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Dynamic magnetic hysteresis in a liquid suspension of acicular maghemite particles

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Particuology 2009年第6期7卷 451-458页

作者： Bronislav E.Kashevsky Sergey B.Kashevsky Igor v.Prokhorov a.v.luikov heat and mass transfer institute Belarus Academy of SciencesP.Brovka str.15Minsk 220072Belarus

This paper presents theoretical and experimental studies on the magnetodynamics and energy absorption in a dilute suspension of small ferromagnetic particles with magnetic hysteresis and mechanical mobility in an AC magnetic field. Experiments with 0.1% suspensions of acicular particles of gamma ferric oxide in solid and liquid matrices, subjected to a 430 Hz magnetic field with an intensity of up to 1200 Oe, revealed important role of particle mobility. The main qualitative and quantitative features of the phenomenon are in agreement with a model of joint magneto-mechanical dynamics of particles with a chain-of-spheres mode of incoherent magnetic reversal.

关键词： High-coercive magnetic particles Magnetic suspensions Dynamic magnetic hysteresis

Effect of the Coulomb and dielectric forces on the onset of Rayleigh-Bénard convection

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Acta Mechanica Sinica 2024年第6期40卷 64-77页

作者： Zhonglin Du Pedro A.vázquez Jian Wu School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China Heilongjiang Key Laboratory of Micro-and Nano-scale Fluid Flow and heat transfer Harbin150001China Departamento de Física Aplicada III ETSIIUniversidad de SevillaSevilla41092Spain

In this paper,the effect of Coulomb and dielectric forces on the onset of Rayleigh-Bénard convection(RBC)in a dielectric liquid layer contained between two parallel electrode plates has been numerically *** different operating conditions have been considered in electrohydrodynamic(EHD)conduction:ohmic and saturation,and variations in the physical properties of the dielectric fluid with *** electric equations and the state equations based on the Boussinesq approximation are integrated in the framework of OpenFOAM buoyantBoussinesqPimpleFoam *** results show that in the ohmic regime,the combined effect of Coulomb and dielectric forces promotes the onset of RBC flow,while in the saturation state,the inhibition of RBC flow by Coulomb force is more *** value of the critical Rayleigh number Ra decreases with increasing electric Reynolds number ReE in the ohmic regime,whereas in the saturation state,the critical Ra increases with increasing *** the saturation regime,the flow field always has a steady flow in the range of parameters ***,the onset of the RBC flow promoted by the dielectric force is more pronounced in the ohmic *** to the presence of the dielectric force,the flow field exhibits periodic oscillatory flow at low electric Reynolds numbers for the range of parameters considered.

关键词： EHD conduction Dielectric force Rayleigh-Bénard convection OpenFOAM

Power-law multi-wave model for COvID-19 propagation in countries with nonuniform population density

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Quantitative Biology 2022年第2期10卷 150-156页

作者： Pavel Grinchuk Sergey Fisenko a.v.luikov heat and mass transfer institute National Academy of Sciences of BelarusMinsk 220072Belarus

Background: The purpose of our study is to develop a quite precise mathematical model which describes epidemics spread in a country with non-uniform population density. This model gives explanation of quite long duration of the peak of a respiratory infection such as the coronavirus disease 2019 (COvID-19).Methods: The theory of kinetic equations and fractal analysis are used in our mathematical model. According to our model, COvID-19 spreading takes the form of several spatio-temporal waves developing almost independently and simultaneously in areas with different population density. The intensity of each wave is described by a power-law dependence. The parameters of the dependence are determined by real statistical data at the initial stage of the disease ***: The results of the model simulation were verified using statistical data for the Republic of Belarus. Based on the developed model, a forecast calculation was made at the end of May, 2020. It was shown that the epidemiological situation in the Republic of Belarus is well described by three waves, which spread respectively in large cities with the highest population density (the first wave), in medium-sized cities with a population of 50−200 thousands people (the second wave), in small towns and rural areas (the third wave). It was shown that a new wave inside a subpopulation with a lower density was born 20−25 days after the appearance of the previous wave. Comparison with actual data several months later showed that the accuracy of forecasting the total number of cases for a period of 3 months for total population in the proposed approach was approximately 3%.Conclusions: The high accuracy mathematical model is proposed. It describes the development of a respiratory epidemic in a country non-uniform population density without quarantine. The model is useful for predicting the development of possible epidemics in the future. An accurate forecast allows to correctly allocating available resources t

