Digital Commons Network^™

Failure Simulations At Multiple Length Scales In High Temperature Structural Alloys, Chao Pu

Doctoral Dissertations

A number of computational methodologies have been developed to investigate the deformation and damage mechanism of various structural materials at different length scale and under extreme loading conditions, and also to provide insights in the development of high-performance materials.

In microscopic material behavior and failure modes, polycrystalline metals of interest include heterogeneous deformation field due to crystalline anisotropy, inter/intra grain or phase and grain boundary interactions. Crystal plasticity model is utilized to simulate microstructure based polycrystalline materials, and micro-deformation information, such as lattice strain evolution, can be captured based on crystal plasticity finite element modeling (CPFEM) in ABAQUS. The comparison …

Spare Parts On Demand Using Additive Manufacturing : A Simulation Model For Cost Evaluation., Stefan Jedeck

Electronic Theses and Dissertations

Little is known about the impact of additive manufacturing in the spare part supply chain. A few studies are available, but they focus on specific parts and their applications only. A general model, which can be adapted to different applications, is nonexistent. This dissertation proposes a decision making framework that enables an interested practitioner/manager to decide whether using additive manufacturing to make spare parts on demand is economical when compared to conventional warehousing strategy. The framework consists of two major components: a general discrete event simulation model and a process of designing a wide range of simulation scenarios. The goal …

Heat Transfer Mechanisms In Water-Based Nanofluids., Masoudeh Ahmadi

Electronic Theses and Dissertations

Nanofluids are a class of heat transport fluids created by suspending nano-scaled metallic or nonmetallic particles into a base fluid. Some experimental investigations have revealed that the nanofluids have remarkably higher thermal conductivities than those of conventional pure fluids and are more suited for practical application than the existing techniques of heat transfer enhancement using millimeter and/or micrometer-sized particles in fluids. Use of nanoparticles reduces pressure drop, system wear, and overall mass of the system leading to a reduction in costs over existing enhancement techniques. In this work, the heat transfer coefficient is determined experimentally using copper oxide (CuO) based …

A Robust Data Exchange Framework For Connected Vehicle Technology Supported Dynamic Transit Operations, Yucheng An

All Theses

Transit systems are an integral part of surface transportation systems. A connected vehicle technology (CVT) supported transit system will assist the users to manage trips both dynamically and efficiently. The primary focus of this research is to develop and evaluate the performance of a secure, scalable, and resilient data exchange framework. In the developed data exchange framework, a new data analytics layer, named Transit Cloud, is used to receive data from different sources, and send it to different users for a Dynamic Transit Operations (DTO) application. The DTO application allows the transit users to request trip information and obtain itineraries, …

Open Source Toolkit For Reentry Object Modeling, Christopher Lloyd Ostrom Ii

Master's Theses

Predicting the mass, position, and velocity of an object during its reentry are critical to satisfy NASA and ESA requirements. This thesis outlines a 3-D orbit and mass determination system for use on low earth orbit as applicable to general objects, of various material and size. The solution uses analytical models to calculate heat flux and aerodynamic drag, with some basic numerical models for simple orbit propagation and mass flow rate due to ablation. The system outlined in this thesis currently provides a framework for rough estimates of demise altitude and final mass, but also allows for many potential accuracy …

Techno-Economic Analysis Of Protein Concentrate Produced By Flash Hydrolysis Of Microalgae, Alexander Nana Yaw Asiedu

Civil & Environmental Engineering Theses & Dissertations

Process simulation and techno-economic analysis of 95wt.% protein concentrate from microalgae has been performed using SuperPro Designer v. 9.0. This work, first of its kind, is focused on the economic analysis of protein concentrate that includes processes such as microalgae cultivation, harvesting, protein extraction and drying steps. A baseline capacity of 160 MT/day protein concentrate production on commercial basis has been analyzed. This throughput requires 336 MT/day dry algae (54 wt.% protein). The amount of carbon dioxide required to grow this quantum of algae is estimated to be 648 MT/day, which is produced from an in situ 21 MW power …

