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Retrospective Theses and Dissertations

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Full-Text Articles in Engineering

Multiresolution Editing For B-Spline Curves And Surfaces, Bo Xu Jan 2008

Multiresolution Editing For B-Spline Curves And Surfaces, Bo Xu

Retrospective Theses and Dissertations

Since 1980 surface modeling has been used in industrial design, CAD and entertainment to create and represent complex forms. Even with this comparatively long history of development, challenges remain in free-form surface modeling. One such challenge is building surface creation and editing techniques that effectively balance the need for local control with the need to control the overall global shape, or sweep of the surface. This dissertation presents a multiresolution approach to the creation of surfaces that allows a designer to more easily manage this balance between local and global control. The techniques presented in this dissertation utilize a wavelet ...


Characterization Of Conductive Surface Printing Via Electric Field Induced Ion Transport, Khiam-How Low Jan 2008

Characterization Of Conductive Surface Printing Via Electric Field Induced Ion Transport, Khiam-How Low

Retrospective Theses and Dissertations

A novel methodology to imprint micron size features on copper surface has been adopted in this study. The process of printing is based on focused electric field induced ion transport across a cation selective NafionRTM membrane. The imprinting technology itself is environmentally benign because electrolyte consists of Sulfuric Acid (H2SO4) and Cupric Sulfate (CuSO4) are encapsulated by NafionRTM membrane in a copper made cathode chamber and it is sealed and recycled. In addition, the imprinted surface does not come in contact with corrosive chemicals which minimize the post cleaning process.;Three different methods of printing were embraced here in this ...


The Role Of Information Flow In Engineering Optimization, Steven Michael Corns Jan 2008

The Role Of Information Flow In Engineering Optimization, Steven Michael Corns

Retrospective Theses and Dissertations

Current optimization techniques work well for single components represented by a single model. However, many of the problems we face today are multi-disciplinary problems requiring the integration of complex models from different fields to gain a more complete understanding of the overall performance of a biological, engineering, or human system. One example is a modern automobile. Multiple systems (such as the power train and electronic engine control system) are designed and built from various assemblies and components, all of which are then integrated into one final product. This design process evokes a systems-of-systems concept that is also found in agricultural ...


Advancing Block-Oriented Modeling In Process Control, Stephanie Diane Loveland Jan 2008

Advancing Block-Oriented Modeling In Process Control, Stephanie Diane Loveland

Retrospective Theses and Dissertations

The increasing pressure in industry to maintain tight control over processes has led to the development of many advanced control algorithms. Many of these algorithms are model-based control schemes, which require an accurate predictive model of the process to achieve good controller performance. Because of this, research in the fields of nonlinear process modeling and predictive control has advanced over the past several decades.;In this dissertation, a new method for identifying complicated block-oriented nonlinear models of processes will be proposed. This method is applied for LNL and LLN "sandwich" block-oriented models and will be shown to accurately predict process ...


Device Quality Low Temperature Gate Oxide Growth Using Electron Cyclotron Resonance Plasma Oxidation Of Silicon, Vishwas Jaju Jan 2008

Device Quality Low Temperature Gate Oxide Growth Using Electron Cyclotron Resonance Plasma Oxidation Of Silicon, Vishwas Jaju

Retrospective Theses and Dissertations

According to Moore's Law, which has been true so far, transistors density on a chip area doubles every two years. This increase in number of transistors requires reduced device dimensions or to say scaling by a factor of ∼0.7. As the device dimensions are shrinking, high temperature processes used in CMOS device fabrication, e.g. thermal oxidation of silicon to grow gate oxide, are becoming incompatible with CMOS processing. High temperature processes could change the impurity profile in Si, produce stresses on Si wafer, and also result in high thermal budget. In the past, many attempts have been ...


