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Title: AN EMPIRICAL GROUNDED THEORY APPROACH TO CHARACTERIZING ADVANCED MATHEMATICAL THINKING IN COLLEGE CALCULUS
Creator: Nabb, Keith A.
Date: 2013, 2013-07
Description: The research literature has made calls for greater coherence and consistency with regard to the meaning and use of the term advanced...
Show moreThe research literature has made calls for greater coherence and consistency with regard to the meaning and use of the term advanced mathematical thinking (AMT) in mathematics education (Artigue, Batanero, & Kent, 2007; Selden & Selden, 2005). Educators and researchers agree that students should be engaged in AMT but it is unclear precisely what is meant by AMT or how these engagements may manifest themselves in student work. Moreover, many contributions are aimed at advancing theory with little effort to connect with classroom practice. The intent of this study was to examine individuals in their natural problem solving states and to empirically describe how AMT might unfold in the context of nonroutine calculus problems. The study was conducted during the spring semester of 2012. Thirteen students solved three nonroutine calculus problems, each loosely couched in theories of AMT—process-concept duality (Gray & Tall, 1994), epistemological obstacle (Bachelard, 1938; Harel & Sowder, 2005; Sierpińska, 1987), and the basic metaphor of infinity of mathematical idea analysis (Lakoff & Núñez, 2000). While empirical instances of these theories were present, students predominantly displayed idiosyncratic strategies by way of imposing mathematical/scientific objects, tools, or concepts on the local domain of the problem space. Efforts to first individualize the task were followed by completing the task through this individualization. Both successful and unsuccessful problem attempts were documented in the form of novel tool usage, visualization, and/or abstraction through communication. x The outcome of this study suggests a need to further examine students’ use of procedures and how students successfully anticipate the utility of these procedures. Additionally, further work is needed to explain both the elevated use of visualization and how/why discussions with others provide momentum for abstracting solutions to contradictory problems. With respect to classroom practice, students’ novel use of well-known mathematics mirrors the habits of research mathematicians in their professional work. Importing such uses into classroom discourse has the potential to deepen connections of mathematics content and to enrich mathematics experiences through nonstandard methods of problem solving.
PH.D in Mathematics Education, July 2013
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Title: SYNTHESIS AND STRUCTURAL INVESTIGATION OF POLYOXOVANADATE SYSTEMS FOR SEMICONDUCTOR NOx SENSING
Creator: Ravikanth Putrevu, Naga
Date: 2013, 2013-12
Description: Nitrogen oxides (NO and NO2 collectively termed as NOx) are the common air pollutants produced from various indoor and outdoor activities. It...
Show moreNitrogen oxides (NO and NO2 collectively termed as NOx) are the common air pollutants produced from various indoor and outdoor activities. It can cause several environmental problems like ground-level ozone, acid rain, particulate matter, smog formation and health problems like malfunctioning of lungs, damaging air flow passages and creating respiratory problems. To detect these gases, sensors with greater sensitivity, lower recovery time and longer life time are needed. Despite the advantages, of the most widely used NOx sensing materials, semiconducting metal oxides have the limitations like higher operating temperatures and unable to customize the materials with better sensitivity and selectivity. So the current research discusses about a new class of metal oxide systems called polyoxovanadates (POV) and its suitability for the ambient operating conditions. These POVs are basically the vanadium oxide clusters synthesized in top-down and bottom-up synthesis procedures. The main advantages of these systems are possible to synthesize in various sizes, shapes, geometries and dimensions which can help identifying the suitable material for a specific gas. The experimental part discusses about the synthesis, characterization and semiconducting sensing properties of different POV systems using various atomic and molecular spectroscopic techniques. In Chapter 2, a 3-D open framework polyoxovanadate material, [Cd3(H2O)12V16 IVV2 VO36(OH)6(AO4)]·24H2O, (A=V,S) (1), composed of secondary building blocks ({V18O42(AO4)} (A=V,S) clusters) interconnected by {-O-Cd-O-} bridging groups, was chosen for understanding the effect of atmospheric oxygen on 1 electronic properties like band gap and resistance, considering the oxygen as a common xiv interferent in ambient gas sensing. The results explain that 1 interacts with oxygen during the aging process and results changing the vanadium oxidation state from +4 to +5 and expanding the coordination sphere of vanadium from 5 to 6. This expansion can alter the band gap by overlapping the more number of O 2p orbitals with V 3d orbitals and resulting the decrease in resistance. The experiments conducted on molecular {V18O42(AO4)} (A=V,S) cluster, (NH4)8[VIV 12VV 6O42(SO4)]·10H2O, (2a), in Chapter 3, also shown the similar change in band gap and resistance during aging process. Based on the results obtained in Chapter 2 and Chapter 3, a {VO6} containing vanadium oxide cluster, (NH4)2[Ni(H2O)5(NH3)]2[V10O28]·4H2O (4), was synthesized and proved in Chapter 4, that the higher coordination number help lowering the band gap and the resistance without need of aging. In Chapter 5, the NOx sensing properties of 1, 2a, 3 and 4 were studied and compared with well studied NOx sensing material, WO3. Based on the sensing characteristics, 1 shows good sensitivity and response time towards both NO and NO2 under ambient conditions than all the other materials. The FTIR spectroscopy results indicated that the NO2 sensing mechanism occurs via nitrate formation.
PH.D in Chemistry, December 2013
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Title: Fabrication and Characterization of High Aspect Ratio Hard X-ray Zone Plates with Ultrananocrystalline Diamond Molds
Creator: Wojcik, Michael J.
Date: 2013, 2013-05
Description: Hard x-ray zone plate development has played an important role in improving x-ray microscopy through ner resolution and greater functional X...
