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2005

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Articles 3001 - 3030 of 3074

Full-Text Articles in Engineering

Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli Jan 2005

Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli

Theses and Dissertations

The field of smart materials is an increasingly growing area of research. In aerodynamics applications especially, transducers have to fulfill a series of requirements such as light weight, size, energy consumption, robustness and durability. Piezoelectric transducers, devices which transform an electrical signal into motion, fulfill many of these requirements. Specifically, piezoelectric composites are of interest due to their added toughness and ease of integration into a structure. Resulting composites have a characteristic initial curvature with accompanying residual stresses that are responsible for enhanced performance, relative to flat actuators, when the active material is energized. A number of transducer designs based …

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A Multi-Agent Approach For Solving Optimization Problems Involving Expensive Resources, Hoong Chuin Lau, H. Wang Jan 2005

A Multi-Agent Approach For Solving Optimization Problems Involving Expensive Resources, Hoong Chuin Lau, H. Wang

Research Collection School Of Computing and Information Systems

In this paper, we propose a multi-agent approach for solving a class of optimization problems involving expensive resources, where monolithic local search schemes perform miserably. More specifically, we study the class of bin-packing problems. Under our proposed Fine-Grained Agent System scheme, rational agents work both collaboratively and selfishly based on local search and mimic physics-motivated systems. We apply our approach to a generalization of bin-packing - the Inventory Routing Problem with Time Windows - which is an important logistics problem, and demonstrate the efficiency and effectiveness of our approach.

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Room-Temperature Atmospheric Pressure Plasma For Biomedical Applications, Mounir Laroussi, Xinpei Lu Jan 2005

Room-Temperature Atmospheric Pressure Plasma For Biomedical Applications, Mounir Laroussi, Xinpei Lu

Electrical & Computer Engineering Faculty Publications

As low-temperature non-equilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little …

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Performance Analysis And Validation Of A Recoverable Flight Control System In A Simulated Neutron Environment, Hong Zhang, W. Steven Gray, Oscar R. Gonzalez Jan 2005

Performance Analysis And Validation Of A Recoverable Flight Control System In A Simulated Neutron Environment, Hong Zhang, W. Steven Gray, Oscar R. Gonzalez

Electrical & Computer Engineering Faculty Publications

This paper introduces a class of stochastic hybrid models for the analysis of closed-loop control systems implemented with NASA's Recoverable Computer System. Such Recoverable Computer Systems have been proposed to insure reliable control performance in harsh environments. The stochastic hybrid models consist of either a stochastic finite-state automaton or a finite-state machine driven by a Markov input, which in turn drives a switched linear discrete-time dynamical system. Their stability and output tracking performance are analyzed using an extension of the existing theory for Markov jump-linear systems. For illustration, a stochastic hybrid model is used to calculate the tracking error performance …

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Stability, Transport And Applications Of Polyaphrons In Porous Media, Le Yan Jan 2005

Stability, Transport And Applications Of Polyaphrons In Porous Media, Le Yan

LSU Doctoral Dissertations

Polyaphrons are a kind of macroemulsion. The most distinctive feature of polyaphrons is their high stability. On the other hand, certain polyaphrons can be effectively destabilized by multivalent ions. In this dissertation, we devise a novel procedure that utilizes the fact that polyaphrons can be destabilized by certain ions to deliver light chemicals to lower the density of dense non-aqueous phase liquid (DNAPL) contaminants in situ. We first investigate how the stability of diluted polyaphrons is affected by the properties of the continuous phase. We find that polyaphrons can be destabilized by a low concentration of Al3+ or Ca2+ in …

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An Evaluation Of Ansys Contact Elements, Serhan Sezer Jan 2005

