Engineering Commons^™

Corrosion Assessment And Enhanced Biocompatibility Analysis Of Biodegradable Magnesium-Based Alloys, Luis Enrique Pompa

Theses and Dissertations - UTB/UTPA

Magnesium alloys have raised immense interest to many researchers because of its evolution as a new third generation material. Due to their biocompatibility, density, and mechanical properties, magnesium alloys are frequently reported as prospective biodegradable implant materials. Moreover, magnesium based alloys experience a natural phenomena to biodegrade in aqueous solutions due to its corrosive activity, which is excellent for orthopedic and cardiovascular applications. However, major concerns with such alloys are fast and non-uniform corrosion degradation. Controlling the degradation rate in the physiological environment determines the success of an implant. In this investigation, three grades of magnesium alloys: AZ31B, AZ91E and …

Detailed Inventory Record Inaccuracy Analysis, Hayrettin Kaan Okyay

Graduate Theses and Dissertations

This dissertation performs a methodical analysis to understand the behavior of inventory record inaccuracy (IRI) when it is influenced by demand, supply and lead time uncertainty in both online and offline retail environment separately. Additionally, this study identifies the susceptibility of the inventory systems towards IRI due to conventional perfect data visibility assumptions. Two different alternatives for such methods are presented and analyzed; the IRI resistance and the error control methods. The discussed methods effectively countered various aspects of IRI; the IRI resistance method performs better on stock-out and lost sales, whereas error control method keeps lower inventory. Furthermore, this …

Designing Customizable Network-On-Chip With Support For Embedded Private Memory For Multi-Processor System-On-Chips, Azad Fakhari

Graduate Theses and Dissertations

The computer industry's transition to multiprocessor systems on chip (MPSoC) architectures is increasing the need for new scalable high-bandwidth on-chip communication

backbones. Network-on-Chip (NoC) interconnects are gaining interest for serving as the on-chip communication infrastructure. The most important issues to be considered in designing a NoC are topology, routing algorithm, flow control, and buffering and also the trade-offs between performance, power, and area.

This research proposes a custom-designed NoC specifically for MPSoCs on FPGAs. The proposed design allows the communication infrastructure to seamlessly scale as the numbers of processors within the chip increases. The design adds a new level of …

Poisson Distributed Individuals Control Charts With Optimal Limits, Negin Enayaty Ahangar

Graduate Theses and Dissertations

The conventional method used in attribute control charts is the Shewhart three sigma limits. The implicit assumption of the Normal distribution in this approach is not appropriate for skewed distributions such as Poisson, Geometric and Negative Binomial. Normal approximations perform poorly in the tail area of the these distributions. In this research, a type of attribute control chart is introduced to monitor the processes that provide count data. The economic objective of this chart is to minimize the cost of its errors which is determined by the designer. This objective is a linear function of type I and II errors. …

Distributed Formation Tracking Control Of Multiple Car-Like Robots, Chunyu Chen

Theses and Dissertations - UTB/UTPA

In this thesis, distributed formation tracking control of multiple car-like robots is studied. Each vehicle can communicate and send or receive states information to or from a portion of other vehicles. The communication topology is characterized by a graph. Each vehicle is considered as a vertex in the graph and each communication link is considered as an edge in the graph. The unicycles are modeled firstly by both kinematic systems. Distributed controllers for vehicle kinematics are designed with the aid of graph theory. Two control algorithms are designed based on the chained-form system and its transformation respectively. Both algorithms achieve …

Manufacture And Characterization Of Silver And Copper Nanostructures Produced Via Forcespun Nylon 6 Nanofibers, Wenqian Zhao

Theses and Dissertations - UTB/UTPA

Nylon 6 nanofibers were produced using the Forcespinning® method and were deposited with silver or copper thin films using the high vacuum thermal evaporation technique for surface functionalization of nanostructures. The changes in surface composition, morphology and surface energy of native and metallic coated Nylon 6 nanofibers were examined. Their antibacterial properties of native, silver or copper coated Nylon 6 nanofibers were tested. Furthermore, the Nylon 6 nanofibers were used as templates in order to obtain silver or copper nanotubes where the polymer was removed after high temperature calcination. The metallic coated Nylon 6 nanofibers and metallic nanotubes morphology and …

