Engineering Commons^™

Trunk Response Analysis Under Sudden Forward Perturbations Using A Kinematics-Driven Model, B. Bazrgari, A. Shirazi-Adl, Christian Larivière

Études primaires

No abstract provided.

Decentralized Adaptive Neural Network Control Of Interconnected Nonlinear Dynamical Systems With Application To Power System, Shahab Mehraeen

Doctoral Dissertations

"Traditional nonlinear techniques cannot be directly applicable to control large scale interconnected nonlinear dynamic systems due their sheer size and unavailability of system dynamics. Therefore, in this dissertation, the decentralized adaptive neural network (NN) control of a class of nonlinear interconnected dynamic systems is introduced and its application to power systems is presented in the form of six papers. In the first paper, a new nonlinear dynamical representation in the form of a large scale interconnected system for a power network free of algebraic equations with multiple UPFCs as nonlinear controllers is presented. Then, oscillation damping for UPFCs using adaptive …

Energy And Voltage Management Methods For Multilevel Converters For Bulk Power System Power Quality Improvement, Atousa Yazdani

Doctoral Dissertations

"Electric arc furnaces (EAFs) are prevalent in the steel industry to melt iron and scrap steel. EAFs frequently cause large amplitude fluctuations of active and reactive power and are the source of significant power quality disturbances. Also EAFs comprise a major portion of industrial loading on the bulk power system. Typically, a static VAR compensator (SVC) or Static Synchronous compensator (STATCOM) are use to provide the reactive power support in order to alleviate the fluctuations in voltage at PCC. Static Synchronous Compensators (STATCOMs) provide a power electronic-based means of embedded control for reactive power support. Integrating an energy storage system …

Wind Power Applications To Groundwater Remediation, Ronald E. Gallagher

Doctoral Dissertations

"The use of renewable energy systems to power groundwater remediation systems seems like an inherently good idea because of potential cost savings and environmental benefits associated with reduced greenhouse gas emissions. Small wind turbine systems marketed for single residence applications may be the appropriate size for remediation systems, and such wind turbines are readily available at reasonable cost. Another benefit of using domestic wind turbine systems is that they are straightforward to install and operate with minimal training. One of the major drawbacks associated with using wind turbines at remediation sites is that site-specific wind velocity data is typically used …

Freeze Casting Of Bioactive Glass And Ceramic Scaffolds For Bone Tissue Engineering, Qiang Fu

Doctoral Dissertations

"The main objectives of this dissertation were to explore the production of bioactive ceramic and glass scaffolds with oriented pore architectures by unidirectional freezing of suspensions, and to characterize the mechanical and biological performance of the scaffolds. Freezing of aqueous suspensions of hydroxyapatite (HA) or bioactive 13-93 glass particles resulted in the formation of scaffolds with a lamellar-type microstructure (pore width = 5-30 µm). The addition of polar organic solvents (such as 60 wt% dioxane) to the aqueous suspensions markedly changed the morphology and size of the oriented pores, giving scaffolds with a columnar-type microstructure and larger pre width (90-110 …

Modeling And Simulation Of High Pressure Composite Cylinders For Hydrogen Storage, Jianbing Hu

Doctoral Dissertations

"Composite hydrogen cylinders provide an efficient means of storage of hydrogen gas for modern hydrogen vehicles. Safety issues arising from the high gas pressure, temperature variation, fire attack, and fracture failures are the main concerns. The focus of this study is to develop a Finite Element (FE) model to predict the performance of composite cylinders subjected to extreme mechanical/thermal loadings and provide guidance for design optimization"--Abstract, page iv.

