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2013

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Articles 781 - 810 of 1209

Full-Text Articles in Mechanical Engineering

Development Of Computational Fluid Dynamics (Cfd) Based Erosion Models For Oil And Gas Industry Applications, Deval Pandya Jan 2013

Development Of Computational Fluid Dynamics (Cfd) Based Erosion Models For Oil And Gas Industry Applications, Deval Pandya

Mechanical and Aerospace Engineering Dissertations - Archive

Erosion prediction plays a critical role in different oil and gas industry segments including drill bit manufacturing, measurement & logging while drilling (M&LWD), and reservoir engineering/completions tools. Recently, Computational Fluid Dynamics (CFD) is used to predict erosion due to multiphase flows in complex geometries. Currently used CFD-based erosion models are able to predict erosion regions fairly accurately in various applications but they are highly inaccurate when it comes topredictions of quantities like erosion rate. Predicted quantities within an order of magnitude of the measured values are common and may be considered acceptable for many applications in the industry simply because …

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Advanced Materials Characterization Based On Full Field Deformation Measurements, A Paige Carpentier Jan 2013

Advanced Materials Characterization Based On Full Field Deformation Measurements, A Paige Carpentier

Mechanical and Aerospace Engineering Dissertations - Archive

Accurate stress-strain constitutive properties are essential for understanding the complex deformation and failure mechanisms for materials with highly anisotropic mechanical properties. Among such materials, glass-fiber- and carbon-fiber-reinforced polymer-matrix composites play a critical role in advanced structural designs. The large number of different methods and specimen types currently required to generate three-dimensional allowables for structural design slows down the material characterization. Also, some of the material constitutive properties are never measured due to the prohibitive cost of the specimens needed. This work shows that simple short-beam shear (SBS) specimens are well-suited for measurement of multiple constitutive properties for composite materials and …

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Multi-Objective Design Optimization Of Beol/Fbeol Region During Chip Attachment To Substrate, Hardik Parekh Jan 2013

Multi-Objective Design Optimization Of Beol/Fbeol Region During Chip Attachment To Substrate, Hardik Parekh

Mechanical and Aerospace Engineering Theses - Archive

Semiconductor industry has recognized the need to replace traditional Al/SiO2 interconnects with Cu/Low-k interconnects in the mainstream electronics devices following the latter's impact on power, RC delay, and cross-talk reduction. However due to lower elastic modulus, strength, and poor adhesion characteristic, reliability of the Cu/Low-k interconnects turns out to be a concern for its integration in the back-end-of-line (BEoL). Flip-chip attachment process (cooling from ~200C to room) can result in critical damage in nano-scale Cu/Low-k interconnects. The objective of this study is to improve the reliability of Cu/Low-k interconnects during die attach reflow process for a specific die to substrate …

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Design And Control Of A Smart Bed For Pressure Ulcer Prevention, Zachary Govier Brush Jan 2013

Design And Control Of A Smart Bed For Pressure Ulcer Prevention, Zachary Govier Brush

Mechanical and Aerospace Engineering Theses - Archive

This work details the design, simulation, and experimental testing of a mechanically actuated smart hospital bed for the prevention of pressure ulcers in hospital patients. The smart hospital bed, or Smartbed, is designed to improve the “turning” process currently performed by health care workers, ensuring that patients are turned consistently and decreasing the labor requirement for caregivers. The mechanical structure of the bed is described, along with its advantages over current Smartbed products. Next, dynamic models of the Smartbed actuating systems are discussed along with descriptions of the devised single-unit and overall bed control systems. The control equations determined in …

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Design And Evaluation Of A Chemical Reactor For The Pyrolysis Wood Pellets, Pawarat Bootpakdeetam Jan 2013

Design And Evaluation Of A Chemical Reactor For The Pyrolysis Wood Pellets, Pawarat Bootpakdeetam

Mechanical and Aerospace Engineering Theses - Archive

Currently there is interest in converting waste biomass into valuable products, such as fuels and specialty chemicals. However, the product composition, yield, the energy required to run the reaction, and the required residence time are all factors influence the economics of the process. Estimate of these factors at the laboratory scale is important for evaluating whether a pilot or demonstration scale study is warranted. In this work, a bench-scale chemical reactor was designed and constructed to conduct the batch pyrolysis of pelletized biomass. The reactor was tested using pine wood pellets as the feedstock. The feedstock weight to reactor volume …

