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Title: NUMERICAL ANALYSIS OF NON-DUCTILE BRACE FRAME WITH KNIFE PLATE DUE TO DYNAMIC LOADS
Creator: Keivan Esfahani, Arshia
Date: 2014, 2014-05
Description: In recent years, typical steel construction in regions of high seismic risk has shifted from moment-resisting frames to concentrically braced...
Show moreIn recent years, typical steel construction in regions of high seismic risk has shifted from moment-resisting frames to concentrically braced frames. As a result of the increased popularity of braced frames, the poor performance of some conventionally braced frames in past earthquakes, and the limited experimental data available on the inelastic response and the failure characteristics of braced-frame systems, a series of experimental and analytical investigations were initiated. Steel concentrically braced frames are common lateral force resisting systems in both new construction and existing buildings. However, the seismic behavior of braced frames designed prior to the adoption of capacity design principles in the 1980s is generally not well understood despite their widespread presence. These older braced frames, termed non-seismic concentrically braced frames (NCBFs) are the subject of a research project titled “NEESR: Collaborative Developments for Seismic Rehabilitation of Vulnerable Braced Frames” that seeks to evaluate NCBFs and determine retrofit strategies. In this project two tests were conducted. First Test examined a full scale two story NCBF in the inverted V configuration subjected to quasistatic cyclic load and this specimen contained a bottom story beam that is considered weak in capacity design. Second Test examined a post-earthquake repair scenario using the damaged NCBF-INV-1 frame in which the bottom story braces and gusset plates were removed and replaced with seismically compact braces with connection designed for in plane buckling. In this work, finite element models developed in Abaqus were validated using data collected from these tests. The outcomes of this research will be a greater understanding of seismic performance of NCBFs, the development of rehabilitation strategies for vulnerable NCBFs, and a robust technique for modeling NCBFs.
M.S. in Civil Engineering, May 2014
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Title: POWER TAKE-OFF AND GRID SUPPORT IN HYBRID VEHICLES USING WOUND FIELD SYNCHRONOUS MACHINES
Creator: Dong, Weizhen
Date: 2016, 2016-07
Description: Energy sectors are undergoing revolutionary changes. Due to environmental concerns and customer desires, a considerable increase of Electric...
Show moreEnergy sectors are undergoing revolutionary changes. Due to environmental concerns and customer desires, a considerable increase of Electric Vehicles (EVs) and Plug-in Hybrid Electric Vehicles (PHEVs) is expected. A technology of Vehicle to Grid (V2G) is emerging in the electric power industry. This technology provides connections between PHEVs and microgrids, and utilize PHEVs as distributed generators for grid support or as backup power sources. With the development of Electric Vehicles, wound field synchronous machines (WFSM) have been used and studied in EV traction motors and generators. For the application of EV technology, WFSMs have several advantages over permanent magnet synchronous machines (IPMSM) and induction machines (IM) including the complete control of the field excitation from the rotor side, higher system and machine efficiencies, and reduced cost due to the absence of rare earth permanent magnets. At the same time, WFSMs can work as generators to realize power take-off and microgrid support for EV tractions. Due to the several advantages of WFSMs in EVs application, this research focuses on the control of the WFSM in PHEVs for power take-off and grid support as a generator. PHEVs internal combustion (IC) engine is considered as a prime mover and would couple to the shaft which is connected to the WFSM. Such PHEVs applications would be used as power supplies for nearby loads and microgrids. This system is able to reduce cost of power electronics converters and directly provides desired AC voltage. This work aims to study the power take-off from hybrid electric vehicles using wound field synchronous machines and operation in microgrids. The feasible HEVs configurations to realize this purpose is studied. The modeling of IC engine, wound field synchronous machine, brushless exciter and distributed generators (DGs) in microgrid is demonstrated. One disadvantage of this application is the time delay during the combustion progress in the IC engine. This delay could affect the stability and dynamic response of the system. At the same time, the IC engine based generators have slower dynamic response compared with power electronic based sources. A state variable voltage regulator and a rotor speed controller are designed to improve the performance of the system. These controllers enable wound field synchronous machines provide desired voltage frequency and voltage magnitude. A real power - frequency droop controller and a reactive power – voltage droop controller are also studied. The droop controllers would keep the stability and better power quality of the system for islanded mode operation and grid-connected mode operation. The droop controllers enable EVs system share loads in a desire portion of power with other DGs in the grid and this reactive power – voltage droop controller would eliminate the circulating reactive power in the whole grid system. The EV’s isolated power take-off operation, islanded mode operation in microgrid with other DGs, and grid connected mode operation in microgrid are discussed. Stabilities, disturbance responses, and load sharing abilities are shown in simulation studies. The results are presented and discussed.
