2018 MU theses - Access restricted to MU
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Item Development of a dual frequency, folded topology, dielectric waveguide lens antenna(University of Missouri--Columbia, 2018) Lamb, Barrett A.; Curry, Randy D.[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI-COLUMBIA AT AUTHOR'S REQUEST.] There is an emerging need for antennas capable of operating in the field of high power microwaves (HPMs) especially those which exhibit high gain, wide bandwidth, and steering. Conventional high gain antennas are often based on large and heavy metal structures which may be reflector based. The weight of a simulated all metal antenna design with the desired gain, bandwidth, and steering was calculated as between 2,000 and 4,000 pounds. Due to a 400-500-pound weight constraint an innovative approach based on a nanodielectric material developed by the Center for Physical and Power Electronics was evaluated. A radiating lens for high power RF has been developed using MU100, a nanocomposite, which exhibits both a high dielectric strength ([approximately] 250 kV/cm) and a high dielectric constant ([approximately] 100) along with a ceramic anti-reflection layer. The material can be manufactured reproducibly in a range of sizes and can be machined to the desired shape. A ceramic with a dielectric constant (10) is utilized between the nanocomposite and the target medium to construct a graded lens capable of coupling to a variety of mediums by adjusting the lens. These lens elements are constructed into an 8x16 element design with a simulated gain of 26.6 dBi with a 3.5 m2 aperture and 0.2 m depth at 1.35 GHz. The antenna system can operate over a wide bandwidth of approximately 250 MHz in the L-Band (1-2 GHz) with a voltage standing wave ratio (VSWR) beneath 1.5 while weighing approximately 400 pounds.Item The relationship between pupil diameter changes and vehicle accidents in a driving simulator environment(University of Missouri--Columbia, 2018) Tang, Rui; Kim, Jung Hyup[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI-COLUMBIA AT AUTHOR'S REQUEST.] The purpose of this study is to explore the relationship between changes in pupil diameter at the moment of a vehicle accident and the severity of the accident. Drivers' pupil diameters were analyzed using an eye-tracking device within a driving simulation environment. The diameter of a pupil changes not only in response to light, but also in response to other factors involving both cognitive and emotional activities. In this study, we hypothesize that the patterns of pupil diameter changes could serve to indicate when an accident occurs as well as the severity of the accident. To investigate the relationship between the drivers' pupil diameter and the seriousness of a car accident, multiple hazardous events were tested in a driving simulation environment. The eye-tracking technology was applied to measure and analyze changes in a driver's visual attention level and pupil dilation during vehicle accident events. The patterns of pupil diameter changes were compared based on the severity of car accidents. The experiment results showed that there was a significant difference in pupil dilation patterns between minor crashes and severe crashes. The slope of the pupil diameter change in major vehicle accidents is steeper than in minor vehicle accidents. Furthermore, the results from the vehicle accident videos and pupillary data show that the drivers attention level and the time to collision have a significant impact on the pattern of pupil diameter changes. The findings of this study provide a new way to develop human-centered driver assistant systems and improve the speed of roadside rescues when an accident occurs. This study will also contribute to the development of an algorithm to measure accident severity levels and better inform emergency medical personnel to enable them to deal with car accidents quickly and efficiently.Item Investigation of finger plate expansion devices behavior(University of Missouri--Columbia, 2018) Mutnbak, Mohammed; Salim, Hani A., 1966-[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI-COLUMBIA AT AUTHOR'S REQUEST.] Finger plate expansion devices are frequently used to account for medium and large expansive or contractive movements and reasonable rotations of two bridge deck slabs. Under high traffic volume, these expansion devices experience some premature damage that affects the structural integrity of the joint, which causes safety concerns for vehicular traffic. Therefore, a group of experimental tests and 3D elastic-plastic finite element models (FEMs) were conducted in this thesis to study the structural behavior and modes of failure of finger plate expansion devices. The experimental results were also used to validate the FEMs of the finger plate expansion devices, from which additional FEM models were evaluated to study the effects of various design parameters. There is a good agreement between the experimental measurements