Abstracts of papers for

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

vol. 41, no. 3 (2000)

Next issue vol. 41, no. 4 (2000)

Contents of issue 3, vol. 41

1. E. Włodarczyk: Effectiveness of high explosives in shaped charges
2. W. Nasalski: Beam switching at a nonlinear-linear interface
3. Z. Dżygadło, I. Nowotarski, A. Olejnik: Nonlinear, regular and chaotic vibrations of an airfoil with a trailing edge flap in supersonic flow
4. R. Trębiński, A. Jackowski, R. Kajak and L. Szymańczyk: Investigations of the influence of the liner manufacturing precision on the penetration capability of shaped charge jets
5. J. Avsec, M. Marčič: Calculation of thermodynamical properties in liquid-gas region
6. Z. Koruba: Gyroscope dynamics and control in a homing rocket with autonomous system of target location
7. T. Niedziela, A. Stankiewicz: Iterative method of regularization with application of advanced technique for detection of contours
8. T. Niedziela, A. Stankiewicz, R. Szymczak: Multi-resolution method for extraction of characteristic features from contour image
9. R. Ostrowski, J. Marczak and Z. Mierczyk: 1.3mm Nd:YAG laser passively and actively Q-switched
10. E. Ratajewicz-Mikołajczak, J. Sikora, J. Starzyński, S. Wincenciak: Comparison of optimal shape design algorithms

E. Włodarczyk: Effectiveness of high explosives in shaped charges

The formula which defines the effectiveness of high explosives (HE) in shaped charges is derived. Fundamental characteristics of the HE are the following: density r_e, velocity of detonation D_J and effective isentropic exponent of products of detonation (PD) g, as well as the quantities describing the liner, i.e. thickness of its wall g, and density of its material r_l. These parameters determine the value of velocity e₀ of the explosively driven liner elements of shaped charge. The results of calculations show that the most effective HE used in shaped charges are: LX-09 (LX-14) and HMX + Inert. This conclusion agrees with the experimentally obtained data [1-3, 9, 21, 22, 23].

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W. Nasalski: Beam switching at a nonlinear-linear interface

Reflection of a beam incident from a nonlinear Kerr medium at a nonlinear-linear dielectric interface is analysed for incidence close to the critical angle of total internal reflection. The problem is formulated and solved within the frame of a reduced variational technique. The solution obtained is interpreted in terms of aberrationless effects of nonlinear propagation and nonspecular effects of nonlinear reflection.

A bistable switch in the reflected beam power, waist position and diameter, as well as in the beam axis direction, is demonstrated. A position of a bistable loop indicates that the nature of the switch is qualitatively different from that predicted by the plane wave analysis. It is shown that these differences result from self-focusing of the incident and reflected beams, their mutual cross-phase modulation and large nonspecular deformations of the reflected beam.

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Z. Dżygadło, I. Nowotarski, A. Olejnik: Nonlinear, regular and chaotic vibrations of an airfoil with a trailing edge flap in supersonic flow

An airfoil in supersonic flow, having deformable nonlinear supports, is an aeroelastic system for which various types of instability, bifurcations and regular or chaotic motions can appear. The airfoil has three degrees of freedom - that is, plunge displacement, angle of pitch and angle of flap deflection. The stiffness force and moments for all those motions are assumed to be nonlinear ones. The airfoil is subjected to the pressure difference produced by its motion in supersonic flow. Stability and bifurcations occurring in the system, limit cycles of self-excited vibrations and regions of regular or chaotic motions have been investigated. The effect of some parameters of the system on the course of linear and nonlinear vibrations has been studied.

