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1
Content available remote

Additional Modification of Thermomagnetic Properties of Objects of Low Relative Permeability in Electromagnetic Field

100%
Medveď D., Zbojovský J., Pavlík M., Ilenin S., Čonka Z., Kanálik M., Kolcunová I., Mészáros A., Beňa L., Kolcun M.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 4
1138-1140
EN
This paper presents the characteristics of the foodstuff heating phenomenon using induction heating process by an induction cooker. The simulation setup was prepared according to the proposed magnetic material and configuration of the pot and induction cooker. The material properties of pot were varied among the several alternatives. The helical coil was designed on the base of the limitation of the induction cooker size and given number of coil turns and coil tube diameter with specific supplied electric current density. The data from the simulation analysis have to determine the enhancing of the highest heat transfer from induction cooker into pot. These data led to the modification of the material and geometrical properties of the pot in accordance to a minimum heating time and enhanced safety operation, especially close to unshielded magnetic objects.
2
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Self-Similar Solidification of Binary Alloys

63%
Alexandrov D., Ivanov A., Malygin A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 4
795-799
EN
The self-similar crystallization process of a binary mixture from a cooled boundary is studied on the basis of two models with a planar front and mushy layer. Approximate analytical solutions of the process describing the solidification with a mushy layer are found. The theory under consideration is in good agreement with experiments carried out by Huppert and Worster for ice growing from aqueous salt solutions.
3
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Analytical Solution for a Problem of Directional Solidification in a Ternary System

63%
Alexandrov D., Ivanov A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 4
786-790
EN
This paper is devoted to new analytic results relating to the nonstationary dynamics of directional solidification of ternary solutions with two moving layers of the phase transition lying between solid and liquid phases. Explicit analytical solutions of the problem under consideration are constructed on the basis of laboratory experiments carried out by Aitta, Huppert and Worster.
4
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Mushy Layer Formation during Solidification οf Binary Alloys from a Cooled Wall: the Role of Boundary Conditions

63%
Alexandrova I., Alexandrov D., Aseev D., Bulitcheva S.
Acta Physica Polonica A
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2009
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vol. 115
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issue 4
791-794
EN
Motivated by metallurgical and geophysical applications we present a mathematical model describing the process of unidirectional solidification of binary melts or solutions, which is based on the classical Stefan thermodiffusion theory with a planar front up to a time of mushy layer initiation and on the quasi-equilibrium theory of solidification with a constitutionally supercooled region afterwards. The role of boundary conditions imposed at the cooled wall is studied in terms of heat flux coefficients describing ultimately nonlinear dynamics of the process.
5
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Thermal Calculation of Ground Contact Structures: New Methods Based on Parametrized Transient Finite Element Thermal Modeling

63%
Nagy B.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-164-B-166
EN
The heat loss at ground contact structures is taken into consideration in building heat loss calculations. However, it implies uncertainties due to the physical properties of the soil as well as the building structure. In this paper, new methods are introduced for calculating the heat loss at ground contact structures. Firstly, it examines the presently used and general calculation methods and their shortcomings. Then a simple-to-use method based on thousands of results of parametrized transient finite element thermal models is shown. In this research, the calculations take the middle-eastern European climate conditions, geothermal gradient and soil properties as well as the relevant harmonized EU standards into account. The equivalent linear heat transfer coefficients, which in this method also contain the effects of thermal bridges, occurring in various conditions are summarized in a table and can be calculated by new formulae also shown in the paper using condition-dependent constants, the ground floor's heat transfer coefficient and the length between the floor and ground level.
6
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Numerical Simulation of Temperature Distribution Field in Beam Bulk in the Simultaneous Presence of Heat Insulation, Heat Flux and Heat Exchange

63%
Kudaykulov A., Zhumadillayeva A.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 1
335-336
EN
In the work at the level of basic laws of conservation of energy combined with the use of quadratic spline functions a resolving system of equations is constructed. Herewith, the procedure is prepared to minimize the functionals of total thermal energy and potential energy of elastic deformation involving temperature field.
7
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Unstable Inverse Heat Transfer Problems in Microelectronics

51%
De Mey G., Bogusławski B., Kos A.
Acta Physica Polonica A
|
2013
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vol. 123
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issue 4
637-641
EN
Inverse heat transfer problems are very important for the thermal testability of integrated circuits. Temperature sensors integrated on the same chip measure in real time the power dissipation in one or more critical heat sources of the circuit in order to prevent overheating. It will be demonstrated that these kinds of problems can give rise to mathematical unstabilities or the ill conditioning of the inverse problem. This statement will be proved with the help of several particular cases.
8
Content available remote