M.S. in Electrical Engineering, July 2016
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Title: IMAGING TISSUE SCAFFOLDS WITH X-RAY PHASE CONTRAST IMAGING
Creator: Doe, Frederick
Date: 2014, 2014-12
Description: A major challenge in tissue engineering is imaging within scaffolds. Biomaterials commonly used in tissue engineering have similar x-ray...
Show moreA major challenge in tissue engineering is imaging within scaffolds. Biomaterials commonly used in tissue engineering have similar x-ray absorption properties to native tissue, so they provide poor contrast in radiography. X-ray phase contrast imaging (XPCI) is an imaging modality that measures light/matter interactions other than absorption. By providing insight into these interactions, x-ray phase contrast imaging has the potential to allow imaging of materials used in biomedical applications. In this thesis, a technique for imaging explanted poly(ethylene glycol) (PEG) hydrogels is presented. PEG is a highly biocompatible polymer with widespread use in biomedical applications. Porous PEG hydrogels were synthesized with 100-150 μm pore size through a salt-leaching technique and loaded with fibrin, a natural protein known to stimulate vascularized tissue formation. The hydrogels were formed in the shape of disks and implanted subcutaneously in the backs of rodent animal models for 1, 2 and 3 weeks. The hydrogels and surrounding tissue were harvested at 1, 2, and 3 weeks. After explanation, the hydrogels were placed in formaldehyde and imaged at the National Light Source at Brookhaven National Laboratory using a multiple image radiography (MIR) technique. Five hundred angles were captured of each sample over 180°, and computed tomography was performed. The samples were compared to histological stains to identify specific tissue features that could be identified in the XPCI images. XPCI allowed imaging of hydrogels and identification of interfaces between native tissue and the PEG material. In addition, tissue invasion into the pores of the scaffold could be identified and could be used to quantify the depth of invasion. Muscle tissue could also be seen, and within muscle fibers were visible. With computed tomography, 3D volumes were constructed, enabling analysis throughout the samples.
M.S. in Biomedical Engineering, December 2014
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Title: ENGINEERING OF CLINICAL-SCALE, IN VITRO VASCULARIZED BONE TISSUE FOR IMPLANTATION
Creator: Gandhi, Jarel K.
Date: 2016, 2016-05
Description: Tissue engineering has been a rapidly expanding field dedicated to regeneration of tissue. The field has focused on application through...
Show moreTissue engineering has been a rapidly expanding field dedicated to regeneration of tissue. The field has focused on application through combinations of 3 key components: cells, signals, and scaffolds. One ambitious combination of all three is the desire to engineer functional tissues in vitro to meet the clinical-demand of organ replacement. While major advances have been made, a critical obstacle that has yet to be overcome is the need to grow large volumes of complex 3D tissue. In this proposal, this issue is addresed in two ways: the use of a perfusion bioreactor system to culture 3D scaffolds to enhance mass transport, and engineering of a vascular network withing the scaffold for rapid perfusion once implanted in vivo. This thesis aims to address both aspects for bone tissue engineering by engineering pre-vascularized, mineralizing scaffolds that can be scaled up to clinically-relevant volumes by using a tubular perfusion bioreactor system (TPS). To address this, 3 aims were addressed. First, 3D culture of endothelial colony forming cells (ECFCs), a clinically-relevant cell population, was demonstrated utilizing fibrin gels within the TPS. The TPS allowed for viable culture of ECFCs within fibrin bead scaffold up to 1 week without a reduction in cell amount or genomic quality of the cells. Second, a co-culture model of angiogenesis utilizing ECFCs and mesenchymal stem cells (MSCs) was demonstrated to reproducibly form pre-formed vessel networks within a mineralizing fibrin scaffold. Data shows that MSC suspension concentration and fibrinogen concentration modulate the angiogenic response. Mineralization is demonstrated without the use of osteogenic media utilizing shear stress within the TPS. Finally, functionality of the pre-formed vessels is demonstrated following implantation to a SCID mouse model. Engineered human vessels showed anastasmosis to the host vasculature, with evidence of interconnected host and human vessel networks as well as formation of hybrid vessels. Additionally, evidence of mineralization within the scaffolds is maintained in TPS-cultured samples. In demonstrating these aims, future work should focus on fortifying the scaffold material to enable addressing implantation and persistence of clinically-relevant tissue volumes. In conclusion, pre-vascularization within bioreactor-cultured scaffolds represents a promising solution for future tissue engineering application.
Ph.D. in Biomedical Engineering, May 2016
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Title: OPERATION ANALYSIS AND LOSS REDUCTION OF MAGNETIC GEAR
Creator: Feng, Yanjun
Date: 2015, 2015-12
Description: In the first part of this thesis, analysis of magnetic gears which includes operation analysis and loss analysis is introduced. With these...
