TEDE Communidade:http://www.bdtd.uerj.br/handle/1/36852024-06-24T12:06:21Z2024-06-24T12:06:21ZPreparação, propriedades estruturais e fotoluminescência sintonizável do LiZnNbO4:Co2+Santos, Rodrigo Dias doshttp://www.bdtd.uerj.br/handle/1/222282024-06-20T14:55:05Z2017-08-04T00:00:00ZTítulo: Preparação, propriedades estruturais e fotoluminescência sintonizável do LiZnNbO4:Co2+
Autor: Santos, Rodrigo Dias dos
Primeiro orientador: Sosman, Lilian Pantoja
Abstract: In this work we present the study of optical and crystallographic properties of the compound LiZnNbO4:Co2+(0,1%). The sample was produced by the acetate method. The crystallographic data and the composition of the samples were obtained by X ray powder difraction. The measurements of photoluminscence resolved in time, photoluminscence resolved in the phase, excitation and time of decay were performed at room temperature and atmospheric pressure. The emission spectrum shows a strong and continous bandfrom 650 nm to 875 nm, attributed to the transitions of Co2+ ion in tetrahedal sites ofLiZnNbO4. The wide band observed indicates that the studied material is promising foruse as source of tunable radiation at room temperature.
Instituição: Universidade do Estado do Rio de Janeiro
Tipo do documento: Dissertação2017-08-04T00:00:00ZDiscriminação de sinais de detectores de partículas utilizando técnicas de aprendizado de máquinaDalto, Dalmo da Silvahttp://www.bdtd.uerj.br/handle/1/222242024-06-19T15:29:26Z2023-08-18T00:00:00ZTítulo: Discriminação de sinais de detectores de partículas utilizando técnicas de aprendizado de máquina
Autor: Dalto, Dalmo da Silva
Primeiro orientador: Nogima, Helio
Abstract: One of the fundamental problems in particle detector instrumentation is optimizing the signal-to-noise ratio in the early stage of electrical pulse collection. Besides adopting ﬁlters and formatting, signal discrimination is usually achieved in electronic signal proces-sing by imposing an amplitude threshold value. This solution is generally enough since the noise has a lower amplitude than the signals in most detectors. However, depending on the application and the type of detector used, this method ﬁlters only a part of the noise,retaining those with high amplitude, and it also has the undesirable eﬀect of eliminating low-amplitude signals. In cases like these, methods of discrimination independent of the size of the electrical signals should be considered. The use of machine learning techniques is an interesting alternative, given the increasing availability of high-speed programmable devices like Field Programmable Gate Arrays (FPGAs) for artiﬁcial intelligence applications. The method considers the diﬀerences in waveforms between signals and noise, which can be used in discriminating the electrical pulses generated by the detectors, regardless of their size. In this dissertation, we present a study of signal discrimination using different machine learning algorithms applied to a scintillator detector. Simulated data of signals and noise and experimental data were used to study signal discrimination using an unsupervised algorithm called Hierarchical Clustering Analysis (HCA) and supervised algorithms such as Random Forest, Deep Neural Networks, and Convolutional Neural Networks. A comparison of the performance of the diﬀerent supervised algorithms with the pulse amplitude discrimination method is presented.
Instituição: Universidade do Estado do Rio de Janeiro
Tipo do documento: Dissertação2023-08-18T00:00:00ZDeterminação de integrais primeiras para sistemas dinâmicos em duas e três dimensões com um algoritmo linearFerreira, Higor Silvahttp://www.bdtd.uerj.br/handle/1/220502024-06-19T16:09:19Z2024-02-29T00:00:00ZTítulo: Determinação de integrais primeiras para sistemas dinâmicos em duas e três dimensões com um algoritmo linear
Autor: Ferreira, Higor Silva
Primeiro orientador: Duarte, Luiz Guilherme Silva
Abstract: This work proposes, initially, a broad approach with regard to the non-classificatory or generalist methods to deal with first and second order ordinary differential equations. More specifically, we will be interested in rational ODE’s (which are directly related to autonomous polynomial differential systems) and, to this end, our starting point consists of the study of theoretical structures introduced by the end of 19th century, in a reference to the works of S. Lie and G. Darboux. In this sense, we present some details contained in each of these theories in order to establish a mixed procedure called the S - function method, which was recently implemented by the UERJ research group working in the topics. It is widely known that such methods present complications when applied to some specific cases, and it will become evident throughout this reading. Thus, implementing and refining algorithms to deal with these type of equations, when integrable, has been the main motivation of the group. Therefore, the development at the very end of this work presents, as a proposal, a highly efficient method that allows us to determine the Darboux polynomials with a linear procedure (the eigenpolynomials of the vector field associated with these equations have fundamental importance for the construction of an integrating factor). In this aspect, we reinforce some ideas which are discussed in the preceding chapters (introducing a notation in conformity with the most recent developments of the group) and definitively establish the algorithms for our purposes, in such a way that, one of them applies to rational first order ODE’s presenting a Darbouxian general solution, while the other two are useful to deal with problems involving second order ODE’s, in subcases that arise as follows: rational second order ODE’s presenting one elementary first integral and one non-Liouvillian first integral; rational second order ODE’s with two Liouvillian first integrals, one of them being elementary. We conclude
with a discussion on the performance of our method in computational terms, which we
can surely assert, beforehand, represents a routine of singular efficiency (due to the linearity of the equations involved in the procedure) in terms of consumed memory and execution time. Additionally, we present an example as an application of our method to an equation of a non-linear oscillator (Duffing van-der Pol) which is of great interest for various applications.
