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Wyniki wyszukiwania dla: COLORECTAL SURGERY
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Gdańsk University of Technology graduates’ length of the labour inactivity period after graduation – years 2014-2018
Dane BadawczeThe dataset includes data from the survey on the Gdańsk University of Technology graduates from years 2014-2018 on length of the labour inactivity period after graduation. The survey was conducted in the period from 2016 to 2020, two years after the respondents obtained graduate status. The research sample included 9413 respondents. To summarize, the...
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Time period when graduates of Gdańsk University of Technology start work after graduation – years 2015-2018
Dane BadawczeThe dataset includes data from the survey on the Gdańsk University of Technology graduates from years 2015-2018 on time period when they start work after graduation. The survey was conducted in the period from 2017 to 2020, two years after the respondents obtained graduate status. The research sample included 7409 respondents. To summarize, the Gdańsk...
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Gdańsk University of Technology graduates’ assessment of individual elements of education in the completed field of study – years 2015-2016
Dane BadawczeThe dataset includes data from the survey on the Gdańsk University of Technology graduates' from the years 2015-2016 on their assessment of individual elements of education in the completed field of study. The survey was conducted in the period from 2017 to 2018, two years after the respondents obtained graduate status. The research sample included...
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Gdańsk University of Technology graduates’ assessment of individual elements of education in the completed field of study – years 2017-2018
Dane BadawczeThe dataset includes data from the survey on the Gdańsk University of Technology graduates' from the years 2017-2018 on their assessment of individual elements of education in the completed field of study. The survey was conducted in the period from 2019 to 2020, two years after the respondents obtained graduate status. The research sample included...
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Quantum corrections to quasi-periodic solution of Sine-Gordon model and periodic solution of phi^4 model
PublikacjaAnalytical form of quantum corrections to quasi-periodic solution of Sine-Gordon model and periodic solution of phi^4 model is obtained through zeta function regularisation with account of all rest variables of a d-dimensional theory. Qualitative dependence of quantum corrections on parameters of the classical systems is also evaluated for a much broader class of potentials u(x) = b^2 f(bx) + C with b and C as arbitrary real constants
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Problem of proper decomposition and initialization of acoustic and entropy modes in a gas affected by the mass force
PublikacjaThe relations connecting perturbations specific for acoustic and entropy modes in an accelerated fluid or in a fluid affected by constant mass force, are derived. They allow to decompose the total vector of perturbations and the overall energy into acoustic and non-acoustic parts uniquely at any instant. In order to do this, three quantities are required, for example total perturbations in entropy, pressure and velocity. The evaluations...
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On analytical solution of stationary two dimensional boundary problem of natural convection
PublikacjaApproximate analytical solution of two dimensional problem for sta- tionary Navier-Stokes, continuity and Fourier-Kirchho equations describ- ing free convective heat transfer from isothermal surface of half innite vertical plate is presented. The problem formulation is based on the typ- ical for natural convection assumptions: the uid noncompressibility and Boussinesq approximation. We also assume that orthogonal to the plate component...
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Green function diagonal for a class of heat equations
PublikacjaA construction of the heat kernel diagonal is considered as element of generalized zeta function theory, which gradient at the origin defines determinant of a differential operator in a technique for regularizing quadratic path integral. Some classes of explicit expressions of the Green function in the case of finite-gap potential coefficient of the heat equation are constructed. An algorithm and program for Mathematica are presented...
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Quantum corrections to phi^4 model solutions and applications to Heisenberg chain dynamics
PublikacjaThe Heisenberg spin chain is considered in φ^4 model approximation. Quantum corrections to classical solutions of the one-dimensional φ^4 model within the correspondent physics are evaluated with account of rest d−1 dimensions of a d-dimensional theory. A quantization of the model is considered in terms of spacetime functional integral. The generalized zeta-function formalism is used to renormalize and evaluate the functional integral...
