Search results

Title: FIELD AND PHOTO-EMISSION IN A SHORT-PULSE, HIGH-CHARGE CESIUM TELLURIDE RF PHOTOINJECTOR
Creator: Wisniewski, Eric E.
Date: 2014, 2014-05
Description: A new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5...
Show moreA new high-charge RF gun is now operating at the Argonne Wakefield Accelerator (AWA) facility at Argonne National Laboratory (ANL). The 1.5 cell 1.3 GHz gun uses a Cesium telluride photocathode driven with a 248 nm laser to provide short-pulse, high charge electron beams for the new 75 MeV drive beamline. The high-gradient RF gun (peak field on the cathode > 80MV/m) is a key piece of the facility upgrade. The large Cs2Te photocathode (diameter > 30 mm) was fabricated in-house. The photo-injector will be used to generate high-charge, short pulse, single bunches (Q > 100 nC) and bunch-trains (Q>1000 nC) for wakefield experiments, typically involving dielectric-loaded accelerating structures. Details of the photocathode fabrication process and the results of associated diagnostic measurements are presented, including QE measurements and work function measurements performed with a Kelvin probe. Field-emitted dark current from the Cs2Te cathode was measured during RF conditioning and characterized. Fowler-Nordheim plots of the data are presented and compared to similar measurements made using a copper cathode in the initial phase of conditioning. The results for cesium telluride exhibited non-linear regions within the Fowler-Nordheim plots similar to previous experimental results for other p-type semiconductors. Results of quantum efficiency (QE) studies are presented with the cathode operating in both single and bunch-train modes. QE uniformity and lifetime studies are presented. During commissioning, the cesium telluride photocathode produced bunch-charge of 100 nC, breaking the previous record. No evidence of bunch-train position-dependence of QE was found when generating four-bunch trains with total charge up to 200 nC.
PH.D in Physics, May 2014
Show less

Title: Method and Apparatus for Detecting Collisions on and Controlling Access to a Transmission Channel
Creator: Campbell, Graham M., Xu, Wenxin
Date: 2009-05-14, 2001-09-18
Description: A method for controlling multiple access of a transmission channel wherein a plurality of different patterns are assigned to a plurality of...
Show moreA method for controlling multiple access of a transmission channel wherein a plurality of different patterns are assigned to a plurality of sending stations so that each sending station corresponds to a unique pattern, preferably a pattern represented by a Binomial coefficient. Each unique pattern is transmitted from a corresponding sending station to the transmission channel by way of a control minislot. Ternary feedback is received from the control minislot. A summation of different patterns within each control minislot are analyzed to detect whether a collision exists between the different patterns within each control minislot.
Sponsorship: Illinois Institute of Technology
United States Patent
Show less

Title: SAFETY TRAINING IN CONSTRUCTION
Creator: Demirkesen, Sevilay
Date: 2011-11-29, 2011-12
Description: The construction industry is one of the most hazardous industries. Therefore, the ways to reduce the number of risks have been a concern for...
Show moreThe construction industry is one of the most hazardous industries. Therefore, the ways to reduce the number of risks have been a concern for construction companies. Safety training is considered as one of the most efficient ways of improving safety record. Therefore, this study aimed to describe the best safety training methods and the most efficient organization in safety training. The study also aimed to show how to take best safety measures to protect construction workers. In this thesis study, a questionnaire was conducted in order to investigate the achievement of safety learning, challenges in a safety training program and the methods of improving safety record. Thus, the questionnaire was e-mailed to 400 contractors in US. The data collected also indicated the importance of safety training in companies’ success in the industry. Additionally, this study presents recommendations on how companies could improve their safety record.
M.S. in Civil Engineering, December 2011
Show less

Title: Method for the Preparation of Titanium Tetrachloride
Creator: Schossberger, Frederic V.
Date: 1958-10-21
Description: Sponsorship: Armour Research Foundation of Illinois Institute of Technology
United States Patent

