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2019

Missouri University of Science and Technology

Doctoral Dissertations

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Articles 61 - 72 of 72

Full-Text Articles in Engineering

Freeform Extrusion Fabrication Of Advanced Ceramics And Ceramic-Based Composites, Wenbin Li Jan 2019

Freeform Extrusion Fabrication Of Advanced Ceramics And Ceramic-Based Composites, Wenbin Li

Doctoral Dissertations

"Ceramic On-Demand Extrusion (CODE) is a recently developed freeform extrusion fabrication process for producing dense ceramic components from single and multiple constituents. In this process, aqueous paste of ceramic particles with a very low binder content ( < 1 vol%) is extruded through a moving nozzle to print each layer sequentially. Once one layer is printed, it is surrounded by oil to prevent undesirable water evaporation from the perimeters of the part. The oil level is regulated just below the topmost layer of the part being fabricated. Infrared radiation is then applied to uniformly and partially dry the top layer so that the yield stress of the paste increases to avoid part deformation. By repeating the above steps, the part is printed in a layer-wise fashion, followed by post-processing. Paste extrusion precision of different extrusion mechanisms was compared and analyzed, with an auger extruder determined to be the most suitable paste extruder for the CODE system. A novel fabrication system was developed based on a motion gantry, auger extruders, and peripheral devices. Sample specimens were then produced from 3 mol% yttria stabilized zirconia using this fabrication system, and their properties, including density, flexural strength, Young's modulus, Weibull modulus, fracture toughness, and hardness were measured. The results indicated that superior mechanical properties were achieved by the CODE process among all the additive manufacturing processes. Further development was made on the CODE process to fabricate ceramic components that have external/internal features such as overhangs by using fugitive support material. Finally, ceramic composites with functionally graded materials (FGMs) were fabricated by the CODE process using a dynamic mixing device"--Abstract, page iv.


Laser Welding Of Metallic Glass To Crystalline Metal In Laser-Foil-Printing Additive Manufacturing, Yingqi Li Jan 2019

Laser Welding Of Metallic Glass To Crystalline Metal In Laser-Foil-Printing Additive Manufacturing, Yingqi Li

Doctoral Dissertations

"The application of metallic glasses has been traditionally limited to parts with small dimensions and simple geometries, due to the requirement of fast cooling during the conventional process of casting. In addition, joining metallic glass to crystalline metal is of interest for many applications that require locally tailored functions and properties, but it is challenging. This research describes a promising additive manufacturing technology, i.e., laser-foil-printing, to make high-quality metallic glass parts with large dimensions and complex geometries and to fabricate multi-material components from metallic glass and crystalline metal. In this research, Zr52.5Ti5Al10Ni ...


Modeling And Simulation Of Micro/Nano-Rod Distribution In Micro Channel Flows, Saman Monjezi Jan 2019

Modeling And Simulation Of Micro/Nano-Rod Distribution In Micro Channel Flows, Saman Monjezi

Doctoral Dissertations

"The behavior of a typical nanorod particle in microscale flows was theoretically investigated, considering the effect of the wall on the rotational and translation motions of the non-spherical particle. Initially, a systematic method using Brownian dynamics simulation of the rotational motion of nanorod was performed to obtain the average orientation distribution of a nanorod in various range of Peclet number and position from the confining wall. Subsequently, the results of the angle distributions simulation were employed to generate a universal mathematical model for the particle orientation distribution, which our model of concentration distribution of high aspect ratio nanorods in the ...


Techno-Economic Optimization And Environmental Life Cycle Assessment Of Microgrids Using Genetic Algorithm And Artificial Neural Networks, Prashant Nagapurkar Jan 2019

Techno-Economic Optimization And Environmental Life Cycle Assessment Of Microgrids Using Genetic Algorithm And Artificial Neural Networks, Prashant Nagapurkar

Doctoral Dissertations

"This dissertation focuses primarily on techno-economic optimization and environmental life cycle assessment (LCA) of sustainable energy generation technologies. This work is divided into five papers. The first paper discusses the techno-economic optimization and environmental life cycle assessment of microgrids located in the USA using genetic algorithm. In this paper, a methodology was developed that assessed the techno-economic and environmental performance of a small scale microgrid located in US cities of Tucson, Lubbock and Dickinson. Providing uninterrupted power the microgrid was composed of seven components -- solar photovoltaics, wind-turbines, lead acid batteries, biodiesel generators, fuel cells, electrolyzers and H2 tanks. The ...


Quantifying Restoration Costs In The Aftermath Of An Extreme Event Using System Dynamics And Dynamic Mathematical Modeling Approaches, Akhilesh Ojha Jan 2019

Quantifying Restoration Costs In The Aftermath Of An Extreme Event Using System Dynamics And Dynamic Mathematical Modeling Approaches, Akhilesh Ojha

Doctoral Dissertations

"Extreme events such as earthquakes, hurricanes, and the like, lead to devastating effects that may render multiple supply chain critical infrastructure elements inoperable. The economic losses caused by extreme events continue well after the emergency response phase has ended and are a key factor in determining the best path for post-disaster restoration. It is essential to develop efficient restoration and disaster management strategies to ameliorate the losses from such events. This dissertation extends the existing knowledge base on disaster management and restoration through the creation of models and tools that identify the relationship between production losses and restoration costs. The ...


