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2013

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Articles 6091 - 6120 of 7289

Full-Text Articles in Engineering

A Friction Prediction Model For Small Si Engines, Avinash Singh Jan 2013

A Friction Prediction Model For Small Si Engines, Avinash Singh

Masters Theses

"A substantial portion of the input fuel energy in an SI engine is lost towards overcoming the frictional forces from various rubbing parts. These frictional losses are very significant in small engines and these losses can be reduced by incorporating some design changes. A semi-empirical friction prediction model was studied and modified with the help of the experimental results for small SI engines. This model is dependent upon engine geometry and speed. The model divides the frictional work into different sub-assemblies of the engine and these sub-assemblies are in turn divided to determine the friction associated with individual components. A …

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Dynamic Contact Analysis Of A Piezoelectrically Driven Ultrasonic Crawler-Actuator, Dwight Santiago Maness Jan 2013

Dynamic Contact Analysis Of A Piezoelectrically Driven Ultrasonic Crawler-Actuator, Dwight Santiago Maness

Masters Theses

"A standing wave ultrasonic motor (SWUM) is presented in this thesis. The actuator is piezoelectrically powered and operates in the first and second bending modes to move forwards and backwards, respectively. The kinematic stability of the crawler, backed by experimental results is shown in the first paper presented in this thesis. This study demonstrates that in the absence of a preload or kinematic constraints, the crawler shows vertical stability. A full transient analysis using the finite element method is performed characterizing the speed and contact variables is conducted in the second paper. The results show that given enough time the …

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Cfd Simulation Of Void Flow In Eccs, Lifeng Wang Jan 2013

Cfd Simulation Of Void Flow In Eccs, Lifeng Wang

Masters Theses

"Emergency core cooling system (ECCS) has been studied extensively for reactor safety. Emergency core cooling system (ECCS) is designed to make sure the reactor core it is protected by providing sufficient heat removal during accident conditions. In a loss-of-coolant-accident (LOCA) scenario, the ECCS is designed to take over the reactor core cooling by drawing water from a reservoir or tank. Voids may be introduced into the ECCS through a variety of means leading to total or partial loss of suction supply, or through gas depressurization resulting from difference in gas saturation pressure and ambient pressure. The transportation of voids through …

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Manual Modification And Plasma Exposure Of Boron Nitride Ceramic To Study Hall Effect Thruster Plasma Channel Material Erosion, Alexander J. Satonik Jan 2013

Manual Modification And Plasma Exposure Of Boron Nitride Ceramic To Study Hall Effect Thruster Plasma Channel Material Erosion, Alexander J. Satonik

Masters Theses

"Worn Hall effect thrusters (HET) show a variety of unique microstructures and elemental compositions in the boron nitride thruster channel walls. Worn thruster channels are typically created by running test thrusters in vacuum chambers for hundreds of hours. Studies were undertaken to manually modify samples of boron nitride without the use of a hall effect thruster. Samples were manually abraded with an abrasive blaster and sandpaper, in addition to a vacuum heater. Some of these samples were further exposed to a xenon plasma in a magnetron sputter device. Sandpaper and abrasive blaster tests were used to modify surface roughness values …

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Quantization Noise Analysis Of A Closed-Loop Pwm Controller That Includes Σ-Δ Modulation, Anupama Balakrishnan Jan 2013

Quantization Noise Analysis Of A Closed-Loop Pwm Controller That Includes Σ-Δ Modulation, Anupama Balakrishnan

Masters Theses

"Σ-Δ modulation is a popular noise shaping technique which is used to move the quantization noise out of the frequency band of interest. Recently, a number of authors have applied this technique to a pulse width modulation (PWM) controller for switching power converters. However, previous analysis has not incorporated the effects of analog-to-digital converter (ADC) resolution or feedback control on the Σ-Δ modulator. In this work, quantization due to ADC resolution and PWM resolution are analyzed, considering the effects of noise-shaping and feedback. A number of simulations have been performed to explore the impact of various design choices on output …

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Paste Development And Co-Sintering Test Of Zirconium Carbide And Tungsten In Freeze-Form Extrusion Fabrication, Ang Li Jan 2013