Show moreIn the first part of this thesis, analysis of magnetic gears which includes operation analysis and loss analysis is introduced. With these analysis, the behavior of magnetic gears are deeply studied for their advantages and disadvantages. Their performance in terms of torque transfer, speed transfer, and the loss are the main focus. With different properties setting for magnetic gear, the influence of these properties to the final performance are also studied. By comparing results from different simulation software and different methods, the results are analyzed more accuracy and detailed. For loss analysis, FFT are utilized for harmonics analysis. This analysis was done by Matlab. All these analysis processes and results lead to the next part of this thesis which is optimization for magnetic gear. The second portion of this thesis focuses on core loss reduction in magnetic gears. Pole shaping similar to what is used in electric machines to reduce electromagnetic torque ripple is introduced to attempt to reduce higher order harmonic flux components in the magnetic gears without reducing power density. In this part, lots of simulation shows the work analysis of magnetic gear to verify the working principle and optimizations results. Large ripple problems of magnetic gear are also found during this part.
M.S. in Electrical Engineering, December 2015
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Title: A 4-Phase Flow Model for Methane Production from an Unconsolidated Hydrate Reservoir
Creator: Hinz, Deniz
Date: 2019
Description: Natural gas from hydrates is extremely abundant as an energy resource; US resource-grade hydrate deposits are estimated to be over 20 times...
Show moreNatural gas from hydrates is extremely abundant as an energy resource; US resource-grade hydrate deposits are estimated to be over 20 times the domestic proved natural gas resources, at approximately 7000 trillion cubic feet (tcf). The theoretical potential of hydrates is immense, but production testing and research remain lacking, which has led to the development of numerous hydrate production numerical simulators for consolidated porous media hydrate reservoirs. However, due to the onset of unconsolidated flow behavior upon significant hydrate dissociation, numerical models haven’t agreed well with the experimental data from the Mallik production tests. Hydrate contributes substantially to the strength of the sediment matrix, such that hydrate-bearing sediment ultimately falls apart exhibiting 4-phase unconsolidated flow behavior of gas, water, hydrate, and sand. In order to better capture the multiphase flow characteristics of gas, water, hydrate, and sand in an unconsolidated gas hydrate reservoir, we have developed a novel 4-phase flow model coupled with numerical simulation of the Mallik 2007/2008 production tests. The model is able to capture the coupled 4-phase hydrodynamics, mass transfer, and heat transfer physics inherent to the unconsolidated hydrate reservoir. Solid deformation is modeled by extending multiphase and granular flow theory to hydrate-bearing sediment. Constitutive models for the solid viscosity and solid pressure are developed to model the change in strength of the sediment as hydrate dissociates and the solid deforms. The solid viscosity is a composite of frictional contributions from the solid normal stress and cohesive contributions from the hydrate. The interphase momentum exchange between the fluid phases (gas and water) and solid phases (hydrate and sand) modeled based on a volume-averaged approach that considers the formation and closure of high-permeability volumes due to dilation and compaction of hydrate-bearing sediment as it deforms. By considering the deformation of solids and the subsequent effect on the permeability, the 4-phase simulations showed good agreement with the experimental data from the Mallik 2007/2008 production phases. The 4-phase modeling approach serves as a proof of concept for the application of granular flow theory to hydrate-bearing sediment. An unconsolidated hydrate reservoir with sustained sand production essentially behaves like a naturally fracking reservoir, exhibiting a dramatic increase in permeability induced solely by depressurization. Conversely, preventing sand production with a sand screen ultimately leads to significant throttling of the gas production rate due to the compaction and accumulation of sand at the sand screen.
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Title: DECISION SUPPORT SYSTEM FOR THE SELECTION OF BUILDING COMPONENTS USING MAINTAINABILITY PRINCIPLES
Creator: Liu, Xuanchang
Date: 2019
Description: Maintainability of a building component refers to how easy it is to maintain the component with minimum cost and downtime. Unfortunately,...
Show moreMaintainability of a building component refers to how easy it is to maintain the component with minimum cost and downtime. Unfortunately, maintainability issues do not receive enough attention in the design stage and cause serious problems in the post-construction stage such as increasing the life cycle cost of the facility, wasting maintenance materials, and unsatisfactory user experience because of downtime. These problems can be prevented if a tool is available that can help designers make the selection for building components based on maintainability in the design stage. This study aims to develop such a tool that allows designers to evaluate a building’s components relative to maintainability and that helps designers to make a maintainability-based selection in the design stage. To achieve this purpose, this study first identifies a checklist of maintenance actions for components of building systems, in this study condensers. Then, a condenser selector system is developed by coding in Java language. Users can run this selector with any browser with or without a connection to the Internet. This condenser selector system relies on a database that is populated by data about maintenance actions obtained from condensers’ guidebooks or from manufacturers. When using the selector, designers can customize the tool according to their preferences or conditions. At the end, the selector ranks the condensers in the database and allows the designer to make an informed maintainability-based selection. The prototype component selection system is a prototype, but can be expanded by augmenting the system to include other components too. Ideally, a maintainability-based selection tool should include all models of all components in building systems. Such a system could be a significant improvement in the current design practice. Considering the maintainability of components in the design stage could enhance maintenance and facility management.
