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1

Effects of variable fluid properties and mixed convection on biomagnetic fluid flow and heat transfer over a stretching sheet in the presence of magnetic dipole

Murtaza M. G., Alam Jahangir, Tzirtzilakis E. E., Shamshuddin Md., Ferdows M.

Journal of Power Technologies

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2023

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Vol. 103, nr 4

193--208

EN

This investigations covers the numerical analysis of a steady biomagnetic fluid flow (BFD) that passed through a two dimensional stretching sheet under the influence of magnetic dipole. The effect of fluid variable viscosity and thermal conductivity are also taken into consideration as assumed to vary as linear function of temperature. Our model mathematically formulated for BFD namely blood which consist of principles of magnetohydrodynamic (MHD) and ferrohydrodynamic (FHD), where blood treated as an electrically conducting fluid as well as polarization. Using similarity transformations, the governing system of partial differential equations are transferred into system of ordinary differential equations (ODE). The resulting coupled non linear ODE is numerically solved by employing bvp4c function technique available in MATLAB software. The effects of pertinent parameters namely ferromagnetic interaction parameter, magnetic field parameter, mixed convection parameter, viscosity variation parameter, Prandtl number, thermal conductivity parameter etc are plotted and discussed adequately for velocity and temperature profile as well as skin friction coefficient and rate of heat transfer. The results revels that velocity profile decreases as enhanced values of ferromagnetic number whereas temperature profile increased. Also found that skin friction coefficient reduces and rate of heat transfer increases by increasing values of thermal conductivity parameter and viscosity variation parameter. For numerical validation a comparisons has been made for some specific values with previous investigators. We hope that the present analysis will present in bio-medical and bio-engineering sciences.

2

Effect of magnetic field on thermosolutal instability of rotating ferromagnetic fluid under varying gravity field

Pundir S. K., Nadian P. K., Pundir R.

International Journal of Applied Mechanics and Engineering

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2021

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Vol. 26, no. 1

201--214

EN

This paper deals with the theoretical investigation of the effect of a magnetic field, rotation and magnetization on a ferromagnetic fluid under varying gravity field. To find the exact solution for a ferromagnetic fluid layer contained between two free boundaries, we have used a linear stability analysis and normal mode analysis method. For the case of stationary convection, a stable solute gradient has a stabilizing effect, while rotation has a stabilizing effect if 0λ > and destabilizing effect if 0λ < . Further, the magnetic field is discovered to have both a stabilizing and destabilizing effect for both 0λ > and 0λ < . It is likewise discovered that magnetization has a stabilizing effect for both 0λ > and 0λ < in the absence of the stable solute gradient. Graphs have been plotted by giving numerical values of various parameters. In the absence of rotation, magnetic field and stable solute gradient, the principle of exchange of stabilities is found to hold true for certain conditions.

3

Electromagnetic system for improving the adhesion of wheels to rails

Osenin Yurij, Antoshkina Lidiya, Sosnov Igor, Shapran Evgeniy, Chesnokov Aleksei

Transport Problems

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2019

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T. 14, z. 1

59--67

EN

The article describes the design of a system used for the improvement of the adhesion of locomotive wheels to rails; the principle of which is based on the electromagnetic feeding of the contact area with the bulk material that has magnetic properties and high hardness (iron scale Fe3O4 and magnetite FeO×Fe2O3). The experimental results of laboratory and bench tests confirming the effectiveness of the proposed system compared with the existing devices using quartz sand to improve the adhesion of wheels to rails are presented. It is concluded that the use of an electromagnetic system for improving the particle supply to the wheel/rail interface is promising.

4

A way of neodymium-iron-boron magnets regeneration in surface-mounted PMSM used in electric vehicles

Łebkowski A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2017

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Vol. 65, nr 5

751--758

EN

The paper describes an efficient method of magnetization of permanent magnets, mounted on synchronous and BLDC motor rotors, which employs an air coil. A developed mathematical model of an electromagnetic circuit is presented, which was simulated in an ANSYS-MAXWELL environment. The performed simulations and experimental tests allowed optimization of the physical process of magnetization of permanent magnets mounted on an electrical machine rotor. The adopted method allowed achieving more favourable conditions of magnetization – less financial expenditure allowed to achieve the same results.