An Innovative New Pouring Design For Steel Castings, Justin Daniel Walker Jan 2008

An Innovative New Pouring Design For Steel Castings, Justin Daniel Walker

Retrospective Theses and Dissertations

Current methods for handling and pouring molten steel into molds are problematic. Bottom pour ladles have a large pour height that translates into high pouring velocities and increased inclusions. Teapot ladles are limited in capacity and are difficult for the operator to manipulate. Both of these systems rely on manual control to deliver the metal to the sprue. This paper presents a new system that includes a redesigned ladle that has a larger capacity than teapot ladles. The movement of the ladle is computer controlled so that it will deliver metal to defined sprue location based on a prescribed flow ...


A Static Analysis Of Maximum Wind Penetration In Iowa And A Dynamic Assessment Of Frequency Response In Wind Turbine Types, Eknath Vittal Jan 2008

A Static Analysis Of Maximum Wind Penetration In Iowa And A Dynamic Assessment Of Frequency Response In Wind Turbine Types, Eknath Vittal

Retrospective Theses and Dissertations

As the energy industry moves into the 21st century the use and research into renewable resources has expanded significantly. Whether it is wind, biomass, or solar, the industry is seeking ways to breakthrough and integrate the newest technologies into their power systems. Wind energy, in particular, has seen significant expansion since the 1980's, with generating capability of wind turbines increasing dramatically from 50 kW to nearly 5 MW presently. Seeking to introduce larger levels of wind generation in the Iowa electricity system, the goal of this thesis was to: First, determine the maximum wind penetration level of the existing ...


Advancements In Pervious Concrete Technology, John Tristan Kevern Jan 2008

Advancements In Pervious Concrete Technology, John Tristan Kevern

Retrospective Theses and Dissertations

Pervious concrete has been used for many years in the southern United States but only recently have stormwater mandates implemented by the United States (U.S.) Environmental Protection Agency (EPA) created interest for more wide-spread installations, especially in freeze-thaw climates. Validation of the freeze-thaw durability of pervious concrete under the most extreme conditions created an opportunity to explore many additional aspects of pervious concrete and to improve durability through additional mixture characterization and new construction practices. While the material components are similar to conventional concrete, the idiosyncratic behavior of pervious concrete requires revaluating material effects and relationships. Many different factors ...


Condenser: A Custom Tool For Capturing And Summarizing Network Traffic For Avalanche And Iseage, Jason Charles Maughan Jan 2008

Condenser: A Custom Tool For Capturing And Summarizing Network Traffic For Avalanche And Iseage, Jason Charles Maughan

Retrospective Theses and Dissertations

The Cyber-world is becoming an environment that is increasingly plagued by botnets and other programs adept at creating distributed and flooding-based attacks. These forms of assault are currently some of the most feared types of attacks being faced by networks.;The Internet Scale Event and Attack Generation Environment (ISEAGE) at Iowa State University, has been established to help researchers study actions and events that happen on the Internet. ISEAGE uses a custom tool, AVALANCHE, to simulate distributed and flooding-based attacks. While AVALANCHE is able to launch large quantities of attack packets, its ability to react and handle the enormity of ...


Computational Studies On The Effect Of Water Impact On An Unmanned Air Vehicle, Gregory Zink Jan 2008

Computational Studies On The Effect Of Water Impact On An Unmanned Air Vehicle, Gregory Zink

Retrospective Theses and Dissertations

Computational Fluid Dynamics (CFD) was used in conjunction with Finite Element Analysis (FEA) to simulate the water splashdown and effects thereof on an Unmanned Air Vehicle (UAV). The CFD simulation utilized time-accurate finite-volume code to model both "compressible" and "incompressible" ensemble averaged Navier-Stokes equations. The model also incorporated the volume of fluid method to track the air-water interface, and dynamic cell remeshing to move the UAV body through the computational domain. The model was verified by comparing pressure histories with experimental test data. There was good agreement in character and magnitude of these results, with some deviance in the inlet ...