Paste Development And Co-Sintering Test Of Zirconium Carbide And Tungsten In Freeze-Form Extrusion Fabrication, Ang Li

Masters Theses

"Ultra-high temperature ceramics are being investigated for future use in aerospace applications due to their superior thermo-mechanical properties, as well as oxidation resistance, at temperatures above 2000°C. However, their brittle properties make them susceptible to thermal shock failure. Components fabricated as functionally graded materials (FGMs) can combine the superior properties of ceramics with the toughness of an underlying refractory metal by fabricating graded composites. This paper discusses the grading of two materials through the use of a Freeze-form Extrusion Fabrication (FEF) system to build FGMs parts consisting of zirconium carbide (ZrC) and tungsten (W). Aqueous-based colloidal suspensions of ZrC and …

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Development Of A Methodology For Pseudo-Rigid-Body Models Of Compliant Segments With Inserts, And Experimental Validation, Raghvendra Sharadchandra Kuber Jan 2013

Development Of A Methodology For Pseudo-Rigid-Body Models Of Compliant Segments With Inserts, And Experimental Validation, Raghvendra Sharadchandra Kuber

Masters Theses

"Compliant mechanisms have shown a great deal of potential in the last few decades in providing better solutions to design problems with numerous benefits; however, their use has been limited due to current challenges in the material selection. With ever increasing focus on the applications of compliant mechanisms, it is necessary to find alternatives to the existing materials and methods of prototyping. The purpose of this work is to develop a methodology for pseudo-rigid-body models of compliant segments with compliant inserts, comprised of a resilient material placed between the layers of a softer material, to alleviate any creep and strength …

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Analysis Of Model Uncertainty In Hydraulic Modeling: The Bstem Application To The Osage River, Annabell Leigh Ulary Jan 2013

Analysis Of Model Uncertainty In Hydraulic Modeling: The Bstem Application To The Osage River, Annabell Leigh Ulary

Masters Theses

"Uncertainty is inevitable when creating any kind of model. A model can be used in the most accurate way possible, if the uncertainties are understood. This study determines the level of uncertainty in the Bank Stability and Toe Erosion Model (BSTEM) of the Osage River downstream of Bagnell Dam between Lake Ozark, MO and Jefferson City, MO. The statistical analysis of the BSTEM model was performed using the aid of SAS statistical computer modeling software. There were 4 different analysis values used to determine the best fit model for all dependent variables. These values include the F-test, the coefficient of …

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Comparison Of Class Ii Injection Well Area Of Review Requirements With Area Of Evaluation For Hydraulically Fractured Wells, Yashesh Jitendra Panchal Jan 2013

Comparison Of Class Ii Injection Well Area Of Review Requirements With Area Of Evaluation For Hydraulically Fractured Wells, Yashesh Jitendra Panchal

Masters Theses

"Since 2010 the US Environmental Protection Agency (EPA) has been proposing plans to study, and has now initiated research regarding the potential impact of hydraulic fracturing processes on drinking water sources. Their work refers to an 'Area of Evaluation' around a hydraulically fractured well, inferring that the wells immediately around hydraulic fractured wells should be studied, to evaluate the conditions of these wells and their potential to contaminate overlying USDWs. Class II injection wells must have a minimum 1/4 mile radius area of review to determine the condition of wells surrounding the proposed injection well. All wells within this AOR …

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Robust Methods For Construction Of Global Potential Energy Surfaces, Phalgun Lolur Jan 2013

Robust Methods For Construction Of Global Potential Energy Surfaces, Phalgun Lolur

Masters Theses

"This thesis is about the development of robust methods for construction of global potential energy surfaces to study the spectroscopy and dynamics of molecular systems. A potential energy surface represents the electronic energy of a molecule as a function of its geometry. This is central to how chemists view molecular systems in terms of motion across a rich energy landscape where barriers separate wells corresponding to different stable structures. The range of molecular distortions defines the potential energy surface. Computing the potential energy surface of a molecule has become a fundamental operation in modern theoretical chemistry studies. The Born-Oppenheimer approximation …

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Transmission Shaft Design For Hydrokinetic Turbine With Reliability Consideration, Goutham Pusapati Jan 2013

