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2008

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Articles 3091 - 3120 of 4190

Full-Text Articles in Engineering

A Hybrid System Dynamics-Discrete Event Simulationapproach To Simulating The Manufacturing Enterprise, Magdy Helal Jan 2008

A Hybrid System Dynamics-Discrete Event Simulationapproach To Simulating The Manufacturing Enterprise, Magdy Helal

Electronic Theses and Dissertations

With the advances in the information and computing technologies, the ways the manufacturing enterprise systems are being managed are changing. More integration and adoption of the system perspective push further towards a more flattened enterprise. This, in addition to the varying levels of aggregation and details and the presence of the continuous and discrete types of behavior, created serious challenges for the use of the existing simulation tools for simulating the modern manufacturing enterprise system. The commonly used discrete event simulation (DES) techniques face difficulties in modeling such integrated systems due to increased model complexity, the lack of data at …

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Project Review Maturity And Project Performance: An Empirical Case Study, Catherine Vergopia Jan 2008

Project Review Maturity And Project Performance: An Empirical Case Study, Catherine Vergopia

Electronic Theses and Dissertations

Many organizations use project management maturity models to improve their project performance. These systematic and sequential frameworks are designed to help organizations quantify their project management maturity and improve their project management processes. However, these models rarely put enough emphasis on project reviews as tools to improve project performance, because, too often, project reviews are considered as non-productive administrative processes. The lack of emphasis on project reviews in project management maturity models is also illustrated by the limited amount of research published on the relationship between project reviews and project performance. Based on the concept of project management maturity models, …

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A Kinetics Study Of Selected Filtration Media For Nutrient Removal At Various Temperatures, Elizabeth Henderson Jan 2008

A Kinetics Study Of Selected Filtration Media For Nutrient Removal At Various Temperatures, Elizabeth Henderson

Electronic Theses and Dissertations

In recent years the nutrient levels of the Upper Floridan aquifer have been increasing (USGS, 2008). An example of this is found in Ocala, Florida where Silver Springs nitrate concentrations have risen from 0.5 mg/L in the 1960 s to approximately 1.0 mg/L in 2003 (Phelps, 2004). Because stormwater is a contributor to surficial and groundwater aquifer recharge, there is an increasing need for methods that decrease nitrogen and phosphorus levels. A laboratory column study was conducted to simulate a retention pond with saturated soil conditions. The objectives of the column studies reported in this thesis were to investigate the …

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Dmarc: A Framework For The Integration Of Dmaic And Dmadv, Abhishek Vootukuru Jan 2008

Dmarc: A Framework For The Integration Of Dmaic And Dmadv, Abhishek Vootukuru

Electronic Theses and Dissertations

The Lean Six Sigma methodology is being applied extensively to tackle many quality related issues in many processes of today s industries. Various companies have benefited greatly from the adoption of Six Sigma and Lean engineering concepts since their introduction, and continue to do so. The DMAIC method that is traditionally adopted in the implementation of the Lean Six Sigma methodology has proven to yield cost saving results in most cases. Yet, industries have found that just improvement of existent process and products to reduce defects, does not quench the customer s growing thirst for greater quality. In order to …

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Methane And Dimethyl Ether Oxidation At Elevated Temperatures And Pressure, Christopher Zinner Jan 2008

Methane And Dimethyl Ether Oxidation At Elevated Temperatures And Pressure, Christopher Zinner

Electronic Theses and Dissertations

Autoignition and oxidation of two Methane (CH4) and Dimethyl Ether (CH3OCH3 or DME) mixtures in air were studied in shock tubes over a wide range of equivalence ratios at elevated temperatures and pressures. These experiments were conducted in the reflected shock region with pressures ranging from 0.8 to 35.7 atmospheres, temperatures ranging from 913 to 1650 K, and equivalence ratios of 2.0, 1.0, 0.5, and 0.3. Ignition delay times were obtained from shock-tube endwall pressure traces for fuel mixtures of CH4/CH3OCH3 in ratios of 80/20 percent volume and 60/40 percent volume, respectively. Close examination of the data revealed that energy …

