Modal analysis of deep-etched low-contrast two-port beam splitter grating

Modal analysis of a deep-etched low-contrast two-port beam splitter grating under Littrow Mounting is presented. The guideline for the design of a subwavelength transmission fused-silica phase grating as high-efficiency grating, polarizing beam splitter (PBS), and two-port beam splitter, is summarized. As an example, a polarization-independent two-port beam splitter grating is designed at wavelength of 1064 nm. We firstly analyzed the physical essence of the grating by the simplified modal method. The guideline for the grating design and the approximate grating parameters are obtained. Then using the rigorous coupled-wave analysis (RCWA) with parameters varying around the approximate ones, Optimum grating parameters can be determined. With the design guideline, the time for the rigorous calculation of the grating profile parameters can be reduced significantly. (C) 2008 Elsevier B.V. All rights reserved

Three-port beam splitter of a binary fused-silica grating

A deep-etched polarization-independent binary fused-silica phase grating as a three-port beam splitter is designed and manufactured. The grating profile is optimized by use of the rigorous coupled-wave analysis around the 785 nm wavelength. The physical explanation of the grating is illustrated by the modal method. Simple analytical expressions of the diffraction efficiencies and modal guidelines for the three-port beam splitter grating design are given. Holographic recording technology and inductively coupled plasma etching are used to manufacture the fused-silica grating. Experimental results are in good agreement with the theoretical values. (c) 2008 Optical Society of America.

Relativistic velocity - potential hydrodynamics and stellar stability

The equations of relativistic, perfect-fluid hydrodynamics are cast in Eulerian form using six scalar "velocity-potential" fields, each of which has an equation of evolution. These equations determine the motion of the fluid through the equation

U_ʋ=µ^-1 (ø,_ʋ + αβ,_ʋ + ƟS,_ʋ).

Einstein's equations and the velocity-potential hydrodynamical equations follow from a variational principle whose action is

I = (R + 16π p) (-g)^1/2 d⁴x,

where R is the scalar curvature of spacetime and p is the pressure of the fluid. These equations are also cast into Hamiltonian form, with Hamiltonian density –T₀⁰ (-g^oo)^-1/2.

The second variation of the action is used as the Lagrangian governing the evolution of small perturbations of differentially rotating stellar models. In Newtonian gravity this leads to linear dynamical stability criteria already known. In general relativity it leads to a new sufficient condition for the stability of such models against arbitrary perturbations.

By introducing three scalar fields defined by

ρ ᵴ = ∇λ + ∇x(xi + ∇xɣi)

(where ᵴ is the vector displacement of the perturbed fluid element, ρ is the mass-density, and i, is an arbitrary vector), the Newtonian stability criteria are greatly simplified for the purpose of practical applications. The relativistic stability criterion is not yet in a form that permits practical calculations, but ways to place it in such a form are discussed.

Efeito magnetocalórico em sistemas ferrimagnéticos

Nesta tese, o efeito magnetocalórico é estudado teoricamente partindo de um hamiltoniano modelo que leva em conta uma rede magnética formada por diversas sub-redes magnéticas acopladas. No hamiltoniano são consideradas as interações de troca, Zeeman e magnetoelástica. Primeiramente, o hamiltoniano é apresentado em sua forma generalizada para R sub-redes magnéticas e a influência dos parâmetros do modelo na temperatura de Nèel e na temperatura de compensação é analisada no sistema com duas sub-redes magnéticas. Encontramos que, dependendo dos parâmetros de troca, arranjos ferrimagnético, antiferromagnético e ferromagnéticos podem ser obtidos. O efeito magnetocalórico foi sistematicamente estudado para diversos arranjos possíveis, posteriormente foi estudado em compostos reais do tipo R3Fe5O12 (RIG), sistema formado por três sub-redes magnéticas. Retornando ao sistema com duas sub-redes magnéticas foi analisada a influência da interação magnetoelástica no efeito magnetocalórico nos arranjos ferrimagnéticos obtidos previamente. Aplicando este modelo para uma estrutura cúbica do tipo perovskita, estudamos o efeito magnetocalórico nos compostos EuZrO3 e EuTiO3. Uma metodologia para a obtenção da magnetização de uma amostra policristalina foi apresentada e ainda estudamos o efeito magnetocalórico anisotrópico de natureza antiferromagnética.

Arduino plataforma mugikor baten erabilera RaspberryPi eta ROS bitartez

Txosten honetan azaltzen den proiektua, auto itxurako robot baten eraikuntzan oinarritzen da. Arduino plataforman oinarritutako robot mugikor baten sorkuntza burutuko da hutsetik, honen kontrola Raspberry Pi ordenagailu txikiaren bitartez eginez. Gainera, azken gailu honi ahalmen handiagoa emateko asmoz, ROS plataforma instalatuko da bertan. Duten kostu baxua dela eta, gaur egun izugarrizko arrakasta lortu dute plataforma guzti hauek, baina proiektu honetan beraien ahalmena neurtu nahi dugu ezaugarri zehatz batzuk dituen robota sortuz.

Marisorgin robotaren simulazioa eta nabigazioa Gazebo-ROS ingurunean

Proiektu honetan RSAIT ikerketa taldearen Marisorgin robotaren simulazioa eta nabigazioa landu dira Gazebo-ROS ingurunean. Robota UPV/EHUko Donostiako Informatika Fakultateko hirugarren solairuan zehar mugituko da, korridore, bulego eta gainontzeko geletatik igaroz. Bestalde, Marisorgin RWI etxeko B21 robota da, lau gurpil ditu eta mugimendu-sistema sinkronoa dauka. Nabigaziorako, robota bere kokapenetik (jatorriko puntua) guk adierazitako puntura (helburuko puntua) mugitu beharko da modu autonomoan.

Reconocimiento de posturas mediante Kinect en ROS

Proyecto de Fin de Grado, especialidad en Computación. Se ha desarrollado un software en ROS para detectar posturas y movimientos de personas. Para ello, se utiliza la información del esqueleto proporcionada por el sensor Kinect y la biblioteca OpenNI. Se ha realizado un enfoque basado en técnicas de aprendizaje supervisado para generar modelos que clasifiquen posturas estáticas. En el caso de los movimientos, el enfoque se ha basado en clustering. Estos modelos, una vez generados, se incluyen como parte del software, que reacciona ante las posturas y gestos que realice un usuario.

NXT eta ROS bidezko zabor biltzailea

LEGOko NXT plaka eta ROS sistemaren arteko konektagarritasuna landu da proiektu honetan. NXT eta ROSen arteko konektagarritasuna aztertu ez ezik, zabor biltzaile baten portaera inplementatu da.

Embedding quantum simulators

79 p.

Symmetry restoration and quantumness reestablishment

A realistic quantum many-body system, characterized by a generic microscopic Hamiltonian, is accessible only through approximation methods. The mean field theories, as the simplest practices of approximation methods, commonly serve as a powerful tool, but unfortunately often violate the symmetry of the Hamiltonian. The conventional BCS theory, as an excellent mean field approach, violates the particle number conservation and completely erases quantumness characterized by concurrence and quantum discord between different modes. We restore the symmetry by using the projected BCS theory and the exact numerical solution and find that the lost quantumness is synchronously reestablished. We show that while entanglement remains unchanged with the particle numbers, quantum discord behaves as an extensive quantity with respect to the system size. Surprisingly, discord is hardly dependent on the interaction strengths. The new feature of discord offers promising applications in modern quantum technologies.