An Evaluation Of Ansys Contact Elements, Serhan Sezer

LSU Master's Theses

The ANSYS code offers stress analysts a variety of contact element options: point-to-surface or surface-to-surface and low-order or high-order elements, in concert with any one of five contact algorithms (augmented Lagrangian, penalty method, etc.). This raises questions as to what option performs best under what circumstances. Here we offer some answers to these questions by examining performance in some numerical experiments. The numerical experiments focus on frictionless contact with a rigid indenter; even so, the number of experiments involved is quite large. The experiments use a battery of test problems with known analytical solutions: contact patch tests with nodes matching …

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Ternary Logic To Binary Bit Conversion Using Multiple Input Floating Gate Mosfets In 0.5 Micron N-Well Cmos Technology, Sowmya Subramanian Jan 2005

Ternary Logic To Binary Bit Conversion Using Multiple Input Floating Gate Mosfets In 0.5 Micron N-Well Cmos Technology, Sowmya Subramanian

LSU Master's Theses

In the present work, a CMOS ternary to binary bit conversion technique has been proposed using multiple input floating gate MOSFETs. The proposed circuit has been implemented in 0.5 µm n-well CMOS technology. The ternary input signals of {-1, 0, +1} are represented as -3 V, 0 V and +3 V, respectively. The ternary input is given as a combination of any two of the three voltage levels and the 4-bit binary output is generated in which the left most bit is sign bit (SB) followed by most significant bit (MSB), second significant bit (SSB) and the least significant bit …

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A Study Of Distributed Clustering Of Vector Time Series On The Grid By Task Farming, Arun B. Nayar Jan 2005

A Study Of Distributed Clustering Of Vector Time Series On The Grid By Task Farming, Arun B. Nayar

LSU Master's Theses

Traditional data mining methods were limited by availability of computing resources like network bandwidth, storage space and processing power. These algorithms were developed to work around this problem by looking at a small cross-section of the whole data available. However since a major chunk of the data is kept out, the predictions were generally inaccurate and missed out on significant features that was part of the data. Today with resources growing at almost the same pace as data, it is possible to rethink mining algorithms to work on distributed resources and essentially distributed data. Distributed data mining thus holds great …

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Spatial And Temporal Estimation Of Pumping And Recharge In Groundwater System Analysis, Sherly Hartono Jan 2005

Spatial And Temporal Estimation Of Pumping And Recharge In Groundwater System Analysis, Sherly Hartono

LSU Doctoral Dissertations

In many parts of the U.S., groundwater is used as the primary or secondary source of water for the public supply, agricultural, and industrial sectors. In southwestern Louisiana, a majority of the water demand is supplied by the Chicot aquifer. Numerical flow models are useful for managing and optimizing groundwater systems. However, many important model parameters are difficult to quantify, exhibit a certain degree of uncertainty, and may vary both spatially and temporally. Two of the most important and sensitive parameters for a regional groundwater model of the Chicot aquifer are pumping rates and recharge. The use of GIS-based methods …

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Experimental Investigation Of Drilling Fluid Formulations And Processing Methods For A Riser Dilution Approach To Dual Density Drilling, John Shelton Jan 2005

Experimental Investigation Of Drilling Fluid Formulations And Processing Methods For A Riser Dilution Approach To Dual Density Drilling, John Shelton

LSU Master's Theses

Oil and natural gas resources in the deepwater Gulf of Mexico are important for the U.S. economy, but development is limited by high costs. Dual density drilling concepts that result in wellbore pressure gradients similar to the natural subsurface gradients can simplify well designs and reduce costs. Riser dilution may be an economical means of achieving such a system. This system would use a low density fluid to dilute the weighted wellbore fluid and give an intermediate density fluid in the riser. Two key concerns addressed in this study are whether a drilling fluid can be formulated that will suspend …

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Remote Power Delivery For Hybrid Integrated Bio-Implantable Electrical Stimulation System, Venkat Reddy Gaddam Jan 2005

Remote Power Delivery For Hybrid Integrated Bio-Implantable Electrical Stimulation System, Venkat Reddy Gaddam