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Optimal Design Of Beams, Shivakumar Samala Jan 2013

Optimal Design Of Beams, Shivakumar Samala

Mechanical and Aerospace Engineering Theses - Archive

Beams are basic structural components that are capable of withstanding load primarily by resisting bending. Unlike Euler-Bernoulli beams, Timoshenko beams undergo both shear deformation and rotational effects, making it suitable for analyzing the behavior of thick or short beams, composite beams and beams that are subjected to high frequency excitation when their wave length becomes shorter. This thesis work focuses on optimal design of straight and tapered Timoshenko beams under static and dynamic constraints for rectangular and circular cross sections. In this work Timoshenko beam static and dynamic equations were studied. The finite element method was used for static and …

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Study Of The Capabilities Of Electrowetting On Dielectric Digital Microfluidics (Ewod Dmf) Towards The High Efficient Thin-Film Evaporative Cooling Platform, Jagath B. Yaddessalage Jan 2013

Study Of The Capabilities Of Electrowetting On Dielectric Digital Microfluidics (Ewod Dmf) Towards The High Efficient Thin-Film Evaporative Cooling Platform, Jagath B. Yaddessalage

Mechanical and Aerospace Engineering Dissertations - Archive

With the current technological advancement, the size of the electronic components is being reduced to smaller and compact sizes. In the meantime, the packaging density and power consumption is ever increasing. To tackle this challenge, an efficient cooling technology is required.Thin-film evaporation is a very efficient cooling technology. A practical application using thin-film evaporation is a spray cooling which is known as the cooling method that can handle very high heat flux. However, a random spray of coolant cannot guarantee a thin coolant film, therefore either local dry-out or flooding may occur, which hampers cooling efficiency significantly. Moreover, bulky spraying …

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Airdata Sensor Based Position Estimation And Fault Diagnosis In Aerial Refueling, Hakki Erhan Sevil Jan 2013

Airdata Sensor Based Position Estimation And Fault Diagnosis In Aerial Refueling, Hakki Erhan Sevil

Mechanical and Aerospace Engineering Dissertations - Archive

Aerial refueling is the process of transferring fuel from one aircraft (the tanker) to another (the receiver) during flight. In aerial refueling operations, the receiver aircraft is exposed to nonuniform wind field induced by tanker aircraft, and this nonuniform wind field leads to differences in readings of airdata sensors placed at different locations on the receiver aircraft. There are advantages and disadvantages of this phenomenon. As an advantage, it is used as a mechanism to estimate relative position of the receiver aircraft inside the nonuniform wind field behind the tanker. Using the difference in the measurements from multiple identical sensors, …

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A Semi-Analytical Approach To Obtain Physical Fields In Heterogeneous Materials, Thanuuj S. Pathapallli Jan 2013

A Semi-Analytical Approach To Obtain Physical Fields In Heterogeneous Materials, Thanuuj S. Pathapallli

Mechanical and Aerospace Engineering Dissertations - Archive

Predicting the macroscopic response of heterogeneous materials has been the subject of extensive research in the engineering community, even more so, in the composites guild. With analytical solutions being almost impossible to obtain for such open ended problems, and numerical techniques being computationally expensive, semi-analytical methods are highly sought after. This dissertation is one such effort aimed at presenting a semi-analytical approach that serves as a confluence of effective analytical and numerical techniques, to solve for engineering fields in a heterogeneous material characterized by inclusions embedded in a matrix medium. The approach essentially involves the analytical derivation of permissible functions, …

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Physically Representative Atomistic Modeling Of Atomic-Scale Friction, Yalin Dong Jan 2013

Physically Representative Atomistic Modeling Of Atomic-Scale Friction, Yalin Dong

