Digital Commons Network^™

Mitigation Emission Strategy Based On Resonances From A Power Inverter System In Electric Vehicles, L. Zhai, Xinyu Zhang, Natalia G. Bondarenko, David Loken, Thomas Van Doren, Daryl G. Beetner

Electrical and Computer Engineering Faculty Research & Creative Works

Large dv/dt and di/dt outputs of power devices in the DC-fed motor power inverter can generate conducted and/or radiated emissions through parasitics that interfere with low voltage electric systems in electric vehicles (EVs) and nearby vehicles. The electromagnetic interference (EMI) filters, ferrite chokes, and shielding added in the product process based on the "black box" approach can reduce the emission levels in a specific frequency range. However, these countermeasures may also introduce an unexpected increase in EMI noises in other frequency ranges due to added capacitances and inductances in filters resonating with elements of the power inverter, and even increase …

Mobile Computing, Internet Of Things, And Big Data For Urban Informatics, Anirban Mondal, Praveen Rao, Sanjay Kumar Madria

Computer Science Faculty Research & Creative Works

Urban informatics is emerging as a new discipline for cities and governments to improve the lives of citizens using information technology. In this advanced seminar, we introduce the key challenges and opportunities in urban informatics, discuss topics in mobile computing, Internet of Things (IoT) and big data analytics, to advance the state-of-the-art in urban informatics and provide interesting use cases. This seminar is designed for academicians, researchers, city administrators/planners, application developers, and research students with background in mobile computing and database systems.

Business Communication Practices From Employers’ Perspectives, Tina A. Coffelt, Matthew J. Baker, Robert C. Corey

Faculty Publications

This study investigates the meaning of communication skills from employers’ perspectives. Students enrolled in a business communication course were asked to contact potential employers in their fields of interest, requesting information about important communication skills in those fields. Using content analysis, two coders familiar with business communication analyzed 52 of the resulting open-ended responses. The analysis of 165 skills suggests employers recall oral communication more frequently than written, visual, or electronic communication skills. Of oral communication subskills, interpersonal communication was mentioned more than other workplace communication skills.

Stress-Induced Birefringence And Fabrication Of In-Fiber Polarization Devices By Controlled Femtosecond Laser Irradiations, Lei Yuan, Baokai Cheng, Jie Huang, Jie Liu, Hanzheng Wang, Xinwei Lan, Hai Xiao

Electrical and Computer Engineering Faculty Research & Creative Works

Optical birefringence was created in a single-mode fiber by introducing a series of symmetric cuboid stress rods on both sides of the fiber core along the fiber axis using a femtosecond laser. The stress-induced birefringence was estimated to be 2.4 x 10^-4 at the wavelength of 1550 nm. By adding the desired numbers of stressed rods, an in-fiber quarter waveplate was fabricated with a insertion loss of 0.19 dB. The stressinduced birefringence was further explored to fabricate in-fiber polarizers based on the polarization-dependent long-period fiber grating (LPFG) structure. A polarization extinction ratio of more than 20 dB was observed …

Cable Shovel Dipper Stress And Fatigue Failure Modeling In Formation Excavation Engineering, Muhammad Azeem Raza

Doctoral Dissertations

"Large capacity shovels are used to achieve economic bulk production in surface mining operations. The suspended payload combined with dipper weight and formation resistive forces results in severe stress loading of the shovel front-end assembly. Material flaws, high stresses and harsh excavation conditions can initiate cracks in the dipper-teeth assembly. High stresses can cause these cracks to propagate to critical lengths resulting in fatigue failure, unscheduled downtimes, costly unplanned repairs, and downstream processing circuit problems. The literature reveals that dipper-related problems significantly reduce shovel up-time. This research is a pioneering effort towards developing a solid frame work for stress profiling, …

Multi-Level Evolutionary Algorithms Resource Allocation Utilizing Model-Based Systems Engineering, Bhanuchander Reddy Poreddy

Doctoral Dissertations

"This research presents an innovative approach to solve the resource allocation problems using Multi-level Evolutionary Algorithms. Evolutionary Algorithms are used to solve resource allocation problems in different domains and their results are then incorporated into a higher level system solution using another Evolutionary Algorithm to solve base camp planning problems currently faced by the U.S. Department of Defense.

