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EN
A compliant beam subjected to large deformation is governed by a multifaceted nonlinear differential equation. In the context of theoretical mechanics, solution for such equations plays an important role. Since it is hard to find closed-form solutions for this nonlinear problem and attempt at direct solution results in linearising the model. This paper investigates the aforementioned problem via the multi-step differential transformation method (MsDTM), which is well-known approximate analytical solutions. The nonlinear governing equation is established based on a large radius of curvature that gives rise to curvature-moment nonlinearity. Based on established boundary conditions, solutions are sort to address the free vibration and static response of the deforming flexible beam. The geometrically linear and nonlinear theory approaches are related. The efficacy of the MsDTM is verified by a couple of physically related parameters for this investigation. The findings demonstrate that this approach is highly efficient and easy to determine the solution of such problems. In new engineering subjects, it is forecast that MsDTM will find wide use.
PL
Przedstawiono analizę pionowych drgań własnych masywnej osiowosymetrycznej sztywnej bryły zagłębionej w jednorodnej inercyjnej półprzestrzeni sprężystej. Zespoloną sztywność półprzestrzeni z więzami nałożonymi przez sztywną bryłę otrzymano z rozwiązania mieszanego osiowosymetrycznego zagadnienia brzegowego dynamicznej teorii sprężystości metodą elementów brzegowych w dziedzinie częstości. Część rzeczywista zespolonej sztywności pionowej reprezentuje sztywność i inercję podłoża, część urojona przedstawia tłumienie związane z rozchodzeniem się fal w półnieskończonym ośrodku sprężystym (tłumienie radiacyjne). Współczynniki sztywności i tłumienia półprzestrzeni są funkcjami częstości drgań. Częstość drgań własnych sztywnej bryły z więzami nałożonymi przez inercyjną półprzestrzeń sprężystą jest pierwiastkiem nieliniowego równania charakterystycznego. Analizę drgań własnych przeprowadzono stosując parametry bezwymiarowe: współczynnik zagłębienia bryły w podłożu, współczynnik masy, współczynnik częstości oraz współczynnik tłumienia radiacyjnego. Przedstawiono zależność współczynnika częstości drgań własnych i współczynnika tłumienia od współczynnika masy i współczynnika zagłębienia. Wyznaczono również współczynniki częstości drgań własnych bryły przy pominięciu tłumienia radiacyjnego oraz w przypadku bryły zagłębionej w półprzestrzeni nieinercyjnej, której pionowa sztywność statyczna jest granicą dynamicznego współczynnika sztywności półprzestrzeni przy częstości dążącej do zera. Różnice między współczynnikami częstości reprezentują wpływ tłumienia radiacyjnego oraz inercji półprzestrzeni.
EN
An analysis of vertical eigenvibration of a massive axisymmetric rigid body embedded in a uniform elastic half-space is presented. The complex-value stiffness of the half-space with the constrains imposed by the rigid body has been obtained from the solution of a mixed axisymmetric boundary value problem of the dynamic elasticity by the boundary element metod in the frequency domain. The real part of the complex-valued stiffness represents the stiffnes and interia of the medium while the imaginary part describes the damping due to energy dissipated by waves propagating away from the foundation (radiation damping). Stiffness and damping coefficients of the half-space are frequency dependent. Eigenfrequency of the rigid body with the constrains imposed by the inertial elastic halfspace is the root of nonlinear characteristic equation. The analysis of the eigenvibration has been realized using the dimensionless parameters: embedment ratio, mass ratio, frequency ratio and radiation damping ratio. Variation of dimensionless eigenfrequency and damping ratio with the mass and embedment ratios are presented. Dimensionless eigenfrequencies at neglected radiation damping and in the case of a massless elastic medium are also computed. The differences between the damped and undamped eigenfrequencies represent the effects of radiation damping and interia of the half-space.
EN
The paper presents the strategy for identifying the shape of defects in the domain defined in the boundary value problem modelled by the nonlinear differential equation. To solve the nonlinear problem in the iterative process the PIES method and its ad-vantages were used: the efficient way of the boundary and the domain modelling and global integration. The identification was performed using the genetic algorithm, where in connection with the efficiency of PIES we identify the small number of data required to the defect’s definition. The strategy has been tested for different shapes of defects.
