Digital Commons Network^™

An Analysis Of Driver Behavior In Response To Warning Beacon Installations On Stop Signs, Qilin Liu

Graduate Theses and Dissertations

Driver gap selection was a principal safety concern at stop-controlled rural intersections. Previous study shows that intersection crashes account for 30 percent of severe crashes and 40 percent crashes happening in rural intersections. Stop sign mounted beacons were installed and evaluated at six selected rural intersections in Iowa. Data were collected before and after installation. The treatments were evaluated by comparing brake activation distance. A two-sample test of means was applied on brake activation distance and logistic regression models were developed to compare driver behavior between before and after installation. The analysis considered differences in driver stopping behavior, including where ...

Choosing Cutoff Values For Correlated Continuous Diagnostic Data To Estimate Sensitivity And Specificity, Yingzhou Du

Graduate Theses and Dissertations

This dissertation includes two projects and an R package for the 1st project, focusing on choosing cutoff values to estimate the sensitivity and specificity for continuous diagnostic tests. A continuous diagnostic test needs to be dichotomized to generate positive and negative test outcomes by choosing a cutoff value. The choice of the cutoff value depends on the estimates of the sensitivity and specificity of the dichotomized test with this cutoff. There are two challenges during this process: 1) a typical experiment to validate a new diagnostic test usually involves multiple observations from the same subjects, resulting in correlated data values ...

Self-Exciting Spatio-Temporal Statistical Models For Count Data With Applications To Modeling The Spread Of Violence, Nicholas John Clark

Graduate Theses and Dissertations

In this dissertation we provide statistical models and inferential techniques for analyzing the number of violent or criminal events as they evolve over space and time. Our research focuses on a class of models we refer to as self-exciting spatio-temporal models. These are a class of parametric models that allow for dependence in a latent structure as well as dependence in the data model combining what is sometimes referred to as observation driven and parameter driven models. This class of models arise from straight-forward assumptions on how violence or crime evolves over space and time and has use in the ...

An Examination Of Ash Elutriation From A Fluidized Bed Regenerator, Dane Erickson

Graduate Theses and Dissertations

The danger of climate change looms in the minds of researchers across the world. To combat this threat, many have focused efforts on the development of clean energy. In this study, the renewable resource that is investigated is biomass, specifically red oak. Energy can be extracted from biomass by fast pyrolysis, where the feedstock is rapidly heated within a reactor to approximately 500℃ in the absence of oxygen. This produces biochar, ash, and condensable gases that, once cooled, become a bio-oil. To optimize economic feasibility, the process must operate continuously. This presents a problem—the presence of ash as a ...

A Design Anthropology Approach To Understanding Human Wildlife Relationships: Monkeys, Local Development And Participant Conservation In Southest Costa Rica, Yibo Fan

Graduate Theses and Dissertations

This project uses a combined methodology of participatory design and ethnographic fieldwork to study human-wildlife relationships and explore better ways to design and implement a monkey crossing bridge in the area of Talamanca, Costa Rica. It also examines how an interdisciplinary methodology can identify the needs of three species of monkeys and local beliefs, and to integrate these things into project design. The project not only answers how participatory design might promote a favorable human-wildlife relationship, but also explores local beliefs about development and conservation. Based on my research, I argue that the design of the bridge and the process ...

An Fpga-Based Hardware Accelerator For Iris Segmentation, Joseph Avey

Graduate Theses and Dissertations

Biometric authentication is becoming an increasingly prevalent way to identify a person based on unique physical traits such as the fingerprint, the face, and/or the iris. The iris stands out particularly among these traits due to its relative invariability with time and high uniqueness. However, iris recognition without special, dedicated tools like near-infrared (NIR) cameras and stationary high-performance computers is a challenge. Solutions have been proposed to target mobile platforms like smart phones and tablets by making use of the RGB camera commonly found on those platforms. These solutions tend to be slower than the former due to the ...

