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Title: DETERMINATION OF REDUNDANCY IN STRUCTURES USING INTERVAL UNCERTAINTY ANALYSIS
Creator: Amirshaghaghi, Sayeh
Date: 2014, 2014-05
Description: Existence of redundancy in structures plays an important role in increasing their safety and reliability. However, using state-of-the-art...
Show moreExistence of redundancy in structures plays an important role in increasing their safety and reliability. However, using state-of-the-art deterministic and probabilistic approaches, all possibilities for estimation of redundancy (e.g. due to occurrence of different damage scenarios) have not been considered. One of the methods to quantify the presence of uncertainties in a system is to use interval variables. In this work, a new method for estimating the redundancy using interval structural analysis is developed. This method, hereafter referred to as Interval Redundancy Analysis (IRA), is robust and considers possibilities of strength reduction for each element leading to failure. Independent intervals for reduction of the strength for five damage scenarios of intact, slightly damage, moderately damaged, severely damaged, and completely damaged as well as strength of each element are considered. A numerical example to show the behavior of the developed method with comparison to Monte-Carlo simulation results is presented.
M.S. in Civil Engineering, May 2014
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Title: NATURAL AGING EFFECT ON DOUBLE AGED ALUMINUM ALLOY AA7075
Creator: Kara, Baris
Date: 2012-04-27, 2012-05
Description: The effect of natural aging (NA) on mechanical properties in double aged aluminum alloys, AA7075, was studied by means of hardness tests,...
Show moreThe effect of natural aging (NA) on mechanical properties in double aged aluminum alloys, AA7075, was studied by means of hardness tests, tensile tests and stress corrosion cracking (SCC) tests. Natural aging can strengthen AA7075 alloys after solution heat treatment, and reaching the stable condition can take years for the alloy. Double aging (DA) is very beneficial method in terms of energy savings and productivity because this method provides the peak hardness in a much shorter time compared to single aging, and DA treatment produces hardness, yield stress and tensile stress which are comparable with those produced by SA. In this study, the alloys were naturally aged for different times before double aging treatment, and the relationship between double aging treatment and natural aging treatment was observed. The results show that different natural aging times do not significantly affect the final mechanical properties of double aged alloys. Consequently, the loading time to aging furnace after solution heat treatment does not play an important role in the double aging treatment of AA7075 alloys.
M.S. in Materials Science and Engineering, May 2012
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Title: ENHANCED DEGRADATION AND PEPTIDE SPECIFICITY OF MMP-SENSITIVE SCAFFOLDS FOR NEOVASCULARIZATION OF ENGINEERED TISSUES
Creator: Sokic, Sonja
Date: 2013, 2013-07
Description: Biomaterial strategies for engineering tissues of clinically relevant size require the formation of rapid and stable neovascularization. The...
Show moreBiomaterial strategies for engineering tissues of clinically relevant size require the formation of rapid and stable neovascularization. The ability of an engineered scaffold to induce vascularization is highly dependent on its rate of degradation. During the process of material degradation, the scaffold should degrade in a manner allowing for cellular infiltration, lumen formation, and extracellular matrix (ECM) synthesis. Matrix metalloproteinases (MMPs) play a key role in mediating cell-induced proteolytic matrix degradation, remodeling, and controlled neovascularization. Poly (ethylene glycol) PEG hydrogels have been extensively investigated as scaffolds for tissue engineering applications due to their ease of chemical modification allowing for the recapitulation of key aspects of the neovascularization process. The goal of the work described in this thesis was to develop strategies to enhance and control the degradation of MMP-sensitive PEG diacrylate (PEGDA) hydrogels without inducing changes to the bulk physical and mechanical properties of the material and to further study the effect of the cleavage site concentration and MMP-sensitive peptide substrate specificity on the rate of neovascularization and tissue remodeling in vitro and in vivo. In the first part of this study, a detailed investigation was completed to investigate the effects of the mechanical and physical properties of the scaffolds as well as the role of proteolytically mediated hydrogel degradation on 3D fibroblast invasion within MMPsensitive PEGDA hydrogels. Initial studies focused on the use of a modified version of a previously published multistep conjugation method to generate degradable PEGDA macromer conjugates containing variations in the number of MMP-sensitive domains. Theoretical and experimental characterization of this multistep conjugation demonstrated xi that this method leads to the formation of multiple species that directly affect the compressive modulus and degradation rate of the scaffold making it difficult to control degradation independent of alterations in the bulk physical and mechanical hydrogel properties. After manipulation of multiple polymerization conditions, hydrogels with similar compressive moduli but different hydrogel degradation rates were synthesized. These initial studies showed that an increase in the incorporation of proteolytically sensitive domains in PEGDA hydrogels of similar modulus lead to enhanced degradation and 3D fibroblast invasion. In this study, the role of soluble FGF-1 on fibroblast invasion within these scaffolds was investigated and it was demonstrated that the inclusion of FGF-1 in the scaffolds results in further enhancement of fibroblast