Engineering Commons^™

Approximate Computing: An Integrated Cross-Layer Framework, Swagath Venkataramani

Open Access Dissertations

A new design approach, called approximate computing (AxC), leverages the flexibility provided by intrinsic application resilience to realize hardware or software implementations that are more efficient in energy or performance. Approximate computing techniques forsake exact (numerical or Boolean) equivalence in the execution of some of the application’s computations, while ensuring that the output quality is acceptable. While early efforts in approximate computing have demonstrated great potential, they consist of ad hoc techniques applied to a very narrow set of applications, leaving in question the applicability of approximate computing in a broader context.

The primary objective of this thesis is to …

Identifying And Prioritizing Critical Success Factors For Fixed Base Operators In The United States: A Mixed Method Approach, Yu Wang

Open Access Dissertations

Fixed Base Operators (FBOs) are major service providers for the general aviation (GA) sector, which closely connect the public with the aviation industry. However, over the past decade, the U.S. GA industry has experienced a decline in the numbers of registered aircraft, pilots, and airports. Due to the fact that FBOs significantly contribute to the aviation industry, further research studies regarding the FBO-sector at a national level are needed. The purpose of this dissertation was to identify and prioritize the critical success factors (CSFs) that promote the success of FBO operations in the United States.

The methodology consisted of a …

Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang

Open Access Dissertations

Lean-burn natural gas engines offer enhanced thermal efficiencies and reduced soot and NOx emissions. However, cycle-to-cycle variability in combustion that can result from unreliable ignition, variability in equivalence ratio and quenching is a challenge. Reliability of ignition can be improved by employing a dual-fuel ignition strategy in which a small quantity of diesel fuel is injected to initiate ignition. Computational studies of n-heptane/methane-air mixing layers are performed to provide insight into the fundamental physics of dual-fuel ignition. The results show that the characteristic time required for steady premixed flame propagation has three components: time for autoignition to occur, time for …

On The Use Of Mechanical And Acoustical Excitations For Selective Heat Generation In Polymer-Bonded Energetic Materials, Daniel C. Woods

Open Access Dissertations

To address security issues in both military and civilian settings, there is a pressing need for improved explosives detection technologies suitable for trace vapor detection. In light of the strong dependence of vapor pressure on temperature, trace vapor detection capabilities may be enhanced by selectively heating target materials by external excitation. Moreover, polymer-bonded energetic materials may be particularly susceptible to heating by mechanical or acoustical excitation, due to the high levels of damping and low thermal conductivities of most polymers. In this work, the thermomechanical response of polymer-based energetic composites and methods for acoustical excitation are investigated in order to …

Matrix-Free Time-Domain Methods For General Electromagnetic Analysis, Jin Yan

Open Access Dissertations

Many engineering challenges demand an efficient computational solution of large-scale problems. If a computational method can be made free of matrix solutions, then it has a potential of solving very large scale problems. Among existing computational electromagnetic methods, the explicit finite-difference time-domain (FDTD) method is free of matrix solutions. However, it requires a structured orthogonal grid for space discretization. In this work, we develop a new time-domain method that naturally requires no matrix solution, regardless of whether the discretization is a structured grid or an unstructured mesh. No dual mesh, interpolation, projection and mass lumping are needed. Furthermore, a time-marching …

Computer Vision-Based Structural Assessment Exploiting Large Volumes Of Images, Chul Min Yeum

Open Access Dissertations

Visual assessment is a process to understand the state of a structure based on evaluations originating from visual information. Recent advances in computer vision to explore new sensors, sensing platforms and high-performance computing have shed light on the potential for vision-based visual assessment in civil engineering structures. The use of low-cost, high-resolution visual sensors in conjunction with mobile and aerial platforms can overcome spatial and temporal limitations typically associated with other forms of sensing in civil structures. Also, GPU-accelerated and parallel computing offer unprecedented speed and performance, accelerating processing the collected visual data. However, despite the enormous endeavor in past …

Photoelectrochemical And Photophysical Studies Of Carbon Nanotube And Molybdenum Disulfide Based Light Harvesting Devices, Hanyu Zhang

Open Access Dissertations

There is a critical need in utilizing solar radiation as a renewable energy source. While photovoltaic solar cells are widely used, much attention has been devoted in the past decade to developing nanotechnology for potential cost reduction and improved device efficiency and reliability. Low-dimensional materials offer unique physical properties which may be exploited for solar energy harvesting and conversion. Understanding their fundamental properties and developing relevant manufacturing strategies will thus pave the road toward high-performance, cost-effective, light-harvesting devices.

