Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/2317

O Doutorado Acadêmico inicio-se em 1998 e pertence ao Programa de Pós-Graduação em Engenharia Elétrica (PPGEE) do Instituto de Tecnologia (ITEC) da Universidade Federal do Pará (UFPA).

Navegar

Agora exibindo 1 - 3 de 3

Acesso aberto (Open Access)
Análise de estruturas planares em THz baseadas em grafeno
(Universidade Federal do Pará, 2016-01-28) NASCIMENTO, Clerisson Monte do; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
In this work we analyse the properties of scattering of electromagnetic waves in graphene surfaces and the planar plasmonic based devices made of the same material, both in THz frequency region. The work is presented in form of four scientific papers. In the first one a numerical analysis of the plasmonic waves propagation in graphene elements is performed. The influence of geometrical configuration, chemical potential variation, angle of incidence and polarizations is analysed. That results give us the information to project two devices (the second and third) based on frequency selective surfaces (FSS) on THz range and that are composed only by graphene elements and dielectric substrates without the insertions of different metals. The first device consists in a THz electromagnetic filter made by an planar array of graphene ring-shaped elements placed in both sides of a dielectric substrate. The second device presents new multifunctional graphene device that can operate either as an electromagnetic, dynamically controlled, filter or as an eletromagnectic switch. Both devices operates based on Fano resonance effect. The fourth paper presents a new method of analysis of periodic planar structure, based on group theory approach. This method takes account the transversal and longitudinal components of induced current in the structure. By using this, one can obtain more information about the device properties than by using exitenting methods, which uses only longitudinal components of the induced currents. As application, we suggest an analyse a periodic array of graphene elements.
Acesso aberto (Open Access)
Desevolvimento de dispositivos eletrônicos orgânicos nano e micro-estruturados: memória volátil, sesores e fotocélulas
(Universidade Federal do Pará, 2011-02-14) REIS, Marcos Allan Leite dos; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work, several nano and microstructured organic devices were developed based on molecules of 4-dimethyl amino azobenzene-2-carboxylic acid (Methyl Red – VM), C60 Fullerene, nanocomposite of Aluminum/Carbon Nanotubes (Al/NC) and polymers: Poly(3, 4- dioxithiophene ethylene)-poly(sulfonate stireno) – PEDOT-PSS and poly(3-hexiltiofeno) – P3HT. These devices are volatile memory, fuel sensors, thermal-piezoresisitive sensor and photocells, which were manufactured by spin-coating, drop casting and chemical vapor deposition, resulting in devices with planar or layer by layer geometry. Morphological, optical, electrical and thermal characterizations were performed on devices, resulting: (a) volatile memory with a bit retention time of 4.5 s, the characteristic curves of current vs. voltage with peak-valley ratios of 8: under a 10:1 voltage positive and negative electrical energized with electrical conductivity of 10-4 S / m (OFF state) to 3.10 S / m (ON) at room temperature, (b) fuel sensors like chemiresistor sensors characteristics with sensitivity to ethanol and gasohol in concentrations of 26.25 ppm, (c) thermal-piezoresistive sensor with polynomial relationship between temperature and electrical resistance, linear relationship between pressure and electrical resistance, more accurate than a K type thermocouple when compared to a mercury thermometer at room temperature, (d) photocells with better performance when doped by Methyl Red showed quantum efficiencies up to 0.04%, real power at 0.27 and power conversion efficiency of 2.0%. These results indicate that electronic devices developed showed a better performance in comparison to similar organics.
Acesso aberto (Open Access)
Estudo do transporte eletrônico em nanoestruturas baseadas em carotenoides e tétrades com fulereno C60
(Universidade Federal do Pará, 2013-04-09) ALEIXO, Vicente Ferrer Pureza; DEL NERO, Jordan; http://lattes.cnpq.br/5168545718455899
In this work it is presented a theoretical study on the electronic structure of a fullerene molecule (C60) with junctions in four terminals based on groups electron donors. tetrathiafulvalene (TTF) – and groups acceptors of electrons – fenilpropanodinilla (FPP) and molecular devices based on Carotenoid derivatives. The transport mechanism investigated for the carotenoids derivatives were utilized for better understanding of Fowler-Nordheim (FN) and Millikan-Lauritsen (ML) plots for the systems based in fullerene C60. In all cases it was possible to confirm that the Millikan- Lauritsen (ML) analysis empirical is also sufficient to describe all aspects the transition voltage spectroscopy (TVS). To study this class of systems, optimize the geometry systematically and observe the electronic transfer calculated by Hartree-Fock and Density Functional Theory (DFT). The results show through a detailed analysis of the molecular charge rearrangement due to an external electric field shows that the charge transport is directly on to the type of junction that this system is submitted of form that the applied voltage suffices to create a saturation potential in the systems in study: fullerene C60 with three terminals of tetrathiafulvalene and one terminal of fenilpropanodinilla (C60-(TTF)3-FPP); fullerene C60 with four terminals of fenilpropanodinilla (C60-(FPP)4). The particularity observed in C60-(FPP)4 is the disposal of the structure to operate with rectifying character for the electronic transport in the presence of orthogonal electric field to terminal data. The results show that we have a Molecular rectifier that works as a macroscopic rectifier.

Navegar

Navegando Teses em Engenharia Elétrica (Doutorado) - PPGEE/ITEC por CNPq "CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA"