Engineering Commons^™

Synthesis Of Lifepo4/C Cathode Nanomaterials For Lithium-Ion Batteries, Chao Cheng

Theses and Dissertations

Lithium-ion batteries have been widely used for many years. The wide application covers such as smart phones, laptops, digital cameras, MP3 players, and electric vehicles. Lithium-ion batteries have become the most important energy storage device in the future. For lithium-ion batteries, the performance of the cathode materials is one of the most important factors. In recent years, the cathode materials have been widely studied including LiCoO2, LiNiO2, LiMnO2, LiMn2O4 and phosphate etc. Among the olivine structure cathode materials, the LiFePO4 (LFP) displays an excellent electrochemical activity and a chemical stability which ensure a high safety. In order to better improve …

Design And Optimization Of Hybrid Energy Storage For Photovoltaic Power Fluctuation Smoothing Based On Frequency Analysis, Ruirui Yang

Theses and Dissertations

A proper design of energy storage system (ESS) can effectively smooth the photovoltaic (PV) output power fluctuation, lower the cost, and improve the power quality and stability.

According to the response characteristics of different energy storage equipment, an optimal hybrid EES sizing method is proposed based on frequency analysis. A hybrid ESS including lead-acid battery, lithium battery and electric double-layer capacitor (EDLC) is selected to smooth out PV power fluctuation and meet both power and energy requirement of the power grid. Fast Fourier Transform (FFT) method is applied for analyzing the spectrum of unwanted PV fluctuation. From the FFT analysis, …

Design, Implementation, And Evaluation Of A Fluorescence Laminar Optical Tomography Scanner For Brain Imaging, Mahya Sheikhzadeh

Theses and Dissertations

Implementation of new instrumentation and techniques for neuroscience research in recent years has opened new avenues in the study of the dynamics of large-scale neural networks such as the brain. In many of these techniques, including fluorescence recordings and optogenetic stimulation, a combination of photonics and molecular genetic methods are exploited to manipulate and monitor neural activities. Such techniques have been proven to be highly efficient in unraveling the mysteries of data processing in the micro circuits of the brain and as a result these techniques are widely used nowadays in most neuroscience labs.

In optogenetics, cell-types of interest are …

Experimental And Numerical Characterization Of Scalable Cellulose Nano-Fiber Composite, Bamdad Barari Barari

Theses and Dissertations

Fiber-reinforced polymer composites have been used in recent years as an alternative to the conventional materials because of their low weight, high mechanical properties and low processing temperatures. Most polymer composites are traditionally made using reinforcing fibers such as carbon or glass fibers. However, there has been recent interest in making these reinforcing fibers from natural resources. The plant-derived cellulose nano-fibers (CNF) are a material with remarkable mechanical properties at the nano-scale that are much superior to the mechanical properties of the traditional natural fibers (such as jute, hemp, kenaf, etc) used in the natural-fiber based polymer composites. Because CNF …

A New Paradigm Of Maximizing The Wind And Solar Penetration– A Economical Assessment, Yuming Chen

Theses and Dissertations

Wind and solar energies are the most potential and widely-used renewable energies. But in most cases these energies cannot be maximized because of transmission line capacity and their remote location. Therefore, this thesis proposes a new paradigm which using battery transportation and logistics instead of transmission line, to maximize wind and solar energies. The main focus of this work is to investigate the economical feasibilities of this new paradigm.

In the first part, different models and application are presented. The purpose is finding an appropriate model which can make full use of existing grid resources such as transmission line and …

Application Of Reynolds Stress Model Using Direct Modeling And Actuator Disk Approaches For A Small-Scale Wind Turbine, Randall Scott Jackson

Theses and Dissertations

The Reynolds Stress Model (RSM) has been avoided for turbulence closure in CFD simulations of wind turbines, largely due to the computational expense and the high potential for numerical instability. The advantage of using RSM is having access to shear stresses that are not available from two-equation RANS-based closure models like k-e and k-w. Access to the shear stresses will aide in the understanding of how the blade design will affect the wake, particularly in the near-wake region. In this research, the RSM turbulence model has been successfully applied in simulating a three-bladed small-scale wind turbine through a direct-model approach …

Coding Strategies For Cochlear Implants Under Adverse Environments, Qudsia Tahmina

Theses and Dissertations

Cochlear implants are electronic prosthetic devices that restores partial hearing in patients with severe to profound hearing loss. Although most coding strategies have significantly improved the perception of speech in quite listening conditions, there remains limitations on speech perception under adverse environments such as in background noise, reverberation and band-limited channels, and we propose strategies that improve the intelligibility of speech transmitted over the telephone networks, reverberated speech and speech in the presence of background noise. For telephone processed speech, we propose to examine the effects of adding low-frequency and high- frequency information to the band-limited telephone speech. Four listening …

Strategic Inventories In A Supply Chain With Vertical Control And Downstream Cournot Competition, Vijayendra Viswanathan

Theses and Dissertations

Strategic Inventory (SI) has been an area of increased interest in theoretical supply chain literature recently. Most of the work so far however, has only considered a supply chain without downstream competition between retailers. Competition is ubiquitous in most market situations, hence, interactions between SI and retailer competition merits study as a first step in bringing the conversations and insights from this stream of literature to the real world.