关键词： COvID-19 forecast model simultaneous waves population density

Audio-frequency heating of particulate magnetic systems

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China Particuology 2007年第1期5卷 84-92页

作者： B.E. Kashevsky I.v. Prokhorov S.B. Kashevsky A.v. luikov heat and mass transfer institute Belarus Academy of Sciences P. Brovka str. 15 Minsk 220072 Belarus

This paper presents theoretical and experimental studies on the magnetodynamics and energy dissipation in suspensions of small ferromagnetic particles with magnetic hysteresis and mechanical mobility in an AC magnetic field. Energy absorption by particles suspended in a solid, liquid or gas environment and subjected to high frequency magnetic fields is of great interest for cancer treatment by hyperthermia, chemical technology, biotechnology and smart materials science. Sub-micron needle-like γ-Fe2O3 particles dispersed in liquid were subjected in this study to a 430 Hz magnetic field with an intensity of up to 10^5 A/m. Dynamic magnetization loops were measured in parallel to the energy dissipated in the samples. Combined magnetomechanical dynamics of particle dispersions was simulated by using a chain-of-spheres model allowing for incoherent magnetic field reversal. In liquid dispersions, within the kilohertz frequency range, the mechanical mobility of particles does not interfere with their hysteretic magnetic reversal that makes heat release comparable to that observed with solids; for instance, in the present study using γ-Fe2O3 particles in liquid subjected to 10^4 Hz field exhibited heat release rates from 250 up to 600W oer 1 cm^3 of the dry oarticle content.

关键词： AC magnetic field Particulate materials Audio-frequency heating

Regulating^(*)COOH intermediate via amino alkylation engineering for exceptionally effective photocatalytic CO_(2) reduction

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Journal of Energy Chemistry 2024年第5期92卷 282-291页

作者： Chengcheng Chen Qiaoyu Zhang Fangting Liu Zhengguo Zhang Qiong Liu Xiaoming Fang Key Laboratory of Enhanced heat transfer and Energy Conservation The Ministry of EducationSchool of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510640GuangdongChina Guangdong Provincial Key Laboratory of Chemical Measurement and Emergency Test Technology(China) Institute of AnalysisGuangdong Academy of Sciences(China National Analytical CenterGuangzhou)Guangzhou 510070GuangdongChina Guangdong Engineering Technology Research Center of Efficient heat Storage and Application South China University of TechnologyGuangzhou 510640GuangdongChina Guangdong Provincial Key Laboratory of Fuel Cell Technology South China University of TechnologyGuangzhou 510640GuangdongChina

Photocatalytic reduction of CO_(2) into fuel represents a promising approach for achieving carbon neutrality,while realizing high selectivity in this process is challenging due to uncontrollable reaction intermediate and retarded desorption of target *** the interface microenvironment of catalysts has been proposed as a strategy to exert a significant influence on reaction outcomes,yet it remains a significant *** this study,amino alkylation was successfully integrated into the melem unit of polymeric carbon nitrides(PCN),which could efficiently drive the photocatalytic CO_(2) *** characterization and theoretical calculations revealed that the introduction of amino alkylation lowers the energy barrier for CO_(2) reduction into^(*)COOH intermediate,transforming the adsorption of^(*)COOH intermediate from the endothermic to an exothermic ***,the as-prepared materials demonstrated outstanding performance in photocatalytic CO_(2) reduction,yielding CO_(2)at a rate of 152.8μmol h^(-1) with a high selectivity of 95.4%and a quantum efficiency of 6.6%.

