Article
Mathematics, Applied
Kazunori Matsui
Summary: A boundary value problem for the stationary Stokes problem and the corresponding pressure-Poisson equation is considered, with a new formulation proposed for the pressure-Poisson problem. Error estimates between solutions to the Stokes problem and the pressure-Poisson problem are established in terms of an additional boundary condition. Traction and pressure boundary conditions introduced by C. Conca et al (1994) are used for the Stokes problem.
DISCRETE AND CONTINUOUS DYNAMICAL SYSTEMS-SERIES S
(2021)
Article
Computer Science, Interdisciplinary Applications
Maryam Samavaki, Yusuf Oluwatoki Yusuf, Arash Zarrin Nia, Santtu Soderholm, Joonas Lahtinen, Fernando Galaz Prieto, Sampsa Pursiainen
Summary: This study presents a dynamic modeling approach for reconstructing the electrical conductivity atlas of the brain and simulating the effects of cerebral arterial circulation. By coupling the pressure-Poisson equation with Fick's law of diffusion, and using boundary conditions based on the Hagen-Poisseuille model, the researchers were able to estimate the blood pressure in cerebral arteries segmented from MRI data.
COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE
(2023)
Article
Cardiac & Cardiovascular Systems
Chiemi Yamazaki, Ryosuke Higuchi, Mike Saji, Itaru Takamisawa, Mamoru Nanasato, Shinichiro Doi, Shinya Okazaki, Harutoshi Tamura, Kei Sato, Hiroaki Yokoyama, Takayuki Onishi, Tetsuya Tobaru, Atsushi Shimizu, Shuichiro Takanashi, Mitsuaki Isobe
Summary: This study evaluated the discrepancy between invasive and ECHO-mPG after transcatheter aortic valve implantation (TAVI) and found that ECHO-mPG could overestimate the true pressure gradient.
INTERNATIONAL JOURNAL OF CARDIOLOGY
(2023)
Article
Physics, Multidisciplinary
Hua-Shu Dou
Summary: For laminar flow in a channel, the Navier-Stokes equation has a non-zero source term and solution; for transitional flow, the velocity profile becomes distorted with inflection points where backward difference is zero; due to singularity, there are no smooth or physically reasonable solutions of the Navier-Stokes equation for transitional flow and turbulence in the global domain.
Article
Engineering, Multidisciplinary
Rodolfo Ruben Rosales, Benjamin Seibold, David Shirokoff, Dong Zhou
Summary: This paper investigates the feasibility of obtaining high-order methods for the incompressible Navier-Stokes equations (NSE) using the Pressure Poisson equation (PPE) and electric boundary conditions (EBC). By using implicit-explicit (IMEX) time-stepping and mixed finite element methods, at least third order accuracy in space and time can be achieved.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Mathematics, Applied
Sang Truong Ha, Hyoung Gwon Choi
Summary: In this study, we propose a new semi-monolithic method for the simulation of fluid-structure interaction (FSI) problems. The method couples the pressure variables of the fluid domain with the displacement variables of the solid domain in a monolithic manner. Experimental results confirm that the proposed method can simulate FSI problems with strong added-mass effect and large deformation effectively. Compared to existing monolithic methods, the proposed method is faster and easier to precondition.
COMPUTERS & MATHEMATICS WITH APPLICATIONS
(2023)
Review
Peripheral Vascular Disease
John S. Floras
Summary: Research on muscle sympathetic nerve activity has shown that it increases with age, sleep fragmentation, and obstructive sleep apnea, with differences in patterns between men and women. While sympathetic nerve activity burst incidence is linked to hypertension, women's sympathetic nerve traffic can increase significantly without causing high blood pressure. Therefore, increased sympathetic nerve activity may be a contributing factor to hypertension, but is not always sufficient to cause hypertension.
Article
Cardiac & Cardiovascular Systems
Eigir Einarsen, Dana Cramariuc, Edda Bahlmann, Helga Midtbo, John B. Chambers, Eva Gerdts
Summary: The study found that in asymptomatic nonsevere aortic valve stenosis and low-gradient severe AS, a higher AT/ET ratio is associated with increased cardiovascular morbidity and mortality.
CIRCULATION-CARDIOVASCULAR IMAGING
(2021)
Article
Health Care Sciences & Services
Chen Chi, Yi Lu, Yiwu Zhou, Jiaxin Li, Yawei Xu, Yi Zhang
Summary: This study investigated the factors influencing the accuracy of noninvasive central blood pressure (cSBP) measurement. The results showed that noninvasive cSBP measurements are comparable to invasive measurements, although they may slightly underestimate true cSBP. The type of BP measurement device used may affect the accuracy of measurement, while the type of calibration method implemented does not have a significant influence.
