The present study investigates experimentally the laminar mixing and heat transfer of a range of helical ribbon and anchor impellers for both Newtonian and inelastic non-Newtonian fluids. The work also correlates the experimental data empirically in the form of dimensionless groups. In order to estimate the relative importance and the effect of all the geometrical parameters on the mixing power and heat transfer, data from the published literature sources will be utilized and combined with the results from this study. Thus, reliable empirical correlations will be obtained which are applicable over the widest range of operating conditions. The study also investigates the ablity of the various impellers to level out temerature distributions. The measurement of these temperature gradients and the impeller power requirements gives a measure of the mixing efficiency of the impeller used.

The present study investigates experimentally the laminar mixing and heat transfer of a range of helical ribbon and anchor impellers for both Newtonian and inelastic non-Newtonian fluids. The work also correlates the experimental data empirically in the form of dimensionless groups. In order to estimate the relative importance and the effect of all the geometrical parameters on the mixing power and heat transfer, data from the published literature sources will be utilized and combined with the results from this study. Thus, reliable empirical correlations will be obtained which are applicable over the widest range of operating conditions. The study also investigates the ablity of the various impellers to level out temerature distributions. The measurement of these temperature gradients and the impeller power requirements gives a measure of the mixing efficiency of the impeller used. / Science Research Council

Environmental noise has for decades been a well known problem, especially in urban areas. As noise requirements for vehicles are sharpened, noise reducing concepts are needed in early design stages requiring accurate simulations to support the design. Specifically for optimization of noise treatments, the absorber performance must be simulated correctly. So called noise encapsulations are placed below the powertrain on heavy vehicles to enclose the engine and reduce noise radiation. The attenuation of the absorbers on these shields must be represented correctly in simulations, even in environments with complex sound field, cooling flow and high temperature variations which may affect the absorber performance. This thesis studies the performance variation due to different absorber representations and due to these factors and how to include this in simulations. It is shown that the material representation significantly affects the attenuation performance in the simulations. Assuming locally reacting absorbers neglects the full interaction between the sound field and the material, which was shown to affect the noise reduction considerably. A measurement method to determine the angular dependent surface impedance was evaluated. It was shown sensitive to small samples and a method to improve accuracy was suggested. Including the angular dependence, either by full resolution or an angular dependent impedance, the field-absorber interaction is included in the simulations and more accurate results are obtained. The influence of flow and temperature fields on the absorber performance was also investigated. A method to include these effects was developed and the attenuation performance shown significant, especially for materials with bulk reaction. In conclusion, thorough knowledge of the material behavior and the field in the applications is required to choose appropriate material representation to enable reliable simulation results.​ / <p>QC 20160311</p>

Esta tese apresenta soluções para o gerenciamento e otimização de temperatura para sistemas de codificação de vídeo baseados nas características da aplicação e no conteúdo dos vídeos digitais. Diferente dos trabalhos estado-da-arte, as soluções propostas nesta tese focam em técnicas de gerenciamento de temperatura no nível da aplicação e características da aplicação codificação de vídeo e as propriedades dos vídeos digitais são explorados para desenvolver soluções termais para a codificação de vídeo com baixas perdas na qualidade de serviço das aplicações. Diversas análises são realizadas considerando a aplicação de codificação de vídeo para entender o comportamento da temperatura durante o processo de codificação para diferentes sequências de vídeo. Com base nos resultados das análises, soluções com diferentes abordagens são propostas para atenuar os efeitos da temperatura nos sistemas de codificação de vídeo. Gerenciamento de temperatura baseado nas características da aplicação para o padrão de codificação HEVC usa uma técnica de