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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Dosimetria usando luminecência opticamente estimulada: aplicações, propriedades físicas e caracterização de materiais dosimétricos / Dosimetry using optically stimulated luminescence: applications, physical properties and dosimeter detectors characterization

Luana de Freitas Nascimento 10 August 2007 (has links)
Dosimetria usando Luminescência Opticamente Estimulada (OSL) é uma área em constante crescimento dentro da ciência e com excelentes perspectivas comerciais. O Óxido de Alumínio crescido na presença de uma atmosfera rica em Carbono (Al 2O3:C) tem fornecido bons resultados como detector luminescente. Esse material apresenta alta sensibilidade à radiação ionizante e boa resposta à estímulos ópticos. Estima-se que cerca de dois milhões de pessoas façam uso de dosímetros com detectores de Al 2O3:C em rotinas de dosimetria individual externa, que por apresentar varias vantagens experimentais acredita-se substituirá as outras duas técnicas dosimétricas mais adotadas: dosimetria fotográfica e termoluminescente. A certificação de uma técnica de dosimetria para uso comercial exige uma série de estudos. Neste trabalho apresentamos contribuições que complementam o entendimento e adoção da técnica de OSL em dosimetria pessoal. Nossa primeira contribuição consiste numa serie de testes de desempenho mostrando a eficácia da técnica para justificar nossa proposta de certificação de dosimetria individual externa usando OSL no Brasil. No intuito de relacionar centros paramagnéticos e o processo de luminescência, apresentamos resultados de espectros de EPR em detectores OSL. Detectamos e classificamos sinais de EPR relacionados a impurezas nas amostras, porem, sinais dos centros luminescentes não foram detectados. Finalmente, apresentamos um estudo preliminar sobre a resposta de luminescência do Al2O3:C quando exposto a diferentes comprimentos de onda de radiação UV. A inexistência de dosimetria de nêutrons por técnicas de OSL motivou o estudo de vários óxidos dopados com Térbio como possíveis candidatos a material dosimétrico. Alguns resultados preliminares do espectro de EPR desses óxidos quando irradiados em campo beta de 90Sr/90Y e da resposta de luminescência em função da luz de excitação para análise dos tipos de armadilhas criadas pela presença do Tb+3 são apresentados. / Dosimetry using Optically Stimulated Luminescence (OSL) is an expanding scientific research area which also shows excellent commercial potential. Aluminum oxide grown in an atmosphere in the presence of Carbon, Al 2O3:C, presented excellent results as a luminescent detector. This material has high sensitivity when exposed to ionizing radiation and good responses to optical stimulation. Over two million people use dosimeters with Al 2O3:C detectors in personal dosimetry procedures. The experimental advantages of using OSL are believed to replace the two other usual techniques: photographic and thermoluminescent dosimetry. To validate the commercial use of a dosimetry technique it is necessary to evaluate a number of studies. In this work we present results which increase our understanding of OSL dosimetry. First we present a number of behavior tests to show the efficiency of the technique for the purpose of justifying the use of OSL in personal dosimetry in Brazil. In an attempt to correlate paramagnetic centers and the luminescence process we present EPR results in OSL detectors. We could detect and classify impurities centers in our samples; however we could not find conclusive results about paramagnetic centers generated by exposition to ionizing radiation. We present a preliminary study about the luminescence behavior from Al 2O3:C when exposed to different UV wavelengths. The nonexistence of a neutron dosimetry using OSL suggested a study of three types of oxides doped with Terbium which are strong candidates as OSL detectors due to their sensitivity to neutron expositions. We present preliminary results of EPR spectroscopy from these oxides when exposed in a beta field of 90Sr/90Y and the luminescent response when the excitation light is used to analyze traps generated by the presence of Tb+3.
62

Síntese e caracterização de elemento sensor de matriz KAISi3O8, dopadas com Mn ou Gd, obtidos pela técnica sol-gel, visando a aplicação em dosimetria das radiações ionizantes por termoluminescência e luminescência opticamente estimulada. / Synthesis and caracterization of sensor element of kalSi3O8 matrix, doped with mn and gd, obtained by sol-gel method, for application in ionizing radiation dosimetry by thermoluminescence and optically stimulated luminescence.