This thesis has investigated single-wall carbon nanotubes (SWCNTs) and molybdenum disulfide (MoS2) nanolayers for their light-harvesting ability in donor-acceptor systems. These materials …

Electrostatic Nanosmearing Architecture Of Additive Functional Groups During High Shear Mixing Of Pharmaceutical Blends, Sajan Kumar Chatarla

Masters Theses

The main objective of the research project is to detect and quantify the rate and extent of nanosmearing of hydrophobic functional groups of additives on multiple pharmaceutical particles during high shear mixing of formulations due to electrostatics affecting critical blend properties on the bulk scale. We accomplished this task by systematically detecting the electrostatics during powder flow and its consequence on the nanosmearing distribution of additives during mixing. In the first stage, the electrostatic behavior of particles was correlated to the powder flow. Secondly, its relative influence on nanosmearing of additives during mixing was determined by developing a methodology to …

Multi-Axial Fiber Optic Reference Strain Sensor For Flexible Dynamics Of Structures, Gabriel Lapilli

Theses and Dissertations

Launch vehicles are in an ever-decreasing weight trend, with bodies becoming more slender to reduce aerodynamic loading. Mass and stiffness tend to be opposing concepts when designing launch vehicles: a stiffer structure means it is usually heavier. Lower stiffness on launch vehicles may produce excessive vibrations during flight, reducing the performance, operating characteristics and safety margins of the vehicle. It also impacts flight dynamics: as the vehicle flies, the orientation of its thrusters and actuators are impacted by the vibrations, creating potential instabilities in the control schemes. This is currently accounted for by using single-point inertial measurements and feeding the …

The Influence Of Resin Rich Volumes On The Mechanical Properties Of Glass Fibre Reinforced Polymer Composites, Grant Lewin

The Plymouth Student Scientist

Glass fibre composite plates were manufactured using several methods to promote increasing levels of fibre volume fraction (Vf), inversely leading to a lower residual resin content and theoretically smaller resin rich volumes (RRV). The aim of this project is to determine the effect of resin rich volumes on the mechanical properties tested and whether they scale with the increase in Vf. Five test plates were manufactured, the first using hand-lamination (HL) with three further plates produced using resin infusion (RI), with infusion occurring under consolidation pressures of 300, 600 and 900mbar. The fifth plate was infused under full vacuum, ~1000mbar …

Nanostructured Morphologies In Glassy Polymer Networks, Brian Greenhoe

Dissertations

The body of this work describes a novel approach for the dispersion of multi-walled carbon nanotubes in a high T_g epoxy prepolymer matrix using a twin screw high-shear continuous reactor. The method demonstrated improves on previous dispersion methods in several ways. It offers increased efficiency through excellent heat transfer, while being solvent-less, scale-able, and tailorable to drive dispersion states to judiciously chosen dispersion states. Furthermore, it was shown that dispersion state and agglomerate morphology can be directed, in several ways, through processing conditions and also by controlling the matrix viscosity profile through cure. Broadband dielectric spectroscopy, optical hot-stage microscopy, …

Design And Synthesis Of Dynamic Covalent Polymer Scaffolds With Controlled Architectures, Emily Annette Hoff

Dissertations

The design and synthesis of functional, controlled polymer architectures is essential to the development of new materials with precise and tailorable properties or applications. The work described in this dissertation focuses on the development of controlled polymer architectures with dynamic linkages for the design of multifunctional materials and surfaces via robust, efficient, and stimuli-responsive strategies.