Mechanical Engineering Faculty Research

Nanotribology is a research field to study friction, adhesion, wear and lubrication occurred between two sliding interfaces at nano scale. This study is motivated by the demanding need of miniaturization mechanical components in Micro Electro Mechanical Systems (MEMS), improvement of durability in magnetic storage system, and other industrial applications. Overcoming tribological failure and finding ways to control friction at small scale have become keys to commercialize MEMS with sliding components as well as to stimulate the technological innovation associated with the development of MEMS. In addition to the industrial applications, such research is also scientifically fascinating because it opens a …

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A New Method For Failure Modes And Effects Analysis And Its Application In A Hydrokinetic Turbine System, Liang Xie Jan 2013

A New Method For Failure Modes And Effects Analysis And Its Application In A Hydrokinetic Turbine System, Liang Xie

Masters Theses

"The traditional failure modes and effects analysis (FMEA) is a conceptual design methodology for dealing with potential failures. FMEA uses the risk priority number (RPN), which is the product of three ranked factors to prioritize risks of different failure modes. The three factors are occurrence, severity, and detection. However, the RPN may not be able to provide consistent evaluation of risks for the following reasons: the RPN has a high degree of subjectivity, it is difficult to compare different RPNs, and possible failures may be overlooked in the traditional FMEA method. The objective of this research is to develop a …

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Part Height Control Of Laser Metal Additive Manufacturing Process, Yu-Herng Pan Jan 2013

Part Height Control Of Laser Metal Additive Manufacturing Process, Yu-Herng Pan

Masters Theses

"Laser Metal Deposition (LMD) has been used to not only make but also repair damaged parts in a layer-by-layer fashion. Parts made in this manner may produce less waste than those made through conventional machining processes. However, a common issue of LMD involves controlling the deposition's layer thickness. Accuracy is important, and as it increases, both the time required to produce the part and the material wasted during the material removal process (e.g., milling, lathe) decrease. The deposition rate is affected by multiple parameters, such as the powder feed rate, laser input power, axis feed rate, material type, and part …

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Low Strain Rate Studies Of Alumina Epoxy Composites Using Piezospectroscopy, Ashley Jones Jan 2013

Low Strain Rate Studies Of Alumina Epoxy Composites Using Piezospectroscopy, Ashley Jones

Electronic Theses and Dissertations

Particulate composites are widely used in many aerospace and military applications as energetic materials, armor materials or coatings and their behavior under dynamic loads have gained increasing significance. The addition of modifiers such as alumina nanoparticles generally facilitates the improvement of the mechanical strength to density ratio due to high specific area and particle rigidity. This allows for sufficient particlematrix bonding and therefore improved stiffness and load transfer in the composite. Photo-luminescent α-alumina nanoparticles when embedded in an epoxy matrix allow for the added benefit of in situ measurements at low strain rates to provide stress-sensitive information using the particle …

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Electrohydrodynamic Manipulation Of Liquid Droplet Emulsions In A Microfluidic Channel, Jonathan Wehking Jan 2013

Electrohydrodynamic Manipulation Of Liquid Droplet Emulsions In A Microfluidic Channel, Jonathan Wehking

Electronic Theses and Dissertations

This work specifically aims to provide a fundamental framework, with some experimental validation, for understanding droplet emulsion dynamics in a microfluidic channel with an applied electric field. Electrification of fluids can result in several different modes of electrohydrodynamics (EHD). Several studies to date have provided theoretical, experimental, and numerical results for stationary droplet deformations and some flowing droplet configurations, but none have reported a method by which droplets of different diameters can be separated, binned and routed through the use of electric fields. It is therefore the goal of this work to fill that void and report a comprehensive understanding …

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Thermo-Mechanical Analysis Of Nano-Imprint Lithography, Bhavik C. Patel Jan 2013

Thermo-Mechanical Analysis Of Nano-Imprint Lithography, Bhavik C. Patel

Mechanical and Aerospace Engineering Theses - Archive

Nanoimprint Lithography is being explored by the semiconductor industries for future high volume fabrication of silicon chips, memory devices and patterned media. Nanolithography and Microlithography has played pivotal role in the field of manufacturing microchips and integrated circuits in semiconductor devices. There is an urge to investigate Nanoimprint lithography, a high-throughput, low-cost and nonconventional lithographic method. Thermal management is a critical area that is necessary to be administrated. As recent advancements are being observed in the field of electronic packaging for thermal optimization, likewise steps are also important in this fabrication process. This process involves a heat that is generated …