and numerical results. In general, welding zones were the sites of crack initiation in most of the cases studied. The numerical results showed that the site of the highest stress concentration was in the weld between the finger plate and the supporting beam top flange. Other sites of stress concentrations were located at vertical stiffener weld and finger base curve. To study the effects of finger thickness, stiffeners presence in both sides of the support beam, a stiffener in the front side and back side of the beam, and supporting beam dimensions, a parametric study was conducted using the validated FEM. The results of the parametric study showed that the finger thickness did not influence the response in the absence of stiffeners. On the other hand, the presence of stiffeners increased the finger plate expansion device stiffness, while decreased the device ductility. All cases investigated in the parametric study indicated that welding areas were the sites of stresses concentrations and failure initiation.Item Exploring factors that affect customer satisfaction and dining intention in hotel restaurants compared to stand-alone restaurants(University of Missouri--Columbia, 2018) Liu, Wanying; Liu, Pei[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI-COLUMBIA AT AUTHOR'S REQUEST.] With the change of time, more and more hotels have chosen to operate food and beverage departments as separate revenue sectors from room departments, aiming to increase the total revenue. In other for hotel restaurant managers to better operate their properties, the process of customer behavior need to be understood. Nevertheless, the extant literature focused on stand-alone restaurants, and limited research has been conducted regarding consumer behavior in hotel restaurant industry. Considering the great differences between stand-alone restaurants and hotel restaurants, this research explores factors affecting customer satisfaction and dining intention in hotel restaurants compared to stand-alone restaurant. The results of this study proved that food and beverage quality, service quality, servicescape, price fairness, restaurant image, and local food accessibility positively affects customer satisfaction in hotel restaurants, and that food and beverage quality, servicescape, price fairness, restaurant image, and locational convenience have significant positive effect on dining intention in hotel restaurants. Whereas in the stand-alone restaurant subsample, the results indicated that food and beverage quality, service quality, servicescape, price fairness, and restaurant image have significant positive effect on customer satisfaction in stand-alone restaurants, and that food and beverage quality, price fairness, and locational convenience have significant positive effect on dining intention. Moreover, customer satisfaction was also verified to have a significant positive effect on dining intention in both types of restaurants.Item The influence of fusarium species on sweet potato plant performance, root yield and quality(University of Missouri--Columbia, 2018) Kaluwasha, Waana; Xiong, Xi[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI-COLUMBIA AT AUTHOR'S REQUEST.] Sweet potato (Ipomoea batatas (L.) Lam.) is a global important food crop, that has recorded an increase in the consumption, and demand for especially organically produced sweet potatoes in recent years. Organic sweet potato growers however, face challenges due to the limited options available to manage soilborne diseases and pests that reduce sweet potato root yield and/or quality, of which Fusarium spp. are a common culprit. This presents a growing need for information under an organic sweet potato production system. The first part of the study evaluated five commonly grown sweet potato cultivars for their tolerance to Fusarium isolates, as well as their yield under field conditions over a two year period. The study revealed that infection by Fusarium isolates resulted in reduced plant vigor, which varied among cultivars. Similarly, the occurrence of Fusarium root rot in storage varied among cultivars, with Centennial proving to be most susceptible compared to Covington. An invitro inoculation study then demonstrated the potential use of Fourier Transform Infrared Spectroscopy to detect changes in root quality following infection by Fusarium. The last part of the study was conducted in collaboration with an organic sweet potato grower to develop a strategy of using cover and/or green manure crops, by evaluating their effects on plant health, weed suppression and root yield in organic production systems. The results showed that tilling the cover crops into the soil as green manure prior to transplanting sweet potato slips resulted in healthier sweet potato plants, greater weed suppression and greater root yield compared to plots without cover crops. Collectively, cultivar selection and incorporation of cover crops in sweet potato production could minimize the effects caused by Fusarium spp.