Tropical Cyclone Wind Hazard Assessment For Southeast Part Of Coastal Region Of China, Sihan Li

Electronic Thesis and Dissertation Repository

Tropical cyclone (TC) or typhoon wind hazard and risk are significant for China. The return period value of the maximum typhoon wind speed is used to characterize the typhoon wind hazard and assign wind load in building design code. Since the historical surface observations of typhoon wind speed are often scarce and of short period, the typhoon wind hazard assessment is often carried out using the wind field model and TC track model. For a few major cities in the coastal region of mainland China, simple or approximated wind field models and a circular subregion method (CSM) have been used …

Guidelines For Scheduling In Primary Care: An Empirically Driven Mathematical Programming Approach, Hyun Jung Alvarez Oh

Doctoral Dissertations

Primary care practices play a vital role in healthcare delivery since they are the first point of contact for most patients, and provide health prevention, counseling, education, diagnosis and treatment. Practices, however, face a complex appointment scheduling problem because of the variety of patient conditions, the mix of appointment types, the uncertain service times with providers and non-provider staff (nurses/medical assistants), and no-show rates which all compound into a highly variable and unpredictable flow of patients. The end result is an imbalance between provider idle time and patient waiting time. To understand the realities of the scheduling problem we analyze …

Thermodynamic And Kinetic Simulation Of Transient Liquid-Phase Bonding, Brad Allen Lindner

Theses and Dissertations

ABSTRACT

THERMODYNAMIC AND KINETIC SIMULATION OF TRANSIENT LIQUID-PHASE BONDING

by

Brad Lindner

The University of Wisconsin-Milwaukee, 2015

Under the Supervision of Professor Benjamin C. Church

The use of numeric computational methods for the simulation of materials systems is becoming more prevalent and an understanding of these tools may soon be a necessity for Materials Engineers and Scientists. The applicability of numerical simulation methods to transient liquid-phase (TLP) bonding is evaluated using a type 316L/MBF-51 material system. The comparisons involve the calculation of bulk diffusivities, tracking of interface positions during dissolution, widening, and isothermal solidification stages, as well as comparison of …

Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows

Graduate Theses and Dissertations

The deleterious effects of atomic and molecular hydrogen on the mechanical properties of metals have long been observed. Although several theories exist describing the mechanisms by which hydrogen negatively influences the failure of materials, a consensus has yet to be reached regarding the exact mechanism or combination of mechanisms. Two mechanisms have gained support in explaining hydrogen’s degradative role in non-hydride forming metals: hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. Yet, the interplay between these mechanisms and microstructure in metallic materials has not been explained. Accordingly, for this thesis, the three main objectives are: (i) to develop a numerical methodology to …

Computational Framework For Small Animal Spect Imaging: Simulation And Reconstruction, Sang Hyeb Lee

Doctoral Dissertations

Small animal Single Photon Emission Computed Tomography (SPECT) has been an invaluable asset in biomedical science since this non-invasive imaging technique allows the longitudinal studies of animal models of human diseases. However, the image degradation caused by non-stationary collimator-detector response and single photon emitting nature of SPECT makes it difficult to provide a quantitative measure of 3D radio-pharmaceutical distribution inside the patient. Moreover, this problem exacerbates when an intra-peritoneal X-ray contrast agent is injected into a mouse for low-energy radiotracers.