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Compressibility Effects On The Non-Linear Receptivity Of Boundary Layers To Dielectric Barrier Discharges, Marie F.C. Denison Jan 2013

Compressibility Effects On The Non-Linear Receptivity Of Boundary Layers To Dielectric Barrier Discharges, Marie F.C. Denison

Mechanical and Aerospace Engineering Theses - Archive

The reduction of drag and aerodynamic heating caused by boundary layer transition is of central interest for the development of hypersonic vehicles. Receptivity to flow perturbation in the form of Tollmien-Schlichting (TS) wave growth often determines the first stage of the transition process, which can be delayed by depositing specific excitations into the boundary layer. Weakly ionized Dielectric Barrier Discharge (DBD) actuators are being investigated as possible sources of such excitations, but little is known today about their interaction with high-speed flows. In this framework, the first part of the thesis is dedicated to a receptivity study of laminar compressible …

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Rotordynamic Performance Of A Rotor Supported By Three Pad Hybird Foil Bearings With Controlled Air Injection, Sandesh Gudemane Jan 2013

Rotordynamic Performance Of A Rotor Supported By Three Pad Hybird Foil Bearings With Controlled Air Injection, Sandesh Gudemane

Mechanical and Aerospace Engineering Theses - Archive

Air Foil Bearings have found their place in the commercial applications of turbo machinery. They are cleaner and more reliable at high speeds than their conventional counterparts (Rolling Element Bearings). Low drag friction and apparently no contact during the operation results in a better service life and superior rotor-dynamic performance of the air foil bearings (AFBs). With these advantages AFB has proved to be a suitable option for oil-free turbo-machinery. Further development in AFBs suggest that pressurizing these bearings externally results in remarkably better load carrying capacity, heat dissipation and a more stable rotor. These externally air pressurized bearings which …

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Improving Cooling Efficiency Of Servers By Replacing Smaller Chassis Enclosed Fans With Larger Rack-Mount Fans, Bharath Nagendran Jan 2013

Improving Cooling Efficiency Of Servers By Replacing Smaller Chassis Enclosed Fans With Larger Rack-Mount Fans, Bharath Nagendran

Mechanical and Aerospace Engineering Theses - Archive

As a common practice in the data center industry, chassis fans are used to direct air flow independent from neighboring servers. However, these fans are less efficient compared to larger rack level counterparts and also operate at higher sound levels. In this study, a novel approach is proposed whereby the smaller chassis enclosed fans are replaced with an array of larger fans, installed behind the stacked servers that share air flow. As a baseline study for comparison of the current scenario, a CPU dominated 1.5U Open Compute server, with four 60mm fans installed within the server, is characterized experimentally for …

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Comparative Analysis Of Widely Used Air Containment Systems In Commercial Data Centers For Maximum Cooling Performance, Kasturi Rangan Rajagopalan Jan 2013

Comparative Analysis Of Widely Used Air Containment Systems In Commercial Data Centers For Maximum Cooling Performance, Kasturi Rangan Rajagopalan

Mechanical and Aerospace Engineering Theses - Archive

Many data centers implement containment systems to improve cooling system performance. Literature review shows that Hot Aisle Containment System (HACS) have higher supply air temperature set point than Cold Aisle Containment Systems (CACS) [1]. CACS in data centers have claims to support higher density loads when compared to HACS systems [2]. Data center owners suggest that containment of a group of racks can be a very effective technique to improve cooling performance. On the other hand, others suggest that fewer area for containment is better than no containment in data centers that favours the partially contained architectures of HACS and …

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Real Time Temperature Prediction In A Data Center Environment Using An Adaptive Algorithm, Vishok Amar Kumar Jan 2013

Real Time Temperature Prediction In A Data Center Environment Using An Adaptive Algorithm, Vishok Amar Kumar

Mechanical and Aerospace Engineering Theses - Archive

Most organizations around the world rely on information systems to run their operations. Data centers are hence a crucial aspect of most organizational operations to ensure business continuity. Disruption in the working of a system can impair the business largely and hence optimizing the environment in which the servers and storage devises of a data center are housed becomes extremely challenging. Most industries design the data center infrastructure to handle peak load conditions thus ensuring a continual functionality of its hosted environment. However, the cost of maintaining such a system is very high. This gives rise to the need of …