A Decision Support System To Measure Product Suitability For Additive Manufacturing Processes, Cynthia De Vasconcellos Barros

Theses and Dissertations - UTB/UTPA

Additive Manufacturing (AM) technologies started arising around 1980’s and they are currently considered to be the third industrial revolution. With improvements in computers, materials, and automated machines, manufacturers across several types of industries are becoming more familiar with AM processes, and it has become more common to see products that are being fabricated by using this new technology. However, there are still questions regarding when it is suitable to use Additive Manufacturing or conventional manufacturing processes depending on different factors. The purpose of this thesis is to create a Decision Support System (DSS) that will help users measure product suitability …

Identifying, Monitoring, Quantifying And Converting Algae To Bio-Fuels In Bio-Reactors, Alice C. Jernigan

Graduate Theses and Dissertations

Growing algae as a source for bio-fuels has become an area of interest due to concerns about global warming and the reliability and ecology of the production of fossil fuels. Dried algae harvested from a pilot water quality improvement technology at the Rockaway Wastewater Treatment Facility in New York were examined as a source of carbohydrates and lipids for the production of bio-fuels in bio-reactors. The length of storage time, storage conditions, sugar and lipid extraction processes, and fuel production were studied. The results show that if the algae is stored dry (0.015 g/g algae even after a year in …

Processing And Characterization Of Zr-Based Metallic Glass By Laser Direct Depositon, Heehun Bae

Open Access Theses

Bulk Metallic Glass has become famous for its exceptional mechanical and corrosion properties. Especially, Zirconium has been the prominent constituent in Bulk Metallic Glass due to its superior glass forming ability, the ability to form amorphous phase with low cooling rate, thereby giving advantages in structural applications.

In this study, Zirconium powder was alloyed with Aluminum, Nickel and Copper powder at an atomic ratio of 65:10:10:15, respectively. Using the ball milling process to mix the powders, Zr65 Al10 Ni 10 Cu15 amorphous structure was manufactured by laser direct deposition.

Laser power and laser scanning speed were optimized to increase the …

Shear Rheological Characterization Of Gel Healing Response And Construction Of Rheo-Piv System, Abhishek Deepak Bawiskar

Open Access Theses

Thermo-reversible gels are solvent-filled 3D networks of polymer chains interconnected by physical (transient) crosslinks. On applying a high shear stress, the crosslinks are broken and these gels show a typical stress-strain behavior due to cohesive fracture of the gel. When heated above a critical temperature and cooled back to room temperature, all the crosslinks are re-formed. Interestingly, partial to full recovery of broken crosslinks is also observed by simply letting the gel stand at room temperature. In this study, the fracture and healing behavior of a model acrylic triblock copolymer gel has been characterized by shear rheometry. A mathematical model …

Phase Field Modeling Of Shear Yielding And Crazing In Glassy Polymer, Yunzhe Mao

Open Access Theses

Glassy polymers are very important in industrial and commercial components manufacturing. For instance, it is used to manufacture polymer-matrix composites, the type of composite used in the Dreamliner 787. But this kind of material is also limited by its tendency to fail in brittle manner. In this study, we use phase field model to characterize the yielding condition of glassy amorphous polymer under a wide range of loading conditions. The main failure mechanisms in amorphous glassy polymers, such as poly-methyl-methacrylate (PMMA), are crazing and shear yielding. Crazing is formed because of the nucleation of micro-voids in the location of stress …

A Framework For Synthesizing Agent-Based Heterogeneous Population Model For Epidemic Simulation, Madih Sahar

Open Access Theses

Social interactions play an important role in spread of a disease. In this thesis we propose a probabilistic approach to synthesize an agent-based heterogeneous population interaction model to study the spatio-temporal dynamics of an air-born epidemic, such as influenza, in a metropolitan area. The proposed methodology is generic in nature and can generate a baseline population for the cities for which detailed population summary tables are not available. The joint probabilities of population demographics are estimated using the International Public Use Microsimulation Data (IPUMS) sample data set. Based on the population density and the socio-economic status, the population is divided …

