Submitted by Maike Costa (maiksebas@gmail.com) on 2017-06-19T14:00:05Z No. of bitstreams: 1 arquivototal.pdf: 7342318 bytes, checksum: dc68cd00ebae607f5275182f51548710 (MD5) / Made available in DSpace on 2017-06-19T14:00:05Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 7342318 bytes, checksum: dc68cd00ebae607f5275182f51548710 (MD5) Previous issue date: 2016-12-02 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This dissertation has as its central point the characterization through the density functional theory (DFT) of the orthorhombic perovskite CaSnO3 belonging to the space group Pbnm, using Gaussian type orbitals. At first, the bulk of the material was explored with the most diverse solids simulation techniques, focusing on the structural evaluation under pressure and frequency calculations, as well as its intensities (Raman and Infrared spectra) evaluated by the newly implemented (In Crystal program) Coupled-Perturbed Hartree-Fock/Kohn- Sham (CPHF/KS). Following, the bulk was again exploited under pressure, including various exchange-correlation type formulations within the DFT theory, as well as the use of routines recently implemented in the Crystal program as: Elastic constants under pressure, directional seismic velocity analysis and quasi-harmonic approximation (QHA). The latter is of great physical, mineralogical and geophysical interest due to its description of a material under conditions of high temperatures and pressures simultaneously. To further explore the possible catalytic properties of the material, the studies the defects, including oxygen vacancies and doping with copper, was carried out focusing on the energy differences and electronic charge analysis, the last, taking into account the Mulliken technique and Hirshfeld-I (available only to developers at present). Those calculation where performed at PBE and PBE0 level (for the doping with Cu only PBE0), with RHF and UHF formulations for the open shell and spin polarized cases. The used supercell (2x2x2) presented an adequate size to work with. The oxygen vacancy formed has the tendency to reduce the Sn neighbors, that form a mid gap close to the Valence Band, and presenting as the most stable formulation the RHF and Singlet (UHF). The oxygen vacancy is here characterized as been a neutral one. In the doping cases, where the tin atom is substituted by a coper one, the most stable case was when the Cu was near the vacancy (first neighbor). To finish the studies on this perovskite, the surface (001) is studied. The surface terminated in -CaO is a bit more stable than the -SnO2 one, however, the first one, using the applied methodology, presented some problems when adsorbing gases, hence been discarded in favor of the -SnO2 one. The CO and NH3 gases are adsorbed over the -SnO2 terminated surface, to evaluate it, charge density maps, density of states (DOS) and Raman intensity where used. The results showed that the CO adsorption is weak, but has a visible response in the Raman spectra. In the NH3 case the adsorption is strong and can be assigned as a chemisorption. In the last, an intense Raman peak appear and it is assigned to a bond between the hydrogen and the surface oxygen and it appear about 3098 cm−1. / Esta tese tem como ponto central a caracterização através da teoria do funcional da densidade (DFT) da perovskita ortorrômbica CaSnO3 pertencente ao grupo espacial Pbnm, pela ótica de orbitais Gaussianos. No primeiro momento, o bulk do material foi explorado com as mais diversas técnicas de simulação de sólidos, com enfoque na avaliação estrutural sob pressão e a frequência, bem como suas intensidades (espectros Raman e no Infravermelho) avaliadas pelo recém implementado (no programa Crystal) Coupled- Perturbed Hartree-Fock/Kohn-Sham (CPHF/KS). Em seguida, o bulk foi novamente explorado sob pressão, incluindo diversas formulações do tipo troca-correlação dentro da teoria do funcional da densidade (DFT), bem como o uso das rotinas recentemente implementadas no programa Crystal como: constantes elásticas sob pressão, análise da velocidade sísmica direcional e a aproximação quase-harmônica (QHA). Esta última é de grande interesse físico, mineralógico e geofísico pela descrição de um material em condições de elevadas temperaturas e pressões simultaneamente. Para explorar as possíveis propriedades catalíticas do material o estudo de defeitos incluindo vacâncias de oxigênio e dopagens com cobre foram incluídas. As análises focam-se nas diferenças energéticas e análise de carga eletrônica, a última, levando em conta a técnica de Mulliken e a de Hirshfeld-I (disponível apenas para desenvolvedores, no presente). Os cálculos foram realizados em nível PBE e PBE0 (para o caso da dopagem apenas PBE0), nas versões RHF e UHF para os casos de camada aberta e polarização de spin. A supercélula utilizada (2x2x2) apresentou tamanho adequado para o trabalho com os defeitos. A vacância de oxigênio quando formada tende a reduzir os Sn vizinhos, que por ventura formam um mid gap próximo à banda de valência (VB), sendo a configuração mais estável a RHF ou Singleto (UHF). A vacância de oxigênio foi caracterizada como uma vacância neutra. Nos cálculos de dopagem em que o estanho é substituído pelo cobre, a situação mais estável é aquela em que o cobre encontra-se como um primeiro vizinho da vacância de oxigênio. Para conclusão do estudo dessa perovskita, a superfície 001 foi avaliada. A superfície terminada em -CaO é um pouco mais estável que a superfície -SnO2, no entanto a primeira - através da metodologia utilizada - teve problemas para adsorção dos gases, dessa forma sendo descartada para os estudos de adsorção aqui realizados. Os gases CO e NH3 estudados sobre a superfície terminada em -SnO2, na avaliação foram utilizados mapas de densidade de carga, densidade de estados (DOS) e espectros Raman. Os resultados indicaram que a adsorção com o CO é fraca, mas possui uma resposta visível no espectro Raman. Já no caso do NH3 a adsorção forte podendo configurar-se como quimissorção. Na última, há o aparecimento de um pico intenso referente à ligação hidrogênio e oxigênio da superfície em torno de 3098 cm−1.

