Doubly fed induction generators (DFIG) are widely used in wind power generation because of their ability to be operated at varying rotational speeds while producing power output at a constant frequency. Electrical dynamics of a DFIG is modeled using field oriented control and represented as fourth order system. This fourth order dynamics exposes a two-time scale behavior. Using singular perturbation techniques the time scales can be separated as slow and fast subsystems. Feedback control schemes can be designed and the closed-loop stability of each model can be compared. In this work, a linear quadratic feedback controller is designed for the DFIG electrical dynamics using exact, reduced order and composite models. The performances of the closed loop models are compared based on the system cost. The robustness and reliability of the control schemes are analyzed for each controller designs based on the nominal system. Based on the analysis and results, the reduced order controller performance is equally as good as the exact and composite designs during steady state operations. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

Older adults speak 20-30% slower than younger adults. A decline in articulatory speed capacity has often been suggested; however, direct investigations on speech motor performance have rarely been conducted. Therefore, this study sought to determine if jaw speed capacity is reduced in older adults. This study included 36 female participants in four age groups: young adult, middle-aged, young-old, and very old. Each participant completed a jaw oscillation task at seven metronome paces. Similar to previous studies on upper limb speed capacity, participants were asked to tap a fixed target with their jaw at each metronome beat. The metronome pace determined the jaw movement duration and the target determined the jaw movement excursions during the experimental conditions. Jaw peak speeds, excursion, and movement durations during the jaw closing strokes were compared between the four age groups. Study outcomes showed that jaw speed capacity was significantly lower in the youngest age group relative to all other age groups. Jaw speed capacity did not significantly differ between middle-aged, young-old, and very old adults. These findings contrasted previous reports of aging studies on limb speed capacity. Further, these findings on jaw speed capacity suggested that jaw peak speed may not be a factor that contributes to a slowed speaking rate in older adults. In the future, jaw speed capacity of male speakers needs to be investigated. Further, aging-related changes in tongue and lip speed capacities also should be determined to gain more comprehensive insights in physiologic factors that may affect speaking rates of older adults. / Thesis (M.A.)--Wichita State University, College of Health Professions, Dept. of Communication Sciences and Disorders

Marshall Mortimer Murdock was one of the most compelling and controversial figures in all of Kansas history. Best known perhaps for establishing the Wichita Eagle in 1872, a newspaper whose primary business it was—as it was in fact for so many newspapers of its time—to ‘boost’ the city which carried its name, Murdock was in fact a newspaper man, a booster, first and foremost. Marshall Murdock, however, was more than just a “master town-builder,” as his friend and colleague, David Leahy, once remarked. Murdock was both essential to and responsible for Wichita’s early successes, and by extension, its near demise and consequent rebuilding in the boom to bust days of the 1880s. Marshall Murdock’s high profile, high powered, and highly charged editorial style was but a microcosm of the man himself. In a life, which embraced his role as Soldier, Statesman, Politician, Printer, Murdock was an archetype of the Gilded Age; he remained unabashedly conservative in politics and principle and sought to encourage always and compel as necessary others in his orbit to champion this same world view. Murdock was to the end of his days a true believer in both the Wichita he knew and the Wichita he envisioned. This was Murdock. / Thesis (M.A.)--Wichita State University, College of Arts and Sciences, Dept. of History

Macrophomina phaseolina, an internationally distributed fungal pathogen, causes a disease known as “charcoal rot” (also known as dry-weather wilt and summer wilt) that clogs vascular tissue and produces yellow, wilted plants with visible fungal sclerotia. Primarily acting in dry, hot conditions, it inflicts extensive economic losses in Midwestern crops such as soybean, alfalfa, sorghum, and cotton. To better understand the molecular mechanisms of the disease a model pathosystem was established using Medicago truncatula to study host-pathogen interactions. 319 ectoypes of M. truncatula were screened using a root-dip method to identify potential variations in host susceptibility (either unusual susceptibility or resistance) to M. phaseolina in hopes of revealing naturally existing genetic variations that can lead to host resistance. In this screen, all ecotypes showed normal disease progression compared to a reference genotype, Jemalong A17. Previous study showed that treatment with jasmonic acid (JA) and ethylene (ET) confer increased resistance to A17 but not to R108, another widely used M. truncatula genotype. To test the hypothesis that the difference in disease progression in A17 and R108 after exogenous treatment with JA and ET was due to differential regulation of the JA/ET pathways in these genotypes, expression of genes representing the JA and ET pathways were compared in A17 and R108 after inoculation with M. phaseolina. The results showed that genes indicative of the JA pathway were induced both faster and stronger in A17 than in R108, and marker genes representing ET pathway were more strongly upregulated in A17 than in R108. Since many of the marker genes used in this study are related to fungal defense and considering that the JA and ET pathways regulate plant defense genes, including those with antifungal properties, it is likely that the varying induction of JA and ET pathways is involved in the different hormonal responses between A17 and R108 to M. phaseolina infection. Testing that hypothesis requires further study of how these marker genes respond to exogenous JA and/or ET treatment in A17 and R108. / Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Biology

