Search results

Title: PHOTOCONDUCTIVE SWITCH IMPLEMENTED WITH GALLIUM ARSENIDE ON SILICON NITRIDE FOR COPLANAR WAVEGUIDE BASED TERAHERTZ SPECTROMETER
Creator: Fu, Xiaohuan
Date: 2015, 2015-12
Description: Over the years, pulsed terahertz (THz) time domain spectroscopy has attracted a lot of interest since it can not only measure the intensity of...
Show moreOver the years, pulsed terahertz (THz) time domain spectroscopy has attracted a lot of interest since it can not only measure the intensity of the transient electric eld but also determine the amplitude and phase of the spectral components that make up the pulse. This provides a convenient method to obtain the molecular network information of chemical or biological samples. Signi cant e orts have been directed towards free space spectroscopy in which THz pulses travel in free space between photoconductive transceivers. Due to di raction limit, the resolution is insu cient for many applications and it results in extreme power requirements or low power densities of the probe pulse. To overcome this issue, we propose a planar THz spectrometer which uses the same photoconductive excitation and detection mechanism as free space spectroscopy, but the excited THz pulses are directly coupled into lithographically de ned coplanar transmission lines. To reduce the power loss in the substrate, a thin lm with lower permittivity is employed to replace the conventional silicon substrate at the location where the coplanar waveguide is fabricated. To obtain high sensitivity, sample can be directly placed on the coplanar waveguide for tight coupling of the eld. Conceptual design and EM simulations have been completed and a variety of experimental studies have been carried out at Argonne National Laboratory to understand the fundamentals of coplanar waveguide. The fabrication of the coplanar waveguide prototype have been conducted at Northern Illinois University. The challenge of building a photoconductive switch with LTG-GaAs on Si3N4 was encountered and an innovative wafer bonding technique was discovered. Several wafer treatments prior to and after wafer bonding have been demonstrated to improve the bonding strength and reduce the defects. A standard pump-probe optics setup has been built at DePaul University and the photoconductive switch have been tested with femtosecond laser. The results con rmed that the photoconductive switches are functioning as design and the device system is ready for THz spectroscopy application. The historical overview of THz spectroscopy research and fundamentals of coplanar waveguide and photoconductive switches are presented in Chapter 1-3, followed by EM simulation, conceptual design in Chapter 4. The details of microfabrication process and the testing results are discussed in Chapter 5 and 6. The project is summarized in Chapter 7.
Ph.D. in Electrical Engineering, December 2015
Show less

Title: RECONFIGURABLE SYSTEM-ON.CHIP SOLUTION FOR ULTRASONIC IMAGING APPLICATIONS
Creator: Gal, Paul
Date: 2015, 2015-12
Description: Ultrasonic system have evolved from a basic single transducer system to full arrays capable of 3-dimensional scans. These advanced systems are...
Show moreUltrasonic system have evolved from a basic single transducer system to full arrays capable of 3-dimensional scans. These advanced systems are design for specific applications and target materials. These systems need to be able to process the vast amount of data that is generated while maintaining portability a flexible and reconfigurable system. Specific hardware accelerators are built to perform ultrasonic signal processing quickly and efficiently. This system allows for a variety of parameters like signal lengths and processing characteristics to be reconfigurable to allow for flexibility for different applications. A system is developed to provide an effective storage and data transfer system which will allows researchers to quickly gather data. Specific compression and reconstruction algorithms are implemented as accelerators to increase the systems overall performance. For data transfer a simple Real Time Operating System and Ethernet connective is developed. This is all implemented on the ZEDBoard Zynq SoC for maximum flexibility and performance.Ultrasonic system have evolved from a basic single transducer system to full arrays capable of 3-dimensional scans. These advanced systems are design for specific applications and target materials. These systems need to be able to process the vast amount of data that is generated while maintaining portability a flexible and reconfigurable system. Specific hardware accelerators are built to perform ultrasonic signal processing quickly and efficiently. This system allows for a variety of parameters like signal lengths and processing characteristics to be reconfigurable to allow for flexibility for different applications. A system is developed to provide an effective storage and data transfer system which will allows researchers to quickly gather data. Specific compression and reconstruction algorithms are implemented as accelerators to increase the systems overall performance. For data transfer a simple Real Time Operating System and Ethernet connective is developed. This is all implemented on the ZEDBoard Zynq SoC for maximum flexibility and performance.Ultrasonic system have evolved from a basic single transducer system to full arrays capable of 3-dimensional scans. These advanced systems are design for specific applications and target materials. These systems need to be able to process the vast amount of data that is generated while maintaining portability a flexible and reconfigurable system. Specific hardware accelerators are built to perform ultrasonic signal processing quickly and efficiently. This system allows for a variety of parameters like signal lengths and processing characteristics to be reconfigurable to allow for flexibility for different applications. A system is developed to provide an effective storage and data transfer system which will allows researchers to quickly gather data. Specific compression and reconstruction algorithms are implemented as accelerators to increase the systems overall performance. For data transfer a simple Real Time Operating System and Ethernet connective is developed. This is all implemented on the ZEDBoard Zynq SoC for maximum flexibility and performance.
M.S. in Electrical Engineering, December 2015
Show less