Transmission Shaft Design For Hydrokinetic Turbine With Reliability Consideration, Goutham Pusapati

Masters Theses

"Hydrokinetic energy, a relatively new kind of renewable energy, can be generated from flowing water in rivers or oceans. Hydrokinetic turbines (HKTs) are a major system for hydrokinetic energy, and the reliability of the HKTs is critical for both their lifecycle cost and safety. The objective of this work is to apply advanced methodologies of reliability analysis and reliability-based design to the transmission shaft design for a horizontal-axis, non-submerged HKT. The deterministic shaft design is performed first by considering failure modes of strength and deflection using distortion energy, maximum shear and deflection theories. Then the reliability analysis of the shaft …

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A Modification Of Freeze-Core Technology For Collecting Granular Fluvial Sediment Samples, David Charles Smith Jan 2013

A Modification Of Freeze-Core Technology For Collecting Granular Fluvial Sediment Samples, David Charles Smith

Masters Theses

"The presence of coarse grained sediment can potentially reduce the effectiveness of conventional sampling methods in recovering fluvial sediments. A modification to freeze-core technology was used to collect fine grained sediments for the purpose of characterizing the extent of heavy metal contamination in fluvial deposits that contain significant amounts of coarse-grained material such as cobbles and boulders. This material greatly reduces the effectiveness of conventional sampling methods. This method uses 2.5-cm and 2.9-cm diameter by 30-cm long finned samplers that were mechanically- and hand-driven into the ground. The sediment is frozen to the outside of the sampler by injecting liquid …

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Wolf Creek Dam: A Case Study Of Foundation Remediation For Dams Built On Karst Foundations, Kyla Justene Erich Jan 2013

Wolf Creek Dam: A Case Study Of Foundation Remediation For Dams Built On Karst Foundations, Kyla Justene Erich

Masters Theses

"Wolf Creek Dam was completed in 1952 as a 5,736-foot long and 258-foot high combination embankment-concrete gravity dam. Its storage capacity of 6 million acre feet makes it the ninth largest reservoir in the nation. The dam was built on a heavily karstified limestone foundation and began exhibiting signs of excess foundation seepage in late 1967. This led to extensive corrective work in the 1970s beneath the earthen core of the embankment to reduce underseepage. In 2006 an independent assessment by the Dam Safety Action Classification (DSAC) Peer Review Panel recommended that Wolf Creek Dam exhibited "Urgent and Compelling" foundation …

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Water Management Capabilities Of Bio-Inspired Flow Field Configurations For Polymer Electrolyte Membrane Fuel Cells, Nicholas Warren Freer Jan 2013

Water Management Capabilities Of Bio-Inspired Flow Field Configurations For Polymer Electrolyte Membrane Fuel Cells, Nicholas Warren Freer

Masters Theses

"Fuel cells have received an increasing amount of attention over the past decade for their power production capabilities. Polymer electrolyte membrane (PEM) fuel cells in particular are researched because of their high power density, large range of operating conditions, green products, and ease of scalability. PEM fuel cells do have a number of issues that reduce their overall performance. These issues include variations in reactant distribution, materials issues for the bipolar plate, and flooding caused by poor water management. Variations in the reactant distribution causes lower overall power output due to regions of low reactant density. This means that optimizing …

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Green Roof Water Quality Impacts And Physicochemical Stability, Grace Ella Harper Jan 2013

Green Roof Water Quality Impacts And Physicochemical Stability, Grace Ella Harper

Masters Theses

"Green roofs can provide environmental benefits and conserve energy; this research evaluated green roof stormwater management, nutrient loading, and erosion prevention for two green roof media. During a pilot study, the runoff quantity and composition from green roof material was evaluated continuously under field conditions for two different media, both tested under planted and unplanted conditions. Water quantity results show over a 40% reduction in runoff from just the growing media and over 60% reduction in runoff with established plants in green roof media over the eight month study. Previous studies have reported a "first flush" of excess nutrients but …

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A New Approach To Nuclear Safeguard Enhancement Through Radionuclide Profiling, Aaron Dawon Peterson Jan 2013

A New Approach To Nuclear Safeguard Enhancement Through Radionuclide Profiling, Aaron Dawon Peterson