Title: BIOLOGICAL STRATEGIES FOR ENHANCEMENT OF LIQUID FUELS: SULFUR REMOVAL FROM PETROLEUM AND BIOETHANOL PRODUCTION
Creator: Wang, Jia
Date: 2013, 2013-12
Description: Rhodococcus baikonurensis CW25 was transformed with the Rhodococcus erythropolis strain IGTS8 desulfurization operon (dszABC, which encodes...
Show moreRhodococcus baikonurensis CW25 was transformed with the Rhodococcus erythropolis strain IGTS8 desulfurization operon (dszABC, which encodes the enzymes of the “4S” desulfurization pathway) or this operon modified to contain a synthetic cysteine-methionine rich “sulpeptide” gene (S1) (dszAS1BC). The two CW25 derivatives were subjected to directed evolution to select faster growing cells using the key 4S pathway substrate dibenzothiophene (DBT) as the sole source of sulfur. Data of cell doubling times verified the success of selection of cultures with increasingly rapid growth. The desulfurization activities of resting cells of early passages demonstrated improvements, and the highest activity of the dszAS1BC-bearing CW25 derivative was 115% higher than that of the CW25 derivative without S1. In addition, a trend of initial high activity was followed by a decrease in subsequent passages. Rates of DBT metabolism of growing cells demonstrated a different trend, probably because the activity of growing cells concurrently reflects the activity of DszABC enzymes and the growth rates of the recombinants. Dry cell weights fluctuated during the evolution process, probably because of variations in the efficiency of the conversion of the sulfur in DBT into sulfite, then into sulfate or biomass, or, for the S1-bearing cells, because the secretion of the S1 peptide from cells might have variable efficiency. A mixed culture of two Paenibacillus species (“W” and “Y”) was isolated that can metabolize DBT at temperatures up to 54 ºC. Strain Y is the only one of the two with desulfurization activity, while strain W enhances the desulfurization ability of Y. The W-Y culture may be a useful starting point for selection of desulfurization cultures with even greater thermal stability. xiii Ethanologenic Escherichia coli strain FBR5 was compared with Vitreoscilla hemoglobin (VHb)-expressing FBR5 (TS3) regarding the concentrations of ATP, NAD+, NADH, NAD+/NADH ratio; and growth and ethanol production at various points during growth. The significant finding was that the NAD+/NADH ratio for TS3 was lower in early growth, but higher in later growth compared to that for FBR5. This is probably because more NADH was required by TS3 for its enhanced ethanol production and VHb-related increased respiration under microaeration conditions.
PH.D in Biology, December 2013
Show less

Title: Apparatus and Method for In Situ Controlled Heat Processing of Hydrocarbonaceous Formations with a Controlled Parameter Line
Creator: Bridges, Jack E.
Date: 2009-05-08, 1985-02-12
Description: A system and method provide for preferential in situ heating of earth formations. A plurality of elongated conductive electrodes are emplaced...
Show moreA system and method provide for preferential in situ heating of earth formations. A plurality of elongated conductive electrodes are emplaced in earth formations in respective spaced rows bounding a particular volume of the earth formations and forming a transmission line, preferably a triplate line, extending in the direction of the electrodes with the particular volume of the earth formations providing a dielectric medium between respective rows of electrodes. Electromagnetic energy is supplied to the transmission line at a frequency at which the spacing between respective rows is less than about twice the skin depth at the frequency of the applied energy. Reactance means are disposed along respective electrodes to provide predetermined effective transmission line characteristics to develop a predetermined heating pattern in the earth formations. The reactance means may be reactances disposed discretely between sections of respective electrodes. The reactance means may also be disposed between respective electrodes and the earth formation, as by a dielectric coating. A heating pattern may be developed to heat hydrocarbon rich deposits preferentially.
Sponsorship: IIT Research Institute
United States Patent
Show less

Title: Gerry-meandering: An Assessment of the Congressional District Model of Depository Allocation (preprint)
Creator: Ahrens, Aric G., Griffin, Luke A.
Date: 2003-06
Description: The preprint of a published article dealing with the effect of allocating Federal Depositories by Congressional district. Conclusions drawn...
Show moreThe preprint of a published article dealing with the effect of allocating Federal Depositories by Congressional district. Conclusions drawn include the fact that due to redistricting that occurs after each decennial census, over time some districts may have within their boundaries a greater number than the two depositories that Congressional district allocation was intended to produce. Likewise, over time shifting boundaries of districts have created districts that have no depositories whatsoever.
Show less

