Engineering Commons^™

Efficient Inelastic Scattering In Atomistic Tight Binding, James A. Charles

Open Access Theses

In this thesis, the coherent and incoherent transport simulation capabilities of the multipurpose nanodevice simulation tool NEMO5 are presented and applied on transport in tunneling field-effect transistors (TFET). A gentle introduction is given to the non-equilibrium Green's function theory. The comparison with experimental resistivity data confirms the validity of the electron-phonon scattering models. Common pitfalls of numerical implementations such as current conservation, energy mesh resolution, and recursive Green's function stability and the applicability of common approximations of scattering self-energies are discussed. The impact of phonon-assisted tunneling on the performance of TFETs is exemplified with a concrete Si nanowire device. The …

Stochastic Modeling And Dem Simulation Of Granular Media Subsidence Due To Underground Activity, Rodrigo Borela Valente

Open Access Theses

Many communities around the world have been established in areas of ongoing, as well as ceased, underground mining activity. Ground movements induced by ore extraction methods and the collapse of abandoned cavities have long been recognized as a hazard to surface structures. A number of approaches have been proposed for the prediction of subsidence in underground mining regions, and their integration to Geographic Information Systems (GIS) can produce a powerful risk management tool. Nevertheless, this application is often limited by either a lack of generality or excessive computational cost of the methods available.

In this work, the stochastic subsidence model …

Fleet Level Environmental Evaluation Of Emission Taxing Scheme And Biofuel: A Combined Optimization And Multi-Actor Approach, Hsun Chao

Open Access Theses

The Fleet Level Environmental Evaluation Tool (FLEET) can assess environmental impacts of various levels of technology and environmental policies on fleet-level carbon emissions and airline operations. FLEET consists of different models to mimic airlines' behaviors and a resource allocation problem to simulate airlines' aircraft deployments on their networks. Additionally, the Multiactors Biofuel Model can conduct biofuel life-cycle assessments and evaluate biofuel developments and assess the effects of new technology on biofuel production costs and unit carbon emissions as well.

In addition, the European Union (EU) initiated an Emission Trading Scheme (ETS) in the European Economic Area, while International Civil Aviation …

Additive Manufacturing Of Carbon Fiber-Reinforced Thermoplastic Composites, Nicholas M. Denardo

Open Access Theses

Additive manufacturing, or 3D printing, encompasses manufacturing processes that construct a geometry by depositing or solidifying material only where it is needed in the absence of a mold. The ability to manufacture complex geometries on demand directly from a digital file, as well as the decreasing equipment costs due to increased competition in the market, have resulted in the AM industry experiencing rapid growth in the past decade. Many companies have emerged with novel technologies well suited to improve products and/or save costs in various industries.

Until recently, the applications of polymer additive manufacturing have been mainly limited to prototyping. …

An Led-Based Image Sensor With Energy Harvesting And Projection Capabilities College Of Technology, Xiaozhe Fan

Open Access Theses

The light emitting diode (LED) technology has experienced great improvements in efficiency and cost reduction since the first visible light LED was invented in 1962. At the same time, because LEDs exhibit excellent photovoltaic performance, their capabilities of sensing light and harvesting energy have also been explored and studied for many years. By triple functionality of LEDs, they are widely used in a variety of research areas including visible light communication, robotics, structured light application and so on. Meanwhile, this triple functionality of LEDs also inspired researchers to combine and implement different functions in one system.