Protein Extraction From Distiller's Grain, Drew John Cookman Jan 2008

Protein Extraction From Distiller's Grain, Drew John Cookman

Retrospective Theses and Dissertations

The drastic increase in ethanol production over the last 10 years has led to overproduction of distiller's grain (DG), an ethanol byproduct. In this study, we investigated the feasibility of extracting the protein from unmilled and milled DG leaving a carbohydrate-rich solid phase that could be used for the production of more ethanol. Protein extractions based on aqueous ethanol (both with and without a pretreatment of a reducing agent), alkaline-ethanol, and aqueous enzyme treatments were compared.;Three methods led to a significant amount of protein being extracted from DG. An enzymatic extraction decreased the crude protein content in the ...


Investigation Of Steel Stringer Bridge Superstructures, Jeremy Craig Koskie Jan 2008

Investigation Of Steel Stringer Bridge Superstructures, Jeremy Craig Koskie

Retrospective Theses and Dissertations

There are hundreds of structurally deficient or functionally obsolete bridges in the state of Iowa. With the majority of these bridges located on rural county roads where there is limited funding available to replace the bridges, diagnostic load testing can be utilized to determine the actual load carrying capacity of the bridge. One particular family or fleet of bridges that has been determined to be desirable for load testing consists of single-span bridges with non-composite, cast-in-place concrete decks, steel stringers, and timber substructures.;Six bridges with poor performing superstructure and substructure from the aforementioned family of bridges were selected to ...


Metabolic Engineering Of Escherichia Coli For The Efficient Utilization Of Plant Sugar Mixture, Madhuresh Kumar Choudhary Jan 2008

Metabolic Engineering Of Escherichia Coli For The Efficient Utilization Of Plant Sugar Mixture, Madhuresh Kumar Choudhary

Retrospective Theses and Dissertations

In recent years, metabolic flux analysis (MFA) has become an important tool in metabolic engineering. The MFA involves the quantification of intracellular metabolic fluxes in a microorganism. The result of MFA is a metabolic flux map that allows the systematic study of cellular responses to genetic and environmental perturbations. Carbon isotope labeling based MFA, with analysis by NMR or GC/MS, have gained wide use in the metabolic engineering community for estimating metabolic fluxes in central carbon metabolism. We are using MFA as a tool to engineer Escherichia coli sugar utilization regulatory (SURS) for the efficient consumption of sugar mixture ...


Predicting Loads On Ground Engaging Tillage Tools Using Computational Fluid Dynamics, Mark Eugene Barker Jan 2008

Predicting Loads On Ground Engaging Tillage Tools Using Computational Fluid Dynamics, Mark Eugene Barker

Retrospective Theses and Dissertations

A new method of evaluating tillage tools using computational fluid dynamics is proposed. Steady-state CFD only and transient two-way fluid-structure interaction simulations were run to predict draft and vertical forces on a spring-reset field cultivator standard. Using CFD the soil was treated as a visco-plastic fluid using the Bingham-plastic material model. Lab tests were run using a rigid flat steel bar and a production field cultivator standard with 178 and 254 mm sweeps for comparison. The results indicate that the method can be used to reasonably predict the draft force to within three standard deviations of the average measured draft ...


Decision Making Limitations From Communication Barriers In Government Structures In Chinese Rural Energy Projects, Nathan Gregory Johnson Jan 2008

Decision Making Limitations From Communication Barriers In Government Structures In Chinese Rural Energy Projects, Nathan Gregory Johnson

Retrospective Theses and Dissertations

Field research was conducted in the Li Cheng District (about 1,200 km 2) of Shan Dong Province. Data collection occurred during a two-week period in July 2006. At that time, seven villages represented all relevant sites in the district that contained gasification technologies. Small-group interviews with village leaders, station managers, and community members were conducted locally. Contact with external government agencies and technology scientists completed the set of potential stakeholders.;This study analyzes the failure of state-owned energy development initiatives in China. Communication barriers in bureaucratic structures and culturally prescribed patterns of interaction were revealed as inhibiting information transfer ...


