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Articles 91 - 110 of 110
Full-Text Articles in Engineering
Fault Detection And Diagnosis For Air Conditioners And Heat Pumps Based On Virtual Sensors, Woohyun Kim
Fault Detection And Diagnosis For Air Conditioners And Heat Pumps Based On Virtual Sensors, Woohyun Kim
Open Access Dissertations
The primary goal of this research is to develop and demonstrate an integrated, on-line performance monitoring and diagnostic system with low cost sensors for air conditioning and heat pump equipment. Automated fault detection and diagnostics (FDD) has the potential for improving energy efficiency along with reducing service costs and comfort complaints. To achieve this goal, virtual sensors with low cost measurements and simple models were developed to estimate quantities that would be expensive and or difficult to measure directly.
A virtual refrigerant charge sensor (VRC) was extended with three approaches for determining refrigerant charge for equipment having variable-speed compressors and …
Graphene Decorated Substrates And Their Interfacial Characteristics, Anurag Kumar
Graphene Decorated Substrates And Their Interfacial Characteristics, Anurag Kumar
Open Access Dissertations
Carbon nanotubes and graphene have been extensively studied for their excellent properties. As research on carbon expands, two major issues face the scientific community: (i) Expanding the scale of synthesis and (ii) Integration of different carbon structures for improved functionality. While significant advancements have been made in large-scale synthesis, room for improvement remains. As the scale of production increases, issues such as time, cost and energy that may otherwise not be very significant, begin to play greater roles. Thus, in order to effectively transition from laboratory prototypes to industrial products, a synthesis method that can address these issues is strongly …
Scalable Autonomous Operations Of Unmanned Assets, Sunghun Jung
Scalable Autonomous Operations Of Unmanned Assets, Sunghun Jung
Open Access Dissertations
Although there have been great theoretical advances in the region of Unmanned Aerial Vehicle (UAV) autonomy, applications of those theories into real world are still hesitated due to unexpected disturbances. Most of UAVs which are currently used are mainly, strictly speaking, Remotely Piloted Vehicles (RPA) since most works related with the flight control, sensor data analysis, and decision makings are done by human operators. To increase the degree of autonomy, many researches are focused on developing Unmanned Autonomous Aerial Vehicle (UAAV) which can takeoff, fly to the interested area by avoiding unexpected obstacles, perform various missions with decision makings, come …
Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz
Numerical Techniques For The Noninvasive Assessment Of Material Properties And Stresses In Soft Biomaterials, Kent David Butz
Open Access Dissertations
The noninvasive measurement of finite displacements and strains in biomaterials by magnetic resonance imaging (MRI) may be shown to enable mathematical estimates of stress distributions and material properties within structures of the body such as articular cartilage or the intervertebral disc. Such methods will allow for non-contact and patient-specific modeling in a manner not currently possible with traditional mechanical testing or finite element techniques. Therefore, the objective of this thesis was to develop computational methods incorporating imaging-based measures of deformation, composition, and local microstructure to permit nondestructive analysis of a range of complex biomechanical systems.
