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Articles 5701 - 5730 of 11510

Full-Text Articles in Engineering

Integrated Systems Health Management As An Enabler For Condition Based Maintenance And Autonomic Logistics, Robert M. Vandawalker Sep 2015

Integrated Systems Health Management As An Enabler For Condition Based Maintenance And Autonomic Logistics, Robert M. Vandawalker

Theses and Dissertations

Health monitoring systems have demonstrated the ability to detect potential failures in components and predict how long until a critical failure is likely to occur. Implementing these systems on fielded structures, aircraft, or other vehicles is often a struggle to prove cost savings or operational improvements beyond improved safety. A system architecture to identify how the health monitoring systems are integrated into fielded aircraft is developed to assess cost, operations, maintenance, and logistics trade-spaces. The efficiency of a health monitoring system is examined for impacts to the operation of a squadron of cargo aircraft revealing sensitivity to and tolerance for …

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Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak Sep 2015

Environmental Degradation Of Nickel-Based Superalloys Due To Gypsiferous Desert Dusts, Matthew B. Krisak

Theses and Dissertations

More than twenty-five years of continuous operation in the dusty environments of Southwest Asia have shown that degradation of gas turbine engine components due to particle ingestion is a serious threat to operations. In particular, the continued push for higher engine operating temperatures has brought a new emphasis to the damage mechanisms (for example CMAS glass formation and hot corrosion) caused by ingested particles forming molten deposits on engine components. Despite decades of research little progress has been made to mitigate the effects of CMAS and hot corrosion degradation to engine components. This research focused on hot corrosion specifically. A …

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Adaptive Automation Design And Implementation, Jason M. Bindewald Sep 2015

Adaptive Automation Design And Implementation, Jason M. Bindewald

Theses and Dissertations

Automations allow us to reduce the need for humans in certain environments, such as auto-pilot features on unmanned aerial vehicles. However, some situations still require human intervention. Adaptive automation is a research field that enables computer systems to adjust the amount of automation by taking over tasks from or giving tasks back to the user. This research develops processes and insights for adaptive automation designers to take theoretical adaptive automation ideas and develop them into real-world adaptive automation system. These allow developers to design better automation systems that recognize the limits of computers systems, enabling better designs for systems in …

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A Feasibility Study On The Application Of The Scriptgene Framework As An Anomaly Detection System In Industrial Control Systems, Charito M. Corvin Sep 2015

A Feasibility Study On The Application Of The Scriptgene Framework As An Anomaly Detection System In Industrial Control Systems, Charito M. Corvin

Theses and Dissertations

Recent events such as Stuxnet and the Shamoon Aramco have brought to light how vulnerable industrial control systems (ICSs) are to cyber attacks. Modern society relies heavily on critical infrastructure, including the electric power grid, water treatment facilities, and nuclear energy plants. Malicious attempts to disrupt, destroy and disable such systems can have devastating effects on a populations way of life, possibly leading to loss of life. The need to implement security controls in the ICS environment is more vital than ever. ICSs were not originally designed with network security in mind. Today, intrusion detection systems are employed to detect …

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Multi-Mode Analysis Of Dual Ridged Waveguide Systems For Material Characterization, Jason G. Crosby Sep 2015

Multi-Mode Analysis Of Dual Ridged Waveguide Systems For Material Characterization, Jason G. Crosby

Theses and Dissertations

In this dissertation, two nondestructive dual ridged waveguide (DRWG) material characterization systems are investigated. The single and clamped DRWG probe geometries were analyzed in previous work; however, that research only incorporated the dominant DRWG mode. Here, that restriction is removed and the existence of evanescent higher- order modes is considered. Theoretical analysis of the single and clamped DRWG probes is presented and discussed. The approach taken here is similar to that presented in previous research: Love's equivalence theorem is used to remove the DRWG apertures which are replaced with equivalent magnetic currents radiating in the presence of the background parallel-plate …

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Novel Applications Of A Thermally Tunable Bistable Buckling Silicon-On-Insulator (Soi) Microfabricated Membrane, Robert A. Lake Sep 2015