Title: MATHEMATICAL MODELING OF POLY(ETHYLENE GLYCOL) DIACRYLATE HYDROGEL SYNTHESIS VIA VISIBLE LIGHT FREE-RADICAL PHOTOPOLYMERIZATION FOR TISSUE ENGINEERING APPLICATIONS
Creator: Lee, Chu-yi
Date: 2013, 2013-05
Description: Crosslinked hydrogels of poly(ethylene glycol) diacrylate (PEGDA) have been extensively used as scaffolds for applications in tissue...
Show moreCrosslinked hydrogels of poly(ethylene glycol) diacrylate (PEGDA) have been extensively used as scaffolds for applications in tissue engineering. In this thesis, PEGDA hydrogels are synthesized using visible light free-radical photopolymeriza- tion (λ = 514 nm) in the presence of the visible light photosensitive dye, EosinY, the co-initiator, triethanolamine (TEA), a comonomer, N-vinyl pyrrolidone (NVP), a crosslinking agent, PEGDA, and an optional PEG monoacrylate monomer that contains the cell adhesive ligand YRGDS. The incorporation level of the YRGDS lig- and as well as the physical and mechanical properties of these hydrogels dictate cell behavior and tissue regeneration. These hydrogel properties may be tuned through variations in polymerization conditions. The goal of this thesis was to develop a math- ematical model for PEGDA hydrogel formation which predicts the incorporation level of YRGDS and the crosslink density of hydrogel as a variety of polymerization con- ditions. This model provides insight into the process of hydrogel crosslinking and in effectively guiding the experimental design of these scaffolds for tissue engineering applications. To accomplish this task two major components comprised the studies of this thesis. The first component involved an investigation of the visible light photo- initiation mechanism of EosinY and TEA, and the second component involved the develop of a hydrogel synthesis model and its validation. Experiments and modeling were used to determine an expression for the rate of initiation of the EosinY/TEA initiation system and to propose a photoinitiation mechanism. In Chapter 2, exper- imental data and parameter fitting were utilized to obtain an empirical expression for the rate of initiation. However, this empirical expression did not consider the ef- fect of inhomogeneous light distribution which is present in this experimental system. The dynamics of light absorption during polymerization were measured under differ- xiv ent conditions in order to gain insight into the kinetic photoinitiation mechanism as well as the rate of initiation. In Chapter 3, a mechanism for this photo-initiation was proposed. Using this mechanism the light absorption dynamics accounting for inhomogeneous light distribution were simulated which were found to be in an agree- ment with the light absorption measurements shown in Chapter 2. Further validation of this proposed mechanism was achieved from polyNVP conversion measurements. This photo-initiation mechanism was implemented in the hydrogel model. In Chapter 4, the hydrogel synthesis model was developed based on the kinetic approach of the method of moments combined with the Numerical Fractionation technique. The model was used to predict the dynamics of hydrogel properties such as gel fraction, crosslink density, and RGD incorporation under various polymerization conditions. Model predictions were compared with experimental data. Three sets of experiments were conducted. In the first set of experiments where hydrogels were formed in the absence of Acryl-PEG-RGD, the total double bond concentration was kept constant while varying the compositions of NVP and PEGDA. The model and the experiments showed a maximum crosslink density for an acrylate to double bond ratio of 0.5 to 0.6. This is related to the synergistic cross-propagation between NVP and PEGDA, which results in an increase in the rate of polymerization leading to higher crosslink density. In the second set of experiments, hydrogels were formed in the presence of Acryl-PEG-RGD to investigate its incorporation as well as the hydrogel crosslink density. The model showed reasonable agreement with the experimental data and in some cases the predicted RGD deviated from the experimental measurements due to changes in volume upon swelling. The effect of swelling was not considered by the model. The calculated crosslink densities were compared with the inverse swelling ratios from the experiments. The reduction of free volume due to the space occupied xv by the unreacted pendant double bonds was not considered by the model. This reduc- tion of free volume affected the apparent swelling ratio obtained from experiments thus resulting in the observed mismatch between the experimental trends and the predicted crosslink density by the model. In the third set of experiments, additional crosslink density measurements were conducted using a PEGDA macromer of lower molecular weight (MW = 575 Da.). The experiments were performed in the absence of Acryl-PEG-RGD. Few cases were not accurately predicted since the model did not consider the reduction in the concentration of available pendant double bonds when gelation occurs. Among the three set of experiments, the hydrogel synthesis model offers reasonable predictions for most of the experimental cases. This model can be used as a guide for experimen- tally designing PEGDA hydrogels with the desired properties for tissue engineering applications.
PH.D in Chemical and Biological Engineering, May 2013
Show less

