Submitted by (lucia.rodrigues@ufrpe.br) on 2016-11-23T12:26:25Z No. of bitstreams: 1 Nelio Oliveira Ferreira.pdf: 784310 bytes, checksum: c0fb98c5a6c058e292abaf3e2e990e8c (MD5) / Made available in DSpace on 2016-11-23T12:26:25Z (GMT). No. of bitstreams: 1 Nelio Oliveira Ferreira.pdf: 784310 bytes, checksum: c0fb98c5a6c058e292abaf3e2e990e8c (MD5) Previous issue date: 2005-08-30 / This article aims to investigate the dual behavior of the light as a result of implementation of a new approach based on the Personal Constructs Theory by George Kelly, specifically, in the Experience Cycle. The five stages of this cycle (anticipation, investment, encounter, validation and constructive revision) had been distributed in three classes during which the conceptions by the students had been followed from the beginning detected through a posttest and through a production of a new poster. There had been investigated the conceptions of wave, particle, frequency and wavelength, as well as the photoelectrons, cutoff potential and cutoff frequency, aiming to register the Photoelectric Effect phenomenon. During the poster production, the acceptable answers had aroused from 64% to 100% concerning the wave definition. Concerning the particle, the results had been even more relevant; no answer was considered true at first, but after the usage of the cycle, they had been all accepted. These results had indicated how clearly the students could then distinguish wave from particle, which had been complemented by the comprehension of essential conceptions to the Photoelectric Effect phenomenon. Therefore, the students had started to understand the corpuscular behavior of the light, in the cited phenomenon, and wavy, in other phenomenon (reflection, refraction, diffraction and interference), as it can be comproved by comparison of the pre-test and the post-test. Concerning the wavelength conceptions, cutoff frequency and photoelectrons, all the answers had became acceptable. Besides, the answers concerning quantum and photon conceptions had cached 91% of the desirable levels frequency had cached 81% and cutoff potential, 64%. Considering that 60% of the answers analyzed were acceptable, it is believed that the usage of Kelly’s Experience Cycle as a methodological tool is extremely effective. / Este trabalho tem o objetivo de investigar o comportamento dual da luz devido a implementação de uma nova abordagem baseada na Teoria dos Construtos Pessoais de George Kelly, mais especificamente, no Ciclo da Experiência. As cinco etapas desse ciclo (antecipação, investimento, encontro, validação e revisão construtiva) foram distribuídas em três aulas durante as quais foram acompanhadas as concepções dos alunos, desde as iniciais, detectadas através de um pré-teste e da produção de um cartaz, até as concepções mantidas ao término da intervenção didática, através de um pós-teste e da produção de um novo cartaz. Foram investigados os conceitos de onda, partícula, freqüência e comprimento de onda, além de fotoelétrons, potencial de corte e freqüência de corte com o intuito de retratar o fenômeno do Efeito Fotoelétrico. Na produção dos cartazes, as respostas consideradas aceitáveis passaram de 64% para 100% no que diz respeito ao conceito de onda. Em relação ao conceito de partícula na produção dos cartazes, os resultados foram ainda mais relevantes, nenhuma resposta foi aceita, inicialmente, contra a aceitação de todas as respostas após a aplicação do ciclo. Estes resultados indicaram a clareza que os alunos passaram a ter ao distinguir onda e partícula, o que foi complementado com a compreensão de conceitos essenciais relacionados com o fenômeno do Efeito Fotoelétrico. Assim, os alunos passaram a compreender o comportamento corpuscular da luz, no referido fenômeno, e ondulatório, em outros fenômenos (reflexão, refração, difração e interferência), como se pôde verificar nos resultados do pré-teste e pós-teste. Em relação aos conceitos de comprimento de onda, freqüência de corte e fotoelétrons, todas as respostas atingiram níveis aceitáveis. Além disso, as respostas a respeito dos conceitos de quantum e fóton atingiram 91% dos níveis desejáveis, freqüência, 82%, e potencial de corte, 64%. Como todos os dados analisados atingiram níveis acima de 60% daqueles desejáveis, acredita-se que a utilização do Ciclo da Experiência de Kelly, como ferramenta metodológica, apresentou-se com bastante eficácia.