Novel Applications Of A Thermally Tunable Bistable Buckling Silicon-On-Insulator (Soi) Microfabricated Membrane, Robert A. Lake

Theses and Dissertations

Buckled membranes are commonly used microelectromechanical systems (MEMS) structures. Recent work has demonstrated that the deflection and stiffness of these membranes can be tuned through localized joule heating. These devices were implemented into the design and fabrication of two novel device applications, a tunable pressure sensor and a steerable micromirror. A differential pressure across the membrane causes de reflection, up or down, which can be measured and related to a specific pressure. By tuning the stiffness of the membrane, its pressure response is varied providing a wider range of application for the pressure sensor. A 2.0mm by 2.0mm square membrane …

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Network Analysis With Stochastic Grammars, Alan C. Lin Sep 2015

Network Analysis With Stochastic Grammars, Alan C. Lin

Theses and Dissertations

Digital forensics requires significant manual effort to identify items of evidentiary interest from the ever-increasing volume of data in modern computing systems. One of the tasks digital forensic examiners conduct is mentally extracting and constructing insights from unstructured sequences of events. This research assists examiners with the association and individualization analysis processes that make up this task with the development of a Stochastic Context -Free Grammars (SCFG) knowledge representation for digital forensics analysis of computer network traffic. SCFG is leveraged to provide context to the low-level data collected as evidence and to build behavior profiles. Upon discovering patterns, the analyst …

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Novel Techniques For Secure Use Of Public Cloud Computing Resources, Kyle E. Stewart Sep 2015

Novel Techniques For Secure Use Of Public Cloud Computing Resources, Kyle E. Stewart

Theses and Dissertations

The federal government has an expressed interest in moving data and services to third party service providers in order to take advantage of the flexibility, scalability, and potential cost savings. This approach is called cloud computing. The thesis for this research is that efficient techniques exist to support the secure use of public cloud computing resources by a large, federated enterprise. The primary contributions of this research are the novel cryptographic system MA-AHASBE (Multi-Authority Anonymous Hierarchical Attribute-Set Based Encryption), and the techniques used to incorporate MA-AHASBE in a real world application. Performance results indicate that while there is a cost …

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Exploitation Of Unintentional Ethernet Cable Emissions Using Constellation Based-Distinct Native Attribute (Cb-Dna) Fingerprints To Enhance Network Security, Timothy J. Carbino Sep 2015

Exploitation Of Unintentional Ethernet Cable Emissions Using Constellation Based-Distinct Native Attribute (Cb-Dna) Fingerprints To Enhance Network Security, Timothy J. Carbino

Theses and Dissertations

This research contributed to the AFIT's Radio Frequency Intelligence (RFINT) program by developing a new device discrimination technique called Constellation-Based Distinct Native Attribute (CB-DNA) Fingerprinting. This is of great interest to the Air Force Research Lab (AFRL), Sensor Directorate, who supported the research and now have new method for improving network security. CB-DNA fingerprints are used to authenticate wired network device identities, thwart unauthorized access, and augment traditional bit-level security measures that area easily bypassed by skilled hackers. Similar to human fingerprint features that uniquely identify individuals, CB-DNA uniquely identifies communication devices and improves the rate at which unauthorized rogue …

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Characterization Of Point Defects In Lithium Aluminate (Lialo2) Single Crystals, Maurio S. Holston Sep 2015

Characterization Of Point Defects In Lithium Aluminate (Lialo2) Single Crystals, Maurio S. Holston

Theses and Dissertations

Lithium aluminate (LiAlO2) is an insulating wide-band gap material currently under development for tritium breeding and radiation detection and dosimetry applications. Point defects are imperfections in a crystal lattice localized over a few atomic lengths that can alter the electrical, mechanical, or optical properties of materials. An understanding of point defect behavior is a necessary precursor for optimizing lithium aluminate for nuclear applications. This dissertation has identified and characterized the major point defects created and induced through x-ray and neutron radiation using electron paramagnetic resonance and fluorescence spectroscopy, thermoluminescence, and optical absorption. This dissertation explains for the first …