Title: HARDWARE/SOFTWARE CO-DESIGN PARTITIONING ALGORITHM FOR MACHINE VISION APPLICATIONS
Creator: Gonnot, Thomas
Date: 2017, 2017-05
Description: Advancements in FPGA technologies now allows the implementation of machine vision using hardware component rather than processors for...
Show moreAdvancements in FPGA technologies now allows the implementation of machine vision using hardware component rather than processors for increased efficiency. The combination of hardware and software implementations, however, can provide even more efficient results by combining the advantages of both technologies. This leads to the problem of partitioning the machine vision algorithms between hardware and software. The hardware/software partition problem is NP-hard, which means that a solution to the problem can be checked in polynomial time, but the time to find the solution is not predictable. Automated methods based on a genetic algorithm or discrete particle swarm optimization algorithm allow a designer to implement computer vision algorithms without concerns for the hardware/software partitioning. Their reliance on randomness to explore different partitioning selections, however, means that the optimum result might not be reached and that the processing time cannot be predicted. This dissertation introduces a model for image processing and computer vision algorithms in a set of elementary blocks, each of which is assigned one or more configuration. This configuration can be either hardware or software and is linked to the corresponding resource utilization and performance. A procedure is also introduced to allocate the different blocks to either hardware or software, and a cost function is defined to evaluate the relevance of the generated design. The implementation of the model and procedure allows for the partitioning of any image processing in polynomial time by checking various implementations and selecting the optimum solution. This thesis includes two test cases used to test the efficiency of the method. The shift-invariant features transform is used to demonstrate the viability of the partitioning results on an algorithm containing multiple image convolution operations in parallel. The neural network, on the other hand, is used to demonstrate the performances of the procedure when machine vision algorithm contains many blocks. Finally, this dissertation present a set of machine vision applications, such as object tracking, object recognition, optical character recognition, facial recognition, and visually impaired assistance. The proposed model and procedure could be included in the design flow of hardware/software co-design tools and provide a library of image processing blocks ready to be implemented. This would allow image processing and computer vision designers would be able to implement any algorithm efficiently in hardware/software co-design without the need to know how to partition it.
Ph.D. in Electrical Engineering, May 2017
Show less

Title: POWER GRID VERIFICATION ON CLOUD
Creator: Gupte, Naval
Date: 2016, 2016-05
Description: Reliability and performance of modern ICs is becoming increasingly susceptible to supply voltage variations. Increased demand for low voltage...
Show moreReliability and performance of modern ICs is becoming increasingly susceptible to supply voltage variations. Increased demand for low voltage integrated circuits has made power grid analysis extremely critical and indispensable in modern design flows. Efficient validation of on-chip power distribution network is computationally demanding because of increasing grid sizes. Power grid simulation is critical for analysis and verification of power supply noises for robust and reliable IC designs. Computational demands to simulate power grids for ICs with increasing complexity is never-ending. Cloud computing platforms can be leveraged to mitigate costs associated with making these resources available. However, since simulation data usually contains sensitive design information, simulating on third-party platforms lead to major security concerns. In this study, we propose a framework for secure power grid simulation on Cloud. A transformation algorithm to hide current excitations is presented, while still allowing a majority of computations to be completed on Cloud. We employ multiple compression strategies to significantly reduce communication and storage overheads. Experiments show that our framework can achieve similar turn-around time as an insecure simulator on Cloud, while securing current excitations and output voltage vectors with reasonable communication and computational overheads. Vectorless technique to grid verification estimates worst-case voltage noises without detailed enumeration of load current excitations. We study voltage noise assessment in RLC models of VDD and GND networks in integrated power grids. Abstract grid model is utilized to abbreviate runtime, while transient constraints capture transitory circuit behaviour. Heuristics are employed to extract constraints that restrict power consumption profiles to realistic scenarios. Multiple linear programming problems are formulated to evaluate bounds on voltage overshoots and undershoots. We propose ways to mitigate storage and computational requirements on processing resources, enabling users to deploy computations on economical Cloud Computing platforms. Recommended solution is parallelizable, thereby reducing the overall verification time. Data compression is applied to fully exploit the compute capabilities of contemporary processors for higher throughputs. Experimental results suggest that the proposed technique is practical and scalable for industrial grids.
Ph.D. in Electrical Engineering, May 2016
Show less

Title: POLARIZATION COUPLING IN SEMICONDUCTOR NANO-DIMERS IN THE TERAHERTZ RANGE
Creator: Hu, Zhijing
Date: 2017, 2017-05
Description: Surface plasmon resonance (SPR) occurs at the interface of a semiconductor and a dielectric when certain conditions are satisfied. SPR is...
Show moreSurface plasmon resonance (SPR) occurs at the interface of a semiconductor and a dielectric when certain conditions are satisfied. SPR is impetus to new sensor and device development in the optical range, with nanoparticles of noble metals taking up major roles. Typical conduction band electron concentrations in semiconductors lead to resonance frequencies in the terahertz and infrared bands. While the response strength is weaker than those exhibited by metals, it can be made up for by the formation of aggregates. The added degree of freedom by doping or carrier injection further enhances the versatility of semiconductor nanoclusters. To obtain a first principle solution to the coupled set of equations for charge carrier transport and electrodynamics in a conductive cluster is a formidable task with a high computational cost. Employing a finite-element based tool, the COMSOL Multiphysics Simulation Software, the interaction inside and outside some elementary semiconductor structures such as slab and sphere have been solved, which revealed the screening of the internal field while displaying dispersion and absorptions effects. The study of semiconductor dimer also showed a significant field enhancement and frequency shift. Under strong applied field, asymmetric polarization within the particles is revealed. The accompanying nonlinear polarization response can be employed to develop new devices. These model structures can serve to provide insight to the analysis and synthesis more complex structures.
Ph.D. in Electrical Engineering, May 2017
Show less