Show moreHard x-ray zone plate development has played an important role in improving x-ray microscopy through ner resolution and greater functional X-ray energy. Similar to circular di raction gratings except with changing period as a function of radius, zone plates are di ractive focusing optics with resolution determined by the outer most zone width (OZW). Hard X-ray zone plates are mostly phase zone plates with a limited e ciency that peaks when the zone material causes a -phase shift on the x-ray, and the zone thickness required can be multiple microns dependent on x-ray energy. The combination of sub-100-nm resolution and peak e ciency for hard xrays requires very high aspect ratio zones. In this dissertation, two materials were used to fabricate high aspect ratio zone plates in a single layer mold and a two layer mold process. Ultrananocrystalline diamond (UNCD) is composed of 2-5 nm diamond grains bounded together with graphitic bonds. This form of diamond can be deposited onto substrates with thickness greater than a micron and with physical properties similar to bulk diamond. Hydrogen silsesquioxane (HSQ) is a spin on glass that is also a high contrast electron beam lithography resist. A thick layer of HSQ can be patterned into high aspect ratio structures and could be used as a pattern transfer mask for several etch recipes. Both of these materials were used to fabricate up to 25 aspect ratio zone plates and with OZW of 60 and 80 nm. Zone plates fabricated with UNCD were the rst high aspect ratio zone plates using a diamond like material and this technique was leveraged into a new fabrication method using two layers as an electroplating mold. Fabricated zone plates were characterized to measure the optical properties to compare with the fabrication properties. After characterization, several zone plate models based on fabricated zone plates were developed and simulated using a wave propagation technique to compare with the characterization data. The results xiii from fabrication, characterization, and simulation of zone plates with 25 aspect ratio will be presented as well as future possibilities for the techniques used.
PH.D in Physics, May 2013
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Title: BAYESIAN MOMENTUM STRATEGY OF EXCHANGE RATES
Creator: Lee, Namhoon
Date: 2011-11, 2011-12
Description: A disagreement has existed between the foreign currency trading community and academic researchers relating to the time series properties of...
Show moreA disagreement has existed between the foreign currency trading community and academic researchers relating to the time series properties of exchange rates. Traders typically view exchange rates as strongly trending prices and suggest that simple rules, based solely on past prices, have generated predictable profits with acceptable risk over most of the floating-rate period. However, many surveys presenting controversial results. This research identifies the non-linear trend momentum in monthly exchange rate and examines the profitability of momentum trading model within exchange rate returns in the context of Bayesian econometrics. A development of Bayesian momentum trading strategy based on trend component of the spot exchange rate is established. First, parameters of momentum model for each main currency are estimated. The momentum is defined as a simple nonlinear function of return series and the model is designed to estimate the expected conditional mean and associated conditional volatilities simultaneously. The empirical results reported several notable confirmation and findings; first, predictability of momentum model with Bayesian approach show better accuracy than model with maximum likelihood estimation or moving average rule in terms of directionality and model fitting. Second, parameters are restricted to be same across the currencies with the assumption that currencies share some degree of commonality within the system. The result confirms that the restricted model work as well as the unrestricted model within the currency model in terms of model fitting and directional accuracy. Third, principal component analysis is used to analyze the exchange rate movements. PCA found that the first principal component shows parallel shift of all currencies and second principal component tilt shift where high yield currencies move down and low yield currencies move up. Fourth, the parameter estimates from the models are used for portfolio allocation ix applying Bayesian Principal Component(PC) GARCH(1,1) model and the portfolio performance is compared with the performance with classical maximum likelihood approach and other benchmarks. The results show that the Bayesian PC-GARCH(1,1) performs better than classical PC-GARCH(1,1) in terms of Sharpe ratio, Value at Risk, Expected shortfall, maximum drawdown and other statistical criteria. Sixth, the GARCH parameter space is found to be non-symmetric confirming that maximum likelihood estimation would have over or under estimated the parameter causing misspecifying the model parameters. The result from this research confirms simple nonlinear momentum model combined with Bayesian approach can be a good forecasting tool, and restricted model can simplify the complexity of parameter space of exchange rate movement. In addition, by correctly detecting the parameter space, Bayesian approach outperforms the classical maximum likelihood approach. Keywords : Bayesian framework, Momentum, Moving Average rules, Carry trade strategy, Mean-variance Optimization, Trading strategy, Metropolis-Hastings Algorithm, Gibbs Sampler
Ph.D. in Management Science, December 2011
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Title: NEW CLASS OF EMBEDDED SPACE TIME BLOCK CODE FOR MIMO WIRELESS COMMUNICATION SYSTEMS
Creator: Norouzi, Mandana
Date: 2015, 2015-12
Description: In this thesis a new class of space time block codes is proposed. Space time code is one solution for the multipath fading communication...
Show moreIn this thesis a new class of space time block codes is proposed. Space time code is one solution for the multipath fading communication systems that limit the reliability and data rate of the communication link. By organizing multiple antennas at the transmitter and receiver, multipath fading can be turned into an advantage, allowing for greater reliability and higher data rates than would otherwise be possible. Without any extra cost of bandwidth, rate and reliability benefits can be achieved. Therefore, having multiple antenna technology is a foundation of current and future wireless systems. In space time coding information, symbols are encoded across two dimensions, the spatial dimension and the time dimension. Information that is transmitted corresponds to multiple antennas at the transmitter and to multiple signaling intervals. In this thesis, we consider the problem of designing a new class of linear space time block codes, in which the information symbols are linearly combined to form a twodimensional code matrix, wherein the rows of the code word matrix correspond to transmission across multiple antennas, and the columns of the matrix correspond to transmission in different time slots. The proposed space time code matrix is achieved based on eigenvalue decomposition (EVD) of the circulant, normal matrix and inverse fast Fourier transform definition (IFFT). These classes of codes have better performance with respect to symbolerror rate (SER) in comparison with other proposed linear space time code matrices in the literature. The proposed code has full rate and embedded diversity. The concept of embedded diversity has been defined in this research. According to that definition ourdesign supports embedded diversity and also has less decoding complexity at the receiver side. The proposed code has been applied to a relay network where nodes do not have four transmit antennas. In this thesis, performance of the code has also been evaluated when the receiver must rely on a noisy, imperfect, estimate of the channel. Channel estimation has been applied based on pilot sequence transmission. A group decodable full rate and full diversity space time block code also has been proposed for two transmit antennas and four time slots, which is applicable to the LTE-Advanced system. This new design also provides full diversity and full rate.
Ph.D. in Electrical Engineering, December 2015
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Title: IMPACT OF RELATIONSHIP FUNCTIONING AND PATIENT MOTIVATION ON ADHERENCE AND WEIGHT LOSS AFTER BARIATRIC SURGERY
Creator: Noth, Kathryn
Date: 2013, 2013-07
Description: Background: Bariatric surgery is the most successful intervention to treat severely obese individuals, yet there is significant variability in...