Elcio Liberato Pires 12 November 2010 (has links)
Neste trabalho, estudou-se as propriedades termoluminescentes e fotoluminescentes (em processo anti-Stokes), além de algumas propriedades químicas e físicas, de amostras sintéticas de KAlSi3O8, dopadas com Mn ou Gd, obtidas por meio da técnica sol-gel. O objetivo principal do estudo foi a obtenção de um novo material, com possibilidades reais de aplicação em dosimetria das radiações ionizantes, como elemento sensor de dosímetros luminescentes. As amostras foram obtidas e trabalhadas na forma de pós com tamanho médio de partícula em 600 nm e suas estruturas composta por uma matriz amorfa e com presença de nano partículas, presente apenas nas amostras dopadas. Os resultados de EPR mostraram que os dopantes incorporaram na matriz sob a valência de Mn2+ e Gd3+ respectivamente. As curvas de emissão TL apresentaram formatos semelhantes para todas as regiões estudadas, com a presença de um pico principal de intensidade alta e reprodutível em torno de 170°C. As curvas de decaimento da LOE da amostra não dopada e dopada com Mn exibiram um decaimento total da luminescência para 40 s de estimulação centrada em 470 nm; por outro lado, a amostra dopada com Gd, exibiu um rápido decaimento da LOE (aproximadamente 71,4 % da intensidade inicial), para os primeiros 40 s de estimulação, seguida por um decaimento mais lento e persistente para o restante do período de estimulação, o que indica claramente a presença de duas componentes de decaimento. As amostras dopadas com Mn apresentaram emissão TL mais intensa em torno 570 nm, sendo mais eficientes para os estudos de TL no VIS; enquanto que, as dopadas com Gd, exibiram emissão mais intensa em 470 nm, porém, devido ao formato dos sinais (presença de um único pico aparente), mostraram-se melhor para os estudos de LOE e TL no UV. As amostras dopadas com 0,5% e 8% em mol de Mn e Gd, respectivamente, apresentaram os sinais luminescentes mais intensos, tanto para LOE quanto para TL. No estudo da dependência energética para diferentes energias de raios-X, o tipo de dopante influenciou no padrão de resposta obtido, tendo sido observado um decréscimo da intensidade luminescente com o aumento da energia para a amostra dopada com Mn; para a amostra não dopada e dopada com Gd, não se observou um padrão de decréscimo ou aumento da intensidade com a energia. As curvas de calibração foram ajustadas por meio de retas com grau de confiabilidade alto (fator R2 próximo a 1), e as menores doses detectáveis variaram entre 20 e 60 mGy aproximadamente. Todas as amostras apresentaram perdas consideráveis de intensidade luminescente com o passar do tempo após irradiação, e que foi de aproximadamente 80%, em média, para os 10 primeiros dias. Concluiu-se que, a princípio, os materiais têm maior possibilidade de aplicação na dosimetria em tempo real do que na dosimetria convencional ou passiva por TLDs, devido a sua alta resposta luminescente. Contudo, estudos futuros a respeito de tratamento térmico prévio, podem viabilizá-los a esta última aplicação. Com relação ao campo de aplicação, sugere-se a dosimetria ambiental, devido aos valores Z obtidos, que estão mais próximos do dos materiais que compões rochas e sedimentos. / In this work the thermoluminescent and photoluminescent properties (in the anti-Stokes process), and some other chemical and physical properties of KAlSi3O8 synthetic samples, doped with Mn or Gd, obtained by sol-gel method, were studied. The main goal of this study was to obtain a new material, with real possibility of application in ionizing radiation dosimetry as sensor element in luminescent dosimeters. The obtained samples were composed of powders with average particle size around 600 nm and they structures were composed of an amorphous matrix with presence of nanoparticles, observed only in the doped samples. The EPR results showed that the dopants incorporated in the matrix in the Mn2+ and Gd3+ valences, respectively. The TL glow curves exhibited a similar pattern for all the studied regions, composed of a main high-intensity and reproducible peak around 170 °C. The OSL shine-down curves for the undoped and Mn doped samples exhibited a total decay of luminescence for 40 s of stimulation centered at 470 nm; on the other hand, Gd doped sample exhibited an quick OSL decay (approximately 71.4 % of the initial intensity), for the first 40 s of stimulation, followed by a slower and more persistent decay, which clearly indicates the presence of two decay components. Mn doped samples showed the highest TL emission around 570 nm, being more efficient for the TL studies in the VIS, while the Gd doped samples exhibited the highest emission at 470 nm; however, due to the obtained curve pattern (with an apparent single peak), they had shown more efficient results for the applications in the UV. The samples doped with 0.5 and 8 mol% of Mn and Gd, respectively, showed the highest luminescent response improvement for OSL and TL. Energetic dependence on different X-rays energies study showed that the dopants changed the obtained response pattern. The Mn doped sample exhibited a decrease in luminescent response, while the Gd and the undoped samples do not show a pattern of decrease or increase in luminescence. The calibration curves were fitted by straight lines with high reliability degree (R2 near to 1), and the lowest detectable doses were between 20 and 60 mGy. All the samples exhibited considerable losses in luminescent intensity with the time after irradiation (about 80% for the firsts 10 days). From the results it was concluded that the studied materials are more applicable to real time than to passive TLD dosimetry, due to their high luminescent response. However, studies about previous heating treatment could make them feasible for the last application. The use of these materials in environmental dosimetry is suggested due to the obtained Z values, which are closer to those which form rocks and sediments.
63

