Orientador: Carlos Alberto dos Reis Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T21:29:13Z (GMT). No. of bitstreams: 1 OtaloraBuitrago_DianaPatricia_M.pdf: 4654440 bytes, checksum: 441fc975cdf8f7e9af7978587263e135 (MD5) Previous issue date: 2012 / Resumo: Este trabalho descreve os procedimentos experimentais e as justificativas que levaram à determinação de uma relação entre a densidade de tensão de ruído em altas frequências e a temperatura da junção de um LED branco de alta eficiência. As medições da densidade de tensão de ruído foram realizadas polarizando o LED com correntes na faixa de 1'mi'A até 326mA e temperaturas de junção desde 24ºC até 120ºC. A realização deste trabalho, que é de cunho exploratório, foi motivada pela busca de mecanismos que permitam a avaliação contínua da temperatura da junção de um LED em operação, tendo em vista sua grande influência na durabilidade do LED. A crescente expansão do uso do LED em lugar das lâmpadas incandescentes e fluorescentes está mudando a indústria da iluminação, trazendo com isto novos desafios. Um destes desafios está na melhoria dos circuitos de acionamento (drivers e fontes de alimentação), que hoje respondem por 59% das falhas nos LEDs. Pesa na confiabilidade destes circuitos a falta do controle da temperatura de junção. Os resultados deste trabalho, apesar de restritos à caracterização de apenas duas amostras de um LED branco de alta eficiência, mostraram nitidamente a presença de um ruído de excesso cuja amplitude tem forte correlação com a temperatura da junção. Foi constatado, nas duas amostras caracterizadas, que a densidade de tensão de ruído medida é equivalente ao que produz um resistor de aproximadamente 13K'ômega' / Abstract: This paper describes the experimental procedures and the reasons that led to determining a relationship between the high-frequencies noise voltage density and the junction temperature of a highefficiency white LED. the measurements of noise voltage density were performed biasing the LED with currents in the range of 1'mi'A up to 326mA and temperatures junction from 24ºC to 120ºC. This work, which is exploratory, was motivated by the search for mechanisms that allow to continually assess the junction temperature of an LED in operation, given its great influence on the lifetime of the LED. The growing expansion of the use of LEDs instead of incandescent and fluorescent bulbs is changing the lighting industry, bringing with it new challenges. One of these challenges is the improvement of the power supplies and driver circuits, which now account for 59% of failures in LEDs. The lack of control of the LED junction temperature in these circuits is one of the issues that respond to their reduces reliability. The outcome of the herein presented work, although only restricted to the characterization of two samples of a high-efficiency white LED, clearly showed the presence of an excess noise whose amplitude has strong correlation with the junction temperature. It was found from the two tested samples, that the measure noise voltage density is equivalent to what is produced by a resistor of approximately 13K'omega' / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