Title: INDEX CODING VIA RANK MINIMIZATION
Creator: Huang, Xiao
Date: 2015, 2015-07
Description: Index codes reduce the number of bits broadcast by a wireless transmitter to a number of receivers with different demands and with side...
Show moreIndex codes reduce the number of bits broadcast by a wireless transmitter to a number of receivers with different demands and with side information. It is known that the problem of finding optimal linear index codes is NP-hard (a worst-case result). Many heuristic solutions based on graph coloring have been proposed. However, graph coloring is also a NP-hard problem, and it only gives an upper bound of the index coding. Motivated by a connection between index coding and rank minimization, this thesis investigates the performance of different heuristics based on rank minimization and matrix completion methods, such as alternating projections and alternating minimization, for constructing linear index codes over the reals. The underlying matrices representing an index coding problem have a special structure that makes celebrated methods, such as nuclear norm minimization, perform badly. The performance of different methods, such as alternating projections, directional alternating projections and alternating minimization are presented, through extensive simulation results on random instances of the index coding problem. This thesis makes the following contributions: 1) The proposed alternating projections method gives the best performance compared to other graph based algorithms in the literature. 2) This proposed method leads to up to 13% savings on average communication cost compared to the well know greedy graph coloring algorithm. 3) The thesis describes how the proposed methods can be used to construct linear network codes for non-multicast networks. Our computer code is available online.
M.S. in Electrical Engineering, July 2015
Show less

Title: ANTI-TUMOR SPLICING: RESTORING THE TUMOR SUPPRESSOR BAX IN MICROSATELLITE UNSTABLE TUMORS
Creator: Haferkamp, Bonnie
Date: 2011-11, 2011-12
Description: Microsatellite instability (MSI) is a hallmark for many tumors, especially colon, endometrial, gastric and bladder. Bax, a tumor suppressor...
Show moreMicrosatellite instability (MSI) is a hallmark for many tumors, especially colon, endometrial, gastric and bladder. Bax, a tumor suppressor and pro-death Bcl-2 family member, is frequently mutated in MSI tumors. A microsatellite mutation produces a frameshift with premature termination, leading to “Bax-negative” tumors. Although low Bax expression in tumors is often associated with poor prognosis, several studies have correlated lack of Bax in MSI tumors with improved prognosis. However, the molecular explanation for this paradox is unknown. Here we show that “Bax-negative” tumors in fact generate a novel family of anti-tumor Bax-MSI isoforms through alternative splicing. The thesis includes two parts. In Chapter One, we fully characterize one Bax-MSI isoform, BaxΔ2. We show that BaxΔ2 is detrimental to cancer cells but through a non-conventional death pathway, with differential sensitivity to chemotherapeutics. In Chapter Two, we present an entire family of Bax-MSI isoforms, and illustrate a potential molecular mechanism behind its production. We show that the frequency of Bax alternative splicing is significantly higher in MSI than non-MSI tumors, and that BaxΔ2 trans splicing requirements are ubiquitous in human cell lines. The discovery of functional Bax isoforms in Bax-mutated tumors may help explain why the apparent loss of Baxα in tumors is sometimes associated with a better prognosis. In addition, the unique sequences of Bax-MSI isoforms can serve as biomarkers for diagnostic and treatment purposes. Importantly, identification of Bax-MSI isoforms will provide a great opportunity from a genetic approach or drug design for treatment of MSI cancer.
Ph.D. in Biology, December 2011
Show less

Title: COMPARISON OF NEUROPSYCHOLOCICAL PROFILES OF CHILDREN WITH ATTENTION.DEFIC ITiHYPERACTIVITY DISORDER (ADHD), READING DISORDER (RD), AND COMORBID ADHD AND RD
Creator: Hinkle, Clayton D.
Date: 2013, 2013-07
Description: The aim of this study was to expand our understanding of the patterns of executive functioning, memory and learning, and reading achievement...
Show moreThe aim of this study was to expand our understanding of the patterns of executive functioning, memory and learning, and reading achievement in older children and adolescents with ADHD, RD, and comorbid ADHD and RD. Each participant completed neuropsychological assessments, including a measure of intelligence and reading achievement, as well as several measures of executive functioning, memory, and learning. Results suggested that children in these diagnostic groups do significantly differ from each other on these tasks, although those with comorbid ADHD and RD did not demonstrate any specific deficits above and beyond those that manifest in either ADHD or RD alone. Clinical and practical implications, as well as directions for future research are discussed.
PH.D in Psychology, July 2013
Show less