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Grabbing The Air Force By The Tail: Applying Strategic Cost Analytics To Understand And Manage Indirect Cost Behavior, Bradley C. Boehmke Sep 2015

Grabbing The Air Force By The Tail: Applying Strategic Cost Analytics To Understand And Manage Indirect Cost Behavior, Bradley C. Boehmke

Theses and Dissertations

Recent and projected reductions in defense spending are forcing the military services to develop systematic approaches to identify cost reduction opportunities and better manage financial resources. In response, the Air Force along with her sister services are developing strategic approaches to reduce front-line mission resources, commonly referred to as the Tooth . However, an underemphasized contributing source of costs are mission support activities, commonly referred to as the Tail . With the tail historically representing a sizable portion of the annual Air Force budget, strategically managing cost behavior of these indirect activities has the opportunity to generate significant cost reductions. …

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An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena Sep 2015

An Analysis Of Conus Based Deployment Of Pseudolites For Positioning, Navigation And Timing (Pnt) Systems, Justin H. Deifel, Albert J. Pena

Theses and Dissertations

The Global Positioning System (GPS) developed and operated by the United States Air Force (USAF) provides a way for users to determine position, navigation and timing (PNT). GPS provides an extraordinary capability that has become instrumental in all aspects of our day to day lives. As new technologies such as automated vehicles and unmanned aircraft continue to be developed, a reliable back up to GPS is required to ensure the PNT data generated in these systems is accurate. This research studies a potential architecture for deploying a nationwide network of ground based pseudolites that would act to supplement and backup …

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Tension-Compression Fatigue Behavior Of 2d And 3d Polymer Matrix Composites At Elevated Temperature, Saleh A. Alnatifat Sep 2015

Tension-Compression Fatigue Behavior Of 2d And 3d Polymer Matrix Composites At Elevated Temperature, Saleh A. Alnatifat

Theses and Dissertations

In this Research effort, the tension-compression fatigue behavior of the 3D and 2D PMCs with 0/90˚ fiber orientation (newly developed) was investigated. These polymer composites consist of an NRPE (high-temperature polyimide) matrix with carbon fiber reinforcement. Compressive properties were assessed at (1) room temperature and (2) elevated temperature with one side, Tright, at 329˚C and the other side open to the ambient air. Tension-compression fatigue tests were conducted at elevated temperature with a frequency of 1 Hz and a ratio of minimum to maximum stress of -1.

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Evaluation Of Control Inputs On The Spin Recovery Of The 8kcab Super Decathlon, Courtney Allen Sep 2015

Evaluation Of Control Inputs On The Spin Recovery Of The 8kcab Super Decathlon, Courtney Allen

Theses and Dissertations

The current Federal Aviation Administration (FAA) response to stall/spin related accidents is prevention through pilot awareness training and encouraging stall proof aircraft design features. Aircraft have an inherent capability to spin. The controls that influence spin recovery have yet to be quantitatively analyzed in a regression analysis. This thesis presents the regression modeling and validation process for the evaluation of control inputs on the spin recovery of the 8KCAB Super Decathlon. The regression models in this thesis explore the control inputs for factors of: rudder, elevator, and aileron. Additionally, this thesis explores the timing of the control inputs factors for …

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Multidimensional Analysis Of Nuclear Detonations, Robert C. Slaughter Sep 2015

Multidimensional Analysis Of Nuclear Detonations, Robert C. Slaughter

Theses and Dissertations

The focus of this research is to develop the methods for 3-dimensional reconstructions and temperature distributions of early time nuclear fireballs. Initial developments have resulted in the first 2-dimensional temperature distribution of a nuclear fireball using digitized film. This same process was then extended to perform the first limb darkening calculations of nuclear fireballs. Limb darkening coefficients were then used to derive a temperature profile of the nuclear fireball as a function of optical path length. A 3-dimensional reconstruction was performed using a variation of a structure from illuminance technique in combination with limb darkening coefficients to produce structure using …