A Sensor Ontology For The Domain Of Firefighting Robots, Amy Renae Wagoner

Open Access Theses

Fires create thousands of dollars in damage and thousands of deaths each year. Firefighters risk their lives everyday and are often killed in action. Firefighting robots may be able to reduce the loss of lives and damage due to fires. Robots are often used for redundant tasks that require the consistency and efficiency of a machine. They are especially optimal for tasks that require strength that exceeds that of a typical human being or for environments that are hazardous to people. Robots' metallic exteriors are far more durable and easier to replace than flesh and blood, thus they are ideal …

Effect Of Multivalent Ions On The Swelling And Mechanical Behavior Of Superabsorbent Polymers (Saps) For Mitigation Of Mortar Autogenous Shrinkage, Qian Zhu

Open Access Theses

The chemical and physical structure-property relationships of model superabsorbent polymer (SAP) hydrogels were characterized with respect to swelling behavior and mechanical properties in different ionic solutions (Na+ , Ca2+ , and Al3+ ). The model hydrogels were composed of poly(sodium acrylate-acrylamide) (PANa-PAM) copolymer with varying concentrations of PANa (0, 17, 33, 67, and 83 wt.%) and covalent crosslinking densities of 1, 1.5, and 2 wt.%. By synthesizing the hydrogels in-house, systems with independently tunable amounts of covalent crosslinking and anionic functional groups were created, allowing for the relative effects of covalent and ionic crosslinking on the properties of the hydrogels …

No And No2 Modeling For Diesel Oxidation Catalyst At Different Thermal Aging Levels, Keqin Zhou

Open Access Theses

Different DOC modeling methods are analyzed and compared. Detailed reaction mechanisms of DOC reaction are discussed and a new NO and NO2 modeling technique is proposed. Experiments are conducted measuring downstream DOC NO and NOx . DOC out NO and NO2 concentrations are modeled as a function of DOC temperature. A robust model is built such that with the input of real time NOx and DOC temperature information, DOC-out NO and NO2 concentrations can be precisely predicted.

As is true with many catalysts, the DOC thermally ages as it operates, which reduces the thermal effectiveness level of the catalyst. This …

Multi-Injector Modeling Of Transverse Combustion Instability Experiments, Kevin "James " Shipley

Open Access Theses

Concurrent simulations and experiments are used to study combustion instabilities in a multiple injector element combustion chamber. The experiments employ a linear array of seven coaxial injector elements positioned atop a rectangular chamber. Different levels of instability are driven in the combustor by varying the operating and geometry parameters of the outer driving injector elements located near the chamber end-walls. The objectives of the study are to apply a reduced three-injector model to generate a computational test bed for the evaluation of injector response to transverse instability, to apply a full seven-injector model to investigate the inter-element coupling between injectors …

Integrated Dc-Dc Boost Converters Using Cmos Silicon On Sapphire Technology, Imaduddin Mohammad

Open Access Theses

With the recent advancements in semiconductor manufacturing towards smaller, faster and more efficient microelectronic systems, the problems of increasing leakage current and reduced breakdown voltage in bulk-CMOS transistors have become substantial in the sub-100-nanometer era. The Peregrine UltraCMOS Silicon-on-Sapphire (SOS) technology that uses highly-insulating sapphire substrate as insulator was introduced to meet the continually growing need for higher performance RF products. The electrically isolated circuit elements in the UltraCMOS technology lead to increased switching speeds and lower power consumption due to reduced junction and parasitic capacitances. Furthermore, the growing need for high-speed switching applications such as boosting a lower voltage …

Particle Deposition On Superhydrophobic Surfaces By Sessile Droplet Evaporation, Mercy G. Dicuangco

Open Access Theses

Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is …

Characterizing The Intra-Warp Address Distribution And Bandwidth Demands Of Gpgpus, Calvin Holic

Open Access Theses

General-purpose Graphics Processing Units (GPGPUs) are an important class of architectures that offer energy-efficient, high performance computation for data- parallel workloads. GPGPUs use single-instruction, multiple-data (SIMD) hardware as the core execution engines with (typically) 32 to 64 lanes of data width. Such SIMD operation is key to achieving high-performance; however, if memory demands of the different lanes in the "warp" cannot be satisfied, overall system performance can suffer.

