Engineering Commons^™

Helical Force Flow: A New Engineering Mechanics Model For Biological Materials, Jeffery S. Thomas

Doctoral Dissertations

"The author has long speculated that the prevalence of helical structures in botany and zoology hints to an optimized pathway for force and/or energy transfer. His goal has been to realize an alternative approach to the standard stress analysis used in engineering in order to more efficiently and accurately deal with biological materials. Improved tools for these natural materials should in turn aid the design and analysis of engineered materials. Following the role of a navigator in leaf C. Levesque's book "Breakthrough Creativity", the author typically searches for ideas in a variety of places, including physics, materials science, biomimetics, dimensional …

Investment Shell Cracking, Edward A. Druschitz

Masters Theses

"Shell cracking is the single greatest problem affecting investment casters. A clearer understanding of the factors affecting the melt profile of the wax can be gained using computational fluid dynamics (CFD) to model the interaction among 1) the thermal conductivity of the wax, 2) the thermal conductivity of the shell, and 3) the temperature of the autoclave during the autoclave de-waxing cycle. The most favorable melt profile results from a high autoclave temperature (438⁰K to 458⁰K) and saturated thermal conductivity of the shell (1.36 to 1.40 Wm⁻¹k⁻¹) in conjunction with a low wax thermal conductivity (0.33 Wm⁻¹k⁻¹). These parameters reduce …

Friction Stir Processing Of Magnesium Alloys, Gaurav Bhargava

Masters Theses

"Magnesium alloys have been fast catching up their attention in applications where both lightweight and exceptional strength is desired. But magnesium alloys suffer formability issues which limit their use to cast applications when designing complicated shapes. Friction stir processing (FSP) is technique for, imparting a fine-grained, homogeneous microstructure by which both strength and ductility can be enhanced. The results from the first part of present work showed that AZ31 alloy when employed the use of FSP, yielded significant strength and ductility gains but on the cost of anisotropy. The cause of anisotropy was investigated to be correlated to texture evolution …

Detection Of Low Cost Radio Frequency Receivers Based On Their Unintended Electromagnetic Emissions And An Active Stimulation, Sarah A. Seguin

Doctoral Dissertations

"Detection of super-regenerative receivers using their unintended electromagnetic emissions at a significant distance is challenging due to high levels of ambient noise. The evolution of an approach used to solve this problem is chronicled within the three papers that combine to form this dissertation. First, a passive detection method was created for detecting devices based on the characterization of their unintended emissions and utilized a cascading correlation method to confirm detection. Using a simple sine-wave stimulation to modify these unintended emissions produced better results over passive detection techniques by improving the signal quality and the consistency of the unintended emissions, …

Real-Time And Portable Microwave Imaging System, Mohammad Tayeb Ahmad Ghasr

Doctoral Dissertations

"Microwave and millimeter wave imaging has shown tremendous utility in a wide variety of applications. These techniques are primarily based on measuring coherent electric field distribution on the target being imaged. Mechanically scanned systems are the simple and low cost solution in microwave imaging. However, these systems are typically bulky and slow. This dissertation presents a design for a 2D switched imaging array that utilizes modulated scattering techniques for spatial multiplexing of the signal. The system was designed to be compact, coherent, possessing high dynamic range, and capable of video frame rate imaging. Various aspects of the system design were …

Emi Chip-To-Tem Cell Coupling For A Microcontroller And Emi Coupling Resulting From Via Transition And Reference Plane Change, Hemant Bishnoi

Masters Theses

"The work presented in this thesis can be broadly categorized under two main headings, estimation of electromagnetic interference (EMI) performance and characterization of EMI performance.

A numerical model of capacitive coupling between two orthogonally crossing double stripline was developed earlier by Kenji Araki and Yoshio Kami at the University of Electro-Communications, Japan. Their model was shown to be accurate up to 3GHz. A verification of their numerical model with full wave simulations is presented here.