Finite strain-based models were developed …
Identification And Quantification Of Nonlinear Behavior In A Disbonded Aluminum Honeycomb Panel Using Single Degree-Of-Freedom Models, Eric Richard Dittman
Identification And Quantification Of Nonlinear Behavior In A Disbonded Aluminum Honeycomb Panel Using Single Degree-Of-Freedom Models, Eric Richard Dittman
Open Access Dissertations
There is not a complete understanding of how damage mechanisms in composite materials react to nondestructive testing inputs. A deeper understanding of composite damage mechanisms and their responses to external vibratory excitation is sought using nonlinear modeling of damping and stiffness characteristics related to the damage. Different types of damping and stiffness single degree-of-freedom models are presented with analysis of their behavior at specific harmonics of the primary resonance of the system. After an understanding of the approximate behaviors of the models is obtained, experimental tests on a damaged specimen are conducted. An aluminum honeycomb sandwich panel is damaged by …
Tooth Cusp Radius Of Curvature As A Dietary Correlate In Primates, Michael Anthony Berthaume
Tooth Cusp Radius Of Curvature As A Dietary Correlate In Primates, Michael Anthony Berthaume
Open Access Dissertations
Tooth cusp radius of curvature (RoC) has been hypothesized to play an important role in food item breakdown, but has remained largely unstudied due to difficulties in measuring and modeling RoC in multicusped teeth. We tested these hypotheses using a parametric model of a four cusped, maxillary, bunodont molar in conjunction with finite element analysis. When our data failed to support existing hypotheses, we put forth and tested the Complex Cusp Hypothesis which states that, during brittle food items breakdown, an optimally shaped molar would be maximizing stresses in the food item while minimizing stresses in the enamel. After gaining …
Scaling Reversible Adhesion In Synthetic And Biological Systems, Michael David Bartlett
Scaling Reversible Adhesion In Synthetic And Biological Systems, Michael David Bartlett
Open Access Dissertations
Geckos and other insects have fascinated scientists and casual observers with their ability to effortlessly climb up walls and across ceilings. This capability has inspired high capacity, easy release synthetic adhesives, which have focused on mimicking the fibrillar features found on the foot pads of these climbing organisms. However, without a fundamental framework that connects biological and synthetic adhesives from nanoscopic to macroscopic features, synthetic mimics have failed to perform favorably at large contact areas. In this thesis, we present a scaling approach which leads to an understanding of reversible adhesion in both synthetic and biological systems over multiple length …
Multiphase Flows With Digital And Traditional Microfluidics, Michael Andrew Nilsson
Multiphase Flows With Digital And Traditional Microfluidics, Michael Andrew Nilsson
Open Access Dissertations
Multi-phase fluid systems are an important concept in fluid mechanics, seen every day in how fluids interact with solids, gases, and other fluids in many industrial, medical, agricultural, and other regimes. In this thesis, the development of a two-dimensional digital microfluidic device is presented, followed by the development of a two-phase microfluidic diagnostic tool designed to simulate sandstone geometries in oil reservoirs. In both instances, it is possible to take advantage of the physics involved in multiphase flows to affect positive outcomes in both.
In order to make an effective droplet-based digital microfluidic device, one must be able to precisely …
Effect Of Total Awake Time On Drivers' Performance And Evaluation Of Training Intervention To Mitigate Effects Of Total Awake Time On Drivers' Performance, Abd Malek Abdul Hamid
Effect Of Total Awake Time On Drivers' Performance And Evaluation Of Training Intervention To Mitigate Effects Of Total Awake Time On Drivers' Performance, Abd Malek Abdul Hamid
Open Access Dissertations
Driving while sleepy, drowsy or fatigued are leading contributors to road crashes. Sleepiness, drowsiness and fatigue usually occur at the end of a prolonged period of time during which an individual has been awake. Although these factors have been heavily researched, it is not clear how one of their primary causes, a prolonged total awake time (TAT), might affect driving skills such as hazard anticipation, hazard mitigation and attention maintenance, three skills that are crucial for safe driving.