Title: INTERACTIONS BETWEEN NANOFLUIDS AND A SOLID SUBSTRATE: ROLE OF pH AND NANOFLUID PARTICLE CONCENTRATION ON THE THREE-PHASE CONTACT ANGLE
Creator: Horiuchi, Hiroki
Date: 2013, 2013-12
Description: We investigate the effect of pH on the interactions between a silica slurry and a silica wafer substrate (TEOS) made by the chemical vapor...
Show moreWe investigate the effect of pH on the interactions between a silica slurry and a silica wafer substrate (TEOS) made by the chemical vapor deposition of tetraethylorthosilicate gas in order to understand the optimization of the Chemical Mechanical Polishing (CMP) process and develop a high-performance silica slurry. The nature of the interactions is probed by the solid-liquid interfacial energy and the electrostatic surface potential at the solid surface. An overview of the CMP process is discussed in Chapter 1. Conventional techniques used to measure the electrostatic potential at the solid/liquid interface, such as the streaming potential and potentiometric titration method, are reviewed. Although there are many techniques for measuring the surface potential of powders, such as potentiometric titration and zeta potential measurement, there is no well-established technique for measuring the surface potential of the silica wafer. Therefore, in this research, we developed a methodology to determine the surface potential and surface charge density of a silica wafer substrate in contact with a slurry. We developed a novel method for calculating the surface potential and surface charge density using the experimental data of the three-phase contact angle in conjunction with the Young- Lippmann and the Poisson-Boltzmann equations. The surface chemistry of silica is discussed in Chapter 2 to elucidate the origin of the surface charge due to the ionization of the silanol groups on a silica wafer. Since the silica wafer is always in contact with the aqueous solution during the CMP process, we specifically focus on the behavior of silica in aqueous solutions. xvi In Chapters 3 and 4, the three-phase contact angle (TPCA) on silica is measured as a function of the pH by the goniometric technique. The surface potential and surface charge density at the silica/water surface are calculated by a model based on the Young- Lippmann equation in conjunction with the Gouy-Chapman model for the electric double layer. In measurements of the TPCA on silica, two distinct regions are identified with a boundary at pH 9.5—showing a dominance of the surface ionization of silanol groups below pH 9.5 and a dominance of the dissolution of silica into the aqueous solution above pH 9.5. Since the surface chemistry changes above pH 9.5, the model is applied to solutions below pH 9.5 (ionization dominant) for the calculation of the surface potential and surface charge density at the silica/aqueous interface. In order to evaluate the model, a galvanic mica cell was made of a mica sheet and the surface potential was measured directly at the mica/water interface. The model results are validated by the experimental data from the literature, as well as the results obtained by the potentiometric titration method and the electro-kinetic measurements. The interactions between the nanofluid and solid surface are explored in Chapter 5. Measurements of three-phase contact angle of the nanofluid on a silica substrate show that the contact angle decreases as the volume fraction increases due to the formation of particle layers on the solid surface. We conclude that it is driven by the depletion attractions between the nanoparticles and a solid surface. In the calculations, the energy (based on Young’s equation) and the structural energy of silica particles (based on statistical mechanics---Henderson’s equation) are in good agreement, indicating that the formation of the nanoparticle layering occurs near the solid surface, as expected. We reference the measurement of the forces between two mica surfaces by Israelachvili and xvii Pashley (1983 and 1984) to calculate the interaction energy against the distance between the two surfaces; we found that the strong repulsive force (hydration force) at a short distance (less than 2 nm) gives rise to enough energy to change the three-phase contact angle. In addition, the calculated inter-particle energy due to the hydration force (by using a statistical mechanics approach, see Trokhymchuck et al. 2001) shows that the hydration force can dramatically increase the inter-particle energy in the case of a volume fraction of water that is from 40 to 45%. The inter-particle energy corresponds to the energy change of 3-5⁰ in the three-phase contact angle, which is same as that found in our experimental data obtained from the contact angle measurements. Finally, we conclude that the hydration force between the silica particles on the solid surface plays an important role in altering the interfacial energy between a solid and liquid.
PH.D in Chemical Engineering, December 2013
Show less

Title: COMPUTER AIDED DIAGNOSIS IN MAMMOGRAPHY WITH CONTENT-BASED IMAGE RETRIEVAL
Creator: Jing, Hao
Date: 2011-11, 2011-12
Description: Computer-aided diagnosis (CAD) for breast cancer, a common form of cancer in women, has been an active research area. This work aims to...
Show moreComputer-aided diagnosis (CAD) for breast cancer, a common form of cancer in women, has been an active research area. This work aims to investigate and develop CAD techniques for clustered microcalcifications (MCCs), which can be an important early sign of breast cancer. The contributions of this work include development of a database of cancer cases and algorithms for detection and classification of MCCs. First, a database consisting of a large number of cases is built from different sources. To support the merging of cases from different data sources, a feature comparison study is conducted between mammograms from screen film and full field digital mammography (FFDM) systems. It is demonstrated that the features extracted from film and FFDM are highly correlated and there is no adverse effect on a CAD task of classification when used together. Second, a spatial point process (SPP) approach is proposed to exploit the spatial distribution among different MCs in a mammogram directly during the detection process. This is different from the conventional approach in which detection algorithms are employed to first identify individual MCs in a mammogram, which are subsequently grouped into clusters by a clustering algorithm. The performance of the proposed approach is demonstrated to be superior to an existing method based on the support vector machine (SVM). Third, in observation of the emerging of large databases from the picture archiving and communication (PAC) systems in the clinics, a retrieval driven approach is proposed for classification of MCCs. In this approach, for a case to be diagnosed (i.e., query), a set of similar cases is retrieved from a database and subsequently is used to train xii an adaptive classifier specifically for the query case using the technique of logistic regression. The proposed approach is demonstrated to lead to significant improvement in classification accuracy. Moreover, the proposed adaptive classification approach is further developed using regularization techniques, where a prior is first derived from a baseline classifier and then used to regularize the adaptive classifier trained with the retrieved cases. The regularized adaptive classifier can be more computationally efficient, and is demonstrated to achieve further improvement in performance.
Ph.D. in Electrical Engineering, December 2011
Show less