Two models are introduced to solve two domain specific models: a logistics model and a power model. The logistic model evaluates routes for logistics vehicles on a daily basis with a goal of reducing fuel usage by delivery trucks. The evaluation includes …

A Domain Independent Method To Assess System Of System Meta-Architectures Using Domain Specific Fuzzy Information, Louis Edward Pape Ii

Doctoral Dissertations

"This research proposes a domain independent method to build and assess systems of systems (SoS) architecture models. A simplified meta-architecture containing each component system's participation and a first order, binary, system-to-system interface is proposed. The method describes how to elicit desired SoS attributes from stakeholders. Measures of the attributes depend on systems' participation and interfaces, that is, on the SoS architecture. The goal is to model a realizable SoS configuration, optimized over multiple attributes. Key attribute measures are combined in a fuzzy inference system to assess an overall fitness measure for any SoS in the meta-architecture. A genetic algorithm is …

On The Spheroidal Graphite Growth And The Austenite Solidification In Ductile Irons, Jingjing Qing

Doctoral Dissertations

"Evolutions of austenite and nodular/spheroidal graphite particles during solidifications of ductile irons were experimentally investigated. Spheroidal graphite particle and austenite dendrite were found nucleated independently in liquid. Austenite dendrite engulfed the spheroidal graphite particles after contact and an austenite shell formed around a spheroidal graphite particle. The graphite diameter at which the austenite shell closed around nodule was determined. Statistically determined graphite size distributions indicated multiple graphite nucleation events during solidification.

Structures in a graphite nodule varied depending on the growth stages of the nodule in ductile iron. Curved graphene layers appearing as faceted growth ledges swept circumferentially around the …

Hierarchical Control Of Complex Manufacturing Processes, Hesam Zomorodi Moghadam

Doctoral Dissertations

"The need for changing the control objective during the process has been reported in many systems in manufacturing, robotics, etc. However, not many works have been devoted to systematically investigating the proper strategies for these types of problems. In this dissertation, two approaches to such problems have been suggested for fast varying systems. The first approach, addresses problems where some of the objectives are statically related to the states of the systems. Hierarchical Optimal Control was proposed to simplify the nonlinearity caused by adding the statically related objectives into control problem. The proposed method was implemented for contour-position control of …

Study Of Heat Transfer Phenomenon During Natural Convection, Muhammad Yousaf

Doctoral Dissertations

"The purpose of the present study was to numerically investigate the effects of the roughness elements on the heat transfer during natural convection. A computational algorithm was developed based on the Lattice Boltzmann method to conduct numerical study in two-dimensional rectangular cavities and Rayleigh-Bénard cell. A single relaxation time Bhatnagar-Gross-Krook model of Lattice Boltzmann method was used to solve the coupled momentum and energy equations in two-dimensional lattices. Computational model was validated against previous benchmark solutions, and a good agreement was found to exist. A Newtonian fluid of Prandtl (Pr) number 1.0 was considered for this numerical study. The range …

Thorium-Based Mixed Oxide Fuel In A Pressurized Water Reactor: A Feasibility Analysis With Mcnp, Lucas Powelson Tucker

Doctoral Dissertations

"This dissertation investigates techniques for spent fuel monitoring, and assesses the feasibility of using a thorium-based mixed oxide fuel in a conventional pressurized water reactor for plutonium disposition. Both non-paralyzing and paralyzing dead-time calculations were performed for the Portable Spectroscopic Fast Neutron Probe (N-Probe), which can be used for spent fuel interrogation. Also, a Canberra ³He neutron detector's dead-time was estimated using a combination of subcritical assembly measurements and MCNP simulations. Next, a multitude of fission products were identified as candidates for burnup and spent fuel analysis of irradiated mixed oxide fuel. The best isotopes for these applications were …

Geotechnical State-Of-The-Art In Guatemala -- Ground Stabilization, Fernando Rafael Callejas Benitez

Doctoral Dissertations

"History provides an understanding of the present and in a way, a guide for the future. The state-of-the-art is often referred to as a snapshot of the most significant works and contributions made in a field of study; In this case the focus is on Guatemalan geotechnical engineering. This study presents a comprehensive description of the different events that impulse geotechnical engineering in Guatemala.