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Quantum corrections to 4 model solutions and applications to Heisenberg chain dynamics
PublikacjaThe Heisenberg spin chain is considered in φ^4 model approximation. Quantum corrections to classical solutions of the one-dimensional φ^4 model within the correspondent physics are valuated with account of rest d − 1 dimensions of a d-dimensional theory. A quantization of the model is considered in terms of space- time functional integral. The generalized zeta-function formalism is used to renormalize and evaluate the functional...
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Study of free convective boundary layer of isothermal lateral surface of axisymmetrical horizontal body
PublikacjaPrzedstawiono rozwiązanie równań Naviera-Stokesa i Fouriera-Kirchhoffa we współrzędnych tau i sigma. Pierwsza jest styczną a druga normalną do konwekcyjnych linii prądu, wzdłuż jakich porusza się ogrzany od powierzchni płyn. Wynik w postaci równania na grubość warstwy przyściennej zweryfikowano dla granicznych przypadków ciała obrotowego o poziomej osi symetrii (stożka poziomego i kołowej pionowej płyty).
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Coupled nonlinear Schrödinger equations in optic fibers theory
PublikacjaIn this paper a detailed derivation and numerical solutions of CoupledNonlinear Schr¨odinger Equations for pulses of polarized electromagnetic wavesin cylindrical fibers has been reviewed. Our recent work has been compared withsome previous ones and the advantage of our new approach over other methods hasbeen assessed. The novelty of our approach lies is an attempt to proceed withoutloss of information within the frame of basic...
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Mode interaction in few-mode optical fibres with Kerr effect
PublikacjaUogólnioną metodę rzutowania do ortogonalnej bazy funkcji poprzecznej współrzędnej Bessela stosuje się do wyprowadzania układów równań nieliniowych Schrodingera. Teoria jest ważna dla paczek falowych w światłowodach i kilku modelach.
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On convergence and stability of a numerical scheme of Coupled Nonlinear Schrödinger Equations
PublikacjaRozważamy rozwiązania numeryczne układu sprężynowych równań nieliniowych Schrödingera. Udowodniliśmy stabilność i zbieżność. Testujemy za pomocą rozwiązań solitonowych.
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Ultrashort Opposite Directed Pulses Dynamics with Kerr Effect and Polarization Account
PublikacjaWe present the application of projection operator methods to solving the problem of the propagation and interaction of short optical pulses of different polarizations and directions in a nonlinear dispersive medium. We restrict ourselves by the caseof one-dimensional theory, taking into account material dispersion and Kerr nonlinearity. The construction of operators is delivered in two variants: for the Cauchy problem and for the...
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Novel Analytic-Numerical Model of Free Convection: with Leading Edge Considered
PublikacjaA novel solution of the free convection boundary problem is represented in analytical form for velocity and temperature for an isothermal vertical plate, as an example. These fields are built as a Taylor Series in the x coordinate with coefficients as functions of the vertical coordinate (y). We restrict ourselves by cubic approximation for both functions. The basic Navier-Stokes and Fourier-Kirchhoff equations and boundary conditions...
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Chaotic modes of systems described by the Liénard equations with a large period of the right-hand side and impact conditions
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Stability by linear approximation for time scale dynamical systems
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Grazing bifurcation and chaotic oscillations of vibro-impact systems with one degree of freedom
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Chaos in vibroimpact systems with one degree of freedom in a neighborhood of chatter generation: II
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Rotating rod and ball
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Constructive Controllability for Incompressible Vector Fields
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The symmetrization method and limit cycles of vibro-impact systems
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A Criterion for Conditional Instability by the First Approximation for Solutions of Differential Systems
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Chaos in vibroimpact systems with one degree of freedom in a neighborhood of chatter generation: I
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Topology of vibro-impact systems in the neighborhood of grazing
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Chaotic invariant sets of vibro-impact systems with one degree of freedom
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Billiard in a rotating half-plane: modeling and dynamics
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Role of Oligosaccharide Chain Polarity in Protein–Glycosaminoglycan Interactions
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Structural stability of invariant sets of vibro-impact systems
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Directed electromagnetic pulse dynamics: projecting operators method
PublikacjaIn this article, we consider a one-dimensional model of electromagnetic pulse propagation in isotropic media, takinginto account a nonlinearity of the third order. We introduce a method for Maxwell's equation transformation on thebasis of a complete set of projecting operators. The operators correspond to wave dispersion branches including thedirection of propagation. As the simplest result of applying the method, we derive a system...