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Title: Photochemical Reaction of Covalent Organic Frameworks: Probing the Changes in Surface Area and Topology of the Frameworks
Creator: Ye, Yuxin
Date: 2019
Description: Covalent organic frameworks (COFs) are a new class of 2-dimensional or 3-dimensional polymers that have rigid and porous structures. COFs are...
Show moreCovalent organic frameworks (COFs) are a new class of 2-dimensional or 3-dimensional polymers that have rigid and porous structures. COFs are widely applied in gas storage, catalysts, photo conductivity, and drug delivery. Since the applications of COFs are highly related to their structures, it is necessary to learn the stability of COFs under certain conditions. In this research, the stability of COFs towards light was mainly focused on. A new tetraphenyl substituted ketone based COF was synthesized and characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, ultraviolet-visible spectroscopy, and powder X-ray diffraction. Infrared spectra proved that this new COF can undergo Norrish type I reaction to release carbon monoxide under UV irradiation, while main structure of this COF was not broken. This thesis will detailly discussed the synthesis and characterization of this new COF, as well as the building blocks, linkers, and other precursors. This thesis will give some inspirations in the study of energy transfer in covalent organic frameworks.
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Title: MULTI-OBJECTIVE OPTIMIZATION FOR LEED - NEW CONSTRUCTION USING GENETIC ALGORITHMS
Creator: ALOTHAIMEEN, IBRAHEEM
Date: 2018
Description: In the U.S., the building sector is responsible for 73% of electricity usage, 38% of CO2 emissions, and 13.6% of potable water. These data...
Show moreIn the U.S., the building sector is responsible for 73% of electricity usage, 38% of CO2 emissions, and 13.6% of potable water. These data indicate that the construction industry negatively impacts the global environment and natural resources. The concept of “sustainability” was introduced to set guidelines for the construction industry to limit its negative environmental impact. To promote sustainability in the construction industry, many organizations have introduced guidelines and rating systems for buildings. One of these rating systems is Leadership in Energy and Environmental Design (LEED) which is the most globally acknowledged system.Although LEED excels in reducing the negative environmental impacts and the energy consumption of buildings, the high costs in the early phases associated with the implementation and pursuit of LEED certification are pushing away some project owners from entering the process. Therefore, to balance these objectives in sustainable projects, an approach which optimizes multiple objectives is needed. In this study, a multi-objective optimization framework, which uses Non-dominated Sorting Genetic Algorithm-II (NSGA-II), is proposed to find the optimal solution in terms of life-cycle cost and sustainability for a new construction project pursuing LEED v4 BD+C certification. A BIM project of a 3-floor educational building was selected as a case study in the research. The study case is used to verify the efficiency and soundness of the proposed model. The results show that the method does indeed lead to optimal solutions.
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Title: QUINODIZATION REACTION OF NAPHTHALENE DIIMIDES TO AFFORD NOVEL P-NAPHTHOQUINODIMETHANE LIGHT-HARVESTING CHROMOPHORES: AROMATICITY, PHOTOPHYSICS AND APPLICATION FOR PHOTON UPCONVERSION
Creator: Shokri, Siamak
Date: 2018
Description: ABSTRACT The chemistry and aromaticity of polycyclic benzenoid hydrocarbons have been a topic of intensive investigations since the early 19th...