5S is a lean tool, which is a visual housekeeping technique that can be implemented in a shop floor to eliminate waste and improve the process. The performance of the 5S tool in a workplace is evaluated using a 5S audit checklist and the observers perform the evaluation. The scores of the completed checklist reflect the performance of 5S tool in the workplace. A study by Natarajan (2011) has shown that the current 5S audit checklist commonly being used in aerospace had low rater-reliability scores in a particular scenario. Therefore the objective of this thesis was to improve the reliability for the 5S audit checklist. First, the content validity of the checklist was tested with the help of five industry people and the checklist was modified. Then, a training procedure was developed on how to rate a workplace using the modified audit checklist. Then a study was performed to test the reliability of the modified checklist. For the study two groups of students were selected as raters. The first group, the control group, did not receive any training. The control group was asked to rate a virtual reality model of a factory workplace using the modified checklist. The second group, the experimental group, received the specially developed training on how to rate a workplace and was asked to rate the same virtual reality model. This study was performed again with a time gap of 3 weeks and the experimental group dint receive any training while doing it for the second time. The obtained results were analyzed using SPSS software and the control group results showed that the modified checklist had impact on improving the rater-reliability scores of the modified checklist but the experimental group results showed that training the raters has helped in improving the rater-reliability of the modified checklist. This suggests that training the raters before audits could produce good results because training will create a common frame of reference within the raters. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Industrial and Manufacturing Engineering

Rapid lateral facies and thickness changes, autogenic processes, and irregular topography of nonmarine rift basins challenge the application of traditional marine sequence stratigraphic techniques. Stratigraphic architecture may be reconstructed with a process-based approach, using interpreted climatic and tectonic controlling processes on sedimentation in addition to observable attributes to correlate sedimentary cycles. This hypothesis is tested for Lower Permian Lucaogou and Hongyanchi low-order cycles (LCs) in the Tarlong-Taodonggou half graben, using outcrop and petrographic data. The exposed graben fill covers 88 km². Depositional environments and controlling sedimentary processes were interpreted on five measured sections, 0.2 – 5 km apart. Microscopic and X-ray Diffraction data on grain composition and texture substantiate field interpretations and minimize stratigraphic miscorrelation. Humid to arid climatic conditions were interpreted using climate-sensitive lithologies, such as paleosols; tectonic movements were interpreted in terms of source area uplift, basin subsidence, and spill-point movement. The Lucaogou-Hongyanchi LC boundary (LCB) separates uppermost Lucaogou fluctuating profundal lacustrine high-order cycles (HC) from basal Hongyanchi fluvial-deltaic HCs, indicating drastic environmental change. The LCB is an erosional unconformity across which the type and magnitude of facies shifts varies greatly across the half-graben. A process based sequence-stratigraphic reconstruction across the LCB enables reconstruction of the three dimensional distribution of lithofacies across the boundary, and provides insights to the potential causes for drastic environmental change. A better understanding of the nature and origins of the LCB may be applicable to other similar nonmarine rift basins. / Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Geology

