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Title: FLOW IN PARTIALLY CONSTRICTED PLANAR CHANNELS - ORIGINS OF VORTEX SHEDDING AND GLOBAL STABILITY OF NAVIER{STOKES SOLUTIONS
Creator: Boghosian, Michael Edward
Date: 2011-04-17, 2011-05
Description: Vortex shedding is a well-known unsteady uid-dynamic phenomenon occur- ring in a variety of ows in nature including stenosed blood vessels. We...
Show moreVortex shedding is a well-known unsteady uid-dynamic phenomenon occur- ring in a variety of ows in nature including stenosed blood vessels. We nd that current hypotheses regarding the origin of vortex shedding do not apply for the inter- nal ow in a partially constricted two-dimensional channel. As a result, we postulate a novel mechanism to explain the origin of vortex splitting and shedding in this ge- ometry. Numerical simulations of the unsteady, two-dimensional, incompressible Navier{ Stokes equations are performed in a channel having a constriction modeled by a two- parameter Gaussian distribution on both channel walls. Reynolds numbers from 1 to 3000 based on inlet half-channel height and mean inlet velocity and constriction ratios of 0:25, 0:5 and 0:75 are considered. The Navier{Stokes solutions are observed to experience a number of bifurca- tions including unsteady behaviour with shear-layer uctuations and vortex shedding downstream of the constriction. A sequence of events is presented describing how a sustained shear layer instability leads to the unsteady vortex shedding phenomenon via a convective instability and a proposed streamwise pressure-gradient mechanism. In addition, a global linear stability analysis is performed on several station- ary Navier{Stokes solutions to determine the long-term temporal behavior of small amplitude perturbations. Finally, the implications of this research on the hemodynamics in the cephalic vein and potential failure of the brachiocephalic stula are addressed.
Ph.D. in Mechanical Engineering, May 2011
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Title: PEDESTRIAN DETECTION AND TRACKING FOR ADVANCED DRIVER ASSISTANCE SYSTEMS
Creator: Mesmakhosroshahi, Maral
Date: 2017, 2017-05
Description: In an effort to reduce driver errors in being the major cause of traffic accidents, there is a lot of research being conducted into the...
Show moreIn an effort to reduce driver errors in being the major cause of traffic accidents, there is a lot of research being conducted into the development of advanced driver assistance systems (ADAS). ADAS is a system aimed at helping the driver in tasks such as pedestrian and vehicle detection, traffic sign recognition and lane detection. Pedestrian detection is one of the major tasks in advanced driver assistance systems (ADAS). Most of the stereo based pedestrian detection algorithms include three major steps: 1. Ground plane estimation 2. Region of interest (ROI) generation 3. Pedestrian classification In this thesis, we present a stereo-based pedestrian detection framework for advanced driver assistance systems by exploiting both color and depth information obtained from a stereo camera installed in a vehicle. In our proposed framework, we first use the vertical gradient of the dense depth map to estimate and discard the ground plane. The boundaries of the ground plane are then searched to detect the pedestrians and the depth values of the boundaries are used to compute the size of the detection windows for detecting pedestrians at different scales. In addition, a depth-based multi-scale ROI extraction method has been proposed to reduce the computation time of ROI extraction. For classifying ROIs to pedestrian and non-pedestrian classes, Histogram of Oriented Gradients (HOG)/Linear support vector machine (SVM) and Integral Channel Features (ICF)/Adaboost are used. To recover the missed pedestrians and improve the detection rate, an ROI tracking algorithm is proposed which incorporates the ROIs extracted from the current frame with theROIs tracked from a reference frame. For additional reduction in search space, we propose a novel algorithm to reduce the number of candidate windows extracted as ROI by taking advantage of the temporal correlation between the adjacent frames. We also propose a method to improve the accuracy of the pedestrian classifi- cation using the aggregated channel features. In this approach, we use the aggregated channel features as our baseline detector and improve it's accuracy using the tanh normalization and Gabor filter. After classification using Adaboost, we use a posi- tive subset of the bounding boxes to classify them again using Convlutional Neural Network to finalize the detection.
Ph.D. in Electrical Engineering, May 2017
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Title: ENSURING SECURITY AND PRIVACY IN BIG DATA SHARING, TRADING, AND COMPUTING
Creator: Jung, Taheo
Date: 2017, 2017-05
Description: We have witnessed huge values of the big data in the last decade, and it is evidential that the data bring large added values to the business...