Show moreBackground: Bariatric surgery is the most successful intervention to treat severely obese individuals, yet there is significant variability in surgical outcome (Hsu et al., 1998, Sarwer, Wadden, & Fabricatore, 2005). Success primarily depends on patients’ ability to make and maintain recommended changes to their lifestyle after surgery. Patients’ ability to make and maintain changes to behavior is impacted by elements of the socioenvironmental context. Prior research on a number of different medical populations suggests that an individual’s partner or spouse may facilitate or hinder behavior change (Sher et al, 2011). Study Aim: The current study examined the role of relationship functioning on patients’ motivation for and adherence to health behavior changes and weight loss (%EWL) after bariatric surgery. Based on self-determination theory, it was hypothesized that better relationship functioning, higher levels of autonomous motivation to make lifestyle changes, and less emotional eating (EE) would be associated with better adherence and %EWL after bariatric surgery. Procedure: Participants were 111 women who had undergone a bariatric procedure at least 2 years prior to study participation and who were also in a monogamous relationship for at least six months. Participants completed a series of online questionnaires that assessed relationship functioning, motivation, EE, adherence to recommended changes after surgery, and %EWL. Results: Results indicated that better relationship functioning and higher levels of autonomous motivation were directly associated with better adherence to recommended changes postsurgery. Better adherence to recommended eating behaviors was related to higher %EWL, and both relationship functioning and autonomous motivation were indirectly x associated with %EWL through their impact on eating behavior adherence. Emotional eating was negatively associated with both %EWL and eating behavior adherence. Conclusions: These findings indicate that both individual (motivation, EE) and couples factors (relationship functioning) directly impact patient outcome after bariatric surgery. Clinical application, limitations, and future directions are discussed.
PH.D in Psychology, July 2013
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Title: RADAR AND COMMUNICATION CO-DESIGN: A CONSTANT ENVELOPE RADCOM SYSTEM
Creator: Testi, Nicolo
Date: 2014, 2014-12
Description: NO ABSTRACT
Ph.D. in Electrical and Computer Engineering, December 2014

Title: POSTTRAUMATIC GROWTH AMONG HIV-SEROPOSITIVE ADOLESCENTS AND YOUNG ADULTS
Creator: Niel, Kristin A.
Date: 2016, 2016-12
Description: An estimated 1,218,400 individuals in the United States were living with HIV/AIDS in 2014 (CDC, November 2015). In addition, 9,731 youth...
Show moreAn estimated 1,218,400 individuals in the United States were living with HIV/AIDS in 2014 (CDC, November 2015). In addition, 9,731 youth between the ages of 13 and 24 were newly diagnosed with HIV, with 81% of those diagnoses between ages 20 and 24. African-Americans accounted for 44% of new infections, with young gay and bisexual men accounting for 72% of new infections in all persons between 13 and 24. Research has suggested that a diagnosis of HIV/AIDS can be experienced as a trauma (Kelly et al., 1998; Nightingale, Sher, Mattson, Thilges, & Hansen, 2011). Posttraumatic growth (PTG) is characterized by significant, positive transformations that may occur in response to trauma and has been linked to improved mental and physical health among people living with cancer and adults living with HIV (Barskova & Oesterreich, 2009); however, these relations have not been sufficiently explored among youth living with HIV/AIDS. This study examined 71 HIV-seropositive youth at an urban medical clinic. It was hypothesized that (1) some youth would experience their HIV diagnosis as traumatic; (2) some youth would experience PTG; (3) higher levels of PTG would be associated with better health-related quality of life; (4) PTG would be positively associated with medical regimen adherence, and this relation would be mediated by serostatus disclosure; (5) PTG would be positively associated with physiological health, and this relation would be mediated by serostatus disclosure; and (6) the relation between serostatus disclosure and PTG would be moderated by social support satisfaction. Analyses revealed that 73.2% of participants experienced their diagnosis as traumatic, and 71.8% reported some level of PTG. A positive relation existed between PTG and the Social Relationships Domain of quality of life (β= .32, p < .01). Serostatus disclosure did not act as a mediator for the relations between PTG and adherence or health; however, there was a negative relation between disclosure and appointment attendance (β = -.46, p < .05). Finally, social support satisfaction moderated the relation between disclosure and PTG, such that the relation was stronger in those with average or high support satisfaction than those with lower satisfaction. Clinical and future research implications of these findings are discussed.
Ph.D. in Psychology, December 2016
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Title: ELECTRIC-HYDRAULIC HYBRID ENERGY STORAGE SYSTEM FOR ELECTRIFIED TRANSPORTATION
Creator: Niu, Geng
Date: 2017, 2017-07
Description: Environmental issues and fossil fuel depletion push the evolution of transportation and electrified transportation into the most likely next...
Show moreEnvironmental issues and fossil fuel depletion push the evolution of transportation and electrified transportation into the most likely next generation. However, there are several challenges in electrification with the major concerns involving the energy storage system. A hybrid energy storage system may provide an opportunity to improve the energy storage system of applications in transportation electrification. Hydraulic systems have been a mature technology for a long time and this study proposes a hydraulic add-on for electric vehicles. The high power density of a hydraulic accumulator could absorb high frequency regenerative braking and support battery discharging during acceleration, which will extend the driving range and reduce the current stress of the battery pack. Several models and controls have been created to evaluate hydraulic add-ons in di↵erent applications. The simulation results show a roughly 30% current stress drop and up to 25% energy saving (Wh/km) on average for city buses and delivery trucks over di↵erent driving cycles. A scaled down prototype vehicle with a novel electric hydraulic hybrid powertrain based on a go-kart chassis was built to perform road tests to validate the simulations results.
Ph.D. in Electrical Engineering, July 2017
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Title: REMOVAL OF BACTERIAL CONTAMINANT FROM MODEL SUBSTRATES USING A MICELLAR NANOFLUID FORMULATION
Creator: Shim, Jiyoung
Date: 2017, 2017-05
Description: The oscillatory structural force (OSF) of a micellar film of sodium dodecyl sulfate (SDS) was monitored with atomic force microscope (AFM)...