invasion in a dosedependent fashion. Further studies were necessary to develop a more controllable and robust approach in tuning scaffold degradation independent of alterations in the bulk physical and mechanical properties. In order to address this, a novel approach was developed to engineer protease-sensitive peptides with multiple proteolytic cleavage sites that could be covalently crosslinked into hydrogels without compromising the physical and mechanical biomaterial properties. This approach avoided the need for utilizing a multistep conjugation process as peptides could be incorporated into the backbone of PEG using a single step conjugation. Using this approach, hydrogels formed with the engineered peptides led to significantly enhanced degradation and neovascularization in vitro as compared to scaffolds with a single protease sensitive peptide between crosslinks. In addition, hydrogels with enhanced susceptibility to degradation promoted vascularization over a wider range of matrix properties. This approach allowed for controlled xii concentration of the proteolytic cleavage sites within the matrix and thus tuning of hydrogel degradation for tissue engineering applications. In the final study, MMP-sensitive peptide substrates specific to degradation by MMPs known to be expressed during neovascularization were screened for degradation and their role in neovascularization. MMP-sensitive PEGDA hydrogels (SSite and TriSite) were synthesized with peptide substrates sensitive to cleavage by MMP-2, MMP- 9, MMP-14, a mixed sequence of MMP-2, 9 and 14, and compared to the peptide substrate used in the previous studies, which is degraded by collagenase enzymes. The hydrogels were evaluated for their sensitivity and specificity to degradation by MMPs, in terms of cleavage site concentration, and for their role in neovascularization and tissue remodeling in vitro and in vivo. The presented approach allows for the incorporation of varying cleavage site concentration and MMP-sensitive peptide substrates into PEG hydrogels without alterations in the mechanical and physical properties of the hydrogels. Results showed that without the incorporation of growth factors in this scaffold, vascularization and tissue invasion was supported in all MMP-sensitive hydrogel groups regardless of the MMP-sensitive peptide substrate embedded in the matrix. In addition, the cleavage site concentration had a profound impact in enhancing vascularization in vitro and tissue invasion in vivo. These techniques can be used to tune the properties of polymer scaffolds for neovascularization and tissue remodeling. In addition, these studies provide insight into the effect of the physical, mechanical, and degradative properties of these systems and on the role of cleavage site concentration, and MMP substrate specificity on xiii neovascularization and tissue invasion within proteolytically degradable PEG hydrogel constructs.
PH.D in Biomedical Engineering, July 2013
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Title: LONG-TERM AEROBIC AND ANAEROBIC TRANSFORMATIONS OF ORGANIC MATTER IN ANAEROBICALLY DIGESTED BIOSOLIDS
Creator: Lukicheva, Irina
Date: 2012-12-05, 2012-12
Description: Long-term anaerobic storage of biosolids in a lagoons type of system as a post-treatment to anaerobic digestion is a proven process for...
Show moreLong-term anaerobic storage of biosolids in a lagoons type of system as a post-treatment to anaerobic digestion is a proven process for further pathogen reduction to produce Class A biosolids. At the same time, final biosolids product could develop odors during storage and handling, limiting the flexibility of biosolids utilization. The goal of this research was to study properties of biosolids under different lengths of aging time to determine the stability of final product for its odor potential. Field lagoons of Metropolitan Water Reclamation District of Greater Chicago were sampled to estimate the spatial and temporal variations in the physical-chemical properties and biological stability indicators, namely, total solids, volatile solids, pH, electric conductivity, total Kjeldahl nitrogen, ammonia-N, nitrite/nitrate-N, accumulated oxygen uptake for the 20-hour respirometric test, soluble protein concentration and headspace concentrations of volatile sulfur compounds. The sampling campaign was performed in October 2009. Two types of lagoons were assessed in this study- high-solids lagoons that are loaded with sludge that was previously anaerobically digested and dewatered on the centrifuges, and low-solids lagoons that are loaded with sludge that was previously digested but not dewatered. The analysis of collected data suggested that for the high-solids lagoons the surface layer biosolids (depth of above 0.15 m) undergo long-term aerobic oxidation resulting in higher degree of final product stabilization. The subsurface layers (depth below 0.15 m) are subjected to anaerobic environment where the conditions allow only the initial rapid organic matter degradation approximately within the first year, followed xii by very slow degradation. In addition, microbiological analyses using Fluorescent in situ Hybridization did not indicate active microbial communities in aged biosolids. The performance of low-solids lagoons in the reduction of the biodegradability parameters was shown to be similar to that of the high-solids lagoons. Low-solids lagoons were shown to perform the dewatering function reducing moisture in the digested sludge from initial 2-3% TS to up to 16% TS. Although the lagoon aged biosolids were found to be stable in comparison with other products, such as composts, further aerobic processes taking place after lagoons, such as air-drying and stock-piling could induce further active biological activity. This could potentially result in the odor formation from the air-dried final product. For these reasons, more research is required on the mechanisms promoting further product degradation after lagoons aging.