Show moreWe have witnessed huge values of the big data in the last decade, and it is evidential that the data bring large added values to the business in various areas. Owing to such opportunities, the data collection and archival became one of the most successful business strategies in the industry, and more and more user-generated data are now being acquired, stored, provisioned, and consumed nowadays. Increased collection made human being more closely involved in the life cycle of the big data characterized by the acquisition, storage, provisioning, and consumption, and larger security and privacy challenges emerged. People’s awareness of such threats led to various efforts by the governments, industry, and academia, and our efforts described in this dissertation also belong to them. We have investigated the security and privacy challenges emerging in various parts of the life cycle big data experience nowadays, and I present our major discoveries in this dissertation which are composed of three major parts: (1) security and privacy in storage of big data; (2) theoretic foundations of privacy-preserving data computing; (3) security in big data trading. We addressed new or existing security/privacy threats existing in different parts of the big data life cycle by either leveraging existing works in intelligent ways or by proposing our novel technologies. The contributions of our discoveries cam be summarized as the protection of user privacy and data security while supporting the original functionalities at negligible extra computation/communication/storage overhead.
Ph.D. in Computer Science, May 2017
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Title: MODELING AND COMPUTATIONAL FLUID DYNAMICS SIMULATION OF A BUBBLING FLUIDIZED BED PROCESS AT DIFFERENT SCALES
Creator: Jang, Jungkee
Date: 2012-11-14, 2012-12
Description: In recent years there has been increased research activity in the experimental and numerical study of gas-solid flow system in the bubbling...
Show moreIn recent years there has been increased research activity in the experimental and numerical study of gas-solid flow system in the bubbling fluidized bed process. The bubbling fluidized bed process have numerous applications in the energy, pharmaceuticals, and chemicals process industries since it has provides a number of advantages such as large heat capacity inside a bed, and rapid heat and mass transfer rate. A reliable design and scale-up approach for a bubbling fluidized bed process requires a very detailed model based on the fundamentals of multiphase transport phenomena. The present works address the simulation and scale-up of rather complex gas-solid flow behavior in bubbling beds using Computational Fluid Dynamics (CFD) approach. The CFD model developed in this study which is based on two fluid model was used to optimize the performance and utilized as a scale-up tool for an isothermal and a non-isothermal bubbling fluidized bed process. For isothermal case, 2-Dimensional and 3-Dimensional simulations of bubbling beds for both PSRI laboratory and large scales fluidized beds using a kinetic theory approach were performed. The FLUENT code was used to conduct the simulations. Our simulation results were validated and refined by comparing them with the laboratory-scale experimental data of PSRI. Then, our modified 2-D and 3-D CFD models were used to predict the large-scale PSRI bubbling fluidized bed performance at different operating conditions. In our 3-D simulations, we used exactly the same bed dimensions and inlet configurations (such as air distributor) as the experimental one to predict the characteristics of gas-solid flow patterns in the PSRI large-scale bubbling fluidized bed. The numerical simulation results compared well with both PSRI large scale experimental xx data on pressure drop and time-averaged void fraction near the wall, which could be a very good proof for demonstrating the capability of CFD as a tool to be used in the design and scale-up of bubbling fluidized bed systems. For non-isothermal case, the set of equations necessary to describe the flow patterns and heat/mass transfer phenomena of bubbling beds at three different scales were developed. CFD simulations were performed to investigate the characteristics of pharmaceutical particle drying process in bubbling fluidized beds at three different scales (e.g., lab, kilo, and 10-kilo scales). The results of CFD simulation were compared with the experimental data obtained at laboratory-scale (Duquesne University experiments), to validate and refine our CFD model. The modified model was used to simulate the drying of the same material in Abbott laboratory kilo and 10-kilo scale units. Our simulation results for solid particles drying as a function of dimensionless time showed that our CFD model along with similar dimensionless group similarity approach can be used as a tool to scale-up the drying process from experimental scale to both kilo-scale and 10-kilo scale fluidized bed dryer. Moreover, to determine the optimum particle mixing, numerical simulations were performed at different particle diameters, bed heights, inlet velocities and inlet velocity distributions, respectively. The numerical simulation results compared well with the experimental data (performed by Duquesne University and Abbott laboratory) on moisture removal rate and outlet gas temperature. This also could be a very good proof for demonstrating the capability of CFD as a tool to be used in the design and scale-up of non-isothermal bubbling fluidized bed processes.
PH.D in Chemical Engineering, December 2012
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Title: DYNAMICS OF VESICLES IN VISCOUS FLUID
Creator: Liu, Kai
Date: 2014, 2014-12
Description: Modeling vesicle dynamics involves a complicated moving boundary problem where uids, thermal uctuations, and vesicle morphology are intimately...
Show moreModeling vesicle dynamics involves a complicated moving boundary problem where uids, thermal uctuations, and vesicle morphology are intimately coupled. In this thesis, we study the dynamics of a two-dimensional membrane in linear viscous ows. In the asymptotic analysis section, we derive deterministic and stochastic equations describing the motion of a slightly perturbed membrane interface. Using a 2nd order Runge-Kutta method, we solve these equations numerically, and explain the formation and development of wrinkling patterns. We then develop a boundary integral method and an immersed boundary method for simulating the nonlinear wrinkling dynamics of a homogenous vesicle in viscous ows. The nonlinear results agree with the asymptotic theory for a nearly circular vesicle, and also agree with experimental results for an elongated vesicle. Using a stochastic immersed boundary method, we investigate the e ects of thermal uctuations in vesicle dynamics. Comparing with the deterministic results, thermal uctuation can lead to the development of odd modes and asymmetric wrinkles. Finally, we investigate the nonlinear wrinkling dynamics of a multi-component vesicle. The model includes a 4th order Cahn-Hilliard type equation describing the phase transitions on the vesicle surface. We nd that for an elongated vesicle with large excess arc length, the inhomogeneous bending introduces nontrivial asymmetric wrinkling and buckling dynamics.