Submitted by Luanna Matias (lua_matias@yahoo.com.br) on 2015-03-23T15:26:24Z No. of bitstreams: 2 Dissertação - Rangel Magalhães Luzin - 2011.pdf: 5253417 bytes, checksum: 4a3879b95b6b8e88185d667c72771ed4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luanna Matias (lua_matias@yahoo.com.br) on 2015-03-23T15:29:27Z (GMT) No. of bitstreams: 2 Dissertação - Rangel Magalhães Luzin - 2011.pdf: 5253417 bytes, checksum: 4a3879b95b6b8e88185d667c72771ed4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-03-23T15:30:11Z (GMT). No. of bitstreams: 2 Dissertação - Rangel Magalhães Luzin - 2011.pdf: 5253417 bytes, checksum: 4a3879b95b6b8e88185d667c72771ed4 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2011-12-20 / This work describes the thermal and photoelectric stability investigation of commercial sunscreens benzophenone-3, octyl methoxycinnamate and octyl salicylate. The purpose was determining thermal and photoelectric (resistance to sunlight) stability. For thermal stability evaluation, thermal ramp was set up in attempt to get closer to conditions which sunscreen could be submitted in manufacture or in people using. In this test each filter was exposed to temperature variations from 30 to 65 °C, in times and speeds of heating, under synthetic air atmosphere. A solar simulator was used for photoelectric stability evaluation. The measures were not performed with samples irradiated at a specific wavelength, but exposed to all wavelengths emitted by the sun, extending from the ultraviolet to infrared, with high reproducibility. The samples were exposed to simulated solar light in five different times, ranging from 30 to 120 minutes. This change aims to understand how the filter behaves with the increased exposure time. Infrared, ultraviolet and NMR spectroscopies were used on structural characterization of the compounds submitted to thermal and photoelectrical evaluation. This study has demonstrated that sunscreens evaluated are thermally stable but photoelectrically unstable. This instability was observed by formation of minor compounds derivative of sunscreens studied. The shift in the chemical equilibrium producing higher concentrations of minor compounds was also observed. These factors change the absorptive capacity of the sunscreens, causing loss of stability in solar protection. Octyl methoxycinnamate and benzophenone 3 have the higher molar absorptivity (23,300 and 14,380, respectively) and presented the higher loss of efficiency, overcoming 20% in 2 hours of exposure. On the other hand octyl salicylate has lower molar absorptivity value (4.130) and presented lower loss of efficiency, overcoming 10% in 2 hours of exposure. The used methodologies have low cost and are viable, representing an interesting tool in stability evaluation of sunscreens already established in cosmetic market or in development. This study also emphasizes the importance of NMR technique that enabled us to identify and quantify all structures modified without any previous separation. The correlation between UV and NMR techniques was also effective to demonstrate that lower losses in molar absorptivity are directly related to lower differences on NMR spectra, as observed in octyl salicylate. / Neste trabalho avaliaram-se as estabilidades térmica e fotoelétrica dos filtros solares benzofenona-3, metoxinamato de octila e salicilato de octila. Para verificação da estabilidade térmica, estabeleceu-se a rampa térmica apropriada, por intermédio de análise térmica, buscando se aproximar de condições reais, as quais o produto final poderia ser submetido. Neste teste cada filtro suportou variações de temperatura de 30 a 65°C, em tempos e velocidades de aquecimento determinados, sob atmosfera de ar sintético. Para a verificação da estabilidade fotoelétrica de filtros solares, utilizou-se de forma inovadora um simulador solar. Portanto, as medidas não foram realizadas com amostras irradiadas em um comprimento de onda ou faixa específica, mas sim, expostas a todos os comprimentos de onda emitidos pelo sol, se estendendo desde o ultravioleta até o infravermelho, com alto grau de reprodutibilidade. Todas as amostras foram submetidas à luz solar simulada com diferentes tempos de exposição, variando de 30 a 120 minutos. Assim, foi avaliado o comportamento do filtro de acordo com o tempo de exposição. Conclui-se deste estudo, que os filtros solares aqui trabalhados são estáveis termicamente, porém instáveis fotoeletricamente. A instabilidade foi observada através da formação de subprodutos derivados dos filtros estudados, bem como deslocamento no equilíbrio químico entre as estruturas envolvidas, aumentando a concentração de produtos minoritários. Estes fatores alteram a capacidade absortiva do filtro, fazendo com que os mesmos não sejam tão estáveis quanto antes da exposição fotoelétrica. O metoxinamato de octila e a benzofenona 3 são os filtros com maiores absortividades molares 23300 e 14380 respectivamente e foram os que apresentaram maior perda de eficiência, aproximando-se dos 20% no período de 2 horas. Por outro lado, o salicilato de octila cuja absortividade molar é de 4130 e sua perda foi próxima aos 10%. As técnicas de infravermelho (IV), ultravioleta (UV) e Ressonância Magnética Nuclear (RMN) foram utilizadas para caracterizar as alterações estruturais, efetividade absortiva e deslocamentos de equilíbrio, resultantes das avaliações térmica e fotoelétrica. Essas metodologias foram eficientes, de fácil aplicação e com observação direta dos resultados. Foram viáveis e de baixo custo, podendo ser aplicadas na caracterização e verificação de estabilidade de filtros já consolidados no mercado de cosméticos ou em desenvolvimento. Destaca-se a importância da técnica de RMN, que possibilitou identificar e quantificar todas as estruturas modificadas, sem métodos de separações prévias. A correlação entre UV e RMN foi efetiva para demonstrar que as menores perdas de absortividade estão também ligadas às menores diferenças no RMN, como observado para o salicilato de octila.