Instituição: Universidade do Estado do Rio de Janeiro
Tipo do documento: Dissertação2024-02-29T00:00:00ZObserváveis em modelos efetivos conﬁnantes: potencial quark–antiquark e momento magnético de núcleonsMena Correa, Carlos Stivenshttp://www.bdtd.uerj.br/handle/1/220392024-06-20T17:15:00Z2023-12-19T00:00:00ZTítulo: Observáveis em modelos efetivos conﬁnantes: potencial quark–antiquark e momento magnético de núcleons
Autor: Mena Correa, Carlos Stivens
Primeiro orientador: Palhares, Letícia Faria Domingues
Abstract: The understanding of hadronic physics, in terms of quarks and gluons, is still an open problem, since the color confinement mechanism still lacks a satisfactory analytical description from first principles. However, in order to address confinement, some approaches have been developed that explore or even manage to access information from the low-energy region of Quantum Chromodynamics (QCD), i.e. the nonperturbative part of QCD, where it is considered that the explanation for confinement may lie. Among the different methods, we focus on those that arise from the nonperturbative consequences of Gribov copies, which modify the infrared behavior of Yang-Mills propagators, especially that of the gluon propagator. At the same time, these approaches are motivated by the nonperturbative first-principle numerical results of lattice QCD. In this thesis, we will study the following models: Gribov–Zwanziger (GZ), refined Gribov–Zwanziger (RGZ), and Curci-Ferrari (CF, or massive gluon model). In the case of the gluon propagator, the nonperturbative information present in these approaches generates a structure of complex poles, which violates the positivity reflection axiom related to the physical interpretation of a particle, which could be considered as an indication of gluon confinement. The search for other signs of confinement in these formalisms is obviously of great importance to establish their role as consistent infrared realizations of QCD. With this in mind, and assuming confinement as something intrinsic to QCD, in this thesis we investigate in some observables the consequences and phenomenological impact of the non-perturbative characteristics of the different approaches mentioned. First, related to the observable of the energy spectrum, we focus on the calculation and analysis of the static potential between a heavy quark–antiquark pair, whose linear behavior, corroborated by lattice QCD, is considered a sign of confinement. Our objective is also to verify the validity of the mentioned approaches and their compatibility with perturbative predictions, and also whether such models can produce quark confinement through a linear potential. Our results indicate that the calculated potentials are in agreement with the high-energy perturbative result and also that these potentials present interesting non-perturbative corrections. In the case of Curci-Ferrari (massive gluon), due to the systematic introduction of more interaction effects that include corrections at one and two loops, these become very significant due to the emergence of a semilinear behavior of its potential in the region of intermediate distances. The other observable studied in this thesis is the magnetic moment, in particular that of the proton. Due to the difficulty that the calculation presents, we adopted the constituent quark model (CQM), which within its own limitations allows us to calculate the magnetic moment of hadrons as a function of the magnetic moments of their constituent quarks. In order to extract the magnetic moment of the quarks and with the aim of studying the phenomenological impact of the different types of propagators of the GZ, RGZ, and CF approaches, we analyzed the quark-photon vertex (QPV) (up to the order of one it loop) focusing on the contribution coming from QCD, which depends on the gluon propagator. Our results indicate that the contributions of the different approaches to the magnetic moment of the quarks are smaller in relation to the perturbative result (massless gluon) since these are suppressed due to the mass terms present in the gluon propagators, which in the GZ and CF cases present a very similar behavior even if the GZ case has imaginary poles and the CF case does not (at tree level). In the RGZ case, due to the more elaborate structure and complex poles of its propagator, more contributions to the magnetic moment of the quarks appear, which may even exceed the value of the perturbative result for certain values of the RGZ parameters. Regarding the magnetic moment of the proton, calculated in CQM, the most interesting result arises when the mass of the constituent quark is adjusted to reproduce the mass of the proton. In this case, by adjusting the mass parameters of the mentioned approaches, we can reproduce the moment of the proton. The values obtained are even comparable to other mass values obtained for the gluon mass.
Instituição: Universidade do Estado do Rio de Janeiro
Tipo do documento: Tese2023-12-19T00:00:00Z