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Probing And Tuning The Size, Morphology, Chemistry And Structure Of Nanoscale Cerium Oxide, Satyanarayana Kuchibhatla Jan 2008

Probing And Tuning The Size, Morphology, Chemistry And Structure Of Nanoscale Cerium Oxide, Satyanarayana Kuchibhatla

Electronic Theses and Dissertations

Cerium oxide (ceria)-based materials in the nanoscale regime are of significant fundamental and technological interest. Nanoceria in pure and doped forms has current and potential use in solid oxide fuel cells, catalysis, UV- screening, chemical mechanical planarization, oxygen sensors, and bio-medical applications. The characteristic feature of Ce to switch between the +3 and + 4 oxidation states renders oxygen buffering capability to ceria. The ease of this transformation was expected to be enhanced in the nanoceria. In most the practical scenarios, it is necessary to have a stable suspension of ceria nanoparticles (CNPs) over longer periods of time. However, the …

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N Multilayer Thin Film Reactions To Form L10 Fept And Exchange Spring Magnets, Bo Yao Jan 2008

N Multilayer Thin Film Reactions To Form L10 Fept And Exchange Spring Magnets, Bo Yao

Electronic Theses and Dissertations

FePt films with the L10 phase have potential applications for magnetic recording and permanent magnets due to its high magnetocrystalline anisotropy energy density. Heat treatment of n multilayer films is one approach to form the L10 FePt phase through a solid state reaction. This thesis has studied the diffusion and reaction of n multilayer films to form the L10 FePt phase and has used this understanding to construct exchange spring magnets. The process-structure-property relations of n multilayer films were systematically examined. The transmission electron microscopy (TEM) study of the annealed multilayers indicates that the Pt layer grows at the expense …

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Development And Application Study Of Nanoscale Thin Film Materials And Polymer Nanocomposites, Hui Chen Jan 2008

Development And Application Study Of Nanoscale Thin Film Materials And Polymer Nanocomposites, Hui Chen

Electronic Theses and Dissertations

This dissertation demonstrated that the manipulation of substances at the molecular or nanometer level can lead to the discovery and development of new materials with interesting properties and important applications. Chapter 1 describes the development of a nanoscale molecular thin film material for corrosion protection. By using a self-assembled monolayer film with a thickness of only about 1 nanometer as a linkage, a covalent bonding was achieved between a polyurethane top coating and an aluminum alloy substrate. This covalent bonding between polymer top coating and the aluminum alloy substrate significantly improved the corrosion resistance of the substrate. Chapter 2 and …

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Effect Of Composition, Morphology And Semiconducting Properties On The Efficiency Of Cuin1-Xgaxse2-Ysy Thin-Film Solar Cells Pre, Sachin Kulkarni Jan 2008

Effect Of Composition, Morphology And Semiconducting Properties On The Efficiency Of Cuin1-Xgaxse2-Ysy Thin-Film Solar Cells Pre, Sachin Kulkarni

Electronic Theses and Dissertations

A rapid thermal processing (RTP) reactor for the preparation of graded CuIn1-xGaxSe2-ySy (CIGSeS) thin-film solar cells has been designed, assembled and is being used at the Photovoltaic Materials Laboratory of the Florida Solar Energy Center. CIGSeS films having the optimum composition, morphology, and semiconducting properties were prepared using RTP. Initially films having various Cu/(In+Ga) ratios were prepared. In the next step selenium incorporation in these films was optimized, followed by sulfur incorporation in the surface to increase the bandgap at the surface. The compositional gradient of sulfur was fine-tuned so as to increase the conversion efficiency. Materials properties of these …

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Application Of Polyelectrolyte Multilayers For Photolithographic Patterning Of Diverse Mammalian Cell Types In Serum Free Medium, Vipra Dhir Jan 2008

Application Of Polyelectrolyte Multilayers For Photolithographic Patterning Of Diverse Mammalian Cell Types In Serum Free Medium, Vipra Dhir