Show moreThe oscillatory structural force (OSF) of a micellar film of sodium dodecyl sulfate (SDS) was monitored with atomic force microscope (AFM) using an attached glass microsphere against a smooth flat and energy homogenous solid substrate. The force versus distance measurements for the 0.03M and 0.06 M SDS micellar solutions were monitored. The force versus distance had an oscillatory decay profile with a period of oscillation which was the same as the micellar diameter. The number of periodic oscillations increased with an increase in the micellar concentration. The OSF in the SDS micellar film confinement was also proved by a thinning single foam film formed from a micellar solution. It was observed that, due to micellar layering, the film thinned in a multiple regular stepwise manner promoted by the OSF. The results obtained by the AFM and thinning single foam film were used in the application of the OSF to remove bacteria from a model solid substrate. The experimental data for the OSF was complemented with modeling research. The theoretical OSF curves were obtained using the statistical mechanics approach. The experimental data and theoretical results for OSF for SDS micellar film were analyzed and found to be in fair agreement with each other. Based on the model prediction calculation, the structural film interaction energy barrier for the both the 0.03 M and 0.06 M SDS micellar solutions was calculated; the estimated structural film interaction energy barrier due to the presence of the OSF was about 10 3 kT / 􀝉􀬶 for the 0.03 M SDS micellar solution and about 5 x 10􀬷 kT /􀝉􀬶for the 0.06 M SDS micellar solution in film with micellar layers at about 25 ºC. Understanding the interactions between bacteria and solid surfaces that result in bacterial adsorption and removal is of immense importance for reducing foodborne illness outbreaks. Here, we used fluorescence microscope in conjunction with the concept of the diffusion of bacteria from the bulk suspension to the substrate and the adsorption isotherm to estimate the adsorption energy for E.coli K12; we obtained a value of about 2.5 kT. This value compares favorably with the value of 2.1 kT reported previously for E.coli NCTC 9002 [49]. We also used the dynamic light scattering method to estimate the radius of gyration of E.coli K12, which has a diameter of about 1 m and a length of 2 m to estimate the effective volume. The radius of gyration was also used to estimate the surface area covered by the bacterium and compared it to the surface area measured from the image taken with fluorescence microscope. A nanofluid formulation comprised of a sodium dodecyl sulfate (SDS) micellar aqueous solution in the presence of an organic acid (as a pH controller) was used to test the E. coli K12 removal from two substrates, polyvinylchloride (PVC) and partially hydrophobic glass. We investigated the bacterial removal efficacy based on the combined effect of the nanofluid’s structural forces and bacterial isoelectric point. We predicted the nanofilm oscillatory structural energy (NOSF) against the E.coli K12 adsorption energy by applying the statistical mechanics approach. Based on the model prediction, the NOSF was estimated at the vertex of three phase contact angle between a bacterium and the substrate (i.e., the wedge film’s interaction energy at one particle layer). The evaluated film’s repulsive energy due to the NOSF was about 15.6  4.4 kT of the 0.02 M SMNF (the SDS micellar nanofluid formulation) and several times higher than the bacterial adsorption energy, 2.5  0.2 kT. These findings suggest that the NOSF is capable of bacteria/microorganism removal from contaminated substrates. Here, we present a methodology based on NOSF to optimize the nanofluid formulation for bacterial substrate removal and bulk inactivation. The results of this study will assist the food industry with the design of proper sanitation and will enhance microbial removal and inactivation strategies.
Ph.D. in Chemical Engineering, May 2017
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Title: USER GENERATED DATA ANALYSIS AND UTILIZATION
Creator: Liu, Shizhu
Date: 2012-12-12, 2012-12
Description: Computer-mediated communication is becoming the most convenient and important way of sharing and exchanging information. The large volume and...
Show moreComputer-mediated communication is becoming the most convenient and important way of sharing and exchanging information. The large volume and diversity of user generated content as well as pervasive user opinions on the web make existing text processing methods ine cient and ine ective. Hence, there is a need for better ways of analyzing and utilizing user generated content. My thesis focuses on user generated data and is composed of two main parts: sentiment analysis and content analysis. I present a case study in which I use machine learning techniques to analyze real-world survey responses. Supervised techniques are exploited to classify customers' loyalty based on their comments and estimate a Net Promoter Score (NPS). NPS is a crucial indicator which has been used as a means of measuring survey results with a single estimator. I de ne three patterns to support generalized sentiment-bearing expression extraction, and design a set of heuristic rules to detect both explicit and implicit negations. By altering existing dependency with detected negations and generalized sentiment-bearing expressions I am able to construct more accurate sentiment features. Our results demonstrate that generalized dependency-based features are more e ective when compared to standard features. For content analysis, the thesis addresses the problem of user generated content summarization. I focus on two sub-problems: how to summarize the novel information from user generated content and how to present the evolutionary theme threads from temporal text collections with summaries. I design two speci c topic models for these two summarization tasks respectively. To discover similar and supplemental topics in user opinions with respect to the descriptive text provided by a publisher, I propose a semi-supervised generative model by casting the local publishers descriptive elds as a prior of a resembling topic. The most representative sentences in user opinions are classi ed based on their sentiment and used to construct a summary of x the comments. To track changes of topics in temporal text collections, I extend the probabilistic model to sentence level and use name entity to make the extracted theme thread easier to understand. Experimental results demonstrate the e ectiveness of the proposed models.
PH.D in Computer Science, December 2012
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Title: LAND USE EFFECTS ON WATER QUALITY: BUILDING A FRAMEWORK FOR CHICAGO RIVER WATERSHED
Creator: Mahdi, Naila Ghidey Ismail
Date: 2012-05-09, 2012-05
Description: The purpose of this study is to introduce a framework that enables a holistic watershed approach that models the dynamics of water quality and...
