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2013

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Articles 5791 - 5820 of 7289

Full-Text Articles in Engineering

The Characterization Of The Effects Of Stress Concentrations On The Mechanical Behavior Of A Micronic Woven Wire Mesh, Steven Kraft Jan 2013

The Characterization Of The Effects Of Stress Concentrations On The Mechanical Behavior Of A Micronic Woven Wire Mesh, Steven Kraft

Electronic Theses and Dissertations

Woven structures are steadily emerging as excellent reinforcing components in dualphase composite materials subjected to multiaxial loads, thermal shock, and aggressive reactants in the environment. Metallic woven wire mesh materials display good ductility and relatively high specific strength and specific resilience. While use of this class of materials is rapidly expanding, significant gaps in mechanical behavior classification remain. This thesis works to address the mechanics of material knowledge gap that exists for characterizing the behavior of a metallic woven structure, composed of stainless steel wires on the order of 25 microns in diameter, and subjected to various loading conditions and …

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On Radar Deception, As Motivation For Control Of Constrained Systems, Hadi Hajieghrary Jan 2013

On Radar Deception, As Motivation For Control Of Constrained Systems, Hadi Hajieghrary

Electronic Theses and Dissertations

This thesis studies the control algorithms used by a team of ECAVs (Electronic Combat Air Vehicle) to deceive a network of radars to detect a phantom track. Each ECAV has the electronic capability of intercepting the radar waves, and introducing an appropriate time delay before transmitting it back, and deceiving the radar into seeing a spurious target beyond its actual position. On the other hand, to avoid the errors and increase the reliability, have a complete coverage in various atmosphere conditions, and confronting the effort of the belligerent intruders to delude the sentinel and enter the area usually a network …

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A Hybrid Constitutive Model For Creep, Fatigue, And Creep-Fatigue Damage, Calvin Stewart Jan 2013

A Hybrid Constitutive Model For Creep, Fatigue, And Creep-Fatigue Damage, Calvin Stewart

Electronic Theses and Dissertations

In the combustion zone of industrial- and aero- gas turbines, thermomechanical fatigue (TMF) is the dominant damage mechanism. Thermomechanical fatigue is a coupling of independent creep, fatigue, and oxidation damage mechanisms that interact and accelerate microstructural degradation. A mixture of intergranular cracking due to creep, transgranular cracking due to fatigue, and surface embrittlement due to oxidation is often observed in gas turbine components removed from service. The current maintenance scheme for gas turbines is to remove components from service when any criteria (elongation, stress-rupture, crack length, etc.) exceed the designed maximum allowable. Experimental, theoretical, and numerical analyses are performed to …

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Biomechanical Factors Influencing Treatment Of Developmental Dysplasia Of The Hip (Ddh) With The Pavlik Harness, Orlando Ardila Jan 2013

Biomechanical Factors Influencing Treatment Of Developmental Dysplasia Of The Hip (Ddh) With The Pavlik Harness, Orlando Ardila

Electronic Theses and Dissertations

Biomechanical factors influencing the reduction of dislocated hips with the Pavlik harness in patients of Developmental Dysplasia of the Hip (DDH) were studied using a simplified three-dimensional computer model simulating hip reduction dynamics in (1) subluxated, and (2) fully dislocated hip joints. The CT-scans of a 6 month-old female infant were used to measure the geometrical features of the hip joint including acetabular and femoral head diameter, acetabular depth, and geometry of the acetabular labrum, using the medical segmentation software Mimics. The lower extremity was modeled by three segments: thigh, leg, and foot. The mass and the location of the …

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The Study Of Photo-Reduction Of Cerium Oxide Nanoparticles In Presence Of Dextran: An Attempt In Understanding The Functionality Of The System, Swetha Barkam Jan 2013

The Study Of Photo-Reduction Of Cerium Oxide Nanoparticles In Presence Of Dextran: An Attempt In Understanding The Functionality Of The System, Swetha Barkam