As part of the description of the state-of-the-practice an investigation of the different human (engineers/contractors) and physical resources (laboratories/field equipment) and their capabilities are presented. An overview of the civil engineering programs is presented. Then, the …

Seismic Anisotropy And Mantle Dynamics Beneath The Central And Western United States, Bin Yang

Doctoral Dissertations

"Various tectonic features and the recent availability of high-quality broadband seismic data from the USArray and other seismic stations in the central and western United States (CWUS) provide a distinct opportunity to test different anisotropy-forming mechanisms. For the first part of the study, a total of 4138 pairs of well-defined shear wave splitting (SWS) parameters observed at 445 stations on the northern Great Plains show systematic spatial variations of anisotropic characteristics. Azimuthally invariant fast orientations subparallel to the absolute plate motion (APM) direction are observed at most of the stations on the Superior Craton and the southern Yavapai province, indicating …

Uncertainty Quantification Applied To The Analysis And Design Of A Hypersonic Inflatable Aerodynamic Decelerator For Spacecraft Reentry, Andrew J. Brune

Doctoral Dissertations

"The primary objective of this research is to investigate the uncertainty in the multidisciplinary analysis of a Hypersonic Inflatable Aerodynamic Decelerator configuration for Mars entry, subject to uncertainty sources in the high-fidelity computational models and the operating conditions. Efficient uncertainty quantification methods based on stochastic expansions are applied to the analysis of the hypersonic flowfield, fluid-structure interaction, and flexible thermal protection system response of a deformable inflatable decelerator. Uncertainty analysis is first applied to the hypersonic flowfield simulations to quantify the uncertainty in the surface convective and radiative heat flux, pressure, and shear stress of a fixed inflatable decelerator, subject …

Static And Dynamic Characterization Of Tied Arch Bridges, John Edward Finke

Doctoral Dissertations

"Tied arch bridges have been designed and constructed since the late 19th century. With their open vista owing to minimalist features tied arch bridges continue to appeal the public. Tied arch bridges are both aesthetic and economical alternates to long span bridges holding a place in the hierarchy of major bridges. They fit in a niche between viable and economical plate girder spans and short cable stayed bridge spans. There are several variations of the tied arch with the most common form being those having vertical hangers, stiff tie girders and slender arch ribs. This tied arch variation is examined …

Adaptive Consensus Based Formation Control Of Unmanned Vehicles, Haci Mehmet Guzey

Doctoral Dissertations

"Over the past decade, the control research community has given significant attention to formation control of multiple unmanned vehicles due to a variety of commercial and defense applications. Consensus-based formation control is considered to be more robust and reliable when compared to other formation control methods due to scalability and inherent properties that enable the formation to continue even if one of the vehicles experiences a failure. In contrast to existing methods on formation control where the dynamics of the vehicles are neglected, this dissertation in the form of four papers presents consensus-based formation control of unmanned vehicles-both ground and …

Model Based Fault Diagnosis And Prognosis Of Class Of Linear And Nonlinear Distributed Parameter Systems Modeled By Partial Differential Equations, Jia Cai

Doctoral Dissertations

"With the rapid development of modern control systems, a significant number of industrial systems may suffer from component failures. An accurate yet faster fault prognosis and resilience can improve system availability and reduce unscheduled downtime. Therefore, in this dissertation, model-based prognosis and resilience control schemes have been developed for online prediction and accommodation of faults for distributed parameter systems (DPS). First, a novel fault detection, estimation and prediction framework is introduced utilizing a novel observer for a class of linear DPS with bounded disturbance by modeling the DPS as a set of partial differential equations.