Ph.D. in Applied Mathematics, December 2014
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Title: VANADIUM OXIDE BASED MATERIALS AS OXIDATIVE DEHYDROGENATION CATALYST: SYNTHESIS, CHARACTERIZATION AND PROPERTIES
Creator: Aydemir, Kadir
Date: 2013, 2013-12
Description: The project concerns with design, synthesis and characterization of molecular and extended structure materials composed of vanadium oxides and...
Show moreThe project concerns with design, synthesis and characterization of molecular and extended structure materials composed of vanadium oxides and evaluation of their catalytic oxidative dehydrogenation (ODH) properties. A long-term objective is to develop an understanding of the structure-property relationships in ODH catalysts. Chapter 1 provides an overview of the field of metal oxides, polyoxometalates, and catalytic oxidative dehydrogenation of propane. This chapter also defines the research problem concerning this thesis and its fundamental and practical significance. Chapters 2-4 describe the synthesis, characterization and ODH properties of a select number of structurally correlated vanadium oxide based materials. The ODH catalysts studied in this work includes molecular compounds - (NH4)8[VIV 12VV 6O42(SO4)0.85(VO4)0.15]·10H2O (NH4-POV) and NH4V10O28, layered structure materials - MgVV 2VIV 2O10·4H2O (MV4) and V2O5, a chain structure - NH4VO3, and a nanostructured three-dimensional framework material - [Co3V18O42(H2O)12 (XO4)]·24H2O (X = V, S) (Co-POV). Their catalytic activities for ODH of propane to propylene - an important industrial feedstock material, were studies and compared in an attempt to get an insight of the structure-property relationships. Chapter 2 discusses synthesis and characterization of a new mixed-valence vanadate, MgVV 2VIV 2O10·4H2O (MV4), an extended structure solid, synthesized hydrothermally and characterized by single-crystal X-ray diffraction, spectroscopic methods, thermogravimetric analyses and temperature dependent magnetic measurements. MV4 represents the first model compound for the naturally occurring mineral melonovanadite, Ca2VV 4VIV 4O20·10H2O. MV4 is an important material with xv structural and electronic properties that are attractive for making it a potential promising ODH catalyst. The framework structure in MV4 consists of vanadium oxide layers crosslinked by {Mg(H2O)4} groups. The vanadium oxide layers are composed of edge shared {VIVO5} square pyramids, forming {V2O8} dimers, which share corners with {VVO4} tetrahedral units. Chapter 2 also discusses synthesis of a novel mixed-valence molecular polyoxovanadate - (NH4)8[VIV 12VV 6O42(SO4)0.85(VO4)0.15]·10H2O (NH4-POV) and its characterization by single-crystal X-ray diffraction, spectroscopic and thermogravimetric analyses. Structure consists of {V18O42} shell composed of 18 edge sharing {VO5} square pyramids, hosting a tetrahedral species {XO4} (X = S, V). Highly reduced molecular structure of NH4-POV makes it a promising ODH catalyst. Chapter 3 describes the ODH properties of a polyoxovanadate based openframework material - [Co3V18O42(H2O)12 (XO4)]·24H2O (X = V, S) (Co-POV). It is composed of {V18O42(XO4)} (X = S, V) building units, which is the molecular cluster present in NH4-POV, interconnected by {-O-Co-O-} bridging groups. Alternatively, since the building unit clusters {V18O42XO4} can be viewed as derived from sheets of V2O5, the 3-D structure of Co-POV can be viewed as made of V2O5 and CoO units. Therefore the ODH property of Co-POV was compared with the ODH property of the molecular cluster NH4-POV on one hand and with the V2O5 and CoO on the other hand. Co-POV was shown to have superior catalytic performance for ODH of propane as compared with its constituent metal oxides, V2O5, CoO and their mixture. ODH of propane reaction over NH4-POV catalyst has higher propylene selectivity of above 60% at moderate temperatures as compared to 37% selectivity of Co-POV catalyst. Supporting NH4-POV on high surface area γ-alumina was shown to improve propane xvi conversion drastically. In this study, highest propylene yield of 13% was achieved at 550 °C by supported NH4-POV catalyst. On the other hand, MV4 showed catalytic activity at marginally low temperature 200 °C due to propane activation energy (Ea) of 27 kJ/mol, the lowest Ea found in this study. Co-POV was utilized as a model compound to describe the effect of varying doses of γ-ray irradiation on the catalytic ODH properties of polyoxometalates for the first time. γ-ray irradiation enhanced catalysts’ selectivity to propylene during the oxidative dehydrogenation of propane. Chapter 4 describes full characterization of the catalysts studied in this work by powder X-ray diffraction analysis, temperature programmed reduction, X-ray absorption fine structure, BET surface area analysis and scanning electron microscopy. Structural changes of catalysts were investigated by comparing characterization results of asprepared, oxygen pretreated and post-catalysis (spent) catalysts. New vanadium oxide phases formed upon oxygen pretreatment. In general, ODH catalysis did not further alter catalysts’ structures.