Braided river response to glacial-drainage capture and climate variations through the last glacial maximum

Rowan, Ann Victoria January 2012 (has links)
Glacial-interglacial cycles drive changes in the discharge and sediment flux from the headwaters of glaciated basins, which are recorded by proglacial fluvial sediments. Linking braided river stratigraphy to the Quaternary climate record could indicate the control of climate-driven variations in discharge and sediment flux on fluvial processes, and the magnitude and frequency of past climate variations. New Zealand is a key location for investigating terrestrial records of Southern Hemisphere climate change. The Late Quaternary braided river deposits on the Canterbury Plains, South Island, New Zealand have formed over the last 400 ka. The coastal cliff marking the southeastern margin of the Canterbury Plains provides excellent exposure of fluvial sediments deposited during the last glacial period, from ~40 ka until the end of the Last Glacial Maximum (LGM) (~18 ka).Deposition at the modern coastline of the Canterbury Plains is interpreted in the context of the climate event stratigraphy for New Zealand, which requires a precise geochronology. This thesis demonstrates the first successful application of optically stimulated luminescence (OSL) dating to glaciofluvial sediments on South Island: a technique that was previously considered unsuitable for this region. Ages produced for the coastal stratigraphy range from 36.7 ± 2.9 to 18.2 ± 1.3 ka, indicating that deposition took place during the last glacial, with little or no postglacial aggradation. Three adjacent catchments on the southern Canterbury Plains - the Rakaia, Ashburton and Rangitata - have undergone glacial-drainage capture during the period represented by the coastal stratigraphy. During glacials, transfluent ice reversed the flow direction in several key tributaries, resulting in dramatic variations in effective drainage area of the Ashburton and Rangitata, and variations in discharge and sediment flux which are recorded in the stratigraphy of these catchments. The magnitude, timing and duration of drainage capture were quantified using the Plummer and Phillips (2003) glacier model. The Ashburton catchment increased to 160% of the modern effective drainage area when temperature change relative to modern conditions exceeded -6°C during the LGM. Meanwhile, the effective drainage area of the Rangitata decreased to 63%, and the Rakaia to 93%, reducing discharge from these catchments. Furthermore, glaciation dramatically affects the seasonality of the annual hydrograph. At four coastal sites, the fluvial stratigraphy was surveyed to investigate possible variations in depositional architecture, due to both climate variations, and glacial-drainage capture in the Ashburton and Rangitata. Unexpectedly, little vertical variation in depositional architecture was found, indicating that the deposits created by the braided rivers represent sediment transport during a similar set of flow (and by inference, climate) conditions. Laterally extensive erosional surfaces separating storeys of one or two flow depths in thickness, in combination with the OSL geochronology, suggest that the gravel-bed braided river stratigraphy primarily records a response to climate variations within glacial maxima, rather than on the scale of the glacial-interglacial cycle.
64

Desenvolvimento e caracterização de dosímetros para monitoração individual de trabalhadores ocupacionalmente expostos à radiação combinando as técnicas de termoluminescência (TL) e luminescência opticamente estimulada (OSL) / Development and characterization of dosimeters for individual monitoring of workers occupationally exposed to radiation combining the techniques of thermoluminescence (TL) and optically stimulated luminescence (OSL)