Analysis Of High Temperature Effects On Piezoelectric Based Ultrasonic Transducers, Prathamesh Bilgunde

Graduate Theses and Dissertations

Under sodium viewing (USV) using ultrasonic pulse-echo techniques offers the potential for the inspection of generation IV, liquid sodium-cooled fast reactors (SFRs) at the hot stand-by temperature (260C). However, the harsh environment effects on the transducer reduce the ultrasonic signal strength which also limits the probability of detection (POD) of the defects.

Current work presents a unified modeling and measurement-based methodology to analyze the high temperature effects on the transducer components. Resonance analysis-based characterization has shown that the conventional d33 piezoelectric parameter is not a sufficient condition to estimate resonance characteristics of high temperature ultrasonic transducers. A full piezoelectric material ...

Development Of A 3d Conceptual Design Environment Using A Commodity Head Mounted Display Virtual Reality System, Gabriel Evans

Graduate Theses and Dissertations

Design processes for engineered systems are resource intensive and have a significant impact on a product’s profitability. Over half of a product’s total costs can be attributed to design stage decisions. The development of product designs often involves creating complex 3D models in a 2D environment, a non-trivial task. Current design workflows involve the utilization of robust modeling software on a 2D display. However, previous research highlights the benefits of visualizing full-scale 3D models in an immersive Virtual Reality (VR) environment. These environments aid a user in understanding complex 3D geometry. Despite the benefits of VR, these systems ...

The Effect Of Delivery Mode On L2 Students' Listening Comprehension Skills: Context Versus Animated Videos, Leyla Karatay

Graduate Theses and Dissertations

This study investigated the effect of different delivery modes on L2 students’ listening

comprehension. A mixed-methods explanatory research design was used to identify whether

animated videos or context videos facilitated better listening comprehension. Fifty-seven ESL undergraduate/graduate students were recruited from an academic speaking and pronunciation course offered at Iowa State University. The effectiveness of the delivery modes was assessed by the participant’s ability to orally summarize the videos. Two trained raters were recruited to rate participants’ audio-recorded summaries. A one-way ANOVA was used to test for a significant difference between mean scores of the two groups. Also, students ...

Lichen Diversity And Conservation Of Northeast Iowa: White Pine Hollow State Preserve And The Lichen Lobaria Pulmonaria, Kathleen M. Thompson

Graduate Theses and Dissertations

A lichen diversity survey of White Pine Hollow State Preserve in Dubuque County, Iowa, was conducted. The study revealed the presence of 117 different lichens, which, when combined with previous records, leads to a total of 147 lichens reported for the preserve. The lichens observed in this study included 13 previously unreported lichens for the State of Iowa and three reported on only one prior occasion. This increases the number of lichens reported for the State of Iowa to a total of 478 from the previous estimate of 465.

The lichen Lobaria pulmonaria (L.) Hoffm. was not amongst the lichens ...

A Worm's Tale: An Evaluation Of The Natural History And Infectious Dynamics Of Parasitodiplogaster Nematodes, Justin Michael Van Goor

Graduate Theses and Dissertations

Mutualisms are interspecific interactions in which the fitnesses of each partner benefit from the association. Mutualisms are ubiquitous and ecologically important in nature and, as a result, a wealth of theoretical and empirical research has been conducted to better understand the interactions between mutualistic partners. However, mutualists are commonly associated with a broader community of interacting organisms that may antagonize, destabilize, or limit the fitness of these partners. In addition to the consistent community-level pressures, organisms must ensure their own fitness through proper sex ratio allocation even if mating patches are isolated and the potential numbers of reproductive individuals are ...

Use Of Cellular Automata-Based Methods For Understanding Material-Process-Microstructure Relations In Alloy-Based Additive Processes, Matthew Rolchigo

Graduate Theses and Dissertations

Deposition of metals through additive manufacturing has garnered research interest as of late due to the large range of potential industry applications. In particular, direct metal deposition processes such as Laser Engineered Net Shaping (LENS) have the ability to construct near net shape parts, open cellular structures, compositionally graded parts, and parts with improved mechanical properties over those manufactured via traditional methods such as casting and forging. To utilize additive processes to their full potential, it is imperative that the relationships among process parameters, development of the molten pool, microstructure, and properties are understood. Our goal in applying computational modeling ...