Orientador: Teresa Dib Zambon Atvars / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T20:25:11Z (GMT). No. of bitstreams: 1 Germino_JoseCarlos_M.pdf: 14479907 bytes, checksum: c9f86b7bc1995a755d797d3af0c41cfc (MD5) Previous issue date: 2014 / Resumo: Nesta dissertação foram estudadas as propriedades fotoluminescentes de alguns compostos de coordenação de Zn(II) com N,N'-bis(salicilidenos) em soluções de THF e DMSO e em estado sólido: N,N'-bis(salicilideno)-1,2-fenilenodiamino - salofeno (KG-15) e seu composto de coordenação de Zn(II) aquo[N,N'-bis(salicilideno)-1,2- fenilenodimino]zinco(II)([Zn(salofeno)(H2O)]; (KG-15/Zn)); N,N'-bis(salicilideno)-4,5- diaminopirimidina - sal-4,5-pym (KG-17) e seu composto de coordenação de Zn(II) aquo[N,N'-bis(salicilideno)-4,5-diaminopirimidina]zinco(II) ([Zn(sal-4,5-pym)(H2O)]; (KG- 17/Zn). Os N,N'-bis(salicilidenos) e seus compostos de coordenação de Zn(II) foram sintetizados, observando-se aumento de cerca de 30 % dos rendimentos reacionais sob irradiação ultrassônica. Foram caracterizados por FTIR, ressonância magnética nuclear 1D de hidrogênio (1H) e de carbono (13C), caracterização estrutural por CHN, no caso dos ligantes realizou-se a caracterização estrutural por difração de raios-X de monocristal, foram também determinados os potenciais de óxido-redução do [Zn(salofeno)(H2O)] por voltametria cíclica e os valores de energia das bandas foram comparados com dados de espectroscopia eletrônica de absorção. As espectroscopias de fluorescência estacionária e resolvida no tempo em solução diluída de THF e de DMSO (apenas KG-17) e no estado sólido mostraram evidências da ocorrência da transferência de prótons no estado eletrônico excitado nos ligantes livres e coordendados. O composto [Zn(salofeno)(H2O)] apresentou eletroluminescência muito fraca em um dispositivo formado por vidro/ITO/PEDOT:PSS/composto de coordenação/Ca/Al muito baixa. Um diodo montado por vidro/ITO/PEDOT:PSS/PVK:(PFOFPen:[Zn(salofeno)(H2O)])/Ca/Al apresentou luminescência do composto de coordenação de Zn(II) devido à processos de transferência de energia entre o PFOFPen (doador) e o [Zn(salofeno)(H2O)] (receptor), além da eletroluminescência do PFOFPen / Abstract: In this dissertation the photoluminescent properties of some coordination compounds of Zn(II) with N,N'-bis(salicylidenes) in THF and DMSO solutions and solid state were studied: N,N'-bis(salicylidene)-1,2-phenylenediamine - salophen (KG-15) and its Zn(II) coordination compounds aquo[N,N'-bis(salicylidene)-1,2- phenylenediaminate]zinc(II) - [Zn(salophen)(H2O)] (KG-15/Zn) , N,N'-bis(salicylidene)- 4,5-diaminepyrimidine - sal-4,5-pym (KG-17) and its Zn(II) coordination compounds aquo[N,N'-bis(salicylidene)-4,5-diaminate]zinc(II) - [Zn(sal-4,5-pym)(H2O)] (KG-17/Zn). The ligands N,N'-bis(salicylidenes) and their Zn(II) coordination compounds were synthesized, observing an increase of about 30 % of the reaction proceeds under ultrasonic irradiation. The ligands and Zn(II) coordination compounds were characterized by FTIR,1D nuclear magnetic resonance of hydrogen (1H) and carbon (13C), structural characterization by CHN elemental analysis, in the case of the ligands the structural characterization was performed by monocrystal X-ray diffraction. The oxyreduction potential of [Zn(salophen)(H2O)] were determined by cyclic voltammetry and the values of the electrochemical energy band gap were compared with optical data. The stationary and time resolved fluorescence spectroscopy of the compounds in dilute solutions of THF and of DMSO (only KG-17) and in solid state showed proton transfer in the electronic excited state locaded on the ligands. The [Zn(salophen)(H2O)] compound exhibit a very low electroluminescence in a device consisting by glass/ITO/PEDOT:PSS/PVK:[Zn(salophen)(H2O)]/Ca/Al. A diode assembled by glass/ITO/PEDOT:PSS/PVK:(PFOFPen:[Zn(salophen)(H2O)])/Ca/Al showed luminescence of Zn(II) coordination compound due to energy transfer processes between PFOFPen (donor) and [Zn(salophen)(H2O)] (acceptor), beyond the electroluminescence of the PFOFPen / Mestrado / Físico-Química / Mestre em Química