PH.D in Environmental Engineering, December 2012
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Title: AN OVERVIEW OF IMPROVED PROBABILISTIC METHODS FOR STRUCTURAL REDUNDANCY ASSESSMENT OF INDETERMINATE TRUSSES
Creator: Pathe, Julien Rene
Date: 2012-07-25, 2012-07
Description: The redundancy of a structure refers to the extent of strength that is not considered in design. For an indeterminate structure a member...
Show moreThe redundancy of a structure refers to the extent of strength that is not considered in design. For an indeterminate structure a member failure does not necessarily induces the loss of integrity or functionality of the structure; rather it will affect its potential for safely carrying any future load. Numerous methods have been introduced in structural reliability literature to measure and implement the redundancy in design. However, in accordance with the semi-probabilistic approach of the codes which aim to develop design method providing consistent level of redundancy within the structure, the probability of failure of the structure has been proposed and is widely used as a redundancy measure. A classical method to compute the probability of failure of the structure based on failure paths is presented as a reference in this thesis. However, although extensively used, this method has major shortcomings which may lead to a misrepresentation of the structure redundancy. By using a geometric representation of members’ limit states associated with a loading regime, the research presented herein proposes an improved method for structural redundancy estimation that may be helpful to overcome problems associated with approximations and inconsistencies inherent in classics methods. Specific assumptions and/or procedures considered in the proposed method are described below. (1) An approximation is given to make the events of member failures mutually exclusive. (2) Geometric calculations are used to determine reliability indices and conditional reliability indices in order to establish closer bounds for the failure probability of individual structural members. (3) System’s failure probability is obtained using the assumption and procedures outlined in (1) and (2) above. (4) To further extend the method beyond geometrical redundancy, and to consider material redundancy, plasticity models commonly used in the structural analyses are considered in this study
M.S. in Civil Engineering, July 2012
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Title: Development and Application of an Occupational Odor Hazard Index
Creator: Wang, Tingting
Date: 2011-04-24, 2011-05
Description: Odors emitted from wastewater treatment and sludge processing facilities may lead to employee complaints regarding discomfort, stress or...
Show moreOdors emitted from wastewater treatment and sludge processing facilities may lead to employee complaints regarding discomfort, stress or disease, and affect productivity and worker turnover in Water Reclamation Plants (WRPs). This study reports and assesses a comprehensive method that estimates the odor perception and associated hazards from exposures to odors in a post-digestion dewatering building in a WRP and its vicinity areas. An Odor Reference Concentration (ORfC) is developed as an index of acceptable odor level. This index is applied to ensure that the majority of building occupants (80 percent or more) do not perceive the odor. This index is developed to fill the lack of a uniform standard and method to assess hazard of exposed individuals to odors in occupational environments and to regulate odor exposures.
A comprehensive odor and odorant concentration database was formulated by a monitoring study in the occupational environment of a post-digestion dewatering building. The presence of odorants in the building are at concentrations below occupational exposure limits but higher than odor detection threshold values. This finding indicates that reducing odorant concentrations below exposure limits does not assure an odor-free environment. A model is formulated and validated for this dewatering building associating odor perception with concentrations of total sulfur compounds and relative humidity and is used for prediction of indoor odor concentrations under various conditions. Odor and odorant emission rates as the strength of sources are input variables of the indoor air quality model. In this study, odor and odorant emission rates from freshly dewatered biosolids in a dewatering building were measured using two widely used dynamic methods: the USEPA flux chamber and wind tunnel, and results from the two methods are not significantly different. Comparison of the two methods indicates that both methods can be used to estimate odor and odorant emission rates but the most effective and efficient method depends on prevailing environmental conditions. The ORfC established based on the comprehensive odor and odorant concentration database for this dewatering building is 13D/T (dilution to threshold). This index is used to evaluate seven control strategies recommended to reduce odor levels. If indoor odor concentrations in the occupational environment exceed the ORfC, then the hazard of odor exposures is unacceptable. Deterministic results of this study indicate that if appropriate control strategy is applied, odor concentration in the dewatering building would reach to below levels that cause unnecessary stress and other effects. The control strategy focus of this work is reduction of the indoor odor perception. But indoor control strategies must not cause outdoor odor problems to surrounding residential areas. Therefore, the potential impact of the control strategy recommended is also investigated in this thesis using the US EPA recommended air dispersion modeling AERMOD. Predictions of hydrogen sulfide concentrations at surrounding areas of the plant indicate that only one strategy, which proposes to add a new exhaust system in the dewatering building, would cause the ambient hydrogen sulfide concentration to be 7% higher than the odor detection threshold; other six strategies would not induce odor annoyance to surrounding areas. Acute and long-term ambient hydrogen sulfide exposure limits based on human health and irritation effects would not be violated under any of the seven control strategies.
Ph.D. in Environmental Engineering, May 2011
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Title: DISCONTINUOUS IN THE NI-CO-AL PRECIPITATION ALLOY SYSTEM
Creator: Liu, Tian
Date: 2014, 2014-05
Description: The synthesis of nanoplates of 0 by use of discontinuous precipitation was investigated in the Ni-Co-Al alloy system. A series of experiments,...