Title: Understanding Construction Workers’ Risk Decisions Using Cognitive Continuum Theory
Creator: Menches, Cindy L., Saxena, Jaya
Date: 2013-09-19, 2013-09-19
Description: The goal of the research presented in this article was to construct a theory about the influence of decision cues on intuitive and...
Show moreThe goal of the research presented in this article was to construct a theory about the influence of decision cues on intuitive and deliberative decision-making in high-hazard construction environments. Drawing from Cognitive Continuum Theory, the article specifies a framework for understanding why and how construction workers make decisions that lead to taking or avoiding physical risks when they encounter daily hazards. A secondary aim of the research was to construct a set of hypotheses about how specific decision cues influence whether a worker is more likely to engage their intuitive impulses or to use careful deliberation when responding to a hazard. These hypotheses are described in this article, and the efficacy of the hypotheses was evaluated using cross-tabulations and nonparametric measures of association. While most of the associations between decision cues and decision mode (i.e., intuition or deliberation) identified in this data set were generally modest, none of the associations were statistically zero, thus indicating that further research is warranted based on theoretical grounds. A rigorous program of theory testing is the next logical step to the research, and the article thus concludes with numerous suggestions for extending the research and testing the proposed hypotheses.
Show less

Title: Hybrid Electric Conversion Kit for Rear-wheel Drive, All Wheel Drive, and Four Wheel Drive Vehicles
Creator: Rodriguez, Fernando, Lukic, Srdjan M., Wirasingha, Sanjaka G., Emadi, Ali
Date: 2012-03-20, 2011-09-06
Description: This invention relates to a parallel hybrid electric conversion kit for a vehicle with an internal combustion engine, a driveshaft and a...
Show moreThis invention relates to a parallel hybrid electric conversion kit for a vehicle with an internal combustion engine, a driveshaft and a transmission, such as, rear wheel drive vehicles, four-wheel drive vehicles, heavy duty multiple-driven-axle vehicles and/or all-wheel drive vehicles. The conversion kit includes a motor-generator, a torque coupler, a battery, a power electronics module and a controller. Suitable torque couplers include transfer cases and/or rear-through differentials. The conversion kit provides an aftermarket solution to increased performance, fuel economy and/or reduced emissions by modifying the drivetrain after the transmission. According to one embodiment of this invention, the control scheme of the installed conversion kit receives input signals from the engine and the motor-generator, but only sends control signals to the motor-generator, facilitating installation of the conversion kit.
Sponsorship: Illinois Institute of Technology
United States Patent
Show less

Title: Magnetic Transuducer Head
Creator: Wiegand, David E.
Date: 1958-10-07
Description: Sponsorship: Armour Research Foundation of Illinois Institute of Technology
United States Patent

Title: FINFET BASED STANDARD CELL LIBRARY CHARACTERIZATION
Creator: Yuan, Yu
Date: 2015, 2015-07
Description: In this work, four standard cell libraries based on FinFET technology have been characterized and implemented. The first library uses the BSIM...
Show moreIn this work, four standard cell libraries based on FinFET technology have been characterized and implemented. The first library uses the BSIM-CMG and PTM-MG models, which represents the common multi-gate devices. Two libraries are based on the BSIM-IMG model, operating in short-gate (corresponding to low-Vt) mode and lowpower (corresponding to high-Vt) mode separately. Synthesis and simulation of BSIMCMG based library is presented and compared to the conventional 45nm CMOS library, FreePDK45. The results show acceptable accuracy of the library based on BSIM-CMG model. For the libraries based on BSIM-IMG model, Short-Gate (SG) mode, Low-Power (LP) mode and the mixed-mode (combining both SG and LP modes) have been analyzed. The results proved that the low-power independent multi-gate FinFET can be used for leakage power reduction, just like the bulk CMOS high-Vt devices. At the end of this work, another library based on CCS model was characterized and verified, which show far better accuracy in terms of both timing and power modeling.
M.S. in Electrical Engineering, July 2015
Show less