PH.D in Chemistry, December 2012
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Title: LATTICE DESIGN OF THE INTEGRABLE OPTICS TEST ACCELERATOR AND OPTICAL STOCHASTIC COOLING EXPERIMENT AT FERMILAB
Creator: Kafka, Gene
Date: 2015, 2015-05
Description: The Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab will serve as the backbone for a broad spectrum of Advanced Accelerator...
Show moreThe Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab will serve as the backbone for a broad spectrum of Advanced Accelerator R&D (AARD) experiments, and as such, must be designed with significant flexibility in mind, but without compromising cost efficiency. The nonlinear experiments at IOTA will include: achievement of a large nonlinear tune shift/spread without degradation of dynamic aperture; suppression of strong lattice resonances; study of stability of nonlinear systems to perturbations; and studies of di↵erent variants of nonlinear magnet design. The ring optics control has challenging requirements that reach or exceed the present state of the art. The development of a complete self-consistent design of the IOTA ring optics, meeting the demands of all planned AARD experiments, is presented. Of particular interest are the precise control for nonlinear integrable optics experiments and the transverse-to-longitudinal coupling and phase stability for the Optical Stochastic Cooling Experiment (OSC). Since the beam time-of-flight must be tightly controlled in the OSC section, studies of second order corrections in this section are presented.
Ph.D. in Physics, May 2015
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Title: AN ENERGY-PRESERVING SCHEME FOR THE POISSON-NERNST-PLANCK EQUATIONS
Creator: Kabre, Julienne
Date: 2017, 2017-07
Description: Transport of ionic particles is ubiquitous in all biology. The Poisson-Nernst- Planck (PNP) equations have recently been used to describe the...
Show moreTransport of ionic particles is ubiquitous in all biology. The Poisson-Nernst- Planck (PNP) equations have recently been used to describe the dynamics of ion transport through biological ion channels (besides being widely employed in semiconductor industry). This dissertation is about the design of a numerical scheme to solve the PNP equations that preserves exactly (up to roundoff error) a discretized form of the energy dynamics of the system. The proposed finite difference scheme is of second-order accurate in both space and time. Comparisons are made between this energy dynamics preserving scheme and a standard finite difference scheme, showing a difference in satisfying the energy law. Numerical results are presented for validating the orders of convergence in both time and space of the new scheme for the PNP system. The energy preserving scheme presented here is one dimensional in space. A highlight of an extension to the multi-dimensional case is shown.
Ph.D. in Applied Mathematics, July 2017
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Title: INVESTIGATION OF PERFORMANCE AND DURABILITY OF POLYMER ELECTROLYTES FOR ELECTROCHEMICAL ENERGY STORAGE AND CONVERSION TECHNOLOGIES
Creator: Jung, Min-suk
Date: 2016, 2016-07
Description: Polymeric ion exchange membranes are integral components of electrochemical conversion/storage devices such as fuel cells, water electrolyzers...
Show morePolymeric ion exchange membranes are integral components of electrochemical conversion/storage devices such as fuel cells, water electrolyzers, and redox flow batteries. There has been dramatic progress in the research and development of cation exchange membranes (CEM). Nafion® (perfluorosulfonic acid membranes) is one example of a state-of-the-art CEM and has been successfully demonstrated in various electrochemical energy devices. Unlike CEMs, anion exchange membranes (AEMs) have been of limited utility to date due to their drawbacks, including poor chemical/mechanical stability and low ionic conductivity. However, alkaline environments result in better activity for electrochemical reactions and afford the possibility of using non-platinum group metal (PGM) electrocatalysts. AEMs, therefore, are still being studied in order to resolve existing challenges in terms of conductivity and stability in alkaline media and in strongly oxidizing solutions. In this work, AEMs derived from different types of polymer backbones were prepared, and their chemical stability and electrochemical property were investigated. Polysulfone (PSF) AEMs were prepared by first chloromethylating polysulfone, then by functionalizing chloromethylated polysulfone (CMPSF) with different base reagents. PSF-trimethylamine (TMA) AEMs showed a 40-fold reduction in vanadium (IV) ion (VO2+) permeability when compared to a Nafion® membrane and exceptional oxidative stability after exposure to a 1.5 M vanadium (V) ion (VO2 +) solution for 90 days. PSF-TMA AEMs were successfully demonstrated in the all-vanadium redox flow battery. Excellent energy efficiencies (>75 %) were attained and sustained over 75 chargedischarge cycles for a vanadium redox flow battery prepared using the PSF-TMA separator. Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) AEMs using diamine was tried with intentions to improve the mechanical stability and electrochemical property of PPO AEM. Crosslinked PPO AEMs (30 ± 4 % at 25 oC) showed less liquid water uptake than non-crosslinked PPO AEMs (46 ± 5% at 25 oC) while maintaining comparable ionic conductivities (hydroxide ion conductivity of 45 mS/cm at 60 oC). Crosslinked PPO AEMs maintained mechanical integrity and still showed some mechanical stability (ultimate tensile strength of 3~4 MPa and elongation at break of 13~17 %) after exposure to 1 M KOH at 60 oC for 14 days, while noncrosslinked PPO AEMs completely lost their mechanical durability. Finally, this dissertation presents research related to perfluorinated AEMs prepared using a Grignard reagent. These membranes exhibited 0.7 mmol/g of Cl- ion exchange capacity (IEC), 20 mS/cm of hydroxide ion conductivity at 20 oC, and 10 % of water uptake at room temperature. The membranes also maintained 90 % of their initial conductivity after an exposure to 1.5 M VO2+ in 3 M H2SO4 solution for seven days.