5

Magnetic properties of La0.7Sr0.3Mn0.85Nb0.15-xMgxO3 system

Troyanchuk I., Tereshko N., Bushinsky M., Fedotova V., Partyka J.

Przegląd Elektrotechniczny

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2016

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R. 92, nr 1

148--150

EN

Structural and magnetization measurements have been performed on the La0.7Sr0.3Mn0.85Nb5+ 0.15-xMg2+ xO3 system. With rise of the Mg2+ content the formal oxidation state manganese increases from +3 (x=0) up to +3.55 (x=0.15). The substitution of Nb5+ with Mg2+ leads to a gradual weakening of the ferromagnetic component while in the x=0.15 compound A-type antiferromagnetic short-range order is stabilized in spite of macroscopic R-3c symmetry. It is suggested that ferromagnetism is originated from superexchange interactions via oxygen.

PL

Przeprowadzono pomiary strukturalne i namagnesowania układu La0.7Sr0.3Mn0.85Nb5+ 0.15-xMg2+ xO3.Wraz ze wzrostem zawartości Mg2+formalny stopień utlenienia manganu wzrasta z +3 (x=0) aż do +3.55 (x=0.15). Zastąpienie Nb5+ poprzez Mg2+prowadzi do stopniowego osłabienia składnika ferromagnetycznego podczas gdy w związku x=0.15 typu A antyferromagnetyczny porządek krótkiego zasięgu jest ustabilizowany pomimo makroskopowej symetrii R-3c. Sugeruje się, że ferromagnetyzm pochodzi z nadwymiany za pomocą tlenu.

6

Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me=Cr, Fe) cobaltites

Troyanchuk I., Bushinsky M., Tereshko N., Fedotova V.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

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2015

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Nr 8

69--76

EN

Magnetic and magnetotransport properties of La0.5Sr0.5Co0.8Me0.2O3 (Me = Cr, Fe) stoichiometric cobaltites has been investigated in magnetic fields up to 14 T. It is shown that doping with Fe ions changes spontaneous magnetization only slightly herewith the Curie point significantly decreases. The chromium doping leads to dramatic decrease of magnetization and the Curie point and a strong increase in magnetoresistance at low temperature. The obtained results indicate that the magnetic interactions between Co and Fe are positive whereas those between Co and Cr ions are negative. Enhancement of magnetoresistance is attributed to the magnetic field induced transition from antiferromagnetic order to ferromagnetic one.

PL

Właściwości magnetyczne i magnetotransportowe stoichiometrycznych kobaltytów zbadano w polach magnetycznych do 14T. Ustalono, że domieszkowanie przez jony Fe zmienia namagnesowanie spontaniczne bardzo słabo w tym czasie jak punkt Curie obniża się znacząco. Domieszkowanie przez atomy chromu powoduje dramatyczne zmniejszenie namagnesowania i obniżenie punktu Curie i mocny wzrost magneto rezystancji w niskich temperaturach. Otrzymane rezultaty wskazują oddziaływanie magnetyczne pomiędzy Co i Fe jest pozytywne w tym czasie jak pomiędzy Co a Cr jest negatywne. Wzmocnienie magnetorezystancji przypisano do pola magnetycznego indukowanego przejściem z antyferromagnetycznego układu do ferromagnetycznego.

7

Reduced equations of magnetic hysteresis generated by quasi-elastic rotations of domains

Włodarski Z., Włodarska J.

Przegląd Elektrotechniczny

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2013

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R. 89, nr 9

274-277

EN

Magnetization processes are described by quasi-elastic rotations of domains. Thanks to this, basic curves of magnetic hysteresis are approximated by the reduced equation. Its extended form takes into account dependence of magnetization on frequency and temperature.

PL

Procesy magnesowania opisano poprzez quasi-sprężyste obroty domen. Dzięki temu podstawowe krzywe histerezy magnetycznej aproksymowano równaniem zredukowanym. Jego rozszerzona postać uwzględnia zależność namagnesowania od częstości i temperatury.