seleção de configuração em tempo de execução para manter a temperatura abaixo dos limites seguros de operação com bons resultados de qualidade de vídeo. Otimização de temperatura baseado em computação imprecisa usa aproximações baseadas em conteúdo para reduzir a temperatura de chips executando o HEVC. Um escalonador de tarefas que usa características da aplicação para guiar o escalonamento de threads focando na redução dos gradientes espaciais de temperatura que são resultantes do desbalanceamento natural de cargas entre as threads da aplicação. As soluções propostas são capazes de reduzir em até 10 ºC a temperatura do chip com perdas insignificantes na eficiência de compressão. Os resultados de qualidade objetiva (medida usando PSNR) são de 12 dBs até 20 dBs maiores quando comparados com trabalhos da literatura. Além disso, o escalonador de tarefas proposto é capaz de eliminar os gradientes espaciais de temperatura maiores que 5 ºC para arquitetura multi-cores. Como principal conclusão, esta tese demonstra que as técnicas de gerenciamento de temperatura que usam o conhecimento da aplicação de maneira conjunta com as propriedades dos vídeos digitais tem um alto potencial para melhorar os resultados de temperatura de sistemas de codificação de vídeo mantendo bons resultados de qualidade visual dos vídeos codificados. / This thesis presents application-driven temperature-aware solutions for next generation video coding systems, such as the High Efficiency Video Coding (HEVC). Different from state-of-the-art works, the proposed solutions raise the abstraction of temperature management to the application-level, where video coding characteristics and video content properties are used to leverage thermal-aware solutions for video coding with low QoS (Quality of Service) degradation. Several video coding and temperature analyses are performed to understand the behavior of temperature when encoding different video sequences. Based on the analyses results, different approaches are proposed to mitigate the temperature effects on video coding systems. Application-driven temperature management for HEVC uses run-time encoder configuration selection to keep temperature under safe operational state while providing good visual quality results. Temperature optimization using approximate computing uses content-driven approximations to reduce the on-chip temperature of HEVC encoding. Application-driven temperature-aware scheduler leverages application-specific knowledge to guide a scheduling technique targeting reducing the spatial temperature gradients that are resulted from the unbalance workload nature of multi-threaded video coding application. The proposed solutions are able to provide up to 10 °C of chip temperature reduction with negligible compression efficiency loss. Besides, when compared with previous works the resulted objective video quality (PSNR) is from 12 dB up to 20 dB higher. Moreover, the proposed scheduler eliminates spatial temperature gradients greater than 5 ºC of multi-core architectures. As conclusion, this thesis demonstrates that leveraging application-specific knowledge and video content properties has a significant potential to improve temperature profiles of video coding systems while still keeping good quality results.

Une zone de constriction dans un micro-canal fluidique peut générer, si le débit est suffisant, un écoulement bi-phasique. Ceci est l’origine de la cavitation hydrodynamique. Les échanges de chaleur latente générés par l’apparition et l’implosion des bulles impliquent une variabilité importante de la température dans les zones au-delà de la constriction. En ajoutant des sondes de température nanométriques dans le fluide et en utilisant un microscope confocal on peut déterminer la température en un point. Ainsi on a pu établir des cartographies thermiques en 2 et 3 dimensions à l’intérieur d’un écoulement stationnaire bi-phasique. La technique permet en outre d’avoir accès à la quantité de gaz ce qui permet de corréler les gradients de température avec les zones de transitions de phases. Des zones de très forts refroidissements sont observées après la constriction, là où les bulles apparaissent. Par contre on n’observe pas les zones d’échauffement attendu à cause de la condensation. Une méthode complémentaire, moins sensible, utilisant la spectroscopie Raman a aussi été utilisée pour confirmer ce résultat. Par ailleurs une nouvelle classe de matériaux luminescents sensible à la température et la pression a été étudiée. Enfin une étude de la production de radicaux lors de l’implosion des bulles a été menée en utilisant la chimiluminescence du luminol. La technique utilisée par comptage de photons a permis de quantifier cette production et une cartographie de l’émission du luminol a permis d’associer celle-ci avec la zone d’implosion