LSU Master's Theses

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. In this work, a remote power delivery system (RPDS) is considered as a means to charge rechargeable batteries that power a Bio-implanted Electrical Stimulation System (BESS). A loosely coupled inductive power transmitter and receiver system has been designed to recharge batteries for a bio-implanted gastric pacer. The transmitter coil is periodically worn around the waist. The receiver coil, rechargeable batteries, battery-charging …

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Mathematical Models For Estimating Volatile Chemical Emissions From Dredging Operations, Kenneth Alexander Fountain Jan 2005

Mathematical Models For Estimating Volatile Chemical Emissions From Dredging Operations, Kenneth Alexander Fountain

LSU Master's Theses

Dredging operations have been a common remediation for contaminated sediment in an effort to reduce the harmful impact on the environment. The objective of this research was to create models used for estimating chemical release to air from remediating the Indiana Harbor and Canal (IHC) as three separate dredging operations; the Dredge Site, Exposed DM CDF, and Ponded CDF. The evaporative flux estimations are based on a two-resistance mass transport path inclusive of both the molecular diffusion in porous media and interfacial airside mass transport resistances. Several chemodynamic algorithms were used in calculating key transport parameters. Laboratory tests were performed …

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Cognitive Memory Effects On Non-Linear Video-Based Learning, Katherine Renee Comeaux Jan 2005

Cognitive Memory Effects On Non-Linear Video-Based Learning, Katherine Renee Comeaux

LSU Master's Theses

During an informative learning process, information, material, facts and ideas are typically conveyed in a linear arrangement. Individuals are frequently distracted during this process with their attention being diverted to an interruption (Internet, phone call, etc). When presented with any new information, the mind evolves through problem solving and evaluation procedures. The way in which that information is processed and perceived depends on: (a) original presentation (b) examination of material and (c) an individualistic measurement of success. However, when faced with an interruption, the person is forced to deal with non-linear arrangement of information. This research investigates nonlinear presentation or …

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Modeling Of Chemical Fate And Transport In The Environment, Andre Marquette Jan 2005

Modeling Of Chemical Fate And Transport In The Environment, Andre Marquette

LSU Master's Theses

The Environmental Engineering discipline remains on the forefront of discovery due to advancements in computer technology, advancements in experimental methods and an ever increasing public interest in mitigating the harmful effects of the chemical process industry. Experimental methods have a critical role in defining environmental processes and effects but are limited in their ability to predict future environmental conditions. Conceptual and mathematical models are needed in order to evaluate the effect of environmental conditions far into the future as well as to extend and apply the knowledge gained from experimentation. Models can be used to predict chemical exposure levels, design …

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Computer-Aided Diagnosis Tool For The Detection Of Cancerous Nodules In X-Ray Images, Pallavi Bomma Jan 2005

Computer-Aided Diagnosis Tool For The Detection Of Cancerous Nodules In X-Ray Images, Pallavi Bomma

LSU Master's Theses

This thesis involves development of a computer-aided diagnosis (CAD) tool for the detection of cancerous nodules in X-ray images. Both cancerous and non-cancerous regions appear with little distinction on an X-ray image. For accurate detection of cancerous nodules, we need to differentiate the cancerous nodules from the non-cancerous. We developed an artificial neural network to differentiate them. Artificial neural networks (ANN) find a large application in the area of medical imaging. They work in a manner rather similar to the brain and have good decision making criteria when trained appropriately. We trained the neural network by the backpropagation algorithm and …

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Transform Techniques And Non-Stationarity With An Emphasis On Network Applications, Phat Piron Jan 2005

Transform Techniques And Non-Stationarity With An Emphasis On Network Applications, Phat Piron

