Wyniki wyszukiwania - Biblioteka Nauki

1

Influence of the composition of M78Si9B13 metallic glasses on their structural stability

100%

Jakubczyk E. , Stępień Z. , Jakubczyk M.

Optica Applicata

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2005

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tom Vol. 35, nr 3

339-346

EN

The structural stability of Co78Si9B13 and Fe78Si9B13 metallic glasses was investigated by differential scanning calorimetry (DSC), X-ray diffraction, Hall effect and electrical resistivity methods. It was found that at first isochronal annealing leads to the formation of a(alfa)-M (M = Co, Fe) phases.This process is followed by the formation of M2B phases. The phases were identified by X-ray diffraction method and their structures were confirmed with the use of quantum chemistry method. The creation of crystalline phases decreases abruptly the Hall and electrical resistivities. The alloy containing Fe appeared to have a much wider range of structural stability.

2

Hydromagnetic unsteady mixed convectionand mass transfer flow past a vertical porous plate immersed in a porous medium with the hall effect

100%

Sharma B. K. , Chaudhary R. C.

Engineering Transactions

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2008

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tom Vol. 56, iss. 1

3-23

EN

The present work is concerned with unsteady mixed convection and mass transfer flow with Hall effect of an electrically conducting incompressible viscous fluid through a porous medium bounded by an infinite vertical plate subjected to suction/injection velocity in the presence of a constant magnetic field. The magnetic field is applied transversely to the direction of the flow. The resulting problem has been solved analytically and the solutions are found for velocity, temperaturę, concentration of the species, skin-friction, surface heat flux and mass flux. The effects of materiał parameters on the flow characteristics are expressed and illustrated/discussed by graphs and table.

3

Hall effect on MHD flow and heat transfer of nanofluids over a stretching wedge in the presence of velocity slip and Joule heating

100%

Su X. , Zheng L.

Open Physics

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2013

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tom 11

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nr 12

1694-1703

EN

This paper deals with the boundary layer flow and heat transfer of nanofluids over a stretching wedge with velocity-slip boundary conditions. In this analysis, Hall effect and Joule heating are taken into consideration. Four different types of water-base nanofluids containing copper (Cu), silver (Ag), alumina (Al2O3), and titania (TiO2) nanoparticles are analyzed. The partial differential equations governing the flow and temperature fields are converted into a system of nonlinear ordinary differential equations using a similarity transformation. The resulting similarity equations are then solved by using the shooting technique along with the fourth order Runge-Kutta method. The effects of types of nanoparticles, the volume fraction of nanoparticles, the magnetic parameter, the Hall parameter, the wedge angle parameter, and the velocityslip parameter on the velocity and temperature fields are discussed and presented graphically, respectively.

4

Hall effect on thermosolutal instability of Walters' (model B') fluid in porous medium

100%

Sunil , Sharma R. C. , Pal M.

Archives of Mechanics

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2001

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tom Vol. 53, nr 6

677-690

EN

The thermosolutal instability of Walters' (model B') fluid in porous medium is considered in the presence of uniform vertical magnetic field to include the effect of Hall currents. For the case of stationary convection, the stable solute gradient and magnetic field have stabilizing effects on the system, whereas the Hall currents have destabilizing effect on the system. The medium permeability has both stabilizing and destabilizing effects on the system depending on the Hall parameter M. The kinematic viscoelasticity has no effect for stationary convection. The kinematic viscoelasticity, stable solute gradient and magnetic field (and the corresponding Hall currents) introduce oscillatory modes in the system, which were non-existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

5

Observation of non-Fermi liquid behaviour in new Yb-based alloys

100%

Tran V. H.

Materials Science Poland

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2007

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tom Vol. 25, No. 2

343--349

EN

In this contribution, after presenting the existing theoretical models, we discuss the evidence for non-Fermi liquid behaviour in Yb(Cu1-xSix)2-y that have been investigated for the last years in our Institute. The alloys crystallize in the hexagonal AlB2 type structure and exhibit a dramatic change in the electronic properties upon change of the electron concentration. Undoped YbSi2-y is an intermediate valent system, whereas the doping with 10% Cu ensures A(T) ??Tn, A(T) ??T and Cp ??T-1/2 dependences. Comparison of the data with the Griffiths phase model shows that this model can describe some of the observed results. We present also a study of the Hall effect. The Hall coefficient at 7 T is found to follow a lnT dependence below 10 K, thus showing the behaviour opposite to that in Fermi-liquid heavy-fermion systems.

6

Magnetic and transport properties of Fe/Si multilayers with various iron thicknesses

100%

Wandziuk P. , Luciński T. , Andrzejewski B.