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The equations for interactions of polarization modes in optical fibres including the kerr effect
PublikacjaWe have derived coupled nonlinear Schro¨ dinger equations (CNLSE) for arbitrary polarized light propagation in a single-mode fibre employing electromagnetic field complete description. We used a basis of transverse eigenmodes with appropriate projecting; hence, the nonlinear constants depend on the waveguide geometry. Accounting for a weak nonlinearity, which is connected to the Kerr effect, we have given explicit expressions for...
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Quantum corections to SG equation solutions and applications
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Theoretical consideration of free convective heat transfer from a round isothermal plate slightly inclined from the vertical
PublikacjaA semi-analytical solution of simplified Navier-Stokes and Fourier-Kirchhoff equations describing free convective heat transfer from a round isothermal surface slightly inclined from the vertical is presented. The solution is based on the assumption, typical for natural convection, that the velocity component normal to the surface is negligibly small in comparison to the tangential one. Next we neglect the nonlinear inertia force...
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Experimental study of natural convection heat transfer from horizontal conic
PublikacjaPrzedstawiono badania eksperymentalne i ich wyniki konwekcji swobodnej w wodzie i powietrzu poziomych stożków o kącie przy podstawie 30, 45 i 60 deg. Wyniki badań wykazują dobrą zgodność z rozwiązaniem teoretycznym i z danymi literaturowymi.
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Study of free convective heat transfer from horizontal conic.
PublikacjaPrzedstawiono teoretyczne rozważania i badania eksperymentalne konwekcji swobodnej od izotermicznej powierzchni poziomego stożka w przestrzeni nieograniczonej. Rozwiązanie przeprowadzono dla wprowadzonego krzywoliniowego układu współrzędnych, opartego na krzywej linii prądu wokół powierzchni stożkowej.
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Natural convection from horizontal conic.
PublikacjaPrzedstawiono rozważania teoretyczne konwekcji swobodnej od powierzchni bocznej poziomego stożka.
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Tollmien- Shlichting and sound waves interaction: nonlinear resonances.
PublikacjaRozpatruje się oddziaływanie różnych typów modów hydrodynamicznych w warstwie lepkiej. Stwierdzono możliwość istnienia oddziaływania rezonansowego.Dokładne równania ewolucyjne kierujące dynamiką warstwy lepkiej zostały wypisane.
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A theoretical consideration of a free convective boundary layer on an isothermal horizontal conic.
PublikacjaPrzedstawiono rozwiązanie analityczne naturalnej konwekcji swobodnej od izotermicznego, poziomego stożka o kącie przy podstawie alfa. Rozwiązanie przeprowadzono w oparciu o typowe dla konwekcji swobodnej założenia upraszczające. Rozwiązania dla przypadków granicznych (poziomy walec i pionowa płyta kołowa) wykazują dobrą zgodność z danymi literaturowymi.
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Interaction of vortical and acoustic waves: from general equations to integrable cases
PublikacjaWyprowadzono operatory rzutu przepływu w warstwie lepkiej przyściennej na podstawowe typy ruchów. Wyprowadzono również układy równań dynamicznych sterujących przepływem. Zaproponowano metody analityczne dalszego rozwiązywania tych równań.
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Different types of solvability conditions for differential operators
PublikacjaSolvability conditions for linear differential equations are usually formulated in terms of orthogonality of the right-hand side to solutions of the homogeneous adjoint equation. However, if the corresponding operator does not satisfy the Fredholm property such solvability conditions may be not applicable. For this case, we obtain another type of solvability conditions, for ordinary differential equations on the real axis, and...
