Feynman graphs in perturbative quantum field theory are replete with infrared divergences caused by the presence of massless particles, how-ever these divergences are known to cancel order-by-order when all virtual and real contributions to a given cross section are summed and smeared against an experimental resolution. In this thesis we treat the infrared problem formally in the language of distribution theory so that we can remove the divergences with local momentum space subtractions using Hadamard's procedure. This is analogous with the BPHZ mechanism for removing UV divergences. Our aim is to show how it is possible to make both the real and virtual subtractions analytically such that we are left with manifestly finite integrands. For the virtual graphs we present a new decomposition of the integrand in momentum space and remove those terms that are divergent. For the real graphs we show how the Taylor expansion of the momentum conserving delta function allows the explicit removal of the divergent part; furthermore we show that the homogeneous properties of the soft structure greatly simplifies this procedure.

<p>Technologies for position sensing and identification are important to have in ubiquitous computing environments. These technologies can be used to track users, devices, and artefacts in the physical milieu, for example, locating the position of a cellular phone in av physical environment. The aim of this thesis was to survey and classify available technologies for location sensing and identification. </p><p>We have made a literature study on both commercial and research-oriented systems and technologies for use in indoor and outdoor environments. We compared the characteristics of the underlying sensing technologies with respect to physical size, sensing method, cost, and accuracy. We conclude the thesis with a set of recommendations to developers and discuss the requirements on future sensing technologies and their use in mobile devices and environments.</p>

Infrared (IR) imaging is a key technology in a variety of military and civilian applications, especially for night vision and remote sensing. Compared with cryogenically cooled IR sensors, uncooled infrared imaging devices have the advantages of being low cost, light weight, and superior reliability. The electro-thermal analysis of a microbolometer pixel is critical to determine both device performance and reliability. To date, most microbolometer analysis research has focused on performance optimization and computation of thermal conductance directly from the geometry. However, modeling of the thermal distribution across the microbolometer pixel is critical for the comprehensive analysis of system performance and reliability. Therefore, this thesis investigates the electro-thermo-mechanical characteristics of a microbolometer pixel considering the effects of joule heating and incoming IR energy. The contributions of the present research include the electro-thermal models for microbolometer and methods of validating thermal distribution using experimental results. The electro-thermal models explain the effect of microbolometer material properties and geometry on device performance and reliability. The research also contributes methods of estimating the thermal conductivity of microbolometer, which take into account different heat transfer mechanisms, including radiation and convection. Previous approaches for estimating the thermal conductance of uncooled microbolometer consider heat conduction via legs from the geometry of the pixel structure and material properties [2]. This approach assumes linear temperature distribution in the pixel legs structure. It also leaves out the various electro-thermal effects existing for multilayer structures. In the present research, a different approach is used to develop the thermal conductance of microbolometer pixel structure. The temperature distribution in the pixel is computed from an electro-thermal model. Then, the average temperature in the pixel microplate and the total heat energy generated by joule heating is utilized to compute the thermal conductance of the structure. The thesis discusses electro-thermal and thermo-mechanical modeling, simulation and testing of Polysilicon Multi-User MEMS Process (PolyMUMPs®) test devices as the groundwork for the investigation of microbolometer performance and reliability in space applications. An electro-thermal analytical and numerical model was developed to predict the temperature distribution across the microbolometer pixel by solving the second order differential heat equation. To provide a qualitative insight of the effect of different parameters in the thermal distribution, including material properties and device geometry, first an explicit formulation for the solution of the electro-thermal coupling is obtained using the analytical method. In addition, the electro-thermal model, which accounts for the effect of IR energy and radiation heat transfer, spreading resistance and transient conditions, was studied using numerical methods. In addition, an analytical model has been developed to compute the IR absorption coefficient of a Thin Single Stage (TSS) microbolometer pixel. The simulation result of this model was used to compute absorbed IR energy for the numerical model. Subsequently, the temperature distribution calculated from the analytical model is used to obtain the deflections that the structure undergoes, which will be fundamental for the reliability analysis of the device. Finite element analysis (FEA) has been simulated for the selected device using commercial software, ANSYS® multiphysics. Finite element simulation shows that the electro-thermal models predict the temperature distribution across a microbolometer pixel at steady-state conditions within 2.3% difference from the analytical model. The analytical and numerical models are also simulated and results for a temperature distribution within 1.6% difference. In addition, to validate the analytical and numerical electro-thermal and thermo-mechanical models, a PolyMUMPs® test device has been used. The test results showed a close agreement with the FEM simulation deflection of the test device.