In this thesis, An …

Design And Analysis Of A High Performance Valve, Jordan M. Garrity

Open Access Theses

Most valves available in the fluid power industry today are capable of achieving either a large flow rate or a quick response time; however, often they are unable to deliver both simultaneously. Commercially available valves that can produce both at the same time require complex geometries with multiple actuation stages and piloting pressures, making them expensive components. To establish their active usage in applications across the fluid power industry, a reduction in price for these components is paramount. The Energy Coupling Actuated Valve (ECAV) is capable of solving the large flow rates with fast actuation speeds trade-off by utilizing a …

Modelling And Control Of A Parallel Through-The-Road Plug-In Hybrid Vehicle, Rohinish Gupta

Open Access Theses

With an increasing number of passenger vehicles, automotive emissions has become a major challenge. Among other pollutants, green house gas (GHG) emissions form a majority of the exhaust coming out of the tail-pipe and are blamed for the rising temperature of the earth. The net carbon emissions due to running a lightduty passenger vehicle are studied in the present thesis. Hybrid electric vehicles have been proven to have lower green house gas emissions than conventional vehicles as electricity is cleaner than fossil fuels.

Using a parallel-through-the-road hybrid architecture vehicle, different power management strategies are studied. To begin with, a detailed …

Service-Level Based Response By Assignment And Order Processing For Warehouse Automation, Zijian He

Open Access Theses

Along with tremendous growth of online sales in this Internet era, unprecedented intensive competition in shortening the delivery time of orders has been occurring among several major online retailers. On the other hand, the idea of customer-oriented service creates a trend of diversified pricing strategy. Different price options are offered to cater to diversified needs of customers. It has become an urgent need for online sales industries to provide the differentiated service levels for different classes of customers with different priorities based on the charging prices and resource constraints of the supply network.

In response to the challenges mentioned above, …

Monitoring Dbms Activity To Detect Insider Threat Using Query Selectivity, Prajwal B. Hegde

Open Access Theses

The objective of the research presented in this thesis is to evaluate the importance of query selectivity for monitoring DBMS activity and detect insider threat. We propose query selectivity as an additional component to an existing anomaly detection system (ADS). We first look at the advantages of working with this particular ADS. This is followed by a discussion about some existing limitations in the anomaly detection system (ADS) and how it affects its overall performance. We look at what query selectivity is and how it can help improve upon the existing limitations of the ADS. The system is then implemented …

A Novel Mode-Switching Hydraulic Hybrid For An On-Highway Vehicle: A Study Of Architecture And Control, Hiral Jayantilal Haria

Open Access Theses

Increasing demand for fossil fuels, their limited reserves and the environmental effects resulting from the transportation sector has raised severe concerns to government agencies, transportation industry as well as the end-users. This has raised interests in improving the fuel economy of road vehicles. One of the promising technologies in this regard is hybridization of vehicle transmission. Hydraulic hybrids have progressively gained acceptance due to their high power density and low component costs relative to their electric counterpart.

Many different hydraulic hybrid architectures have been developed to achieve better power management and regenerative braking and have been tested for performance and …

Ab Initio Based State Specific Modeling Of N2+O System, Han Luo

Open Access Theses

Nitrogen and atomic oxygen play an important role in high temperature gas systems. Their Zeldovich reaction product nitric oxide not only affects aerothermal loads and emissions of hypersonic vehicles, but also has the possibility to influence the efficiency of hypersonic propulsion. Atomic oxygen induced nitrogen dissociation is another reaction mechanism of the N2+O system. However, due to the difficulty of conducting ground tests, there are no experimental data for this reaction now. Thermo-chemical nonequilibrium could make the problem more difficult since experiments could only track macroscopic gas properties instead of internal energy distribution. On the other hand, current reaction and …

The Effect Of Static And Dynamic Aging On Fatigue Behavior Of Sn3.0ag0.5cu Solder Alloy, Yiran Li

Open Access Theses

In microelectronic assemblies, solder joints serve as interconnection between different packaging levels and are an important cause for the failure of microelectronic products. Sn-Ag-Cu solder alloys became important after lead-based solder alloys were caused to be discarded by regulations in European Union and Japan. However, the constitutive behavior of Sn-Ag-Cu alloys is not as well understood as lead-based solder alloys, and many studies confirm the aging of these alloys with time. The aging of Sn-Ag-Cu alloys and its effect on mechanical behavior challenges the reliability prediction of microelectronic assemblies. In this study, the effect of pretest isothermal aging and in-test …