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Constructive Controllability for Incompressible Vector Fields
PublikacjaWe give a constructive proof of a global controllability result for an autonomous system of ODEs guided by bounded locally Lipschitz and divergence free (i.e. incompressible) vector field, when the phase space is the whole Euclidean space and the vector field satisfies so-called vanishing mean drift condition. For the case when the ODE is defined over some smooth compact connected Riemannian manifold, we significantly strengthen...
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Linear Time-Varying Dynamic-Algebraic Equations of Index One on Time Scales
PublikacjaIn this paper, we introduce a class of linear time-varying dynamic-algebraic equations (LTVDAE) of tractability index one on ar- bitrary time scales. We propose a procedure for the decoupling of the considered class LTVDAE. Explicit formulae are written down both for transfer operator and the obtained decoupled system. A projector ap- proach is used to prove the main statement of the paper and sufficient conditions of decoupling...
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Topological Behaviour of Solutions of Vibro-Impact Systems in the Neighborhood of Grazing
PublikacjaThe grazing bifurcation is considered for the Newtonian model of vibro-impact systems. A brief review on the conditions, sufficient for the existence of a grazing family of periodic solutions, is given. The properties of these periodic solutions are discussed. A plenty of results on the topological structure of attractors of vibro-impact systems is known. However, since the considered system is strongly nonlinear, these attractors...
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Rotating rod and ball
PublikacjaWe consider a mechanical system consisting of an infinite rod (a straight line) and a ball (a massless point) on the plane. The rod rotates uniformly around one of its points. The ball is reflected elastically when colliding with the rod and moves freely between consecutive hits. A sliding motion along the rod is also allowed. We prove the existence and uniqueness of the motion with a given position and velocity at a certain time...
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Inverse shadowing and related measures
PublikacjaWe study various weaker forms of the inverse shadowing property for discrete dynamical systems on a smooth compact manifold. First, we introduce the so-called ergodic inverse shadowing property (Birkhoff averages of continuous functions along an exact trajectory and the approximating one are close). We demonstrate that this property implies the continuity of the set of invariant measures in the Hausdorff metric. We show that the...
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Weak forms of shadowing in topological dynamics
PublikacjaWe consider continuous maps of compact metric spaces. It is proved that every pseudotrajectory with sufficiently small errors contains a subsequence of positive density that is point-wise close to a subsequence of an exact trajectory with the same indices. Also, we study homeomor- phisms such that any pseudotrajectory can be shadowed by a finite number of exact orbits. In terms of numerical methods this property (we call it multishadowing)...
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Stability by linear approximation for time scale dynamical systems
PublikacjaWe study systems on time scales that are generalizations of classical differential or difference equations and appear in numerical methods. In this paper we consider linear systems and their small nonlinear perturbations. In terms of time scales and of eigenvalues of matrices we formulate conditions, sufficient for stability by linear approximation. For non-periodic time scales we use techniques of central upper Lyapunov exponents...
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One-dimensional chaos in a system with dry friction: analytical approach
PublikacjaWe introduce a new analytical method, which allows to find chaotic regimes in non-smooth dynamical systems. A simple mechanical system consisting of a mass and a dry friction element is considered. The corresponding mathematical model is being studied. We show that the considered dynamical system is a skew product over a piecewise smooth mapping of a segment (the so-called base map). For this base map we demonstrate existence of...
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The saga of a fish: from a survival guide to closing lemmas
PublikacjaIn the paper by D. Burago, S. Ivanov and A. Novikov, “A survival guide for feeble fish”, it has been shown that a fish with limited velocity can reach any point in the (possibly unbounded) ocean provided that the fluid velocity field is incompressible, bounded and has vanishing mean drift. This result extends some known global controllability theorems though being substantially nonconstructive. We give a fish a different recipe...