Search results for "DOMAIN"
showing 10 items of 2485 documents
High resolution x-ray investigation of periodically poled lithium tantalate crystals with short periodicity
2009
Domain engineering technology in lithium tantalate is a well studied approach for nonlinear optical applications. However, for several cases of interest, the realization of short period structures (< 2 ��m) is required, which make their characterization difficult with standard techniques. In this work, we show that high resolution x-ray diffraction is a convenient approach for the characterization of such structures, allowing us to obtain in a nondestructive fashion information such as the average domain period, the domain wall inclination, and the overall structure quality.
A wideband THz Time Domain Spectroscopy table-top system based on ultrafast pulsed laser: Model and experiments
2014
We present an analytical model carefully describing the time-frequency behavior of all the stages composing our whole Terahertz Time Domain Spectroscopy laser based system, from the THz pulses generation via Optical Rectification, to their detection through Electro-Optic Sampling technique, by way of diffraction, collecting and focusing effects. In order to prove the effectiveness of our work, we report on the comparison among the experimental waveforms and the simulation results.
Experimental demonstration of hyperbolic patterns.
2008
We give experimental evidence of hyperbolic patterns in a nonlinear optical resonator. Such transverse patterns are a new kind of 2D dissipative structures, characterized by a distribution of the active modes along hyperbolas in the transverse wave-vector domain, in contrast with the usual (elliptic) patterns where the active modes distribute along rings. The hyperbolic character is realized by manipulating diffraction inside the optical resonator with cylindrical lenses. We also investigate theoretically hyperbolic patterns in corresponding Swift-Hohenberg models.
Wideband THz time domain spectroscopy based on optical rectification and electro-optic sampling
2013
We present an analytical model describing the full electromagnetic propagation in a THz time-domain spectroscopy (THz-TDS) system, from the THz pulses via Optical Rectification to the detection via Electro Optic-Sampling. While several investigations deal singularly with the many elements that constitute a THz-TDS, in our work we pay particular attention to the modelling of the time-frequency behaviour of all the stages which compose the experimental set-up. Therefore, our model considers the following main aspects: (i) pump beam focusing into the generation crystal; (ii) phase-matching inside both the generation and detection crystals; (iii) chromatic dispersion and absorption inside the c…
Unfolding a transmembrane helix dimer: A FRET study in mixed micelles
2009
The exact nature of membrane protein folding and assembly is not understood in detail yet. Addition of SDS to a membrane protein dissolved in mild, non-polar detergent results in formation of mixed micelles and in subsequent denaturation of higher ordered membrane protein structures. The exact nature of this denaturation event is, however, enigmatic, and separation of an individual helix pair in mixed micelles has also not been reported yet. Here we followed unfolding of the human glycophorin A transmembrane helix dimer in mixed micelles by fluorescence spectroscopy. Energy transfer between differently labelled glycophorin A transmembrane helices decreased with increasing SDS mole fractions…
Weakened acute type condition for tetrahedral triangulations and the discrete maximum principle
2000
We prove that a discrete maximum principle holds for continuous piecewise linear finite element approximations for the Poisson equation with the Dirichlet boundary condition also under a condition of the existence of some obtuse internal angles between faces of terahedra of triangulations of a given space domain. This result represents a weakened form of the acute type condition for the three-dimensional case.
The Dirichlet problem for the total variation flow
2001
Suppose that Ω is an open bounded domain with a Lipschitz boundary. The purpose of this chapter is to study the Dirichlet problem $$ \left\{ \begin{gathered} \frac{{\partial u}} {{\partial t}} = div\left( {\frac{{Du}} {{\left| {Du} \right|}}} \right)in Q = \left( {0,\infty } \right) \times \Omega , \hfill \\ u\left( {t,x} \right) = \phi \left( x \right)on S = \left( {0,\infty } \right) \times \partial \Omega , \hfill \\ u\left( {0,x} \right) = u_0 \left( x \right)in x \in \Omega \hfill \\ \end{gathered} \right. $$ (5.1) where u0 ∈ L1(Ω) and ϕ ∈ L1 (∂Ω). This evolution equation is related to the gradient descent method used to solve the problem $$ \begin{gathered} Minimize \int {_\Omega \lef…
Shape optimization for monge-ampére equations via domain derivative
2011
In this note we prove that, if $\Omega$ is a smooth, strictly convex, open set in $R^n$ $(n \ge 2)$ with given measure, the $L^1$ norm of the convex solution to the Dirichlet problem $\det D^2 u=1$ in $\Omega$, $u=0$ on $\partial\Omega$, is minimum whenever $\Omega$ is an ellipsoid.
Multiple positive solutions for singularly perturbed elliptic problems in exterior domains
2003
Abstract The equation − e 2 Δ u + a e ( x ) u = u p −1 with boundary Dirichlet zero data is considered in an exterior domain Ω = R N ⧹ ω ( ω bounded and N ⩾2). Under the assumption that a e ⩾ a 0 >0 concentrates round a point of Ω as e →0, that p >2 and p N /( N −2) when N ⩾3, the existence of at least three positive distinct solutions is proved.
Rough Set Algebras as Description Domains
2009
Study of the so called knowledge ordering of rough sets was initiated by V.W. Marek and M. Truszczynski at the end of 90-ies. Under this ordering, the rough sets of a fixed approximation space form a domain in which every set ↓ is a Boolean algebra. In the paper, an additional operation inversion on rough set domains is introduced and an abstract axiomatic description of obtained algebras of rough set is given. It is shown that the resulting class of algebras is essentially different from those traditional in rough set theory: it is not definable, for instance, in the class of regular double Stone algebras, and conversely.