Electronic Theses and Dissertations

Malignant melanoma cancer is the sixth common cancer diagnosed in the United States. Surgery, chemotherapy and radiation are some of the successful techniques in killing tumor cells. However, in these techniques, it is not easy to distinguish tumor cells from the healthy once which inadvertently get exposed to chemical agent/radiation. Therefore it is required to develop an anticancer agent which selectively kills the cancer cells, while still protecting the normal tissues. In our preliminary work, we have shown that Dextran (1000Da) coated Cerium oxide nanoparticles (Dex-CNPs) selectively kills the cancer cells (50% killing at a concentration of 150μM) without inducing …

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The Effects Of Assumption On Subspace Identification Using Simulation And Experiment Data, Yoonhwak Kim Jan 2013

The Effects Of Assumption On Subspace Identification Using Simulation And Experiment Data, Yoonhwak Kim

Electronic Theses and Dissertations

In the modern dynamic engineering field, experimental dynamics is an important area of study. This area includes structural dynamics, structural control, and structural health monitoring. In experimental dynamics, methods to obtain measured data have seen a great influx of research efforts to develop an accurate and reliable experimental analysis result. A technical challenge is the procurement of informative data that exhibits the desired system information. In many cases, the number of sensors is limited by cost and difficulty of data archive. Furthermore, some informative data has technical difficulty when measuring input force and, even if obtaining the desired data were …

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Analysis And Design Optimization Of Multiphase Converter, Kejiu Zhang Jan 2013

Analysis And Design Optimization Of Multiphase Converter, Kejiu Zhang

Electronic Theses and Dissertations

Future microprocessors pose many challenges to the power conversion techniques. Multiphase synchronous buck converters have been widely used in high current low voltage microprocessor application. Design optimization needs to be carefully carried out with pushing the envelope specification and ever increasing concentration towards power saving features. In this work, attention has been focused on dynamic aspects of multiphase synchronous buck design. The power related issues and optimizations have been comprehensively investigated in this paper. In the first chapter, multiphase DC-DC conversion is presented with background application. Adaptive voltage positioning and various nonlinear control schemes are evaluated. Design optimization are presented …

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Rf Power Amplifier And Oscillator Design For Reliability And Variability, Shuyu Chen Jan 2013

Rf Power Amplifier And Oscillator Design For Reliability And Variability, Shuyu Chen

Electronic Theses and Dissertations

CMOS RF circuit design has been an ever-lasting research field. It gained so much attention since RF circuits have high mobility and wide band efficiency, while CMOS technology has the advantage of low cost and better capability of integration. At the same time, IC circuits never stopped scaling down for the recent many decades. Reliability issues with RF circuits have become more and more severe with device scaling down: reliability effects such as gate oxide break down, hot carrier injection, negative bias temperature instability, have been amplified as the device size shrinks. Process variability issues also become more predominant as …

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Chemophysical Characteristics And Application Of Biosorption Activated Media (Bam) For Copper And Nutrient Removal In Stormwater Management, Jamie Jones Jan 2013

Chemophysical Characteristics And Application Of Biosorption Activated Media (Bam) For Copper And Nutrient Removal In Stormwater Management, Jamie Jones

Electronic Theses and Dissertations

For high groundwater table areas, stormwater wet detention ponds are utilized as the preferred stormwater management throughout the state of Florida. Previous research has found that accumulations of nutrients, algae, heavy metals, pesticides, chlorophyll a, fecal coliform bacteria and low concentrations of dissolved oxygen (DO) are common characteristics of stormwater wet detention ponds. Although these pollutant levels are not regulated within the ponds, states are required to compute the pollutant load reductions through total maximum daily load (TMDL) programs to meet the water quality requirements addressed by the Clean Water Act (CWA). In this study, field sampling data of stormwater …

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Manufacturing Of Single Solid Oxide Fuel Cells, Jonathan Torres-Caceres Jan 2013