There are two challenges in handling such heavy demand for memory bandwidth. First, the hardware necessary to coalesce multiple accesses to the same cache block--a key function necessary to reduce the demand …

Increasing The Supply Of Affordable Housing In Urban India - Mumbai, Upasna Viswanathan

Open Access Theses

The need for housing in today's world is irrefutable. The growing population, accompanied with the fast pace of urbanization, are producing great housing demand, in urban areas in particular. This study focused on one segment of housing - affordable housing, in Mumbai, India, the demand for which has been on a steady rise over the past decade. Though traditionally the State was the provider of affordable housing, private sector has been increasingly involved in the segment, beginning the economic meltdown of 2008-2009. Yet there is a huge demand-supply gap that exists, which needs to be filled. The researcher looks at …

Effectiveness Of Air Sealing Measures And Other Energy Retrofit Measures In Lafayette Energy Improvement Program, Jia Ye

Open Access Theses

From September 2011 to March 2013, the City of Lafayette, IN implemented Lafayette Improvement Program. The goal of this project was to "increase energy efficiency of existing homes through retrofitting, thereby lowering the costs of home ownership within the Vinton and Glen Acres Neighborhood Target Area (The City of Lafayette, 2011)." Energy audit companies carried out before blower door test and after blower door test to identify air tightness of subjects. This paper finds out there was an improvement in air tightness in the population of 85 houses and the degree of improvement was between 16.85% and 17.85%.

Change point …

Developing An Embedded System Solution For High-Speed, High-Capacity Data Logging For A Size-Constrained, Low-Power Biomechanical Telemetry System And Investigating Components For Optimal Performance, Brandon Blaine Gardner

Open Access Theses

The Purdue Neurotrauma Group (PNG) seeks to develop a biomechanical telemetry system capable of monitoring and storing athletes' head motions with the intention of identifying when a player may be at risk of neurophysiological damage, especially brain damage. A number of commercially-available systems exist with a similar goal; however, each of these systems discards information below an acceleration threshold. Research by PNG indicates that any acceleration may contribute to brain damage and that, because of this, an event-based model is insufficient for a proper understanding of an athlete's neurophysiological health. Continuous-time monitoring of head accelerations is therefore necessary. To facilitate …

The Development Of 6.7% Efficient Copper Zinc Indium Selenide Devices From Copper Zinc Indium Sulfide Nanocrystal Inks, Brian Kemp Graeser

Open Access Theses

As solar cell absorber materials, alloys of CuIn(S,Se)2 and Zn(S,Se) provide an opportunity to reduce the usage of indium along with the ability to tune the band gap. Here we report successful synthesis of alloyed (CuInS2 )0.5(ZnS)0.5 nanocrystals by a method that solely uses oleylamine as the liquid medium for synthesis. The reactive sintering of a thin film of these nanocrystals via selenization at 500 °C results in a uniform composition alloy (CuIn(S,Se)2 )0.5 (Zn(S,Se)) 0.5 layer with micron size grains. Due to the large amount of zinc in the film, the sintered grains exhibit the zinc blende structure instead …

Microstructural Indicators Of Transition Mechanisms In Time-Dependent Fatigue Crack Growth In Nickel Base Superalloys, Ann Elizabeth Heeter

Open Access Theses

Gas turbine engines are an important part of power generation in modern society, especially in the field of aerospace. Aerospace engines are design to last approximately 30 years and the engine components must be designed to survive for the life of the engine or to be replaced at regular intervals to ensure consumer safety. Fatigue crack growth analysis is a vital component of design for an aerospace component. Crack growth modeling and design methods date back to an origin around 1950 with a high rate of accuracy. The new generation of aerospace engines is designed to be efficient as possible …

Cztsse Thin Film Solar Cells : Surface Treatments, Chinmay S. Joglekar

Open Access Theses

Chalcopyrite semiconducting materials, specifically CZTS, are a promising alternative to traditional silicon solar cell technology. Because of the high absorption coefficient; films of the order of 1 micrometer thickness are sufficient for the fabrication of solar cells. Liquid based synthesis methods are advantageous because they are easily scalable using the roll to roll manufacturing techniques.