Title: PREPARATION FOR IMPLANTATION OF AN INTRACORTICAL VISUAL PROSTTIESIS IN A HUMAN: WORKING TOWARDS SATURATION
Creator: Troyk, Melissa J
Date: 2017, 2017-07
Description: The research focused on restoring visual perception via a vision prosthetic is progressing at a rapidly advancing rate. Previous research on...
Show moreThe research focused on restoring visual perception via a vision prosthetic is progressing at a rapidly advancing rate. Previous research on the experiences and perspectives of past, current, and potential vision prosthesis users has demonstrated that the decision to obtain a vision prosthetic is driven by a variety of unique factors and variables that merge with one another during the process of deciding to participate in clinical vision prosthesis research (Lane, Huyck, Troyk, & Schug, 2012; Lane, Nitsch, Huyck, Troyk, & Schug, 2014; Lane, Nitsch, & Troyk, 2015). The purpose of the current study was twofold: 1) to determine if our understanding of the experiences and perspectives of potential vision prosthesis users was nearing saturation, and 2) to understand the perspectives of potential vision prosthesis users who are veterans. Data were analyzed in accordance with qualitative analysis procedures. Results identified several new themes and subthemes that were determined to be important to our understanding of potential users’ perspectives of an intracortical vision prosthesis device. A preliminary framework is proposed for understanding how the identified themes and subthemes merge during the process of deciding to participate in an experimental vision prosthesis human clinical trial. The results demonstrated that while progress has been made, there is still more to learn about blind individuals’ perspectives of vision prostheses and how they would decide to participate in vision prosthesis research.
M.S. in Psychology, July 2017
Show less

Title: PROPOSITION AND EVALUATION OF A NEW DAMPER, CALLED ROTATIONAL CYLINDRICAL FRICTION DAMPER (RCFD)
Creator: Divani, Abbass
Date: 2013, 2013-12
Description: The objective of this study is to propose and evaluate an innovative frictional damper for structural systems, called Rotational Cylindrical...
Show moreThe objective of this study is to propose and evaluate an innovative frictional damper for structural systems, called Rotational Cylindrical Friction Damper (RCFD), which does not bear limitation of previously proposed systems and yet maintains their advantages. Different kinds of energy dissipaters have been studied and used in structural systems in recent years. They perform more effectively compared to structures without any energy dissipater. Each of previously employed devices has its advantages and limitations. In this report, applicability of previous energy dissipaters will be investigated; then the proposed damper, RCFD, will be introduced, and the performance of RCFD will be evaluated under lateral load using ABAQUS software. RCFD consists of a shaft, a cylinder and proper assembly of braces so that the bracing members make the cylinder and shaft move in opposite circular directions under defined load. The assemblage of braces depends on type of bracing system that is employed. When load in bracing member exceeds the buckling load of the member, it overcomes the friction between the shaft and inner surface of the cylinder and while providing the ductility demand of the structure, it absorbs the energy of the seismic load, and it will work like a safety valve to protect main structural members from inelastic deformation. In spite of other types of frictional dampers, RCFD does not use and reduces the construction cost of high strength bolts. There is no limitation for the size and fitness of the bracing members more than that is for conventional design of braced frames. When we prove the performance of RCFD, some of the requirements of conventional design such as requirement of section F2 of Seismic Provisions for Structural Steel Buildings, AISC 341-10, will be eliminated. The pressure needed for developing friction is provided by heating the shaft and placing it into the cylinder with slightly smaller xiii diameter. It is simple to design and construct and does not have the limitation of other kinds of frictional damper systems. It can also be installed with little or no modification on any kind of Braced Frames or to retrofit Moment Frames. In this study, RCFD will be installed and evaluated on an Inverted V Concentrically Braced Frame, although installation of the RCFD on X Braced frame will be illustrated.
M.S. in Civil Engineering, December 2013
Show less