Manufacturing Of Single Solid Oxide Fuel Cells, Jonathan Torres-Caceres

Electronic Theses and Dissertations

Solid oxide fuel cells (SOFCs) are devices that convert chemical energy into electrical energy and have the potential to become a reliable renewable energy source that can be used on a large scale. SOFCs have 3 main components; the electrolyte, the anode, and the cathode. Typically, SOFCs work by reducing oxygen at the cathode into O2- ions which are then transported via the electrolyte to the anode to combine with a fuel such as hydrogen to produce electricity. Research into better materials and manufacturing methods is necessary to reduce costs and improve efficiency to make the technology commercially viable. The …

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Automated Hybrid Singularity Superposition And Anchored Grid Pattern Bem Algorithm For The Solution Of The Inverse Geometric Problem, Marcus Ni Jan 2013

Automated Hybrid Singularity Superposition And Anchored Grid Pattern Bem Algorithm For The Solution Of The Inverse Geometric Problem, Marcus Ni

Electronic Theses and Dissertations

A method for solving the inverse geometrical problem is presented by reconstructing the unknown subsurface cavity geometry using boundary element methods, a genetic algorithm, and Nelder-Mead non-linear simplex optimization. The heat conduction problem is solved utilizing the boundary element method, which calculates the difference between the measured temperature at the exposed surface and the computed temperature under the current update of the unknown subsurface flaws and cavities. In a first step, clusters of singularities are utilized to solve the inverse problem and to identify the location of the centroid(s) of the subsurface cavity(ies)/flaw(s). In a second step, the reconstruction of …

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Multi-Physics Modeling Of Geomechanical Systems With Coupled Hydromechanical Behaviors, Ahmad Mohamed Jan 2013

Multi-Physics Modeling Of Geomechanical Systems With Coupled Hydromechanical Behaviors, Ahmad Mohamed

Electronic Theses and Dissertations

Geotechnical structures under realistic field conditions are usually influenced with complex interactions of coupled hydromechanical behavior of porous materials. In many geotechnical applications, however, these important coupled interactions are ignored in their constitutive models. Under coupled hydromechanical behavior, stress in porous materials causes volumetric change in strain, which causes fluid diffusion; consequently, pore pressure dissipates through the pores that results in the consolidation of porous material. The objective of this research wasto demonstrate the advantages of using hydromechanical models to estimate deformation and pore water pressure of porous materials by comparing with mechanical-only models. Firstly, extensive literature survey was conducted …

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Investigation On Electrical Properties Of Rf Sputtered Deposited Bcn Thin Films, Adithya Prakash Jan 2013

Investigation On Electrical Properties Of Rf Sputtered Deposited Bcn Thin Films, Adithya Prakash

Electronic Theses and Dissertations

The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. In order to reduce the time delay, it is necessary to introduce a wiring metal with low resistivity and …

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A Novel Nonlinear Mason Model And Nonlinear Distortion Characterization For Surface Acoustic Wave Duplexers, Li Chen Jan 2013

A Novel Nonlinear Mason Model And Nonlinear Distortion Characterization For Surface Acoustic Wave Duplexers, Li Chen

Electronic Theses and Dissertations

Surface acoustic wave (SAW) technology has been in use for well over one century. In the last few decades, due to its low cost and high performance, this technology has been widely adopted in modern wireless communication systems, to build filtering devices at radio frequency (RF). SAW filters and duplexers can be virtually found inside every mobile handset. SAW devices are traditionally recognized as passive devices with high linear signal processing behavior. However, recent deployments of third generation (3G) and fourth generation (4G) mobile networks require the handsets to handle an increasing number of frequency bands with more complex modulation …

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Tailoring The Properties Of Polyelectrolyte Coated Cerium Oxide Nanoparticles As A Function Of Molecular Weight, Shashank Saraf Jan 2013

Tailoring The Properties Of Polyelectrolyte Coated Cerium Oxide Nanoparticles As A Function Of Molecular Weight, Shashank Saraf