Microstructural Influence On Dynamic Properties Of Age Hardenable Femnal Alloys, Ryan A. Howell

Doctoral Dissertations

"A lightweight castable alloy was sought to reduce the MIL-PRF-32269 class II cast steel perforated armor's weight with the requirement that the material had to be manufactured utilizing existing foundry technology and without incurring large alloy cost increases to meet property requirements. Literature on wrought age hardenable Fe-Mn-Al-C alloys suggested this alloy system could achieve weight reduction through high aluminum concentrations with the highest reported strengths exceeding 2 GPa for a Fe-30Mn-9Al-0.9C composition. Even though ballistic testing had not been conducted on this system, high strain rate data of wrought alloys showed excellent work hardenability; greater than existing ballistic metals. …

Emi Failure Analysis Techniques And Noise Prediction For Trace Crossing Split Planes, Weifeng Pan

Doctoral Dissertations

"A variety of methods exist that help locate the source, coupling path, and antenna in an electromagnetic interference (EMI) problem. No single method is the best option in all cases. A good electromagnetic compatibility (EMC) engineer should understand and have experience with a wide range of failure analysis methods and thus, be able to select the most appropriate ones for a given problem. The first three papers are from a series of articles, which explains a set of methods for the analysis of EMI failures. Each method is categorized based on two criteria: 1) the elements in an EMI problem …

Detection Of Low Cost Radio Frequency Receivers Based On Their Unintended Electromagnetic Emissions And An Active Stimulation, Sarah A. Seguin

Doctoral Dissertations

"Detection of super-regenerative receivers using their unintended electromagnetic emissions at a significant distance is challenging due to high levels of ambient noise. The evolution of an approach used to solve this problem is chronicled within the three papers that combine to form this dissertation. First, a passive detection method was created for detecting devices based on the characterization of their unintended emissions and utilized a cascading correlation method to confirm detection. Using a simple sine-wave stimulation to modify these unintended emissions produced better results over passive detection techniques by improving the signal quality and the consistency of the unintended emissions, …

Seismic Behavior Of Circular Reinforced Concrete Bridge Columns Under Combined Loading Including Torsion, Suriya Prakash Shanmugam

Doctoral Dissertations

"Reinforced concrete (RC) columns of skewed and curved bridges with unequal spans and column heights can be subjected to combined loading including axial, flexure, shear, and torsion loads during earthquakes. The combination of axial loads, shear force, and flexural and torsional moments can result in complex failure modes of RC bridge columns. This study carried out experimental and analytical studies to investigate the seismic performance of circular RC columns under combined loading including torsion. The main variables considered here were (i) the ratio of torsion-to-bending moment (T/M), (ii) the ratio of bending moment-to-shear (M/V) or shear span (H/D), and (iii) …

An Experimental And Numerical Investigation Of Flapping And Plunging Wings, Taylor A. Swanson

Doctoral Dissertations

"Micro air vehicles, or MAVs, are of current interest for a multitude of uses to which they, being small, unmanned vehicles, are uniquely suited. Among the proposed uses are exploration, reconnaissance, and communications. They can be deployed inside buildings, where their small size, hovering capability, and maneuverability, are important factors. Due to their small size, they operate at low Reynolds numbers where conventional flying mechanisms are not advantageous. Thus, attempts have been made to learn from natural flyers like insects and birds. Natural flight is accomplished by flapping wings, and this idea has been proposed for certain types of MAVs …

Helical Force Flow: A New Engineering Mechanics Model For Biological Materials, Jeffery S. Thomas

Doctoral Dissertations

"The author has long speculated that the prevalence of helical structures in botany and zoology hints to an optimized pathway for force and/or energy transfer. His goal has been to realize an alternative approach to the standard stress analysis used in engineering in order to more efficiently and accurately deal with biological materials. Improved tools for these natural materials should in turn aid the design and analysis of engineered materials. Following the role of a navigator in leaf C. Levesque's book "Breakthrough Creativity", the author typically searches for ideas in a variety of places, including physics, materials science, biomimetics, dimensional …

Advanced Current-Mode Control Techniques For Dc-Dc Power Electronic Converters, Kai-Tak Wan

Doctoral Dissertations

"There are many applications for dc-dc power electronic converters in industry. Considering the stringent regulation requirements, control of these converters is a challenging task. Several analog and digital approaches have already been reported in the literature. This work presents new control techniques to improve the dynamic performance of dc-dc converters"--Abstract, page iv.