Infrared (IR) imaging is a key technology in a variety of military and civilian applications, especially for night vision and remote sensing. Compared with cryogenically cooled IR sensors, uncooled infrared imaging devices have the advantages of being low cost, light weight, and superior reliability. The electro-thermal analysis of a microbolometer pixel is critical to determine both device performance and reliability. To date, most microbolometer analysis research has focused on performance optimization and computation of thermal conductance directly from the geometry. However, modeling of the thermal distribution across the microbolometer pixel is critical for the comprehensive analysis of system performance and reliability. Therefore, this thesis investigates the electro-thermo-mechanical characteristics of a microbolometer pixel considering the effects of joule heating and incoming IR energy. The contributions of the present research include the electro-thermal models for microbolometer and methods of validating thermal distribution using experimental results. The electro-thermal models explain the effect of microbolometer material properties and geometry on device performance and reliability. The research also contributes methods of estimating the thermal conductivity of microbolometer, which take into account different heat transfer mechanisms, including radiation and convection. Previous approaches for estimating the thermal conductance of uncooled microbolometer consider heat conduction via legs from the geometry of the pixel structure and material properties [2]. This approach assumes linear temperature distribution in the pixel legs structure. It also leaves out the various electro-thermal effects existing for multilayer structures. In the present research, a different approach is used to develop the thermal conductance of microbolometer pixel structure. The temperature distribution in the pixel is computed from an electro-thermal model. Then, the average temperature in the pixel microplate and the total heat energy generated by joule heating is utilized to compute the thermal conductance of the structure. The thesis discusses electro-thermal and thermo-mechanical modeling, simulation and testing of Polysilicon Multi-User MEMS Process (PolyMUMPs®) test devices as the groundwork for the investigation of microbolometer performance and reliability in space applications. An electro-thermal analytical and numerical model was developed to predict the temperature distribution across the microbolometer pixel by solving the second order differential heat equation. To provide a qualitative insight of the effect of different parameters in the thermal distribution, including material properties and device geometry, first an explicit formulation for the solution of the electro-thermal coupling is obtained using the analytical method. In addition, the electro-thermal model, which accounts for the effect of IR energy and radiation heat transfer, spreading resistance and transient conditions, was studied using numerical methods. In addition, an analytical model has been developed to compute the IR absorption coefficient of a Thin Single Stage (TSS) microbolometer pixel. The simulation result of this model was used to compute absorbed IR energy for the numerical model. Subsequently, the temperature distribution calculated from the analytical model is used to obtain the deflections that the structure undergoes, which will be fundamental for the reliability analysis of the device. Finite element analysis (FEA) has been simulated for the selected device using commercial software, ANSYS® multiphysics. Finite element simulation shows that the electro-thermal models predict the temperature distribution across a microbolometer pixel at steady-state conditions within 2.3% difference from the analytical model. The analytical and numerical models are also simulated and results for a temperature distribution within 1.6% difference. In addition, to validate the analytical and numerical electro-thermal and thermo-mechanical models, a PolyMUMPs® test device has been used. The test results showed a close agreement with the FEM simulation deflection of the test device.

The ultimate application of this work is constraining the optical properties of cirrus particles, which are poorly understood, by providing an automatic method, using all-sky cameras and an infrared radiometer, to identify the occurrence of the 22° halo formed by cirrus. This is done by interpreting all sky images in terms of a scattering phase function (SPF), from which the halo ratio (HR) is calculated, and by implementing a cirrus detection algorithm to associate HR measures to ice cloud occurrences. Cirrus reflectivity at solar wavelengths is inversely related to the HR which, being an indirect measure of the regularity of the shape of the ice crystals forming the cloud, relates in turn inversely to the asymmetry parameter g. Therefore, the method proposed here to derive statistics of HRs is expected to reduce the uncertainty over the optical and microphysical properties of cirrus. The light intensity measured by the all sky camera is transformed into a scattering phase function, from which the halo formation is identified. This is done by developing image transformations and corrections needed to interpret all sky images quantitatively in terms of scattering phase function, specifically by transforming the original image from the zenith-centred to the light-source-centred system of coordinates and correcting for the air mass and for vignetting. The SPF is then determined by averaging the image brightness over the azimuth angle and the HR by calculating the ratio of brightness at two scattering angles in the vicinity of the 22° halo peak. The instrument transformation and corrections are performed using a series of Matlab scripts. Given that the HR is an ice cloud characteristic and since the method needs additional temperature information if the halo observation is to be associated with cirrus, a cirrus detection algorithm is necessary to screen out non-ice clouds before deriving reliable HR statistics. Cloud detection is determined by quantifying the temporal fluctuations of sky radiance, expressed as brightness temperature (BT), through De-trended Fluctuation Analysis and setting a clear sky fluctuation threshold. Cloud phase discrimination instead is achieved through first constructing an analytic radiative transfer model to obtain an estimate for average molecular absorption cross-section of water vapour within the spectral window of the radiometer. This is done to model the down-welling clear sky radiance, which is in turn used to correct cirrus emissivity and ultimately determine a dynamic BT threshold for the transition from ice to liquid-containing clouds. In addition to the molecular cross section the screen level air temperature and integrated water vapour are used as input parameters to the model. The utilisation of the all sky camera for such quantitative measurement was the particularly novel aspect of this work; this has not been done previously to the best of my knowledge. The cirrus detection method proposed is also innovative in that with respect to previous works it does not rely on the use of additional techniques such as LIDAR or microwave radiometry for discriminating cloud phase. Furthermore, the cirrus threshold proposed is not fixed but accounts for the attenuating properties of the atmosphere below the cloud. Once the cirrus detection algorithm is validated and cirrus occurrences determinable, the HR could be extended to estimating the asymmetry parameter and crystal roughness. These are retrievable, for instance, from in-situ observations of single ice crystal 2D scattering patterns from cloud probes of the SID (Small Ice Detector) type. This would be significant for the constraining of the optical and microphysical properties of cirrus.