Analysis Of Structural And Functional Brain Networks, Jun Young Jeong

Open Access Theses

The brain is a representative example of a network. It consists of numerous spatially distributed regions that continuously exchange information through structural connections. In the past decade, an increasing number of studies have explored the brain network in both structural and functional aspects; they have begun to decipher complex brain wirings, as well as elucidate how the rich functionality emerges from this architecture. Based upon previous studies, this thesis addresses three critical gaps in the field. (I) Although it is known that the community structures of brain network are spatially overlapping, conventional studies have focused on grouping brain regions into …

Parametric And Design Analysis On Thermoelectric Generators, Shouyuan Huang

Open Access Theses

In facing the limited energy source reserves and environmental problems, thermoelectric generators (TEGs) are one of the promising waste heat recovery systems. The modern TEGs for exhaust stream (e.g. from automobiles) can improve the fuel economy by around 5%, taking advantage of the recent developed thermoelectric (TE) materials.

In this work, we aimed at designing a TEG as an add-on module for a gas-phase heat exchanger with maximized power output, and without negative impact (e.g. maintaining a minimum heat dissipation rate from the hot side). We first developed a parametric optimization algorithm using response surface method (RSM) and genetic algorithm …

Influence Of Stormwater Control Measures On Watershed Hydrology And Biogeochemical Cycling, Colin D. Bell

Open Access Dissertations

Urban development replaces vegetation with impervious surfaces and natural drainage channels with pipe networks that quicken flow paths and alter hydrologic regimes. Additionally, the import of food, application of fertilizer to lawns and gardens, and heightened atmospheric deposition increases nutrient availability in urban landscapes. These excess nutrients are ultimately routed to streams through the pipe networks before it can be processed by the vegetation and microorganisms of the landscape. This combination of physical and chemical disturbances impacts stream ecosystems and degrades their ability to perform valuable services such as removal of nutrients, degradation of pollutants, and provision of recreational and …

Investigation Of Digital Pump/Motor Control Strategies, Farid El Breidi

Open Access Dissertations

A pump is the heart of fluid power systems, it has a significant impact on the efficiency of many fluid power systems. Motors are the most common rotary actuators in fluid power systems. State-of-the-art pump/motor units can achieve efficiencies higher than 90% when operating at maximum displacement; however, as the displacement drops, the efficiency of these units drops to below 50%. A new digital pump/motor design aims at increasing these efficiencies by utilizing two electrically controlled high speed on/off valves per displacement chamber; these valves provide the ability to achieve variable displacement and allow freedom in choosing operating strategies. Such …

A Mixed Methods Study On Choice Of Media Influence On Construction Industry Communication, Luciana De Cresce El Debs

Open Access Dissertations

This study focuses on the use of different communication media for solving problems in the construction industry. The focus of this research is on design-problems containing spatial information and are informally reported between site supervision and design professionals. Due to the fragmented nature of the construction industry, miscommunication is a well-known and common problem. Yet, this fragmented nature is necessary in order to build a complex product involving many different types of professionals. To better understand the issue, this study uses previous literature, such as those published on media richness theory, problem-solving strategy, and construction specific communications, in a three-phased …

Modeling Transport Phenomena And Uncertainty Quantification In Solidification Processes, Kyle S. Fezi

Open Access Dissertations

Direct chill (DC) casting is the primary processing route for wrought aluminum alloys. This semicontinuous process consists of primary cooling as the metal is pulled through a water cooled mold followed by secondary cooling with a water jet spray and free falling water. To gain insight into this complex solidification process, a fully transient model of DC casting was developed to predict the transport phenomena of aluminum alloys for various conditions. This model is capable of solving mixture mass, momentum, energy, and species conservation equations during multicomponent solidification. Various DC casting process parameters were examined for their effect on transport …

Enabling A Sustainable Economy Through Energy Systems Modeling: Solar-Centric, Efficient, Integrated And Continuous Process Synthesis And Optimization, Emre Gencer