Submitted by Nadir Basilio (nadirsb@uninove.br) on 2018-06-15T14:18:54Z No. of bitstreams: 1 Paulo Roberto Vicente de Paiva.pdf: 1229830 bytes, checksum: dd6855853f5863b4ff76e7eb6ac01830 (MD5) / Made available in DSpace on 2018-06-15T14:18:54Z (GMT). No. of bitstreams: 1 Paulo Roberto Vicente de Paiva.pdf: 1229830 bytes, checksum: dd6855853f5863b4ff76e7eb6ac01830 (MD5) Previous issue date: 2016-02-03 / Background/Aim: Cryotherapy for post-exercise recovery remains widely used despite the lack of quality evidence. Photobiomodulation Therapy (PBMT) studies have demonstrated positive scientific evidence to suggest its use. The study aims to evaluate PBMT and cryotherapy as a single or combined treatment on skeletal muscle recovery after eccentric contractions of knee extensors. Methods: Fifty healthy male volunteers were recruited and randomized into five groups (PBMT, Cryotherapy, Cryotherapy+PBMT, PMBT+Cryotherapy or Placebo) for a randomized, double-blinded, placebo-controlled trial that evaluated exercise performance (maximum voluntary contraction - MVC), delayed onset muscle soreness (DOMS), and muscle damage (Creatine Kinase - CK). Assessments were performed at baseline, immediately after, and at 1, 24, 48, 72 and 96 hours. Comparator treatments was performed 3 minutes after exercise and repeated at 24, 48 and 72 hours. PBMT was applied with GameDay™ (905nm super-pulsed laser, 875nm and 640nm LEDs combined, Multi Radiance Medical™), and cryotherapy by flexible rubber ice packs. Results: PBMT alone was optimal for post-exercise recovery with improved MVC, decreased DOMS and CK activity (p<0.05) from 24 to 96 hours compared to placebo, cryotherapy and Cryotherapy+PBMT. In the PBMT+Cryotherapy group, the effect of PBMT was decreased (p>0.05), but demonstrated significant improvement in MVC, decreased DOMS and CK activity (p<0.05). Cryotherapy as single treatment and Cryotherapy+PBMT were similar to placebo (p>0.05). Conclusions: We conclude that PBMT used as single treatment is the best modality for enhancement of post-exercise restitution, leading to complete recovery to baseline levels from 24 hours after high-intensity eccentric contractions. / A recuperação pós-exercício é de fundamental importância no esporte de alto rendimento e atualmente vários recursos são utilizados com este intuito, dos quais podemos destacar a recuperação ativa, massagem, terapia de contraste com água fria e água quente, hidroterapia, anti-inflamatórios não esteroidais, crioterapia, laserterapia de baixa potência, entre outros. A crioterapia é um dos recursos mais utilizados e que consiste no uso de gelo ou de água em temperaturas baixas para acelerar a recuperação pós-exercício, contudo, a sua evidência científica é extremamente limitada e controversa. Estudos recentes envolvendo fototerapia têm demonstrado resultados positivos no retardo da fadiga muscular e na recuperação de marcadores bioquímicos relacionados a recuperação muscular. Contudo, diversos fatores ainda permanecem desconhecidos, tais como: doses e parâmetros ideais de aplicação, mecanismos de ação, os efeitos em exercícios de longa duração e os efeitos em longo prazo na recuperação musculoesquelética. Da mesma maneira, ainda não são totalmente conhecidos os efeitos da combinação de diferentes fontes de luz (lasers e LEDs) sobre a performance e recuperação muscular pós-exercício. Objetivo: Com estes fatores em mente, o presente projeto de pesquisa tem como objetivo determinar os efeitos da fototerapia com lasers e LEDs e da crioterapia utilizadas isoladamente ou combinadas na recuperação muscular pós-exercício excêntrico de extensores de joelho. Métodos: Será realizado um ensaio clínico randomizado, placebo-controlado e duplo-cego, com a participação voluntária de indivíduos saudáveis. Analisaremos parâmetros relativos ao desempenho físico dos voluntários (pico de torque / contração voluntária máxima - CVM), dor muscular tardia (DMT) através da escala visual analógica (EVA) e marcador bioquímico de dano muscular (creatina quinase - CK). Resultados: A terapia de fotobiomodulação (PBMT) isolada foi ótima para recuperação pós-exercício com melhora da contração voluntária máxima (MVC), diminuição de dor muscular tardia (DOMS) e atividade de creatina quinase (CK) (p<0.05) de 24 a 96 horas em comparação com Placebo, Crioterapia e Crioterapia+PBMT. No grupo PBMT+Crioterapia, o efeito de PBMT foi diminuído (p>0.05), mas demonstrou melhoras significativas na MVC, diminuiu DOMS e atividade de CK (p<0.05). O tratamento isolado com Crioterapia e Crioterapia+PBMT foi similar ao Placebo (p>0.05). Conclusão: Nós concluímos que o uso isolado do tratamento PBMT é a melhor modalidade para acelerar a recuperação pós-exercício, levando a completa recuperação aos níveis basais em 24 horas após contrações excêntricas de alta intensidade.