Various treatments are explored in this study to enhance the performance of the selenized CZTS film based solar cells. Thiourea can be used as a sulfur source and can be used to tune band gap of CZTSSe. Bromine etching can be used to manipulate the …

Excessive Delays In Closeouts Can Be Removed With The Adaptation Of Better Practices, Vasudha Kaul

Open Access Theses

Until recent times, closeout was not given its due diligence simply because the damage it created was not appreciated. Literature, thought-provoking discussions and thoughtful deliberations have punctuated the absolute need for a project closeout planning at the very beginning of a project. Many experienced project managers fail to plan the closeout of a job and concentrate solely on completing the contractual scope of work without paying much heed to the final percent of construction projects, the one percent that is an extremely time-consuming and expensive process if not catered for well in advance. The closeout stage is given its due …

Characterizing Habituation Using The Time-On-Task Metric In An Iris Recognition System, Jacob A. Hasselgren

Open Access Theses

This thesis presents a characterization of biometric habituation in an iris recognition study using qualitative analysis of a distributed habituation survey and quantitative analysis of iris images collected in 2010 and 2012. The performed analyses answered the following two questions: a) How consistently does the biometric community define habituation?; and b) Does the time-on-task variable provide enough evidence to indicate the existence of habituation in an iris recognition system? The qualitative analysis examined responses to 12 habituation-related questions from 13 biometric experts to identify common themes that not only determined definition consistency but also characterized critical components often omitted from …

The Hong Kong-Zhu Hai-Macau Bridge: Impacts On The Greater Pearl River Delta, Jun He

Open Access Theses

This research looks at the impacts of megaprojects on their host regions through a case study of the Hong Kong-Zhu Hai-Macau Bridge (HZMB). The purpose of this study is to analyze the potential economic impact of the HZMB on the region through existing data and stakeholder interviews. The research will specifically focus on megaprojects' impacts on tourism industry and economic development in general. The research results are aimed to address the four research objectives of the study, which are similarities and differences between the HZBM and other megaprojects, common issues involved in developing megaprojects, the future impacts of the HZMB …

Unsteady Forces On A Spherical Particle Accelerating Or Decelerating In An Initially Stagnant Fluid, Yashas Mudlapur Phaneesh Keshav

Open Access Theses

Flows with particles play an important role in a number of engineering applications. These include trajectories of droplets in sprays in fuel-injected-reciprocating-piston and gas-turbine engines, erosion of materials due to particle impact on a surface, and deposition of materials on surfaces by impinging droplets or particles that could solidify or bond on impact. For these applications, it is important to understand the forces that act on the particles so that their trajectories could be predicted.

Considerable work has been done on understanding the forces acting on spherical particles, where the Reynolds numbers (Rep ) based on the particle …

Probabilistic Fault Detection And Diagnostics For Packaged Air-Conditioner Outdoor-Air Economizers, Andrew L. Hjortland

Open Access Theses

Poor economizer control, economizer damper failure, and excess outdoor-air contribute to these performance degradations. In order to promote optimal rooftop air-conditioner (RTU) performance and reduce operating costs, an automated fault detection and diagnostics (AFDD) tool has been designed for RTUs with integrated economizers. Based on previously proposed methods, the proposed method advances the economizer fault detection and diagnosis components by using statistical classifiers in order to provide more robust, probabilistic fault outputs. A set of air-side virtual sensors has also been added to the method in order to expand the applicable range of conditions fault detection and diagnostics can be …