Malthez, Anna Luiza Metidieri Cruz, 1985- 28 August 2018 (has links)
Orientadores: Vera Lúcia da Silveira Nantes Button, Marcelo Baptista de Freitas / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-28T09:42:26Z (GMT). No. of bitstreams: 1 Malthez_AnnaLuizaMetidieriCruz_D.pdf: 4070699 bytes, checksum: 5b502eb8b2975aac6052df7ad659d32a (MD5) Previous issue date: 2015 / Resumo: Neste estudo foi desenvolvido um dosímetro (monitor individual) para monitoração externa de indivíduos ocupacionalmente expostos à radiação (raios X e gama) que faz o uso simultâneo das técnicas de termoluminescência (TL) e luminescência opticamente estimulada (OSL - Optically Stimulated Luminescence), combinado às diferentes características dosimétricas de detectores já utilizados com a técnica TL na rotina dos Serviços de Monitoração Individual Externa (SMIEs) no Brasil (LiF:Mg,Ti ¿ TLD100, CaF2:natural, CaSO4:Dy - IPEN) e detectores utilizados com a técnica OSL, ainda pouco explorados na monitoração individual (BeO ¿ Thermalox 995) e recentemente autorizados a serem utilizados com a técnica OSL no país (Al2O3:C - Luxel). Para o desenvolvimento do monitor, diversas características intrínsecas e dosimétricas dos detectores empregando as técnicas TL e OSL em três diferentes equipamentos leitores foram avaliadas. Testes de desempenho foram aplicados ao monitor desenvolvido, conforme critérios estabelecidos no país e no exterior (CASEC e IEC, respectivamente). Os resultados obtidos demonstram que as respostas TL e OSL dos detectores dependem fortemente da configuração do leitor utilizado, da técnica empregada (TL ou OSL) e do tipo de sinal avaliado, no caso da técnica OSL (OSL total ou inicial). Assim é fundamental uma análise prévia de características intrínsecas do material, como comprimento de onda principal da emissão luminescente, tipo (inicial ou total) e magnitude (doses baixa, moderada ou alta) do sinal que será avaliado para a escolha adequada dos parâmetros do leitor (filtros, máscaras, potência, entre outros) empregando as duas técnicas. Os resultados obtidos com a técnica OSL reforçam seu uso na monitoração individual no Brasil, uma vez que estavam em acordo com a técnica TL, amplamente empregada pelos SMIEs nacionais. Além da determinação de dose individual, normalmente empregada na monitoração de trabalhadores, o dosímetro desenvolvido permite também estimar doses acumuladas ao longo do tempo, empregando a técnica OSL nos detectores de Al2O3:C ou BeO, sendo que no caso deste último, a dose única (ou individual) também pode ser determinada com a técnica TL aplicada simultaneamente no mesmo detector. Após a avaliação das respostas em energia dos detectores, um algoritmo foi desenvolvido, testado e validado para avaliar fatores de correção com respeito à energia, baseado na razão entre as respostas de um par de detectores TL e OSL. Os resultados demonstraram que as diferentes razões entre os sinais provenientes do par, permitem avaliar de forma precisa a qualidade da radiação à qual o par de detectores foi exposto. O monitor desenvolvido possui três configurações diferentes de pares de detectores, Al2O3:C/LiF:Mg,Ti, Al2O3:C/BeO e CaSO4:Dy/BeO. Ele apresenta como principais vantagens, em relação aos dosímetros já existentes em uso comercialmente, a possibilidade de poder inferir informações sobre a dose e qualidade da radiação (energia efetiva) sem a utilização de filtros e com diminuição das incertezas associadas, avaliar doses acumuladas ao longo do tempo com o mesmo dosímetro e combinar todas as características dos detectores associadas às técnicas TL e OSL, simultaneamente em um mesmo dosímetro. Os resultados dos testes de desempenho do monitor apresentaram conformidade com os critérios nacionais e internacionais estabelecidos, e contribuíram para que os critérios nacionais utilizados para a técnica TL possam ser estendidos para a técnica OSL / Abstract: In this study a dosimeter (personal monitor) for external monitoring of individuals occupationally exposed to radiation (X and gamma rays) was developed using simultaneously thermoluminescent (TL) and optically stimulated luminescence (OSL) techniques. Intrinsic characteristics of detectors already used with TL technique in External Individual Monitoring Services routine in Brazil (LiF:Mg,Ti ¿ TLD 100, CaF2:natural and CaSO4:Dy ¿ IPEN) were combined to detectors used with OSL technique, one less explored (BeO ¿ Thermalox 995), and other recently approved (Al2O3:C - Luxel) to be used in individual monitoring in the country (Al2O3:C - Luxel). During the monitor development, several intrinsic and dosimetric characteristics of detectors were evaluated employing TL and OSL techniques in three different reader equipments. Performance tests were applied to the developed monitor according to national and international established criteria (CASEC and IEC, respectively). The obtained results showed that the responses of TL and OSL detectors are strongly dependent on reader configuration, employed technique (TL and OSL) and, in the particular case of OSL technique, also the signal (total or initial OSL). Therefore, a previous analysis of the intrinsic characteristics of the material, as the main wavelength of the luminescent emission, the signal type (initial or total) and dose magnitude (low, moderate or high) must to be made in order to select the reader configuration (filters, power, and others) used with each technique. The results obtained with OSL technique reinforce its use in Brazil, as they were in agreement with TL technique, which is already largely used by national EIMS. In addition to the assess of individual dose, usually employed in workers monitoring, the developed dosimeter allows evaluating accumulated dose over time using OSL technique with Al2O3:C or BeO detectors, and single or individual doses can be evaluated applying TL technique simultaneously applied in the same detector. After the evaluation of the energy response of detectors, an algorithm was developed, tested and validated to assess correction factors with respect to energy, based on the ratio of the responses of a pair of TL and OSL detectors. The results confirm that the different ratios between signals from a detector pair allow to evaluate more accurately the radiation quality to that the pair of detectors were exposed. The monitor was developed with three different arrangements of pairs of detectors, Al2O3:C/LiF:Mg,Ti, Al2O3:C/BeO and CaSO4:Dy/BeO. It presents as main advantages, compared to existing commercial dosimeters in use, the possibility to infer information on the dosage and quality of radiation (effective energy) without the use of filters and reducing associated uncertainties, to assess cumulative doses over time with the same dosimeter, and to combine all features of the detectors associated with TL and OSL techniques, simultaneously, in the same dosimeter. The results of the performance tests of the developed monitor were in accordance to national and international criteria, and contributed to that the national criteria, used for TL technique, can also be extended to the OSL technique / Doutorado / Engenharia Biomedica / Doutora em Engenharia Elétrica
65