Ph.D. in Chemical Engineering, July 2016
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Title: LOAD ANALYSIS BASED ON MACHINE LEARNING IN POWER SYSTEMS
Creator: Lu, Dan
Date: 2017, 2017-05
Description: The dissertation is composed by four parts, first, load sampling for SCUC based on Principal Component Analysis (PCA) and Kernel Density...
Show moreThe dissertation is composed by four parts, first, load sampling for SCUC based on Principal Component Analysis (PCA) and Kernel Density Estimation (KDE); second, load forecasting based on PCA and Bayesian ridge regression; third, anomalies detection based on Machine Learning methodology; fourth the long-term planning of Battery-based Energy Storage Transportation (BEST) in power system. Mathematical models are constructed to fulfill the research of the three targets, and numerical examples are used to test the models. The first three parts are based on PCA, which reduced the load dimensions. In the first part, a robust power system Unit Commitment (UC) is the aim to fulfil the possible load. In the second part, a novel short-term nodal load forecasting is raised to give better prediction of the next day load to improve the next data UC scheduling. In the third part, anomalies are detected in the reduced power flow space based on the pattern identified in the lower dimensional space. The purpose of the fourth part is to find ways of better utilizing the existing resources from integrating the frontier technology, the mobility of more compact and higher capacity batteries. Mix-integer programming (MIP) is used in the formulation.
Ph.D. in Electrical Engineering, May 2017
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Title: THE TEMPORAL RELATIONSHIP BETWEEN DEPRESSION AND THE CONVERSION TO DEMENTIA: A RETROSPECTIVE ANALYSIS
Creator: Rog, Lauren
Date: 2011-07, 2011-07
Description: A relationship between depression and the dementing process has been fairly well established in both patients with mild cognitive impairment ...
Show moreA relationship between depression and the dementing process has been fairly well established in both patients with mild cognitive impairment (MCI) and dementia (e.g., Apostolova and Cummings, 2008; Lyketsos et al., 2002; Starkstein et al., 2005). However, less clear is the temporal role depression plays in the dementing process, with the possibilities including depression as a risk factor, a prodrome, or a consequence of dementia. Variables that have been considered to affect this relationship include gender, depression severity, lifetime history of depression, and etiology of cognitive decline. The current study examined the temporal relationship between depression and dementia in a sample of 218 patients with MCI or dementia who were seen for at least one follow-up visit at the neuropsychology service of an urban university medical center. Results did not reveal support for either the prodrome or the risk factor hypothesis of the depression-dementia relationship. However, it was found that people with a past history of depression who did not show depressive symptoms concurrent with their cognitive decline converted most quickly to dementia, suggesting a unique depression-dementia relationship in people with earlier-life depression.
Ph.D. in Clinical Psychology, July 2011
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Title: STEREO-BASED DEPTH MAP PROCESSING: ESTIMATION AND REFINEMENT
Creator: Loghman, Maziar
Date: 2016, 2016-12
Description: During the past decade, research in 3D video has become a hot topic owing to advancements in both hardware and software. Amongst different...