Devising A More Robust Automated Detection Method Using Audio Frequency Spectra, Gregory Stargell Jan 2008

Devising A More Robust Automated Detection Method Using Audio Frequency Spectra, Gregory Stargell

Retrospective Theses and Dissertations

The space shuttle, Columbia had a suitcase piece of the SOFI strike the wing of the shuttle causing its demise. Detection methods were evaluated to detect defects in the foam. One of the methods being free field acoustics was explored. Previous works were done in this area, and it showed promise as it was able to detect defects. However all defects or the defects that had significance to the eye was not detected. The method developed before is looked into and was improved upon addressing the problems. Developing a baseline curve and region to compare the data would be two ...


Nutrient Recycling In Biofuel Production Systems: Biomass Ash Pelleting, Ethanol Co-Product Allocation, And A Beef-Ethanol Production System Analysis, Katherine A. Edwards Jan 2008

Nutrient Recycling In Biofuel Production Systems: Biomass Ash Pelleting, Ethanol Co-Product Allocation, And A Beef-Ethanol Production System Analysis, Katherine A. Edwards

Retrospective Theses and Dissertations

Relative to fossil fuels, biofuels help to close the carbon cycle; however other essential nutrient cycles remain open. When biomass is removed from the agricultural landscape for biofuel production, essential plant nutrients such as nitrogen (N), phosphorus (P), and potassium (K) are also removed and concentrate in biorefinery waste streams and low value co-products. This thesis comprises three analyses related to nutrient cycles in the emerging bioeconomy. In the first, combusted biomass ash was pelleted and evaluated as a potential fertilizer. In the second, an energy co-product credit for corn dry grind ethanol production has been determined by examining the ...


Monitoring Vegetative Treatment System Performance For Open Beef Feedlot Runoff Control, Ishadeep Khanijo Jan 2008

Monitoring Vegetative Treatment System Performance For Open Beef Feedlot Runoff Control, Ishadeep Khanijo

Retrospective Theses and Dissertations

Vegetative treatment systems (VTS) are an alterative technology designed to control runoff from open beef feedlots. A VTS consists of a solids settling basin (SSB) followed by a vegetative treatment area (VTA) or a combination of vegetative infiltration basin (VIB) and a VTA. Four sites were monitored in 2006 and 2007 to evaluate the performance of the VTSs in Iowa. In 2006, the percent runoff control at Central IA 1 & 2 and Northwest IA 1 & 2 was measured as 99, 74, 96, and 98 respectively. In 2007, the SSB outlets were actively managed and the percent runoff control at Central ...


Visualizing Fluidized Beds With X-Rays, Nathan Paul Franka Jan 2008

Visualizing Fluidized Beds With X-Rays, Nathan Paul Franka

Retrospective Theses and Dissertations

This study applies minimum fluidization velocity experiments, X-ray computed tomography (CT), X-ray stereography, and particle tracking to fluidized beds of glass beads, ground walnut shell, and ground corncob operating with a variety of flow conditions. 3-D local, time-averaged gas holdup is calculated from CT data, while dynamic features are captured by X-ray stereography. The results show that CT is most effective on glass bead fluidized beds. Due to high X-ray attenuation, glass bead CT data has higher resolution than walnut shell and corncob beds. Glass bead gas holdup data also feature the lowest noise due to the high homogeneity of ...


Peasant Communities, The First Link Of The Commodity Chain Of Vicuña Fiber, Liliana L. Lay Lisung Jan 2008

Peasant Communities, The First Link Of The Commodity Chain Of Vicuña Fiber, Liliana L. Lay Lisung

Retrospective Theses and Dissertations

Vicuna fiber has a high value in the textile and fashion industry and is seen on the runways of the most selective and luxurious clothing designers in Europe. However, the vicuna fiber process and commodity chain are little known. This thesis presents the commodity chain of vicuna fiber and the positive and negative impacts that vicuna fiber commercialization generates in Peruvian peasant communities. The research, based on in-depth interviews and document analysis, studies the development of this buyer-driven chain, the social actors' roles, and the policies and legislation implemented to preserve vicuna species. In response to consumption demands, the marketing ...