LSU Master's Theses

The recent years brought a phenomenal development of Internet. It is, therefore, important to find some ways to improve the performances. The first step in this direction is the characterization and modeling of the network traffic. It has been tested that the network traffic behaves like a self-similar process, while packets interarrivals time possess the long-range dependence property. In particular, we model them by using fractional Brownian motion and fractional Gaussian noise, respectively. Note that, the former is just the cumulative sum of the latter. By using these concepts, the traffic characterization reduces to the estimation of one value: the …

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Flow And Temperature Measurements In A Linear Turbine Blade Passage With Leading Edge And Endwall Contouring And With And Without Film Cooling, Ross James Gustafson Jan 2005

Flow And Temperature Measurements In A Linear Turbine Blade Passage With Leading Edge And Endwall Contouring And With And Without Film Cooling, Ross James Gustafson

LSU Master's Theses

Gas turbine efficiency can be improved by increasing the turbine inlet temperature. Secondary flows created in the turbine blade passage cause pressure losses and increase the thermal blade loading on the endwall, thus limiting the combustion temperature. Pressure losses, or aerodynamic losses, extract energy from the fluid, leaving less for torque or thrust production. Secondary flows also cause greater non-uniformity in the exit flow from each blade stage, which decreases the stage efficiency. Weakening secondary flows will lower pressure losses and endwall heat transfer. The following research will explore concepts for weakening the secondary flows through the use of (a) …

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Experimental Investigation Of Stick-Slip Behavior In Granular Materials, Lynne E. Roussel Jan 2005

Experimental Investigation Of Stick-Slip Behavior In Granular Materials, Lynne E. Roussel

LSU Master's Theses

The mechanical behavior of granular materials is highly dependent on the arrangement of particles, particle groups, and associated pore spaces. Changes in the internal structure due to large deformation may cause changes in the mechanical behavior. The changes include: particle sliding, rolling, and interaction; shear band formation; and fabric anisotropy. During those changes, stick-slip behavior may take place between the granular particles. The objective of the thesis is to study the factors that influence the stick-slip behavior of granular materials. The influence of particle size, uniformity, confining pressure, density, and strain rate are investigated in this thesis. A series of …

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Multivariate Hydrological Frequency Analysis And Risk Mapping, Lan Zhang Jan 2005

Multivariate Hydrological Frequency Analysis And Risk Mapping, Lan Zhang

LSU Doctoral Dissertations

In hydrological frequency analysis, it is difficult to apply standard statistical methods to derive multivariate probability distributions of the characteristics of hydrologic or hydraulic variables except under the following restrictive assumptions: (1) variables are assumed independent, (2) variables are assumed to have the same marginal distributions, and (3) variables are assumed to follow or are transformed to normal distribution. Relaxing these assumptions when deriving multivariate distributions of the characteristics of correlated hydrologic and hydraulic variables. The copula methodology is applied to perform multivariate frequency analysis of rainfall, flood, low-flow, water quality, and channel flow, using data from the Amite river …

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Musculoskeletal Disorders In Dentistry, Frank Maurice Pitts Jan 2005

Musculoskeletal Disorders In Dentistry, Frank Maurice Pitts

LSU Master's Theses

Because of the common occurrence of pain experienced by dental professionals during the course of a workday and throughout their career, an epidemiological and a field study were performed in an effort to contribute to the prevention of musculoskeletal disorders in dentistry. The aim of the thesis is two fold: to assess the perception of occupational pain and discomfort felt by dentists through a perception based survey and to assess the muscle behavior of dentists during isotonic postures while performing various dental procedures on their first and last patients in a given work day. One hundred (100) dentists participated in …

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An Application Of Parallel Computation To Collaborative Optimization, Shahab Nayyer Jan 2005

An Application Of Parallel Computation To Collaborative Optimization, Shahab Nayyer