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R. Trębiński, A. Jackowski, R. Kajak and L. Szymańczyk: Investigations of the influence of the liner manufacturing precision on the penetration capability of shaped charge jets

The influence of the liner manufacturing precision on shaped charge jet characteristics and its penetration capability were investigated. Precise measurements of the liner thickness were performed and maximum deviations from the mean thickness were determined. The deviations are accepted as a measure of the liner manufacturing precision. Shaped charges were prepared with liners varying in precision. Maximum values of the lateral jet velocity were determined on the basis of analysis of jet radiographs, and the correlation between them and the liner precision was examined. Depths of jets penetration into the monolithic steel targets were measured and compared with the results of the liner precision measurements. On this basis, some conclusions concerning the influence of the liner precision on the penetration capability of jets were drawn.

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J. Avsec, M. Marčič: Calculation of thermodynamical properties in liquid-gas region

The paper presents the mathematical model used for the computation of thermodynamic functions of state in the liquid and gas domain, with the aid of statistical thermodynamics of Lennard-Jones fluid. To calculate the thermodynamic properties of a real fluid, we used the Johnson-Zollweg-Gubbins model based on the modified Benedict-Webb-Rubin equation of state, the Chunxi-Yigui-Jiufang equation of state based on the simple perturbation theory, and the complex Tang-Tong-Lu model based on the solution of the Ornstein-Zernike equation obtained by means of the perturbation theory. The analytical results are compared with the thermodynamical data, and with the results obtained from classical thermodynamics.

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Z. Koruba: Gyroscope dynamics and control in a homing rocket with autonomous system of target location

The paper presents a mathematical model of space scanning and a detected target tracking in a homing rocket. The optimum programme and stabilising control for an elastically suspended gyroscope, being a drive in the space scanning system, was selected. The dynamics of a controlled gyroscope on elastic suspension at the instant of target detection and the rocket control system switch-on was also investigated.

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T. Niedziela, A. Stankiewicz: Iterative method of regularization with application of advanced technique for detection of contours

This paper proposes a novel iterative method of regularization with application of an advanced technique for detection of contours. To eliminate noises, the properties of convolution of functions are utilized. The method can be accomplished in a simple neural cellular network, which creates the possibility of extraction of contours by automatic image recognition equipment.

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T. Niedziela, A. Stankiewicz, R. Szymczak: Multi-resolution method for extraction of characteristic features from contour image

A method for extraction of characteristic features of objects from digital images is proposed. The characteristic features are connected with angles between the contour segments inside the regions of dimensions determined by the level of resolution. The information on spatial orientation of contour segments is obtained from the behaviour of the image function gradient on the contour. The angles between contour-line segments are determined from the histogram of contour angles respectively for the resolutions selected.

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R. Ostrowski, J. Marczak and Z. Mierczyk: 1.3mm Nd:YAG laser passively and actively Q-switched

The paper presents experimental results of investigation of flashlamp pumped Nd:YAG laser operated at wavelengths l = 1.318 mm, l = 1.338 mm, l = 1.356 mm, l = 1.414 mm and l = 1.444 mm. Thresholds and resonator losses at these lines have been determined. The laser was also operated at line 1.318 mm in the Q-switched mode, both active and passive. In active Q-switching, output pulses up to 29 mJ energy and pulsewidth of 41 ns have been obtained. In passive Q-switching with V³⁺:YAG crystalline saturable absorber, on the other hand, output pulses up to 4.5 mJ energy and 35 ns duration have been generated. Moreover, an intracavity Raman laser producing 1.53 mm radiation when pumped by Nd:YAG laser operated at 1.318 mm is presented. Output Raman pulses up to 10 mJ energy have been obtained. Raman beam cleanup and 36 % energy conversion efficiency have been observed.

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E. Ratajewicz-Mikołajczak, J. Sikora, J. Starzyński, S. Wincenciak: Comparison of optimal shape design algorithms

The paper focuses on the presentation and comparison of the three most popular approaches to the optimal design: the genetic algorithm, application of the artificial neural networks and the classical deterministic optimization. These methods are used to solve a very classical test problem of pure optimal shape design by moving the nodes of the finite element grid. The obtained results are compared.

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