Title: SLIDING MODE CONTROL OF CONVERTERS WITH AN INDEPENDENT NEUTRAL POINT
Creator: Ghosh, Somsubhra
Date: 2017, 2017-07
Description: With the increasing footprint of renewable energy, the drive towards a cleaner environment has consistently pushed forward the development of...
Show moreWith the increasing footprint of renewable energy, the drive towards a cleaner environment has consistently pushed forward the development of power electronics based power converters. While the basic principles of operating the power electronics in these power converters have been very effective in providing for a very efficient system, new topologies and advanced control strategies enable us to achieve a still higher efficiency, simplification and help us overcome some of the fundamental problems encountered in operation. One of the fundamental requirements of the power electronic converters is that they require a significantly large output capacitors. it is necessary to remove ripples in the rectified AC voltage. Numerous approaches have been presented in the past to overcome these issues including the addition of a ripple compensator to a conventional H-Bridge rectifier as well as using one leg of the H-Bridge itself as a neutral leg. A new controller; based on sliding mode has been proposed here to a neutral leg topology as well as the conventional H-Bridge topology of a single-phase power converter. In case of a rectifier, the ripple energy is separated and directed towards the lower split capacitor present at the neutral leg so that the upper split capacitor may have very small ripples while in case of an inverter the lower capacitor actually acts as an independently controlled DC source. all the while the capacitance is kept to be very small. The control of the two legs in the rectifier is performed independently granting the controller an extra degree of freedom and an easier extrapolation to the 3-phase implementation. The controller operates the power electronic switches to regulate the input grid current and achieve unity power factor as well as to maintain a stable DC bus voltage removing the need for any other power factor correction circuit.
M.S. in Electrical Engineering, July 2017
Show less

Title: ADVANCES IN VEHICLE-TERRAIN INTERACTION MODELING FOR SMALL, RIGID-WHEELED VEHICLES OPERATING ON DEFORMABLE TERRAIN
Creator: Meirion-griffith, Gareth
Date: 2012-04-22, 2012-05
Description: This thesis presents advances in the eld of terramechanics, the study of ve- hicle mobility performance, for small, rigid-wheeled vehicles...
Show moreThis thesis presents advances in the eld of terramechanics, the study of ve- hicle mobility performance, for small, rigid-wheeled vehicles operating on deformable terrain. Speci cally, the thesis proposes new models for vehicle performance model- ing through the development of novel pressure-sinkage equations. The semi-empirical equations of terramechanics, rst developed by Bekker in the 1950s, couple vehicle mobility systems and terrain geotechnical properties to yield an understanding of the manner in which traction is developed o -road. This is important because on de- formable terrain mobility is often limited not by the vehicle's torque or power, but by the strength of the terrain and its ability to support locomotion. Classical terramechanics models have proven to be instrumental in the design, modeling, and operation of large, man-driven vehicles for applications such as agri- cultural, military, and commercial transport. However, these models are not appro- priate for vehicles with wheels less than approximately 50 cm in diameter [MGS11a] [SMGSM08] [RBC02]. This is a critical problem because of the increasing prolifer- ation of small, robotic vehicles. In particular, space agencies such as the National Aeronautics and Space Administration (NASA), the Japanese Aerospace Exploration Agency (JAXA), and the European Space Agency (ESA) have shown great interest in the application of terramechanics to planetary exploration rover mobility. At the inception of the author's research, several independent sources had noted the limited accuracy of classical terramechanics models for small-wheeled vehi- cles. However, an understanding of the cause of these inaccuracies was absent. This thesis provides an understanding of these inaccuracies, their cause, and a solution. Using laboratory experiments, fi eld test data, theoretical development, and vehicle simulation, this thesis proposes a modi fied terramechanics framework for predicting small, rigid-wheel traction.
Ph.D. in Mechanical and Aerospace Engineering, May 2012
Show less

Title: LAKESHORE CITY: A PROPOSAL FOR SOCIAL SUSTAINABILITY
Creator: Karpuzi, Isida
Date: 2013-04-25, 2013-05
Description: After the collapse of the steel industry, the US Steel South Works plant left behind a vacant 600-acre area of lakefront land and thousands of...
Show moreAfter the collapse of the steel industry, the US Steel South Works plant left behind a vacant 600-acre area of lakefront land and thousands of unemployed workers that had inhabited the adjacent neighborhood of South Chicago. This thesis proposes the revitalization of this abandoned area through the development of a new community called Lakeshore City. The design of the new city is informed by the social and economic issues that have kept South Chicago in a poor condition since the closing of the mill and it is based on the solutions to those issues. Through adding diversified program, enhancing connectivity, and encouraging human interaction, Lakeshore City attempts to create a contemporary and socially sustainable living environment that can bring new prosperity to its surrounding neighborhood.
M.S. in Architecture, May 2013
Show less