In Chapter III, a post-polymerization modification strategy based on ambient temperature nucleophilic chemical deblocking of polymer scaffolds bearing N-heterocycle blocked isocyanate moieties is reported. Room temperature RAFT polymerization of three azole-N-carboxamide methacrylates, including 3,5-dimethyl pyrazole, imidazole, and 1,2,4-triazole derivatives, afforded reactive polymer scaffolds …

Low Temperature Flexible Perovskite Solar Cell With Mesoporous Tio2 Electron Transport Layer In High Humidity Environment, Felipe De La Torre

Theses and Dissertations

Perovskite solar cells are the fastest advancing solar technology to date with efficiencies increasing from 3.9% to more than 21% within a few years. They have emerged as a possible alternative to silicon photovoltaics due to their exceptional photovoltaic performance, light absorbing properties, and low-cost fabrication with methylammonium lead iodide (CH3NH 3PbI3) getting considerable interest in research and development. However, there are still many challenges that must be addressed for perovskite solar cells to replace contemporary solar cells, such as improving their stability, making them nonhazardous, further increasing their efficiency, and developing better techniques for large scale fabrication. In this …

Forcespinning®: An Alternative Method To Fabricate Metal Oxide/Carbon Composite Nanofiber Anodes For Li-Ion Batteries, Luis Zuniga

Theses and Dissertations

Metals and their respective oxides have been highly regarded as next generation anode materials for lithium-ion batteries (LIBs). In this research work the electrochemical performance of Sn, SnO2, and TiO2. With the advantages of nanotechnology and the Forcespinning® method of fabricating micro and nanofibers, binder-free anodes are produced from metal or metal oxide/carbon composite microfibers. Through these microfibers the electrochemical performance of the above mentioned materials are significantly improved due to the increased surface area per volume providing a large number of reaction sites for the anode materials. Further performance enhancement was achieved by also modifying the fiber microstructure to …

Wettability Of Nonwoven Polymeric Nanofiber Mats, Edgar Munoz

Theses and Dissertations

The wettability of heterogeneous materials has been attracting special interest by academia and industrial sector given the need to development self-cleaning Nonwoven nanofiber mats have demonstrated potential given its hydrophobicity granted by the ultimate structure of the system, small fiber diameter and small pores giving rise to effects such as the Cassie-Baxter. This thesis analyzed the wettability of a wide range of polymeric systems. Nanofiber mats were manufactured using the Forcespinning® technology. Samples were prepared at different polymeric concentrations and rotational speeds to alter fiber size; density of the mat was also altered to evaluate the effect of porosity on …

Optimizing Border Security With Stochastic And Deterministic Strategies, Gabriel A. Rueda

Theses and Dissertations

International trade and border security have always been linked together, and so has the need to find ways to improve security decisions. The United States and bordering countries benefit from the North American Free Trade Agreement (NAFTA), but amongst the positive effects of NAFTA there is a looming drug threat that effects the bi-national supply chains. In 2015 Customs and Border Protections (CBP) processed over 72,000 trucks, rail, and sea containers a day. CBP also seized 3.4 million pounds of narcotics, the majority of them at the ports of entry. With unknown threats using commercial vehicles to transport their illicit …

Knee Joint Internal Forces During Squat Jump Exercise, Ricardo Moreno

Theses and Dissertations

The purpose of this research is to investigate muscular ligament and joint contact forces produced during squat jump exercise. An inverse dynamics, two dimensional, leg model is used to describe the motion in the sagittal plane. The lower extremity model includes two bones, tibia and femur, tibio-femoral ligaments, and muscles such as quadriceps, hamstrings, and gastrocnemius. The ligaments are anatomically modeled as nonlinear strings, but the femoral condyle is modeled as a circle and the tibial plateau as a straight line. Experimental squat jump exercises are conducted to obtain the ground reaction forces, the angular accelerations, and centroid linear acceleration …

Study Of Selective Laser Remelting Of 316l S.S. To Reduce Roughness On Inclined Surface, Jafar Ghorbani

Theses and Dissertations

Additive manufacturing (AM) technologies are increasingly competing with subtractive methods, and there are promising applications for additive technologies that are hybrid with traditional manufacturing methods. Poor surface roughness of additive manufactured parts continues to be a major challenge especially for advanced functional parts. In this study, effect of processing parameters are evaluated, optimized and verified by using the Box–Behnken design of experiment method. The results, for the first time, reveal that surface remelting has the potential to become a high speed approach for improving the roughness of non-horizontal surface of additive manufactured parts.