We present here a two-period and a three-period model of one manufacturer supplying an identical product to two retailers who form a Cournot duopoly. We also study a Commitment contract, where …

Covert Contrast: The Acquisition Of Mandarin Tone 2 And Tone 3 In L2 Production And Perception, Liya Mar

Theses and Dissertations

This dissertation investigates the occurrence of an intermediate stage, termed a covert contrast, in the acquisition of Mandarin Tone 2 (T2) and Tone 3 (T3) by adult speakers of American English. A covert contrast is a statistically reliable distinction produced by language learners that is not perceived by native speakers of the target language (TL). In second language (L2) acquisition, whether a learner is judged as having acquired a TL phonemic contrast has largely depended on whether the contrast was perceived and transcribed by native speakers of the TL. However, categorical perception has shown that native listeners cannot perceive a …

Effects Of Surface Topography And Vibrations On Wetting: Superhydrophobicity, Icephobicity And Corrosion Resistance, Rahul Ramachandran

Theses and Dissertations

Concrete and metallic materials are widely used in construction and water industry. The interaction of both these materials with water and ice (or snow) produces undesirable results and is therefore of interest. Water that gets absorbed into the pores of dry concrete expands on freezing and can lead to crack formation. Also, the ice accretion on concrete surfaces such as roadways can have disastrous consequence. Metallic components used in the water industry undergo corrosion due to contact with aqueous corrosive solutions. Therefore, it is desirable to make concrete water/ice-repellent, and to make metallic surfaces corrosion-resistant.

Recent advances in micro/nanotechnology have …

Multi-Scale Modeling Of Particle Reinforced Concrete Through Finite Element Analysis, Mir Zunaid Shams

Theses and Dissertations

Concrete is the main constituent material in many structures. The behavior of concrete is nonlinear and complex. Increasing use of computer based methods for designing and simulation have also increased the urge for the exact solution of the problems. This leads to difficulties in simulation and modeling of concrete structures. A good approach is to use the general purpose finite element software, e.g ANSYS . Normal strength concrete is a composite material represented by mechanically strong aggregates of various shapes and sizes incorporated into weaker cementitious matrix. A number of simplified homogenized models have been reported in the literature to …

Monitoring Cellular Metabolism With Near-Infrared Spectroscopy, Jeffrey Jay Sugar

Theses and Dissertations

Aims: Although NIRS oximetry has been widely used in clinical and research settings to monitor oxygen consumption in muscles (1), it is not necessarily able to obtain cellular metabolic levels directly. Oxygen saturation will only change with aerobic metabolism (2); however, anaerobic metabolism cannot be assessed by monitoring oxygen saturation. This work aims to measure cell oxygenation and blood oxygenation, simultaneously, by applying oximetry to hemoglobin/deoxyhemoglobin and to cytochrome c oxidase (CCOX). A custom build NIRS device called the cytoximeter was constructed to achieve this goal. This work could have important impacts on monitoring neurological diseases, Postural Tachycardia Syndrome (POTS), …

Improved Attribute-Based Encryption With Fpga For Automatic Appliance Control Application In Smart Grid, Xueqing Wang

Theses and Dissertations

In this thesis, the author describes the privacy violation issues in smart grid with Automatic Appliance Control applications, and explains the security threats related to it. The smart grid is a sensitive and sophisticated system in real life operation. A mass of data including the remote control commands and users’ energy consumptions is transmitted between the utility companies and other devices in the smart grid such as the substations, smart meters, smart home appliances and much more. Without efficient cryptographic methods, an adversary may hack into the data or the remote control commands and extrapolates a resident’s activity model. Therefore, …

Numerical Simulation Of Slow Drying In Porous Media Using Pore Network Model, Zhenyu Xu

Theses and Dissertations

In our first model, an internal and external coupled solver is presented to simulate the slow drying of a porous medium placed adjacent to a laminar flow of air in a slit. The porous medium is represented by a 20×20 pore-network model: the invasion-percolation algorithm is employed to simulate moisture redistribution; water-vapor migration in empty network is estimated using the purely diffusive approach. The external flow-field, unchanged during the drying simulation, is computed in the beginning using the Navier-Stokes equations. Subsequent water-vapor transport is modeled using a convection-diffusion type transport equation. A unique pore-to-cell meshing method and a novel unified …

Numerical And Experimental Study Of Liquid Breakup Process In Solid Rocket Motor Nozzle, Yi-Hsin Yen

Theses and Dissertations

Rocket propulsion is an important travel method for space exploration and national defense, rockets needs to be able to withstand wide range of operation environment and also stable and precise enough to carry sophisticated payload into orbit, those engineering requirement makes rocket becomes one of the state of the art industry. The rocket family have been classified into two major group of liquid and solid rocket based on the fuel phase of liquid or solid state. The solid rocket has the advantages of simple working mechanism, less maintenance and preparing procedure and higher storage safety, those characters of solid rocket …

A Study Of The Hydrostatic And Hydrodynamic Properties Of Aeoliscus Straigatus, Jeremy J. Keifenheim

Theses and Dissertations

Aeoliscus strigatus is a highly maneuverable fish found in the Indo-Pacific region. It boasts a unique head down posture and employs median paired fin propulsion to perform precise movements. The need for highly maneuverable underwater AUVs for exploration and testing drove the examination of the hydrostatics and hydrodynamics influencing Aeoliscus. To determine the stability of Aeoliscus the center of gravity and buoyancy were found. Center of gravity was experimentally located using the three plumb line method while center of buoyancy was located using two separate methods. The first method utilized the measured buoyant force, a rigidly mounted fish and a …

Analysis, Design And Implementation Of A Resonant Solid State Transformer, Mohamad Zouheir Sabbah

Theses and Dissertations

This thesis discusses the design of a full-bridge resonant LLC Solid State Transformer. The proposed topology uses a high-frequency transformer which helps minimizing its cost and size, and enables operating at varying load conditions. By using a resonant circuit, soft switching is achieved. Commutation techniques are discussed, namely ZVS and ZCS. Both concepts are applied on different legs of the H-bridge. Pulse frequency modulation (PFM) and Phase Shifting Modulation (PSM) are utilized to control this resonant converter. One of the requirements of this work is to achieve a tightly regulated DC bus voltage. This was shown to be achieved using …