8

Triple- diffusive convection in a micropolar ferrofluid in the presence of rotation

Chand S.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 2

307--327

EN

This paper deals with the theoretical investigation of the triple-diffusive convection in a micropolar ferrofluid layer heated and soluted below subjected to a transverse uniform magnetic field in the presence of uniform vertical rotation. For a flat fluid layer contained between two free boundaries, an exact solution is obtained. A linear stability analysis theory and normal mode analysis method have been employed to study the onset convection. The influence of various parameters like rotation, solute gradients, and micropolar parameters (i.e., the coupling parameter, spin diffusion parameter and micropolar heat conduction parameter) on the onset of stationary convection has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large value of the buoyancy magnetization parameter M1 (ratio of the magnetic to gravitational forces). The principle of exchange of stabilities is found to hold true for the micropolar fluid heated from below in the absence of micropolar viscous effect, microinertia, solute gradient and rotation. The oscillatory modes are introduced due to the presence of the micropolar viscous effect, microinertia , solute gradient and rotation, which were non-existent in their absence. In this paper, an attempt is also made to obtain the sufficient conditions for the non-existence of overstability.

9

Elektronowy rezonans paramagnetyczny nanokompozytów (CoFeZr)x(Al2O3)(100-x) wytwarzanych rozpylaniem jonowym

Zhukowski P., Kołtunowicz T. N., Sidorenko J., Fedotova J.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 7a

324-326

PL

W pracy przedstawiono wyniki badań metodą elektronowego rezonansu paramagnetycznego (EPR) właściwości magnetycznych nanokompozytów (CoFeZr)x(Al2O3)(100-x) wytworzonych rozpylaniem jonowym w atmosferze argonu (próbki beztlenowe) oraz argonu i tlenu (próbki tlenowe). Ustalono, że w badanych materiałach występuje pojedyncza linia EPR, parametry której Hmin, Hmax, Hg oraz czynnik g wykazują silną zależność kątową. Jest ona związana ze zmianą czynnika rozmagnesowania z kątem ustawienia próbki w stosunku do wektora natężenia pola magnetycznego. Wektor namagnesowania w próbkach beztlenowych jest większy, niż w próbkach tlenowych co jest związane z udziałem części atomów metali w związkach z tlenem. Wygrzewanie termiczne do Ta = 450°C powoduje wzrost wektora namagnesowania i czynnika g.

EN

The paper presents results of studies with the method of electron paramagnetic resonance (EPR) on properties of magnetic nanocomposites (CoFeZr)x(Al2O3)(100-x) produced by ion sputtering in an argon atmosphere (anaerobic samples) or argon and oxygen atmosphere (aerobic samples). It was found that there is a single EPR line in the material studied which parameters like Hmin, Hmax, Hg and a factor g show a strong angular dependence. It is connected with the change of the demagnetization factor according to the sample set angle relative to the vector of magnetic field strength. Magnetization vector in the anaerobic samples is larger than in aerobic samples that is connected with the participation of the certain metal atoms in compounds with oxygen. Thermal annealing up to the value of Ta = 450°C causes increase of the magnetization vector and the factor g.

10

Effect of suspensed particles, magnetic field and rotation on thermal stability of ferromagnetic fluids

Aggarwal A. K., Verma A.

International Journal of Applied Mechanics and Engineering

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2012

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Vol. 17, no. 4

1109-1122

EN

The effect of suspended particles, magnetic field, magnetization and rotation on the thermal stability of a ferromagnetic fluid heated from below is considered. Using a linearized stability theory and normal mode analysis for a fluid layer between two free boundaries, an exact solution is obtained. A dispersion relation governing the effects of suspended particles, magnetic field, magnetization and rotation is derived. For the case of stationary convection, it is found that a suspended particle has a destabilizing effect whereas rotation and magnetization have a stabilizing effect on the system. The magnetic field has a stabilizing effect on the system under certain conditions. The effects of various parameters on the thermal stability are depicted graphically also and the results are in agreement with analytical solutions. The principle of exchange of stabilities is found to hold true for the ferromagnetic fluid heated from below in the absence of rotation and the magnetic field. The oscillatory modes are introduced due to the presence of rotation and the magnetic field which were non-existent in their absence.