An Analytical Study of Nonlinear Vibrations οf Buckled Euler-Bernoulli Beams

51%
Pakar I., Bayat M.
Acta Physica Polonica A
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2013
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vol. 123
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issue 1
48-52
EN
The current research deals with a way of using a new kind of periodic solutions called He's max-min approach for the nonlinear vibration of axially loaded Euler-Bernoulli beams. By applying this technique, the beam's natural frequencies and mode shapes can be easily obtained and a rapidly convergent sequence is obtained during the solution. The effect of vibration amplitude on the non-linear frequency and buckling load is discussed. To verify the results some comparisons are presented between max-min approach results and the exact ones to show the accuracy of this new approach. It has been discovered that the max-min approach does not necessitate small perturbation and is also suitably precise to both linear and nonlinear problems in physics and engineering.
9
Content available remote

Numerical Analysis of the Rapid Solidification Process of NiTi Binary Alloy

51%
Ternik P., Zadravec M., Svetec M., Rudolf R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1
43-47
EN
The objective of the present work is to analyse the solidification process of NiTi binary alloy. The physical medium is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. The results are presented for the velocity and temperature field, as well as for the NiTi mass fraction during the solidification process.
10
Content available remote

Phototermal Spectra of Inhomogeneous Coatings

51%
Popovic M., Galovic S., Stojanovic Z.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
535-537
EN
In this paper we demonstrate a theoretical study for photothermal measurements on inhomogeneous coatings. First, a general photothermal mathematical model for thermal gradient materials is presented. Then, we discuss the effects of inhomogeneous thermal properties in photothermal amplitude and phase spectra of coatings. Finally, a method for quantitative depth profiling that makes use of prior knowledge about the type of profile existing in a sample to reduce the instabilities associated with the mathematically ill conditioned task is demonstrated.
11
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Effect of Phase Change Materials on Time Lag, Decrement Factor and Heat-Saving

51%
Bilgin F., Arıcı M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
1102-1105
EN
In this study, the effect of phase change materials on the time lag, decrement factor and heat-saving is examined numerically. The calculations are conducted for four different cities located at different climatic zones in Turkey, considering both summer and winter conditions, in order to explore the potential heating and cooling energy savings by employing phase change materials. A solar-air temperature, which is a function of time and solar radiation, was taken into consideration as external boundary condition for each city. The results of the present study show that employment of phase change materials in walls of the buildings has a pronounced effect on the time lag and decrement factor. It is concluded that a significant amount of heating energy can be saved and thermal comfort can be enhanced considerably by incorporating phase change materials into external walls. However, a proper phase change material must be selected, considering different climatic conditions.
12
Content available remote

Modeling of Processes Taking Place during Powder Coating Treatment by an Electron Beam or a Plasma Jet

51%
Alontseva D., Krasavin A., Kolesnikova T., Russakova A.
Acta Physica Polonica A
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2014
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vol. 125
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issue 6
1275-1279
EN
This paper considers the problem of finding the temperature field in two-layer metallic materials heated by a moving source of radiation. It describes developed by the authors numerical method for solving the problem of heating a two-layer plate by a moving axially symmetric surface heat source with regard to the function of distribution of the power density of the beam for which the program of computation in C^{++} was implemented. The calculation results were used for selecting the optimal parameters (speed and power density of the source) of modifying radiation of protective powder coatings on steel substrates.
13
Content available remote

Non-Polynomial Spline Method for a Time-Dependent Heat-Like Lane- Emden Equation

45%
Caglar S., Ucar M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1
262-264
EN
In this study, a time-dependent heat-like Lane-Emden equation is solved by using a non-polynomial spline method. An example is solved to assess the accuracy of the method. The numerical results are obtained for different values (n) of equation. The results indicate that non-polynomial spline method is effectively implemented. It is seen that results are compatible with exact solutions and consistent with other existing numerical methods.
14
Content available remote

A Finite-Element Flash Method for Measuring Thermal Conductivity of Liquid

45%
Mamczur J., Wasilewski A., Więcek T.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 2
193-195
EN
A laser beam is used to heat a portion of liquid closed in a vessel from the top of it to avoid convection. The temperature is measured at the bottom of the vessel by a laser waveguide sensor. The heating and measuring methods allow using a small amount of liquid of the order of a milliliter fraction. The heat flow through the liquid as well as the surrounding vessel and space is modeled by the finite-element method to calculate the temperature at the bottom vs. time. Thus obtained dependence is used then as a fitting function to get the liquid thermal conductivity among some other fitting parameters.
15
Content available remote

Single Pulse Laser Ablation of AISI 316L Stainless Steel Surface Using Nd:YAG Laser Irradiation

38%
Demir P., Kacar E., Akman E., Demir A.
Acta Physica Polonica A
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2014
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vol. 125
|
issue 2
439-441
EN
The interaction of single-pulse Nd:YAG laser, operating at 1064 nm wavelength and 6 ns pulse duration, with AISI 316L stainless steel target surface was investigated experimentally and theoretically. Surface modification of stainless steel using laser irradiation was studied by observing the effects of varying incident laser pulse intensities on surface morphology. Surface structure of laser treated stainless steel was determined by optical microscopy and profilometry analyses. Numerical calculation by heat transfer equation was performed for single laser pulse irradiation. The results, obtained by theoretical and experimental processes, of the interaction between single-pulse Nd:YAG laser irradiation and AISI 316L stainless steel target surface are reported.
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