Novel Modulated Antennas And Probes For Millimeter Wave Imaging Applications, Mohamed A. Abou-Khousa

Doctoral Dissertations

"Microwave and millimeter wave (300 MHz - 300 GHz) imaging techniques have shown great potential for a wide range of industrial and medical applications. These techniques are fundamentally based on measuring relative and coherent electromagnetic fields distributions, e.g., electric fields, around the object to be imaged. Various imaging systems can be devised for measuring relative electric field distributions; each with it own advantages and limitations. This dissertation is focused on addressing critical challenges related to the practical implementation of various microwave and millimeter wave imaging systems. Specifically, this research is meant to achieve three main objectives related to designing efficient …

A Control-Theoretical Fault Prognostics And Accommodation Framework For A Class Of Nonlinear Discrete-Time Systems, Balaje T. Thumati

Doctoral Dissertations

"Fault diagnostics and prognostics schemes (FDP) are necessary for complex industrial systems to prevent unscheduled downtime resulting from component failures. Existing schemes in continuous-time are useful for diagnosing complex industrial systems and no work has been done for prognostics. Therefore, in this dissertation, a systematic design methodology for model-based fault prognostics and accommodation is undertaken for a class of nonlinear discrete-time systems. This design methodology, which does not require any failure data, is introduced in six papers. In Paper I, a fault detection and prediction (FDP) scheme is developed for a class of nonlinear system with state faults by assuming …

Analysis Using Surface Wave Methods To Detect Shallow Manmade Tunnels, Niklas Henry Putnam

Doctoral Dissertations

"Multi-method seismic surface wave approach was used to locate and estimate the dimensions of shallow horizontally-oriented cylindrical voids or manmade tunnels. The primary analytical methods employed were Attenuation Analysis of Rayleigh Waves (AARW), Surface Wave Common Offset (SWCO), and Spiking Filter (SF). Surface wave data were acquired at six study sites using a towed 24-channel land streamer and elastic-band accelerated weight-drop seismic source. Each site was underlain by one tunnel, nominally 1 meter in diameter and depth. The acquired surface wave data were analyzed automatically. Then interpretations compared to the field measurements to ascertain the degree of accuracy. The purpose …

Applications Of Sensor Arrays In Acoustic And Seismic Signal Processing, Peng Xie

Doctoral Dissertations

"This work investigates the applications of sensor arrays in the areas of acoustic and seismic signal processing. It comprises three papers.

The first paper explores the problem of blind source separation (BSS) for convolutive acoustic signals. It concentrates on the well known permutation and amplitude problems in frequency-domain BSS and proposes a new hybrid approach to solve them. This approach connects the separation processes across all frequency bins, and relies on a novel permutation control unit. This framework could greatly reduce computational load and improve separation performance. Synthesized and real-world experiments demonstrate its efficiency.

The second paper investigates a new …

Fundamentals Of Friction Stir Spot Welding, Harsha Badarinarayan

Doctoral Dissertations

"The recent spike in energy costs has been a major contributor to propel the use of light weight alloys in the transportation industry. In particular, the automotive industry sees benefit in using light weight alloys to increase fuel efficiency and enhance performance. In this context, light weight design by replacing steel with Al and/or Mg alloys have been considered as promising initiatives. The joining of structures made of light weight alloys is therefore very important and calls for more attention. Friction Stir Spot Welding (FSSW) is an evolving technique that offers several advantages over conventional joining processes.