11

Thermoconvective magnetized ferrofluid with internal angular momentum: a nonlinear stability analysis

Sunil, Mahajan A.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 2

557-580

EN

The generalized energy method is developed to study the nonlinear stability analysis for a magnetized ferrofluid layer heated from below with intrinsic rotation of the particles, in the stress-free boundary case. The mathematical emphasis is on how to control the nonlinear terms caused by the magnetic body force, inertia forces and body couple on a fluid element. By introducing a suitable generalized energy functional, we perform a nonlinear energy stability (conditional) analysis. It is found that the nonlinear critical stability magnetic thermal Rayleigh number does not coincide with that of the linear instability analysis, and thus indicates that the subcritical instabilities are possible. However, it is noted that, in the case of non-ferrofluid, the global nonlinear stability Rayleigh number is exactly the same as that for linear instability. For lower values of magnetic parameters, this coincidence is immediately lost. The effect of the magnetic parameter M3, coupling parameter N1, and spin diffusion parameter N3, on the subcritical instability region has also been analyzed. It is shown that with the increase of the magnetic parameter (M3) the subcritical instability region between the two theories decreases quickly while with the increase of N1 and N3, the subcritical instability region between the two theories increases. We also demonstrate coupling between the buoyancy and magnetic forces in the nonlinear energy stability analysis as well as in the linear instability analysis.

12

Analysis of magnetic disturbances of plane caused by permanent magnetization of it's ferromagnetic elements and analysis of magnetic field of chosen class of objects

Wołoszyn M.

Poznan University of Technology Academic Journals. Electrical Engineering

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2009

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No 60

35-43

13

Magnetisation and Electron Spin Resonance of the colossal magnetoresistive La0.67Ca0.33Mn1-x FexO3

Zając T., Folcik L., Chmist J., Kołodziejczyk A., Drulis H., Krop K., Gritzner G.

Materials Science Poland

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2006

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Vol. 24, No. 3

795--801

EN

We report magnetisation and electron spin resonance (ESR) measurements on colossal magnetoresistive manganites La0.67Ca0.33Mn1-x FexO3 with x = 0, 0.01, 0.03, 0.06, 0.10 and 0.15 in the vicinity of the magnetic (TC) and metal- insulator (TMI) transition temperatures. Above TC the resonance lines with g?2 are caused by the ferromagnetic metallic clusters exhibiting the double exchange interaction between Mn3+-Mn4+ ions. The lines were observed with cooling far below both TC and TMI and were fitted by Dysonian line-shape. Temperature dependences of the linewidths exhibited a minimum value at Tmin?1.25 TC followed by an increase of the width with further cooling toward TC. The anomalous behaviour of the line-width below Tmin is due to an appearance of a ferromagnetic metallic phase within the paramagnetic matrix. The role of phase segregation in which the compounds are phase - separated into a mixture of ferromagnetic and paramagnetic regions is discussed.

14

Właściwości i wytwarzanie cieczy magnetycznych

Kazimierska K., Kaczmarek M., Nowak B.

Zeszyty Naukowe. Mechanika / Akademia Techniczno-Rolnicza w Bydgoszczy

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2004

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Z. 54(243)

167-178

PL

Ferro-ciecze są materiałami magnetycznymi, naturalnie nie występującymi w przyrodzie. Z uwagi na rosnącą liczbę zastosowań tych materiałów (głównie w medycynie, przemyśle wydobywczym i technice) opracowano szereg metod ich otrzymywania. W pracy przestawiono jedną z metod chemicznego uzyskiwania cieczy magnetycznej. Następnie opisano wyniki własnych badań magnetycznych cieczy wytworzonej na bazie syntezy chemicznej.

EN

Ferrofluids are stable colloidal suspensions of magnetic particles in carrier liquids. The fluids are superparamagnetic having specific magnetic and mechanical properties in the presence of magnetic field. In this paper one of the technique of preparation of the ferrofluids based on chemical synthesis is described. Then, magnetic measurements for the obtained magnetic fluid clearly show that it is material owing magnetic properties.

15

O metodzie magnetycznej pamięci metalu

Lisiecki J.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych. Technika Lotnicza

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2004

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nr 18

51-84

PL

Przedstawiono podstawowe zagadnienia fizyczne dotyczące metody magnetycznej pamięci metalu należącej do grupy metod badań nieniszczących. Pokazano i omówiono wyniki pomiarów składowej normalnej rozproszonego pola magnetycznego H y p na próbkach ze stali 08X i Bw14G rozciąganych w zakresie do granicy plastyczności. Pokazano przebiegi pola rozproszonego na próbce poddanej silnemu odkształceniu plastycznemu oraz na próbkach z wprowadzonymi sztucznymi wadami w postaci otworów o różnej średnicy.