Electronic Theses and Dissertations

Integration of living cells with novel microdevices requires the development of innovative technologies for manipulating cells. Chemical surface patterning has been proven as an effective method to control the attachment and growth of diverse cell populations. Patterning polyelectrolyte multilayers through the combination of layer-by-layer self-assembly technique and photolithography offers a simple, versatile and silicon compatible approach that overcomes chemical surface patterning limitations, such as short-term stability and low protein adsorption resistance. In this study, direct photolithographic patterning of PAA/PAAm and PAA/PAH polyelectrolyte multilayers was developed to pattern mammalian neuronal, skeletal and cardiac muscle cells. For all studied cell types, PAA/PAAm …

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Water Footprint Of Aviation Fuel Synthesis By The Fischer Tropsch Process Using Sugar Cane Waste & Landfill Gas As Feedstocks, Slim Menzli Jan 2008

Water Footprint Of Aviation Fuel Synthesis By The Fischer Tropsch Process Using Sugar Cane Waste & Landfill Gas As Feedstocks, Slim Menzli

Electronic Theses and Dissertations

The recent spikes in oil prices have spurred an already bullish demand on biofuels as a source of alternative energy. However, the unprecedented price records set simultaneously by staple food have raised high concerns about potential impacts of biofuels on the global agricultural landscape as fuel and food markets are being inextricably coupled. The revival of interest in the Fischer-Tropsch (FT) process comes into full force since it offers a promising way to produce carbon-neutral liquid fuels which are readily usable with today's existing infrastructure. The FT synthesis offers the possibility of using crop waste as feedstock instead of the …

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Fundamental Study Of Fc-72 Pool Boiling Surface Temperature Fluctuations And Bubble Behavior, Alison Griffin Jan 2008

Fundamental Study Of Fc-72 Pool Boiling Surface Temperature Fluctuations And Bubble Behavior, Alison Griffin

Electronic Theses and Dissertations

A heater designed to monitor surface temperature fluctuations during pool boiling experiments while the bubbles were simultaneously being observed has been fabricated and tested. The heat source was a transparent indium tin oxide (ITO) layer commercially deposited on a fused quartz substrate. Four copper-nickel thin film thermocouples (TFTCs) on the heater surface measured the surface temperature, while a thin layer of sapphire or fused silica provided electrical insulation between the TFTCs and the ITO. The TFTCs were micro-fabricated using the liftoff process to deposit the nickel and copper metal films. The TFTC elements were 50 microns wide and overlapped to …

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High Performance Zno Varistors Prepared From Nanocrystalline Precursors For Miniaturised Electronic Devices, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh Jan 2008

High Performance Zno Varistors Prepared From Nanocrystalline Precursors For Miniaturised Electronic Devices, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh

Articles

An industrially viable solution-based processing route using minimal amounts of solvent has been used to prepare bulk quantity nanopowders (average particle size 15.3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterised. The preparation of varistors from nanopowders has been optimised by studying the effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 C for 2 hours, a temperature that is significantly lower than that used in the current industrial process. Highly dense varistor discs prepared from the sintered material produce devices, with …

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Antenna Design Considerations For High Specific Absorption Rate In Local Hyperthermia Treatment, Max Ammann, Sergio Curto, Xiulong Bao, Patrick Mcevoy Jan 2008

Antenna Design Considerations For High Specific Absorption Rate In Local Hyperthermia Treatment, Max Ammann, Sergio Curto, Xiulong Bao, Patrick Mcevoy

Conference papers

The design of a miniaturised low-profile efficient hyperthermia applicator is presented. The efficiency is attributed to small size, resilience to detuning and wide bandwidth. The antenna provides a high value of SAR and is well matched to tissue, even at close distances.