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Finite Element Analysis And Experimentation Of An Icosahedron Frame Under Compression, Mohammed Alghofaily Sep 2015

Finite Element Analysis And Experimentation Of An Icosahedron Frame Under Compression, Mohammed Alghofaily

Theses and Dissertations

A nonlinear analysis of a 3D icosahedron frame was conducted using ABAQUS, under a compressive load in which collapse occurs. The frame was created in SolidWorks using the material properties of the 3D plastic building material VeroBlue. Two considerations were made: the computational features of the frame, and the comparison between the experimental solution to the numerical solution. Two studies were also considered in this research: The first study was a comparison between the seven-inch and the four-inch icosahedron model with identical weight to buoyancy ratios; and the second study was a comparison between the seven-inch icosahedrons frame, with the …

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A Nonequilibrium Finite-Rate Carbon Ablation Model For Radiating Earth Re-Entry Flows, Christopher R. Alba Sep 2015

A Nonequilibrium Finite-Rate Carbon Ablation Model For Radiating Earth Re-Entry Flows, Christopher R. Alba

Theses and Dissertations

Vehicles entering planetary atmospheres at high speed require an ablative heat shield in order to withstand the high thermal energy flux to the body. The interaction between the ablative products and the flow field is not well characterized. Numerical simulations were conducted to investigate the influence of carbon ablation on shock layer radiation. Data collected from experiments performed in the X-2 expansion tunnel at the University of Queensland was used to compare to the simulations. The model was a short half-cylinder made of isomolded graphite and was tested in 8.6 km/s Earth entry flow. The model surface was heated within …

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Secure Wearable Systems With Wireless Phy-Layer Information, Lu Shi Sep 2015

Secure Wearable Systems With Wireless Phy-Layer Information, Lu Shi

Theses and Dissertations

In wireless wearable system such as body area network (BAN), device authentication and secret key extraction are essential for trustworthy and reliable gathering and delivery of user’s critical health information. Traditional authentication solutions depend on prior trust among nodes whose establishment would require either key pre-distribution or non-intuitive participation by inexperienced users. Most existing non-cryptographic authentication schemes require advanced hardware or significant modifications to the system software, which are impractical for BANs. Recently, most wireless network security schemes merely based on physical layer characteristics tackle device authentication and secret key extraction, but separately. It remains an open problem to simultaneously …

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Performance Evaluation And Qos Enhancement Of Sip-Based Protocols For Ims Services, Rania Nazar Saleem Sep 2015

Performance Evaluation And Qos Enhancement Of Sip-Based Protocols For Ims Services, Rania Nazar Saleem

Theses and Dissertations

Of the various types of VoIP handling protocols, the Session Initiation Protocol (SIP) is an application layer protocol considered to be the most commonly used signaling protocol in the VoIP services industry. It is used for the purpose of creation, modification, and termination of sessions that contain multimedia streams at the endpoints known as User Agents (UA). SIP was standardized by the Internet Engineering Task Force (IETF) and is designed to work with other IETF Internet protocols to establish a full multimedia session. SIP is also the basis for the operation of IP Multimedia Subsystem (IMS), which forms the essential …

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Particle Filtering For Eeg Source Localization And Constrained State Spaces, Bradley Ebinger Sep 2015

Particle Filtering For Eeg Source Localization And Constrained State Spaces, Bradley Ebinger

Theses and Dissertations

Particle Filters (PFs) have a unique ability to perform asymptotically optimal estimation for non-linear and non-Gaussian state-space models. However, the numerical nature of PFs cause them to have major weakness in two important areas: (1) handling constraints on the state, and (2) dealing with high-dimensional states. In the first area, handling constraints within the PF framework is crucial in dynamical systems, which are often required to satisfy constraints that arise from basic physical laws or other considerations. The current trend in constrained particle filtering is to enforce the constraints on all particles of the PF. We show that this approach …

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Novel Methodologies For Locomotion Mode Identification In Lower Limb Prosthesis, Taimoor Afzal Sep 2015

Novel Methodologies For Locomotion Mode Identification In Lower Limb Prosthesis, Taimoor Afzal