Show moreABSTRACT The chemistry and aromaticity of polycyclic benzenoid hydrocarbons have been a topic of intensive investigations since the early 19th century. The concept of aromaticity has played a crucial role in organic chemistry and related fields; and it expanded very rapidly for its ability to explain the stability, electronic structures and physical properties of π-conjugated molecules. Besides benzenoid structures, chemists have also investigated quinoidal systems, which have been shown to exhibit unique aromaticity and physical properties in the ground state. Notably, it is customary to draw quinoidal polycycles as a mixture of closed– and open–shell structures. While closed–shell quinoids do exhibit interesting physical and electronic properties, the open–shell forms can be related to benzenoids with the presence of radicals or unpaired electrons. In this context, it has been demonstrated that open–shell quinoids can have both singlet and triplet multiplicity in their ground state. In this thesis, I will demonstrate that this feature can be tuned/suppressed through clever design of the molecular framework that contains a quinoidal moiety. Often, quinoids can be labeled as aromatic like benzenoids or (anti)/pro-aromatic depending on the molecular framework. Before labeling a quinoidal compound as aromatic or (anti)/pro-aromatic, it is important to define the different aromaticity rules and their influence on the corresponding physical and electronic properties of the system(s) of interest. Chemists have relied on two main aromaticity rules (Hückel vs. Baird) to predict the nature, electronic, and physical properties of quinoidal structures and related systems. We proposed and synthesized novel quinoidal naphthalene derivatives (QDM) that exhibit “compromised” aromaticity in the ground state. A combination of computation and photophysical methods were employed to: i) decipher the reaction mechanism during the formation of the new poly-heterocyclic structures, ii) investigate their ground state and excited state opto-electronic properties, and iii) explore the nature and aromaticity of the corresponding excited state species. Additionally, the QDM was used as light-harvesting triplet sensitizers to achieve photon upconversion. This dissertation will first present a historical perspective in the investigation of various polycyclic aromatic systems that exhibit interesting aromaticity. Then, in chapter 2, I will detail the synthetic route and corresponding mechanism during the preparation of thio-QDM. The characterization and photophysical properties including the transient absorption spectra and excited state dynamics and kinetics of these chromophores will also be discussed. In chapter 3, I will discuss the use of QDM as light-harvesting energy donor to sensitize perylene and achieve triplet-triplet annihilation photon upconversion. The mechanism of this non-linear photophysical process will also be highlighted. Finally, the conclusion chapter will introduce future perspectives in the synthesis of derivatives of QDM.
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Title: INDUSTRIALIZED BUILDING CONSTRUCTION MODELS FOR TORNADO AFTERMATH RECOVERY
Creator: Alves de Carvalho, Augusto
Date: 2019
Description: Some researchers have reported that the number of disasters is expanding in scale and occurrences. Today, humanity occupies more land than...
Show moreSome researchers have reported that the number of disasters is expanding in scale and occurrences. Today, humanity occupies more land than forty years ago. Due to this, existing communities are prone to higher chances of being affected by disasters. Consequently, the number of natural disasters and losses have increased through time. Recent research work indicates that construction of new houses takes the majority of the recovery time; for example, In Joplin tornado aftermath, the development of new houses took the longest part of the recovery time (D. J. Smith & Sutter, 2013). The disaster industry sees housing and shelter as a product. The procurement is done on a necessity basis. The product --tents, inter-shelters, trailers, permanent dwellings, or any property to rent-- has to be ready whenever required. Therefore, after calculating the construction capacity in tornado regions, a methodology is proposed to compare four different robust industrialized building construction alternatives, keeping components, modules, and pieces in stock. Comparing them will provide information about which format is more appropriate for a profitable company or even a public entity, to respond and recover from a disaster faster.
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Title: The Role of Ethnic Similarity, Perceived Communication Style Deviation, and Cultural Intelligence in Leader-Member Exchange and Trust
Creator: Polyashuk, Yelena
Date: 2019
Description: This study examined those factors that contribute to a better working relationship between a leader and a subordinate or make that working...
Show moreThis study examined those factors that contribute to a better working relationship between a leader and a subordinate or make that working relationship challenging. Specifically, we investigated the effect of ethnic configuration within the leader-subordinate dyad and perceived dissimilarity on Leader-Member Exchange (LMX) and trust. Communication style deviation was tested as a mediator between actual, as well as perceived dissimilarity and relational outcomes. Cultural Intelligence (CQ) was included as a moderator, the presence of which could ameliorate the negative impact of dissimilarity on LMX and trust. In order to test these predictions, a survey was administered to 614 participants. Participants were working students at an urban, Midwestern, public university. Results showed that in presence of low CQ among respondents, there was a negative impact of ethnic dissimilarity on LMX. However, no impact of ethnic similarity/dissimilarity on trust was found. Specific dyad composition of the leader-subordinate dyad had no significant impact on LMX or trust. Finally, communication style deviation partially mediated the relationship between perceived dissimilarity and the two outcome variables of LMX and trust. These findings revealed that in order to build a high-quality relationship within an ethnically diverse leader-subordinate dyad, both CQ and alignment in communication style are of consequence.
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Title: Unsupervised Learning of Visual Odometry Using Direct Motion Modeling
Creator: Andrei, Silviu Stefan
Date: 2020
Description: Data for supervised learning of ego-motion and depth from video is scarce and expensive to produce. Subsequently, recent work has focused on...
Show moreData for supervised learning of ego-motion and depth from video is scarce and expensive to produce. Subsequently, recent work has focused on unsupervised learning methods and achieved remarkable results which surpass in some instances the accuracy of supervised methods. Many unsupervised approaches rely on predicted monocular depth and so ignore motion information. Moreover, unsupervised methods which do incorporate motion information do so only indirectly by designing the depth prediction network as an RNN. Hence, none of the existing methods model motion directly. In this work, we show that it is possible to achieve superior pose estimation results by modeling motion explicitly. Our method uses a novel learning-based formulation for depth propagation and refinement which transforms predicted depth maps from the current frame onto the next frame where it serves as a prior for predicting the next frame's depth map. Experimental results demonstrate that the proposed approach surpasses state of the art techniques for the pose prediction task while being better or on par with other methods for the depth prediction task.
