European Society of Computational Methods in Sciences and Engineering
Keywords: two-sided approach method, Green’s functions method, strongly invariant cone
segment, heterotone operator, nanoelectromechanical system
Mathematics Subject Classification: 34B15; 34B18
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Monday, September 14. 2020
A New Conjugate Gradient Method with Descent Properties and its Application to Regression analysis
Ibrahim Mohammed Sulaiman1, Mustafa Mamat1*
1Faculty of Informatics and Computing, Universiti Sultan Zainal Abidin, 21300 Terengganu, Malaysia
corresponding author: *must@unisza.edu.my
sulaimanib@unisza.edu.my
Submitted 24/07/2019, Revised 13/01/2020, 2nd revised: 11/06/2020, accepted: 09/09/2020
Abstract: The area of unconstrained optimization has been enjoying vivid growth recently, with significant progress on numerical innovative techniques. The classical technique for obtaining the solution of this problem is the Conjugate Gradient (CG) scheme, due to its rapid convergence rate with low memory requirements. However, recent variations of CG methods are complicated and computationally expensive. This paper presents a new and efficient CG parameter with descent condition for solving optimization problems. The convergence result of this method is established under exact and inexact line search. The proposed method is applied to real-life problems in regression analysis. Numerical results have been reported to illustrate the efficiency and robustness of the proposed method.
© European Society of Computational Methods in Sciences and Engineering
Keywords: Optimization; exact line search; global convergence; conjugate gradient method;
Mathematics Subject Classification: 90C53; 65K05
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