Show moreDuring the past decade, research in 3D video has become a hot topic owing to advancements in both hardware and software. Amongst different methods proposed for representing 3D data, multi-view video plus depth (MVD) format has gained a lot of attention. Most of such 3D algorithms rely on a per-pixel depth representation of the scene called a depth map. Depth maps are very useful for rendering virtual views and have lead to advancements in 3D compression algorithms. Generating an accurate and dense depth map is one of the important prerequisite for many 3D video applications. In this thesis, we highlight the following major problems in MVD. * Depth map estimation * Depth map refinement * Depth map coding In order to generate an accurate depth map, we propose a method based on Census transform with adaptive window patterns and semi-global optimization. A modified cross-based cost aggregation technique is proposed which helps to calculate a more reliable depth map. In order to further enhance the quality of the generated depth map, a novel multi-resolution anisotropic diffusion based algorithm is presented. The proposed depth refinement algorithm computes a dense depth map in which the holes have been filled and the object boundaries are sharpened. The next part of the research is based on depth map coding. In depth map coding, a considerable amount of time is required to investigate the mode decision pro- cess for every block of depth pixels. However, in real-time purposes, we can partially skip the mode selection step. In this thesis, we propose a novel depth intra-coding scheme for 3D video coding based on HEVC standard. The core idea of the proposed method is motivated by the fact that depth maps have specific characteristics that distinguish them from those of color images. By analyzing the reference depth maps based on homogeneousness of different regions, for some particular blocks, the DMM full-RD search is skipped and the mode is selected based on the previous similar tree- blocks. By this means, the time complexity of the encoding process is significantly reduced.
Ph.D. in Electrical Engineering, December 2016
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Title: MAXIMIZATION OF SYSTEM UTILITY VALUE FOR TIME-SENSITIVE APPLICATIONS
Creator: Li, Shuhui
Date: 2014, 2014-12
Description: Many applications are time-sensitive in the sense that the usefulness or the quality of their end results depends on their completion time....
Show moreMany applications are time-sensitive in the sense that the usefulness or the quality of their end results depends on their completion time. Examples of this type of applications are threat detections in air defense systems [97], radar trackings [36, 85], mobile navigations by Google [79, 44], and online gaming by Nintendo [38], to name a few. Take the threat detection application as an example, clearly, the earlier a threat is detected, the higher utility the application provides, as earlier detection provides more time to eliminate the threat [97]. This demonstrates the time-sensitivity of its utility. Here, the term `utility' means the actual bene t that accrues from the delivery of services [16]. The dependence between an application's accrued utility and its completion time is often modeled by a Time Utility Function (TUF). Apparently, when a system has multiple time-sensitive applications competing for the resources, a question arises: how to schedule their execution orders such that the system can yield maximal accrued utility? This thesis is to address the question. In this thesis, two categories of scheduling problems for time-sensitive applications are investigated: single-task applications in uni-processor systems and parallel multi-task applications in multi-processor systems. For the rst category, a two-TUF application model with given execution time is introduced and two scheduling algorithms for this model are proposed. Di erent from the conventional one-TUF model which only considers the gain utility, the developed model can deal with both the gain and the penalty utilities. The model is further extended to cope with applications whose exact execution times are not known at a priori, rather only their probabilistic execution time distributions are known. For applications with variable execution times, the di culty is how to make judicious decisions about when to start, continue or abort the applications. For the second category, i.e., for parallel multi-task applications in multi-processor systems, di erent from the widely investigated sequential multi-task applications, a parallel multi-task application's execution can have both spatial and temporal in uence on other applications. We propose a metric to measure the spatial-temporal interference among parallel multi-task and time-sensitive applications with respect to accrued utility. Based on the metric, a 2-approximation algorithm is introduced for systems operate in discrete time domains and its lower bound of system total accrued utility value is proved. We also develop a heuristic scheduling algorithm to maximize system's total accrued utility value for continuous time systems. Finally, the thesis discusses how methodologies developed in the thesis can be applied to reduce system's operational cost without sacri cing applications' quality of service. We propose a model to bridge together two orthogonal scheduling criteria, i.e., the system operational cost and application response time, and solve the problem by transforming it to a system accrued utility value optimization problem. The research uses both theoretical and experimental approaches. Theorems and lemmas are developed to provide the foundations for our solutions, and at the same time, extensive experiments are conducted to empirically evaluate the performances of the developed solutions.
Ph.D. in Computer Science, December 2014
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Title: UNMANNED AIRCRAFT SYSTEM SENSE AND AVOID INTEGRITY AND CONTINUITY
Creator: Jamoom, Michael B.
Date: 2016, 2016-05
Description: This thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating...
Show moreThis thesis describes new methods to guarantee safety of sense and avoid (SAA) functions for Unmanned Aircraft Systems (UAS) by evaluating integrity and continuity risks. Previous SAA e↵orts focused on relative safety metrics, such as risk ratios, comparing the risk of using an SAA system versus not using it. The methods in this thesis evaluate integrity and continuity risks as absolute measures of safety, as is the established practice in commercial aircraft terminal area navigation applications. The main contribution of this thesis is a derivation of a new method, based on a standard intruder relative constant velocity assumption, that uses hazard state estimates and estimate error covariances to establish (1) the integrity risk of the SAA system not detecting imminent loss of “well clear,” which is the time and distance required to maintain safe separation from intruder aircraft, and (2) the probability of false alert, the continuity risk. Another contribution is applying these integrity and continuity risk evaluation methods to set quantifiable and certifiable safety requirements on sensors. A sensitivity analysis uses this methodology to evaluate the impact of sensor errors on integrity and continuity risks. The penultimate contribution is an integrity and continuity risk evaluation where the estimation model is refined to address realistic intruder relative linear accelerations, which goes beyond the current constant velocity standard. The final contribution is an integrity and continuity risk evaluation addressing multiple intruders. This evaluation is a new innovation-based method to determine the risk of mis-associating intruder measurements. A mis-association occurs when the SAA system incorrectly associates a measurement to the wrong intruder, causing large errors in the estimated intruder trajectories. The new methods described in this thesis can help ensure safe encounters between aircraft and enable SAA sensor certification for UAS integration into the National Airspace System.