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Kinetics And Reaction Products Of Ozone And Surface-Bound Squalene, J. R. Wells, Glenn Morrison, Beverly K. Coleman Jan 2008

Kinetics And Reaction Products Of Ozone And Surface-Bound Squalene, J. R. Wells, Glenn Morrison, Beverly K. Coleman

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Because of the high occupant density in aircraft, the surface chemistry of ozone and squalene, an important component of skin oil, was evaluated. a reaction probability of 45±14) x 10 -5 was determined for the reaction of squalene (2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22- tetracosahexaene) with ozone (50 parts per billion (ppb)) on a glass plate surface using the Field and Laboratory Emission Cell (FLEC) Automation and Control System (FACS). to more clearly define part of squalene's indoor environment degradation mechanism, gas-phase and surface-bound products of the squalene+O3 reaction were also investigated. Emitted products were captured in solution, derivatized with O-(2,3,4,5,6pentafluorobenzyl) hydroxylamine (PFBHA), and analyzed …

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Flexural Behavior And Strength Of Cold-Formed Steel L-Headers, Jesse Pauls, Lei Xu, S. R. Fox Jan 2008

Flexural Behavior And Strength Of Cold-Formed Steel L-Headers, Jesse Pauls, Lei Xu, S. R. Fox

American Iron and Steel Institute (AISI) Specifications, Standards, Manuals and Research Reports (1946 - present)

No abstract provided.

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Extension Of The Poiseuille Formula For Shear-Thickening Materials And Application To Self-Compacting Concrete, Dimitri Feys, Ronny Verhoeven, Geert De Schutter Jan 2008

Extension Of The Poiseuille Formula For Shear-Thickening Materials And Application To Self-Compacting Concrete, Dimitri Feys, Ronny Verhoeven, Geert De Schutter

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In Practice, While Placing Concrete in a Formwork by Pumping, the Pressure Generated by the Pump is Not Controlled. in Order to Enhance the Safety on the Worksite, and in View of the Current Economic and Ecologic Arguments, It Would Be Useful to Dispose of an Equation Able to Predict Pressure Losses based on the Rheological Properties of the Concrete and the Pipe Configuration. This Paper Describes the Derivation of an Extended Version of the Poiseuille Formula, for Shear-Thickening Materials with a Yields Stress, Described by the Modified Bingham Equation. This Formula is Applied to Flow-Tests with Self-Compacting Concrete. the …

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Information Technology Systems And Services, Doris Bornhoeft Jan 2008

Information Technology Systems And Services, Doris Bornhoeft

UND Departmental Histories

This departmental history was written on the occasion of the UND Quasquicentennial in 2008.

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Information Systems And Business Education, University Of North Dakota Jan 2008

Information Systems And Business Education, University Of North Dakota

UND Departmental Histories

This departmental history was written on the occasion of the UND Quasquicentennial in 2008.

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Elastic Secondary Flows Of Semidilute Dna Solutions In Abrupt 90° Microbends, Shelly Gulati, Dorian Liepmann, Susan Muller Jan 2008

Elastic Secondary Flows Of Semidilute Dna Solutions In Abrupt 90° Microbends, Shelly Gulati, Dorian Liepmann, Susan Muller

All Faculty Articles - School of Engineering and Computer Science

Secondary flows that are absent in Newtonian flows are found for semidilute λ-DNA solutions in abrupt planar 90° microbends at modest levels of elasticity. Flow visualization and microparticle image velocimetry experiments show that a vortex, which is present in the inner, upstream corner of the bend, grows with increasing Reynolds and Weissenberg number (9.9 × 10 −7 < Re < 3.1 × 10 −2, 0.41 < Wi < 126).The vortex growth is quantified as a function of elasticity; at high elasticity, the vortex occupies a significant fraction of the upstream channel and distorts the primary flow. The presence of elastic vortices, in which molecules can become trapped for long times, has implications for the design of microdevices for the processing of biological macromolecules.