Development Of A Fundamental Autonomous Ground Vehicle Cruise Control Using Matlab And Simulink, Luis F. Martinez

Theses and Dissertations

This study presents and describes the development of a fully autonomous vehicle cruise control system covering the vehicle dynamics and control design needed to simulate such system. It encompasses obstacle avoidance, intelligent-and-optimal lane change as well as adaptive behavior. This study offers a comprehensive two-dimensional cruise control with three degrees of freedom and it is designed using active obstacle avoidance controllers. It also includes optimized fuzzy logic for optimal vehicle trajectory and an extensive array of control law methodology. The end work shows a complete simulation run using MATLAB and Simulink.

Bs News November/December

Building Services Engineering

No abstract provided.

Synthesis, Characterization, And Fabrication Of All Inorganic Quantum Dot Leds, Haider Baqer Salman

Graduate Theses and Dissertations

Quantum Dot LEDs with all inorganic materials are investigated in this thesis. The research was motivated by the potential disruptive technology of core shell quantum dots in lighting and display applications. These devices consisted of three main layers: hole transport layer (HTL), electron transport layer (ETL), and emissive layer where the emission of photons occurs. The latter part was formed of CdSe / ZnS core-shell quantum dots, which were synthesized following hot injection method. The ETL and the HTL were formed of zinc oxide nanocrystals and nickel oxide, respectively. Motivated by the low cost synthesis and deposition, NiO and ZnO …

Growth Of Gesn And Gepb Alloy Films Using Thermal Evaporator, Hakimah Alahmed

Graduate Theses and Dissertations

Silicon is the most important semiconductor material used in microelectronic devices. As the number of transistors keep doubling every 24 months (Moore’s law), transistors continue scaling down in size, electrical interconnect is reaching its limits to keep up with the scaling down rate in integrated circuits. These limitations are related to interconnect density and power consumption. Hence, replacing electrical interconnect with optical interconnect on the chip or between chips has the ability to overcome these limitations. However, silicon has poor light emitting efficiency, and other substitutes such as III-V materials are not suitable due to high cost, lattice mismatch, and …

Multiscale Mechanics Of Bone: Examining The Influence Of Genetic Alterations, Brendyn James Miller

Theses and Dissertations

This MSc thesis investigates how genetic alterations involved in the synthesis of proteins or in the regulation of tissue remodeling affects the composition, structure and mechanics of bone at the multiscale levels. This was accomplished by performing two mouse model studies. In the first study, bone properties of TIMP-3 knock-out (Timp-3⁻ˊ⁻) mice were examined by performing mechanical testing, µCT analysis, and FTIR analysis. Results demonstrated that the mechanical integrity of the Timp-3⁻ˊ⁻ bone was compromised. Decreased values for the yield and ultimate load, stress capacity, and fracture toughness were observed in both the TIMP-3 deficient bones. These reductions in the …

How A Systematic Approach To Uncertainty Quantification Renders Molecular Simulation A Quantitative Tool In Predicting The Critical Constants For Large N-Alkanes, Richard Alma Messerly

Theses and Dissertations

Accurate thermophysical property data are crucial for designing efficient chemical processes. For this reason, the Design Institute for Physical Properties (DIPPR 801) provides evaluated experimental data and prediction of various thermophysical properties. The critical temperature (T_c), critical density (ρ_c), critical pressure (P_c), critical compressibility factor (Z_c), and normal boiling point (T_b) are important constants to check for thermodynamic consistency and to estimate other properties. The n-alkane family is of primary interest because it is generally assumed that other families of compounds behave similarly to …

