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1
Content available Boundary effects on electrothermal convection in a dielectric fluid layer
Ravisha M., Raghunatha K. R., Mamatha A. L., Shivakumara I. S.
Archives of Thermodynamics
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2019
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Vol. 40, no 1
3--19
EN
The instability characteristics of a dielectric fluid layer heated from below under the influence of a uniform vertical alternating current (AC) electric field is analyzed for different types of electric potential (constant electric potential/ electric current), velocity (rigid/free) and temperature boundary conditions (constant temperature/heat flux or a mixed condition at the upper boundary). The resulting eigenvalue problem is solved numerically using the shooting method for various boundary conditions and the solution is also found in a simple closed form when the perturbation heat flux is zero at the boundaries. The possibility of a more precise control of electrothermal convection (ETC) through various boundary conditions is emphasized. The effect of increasing AC electric Rayleigh number is to hasten while that of Biot number is to delay the onset of ETC. The system is more stable for rigid-rigid boundaries when compared to rigid-free and least stable for free-free boundaries. The change of electric potential boundary condition at the upper boundary from constant electric potential to constant electric current is found to instill more stability on the system.
2
Content available remote The fourier series implementation issues in the tolerance modeling of thermal conductivity of periodic composites
Kula D., Wierzbicki E.
Engineering Transactions
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2015
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Vol. 63, iss. 1
77--92
EN
The aim of this study is to propose a partially-averaged model of heat conduction in simple micro-periodic composite conductors. In this model, as in many known models of this type, the type of microstructure is represented by the single scalar parameter, which is referred to as microstructure parameter. Unlike other known averaged models of this type, the resulting model allows for the formulation exact solutions to initial-boundary value problems formulated for the parabolic heat conduction equation. If tolerance approximations will be applied to averaged temperature filed this model becomes asymptotically exact model. The term “asymptotically exact model” refers to models in the framework of which solutions coincident with exact solutions to the mentioned problems for the parabolic heat transfer equation when the microstructure parameter tends to zero.
3
Content available remote From tolerance modeling to exact description of heat conduction in biperiodic composites
Wierzbicki E., Mazewska M.
Engineering Transactions
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2015
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Vol. 63, iss. 1
133--142
EN
In the paper we study the temperature boundary effect behavior in the dividing wall made of a composite conductor in which every area parallel to the outside and the inside plane areas has identical biperiodic structure. The proposed modeling approach is restricted to the hexagonal case of bi-periodicity in which the hexagonal cell can be divided onto three rhombus parts with different thermal properties. Considerations deal with anisotropic conductors.
4
Content available Boundary effect behavior in the hexagonal-type biperiodic structures with rotational symmetry
Mazewska M., Kula D., Wierzbicki E.
Journal of Applied Mathematics and Computational Mechanics
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2014
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Vol. 13, nr 2
73--85
EN
The report presents a study of the thermal boundary effect behaviour in the hexagonal-type rigid conductors. Every hexagonal cell of the conductor is made of three rhombus parts. Some special cases of a considered conductor with rhombus parts built of two layers of different isotropic material are analyzed. The tolerance averaging approach is used as a tool of modeling. The most important result of the paper is specification of parameters which determine the character and the intensity of the boundary effect behavior. Introduced in the contribution the boundary effect intensity parameter is suggested to be treated as a certain measure of the intensity of boundary effect behavior.
5
Content available Correlation of parameters describing microstructure of hardened cement slurry for the purpose of increasing tightness of cement mantle
Kremieniewski M., Stryczek S., Wiśniowski R.
AGH Drilling, Oil, Gas
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2014
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Vol. 31, no. 3
413--421
EN
The results of laboratory experiments on fresh cement slurries are presented in this paper. The samples of hardened cement slurry were hydrated for 28 days in wellbore-like conditions and then analyzed for parameters describing their microstructure. The obtained results created a basis for a correlation analysis of parameters of microstructure of hardened cement slurries. The dependences having the big-gest effect on increasing the tightness of the cement mantle were also addressed to.
6
Content available Reduction of boundary effect during structural damage identification using wavelet transform
Katunin A.
Selected Engineering Problems
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2012
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nr 3
97--102
EN
The wavelet transform seems to be effective tool for signal processing of modal data in the problems of structural damage detection and identification. However, the application of wavelet transform is connected with the occurrence of boundary effect, which may cause wrong conclusion about damage localization. In the following paper the problem of boundary effect was discussed and the methods of its reduction were presented. A comparative study of different approaches of the boundary effect reduction was performed and its results were analyzed.
7
On the boundary effect in elastodynamics of laminated solids
Wierzbicki E., Łacińska L.