In another work done by Shaohua Li, dynamic currents in the power pins of a microcontroller were predicted by using an IC model. The ultimate …

Applications Of Swarm, Evolutionary And Quantum Algorithms In System Identification And Digital Filter Design, Bipul Luitel

Masters Theses

"The thesis focuses on the application of computational intelligence (CI) techniques for two problems - system identification and digital filter design. In system identification, different case studies have been carried out with equal or reduced number of orders as the original system and also in identifying a blackbox model. Lowpass, Highpass, Bandpass and Bandstop FIR and Lowpass IIR filters have been designed using three algorithms using two different fitness functions. Particle Swarm Optimization (PSO), Differential Evolution based PSO (DEPSO) and PSO with Quantum Infusion (PSO-QI) algorithms have been applied in this work"--Abstract, page iii.

Development Of A One Dimensional Subsurface Contaminant Transport Model With Stochastic Applications, Benjamin Waldon Johnson

Masters Theses

"Contaminant source release history is a necessary element of contaminant mass transport simulation in the saturated zone. The source release history is unknown at many sites, and many inverse models have been developed to define finite release histories. To define a likely domain of three source history parameters, a mass balancebased one dimensional approach is developed and tested by discretizing the spatial domain into bands. By incorporating the approach in a spreadsheet model, observed data is represented by both variable length and constant length bands of analysis. Each representation of observed data was tested to determine the most appropriate band …

Modeling And Analysis Of Noise Coupling In Multilayer Power/Ground Planes, Gang Feng

Doctoral Dissertations

"The simultaneous switching noise (SSN) in a multilayer power delivery network (PDN) is a critical problem in high-speed printed circuit board (PCB) designs. Full-wave methods are not computationally efficient for analyzing PCB structures normally with a multi-scale nature. In this thesis, a model for multilayer power/ground planes is proposed using basic plane pair blocks derived from the cavity model combined with the segmentation technique. Vias and other circuit elements can further be easily integrated in the multilayer plane model. As a result, the entire PDN model is much more computationally efficient than full-wave methods. Experimental and numerical results have validated …

Freeze Casting Of Bioactive Glass And Ceramic Scaffolds For Bone Tissue Engineering, Qiang Fu

Doctoral Dissertations

"The main objectives of this dissertation were to explore the production of bioactive ceramic and glass scaffolds with oriented pore architectures by unidirectional freezing of suspensions, and to characterize the mechanical and biological performance of the scaffolds. Freezing of aqueous suspensions of hydroxyapatite (HA) or bioactive 13-93 glass particles resulted in the formation of scaffolds with a lamellar-type microstructure (pore width = 5-30 µm). The addition of polar organic solvents (such as 60 wt% dioxane) to the aqueous suspensions markedly changed the morphology and size of the oriented pores, giving scaffolds with a columnar-type microstructure and larger pre width (90-110 …

Information Archival And Reuse: Drawing Conclusions From The Past, Matt R. Bohm

Doctoral Dissertations

"Over the last few decades design researchers have put forward theories and proposed methodologies that increase the chance that a design team will reliably arrive at the optimal solution to a given design problem. Studies, however, bear out that theories and methodologies alone will not guarantee an optimal or even good design solution. Instead, a breadth of knowledge across multiple engineering domains and the time and tools to thoroughly evaluate the design space are as important as any prescriptive design method. This work presents a set of underlying engineering technologies to define, archive and reuse product design knowledge to provide …

Spacecraft Formation Flight At Sun-Earth/Moon Libration Points, Douglas Robert Tolbert

Doctoral Dissertations

"Formations of spacecraft, positioned near the libration points of the Sun- Earth/Moon system, have recently received an increase in interest in response to a variety of mission needs. Specifically, missions such as the Micro Arcsecond X-Ray Imaging Mission (MAXIM), Terrestrial Pathfinder (TPF), Stellar Imager (SI) and the European Space Agency's DARWIN all baseline formations of spacecraft to satisfy mission requirements. Replacing the traditional single spacecraft mission with multiple small spacecraft flying in formation is advantageous for these missions, especially when establishing a virtual aperture. These types of formations allow for higher resolution observations than with a single, conventional aperture. The …