关键词： Polymeric carbonnitride Regulate intermediate Photocatalytic CO_(2)reduction Amino alkylation ^(*)COOH adsorption

Study of cobalt ferrite nanosuspensions for low-frequency ferromagnetic hyperthermia

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Particuology 2008年第5期6卷 322-333页

作者： Bronislav E.Kashevsky vladimir E.Agabekov Sergei B.Kashevsky Katsiaryna A.Kekalo Elena Yu.Manina Igor v.Prokhorov vladimir S.Ulashchik a.v.luikov heat and mass transfer institute Belarus Academy of Sciences P.Brovka Str.15Minsk 220072Belarus institute of Chemistry of New Materials Belarus Academy of SciencesSkoriny Str.36Minsk 220141Belarus institute of Physiology Belarus Academy of SciencesAkademicheskaiy Str.28Minsk 220072Belarus

High-coercive cobalt ferrite nanoparticles were synthesized and studied for magnetic hyperthermia by direct injection of their suspension into a tumor and application of a strong audio-frequency magnetic field for heating. Physical （dynamic magnetic hysteresis and heat generation in both liquid and solid dispersions）, biological （toxicity and penetration of particles in therapeutic quantities into mouse tumor tissue） as well as other properties of the particles were studied. A model was developed to describe the magnetodynamics in suspensions of magnetic nanoclusters with an account for both Brownian and regular rotations, to provide understanding of observed phenomena. The experimental and theoretical techniques developed have formed a basis for controllable synthesis of the magnetic nanoparticles for low-frequency heat generation in medical and other applications.

关键词： Cobalt ferrite nanoparticles Magnetic suspensions Dynamic magnetic hysteresis Medical hyperthermia

Channel Flows in Plate heat Exchangers with the Aid of Particle Tracking velocimetry

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Open Journal of Fluid Dynamics 2024年第3期14卷 163-183页

作者： Felipe José dos Santos Leonel Edward Beckedorff Kleber vieira de Paiva Jorge Luiz Goes Oliveira PETROBRASPetrleo Brasileiro S.A. Rio de Janeiro Brazil institute of Fluid Mechanics and heat transfer Technische Universitt Wien Vienna Austria Department of Mobility Engineering Federal University of Santa Catarina Joinville Brazil

Channel flows of Plate heat Exchangers (PHEs) were assessed by experiments with three different chevron angle arrangements in turbulent regime. Two chevron angles were selected to assess low and high pressure drop channels, besides a third mixed configuration as to achieve in-between results regarding hydraulic performance. Friction factor correlations were provided with the channel Reynolds number ranging from 1175 to 8325. Two-dimensional (2D) mean velocity field was obtained by Particle Tracking velocimetry (PTv) with Reynolds number equal to 3450. To the best of our knowledge, this is the first experimental study that quantified the complete 2D velocity field of a typical PHE channel. This value allowed comparison with literature results of Plate and Shell heat Exchanger (PSHE) channels with the same Reynolds number. PSHE mean velocity field is highly heterogeneous as compared to the one obtained for PHE channels. Peak velocity magnitude in the PSHE center is 50% higher than its bulk velocity, whereas this value is only 15% higher in the PHE center. Pressure drop in PHE mixed channels cannot be approximated by averaging chevron angles: furrow flow prevailed in the specified conditions. The axial velocity is asymmetric regarding the vertical plane. Smooth streamlines prevail in the channel inlet. Recirculation zones at the channel exit affect pipe flow in the manifold outlet with swirling flow structures. The necessary length to obtain fully developed pipe flow at the channel outlet was estimated. Significant velocity components occur in the distribution areas and can limit the heat exchanger performance. The results reported herein are essential to understand how the PHE channel geometry affects the velocity field and, therefore, local heat transfer and dissipation processes.