Title: DEGRADATION RATE MODEL TO ESTIMATE SOIL CARBON SEQUESTRATION
Creator: Zhai, Wenjuan
Date: 2016, 2016-05
Description: Concern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better...
Show moreConcern over climate change as a consequence of carbon dioxide (CO2) emissions from human activities has resulted in efforts to better understand potential mitigation measures such as carbon sequestration in soils. Processes shaping natural carbon sequestration may be used to remove excess CO2 from combustion and other anthropogenic sources of carbon, and, alleviate concerns over climate change. Land application of biosolids is a process that increases the amount of soil carbon sequestration and may produce carbon credits in accordance with the definition of UN Climate Change Convention. A dynamic degradation rate model (DRM) has been developed based on a mass balance and first order kinetics to describe the soil organic carbon (SOC) decomposition process, which provides insights on carbon sequestration due to microbial biomass, SOC, CO2 emission rates, residence time of sequestered carbon, and biomass to biosolids ratios. A curve fitting approach was used to produce a best fit average degradation rate for biosolids degradation and microbial biomass yield. This study employed a 34-year biosolids application database from the literature to determine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory resultsdetermine the amount of carbon sequestered in 41 strip-mined Illinois fields. The DRM application identifies two SOC phases in soil. Soil organic carbon gain in phase one (first 10 yrs) is primarily due to biosolids C application remaining and accumulation while in phase two, SOC gain is due to biomass or C sequestration. Carbon sequestration changes with time relate to variations in biosolids application amounts (10 and 18 Mg ha-1 yr-1), different degradation rate constants (0.04yr-1 to 0.16yr-1), and biomass yields (35 to 40%). Additionally, comparison between model simulation results and laboratory results provided by a yearlong study indicates that higher temperatures and moisture content and finer soils are related to larger degradation rates. To summarize, this study has the following contributions: (1) developed a degradation rate model which simulates the biosolids degradation process in soil and identifies two SOC phases in soil, and quantifies the biosolids degradation rate constant, biomass yield, and the C sequestered amount for multiple and long term soil application; (2) assessed the effect of changes in the amount of biosolids applied, soil type, and weather conditions on the C degradation rate by comparing model results to laboratory data; and (3) provides an easy quantitative method for predicting C sequestration from biosolids added to soil.
Ph.D. in Environmental Engineering, May 2016
Show less

Title: SURFACE CHARACTERIZATION OF NIOBIUM FOR SUPERCONDUCTING RF CAVITIES
Creator: Cao, Chaoyue
Date: 2014, 2014-07
Description: Surface characterization techniques including point contact tunneling (PCT) spectroscopy and Raman spectroscopy have been employed to study...
Show moreSurface characterization techniques including point contact tunneling (PCT) spectroscopy and Raman spectroscopy have been employed to study the surface of niobium (Nb) superconducting radio frequency (SRF) cavities. PCT spectroscopy provides a direct means of measuring the surface superconductivity, which is closely correlated with the cavity’s performance characterized by the quality factor Q. Cavities with remarkably high Q show near ideal tunneling spectra with sharp coherent peaks and low zero bias conductance, consistent with the Bardeen-Cooper-Schrie↵er (BCS) density of states (DOS), and bulk gap parameter, " = 1.55 -1.6 meV. Cavities with Q-drop often exhibit strong non-uniform heating during RF operations, with high loss regions identified as hot spots. PCT spectra on hot spots reveal suppressed superconductivity, broadened DOS and Kondo tunneling, consistent with magnetic impurities on the surface. Raman spectra on hot spots indicate the presence of various impurities on the surface including amorphous carbon, C-H chain compounds and NbC, providing insights into the formation of hot spots. The origin of the impurities is unclear at present but it is suggested that particular processing steps in SRF cavity fabrication may be responsible.
Ph.D. in Physics, July 2014
Show less