The Effect Of Manure Application Timing On The Persistence Of Phenotypic And Genotypic Antibiotic Resistance In Tile-Drained Hapludolls, Elliot George Rossow

Graduate Theses and Dissertations

The application of swine manure to agricultural fields increases the abundance of antibiotic resistance genes (ARG) and antibiotic resistant bacteria (ARB) in soils. While manure-associated antibiotic resistant bacteria persist following application, there is potential for their transport through tile drainage. The environmental survival of bacteria in soil has been related to moisture and temperature, therefore differences in these environmental conditions between spring and fall soils may cause manure associated antibiotic resistance to behave differently following application. This encouraged exploring differences in the persistence of antibiotic resistant bacteria and antibiotic resistance genes in soil when manure is applied at different times ...

Exploring Granger Causality In Dynamical Systems Modeling And Performance Monitoring, Homagni Saha

Graduate Theses and Dissertations

Data-driven approaches are becoming increasingly crucial for modeling and performance

monitoring of complex dynamical systems. Such necessity stems from complex interactions

among sub-systems and high dimensionality that render majority of rst-principle based

methods insucient. This work explores the capability of a recently proposed probabilistic

graphical modeling technique called spatiotemporal pattern network (STPN) in capturing

Granger causality among observations in a dynamical system. In this context, we introduce

the notion of Granger-STPN (G-STPN) inspired by the notion of Granger causality. We

compare the metrics used in the two frameworks for increasing memory in a dynamical

system, and show that the metric ...

Investigating Conference Attendee’S Mobile Application Adoption Behavior: An Ecological Perspective, Nripendra Singh

Graduate Theses and Dissertations

The fast growing conference industry has a positive impact on the economy. The industry has been criticized for its resource use intensity, and for having a negative impact on the environment. This study focused on understanding the predictors of green information system (conference apps) adoption behavior, which may help reduce negative environmental impact in future. While there was enough evidence of conference apps implementation by the conference industry, there was limited evidence of its adoption by conference attendees. Thus, the purpose of this study was to investigate conference attendees’ conference apps adoption behavior.

As conference apps are helpful in reducing ...

Investigation Of Fundamental Transport And Physicochemical Phenomena In Lignocellulosic Fast Pyrolysis, Jordan A. Tiarks

Graduate Theses and Dissertations

Fast pyrolysis of biomass has the potential for high-yield production of valuable fuels and chemicals from renewable biological and agricultural waste feedstocks. Optimization of this technology is dependent on developing a deeper understanding of the complex transport and kinetic phenomena which drive product formation. In this dissertation, direct, time-resolved imaging of feedstock degradation and product formation mechanisms for the pyrolysis of whole biomass and several of its components has been made inside an optically accessible pyrolysis reactor. The reactor thermal and transport characterization allows the determination of dominant mechanisms of pyrolysis product formation in the multiphase reacting environment. This novel ...

Secret Key Establishment From Common Randomness Represented As Complex Correlated Random Processes: Practical Algorithms And Theoretical Limits, Mohammad R. Khalili Shoja

Graduate Theses and Dissertations

Establishing secret common randomness between two or multiple devices in a network resides at the root of communication security. In its most frequent form of key establishment, the problem is traditionally decomposed into a randomness generation stage (randomness purity is subject to employing often costly true random number generators) and an information-exchange agreement stage, which relies either on public-key infrastructure or on symmetric encryption (key wrapping).

This dissertation has been divided into two main parts. In the first part, an algorithm called KERMAN is proposed to establish secret-common-randomness for ad-hoc networks, which works by harvesting randomness directly from the network ...

Value Of U.S. Higher Education Among Students From China And Russia, Inna Kuznetsova

Graduate Theses and Dissertations

Chinese students are currently the largest group of international students pursuing higher education in the U.S. The number of Chinese students has been steadily increasing in the last decade, but many researchers warn that international student mobility should not be taken for granted. Other countries such as the U.K, Australia, New Zealand, and Russia have established themselves as strong competitors in the unstable international higher education market. While many Russian students pursue higher education abroad, the number of Russian international students in U.S. higher education institutions is low. Given the multiple political, economical, and educational similarities between ...