To relax the state measurability …

Modeling Gas Inflow For Extremely Low Permeability Shale Using Cfd, Chatetha Chumkratoke

Doctoral Dissertations

"Computational fluid dynamics (CFD) has been used to model 2-D well inflow over a range of permeabilities to study the impact of various well completion strategies (Augustine, 2011). Augustine's 2-D model was subsequently extended for 3-D flow by Thepporprapakorn (2013), for gas flow in the permeability range of tight gas (0.01 mD).

This work presents a 3-D CFD model of gas inflow valid for extremely low ranges of permeability (0.00001 mD). In extremely low permeability, gas flow is complex and includes flow from fractures, flow through porous media, and diffusive gas transport. Diffusive gas transport is important when strong density …

Algorithms Leveraging Smartphone Sensing For Analyzing Explosion Events, Srinivas Chakravarthi Thandu

Doctoral Dissertations

"The increasing frequency of explosive disasters throughout the world in recent years have created a clear need for the systems to monitor for them continuously to improve the post-disaster emergency events such as rescue and recovery operations. Disasters both man-made and natural are unfortunate and not preferred, however monitoring them may be a lifesaving phenomenon in emergency scenarios. Dedicated sensors deployed in the public places and their associated networks to monitor such events may be inadequate and must be complemented for making the monitoring more pervasive and effective. In the recent past, modern smartphones with significant processing, networking and storage …

Proactive Strategies In Personal Dose Monitoring, Prevention And Mitigation, Manish Kumar Sharma

Doctoral Dissertations

"At certain threshold, nuclear radiation (like x-rays and gamma-rays) may adversely impact the health of living tissues. The exposure to these radiations in nuclear facilities is measured by devices called dosimeters. The devices are generally worn on the torso and are monitored by health physics division to report the radiation dose received by the personnel. However, this approach is not proactive--since the dosimeters reflect the dose that has already been absorbed in the body of the wearer.

This work presents a scheme to proactively avoid large dose acquisition at radiation-prone facilities. The work was divided into three major segments: (i) …

Blended Learning Citation Patterns And Publication Networks Across Seven Worldwide Regions, Kristian J. Spring, Charles R. Graham

Faculty Publications

The field of international blended learning (BL) is primed to benefit from stronger communication and collaboration. Collaboration is currently limited, and regions vary greatly in terms of citations. However, BL is growing worldwide and each region is an important part of the community. The goal of this research is to explore where the most impactful conversations about BL worldwide are occurring and how, if at all, are they connected to one another in terms of citations and publications. We present here the most cited BL articles from each region, the journals that publish these articles, and citation and publication patterns …

Applying Basic Gamification Techniques To It Compliance Training: Evidence From The Lab And Field, Ryan J. Baxter, D. Kip Holderness, David A. Wood

Faculty Publications

Companies depend on strong internal controls to protect the integrity of accounting information systems. IT security and data privacy training are critical controls to safeguarding company information. However, employees often dislike the training, which can cause a lack of attention to and poor understanding of training concepts, leading to less effective internal controls. To improve the training experience, companies are implementing principles of games into employee training modules; a practice known as gamification. Using a laboratory experiment of data privacy training and a field study involving a publicly-traded bank’s rollout of IT security training, we test whether a training environment …

A Novel Relaxed Hierarchical Equivalent Source Algorithm (Rhesa) For Electromagnetic Scattering Analysis Of Dielectric Objects, Xin Fu, Li (Lijun) Jun Jiang, Hong Tat Ewe

Electrical and Computer Engineering Faculty Research & Creative Works

A novel relaxed hierarchical algorithm based on the surface equivalence principle for the volume integral equations (VIEs) is proposed in this work. The equivalent sources residing on relaxed spherical equivalence surfaces are established by exact integral formulations. The equivalence surfaces are exploited hierarchically to accelerate matrix–vector product in iterative solutions for the VIEs. The computation time and memory cost complexity of the proposed algorithm for dielectric scatters scale as O(N4/3) and O(N) , respectively. Numerical examples validate the accuracy and capability of the proposed algorithm.