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Title: AN EMPIRICAL APPROACH TO GASSIFICATION PROCESS MODELING AND ASSESSMENT
Creator: Rahmaninejad, Fatemeh
Date: 2013-05-01, 2013-05
Description: There has been growing interest in estimating the flow rate and composition of fuel gases produced from gasification of coal and other...
Show moreThere has been growing interest in estimating the flow rate and composition of fuel gases produced from gasification of coal and other carbonaceous solid fuels. In general, coal gasification processes are complex, and because of the high costs associated with the experimental investigations, modeling and simulation tools are needed to assist with the design, analysis, and optimization of these complex processes. Most of the efforts in the development of gasifier models have focused on two different approaches; equilibrium modeling and kinetic modeling. The chemical equilibrium approach assumes the gasification reactions have sufficiently fast kinetics and reach global chemical reaction equilibria, which leads to over-prediction of the extent of the gasification reactions [1, 2, 3]. On the other hand, the kinetic based models require detailed knowledge of hydrodynamic and reaction kinetics of the heterogeneous and homogeneous chemical reactions [4, 5]. Because of the dependence of the product gas (composition and flow rate) on a broad ranges of certain key operating variables such as gasifier design, configuration, and coal type the gasification model needs to take into account the effect of those parameters based on available experimental data. In this study, a versatile and user-friendly gasifier simulation model was developed which incorporates a MS Excel interface aiming to provide a guide to gasification process analysis, evaluation and improvement. The model uses a set of empirical “default” correlations, for the reaction conversions that were obtained from xi regression analysis of the available experimental data to predict the syngas composition, flow rate, and performance of the gasifier based on the operating conditions specified by the user. The results of the parametric studies performed for assessment of the effect of operating conditions are discussed and presented.
M.S. in Chemical Engineering, May 2013
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Title: Exploring the experience of work-family conflict among low-wage, immigrant workers
Creator: Pickett, Meghan
Date: 2019
Description: Work-family conflict is a well-studied and long-standing construct; however, there is a fundamental gap in our understanding of the construct...
Show moreWork-family conflict is a well-studied and long-standing construct; however, there is a fundamental gap in our understanding of the construct when it is applied to minority populations. The current study considered a unique group who sit at an intersection of challenges – low-wage, immigrant workers – to identify if traditional antecedents were predictive in this new group. Additional conceptualizations of work-family conflict are also considered. Results suggest that typical antecedents do not display the same significance and that alternative measures of work-family conflict should be considered. Conclusions and implications to the study of work-family conflict research are discussed.
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Title: Temporal and Spatial Properties of the Negative Bold Response in the DMN
Creator: Gholipour Picha, Saman
Date: 2024
Description: The Negative Blood Oxygen Level Dependent (BOLD) Response (NBR) remains less explored than its positive counterpart (PBR) in functional...
Show moreThe Negative Blood Oxygen Level Dependent (BOLD) Response (NBR) remains less explored than its positive counterpart (PBR) in functional Magnetic Resonance Imaging (fMRI) studies. This dissertation aims to advance the understanding of the NBR by investigating its task-specific spatial patterns, comparing its specificity to the PBR, validating its reproducibility across different subject groups, examining its relationship with functional connectivity patterns during cognitive tasks, and assessing its linearity with respect to stimulus duration.Firstly, we analyzed the spatial patterns of NBR and PBR across a diverse set of cognitive tasks using a novel paradigm that grouped twelve tasks into four cognitive domains. Our findings revealed that both NBR and PBR exhibit distinct, task-specific spatial patterns, with the NBR predominantly occurring within the Default Mode Network (DMN). Notably, the NBR demonstrated greater task specificity compared to the PBR, suggesting a unique role in differentiating cognitive processes. To validate these observations, we replicated the analyses in a separate cohort, confirming the reproducibility and consistency of the task-specific NBR spatial patterns across different subject groups. This consistency underscores the reliability of NBR patterns and their potential generalizability. Additionally, we investigated the functional connectivity patterns of major brain networks during cognitive tasks. Our analyses showed that functional connectivity within networks such as the DMN and the dorsal attention network (DAN) remained stable across different tasks. This implies that task-specific BOLD signal changes are likely not due to alterations in functional connectivity but result from local neural dynamics. Furthermore, we assessed the linearity of the NBR with respect to stimulus duration. Contrary to our initial hypothesis, the NBR did not exhibit a clear linear relationship with stimulus duration, differing from the established linearity of the PBR. This suggests fundamental differences in neurovascular coupling mechanisms between positive and negative BOLD responses and indicates that linear models may not suffice for accurately analyzing NBR data. Methodologically, we developed a robust fMRI data analysis pipeline incorporating motion correction, distortion correction using TopUp, spatial normalization via an in-house technique utilizing outputs from FreeSurfer and ANTs, and noise reduction through ICA-AROMA. This pipeline ensured high-quality preprocessing and reliable first-level statistical analyses. In conclusion, this research enhances the understanding of the NBR by highlighting its greater task specificity and non-linearity compared to the PBR. The findings emphasize the importance of considering both activation and deactivation processes in cognitive neuroscience. They have significant implications for theoretical models of brain function, analytical approaches in fMRI research, and potential clinical applications, paving the way for future investigations into the complex dynamics of neural activation and deactivation.