Title: The Effect of Salmonella Enteritidis on the Thermal Properties of Egg Albumen and Yolk
Creator: Chadha, Isha
Date: 2011-11-27, 2011-12
Description: Salmonella-inoculated and uninoculated fresh eggs were microwave processed to achieve pasteurization. However, quality degradation was...
Show moreSalmonella-inoculated and uninoculated fresh eggs were microwave processed to achieve pasteurization. However, quality degradation was observed in the albumen of inoculated eggs but not in the uninoculated eggs although the processing was the same. Previous work showed that dielectric properties of egg albumen and yolk do not change in the presence of the bacteria. A new hypothesis was therefore proposed that heat capacity is affected by its presence. If an egg has a lowered heat capacity it will become hotter for a given amount of microwave energy input than eggs having normal heat capacities. The goal of the experiments was to determine whether Salmonella at varying concentrations and different incubation times affects the temperature-dependent thermal properties of egg albumen and yolk during in-shell growth. Although the main concern was Salmonella’s effect on the heat capacity of albumen, the equipment used could measure thermal conductivity as well and measurements on yolk were included for completeness. The thermal properties of both egg albumen and yolk were measured by the KD2 Pro thermal properties analyzer (Decagon Instruments, Pullman, WA) via the supplied 30 mm dual-needle sensor. Variables were temperature (7oC, 30oC, 40oC, 50oC, 55oC and 60oC), bacterial inoculum (0, 103, 106, 108 cfu/ml) and incubation time (0 or 30 hours). The measurements showed no significant difference in thermal properties between inoculated and uninoculated samples of egg albumen and yolk regardless of change in temperature, bacterial concentration and incubation period. The absence of an effect on either the dielectric (previous study) or thermal (present study) parameters by the presence of Salmonella leaves unexplained the quality differences between similarly processed inoculated and uninoculated eggs. A biochemical explanation based on the interaction between metabolic byproducts and egg proteins, affecting how they denature, is a topic for future research.
M.S. in Food Safety and Technology, December 2011
Show less

Title: RATE AND TEMPERATURE DEPENDENT MECHANICAL BEHAVIOR AND MODELING OF AL-CU ALLOY SYSTEM
Creator: Tran, Henry
Date: 2011-12-19, 2011-12
Description: Deformation of materials in army applications such as fragment impact, projectile penetration and air blast/shock waves involves high strain...
Show moreDeformation of materials in army applications such as fragment impact, projectile penetration and air blast/shock waves involves high strain rates, large strains, high pressures and rapid changes in temperature, where overall performance ultimately depends on the evolution of flow stress, failure initiation and propagation, generally in the form of adiabatic shear banding (ASB), under these severe loading conditions. Some of 2XXX series aluminum-copper (Al-Cu) alloys such as Al 2519-T87 have been successfully used in Lightweight Armored Vehicles in the U.S. Army because of their good ballistic properties. More recently, an Al-Cu-Mg-Ag alloy designated as Al 2139-T8 has emerged in 2004 as a strong candidate in damage critical applications with higher strength and high-strain-rate performance than its predecessors. Its better ballistic performance is believed to be due to the underlying microstructure. The objective of this study is to investigate mechanical and deformation behavior of Al-Cu material system to develop a fundamental understanding of the effect of composition and microstructural features on overall dynamic behavior. To this end, a systematic approach is adopted to start from single crystal Al and move towards polycrystalline Al, then Al-Cu, and all the way to Al-Cu-Mg-Ag system. Current thesis study constitutes a part of this ongoing work and, therefore, only covers single crystal Al ([001] and [111] directions), polycrystalline Al, and Al-0.1%Cu. Compressive mechanical response of each one of these materials has been investigated in a wide strain rate range that covers quasi-static (from 10-4 to 100 s-1) and dynamic (from 102 to 104 s-1) strain rate regimes. With the exception of single crystal Al (because of limited supplies), additional experiments have been conducted at 120C and 220C within the same strain rate range to understand their thermal softening behavior in varying strain rate regimes. Based on and driven by experimental results, a modified Johnson-Cook model is proposed to describe their rate and temperature dependent constitutive behavior. Finally, in order to investigate susceptibility of these materials and varying microstructures to adiabatic shear localization the two specimen geometries, namely “top hat” and “shear-compression specimen”, have been evaluated. In this evaluation, emphasis is placed upon reliable quantification of strain field within the gage section. Shear compression specimen has been identified to be the best candidate to use in future studies that will explore the tendency of each one of these materials to failure by adiabatic shear banding.
M.S. in Mechanical and Aerospace Engineering, December 2011
Show less