The first experiment investigated how these three driving skills are affected by prolonged TAT, and if so to what extent. Forty-eight participants …
Techno-Economic Feasibility Study Of Ammonia Plants Powered By Offshore Wind, Eric R. Morgan
Techno-Economic Feasibility Study Of Ammonia Plants Powered By Offshore Wind, Eric R. Morgan
Open Access Dissertations
Ammonia production with offshore wind power has the potential to transform energy and fertilizer markets within the United States. The vast offshore wind resource can be converted directly into liquid ammonia using existing technologies. The liquid ammonia can then be transported around the country via rail, truck, barge or pipeline and used as either a fertilizer or a fuel. This thesis reviews the technologies required for all-electric, wind-powered ammonia production and offers a simple design of such a system. Cost models based on the physical equipment necessary to produce ammonia with wind power are developed; offshore wind farm cost models …
A Study On Small Scale Intermittency Using Direct Numerical Simulation Of Turbulence, Saba Almalkie
A Study On Small Scale Intermittency Using Direct Numerical Simulation Of Turbulence, Saba Almalkie
Open Access Dissertations
Theory of turbulence at small scales plays a fundamental role in modeling turbulence and in retrieving information from physical measurements of turbulent flows. A systematic methodology based on direct numerical simulations of turbulent flows is developed to investigate universality of small scale turbulence. Understanding characteristics of the small scale intermittency in turbulent flows and the accuracy of the models, measurements, and theories in predicting it are the main objectives. The research is designed to address two central questions; 1) possible effects of large scale anisotropies on the small scale turbulence and 2) potential biases in characterizing small scale turbulence due …
The Oriented-Eddy Collision Model, Michael Bernard Martell Jr.
The Oriented-Eddy Collision Model, Michael Bernard Martell Jr.
Open Access Dissertations
The physical and mathematical foundations of the Oriented-Eddy Collision turbulence model are provided through a discussion of the Reynolds averaged Navier-Stokes (RANS) equations, probability density functions (PDF), PDF collision models, Reynolds stress transport models (RSTM), and two-point correlations. Behavior of the Oriented-Eddy Collision turbulence model near solid boundaries is examined in depth. The Oriented-Eddy Collision turbulence model treats turbulence in a novel way: the average behavior of a turbulent flow can be modeled as a collection of interacting fluid particles, or eddies, which have inherent orientation. The model is cast in the form of a collection of Reynolds stress transport …
Acceleration Of Cfd And Data Analysis Using Graphics Processors, Ali Khajeh Saeed
Acceleration Of Cfd And Data Analysis Using Graphics Processors, Ali Khajeh Saeed
Open Access Dissertations
Graphics processing units function well as high performance computing devices for scientific computing. The non-standard processor architecture and high memory bandwidth allow graphics processing units (GPUs) to provide some of the best performance in terms of FLOPS per dollar. Recently these capabilities became accessible for general purpose computations with the CUDA programming environment on NVIDIA GPUs and ATI Stream Computing environment on ATI GPUs. Many applications in computational science are constrained by memory access speeds and can be accelerated significantly by using GPUs as the compute engine. Using graphics processing units as a compute engine gives the personal desktop computer …
The Aerodynamics And Near Wake Of An Offshore Floating Horizontal Axis Wind Turbine, Thomas Sebastian
The Aerodynamics And Near Wake Of An Offshore Floating Horizontal Axis Wind Turbine, Thomas Sebastian
Open Access Dissertations
Offshore floating wind turbines represent the future of wind energy. However, significant challenges must be overcome before these systems can be widely used. Because of the dynamics of offshore floating wind turbines -- surge, sway, heave, roll, pitch, and yaw -- and the resulting interactions between the rotor and generated wake, the aerodynamic analysis methods and design codes that have found wide use throughout the wind energy industry may be inadequate. Application of these techniques to offshore floating wind turbine aerodynamics may result in off-optimal designs, effectively handicapping these next-generation systems, thereby minimizing their full potential. This dissertation will demonstrate …
A Numerical Study Of Droplet Formation And Behavior Using Interface Tracking Methods, Sandeep Menon
A Numerical Study Of Droplet Formation And Behavior Using Interface Tracking Methods, Sandeep Menon
Open Access Dissertations