Nonlinear Device Characterization And Second Harmonic Impedance Tuning To Achieve Peak Performance For A Sic Power Mesfet Device At 2ghz, Saalini Valli Sekar Jan 2008

Nonlinear Device Characterization And Second Harmonic Impedance Tuning To Achieve Peak Performance For A Sic Power Mesfet Device At 2ghz, Saalini Valli Sekar

Retrospective Theses and Dissertations

This thesis presents a way to make nonlinear device measurements for a power MESFET device using the load pull system. The device was characterized at the fundamental and second harmonic frequencies during large signal operation. The data thus collected was used in designing the input and output impedance matching networks that would optimize the performance of the device. A power MESFET device like the one used to conduct this experiment is mainly used in designing power amplifiers for communication systems including the transmitters used in satellites. Therefore efficiency of the part is of the utmost importance. By characterizing the device ...


Characterization Of Actuator Behaviors Of Ferrogels Obtained From Physical And Chemical Cross-Linking Methods, Geunhyung Park Jan 2008

Characterization Of Actuator Behaviors Of Ferrogels Obtained From Physical And Chemical Cross-Linking Methods, Geunhyung Park

Retrospective Theses and Dissertations

Ferrogels are soft polymer materials containing a filler of magnetic particles that allow the material to be activated by magnetic fields. These materials have shown capabilities for large strains, fast response, ease of synthesis and biocompatibility and have potential applications including artificial muscles, controlled drug release systems, and hyperthermia cancer treatment. In this work, the actuator behavior for a selection of ferrogel compositions and synthesis methods are characterized including their free strain and loading behavior. Samples were synthesized using either chemical or physical methods using Sodium Tetra-borate (Na2B4O7 · 10(H2O)) or freeze-thaw cycle, respectively. Compositions consisting of PVA of 4 ...


Computer Aided Process Planning For Rapid Prototyping Using A Genetic Algorithm, Alex Renner Jan 2008

Computer Aided Process Planning For Rapid Prototyping Using A Genetic Algorithm, Alex Renner

Retrospective Theses and Dissertations

This thesis presents a new method for Computer Aided Process Planning (CAPP) for a subtractive Rapid Prototyping (RP) process. The "CNC-RP" process uses a 4-axis CNC machining center to create parts with flat end-mills. The objective is to determine the optimal system parameters for the RP process - those that enable parts to be created in a shorter amount of time. Two main contributions make this possible. First, a method of generating different machining orientation sets enables the part to be created with the same level of safety and quality available with the current system. Second, machining time is related to ...


Effects Of Substrate And Co-Culture On Neural Progenitor Cell Differentiation, Erin Boote Jones Jan 2008

Effects Of Substrate And Co-Culture On Neural Progenitor Cell Differentiation, Erin Boote Jones

Retrospective Theses and Dissertations

For stem and progenitor cells to become clinically useful, the factors that influence their differentiation must be better understood. The interaction between progenitor cells and their environment is thought to be one of the main influences on differentiation. This thesis examines the effects of media conditioned by primary astrocytes and extracellular matrix protein surface coatings on the differentiation of neural progenitor cells.


An Adaptive Quadrature-Free Implementation Of The High-Order Spectral Volume Method On Unstructured Grids, Robert Evan Harris Jan 2008

An Adaptive Quadrature-Free Implementation Of The High-Order Spectral Volume Method On Unstructured Grids, Robert Evan Harris

Retrospective Theses and Dissertations

An efficient implementation of the high-order spectral volume (SV) method is presented for multi-dimensional conservation laws on unstructured grids. In the SV method, each simplex cell is called a spectral volume (SV), and the SV is further subdivided into polygonal (2D), or polyhedral (3D) control volumes (CVs) to support high-order data reconstructions. In the traditional implementation, Gauss quadrature formulas are used to approximate the flux integrals on all faces. In the new approach, a nodal set is selected and used to reconstruct a high-order polynomial approximation for the flux vector, and then the flux integrals on the internal faces are ...