The varied properties of Silicon Carbide (SiC) are helping to launch the material into many new applications, particularly in the field of novel semiconductor devices. In this work, the cubic form of SiC is of interest as a basis for developing integrated optical components. Here, the formation of a suitable SiO2 buried cladding layer has been achieved by high dose oxygen ion implantation. This layer is necessary for the optical confinement of propagating light, and hence optical waveguide fabrication. Results have shown that optical propagation losses of the order of 20 dB/cm are obtainable. Much of this loss can be attributed to mode leakage and volume scattering. Mode leakage is a function of the effective oxide thickness, and volume scattering related to the surface layer damage. These parameters have been shown to be controllable and so suggests that further reduction in the waveguide loss is feasible. Analysis of the layer growth mechanism by RBS, XTEM and XPS proves that SiO2 is formed, and that the extent of formation depends on implant dose and temperature. The excess carbon generated is believed to exit the oxide layer by a number of varying mechanisms. The result of this appears to be a number of stable Si-C-O intermediaries that form regions to either depth extreme of the SiO2 layer. Early furnace tests suggest a need to anneal at temperatures approaching the melting point of the silicon substrate, and that the quality of the virgin material is crutial in controlling the resulting oxide growth.

Organic electronic devices are sustainable alternatives to the conventional electronics, due to their advantages of low cost, mechanical flexibility and wide range of applications. With the myriad list of organic materials available today, the opportunities to imagine new innovative devices are immense. Organic electronic devices such as OLEDs (organic light emitting diode), OPVs (Organic photovoltaics) and OFETs (organic field effect transistors) are among the leading device categories. Although OLED’s have been a huge commercial success, other categories are not lagging. Radical thinking is necessary to improve on the current performances of these devices. One such thinking is to combine the versatile ZnO (Zinc Oxide) material to organic semiconductors. This can be achieved by exploiting the dual nature of ZnO’s semiconducting and piezoelectric property. Many devices have used ZnO in combination with organic semiconductors for applications ranging from sensors, photovoltaics, OFET’s, memory and many others. The goal of the work is to incorporate the piezoelectric nature of hydrothermally grown ZnO nanowires for Opto-electronic applications. Although the initial research work was done on incorporating the piezo effect of bulk grown ZnO nanowires in improving the efficiency of an OPV, we discovered a unique memory effect in this device by incorporating ZnO nanowires in an inverted organic photovoltaic architecture. The device switched between a rectifying response in dark to resistive behavior under illumination with a finite transition time and was reversible. Since then we decided to explore few of the opto-electronic applications of this technology. The synthesis and characterization of crystalline ZnO nanowires, nanoforest and planar ZnO nanofilm are reported along with the application of these ZnO nanostructures in optoelectronic devices. Noncentro symmetry of crystalline ZnO nanostructures makes it an excellent candidate to be used as piezo functional material and these nanostructures are characterized using electrochemical cell containing ZnO electrode as the working electrode. ZnO nanostructures like nanowires, nanoforest and planar nanofilm are similarly characterized for piezo property using electrochemical technique. Different devices require distinguishing physical and electrical properties of ZnO nanostructures, hence morphology, effect of pre-strain, surface area, surface coverage and thickness of these nanostructures were evaluated for its piezoresponse. It is shown that it was possible to obtain similar piezoresponse among different ZnO nanostructures in addition to taking advantage of the structural benefits among various categories of nanostructures as per requirement. The presented research can be used as the proof-of-the-concept that ZnO nanostructures can be designed and fabricated with a prestrain to adjust the piezo response of the material under external forces. Therefore, the structure with the prestrain can be employed in various electronic and optical devices where the piezo voltage can be used for adjusting the energy band bending at an interface.