AC ELECTROTHERMAL MICROFLUIDIC TWEEZERS: CHARACTERIZATION AND APPLICATIONS

Kshitiz Gupta (12401317) 11 April 2022 (has links)
<p>Microfluidics has established itself as a key technology in a wide range of fields including pharmaceuticals, point-of-care diagnostics, thermal management, and space technology. Most of these applications involve manipulation of small quantities (micro – nanoliters) of fluids and various particles or biological cells suspended in them. These platforms employ mechanical, thermal, acoustic, magnetic, optical, electric and many other means for creating particle and fluid motion. Many biological applications require handling cells that are vulnerable to getting damaged if proper physiological conditions are not maintained or if excessive force is applied on them. The non-invasive nature of optical and electrical micro-manipulation techniques such as rapid electrokinetic patterning (REP) has proven to be of great importance in such applications. These techniques enable handling, transportation, sorting and arrangement of fragile synthetic micro/nanoparticles and biological cells without compromising their structure and surface properties.</p> <p>REP is a recently developed micro-manipulation tool that employs optically induced electrothermal vortices to create custom flow patterns. Particle suspensions are entrained in these vortices and are trapped on an electrode surface through AC electrokinetic mechanisms. This work focuses on characterizing a REP trap and discusses its potential applications in handling biological cells. Polystyrene microparticles are confined in a REP trap and a MATLAB program is used to track their motion inside the trap. The tracked particle trajectory reveals that the potential energy of the trapped particle is parabolic and hence the trap is Hookean in nature. The trap is modelled as a spring-mass system and the stiffness coefficient of that system is found to be of the order of 10<sup>-15</sup> N/μm. The origin of the restoring force in the spring-mass model is found to be the drag force created by the electrothermal vortex. The ability to exert ultra-small forces in a stable trap enables REP to be used in various non-invasive particle manipulation applications.</p> <p>The transient nature of REP is studied using numerical modeling and particle image velocimetry (PIV) analysis of a vortex created by a moving laser spot. A numerical model suggests that custom-shaped steady state REP vortices can be created via superposition of multiple axisymmetric circular shaped vortices. However, the method of superposition cannot be extended to transient traps and a more involved 3D model is required to simulate them. The laser spot is scanned back-and-forth in a line with different speeds to create transient REP vortices. The PIV analysis, in agreement with the numerical model, shows that the location of the moving vortex is undiscernible at high speeds. Moreover, the circular shaped vortex is stretched out into a line when the laser scanning frequencies are more than 15 Hz.</p> <p>The particle-electrode attraction force, which entraps the particles at the electrode surface, is characterized using particle diffusometry (PD) and defocusing particle tracking. PD is used to measure the diffusion coefficient of polystyrene particles under different electric field parameters near an electrode surface. It is found that the particle diffusivity decreases with a decrease in the electric field frequency from 150 – 30 kHz and with an increase in the applied voltage from 4 – 8 V<sub>pp</sub>. A MATLAB program is used to track the number of in-focus particles and their distance from the electrode surface. A histogram of the particles’ distance from the electrode surface shows an increase in the particle concentration near the electrode at low frequencies (30 – 60 kHz). These observations suggest that the average height of an entrapped particle decreases with a decrease in applied field frequency and an increase in applied voltage. This suggests that the attractive trapping force is significant at 30 kHz but diminishes at around 150 kHz.</p> <p>Salt and sugar-based isotonic media used for cell suspensions pose several challenges for electrokinetic mechanisms such as REP. Various solutions to overcome these challenges for bio-manipulation applications are discussed in this work. The presence of DC offset in the AC electric field is found to enhance particle entrapment in sugar-based media. The effect of DC offset on trapping performance in bio-relevant media is assessed by measuring the stability of the REP trap. This work also shows entrapment and manipulation of Mice pancreatic cancer cells (KPC2) suspended in the sugar-based isotonic media using REP. The biological applications of the REP technology are highly promising, but they have not yet been well-explored. This work lays the foundation of understanding how REP can be operated in high osmolarity media for bio-manipulation applications.</p>
66