Masters Theses

"The United States has led the effort to promote peaceful use of nuclear power amongst states actively utilizing it as well as those looking to deploy the technology in the near future. With the attraction being demonstrated by various countries towards nuclear power comes the concern that a nation may have military aspirations for the use of nuclear energy. The International Atomic Energy Agency (IAEA) has established nuclear safeguard protocols and procedures to mitigate nuclear proliferation. The work herein proposed a strategy to further enhance existing safeguard protocols by considering safeguard in nuclear fuel design. The strategy involved the use …

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A Computational Study Of Driven Micro-Cavities In Supersonic Flat Plate Flow, Thomas Ryan Rehmeier Jan 2013

A Computational Study Of Driven Micro-Cavities In Supersonic Flat Plate Flow, Thomas Ryan Rehmeier

Masters Theses

"Driven micro-cavities embedded in the wall beneath turbulent supersonic boundary layers are analyzed using two-dimensional computational fluid dynamics. This concept is a passive flow control technique in which very small cavities formed by arrays of thin vertical walls are oriented transverse to the flow direction and underlie the boundary layer. The purpose is to reduce or eliminate skin friction drag. Various micro-cavity configurations were analyzed at locations (0.1 m and 1 m) downstream of the leading edges of flat plates, for free-stream Mach numbers of 1.2, 2.0, and 3.0. Results focus on net drag reduction achieved, cavity flow-field effects, perforation …

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Effect Of Mix Parameters On Longevity Of Bituminous Mixtures, Clayton Reichle Jan 2013

Effect Of Mix Parameters On Longevity Of Bituminous Mixtures, Clayton Reichle

Masters Theses

"This study was performed to evaluate the effects of varying aggregate sources, aggregate gradations on the stripping and rutting potential of bituminous based plant mixes specified by the Missouri Department of Transportation. The different aggregate combinations included two different aggregate sources (Potosi Dolomite and Jefferson City Dolomite) including two variations for the Jefferson City Dolomite mix to simulate a marginally in-specification mix and an out-of-specification but in-field tolerance mix. The "field" mix simulated the marginal mix where field tolerance of high dust and low binder content were maximized. All three mixes were evaluated for stripping susceptibility using the Tensile Strength …

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Liquid Phase Sintering Of 20bi(Zn₀.₅Ti₀.₅)O₃-80batio₃ Dielectrics With Bismuth-Zinc-Borate And Bismuth Borosilicate Glasses, David I. Shahin Jan 2013

Liquid Phase Sintering Of 20bi(Zn₀.₅Ti₀.₅)O₃-80batio₃ Dielectrics With Bismuth-Zinc-Borate And Bismuth Borosilicate Glasses, David I. Shahin

Masters Theses

"Dielectrics in the Bi(Zn₀.₅Ti₀.₅O₃-BaTiO₃ system (specifically 20BZT-80BT, in mol%) are promising candidates for high energy density capacitor applications due to broad temperature-dependent dielectric constant maxima and a relatively field-independent permittivity. Bulk samples require sintering temperatures of greater than 1180ºC to reach useful densities. Due to incompatibility of Bi with low-pO₂ processing, BZT-BT-based multilayer capacitors must utilize noble metal electrodes that resist oxidation during sintering. Sintering temperatures must be reduced to allow use of less expensive electrode materials (Cu, etc.). This work studies the reduced temperature sintering behavior and dielectric properties of BZT-BT sintered with 30 Bi₂O₃-30ZnO-40B₂O₃ and 50Bi₂O₃-25B₂O₃-25SiO₂ (mol%) liquid …

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Design And Analysis Of An Open-Ended Waveguide Probe For Material Characterization, Matthew Alan Kempin Jan 2013

Design And Analysis Of An Open-Ended Waveguide Probe For Material Characterization, Matthew Alan Kempin

Masters Theses

"Nondestructive evaluation of stratified (layered) composite structures at microwave and millimeter wave frequencies is of great interest in many applications where simultaneous determination of the complex dielectric properties and thicknesses of multiple layers is desired. Open-ended rectangular waveguide probes are effective tools for this purpose. The technique requires a full-wave electromagnetic model that accurately calculates the complex reflection coefficient as a function of frequency and material properties. Subsequently, this information is used in conjunction with the measured complex reflection coefficient to evaluate the sought for material properties. This thesis presents simulated and measured data to investigate the influence that measurement …