Ph.D. in Mechanical and Aerospace Engineering, May 2016
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Title: NOVICE HIGH SCHOOL SCIENCE TEACHERS: LESSON PLAN ADAPTATIONS
Creator: Scharon, Aracelis Janelle
Date: 2013, 2013-05
Description: The Next Generation Science Standards (NRC, 2013) positions teachers as responsible for necessary decision making about how their intended...
Show moreThe Next Generation Science Standards (NRC, 2013) positions teachers as responsible for necessary decision making about how their intended science lesson plan content supports continuous student science learning. Teachers interact with their instructional lesson plans in dynamic and constructive ways. Adapting lesson plans is complex. This process of adapting lesson plans may play an important role in affording and constraining teachers’ actions and students’ learning (Brown, 2009). This study explored how five novice chemistry teachers (under 4 years of total teaching experience) at five Midwestern high schools adapted or retained their honors chemistry instructional lesson plans, and what associated contextual factors influenced their decisions. Using a case study design, this study was conducted during the fall semester of 2013 when teachers were focusing on introductory chemistry topics. Three frameworks (pedagogical content knowledge (PCK), teacher decision making, and pedagogical discontentment and self-efficacy) were used to investigate the relationships between teacher adaptations, contextual factors and decision making. The outcome of this study was the identification of 15 types of adaptations and 17 relevant contextual factors. Contextual factors were categorized by factors that relate to students or the teacher. Adaptations were categorized into three overarching types of adaptations. Lesson plan adaptations and contextual factors are discussed in the context of research on teacher decision making and lesson plan adaptations.
PH.D in Science Education, May 2013
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Title: ANALYSIS OF LOW DIMENSIONAL MAGNETIC SYSTEMS CONTAINING CHROMIUM(III) AND COBALT(II) LIGATED BY THE SQUARATE LIGAND: MAGNETIC CHARACTERIZATION, BIOLOGICAL CHARACTERIZATION, INSTRUMENTAL DEVELOPMENT, AND SOFTWARE DEVELOPMENT
Creator: Mcneely, James Halley
Date: 2013, 2013-07
Description: A large series of Chromium(III) and Cobalt(II) complexes containing the C4O4 (squarate) ligand have been synthesized and characterized...
Show moreA large series of Chromium(III) and Cobalt(II) complexes containing the C4O4 (squarate) ligand have been synthesized and characterized magnetically. These complexes include simple dimeric Cr(III) systems that display a wide range of isotropic exchange couplings. One of these dimers shows interesting biological activity pertaining to the cellular uptake of glucose. This same compound also enhanced proton relaxation in T1 and T2 NMR studies. Computational work done on these dimeric systems showed excellent agreement with experimental results, and was used to confirm the structure of the complexes. The effect of the bridging squarate ligand was also studied computationally. The squarate ligand significantly contributed to the exchange coupling in the dimeric systems, and was shown to behave countercomplementary to the μ-hydroxo bridges. This is the first explicit observation of countercomplementarity in Chromium(III) systems. Co3(OH)2(C4O4) · 3H2O, a cobalt chain structure featuring an interesting low temperature spin-idle phase, was also synthesized. It was found that based on storage conditions, this compound either stays stable after grinding or transforms into the structure Co(C4O4)(H2O)2. In addition, grinding the sample shows an out-of-phase maxima at ≥6 K that has a frequency dependence characteristic of a spin glass. A new software package was also developed to simulate Electron Paramagnetic Resonance (EPR) spectra using full numerical diagonalization of the secular equation. This program was written using Wolfram Mathematica, and holds several advantages over currently available software. These advantages include a graphical user-interface and parallelization capabilities
PH.D in Chemistry, July 2013
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Title: NON-INTRUSIVE LOAD MONITORING AND DEMAND RESPONSE FOR RESIDENTIAL ENERGY MANAGEMENT
Creator: Iwayemi, Abiodun
Date: 2016, 2016-05
Description: Compared to cellphone bills which itemize billing into local, international, text messaging, and data, todays electricity bills are opaque....