Show moreThe synthesis of nanoplates of 0 by use of discontinuous precipitation was investigated in the Ni-Co-Al alloy system. A series of experiments, such as heat treatment, cold rolling, and electrolytic etching, have been performed to develop the desired microstructure. Nanostructured materials have great potential in a number of applications, such as catalysis, light weight structural materials, thermal management and pollution reduction. Kinetic information of the Ni-Co-Al alloy was obtained through measuring the optical micrographs of samples aged at di erent temperatures. The morphology of the nanostructure of the Ni-Co-Al alloy was investigated using scanning electron microscopy (SEM). The mechanical property (hardness) of the Ni-Co-Al alloy was obtained in di erent conditions as well. The Ni-Co-Al alloys were recrystallized in di erent ways. The texture of the alloys were determined using electron backscattered di raction (EBSD). After analyzing those experimental results, we nd that the discontinuous precipitation goes to completion in the Ni-Co-Al alloy. The discontinuous precipitates present a lamellar structure. The size of plates is similar with the spacing between plates and achieves a nanoscale architecture. The TTT curve of the Ni-Co-Al alloy with a composition of 43 at.% Ni, 48 at.% Co and 9 at.% Al provides abundant kinetic information. Further work is needed to produce a strong cube texture ((100) planes parallel to the foil surface).
M.S. in Materials Engineering, May 2014
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Title: COATING OF BORON NITRIDE THIN FILM ON TITANIUM
Creator: Huang, Mairui
Date: 2013, 2013-12
Description: To improve the wear resistance of titanium and extend its service life, coating boron nitride thin films on the surface of titanium matrix was...
Show moreTo improve the wear resistance of titanium and extend its service life, coating boron nitride thin films on the surface of titanium matrix was studied in this work. To obtain surface property enhancement, the samples were coated by isothermal sintering at 1000°C – 1400°C in a vacuum furnace for 2h, 4h or 6h. The microstructure of the thin film was investigated employing X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). To identify the composition of interlayers between BN and Ti, EDS analysis was run through the whole reaction zone. It showed that the BN was being consumed, titanium borides (TiB and TiB2), titanium nitride (TiN1-x), and solid solution of nitrogen in titanium (α-Ti (N)) layers formed at the interface between the BN coating and Ti matrix. Correspondingly, the XRD analysis indicated that TiB, TiB2, TiN, and α-Ti(N) phases were presented in good agreement with the EDS result. The layers grew fast in the sintering process which benefited from the fine grain size and highly oriented layers grown in the reaction zone. However, the well-known parabolic diffusional growth is only part of mechanisms for explaining the reactiondiffusion kinetics. The diffusion paths were obtained from the phase sequences at the interface between BN and Ti and thus could be represented on the isothermal section of the B-N-Ti ternary diagram. Moreover, the influence of the sintering temperature and the length of the actual sintering period on the layer sequences and thickness of the reaction zone were investigated. The micro-hardness test results showed that the Ti matrix with deposited BN thin films exhibited significant increased surface hardness. Obviously, the surface hardness xiii rose along with sintering temperature and holding time, and the hardness could be improved over 50%.
M.S. in Materials Science and Engineering, December 2013
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Title: THE EUML-ARC PROGRAMMING MODEL
Creator: Marth, Kevin
Date: 2014, 2014-07
Description: The EUML-ARC programming model shows that the increasing parallelism available on multi-core processors requires evolutionary (not...
Show moreThe EUML-ARC programming model shows that the increasing parallelism available on multi-core processors requires evolutionary (not revolutionary) changes in software design. The EUML-ARC programming model combines and extends software technology available even before the introduction of multi-core processors to provide software engineers with the ability to specify software systems that expose abstract platform-independent parallelism. The EUML-ARC programming model is a synthesis of Executable UML, the Actor model, role-based modeling, split objects, and aspect-based coordination. Computation in the EUML-ARC programming model is structured in terms of semantic entities composed of actor-based agents whose behaviors are expressed in hierarchical state machines. An entity is composed of a base intrinsic agent and multiple extrinsic role agents, all with dedicated conceptual threads of control. Entities interact through their role agents in the context of featureoriented collaborations orchestrated by coordinator agents. The conceptual threads of control associated with the agents in a software system expose both intra-entity and inter-entity parallelism that is mapped by the EUML-ARC model compiler to the hardware threads available on the target multi-core processor. The hardware and software e ciency achieved with representative benchmark systems show that the EUML-ARC programming model and its compiler can exploit multi-core parallelism while providing a productive model-driven approach to software development.
Ph.D. in Computer Science, July 2014
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Title: INSTANTANEOUS DETECTION OF SPATIAL GRADIENT ERRORS IN DIFFERENTIAL GNSS
Creator: Jing, Jing
Date: 2014, 2014-12
Description: Differential GNSS (Global Navigation Satellite System) is currently being ex- tended using a high integrity Ground Based Augmentation System ...