The fundamentals aspects …

Modeling And Analysis Of Noise Coupling In Multilayer Power/Ground Planes, Gang Feng

Doctoral Dissertations

"The simultaneous switching noise (SSN) in a multilayer power delivery network (PDN) is a critical problem in high-speed printed circuit board (PCB) designs. Full-wave methods are not computationally efficient for analyzing PCB structures normally with a multi-scale nature. In this thesis, a model for multilayer power/ground planes is proposed using basic plane pair blocks derived from the cavity model combined with the segmentation technique. Vias and other circuit elements can further be easily integrated in the multilayer plane model. As a result, the entire PDN model is much more computationally efficient than full-wave methods. Experimental and numerical results have validated …

Quality Of Service Provisioning Through Resource Allocation And Data Aggregation In Wireless Sensor Networks, Carl Larsen

Doctoral Dissertations

"In this dissertation, improvement of quality of service (QoS) provisioning in wireless sensor networks (WSN) is examined using four different methods. The first two focus on allocation of limited resources in the face of changing network and channel conditions, and thus improving performance in terms of throughput and delay. The second two methods focus on using data aggregation to minimize the size and number of packet transmissions reducing the energy consumption and improving network lifetime.

Therefore, in the first paper a novel adaptive and distributed fair scheduling (ADFS) protocol for WSN is presented that allocates the channel bandwidth in proportion …

Advanced Control Techniques For Doubly Fed Induction Generator-Based Wind Turbine Converters To Improve Low Voltage Ride-Through During System Imbalances, Murali M. Baggu

Doctoral Dissertations

A doubly-fed induction generator (DFIG) applied to wind power generation is under study for low voltage ride-through application during system disturbances. Conventional dq axis current control using voltage source converters for both the grid side and the rotor side of the DFIG are analyzed and simulated. DFIG operation is investigated under balanced and unbalanced system disturbances. A conventional d-axis and q-axis control applied to a voltage source converter (VSC) during a system imbalance exhibits oscillations in the stiff DC link voltage as well as in the real and reactive powers of the converter. Multiple advanced control methods are explored and …

Information Archival And Reuse: Drawing Conclusions From The Past, Matt R. Bohm

Doctoral Dissertations

"Over the last few decades design researchers have put forward theories and proposed methodologies that increase the chance that a design team will reliably arrive at the optimal solution to a given design problem. Studies, however, bear out that theories and methodologies alone will not guarantee an optimal or even good design solution. Instead, a breadth of knowledge across multiple engineering domains and the time and tools to thoroughly evaluate the design space are as important as any prescriptive design method. This work presents a set of underlying engineering technologies to define, archive and reuse product design knowledge to provide …

Material Flow And Microstructure Evolution In Friction Stir Welding Of Aa6111 Alloy Sheets, Manasij Kumar Yadava

Doctoral Dissertations

"Material flow and microstructure evolution are the two important aspects of the Friction stir welding (FSW) technique, which control the properties and performance of the friction stir welds. The present work investigates these two aspects of the FSW with main emphasis on the friction stir lap joints (FSLJs) on the AA6111 sheets. Due to the characteristic material flow during FSW, the faying surfaces in FSLPs are deposited in and around the weld nugget and create unavoidable defects. These defects reduce the load carrying thickness of the joints by providing an easy path for the weld failure. Therefore, to control the …

Protein Responsive Synthetic Materials For Biomedical Applications, Youyou Zheng

Doctoral Dissertations

"The production of synthetic materials with molecular recognition abilities towards biomacromolecules has been widely researched because of its potential applications in separations, sensing, therapeutics, etc. While molecular imprinting has become a commercially viable method for the production of synthetic materials with molecular recognition abilities towards small molecules, little success has been recorded towards protein targets. Proteins are difficult to imprint as they present a number of epitopes for imprinting, are difficult to remove from the completed material, and are incompatible with the densely crosslinked structures required. As a result, a novel surface molecular imprinting technique was developed to synthesize polymeric …

The Role Of Friction Stir Processing On The Microstructure And Mechanical Properties Of A Cast Aluminum Alloy, Saumyadeep Jana