Cross-Plane Thermal Transport In Graphene-Based Structures, Meng Han

Graduate Theses and Dissertations

Thermal transport properties in graphene and graphene-based materials have been extensively studied due to the extremely high intrinsic thermal conductivity of graphene and its broad applications. However, most of the research is focused on the mass production and thermal transport improvement, while the layered structure and the corresponding large anisotropy in thermal transport are lack of attention. In this work, several graphene-based structures are investigated to uncover the energy coupling between graphene and substrate and between graphene layers. The thermal conductance induced by few-layered graphene (Gr) sandwiched between β-phase tungsten (β-W) films is first studied. Our differential method is able ...

Evaluation Of Nitrogen And Potassium Interactions In Corn, Jackson Hirniak

Graduate Theses and Dissertations

Research is needed to further evaluate N by K interactions in crops. The objective of this study was to evaluate potential interactions in corn (Zea mays L.). Two long-term trials with continuous corn were evaluated from 2013 to 2017 in two Iowa soils. Annual treatments were the combinations of five N rates (0-336 kg N ha-1) and four K rates (0-66 kg K ha-1) replicated three times. Grain yield, ear-leaf (R1 stage) and grain (at harvest) N and K concentrations, N and K removed with grain harvest, and post-harvest soil-test K (STK) (15-cm depth) were measured each year. Leaf N ...

Exploration Of Alnico Permanent Magnet Microstructure And Processing For Near Final Shape Magnets With Solid-State Grain Alignment For Improved Properties, Aaron Gregory Kassen

Graduate Theses and Dissertations

Economic uncertainty in the rare earth (RE) permanent magnet (PM) marketplace as well as a quickly evolving electric drive motor market which has decided to leverage permanent magnet synchronous AC drive (PMAC) motors as the motor of choice, has driven renewed research in RE-free permanent magnets such as “alnico.” Alnico, essentially an Al-Ni-Co-Fe magnet alloy, was displaced for high energy density applications by RE-containing magnets in the 1970’s due to their high-energy performance and high coercivities.

The current PMAC development trajectory requires the development of a sustainable magnet material choice, which not only has impressive mechanical properties, such as ...

Real Options Models And Analyses For Energy Transportation Systems With Jump And Diffusion Processes: Electric Power Transmission Planning And Fuel-Carrying Ship Design, Fikri Kucuksayacigil

Graduate Theses and Dissertations

Investments in transportation sector have arisen as significant problems due to the substantial cost of maintaining required level of service. Energy transportation draws a particular attention. In this dissertation, we focus on two special forms of energy transportation problems. On the one hand, we study the quantification of value of expansion investments in high-voltage power lines. On the other hand, we quantify the value of expansion of capacities for U.S. Navy transportation ships. Problems are subject to severe uncertainties being in the form of smooth changes and discrete disruptions. We use geometric Brownian motion and Poisson arrival processes to ...

Investment Decision-Making In Clean Energy Under Uncertainties: A Real Options Approach, Yihua Li

Graduate Theses and Dissertations

International commitments on emission reduction and the deterioration of fossil energy resources have caused more research attention to clean energy production. Getting the optimal investment portfolio in infrastructure for energy supply and consumption is a minimum requirement to enable the transition towards a sustainable energy system. Due to their environmental benefits, advanced biofuel and clean power generation are expected to play an important role in the future in transportation sector and electricity sector, respectively. In this dissertation, a real options approach is adopted for valuating clean technology investment portfolios under uncertainty, exploring managerial insights, and examining policy implications. The dissertation ...

The Genetic Basis Of Feed Efficiency In Swine Divergently Selected For Residual Feed Intake, Emily Mauch

Graduate Theses and Dissertations

Feed efficiency is an economically important trait in the swine industry since feed accounts more than 50% of total production costs. A measure of feed efficiency, residual feed intake (RFI), is defined as the difference between observed and expected feed intake based on production and maintenance requirements. Since 2001 at Iowa State University (ISU), divergent selection for improved (Low RFI) and reduced feed efficiency (High RFI) has been conducted in Yorkshire pigs for ten generations. Using these selection lines, the over-arching objective of this dissertation was to further our knowledge of the biological and genetic basis of RFI in pigs ...