des bulles / A constriction in the microchannel can be used to establish a two-phase flow, when a sufficient liquid flux is introduced. This is known as hydrodynamic cavitation. The latent heat resulting from the growing and collapsing vapor bubbles makes it interesting to observe the temperature conditions in the flow downstream of the constriction. Using fluorescence microscopy, with the addition of temperature sensitive nano probes into the working fluid, we can determine the temperature at a single point, averaged over the integration time. Coupled with a confocal microscope, we were able to produce two and three dimensional temperature maps of the steady state flow in the microchannel by the use of ratiometric intensity measurements. This technic allows us to observe temperature gradients in two-phase flow as well yielding the void fraction information. Areas of substantial cooling are observed downstream the constriction in the two-phase flow, linked to the bubble growth, while heating regions due to condensations are missing. A complementary, yet less sensitive probe-less technique using the inherent Raman scattering signal of the liquid, was used to confirm the findings. A separate study evaluating a new group of luminescent materials for optical temperature and pressure probes is performed and discussed herein. Finally, the luminol chemiluminescent reaction with radicals produced by the cavitating flow, is used to obtain a corresponding photon yield. By counting the photons produced, an estimate on the radical yield can be obtained. Additionally, rudimentary mapping of the chemiluminescence signal allows the localization of the bubble collapse regions

Many cutting-edge computer and electronic products are powered by advanced Systems-on-Chip (SoC). Advanced SoCs encompass superb performance together with large number of functions. This is achieved by efficient integration of huge number of transistors. Such very large scale integration is enabled by a core-based design paradigm as well as deep-submicron and 3D-stacked-IC technologies. These technologies are susceptible to reliability and testing complications caused by thermal issues. Three crucial thermal issues related to temperature variations, temperature gradients, and temperature cycling are addressed in this thesis. Existing test scheduling techniques rely on temperature simulations to generate schedules that meet thermal constraints such as overheating prevention. The difference between the simulated temperatures and the actual temperatures is called temperature error. This error, for past technologies, is negligible. However, advanced SoCs experience large errors due to large process variations. Such large errors have costly consequences, such as overheating, and must be taken care of. This thesis presents an adaptive approach to generate test schedules that handle such temperature errors. Advanced SoCs manufactured as 3D stacked ICs experience large temperature gradients. Temperature gradients accelerate certain early-life defect mechanisms. These mechanisms can be artificially accelerated using gradient-based, burn-in like, operations so that the defects are detected before shipping. Moreover, temperature gradients exacerbate some delay-related defects. In order to detect such defects, testing must be performed when appropriate temperature-gradients are enforced. A schedule-based technique that enforces the temperature-gradients for burn-in like operations is proposed in this thesis. This technique is further developed to support testing for delay-related defects while appropriate gradients are enforced. The last thermal issue addressed by this thesis is related to temperature cycling. Temperature cycling test procedures are usually applied to safety-critical applications to detect cycling-related early-life failures. Such failures affect advanced SoCs, particularly through-silicon-via structures in 3D-stacked-ICs. An efficient schedule-based cycling-test technique that combines cycling acceleration with testing is proposed in this thesis. The proposed technique fits into existing 3D testing procedures and does not require temperature chambers. Therefore, the overall cycling acceleration and testing cost can be drastically reduced. All the proposed techniques have been implemented and evaluated with extensive experiments based on ITC’02 benchmarks as well as a number of 3D stacked ICs. Experiments show that the proposed techniques work effectively and reduce the costs, in particular the costs related to addressing thermal issues and early-life failures. We have also developed a fast temperature simulation technique based on a closed-form solution for the temperature equations. Experiments demonstrate that the proposed simulation technique reduces the schedule generation time by more than half.