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Title: CO2 CAPTURE AND HYDROGEN PRODUCTION IN SORBENT ENHANCED WATER-GAS SHIFT (SEWGS) PROCESS WITH REGENERABLE SOLID SORBENT
Creator: Zarghami Khanehsar, Shahin
Date: 2015, 2015-07
Description: Carbon dioxide emission from fossil fuel combustion and its impact on global warming is one of the most critical environmental issues nowadays...
Show moreCarbon dioxide emission from fossil fuel combustion and its impact on global warming is one of the most critical environmental issues nowadays. Coal as a main source of produce energy is the most CO2-intensive fossil fuel. Advanced power generation processes that use gasification technology, such as Integrated Gasification Combined Cycle (IGCC), which offer higher efficiency, are among the leading contenders for power generation in the 21st century. In an IGCC process, because of high pressure, carbon dioxide in the fuel gas is at higher concentration, which can be captured and sequestered at lower costs. Utilization of regenerable MgO-based sorbents has been shown to be an effective method for capturing CO2 from gasification-based processes at elevated temperatures and pressures (i.e. p > 20 atm and 330° < T < 450°C). Low cost MgO based sorbent can be prepared through modification of natural dolomite. The reactivity of the sorbent in carbonation/regeneration cycles has a significant impact on the economics of the proposed regenerable process. Although the sorbent can be regenerated in successive cycles, the sorbent reactivity and capacity gradually decline during the cyclic process. Therefore, it is crucial to develop a better understanding on the role of the key parameters affecting the reactivity of the sorbent going through the cyclic carbonation/regeneration process. In this work, a systematic study on the sorbent preparation parameters (i.e., calcination temperature, calcination duration, calcination temperature ramp, potassium concentration, impregnation duration, drying temperature, re-calcination temperature, and re-calcination duration) was conducted to understand the effect of each parameter on the overall capacity and reactivity of the sorbent. The concentration of potassium additive (as carbonation reaction promoter) has the most significant effect on the reactivity of the sorbent and the optimum K/Mg molar ratio appears to be in the range of 0.1-0.16. The reactivity of the sorbent toward carbon dioxide at various operating conditions (i.e. temperature, CO2 concentration and steam concentration) was experimentally evaluated. The presence of steam significantly improves the reactivity of the sorbent which is attributed to formation of more favorable pore structure as well as the existence of a parallel carbonation reaction pathway involving the formation of a transient MgO.H2O* compound. The optimum carbonation reaction temperature in the presence of steam is around 380˚C. The effect of cycling on CO2 capture capacity of MgO-based sorbent was also experimentally investigated in this work. Series of carbonation/regeneration cycles (up to 25) have been carried out in a dispersed bed reactor to determine the effect of various variables on long term durability of the sorbent. The gradual loss of CO2 sorption capacity appears to be mainly due to loss potassium (a carbonation reaction promoter) in the cyclic process. Durability of the sorbents improves in the presence of steam, which is likely due to the favorable changes in the pore structure of the sorbents. A kinetic model was developed to fit the reactivity curves obtained from the dispersed bed tests at different operating conditions which was needed to predict the sorbent/catalyst performance in the regenerative process. Model parameters were defined and discussed for each of the operating conditions, as well as dispersed bed cyclic tests. Furthermore, the thermal behavior and the kinetics of partial decomposition of dolomite were studied in a dispersed-bed reactor to improve the reactivity of the sorbent. The microstructure and the nature of the solid products were found to be strongly dependent on the CO2 partial pressure near the reacting interface and on the decomposition temperature. A significant increase in the rate of the dolomite decomposition reaction was found in the presence of steam. Steam improves the kinetics of decomposition, modifies the radial distribution of the pores; and improves the connectivity of the pores inside the dolomite particles, which decreases the diffusion resistance of produced carbon dioxide inside the particle. A shrinking core model with variable product layer diffusivity was used to fit the experimental data and determine the kinetic parameters of the dolomite decomposition reaction. The results indicate that transport of CO2 across the reacting interface in the porous particle was the main limiting factor in the decomposition reaction at the experimental conditions investigated. A lab-scaled high-pressure/high-temperature packed-bed reactor was utilized to evaluate the performance of the sorbent in simultaneous water-gas shift reaction and sorbent carbonation environment. It was shown that the CO2 in the coal gas can be removed by regenerable MgO-based sorbents at temperatures around 350°C, and the CO2 removal can shift WGS reaction to enhance hydrogen production. Therefore, Sorbent Enhanced Water-Gas-Shift (SEWGS) can result in much higher hydrogen production without lowering the temperature, leading to higher overall process efficiency.