Electronic Theses and Dissertations

The application of Cerium oxide nanoparticles (CNPs) for therapeutic purposes requires a stable dispersion of nanoparticles in biological environment. The objective of this study is to tailor the properties of polyelectrolyte coated CNPs as a function of molecular weight to achieve a stable and catalytic active dispersion. This was achieved by coating CNPs with polyacrylic acid (PAA) which increased the dispersion stability of CNPs and enhanced the catalytic ability. The stability of PAA coating was analysed using the change in the Gibbs free energy computed by Langmuir adsorption model. The adsorption isotherms were determined using soft particle electrokinetics which overcomes …

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First Principle Studies Of Cu-Carbon Nanotube Hybrid Structures With Emphasis On The Electronic Structures And The Transport Properties, Chengyu Yang Jan 2013

First Principle Studies Of Cu-Carbon Nanotube Hybrid Structures With Emphasis On The Electronic Structures And The Transport Properties, Chengyu Yang

Electronic Theses and Dissertations

Carbon nanotubes have been regarded as ideal building blocks for nanoelectronics and multifunctional nanocomposites due to their exceptional strength, stiffness, flexibility, as well as their excellent electrical properties. However, carbon nanotube itself has limitations to fulfill the practical application needs: 1) an individual carbon nanotube has a low density of states at the Fermi level, and thus its conductivity is only comparable to moderate metals but lower than that of copper. 2) Metallic and semiconducting nanotubes are inherently mixed together from the synthesis, and the selection/separation is very difficult with very low efficiency. 3) Carbon nanotubes alone cannot be used …

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Transient Multi-Scale Computational Fluid Dynamics (Cfd) Model For Thrombus Tracking In An Assit Device Vascular Bed, Ruben Osorio Jan 2013

Transient Multi-Scale Computational Fluid Dynamics (Cfd) Model For Thrombus Tracking In An Assit Device Vascular Bed, Ruben Osorio

Electronic Theses and Dissertations

Heart failure occurs when the heart is not capable to pump blood at a sufficient rate to meet the demands of the body. Depending on the health of the heart, doctors may recommend a heart transplant, but finding a suitable donor is often a long duration process and the patient might be at an advance condition or the patient is not adequate for a heart transplant. In such cases Ventricular assist devices (VAD) are implemented. The purpose of a VAD is to aid the heart to pump the correct amount of blood, by doing so it relives the load that …

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Polymer Optical Fibers For Luminescent Solar Concentration, Esmaeil Banaei Jan 2013

Polymer Optical Fibers For Luminescent Solar Concentration, Esmaeil Banaei

Electronic Theses and Dissertations

Luminescent solar concentrators (LSC’s) are promising candidates for reducing the cost of solar power generation. Conventional LSC’s are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends …

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Transient And Distributed Algorithms To Improve Islanding Detection Capability Of Inverter Based Distributed Generation, Mohamed Al Hosani Jan 2013

Transient And Distributed Algorithms To Improve Islanding Detection Capability Of Inverter Based Distributed Generation, Mohamed Al Hosani

Electronic Theses and Dissertations

Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to …

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Active Learning With Unreliable Annotations, Liyue Zhao Jan 2013

Active Learning With Unreliable Annotations, Liyue Zhao

Electronic Theses and Dissertations

With the proliferation of social media, gathering data has became cheaper and easier than before. However, this data can not be used for supervised machine learning without labels. Asking experts to annotate sufficient data for training is both expensive and time-consuming. Current techniques provide two solutions to reducing the cost and providing sufficient labels: crowdsourcing and active learning. Crowdsourcing, which outsources tasks to a distributed group of people, can be used to provide a large quantity of labels but controlling the quality of labels is hard. Active learning, which requires experts to annotate a subset of the most informative or …

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Total Ownership Cost Modeling Of Technology Adoption Using System Dynamics: Implications For Erp Systems, Behzad Esmaeilian Jan 2013