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A Computational Model To Characterize Different Flow Regimes For Microscale Re-Entry Satellites, Sudharsan Thiruvenkadam Jan 2013

A Computational Model To Characterize Different Flow Regimes For Microscale Re-Entry Satellites, Sudharsan Thiruvenkadam

Mechanical and Aerospace Engineering Theses - Archive

Atmospheric re-entry vehicles experience different flow regimes during flight due to the change in atmospheric density along the re-entry trajectory. This change in density creates non-equilibrium regions on the order of mean free path, called Knudsen layer. In the design of atmospheric re-entry vehicles, the flux variations near the wall of the re-entry vehicles are of critical importance. Traditional CFD simulations that use Navier-Stokes equations fail to predict the flow in the Knudsen layer. The Direct Simulation Monte Carlo (DSMC) method is accurate for all flow regimes, and correctly models the Knudsen layer but is computationally expensive. The computational cost …

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Numerical Analysis Of The Thermodynamic Properties Of Various Gaseous Species, Addison Alexander Jan 2013

Numerical Analysis Of The Thermodynamic Properties Of Various Gaseous Species, Addison Alexander

Lewis Honors College Capstone Collection

In the field of Fluid Mechanics, the determination of various thermodynamic properties of substances is of utmost importance. Many calculations require values for internal energy or specific heats. If experimental data does not exist to facilitate these calculations, an approximation must be made. This report analyzes three different approximation approaches to examine their relative strengths and weaknesses. The first approach, the Exact Method, uses NASA thermodynamic data to give a numerical interpolation. The second, the Summation Method, breaks up the total energy of the species into different contributions and performs an approximation based on thermodynamic theory. Finally, the Spectroscopic Method …

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Planning And Control Of Swarm Motion As Continua, Hossein Rastgoftar Jan 2013

Planning And Control Of Swarm Motion As Continua, Hossein Rastgoftar

Electronic Theses and Dissertations

In this thesis, new algorithms for formation control of multi agent systems (MAS) based on continuum mechanics principles will be investigated. For this purpose agents of the MAS are treated as particles in a continuum, evolving in an n-D space, whose desired configuration is required to satisfy an admissible deformation function. Considered is a specific class of mappings that is called homogenous where the Jacobian of the mapping is only a function of time and is not spatially varying. The primary objectives of this thesis are to develop the necessary theory and its validation via simulation on a mobile-agent based …

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Generation And Printing Of Strictly Monodisperse Droplets, Hongxu Duan Jan 2013

Generation And Printing Of Strictly Monodisperse Droplets, Hongxu Duan

Electronic Theses and Dissertations

Highly monodisperse droplets are attracting great attention both in many research areas, such as aerosol science, combustion, and Nano-manufacturing. This thesis invents a novel aerosol generator: “Periodic Electro Hydro-dynamic Chopper” termed as “PEHD chopper”, and develops a new method to directly print micro-patterns with monodisperse droplets. The principle of the PEHD chopper is to use the fringe electric field of a capacitor to introduce controlled perturbation on a liquid jet. We first derived the governing equations for a circular inviscid liquid jet under transverse electric fields. The electric fields were obtained through numerical simulation. Then we used a high speed …

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Experimental Investigation Of Breakup And Coalescence Characteristics Of A Hollow Cone Swirling Spray, Joshua Lee Jan 2013

Experimental Investigation Of Breakup And Coalescence Characteristics Of A Hollow Cone Swirling Spray, Joshua Lee

Electronic Theses and Dissertations

Atomization can be achieved by discharging liquid at relative high velocities into a slow moving environment (hydraulic nozzles) or by discharging liquid at low velocities into a fast moving gas flow (air-blast nozzles). These two types of injector nozzles are featured in majority of the industry applications such as power generation, food or pharmaceutical powder formation, spray painting, petroleum refining, and thermal sprays. The most common atomizer used in combustion engines is the pressure-swirl nozzle (Simplex nozzle) to obtain a homogenous mixture at different equivalence ratios. The experimental studies performed with pressure-swirl nozzles have reported contradictory results over the last …