Esta tese apresenta soluções para o gerenciamento e otimização de temperatura para sistemas de codificação de vídeo baseados nas características da aplicação e no conteúdo dos vídeos digitais. Diferente dos trabalhos estado-da-arte, as soluções propostas nesta tese focam em técnicas de gerenciamento de temperatura no nível da aplicação e características da aplicação codificação de vídeo e as propriedades dos vídeos digitais são explorados para desenvolver soluções termais para a codificação de vídeo com baixas perdas na qualidade de serviço das aplicações. Diversas análises são realizadas considerando a aplicação de codificação de vídeo para entender o comportamento da temperatura durante o processo de codificação para diferentes sequências de vídeo. Com base nos resultados das análises, soluções com diferentes abordagens são propostas para atenuar os efeitos da temperatura nos sistemas de codificação de vídeo. Gerenciamento de temperatura baseado nas características da aplicação para o padrão de codificação HEVC usa uma técnica de seleção de configuração em tempo de execução para manter a temperatura abaixo dos limites seguros de operação com bons resultados de qualidade de vídeo. Otimização de temperatura baseado em computação imprecisa usa aproximações baseadas em conteúdo para reduzir a temperatura de chips executando o HEVC. Um escalonador de tarefas que usa características da aplicação para guiar o escalonamento de threads focando na redução dos gradientes espaciais de temperatura que são resultantes do desbalanceamento natural de cargas entre as threads da aplicação. As soluções propostas são capazes de reduzir em até 10 ºC a temperatura do chip com perdas insignificantes na eficiência de compressão. Os resultados de qualidade objetiva (medida usando PSNR) são de 12 dBs até 20 dBs maiores quando comparados com trabalhos da literatura. Além disso, o escalonador de tarefas proposto é capaz de eliminar os gradientes espaciais de temperatura maiores que 5 ºC para arquitetura multi-cores. Como principal conclusão, esta tese demonstra que as técnicas de gerenciamento de temperatura que usam o conhecimento da aplicação de maneira conjunta com as propriedades dos vídeos digitais tem um alto potencial para melhorar os resultados de temperatura de sistemas de codificação de vídeo mantendo bons resultados de qualidade visual dos vídeos codificados. / This thesis presents application-driven temperature-aware solutions for next generation video coding systems, such as the High Efficiency Video Coding (HEVC). Different from state-of-the-art works, the proposed solutions raise the abstraction of temperature management to the application-level, where video coding characteristics and video content properties are used to leverage thermal-aware solutions for video coding with low QoS (Quality of Service) degradation. Several video coding and temperature analyses are performed to understand the behavior of temperature when encoding different video sequences. Based on the analyses results, different approaches are proposed to mitigate the temperature effects on video coding systems. Application-driven temperature management for HEVC uses run-time encoder configuration selection to keep temperature under safe operational state while providing good visual quality results. Temperature optimization using approximate computing uses content-driven approximations to reduce the on-chip temperature of HEVC encoding. Application-driven temperature-aware scheduler leverages application-specific knowledge to guide a scheduling technique targeting reducing the spatial temperature gradients that are resulted from the unbalance workload nature of multi-threaded video coding application. The proposed solutions are able to provide up to 10 °C of chip temperature reduction with negligible compression efficiency loss. Besides, when compared with previous works the resulted objective video quality (PSNR) is from 12 dB up to 20 dB higher. Moreover, the proposed scheduler eliminates spatial temperature gradients greater than 5 ºC of multi-core architectures. As conclusion, this thesis demonstrates that leveraging application-specific knowledge and video content properties has a significant potential to improve temperature profiles of video coding systems while still keeping good quality results.