Technologies for position sensing and identification are important to have in ubiquitous computing environments. These technologies can be used to track users, devices, and artefacts in the physical milieu, for example, locating the position of a cellular phone in av physical environment. The aim of this thesis was to survey and classify available technologies for location sensing and identification. We have made a literature study on both commercial and research-oriented systems and technologies for use in indoor and outdoor environments. We compared the characteristics of the underlying sensing technologies with respect to physical size, sensing method, cost, and accuracy. We conclude the thesis with a set of recommendations to developers and discuss the requirements on future sensing technologies and their use in mobile devices and environments.

The theory of orientation polarization and dielectric relaxation was developed by P. Debye more than 100 years ago. It is based on approximating a molecule by a sphere having one or more dipole moments. By that the detailed intra- and intermolecular interactions are explicitly not taken into consideration. In this article, the principal limitations of the Debye approximation are discussed. Taking advantage of the molecular specificity of the infrared (IR) spectral range, measurements of the specific IR absorption of the stretching vibration (OH) (at 3370 cm1) and the asymmetric as(CH2) (at 2862.9 cm1) are performed in dependence on the frequency and the strength of external electric fields and at varying temperature. The observed effects are interpreted as caused by orientation polarization of the OH and the adjacent CH2 moieties.

The use of a CO2 infrared (IR) laser and photocatalysis for water treatment microorganism disinfection purposes was investigated. During CO2 infrared (IR) laser treatment E. cloacae inactivation was comparable to inactivation via ultraviolet (UV) treatment; however no inactivation of the more resistant B. subtilis endospores occurred. Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy of the bacterial cells displayed increased polysaccharide contents after IR treatment. FTIR and Raman spectroscopy of simple carbohydrates before and after IR laser treatment displayed no spectral changes, with the exception of N-acetyl-D-glucosamine (NAG), which was partially attributed to sampling techniques. E. cloacae inactivation during IR treatment was attributed to localised and overall temperature increases within the water. Due to the inability to inactivate B. subtilis endospores this technique is not suitable for water treatment purposes. Photocatalytic water treatment using novel TiO2 colloids prepared via a postsynthetic microwave-modification process (MW-treated) was also examined. These colloids were characterised using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses and compared to Degussa P25 and convection hydrothermally-treated (HT-treated) TiO2. Slurry suspensions displayed comparable E. coli inactivation rates, so the colloids were examined in immobilised form using both a model organic degradant, oxalic acid, and E. coli. Oxalic acid degradation studies showed that the MW-treated colloids displayed similar inactivation rates to the HT-treated TiO2, due to their pure anatase composition, while Degussa P25 displayed higher inactivation rates. Investigations into the effect of shortening UV wavelength were also performed. Degussa P25 was the only catalyst which displayed higher apparent quantum yields upon shortening the UV wavelength, which was attributed to its mixed-phase anatase-rutile composition. As E. coli inactivation was observed using distilled water, photocatalysis in natural river water was trailed. It was discovered that the pH had to be lowered from 7.5 to 5.0 and the initial cell concentration must be approximately 1 x 103 colony forming units (CFU) per cm3 or less for inactivation to be observed during a 5 hour treatment period. At a catalyst loading of 1.0 mg per cm2, Degussa P25 absorbed all the applied UVA irradiation; however the MW- and HT-treated TiO2 colloids did not due to their smaller particle size. Therefore sandwich experiments were devised to evaluate the effect of unabsorbed UV irradiation within the system. Small colony variants were identified after photocatalytic and UV treatment, which pose a potential threat to public health. Further investigation of the different TiO2 colloids was performed using in situ FTIR, both with and without an applied potential and compared to a thermally prepared TiO2 catalyst. The latter displayed potential dependent photocatalysis, while the mesoporous TiO2 catalysts displayed potential independent photocatalysis. All catalyst types displayed increased degradation rates upon the application of a positive bias, which was followed in situ via the production of CO2. Sodium oxalate and NAG was examined for photocatalytic degradation, both of which were degraded to CO2, with proposed break-down products identified when using NAG.