Widespread use of organic light emitting diodes (OLEDs) in solid state lighting and display technologies require efficiency and lifetime improvements, as well as cost reductions, inclusive of the transparent conducting oxide (TCO). Indium tin oxide (ITO) is the standard TCO anode in OLEDs, but indium is expensive and the Earth's reserve of this element is limited. Zinc oxide (ZnO) and its variants such as aluminum-doped ZnO (AZO) exhibit comparable electrical conductivity and transmissivity to ITO, and are of interest for TCO applications. However, the workfunction of ZnO and AZO is smaller compared to ITO. The smaller workfunction of AZO results in a higher hole injection barrier at the anode/organic interface, and methods of tuning its workfunction are required. This dissertation tested the hypothesis that workfunction tuning of AZO films could be achieved by surface modification with electronegative oxygen and fluorine plasmas, or, via use of nanoscale transition metal oxide layers (MoOx, VOx and WOx). Extensive UPS, XPS and optical spectroscopy studies indicate that O2 and CFx plasma treatment results in an electronegative surface, surface charge redistribution, and a surface dipole moment which reinforces the original surface dipole leading to workfunction increases. Donor-like gap states associated with partially occupied d-bands due to non-stoichiometry determine the effective increased workfunction of the AZO/transition-metal oxide stacks. Reduced hole injection barriers were engineered by ensuring that the surface ad-layers were sufficiently thin to facilitate Fowler-Nordheim tunneling. Improved band alignments resulted in improved hole injection from the surface modified AZO anodes, as demonstrated by I-V characterization of hole only structures. Energy band alignments are proposed based on the aforementioned spectroscopies. Simple bilayer OLEDs employing the surface modified AZO anodes were fabricated and characterized to compare their performance with standard ITO. Anodes consisting of AZO with MoOx or VOx interfacial layers exhibited 50% and 71% improvement in power efficiency (PE) and external quantum efficiency (EQE), respectively, compared to ITO at a working voltage of 9 V. The efficiencies of dipole reinforced AZO (O2/CFx plasma treated) anodes were comparable to ITO. The improved performance of the surface modified AZO anodes compared to as-deposited AZO is ascribed to improved hole injection, improved charge balance, and improved radiative recombination kinetics. The results suggest that surface modified AZO anodes are a promising alternative to ITO, given the lower cost and Earth abundance of Al and Zn.

By using phosphorescent and thermally activated delayed fluorescence emitters, the internal quantum efficiency of organic light-emitting diodes (OLEDs) can now reach 100%. However, a major fraction of generated photons is trapped inside the device, because of the intrinsic multi-layer device structure and the mismatch of refractive indices. This thesis comprises different approaches for the efficiency enhancement of planar OLEDs. In particular, outcoupling strategies to extract trapped photons to obtain highly efficient OLEDs are investigated.

In recent decades, the negative effects of artificial light at night on natural ecosystems have attracted the attention of ecologists. Studies have shown that artificial light at night leads to a considerable reduction in insects and has a worrying impact on terrestrial ecosystems, including nocturnal insects (e.g. Lepidoptera) such as moths. Warm white light is generally expected to have a lower ecological impact compared with cold white light which has a higher proportion of blue light (&lt; 500 nm). The aim of this study is to investigate the impact of three light emitting diode (LED) light sources with different spectral power distributions on the responses of the greater wax moth (Galleria mellonella) under controlled experimental settings. In this experiment, three light sources with different spectral power distribution and dark condition were used and the start response time, time active, time flap wings, time flap wings / time active, main activity area and stop area of the greater wax moth were investigated. The light treatment used were: (1) darkness (n = 13); (2) warm-white light (correlated color temperature of 2675 K, n = 12); (3) white light (4070 K, n = 4); (4) cold white light (6200 K, n = 8). The experiment was performed in a rectangular light-tight box under controlled conditions. Main activity area showed significant difference between warm-white light and cold white light. With cold white light, a larger proportion of the moths were active in the area with the highest light levels, while the main activity area in the warm white light was in the zone with the lowest light levels. Other variables, however, did not show significant differences. The conclusion is that warm white light had a lower ecological impact than cold white light due to a larger proportion of moth is attracted to areas with stronger light. The results support the notion that in outdoor environments, warm white LEDs (maximum 3000 K) should be preferred compared to cold white light LEDs (over 3000 K), to reduce the impact on insects such as moths. The low correlated color temperature light sources used outdoors deserves more in-depth development and research.

