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EN
This paper describes a question of evaluation necessity of bridge cranes using the method of limit deformation state and oscillation damping. The solution was performed by means of theoretical analysis and an experimental verification at the selected bridge crane. The final result sounds that in the case of a correct strength computing of given bridge crane, it is not necessary to also check deformation and damping of oscillation as well.
EN
The working process and regularities of the functioning of vibrating and vibro-impact machines based on hydroimpulse drive with a singlestage valve pulser are analyzed. The essential characteristics determining the conditions for the excitation and existence of periodic oscillations of the valve-pulser shut-off valve are determined. Using the criterion of A. Hurwitz, based on the differential equation of motion, the existence of undamped periodic oscillations of the valve-pulser shut-off valve is analytically justified.
PL
Przeanalizowano działanie i regularność pracy maszyn wibracyjnych oraz maszyn poddawanych wibracjom opartych na napędzie hydro-impulsowym z jednostopniowym zaworem impulsowym. Określono podstawowe cechy wpływające na warunki wzbudzenia oraz występowania drgań okresowych zaworu impulsowego. Przy zastosowaniu kryterium A. Hurwitza, opartego na równaniu różniczkowym ruchu, istnienie nietłumionych drgań okresowych zaworu impulsowego jest analitycznie uzasadnione.
EN
This paper deals with the oscillation of a certain class of second order difference equations with a sub-linear neutral term. Using some inequalities and Riccati type transformation, four new oscillation criteria are obtained. Examples are included to illustrate the main results.
4
EN
The springing support in a driver’s seat is a very serious issue, such that manufacturers are increasing their efforts to optimize the dynamic properties of this kind of seat. The main optimization criterion is vibration insulation efficiency with regard to health research and associated health standards and regulations. This article deals with the definition of the optimal driver’s seat properties in relation to two examples of springing systems with different kinds of damping. The first case involves the springing support of a driver’s seat that uses a pneumatic spring and a telescopic hydraulic damper. In the second case, the damping effect is achieved by two pneumatic springs whose forces effect a phase shift due to a throttle valve located in the connecting piping system.
5
Content available remote Oscillation of higher-order half-linear neutral differential equations
EN
In this paper, we establish some new oscillation criteria for the higher-order half-linear neutral differential equation (…). An example is given to illustrate the main results.
EN
An unsteady hydromagnetic Couette flow of class-II of a viscous incompressible electrically conducting fluid in a rotating system is studied. The fluid flow within the channel is induced due to non-torsional oscillations of the upper plate of the channel. An exact solution of the governing equations is obtained by the Laplace transform technique. The numerical solution of the fluid velocity is depicted graphically whereas numerical values of shear stress at the plates are presented in a tabular form for various values of the magnetic parameter, rotation parameter and frequency parameter.
EN
An oscillatory MHD convective and mass transfer flow of an electrically conducting, viscous, incompressible fluid in a rotating porous channel filled with a porous medium has been analyzed. Effects of radiation and chemical reaction are also considered. The two porous plates are subjected to a constant injection and suction. It is considered that the influence of the uniform magnetic field acts normal to the flow. The entire system rotates about an axis normal to the planes of the plates with uniform angular velocity [...]. Expressions for velocity, temperature, concentration, and amplitude and phase angle of skin-friction, the Nusselt number and Sherwood number are obtained. The results obtained for velocity are discussed for small (...) and large (...) rotation of the channel with the help of graphs.
EN
A class of third-order nonlinear neutral differential equation (r(t)(y"(t)) α)' + q(t) f(x(σ (t))) = 0 is investigated in this paper, where y(t) = x(t) + p(t)x(?(t)), and ? > 0 is any quotient of odd integers. Using a new method, we obtain some sufficient conditions for the oscillation of the above equation, and some known oscillation criteria be extended. An example is inserted to illustrate the result.
9
Content available remote Exact solution of an oscillatory MHD flow in a channel filled with porous medium
EN
An exact solution of an oscillatory MHD flow of a viscous, incompressible and electrically conducting fluid in an infinite horizontal channel is presented. The channel is filled with a porous medium and a magnetic field is applied perpendicular to the plates of the channel. During the analysis it is found that the mathematical formulation and the solution obtained of the problem by Makinde and Mhone (2005) are both wrong. Equations (2.1) to (2.4) do not govern the flow problem shown geometrically in their Fig.1. This important flow problem is again formulated mathematically in the present paper and a fresh and a correct closed form analytical solution is obtained. The validity and correctness of the present solution is verified by the limiting case for H=s=0. In this case of oscillatory flow in the absence of a magnetic field and through ordinary medium the solution reduces to the well known result obtained by Schlichting and Gersten (2001). The results are discussed in detail with the help of graphs for the variations of different flow parameters.