EN
Motivated by the two-step directional Newton method considered by Argyros and Hilout (2010) for approximating a zero X* of a differentiable function F defined on a convex set D of a Hilbert space H, we consider a two-step Newton–Lavrentiev method (TSNLM) for obtaining an approximate solution to the nonlinear ill-posed operator equation F(x)=f, where F : D(F) ⊆ X → X is a nonlinear monotone operator defined on a real Hilbert space X. It is assumed that F(∧x)=f and that the only available data are fδ with ||f- fδ||≤δ. We prove that the TSNLM converges cubically to a solution of the equation F(x)+α(x-x0)= fδ (such solution is an approximation of ∧x) where x0 is the initial guess. Under a general source condition on x0-∧x, we derive order optimal error bounds by choosing the regularization parameter α according to the balancing principle considered by Perverzev and Schock (2005). The computational results provided endorse the reliability and effectiveness of our method.
5
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]
6
Content available remote Matematiceskoe modelirovanie nelinejnoj dinamiki i massoperenosa
EN
In the message the methods of the decision of nonlinear dynamics and mass transfer are presented. The methods are illustrated on examples of a wave liquid films flow, mass transfer in a wave films, and mass transfer involving the inlet portion in different regimes. The laws of occurrence of self-organizing and chaos are submitted.
EN
In the paper, a dynamic analysis of gas-lubricated hybrid circular bearings is made. The mathematical model is the Reynolds equation in unsteady regimes along with the boundary conditions for a multiple connected domain. Within the hypothesis of a periodic relative motion of bearing surfaces, the method of small perturbations is used. The equations of the model are solved numerically using a difference finite method and finally, the curves of variation of the critical mass versus the eccentricity are obtained.
PL
Analiza dynamiki mechanizmów wymaga rozwiązywania nieliniowych równań różniczkowych. Są nimi równania Lagrange ’a , które są równaniami drugiego rzędu. Są nimi równania Lagrange ’a , które są równaniami drugiego rzędu. W postaci tensorowej zapiszemy je następująco [wzór] W szczególnym przypadku, układów o jednym stopniu swobody redukują się one do postaci [2, 3]: [wzór]
EN
Mechanism dynamics analysis demands the solution of the complicated non-linear differential equations. These equations are derived on the basis of Lagrange equations of the second order and they are the tensor equations in the form: [formula] For the systems of single degree of freedom the system of equations (A) is reduced to a single equation in the form: [formula]
10
Content available remote Optimization problems with convex epigraphs. Application to optimal control
EN
For a class of infinite-dimensional minimization problems with nonlinear equality constraints, an iterative algorithm for finding global solutions is suggested. A key assumption is the convexity of the "epigraph", a set in the product of the image spaces of the constraint and objective functions. A convexification method involving randomization is used. The algorithm is based on the extremal shift control principle due to N.N. Krasovskii. An application to a problem of optimal control for a bilinear control system is described.
EN
For an age-dependent model with a dominant age class an w-periodic regime of the population size is sought by means of impulsive perturbations. For both noncritical and critical cases of first order the problem is reduced to operator systems solvable by a convergent simple iteration method.
13
Content available remote Recent advances in solvers for nonlinear algebraic equations
EN
In this paper the performance of four solvers for systems of nonlinear algebraic equations applied to a number of test problems with up to 250 equations is discussed. These problems have been collected from research papers and from the Internet and are often recognized as ``standard'' tests. Solver quality is assessed by studying their convergence and sensitivity to simple starting vectors. Experimental data is also used to categorize the test problems themselves. Future research directions are summarized.
14
Content available remote Finite element method for a nonlinear problem
EN
We consider the nonlinear eigenvalue problem of a nonlinear partial differential equation under Dirichlet boundary condition in a two-dimensional space. The classical solutions are given for rectangular domains. We give numerical solutions obtained by finite element method for the first eigenvalue and eigenfunctions and we analyze the error in the approximate finite element solutions.
15
Content available remote A certain approximate solutions of nonlinear flutter equation
EN
A nonlinear integro-differential flutter equation of a thin airfoil placed in an incompressible flow is solved by two different methods. The first method involves the center-manifold reduction and gives the asymptotic limit cycle amplitude and frequency in terms of power series expansions. The second method replaces the integro-differential equation by an approximate set of first-order ordinary differential equations which are solved by using bifurcation and continuation software package. A comparison of these two methods shows that the domain of a good agreement between them varies significantly depending on the parameters of the problem.
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