Performance Enhancement Of Equivalence Principle Algorithm, Xin Fu, Li (Lijun) Jun Jiang, Zu Hui Ma, Shi Quan He

Electrical and Computer Engineering Faculty Research & Creative Works

The conventional equivalence principle algorithm (EPA) exploits cubical surfaces to support equivalent sources. However, it introduces strong discontinuities due to sharp edges and corners. In this letter, a spherical surface is employed as the equivalence surface to avoid singularities from nonsmoothness. To achieve better accuracy, the meshless sampling scheme is used for integral operators on the spherical equivalence surface. The numerical examples are provided to validate the performance enhancement of EPA through the proposed method.

Electrostatically-Actuated 4h-Sic In-Plane And Out-Of-Plane High Frequency Mems Resonator, Allen V. Lim, Tutku Karacolak, Jheng Yi Jiang, Chih Fang Huang, Feng Zhao

Electrical and Computer Engineering Faculty Research & Creative Works

As a wide bandgap and single crystalline semiconductor, 4H-polytype silicon carbide (4H-SiC) is an excellent material choice for devices operating in harsh environments of high temperature, high pressure, radiation, chemical and biomedical, etc. In this letter, an electrostatically actuated 4H-SiC micro resonator was fabricated by dopant-selective photoelectrochemical etching of n-p-n homoepitaxial structure. Resonant frequencies of 3.463 MHz (out-of-plane) and 16.9 MHz (in-plane) were attained, and they are in good agreement with theoretical calculation. To the best of our knowledge, these frequencies are the highest values ever reported from single crystalline 4H-SiC MEMS resonators.

Effects Of Electrode Materials On Charge Conduction Mechanisms Of Memory Device Based On Natural Aloe Vera, Zhe Xi Lim, Sasidharan Sreenivasan, Yew Hoong Wong, Feng Zhao, Kuan Yew Cheong

Electrical and Computer Engineering Faculty Research & Creative Works

Resistive switching behaviors in Aloe vera films are being explored for nonvolatile memory applications. A simple structure in which the Aloe vera films sandwiched in between a top and bottom electrode are used. The switching behaviors of the devices in which the Aloe vera film is dried at different temperatures and the roles of top electrode materials (Al and Ag) are investigated. Current density-voltage measurements reveal that filamentary conduction is the dominant conduction process inducing resistive switching characteristics in Aloe vera films. Device with Al-Top electrode requires a forming voltage higher than devices with Ag-Top electrode, due to the tendency …

Modeling Resilience In System Of Systems Architecture, Paulette Acheson, Cihan H. Dagli

Engineering Management and Systems Engineering Faculty Research & Creative Works

System of Systems (SoS) can be represented by the SoS architecture which defines the constituent systems and their interfaces. SoS delivers capabilities beyond what the systems working independently can provide. Resiliency of the SoS is becoming increasingly more important and necessary for mission success. Resiliency can be defined as the ability of the SoS architecture to defend against emerging threats. This defense means adapting the SoS architecture to handle the new threat. As a new threat is uncovered, the SoS architecture evolves to a new SoS architecture resilient to the new threat. This paper presents a novel approach to modeling …

Co-Doping Of Magnesium With Indium In Nitrides: First Principle Calculation And Experiment, Zhiqiang Liu, Binglei Fu, Xiaoyan Yi, Guodong Yuan, Junxi Wang, Jinmin Li, Luna, Ian Ferguson

Electrical and Computer Engineering Faculty Research & Creative Works

In this work, an effective strategy for achieving efficient p-type doping in wide bandgap nitride semiconductors was proposed to overcome the fundamental issue of high activation energy. We demonstrated that a hole concentration as high as 1.4 x 1018 cm-3 could been achieved through In-Mg co-doping. The electronic structure of the system and the formation energy of impurity were analyzed via first principal calculation to clarify the underlying physics and the ambiguity in understanding of the origin of the high hole concentration. Our results indicated that the original valence band maximum of the host materials could be modified, thus improving …