Show moreThe purpose of this study is to introduce a framework that enables a holistic watershed approach that models the dynamics of water quality and landuse in a highly urbanized watershed. The landuse-water quality relationship is a complex relationship and has not been adequately addressed for highly urbanized watersheds. Factors such as inadequate urban planning, increase of impervious areas and dynamics of population growth are some of the reasons for the complex relationship. Also point sources are always easy to be identified and controlled unlike nonpoint sources such as urban storm runoff. Both quantities and transport pathways of pollutant inputs are impacted by land use in the watershed. So, examining the factors that govern the relationship between different land uses and water quality within a watershed can give insights and important information about existing and potential sources of contamination. The two backbone concepts in this study are the holistic watershed perspective and the role of historical data records as part of assessment, modeling and integration tools of the watershed framework. Analysis of the records will explain watershed conditions identifying the major problem areas and justify the modeling and post analysis procedures. Data sources are often important but data availability, heterogeneity and conformity are the main challenges in integrating these sources. This research presents an approach to integrate the watershed data in a single repository and methodologies for analyzing and assessing the watershed using data warehouse and data mining technologies. A multi-dimensional model that supports complex querying of watershed data and discovery of trends and patterns in data by incorporating 40 years worth of watershed data from different source agencies in a central repository is introduced. Also, the discipline of data driven modeling was introduced in this thesis using the developed central repository. Several regression and classification algorithms were presented and assessed for their appropriateness for predicting total nitrates using few watershed attributes. The results show acceptable prediction accuracy. Five years of water quality simulation using the multi-purpose environmental analysis system BASINS coupled with the comprehensive, conceptual, and continuous simulation watershed scale model HSPF resulted in export coefficients for level (III), detailed land use for the Chicago River watershed. The water quality simulation approach utilized in this research to generate the coefficients constitutes a new contribution to the Chicago River watershed and other highly urbanized watersheds. The continuous calibrated and validated model can be used in the investigation and analysis of different scenarios and possible future conditions, thus providing a planning tool for regulatory environmental agencies. The data driven models developed can be used as operation tool to maintain the water quality parameters especially if TMDL and WQS are developed for Chicago River Watershed. So the framework proposed for this study can be considered robust with the proposed integration, planning and operating techniques and tools. Furthermore, an optimization tool is introduced in the future work section.
Ph.D. in Environmental Engineering, May 2012
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Title: TOWARDS REDUCING BUILDING ENERGY CONSUMPTION: COMPARISON OF THE RESIDENTIAL PLANNING PATTERNS IN BEIJING, SHANGHAI AND GUANGZHOU
Creator: Wang, Nan
Date: 2013, 2013-07
Description: The objective of this research is to investigate the influence of urban planning patterns on building energy consumption in different climate...
Show moreThe objective of this research is to investigate the influence of urban planning patterns on building energy consumption in different climate zones. Urban planning patterns affect the thermal performance and energy efficiency of buildings. This research focuses on the planning aspects, explores the energy consumption of a group of buildings with different planning pattern by utilizing single building as a baseline, and identifies planning patterns that can help to reduce the total heating and cooling energy consumption of the buildings. The investigations are carried out in the three largest cities in China – Beijing, Shanghai, and Guangzhou, which represent different climate zones. The results of these three cities are compared to find out the influence of local climate on building energy consumption. Different planning patterns are investigated in this research through changing building parameters: aspect ratio, orientation and layout. It is found that these parameters have important influence on reducing building’s energy consumption. It is also found that in different climate conditions, the influence of planning patterns on building’s energy consumption is different, which suggests that the selection of planning pattern will be different for each location. This research makes a significant contribution to the reduction of building energy consumption from urban planning perspective. In addition, two case studies of carefully selected residential communities with fixed site and fixed density are evaluated, and some suggestions for improvement are proposed as a result of the study. Such suggestions can help to propose a prototype model guiding the future architectural and urban planning work.
PH.D in Architecture, July 2013
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Title: ADVANCED BASE DRIVERS FOR SILICON CARBIDE BJTs
Creator: Pozo Arribas, Alejandro
Date: 2017, 2017-07
Description: This thesis focuses on the optimization of base drivers for SiC BJTs and presents a novel driver topology that targets minimum power...
Show moreThis thesis focuses on the optimization of base drivers for SiC BJTs and presents a novel driver topology that targets minimum power consumption. SiC BJTs have been studied for over a decade, during which time, they have been proven to have superior performance than Si IGBTs and even other normally-off SiC devices such as MOSFETs. Despite this, SiC BJTs are the least popular among the family of SiC power switches. As current controlled devices, BJTs require a continuous sup- ply of current through the base during the on-time. And, even though current gains over 100 have been reported, the base current required translates into a considerable amount power consumed by its driver, compared to its competitors. This power can affect the overall efficiency of a converter if the driver circuit is not designed properly. Since, the driver represents a key system for the success of SiC BJTs as power semiconductor devices, this thesis conducts a comprehensive evaluation of previous solutions and an analysis of the driver power losses to identify the optimal driver configuration. As a conclusion of this study, a novel topology is proposed, designed and built for its latter validation through experimental tests. The proposed solution allows the replacement of a SiC MOSFET or Si IGBT and driver with a SiC BJT and driver without the need of a current sensor or a dedicated DSP/FPGA. The driver power consumption is minimized with a proportional base current design based on a MHz synchronous buck converter operating as a Class D amplifier. This switched mode power amplifier uses a reference signal to provide a voltage that causes a base current proportional to the instantaneous collector current. The reference signal is generated with a high bandwidth sensor that measures the instantaneous voltage drop across the BJT (vCE) during the on-time. Hence, current sensors are avoided. Different alternatives for a voltage sensor are discussed and analyzed through simulations and experimental results. Moreover, the use of vCE to estimate the instantaneous collector current makes the proposed driver a temperature-sensitive design. For the first time, a proportional base current driver generates a base current proportional to the instantaneous collector current taking into account the effect of temperature on the DC current gain. Moreover, all this is achieved with solely analog electronics in a standalone solution. A 1.5kW Boost converter was built to validate the proposed driver under different collector currents and operating temperatures. In order to show the performance improvement offered by the proposed solution, the same Boost converter was operated with a commercial base current driver. This exercise showed a reduction of the driver power consumption by up to a factor of 4 without affecting the efficiency of the Boost converter. The switching behavior of a SiC BJT operated with the proposed driver and some of its limitations are discussed. These have, in fact, motivated additional research to develop efficient, isolated MHz regulators for faster operating frequencies of the SiC BJT. In addition, a new over-current protection integrated into the proposed driver is suggested and tested with interrupt times of less than 500ns for a collector current of 50A.