In this master thesis, compact antenna design aimed towards naval applicationshave been designed, analyzed and evaluated. There is a recentinterest in the development of compact antennas to be used for smallersubmarine models, and with a smaller hull on a submarine, communicationand antenna systems must be adapted and minimized, which limitsantenna design. With two limiting cylindrical volumes with maximumallowed dimensions r = 10 cm, h = 50 cm and r = 5 cm, h = 90 cm,the antennas would operate on the upper to lower V/UHF band, radiatehemispherically and have a high RHCP purity. It was found that the mostappropriate antenna structure for both volumes was QHA design. Afterthe design and analysis process was completed, it was concluded that theshorter antenna design could meet all requirements set while the longerantenna design did not meet all requirements but could still establish agood communication link on the higher frequencies. Antenna prototypesbased on the produced design were constructed and measured and, despiteminor deviations, veried that the results obtained from this thesis werereliable. / I denna mastersuppsatsen har kompakta antenner riktade mot marinaapplikationer designats, analyserats och utvarderats. Det nns ett intressefor utvecklingen av kompakta antenner som ska anvandas for mindreubatsmodeller och med ett mindre skrov pa en ubat maste kommunikationsochantennsystemen anpassas och minimeras darefter, vilket begransarantenndesignen. Med tva begransande cylindriska volymer med maximalttillatna dimensioner r = 10 cm, h = 50 cm samt r = 5 cm,h = 90 cm, skulle antennerna verka pa det ovre till lagre V/UHF-bandet,strala hemisfariskt och ha en hog RHCP-renhet. Det konstaterades attden lampligaste antennstrukturen for bada volymen var QHA-design. Efteratt design- och analysprocessen slutforts drogs slutsatsen att den kortareantenndesignen kunde uppfylla alla krav som stalldes medan den langreantenndesignen inte uppfyllde alla krav men fortfarande kunde upprattaen bra kommunikationslank pa de hogre frekvenserna. Antennprototyperbaserade pa de framtagna designerna konstruerades och mattes och, trotsmindre avvikelser, verierade att de erhallna resultaten fran denna avhandlingvar tillforlitliga.

Sewer and oil pipeline spillage issues have become major causes of pollution in urban and rural areas usually caused by blockages in the water storage and drainage system, and oil spillage of underground oil pipelines. An effective way of avoiding this problem will be by deploying some mechanism to monitor these installations at each point in time and reporting unusual liquid activity to the relevant authorities for prompt action to avoid a flooding or spillage occurrence. This research work presents a low cost energy efficient liquid level monitoring technique using Radio Frequency Identification Technology. Passive UHF RFID tags have been designed, modelled and optimized. A simple rectangular tag, the P-shaped tag and S-shaped tag with UHF band frequency of operation (850-950 MHz) has been designed and modelled. Detailed parametric analysis of the rectangular tag is made and the optimised design results analysed and presented in HFSS and Matlab. The optimised rectangular tag designs are then deployed as level sensors in a gully pot. Identical tags were deployed to detect 4 distinct levels in alternate positions and a few inches in seperation distance within the gully pot height (Low, Mid, High and Ultra high). The radiation characteristic of tag sensors in deployment as modelled on HFSS is observed to show consistent performance with application requirements. An in-manhole chamber antenna for an underground communication system is analysed, designed, deployed and measured. The antenna covers dual-band impedance bandwidths (i.e. 824 to 960 MHz, and 1710 to 2170 MHz). The results show that the antenna prototype exhibits sufficient impedance bandwidth, suitable radiation characteristics, and adequate gains for the required underground wireless sensor applications. Finally, a Linearly Shifted Quadrifilar Helical Antenna (LSQHA) designed using Genetic Algorithm optimisation technique for adoption as an RFID reader antenna is proposed and investigated. The new antenna confirms coverage of the RFID bandwidth 860-960 MHz with acceptable power gain of 13.1 dBi.