Title: Functionalized Polyoxovanadates: Synthesis, Characterization and Properties
Creator: Zheng, Yujuan
Date: 2012-04-30, 2011-12
Description: The compound [NaVIV6O6{(OCH2CH2)2NCH2CH2OH}6]Cl.H20, designated C0 in this report, an Anderson type structure, contains a single nitrogen atom...
Show moreThe compound [NaVIV6O6{(OCH2CH2)2NCH2CH2OH}6]Cl.H20, designated C0 in this report, an Anderson type structure, contains a single nitrogen atom in place of a single oxygen atom in each of the six vanadium-oxygen octahedra. Attached to each nitrogen are two alkoxide arms (-O-C-C-) which terminate on separate oxygen atoms of the octahedra. A third ethoxy group (-CH2-CH2-OH) dangles freely from each nitrogen atom. The functionalized cationic core [NaVIV6O6{(OCH2CH2)2NCH2CH2OH}6]+ is generated in situ and is cationic with a charge of +1. Chloride is the counteranion. Each vanadium addenda atom is the +4 oxidation state, and the six unpaired electrons result in interesting magnetic properties. C0 is obtained by reaction of a vanadium oxide source triethanolamine. The purpose of the research described here was to adapt the synthetic protocol associated with triethanolamine to other similar ligands. Ligand choice was motivated by the broader goal of this research group to form (extended) hybrid electronic and magnetic materials by chemically bonding POM cores to chemically interesting ligands, such as dyes or other POM cores. In this regard, the original triethanolamine derivative has a number of shortcomings; chief among them is the inaccessibility of the alcoholic functional group chemistry---due to its low pH---that otherwise might have been used to form linkages through the dangling alkoxy arms. Additionally, linkages containing paraffinic carbon (-C-C-), which is not a good conduit of electronic interaction, are chemically undesirable where the synthetic goal is hybrid structures with interesting electronic and magnetic properties. The results associated with the three ligands, diethanolamine, N,N'-Bis(2-hydroxyethyl)ethylenediamine, and N,N-Bis(2-hydroxyethy) ethylenediamine, are described herein. Diethanolamine was chosen because---based on a structural comparison to triethanolamine---it was expected to produce a structure having a hydrogen atom in place of the dangling ethoxy arms, which was indeed the result. We considered this structure highly desirable becasue of the potential lability of the hydrogen atom (-N-H), which would allow us to functionalist the core directly. The resulting compounds are characterized by single-crystal X-ray diffraction, elemental analysis, mass spectroscopy, thermogravimetric analysis, FT-IR and UV-Vis spectroscopy, maganometric titration, temperature-dependent magnetic susceptibility measurements, and cyclic voltammetry. The results of the cyclicvoltammetric investigation are consistent with the labile hydrogen atom (-N-H).
M.S. in Chemistry, December 2011
Show less

Title: MULTIPLE-INPUT MULTIPLE-OUTPUT NONLINEAR CONTROL OF SELECTIVE CATALYTIC REDUCTION SYSTEMS
Creator: Dong, Siwei
Date: 2015, 2015-05
Description: Selective catalytic reduction (SCR) is one of the most promising solutions to meet the future nitrogen oxides (NOx) emissions regulations for...
Show moreSelective catalytic reduction (SCR) is one of the most promising solutions to meet the future nitrogen oxides (NOx) emissions regulations for heavy-duty diesel vehicles. However, such vehicles often operate in highly transient operations in which mobile selective catalytic reduction systems encounter significant efficiency challenges, especially when the engine is under a low load. A detailed simulation model of the SCR system was developed in the Gamma Technologies simulation suite and a baseline model of feedback control on SCR was constructed. Experiment data for the exhaust gas composition and conditions from a Cummins ISB engine was used to provide the input parameters for the SCR model. The results reveal that in the low-load conditions, the efficiency of NOx reduction in the SCR system is very low, and the level NOx concentration exiting the vehicle could be over 5 times than the limitation set by the US Environmental Protection Agency (EPA). However, these issues are encountered in part due to the fact that current SCR controls focus solely on the aftertreatment components and treat the incoming engine output conditions as system disturbances. To address the low NOx conversion problems encountered in low load conditions, a new integrated engine and aftertreatment control model was designed. This integrated approach improves the SCR system efficiency by using available feedback and modulating the upstream air/fuel ratio to provide more favorable SCR inlet conditions. From experiment data analysis, the engine’s air/fuel ratio is shown to have a critical impact on exhaust gas temperature and exhaust oxygen fraction, which highly affect the SCR reactions. In order to integrate the engine and aftertreatment system, a model of the SCR dynamics was created and validated and a simple model of the relationship between the engine’s air/fuel ratio and resulting exhaust temperature and composition is leveraged. The new model-based control strategy is proven to be effective to improve SCR system performance at low-load operations. With a small value shift in air/fuel ratio, the efficiency of low-load SCR system can increase from 40% to 85% at low load operating conditions.
M.S. in Mechanical and Aerospace Engineering, May 2015
Show less