Open Access Dissertations

The expected increase in food, energy and water demand due to increase in population and change in consumption habits in conjunction with diminishing fossil fuel reserves and increasing greenhouse gas emissions urge the development and implementation of alternative energy conversion techniques using renewable energy for a sustainable economy. Among renewable energy sources, solar energy is prominent due to its abundance. A sustainable economy can be created by producing building blocks foundational to meeting all basic human needs of daily existence. However, intermittencies and limitations on land area dedicated to harness solar energy are the major obstacles on widespread implementation of …

Supporting Space Systems Design Via Systems Dependency Analysis Methodology, Cesare Guariniello

Open Access Dissertations

The increasing size and complexity of space systems and space missions pose severe challenges to space systems engineers. When complex systems and Systems-of-Systems are involved, the behavior of the whole entity is not only due to that of the individual systems involved but also to the interactions and dependencies between the systems. Dependencies can be varied and complex, and designers usually do not perform analysis of the impact of dependencies at the level of complex systems, or this analysis involves excessive computational cost, or occurs at a later stage of the design process, after designers have already set detailed requirements, …

Interactive Logical Analysis Of Planning Domains, Rajesh Kalyanam

Open Access Dissertations

Humans exhibit a significant ability to answer a wide range of questions about previously unencountered planning domains, and leverage this ability to construct “general-purpose'' solution plans for the domain.

The long term vision of this research is to automate this ability, constructing a system that utilizes reasoning to automatically verify claims about a planning domain. The system would use this ability to automatically construct and verify a generalized plan to solve any planning problem in the domain. The goal of this thesis is to start with baseline results from the interactive verification of claims about planning domains and develop the …

Experimental, Theoretical And Computational Modeling Of Flow Boiling, Flow Condensation And Evaporating Falling Films, Chirag Rajan Kharangate

Open Access Dissertations

The transition from single-phase to two-phase thermal systems in future space vehicles demands a thorough understanding of phase change methods in reduced gravity, including microgravity. In this study, phase change methods like flow boiling, flow condensation and evaporative falling-films are investigated experimentally, theoretically and computationally.

The experimental part of the study consists of an investigation of the influence of inlet subcooling and two-phase inlet on flow boiling heat transfer and critical heat flux in a horizontal 2.5-mm wide by 5-mm high rectangular channel in different orientations with respect to Earth gravity using FC-72 as working fluid. High-speed video imaging is …

Response Of High-Strength Steel Reinforced Concrete Structures To Simulated Earthquakes, Lucas Laughery

Open Access Dissertations

In reinforced concrete (RC) structures expected to resist earthquake demands, substituting smaller amounts of high-strength steel for conventional steel reinforcement can help reduce reinforcement congestion and placement costs while keeping strength unchanged.

Provided cross-sectional dimensions remain unchanged, reducing the amount of longitudinal steel in a member will result in a member with similar initial stiffness but lower post-cracking stiffness. Nominal strength can be kept nearly the same if this reduction in the amount of steel is accompanied by a corresponding increase in the strength of the steel. The topic of this investigation is whether two frames with the same initial …

Information Inference For Cyber-Physical Systems With Application To Aviation Safety And Space Situational Awareness, Sangjin Lee

Open Access Dissertations

Due to the rapid advancement of technologies on sensors and processors, engineering systems have become more complex and highly automated to meet ever stringent performance and safety requirements. These systems are usually composed of physical plants (e.g., aircraft, spacecraft, ground vehicles, etc.) and cyber components (e.g., sensing, communication, and computing units), and thus called as Cyber-Physical Systems (CPSs). For safe, efficient, and sustainable operation of a CPS, the states and physical characteristics of the system need to be effectively estimated or inferred from sensing data by proper information inference algorithms. However, due to the complex nature of the interacting multiple-heterogeneous …