Title: Development of a novel ultra-nanocrystalline diamond (UNCD) based photocathode and exploration of its emission mechanisms
Creator: Chen, Gongxiaohui
Date: 2020
Description: High quality electron sources are one of the most commonly used probing tools used for the study of materials. Photoemission cathodes, capable...
Show moreHigh quality electron sources are one of the most commonly used probing tools used for the study of materials. Photoemission cathodes, capable of producing ultra-short and ultra-high intensity beams, are a key component of accelerator based light sources and some microscopy tools. High quantum efficiency (QE), low intrinsic emittance, and long lifetime (or good vacuum tolerance) are three of the most critical features for a photocathode; however, these are difficult to achieve simultaneously and trade-offs need to be made for different applications. In this work, a novel semi-metallic material of nitrogen-incorporated ultrananocrystalline diamond ((N)UNCD) has been studied as a photocathode. (N)UNCD has many of the unique diamond properties, such as low intrinsic as-grown surface roughness (at the order of 10~nm) due to its nanometer scale crystalline size, relatively long lifetime in air, high electrical conductivity with nitrogen doping, and potentially high QE performance due to the high grain boundary densities where most of electron emission occurs. High contrast interference of incident and reflected radiation within (N)UNCD thin films was observed, and this feature allows fast thickness determination based on an analytical optics methodology. This method has been extended to study and calculate the etching rates of two commonly used O$_2$ and H$_2$ plasmas for use with future (N)UNCD microfabrication processes. The mean transverse energy (MTE) of (N)UNCD was determined over a wide UV range in a DC photogun. Unique MTE behavior was observed; it did not scale with photon energy unlike most metals. This behavior is associated with emission from spatially-confined states in the graphite regions (with low electron effective mass) between the diamond grains. Such behavior suggests that beam brightness many be increased by the simple mechanism of increasing the photon energy so that the QE increases, while the MTE remains constant.Two individual (N)UNCD photocathodes synthesized two years apart have been characterized in a realistic RF photogun. Both the QE and intrinsic emittance were characterized. It was found that the QE of $\sim4.0\times 10^{-4}$, is more than an order of magnitude higher than that of most commonly used metal cathodes (such as Cu and Nb). The intrinsic emittance (0.997~$\mu$m/mm) is comparable to that of photocathodes now deployed in research accelerators. The most impressive feature is the excellent robustness of (N)UNCD material; there was no evidence of performance degradation, even after years-long atmospheric exposure. The results of this work demonstrate that a cathode made of (N)UNCD material is able to achieve balanced performance of three of the primary critical photocathode figures-of-merit.
Show less

Title: Characterization of Radiation Damage Effects in High-Energy Neutrino Target Graphite using Low-Energy Ions
Creator: Burleigh, Abraham C.
Date: 2023
Description: Exposure of graphite targets to high intensity proton beams at neutrino production facilities causes changes in the target material that can...
Show moreExposure of graphite targets to high intensity proton beams at neutrino production facilities causes changes in the target material that can result in a shortened operation lifetime. The dominant factors in this process are currently thought to be mechanical in nature resulting primarily from microstructural effects that lead to thermal and structural changes in bulk material properties. As currently planned beam facilities with increased proton energy and intensity begin to come online it will be important to thoroughly understand these processes, and ideally to be able to predict the effects of new beam designs on target properties. Direct analysis of targets exposed to existing high-energy proton beams is complicated by several factors, such as very limited access to proton beam facilities, high associated costs, irradiation times on the order of months, and the resulting radioactivity of irradiated samples that requires special facilities for post-irradiation examination. Much of the existing literature concerning irradiation damage in graphite has been focused on the needs of the nuclear engineering community, however high-energy proton targets operate in a much different environment. In comparison to graphite irradiated in a nuclear reactor, graphite used in proton beam targets receives a higher dose rate, have greater gas production, and experience short irradiation pulses as opposed to continuous irradiation. Low-energy ion irradiation offers a method of inducing similar levels of radiation damage to high-energy protons while avoiding many of the difficulties and limitations associated with high-energy proton beams and the corresponding activated specimen testing. My research described in this thesis focused on investigating how low-energy ion irradiation could be used to induce the same or similar types of microstructural alteration and mechanical property degradation as that seen in high-energy neutrino production target graphites by varying damage levels and irradiation temperatures prior to post-irradiation characterization.
Show less

Title: Investigation of Electrochemical Properties and Fabrication of Lithium- and Sodium-ion Batteries
Creator: Chen, Changlong
Date: 2023
Description: Since the successful commercialization of Li-ion battery, the opportunity in creating a sustainable world with evenly-distributed energy...
Show moreSince the successful commercialization of Li-ion battery, the opportunity in creating a sustainable world with evenly-distributed energy supply and less environmental concerns has been significantly increased. This triggered tremendous efforts from both academy and industry in building better Li-ion batteries. Along the research and development over past 30 years, the performance of current Li-ion batteries has met some basic needs in our daily life, such as powering electronic devices and electric vehicles for a short time, while superior capabilities, like extended operating life, stable function under extreme circumstances, is always pursued. Under the pressure from these ever-growing demands, the corresponding Li-ion battery production is faced with a lot of new challenges. Regarding the battery production, the present Li-ion battery manufacturing heavily relies on the use of certain repo-toxic solvent, N-methyl-2-pyrrolidone (NMP), which arouses safety concerns to human health. In the pursuit of a higher energy density, silicon anode, bearing ten times the gravimetric capacity of commercially-dominating graphite anode, is intensively studied as the anode material for next-generation Li-ion batteries. However, its degradation mechanism is not completely revealed yet, which makes the methods of effective optimizations hard to be developed. In terms of the cost control, Na-ion batteries have been revisited and have received extra attention in the past decade owing to the abundance in raw materials and the high compatibility with state-of-art Li-ion industry while blank space in understanding primary electrochemical properties, such as impedance signals, has not been totally filled. This will also cause the misunderstandings in such interpretation and, thereby, postpone the pace of relevant advancement. Targeting these proposed issues, this thesis provides a series of feasible solutions via careful investigation and rational analysis with the aid of various advanced (non)electrochemical techniques, which offers a few unique perspectives in studying Li- and Na-ion batteries, and further facilitates the following research and development in the corresponding communities.
Show less