Esta tese apresenta soluções para o gerenciamento e otimização de temperatura para sistemas de codificação de vídeo baseados nas características da aplicação e no conteúdo dos vídeos digitais. Diferente dos trabalhos estado-da-arte, as soluções propostas nesta tese focam em técnicas de gerenciamento de temperatura no nível da aplicação e características da aplicação codificação de vídeo e as propriedades dos vídeos digitais são explorados para desenvolver soluções termais para a codificação de vídeo com baixas perdas na qualidade de serviço das aplicações. Diversas análises são realizadas considerando a aplicação de codificação de vídeo para entender o comportamento da temperatura durante o processo de codificação para diferentes sequências de vídeo. Com base nos resultados das análises, soluções com diferentes abordagens são propostas para atenuar os efeitos da temperatura nos sistemas de codificação de vídeo. Gerenciamento de temperatura baseado nas características da aplicação para o padrão de codificação HEVC usa uma técnica de seleção de configuração em tempo de execução para manter a temperatura abaixo dos limites seguros de operação com bons resultados de qualidade de vídeo. Otimização de temperatura baseado em computação imprecisa usa aproximações baseadas em conteúdo para reduzir a temperatura de chips executando o HEVC. Um escalonador de tarefas que usa características da aplicação para guiar o escalonamento de threads focando na redução dos gradientes espaciais de temperatura que são resultantes do desbalanceamento natural de cargas entre as threads da aplicação. As soluções propostas são capazes de reduzir em até 10 ºC a temperatura do chip com perdas insignificantes na eficiência de compressão. Os resultados de qualidade objetiva (medida usando PSNR) são de 12 dBs até 20 dBs maiores quando comparados com trabalhos da literatura. Além disso, o escalonador de tarefas proposto é capaz de eliminar os gradientes espaciais de temperatura maiores que 5 ºC para arquitetura multi-cores. Como principal conclusão, esta tese demonstra que as técnicas de gerenciamento de temperatura que usam o conhecimento da aplicação de maneira conjunta com as propriedades dos vídeos digitais tem um alto potencial para melhorar os resultados de temperatura de sistemas de codificação de vídeo mantendo bons resultados de qualidade visual dos vídeos codificados. / This thesis presents application-driven temperature-aware solutions for next generation video coding systems, such as the High Efficiency Video Coding (HEVC). Different from state-of-the-art works, the proposed solutions raise the abstraction of temperature management to the application-level, where video coding characteristics and video content properties are used to leverage thermal-aware solutions for video coding with low QoS (Quality of Service) degradation. Several video coding and temperature analyses are performed to understand the behavior of temperature when encoding different video sequences. Based on the analyses results, different approaches are proposed to mitigate the temperature effects on video coding systems. Application-driven temperature management for HEVC uses run-time encoder configuration selection to keep temperature under safe operational state while providing good visual quality results. Temperature optimization using approximate computing uses content-driven approximations to reduce the on-chip temperature of HEVC encoding. Application-driven temperature-aware scheduler leverages application-specific knowledge to guide a scheduling technique targeting reducing the spatial temperature gradients that are resulted from the unbalance workload nature of multi-threaded video coding application. The proposed solutions are able to provide up to 10 °C of chip temperature reduction with negligible compression efficiency loss. Besides, when compared with previous works the resulted objective video quality (PSNR) is from 12 dB up to 20 dB higher. Moreover, the proposed scheduler eliminates spatial temperature gradients greater than 5 ºC of multi-core architectures. As conclusion, this thesis demonstrates that leveraging application-specific knowledge and video content properties has a significant potential to improve temperature profiles of video coding systems while still keeping good quality results.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-27T17:30:21Z No. of bitstreams: 1 JAILSON ALVES DA NÓBREGA - DISSERTAÇÃO PPGEM 2014..pdf: 8059019 bytes, checksum: 3342c79a6597e27674ae52970211493c (MD5) / Made available in DSpace on 2018-04-27T17:30:21Z (GMT). No. of bitstreams: 1 JAILSON ALVES DA NÓBREGA - DISSERTAÇÃO PPGEM 2014..pdf: 8059019 bytes, checksum: 3342c79a6597e27674ae52970211493c (MD5) Previous issue date: 2014-12-03 / Capes / Muitas são as variações metalúrgicas sofridas pelo material quando o mesmo é submetido a um ciclo térmico de soldagem, exercendo uma considerável influência sobre as suas propriedades mecânicas e mais especificamente sobre os níveis de tensões residuais. Na fase de projeto, uma dessas alternativas para a avaliação dos ciclos térmicos e tensões residuais de soldagem é o emprego de simulação via métodos computacionais. A partir disto, neste trabalho foi desenvolvida uma metodologia numérica para determinar o campo de temperatura e tensões residuais transversais em juntas soldadas. As simulações numéricas foram realizadas por meio de um software comercial, ABAQUS®, baseado no Método de Elementos Finitos (MEF). Foram considerados fenômenos que fazem a modelagem matemática do processo de soldagem de forma a torná-la mais robusta. Foi utilizada a fonte de calor analítica proposta por Goldak, capaz de modelar a entrada de calor. Foram avaliados os parâmetros de entrada, tais como: Corrente, voltagem, velocidade de soldagem e temperatura inicial da chapa virtual. Para