Material Flow And Microstructure Evolution In Friction Stir Welding Of Aa6111 Alloy Sheets, Manasij Kumar Yadava

Doctoral Dissertations

"Material flow and microstructure evolution are the two important aspects of the Friction stir welding (FSW) technique, which control the properties and performance of the friction stir welds. The present work investigates these two aspects of the FSW with main emphasis on the friction stir lap joints (FSLJs) on the AA6111 sheets. Due to the characteristic material flow during FSW, the faying surfaces in FSLPs are deposited in and around the weld nugget and create unavoidable defects. These defects reduce the load carrying thickness of the joints by providing an easy path for the weld failure. Therefore, to control the …

Quality Of Service Provisioning Through Resource Allocation And Data Aggregation In Wireless Sensor Networks, Carl Larsen

Doctoral Dissertations

"In this dissertation, improvement of quality of service (QoS) provisioning in wireless sensor networks (WSN) is examined using four different methods. The first two focus on allocation of limited resources in the face of changing network and channel conditions, and thus improving performance in terms of throughput and delay. The second two methods focus on using data aggregation to minimize the size and number of packet transmissions reducing the energy consumption and improving network lifetime.

Therefore, in the first paper a novel adaptive and distributed fair scheduling (ADFS) protocol for WSN is presented that allocates the channel bandwidth in proportion …

Analysis Of Lesion Border Segmentation Using Watershed Algorithm, Hanzheng Wang

Masters Theses

"Automatic lesion segmentation is an important part of computer-based skin cancer detection. A watershed algorithm was introduced and tested on benign and melanoma images. The average of three dermatologists' manually drawn borders was compared as the benchmark. Hair removing, black border removing and vignette removing methods were introduced in preprocessing steps. A new lesion ratio estimate was added to the merging method, which was determined by the outer bounding box ratio. In postprocessing, small blob removing and border smoothing using a peninsula removing method as well as a second order B-Spline smoothing method were included. A novel threshold was developed …

Automatic Vessel And Telangiectases Analysis In Dermoscopy Skin Lesion Images, Beibei Cheng

Masters Theses

"The blood vessels are part of the circulatory system and function to transport blood throughout the body. Vessels have their own features such as distinctive color compared to surrounding skin as well as distinctive curved and/or linear shape. Telangiectases are small dilated blood vessels near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. In this research, image analysis techniques are investigated to detect vessels in dermoscopy skin lesion images. Machine vision and neural network methods are explored to discriminate skin lesions containing telangiectases from those containing normal vessels. A vessels Detection technique …

Localization Of Nodes In Wired And Wireless Networks, Hindu Kothapalli

Masters Theses

"This thesis focuses on the implementation of algorithms for localization of nodes in wired and wireless networks. The thesis is organized into two papers. The first paper presents the localization algorithms based on time of arrival (TOA) and time difference of arrival (TDOA) techniques for computer networks such as the Internet by using round-trip-time (RTT) measurements obtained from known positions of the gateway nodes. The RTT values provide an approximate measure of distance between the gateway nodes and an unknown node. The least squares technique is then used to obtain an estimated position of the unknown node. The second paper …

Inclusion Modification In Steel Castings Using Automated Inclusion Analysis, Vintee Singh

Masters Theses

"The objective of this research is to study the effects of changing the melt and ladle practices (deoxidation, slag, refractory types, etc.) in steel foundries on the cleanliness and toughness of steel castings. This study used an automated inclusion analyzer ASPEX PICA-1020, which provides a rapid and accurate method for determining the composition, size, number, and spacing of the inclusions present in steel samples. The first step in this research was to complete a series of industrial tests to benchmark the current foundry ladle practices with respect to cleanliness of the cast steel. Trials were conducted at steel foundries using …

Public-Private Partnerships In High Risk Transportation Projects, Kiran Rangarajan