Show moreDifferential GNSS (Global Navigation Satellite System) is currently being ex- tended using a high integrity Ground Based Augmentation System (GBAS) to enable civil aircraft precision approach and landing. Differential GPS carrier phase measure- ments between ground-based GBAS reference antennas can provide the means to de- tect and isolate certain signal-in-space (SIS) failures and anomalies that are hazardous to aircraft, most notably ionospheric anomalies and ephemeris failures, which can be characterized as spatial range error gradients. In this research, we develop a monitor capable of instantaneously detecting multi-dimensional spatial gradient faults. The existence of large gradients, while rare, has prompted the development of numerous ground monitors for their detection. One drawback of previously proposed monitors is that their performance for a given ground antenna con guration is de- pendent on how antennas are paired to form measurement differences. In contrast, in this work a new monitor approach is developed to provide consistent detection performance, regardless of how the antennas are paired, by combining measurements from multiple, spatially separated ground antennas through a null space transforma- tion. It is shown that the `null space' monitor signi cantly improves the detection performance over existing fault detection algorithms and enables GBAS to support Category III precision approach and landing. The instantaneous carrier phase monitor cannot detect all gradients due to the presence of integer cycle ambiguities. These ambiguities cannot be resolved because the gradient magnitude is unknown a priori. Furthermore, it has been shown that the performance of such monitors is highly dependent on the reference antenna topol- ogy. The range of detectable gradients for all carrier phase monitors depends on two factors: the number of antennas and their con guration. One can always expand the detection range by using many antennas, but only at greatly increased operational cost. Optimizing antenna con guration has been overlooked as a means to improve performance; simple, heuristic arguments typically prevail in the associated siting decisions. For example, when given four antennas it is generally assumed that they should be sited in a square arrangement to balance performance in all directions. However, such heuristics do not provide the maximum detectable range of gradients, and exploiting the freedom to choose the antenna topology can dramatically expand the detectable range. Due to the presence of carrier phase cycle ambiguities, the re- sulting optimization problem is a constrained, mixed integer nonlinear programming problem. By solving the nonlinear program, the optimal GBAS antenna topology that maximizes the range of detectable gradients can be found for any number of antennas. For ionospheric fronts, the magnitude of the resulting gradient is bounded. However, orbit ephemeris faults can be arbitrarily large. The monitor must be able to detect all large gradients. To detect gradients beyond the capability of the car- rier phase monitor, code phase measurements are integrated into the monitor. Al- though we show this allows for the detection of all gradients, the number and spacing of ground antennas may not be suitable for all ground stations. Therefore, dual frequency carrier phase measurements are also considered to reduce the number of antennas required to achieve the desired detection performance. Finally, a search algorithm is developed to nd the antenna topology that enables the null space mon- itor to detect all hazardous gradients using code and dual frequency carrier phase measurements.
Ph.D. in Mechanical and Aerospace Engineering, December 2014
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Title: ISOGEOMETRIC ANALYSIS VIA TRIANGULATION
Creator: Jaxon, Noah
Date: 2013-05-15, 2013-05
Description: We present a method for isogeometric analysis on a triangulation of a domain bounded by NURBS curves. In this method, both the geometry and...
Show moreWe present a method for isogeometric analysis on a triangulation of a domain bounded by NURBS curves. In this method, both the geometry and the physical eld are represented by bivariate splines in Bernstein B ezier form over the triangulation. We describe a set of procedures to construct a parametric domain and its triangulation from a given physical domain, construct Cr-smooth basis functions over the domain, and establish a rational Triangular B ezier Spline (rTBS) -based geometric mapping that Cr smoothly maps the parametric domain onto the physical domain and exactly recovers NURBS boundaries. As a result, this approach can achieve automated meshing of objects with complex topologies and allows highly localized re nement. Isogeometric analysis of problems from linear elasticity and advectiondi usion analysis are demonstrated.
M.S. in in Mechanical Engineering, May 2013
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Title: RECEIVER AUTONOMOUS INTEGRITY MONITORING AGAINST ORBIT EPHEMERIS FAULTS IN CARRIER PHASE DIFFERENTIAL GPS
Creator: Stevanovic, Stefan
Date: 2013-04-18, 2013-05
Description: This work investigates the potential of the Global Positioning System (GPS) to enable a safe approach for rendezvous applications including...