A human body can carry out many physiological complex processes which can be mechanical, electrical or bio-chemical. Each mechanical activity generates a signal that describes the characteristics of the particular action in the form of pressure or temperature. Any irregularity in the process changes the usual functioning thus affecting the performance of the system. Several techniques were introduced to evaluate these muscular signals in order to get a deeper understanding of the medical abnormalities. Displacement sensors, laser optics, electrodes, accelerometers and microphones are some of the widely used devices in measuring the electrical and mechanical activities produced in the muscles. The aim of this thesis project was to find and implement a simple non-contact optical method to measure and monitor the displacements caused on the surface of the skin due to muscular movements. In this study, a device was developed using photo electric sensors that can record surface changes caused on the skin due to the movements forearm muscles.

Electron orbital theory was applied to the design of the geometrical structure of an electron multiplier for an image intensifier. A special structure satisfying production requirements was studied. Electron optical calculations consisted of determining the potential distribution and tracing the electron trajectories. Liebmann’s procedure was used to solve Laplace’s equation with constant potentials on the multiplier electrodes as boundary conditions. The trajectories were determined by solving the equation of motion in an electrostatic field using a Runge-Kutta procedure. The initial conditions for the trajectories were the initial energies, initial positions, and the initial directions of the secondary electrons. The plotted trajectories indicated the feasibility of an electron multiplier of the type studied.

The COmpton Spectrometer and Imager (COSI) is a space telescope that aims to study the soft gamma regime (0.2-5 MeV), capable of performing spectroscopy, imaging and polarimetry of cosmic gamma sources. COSI will use an active shield made of Bismuth Germanium Oxide (BGO), a known scintillator material, in order to reduce the instrumental background produced by primary and secondary particles. When a cosmic ray particle or gamma interacts with the active shield, they will produce scintillation photons. Thanks to the optical coupling of photomultipliers tubes (PMT) to the BGO walls, it is possible to detect these scintillation photons and remove the background events from the analysis with the Compton telescope. IRAP (Research Institute in Astrophysics and Planetology) is the organization responsible of providing the photodetector (PMT with its electronics and mechanics) design to the COSI mission. The main objective of my internship is to study the performance of the photodetector of the active shield, focusing on the development of simulations with Geant4. The first study investigates the propagation of optical photons inside a PMT, comparing an analytical method versus a Geant4 simulation. Geant4 perfectly simulates the transmission and reflection of photons. However, if some of the photons are absorbed by the materials, Geant4 starts to slightly differ. This happens because the absorption is computed with different physic processes in both models. The second study is focused on obtaining measurements from the PMTs at the laboratory. The pulse amplitude at the preamplifier level is analysed, as well as the transmission of the Si pad. The third and fourth studies are focused on the simulation, with Geant4, of the performance of a PMT optically coupled to two different scintillator materials, CsI(Tl) and BGO, respectively. The correct set-up of a simulation is always critical, especially for a space mission like COSI. Both studies aim to find the correct set-up in order to get the most precise simulation. The results are great, showing a really good correlation between the simulation and the real data. During the fifth study, I updated the photodetector engineering model, called DACS (Detector for the AntiCoincidence System), taking into consideration the new electronic board designs and the previous engineering models. The results obtained in this thesis help to understand the performance of the photodetectors that will be used on the COSI telescope, as well as to show the benefits of using a toolkit like Geant4 in projects with propagation of scintillation photons.

Made available in DSpace on 2016-04-28T14:16:12Z (GMT). No. of bitstreams: 1 Arthur Issa Mangili.pdf: 986316 bytes, checksum: 5bd8636e8f419fb55e6f9132606a92dc (MD5) Previous issue date: 2011-05-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study aimed to analyze the experiments made by Heinrich Rudolph Hertz about the photoelectric effect. To this end, we consulted the work Electric Waves: Being Researches On The Propagation Of Electric Action With Finite Velocity Through Space, mainly the part in which the experiment that refers to the photoelectric effect is described. So we want to understand in which context such effect is discussed, looking for evidence that has arisen its discovery / Este estudo teve por objetivo analisar os experimentos realizados por Heinrich Rudolph Hertz relativos ao efeito fotoelétrico. Para tanto, consultamos a obra Electric Waves: Being Researches on the Propagation of Electric Action With Finite Velocity Through Space, principalmente a parte em que o experimento que se refere ao efeito fotoelétrico é descrito. Buscamos assim compreender em que contexto tal efeito é abordado, procurando indícios que sugiram a sua descoberta