Masters Theses

"This research examines Public-Private Partnerships (PPPs) between private firms and City of Chamois, Missouri to establish a ferry boat service across the Missouri River. The study illustrates the role of PPPs in managing high risk transportation projects for rural economic development. The research study was designed to accomplish three objectives. First, understand and study the high risk transportation industry which included analyzing other ferry services in and around the region, and identifying potential risks involved in a ferry boat project. Second, study various models of PPPs, identify the attributes of each model and select appropriate models based on local and …

Modeling Of Wear And Oxidation Behavior Of A Carbon/Carbon Multidisk Clutch, Shankar Nagaraj

Masters Theses

"Carbon/carbon composites are a family of advanced composite materials. They are the most advanced form of carbon and consist of a fiber, based on carbon precursors, embedded in a carbon matrix. They are extensively used in design of sliding contact systems such as clutches and brakes because of their low weight, excellent thermal and mechanical properties, chemical inertness and self lubricating capability. They retain their mechanical strength in inert atmospheres up to 2000° C. However, in oxidizing environments, C/C composites rapidly react with oxygen forming gaseous carbon oxides around 450° C.

In the present study a C/C composite clutch assembly …

In-Plane Behavior Of Strengthened Unreinforced Masonry Infill Walls With Alternative Wood-Fiber Fly Ash Material, Yosuke Tanizawa

Masters Theses

"This research investigates the potential for an alternative masonry product to use in masonry infill wall systems. The study also investigates the effects of an external fiber reinforced polymer (FRP) strengthening system on in-plane behavior of the alternative unreinforced masonry (URM) walls. The alternative masonry product is produced in a solid unit configuration and utilizes recycled white oak wood-fibers and an ASTM Class-C fly ash as its raw materials. The external strengthening system investigated consists of an elastomeric polyurea surface coating with and without integrated discrete chopped E-glass fibers which is directly sprayed on the URM wall surfaces. The alternative …

The Effects Of Water To Fuel Ratio On The Kinetics Of Supercritical Water Reformation Of Jet Fuel, Satya Putta

Masters Theses

"The noncatalytic direct reformation of jet fuel was studied in a supercritical water medium using a specially designed 400-mL Haynes® 230 alloy tubular reactor. The experiments were conducted at 1042±5 K, 240.9±0.1 bar, and at water flow rates of 7.5, 15, 30 g/min with varying water-to-fuel feed ratios of 7.5, 15 and 30. The principal reactions are direct reformation of jet fuel into hydrogen and carbon oxides and pyrolysis of jet fuel into lighter hydrocarbons and coke. The effluent gas contained H₂, CO, CO₂ and CH₄, with smaller concentrations of C₂H₄ and C₂H₆. This thesis discusses the effects of the …

Investigation Of Selective Laser Sintering Of Zirconium Diboride Parts, Shashwatashish Pattnaik

Masters Theses

"This research investigates the fabrication of three-dimensional parts from ZrB₂, an ultra high temperature ceramic (UHTC), using the selective laser sintering (SLS) process. Based on an experimental investigation, optimum values for the SLS parameters (scan speed, laser power, energy density, scan spacing and layer thickness), used on a DTM Sinterstation 2000, were determined to build green ZrB₂ parts with high integrity and sharp geometrical features. This was done by melting the polymer binder used to bond the ceramic particles layer-by-layer according to the cross-section of a CAD model. The use of a sacrificial plate to eliminate cracks in the bottom …

On-Line Depth Measurement Of Micro-Scale Laser Drilled Holes, Rock Allen Powell

Masters Theses

"A micron-precision micro-hole depth detection scheme has been developed which utilizes a confocal structure and a photomultiplier tube as a photodetector. This scheme is experimentally confirmed to posses an accuracy of greater than 95% for micro-holes on the order of one-hundred microns in diameter and tens of microns in depth and could be easily be integrated for the control of industrial and research oriented laser micro-machining process"--Abstract, page iii.

