http://hdl.handle.net/2374.OX/4079 2013-05-20T00:02:54Z http://hdl.handle.net/2374.OX/103894 A study on the use of polarized light in application to noninvasive tissue diagnostics Li, Yanfang In this dissertation, multiple investigations on the implementation and use of polarized light for noninvasive diagnostics in turbid media are reported on and discussed. The first study focuses on the development and construction of an automated Mueller matrix imaging system. In the first investigation, a method was developed to estimate the scattering coefficient contribution as a function of particle size in complex mixtures of polystyrene spheres. A partial least squares approach is used to accurately predict the individual scattering coefficient contributions in phantoms containing 0.2, 0.5, 1, and 2 µm diameter spheres. It is also shown how scattering type is encoded within the Mueller matrix. In addition, the backscattered Mueller matrix of cultured normal human melanocytes, HEMn-LP, and melanoma cells, WM115 and WM793, are investigated for potential cell characterization. These results indicate that the mitochondria contribute significantly to the backscattering polarization signals. In the second investigation, Mueller matrix imaging is applied for in vitro collagen degradation classification. Four different levels of collagen degradations were imposed on in vitro human dermis via collagenase type IA-s. Polar decomposition of the Mueller matrix was performed to better interpret the image-based measurements for the optical differentiation between the degraded and normal dermis. Combining these results in conjunction with the Mueller matrix elements, the extracted features were analyzed by classification tree to develop an accurate classification model. Such methods may eventually lead to the development of improved diagnostic tools capable of characterizing and distinguishing between tissue abnormalities. The final investigation involves the application of diffuse reflectance polarization imaging to detect glucose concentration levels in highly scattering turbid media. Through the application of partial least squares regression, it is shown that accurate glucose predication in highly scattering media can be achieved. Furthermore, through the use of principal component analysis, the correlation between changes in the scattering coefficient and optical activity in relation to glucose concentration within the polarization image measurements is demonstrated. The findings of this basic research could be potentially extended to biological tissue for the eventual development of a noninvasive physiological glucose monitor. 2009-04-09T21:44:05Z http://hdl.handle.net/2374.OX/103892 Identification of Factors Affecting Contaminant Levels and Determination of Infiltration of Ambient Contaminants in Public Transport Buses Operating on Biodiesel and ULSD Fuels Kadiyala, Akhil This experimental project presents a comprehensive study of indoor pollutant behavior in the public transport buses in the city of Toledo running on alternative fuels and an understanding of the contribution of outdoor pollutant concentrations to in-vehicle pollutant levels. The indoor pollutants monitored are particulate matter, carbon dioxide, carbon monoxide, sulphur dioxide, nitric oxide, and nitrogen dioxide. Temperature and relative humidity are also measured inside the vehicle in addition to the in-vehicle pollutants. The various factors affecting indoor air quality are indoor sources of pollutants (people, furniture, etc.), ventilation, outdoor air quality, meteorology, pollutant decay, and vehicular traffic. The diurnal, monthly, and seasonal variations of the pollutants are studied. The pollutant level buildup within a bus compartment is due to a combination of different factors and not a result of variation due to a single variable. As the bus is in motion and factors influencing the indoor pollutant levels keep changing randomly, it is difficult to identify specific monthly and seasonal trends. However, pollutant concentration levels are found to be highly influenced by peak hours in the morning and evening and a discussion is provided on identifying the factors that could have influenced monthly and seasonal variations. Relatively higher pollutant concentrations are observed for majority of the pollutants in winter when there is not much air exchange in the bus compartment. The trend study revealed that the concentrations were mainly influenced by peak hours, ventilation settings, vehicular traffic, passenger ridership, and meteorology. The factors influencing pollutant levels with respect to month and season are identified. The regression tree analysis helped identify the various factors affecting in-vehicle pollutant levels and the relationships between independent variables and indoor pollutant concentrations. The meteorological effect study revealed wind direction to be the most significant meteorological variable for all the gaseous pollutants while particulate matter levels are found to be mainly influenced by ambient PM2.5 concentrations and visibility. Different combinations of variables were able to explain the trends of monitored indoor pollutants. The contribution of ambient concentration to the indoor concentration levels was determined by calculating