Materials Science Poland

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2007

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tom Vol. 25, No. 2

599--602

EN

Resistivity, temperature coefficient of resistance and magnetization as functions of iron thickness have been studied in a series of magnetron sputtered Fe/Si multilayers with constant Si layer thickness. At the Fe/Si interfaces, a significant amount of deposited iron is transformed into nonmagnetic (0.5 nm) and ferromagnetic (up to 2 nm) nonuniform Fe-Si mixture with a gradient of Fe concentration. Finally, for iron thicknesses above 2.5 nm a bcc-Fe phase appears.

7

Quantitative mobility spectrum analysis (QMSA) in multi-layer semiconductor structures

88%

Antoszewski J. , Faraone L.

Opto-Electronics Review

|

2004

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tom Vol. 12, No. 4

347-352

EN

For modern semiconductor heterostructures containing multiple populations of distinct carrier species, conventional Hall and resistivity data acquired at a single magnetic field provide far less information than measurements as a function of magnetic field. However, the extraction of reliable and accurate carrier densities and mobilities from the field-dependent data can present a number of difficult challenges, which were never fully overcome by earlier methods such as the multi-carrier fit, the mobility spectrum analysis of Beck and Anderson, and the hybrid mixed-conduction analysis. More recently, in order to overcome the limitations of those methods, several research groups have contributed to development of the quantitative mobility spectrum analysis (QMSA), which is now available as a commercial product. The algorithm is analogous to a fast Fourier transform, in that it transforms from the magnetic field B domain to the mobility ž domain. QMSA converts the field-dependent Hall and resistivity data into a visually-meaningful transformed output, comprising the conductivity density of electrons and holes in the mobility domain. In this article, we apply QMSA to both synthetic and real experimental data that are representative of modern semiconductor structures.

8

Determination of the LO phonon energy by using electronic and optical methods in AlGaN/GaN

88%

Celik O. , Tiras E. , Ardali S. , Lisesivdin S. , Ozbay E.

Open Physics

|

2012

|

tom 10

|

nr 2

485-491

EN

The longitudinal optical (LO) phonon energy in AlGaN/GaN heterostructures is determined from temperature-dependent Hall effect measurements and also from Infrared (IR) spectroscopy and Raman spectroscopy. The Hall effect measurements on AlGaN/GaN heterostructures grown by MOCVD have been carried out as a function of temperature in the range 1.8-275 K at a fixed magnetic field. The IR and Raman spectroscopy measurements have been carried out at room temperature. The experimental data for the temperature dependence of the Hall mobility were compared with the calculated electron mobility. In the calculations of electron mobility, polar optical phonon scattering, ionized impurity scattering, background impurity scattering, interface roughness, piezoelectric scattering, acoustic phonon scattering and dislocation scattering were taken into account at all temperatures. The result is that at low temperatures interface roughness scattering is the dominant scattering mechanism and at high temperatures polar optical phonon scattering is dominant.

9

Effect of randomness on anomalous Hall coefficient in antiferromagnet U2PdGa3

88%

Tran V. H.

Materials Science Poland

|

2008

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tom Vol. 26, No. 4

1069--1075

EN

The Hall effect has been studied for antiferromagnet U2PdGa3. In the paramagnetic state, the Hall data can be interpreted in terms of skew scattering theory for heavy-fermion systems. We observe a large contribution of anomalous Hall coefficient, indicating a dominated contribution of incoherent skew scattering by uranium 5f moments. Interesting behaviour of the RH(T) dependence is found at low temperatures. The RH(T) curve displays a plateau between T* = 12 and TN = 33 K, followed by a shoulder with further decreasing temperature. The appearance of the anomaly around T* suggests the existence of a new scattering mechanism, in addition to well known skew and jump-side scatterings. We compare the Hall data of U2PdGa3 with those observed for strongly correlated electron systems and with those of spin-glasses. Like the latter systems, non-zero spin chirality seems to play a considerable role in the anomalous Hall effect of U2PdGa3.

10

Hall effect on thermal instability of Walters' (model B?) fluid in a porous medium

88%

Sunil , Kumar P.

Applied Mechanics and Engineering

|

2000

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tom Vol. 5, no 3

655-671

EN

The thermal instability of Walters' (model B') fluid in a porous medium is considered in the presence of a uniform vertical magnetic field to include the effect of Hall currents. For the case of stationary convection, the magnetic field has the stabilizing effect on the system, whereas the Hall currents have destabilizing effect on the system. The porous medium permeability has both stabilizing and destabilizing effects on the system depending on the Hall parameter M. The kinematic viscoelasticity has no effect on stationary convection. The kinematic viscoelasticity and magnetic field (and corresponding Hall currents) introduce oscillatory modes in the system, which were nonexistent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

11

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

88%

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

Computer Assisted Mechanics and Engineering Sciences

|

2007

|

tom 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.

