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EN
The generalized conditional symmetry method is useful tool in finding symmetry reductions and constructing exact solutions of some nonlinear evolution equations. This paper considers a general form of the equation u,= K(t,u,ux), where the subscripts denote differentiation with respect to indicated variables. The construction of some exact solutions of the nonlinear diffusion equation with power law diffusivity is investigated by using the generalized conditional symmetry approach.
PL
Ważna metodą w badaniu nieliniowych równań różniczkowych cząstkowych jest podejście oparte na koncepcji uogólnionej symetrii warunkowej. Celem pracy jest zaprezentowanie jednolitego ujęcia zagadnienia w celu znalezienia nowych, ściłych rozwiązań nieliniowego równania ewolucyjnego postaci u = K(t,u,ux), gdzie indeksy oznaczają różniczkowanie względem wskazanych zmiennych. Wykorzystując metodę uogólnionej symetrii warunkowej znaleziono przykładowe, scisłe rozwiązanie nieliniowego równania dyfuzji z potęgowym współczynnikiem dyfuzji.
2
100%
Open Physics
|
2014
|
tom 12
|
nr 12
830-835
EN
We present exact analytical results for bright and dark solitons in a type of one-dimensional spatially inhomogeneous nonlinearity. We show that the competition between a homogeneous self-defocusing (SDF) nonlinearity and a localized self-focusing (SF) nonlinearity supports stable fundamental bright solitons. For a specific choice of the nonlinear parameters, exact analytical solutions for fundamental bright solitons have been obtained. By applying both variational approximation and Vakhitov-Kolokolov stability criterion, it is found that exact fundamental bright solitons are stable. Our analytical results are also confirmed numerically. Additionally, we show that a homogeneous SF nonlinearity modulated by a localized SF nonlinearity allows the existence of exact dark solitons, for certain special cases of nonlinear parameters. By making use of linear stability analysis and direct numerical simulation, it is found that these exact dark solitons are linearly unstable.
3
Content available remote Dynamics of Shallow Water Waves with Various Boussinesq Equations
100%
EN
Attempt has been made to construct the solitary waves and shock wave solutions or domain walls (in higher dimension) for various Boussinesq equations. The method of undetermined coefficients have been used to explore the exact analytical solitary waves and shock wave solutions in terms of bell-shaped sech^p function and kink-shaped tanh^p function for the considered equations. The Boussinesq equation in the (1+1)-dimensional, the (2+1)-dimensional and the (3+1)-dimensional equations are studied and the parametric constraint conditions and uniqueness in view of both solitary waves and shock wave solutions are determined. Such solutions can be valuable and desirable for explaining some nonlinear physical phenomena in nonlinear science described by the Boussinesq equations. The effect of the varying parameters on the development of solitary waves and shock wave solutions have been demonstrated by direct numerical simulation technique.
EN
The velocity field corresponding to the unsteady motion of a viscous fluid between two side walls perpendicular to a plate is determined by means of the Fourier transforms. The motion of the fluid is produced by the plate which after the time t = 0, applies an oscillating shear stress to the fluid. The solutions that have been obtained, presented as a sum of the steady-state and transient solutions satisfy the governing equation and all imposed initial and boundary conditions. In the absence of the side walls they are reduced to the similar solutions corresponding to the motion over an infinite plate. Finally, the influence of the side walls on the fluid motion, the required time to reach the steady-state, as well as the distance between the walls for which the velocity of the fluid in the middle of the channel is unaffected by their presence, are established by means of graphical illustrations.
5
Content available remote Exact N-envelope-soliton solutions of the Hirota equation
100%
EN
We discuss some properties of the soliton equations of the type ś u/ś t = S[u, u], where S is a nonlinear operator differential in x, and present the additivity theorems of the class of the soliton equations. On using the theorems, we can construct a new soliton equation through two soliton equations with similar properties. Meanwhile, exact N-envelope-soliton solutions of the Hirota equation are derived through the trace method.
EN
A method for obtaining the exact solution for the total variation denoising problem of piecewise constant images in dimension one is presented. The validity of the algorithm relies on some results concerning the behavior of the solution when the parameter λ in front of the fidelity term varies. Albeit some of them are well-known in the community, here they are proved with simple techniques based on qualitative geometrical properties of the solutions.