Show moreThis work investigates the potential of the Global Positioning System (GPS) to enable a safe approach for rendezvous applications including shipboard landing of military aircraft. GPS has been shown to have the necessary accuracy for such an operation, and could potentially replace the existing radar or laser based systems. [Kha08][WPF08]1 However, to ensure safe operation, GPS must also be able to avoid hazardous situations. Shipboard aircraft approach navigation is an example rendezvous application requiring both high accuracy and high integrity. In this work, GPS measurement error models and orbit ephemeris fault (OEF) detection algorithms are developed for rendezvous applications, and performance is analyzed for the aircraft shipboard landing application. Both reference station and user based monitors can be used for orbit ephemeris fault detection. The available reference monitors either require a stationary reference receiver, or cannot protect against all types of orbit ephemeris faults. As an alternative, this work develops and investigates the use of receiver autonomous integrity monitoring (RAIM), which is user-based. Two contrasting algorithms, differential RAIM (DRAIM) and relative RAIM (RRAIM) are derived and analyzed for a realistic shipboard landing application. DRAIM is most effective when the aircraft first begins the approach. On the other hand, RRAIM performs best near the end of the approach. Assessing integrity risk is shown to be a major challenge for the RRAIM algorithm. Thus, a new unified RAIM (URAIM) concept is introduced. It seamlessly integrates DRAIM and RRAIM into a single detection algorithm, and also facilitates integrity risk evaluation. This is because the URAIM measurement equation can be used for both position estimation as well as fault detection. 1Corresponding to references in the Bibliography. xii Since high accuracy is desired, fixing integer cycle ambiguities is required. The Enforced Position-Domain Integrity-Risk Cycle Resolution Algorithm (EPIC) method of integrity risk bounding is used along with the URAIM fault detection algorithm in what we call the EPIC-URAIM algorithm. In general, the OEF will interfere with the cycle resolution process. In this work, the EPIC integrity risk bound formula is modified to account for the presence of an OEF. The EPIC-URAIM algorithm is simulated for 1507 sea-based locations around the globe. An average global availability of accuracy and integrity of 98.6% is achieved. This work illustrates the feasibility of detecting orbit ephemeris faults with integrity, while simultaneously meeting stringent accuracy requirements for real-time rendezvous navigation applications.
M.S. in Mechanical and Aerospace Engineering, May 2013
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Title: IMPACT OF WORK FLOW DISRUPTIONS, PROJECT CHARACTERISTICS AND FOREMEN CHARACTERISTICS ON IMPROVISATIONAL DECISIONS AND ACTIONS ON CONSTRUCTION SITES
Creator: Kleps, Stephen M.
Date: 2013, 2013-12
Description: Disruptions on construction sites are a constant issue and unfortunately can have negative impacts on the workflow and productivity of the...
Show moreDisruptions on construction sites are a constant issue and unfortunately can have negative impacts on the workflow and productivity of the impacted crews. As a result of these disruptions, foremen must quickly generate improvised solutions to the disruptions to keep the work of their crew progressing. Yet the mechanics of how exactly this improvisational decision making is occurring has not been previously studied. To address this void in the literature, this study examined the factors that may influence a foremen's ability to improvise, such as the type of disruption, the jobsite characteristics, and the personality, experience, and education of the foremen, in relation to the level of improvisation occurring. To accomplish this, this study collected data from 50 foremen within the electrical construction industry to measure to what degree they improvised and with what speed they improvised in response to their daily disruptions, resulting in 244 recorded disruption incidents. In analyzing these incidents with multilevel modeling analysis techniques, it was determined that the type of disruption did not have as large of an effect on the degree and speed of the resulting improvisation as originally hypothesized. In addition, it was found that factors such as the level of cooperation on the job site, the time pressure on the foremen, and the level of collaboration on the job site influenced the degree and speed of the improvisation. Yet the factors that explained the largest total variance in both the degree and speed of improvisation were the personality traits of the foremen. Thus, these findings emphasize the importance of foremen on job sites, while also documenting how improvisation is occurring on job sites.
PH.D in Civil Engineering, December 2013
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Title: BOUNDING ESTIMATION INTEGRITY RISK FOR LINEAR SYSTEMS WITH STRUCTURED STOCHASTIC MODELING UNCERTAINTY
Creator: Langel, Steven Edward
Date: 2014, 2014-05
Description: Safety critical estimation applications require quantification of integrity risk, which is the probability of the state estimate error...
Show moreSafety critical estimation applications require quantification of integrity risk, which is the probability of the state estimate error exceeding predefined bounds of acceptability. Integrity risk can only be evaluated when the state estimate error probability density function is precisely known, necessitating stochastic models that exactly describe measurement noise and disturbance inputs. Uncertainty in these models directly results in inaccurate assessments of integrity risk. This dissertation develops the first implementable methods to upper bound integrity risk when the autocorrelation functions of stochastic inputs reside between upper and lower bounding functions. The first part of this work considers real-valued estimation applications that use the Kalman filter or batch weighted least squares estimator. Explicit relations are developed between the estimate error variance and autocorrelation functions using a new generalized covariance matrix derived in this dissertation. From these expressions, two methods are provided to upper bound integrity risk. The first method enables fast computation of a conservative bound, and the second method produces the minimum upper bound via semi-definite optimization. Mixed real/integer estimation applications utilizing integer bootstrapping are the focus of the second part of this work. The integrity risk bound is formally defined as the global solution to a non-convex optimization problem over a polytope. Determination of the polytopic region is difficult, and two bounding approaches are initially developed for a circumscribing hyper-rectangular feasible region. Using an innovative method to define the polytope together with linear programming, a third method is derived to upper bound integrity risk over the true polytopic feasible region.