12

Series solution of hydromagnetic flow and heat transfer with Hall effect in a second grade fluid over a stretching sheet

88%

Ayub M. , Zaman H. , Ahmad M.

Open Physics

|

2010

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tom 8

|

nr 1

135-149

EN

We examine the problem of flow and heat transfer in a second grade fluid over a stretching sheet [K. Vajravelu, T. Roper, Int. J. Nonlinear Mech. 34, 1031 (1999)]. The equations considered by Vajravelu and Roper [K. Vajravelu, T. Roper, Int. J. Nonlinear Mech. 34, 1031 (1999)], are found to be incorrect in the literature. In this paper, we not only corrected the equation but found a useful analytic solution to this important problem. We also extended the problem for hydromagnetic flow and heat transfer with Hall effect. The explicit analytic homotopy solution for the velocity field and heat transfer are presented. Graphs for the velocity field, skin friction coefficient, and rate of heat transfer are presented. Tables for the skin friction coefficient and rate of heat transfer are also presented. The convergence of the solution is also properly checked and discussed.

13

Study of the effect of localised axial magnetic field on discharge current using the Hall effect

75%

Paingankar A. , Chitra N. , Shirodkar V.

Journal of Technical Physics

|

1998

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tom Vol. 39, no 2

221-235

EN

The influence of localised axial magnetic field on discharge current in a low pressure, fry air dc discharge has been studied. The distinctive nature of the variation in discharge current was found to depend on the region to which the axial magnetic field was applied. In order to qualitatively explain this phenomenon, various plasma parameters in each region of discharge have been determined using Hall effect.

14

Hall effects on isothermal vertical plate with uniform mass diffusion in the presence of rotating fluid and chemical reaction of first order

75%

Dhananjeya Kumaar V. S. A. , Muthucumaraswamy R.

International Journal of Applied Mechanics and Engineering

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2017

|

tom Vol. 22, no. 1

111--121

EN

An exact solution of the combined study of Hall effects on a vertical plate with a rotating fluid in the presence of a homogeneous chemical reaction of first order has been analysed. The dimensionless governing coupled partial differential equations are tackled using the usual Laplace transform technique. The sway of the Hall parameter, Hartmann number, Grashof number, Prandtl number, Schmidt number, chemical reaction parameter on the axial velocity and concentration of the fluid has been depicted graphically. When the non-dimensional angular velocity, Ω=2M21+m.2, the transverse velocity component vanishes, thereby the axial velocity of the fluid attains the maximum value. It is noted that with increase in the Hall parameter, thermal Grashof number and mass Grashof number, the axial velocity of the fluid increases significantly.

15

Hall effect in strongly correlated electron systems

75%

Tran V. H.

Materials Science Poland

|

2006

|

tom Vol. 24, No. 3

669--673

EN

This work provides a brieft survey of the Hall effect data collected on some strongly correlated electron systems. The experimental results illustrate the behaviour of heavy-fermion system UCu5Al, heavy-fermion semiconductor U2Ru2Sn, ferromagnetic sueperconductor under pressure UGe2, and ferromagnet with a 2D weak localization effect UCo0.5Sb2.

16

Peculiarities of quantum magnetotransport in In₀.₅₃Ga₀.₄₇As/In₀.₅₂Al₀.₄₈As heterostructures grown on (100) InP

75%

Przesławski T.

Electron Technology : Internet Journal

|

2007

|

tom Vol. 39, nr 2

1-3

EN

Magnetotransport properties of the Si δ- doped In₀.₅₃Ga₀.₄₇As/In₀.₅₂Al₀.₄₈As heterostructures grown on (100)InP substrates were investigated by performing classical Van der Pauw Hall effect as well as high field quantum magnetotransport measurements. The results of the conventional Hall measurements are ambiguous because the mobility obtained at liquid helium occurred to be smaller than at room temperature. The qualitative analysis of the conductivity tensor revealed at least two conducting channels. Thus, the properties of whole structure are limited by the low mobility of the parasitic parallel conduction layer. On the other hand, the fast Fourier transform of the quantum magnetooscillations consists of a lot of frequencies. None of them can not be attributed to the presence of the two-dimensional electron gas (2DEG) in a single quantum well. We interpret our rich Fourier spectrum as due to quantum interference (QI) between open electron path commonly found in superlattices structures.

17

Kondensator wzorcowy 10 nF z dielektrykiem ceramicznym

75%

Koszarny M. , Jursza J. , Szutkowski J. , Jasiński R. , Szterk P.