Nanophotonics For Dark Materials, Filters, And Optical Magnetism, Mengren Man

Open Access Dissertations

Research on nanophotonic structures for three application areas is described, a near perfect optical absorber based on a graphene/dielectric stack, an ultraviolet bandpass filter formed with an aluminum/dielectric stack, and structures exhibiting homogenizable magnetic properties at infrared frequencies. The graphene stack can be treated as a effective, homogenized medium that can be designed to reflect little light and absorb an astoundingly high amount per unit thickness, making it an ideal dark material and providing a new avenue for photonic devices based on two-dimensional materials. Another material stack arrangement with thin layers of metal and insulator forms a multi-cavity filter that …

Modeling Of Frame Structures Undergoing Large Deformations And Large Rotations, Hui Liu

Open Access Dissertations

Numerical simulation of large-scale problems in structural dynamics, such as structures subject to extreme loads, can provide useful insights into structural behavior while minimizing the need for expensive experimental testing for the same. These types of problems are highly non-linear and usually involve material damage, large deformations and sometimes even collapse of structures. Conventionally, frame structures have been modeled using beam-frame finite elements in almost all structural analysis software currently being used by researchers and the industry. However, there are certain limitations associated with this modeling approach. This research focuses on two issues, in particular, of modeling frame structures undergoing …

Efficient Modeling Of Sound Source Radiation In Free-Space And Room Environments, Yangfan Liu

Open Access Dissertations

Motivated by the need to develop efficient acoustics simulations for sources in different room environments, a modeling procedure has been proposed that consists of two steps in general: (1) the modeling of the free-space radiation of the source based on measurements in a anechoic environment, and (2) the prediction of the sound field in a room environment based on that free-space information.

To achieve a high modeling efficiency, i.e., to reduce the number of modeling parameters while still maintaining acceptable accuracy, a Multipole Equivalent Source Model (ESM) with undetermined source locations has been developed for the free-space sound field prediction. …

Three Dimensional Moving Pictures With A Single Imager And Microfluidic Lens, Chao Liu

Open Access Dissertations

Three-dimensional movie acquisition and corresponding depth data is commonly generated from multiple cameras and multiple views. This technology has high cost and large size which are limitations for medical devices, military surveillance and current consumer products such as small camcorders and cell phone movie cameras. This research result shows that a single imager, equipped with a fast-focus microfluidic lens, produces a highly accurate depth map. On test material, the depth is found to be an average Root Mean Squared Error (RMSE) of 3.543 gray level steps (1.38\%) accuracy compared to ranging data. The depth is inferred using a new Extended …

Methods To Facilitate Community Participation In Humanitarian Engineering Projects: Laying The Foundation For A Learning Platform, Andrea Mazzurco

Open Access Dissertations

Humanitarian engineering (HE) is a new interdisciplinary field that is rapidly emerging worldwide. Many not-for-profit organizations such as Engineers Without Borders, Practical Action, and International Development Enterprise have been flourishing with the goal of providing technological solutions to those who need them the most. In engineering programs across the U.S., HE, service-learning, community engagement, and similar programs are gaining popularity because they offer an efficient way to meet ABET accreditation criteria, while also teaching valuable technical and professional skills to engineering students. However, the cultural, social, and political differences among communities and engineers often add degrees of difficulty that cannot …

Best Matching Processes In Distributed Systems, Mohsen Moghaddam

Open Access Dissertations

The growing complexity and dynamic behavior of modern manufacturing and service industries along with competitive and globalized markets have gradually transformed traditional centralized systems into distributed networks of e- (electronic) Systems. Emerging examples include e-Factories, virtual enterprises, smart farms, automated warehouses, and intelligent transportation systems. These (and similar) distributed systems, regardless of context and application, have a property in common: They all involve certain types of interactions (collaborative, competitive, or both) among their distributed individuals—from clusters of passive sensors and machines to complex networks of computers, intelligent robots, humans, and enterprises. Having this common property, such systems may encounter common …