PH.D in Mechanical and Aerospace Engineering, May 2014
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Title: SIMULATIONS OF CENTERLINE DEFECT CLOSURE IN OPEN DIE FORGING
Creator: Gangatirkar, Suhasini
Date: 2014, 2014-12
Description: Open die forging is a technique widely used to achieve desired shape and sound mechanical properties. Due to large sizes, the ingots often...
Show moreOpen die forging is a technique widely used to achieve desired shape and sound mechanical properties. Due to large sizes, the ingots often have internal defects such as porosity, shrinkage cavities which damage the overall quality of the final product and affect the mechanical properties of the material. The voids developed during cooling of the ingot have to be treated in the initial forming operation known as cogging which depends on parameters such as die width ratio, die overlap, feed ratio, die shape etc. In this work, finite element method has been used to identify different aspects affecting centerline defect closure, material properties, effect of friction coefficient, relationship between effective strain and the grain size. FORGE 2011 and FORGE NxT 1.0 by Transvalor Corp were used to create numerical models. The material used in this case is H13. Material data and compression test samples were obtained from experiments in a Gleeble 3500. Physical experiments carried out on the Gleeble 3500 were used to determine the coefficient of friction for samples treated at different temperature, strain and strain rates. The effect of these parameters on coefficient of friction was studied in later part of the study. The formulae from the literature used to calculate the coefficient of friction was validated by using simulation models of the compression test samples. These samples were also used to study fraction recrystallized for a particular sample to study the relationship between effective strain and microstructure. Comparisons between validation experiments and simulations showed that there was good agreement between the two and established the effective strain criterion for void closure. From the conclusions obtained from validation experiments, optimal pass schedule was developed to ensure closure of internal voids and uniform distribution of effective strain along centerline for sound quality of the workpiece by changing die overlap percentage every two passes.
M.S. in Material Science Engineering, December 2014
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Title: SYNTHESIS, PURIFICATION AND CRYSTAL GROWTH OF INDIUM IODIDE SEMICONDUCTORS
Creator: Bertorello, Charles
Date: 2012-04-23, 2012-05
Description: The indium monoiodide (InI) semiconductor is a promising candidate for Gamma-ray and X-ray radiation detector devices. The high atomic number...
Show moreThe indium monoiodide (InI) semiconductor is a promising candidate for Gamma-ray and X-ray radiation detector devices. The high atomic number of indium (In) and iodine (I), along with high density, give the InI detector a higher photon stopping power (attenuation coe cient) compared to germanium based detectors and comparable to that of CdT e. Based on the previous research on melt synthesis and vapor synthesis by Dr. Ostrogorsky at Rensselaer Polytechnic Institute (RPI) and Dr. Burger at Fisk University from 2006 to 2009, the present work improves the purity of indium monoiodide by demonstrating the e ciency of zone re ning of this material. A segregation coe cient study is presented based on a Glow Discharge Mass Spectrometry (GDMS) and an Instrumental Gas Analysis (IGA) analyses performed by Evans Analytical Group (EAG). Two indium monoiodide crystals were grown using the Vertical Bridgman technique and analyses done on one of the crystals shown a resistivity of 3 109 .cm which is the second highest value reported. Indium monoiodide synthesized and puri ed in this current study was used to grow several Czochralski crystals.
M.S. in Mechanical, Materials, and Aerospace Engineering, May 2012
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Title: RE-POSITIONING THE CHICAGO BOULEVARD SYSTEM: TOWARDS THE DEFINITION OF AN ACTIVE URBAN INFRASTRUCTURE
Creator: Vadacca, Anna
Date: 2016, 2016-05
Description: How can urban infrastructures be reinterpreted based on their social potential? The thesis discusses the value that infrastructures can have...
Show moreHow can urban infrastructures be reinterpreted based on their social potential? The thesis discusses the value that infrastructures can have in relation to mobility and quality of life, in the context of the urban project, and proposes an example of how underutilized spaces, that pertains to an outdated model of the city, can be re-configured as adaptable and dynamic infrastructures. The Boulevard System of Chicago emerged during the process of “beautification” that the “City Beautiful” movement fostered in the 19th century. From being the “Emerald Necklace”, as it was known, the Boulevard System became today a fragmented infrastructure that mirrors the socio-economic segregation of Chicago neighborhoods. Within the archipelago of different urban realities of the city, the Boulevard System represents today an under-utilized urban space that reinforces the already existing urban thresholds between different urban communities. The goal of the research is to re-think the Boulevard System as a new transportation corridor, able to interact with other urban systems. The proposal for the boulevards is part of an Infrastructure Plan for Chicago that aims to propose ways inwhich different actions on infrastructure can revitalize the City. The idea is to re-activate the boulevard through a series of interventions, articulated around the re-connection of the fragmented system, as a new “ring” infrastructure, and the engagement with the surrounding specificities. The proposed Bus Rapid Transit system should offer an experience through the parks in Chicago and support its reactivation through the promotion of activities and events. Furthermore, the creation of a hub around the Garfield Green Line station is meant to propose a more engaging transit experience around the city of Chicago.