LSU Master's Theses

Multidisciplinary Design Optimization (MDO) has evolved as a discipline which provides a body of methods and techniques to assist engineers in solving large scale design problems. There are many frameworks for formulating MDO problems. These frameworks can be broadly classified as single-level or bi-level formulations. Collaborative Optimization (CO) is one of the popular bi-level formulations to solve an MDO problem. There are numerous design optimization problems which are highly CPU time intensive and require a long simulation time. With the advent of cheaper and faster available PC’s, distributed parallel computer clusters have become very popular. These clusters provide large computing …

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Traffic Engineering In Multiprotocol Label Switching Vpns, Vinay Kumar Desai Jan 2005

Traffic Engineering In Multiprotocol Label Switching Vpns, Vinay Kumar Desai

LSU Master's Theses

The changing nature of Internet-based applications is imposing stricter demands on the performance of the Internet. For many new applications requiring differentiated quality of service, the best effort model of the internet is no longer adequate. Multiprotocol label switching (MPLS) overlays a connection oriented network on the connection-less IP networks, thereby addressing several shortcomings of the IP network. MPLS improves the forwarding speed, and it provides a virtual path capability to efficiently carry differentiated services. Additionally, MPLS enables traffic engineering by explicit traffic engineering tunnels to be set up across the network to utilize all available bandwidth in an efficient …

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Flame Synthesis Of Carbon-Nanostructures, Saritha Perla Jan 2005

Flame Synthesis Of Carbon-Nanostructures, Saritha Perla

LSU Master's Theses

Ever since their discovery carbon nanostructures (nanotubes and nanofibers) have attracted a lot of interest, due to their striking physical, chemical, mechanical and electrical properties, and paves the path to a wide range of applications. Large quantities of these structures are necessary to make their applications viable. The challenge is to produce them in bulk and in an economical way. Current methods like Arc discharge have the disadvantages of short tube lengths, CVD generated nanomaterials are often riddled with defects and although laser ablation method produces pure and high yield of nanotubes, is a costly technique with expensive lasers and …

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Improvements In Groundwater Flow Modeling Through The Integration Of Resistivity Logs And Hydraulic Conductivity And The Use Of Variogram Uncertainty, Asheka Rahman Jan 2005

Improvements In Groundwater Flow Modeling Through The Integration Of Resistivity Logs And Hydraulic Conductivity And The Use Of Variogram Uncertainty, Asheka Rahman

LSU Doctoral Dissertations

This study developed a coregionalized model to estimate hydraulic conductivity using spatial cross correlation between hydraulic conductivity and borehole geophysical data (a transform of the formation factor). An experimental pseudocross variogram is used instead of a cross variogram because data are not collocated. Experimental variogram uncertainty is investigated using confidence intervals for the experimental variogram calculated assuming variogram sills are lognormally distributed. These intervals are used for sensitivity modeling using kriging, cokriging, simulation and cosimulation. The hydraulic conductivity fields generated by kriging, cokriging, simulation, and cosimulation are then used in a high-resolution groundwater model created using telescopic mesh refinement (TMR) …

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A Programmable Cmos Decimator For Sigma-Delta Analog-To-Digital Converter And Charge Pump Circuits, Raghavendra Reddy Anantha Jan 2005

A Programmable Cmos Decimator For Sigma-Delta Analog-To-Digital Converter And Charge Pump Circuits, Raghavendra Reddy Anantha

LSU Master's Theses

PROGRAMMABLE DECIMATOR FOR SIGMA-DELTA ANALOG-TO-DIGITAL CONVERTER: In this work a programmable decimator design has been presented in 1.5 μm n-well CMOS process for integration with an existing modulator to form a sigma-delta analog-to-digital converter (ADC). The decimator is implemented using a second order Cascaded Integrator Comb (CIC) filter and can be programmed to work with two different oversampling ratios of 64 and 16. The input to the decimator is provided from a first order modulator. With oversampling ratios of 64 and 16, an output resolution of 10-bit and 7-bit, respectively are achieved for the ADC. The ADC can be operated …

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Knowledge-Based Fault Detection Using Time-Frequency Analysis, Venkata S. Vongala Jan 2005