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New Sensorless, Efficient Optimized And Stabilized V/F Control For Pmsm Machines, Seyed Hesam Jafari Jan 2013

New Sensorless, Efficient Optimized And Stabilized V/F Control For Pmsm Machines, Seyed Hesam Jafari

Masters Theses

"With the rapid advances in power electronics and motor drive technologies in recent decades, permanent magnet synchronous machines (PMSM) have found extensive applications in a variety of industrial systems due to its many desirable features such as high power density, high efficiency, and high torque to current ratio, low noise, and robustness. In low dynamic applications like pumps, fans and compressors where the motor speed is nearly constant, usage of a simple control algorithm that can be implemented with least number of the costly external hardware can be highly desirable for industry. In recent published works, for low power PMSMs, …

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Communication Protocols For Integrated Fiber Optic Sensor Interrogator, Tameem Ahmed Khan Jan 2013

Communication Protocols For Integrated Fiber Optic Sensor Interrogator, Tameem Ahmed Khan

Masters Theses

"Fiber optic sensors have gained rapid recognition in sensing environmental factors such as strain, stress, acoustics, pressure, temperature among emerging other sensing applications. Major advantages of fiber based systems are small size, light weight, multiplex-ability of sensors on a single fiber, and immunity to Radio Frequency (RF) interference. However, single most major disadvantage of such technology is that traditionally the interrogation systems are typically bulky and heavy lab only equipment. Embed-ability of sensors into different structures and environments requires that the whole systems (sensors + interrogator) be small, modular and portable. This thesis presents such a custom Fiber optic Sensor …

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Harmonic Compensation In A Grid Using Doubly Fed Induction Generators, Omkar Amol Ghatpande Jan 2013

Harmonic Compensation In A Grid Using Doubly Fed Induction Generators, Omkar Amol Ghatpande

Masters Theses

"Ideally, electric utilities are expected to deliver a sinusoidal voltage with a constant rated frequency, while customers are expected to draw a sinusoidal current with unity power factor. The recent widespread use of harmonic producing equipment in industrial applications, especially non-linear loads, has increased the distortion of electric currents and voltages in transmission and distribution systems. This thesis proposes a method of using multiple reference frame theory for measuring and mitigating harmonic currents of nonlinear loads using a doubly fed induction generator. The most significant low-order harmonics to be compensated are calculated using a multiple reference frame harmonic observer. This …

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Insufficient Ct Data Reconstruction Based On Directional Total Variation (Dtv) Regularized Maximum Likelihood Expectation Maximization (Mlem) Method, Fahima Fahmida Islam Jan 2013

Insufficient Ct Data Reconstruction Based On Directional Total Variation (Dtv) Regularized Maximum Likelihood Expectation Maximization (Mlem) Method, Fahima Fahmida Islam

Masters Theses

"Sparse tomography is an efficient technique which saves time as well as minimizes cost. However, due to few angular data it implies the image reconstruction problem as ill-posed. In the ill posed problem, even with exact data constraints, the inversion cannot be uniquely performed. Therefore, selection of suitable method to optimize the reconstruction problems plays an important role in sparse data CT. Use of regularization function is a well-known method to control the artifacts in limited angle data acquisition. In this work, we propose directional total variation regularized ordered subset (OS) type image reconstruction method for neutron limited data CT. …

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Direct Shear Transfer Of Lightweight Aggregate Concretes With Non-Monolithic Interface Conditions, Dane Michael Shaw Jan 2013

Direct Shear Transfer Of Lightweight Aggregate Concretes With Non-Monolithic Interface Conditions, Dane Michael Shaw

Masters Theses

"This thesis describes the results of a study initiated to examine the influence of concrete unit weight on the direct shear transfer across an interface of concretes cast at different times. This type of interface is common with structural precast concrete connections, such as corbels, for which shear friction design provisions are commonly used. Increasing use of lightweight aggregate concretes prompted this investigation to determine the appropriateness of current shear friction design provisions with respect to all-lightweight and sand-lightweight concrete. The experimental investigation included thirty-six push-off test specimens, each of which was constructed with a cold-joint at the interface shear …