No description available.

No description available.

No description available.

Over the last decades organic light-emitting diodes (OLEDs) and organic solar cells (OSCs) have gained considerable attention as efficient, flexible, lightweight, and potentially low-cost technology for lighting and display applications or as a renewable energy source, respectively. However, achieving long-term stability remains challenging. Revealing and understanding aging processes is therefore of great interest. This work presents fundamental investigations to understand and circumvent organic device degradation. In the first part, single materials used in organic devices were investigated. By tailoring an attenuated total reflection infrared (ATR-IR) spectrometer to the specific needs and subsequent measurements, it is shown that the tris(8-hydroxyquinoline)aluminum (Alq3) molecule, a well known fluorescent green emitter, degrades during air exposure by the formation of carbonyl groups. By using a laser desorption/ionization time of flight mass spectrometer (LDI-TOF-MS) it was shown that a,w-bis-(dicyanovinylen)-sexithiophen (DCV6T-Bu4), a well known small-molecule material which is used as part of the active layer, reacts with oxygen during ultraviolet (UV) irradiation. By using climate boxes and a sun simulator the impact of dry and humid air as well as sunlight on C60, a widely-used acceptor molecule in organic solar cells, was investigated. The breaking of the C60 cage to C58 and C56 and the further reaction of these components with oxygen as well as the dimerization of C58 and C56 molecules were found. The degradation products such as C58O increase with air exposure time but they are independent of the humidity level of the ambient air as well as sunlight irradiation. Subsequent annealing leads to a decrease of the C58O concentration. Many efficient n-dopants are prone to degradation in air, due to the low ionization potentials, thereby limiting the processing conditions. It was found that the air exposure of the highly efficient n-dopant tetrakis(1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinato)ditungsten(II) (W2(hpp)4) leads to oxidation reactions of the molecule to [W(hpp)2 + O] and other degradation products. The decay constant of W2(hpp)4 and the matching mean growth time of the [W(hpp)2 + O] degradation as well as a second very quick degradation of the dopant could be determined. The two decay constants can be explained by the assumption that W2(hpp)4 molecules, which are involved in the charge transfer, do degrade slower due to the fact that the charge transfer leads to a downshift of the energy levels of the W2(hpp)4 molecule. Apart from the properties of the organic materials, other effects such as the impact of different purification systems on the material purity as well as the dependence of material purity on the OLED lifetime has been investigated. No correlations between the purification grade and the amount of impurities were found. OLEDs which contain N,N\'-di(naphthalen-1-yl)-N,N\'-diphenyl-benzidine (alpha-NPD) purified in a vertically interlaced stainless steel sublimation systems shows slightly higher external quantum efficiencies compared to tube-based vacuum sublimation systems. The devices which contain alpha-NPD purified by a sublimation system have an extended lifetime. Finally, the impact of residual gases during device fabrication on OLED lifetime and electrical characteristics was investigated. It was found that water vapor introduces an additional series resistance to the OLED, while the other gases do not influence the electric characteristics. The presence of nitrogen or oxygen impacts the lifetime of the OLEDs by the same amount. Nitrogen is non-reactive, this leads to the conclusion that the influence of nitrogen and oxygen on the OLED lifetime is of non-chemical nature, such as changes in the morphology of the organic layers. Water vapor introduces an additional, even faster degradation process within the first hours of OLED operation. As major sources of device degradation, the dimerization of 4,7-diphenyl-1,10-phenanthroline (BPhen) as well as the complexation reaction of alpha-NPD with a bis(1-phenylisoquinoline)iridium(III) (Ir(piq)2) fragment was identified.