validação dos resultados térmicos, foi utilizada uma chapa virtual do aço API 5L X70 soldada pelo processo FCAW. Nas demais simulações térmicas e mecânicas foram utilizadas uma chapa virtual do aço API 5L X80 soldadas pelos processos GTAW e SMAW. Foi possível observar neste estudo a influência da temperatura de pré-aquecimento e de interpasse sobre os gradientes térmicos e ciclos térmicos na junta soldada, além das mudanças nos valores das temperaturas de pico e do tempo de resfriamento entre 800 e 500 °C (∆t8/5) quando avaliados em diferentes regiões da junta soldada. Com relação às tensões residuais transversais, verificaram-se mudanças no perfil destas tensões quando aplicado mais de um passe da soldagem virtual podendo o modelo servir de base para trabalhos futuros. / Many are the metallurgical variations suffered by the material when it is subjected to a weld thermal cycle, which promote a considerable influence on mechanical properties, and specifically on the welded joint residual stresses. In the project phase, one of these alternatives is the use of computational methods via simulation. So, in this work a numerical methodology to determine the temperature field and transverse residual stresses was developed. The numerical simulations were implemented using a commercial software ABAQUS® based on finite element method (FEM). In addition, a source of heat proposed by Goldak, able to model the heat input value was used. Input parameters, such as: Current, voltage, speed and initial temperature of the virtual plate were also evaluated. To validate the thermal results and the other thermal and mechanical simulations a virtual plate of API 5L X70 and API 5L X-80 steel welded by the FCAW and GTAW and SMAW processes respectively was used. The results showed that it was possible to evaluate the influence of preheat and interpass temperature on the weld thermal gradients and thermal cycling, as well as the change in peak temperature and cooling time between 800 and 500 (∆t8/5) values in different regions of the welded joint. In relation to the transverse residual stresses, it was showed that there were changes in its profile when it was applied more than one weld pass which can serve as base model for future work in this area.

Liquid crystals (LCs) are important materials for flat panel display and photonic devices. Most LC devices use electrical field-, magnetic field-, or temperature-induced refractive index change to modulate the incident light. Molecular constituents, wavelength, and temperature are the three primary factors determining the liquid crystal refractive indices: ne and no for the extraordinary and ordinary rays, respectively. In this dissertation, we derive several physical models for describing the wavelength and temperature effects on liquid crystal refractive indices, average refractive index, and birefringence. Based on these models, we develop some high temperature gradient refractive index LC mixtures for photonic applications, such as thermal tunable liquid crystal photonic crystal fibers and thermal solitons. Liquid crystal refractive indices decrease as the wavelength increase. Both ne and no saturate in the infrared region. Wavelength effect on LC refractive indices is important for the design of direct-view displays. In Chapter 2, we derive the extended Cauchy models for describing the wavelength effect on liquid crystal refractive indices in the visible and infrared spectral regions based on the three-band model. The three-coefficient Cauchy model could be used for describing the refractive indices of liquid crystals with low, medium, and high birefringence, whereas the two-coefficient Cauchy model is more suitable for low birefringence liquid crystals. The critical value of the birefringence is deltan~0.12. Temperature is another important factor affecting the LC refractive indices. The thermal effect originated from the lamp of projection display would affect the performance of the employed liquid crystal. In Chapter 3, we derive the four-parameter and three-parameter parabolic models for describing the temperature effect on the LC refractive indices based on Vuks model and Haller equation. We validate the empirical Haller equation quantitatively. We also validate that the average refractive index of liquid crystal decreases linearly as the temperature increases. Liquid crystals exhibit a large thermal nonlinearity which is attractive for new photonic applications using photonic crystal fibers. We derive the physical models for describing the temperature gradient of the LC refractive indices, ne and no, based on the four-parameter model. We find that LC exhibits a crossover temperature To at which dno/dT is equal to zero. The physical models of the temperature gradient indicate that ne, the extraordinary refractive index, always decreases as the temperature increases since dne/dT is always negative, whereas no, the ordinary refractive index, decreases as the temperature increases when the temperature is lower than the crossover temperature (dno/dT<0 when the temperature is