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Attitude Determination Using Imaging Lidar, Camille Decoust Jan 2008

Attitude Determination Using Imaging Lidar, Camille Decoust

Master's Theses - Daytona Beach

The purpose of this study is to determine the attitude of an out of control object using a new technology called lidar (Light Ranging and Detection). As the number of spacecraft continues to grow, it is paramount to introduce a new type of autonomous on-orbit satellite inspection and repair involving docking. Traditional space vision technology is based on video systems. This method is limited by the necessity of operating when the target is illuminated by the sunlight or using its own source of illumination. The use of laser imaging technology offers an elegant solution to these challenges. This approach allows …

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Entrepreneurial Spirit In Government Managed Enterprises: Evidence From The U.S. General Aviation Airports, Vitaly S. Guzhva, Massoud Bazargan, David A. Byers Jan 2008

Entrepreneurial Spirit In Government Managed Enterprises: Evidence From The U.S. General Aviation Airports, Vitaly S. Guzhva, Massoud Bazargan, David A. Byers

Management, Marketing and Operations - Daytona Beach

While a number of studies introduce entrepreneurship in the public sector, there is still a need for empirical research in this field. We use a survey of U.S. general aviation airport managers to investigate the benefits of entrepreneurial spirit in public sector management. The results of logistic regressions suggest that the airport managers’ beliefs in importance of self-sustainability significantly improve the likelihood of general aviation airports to be self-sustaining. On the other hand, the airport specific characteristics, such as a favorable location, county population, and others are not statistically significant in achieving self-sustainability. Our findings support the literature that argue …

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Analysis Of Information Remaining On Hand Held Devices Offered For Sale On The Second Hand, Andy Jones, Craig Valli, Iain Sutherland Jan 2008

Analysis Of Information Remaining On Hand Held Devices Offered For Sale On The Second Hand, Andy Jones, Craig Valli, Iain Sutherland

Journal of Digital Forensics, Security and Law

The ownership and use of mobile phones, Personal Digital Assistants and other hand held devices is now ubiquitous both for home and business use. The majority of these devices have a high initial cost, a relatively short period before they become obsolescent and a relatively low second hand value. As a result of this, when the devices are replaced, there are indications that they tend to be discarded. As technology has continued to develop, it has led to an increasing diversity in the number and type of devices that are available, and the processing power and the storage capacity of …

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Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed By Microstrip Line, Xiulong Bao, Max Ammann Jan 2008

Dual-Frequency Dual-Sense Circularly-Polarized Slot Antenna Fed By Microstrip Line, Xiulong Bao, Max Ammann

Articles

A new design of a dual-frequency dual circularly-polarized slot antenna is presented. The dual-frequency is achieved using a single-layer microstrip-fed configuration coupled to a modified annular-slot antenna. The dual sense circular-polarization is obtained by four unequal linear slots which augment the annular slot. Experimental results show the proposed antenna has good circular polarization characteristics for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP). The 10 dB return loss impedance bandwidths for the lower (RHCP) and higher (LHCP) bands are 26.7% and 11.3%, respectively. The 3 dB axial-ratio bandwidths are 6.1% and 6.0% with respect to 1.5 GHz (RHCP) …

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Nano Quasicrystal Formation And Local Atomic Structure In Zr––Pd And Zr––Pt Binary Metallic Glasses, Junji Saida, Takashi Sanada, Shigeo Sato, Muneyuki Imafuku, Chunfei Li, Akihisa Inoue Jan 2008

Nano Quasicrystal Formation And Local Atomic Structure In Zr––Pd And Zr––Pt Binary Metallic Glasses, Junji Saida, Takashi Sanada, Shigeo Sato, Muneyuki Imafuku, Chunfei Li, Akihisa Inoue

Center for Electron Microscopy and Nanofabrication Publications and Presentations

Formation of the nanoscale icosahedral quasicrystalline phase (I-phase) in the melt-spun Zr70Pd30 and Zr80Pt20 binary metallic glasses were reported. Local atomic structure in the glassy and quasicrystal (QC)-formed states were also analyzed by XRD and EXAFS measurements in order to investigate the formation mechanism of QC phase. The distorted icosahedral-like local structure can be identified around Zr atom in the Zr70Pd30 metallic glass. In the QC formation process, a change of local environment around Zr is detected, in which the approximately one Zr atom substitutes for one Pd atom. In contrast, …