infiltration factors using two different methods for both biodiesel and ULSD buses. The analysis revealed that the indoor air quality levels are better in a biodiesel bus as compared to the ULSD bus. It was also observed that nearly 50-70% of the pollutants found indoors are generated outdoors for all the pollutants except nitrogen dioxide. Exposure of passengers and drivers to the indoor pollutants monitored were determined using time weighted concentration and compared to available health standards. The study revealed that the drivers are safe from exposure to gaseous as well as particulate contaminants. It is hoped that this study and analysis of in-vehicle pollutant trends will provide crucial information to indoor air quality regulators and decision makers in understanding the IAQ in transit vehicles and to regulate the indoor air quality standards. 2009-04-09T21:43:51Z http://hdl.handle.net/2374.OX/103890 Optimal Call Admission Control Policies in Wireless Cellular Networks Using Semi Markov Decision Proces Ni, Wenlong This dissertation investigates the optimal call admission control (CAC) policies for Non Priority Scheme (NPS) and Reserved Channel Scheme (RCS) in wireless cellular networks for the following cases: 1. Homogenous traffic in a cell; 2. Multimedia traffic in a cell; 3. Homogenous traffic in a network; 4. Multimedia traffic in a network. Both new call and handoff call arrival processes are assumed to be Poisson processes, and the call holding times are exponentially distributed with different rate for new calls and handoff calls. Admitting each call would bring a reward to the network provider but holding each call in the system would also incur some cost to the provider. This dissertation focuses on the optimization problem of when to admit or reject a call in order to achieve the maximum reward. By establishing an infinite horizon discounted Semi Markov Decision Process (SMDP) model, this research verifies that the optimal policies of all the four cases mentioned above are state-related control policies for NPS as well as RCS. More over, this research also finds that optimal control policy for Case (1) above is still state-related control policy even if the combined arrival process for new and handoff calls are described by General Distribution. The numerical results presented in this dissertation in both tables and diagrams for all of the above cases are consistent with the theoretical results derived. 2009-04-09T21:43:38Z http://hdl.handle.net/2374.OX/103888 Effects of Microcrystallinity on Physical Aging and Environmental Stress Cracking of Poly (ethylene terephthalate) (PET) Zhou, Hongxia The dependence of polymer properties on structure has been of great practical importance. In this study, the microstructures of two types PET copolymer sheets made from different polymerization process and catalyst systems have been characterized in terms of density, crystallinity, modified structural factor, conformational isomer contents, as well as spherulite sizes. The relation of microcrystallinity to physical aging and environmental stress cracking was systematically evaluated. It is found that physical aging occurs in both amorphous and semi-crystalline PET stored above room temperature, but below the glass transition. Some physical property changes resulting from aging were recorded. Results indicate that after aging, samples become denser, exhibit higher glass transition temperatures, higher enthalpy of relaxation values (ΔH), as well as less trans and more gauche isomers. Tensile mechanical evaluations show that aging causes elongation to break to decrease dramatically. There is a correlation between the enthalpy of relaxation and the mode of failure. The critical ΔH also decreases linearly as levels of crystallinity increase. Activation energies for onset of embrittlement were calculated and morphological contributions to failure are discussed. The mechanism of physical aging was investigated. Differential scanning calorimetry (DSC) measurements were conducted to record a series enthalpy of relaxation values of the storage at different temperature for various times. The data were further analyzed with a semi-empirical Cowie-Ferguson (CF) model. Comparisons were made among different samples and storage temperatures. Results indicate that the rate of aging is accelerated by temperature and that the presence of a crystalline phase reduces the amount of amorphous regions available for aging and hinders the relaxation process. Dynamic differential scanning calorimetry (DDSC) experiments illustrated the existence of two amorphous regions in semi-crystalline PET, the contribution of each region to aging was resolved for samples aged at 65°C. Moisture absorption investigations demonstrated that moisture is one of the important factors affecting aging and that its effects cannot be ignored even for samples with high crystallinity. Environmental stress cracking resistance (ESCR) behavior of semi-crystalline PET was studied as a function of crystalline content and aging effect. With increasing crystallinity, critical stress was found to decrease linearly. Tie-molecules theory was used to explain the behavior. Physical aging reduced the ESCR of PET and lead to shortened service lifetime of materials. 2009-04-09T21:43:25Z