Theses and Dissertations

Lower limbs enable human beings to move in an uncomplicated manner. They support the weight of the body, provide postural stability while moving the body forward and even move it backwards. Regardless of the environment these limbs have the capacity to adapt to any terrain. However, disability as a result of amputation may lead a person to live a dismal life. The deficiency of the ability to walk can have undesirable effect on the amputee from both the physical and psychological point of view. Use of prosthetic devices helps in overcoming this deficiency. The use of prostheses goes back to …

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An Improved Dynamic Particle Packing Model For Prediction Of The Microstructure In Porous Electrodes, Chien-Wei Chao Sep 2015

An Improved Dynamic Particle Packing Model For Prediction Of The Microstructure In Porous Electrodes, Chien-Wei Chao

Theses and Dissertations

The goal of this work is to develop a model to predict the microstructure of Li-ion batteries, specifically focusing on the cathode component of the batteries. This kind of model has the potential to assist researchers and battery manufacturers who are trying to optimize the capacity, cycle life, and safety of batteries. Two dynamic particle packing (DPP) microstructure models were developed in this work. The first is the DPP1 model, which simulates the final or dried electrode structure by moving spherical particles under periodic boundaries using Newton's laws of motion. The experience derived from developing DPP1 model was beneficial in …

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Calibration And Validation Of The Rapidscat Scatterometer Using Natural Land Targets, Nathan Mark Madsen Sep 2015

Calibration And Validation Of The Rapidscat Scatterometer Using Natural Land Targets, Nathan Mark Madsen

Theses and Dissertations

RapidScat is a Ku-band scatterometer that was launched September 2014 and is currently operating on the International Space Station. It estimates ocean vector winds through accurate measurement of the normalized radar coefficient (σ0) of the ocean surface. In order to ensure the accuracy of σ0 measurements and consistency with previous Ku-band scatterometers, post-launch calibration and validation is necessary. Calibration and validation is performed using natural land targets, namely the Amazon and Congo rainforests, to complement calibration efforts over the ocean. The σ0 response of the targets is estimated with respect to viewing angle and time of …

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Bending Behavior Of Carbon/Epoxy Composite Isobeam Structures, Brandon A. Asay Sep 2015

Bending Behavior Of Carbon/Epoxy Composite Isobeam Structures, Brandon A. Asay

Theses and Dissertations

This research demonstrated the fabrication, flexural testing, and analysis of nominally 5 ft (1.5 m) 6-bay and 10 ft (3 m) 12-bay carbon/epoxy IsoBeam™ structures. The rectangular cross-section was 5 in (12.7 cm) wide by 10 in (25.4 cm) high. The IsoBeam structure is a composite lattice structure that is a geometric derivative of the IsoTruss® structure. Modifying the geometry to yield a rectangular cross-section provides additional applications for these beams as structural elements in buildings, aircraft, vehicles, and other structures. The diameters of the constituent members of the IsoBeam, namely the longitudinal and diagonal members, were sized such that …

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An Approach For Designing Origami-Adapted Products With Aerospace Mechanism Examples, Jessica Morgan Sep 2015

An Approach For Designing Origami-Adapted Products With Aerospace Mechanism Examples, Jessica Morgan

Theses and Dissertations

The objective of this research is to develop a design process for origami-adapted products and demonstrate it using aerospace mechanism examples. Origami-adapted design is a type of origami-based design. Origami-based design ranges from abstract to concrete applications of origami to design and includes: origami-inspired design, origami-adapted design, and origami-applied design. Origami-adapted design adapts origami fold patterns into products while preserving functionality. Some of the desirable attributes of origami that are sought after in design include: 1) reduced number of parts, 2) stowability, 3) deployability, 4) transportability, 5) manufacturability from a flat sheet of material, 6) ease of miniaturization, 7) a …

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Augmented Reality In Android Devices, Fatima Aldaeif Aug 2015

Augmented Reality In Android Devices, Fatima Aldaeif

Theses and Dissertations

Augmented Reality is a computer graphic system combines a virtual object with a real physical world, and this work present kind of augmented reality which is called a 3D Eyeglasses Try-on real time tracking system, with help of the mobile phone camera. This system follow the motion of the face user, and renders the glasses immediately in front of the user eyes. This thesis tells that Android OpenCV SDK is applied to recognize the features, extract the characteristic target and make the camera calibration to create an Augmented Reality application.

