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1

Double-diffusive convection of synovial (couple-stress) fluid in the presence of Hall current through a porous medium

Singh M.

International Journal of Applied Mechanics and Engineering

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2018

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Vol. 23, no. 4

963--976

EN

An investigation made on the effect of Hall currents on double-diffusive convection of a compressible synovial (couple-stress) fluid in the presence of a horizontal magnetic field through a porous layer is considered. The analysis is carried out within the framework of linear stability theory and normal mode technique. A dispersion relation governing the effects of viscoelasticity, compressibility, magnetic field and porous layer is derived. For the stationary convection, a synovial fluid behaves like an ordinary Newtonian fluid due to the vanishing of the viscoelastic parameter. The stable-solute gradient, compressibility, and magnetic field have postponed the onset of convection, whereas Hall currents and medium permeability have not postponed the onset of convection, moreover, a synovial fluid has a dual character in the presence of Hall currents, whereas in the absence of Hall current in synovial fluid have postponed the onset of convection, which is in contrast in case of thermal convection couple-stress fluid with same effects. These analytic results are confirmed numerically and the effects of various parameters are depicted graphically. It has been observed that oscillatory modes are introduced due to the presence of viscoelasticity, magnetic field, porous medium and Hall currents which were non- existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

2

Wykorzystanie zjawisk kwantowych w pomiarach napięcia elektrycznego i rezystancji

Orzepowski M.

Przegląd Elektrotechniczny

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2008

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R. 84, nr 5

142-145

PL

Artykuł przedstawia wykorzystanie zjawisk kwantowych do odtwarzania i przenoszenia jednostek miar napięcia elektrycznego oraz rezystancji. Zawiera on opis zjawisk kwantowych wykorzystywanych we wzorcach pierwotnych Laboratorium Wzorców Wielkości Elektrycznych Głównego Urzędu Miar. Artykuł opisuje stanowiska pomiarowe wzorców napięcia i rezystancji, jak również system przekazywania jednostek tych wielkości.

EN

The article introduces using quantum phenomena in reproduction and transfer of voltage and resistance units. It contains quantum phenomena description used in primary standards utilized in Central Office’s of Measures (GUM) Laboratory of Electric Quantities. The article describes measurement systems of voltage and resistance standards and unit measurement transfer system of this quantities.

3

Influence of the magnetic field on the charge transport in InxGa1-xAs (0 x ≤ x ≤ 1) MBE layers

Wolkenberg A., Przesławski T.

Elektronika : konstrukcje, technologie, zastosowania

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2008

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Vol. 49, nr 2

72-75

EN

The Hali effect and magnetoresistance measurements in InxGa1-xAs alloys have been carried out over the entire range of compositions x(x=0, x=0.53 and x=1) in the magnetic field up to 1.5 T. InGaAs layers were grown by molecular beam epitaxy (MBE) onto GaAs and InP substrates. Despite the large lattice mismatch (≤ 7.2%) InxGa1-xAs layers showed excellent morphological and structural properties as determined by double crystal X-ray diffraction. Heteroepitaxially grown InAs and In0.53Ga0.47As layers exhibited pronounced maximum of Hali coefficient at temperaturę about ~60 K, which is characteristic of impurity-band transport. Additionally all InGaAs layers showed several anomalous behaviour like strong non-linear character in the magnetic field dependence of their Hali coefficients, non-quadratic weak magnetic field dependence of magnetoresistance, and the temperature dependence of their electron mobility. These are attributed to inhomogeneous distribution of misfit dislocation, and are interpreted in terms of two-layer model, one with bulk like and the other with strongly dislocated region at the heterointerface.

PL

Pomierzono zjawisko Halla i magnetorezystancje w stopach InxGa1-xAs przy różnych wartościach x (x = 0, x=0,53 i x= 1) w polach magnetycznych do 1,5 T. Warstwy InGaAs były osadzane na podłożach z GaAs i InP w procesie MBE. Pomimo dużego niedopasowania sieciowego (≤ 7,2%) warstwy InxGa1-xAs wykazują dobrą strukturę, co wynika z badań XRD. Heteroepitaksjalne warstwy InAs i In0.53Ga0.47As wykazują się maksimum współczynnika Halla w temperaturze ~60 K charakterystyczną dla transportu przez pasmo domieszek. Ponadto warstwy InGaAs wykazują silnie nieliniowy charakter zależności współczynnika Halla od pola magnetycznego, niewielkie odchylenie od zależności kwadratowej magnetorezystancji od pola magnetycznego i zależność temperaturową ruchliwości elektronów. Przypisujemy to niehomogenicznemu rozkładowi dyslokacji niedopasowania i interpretujemy to w modelu dwuwarstwowym, składającym się z warstwy obszaru objętościowego i warstwy międzypowierzchniowej przy podłożu, silnie wzbogaconej dyslokacjami.

4

MHD flow and heat transfer of a Bingham fluid in an eccentric annulus with the Hall effect

Sayed-Ahmed M. E., Attia H. A.

Computer Assisted Mechanics and Engineering Sciences

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2007

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Vol. 14, No. 1

25-42

EN

The steady laminar flow and heat transfer of an incompressible, electrically conducting, non-Newtonian Bingham fluid in an eccentric annulus are studied in the presence of an external uniform magnetic field. The inner cylinder is subject to a constant heat flux while the outer cylinder is adiabatic and, the viscous and Joule dissipations are taken into consideration. The governing momentum and energy equations are solved numerically using the finite difference approximations. The velocity, the temperature, the volumetric flow rate and the average Nusselt number are computed for various values of the physical parameters.