JOURNAL OF PERSONALIZED MEDICINE
(2022)
Article
Engineering, Biomedical
Pang Wu, Zhongrui Bai, Lirui Xu, Peng Wang, Xianxiang Chen, Lidong Du, Xiaoran Li, Zhan Zhao, Zhen Fang
Summary: The volume-clamp method (VCM) is a commonly used non-invasive continuous blood pressure (BP) monitoring technique. We propose two new methods, namely the proportional value method (PVM) and the uninterrupted V0 tracking method (UVTM), to address the challenges in determining the volume setpoint (V0) and resetting it during the closed-loop phase. PVM determines V0 by analyzing the shape index of the plethysmographic signal, while UVTM tracks changes in V0 without interrupting BP measurement. Experimental results demonstrate the accuracy and reliability of PVM and UVTM, highlighting their potential for integration into VCM-based BP monitoring devices.
BIOMEDICAL SIGNAL PROCESSING AND CONTROL
(2023)
Article
Medicine, Research & Experimental
Mengyao Yu, Catherine Tcheandjieu, Adrien Georges, Ke Xiao, Helio Tejeda, Christian Dina, Thierry Le Tourneau, Madalina Fiterau, Renae Judy, Noah L. Tsao, Dulguun Amgalan, Chad J. Munger, Jesse M. Engreitz, Scott M. Damrauer, Nabila Bouatia-Naji, James R. Priest
Summary: Genetic and clinical studies of mitral valve annular diameter revealed genetic determinants of mitral valve biology and associated clinical correlations. Computationally estimated phenotypes derived from medical imaging play an important role in genetic discovery and clinical risk prediction.
Article
Engineering, Civil
Xueying Yu, Yanlin Shao, David R. Fuhrman, Yunxing Zhang
Summary: A novel two-dimensional numerical wave tank based on the two-phase Navier-Stokes equations is presented in this paper. The GHPC method, originally proposed for the constant-coefficient Poisson equation, is demonstrated to be applicable for two-phase flow problems by introducing a pressure-correction method. The accuracy and convergence rate of the numerical model are validated through wave generation and propagation, as well as comparisons with benchmark results for wave-structure-interaction problems.
COASTAL ENGINEERING
(2023)
Article
Engineering, Biomedical
A. Cavallo, E. Gasparotti, P. Losi, I. Foffa, T. Al Kayal, E. Vignali, S. Celi, G. Soldani
Summary: The study introduces a novel polyurethane valve with promising capabilities in terms of valve crimping, durability, and fluid dynamic performance. It offers advantages such as low cost production and the ability to tailor the device based on patient imaging data. The selected biomaterial also shows potential for a device that may not require permanent anticoagulation and is less likely to experience calcification.
JOURNAL OF THE MECHANICAL BEHAVIOR OF BIOMEDICAL MATERIALS
(2021)
Article
Mathematics, Applied
Jin Li, Zhilin Li, Kejia Pan
Summary: In this study, new high order compact finite difference schemes are developed to accurately approximate the derivatives of the solutions to some elliptic partial differential equations (PDEs). The convergence analysis shows that the accuracy of the computed derivatives is the same as that of the solution. The developed schemes take into account the partial differential equations, including the source term and/or the boundary conditions, and have important applications in solving incompressible Stokes equations with periodic boundary conditions.
APPLIED MATHEMATICS AND COMPUTATION
(2023)
Article
Medicine, Research & Experimental
Masayo Koide, Osama F. Harraz, Fabrice Dabertrand, Thomas A. Longden, Hannah R. Ferris, George C. Wellman, David C. Hill-Eubanks, Adam S. Greenstein, Mark T. Nelson
Summary: Chronic hypertension disrupts brain microcirculation by reducing the activity of the capillary endothelial cell inward-rectifier potassium channel Kir2.1. Amlodipine, a calcium channel blocker, but not losartan, an angiotensin II type 1 receptor blocker, can prevent hypertension-related damage to functional hyperemia. The losartan-induced aldosterone breakthrough may lead to elevated plasma aldosterone levels and contribute to the decline in functional hyperemia.
JOURNAL OF CLINICAL INVESTIGATION
(2021)
Article
Mathematics, Applied
Michal Bathory, Miroslav Bulicek, Josef Malek
Summary: In this study, we prove the existence of a weak solution for a system governing an unsteady flow of a viscoelastic fluid in three dimensions, for arbitrarily large time interval and data. By properly choosing constitutive relations for the Helmholtz free energy and for the energy dissipation, we are able to show that the tensor B enjoys the same regularity as the velocity v in the classical three-dimensional Navier-Stokes equations. Furthermore, using a suitable approximation scheme, we demonstrate that B remains positive definite if the initial datum was a positive definite matrix.