Knowledge-Based Fault Detection Using Time-Frequency Analysis, Venkata S. Vongala

LSU Master's Theses

This work studies a fault detection method which analyzes sensor data for changes in their characteristics to detect the occurrence of faults in a dynamic system. The test system considered in this research is a Boeing-747 aircraft system and the faults considered are the actuator faults in the aircraft. The method is an alternative to conventional fault detection method and does not rely on analytical mathematical models but acquires knowledge about the system through experiments. In this work, we test the concept that the energy distribution of resolution than the windowed Fourier transform. Verification of the proposed methodology is carried …

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Mapping Weak Multidimensional Torus Communications On Optical Slab Waveguides, Karthik Sethuraman Jan 2005

Mapping Weak Multidimensional Torus Communications On Optical Slab Waveguides, Karthik Sethuraman

LSU Master's Theses

This thesis deals with the mapping of communication of a d-dimensional weak torus on an optical medium. Our results are derived in the setting of a sawtooth slab waveguide. The mapping aims to reduce the number and cost of optical components, by exploiting the fact that not all edges of a weak topology are used simultaneously. This approach allows for a better utilization of the huge bandwidth of an optical slab waveguide; currently the cost and size of optical components external to the optical communication medium are the primary bottleneck of an optical interconnect. We introduce the notion of adjacency …

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Measurement And Modeling Of Fluid-Fluid Miscibility In Multicomponent Hydrocarbon Systems, Subhash C. Ayirala Jan 2005

Measurement And Modeling Of Fluid-Fluid Miscibility In Multicomponent Hydrocarbon Systems, Subhash C. Ayirala

LSU Doctoral Dissertations

Carbon dioxide injection has currently become a major gas injection process for improved oil recovery. Laboratory evaluations of gas-oil miscibility conditions play an important role in process design and economic success of field miscible gas injection projects. Hence, this study involves the measurement and modeling of fluid-fluid miscibility in multicomponent hydrocarbon systems. A promising new vanishing interfacial tension (VIT) experimental technique has been further explored to determine fluid-fluid miscibility. Interfacial tension measurements have been carried out in three different fluid systems of known phase behavior characteristics using pendent drop shape analysis and capillary rise techniques. The quantities of fluids in …

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3-Dimensional Flow Measurements In Square Coaxial Jets, Thomas Lagarde Jan 2005

3-Dimensional Flow Measurements In Square Coaxial Jets, Thomas Lagarde

LSU Master's Theses

Results from un-forced experiments conducted in the three-dimensional flow emanating from coaxial contoured nozzles with square cross section and parallel sides are presented and discussed. Two experiments were conducted with the inner to outer jet nominal velocity ratio equal to l=0.5 and l=1.5. The Reynolds number of the outer jet based on the hydraulic diameter of the outer nozzle exit was in both cases 16,000. A multi-position hot-wire anemometry method was used for measurements in the three-dimensional turbulent flow using a dual film sensor (X-probe). A methodology was developed and implemented to derive the mean-velocity components and Reynolds stresses corrected …

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Relative Permeability And Wettability Implications Of Dilute Surfactants At Reservoir Conditions, Ayodeji Adebola Abe Jan 2005

Relative Permeability And Wettability Implications Of Dilute Surfactants At Reservoir Conditions, Ayodeji Adebola Abe

LSU Master's Theses

The improvement or increase of oil recoverable from discovered reservoirs has always been a very important issue as this helps to meet ever growing energy demand. Several methods have been put forward as means of achieving this objective. Chemical flooding, using surfactants has been considered in enhanced oil recovery processes. Surfactants are used primarily to lower oil-water interfacial tension (IFT) and thus improve production. However, surfactants possess the ability to alter rock wettability and hence increase oil production. Previous investigations were performed at ambient conditions using stocktank oil. Extrapolation of the findings from the ambient conditions testing to reservoir conditions …

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