Development Of Lidar Assisted Terrestrial Radar Interferometry For Rock Deformation Monitoring, Ricardo Javier Romero Ramirez Jan 2019

Development Of Lidar Assisted Terrestrial Radar Interferometry For Rock Deformation Monitoring, Ricardo Javier Romero Ramirez

Doctoral Dissertations

"Rock and soil slope movements cost millions of dollars annually. During the past few decades, engineers have relied on traditional methods to detect slope movements. These tools are valuable for small spatial areas but, may not be adequate or cost effective for large spatial areas. Remote sensing methods such as terrestrial laser scanning (TLS) and terrestrial radar interferometry (TRI) provide excellent spatial coverage, and with adequate post-data-processing software, sub-millimetric scale deformation sensitivity can be achieved.

This work will present a comparative experimental study between TLS and TRI. The comparative experimental study will allow us to achieve the two main objectives ...


Pressure Versus Impulse Graph For Blast-Induced Traumatic Brain Injury And Correlation To Observable Blast Injuries, Barbara Rutter Jan 2019

Pressure Versus Impulse Graph For Blast-Induced Traumatic Brain Injury And Correlation To Observable Blast Injuries, Barbara Rutter

Doctoral Dissertations

"With the increased use of explosive devices in combat, blast induced traumatic brain injury (bTBI) has become one of the signature wounds in current conflicts. Animal studies have been conducted to understand the mechanisms in the brain and a pressure versus time graph has been produced. However, the role of impulse in bTBIs has not been thoroughly investigated for animals or human beings.

This research proposes a new method of presenting bTBI data by using a pressure versus impulse (P-I) graph. P-I graphs have been found useful in presenting lung lethality regions and building damage thresholds. To present the animal ...


Investigating Blast Fume Propagation, Concentration And Clearance In Underground Mines Using Computational Fluid Dynamics (Cfd), Raymond Ninnang Tiile Jan 2019

Investigating Blast Fume Propagation, Concentration And Clearance In Underground Mines Using Computational Fluid Dynamics (Cfd), Raymond Ninnang Tiile

Doctoral Dissertations

"Blasting activities using standard industry explosives is an essential component of underground hard rock mining operations. Blasting operations result in the release of noxious gases, presenting both safety and productivity threats. Overestimation of post-blast re-entry time results in production losses, while underestimation leads to injuries and fatalities. Research shows that most underground mines simply standardize post-blast re-entry times based on experiences and observations. Few underground mines use theoretical methods for calculating post-blast re-entry time. These theoretical methods, however, are unable to account for the variations in the blasting conditions. Literature review shows that: (i) there is currently no means of ...


Military Applications Of Geological Engineering, Stephen H. Tupper Jan 2019

Military Applications Of Geological Engineering, Stephen H. Tupper

Doctoral Dissertations

"This work examines the premise that military engineering and geological engineering are intellectually paired and overlapped in practice to a significant extent. Geological engineering is an established, albeit young, academic discipline that enjoys wide industry and civil demand and is supported by many professional organizations. In contrast, military engineering is an ancient, empirically derived training or "OJT" program with practice-based trade-associations that has narrow government-only utility. The premise is formed by decades-long observation of U. S. Army military engineer officers completing a Master of Science degree in geological engineering as a complement to their practice-based training in military engineering at ...


2x-Thru, 1x-Reflection, And Thru-Line De-Embedding: Theory, Sensitivity Analysis, And Error Corrections, Bichen Chen Jan 2019

2x-Thru, 1x-Reflection, And Thru-Line De-Embedding: Theory, Sensitivity Analysis, And Error Corrections, Bichen Chen

Doctoral Dissertations

"Due to the simplicity of design and measurement, as well as the accuracy of results, the 2X-Thru de-embedding (2XTD), 1X-Reflection de-embedding (1XRD), and Thru-Line de-embedding (TLD) have been replaced the traditional de-embedding algorithms, such as TRL and SOLT. In this dissertation, theory of 2n-port 2XTD, 1XRD, and TLD are completely derived first. The self-error reduction schemes is introduced to mitigate the de-embedding errors due to non-ideal manufacturing effects of non-zero mode conversion terms, as well as the asymmetric, and manufacturing variations. The validations are performed on both theory and self-error reduction through simulation and measurements cases. The 2X-Thru ...


Electrodeposition Of Epitaxial Metal Thin Films On Silicon For Energy Conversion And Flexible Electronics, Qingzhi Chen Jan 2019

Electrodeposition Of Epitaxial Metal Thin Films On Silicon For Energy Conversion And Flexible Electronics, Qingzhi Chen

Doctoral Dissertations

"This research focuses on epitaxial electrodeposition of two coinage metals: Au and Ag thin films on the silicon surface and their applications in flexible electronics and energy conversion and storage. The first paper: Photoelectrochemistry of ultrathin, semi-transparent, and catalytic gold films electrodeposited epitaxially onto n-silicon (111) describes the epitaxial electrodeposition of Au thin films on n-type Si using a simple HAuCl4 bath and the photoelectrochemical properties of the Au-Si junction barrier. The effect of the Au layer on the interfacial energetics as well as the stability of the photoelectrode as a function of the Au coverage/thickness is determined in ...


Nanomorphology Dependent Optical And Mechanical Properties Of Aerogels, Chandana Mandal Jan 2019

Nanomorphology Dependent Optical And Mechanical Properties Of Aerogels, Chandana Mandal

Doctoral Dissertations

"Aerogels are very low density, light weight open pore materials. A hypothesis that is under intense current investigation by the scientific community states that the mechanical properties of nanostructured polymers depend on their nanomorphology. Aerogels are nanostructured ultra-lightweight nanoporous materials with skeletal frameworks that can display a wide range of nanomorphologies. Thereby aerogels comprise a suitable platform for testing not only that hypothesis but also a wide range of other properties such as light scattering for applications, for example, in thermally insulating windows.

To study the mechanical properties of nanostructured matter as a function of nanomorphology, various shape-memory polyurethane aerogels ...