Total Ownership Cost Modeling Of Technology Adoption Using System Dynamics: Implications For Erp Systems, Behzad Esmaeilian

Electronic Theses and Dissertations

Investment in new technologies is considered by firms as a solution to improve their productivity, product and service quality and their competitive advantages in the global market. Unfortunately, not all technology adoption projects have met their intended objectives. The complexity of technology adoption along with little consideration of the long term cost of the technology, are among the factors that challenge companies while adopting a new technology. Companies often make new technology adoption decision without enough attention to the total cost of the technology over its lifecycle. Sometimes poor decision making while adopting a new technology can result in substantial …

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Integrated Data Fusion And Mining (Idfm) Technique For Monitoring Water Quality In Large And Small Lakes, Benjamin Vannah Jan 2013

Integrated Data Fusion And Mining (Idfm) Technique For Monitoring Water Quality In Large And Small Lakes, Benjamin Vannah

Electronic Theses and Dissertations

Monitoring water quality on a near-real-time basis to address water resources management and public health concerns in coupled natural systems and the built environment is by no means an easy task. Furthermore, this emerging societal challenge will continue to grow, due to the ever-increasing anthropogenic impacts upon surface waters. For example, urban growth and agricultural operations have led to an influx of nutrients into surface waters stimulating harmful algal bloom formation, and stormwater runoff from urban areas contributes to the accumulation of total organic carbon (TOC) in surface waters. TOC in surface waters is a known precursor of disinfection byproducts …

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Interdiffusion Reaction Between Uranium-Zirconium And Iron, Young Joo Park Jan 2013

Interdiffusion Reaction Between Uranium-Zirconium And Iron, Young Joo Park

Electronic Theses and Dissertations

U-Zr metallic fuels cladded in Fe-alloys are being considered for application in an advanced Sodium-Cooled Fast Reactor (SFR) that can recycle the U-Zr fuels and minimize the long-lived actinide waste. To understand the complex fuel-cladding chemical interaction of the U-Zr metallic fuel with Fe-alloys, a systematic multicomponent diffusion study was carried out using solid-to-solid diffusion couples. The U-10 wt.% Zr vs. pure Fe diffusion couples were assembled and annealed at temperatures, 630, 650 and 680°C for 96 hours. Development of microstructure, phase constituents, and compositions developed during the thermal anneals were examined by scanning electron microscopy, transmission electron microscopy and …

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Routing, Localization And Positioning Protocols For Wireless Sensor And Actor Networks, Mustafa Akbas Jan 2013

Routing, Localization And Positioning Protocols For Wireless Sensor And Actor Networks, Mustafa Akbas

Electronic Theses and Dissertations

Wireless sensor and actor networks (WSANs) are distributed systems of sensor nodes and actors that are interconnected over the wireless medium. Sensor nodes collect information about the physical world and transmit the data to actors by using one-hop or multi-hop communications. Actors collect information from the sensor nodes, process the information, take decisions and react to the events. This dissertation presents contributions to the methods of routing, localization and positioning in WSANs for practical applications. We first propose a routing protocol with service differentiation for WSANs with stationary nodes. In this setting, we also adapt a sports ranking algorithm to …

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Thermoacoustic Riemann Solver Finite Volume Method With Application To Turbulent Premixed Gas Turbine Combustion Instability, Perry Johnson Jan 2013

Thermoacoustic Riemann Solver Finite Volume Method With Application To Turbulent Premixed Gas Turbine Combustion Instability, Perry Johnson

Electronic Theses and Dissertations

This thesis describes the development, verification, and validation of a three dimensional time domain thermoacoustic solver. The purpose of the solver is to predict the frequencies, modeshapes, linear growth rates, and limit cycle amplitudes for combustion instability modes in gas turbine combustion chambers. The linearized Euler equations with nonlinear heat release source terms are solved using the finite volume method. The treatment of mean density gradients was found to be vital to the success of frequency and modeshape predictions due to the sharp density gradients that occur across deflagration waves. In order to treat mean density gradients with physical fidelity, …