Ph.D. in Chemical Engineering, July 2015
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Title: THE RELATIONS OF LEADER EMPOWERING BEHAVIORS ON EMPLOYEE PERFORMANCE: MODERATED BY GENDER DYAD COMPOSITION
Creator: Zigun, David J
Date: 2016, 2016-07
Description: This study examined the possible moderating effect of gender dyadic composition on the relationship between Leadership Empowering Behaviors ...
Show moreThis study examined the possible moderating effect of gender dyadic composition on the relationship between Leadership Empowering Behaviors (LEBs) and employee performance across 221 supervisor-subordinate dyads in a Fortune 500 Midwestern U.S. company. The relationships between LEBs and employee performance moderated by gender dyadic composition were examined, as well as possible group differences of LEB ratings between gender dyad group membership. The goal of this study was to test the moderating role of gender dyadic composition on the relationship between LEBs and employee performance. This study obtained both supervisor ratings of employee performance and employee ratings of LEBs, allowing for the use of multi-source data. Results supported the expected relationship between LEBs and employee performance but neither indications of a moderating effect by gender dyads were found, nor were there group differences in perceptions of LEBs. This study adds to the existing literature because previous research has predominantly focused on examining employee perceptions of LEBs and related outcomes, but this was the first study to explore the potential moderating effect of gender dyads in this relationship. Implications of this study are explored.
M.S. in Psychology, July 2016
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Title: OPTIMAL MATERIAL SELECTION MODEL FOR LEED CERTIFICATION USING GENETIC ALGORITHMS
Creator: Kim, Taehyoung
Date: 2012-12-16, 2012-12
Description: Material selection is an important part of building design because it has great impact on the environment, as buildings during/after...
Show moreMaterial selection is an important part of building design because it has great impact on the environment, as buildings during/after construction are responsible for a large portion of carbon emissions and use many resources and considerable energy. Selecting green materials is an emergent issue in both design firms and construction companies. Green building certification such as LEED systems originated from the desire to improve environmental, economic, financial, and social benefits. The current approach to material selection for sustainability is based only on the designer’s past experiences. An arbitrary approach based on subjective opinions causes unnecessary expense, longer construction duration, and failure to meet desired environmental goals. In order to help decision-makers with the selection of the right materials, this study proposes a model that uses Genetic Algorithms in MATLAB and that optimizes the desired points in LEED Certification within budget constraints. This model can be applied to any project that is pursuing LEED Certification. If the user specifies the desired LEED points, the system recommends the least expensive combination of materials extracted from a database containing detailed information about a large member of materials. The modified model uses multi-objective genetic algorithms to establish trade-off between budget constraints and LEED points. The proposed system is expected to be a useful tool for inexperienced designers and a valuable guideline for designers with extensive experience.
M.S. in Civil Engineering, December 2012
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Title: AUTOMATED PROGRESS CONTROL USING LASER SCANNING TECHNOLOGY
Creator: Zhang, Chengyi
Date: 2013, 2013-05
Description: Assessing progress in different construction activities at the end of every payment period is time consuming and requires specialized...
Show moreAssessing progress in different construction activities at the end of every payment period is time consuming and requires specialized personnel employed by the contractor and the owner. Automatic progress control that requires a minimum amount of human involvement could reduce the time spent on this activity, reduce the number of personnel used, reduce the cost involved, reduce disagreements between contractor and owner, and add to the overall efficiency of project management. Attempts have been made in the past to resolve this issue using image processing and other techniques but the results have not been satisfactory. A new attempt was made to set up a system that can assess progress control with minimum human input and the results are presented in this paper. The experiment made use of laser scanning technology and was conducted both in laboratory conditions and construction sites. The initial results from laboratory condition appear to be promising but there are still obstacles to surmount. The system is robust and accurate in laboratory conditions and constitutes proof of concept. Improvements are made to accelerate the registration process of multiple scans, to reduce the noise data, to recognize objects of irregular shape, and to assess the practicality and economic feasibility of such a system when applying this system in real construction sites. Keywords: Construction scheduling, progress control, laser scanning
PH.D in Civil Engineering, May 2013
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