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Tensile Failure During Structural Development Of Single-Layer Buckle Folds, Xiaolong Liu Jan 2013

Tensile Failure During Structural Development Of Single-Layer Buckle Folds, Xiaolong Liu

Masters Theses

"Folds and fold trains of sedimentary strata are among the most common structural traps systems for hydrocarbon reservoirs. The existence of tensile fractures associated to buckle folding is associated to the distribution of extensional strain in the outer arc of the fold hinges. This study investigates the conditions under which tensile stresses develop due to buckling in a realistic in situ stress scenario. By applying a 2D finite element modeling approach, the influence of realistic mechanical stratigraphy (including strain rate, overburden depth, competence contrasts, viscosity, and permeability) on the development of single-layer buckle folds with Newtonian viscous rheology is studied. …

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Constructing Conducted Emission Models For Integrated Circuits, Shuai Jin Jan 2013

Constructing Conducted Emission Models For Integrated Circuits, Shuai Jin

Masters Theses

"Conducted emissions, noise conducted out of integrated circuit pins, play an important role in determining the system level EMC performance. Characterizing conducted emissions from ICs is investigated and the corresponding noise models are developed in this thesis. Both simulation IBIS and measurement based methods for noise-model construction are studied. The constructed noise source model for a test IC is applied in system-level simulations and the calculated far field radiation is validated with measurements. The agreement in the simulated and measured results demonstrates the effectiveness of the constructed model for characterizing the conducted emissions from an IC I/O pin"--Abstract, page iii.

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Examining The Efficiency Of Multimodal Transportation Systems: A Systems Dynamics Approach, Lizzette Pérez-Lespier Jan 2013

Examining The Efficiency Of Multimodal Transportation Systems: A Systems Dynamics Approach, Lizzette Pérez-Lespier

Masters Theses

"With international trade becoming a big part of the world's economic activity, the demand for good freight transportation systems has grown substantially. The appropriate use of transportation is an integral part of the supply chain's effectiveness. Therefore, the continuous economic globalization, the growing demand for speed-to-market product delivery, and the need to manage global supply chains more effectively, has led to the sustained increase in demand towards multimodal transportation systems (MTS). MTS play an essential role in corporations competing in global markets in the 21st century. In transportation, the effectiveness and efficiency of the whole system depends upon the interconnectivity …

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Modeling Of Fracture And Durability Of Paste-Bonded Composite Joints Subjected To Hygro-Thermal-Mechanical Loading, David Lee Harris Jan 2013

Modeling Of Fracture And Durability Of Paste-Bonded Composite Joints Subjected To Hygro-Thermal-Mechanical Loading, David Lee Harris

Masters Theses

"The objective of the research is to characterize the behavior of composite/composite joints with paste adhesive using both experimental testing and analytical modeling. In comparison with the conventional tape adhesive, joining composites using paste adhesive provides several advantages. The carbon fiber laminate material systems employed in this study included IM7 carbon fibers and 977-3 epoxy matrix assembled in prepreg tape, and AS4 carbon fibers and 977-3 epoxy matrix as a five-harness satin weave. The adhesive employed was EA 9394 epoxy. All laminates and test specimens were fabricated and inspected by Boeing using their standard propriety procedures. Three types of test …

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Trough-Silicon-Via Inductor: Is It Real Or Just A Fantasy?, Rongbo Yang Jan 2013

Trough-Silicon-Via Inductor: Is It Real Or Just A Fantasy?, Rongbo Yang

Masters Theses

"Through-silicon-vias (TSVs) can potentially be used to implement inductors in three-dimensional (3D) integrated system for minimal footprint and large inductance. However, different from conventional 2D spiral inductor, TSV inductors are buried in lossy substrate, thus suffering from low quality factors. This thesis presents how various process and design parameters affect their performance. A few interesting phenomena that are unique to TSV inductors are observed. We then proposed a novel shield mechanism utilizing the micro-channel, a technique conventionally used for heat removal, to reduce the substrate loss. The technique increases the quality factor and inductance of the TSV inductor by up …

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