Ph.D. in Electrical Engineering, July 2017
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Title: THE EFFECT OF RUTHENIUM ADDITION ON THE PHASE EQUILIBRIA, MECHANICAL PROPERTIES AND OXIDATION RESISTANCE OF TIAL-BASED ALLOYS
Creator: Liu, Qizheng
Date: 2012-05-11, 2011-12
Description: The high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this...
Show moreThe high temperature phase equilibria in the Ti-Al-Ru ternary system have been investigated but there remain some ambiguous regions. In this work arc-melted alloys were studied using scanning electron microscopy, X-ray diffraction and optical microscopy to determine the isothermal section of Ti-Al-Ru system at 1200°C. The lattice parameters were calculated from X-ray diffraction pattern for some compounds, including LI, 8-Ruso(TixAlso-x) and (AI6o-xTix)Ru4o. The lattice parameter of these three phases generally increases with Ti content. Enthalpy of formation was also measured for LI and 8-Ruso(TixAlso_x) with direct synthesis calorimeter to compare with the lattice parameter change. The enthalpy of formation of LI matches its lattice parameter change, but 8-Ruso(TixAlso_x) shows a reversed trend. It suggests that addition of Ti introduces a stronger bonding in the 8-B2 phase super-lattice. The phase equilibria are discussed in comparison with published research work. A new three phase region was detected for L t, Y and Til_xAl 1+x by X-ray diffraction. The homogeneity region of (AI6o-xTix)RU4o was found to be much higher than previously reported, with almost constant Ru content. The results from the ternary isothermal section also help to clarify the uncertain parts of the binary Ti-Al phase diagram. Three ternary eutectic reaction temperatures were measured with differential scanning calorimetry and the results were compared with the published liquidus projection. The high temperature compression behavior of TiAl-Ru alloys was studied at different temperatures and strain rates. Ru was found to have a strong strengthening effect on TiAI alloys. However the Ru addition amount was limited by its low solubility in y-TiAI and U2-Ti3AI, and the detrimental effect of excessive ternary phase precipitation. Furthermore, the melting temperature decreases when Ru 2:0.6at% as the alloy composition approaches a ternary eutectic point. The strengthening mechanism is discussed and two separate mechanisms are proposed, viz. solid solution strengthening and refined colony strengthening. Intergranular cracks were found in the alloys with low Ru or no Ru addition, but were barely detected as Ru content increased to above 0.6 at.%. It was suggested that Ru showed a beneficial effect on both strength and ductility of TiAI alloys due to the refined colony size. Three-point bend test results showed that the Ru addition can also improve the room temperature ductility of TiAl alloys. Hot workability was increased according to the compression tests. Thermal-mechanically treated TiAI-Ru had much smaller grain size than the heat-treated samples due to dynamic recrystallization. But it did not show superior strength in the compression test compared to the heat-treated samples. The Zener-Hollomon parameter was calculated from the compression strength of heat-treated TiAI-Ru alloys. Its relationship with dynamic recrystallization and hot work is discussed. The mechanical properties of TiAI-Ru alloys are compared with TiAI-Nb samples and demonstrate a promising combination of strength and ductility. The high-temperature oxidation resistance ofTiAI alloys with constant AI content and different alloying elements was tested with thermogravimetric calorimeter. Both Ru and Nb additions were found to have beneficial effect on the oxidation resistance ofTiAI alloys. While TiAI-Ru showed a slight improvement on the oxidation behavior, TiAI-Nb alloys had much better performance in comparison with TiAI alloys. Complicated oxide scale structure was characterized with the assistance of X-ray diffraction, scanning electron microscopy and Energy-dispersive X-ray spectroscopy analysis. The different oxide scale structure among the TiAl, TiAl-Ru and TiAl-Nb alloys were discussed with respect to their thickness, spatial pattern and composition gradient. The poor oxidation resistance of TiAI alloys at the testing temperature was determined to be attributed to the competition growth between Ah03 as well as Ti02, and the lack of a thick continuous Ah03 layer. The outward diffusion of Ti was found to be the controlling factor and the growth of Ti02 on top level of the oxide scale destroyed the initial Ah03 protection. RU02 was found to be the natural marker of the oxidation process in TiAl-Ru alloys due to its slow diffusion. The repartitioning of Ru in the oxide/substrate boundary was revealed to be the reason of its slight beneficial effect. Nb20 S layer was observed in the oxide scale of TiAl-Nb alloys and it played the role of blocking the outward diffusion of Ti. Thus Nb addition can suppress the growth of Ti02 and promote the formation of a continuous AI 20 3 layer. Treating the TiAI alloys by dipping in hydrofluoric (HF) acid was found to have a dramatic beneficial effect on TiAI alloys. Alloying elements have reversed effect on the HF dipping due to the reduced reaction rate with HF acid. The oxidation rate constant and activation energy were calculated for TiAI alloys with/without alloying addition. They were compared with the published data and the trend with composition change was discussed.
Ph.D. in Materials Science and Engineering, December 2011
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Title: SECURITY AND PERFORMANCE OPTIMIZATION FOR WIRELESS COMMUNICATIONS
Creator: Wang, Qian
Date: 2012-04-13, 2012-05
Description: Today’s communication systems rely heavily on wireless technologies. The large scale proliferation of wireless technology brings with it a...
Show moreToday’s communication systems rely heavily on wireless technologies. The large scale proliferation of wireless technology brings with it a more serious concern for security since wireless communications introduce multiple avenues for attack and penetration into a network. This dissertation studies two important and fundamental problems in wireless communication security: secure secret key establishment and anti-jamming communication. This dissertation extends the current body of knowledge by proposing a suite of new and novel solutions to enhance and optimize the system performance. A comprehensive study including theoretical analysis and simulative evaluation shows that the proposed solutions can be applied in highly dynamic networking scenarios where traditional security mechanisms may not be sufficient by themselves. The first part of this dissertation develops a novel cooperative key generation protocol to facilitate high-rate key generation in narrowband fading channels, where two keying nodes extract the phase randomness of the fading channel with the aid of relay node(s). In particular, a theoretical upper bound and a more practical upper bound on the maximum secret key rate are successfully established. Numerical examples and simulation studies are also presented to demonstrate that the key rate can be improved by a couple of orders of magnitude compared to the existing physical layer based key generation approaches. The second part of this dissertation develops an adaptive uncoordinated frequency hopping (UFH) protocol for anti-jamming wireless communications. This section of the dissertation introduces the online optimization theory into the solution space and makes the thorough quantitative performance characterization possible for UFH-based anti-jamming communications. The optimality of the proposed algorithms is analytically proved under various message coding scenarios. Simulation results are presented demonstrating the jamming resilience of the learning-based UFH algorithm. The final part of this dissertation presents a jamming-resistant multi-radio multi-channel opportunistic spectrum access protocol for cognitive radio networks (CRNs), where the secondary sender and receiver adaptively choose their channels to operate to maximize the throughput. The convergence of the learning algorithm is investigated and an upper bound on the performance difference between the secondary sender and receiver’s optimal strategies is obtained. The simulation results in this section validate the theoretical analysis and show that even if facing a powerful jammer using myopic policy, the proposed design is still very effective and has strong resilience against jamming.