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Developing Pavement Performance Prediction Models For The State Of Arkansas, Lena Baker Abu-Ennab Aug 2015

Developing Pavement Performance Prediction Models For The State Of Arkansas, Lena Baker Abu-Ennab

Theses and Dissertations

Pavement management systems (PMS) provide a methodology for synthesizing all the activities related to the pavement network. These include all the activities involved in the planning and programming, design, construction, maintenance, and rehabilitation (1). The effective implementation and utilization of PMS requires a systematic approach involving condition assessment and performance modelling. A very important part of such approach is the use of pavement performance prediction models to predict the future condition of pavements based on present condition. This study presents a methodology used to develop network level pavement performance prediction models for the pavement network in the state of Arkansas. …

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Synthesis And Characterization Of Vanillyl Alcohol Based Thermosetting Epoxy Resins, Eric Hernandez Aug 2015

Synthesis And Characterization Of Vanillyl Alcohol Based Thermosetting Epoxy Resins, Eric Hernandez

Theses and Dissertations

Lignin is a natural and abundant renewable material composed of crosslinked phenylpropenyl units that when strategically depolymerized could potentially yield renewable bio-based aromatic building blocks for applications in high-performance thermosetting epoxy resins. Vanillyl alcohol, a lignin derived aromatic diol, is a potential platform chemical for the production of renewable bisphenols and epoxy thermosets. A new bio-based bisphenol (bisguaiacol) was synthesized via electrophilic aromatic condensation of vanillyl alcohol and guaiacol, from which diglycidyl ether of bisguaiacol (DGEBG) was prepared via epoxidation with epichlorohydrin.The thermomechanical properties of DGEBG blended with a commercial BPA-based epoxy resin and cured with a diamine were investigated …

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Corrosion Fatigue Crack Growth Behavior At Notched Hole In 7075-T6 Under Biaxial And Uniaxial Fatigue With Different Phases, Ali Khawagi Aug 2015

Corrosion Fatigue Crack Growth Behavior At Notched Hole In 7075-T6 Under Biaxial And Uniaxial Fatigue With Different Phases, Ali Khawagi

Theses and Dissertations

This research investigates fatigue crack propagation behavior in both air and saltwater (3.5% NaCl) environments from pre-cracked notched circular hole in a 7075-T6 cruciform specimen. With stress ratio of 0.5, biaxility stress ratio of unity, and frequency of applied load of 10 Hz, the crack growth behavior was investigated under in-plane biaxial tension-tension fatigue with 45⁰, 90⁰ and 180⁰ phase difference conditions and then compared to previous fatigue tests with no phase difference to study the effect of changing the phase differences between the applied loads on the crack growth rate. Finite Element Analysis (FEA) was used to calculate cyclic …

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Miniaturized Wideband Planar Soft Surfaces For Mutual Coupling Reduction Between Antenna Elements, Said A. Abushamleh Aug 2015

Miniaturized Wideband Planar Soft Surfaces For Mutual Coupling Reduction Between Antenna Elements, Said A. Abushamleh

Theses and Dissertations

Miniaturized electromagnetic soft surfaces have promising applications in contemporary wideband portable wireless devices including, Multiple Input Multiple Output (MIMO) systems, dual frequency applications, and mutual coupling reduction among antennas in user terminals utilizing MIMO schemes such as in 4th generation Long-Term Evolution (4G-LTE). The use of textured metallic surfaces over grounded dielectric slab with vias for the suppression of electromagnetic wave propagation for applications including, but not limited to, mutual coupling reduction among closely-spaced antenna elements in antenna arrays, bandwidth enhancement, and gain enhancement has been extensively researched during the past two decades. In this dissertation, novel one-dimensional (1-D) periodic …

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