Show moreCompared to cellphone bills which itemize billing into local, international, text messaging, and data, todays electricity bills are opaque. Residential electricity customers receive a monthly bill detailing their aggregate energy usage, without any insight into which appliances are responsible for what proportions of their bill. We therefore created a Non-intrusive load monitoring framework that uses only data available from smart meters and the price signals from the Electric utility, and combine it with Optimal Stopping Rule-based schedulers to create a framework to equip residents with the information they need to be more energy efficient while balancing their costs and comfort. Non-intrusive load monitoring provides homeowners with detailed feedback on their electricity usage, but an open area is automated appliance labeling and the creation of generalizable appliance models that can be trained in one home, and deployed in another. Manually labeling such events to use them for disaggregating residential appliances is a costly and tedious task, and we developed two approaches for semisupervised learning of appliance signatures. The first approach uses 1-Nearest neighbor semi-supervised learning, and we developed a stopping criterion which reduces the likelihood of mislabeling appliance instances. This approach was extended to a cluster-then-label semi-supervised learning approach which can use only 3 labeled samples of each appliance to label and classify similar appliances within the home. Our approach enables the comparison of unequal length time series, and incorporates additional features extracted from the appliance time series. Finally, we develop a hybrid framework that combines detailed appliance models learned via Non-intrusive load monitoring with optimal stopping rule schedulers. We evaluated the performance of these models in terms of cost and delay, and explored the effect that errors in the real-time price and appliance models have on appliance running costs to demonstrate how our approach outperforms scheduling using only day head prices.
Ph.D. in Electrical Engineering, May 2016
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Title: MODELING STRATEGIC COMPETITION, TACTICAL DESIGN, AND OPERATIONAL PLANNING TO IMPROVE SUPPLY CHAIN PERFORMANCE
Creator: Li, Chia-hang
Date: 2017, 2017-05
Description: A supply chain is a network of facilities responsible for the production and delivery of goods and services from the initial raw materials to...
Show moreA supply chain is a network of facilities responsible for the production and delivery of goods and services from the initial raw materials to the end customers. Supply chain management, therefore, involves management of activities both within and among the organizations throughout the chain at every level of business management. In this dissertation, we address three specific supply chain problems at three distinct level of business management: (1) Operational capacity and production planning; (2) Tactical closed-loop channel structure design; and (3) Strategic platform competition. In each work, we identify strategies that lead the supply chain improvements.
Ph.D. in Management Science, May 2017
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Title: MOLECULAR MECHANISMS UNDERLYING SALMONELLA SURVIVAL ON SURFACE OF SELECTED NUTS AND FRUITS
Creator: Li, Ye
Date: 2017, 2017-07
Description: Salmonella enterica is the leading cause of bacterial foodborne illness in the United States. In recent years, S. enterica has been frequently...
Show moreSalmonella enterica is the leading cause of bacterial foodborne illness in the United States. In recent years, S. enterica has been frequently linked to foodborne outbreaks associated with nuts and fruits; however, the underlying mechanisms of such association have not been fully understood. In the first part of this study, we evaluated the impact of various environmental factors and food surface attributes on the attachment and survival of five S. enterica strains representing serotypes Typhimurium, Enteritidis, Montevideo, Mbandanka, and Braenderup on three different raw nuts (i.e. black peppers, almonds and hazelnuts) and two different S. enterica strains including serotypes Typhimurium and Enteritidis on two fresh fruits (i.e. grape tomatoes and cantaloupes) under storage conditions relevant to industrial practice. We observed significant inter-strain variations in S. enterica survival on nut and fruit surface. A direct correlation was found between the nut and fruit surface roughness and S. enterica attachment and survival. Lower relative humidity (20%) and higher storage temperature (25oC) resulted in significant S. enterica reduction on nut shells. Lower storage temperature at 4oC significantly reduced S. enterica population on grape tomatoes. In the second part of this study, we used a newly-developed transposon mutagenesis library in S. enterica serotype Enteritidis genome and highthroughput sequencing analysis to identify genes with potential roles in S. enterica attachment to and survival on almonds and grape tomatoes. A total of 336 and 210 S. enterica genes displayed significant selection on almonds and grape tomatoes over a 7-d storage period at 25oC (p<0.05), respectively. Our results suggest that various food attributes, environmental factors as well as bacterial determinants collectively contribute to the survival and persistence of S. enterica on nuts and fruits, providing new data for future development of knowledge-based intervention strategies.
Ph.D. in Biology, July 2017
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Title: HIGH-FREQUENCY TRADING, LOW-FREQUENCY TRADING AND THE LIMIT ORDER MARKET
Creator: Li, Kun
Date: 2015, 2015-07
Description: The emergence of High-Frequency Trading (HFT) has met with mixed reactions in both investment and academic communities. However, there still...
Show moreThe emergence of High-Frequency Trading (HFT) has met with mixed reactions in both investment and academic communities. However, there still exist gaps on distinguishing and interpreting the impact of HFT on the Low-Frequency Trading (LFT) side. In this thesis, I present three chapters that address the impact of HFT to LFT. I find evidence to distinguish trading generated by HFT in the limit order market, and consequently apply to explore how HFT affects LFT in terms of the liquidity and the order execution quality. In addition, I further explore the fleeting orders generated by HFT and their impact on the liquidity of LFT.
Ph.D. in Management Science, July 2015
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