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A Simplified Model Of The Internal Combustion Engine, Christofer Neff Jan 2013

A Simplified Model Of The Internal Combustion Engine, Christofer Neff

Undergraduate Journal of Mathematical Modeling: One + Two

This project further investigates a model of a simplified internal combustion engine considered by Kranc in 1977. Using Euler’s method for ordinary differential equations, we modeled the interaction between the engine’s flywheel and thermodynamic power cycle. Approximating with sufficiently small time intervals (0.001 seconds over a period of 12 seconds) reproduced Kranc’s results with the engine having an average angular velocity of 72/sec.

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Multi-Level Parallelism For Incompressible Flow Computations On Gpu Clusters, Dana A. Jacobsen, Inanc Senocak Jan 2013

Multi-Level Parallelism For Incompressible Flow Computations On Gpu Clusters, Dana A. Jacobsen, Inanc Senocak

Mechanical and Biomedical Engineering Faculty Publications and Presentations

We investigate multi-level parallelism on GPU clusters with MPI-CUDA and hybrid MPI-OpenMP-CUDA parallel implementations, in which all computations are done on the GPU using CUDA. We explore efficiency and scalability of incompressible flow computations using up to 256 GPUs on a problem with approximately 17.2 billion cells. Our work addresses some of the unique issues faced when merging fine-grain parallelism on the GPU using CUDA with coarse-grain parallelism that use either MPI or MPI-OpenMP for communications. We present three different strategies to overlap computations with communications, and systematically assess their impact on parallel performance on two different GPU clusters. Our …

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A Computational Approach To Simulating The Performance Of A 24-Hour Solar-Fuel Cell-Hydrogen Electric Power Plant, Michael K. Gustafson Jan 2013

A Computational Approach To Simulating The Performance Of A 24-Hour Solar-Fuel Cell-Hydrogen Electric Power Plant, Michael K. Gustafson

Browse all Theses and Dissertations

World energy demand has risen from about 375 exajoules (EJ) in 1990 to around 600 EJ today. The Energy Information Administration predicts that by the year 2035, this figure will rise to around 800 EJ. This places large stresses on the electric generation infrastructure. Increasingly this demand is being met by renewable energy sources. There are several reasons this is the case. The prices of renewables are dropping quickly and reaching grid parity in more regions. Utilizing renewable energy generation can help achieve energy security: adverse weather or military conflicts are less likely to impact supply routes when energy is …

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Valence-Length Correlations For Chemical Bonds From Atomic Orbital Exponents, F. D. Hardcastle Jan 2013

Valence-Length Correlations For Chemical Bonds From Atomic Orbital Exponents, F. D. Hardcastle

Journal of the Arkansas Academy of Science

Pauling’s empirical bond valence-length correlation has proven valuable because it offers a quick and convenient way of checking and evaluating molecular structures and determining oxidation states from measured bond lengths. In this study, a simplified quantum-mechanical approach was used to derive Pauling’s empirical bond valence-length relationship by considering overlap of hydrogen-like orbitals. An expression for the b “empirical” fitting parameter was derived in terms of atomic-orbital exponents. A new set of orbital exponents is presented using published atomic/covalent radii and a continuous function for the effective principal quantum. The b parameters calculated from the orbital exponents are consistent with bond …

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Consensus Protocols In Networked Multiagent Systems For Cluttered And Hostile Environments, Gerardo De La Torre, Eric N. Johnson, Tansel Yucelen Jan 2013

Consensus Protocols In Networked Multiagent Systems For Cluttered And Hostile Environments, Gerardo De La Torre, Eric N. Johnson, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Consensus refers to the agreement of networked agents upon certain quantities of interest and has widespread applications in diverse areas in science and engineering. This paper focuses on a new consensus protocol for networked multiagent systems operating in cluttered and hostile environments. Specifically, a consensus optimization algorithm is introduced that renders the Laplacian potential to be a nonincreasing function while minimizing a cost function and satisfying state and cost constraints. In addition, we show how to choose this cost function and the aforementioned constraints in order to decay the Laplacian potential to zero strictly. The proposed framework depends on a …

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