Computer Simulations of Dynamic Response of Ferrofluids on an Alternating Magnetic Field with High Amplitude

The response of ferrofluids to a high-amplitude AC magnetic field is important for several applications including magnetic hyperthermia and biodetection. In computer simulations of the dynamic susceptibility of a ferrofluid outside the linear response region, there are several problems associated with the fact that an increase in the frequency of the AC field leads to the appearance of additional computational errors, which can even lead to unphysical results. In this article, we study the dependence of the computational error arising in the computer simulation of the dynamic susceptibility on the input parameters of the numerical algorithm: the length of the time step, the total number of computer simulation periods, and averaging period. Computer simulation is carried out using the Langevin dynamics method and takes Brownian rotational relaxation of magnetic particles and interparticle interactions into account. The reference theory [Yoshida T.; Enpuku K. Jap. J. Ap. Phys. 2009] is used to estimate computational error. As a result, we give practical recommendations for choosing the optimal input parameters of the numerical algorithm, which make it possible to obtain reliable results of the dynamic susceptibility of a ferrofluid in a high-amplitude AC field in a wide frequency range. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by the Ministry of Science and Higher Education of the Russian Federation (Ural Mathematical Center project No. 075-02-2021-1387)

The movement of capital in the field of information services

Modern economic development of the world community to make sure that all the changes and transformations can be resolved under the influence of the institutional environment. Investigation of the process of connectedness, which leads to the transformation of the capital in the form of a virtual existence and defines the main factors influencing its formation. A list of these factors is changing rapidly, but the driving factor is the uncertainty of the market situation, which could inflict the threat risk of loss of capital. In this regard, the base part of a flexible enterprise management tool on the market of information services can be a mechanism of risk assessment and study of performance criteria investment decisions to create the conditions to access information through enhanced Internet - space. Development and use of risk assessment techniques in conditions of transparency prevents deformation of the economic space, and to stimulate the accumulation of virtual and real capital

Non-convex polygons clustering algorithm

A clustering algorithm is proposed, to be used as a preliminary step in motion planning. It is tightly coupled to the applied problem statement, i.e. uses parameters meaningful only with respect to it. Use of geometrical properties for polygons clustering allows for a better calculation time as opposed to general-purpose algorithms. A special form of map optimized for quick motion planning is constructed as a result

Vessel Wall Models for Simulation of Atherosclerotic Vascular Networks

There are two mathematical models of elastic walls of healthy and atherosclerotic blood vessels developed and studied. The models are included in a numerical model of global blood circulation via recovery of the vessel wall state equation. The joint model allows us to study the impact of arteries atherosclerotic disease of a set of arteries on regional haemodynamics

Multiscale models of blood flow in the compliant aortic bifurcation

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Patient-specific blood flow modelling for medical applications

Patient-specific blood flow modelling helps to predict surgical operation results, gives new noninvasive diagnostic methods, allows to investigate physiology of vascular pathologies. We develop numerical models for such medical applications. 1D blood flow model describes hemodynamics in the whole vascular network. 3D model of fluid flow can be embedded in the 1D model to zoom the domain of interest or to take into account pathologies or implants. We personalize the model, using patient-specific vascular structure and parameters. For some vascular regions extraction of patient-specific geometry can be automatic within developed technology. We verified the 1D model of blood flow. Two examples of real medical applications are presented. The method for FFR estimation is proposed. Also we used the 1D model for prediction of surgical occlusion treatment

Microstructure of Bidisperse Ferrofluids in a Monolayer

In the present study we briefly analyze the cluster structures observed in the model bidisperse ferrofluid constrained in quasi-2D (q2D) layer in the absence of an externally applied magnetic field. We use a combination of a DFT approach and molecular dynamic simulation to quantitatively describe various chain and ring structures and their equilibrium area fractions. We also show that to reach a good agreement between simulation data and theoretical predictions in q2D geometry in theory one needs to allow for more possible chain configurations than in the bulk system. We provide preliminary explanations why the microstructure of bulk bidisperse ferrofluids differs noticeably from the one in q2D layer.Peer reviewe