Selecting Cloud Platform Services Based On Application Requirements, Bridger Ronald Larson

Theses and Dissertations

As virtualization platforms or cloud computing have become more of a commodity, many more organizations have been utilizing them. Many organizations and technologies have emerged to fulfill those cloud needs. Cloud vendors provide similar services, but the differences can have significant impact on specific applications. Selecting the right provider is difficult and confusing because of the number of options. It can be difficult to determine which application characteristics will impact the choice of implementation. There has not been a concise process to select which cloud vendor and characteristics are best suited for the application requirements and organization requirements. This thesis …

Psychophysiological Analysis Of A Pedagogical Agent And Robotic Peer For Individuals With Autism Spectrum Disorders., Mohammad Nasser Saadatzi

Electronic Theses and Dissertations

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by ongoing problems in social interaction and communication, and engagement in repetitive behaviors. According to Centers for Disease Control and Prevention, an estimated 1 in 68 children in the United States has ASD. Mounting evidence shows that many of these individuals display an interest in social interaction with computers and robots and, in general, feel comfortable spending time in such environments. It is known that the subtlety and unpredictability of people’s social behavior are intimidating and confusing for many individuals with ASD. Computerized learning environments and robots, however, prepare a predictable, …

A Cad System For Early Diagnosis Of Autism Using Different Imaging Modalities., Marwa Maher Tawfik Ismail

Electronic Theses and Dissertations

The term “autism spectrum disorder” (ASD) refers to a collection of neuro-developmental disorders that affect linguistic, behavioral, and social skills. Autism has many symptoms, most prominently, social impairment and repetitive behaviors. It is crucial to diagnose autism at an early stage for better assessment and investigation of this complex syndrome. There have been a lot of efforts to diagnose ASD using different techniques, such as imaging modalities, genetic techniques, and behavior reports. Imaging modalities have been extensively exploited for ASD diagnosis, and one of the most successful ones is Magnetic resonance imaging(MRI),where it has shown promise for the early diagnosis …

An All-In-One Debugging Approach: Java Debugging, Execution Visualization And Verification, Beinan Wang

Dissertations - ALL

We devise a widely applicable debugging approach to deal with the prevailing issue that bugs cannot be precisely reproduced in nondeterministic complex concurrent programs. A distinct efficient record-and-playback mechanism is designed to record all the internal states of execution including intermediate results by injecting our own bytecode, which does not affect the source code, and, through a two-step data processing mechanism, these data will be aggregated, structured and parallel processed for the purpose of replay in high fidelity while keeping the overhead at a satisfactory level. Docker and Git are employed to create a clean environment such that the execution …

Aluminum Is More Tightly Bound In Soil After Wollastonite Treatment To A Forest Watershed, Weiyao Gu

Dissertations - ALL

Aluminum concentrations decreased on soil exchange sites and in soil solutions after a whole-watershed wollastonite (CaSiO3) treatment at the Hubbard Brook Experimental Forest in New Hampshire. This study was conducted to determine whether these decreases could be explained by changes in organically bound Al (Alorg) in soils. The concentrations of Alorg, exchangeable Al (AlKCl) and other chemical properties in organic (Oi + Oe, Oa) and 0-10 cm mineral soil layers were measured using samples collected prior to treatment (1998) and afterwards (2002, 2006, 2010 and 2014). Compared to pre-treatment values, Alorg concentrations in the Oa horizon and the 0-10 cm …

The Economy Of Preventive Maintenance Of Concrete Bridges Due To Corrosion, Haotian Zhang

Dissertations - ALL

The current practice for physical evaluation and delayed maintenance of deteriorated concrete bridge is fundamentally wrong. This research presents a new approach for the evaluation of the condition states of steel reinforced concrete bridge members, which is based on their chemical conditions instead of the physical deficiencies such as cracks and delamination. Using the proposed chemical based inspection approach, a more effective and economic preventive maintenance plan could be achieved. The available non-destructive evaluation (NDE) methods and preventive maintenance measure are identified. Since the chloride induced corrosion is the major factor that dictates the service life of the steel reinforced …