Improving Solution Characteristics Of Particle Swarm Optimization Through The Use Of Digital Pheromones, Parallelization, And Graphical Processing Units (Gpus), Vijay Kiran Kalivarapu Jan 2008

Improving Solution Characteristics Of Particle Swarm Optimization Through The Use Of Digital Pheromones, Parallelization, And Graphical Processing Units (Gpus), Vijay Kiran Kalivarapu

Retrospective Theses and Dissertations

Deterministic optimization methods such as steepest descent, conjugate gradient and Newton's methods are known for their robustness in iteratively reducing the objective function value for minimization problems. However, they are primarily suitable for solving single objective function problems that are unimodal and continuous. With increased sophistication in engineering problems, multimodal and multi-objective problems have become more prevalent drastically reducing the effectiveness of deterministic methods. This led to the development of heuristic methods, particularly evolutionary methods such as Genetic Algorithms, Ant Colony Optimization, and Particle Swarm Optimization. These methods have multiple design points exploring the design space over iterations as ...


Evaporation Induced Self-Assembly Of Ordered Structures From A Capillary-Held Solution, Suck Won Hong Jan 2008

Evaporation Induced Self-Assembly Of Ordered Structures From A Capillary-Held Solution, Suck Won Hong

Retrospective Theses and Dissertations

The use of spontaneous self-assembly as a lithography and external fields-free means to construct well-ordered, often intriguing structures has received much attention as a result of the ease of producing complex structures with small feature sizes. Self-assembly via irreversible solvent evaporation of a droplet containing nonvolatile solutes (polymers, nanoparticles, and colloids) represents one such case. However, the flow instabilities within the evaporating droplet often result in irregular dissipative structures (e.g., convection patterns and fingering instabilities). Therefore, fully utilizing evaporation as a simple tool for creating well-ordered structures that have numerous technological applications requires delicate control over several factors, including ...


Phased Array System Design, Shannon Wanner Jan 2008

Phased Array System Design, Shannon Wanner

Retrospective Theses and Dissertations

This dissertation presents a new architecture for controlling the amplitude and phases of signals in a fully integrated phased array system. The phase shifting is performed at baseband and is up-converted to a RF band using a phased locked loop as a frequency synthesizer which allows for precise control of the RF phases. A structure for a phase aid is presented for a fast phase hopping system. A mathematical model was shown for an adjustable amplification within a phased locked loop to mitigate phase distortion. A mutual coupling correctional network was proposed to mitigate pattern distortion induced from the active ...


Systems Approach Based Solution To Fundamental Limitations In Unraveling Spatial And Temporal Regimes In Nano-Interrogation And Nano-Positioning, Tathagata De Jan 2008

Systems Approach Based Solution To Fundamental Limitations In Unraveling Spatial And Temporal Regimes In Nano-Interrogation And Nano-Positioning, Tathagata De

Retrospective Theses and Dissertations

A design scheme that achieves an optimal tip-sample force regulation with an ideal topography image reconstruction is presented. It addresses the problem of obtaining accurate sample profiles when scanning at high bandwidth while maintaining a constant cantilever-tip sample force in atomic force microscopes. It is shown that the proposed scheme provides a faithful replica of the sample at all relevant scanning speeds limited only by the inaccuracy in the model for the atomic force microscope. This provides an improvement over existing designs where the sample profile reconstruction is typically bandwidth limited. The experimental results corroborate the theoretical development.;Conventional imaging ...


Noise Analysis For Switched-Capacitor Circuitry, Yingkun Gai Jan 2008

Noise Analysis For Switched-Capacitor Circuitry, Yingkun Gai

Retrospective Theses and Dissertations

Track and hold circuits play a key role in mixed-signal, analog to digital interfaces. They are often used as part of the analog to digital conversion (ADC) process whereby a time-varying analog signal is sampled at the transition of a clock signal and subsequently held for a part of the conversion process. This approach is used, in part, because the remainder of the ADC conversion process is adversely affected if the input signal varies during the conversion.;Noise, and in particular thermal noise, is recognized as a major bottleneck limiting the performance of switched-capacitor circuits and it is essential that ...