EN

Most essential physical aspects of the method of magnetic memory of metals have been presented. This method is one of NDT (non-destructive testing) methods. Measurements of the normal component of a magnetic leakage field H y p have also been presented, using specimens of the 08X and Bw14G steels exposed to tensile tests, i.e. to stretching, until the yield point was reached. Changes of the field of leakage have been shown using a specimen subjected to heavy plastic strain and specimens with artiticial detects, e.g. boreholes of different diameters.

16

Temperature dependence of the magnetization in Sm-Fe-N magnets with different grain size

Pawlik P., Wysłocki J. J., Olszewski J., Leonowicz M., Kaszuwara W.

Archiwum Nauki o Materiałach

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2002

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T. 23, nr 1

5-18

EN

The temperature dependence of the magnetization in Sm-Fe-N permanent magnets produced by reactive diffusion method with different grain size (from 8.6 to 0.97 micrometer), were investigated. Applying X-ray diffraction and Moessbauer spectroscopy, it was found that this magnet consists of hard magnetic phases: Sm2Fe17N0.86 and SmFe5 and soft magnetic alpha-Fe phase. Furthermore, the volume fractions of these phases were determined. The measurements of temperature dependence of magnetization reveal an unusual increase of magnetization just below Curie temperature. This is related to the changes in the volume fractions of the constituent phases, in particular to the increase in the alpha-Fe phase with high value of saturation magnetization Ms, and the decrease in hard magnetic Sm2Fe17N0.86 phase.

PL

Zbadano wpływ temperatury na namagnesowanie magnesów Sm-Fe-N o różnej wielkości ziarna (od 8,6 do 0,97 mikrometra), wytworzonych metodą dyfuzji reaktywnej. Stosując dyfrakcję rentgenowską i spektroskopię moessbauerowską, stwierdzono, że badany magnes składa się z magnetycznie twardych faz: Sm2Fe17N0,86 i SmFe5 oraz fazy magnetycznie miękkiej alfa-Fe. Ponadto określono udziały objętościowe poszczególnych faz. Pomiary zależności namagnesowania od temperatury pozwoliły stwierdzić nietypowy wzrost namagnesowania w temperaturach bliskich temperaturze Curie, związany ze zmianą zawartości objętościowej faz składowych, a w szczególności wzrostem zawartości fazy alfa-Fe o wysokiej wartości namagnesowania nasycenia Ms oraz spadkiem zawartości fazy magnetycznie twardej Sm2Fe17N0.86.

17

The influence of a microstructure on magnetic properties and electric resistivity of Cu-Co GMR stripes

Dubiel B., Figiel H., Ciura F., Czyrska-Filemonowicz A.

Inżynieria Materiałowa

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2001

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R. XXII, nr 4

286-289

EN

The Cu-10 wt %Co melt spun ribbons with giant magneto-resistance (GMR) properties were aged at 773 K for 0.5, 1, 2, 4, 16 and 32 hours. Quantitative transmission electron microscopy (TEM) microstructural analysis have been carried out to determine size distributions of beta -Co precipitates. The results of magnetisation, coercitivity and electrical magneto-resistivity measurements were correlated with the mean diameters of coherent beta-Co particles. It was shown, that the maximum GMR is achieved for the mean diameters of beta-Co particles less than 10 nm, whereas for larger particles the GMR effect is strongly reduced.

PL

Otrzymane metodą krystalizacji z ciekłej strugi taśmy stopu Cu-10% wag.Co, wykazującego gigantyczny magnetoopór, wyżarzono w temperaturze 773 K przez 0,5, 1, 2, 4, 16 i 32 godziny. W celu określenia rozkładów wielkości wydzieleń beta--Co po różnych wariantach wyżarzania przeprowadzono ilościową analizę mikrostruktury metodami transmisyjnej mikroskopii elektronowej. Wyniki pomiarów namagnesowania, koercji i magnetooporu skorelowano z wartościami średniej średnicy koherentnych wydzieleń beta-Co. Wykazano, że stop wykazuje maksymalny magnetoopór, gdy średnia średnica wydzieleń jest mniejsza niż 10 nm. Wzrost średniej wydzieleń powyżej 10 nm sprawia, że efekt magnetooporu wyraźnie maleje.