Ph.D. in Electrical Engineering, May 2012
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Title: LOCALIZATION OF WIND TURBINE NOISE USING A COMPACT MICROPHONE ARRAY WITH ADVANCED BEAMFORMING ALGORITHMS
Creator: Ramachandran, Rakesh Chandran
Date: 2014, 2014-12
Description: The knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been...
Show moreThe knowledge of noise source location on a wind turbine is crucial for de- signing low noise wind turbines. Even though there has been considerable e ort to theoretically predict the noise from wind turbines in the past, very few experimental investigations have been performed to validate these models. Currently, compliance standards for wind turbine noise are based on single microphone measurements at various designated locations around a wind turbine. This only provides amplitude and frequency data of the overall wind turbine noise. However, it is impossible to locate noise sources, and to understand the dominant noise generation mechanism, using single microphone measurements. A sophisticated method, namely, the use of a microphone phased array with beamforming is necessary to locate the noise sources. Even though microphone arrays have been widely used to study aircraft yover and jet noise, it has just recently found application in locating wind turbine noise. Typical microphone arrays that have been used in the past for monitoring aircraft noise and wind turbine noise are very large ranging up to 270 m2 in area with about 148 mi- crophones. The setup is xed for a particular wind turbine and takes a considerable amount of time. In this thesis it is shown that a compact microphone array (with 24 microphones spread over 1.5 m2) is su cient to locate and separate wind turbine noise sources successfully. It is also shown that in order to use a compact micro- phone array, advanced deconvolution based beamforming methods such as DAMAS, CLEAN-SC, LP, and TIDY are necessary. However, before attempting to validate our idea, it is necessary to understand the concept of array resolution and di erent methods to improve it. We start with an in-depth study on the microphone array resolution and the e ect of di erent beamforming algorithms on it. This study has resulted in several interesting results: (i) The resolution limits that govern the resolution of the imaging system in optics also govern the resolution of microphone array. (ii) The resolution is a function of source frequency, diameter of the array, separation distance between sources, and the distance between the array and the sources. (iii) The resolution lost due to the compact microphone array can be recovered by using deconvolution algorithms. (iv) Di erent algorithms are useful for di erent scenarios; CLEAN-SC is most e cient in extracting the dominant noise source from the source map, LP is e cient in locating multiple or extended noise sources, and TIDY is e cient in locating moving sources. (v) LP and DAMAS show superresolution. (vi) The dynamic range of source maps could be improved by eliminating the diagonal elements of CSM or CCM but care should be take as this could also eliminate weak sources. Following this study, we discuss the results from the full scale large wind tur- bine noise measurements. Our study focuses on the ability of a compact microphone array to successfully locate both mechanical and aerodynamic noise sources on the wind turbine. Several interesting results have emerged from this study: (i) A compact microphone array is su cient to perform a detailed study on wind turbine noise if advanced deconvolution methods are applied. (ii) Noise sources on the blade and on the nacelle can clearly be separated. (iii) Noise of the blades is dominated by trailing edge noise which is frequency dependent and is distributed along the length of the blade with the dominant noise source closer to the tip of the blade. (iv) The LP and DAMAS algorithms represent the distributed trailing edge noise source better than CLEAN-SC and conventional beamforming. (v) Additional tonal noise produced dur- ing yawing operation is believed to be radiating from the tower of the wind turbine that acts like a resonator. (vi) Ground re ection is not believed to have a signi cant e ect on noise source location estimates in this study. (vii) The asymmetry in the aerodynamic noise is attributed to the Doppler ampli cation e ect. Finally, the noise measurements made on the small scale wind turbine showed that the compact array was successfully able to separate out the mechanical and aerodynamic noise. The mechanical noise from the nacelle was found to be the dominant noise source below 3000 Hz and the aerodynamic noise from the blades was found to be dominant above 3000 Hz. The asymmetry in the aerodynamic noise was also present in this case. The study on mechanical noise found that gear box was the dominant noise source. It is hoped that the work presented in this thesis will serve as a guide to researchers who intend to use compact microphone arrays with advanced beamforming algorithms in the future and also to those who intend to validate theoretical models of wind turbine noise.
Ph.D. in Mechanical and Aerospace Engineering, December 2014
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Title: METHODOLOGY FOR PERFORMANCE BASED TRANSPORTATION SYSTEMS MANAGEMENT SIMULTANEOUSLY CONSIDERING DEMAND AND SUPPLY, WITH PRICING CONSIDERAnON
Creator: Patel, Harshingar
Date: 2015, 2015-05
Description: The ever growing demands for the use of transportation infrastructure and its maintenance and repairs at an acceptable level of service are...
Show moreThe ever growing demands for the use of transportation infrastructure and its maintenance and repairs at an acceptable level of service are the prime concern for transportation agencies today. The available financial resources can never be sufficient to match the exorbitantly high requirements for construction, maintenance and rehabilitation of transportation systems. With the advent of the technological revolution, the intelligence transfer amongst various engineering fields has made it possible to reduce transportation costs. However, the slow growing budget caused by economic recession and revenue decrease over time puts transportation agencies under enormous pressure to effectively restore the deteriorated transportation facility and system operation conditions under the budget constraint. The proposed research aims to utilize the concept of roadway pricing coupled with a holistic framework of asset management to support performance-based management of transportation systems and help transportation agencies achieve the future vision of the nation's strategic planning requirements to enable sustainable management of the system. A computational study for the City of Chicago’s central district is conducted by using the proposed roadway pricing framework. The proposed roadway pricing framework can be utilized for urban as well as rural regions, by public as well as private agencies, to manage the system in a sustainable manner, by means of fair pricing to the users of the system, for their facility condition and usage impacts.