In this dissertation, we design and develop a complete computational framework for the entire SPECT scan procedure from the radio-pharmaceutical …

Formal Specification And Refinement Of The Navigation Tasks Of Autonomous Robots, Eman Rabiah Rabiah

Theses

Autonomous robots are hybrid systems whose role in our daily life is becoming increasingly critical. They are tasked with various activities requiring reliability, safety, and correctness of their software-controlled behavior. Formal methods have been proved effective in addressing development issues associated with these software qualities. However, even though autonomous robot navigation is a primordial function, there is no research dealing with enhancing reliability of the navigation algorithms. Thus, our focus is to investigate this type of algorithms, and specifically path planning, a fundamental and critical functionality supporting autonomy. We formally address the issue of enhancing reliability of the widely-used A* …

Toward A Theory Of Multi-Method Modeling And Simulation Approach, Mariusz A. Balaban

Computational Modeling & Simulation Engineering Theses & Dissertations

The representation via simulation models can easily lead to simulation models too simple for their intended purpose, or with too much detail, making them hard to understand. This problem is related to limitations of the modeling and simulation methods. A multi-method Modeling and Simulation (M&S) approach has the potential for improved representation by taking advantage of methods' strengths and mitigating their weaknesses. Despite a high appeal for using multiple M&S methods, several related problems should be addressed first. The current level of theoretical, methodological, and pragmatic knowledge related to a multi-method M&S approach is limited. It is problematic that there …

Modeling And Simulation Of Evacuation Plan For Hancock Stadium, Nirmal Neranjan Weerasekara

Theses and Dissertations

The goal of this study is to use Modeling and Simulation of Evacuation Plan (MSEP) to support management to execute proper evacuation plan in case of emergency at Hancock Stadium in Illinois State University. Analyses of the research literature and evacuation scenarios are used to build a simulation system that will connect a description of emergency and evacuation situation with its context. It shows how an evacuation plan actually functions. The results of the study will help safety managers to understand the current situations of evacuation according to the specific simulation scenarios. The evacuation simulation is categorized according to the …

Experimental And Numerical Study Of High-Speed Friction Stir Spot Welding Of Advanced High-Strength Steel, Utsab Karki

Theses and Dissertations

With the desire to lighten the frame while keeping or increasing the strength, Advanced High-Strength Steels (AHSS) have been developed for use in the automotive industry. AHSS meet many vehicle functional requirements because of their excellent strength and acceptable ductility. But joining AHSS is a challenge, because weldability is lower than that of mild steels. Friction stir spot welding (FSSW) is a solid state joining process that can provide a solution to the weldability issues in AHSS, but FSSW has not been studied in great detail for this application. In this work, Si3N4 tools were used for FSSW experiments on …

The Programmatic Generation Of Discrete-Event Simulation Models From Production Tracking Data, Christopher Rand Smith

Theses and Dissertations

Discrete-event simulation can be a useful tool in analyzing complex system dynamics in various industries. However, it is difficult for entry-level users of discrete-event simulation software to both collect the appropriate data to create a model and to actually generate the base-case simulation model. These difficulties decrease the usefulness of simulation software and limit its application in areas in which it could be potentially useful. This research proposes and evaluates a data collection and analysis methodology that would allow for the programmatic generation of simulation models using production tracking data. It uses data collected from a GPS device that follows …

Compressibility Measurement And Modeling To Optimize Flow Simulation Of Vacuum Infusion Processing For Composite Materials, Paul Hannibal

Theses and Dissertations

Out-of-autoclave manufacturing processes for composite materials are increasing in importance for aerospace and automotive industries. Vacuum Infusion processes are leading the push to move out of the autoclave. An understanding of the various process parameters associated with resin infusion is necessary to produce quality product. Variance in compaction, resin, and vacuum pressures are studied, concentrating on developing a compaction pressure profile as it relates to fiber volume fraction. The purpose of this research is twofold: (1) to show and quantify the existence of a resin pressure gradient in compression testing using rigid tooling, and (2) to use measured test data …

Aerospike Rocket Motor Structural Webbing, Andrew Brock

Master's Theses

A labscale hybrid rocket motor test stand has been developed for research at Cal Poly. The primary focus of research using this rig has been the development of regenerative cooling techniques using nitrous oxide as coolant and oxidizer, as well as validation of technologies relating to the annular aerospike nozzle. In order to prevent undesirable deflection of the cantilevered spike, a structural stiffening web, referred to as “The Spider,” is proposed. The Spider resembles a three-spoked wheel, with the aerospike held by the inner hub and the chamber walls abutting the outer radius.

