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1

Mathematical model of single-phase induction motors with auxiliary winding resistance

Malyar V., Malyar A.

Przegląd Elektrotechniczny

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2018

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R. 94, nr 12

33--37

EN

A method and algorithm for computing static curves of single-phase induction motors with an auxiliary winding resistance are proposed. The method relies on a mathematical model of the induction motor that takes into account the magnetic path saturation and current displacement in the rotor bars. The problem is solved as a boundary-value one for the system of differential equations describing the processes in the motor in the differential coordinates axes.

PL

Opisano metodę I algorytm oblicznia zależności statycznej jednofazowego silnika indukcyjnego z pomocniczym uzwojeniem. W modelu matematycznym uwzględniono nasycanie sie obowdu magnetycznego I rozkład prądu w prętach wirnika.

2

A Rough Estimation of Acoustics of the Cuboidal Room with Impedance Walls

Kocan-Krawczyk A., Brański A.

Archives of Acoustics

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2018

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Vol. 43, No. 2

227--233

EN

The cuboidal room acoustics field is modelled with the Fourier method. A combination of uniform, impedance boundary conditions imposed on walls is assumed, and they are expressed by absorption coefficient values. The absorption coefficient, in the full range of its values in the discrete form, is considered. With above assumptions, the formula for a rough estimation of the cuboidal room acoustics is derived. This approximate formula expresses the mean sound pressure level as a function of the absorption coefficient, frequency, and volume of the room separately. It is derived based on the least-squares approximation theory and it is a novelty in the cuboidal room acoustics. Theoretical considerations are illustrated via numerical calculations performed for the 3D acoustic problem. Quantitative results received with the help of the approximate formula may be a point of reference to the numerical calculations.

3

On the uniqueness conditions and bifurcation criteria in coupled thermo-elasto-plasticity

Śloderbach Z.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 1

199--227

EN

The global and local conditions of uniqueness and the criteria excluding a possibility of bifurcation of the equilibrium state for small strains are derived. The conditions and criteria are derived analyzing the problem of uniqueness of solution of the basic incremental boundary problem of coupled generalized thermo-elasto-plasticity. This paper is a continuation of some previous works by the author, but contains new derivation of the global and local criteria excluding a possibility of bifurcation of the equilibrium state for a comparison body dependent on statically admissible fields of stress velocity. All the thermal elastoplastic coupling effects, non-associated laws of plastic flow and influence of plastic strains on thermoplastic properties of a body were taken into account in this work. Thus, the mathematical problem considered here is not a self-conjugated problem. The paper contains four Appendices A, B, C and D where the local necessery and sufficient conditions of uniqueness have been derived.