With the world’s growing use of autonomous unmanned aerial systems (UASs), there is also a growing need for higher education to teach students how to design and implement the autopilot systems that many of these UASs depend on to perform their designed missions. Given the inherent cost and complexity of these systems, it has been difficult in recent years to provide students the hands-on experience that is crucial to understanding how these autopilot systems work. Another stumbling block to implementing this type of education has been the proprietary nature of autopilots, which restricts the ability to modify/enhance the autopilot. The good news is that autopilot-related components continue to become lighter and cheaper, which has created the development of open software/hardware platforms. Arduino is one such microcontroller that has come to the forefront as a leader in the open software/hardware autopilot system market. The goal of this study was to determine whether or not an Arduino-based autopilot system would be a viable candidate for implementation into higher education at a design level. A series of flight tests were performed to discover the strengths and weaknesses of this product in order to help determine how easy or difficult it would be to integrate it into undergraduate studies. Results from the flight tests show that this autopilot system is fairly robust and has a wide range of functionality. Through these tests, it has been concluded that the Arduino-based ArduPilot-Mega microcontroller would be a worthwhile educational tool and is an inexpensive alternative to proprietary autopilot systems. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering

Virtualization is one of the key technologies which help in server consolidation, disaster recovery, and dynamic load balancing. The ratio of virtual machine to physical machine can be as high as 1:10, and this makes caching a key parameter, which affects the performance of Virtualization. Researchers have proposed the idea of having an exclusive hypervisor cache at the Virtual Machine Monitor (VMM) which could ease congestion and also improve the performance of the caching mechanism. Traditionally the Least Recently Used (LRU) algorithm is the cache replacement policy used in most caches. This algorithm has many drawbacks, such as no scan resistance, and hence does form an ideal candidate to be utilized in the hypervisor cache. To overcome this, this research focuses on development of a new algorithm known as the “Probability Based Cache Replacement Algorithm”. This algorithm does not evict memory addresses based on just the recency of memory traces, but it also considers the access history of all the addresses, making it scan resistant. In this research, a hypervisor cache is simulated using a C program and different workloads are tested in order to validate our proposal. This research shows that there is considerable improvement in performance using the Probability Based Cache Replacement Algorithm in comparison with the Traditional LRU algorithm. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science

Automotive crash has garnered significant attention in the recent years with increasing fatality and safety concerns. Substantial effort and great amount of time and expertise has been directed towards the issues related to crashworthiness such as impact, rollover scenarios and restraint performance. Automotive rollover is one of those important concerns for the auto industry as the fatality rates and death causing conditions are vital compared to other crashes. In the past few decades, research has been focused towards developing efficient roof structure by implementing crashworthy structures, to protect or at least reduce the severity of the accident to the occupants of the vehicle during an event of a rollover. Studies have been carried in this area in developing efficient crashworthy structures. As the technology is evolving, researchers have found that thin walled tubes filled with foam materials possess high energy absorption properties compared to empty crashworthy structures. Further research in this has area led to the interference of nanotechnology, which implements emerging techniques in developing advanced materials for engineering applications. Scientists were able to develop low density, lightweight foams with high energy-absorption characteristics with these techniques. The purpose of this thesis is to analyze and evaluate the performance of low density carbon nanofoam (CNF) as an energy absorbing material in improving the roof strength of the vehicle. The LS- DYNA code, a non-linear dynamic finite element solver is utilized to accomplish this study. First, a three- point bending test simulation is carried as component level testing to analyze the behavior of foam materials. Then, the energy absorbing characteristics of a hollow tube is studied and the results are compared with regular polyurethane (PU) foam and carbon nanofoam inserts into the hollow tube, under similar conditions. Finally, PU foam and CNF is applied into the critical areas of roof supporting structures as two different conditions and static roof crush and dynamic inverted drop test simulations are conducted depicting an actual rollover scenario to study the crashworthy behavior of the vehicle roof with and without the foam. This study highlights that carbon nanofoam is found to be more effective compared to the regular polyurethane foam exhibiting better energy absorption characteristics. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering

Storage resources are being consolidated and have led to the increased demand in sharing storage, depending on the type of application or class of customers. In such a scenario, cache consolidation becomes increasingly necessary. An analysis of cache utilization at various levels in a Storage Area Network such as the server cache, the virtual machine cache, and the array controller cache was done, drawing conclusions from the response time and execution time. A proposal is made for dynamic cache allocation algorithm in a virtualization environment, which takes into account the usage trends and varies the allocation depending on the type of the workload. The dynamic cache allocation algorithm helps in adapting the cache space available for a particular virtual machine based on the number of requests and the cache miss affected, with respect to a threshold value which is individual to each VM. The caching mechanism proposed in this work is an isolated, unshared, dynamic cache, where caching is done on the hypervisor instead of the virtual machines. Also, we prove by experimental results that a static allocation of the cache is not suitable for a varying workload in a virtualized setup. / Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science