EN
This paper deals with the longitudinal flow of a generalized Maxwell fluid in an infinite circular cylinder, due to the longitudinal variable time-dependent shear stress that is prescribed on the boundary of the cylinder. The fractional calculus approach in the constitutive relationship model of a Maxwell fluid is introduced. The velocity field and the resulting shear stress are obtained by means of the Laplace and finite Hankel transforms and satisfy all the imposed initial and boundary conditions. The solutions corresponding to ordinary Maxwell fluids as well as those for Newtonian fluids are obtained as limiting cases of our general solutions. Finally, the influence of the fractional coefficient on the velocity and shear stress of the fluid is analyzed by graphical illustrations.
8
Content available remote Solving nonlinear evolution equation system using two different methods
88%
EN
This paper deals with constructing more general exact solutions of the coupled Higgs equation by using the (G0/G, 1/G)-expansion and (1/G0)-expansion methods. The obtained solutions are expressed by three types of functions: hyperbolic, trigonometric and rational functions with free parameters. It has been shown that the suggested methods are productive and will be used to solve nonlinear partial differential equations in applied mathematics and engineering. Throughout the paper, all the calculations are made with the aid of the Maple software.
EN
This paper deals with a class of free vibrations for a two-span, two-lane steel-concrete bridge. The deck structure is modeled as a thin, homogeneous, orthotropic plate stiffened by beams running along the longitudinal direction of the bridge. The method of separation of variables is used to find exact solutions for a class of free vibrations of the structure. A comparison between analytical and experimental natural frequencies and vibration modes of the bridge is presented and discussed.
PL
Praca dotyczy analizy pewnej klasy drgań swobodnych dwuprzęsłowego, dwujezdniowego mostu stalowo-betonowego. Przęsło zamodelowano jako cienką, jednorodną, ortotropową płytę usztywnioną belkami zamocowanymi w kierunku wzdłużnym mostu. Do znalezienia dokładnych rozwiązań problemu drgań swobodnych modelu zastosowano metodę rozdzielenia zmiennych. Na koniec zaprezentowano i przedyskutowano porównanie częstości własnych i postaci drgań własnych modelu z wynikami zarejestrowanymi na rzeczywistej konstrukcji.
EN
In analyzing the contact behavior of a material indented by a moving punch, of much importance are the contributions of the moving velocity and material property. The present paper develops a smoothly moving contact model for orthotropic materials indented by a rigid punch. Based on fundamental solutions of each eigenvalue case, the mixed boundary-value problem is reduced to a Cauchy type singular integral equation by applying the Galilean transformation and Fourier transform. Particularly, the exact solution of the obtained singular integral equation is presented, and closed-form expressions of the physical quantities are given for a flat punch and a cylindrical punch. Figures are plotted to show the influences of the moving velocity, material properties and other loadings on the contact behaviors and to reveal the surface damage mechanism, which may provide useful guidelines for material’s designing and optimization.
11
75%
Open Physics
|
2013
|
tom 11
|
nr 3
279-290
EN
The one-dimensional Schrödinger’s equation is analysed with regard to the existence of exact solutions for decatic polynomial potentials. Under certain conditions on the potential’s parameters, we show that the decatic polynomial potential V (x) = ax 10 + bx 8 + cx 6 + dx 4 + ex 2, a > 0 is exactly solvable. By examining the polynomial solutions of certain linear differential equations with polynomial coefficients, the necessary and sufficient conditions for corresponding energy-dependent polynomial solutions are given in detail. It is also shown that these polynomials satisfy a four-term recurrence relation, whose real roots are the exact energy eigenvalues. Further, it is shown that these polynomials generate the eigenfunction solutions of the corresponding Schrödinger equation. Further analysis for arbitrary values of the potential parameters using the asymptotic iteration method is also presented.
Open Physics
|
2013
|
tom 11
|
nr 8
984-994
EN
Some new conservation laws for the transient heat conduction problem for heat transfer in a straight fin are constructed. The thermal conductivity is given by a power law in one case and by a linear function of temperature in the other. Conservation laws are derived using the direct method when thermal conductivity is given by the power law and the multiplier method when thermal conductivity is given as a linear function of temperature. The heat transfer coefficient is assumed to be given by the power law function of temperature. Furthermore, we determine the Lie point symmetries associated with the conserved vectors for the model with power law thermal conductivity.