Doctoral Dissertations

"Al-7Si-0.6Mg is one of the most important cast aluminum alloys because of its attractive mechanical properties and high castability. Microstructurally, the alloy consists of primary aluminum dendrites with eutectic Si particles in the interdendritic region. This makes the alloy quasi-brittle in nature which affects the ductility of the alloy to a great extent. In order to improve the ductility, the eutectic Si particles need to be refined which so far has been achieved by chemical and/or thermal modification. Friction stir processing (FSP) on the other hand can achieve the same through plastic deformation, and therefore replace the cast structure with …

Large Eddy Simulation Of Turbulent Premixed Combustion In Gas Turbines, Ashoke De

LSU Doctoral Dissertations

An artificially Thickened Flame (TF) approach based on LES framework is used to model the turbulent premixed combustion in gas turbine combustors. A number of variants of the Thickened Flame approach including a modified version of TF model have been studied in details. In the TF model, the flame front is artificially thickened to resolve on LES computational grid. With this approach, reaction rate modeling does not require any ad-hoc closure assumptions. However, suitable modifications have to be made to compensate for flame thickening. To verify the predictive capability of the models, a stoichiometric methane-air flame on Bunsen burner type …

Scheduling And Reconfiguration Of Interconnection Network Switches, Krishnendu Roy

LSU Doctoral Dissertations

Interconnection networks are important parts of modern computing systems, facilitating communication between a system's components. Switches connecting various nodes of an interconnection network serve to move data in the network. The switch's delay and throughput impact the overall performance of the network and thus the system. Scheduling efficient movement of data through a switch and configuring the switch to realize a schedule are the main themes of this research. We consider various interconnection network switches including (i) crossbar-based switches, (ii) circuit-switched tree switches, and (iii) fat-tree switches. For crossbar-based input-queued switches, a recent result established that logarithmic packet delay is …

An Uncertainty-Based Approach To The Total Maximum Daily Load Development, Abhijit Patil

LSU Doctoral Dissertations

A Bayesian-updating approach is developed to the estimation of the total uncertainty-based Margin of Safety (MOS) for Total Maximum Daily Load calculations using the watershed modeling tool HSPF. In order to determine the prior, likelihood, and posterior distributions of uncertainties involved in Bayesian approach, various probability density functions are derived. The temperature measurement induced uncertainty in dissolved oxygen simulation is found to be normally distributed. The temporal scale uncertainty in weather data decreases with decreasing temporal resolution. The temporal-scale uncertainties in the rainfall and temperature data follow a Weibull and general extreme value distributions, respectively. The spatial-resolution uncertainty in simulated …

Slab-On-Girder Prestressed Concrete Bridges: Linear And Nonlinear Finite Element Analysis And Experimental Load Tests, Marcio Costa Araujo

LSU Doctoral Dissertations

“A diaphragm is a transverse stiffener, which is placed between girders in order to maintain section geometry”, (AASHTO, 2002). Intermediate diaphragms, usually placed at the midspan or third points of a bridge, are thought to contribute to the overall distribution of live loads in bridges. Cast-in-place concrete intermediate diaphragms were investigated in this study in order to assess their load distribution effectiveness in prestressed concrete I-girder bridges. Finite element packages (Ansys and GT STRUDL) were used to perform the analyses for multiple bridge configurations, including a parametric study of span length, girder spacing, and concrete strength. It was found that …

Multiphase Flows In Polymer Microfluidic Systems, Namwon Kim

LSU Doctoral Dissertations

Continuous delivery of segmented reagents using pressure-driven multiphase flow in microchannels is a promising technology for high throughput microfluidic bioassays. Separation and encapsulation of the target reagents with another inert fluid provide many advantages over single phase flow in microfluidic applications of biotechnology. In order to achieve these advantages and control these multiphase flows, it is necessary to understand their generation and transport characteristics as influenced by geometrical miniaturization, channel wall properties, the effects of surfactants and operating conditions. For gas-liquid two-phase flow, dry air and deionized water were driven into hot embossed PMMA microchannels with 200 μm square test …