Face recognition and lip localization are two main building blocks in the development of audio visual automatic speech recognition systems (AV-ASR). In many earlier works, face recognition and lip localization were conducted in uniform lighting conditions with simple backgrounds. However, such conditions are seldom the case in real world applications. In this paper, we present an approach to face recognition and lip localization that is invariant to lighting conditions. This is done by employing infrared and depth images captured by the Kinect V2 device. First we present the use of infrared images for face detection. Second, we use the face’s inherent depth information to reduce the search area for the lips by developing a nose point detection. Third, we further reduce the search area by using a depth segmentation algorithm to separate the face from its background. Finally, with the reduced search range, we present a method for lip localization based on depth gradients. Experimental results demonstrated an accuracy of 100% for face detection, and 96% for lip localization.

The objective of this dissertation is to shed light on the physical properties of InN epilayers grown by High-Pressure Chemical Vapor Deposition (HPCVD) for optical device applications. Physical properties of HPCVD grown InN layers were investigated by X-ray diffraction, Raman scattering, infrared reflection spectroscopies, and atomic force microscopy. The dependencies of physical properties as well as surface morphologies of InN layers grown either directly on sapphire substrates or on GaN/sapphire templates on varied growth conditions were studied. The effect of crucial growth parameters such as growth pressure, V/III molar ratio, precursor pulse separation, substrate material, and mass transport along the flow direction on the optical and structural properties, as well as on the surface morphologies were investigated separately. At present, growth of high-quality InN material by conventional growth techniques is limited due to low dissociation temperature of InN (~600 ºC) and large difference in the partial pressures of TMI and NH3 precursors. In this research, HPCVD technique, in which ambient nitrogen is injected into reaction zone at super-atmospheric growth pressures, was utilized to suppress surface dissociation of InN at high temperatures. At high pressures, long-range and short-range orderings indicate that c-lattice constant is shorter and E2(high) mode frequency is higher than those obtained from low-pressure growth techniques, revealing that InN structure compressed either due to a hydrostatic pressure during the growth or thermal contraction during the annealing. Although the influence of varied growth parameters usually exhibit consistent correlation between long-range and short-range crystalline orderings, inconsistent correlation of these indicate inclination of InN anisotropy. InN layers, grown directly on α-sapphire substrates, exhibit InN (1 0 1) Bragg reflex. This might be due to a high c/a ratio of sapphire-grown InN epilayers compared to that of GaN/sapphire-grown InN epilayers. Optical analysis indicates that free carrier concentration, ne, in the range of 1–50 × 1018 cm–3 exhibits consistent tendency with longitudinal-optic phonon. However, for high ne values, electrostatic forces dominate over inter-atomic forces, and consistent tendency between ne and LO phonon disappears. Structural results reveal that growth temperature increases ~6.6 ºC/bar and V/III ratio affects indium migration and/or evaporation. The growth temperature and V/III ratio of InN thin films are optimized at ~850 ºC and 2400 molar ratio, respectively. Although high in-plane strain and c/a ratio values are obtained for sapphire-grown epilayers, FWHM values of long-range and short-range orderings and free carrier concentration value are still lower than those of GaN/sapphire-grown epilayers. Finally, vibrational and optical properties of chalcopyrite ZGP crystal on the (001), (110), and (10) crystalline planes were investigated by Raman scattering and infrared (IR) reflection spectroscopies. Raman scattering exhibits a nonlinear polarizability on the c-plane, and a linear polarizability on the a- and b-planes of ZGP crystal. Also, birefringence of ZGP crystal was calculated from the hydrostatic pressure difference between (110) and (10) crystalline planes for mid-frequency B2(LO) mode.