ADVANCES IN NONLINEAR ANALYSIS
(2021)
Article
Mathematics, Applied
Anna Abbatiello, Miroslav Bulicek, Tomas Los, Josef Malek, Ondrej Soucek
Summary: The study focused on investigating mathematical properties of the system of nonlinear partial differential equations that describe evolutionary processes in water-saturated granular materials. It was found that the unconsolidated solid matrix behaves as an ideal plastic material before activation and then flows as a Newtonian or a generalized Newtonian fluid. The plastic yield stress is non-constant and depends on the difference between lithostatic pressure and pressure of the fluid in pore space, with research conducted on unsteady three-dimensional flows subject to stick-slip boundary conditions in an impermeable container.
ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK
(2021)
Article
Engineering, Multidisciplinary
K. Tuma, M. Rezaee-Hajidehi, J. Hron, P. E. Farrell, S. Stupkiewicz
Summary: This study investigates large-scale 3D martensitic microstructure evolution problems using a finite-element discretization of a finite-strain phase-field model. The model incorporates various crystallography of transformation and elastic anisotropy of the phases, and demonstrates robustness and good parallel scaling performance in a 3D simulation of microstructure evolution during nano-indentation. The finite-element discretization relies on the PETSc solver library and efficiently solves the large systems of linear equations arising from the model.
COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING
(2021)
Article
Neurosciences
Emily R. Nordahl, Susheil Uthamaraj, Kendall D. Dennis, Alena Sejkorova, Ales Hejcl, Jaroslav Hron, Helena Svihlova, Kent D. Carlson, Yildirim Bora Suzen, Dan Dragomir-Daescu
Summary: Computational fluid dynamics has been used to study hemodynamic properties related to cerebral aneurysm rupture. This retrospective study analyzed hemodynamic and morphological changes in four patient-specific aneurysms, finding that growth is associated with low wall shear stress and high velocity gradients. A new finding was that an increase in kinetic energy seemed correlated to the change in aneurysm volume.
Article
Mechanics
O. Outrata, M. Pavelka, J. Hron, M. La Mantia, J. I. Polanco, G. Krstulovic
Summary: The study examines the use of particles to capture the dynamics of isolated vortex rings in a quiescent fluid through numerical simulations. Lagrangian pseudovorticity field can be used to estimate the propagation velocity and growth of isolated vortex rings, but reconstruction of corresponding vorticity fields remains challenging. Particles with high inertia may bias the pseudovorticity fields, impacting the estimation of vortex ring properties.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Miroslav Bulicek, Erika Maringova, Josef Malek
Summary: The study investigates systems of nonlinear partial differential equations of parabolic type by introducing an additional implicit equation to relate the flux function to the spatial gradient of the unknown. By formulating four conditions concerning the form of the implicit equation, it is shown that these conditions describe a maximal monotone p-coercive graph. The study establishes the global-in-time and large-data existence of a weak solution and its uniqueness through adopting and generalizing Minty's method of monotone mappings.
MATHEMATICAL MODELS & METHODS IN APPLIED SCIENCES
(2021)
Article
Engineering, Multidisciplinary
R. Chabiniok, J. Hron, A. Jarolimova, J. Malek, K. R. Rajagopal, K. Rajagopal, H. Svihlova, K. Tuma
Summary: This study aims to understand the flow characteristics of three-dimensional incompressible Navier-Stokes fluid in tubes with a sinusoidal extension. The research is significant for its implications on blood flow through the aortic root, and reveals variations in flow attributes under different slip conditions.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2022)
Article
Mathematics, Applied
Josef Malek, Ondrej Soucek
Summary: Within the theory of interacting continua, a model for a heat conducting mixture of two interacting fluids is developed. The model describes the densities and velocities for each fluid, as well as the temperature field for the mixture as a whole. The response of the material is determined using a general thermodynamic framework that considers the energy storage and entropy production.
ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK
(2022)
Article
Mathematics, Applied
Miroslav Bulicek, Tomas Los, Yong Lu, Josef Malek
Summary: This article discusses the use of higher-order viscoelastic rate-type fluid models to describe the behavior of materials with complex microstructures. The Burgers model, which is a second-order viscoelastic rate-type fluid model, is introduced as a standard model that can be viewed as a mixture of two first-order Oldroyd-B models. The article focuses on studying a generalization of the Burgers model that combines two Giesekus viscoelastic models with different relaxation mechanisms. The existence of weak solutions to this generalized model, subject to no-slip boundary conditions, is proven in two spatial dimensions. A complete proof of global-in-time existence of weak solutions to the Giesekus model in two spatial dimensions is also provided as a specific case.
