Search results for " VR"

Nota bio-bibliografica a: Amo, ergo sum

2021

Bio-bibliographic note relating to Nikiforos Vrettakos

A numerical study of the small dispersion limit of the Korteweg-de Vries equation and asymptotic solutions

2012

Abstract We study numerically the small dispersion limit for the Korteweg–de Vries (KdV) equation u t + 6 u u x + ϵ 2 u x x x = 0 for ϵ ≪ 1 and give a quantitative comparison of the numerical solution with various asymptotic formulae for small ϵ in the whole ( x , t ) -plane. The matching of the asymptotic solutions is studied numerically.

Metaphors in the descriptions of U.S. - Soviet/Russian summits in Newsweek and Novoje vremja

1999

Stationary problems for equation of the KdV type and dynamical r-matrices

1995

We study a quite general family of dynamical $r$-matrices for an auxiliary loop algebra ${\cal L}({su(2)})$ related to restricted flows for equations of the KdV type. This underlying $r$-matrix structure allows to reconstruct Lax representations and to find variables of separation for a wide set of the integrable natural Hamiltonian systems. As an example, we discuss the Henon-Heiles system and a quartic system of two degrees of freedom in detail.

Numerical study of a multiscale expansion of the Korteweg de Vries equation and Painlev\'e-II equation

2007

The Cauchy problem for the Korteweg de Vries (KdV) equation with small dispersion of order $\e^2$, $\e\ll 1$, is characterized by the appearance of a zone of rapid modulated oscillations. These oscillations are approximately described by the elliptic solution of KdV where the amplitude, wave-number and frequency are not constant but evolve according to the Whitham equations. Whereas the difference between the KdV and the asymptotic solution decreases as $\epsilon$ in the interior of the Whitham oscillatory zone, it is known to be only of order $\epsilon^{1/3}$ near the leading edge of this zone. To obtain a more accurate description near the leading edge of the oscillatory zone we present a…

Trivial S-Matrices, Wigner-Von Neumann Resonances and Positon Solutions of the Integrable Nonlinear Evolution Equations

1996

It is well known that the scattering matrix is different from the unit matrix in the case of 1-dimensional Schrodinger operator with smooth rapidly decreasing nonzero potential. This no more true in the case of the slowly decreasing and oscillating potentials for which the absence of scattering is accompanied by the occurrence of the Wigner-von Neumann resonances embedded in the positive absolutely continuous spectrum. Taken as initial conditions in the KdV like integrable partial differential equations these potentials generate interesting family of explicit solutions. Below we will call them positon or multipositon solutions. The interaction of an arbitrary finite number of positons and s…

Some evolution equations arising in physics

1983

In this paper we consider a new series of evolution equations generalizing the Korteweg-deVries (KdV) and Burgers equations, and we report recent advances on these equations together with the physical phenomena where they arise. In particular we consider a generalized Burgers' equation and we sketch a method for solution in series by using the theory of Sobolevskij and Tanabe. Then we study the KdV equation with nonuniformity terms and we describe various physical interpretation of this equation. We consider various particular cases in which varying solitonic solutions exist. Also we sketch a unicity theorem. Finally modified Burgers-KdV equations are considered.

L’evoluzione delle tecniche di rilevamento negli ultimi quindici anni. Il globo celeste di Mattheus Greuter

2011

Un primo rilevamento del globo celeste di Mattheus Greuter è stato effettuato dallo scrivente nel 1994 con l’impiego di tecniche topografiche e fotogrammetriche tradizionali, prima delle operazioni di restauro che hanno restituito al mappamondo il suo aspetto originario. Nel mese di giugno di quest’anno è stato eseguito un secondo rilevamento con l’impiego delle tecniche più recenti (laser scanning, fotogrammetria digitale). Il confronto fra i due rilevamenti fornisce interessanti indicazioni per valutare l’evoluzione delle tecniche in questi quindici anni.

Figure dell'immersività

2021

Con l’avvento delle tecnologie digitali si assiste progressivamente al diffondersi del termine immersività. Questo lemma, che ha la sua radice nel latino mergĕre, tuffare, rimanda a forme esperienziali di un corpo completamente avvolto e inglobato, e rende conto di un rapporto con l’immagine, e in generale con l’oggetto di conoscenza, da una dimensione puramente astantiva a una immersiva, in cui l’esperienza si fa presenza (Eugeni 2018). In questa accezione, l’effetto immersivo solleva una serie di questioni che chiamano in causa la dimensione genealogica delle varie forme mediali e le strategie di costruzione dell’esperienza estetica elaborate in seno alla storia delle arti e delle immagin…

I pedikì ilikia kie to travma tu polemu stin piisi kie ta diigimata tu Nikiforu Vrettaku

2021

About Vrettakos' poems and tales about his staying in Trogen (Switzerland)