13
Content available remote Exact solutions for unsteady incompressible viscous fluid flows
75%
EN
Two-dimensional, unsteady, laminar equations of motions of an incompressible fluid with variable viscosity are considered. The problem investigated is the flow for which the vorticity distribution is proportional to the stream function perturbed by a generalized uniform stream making an angle with the positive x-axis. Employing transformation variables, the goveming Navier-Stocks Equations (NSE) are transformed into steady state equations and then simple ordinary differential equations and a class of exact solutions are obtained. Several graphs of physical interest of streamline are also displayed and discussed.
EN
We study the time-dependent Schrödinger equation (TDSE) with an effective (position-dependent) mass, relevant in the context of transport phenomena in semiconductors. The most general form-preserving transformation between two TDSEs with different effective masses is derived. A condition guaranteeing the reality of the potential in the transformed TDSE is obtained. To ensure maximal generality, the mass in the TDSE is allowed to depend on time also.
EN
Using appropriate transformations, the differential equations of free longitudinal vibration of bars with variably distributed mass and axial stiffness are reduced to Bessel?s equations or ordinary differential equations with constant coefficients by selecting suitable expressions, such as power functions and exponential functions, for the distributions of mass and axial stiffness. Exact analytical solutions to determine the longitudinal natural frequencies and mode shapes for a one step non-uniform bar are derived and used to obtain the general solution and the frequency equation of a multi-step non-uniform bar with various boundary conditions, including non-classical cases. This approach which combines the transfer matrix method and closed form solutions of one step bars leads to a single frequency equation for any number of steps.
16
Content available remote Exact solutions to an incompressible second-grade fluid flow equations
63%
EN
Employing complex variables and complex functions the exact solutions to equations governing the motion of an incompressible second-grade fluid are determined.
EN
The procedure of integrating the third-order Chazy differential equation with six singularities is presented, when the first six coefficients are equal to ±1/2, ± 1, ± 2. For five third-order differential equations it is shown that their general solutions are expressed via the elliptic functions. Two-parameter families of solutions in elliptic functions and one-parameter families of solutions in elementary functions are presented. The proposed integration method can be realized for the differential Chazy equation in those cases when the first six coefficients have values for which it is possible to solve a special algebraic equation of the fifth degree in radicals.
PL
W artykule rozpatrzona została metoda rozwiązania równania różniczkowego Chazy’ego trzeciego rzędu, zawierającego sześć osobliwości w przypadku, gdy sześć pierwszych współczynników równa się ± 1/2, ± 1, ± 2. Dla pięciu równań różniczkowych trzeciego rzędu znaleziono ich ogólne rozwiązania za pomocą funkcji eliptycznych. Przedstawione zostały rodziny rozwiązań dwuparametrycznych za pomocą funkcji eliptycznych oraz rodziny rozwiązań jednoparametrycznych za pomocą funkcji elementarnych. Proponowana metoda rozwiązania może być zrealizowana dla równania różniczkowego Chazy’ego w tych przypadkach, gdy pierwsze sześć współczynników ma wartości, dla których istnieje możliwość rozwiązania szczególnego równania algebraicznego piątego stopnia za pomocą pierwiastków.
EN
In the article the combined algorithm for finding conservation laws and implectic operators has been proposed. Using the Novikov-Bogoyavlensky method the finite dimensional reductions have been found. The structure of invariant submanifolds has been examined. Having analyzed phase portraits of Hamiltonian systems, partial periodical solutions have been found.
EN
In the current paper some applications of the packet MAPLE (v. 9.5) for analytic solying of certain nonline partial differential eguations have been presented. Additionally, for graphic presentation of the found solutions packet MATHEMATICA (v. 5.1) has been applied.
PL
W niniejszej pracy zostały przedstawione zastosowania pakietu MAPLE (wersja 9.5 do analitycznego znajdywania rozwiązań wybranych nieliniowych równań różniczkowych cząstkowych. Do prezentacji graficznej tych rozwiązań użyto pakietu MATHEMATICA (wersje 5.1).
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