Wyniki wyszukiwania - Biblioteka Nauki

1

Time dependent magnetically induced variations in optical transmission of magnetite nanoparticle aqueous suspension

100%

Malynych S. , Moroz I.

Open Physics

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2012

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tom 10

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nr 1

159-165

EN

We observe time dependent variations in the light intensity transmitted through an aqueous suspension of Fe3O4 nanoparticles caused by applied DC magnetic field. Two types of variations can be distinguished. Fast response takes less than 1ms while slow variations occur at the time interval fromseconds to hundreds of minutes. Possible mechanisms of these variations are discussed. Formation of chain-like structures consisted from iron oxide nanoparticles is responsible for the slow variations. It is also accompanied by a diffraction pattern when the magnetic field is orthogonal to the light beam. Fast variations are due to particle rotation and reorientation of the magnetic moment inside a nanoparticle.

2

Effect of dust particles on a Soret- driven ferrothermohaline convection in a rotating medium

89%

Hemalatha R. , Sekar R. , Vaidyanathan G.

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tom Vol. 17, no. 2

367-381

EN

In ferrofluids three components namely, the core, surfactant and carrier fluids coexist. Thermal convection in a multicomponent fluid has wide applications in industrial, ionospheric and geothermal systems. In this paper the effect of dust particles on a Soret-driven ferrothermohaline convection in a rotating system heated and soluted from below subjected to a transverse uniform magnetic field is examined using linear stability analysis. An exact solution is obtained for the case of two free boundaries. Both stationary and oscillatory instabilities are investigated. The oscillatory modes are introduced due to the presence of dust particles, the stable solute gradient and rotation and the oscillatory modes are not allowed in their absence. In the case of stationary convection, the non-buoyancy magnetization parameter, the dust particle parameter destabilize the system. The Soret-coefficient, rotation and the stable solute gradient stabilize the system. The results are presented graphically.

3

Matematyczny model działania uniwersalnego manometru indukcyjnego wypełnionego ferrofluidem

89%

Bednarek S. , Tyran P.

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2011

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tom R. 87, nr 8

243-247

PL

W artykule opisano budowę nowego typu manometru indukcyjnego własnej konstrukcji, w którym w jako rdzeń wykorzystano słupek ferrofluidu wsuwany pod działaniem ciśnienia do cewki pomiarowej. Wyjaśniono zasadę działania tego manometru i przeprowadzono jej ilościową analizę. W wyniku tego wyprowadzono wzory wyrażające zależność wskazywanego napięcia od mierzonego ciśnienia. Podano też dane techniczne zbudowanych prototypów manometrów.

EN

Construction of the self made new type manometer is presented in this article. The ferrofluid column is applied as core shifted into coil by measured pressure in this instrument. Operation principle of the mentioned manometer is explained and quantity analyze its given. In result its the formulas describing dependence of the pointed voltage on measured pressure are derived. Technical specification of the constructed manometer are also given.

4

Actuator with Ferromagnetic Plunger Working in Ferrofluidic Liquid

75%

Polcar P. , Kropík P. , Ulrych B.

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2012

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tom R. 88, nr 7b

214-216

EN

An electromagnetic actuator with a plunger moving in a ferrofluidic liquid is suggested and modeled. The paper analyses its principal operation characteristics.

PL

Zaproponowano nowy siłownik (aktuator) z popychaczem poruszającym się w cieczy typu ferrofluid. W artykule opisano główne cechy tego urządzenia.

5

Effect of rotation on ferrofluid based squeeze film of various shapes between two annular plates

75%

Shah R. C.

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2007

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tom Vol. 12, no 2

515-525

EN

This paper studied the ferrofluid squeeze film, formed when the upper annular rotating plate of various shapes (viz. secant, exponential and flat) approaches the lower flat annular one normally. Expressions for pressure, load capacity and response time are obtained for a constant transverse magnetic field in each case. The results show that load capacity and response time are found to increase when the volume fraction of the particles and rotation of the upper plate increased for alI shapes of the upper plate. In the case of curvature of the upper plate, load capacity and response time are found to increase with the increase of curvature of the exponential upper plate but decreased for the secant shaped plate.

6

Soret-driven thermohaline convection in dusty ferrofluids saturating a porous medium

63%

Sekar R. , Vaidyanathan G. , Hemalatha R.

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2008

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tom Vol. 13, no 4

1003-1018

EN

The Soret driven thermoconvective instability in multicomponent fluids has wide applications in heat and mass transfer. This paper deals with the theoretical investigation of the effect of dust particles on a Soret-driven ferro thermohaline convection heated and soluted from below subjected to a transverse uniform magnetic field in a porous medium. The Brinkmann model is used. An exact solution is obtained for the case of two free boundaries. Both stationary and oscillatory instabilities are investigated using the linear stability analysis and normal mode technique. It is found that the system stabilizes only through stationary mode. The non-buoyancy magnetization parameter, the dust particle parameter and large values of permeability of the porous medium are found to destabilize the system. The Soret coefficient and the stable solute gradient stabilize the system. The results are presented graphically.

7

Effect of rotation on double-diffusive convection in a magnetized ferrofluid with internal angular momentum saturating a porous medium

63%

Sunil , Mahajan A.

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2008

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tom Vol. 13, no 4

1059-1078

EN

This paper deals with the theoretical investigation of the effect of rotation in a magnetized ferrofluid with internal angular momentum, heated and soluted from below saturating a porous medium and subjected to a transverse uniform magnetic field. 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 of convection. The influence of various parameters on the onset of stationary convection such as rotation, medium permeability, solute gradient, magnetization and internal angular momentum parameters (i.e., coupling parameter, spin diffusion parameter and heat conduction parameter) has been analyzed. The critical magnetic thermal Rayleigh number for the onset of instability is also determined numerically for sufficiently large values of buoyancy magnetization parameter and results are depicted graphically. The principle of exchange of stabilities is found to hold true for the ferrofluid with internal angular momentum saturating a porous medium heated from below in the absence of rotation, coupling between vorticity and spin, microinertia and solute gradient. The oscillatory modes are introduced due to the presence of the rotation, coupling between vorticity and spin, microinertia and solute gradient, 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.

8

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

63%

Sunil , Mahajan A.

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2011

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tom 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.

9

Effect of presence of dust particles on soret-driven ferrothermohaline convection

63%

Sekar R. , Vaidyanathan G. , Hemalatha R.

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2009

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tom Vol. 14, no 2

509-522

EN

Soret driven thermoconvective instability in multicomponent fluids has wide applications in heat and mass transfer. This paper deals with the theoretical investigation of the effect of dust particles on Soret-driven thermohaline convection in a ferrofluid, heated and soluted from below subjected to a transverse uniform magnetic field. An exact solution is obtained for the case of two free boundaries. A linear stability analysis is used. A normal mode technique is applied. Both stationary and oscillatory instabilities are investigated. It is found that the system stabilizes through stationary mode. The non-buoyancy magnetization parameter and the dust particle parameter are found to destabilize the system. The Soret coefficient and the stable solute gradient tend to stabilize the system. The results are presented graphically.