An adaptive remeshing algorithm has been developed for multiphase flow simulations using the moving-mesh interface tracking (MMIT) technique. The edge-swapping algorithm uses the Delaunay criterion (in 2D) and a dynamic programming technique (in 3D) to maximize the quality of mesh primitives surrounding edges in the mesh, and performs local remeshing to minimize interpolation errors. Edge bisection and contraction operations are also performed to adjust the mesh resolution around important features like fluid-interfaces, driven by a local length scale estimation algorithm that is efficient and easily parallelized. Flow-field interpolation after reconnection is achieved using a conservative, second-order accurate remapping scheme that …
Engineering Modeling, Analysis And Optimal Design Of Custom Foot Orthotic, Lieselle Enid Trinidad
Engineering Modeling, Analysis And Optimal Design Of Custom Foot Orthotic, Lieselle Enid Trinidad
Open Access Dissertations
This research details a procedure for the systematic design of custom foot orthotics based on simulation models and their validation through experimental and clinical studies. These models may ultimately be able to replace the use of empirical tables for designing custom foot orthotics and enable optimal design thicknesses based on the body weight and activities of end-users. Similarly, they may facilitate effortless simulation of various orthotic and loading conditions, changes in material properties, and foot deformities by simply altering model parameters. Finally, these models and the corresponding results may also form the basis for subsequent design of a new generation …
The Parameter Signature Isolation Method And Applications, James Richard Mccusker
The Parameter Signature Isolation Method And Applications, James Richard Mccusker
Open Access Dissertations
The aim of this research was to develop a method of system identification that would draw inspiration from the approach taken by human experts for simulation model tuning and validation. Human experts are able to utilize their natural pattern recognition ability to identify the various shape attributes, or signatures, of a time series from simulation model outputs. They can also intelligently and effectively perform tasks ranging from system identification to model validation. However, the feature extraction approach employed by them cannot be readily automated due to the difficulty in measuring shape attributes. In order to bridge the gap between the …
Modeling Of Flash Boiling Flows In Injectors With Gasoline-Ethanol Fuel Blends, Kshitij Deepak Neroorkar
Modeling Of Flash Boiling Flows In Injectors With Gasoline-Ethanol Fuel Blends, Kshitij Deepak Neroorkar
Open Access Dissertations
Flash boiling may be defined as the finite-rate mechanism that governs phase change in a high temperature liquid that is depressurized below its vapor pressure. This is a transient and complicated phenomenon which has applications in many industries. The main focus of the current work is on modeling flash boiling in injectors used in engines operating on the principle of gasoline direct injection (GDI). These engines are prone to flash boiling due to the transfer of thermal energy to the fuel, combined with the sub-atmospheric pressures present in the cylinder during injection. Unlike cavitation, there is little tendency for the …
Modeling Of Thermal Non-Equilibrium In Superheated Injector Flows, Shivasubramanian Gopalakrishnan
Modeling Of Thermal Non-Equilibrium In Superheated Injector Flows, Shivasubramanian Gopalakrishnan
Open Access Dissertations
Among the many factors that effect the atomization of a fuel spray in a com- bustion chamber, the flow characteristics of the fuel inside the injector nozzle play significant roles. The enthalpy of the entering fuel can be elevated such that it is higher than the local or downstream saturation enthalpy, which will result in the flash-boiling of the liquid. The phase change process dramatically effects the flow rate and has the potential to cause subsonic two-phase choking. The timescale over which this occurs is comparable to the flow-through time of the nozzle and hence any attempt to model this …
The Analytical Modeling Of The Thermometric Performance Of Total Temperature Thermocouple Probes, Leroy Bertram Butler
The Analytical Modeling Of The Thermometric Performance Of Total Temperature Thermocouple Probes, Leroy Bertram Butler
Open Access Dissertations
A total temperature thermocouple probe immersed in a moving gas stream undergoes thermal energy exchange by means of forced convection between the thermocouple wires and the flowing gas stream, conduction along the thermocouple wires to the probe mount, and radiation between the thermocouple junction wires and any surrounding structure. In general, the thermocouple junction does not indicate the true (stagnation) temperature of the gas stream, thus necessitating the calibration of total temperature probes to obtain correct temperature measurements.
Two models are developed to predict the temperature indicated by a total temperature probe (utilizing type K thermocouple wire) for a given …