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Kentucky Water Resources Research Institute Annual Technical Report Fy 2007, Kentucky Water Resources Research Institute, University Of Kentucky Jan 2008

Kentucky Water Resources Research Institute Annual Technical Report Fy 2007, Kentucky Water Resources Research Institute, University Of Kentucky

KWRRI Annual Technical Reports (USGS’s 104b Grant Program)

The 2007 Annual Technical Report for Kentucky consolidates reporting requirements of the Section 104(b) base grant award into a single document that includes: 1) a synopsis of each student research enhancement project conducted during the period, 2) citations for related publications, reports, and presentations, 3) a description of information transfer activities, 4) a summary of student support during the reporting period, and 5) notable awards and achievements during the year.

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Photovoltaic Cells Based On Copper Phthalocyanine And Cadmium Sulfide Heterojunction, Sandeep Kumar Marda Jan 2008

Photovoltaic Cells Based On Copper Phthalocyanine And Cadmium Sulfide Heterojunction, Sandeep Kumar Marda

University of Kentucky Master's Theses

This work focuses on the solar cell based on the heterostructure formed between Copper Phthalocyanine (CuPc) and Cadmium Sulfide (CdS). Two different fabrication techniques were used for depositing the organic and inorganic layers of CuPc and CdS layers respectively. CuPc was deposited by electrodeposition while CdS was deposited by chemical bath deposition. Hybrid CdS/CuPc thin films were obtained from CdS films grown on Glass/ITO by chemical bath deposition followed by electrodeposition of CuPc onto these films and annealing at 250˚C after the deposition of each layer. The maximum open circuit voltage (Voc) and the short circuit current density …

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Combining The Wind Power Generation System With Energy Storage Equipments, Ming-Shun Lu Jan 2008

Combining The Wind Power Generation System With Energy Storage Equipments, Ming-Shun Lu

Electrical Engineering Theses - Archive

With the advance in wind turbine technologies, the cost of wind energy becomes competitive with other fuel-based generation resources. Due to the price hike of the fossil fuel and the concern of the global warming, the development of wind power has rapidly progressed over the last decade. The annual growth rate of the wind generation installation has exceeded 26% since 1990s. Many countries have set goal for high penetration levels of wind generations. Recently, several large-scale wind generation projects have been implemented all over the world. It is economically beneficial to integrate very large amounts of wind capacity in power …

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Hybrid Video Coding Design With Variable Size Integer Transforms And Structural Similarity, Att Kruafak Jan 2008

Hybrid Video Coding Design With Variable Size Integer Transforms And Structural Similarity, Att Kruafak

Electrical Engineering Dissertations - Archive

This research proposes a block-based video codec design with two objectives. The first goal is to propose a method for intraframe that improves the rate-distortion (peak signal-to-noise ratio versus bit rate) of a fixed-size transform encoder. The proposed method uses three integer transform sizes (4x4), (8x8), and (16x16). The codec also adopts H.264-like spatial prediction to intraframe encoding. For simplicity of the design, Huffman variable-length code is used as entropy encoding. For intraframe encoding, the simulations show rate-distortion improvement over JPEG and JPEG2000. In some test sequences, the simulations also show improvement over H.264 (baseline profile at low complexity mode …

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Complex Directional Wavelet Transforms: Representation, Statistical Modeling And Applications, An Phuoc Nhu Vo Jan 2008

Complex Directional Wavelet Transforms: Representation, Statistical Modeling And Applications, An Phuoc Nhu Vo

Electrical Engineering Dissertations - Archive

The thesis presents an new image decomposition for feature extraction, which is called the pyramidal dual-tree directional filter bank (PDTDFB). The image representation has an overcomplete ratio of less than 8/3 and uses a separable filter bank implementation structure. We discuss how to utilize both magnitude and phase information obtained from the PDTDFB for the purpose of texture image retrieval. The relative phase, which is the difference of phases between two adjacent complex coefficients, has a linear relationship with the angle of dominant orientation within a subband. This information is incorporated to form a new feature vector called CDFB-RP. Another …

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