The Spider, placed upstream of the nozzle, …

A Framework For Safety Training Using Virtual Reality Software, Rana Riad

Electronic Theses and Dissertations

Safety training is a vital component to the well-being of individuals in all industries. With technology advancing at the current pace, conventional training methods are no longer the most effective way to communicate information. There is a strong need for safety training that incorporates new methods and forms of communication to obtain higher levels of comprehension. Virtual reality systems offer a highly customizable and interactive form of delivering information to users. This research addresses major gaps in the field of safety training using virtual reality systems and provides a design framework for creating a virtual safety-training system. A model for …

An Embodied Approach To Evolving Robust Visual Classifiers, Karol Zieba

Graduate College Dissertations and Theses

From the very creation of the term by Czech writer Karel Capek in 1921, a "robot" has been synonymous with an artificial agent possessing a powerful body and cogitating mind. While the fields of Artificial Intelligence (AI) and Robotics have made progress into the creation of such an android, the goal of a cogitating robot remains firmly outside the reach of our technological capabilities. Cognition has proved to be far more complex than early AI practitioners envisioned. Current methods in Machine Learning have achieved remarkable successes in image categorization through the use of deep learning. However, when presented with novel …

Advancement And Validation Of A Plug-In Hybrid Electric Vehicle Model Utilizing Experimental Data From Vehicle Testing, Kevin Lloyd Snyder

Wayne State University Theses

The objective of the research into modeling and simulation was to provide an iterative improvement to the Wayne State EcoCAR 2 team's math-based design tools for use in evaluating different outcomes based on hybrid powertrain architecture tweaks, controls code development and testing. This thesis includes the results of the team's work in the EcoCAR 2 competition for university student teams to create and test a plug-in hybrid electric vehicle for reducing petroleum oil consumption, pollutant emissions, and Green House Gas (GHG) emissions.

Plant model validations and advancements brought the vehicle plant model directionally closer to the actual vehicle's experimental data …

Analytical And Numerical Validation Of Nozzle Spray Measurement Data Obtained From A Newly Developed Production System, Iddrisu Seidu

ETD Archive

A newly developed production test stand for measuring the spray angle of a pressure swirl atomizer was constructed and used to measure a product line of these pressure swirl atomizers -- the macrospray atomizer. This new test stand, utilizing constant temperature hot wire anemometers, captures the spray angle data based on the voltage drop the hot wire probes see as they traverse the spray cone of the atomizer and as fluid droplets impinge upon the wire. Datasets acquired from the experiments are compared and correlated with computational fluid dynamics (CFD) simulation data. In addition, angles obtained from another type of …

Dynamic Model Of A Non-Linear Pneumatic Pressure Modulating Valve Using Bond Graphs, Christopher L. Brubaker

ETD Archive

This research develops a mathematical model of the dynamic pressure response to a variable travel input of a pneumatic pressure modulating valve intended for use in a vehicle air brake system. Generically, the valve is a multi-domain system consisting of a mechanical portion and a pneumatic portion. Included in the mechanical portion of the model are compliance of the springs, inertia of the components, and resistance of the sliding components. The pneumatic portion of the model includes capacitance due to the compressibility of the gas, flow resistance through connected plumbing, and flow resistance through the valve control orifices. The development …