Article
Mathematics, Applied
Miroslav Bulicek, Josef Malek, Casey Rodriguez
Summary: This paper studies the partial differential equations governing the two-dimensional flows of a robust class of viscoelastic rate-type fluids with stress diffusion. The incompressible Navier-Stokes equations are generalized by introducing an additional term in the constitutive equation for the Cauchy stress expressed in terms of a positive definite tensor B. The evolution of tensor B follows a diffusive variant of a combination of Oldroyd-B and Giesekus models. The study proves the existence of a unique globally defined weak solution for arbitrary initial data and appropriate forcing in spatially periodic problems, and more regular initial data and forcing result in a solution with B positive definite everywhere.
JOURNAL OF MATHEMATICAL FLUID MECHANICS
(2022)
Article
Mathematics, Applied
Miroslav Bulicek, Josef Malek, Vit Prusa, Endre Suli
Summary: This paper proves the existence of large-data global-in-time weak solutions to an evolutionary PDE system describing flows of incompressible heat-conducting viscoelastic rate-type fluids, subject to specific boundary conditions. The thermodynamic foundations are developed and used to establish critical structural relations and to motivate the definition of weak solutions. The model, with a purely spherical extra stress tensor, presents challenges that require innovative mathematical ideas to address the complex structure of the associated internal energy and entropy and energy fluxes.
SIAM JOURNAL ON MATHEMATICAL ANALYSIS
(2021)
Article
Engineering, Multidisciplinary
R. Chabiniok, J. Hron, A. Jarolimova, J. Malek, K. R. Rajagopal, K. Rajagopal, H. Svihlova, K. Tuma
Summary: The study focuses on flows of incompressible Navier-Stokes fluid in a tubular domain with Navier's slip boundary condition on an impermeable wall. By implementing the Nitsche method, the study successfully demonstrates the incorporation of impermeability condition on the wall, and highlights the influence of numerical implementation on computational results. Various quantities of interest such as dissipation, wall shear stress, vorticity, and pressure drop are identified and their computational approximation is documented. The study aims to develop a robust computational tool suitable for real complex geometries relevant to engineering and medicine, based on computations using a known analytical solution in the context of flows in large arteries.
APPLICATIONS IN ENGINEERING SCIENCE
(2021)
Article
Engineering, Multidisciplinary
Tohya Kanahama, Motohiro Sato
Summary: This study theoretically explains the effect of initial deflection and initial slope on self-buckling characteristics of heavy columns and proposes a formula characterizing the self-buckling problem. The results show that the greatest height is proportional to the 2/3 power of radius, and the formula can potentially predict the height of tree-like natural structures.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
Article
Engineering, Multidisciplinary
Aps Selvadurai, Alexander P. Suvorov
Summary: This paper examines the torsion of a solid cylinder made of a fluid-saturated porous medium with a hyperelastic porous skeleton. It analyzes the mechanics of the twisted cylinder in both short-term and long-term behaviors, using numerical solutions and the ABAQUSTM finite element code.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
Article
Engineering, Multidisciplinary
S. Kanaun
Summary: This study focuses on spherical radially transverse isotropic heterogeneous inclusions in homogeneous isotropic conductive host media. The volume integral equation for the field in the medium with an isolated inclusion subjected to a constant external field is solved using Mellin-transform technique. The method allows revealing tensor structure of the solution with precision to one scalar function of radial coordinate. The study also investigates the influence of neutral inclusions and conductivity coefficients on the effective conductivity of the composite material.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
Article
Engineering, Multidisciplinary
Marinos Kattis, Vassilis Tsitsos, Vassilis Karatzaferis
Summary: The proposed model utilizes continuum mechanics to describe the mechanical behavior of a weakened interface between materials with microstructure, simulating the weakened interface using a surface elastic medium adhering on either side with bulk elastic continua. The model is able to investigate the effect of a weakened interface on stress concentration around inhomogeneities embedded in an unbounded matrix of Cosserat materials.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
Article
Engineering, Multidisciplinary
Shixiang Zhao, Yu. V. Petrov, Yuyi Zhang, G. A. Volkov, Zejian Xu, Fenglei Huang
Summary: This paper theoretically studies the thermal softening related to stress relaxation using the incubation time approach and examines the temperature-time correspondence. The developed relaxation model of plasticity (RP model) is analyzed and compared with other constitutive models and artificial neural networks. The advantages and disadvantages of different models are discussed, and the differences between the ANN model and other constitutive models are examined.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
Article
Engineering, Multidisciplinary
Ivan I. Argatov, Federico J. Sabina
Summary: This study models a seismic metabarrier as a cluster of single-degree-of-freedom resonator units and considers the scattering effects on pulsed Rayleigh waves caused by the vertical displacements of the resonators and the normal contact forces. The variation of the amplitude reduction factor due to the model parameters variation is studied in detail.
INTERNATIONAL JOURNAL OF ENGINEERING SCIENCE
(2024)