Title: Effect of Phosphorus Additions on Polycrystalline Ni-base Superalloys
Creator: Li, Linhan
Date: 2020
Description: In recent years, advanced polycrystalline Ni-base superalloys have been developed with elevated levels of γ′ forming elements and high level...
Show moreIn recent years, advanced polycrystalline Ni-base superalloys have been developed with elevated levels of γ′ forming elements and high level of refractory elements as solid-solution strengtheners in an effort to extend the temperature capability. Moreover, the properties of the grain boundaries become more important and this necessitates the need to study of effects of minor additions of interstitial P for grain structure optimization. Due to the increased level of refractory elements employed, powder-processed Ni-base superalloys tend to have a high propensity to form Topologically Close-Packed (TCP) phases, which was found to be further promoted by the addition of P. A systematic study of the phase stability of high refractory content powder-processed Ni-base superalloys with three levels of P additions revealed an increased tendency to form Laves phase as a function of P additions. Additions of P were discovered to not only depress the incipient melting temperature to stabilize the eutectic Laves phase, but also promote Laves phase formation during the aging heat treatment and the following isothermal exposure. During the thermal exposure, excessive formation of Laves phase promoted the formation of a basket-weave structure comprised of an intertwined mixture of Laves and Sigma phase. The stabilization of the Laves phase structure due to P additions was found to be consistent with Density Functional Theory (DFT) calculations and could be rationalized through structure maps that relate the valence electron concentration and relative size differences. Additionally, a variation of grain structure obtained via either a sub-solvus or super-solvus solution heat treatment was noted to some extent vary the P segregation level at high-angle grain boundaries, thereby affecting the phase stability. For a sub-solvus solutioned grain structure that possessed a high length density of high-angle grain boundaries, the Laves phase formation was depressed for alloys with a low level of P addition. However, the phase stability variation associated with Laves phase formation was moderate when high concentrations of P were present. The effect of P addition on the γ′ microstructure variation is limited, which was confirmed by microstructure observations as well as through the short-term 0.6%-strain stress relaxation tests at high temperature. Heat treatment variations to modify the secondary and tertiary γ′ microstructures were discovered to exert a much more significant influence on the 0.6%-strain stress relaxation behavior. When a higher initial strain of 2% was applied, the stress relaxation behavior of the powder-processed Ni-base superalloys was found to be microstructure independent. The creep ductility of Waspaloy was determined to be notably reduced by the P additions due to the enhanced precipitation of M23C6 carbide at the grain boundaries. Excessive precipitation of M23C6 carbide increased the likelihood of brittle fracture when tested under low temperature/high stress creep conditions. However, the P addition as well as the excessive precipitation of M23C6 carbide did not impact the creep behavior as the dominant deformation was transgranular in nature when tested under high temperature/low stress conditions.
Show less

Title: Nanopore sensing for environmental and biomarker analysis
Creator: Arora, Pearl
Date: 2024
Description: Nanopore stochastic sensing is a powerful analytical tool for detecting target molecules through a nanoscale pore. The analyte and electrolyte...
Show moreNanopore stochastic sensing is a powerful analytical tool for detecting target molecules through a nanoscale pore. The analyte and electrolyte ions are subjected to a voltage bias which drives them to translocate through the nanopore, resulting in disruptions in the ionic current. These disruptions are translated to blockage events which can serve as a signature of the analyte. Owing to its unique features of single-molecule and label-free sensing, nanopore technique has been exploited in a wide array of applications such as detection of metal ions, proteins, DNA, microRNA, toxic agents etc. In this dissertation, projects showcasing nanopore’s sensing capability of different biomarkers and in the detection of a wide range of target molecules based on non-covalent interactions are presented. Particularly in the first two projects, nanopore detection of ferric ions relevant to environmental regulation as well as a biomarker for human health and a miRNA-based biomarker for oral cancer and oral related diseases are summarized. Ferric ions, which are benign if present in balanced quantities but can be toxic otherwise, are detected by using an engineered multifunctional nanopore and a chelating organophosphonic acid ligand. The chelate complex formed after ferric ions bind to ligand gives significantly different event signatures than the free ligand in the solution enabling ferric ion detection. Even in the presence of interfering ions, the ferric ions could be recognized easily because of the conformational changes brought in the nanopore lumen by the interaction of the interfering metal ions with the His-tags of the nanopore which in turn resulted in variations in the characteristics of blocking events. In the second project, miR31, an oral cancer biomarker, is selectively detected with the help of an engineered nanopore, and a DNA based probe. Several probes with variations in length, composition and position of the overhangs or probes with no overhangs were compared and studied as the probes play a crucial role in capturing the target of interest with high specificity. Our strategically designed probe emerged as the most effective in capturing the target even in presence of large background from human saliva samples and enhanced the sensitivity of the system. In the first two projects, nanopores are utilized for selective and specific detection of certain target molecules. However, in order to analyze diverse range of analytes, numerous sensing systems have to be constructed which can be a time-consuming and challenging task. To circumvent this limitation, in the third project, diverse recognition sites based on various non-covalent interactions are incorporated into the α-hemolysin protein pore to achieve detection of not just a single analyte but broad category of molecules such as cations, anions, aromatic and hydrophobic compounds.
Show less

repository.iit

Search the repository

Pages

Pages