M.S. in Architecture, May 2016
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Title: LOW POWER METHODOLOGIES USING UNIFIED POWER FORMAT
Creator: Varsha
Date: 2012-11-14, 2012-12
Description: This thesis would be incomplete without the mention of people who made it possible and encouraged me at every step along the way. I would like...
Show moreThis thesis would be incomplete without the mention of people who made it possible and encouraged me at every step along the way. I would like to thank Spenser for helping me with the scripts, design of the architectures and always being ready to assist timely with so many issues. My immense gratitude goes to my advisor and mentor Dr. Erdal Oruklu, who pushed me at every step to achieve my best, drove me to explore new avenues, think new ideas and rethink old ones. I am truly thankful to him for his guidance, believing in me and giving me this opportunity to work under him. Thanks to my committee members Dr. Jafar Saniie and Dr. Tricha Anjali for their insights and suggestions. My heartfelt thanks goes to Hirva, Sneha, Pavan, Sagar, Mateen, Pooja and Neha for their continued support and encouragement throughout. Special thanks to Pavan and Sagar for assisting with the architectures and Mateen for helping with the documentation. Thanks to Krishna for being the go-to person for LATEX issues and always being there to help. Thanks to Santhosh and innumerous friends and acquaintances who helped unconditionally in so many ways. My family has been instrumental in the execution of my thesis. Thanks to my sister for inspiriting me, my brother-in-law for his endless encouragement and advice, their continued support along with my uncle, and my family for standing by me. Finally, this thesis is dedicated to my parents, for never giving up on me, believing in me and letting me pursue my dreams.
M.S. in Electrical Engineering, December 2012
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Title: REAL-TIME TRAFFIC SIGN RECOGNITION WITH RECONFIGURABLE HARDWARE
Creator: Waite, Sheldon
Date: 2012-07-12, 2012-07
Description: This work describes an implementation of a system that recognizes tra c signs within an image or video frame. In addition it covers a brief...
Show moreThis work describes an implementation of a system that recognizes tra c signs within an image or video frame. In addition it covers a brief history of automotive technology and the safety motivations for the technology presented here. An algo- rithm is presented that takes RGB image data, extracts relevant pixels, lters the image, labels prospective tra c signs and evaluates them against template tra c sign images. Furthermore a system is described that uses a Virtex 5 Xilinx FPGA and the EDK tool kit to create an embedded processor and a hardware IP periph- eral that together implement the algorithm. This implementation is shown to have positive results both in terms of timing performance and accuracy.
M.S. in Computer Engineering, July 2012
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Title: SCALABLE RESOURCE MANAGEMENT SYSTEM SOFTWARE FOR EXTREMESCALE DISTRIBUTED SYSTEMS
Creator: Wang, Ke
Date: 2015, 2015-07
Description: Distributed systems are growing exponentially in the computing capacity. On the high-performance computing (HPC) side, supercomputers are...
Show moreDistributed systems are growing exponentially in the computing capacity. On the high-performance computing (HPC) side, supercomputers are predicted to reach exascale with billion-way parallelism around the end of this decade. Scientific applications running on supercomputers are becoming more diverse, including traditional large-scale HPC jobs, small-scale HPC ensemble runs, and fine-grained many-task computing (MTC) workloads. Similar challenges are cropping up in cloud computing as data-centers host ever growing larger number of servers exceeding many top HPC systems in production today. The applications commonly found in the cloud are ushering in the era of big data, resulting in billions of tasks that involve processing increasingly large amount of data. However, the resource management system (RMS) software of distributed systems is still designed around the decades-old centralized paradigm, which is far from satisfying the ever-growing needs of performance and scalability towards extreme scales, due to the limited capacity of a centralized server. This huge gap between the processing capacity and the performance needs has driven us to develop next-generation RMSs that are magnitudes more scalable. In this dissertation, we first devise a general system software taxonomy to explore the design choices of system software, and propose that key-value stores could serve as a building block. We then design distributed RMS on top of key-value stores. We propose a fully distributed architecture and a data-aware work stealing technique for the MTC resource management, and develop the SimMatrix simulator to explore the distributed designs, which informs the real implementation of the MATRIX task execution framework. We also propose a partition-based architecture and resource sharing techniques for the HPC resource management, and implement them by building the Slurm++ real workload manager and the SimSlurm++ simulator. We study the distributed designs through real systems up to thousands of nodes, and through simulations up to millions of nodes. Results show that the distributed paradigm has significant advantages over centralized one. We envision that the contributions of this dissertation will be both evolutionary and revolutionary to the extreme-scale computing community, and will lead to a plethora of following research work and innovations towards tomorrow’s extremescale systems.
Ph.D. in Computer Science, July 2015
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