lower than To) and increases as the temperature increases when the temperature is higher than the crossover temperature (dno/dT>0 when the temperature is higher than To ). Measurements of LC refractive indices play an important role for validating the physical models and the device design. Liquid crystal is anisotropic and the incident linearly polarized light encounters two different refractive indices when the polarization is parallel or perpendicular to the optic axis. The measurement is more complicated than that for an isotropic medium. In Chapter 4, we use a multi-wavelength Abbe refractometer to measure the LC refractive indices in the visible light region. We measured the LC refractive indices at six wavelengths, lamda=450, 486, 546, 589, 633 and 656 nm by changing the filters. We use a circulating constant temperature bath to control the temperature of the sample. The temperature range is from 10 to 55 oC. The refractive index data measured include five low-birefringence liquid crystals, MLC-9200-000, MLC-9200-100, MLC-6608 (delta_epsilon=-4.2), MLC-6241-000, and UCF-280 (delta_epsilon=-4); four middle-birefringence liquid crystals, 5CB, 5PCH, E7, E48 and BL003; four high-birefringence liquid crystals, BL006, BL038, E44 and UCF-35, and two liquid crystals with high dno/dT at room temperature, UCF-1 and UCF-2. The refractive indices of E7 at two infrared wavelengths lamda=1.55 and 10.6 um are measured by the wedged-cell refractometer method. The UV absorption spectra of several liquid crystals, MLC-9200-000, MLC-9200-100, MLC-6608 and TL-216 are measured, too. In section 6.5, we also measure the refractive index of cured optical films of NOA65 and NOA81 using the multi-wavelength Abbe refractometer. In Chapter 5, we use the experimental data measured in Chapter 4 to validate the physical models we derived, the extended three-coefficient and two-coefficient Cauchy models, the four-parameter and three-parameter parabolic models. For the first time, we validate the Vuks model using the experimental data of liquid crystals directly. We also validate the empirical Haller equation for the LC birefringence delta_n and the linear equation for the LC average refractive index . The study of the LC refractive indices explores several new photonic applications for liquid crystals such as high temperature gradient liquid crystals, high thermal tunable liquid crystal photonic crystal fibers, the laser induced 2D+1 thermal solitons in nematic crystals, determination for the infrared refractive indices of liquid crystals, comparative study for refractive index between liquid crystals and photopolymers for polymer dispersed liquid crystal (PDLC) applications, and so on. In Chapter 6, we introduce these applications one by one. First, we formulate two novel liquid crystals, UCF-1 and UCF-2, with high dno/dT at room temperature. The dno/dT of UCF-1 is about 4X higher than that of 5CB at room temperature. Second, we infiltrate UCF-1 into the micro holes around the silica core of a section of three-rod core PCF and set up a highly thermal tunable liquid crystal photonic crystal fiber. The guided mode has an effective area of 440 ƒÝm2 with an insertion loss of less than 0.5dB. The loss is mainly attributed to coupling losses between the index-guided section and the bandgap-guided section. The thermal tuning sensitivity of the spectral position of the bandgap was measured to be 27 nm/degree around room temperature, which is 4.6 times higher than that using the commercial E7 LC mixture operated at a temperature above 50 degree C. Third, the novel liquid crystals UCF-1 and UCF-2 are preferred to trigger the laser-induced thermal solitons in nematic liquid crystal confined in a capillary because of the high positive temperature gradient at room temperature. Fourth, we extrapolate the refractive index data measured at the visible light region to the near and far infrared region basing on the extended Cauchy model and four-parameter model. The extrapolation method is validated by the experimental data measured at the visible light and infrared light regions. Knowing the LC refractive indices at the infrared region is important for some photonic devices operated in this light region. Finally, we make a completely comparative study for refractive index between two photocurable polymers (NOA65 and NOA81) and two series of Merck liquid crystals, E-series (E44, E48, and E7) and BL-series (BL038, BL003 and BL006) in order to optimize the performance of polymer dispersed liquid crystals (PDLC). Among the LC materials we studied, BL038 and E48 are good candidates for making PDLC system incorporating NOA65. The BL038 PDLC cell shows a higher contrast ratio than the E48 cell because BL038 has a better matched ordinary refractive index, higher birefringence, and similar miscibility as compared to E48. Liquid crystals having a good miscibility with polymer, matched ordinary refractive index, and higher birefringence help to improve the PDLC contrast ratio for display applications. In Chapter 7, we give a general summary for the dissertation.