Title: LINEAR AND NONLINEAR BEHAVIOR OF TRANSIENT LIFT RESPONSE TO PULSE-ACTUATION
Creator: An, Xuanhong
Date: 2014, 2014-07
Description: The transient lift coe cient for a NACA0009 airfoil with pulsed jet actuation type of active ow control at stall conditions is investigated....
Show moreThe transient lift coe cient for a NACA0009 airfoil with pulsed jet actuation type of active ow control at stall conditions is investigated. The experimental mea- surements show the lift coe cient dependence to a single-pulse with di erent pulse widths and amplitudes. Based on the single-pulse with optimal parameters, multi- pulse and continuous pulse actuation cases are studied, which indicate that the pulse interval is the major factor of the active ow control system capability. Linear and nonlinear model are used to predict the lift coe cient variation for di erent input signals to the actuators. A combined nonlinear model is introduced to predict lift coe cient change due to arbitrary unsteady pitching motion with active ow control.
M.S. in Mechanical and Aerospace Engineering, July 2014
Show less

Title: BIG DATA SYSTEM INFRASTRUCTURE AT EXTREME SCALES
Creator: Zhao, Dongfang
Date: 2015, 2015-07
Description: Rapid advances in digital sensors, networks, storage, and computation along with their availability at low cost is leading to the creation of...
Show moreRapid advances in digital sensors, networks, storage, and computation along with their availability at low cost is leading to the creation of huge collections of data { dubbed as Big Data. This data has the potential for enabling new insights that can change the way business, science, and governments deliver services to their consumers and can impact society as a whole. This has led to the emergence of the Big Data Computing paradigm focusing on sensing, collection, storage, management and analysis of data from variety of sources to enable new value and insights. To realize the full potential of Big Data Computing, we need to address several challenges and develop suitable conceptual and technological solutions for dealing them. Today's and tomorrow's extreme-scale computing systems, such as the world's fastest supercomputers, are generating orders of magnitude more data by a variety of scienti c computing applications from all disciplines. This dissertation addresses several big data challenges at extreme scales. First, we quantitatively studied through simulations the predicted performance of existing systems at future scales (for example, exascale 1018 ops). Simulation results suggested that current systems would likely fail to deliver the needed performance at exascale. Then, we proposed a new system architecture and implemented a prototype that was evaluated on tens of thousands nodes on par with the scale of today's largest supercomputers. Micro benchmarks and real-world applications demonstrated the e ectiveness of the proposed architecture: the prototype achieved up to two orders of magnitude higher data movement rate than existing approaches. Moreover, the system prototype was incorporated with features that were not well supported in conventional systems, such as distributed metadata management, distributed caching, lightweight provenance, transparent compression, acceleration through GPU encoding, and parallel serialization. Towards exploring the proposed architecture at millions of node scales, simulations were conducted and evaluated with a variety of workloads, showing near linear scalability and orders of magnitude better performance than today's state-of-the-art storage systems.
Ph.D. in Computer Science, July 2015
Show less

repository.iit

Search the repository

Pages

Pages

Enabled Filters

Refine Results

Type

Date

Academic status of creator

Department

Subject

Creator

Part of

Rights