Metrologia i Probiernictwo : biuletyn Głównego Urzędu Miar

|

2018

|

tom nr 2 (21)

50--52

PL

W ramach prac badawczo-rozwojowych, w Samodzielnym Laboratorium Elektryczności i Magnetyzmu Głównego Urzędu Miar zaprojektowano, opracowano i wykonano czterozaciskowy kondensator wzorcowy o wartości 10 nF, z dielektrykiem ceramicznym. Kondensator został umieszczony w termostacie z wbudowanym elektronicznym układem sterowania, który zapewnia bardzo precyzyjne utrzymywanie określonej temperatury. Układ sterowania może być zasilany ze stacjonarnego źródła zasilania lub z dodatkowego akumulatora. Opracowany wzorzec charakteryzuje się bardzo dobrą stabilnością wartości pojemności elektrycznej dla danej częstotliwości oraz małą wartością stratności. Wzorzec ten jest niezbędnym elementem dla transferu jednostki miary pojemności elektrycznej z kwantowego efektu Halla.

EN

In Electricity and Magnetism Laboratory of the Central Office of Measures, a four-terminal reference capacitor 10 nF (with a ceramic dielectric) was designed, developed and made. The capacitor has been placed in a thermostat with a built-in electronic control system which can be powered from a stationary power source or from an additional battery. The developed standard is characterized by a very good stability of the capacitance value for a given frequency and a low loss value tan δ. This capacitor is a necessary element for the transfer of the unit of capacitance from the quantum Hall effect.

18

Effect of substrate temperature on the electrical and optical properties of electron beam evaporated indium antimonide thin films

75%

Rahul , Verma A. K. , Tripathi R. N. , Vishwakarma S. R.

Materials Science Poland

|

2012

|

tom Vol. 30, No. 4

375--381

EN

Thin films of non-stoichiometric indium antimonide (In0:66Sb0:34) have been deposited by electron beam evaporation technique on glass substrates at different substrate temperatures, (300-473 K). The films have polycrystalline nature with zinc blende structure. The decrease in electrical resistivity with increasing temperature shows semiconducting behavior. Hall measurements indicate that the films are of n-type. Optical transmission spectra of as deposited thin films have been measured at different substrate temperatures. All the electrical parameters i.e. electron mobility (m), carrier concentration (n), resistivity (r), activation energy and band gap (Eg) have been found to be temperature dependent. Suitable explanations are given in the paper.

19

Metodyka określania parametrów elektrycznych warstw GaSb osadzonych na przewodzącym podłożu

63%

Kotowski M. , Czuba K. , Smoczyński D. , Jasik A.

Przegląd Elektrotechniczny

|

2019

|

tom R. 95, nr 9

123--126

PL

W artykule podjęto próbę określenia parametrów warstw epitaksjalnych GaSb o różnej koncentracji atomów berylu osadzonych na przewodzących podłożach GaSb o dziurowym typie przewodnictwa. Wykorzystano do tego zaproponowany w literaturze model wielowarstwowy, który zweryfikowano przez pomiar parametrów elektrycznych warstwy GaSb osadzonej na półizolującym podłożu GaAs. Stwierdzono, że model pozwala poprawnie określać parametry elektryczne warstw wówczas, gdy przewodność całej struktury jest większa niż przewodność podłoża. W przypadku odwrotnym otrzymano zawyżone wartości ruchliwości nośników w temperaturze pokojowej w porównaniu do wartości uzyskanych w temperaturze 77 K dla koncentracji nośników ok. 5 x 1017 cm3.

EN

In the paper, an attempt was made to determine electrical parameters of GaSb:Be layers with various doping concentration grown on conductive p-type substrate. A multi-layer model proposed by Arnaudov et al [10] was used. To verify it, the model was applied to the experimental data obtained for GaSb/GaAs(SI) sample. It was proven that the model correctly calculates electrical parameters, when the conductivity of the entire sample is larger than that of a substrate. In the opposite situation, overestimated values of hole mobility at room temperature were obtained for GaSb layer with p = 5 x 1017 cm3 in comparison with correct values at 77 K.

20

Phase transitions in Co78Si9B13 and Fe78Si9B13 metallic glasses induced by isochronal annealing

63%

Jakubczyk E.

Materials Science Poland

|

2006

|

tom Vol. 24, No. 4

1027--1036

EN

The crystallization process of Co78Si9B13 and Fe72Si9B13 metallic glasses was stimulated by isochronal annealing at various temperatures (573-823 K). By the DSC, X-ray diffraction, Hall and electrical resistivity measurements it was found that the crystallization proceeds through two main stages. At the first stage, alfa-Co and alfa-Fe phases are formed and at the second stage Co2B and Fe2B phases are crystallized. During the crystallization, the ferromagnetic ordering of both alloys is still conserved. Fe78Si 9B13 alloy has a much wider range of structural stability. The activation energy determined from DSC measurements and the total energy of the created phases obtained by quantum chemistry method confirmed the sequence and the type of the created phases. The creation of crystalline phases from the amorphous matrix was related to a distinct decrease of the electrical and Hall resistivities and the spontaneous Hall coefficient.