Rational Construction By Molecular Dynamics Modeling And Simulations Of Porous Adsorbent Media For Bioseparation, Enrico Riccardi

Doctoral Dissertations

"Ion-exchange chromatography employing porous adsorbent particles or monoliths in which charged ligands are immobilized onto polymeric extender molecules grafted on the pore surfaces of a base matrix has become a very important method for bioseparations. In this dissertation, a novel fundamental and systematic methodology has been developed that uses the molecular dynamics (MD) modeling and simulation approach to rationally design, construct, and characterize polymeric porous adsorbent media and study the transport and adsorption of a charged biomolecule (desmopressin) in a representative adsorbent medium. The MD results have also been utilized in a macroscopic model to study the large-scale dynamic behavior …

The Role Of Friction Stir Processing On The Microstructure And Mechanical Properties Of A Cast Aluminum Alloy, Saumyadeep Jana

Doctoral Dissertations

"Al-7Si-0.6Mg is one of the most important cast aluminum alloys because of its attractive mechanical properties and high castability. Microstructurally, the alloy consists of primary aluminum dendrites with eutectic Si particles in the interdendritic region. This makes the alloy quasi-brittle in nature which affects the ductility of the alloy to a great extent. In order to improve the ductility, the eutectic Si particles need to be refined which so far has been achieved by chemical and/or thermal modification. Friction stir processing (FSP) on the other hand can achieve the same through plastic deformation, and therefore replace the cast structure with …

Automatic Detection Of White Areas In Dermoscopy Images, Ankur Dilip Dalal

Masters Theses

"This thesis presents an algorithm for automatically segmenting the white areas in dermoscopy images. The algorithm includes preprocessing of images, plotting the histogram (RGB) and calculating the average and standard deviation values (RGB) of the lesion. A threshold value for each color plane is determined using these parameters and white areas are automatically segmented. Various image features such as decile percentages and globule features are extracted and given to a neural network. The proposed algorithm has produced a maximum diagnostic accuracy of 94.67% and, when the lesions which touch the image border are removed from the set, the diagnostic accuracy …

Friction Stir Processing Of Laser Metal Deposited Ti-6al-4v, Romy Francis

Masters Theses

"Laser metal deposition (LMD) can form near net shaped components for aerospace applications. Ti-6Al-4V is a widely used aerospace alloy and fabrication of this alloy using LMD is gaining popularity. Improved mechanical properties are always a requirement in aerospace alloys and research is constantly being conducted to improve the properties of components formed from this alloy. Friction Stir Processing (FSP) in the past has been used as a method to change the surface properties of materials through microstructural modifications. The changes in properties can include hardness, corrosion resistance, fatigue strength, etc. The first section of this thesis is based on …

Zigbee-Enabled Structural Health Monitoring Using The Smartbrick System, Tyler Harms

Masters Theses

"This thesis describes the design, testing, and proposed extended field test of a wireless sensor network based on the SmartBrick, a structural health monitoring (SHM) device developed at Missouri S&T. The SmartBrick serves as the base station for the network, which utilizes additional sensor nodes to monitor the structure. Each node measures a range of environmental and structural phenomena, including vibration, tilt, humidity, and strain. The nodes use Zigbee short-range communication to transmit their data to the base station, which in turn uses the GSM cellular network to provide long-range communication capability and support for remote control.

Unlike many SHM …

Maximum Likelihood Fusion For Detection Of Led Precursors Using Laser-Induced Breakdown Spectroscopy, Pratik Shah

Masters Theses

"Improvised Explosive Devices (IEDs) pose an increasing threat to the safety of soldiers and civilians in embattled areas. The use of compounds such as RDX complicates the detection of IEDs, as these compounds are often hard to identify in the presence of contaminants such as alcohol, oils and dust. Spectroscopic techniques such as Laser-Induced Breakdown Spectroscopy (LIBS) and Raman have shown promise for the detection of explosive compounds; however, their accuracy is limited, as noise can cause variations in the peak strengths and locations that they utilize for classification.

The research presented in this thesis applies signal processing to the …