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High Volume Fraction Mg-Based Nanocomposites: Processing, Microstructure And Mechanical Behavior, Jinling Liu Jan 2013

High Volume Fraction Mg-Based Nanocomposites: Processing, Microstructure And Mechanical Behavior, Jinling Liu

Electronic Theses and Dissertations

Mg-based metal matrix nanocomposites (MMNCs) with mechanical properties, superior to those of coarse-grained composites, are promising structural materials for applications in the automotive and aerospace industries. The research in this area was primarily focused earlier on either micro-scaled reinforcements or nano-scaled reinforcements with very low volume fractions. MMNCs with high volume fractions have not been explored yet. In this research, we study the processing, microstructures and properties of MMNCs containing ceramic nanoparticles up to 30 vol.%. We first investigated the mechanical alloying of Al2O3 nanoparticles and pure Mg under high-energy ball milling conditions. The phase evolution and their distribution were …

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Study Of Transport Phenomena In Carbon-Based Materials, Walid Aboelsoud Jan 2013

Study Of Transport Phenomena In Carbon-Based Materials, Walid Aboelsoud

Electronic Theses and Dissertations

In air-cooled heat exchangers, air-side thermal resistance is usually the largest compared to conduction and liquid-side thermal resistances. Thus, reducing the air-side thermal resistance with fin-like structures can greatly improve overall cooling performance. The performance of these structures is usually characterized by the rate of heat which can be transferred and the pumping power required. One promising solution is to use a high-thermal-conductivity material with a large surface per unit volume such as carbon foam. This study presents a method of utilizing V-shape corrugated carbon foam. The air-side heat transfer coefficient and the pressure drop across the foam have been …

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Success In Technology Organizations, Joseph Bass Jan 2013

Success In Technology Organizations, Joseph Bass

Electronic Theses and Dissertations

In today’s economic environment, it is advantageous for technology organizations to be cognizant of prevalent influences on success and failure and to incorporate this knowledge into their business and innovation strategies. Technology organizations were defined within this research as those in the business of created competence which is expressed in terms of entities consisting of devices, procedures, and acquired human skills (Clarke, 2005). Although, no organization contains the ideal mix of culture and ideological emphases, some have amassed impressive track records of great success. A literature review was used to identify factors relevant within similar contexts such as influences on …

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Distributed Extremum Seeking And Cooperative Control For Mobile Cooperative Communication Systems, Said Alabri Jan 2013

Distributed Extremum Seeking And Cooperative Control For Mobile Cooperative Communication Systems, Said Alabri

Electronic Theses and Dissertations

In this thesis, a distributed extremum seeking and cooperative control algorithm is designed for mobile agents to disperse themselves optimally in maintaining communication quality and maximizing their coverage. The networked mobile agents locally form a virtual multiple-input multipleoutput (MIMO) communication system, and they cooperatively communicate among them by using the decode and forward cooperative communication technique. The outage probability is used as the measure of communication quality, and it can be estimated real-time. A general performance index balancing outage probability and spatial dispersion is chosen for the overall system. The extremum seeking control approach is used to estimate and optimize …

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Exploring The Innovation Environment Within The Systems Engineering Context Of A Defense Organization: A Preliminary Framework, Khaled Odeh Jan 2013

Exploring The Innovation Environment Within The Systems Engineering Context Of A Defense Organization: A Preliminary Framework, Khaled Odeh

Electronic Theses and Dissertations

Innovation may involve the introduction of ideas for designing or producing new products, or introducing improvements to products, processes, services or any other aspect of an organization to the market place. A major element for measuring organizational strength is its perception of innovation and the ability of the organization to build on and sustain such strength. While there is no shortage of research and study materials on innovation, there is, however, a shortage of thorough and realistic analysis of the intersection of innovation management, and measurement of innovation within the systems engineering context of defense organizations. In addition, while most …

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