Zeszyty Naukowe Politechniki Świętokrzyskiej. Nauki Techniczne
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2007
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Z. 6
45-54
EN
The object of the contribution is the analysis of a certain aspects of the boundary effect behaviour in elastodynamics of FGM-type multiphase laminated composites. The aim of the paper is to answer the question what kind of assumptions are enough to be taken into account in the framework of the simplified tolerance model for the elastodynamics of the considered laminates the boundary effect will be observed. The answer to this question is obtained for a certain class of two-phased FGM-type laminates and for tolerance description based on the exclusively one arbitrary shape function.
PL
Przedmiotem rozważań jest analiza zjawisk typu warstwy brzegowej w elastodynamice wielofazowych laminatów z gradacją własności efektywnych. Celem pracy jest odpowiedź na pytanie, przy jakich założeniach przyjętych w ramach uproszczonego tolerancyjnego modelu elastodynamiki takich laminatów efekt brzegowy jest obserwowany. Odpowiedź na to pytanie uzyskano dla pewnej klasy dwufazowych laminatów typu FGM i tolerancyjnego modelu z jedną funkcją kształtu, której postać nie musi być precyzowana dla realizacji celu pracy.
8
Interpretacja badań CPT w komorze kalibracyjnej
Bałachowski L. B.
Prace Naukowe Instytutu Geotechniki i Hydrotechniki Politechniki Wrocławskiej. Konferencje
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2007
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Vol. 76, nr 42
25-32
PL
W referacie oszacowano wpływ warunków brzegowych na opór na wciskanie końcówki CPT w świeżych zasypach z piasku Lubiatowo. Badania przeprowadzono w komorze kalibracyjnej przy stałym naprężeniu bocznym oraz w warunkach braku odkształceń bocznych masywu gruntowego dla piasku średnio zagęszczonego i zagęszczonego. Wyniki badań zestawiono w zależności od składowej pionowej stanu naprężenia. Dodatkowo przeprowadzono badania z zastosowaniem ministożka CPT oraz wykorzystano opór na ostrzu dylatometru. Stwierdzono wyraźny wpływ warunków brzegowych na opór na stożku CPT, zwłaszcza w piasku zagęszczonym i przy niskim poziomie naprężenia w komorze. Oszacowano wartość oporu na stożku niezależnego od wpływu warunków brzegowych.
EN
Estimation of boundary effect on cone resistance in fresh deposits of Lubiatowo Sand. The calibration chamber tests were performed at constant lateral stress or no volume changes condition in lateral cell for medium dense and dense sand. The test results are presented as a function of vertical stress applied. Some additional tests were executed with mini-cone and blade resistance of dilatometer was used in the interpretation. A distinct boundary effect was found, especially in dense sand and for low level of vertical stress applied in the chamber. Free-field value of cone resistance was estimated.
9
Content available remote Boundary and initial fluctuation effect on dynamic behaviour of a laminated solid
Łacińska L., Wierzbicki E.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2005
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Vol. 4, nr 1
110-122
EN
In the paper an approximate description of the evolution of boundary traction fluctuations in the two-component linear-elastic laminates is discussed. In the paper [1] it has been shown that in the framework of the tolerance averaged model of linear elastodynamics of the aforementioned laminates, cf. [2], in the first approximation such evolution is independent of the mean (averaged) displacement. The aim of this contribution is to discuss solutions to the boundary problem formulated in [1].
10
Content available remote Boundary Efects in Dynamics of Laminated Elastic Half-space
Augustowska-Łacińska L.
Vibrations in Physical Systems
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2004
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Vol. 21
59--62
11
Główne problemy w pomiarach mechanicznych właściwości kompozytów włóknistych
Ochelski S.
Inżynieria Materiałowa
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2003
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R. XXIV, nr 1
14--20
PL
Omówiono problemy, z jakimi można się spotkać prowadząc badania doświadczalne właściwości mechanicznych kompozytów włóknistych. W badaniach tych przeważnie zadane są obciążenia, przy których dokonywany jest pomiar odkształceń. W kompozytach włóknistych o strukturze niesymetrycznej, prostemu obciążeniu, jak rozciąganiu, ściskaniu lub ścinaniu nie odpowiadają proste deformacje, jak w przypadku materiałów izotropowych, lecz odkształcenia sprzężone. Analizę efektów sprzężenia odkształceń oparto na zależności pomiędzy siłami i momentami płytowymi, a odkształceniami powierzchni środkowej oraz krzywiznami tej powierzchni.
EN
Some problems one can find doing research into mechanical properties of fibrous composites has been discussed in this paper. Strains measurements has predominantly been made under assumption of occurence of a given load. Unlike isotropic materials the fibrous composites having asymmetrical structure don't respond to the simple load (stretching, compression or shearing) causing typical deformations, but most often produce coupled strains. Analysis of coupled strain effects has been based on the dependence of forces and plate moments and central surface strains as well as their curvatures dependence.
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