Abstracts of papers for

vol. 41, no. 1 (2000)

Next issue vol. 41, no. 2 (2000)

Contents of issue 1, vol. 41

1. E. Włodarczyk: The intensity of a shock wave created by decomposition of an arbitrary discontinuity
2. E. Włodarczyk: On the shape of the annular detonation wave front
3. R. Fedorowicz: Solution of the second kind boundary - initial problem for the equations describing the transmission of natural gas in large networks
4. A. Chanda, P. K. Das, A.K. De and J. Das: Self-similarity in the decay of homogeneous and isotropic turbulence
5. M. Aleksiejuk, M.A. Knyazev: Polarization of ferroelectric ceramics in alternating field
6. Z. Werner, J. Langner, J. Stanisławski and J. Białoskórski: Detection of microsecond plasma pulses in MW range
7. V.J. Pauk: Heat-balance integral method in solidification problems involving small spatial perturbations
8. J. Owsik, A. Zarwalska, A.F. Kotyuk and M.V. Ulanovsky: Laser emission spectro-analyser - instrument for non-destructive checking and diagnostics

   Brief Notes

9. T. Łukaszewicz and P. Mrozek: Electric properties of the glass-Al joint

E. Włodarczyk: The intensity of a shock wave created by decomposition of an arbitrary discontinuity

It was shown that the intensity of a shock wave created by a decomposition of a discontinuity in configuration A is strictly limited even for extremely high initial pressure in one of two gases being in contact. Furthermore, it was found that extreme parameters of the shock wave are linearly dependent on a Riemann invariant. The problem has obtained no attention as yet. Researchers and engineers dealing with internal ballistics, shock tubes and the theory of shock and detonation waves propagation in mixtures of gases may be able to apply the results of the present paper.

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E. Włodarczyk: On the shape of the annular detonation wave front

The approximate shape was determined analytically of the surface of the spatially two-dimensional detonation wave front, cycle-initiated on the external surface of a cylindrical explosive charge. The results can be applied, among other things, in computer simulation of cumulation processes.

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R. Fedorowicz: Solution of the second kind boundary - initial problem for the equations describing the transmission of natural gas in large networks

The aim of this paper is to compare the solutions of the first and second kind boundary problems with the results of the measurements in large, high-pressure networks. The solution is achieved by the finite difference method with iteration. The work enables the explanation of the small discrepancy between measurement and calculation which takes place for the model with boundary conditions of the first kind. The method of solution is described in [10]. The calculated results are compared with the measured one. Additional difficulties are caused by incompleteness of parameters, such as roughness, gas consumption and delivery.

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A. Chanda, P. K. Das, A.K. De and J. Das: Self-similarity in the decay of homogeneous and isotropic turbulence

Decay of turbulent energy in isotropic and homogeneous conditions has been discussed from the point of view of geometrical and statistical self-similarity. Assuming the presence of self-similar eddies in the inertial subrange, a model of the inertial transfer of turbulent energy in the sense of fractal has been built. A method to extend the model to multifractal formalism has been also suggested.

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M. Aleksiejuk, M.A. Knyazev: Polarization of ferroelectric ceramics in alternating field

The problem of studying the behaviour of polarization for ferroelectric ceramics in the external alternating electric field is considered. For the model of constant dipoles with fixed masses, are presented the analytical expressions for polarization in two cases of large and small damping. The peculiarities of the mechanism of transition from meta-stable multi-domain state in ferroelectric ceramic crystal to a stable one-domain state are shown.

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Z. Werner, J. Langner, J. Stanisławski and J. Białoskórski: Detection of microsecond plasma pulses in MW range

The paper presents the preliminary results of the investigations on the detection of high power plasma pulses. Three types of detectors were examined: pyroelectric sensor, plasma-to-IR radiation converter, and thin film differential thermocouple sensor. The operation of the detectors was studied for microsecond range of the plasma pulse duration. Numerical simulation of the thermal evolution of multi-layer structures was used to optimise the design of the detectors. It is concluded that thermocouple sensors are able to provide the most reliable data. Directions of further development of this kind of sensors are discussed.

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V.J. Pauk: Heat-balance integral method in solidification problems involving small spatial perturbations

The heat-balance integral method is applied to solve the solidification problem involving a small spatial periodic fluctuations in the mold temperature. These initial irregularities lead to perturbations in the temperature field and the planar solidification line. The problem is reduced to linear differential equations for amplitudes of the interface perturbations and solutions are presented in closed forms. The numerical analysis is performed for a sinusoidal perturbation. Presented results show the oscillations in the solidification front as a function of time and parameters of the problem. The stability of an interface between solid and liquid phases is investigated.

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J. Owsik, A. Zarwalska, A.F. Kotyuk and M.V. Ulanovsky: Laser emission spectro-analyser - instrument for non-destructive checking and diagnostics

A portable laser emission spectro-analyser for analysis of chemical constitution of materials is described in the paper and examples of its applications are given.

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T. Łukaszewicz and P. Mrozek: Electric properties of the glass-Al joint

Physical properties of the glass-Al joint were investigated. At an elevated temperature, constant potential difference is established at the joint.
PACS Index number: 77.65.-j

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