APPLICATION OF NANODIAMONDS FOR BIOLOGICAL INVESTIGATION / ダイヤモンドナノ粒子の生体計測応用に関する研究

Sotoma, Shingo 23 March 2015 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19002号 / 工博第4044号 / 新制||工||1622(附属図書館) / 31953 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 白川 昌宏, 教授 田中 庸裕, 教授 濵地 格 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM
67

The Chronology of Glacial Landforms Near Mongo, Indiana – Evidence for the Early Retreat of the Saginaw Lobe

Valachovics, Thomas Richard 09 September 2019 (has links)
No description available.
68

Reduced Susceptibility Of Deformation Due To Vibrational And Gravitational Effects On A Focus Variable Adaptive Lens

Relina, Victoriya 01 January 2013 (has links)
Orthodox optical devices, such as lenses, mirrors, and prisms, are composed of solidstate materials, which although well studied and implemented ubiquitously are severely limited in their adaptable properties. An arguably new field of adaptive optics has emerged to further expand photonic manipulation competences of optical components. Fluid-based adaptive optical components were introduced as early as 1968 [1]; such components have the ability to change the shape of their interface surface, thus allowing for a variable curvature profile. The method of manipulation varies greatly, as does the range of surface deformations. A solid-state optical component is affected by system vibration variation only (difference in vibration from one component to the other due to damping effect). By comparison, two large limiting factors of a fluid-based adaptive optical component are the effect of local vibrations on the surface of the device and gravitational effect (when the optical axis of a lens is positioned parallel to gravitational pull). Such a gravitational effect has been mitigated by the invention of the mechanical electrowetting lens [2], which uses density matching of two liquids that make up an adaptive lens. However, this configuration creates an extra limiting factor of density matching two optically clear fluids with a desirable transmission spectrum. This method can also become bulky when a large aperture is needed. In this thesis, two adaptive lens systems are explored. Principles of operation, performance, limitations, as well as future improvements are studied and theorized. iv The first lens uses an optically clear elastomer as the substrate of an adaptive lens and a primitive mechanical manipulation to turn a plano–plano lens into a plano–convex lens. The second lens is composed of an optically clear gel rather than a fluid. Both methods exhibit excellent optical properties regardless of the orientation about the gravitational pull and significantly limit local vibration affects simply by the physical nature of the chosen materials.
69

Optically Thick Clumps – Not the Solution to the Wolf-Rayet Wind Momentum Problem?

