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Articles 1 - 13 of 13

Full-Text Articles in Mechanical Engineering

Numerical Comparison Of Thermal And Kinetic Modification Of Hydrogen And Oxygen, John Benjamin Gaither Jan 2011

Numerical Comparison Of Thermal And Kinetic Modification Of Hydrogen And Oxygen, John Benjamin Gaither

Masters Theses

"This document describes a new modeling technique used to compare thermal and kinetic modification of hydrogen and oxygen gas. The thermal model uses an equilibrium thermodynamic analysis to determine the heat required for given mole fractions of molecular and dissociated products. A kinetic model is developed for a mono-energetic electron beam and a Maxwellian energy distribution. The kinetic model uses electron impact cross sections for excitation, dissociation, and ionization tabulated from available source data between 0-1000 eV. Cross sections are used to calculate forward reaction rates, electron penetration depths, and associated product concentrations for excited, dissociated, and ionized species. The ...


Development Of Hybrid Composite Bipolar Plates For Proton Exchange Membrane Fuel Cells, Nathaniel James Richie Jan 2011

Development Of Hybrid Composite Bipolar Plates For Proton Exchange Membrane Fuel Cells, Nathaniel James Richie

Masters Theses

"Bipolar plates are one of the most expensive components of a PEM fuel cell and by far the heaviest. Bipolar plates are responsible for providing flow fields for reaction gases, acting as current collectors for electrons liberated during the chemical reaction inside the cell, and providing structural support for the fuel cell stack. Current PEM fuel cell bipolar plate technology is built on the use of sintered graphite which is costly and requires time-consuming machining. Furthermore, due to the brittle nature of graphite, plates must be made relatively thick which adds significant weight and volume to larger stacks, such as ...


Integrated Reliable And Robust Design, Gowrishankar Ravichandran Jan 2011

Integrated Reliable And Robust Design, Gowrishankar Ravichandran

Masters Theses

"The objective of this research is to develop an integrated design methodology for reliability and robustness. Reliability-based design (RBD) and robust design (RD) are important to obtain optimal design characterized by low probability of failure and minimum performance variations respectively. But performing both RBD and RD in a product design may be conflicting and time consuming. An integrated design model is needed to achieve both reliability and robustness simultaneously. The purpose of this thesis is to integrate reliability and robustness. To achieve this objective, we first study the general relationship between reliability and robustness. Then we perform a numerical study ...


Impact Of Combustion Phasing On Energy And Availability Distributions Of An Internal Combustion Engine, Shawn Nicholas Wildhaber Jan 2011

Impact Of Combustion Phasing On Energy And Availability Distributions Of An Internal Combustion Engine, Shawn Nicholas Wildhaber

Masters Theses

"High fuel efficiency has become an extremely desirable trait for internal combustion engines. This motivation has driven extensive research on methods to improve fuel efficiency on engines of various sizes. Many of these methods involve changes to the properties of the combustion process. One way to induce these property changes is through varying the phasing of combustion. Combustion phasing can be defined as the time in the engine cycle, specifically the compression and expansion strokes, where combustion occurs. A change in combustion phasing causes a change in combustion duration. The duration of combustion impacts how the energy and work potential ...


Solar Powered Residential Hydrogen Fueling Station, Aanchal Shah Jan 2011

Solar Powered Residential Hydrogen Fueling Station, Aanchal Shah

Masters Theses

"Interest towards the hydrogen fuel technology is increasing but its potential benefits will not be felt until hydrogen vehicles and the fueling infrastructure captures a substantial market share. Though there has been a rapid progress in the hydrogen fuel cell technology, a major challenge to the commercialization of fuel cell vehicles is the lack of hydrogen fueling infrastructure. The development of a commercial hydrogen fueling station is a challenge due to its high initial cost and safety concerns. Residential fueling stations provide an innovative solution to this issue since they also produce electricity and heat for the residential buildings in ...


Bi-Harmonic Atomic Force Microscopy, Santosh R. Kodandarama Jan 2011

Bi-Harmonic Atomic Force Microscopy, Santosh R. Kodandarama

Masters Theses

"In tapping mode atomic force microscopy, surface features are measured indirectly via the amplitude of the tapping cantilever. A change in surface profile is detectable only if it results in an amplitude change that is significant enough to be measured by the optics. Previous works have focused on improving sensitivity through the system's Q-factor, either by changing physical cantilever properties or using feedback control, but those approaches undesirably slow down the dynamic response. In this work we take a novel approach to sensitivity amplification by reshaping the tapping trajectory. By shaping the trajectory so that the probe spends a ...


Effect Of Initial Conditions On Molecular Mixing In A High Schmidt-Number Rayleigh-Taylor Mixing Layer, Lakshmi Ayyappa Raghu Mutnuri Jan 2011

Effect Of Initial Conditions On Molecular Mixing In A High Schmidt-Number Rayleigh-Taylor Mixing Layer, Lakshmi Ayyappa Raghu Mutnuri

Masters Theses

"Characterizing molecular mixing in Rayleigh-Taylor instability (RTI) driven flows where the density and velocity fields are coupled is essential for developing exacting predictive models. Sensitivity of the Rayleigh Taylor mixing layer to initial conditions is a topic that is being explored extensively in interests of accurate turbulent mix model development and its direct consequence in various applications like design of inertial confinement fuel capsule and atmospheric modeling. As part of the current work, an experimental investigation of the effect of initial conditions on molecular mixing in a low Atwood number(~7.5 x 10⁻⁴), high Schmidt number(~1000), RTI ...