Genome Size Evolution And Domestication In Gossypium, Emma Ruth Miller

Graduate Theses and Dissertations

Genome size varies 64,000-fold across all eukaryotes, but the evolutionary forces that shape genome size are incompletely understood. Natural selection is likely acting on genome size, as inferred from correlations with various physiological and environmental factors. There is relatively little literature when it comes to studying the effects of artificial selection on genome sizes in domesticated crops. In this project, intraspecific variation was studied between wild and domesticated accessions in the genus Gossypium using flow cytometry. Whole genome resequencing data were also used to analyze repetitive elements for increased or decreased abundance. Both genome size and particular repetitive families ...

Interactions Of Mycoplasma Hyopneumoniae With Extracellular Traps, Clair Mitzelfeldt

Graduate Theses and Dissertations

Mycoplasma hyopneumoniae is the causative agent of enzootic pneumonia in swine. Infection with M. hyopneumoniae results in a mild, chronic disease and is further complicated by the establishment of other secondary infections. M. hyopneumoniae has finite biosynthetic capabilities, including a deficit in de novo nucleotide synthesis. Recent research has demonstrated that neutrophils can produce extracellular traps (ETs), chromatin nets decorated with granular proteins released into the extracellular environment for the purpose of interacting and sequentially eliminating pathogens. We hypothesized that M. hyopneumoniae was able to utilize a membrane nuclease to obtain nucleotides from extracellular traps to synthesize its own DNA ...

User-Packaging Interaction (Upi): A Comprehensive Research Platform And Techniques For Improvement, Evaluation, And Design, Ahmad Abdelhafiz Mumani

Graduate Theses and Dissertations

Users are expected to interact with their packages through product life cycles with either good or bad experiences, depending on packaging design, which can be characterized by physical and verbal features, such as size, shape, symbols, picture, etc. User packaging interaction (UPI) field has evolved with the aim to provide user-friendly packages, which support performing tasks such as, opening, handling, disposing, and checking-out. A great deal of work addressing issues, related to packaging, and suggesting potential improvements has been directed toward UPI. However, this work is not easily accessible to researchers as it lacks a cohesive structure of UPI stages ...

Data Augmentation For Supervised Learning With Generative Adversarial Networks, Manaswi Podduturi

Graduate Theses and Dissertations

Deep learning is a powerful technology that is revolutionizing automation in many industries. Deep learning models have a numerous number of parameters and tend to over-fit very often. Data plays a major role to successfully avoid overfitting and to exploit recent advancements in deep learning. However, collecting reliable data is a major limiting factor in many industries. This problem is usually tackled by using a combination of data augmentation, dropout, transfer learning, and batch normalization methods. In this paper, we explore the problem of data augmentation and common techniques employed in the field of image classification. The most successful strategy ...

The Role Of Biosolids-Derived Dissolved Organic Matter On The Interaction Of Selected Endocrine-Disrupting Chemicals With Two Alluvial Soils, Fritzie Rivas

Graduate Theses and Dissertations

Overpopulation is one of the major causes of many environmental problems we experience today. With increasing population, the demand for quality food and clean water is becoming difficult to realize. Although with advancement in technology, we are still able to cope with the demand, but eventually we will exhaust the supply for quality food and clean water as well as the different methods of achieving them.

Quality food and clean water are necessities to live. To help in delivering these needs, federal regulations and policies were developed and implemented to protect the public from environmental contaminants that might be hazardous ...

Remote Maintenance Assistance Using Real-Time Augmented Reality Authoring, Jonathan A. Schlueter

Graduate Theses and Dissertations

Maintenance operations and lifecycle engineering have largely been considered one of the most expensive and time-consuming components for industrial equipment. Numerous organizations continually devote large quantities of resources towards maintaining equipment. As such, any optimizations that would reduce maintenance errors and expenses could lead to substantial time and cost savings. Unfortunately, there are often not enough specialists to meet the demand, forcing localized technicians to perform on-site maintenance on equipment outside their area of expertise. Augmented reality (AR) is one technology that has already been shown to improve the maintenance process. While powerful, AR has its own set of challenges ...