EN
Effects of Hall current on an unsteady hydromagnetic Couette flow, induced due to an accelerated movement of the lower plate of the channel in a rotating system when the fluid flow is permeated by an inclined magnetic field is studied. An exact solution for the fluid velocity is obtained by the Laplace transform technique. The expression for the shear stress at the moving plate is also derived. An asymptotic behavior of the solution is analyzed for small and large values of time to gain some physical insight into the flow-pattern. It is found that Hall current, rotation and angle of inclination of the magnetic field tend to accelerate fluid flow in both the primary and secondary flow directions, whereas the magnetic field has a tendency to retard fluid flow in both the primary and secondary flow directions.
EN
This article presents the generation of the oscillation of [alfha, beta, ghama] rhythms which is directly connected with mutual correlations that occur between populations of pyramidal cells and interneurons. The significance of the oscillation of particular rhythms in the universal EEG signal is described. It is especially helpful during creating population models of this signal, which demonstrates its stochastic nature.
12
Content available remote Eliminacja oscylacji w układzie zasilania pojazdu trakcyjnego
PL
W artykule przedstawiona została nowa metoda sterowania układem napędowym z silnikiem indukcyjnym, umożliwiająca eliminację oscylacji napięcia na kondensatorze obwodu pośredniczącego falownika zasilanego z tramwajowej lub trolejbusowej sieci trakcyjnej. Zaburzenia tego typu są charakterystyczne dla układów trakcyjnych, w których jest stosowany wejściowy filtr RLC o słabym tłumieniu. W artykule zostały zamieszczone rozważania teoretyczne i badania symulacyjne potwierdzające skuteczność proponowanej metody.
EN
In this article the new method of power supply voltage oscillation elimination was presented. These types of disturbances are typical in voltage converter fed traction vehicle with low dumped RLC input filter. Analytical approach and simulation results showing efficiency of proposed method was included.
EN
Modern methods of motor drives control are ought to be high precision and quality. This quality is achieved through a rapid and accurate realization of given electromagnetic torque which is insensitive to inverter voltage changes. As a result of using such control methods, a whole system can be considered as an element on constant power for constant angular velocity of the rotor, which leads to occurrence of negative admittance in presence of voltage changes. When an inverter input filter has a high inductance value, negative admittance leads to the excitation of input filter voltage oscillations, whose amplitude often exceeds 50% of nominal voltage. Such a perturbations of inverter voltage can lead to unstable work of electric drive or to damaging one of the inverter elements. The article outlined a method for stabilizing an inverter voltage, through an additional admitance which compensates an unstable component of system. Theoretical considerations and practical algorithm are included. As confirmation of the high efficiency of the proposed algorithm, article contains computer simulation, tests and results.
EN
In this paper, we will establish some oscillation criteria for the third-order neutral delay differential equations (x(t) - a(t)x(τ (t)))''' + p(t)x(δ (t)) = 0, t ≥ t 0. To the best of our knowledge nothing is known regarding the qualitative behavior of these equations. Our results in this paper extend the results given in [Hanan, Oscillation criteria for third order differential equations, Pacific J. Math. 11 (1961) 919-944]. Some examples are considered to illustrate the main results.
EN
In this paper, oscillatory and asymptotic property of solutions of a class of nonlinear neutral delay differential equations of the form (E) ...[wzór] and ...[wzór] are studied under the assumptions ...[wzór] and ...[wzór] for various ranges of p(t). Sufficient conditions are obtained for existence of bounded positive solutions of (E).
EN
In this paper we obtain oscillation criteria for solutions of homogeneous and nonhomogeneous cases of second order neutral differential equations with positive and negative coefficients. Our results improve and extend the results of Manojlović, Shoukaku, Tanigawa and Yoshida [6].
17
Content available remote Oscillation criteria for third order nonlinear difference equations
EN
We shall establish some new criteria for the oscillation of third order nonlinear difference equations of the form ...[wzór]
18
Content available remote On the dynamics of the difference equation xn+1 = ...[wzór]
EN
This paper studies the global behavior of the difference equation xn+1 = ...[wzór], n = 0, 1, 2, ... with non-negative parameters and non-negative initial conditions where k is an odd number.
19
Content available Hybrid drive vibration sources analysis
EN
The paper is an introductory session dedicated to the sources of vibrations in a hybrid drive, which is meant to propel special tracked vehicle. The analysis was performed according to stand test results of a hybrid drive. It is aimed on individual modes of operation and modes ensuing from cooperation of diesel drive and electric drive.
20
Content available remote Recent investigations in dynamics of continuous systems subjected to moving load
EN
The paper is devoted to the study of continuous systems subjected to moving loads. Several cases of dynamical problems are considered, where the motion of elastically supported beams are excited by a moving concentrated force. In particular, we study interactions with periodic structure of the medium. Earlier results on one-dimensional structures are extended to the case of a set of plates.
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