Design And Development Of Manufacturing Methods For Manufacturing Of Pem Fuel Cell Mea's, Nikhil Pramod Kulkarni Jan 2011

Design And Development Of Manufacturing Methods For Manufacturing Of Pem Fuel Cell Mea's, Nikhil Pramod Kulkarni

Masters Theses

"This thesis focuses on design and manufacturing of Fuel cell components using Additive Manufacturing techniques and then in the later part on design and manufacturing of Membrane Electrode Assembly (MEA) which is a very important component in fuel cells. Additive manufacturing methods are fast and efficient manufacturing methods which are additive building up components layer by layer instead of conventional subtractive manufacturing techniques. This ensures low cost and faster manufacturing. Additive manufacturing is important for fuel cell component manufacturing since it is important in fuel cells to minimize wastage and reduce the cost. MEA is the basis of the cost ...


Processing And Mechanical Characterization Of Polyurea Aerogels, Jared M. Loebs Jan 2011

Processing And Mechanical Characterization Of Polyurea Aerogels, Jared M. Loebs

Masters Theses

"The use of aerogels historically has been limited to extreme cases largely in part to the nature of their mechanical properties. Until recently many aerogels produced have been brittle and weak, though looking at their specific strength would suggest otherwise. This thesis outlines the processing and major mechanical properties of a relatively new type of aerogel, polyurea aerogel, that shows promise in a variety of fields including structures.

Processing polyurea aerogel begins with a liquid solution that solidifies to form a solid gel filled with liquid that is later removed by supercritical drying. Once dry, polyurea aerogels are difficult to ...


Design Of A Hydrogen Community For Santa Monica, Vijay Mohan Jan 2011

Design Of A Hydrogen Community For Santa Monica, Vijay Mohan

Masters Theses

"Hydrogen systems infrastructure development and fuel cell vehicles (FCVs) have the potential to replace the gasoline internal combustion engine vehicles thus increasing energy security and reducing greenhouse gas emissions. Hydrogen fueling infrastructure development is critical for the commercialization and consumer acceptability of the FCVs, thus recognizing hydrogen as an affordable transportation fuel. This paper presents the conceptual design of a scalable and reproducible hydrogen fueling station in Santa Monica, California. The various hydrogen production technologies have been evaluated and the usage of renewable energy sources such as biogas and landfill gas has been emphasized. The technical specifications of the hydrogen ...


3-Dimensional Computational Fluid Dynamics Modeling Of Solid Oxide Fuel Cell Using Different Fuels, Sachin Laxman Puthran Jan 2011

3-Dimensional Computational Fluid Dynamics Modeling Of Solid Oxide Fuel Cell Using Different Fuels, Sachin Laxman Puthran

Masters Theses

"Solid oxide fuel cell (SOFC) technology has been of great interest over many years due to its flexibility in using different fuels for operation; including the fundamental fuel i.e. Hydrogen. Various computational and numerical models have been developed along with experimental work to evaluate the performance as well as to identify and overcome the problems faced in the development of SOFC's. In an attempt to achieve efficient operation with respect to design and combined thermal and electrochemical perspective, the main objective of the proposed study is to present a three-dimensional computational model, which will serve as a framework ...


Design And Control Of A Multi-Axis Micro-Electro-Mechanical System Array For Coordinated Micro-Manipulation, Patrick Jesse White Jan 2011

Design And Control Of A Multi-Axis Micro-Electro-Mechanical System Array For Coordinated Micro-Manipulation, Patrick Jesse White

Masters Theses

"Micro-electro-mechanical system design and implementation is a field that has received much attention over the past few decades. These robotic systems with features on the micro-scale have an unparalleled opportunity to change the way scientists interact with and understand micro and nano-scale phenomenon. Their capabilities allow experimentation that cannot be achieved with standard macro-scale equipment. Potential applications range from observing biological processes in living cells, to smart materials that automatically detect microcracks. So far, however, only a few truly successful applications have been realized. One of the most elusive goals in MEMS design is creating a system capable of coordinated ...


Analysis And Modeling Of Depth-Of-Cut During End Milling Of Deposited Material, Haythem Gaja Jan 2011

Analysis And Modeling Of Depth-Of-Cut During End Milling Of Deposited Material, Haythem Gaja

Masters Theses

"This study addresses depth-of-cut detection and tool-workpiece engagement using an acoustic emission monitoring system during milling machining for a deposited material. Online detection of depth-of-cut presents many technical difficulties. Researchers have used various types of sensors and methods to assess the depth-of-cut and surface errors. Due to the strong correlation between acoustic emission and cutting depth during the depth end milling process, it is useful to forecast the depth-of-cut from the acoustic emission signal. This work used regression analysis to model and detect the depth-of-cut. The experiments were carried out on a Fadal vertical 5-Axis computer numerical control machine using ...