Brown, J., Cassinelli, J., Li, Q., Kholtygin, A., Ignace, Richard 01 October 2004 (has links) (PDF)
The hot star wind momentum problem eta = M-upsiloninfinity/(L/c) much greater than 1 is revisited, and it is shown that the conventional belief, that it can be solved by a combination of clumping of the wind and multiple scattering of photons, is not self-consistent for optically thick clumps. Clumping does reduce the mass loss rate. M, and hence the momentum supply, required to generate a specified radio emission measure epsilon, while multiple scattering increases the delivery of momentum from a specified stellar luminosity L. However, in the case of thick clumps, when combined the two effects act in opposition rather than in unison since clumping reduces multiple scattering. From basic geometric considerations, it is shown that this reduction in momentum delivery by clumping more than offsets the reduction in momentum required, for a specified epsilon. Thus the ratio of momentum deliverable to momentum required is maximal for a smooth wind and the momentum problem remains for the thick clump case. In the case of thin clumps, all of the benefit of clumping in reducing lies in eta reducing. M for a given epsilon so that extremely small filling factors f approximate to 10(-4) are needed. It is also shown that clumping affects the inference of M from radio epsilon not only by changing the emission measure per unit mass but also by changing the radio optical depth unity radius R-rad, and hence the observed wind volume, at radio wavelengths. In fact, for free-free opacity proportional to n(2), contrary to intuition, R-rad increases with increasing clumpiness.
70

TIMING OF THE EMPLACEMENT OF ANCIENT COASTAL DEPOSITS OF GEORGIA AIDED BY GROUND PENETRATING RADAR AND DETERMINED BY OPTICALLY STIMULATED LUMINESCENCE AND ELECTRON SPIN RESONANCE OPTICAL DATING

Hendricks, Robert R. January 2016 (has links)
ESR, OSL and TT-OSL dating methods were applied to samples collected from six of the Ancient Coastal Deposits (ACDs) along the southern Georgia Coastline. Samples were collected from the Princess Anne (the youngest and most seaward ACD), Pamlico, Talbot, Penholoway, Wicomico, and Okefenokee ACDs with the goal of determining the age of formation of these features. Ground Penetrating Radar (GPR) was used to determine the subsurface morphology and target lithologies for age determination. OSL and TT-OSL dating was attempted on samples collected from the youngest two ACDs, the Pamlico and Princess Anne, at McMaster Universities AGE Lab. ESR samples collected from all of the ACDs studied were measured at Florida State University as well as Osaka University. ESR analysis measured the Al signal, the Ti-Li signal, measured using two different methods, as well as the Ti-H signal. A number of low additive dose points were added to the ESR dose plan to attempt to create a better dose response curve for the low saturating Ti-H signal in attempt to better utilize the signal. While the geochronological methodology did not prove useful for determining the age of all of the ACDs it did result in depositional age estimates for the Cypresshead Formation at 433-2978 ka and Satilla Formations at 243-417 ka using the Ti-Li ESR signal as a maximum age estimate. The GPR, ESR, and core data all point to the conclusion that the ACDs of the Georgia Coast are geomorphic modifications and not the result of a unique depositional process. Based on the discrepancy between the depositional age of the Cypresshead and Satilla Formations as determined by ESR in this study and the ages of the ACDs published by others from Georgia (Markewich et.al., 2013) or other areas of the Atlantic Coast (Wehmiller, 2004; Willis, 2006) it can be concluded that paleo sea-levels modified the Cypresshead and Satilla Formations in to the morphology seen today at some point after their initial deposition. / Dissertation / Doctor of Philosophy (PhD) / ESR, OSL and TT-OSL dating methods were applied to samples collected from six of the Ancient Coastal Deposits (ACDs) along the southern Georgia Coastline with the goal of determining the age of formation of these features. Ground Penetrating Radar (GPR) was used to determine the subsurface morphology and target lithologies for age determination. A number of low additive dose points were added to the ESR dose plan to attempt to create a better dose response curve for the low-dose saturation of the Ti-H signal in attempt to better utilize the signal. While the geochronological methodology did not prove useful for determining the age of all of the ACDs, it did result in depositional age estimates for the Cypresshead Formation at 433-2978 ka and Satilla Formations at 243-417 ka. The GPR, ESR, and core data all point to the conclusion that the ACDs of the Georgia Coast are geomorphic features without unique depositional events.

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