Sewer and oil pipeline spillage issues have become major causes of pollution in urban and rural areas usually caused by blockages in the water storage and drainage system, and oil spillage of underground oil pipelines. An effective way of avoiding this problem will be by deploying some mechanism to monitor these installations at each point in time and reporting unusual liquid activity to the relevant authorities for prompt action to avoid a flooding or spillage occurrence. This research work presents a low cost energy efficient liquid level monitoring technique using Radio Frequency Identification Technology. Passive UHF RFID tags have been designed, modelled and optimized. A simple rectangular tag, the P-shaped tag and S-shaped tag with UHF band frequency of operation (850-950 MHz) has been designed and modelled. Detailed parametric analysis of the rectangular tag is made and the optimised design results analysed and presented in HFSS and Matlab. The optimised rectangular tag designs are then deployed as level sensors in a gully pot. Identical tags were deployed to detect 4 distinct levels in alternate positions and a few inches in seperation distance within the gully pot height (Low, Mid, High and Ultra high). The radiation characteristic of tag sensors in deployment as modelled on HFSS is observed to show consistent performance with application requirements. An in-manhole chamber antenna for an underground communication system is analysed, designed, deployed and measured. The antenna covers dual-band impedance bandwidths (i.e. 824 to 960 MHz, and 1710 to 2170 MHz). The results show that the antenna prototype exhibits sufficient impedance bandwidth, suitable radiation characteristics, and adequate gains for the required underground wireless sensor applications. Finally, a Linearly Shifted Quadrifilar Helical Antenna (LSQHA) designed using Genetic Algorithm optimisation technique for adoption as an RFID reader antenna is proposed and investigated. The new antenna confirms coverage of the RFID bandwidth 860-960 MHz with acceptable power gain of 13.1 dBi. / Petroleum Technology Development Fund (PTDF) and National Space Research and Development Agency (NASRDA).

The objectives of this research work are to investigate, design and implement circularly-polarized antennas to be used for handheld satellite mobile communication and wireless sensor networks. Several antennas such as Quadrifilar Spiral Antennas (QSAs), two arm Square Spiral and stripline or coaxially-fed microstrip patch antennas are developed and tested. These antennas are investigated and discussed to operate at L band (1.61-1.6214GHz) and ISM band (2.4835-2.5GHz) A substantial size reduction was achieved compared to conventional designs by introducing special modifications to the antenna geometries. Most of the antennas are designed to produce circularly-polarized broadside-beam except for wireless sensor network application a circularly-polarized conical-beam is considered. The polarization purity and Specific Absorption Rate (SAR) of two dual-band antennas for satellite-mobile handsets next to the human head are investigated and discussed, using a hybrid computational method. A small distance between the head and the handset is chosen to highlight the effects of the relatively high-radiated power proposed from this particular antenna. A Genetic Algorithm in cooperation with an electromagnetic simulator has been introduced to provide fast, accurate and reliable solutions for antenna design structures. Circularly-polarized quadrifilar helical antenna handset and two air-dielectric microstrip antennas were studied. The capabilities of GA are shown as an efficient optimisation tool for selecting globally optimal parameters to be used in simulations with an electromagnetic antenna design code, seeking convergence to designated specifications. The results in terms of the antenna size and radiation performance are addressed, and compared to measurements and previously published data.

The objectives of this research work are to investigate, design and implement circularly-polarized antennas to be used for handheld satellite mobile communication and wireless sensor networks. Several antennas such as Quadrifilar Spiral Antennas (QSAs), two arm Square Spiral and stripline or coaxially-fed microstrip patch antennas are developed and tested. These antennas are investigated and discussed to operate at L band (1.61-1.6214GHz) and ISM band (2.4835-2.5GHz) A substantial size reduction was achieved compared to conventional designs by introducing special modifications to the antenna geometries. Most of the antennas are designed to produce circularly-polarized broadside-beam except for wireless sensor network application a circularly-polarized conical-beam is considered. The polarization purity and Specific Absorption Rate (SAR) of two dual-band antennas for satellite-mobile handsets next to the human head are investigated and discussed, using a hybrid computational method. A small distance between the head and the handset is chosen to highlight the effects of the relatively high-radiated power proposed from this particular antenna. A Genetic Algorithm in cooperation with an electromagnetic simulator has been introduced to provide fast, accurate and reliable solutions for antenna design structures. Circularly-polarized quadrifilar helical antenna handset and two air-dielectric microstrip antennas were studied. The capabilities of GA are shown as an efficient optimisation tool for selecting globally optimal parameters to be used in simulations with an electromagnetic antenna design code, seeking convergence to designated specifications. The results in terms of the antenna size and radiation performance are addressed, and compared to measurements and previously published data.