Combustion Kinetics Of Advanced Biofuels, Ghazal Barari

Electronic Theses and Dissertations

Use of biofuels, especially in automotive applications, is a growing trend due to their potential to lower greenhouse gas emissions from combustion. Ketones are a class of biofuel candidates which are produced from cellulose. However, ketones received rather scarce attention from the combustion community compared to other classes such as, alcohols, esters, and ethers. There is little knowledge on their combustion performance and pollutant generation. Hence their combustion chemistry needs to be investigated in detail. Diisopropyl ketone (DIPK) is a promising biofuel candidate, which is produced using endophytic fungal conversion. A detailed understanding of the combustion kinetics of the oxidation …

Electron-Beam Patterning Of Teflon Af For Surface Plasmon Resonance Sensing, Mansoor A. Sultan

Theses and Dissertations--Electrical and Computer Engineering

Variable pressure electron beam etching and lithography for Teflon AF has been demonstrated. The relation between dose and etching depth is tested under high vacuum and water vapor. High resolution structures as small as 75 nm half-pitch have been resolved. Several simulation tools were tested for surface plasmon excitation. Grating based dual mode surface plasmon excitation has been shown numerically and experimentally.

Modeling Social Norms In Real-World Agent-Based Simulations, Rahmatollah Beheshti

Electronic Theses and Dissertations

Studying and simulating social systems including human groups and societies can be a complex problem. In order to build a model that simulates humans' actions, it is necessary to consider the major factors that affect human behavior. Norms are one of these factors: social norms are the customary rules that govern behavior in groups and societies. Norms are everywhere around us, from the way people handshake or bow to the clothes they wear. They play a large role in determining our behaviors. Studies on norms are much older than the age of computer science, since normative studies have been a …

Information Propagation Algorithms For Consensus Formation In Decentralized Multi-Agent Systems, Christopher Hollander

Electronic Theses and Dissertations

Consensus occurs within a multi-agent system when every agent is in agreement about the value of some particular state. For example, the color of an LED, the position or magnitude of a vector, a rendezvous location, the most recent state of data within a database, or the identity of a leader are all states that agents might need to agree on in order to execute their tasking. The task of the decentralized consensus problem for multi-agent systems is to design an algorithm that enables agents to communicate and exchange information such that, in finite time, agents are able to form …

A New Methodology For Evaluating The Effectiveness Of Bus Rapid Transit Strategies, Ahmad Alomari

Electronic Theses and Dissertations

Over the last few years, public transportation has become more desirable as capacity of existing roadways failed to keep up with rapidly increasing traffic demand. Buses are one of the most common modes of public transportation with low impact on network capacity, especially in small and congested urban areas. However, the use of regularly scheduled buses as the main public transport mode can become useless with the presence of traffic congestion and dense construction areas. In cases like these, innovative solutions, such as bus rapid transit (BRT), can provide an increased level of service without having to resort to other, …

Using The Delta-Model For End-Stage Liver Disease To Improve The Decision-Making Process For The Donor Liver System, Joanne Chin

Walden Dissertations and Doctoral Studies

The purpose of this experimental research was to determine whether using delta-MELD as a criterion for the liver transplant patient selection process could improve the U.S. liver allocation system. This research closed a gap in current literature on the utility of delta-MELD for liver transplant patient selection. The frameworks of systems theory, the analytic hierarchy process, and the Kalman filter contributed to the development of 2 simulation models of the liver allocation system: one that used delta-MELD and one that did not use delta-MELD. The research question examined whether using delta-MELD could improve the liver allocation system by reducing the …

The Effect Of Videogame Play On Robotic Surgery Skill Acquisition, Alyssa Tanaka

Electronic Theses and Dissertations

Robotic surgery uses innovative technology to transcend a surgeon's skills when performing complex procedures. Currently, the only FDA approved robotic system is Intuitive's da Vinci Surgical System. While this system offers many advantages over other minimally invasive techniques, it also introduces a need for specialized training. Virtual reality simulators have emerged as valuable tools for standardized and objective robotic surgery skill training and assessments. In recent years, the idea of using video game technology in surgical education for laparoscopy has also been explored; however few have attempted to make a connection between video game experience and robotic surgical skills. Thus, …