关键词： PHE PTv PSHE Friction Factor Chevron

Harvesting Energy via Water Movement and Surface Ionics in Microfibrous Ceramic Wools

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Energy & Environmental Materials 2024年第6期7卷 332-341页

作者： Manpreet Kaur Avinash Alagumalai Omid Mahian Sameh M.Osman Tadaaki Nagao Zhonglin Wang Research Center for Materials Nanoarchitectonics(WPI-MANA) National Institute for Materials Science(NIMS)1-1 NamikiTsukuba 305-0044IbarakiJapan Department of Chemical and Petroleum Engineering University of Calgary2500 University Dr.NWCalgaryAB T2N 1N4Canada Department of Mechanical Engineering GMR Institute of TechnologyRajamAndhra Pradesh 532127India Faculty of Mechanical Engineering and Mechanics Zhejiang Provincial Engineering Research Center for the Safety of Pressure Vessel and PipelineNingbo UniversityNingbo 315211China Department of Chemical Engineering Imperial College LondonLondon SW72AZUK Beijing institute of Nanoenergy and Nanosystems Chinese Academy of SciencesBeijing 100083China Chemistry Department College of ScienceKing Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia Department of Condensed Matter Physics Hokkaido UniversitySapporoHokkaido 060-0810Japan School of Materials Science and Engineering Georgia Institute of TechnologyAtlanta 30332GAUSA Laboratory on Convective heat and mass transfer Tomsk State UniversityTomsk 634045Russia

Due to the push for carbon neutrality in various human activities,the development of methods for producing electricity without relying on chemical reaction processes or heat sources has become highly ***,the challenge lies in achieving microwatt-scale outputs due to the inherent conductivity of the materials and diverting electric *** address this challenge,our research has concentrated on utilizing nonconductive mediums for water-based low-cost microfibrous ceramic wools in conjunction with a NaCl aqueous solution for power *** main source of electricity originates from the directed movement of water molecules and surface ions through densely packed microfibrous ceramic wools due to the effect of dynamic electric double *** occurrence bears resemblance to the natural water transpiration in plants,thereby presenting a fresh and straightforward approach for producing electricity in an ecofriendly *** generator module demonstrated in this study,measuring 12×6 cm^(2),exhibited a noteworthy open-circuit voltage of 0.35 v,coupled with a short-circuit current of 0.51 *** low-cost ceramic wools are suitable for ubiquitous,permanent energy sources and hold potential for use as self-powered sensors and systems,eliminating the requirement for external energy sources such as sunlight or heat.

关键词： ceramic microfibers energy harvesting power generation self-powered systems water evaporation

A rened analytical model for reconstruction problems in diuse reectance spectroscopy

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Journal of Innovative Optical Health Sciences 2024年第5期17卷 33-51页

作者： Ekaterina Sergeeva Daria Kurakina Ilya Turchin and Mikhail Kirillin A.v.gaponov-grekhov institute of applied physics of the russian academy of sciences ulyanov st.46 603950nizhny novgorodrussia

A rened analytical model of spatially resolved diffuse reectance with small source-detector separations(SDSs)for the in vivo skin studies is *** to the conventional model developed by Farrell et al.,it accounts for the limited acceptance angle of the *** rened model is validated in the wide range of optical parameters by Monte Carlo simulations of skin diffuse reectance at SDSs of units of *** of uniform dermis and two-layered epidermis-dermis structures are *** accuracy of the rened model compared to the conventional one is demonstrated in the separate,constraint-free reconstruction of absorption and reduced scattering spectra of uniform dermis from the Monte Carlo simulated *** the case of epidermis-dermis geometry,the recovered values of reduced scattering in dermis are overestimated and the recovered values of absorption are underestimated for both analytical ***,in the presence of a thin mismatched topical layer,only the effective attenuation coe±cient of the bottom layer can be accurately recovered using a diffusion theorybased analytical model while separate reconstruction of absorption and reduced scattering fails due to the inapplicability of the method of ***-ndings require implementation of more sophisticated models of light transfer in inhomogeneous media in the recovery algorithms.

关键词： Diffuse reffectance spectroscopy in vivo skin studies optical properties reconstruction diffuse approximation Monte Carlo simulations method of images