Current state-of-the-art environmental, clinical, and in-vivo radiation sensing systems utilizing various inorganic and tissue-equivalent plastic scintillators are not user friendly, suffer from electron-beam-generated noise, and are difficult to deploy successfully for real-time dosimetry. A robust, real-time detection system using different scintillating materials coupled to solid-state detectors by optical fibers is developed. This system enables radiation monitors/clinicians to conduct meaningful real-time measurements using different inorganic scintillators or organic, tissue-equivalent plastic scintillators in harsh clinical and environmental environments. Recent solid state photomultiplier (SSPM) technology has matured, reaching a performance level that is suitable for replacement of the ubiquitous photomultiplier tube in selected applications for environmental radiation monitoring, clinical dosimetry, and medical imaging purposes. The objective of this work is laboratory and clinical testing of the Hamamatsu MPPC (S10362-11-050C), Photonique SSPM (0810G1), and Voxtel SiPM (SQBF-EKAA/SQBF-EIOA) SSPMs coupled to different inorganic scintillator crystals (Prelude 420, BGO), inorganic doped glass scintillator material SiO₂: Cu²⁺, and organic BCF-12 plastic scintillating fibers, used as detector elements. Both polymer optical fibers (POFs) and glass optical fibers (GOFs) are used as signal conduits for laboratory and clinical testing. Further, reduction of electron-beam-generated Cerenkov light in optical fibers is facilitated by the inclusion of metalized air-core capillary tubing between the BCF-12 plastic scintillating fiber and the POF. Dose linearity, percent depth dose, and angular measurements for 6 MV/18 MV photon beams and 9 MeV electron beams are compared using the Hamamatsu MPPC with-and without the use of the metalized air-core capillary tubing for BCF-12 plastic scintillating fiber. These same measurements are repeated for SiO₂: Cu²⁺ scintillator material without air-core capillary tubing. / Graduation date: 2012

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-10-19T12:34:29Z No. of bitstreams: 1 PDF - Joana Menara Souza Soares.pdf: 2514459 bytes, checksum: 19c69f29bb7ad433f442d2f53400b037 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-10-19T17:11:24Z (GMT) No. of bitstreams: 1 PDF - Joana Menara Souza Soares.pdf: 2514459 bytes, checksum: 19c69f29bb7ad433f442d2f53400b037 (MD5) / Made available in DSpace on 2016-10-19T17:11:24Z (GMT). No. of bitstreams: 1 PDF - Joana Menara Souza Soares.pdf: 2514459 bytes, checksum: 19c69f29bb7ad433f442d2f53400b037 (MD5) Previous issue date: 2016-08-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Currently, much has been discussed about the presence and importance of the History of Science (HC) in teaching physics. Associado a essa premissa, temos visto uma crescente produção de trabalhos acadêmicos, na qual se tem enfatizado uma abordagem histórica e filosófica inserida em conteúdos dessa disciplina. It is clear, however, that some of these jobs do not come to the teacher, leaving them at the mercy of distorted stories and / or simplified, present in most textbooks (LD), which ends up reinforcing some known scientific myths, transmitting false historical concepts to students and teachers. So, considering the importance of HC, we highlight the importance of examining the presence of this interrelationship in Physics textbooks for higher education by checking whether or not a historical proper transpositions on the photoelectric effect and how these materials, which They aim to train the teacher present the historical context of the phenomenon in question. Analysis and discussion of the results presented here should be based on some criteria that take into account historical aspects of the phenomenon as well as science, noting the presence of scientific myths and distorted bibliographic reports on the scientists involved. / Atualmente, muito se discute sobre a presença e a importância da História da Ciência (HC) no ensino de Física. Associada a essa premissa, temos visto uma crescente produção de trabalhos acadêmicos, na qual se tem enfatizado uma abordagem histórica e filosófica inserida em conteúdos dessa disciplina. Percebe-se, por outro lado, que alguns desses trabalhos não chegam ao professor, deixando-os a mercê de histórias distorcidas e/ou simplificadas, presentes na maioria dos livros didáticos (LD), o que termina por reforçar alguns conhecidos mitos científicos, transmitindo falsas concepções históricas a estudantes e professores. Assim, considerando a importância da HC, destacamos a relevância de se examinar a presença dessa inter-relação nos livros didáticos de Física para o ensino superior, verificando se há ou não umas transposições históricas adequadas, sobre o efeito fotoelétrico e como esses materiais, que visam formar o professor apresentam o contexto histórico do fenômeno em questão. A análise e discussão dos resultados aqui apresentados tomam como base alguns critérios que levam em consideração aspectos históricos do fenômeno e bem como da ciência, atentando para presença de mitos científicos e de relatos bibliográficos distorcidos sobre os cientistas envolvidos.