Ph.D. in Civil Engineering, May 2015
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Title: 3D COMPRESSION ALGORITHMS AND SYSTEM-ON-CHIP DESIGN FOR ULTRASONIC IMAGING APPLICATIONS
Creator: Govindan, Pramod
Date: 2015, 2015-05
Description: Ultrasonic systems are widely used in imaging applications for nondestructive evaluation, quality assurance and medical diagnosis. These...
Show moreUltrasonic systems are widely used in imaging applications for nondestructive evaluation, quality assurance and medical diagnosis. These applications require large volumes of data to be processed, stored, and/or transmitted in real-time. Therefore, it is essential to compress the acquired ultrasonic radio frequency (RF) signal without inadvertently degrading desirable signal features. Signal fidelity, computational speed and resource utilization are the major parameters to be considered while designing the architecture for the compression algorithm. In this study, two algorithms for ultrasonic signal compression are analyzed based on: sub-band elimination using discrete wavelet transform; and decimation/interpolation using time-shift property of Fourier transform. Both algorithms offer high signal reconstruction quality with a peak signal-to-noise ratio (PSNR) between 36 dB to 39 dB for minimum 80% compression. The computational loads and signal reconstruction quality are examined in order to determine the best compression method in terms of the choice of DWT kernel, sub-band decomposition architecture and computational efficiency. Furthermore, for compressing a large amount of volumetric information, 3D compression algorithms are designed by utilizing the temporal and spatial correlation properties of the ultrasonic RF signals. The performance analysis indicates that the 3D compression algorithm presented in this study offers an overall 3D compression ratio of 95% with a minimum PSNR of 27 dB. Furthermore, the DWT based ultrasonic 3D data compression algorithm is implemented on a reconfigurable ultrasonic system-on-chip hardware platform targeted for real-time ultrasonic imaging applications. The reconfigurable platform allows analysis of multiple architectures to suit various applications. In this study, hardware andtemporal and spatial correlation properties of the ultrasonic RF signals. The performance analysis indicates that the 3D compression algorithm presented in this study offers an overall 3D compression ratio of 95% with a minimum PSNR of 27 dB. Furthermore, the DWT based ultrasonic 3D data compression algorithm is implemented on a reconfigurable ultrasonic system-on-chip hardware platform targeted for real-time ultrasonic imaging applications. The reconfigurable platform allows analysis of multiple architectures to suit various applications. In this study, hardware and software architectures of the 3D ultrasonic compression algorithm implemented on Xilinx Zynq all programmable system-on-chip platform are discussed, along with the analysis of computational performance. Both implementations provide a high signal compression ratio of about 98% with good quality signal reconstruction. This study demonstrates that, compressing 33 MBytes of experimental ultrasonic 3D data into 0.42 MBytes requires only 84 millisecond for hardware architecture, and one minute for software architecture, making both designs highly suitable for real-time ultrasonic imaging applications. Furthermore, the 3D compression is implemented by using OpenCL, which is adaptable to various platforms such as CPUs, GPUs and FPGAs. Therefore, OpenCL provides similar computational performance as that of hardware architecture, and the same flexibility as that of software implementation. This study demonstrates that the OpenCL implementation of ultrasonic 3D compression algorithm on Nvidia GT 750M graphical processing unit (GPU) completes the operation in less than one second.
Ph.D. in Electrical and Computer Engineering, May 2015
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Title: NETWORK SELECTION WITH LOAD MANAGEMENT IN HETEROGENEOUS WIRELESS NETWORKS
Creator: Ahmed, Syed Qutubuddin
Date: 2013, 2013-12
Description: With the growth of data-capable, multi-interface wireless and mobile devices, a lot of research work is being done on handover management and...
Show moreWith the growth of data-capable, multi-interface wireless and mobile devices, a lot of research work is being done on handover management and network selection in heterogeneous environment. Many researchers have proposed several strategies and policies for selecting the appropriate network. These policies di er among each other due to various reasons. The state and load of networks, number and types of wireless networks considered, and preferences of users are some of the reasons that attribute to di erences in those proposed policies. As a result, the applicability and e ciency of those policies depend upon certain situations and circumstances. We propose, in this research, a new concept that will help in utilizing these various policies in a manner that will give better results in a longer run and in various kinds of situations. We have a pool of policies available, and our proposed method will select the policy that is most appropriate according to the current state of user. We modeled this problem as a Markov Decision Process. Since the overall goal is that a user should be able to select an appropriate wireless network according to its service requirements and seamlessly handover to that network regardless of the underlying wireless technology being used. Since di erent sets of methodologies can exist to deal with this issue, we also propose an alternative mechanism that would facilitate a particular user to connect to the most appropriate network in a way that is bene cial to the overall network and its users as a whole. A trusted third party entity receives handover requests from a set of users along with their preferences, takes into consideration current network state of available service providers, and assigns each user to an appropriate network resource. We call this mechanism "Network Assisted Network Selection (NANS)" and it combines network-based, service-based and user-based criteria for network selection, and uses Generalized Assignment Problem (GAP) to assign the network resources to a set of users. ix Mobile Access Gateway (MAG) is a component of Proxy Mobile IPv6 (PMIPv6) which provides network-layer transparent mobility to mobile nodes (MN). MAG serves a local geographical area and mobile nodes in its vicinity may attach to it to get the mobility services from its controlling PMIPV6 domain. Since MAG is the point of attachment of mobile nodes, negotiated and guaranteed quality of service (QoS) is af- fected in case of service disruptions and overload of the MAG. To avoid and minimize the degradation of quality of service, we propose e ective mechanisms to share the load of a ected MAG with the MAG(s) that are working under normal conditions. We propose to handover certain mobile nodes to other MAGs depending upon their geographical serving area and current capacity. Furthermore, location of mobile node, its quality of service pro le, direction of motion and its multi-interface capability are major factors in selecting the mobile nodes for handover.
PH.D in Computer Engineering, December 2013
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