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2010

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Articles 7621 - 7650 of 8621

Full-Text Articles in Physical Sciences and Mathematics

Waves In Materials With Microstructure: Numerical Simulation, Mihhail Berezovski, Arkadi Berezovski, Juri Engelbrecht Jan 2010

Waves In Materials With Microstructure: Numerical Simulation, Mihhail Berezovski, Arkadi Berezovski, Juri Engelbrecht

Publications

Results of numerical experiments are presented in order to compare direct numerical calculations of wave propagation in a laminate with prescribed properties and corresponding results obtained for an effective medium with the microstructure modelling. These numerical experiments allowed us to analyse the advantages and weaknesses of the microstructure model.

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Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet Jan 2010

Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet

Electronic Theses and Dissertations

We discuss the role of symmetries in the dissociative recombinations (DR) of three polyatomic ions, namely the linear HCO+ (formyl) ion and the two highly symmetric H+3 and H3O+ (hydronium) molecular ions. Regarding the HCO+ ion, we apply a quantum mechanical treatment using the Multi-channel Quantum Defect Theory (MQDT) formalism to describe the ion-electron scattering process. Our study takes into account the Renner-Teller effect in order to model the non Born-Oppenheimer vibronic coupling in linear polyatomic ions. The coupling has shown to represent the main mechanism responsible for electronic capturing in highly excited Rydberg states associated with excited vibrational levels …

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A Sketch-Based Language For Representing Uncertainty In The Locations Of Origin Of Herbarium Specimens, Barry J. Kronenfeld, Andrew Weeks Jan 2010

A Sketch-Based Language For Representing Uncertainty In The Locations Of Origin Of Herbarium Specimens, Barry J. Kronenfeld, Andrew Weeks

Barry J. Kronenfeld

Uncertainty fields have been suggested as an appropriate model for retrospective georeferencing of herbarium specimens. Previous work has focused only on automated data capture methods, but techniques for manual data specification may be able to harness human spatial cognition skills to quickly interpret complex spatial propositions. This paper develops a formal modeling language by which location uncertainty fields can be derived from manually sketched features. The language consists of low-level specification of critical probability isolines from which a surface can be uniquely derived, and high-level specification of features and predicates from which low-level isolines can be derived. In a case …

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Fast Response Dual Frequency Liquid Crystal Materials, Qiong Song Jan 2010

Fast Response Dual Frequency Liquid Crystal Materials, Qiong Song

Electronic Theses and Dissertations

Dual frequency liquid crystal (DFLC) exhibits a positive dielectric anisotropy at low frequencies and negative dielectric anisotropy at high frequencies. The frequency where dielectric anisotropy is zero is called crossover frequency. DFLC can achieve fast rise time and fast decay time with the assistance of applied voltage. However, one drawback of DFLC is that it has dielectric heating effect when driven at a high frequency. Thus, the first part of this dissertation is to develop low crossover frequency DFLC materials. The dielectric relaxation and physical properties of some single- and double-ester compounds were investigated. Experimental results indicate that the double-ester …

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Response-Calibration Techniques For Antenna-Coupled Infrared Sensors, Peter Krenz Jan 2010

Response-Calibration Techniques For Antenna-Coupled Infrared Sensors, Peter Krenz

Electronic Theses and Dissertations

Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous …

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Molecular Dynamics Studies Of Simple Model Fluids And Water Confined In Carbon Nanotube, Jun Wang Jan 2010

Molecular Dynamics Studies Of Simple Model Fluids And Water Confined In Carbon Nanotube, Jun Wang

Department of Chemistry: Dissertations, Theses, and Student Research

Molecular Dynamics (MD) simulation is one of the most important computational techniques with broad applications in physics, chemistry, chemical engineering, materials design and biological science. Traditional computational chemistry refers to quantum calculations based on solving Schrodinger equations. Later developed Density Functional Theory (DFT) based on solving Kohn-Sham equations became the more popular ab initio calculation technique which could deal with ~1000 atoms by explicitly considering electron interactions. In contrast, MD simulation based on solving classical mechanics equations of motion is a totally different technique in the field of computational chemistry. Electron interactions were implicitly included in the empirical atom-based potential …

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Lattice Thermal Conductivity Of Freestanding Gallium Nitride Nanowires, Jie Zou Jan 2010

Lattice Thermal Conductivity Of Freestanding Gallium Nitride Nanowires, Jie Zou

Jie Zou

aip Publishers Publications Topics | Librarians Authors Your access is provided by: Eastern Illinois University Register to create your user account, or sign in if you have an existing account Additional sign in Sign in via Shibboleth/Athens My cart Export citations Add to my favorites Recommend to library Subscribe to email alerts Submit an article Reprints & Permissions Subscribe to RSS Access Key Free Content Open Access Content Subscribed Content Free Trial Content Home > Publishers > AIP Publishing > Journal of Applied Physics > Volume 108, Issue 3 > Article banner image F Lattice thermal conductivity of freestanding gallium nitride nanowires Download PDF Jie …

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Magnetic And Optical Properties Of Multiferroic Gdmno3 Nanoparticles, X. L. Wang, D. Li, T. Y. Cui, Parashu Kharel, W. Liu, Z. D. Zhang Jan 2010

Magnetic And Optical Properties Of Multiferroic Gdmno3 Nanoparticles, X. L. Wang, D. Li, T. Y. Cui, Parashu Kharel, W. Liu, Z. D. Zhang

Department of Physics and Astronomy: Faculty Publications

The magnetic and optical properties of multiferroic GdMnO3 nanoparticles synthesized by a polymerized complex method have been investigated. The GdMnO3 nanoparticles crystallized in orthorhombic perovskite-type structure. The zero-field-cooled and field-cooled magnetizations show that complicated magnetic transitions occur in a temperature range from 2 to 60 K, which were confirmed by magnetic hysteresis loops. Three shoulder absorption peaks centered at about 2.0, 2.3, and 2.7 eV are attributed to the Mn (3d)-electronic transitions, while an absorption peak at around 4.1 eV corresponds to the charge-transfer transitions between O (2p) and Mn (3d) states. UV emission at about 396 and …

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Table Of Contents Jan 2010

Table Of Contents

Journal of Digital Forensics, Security and Law

No abstract provided.

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Utilizing The Technology Acceptance Model To Assess The Employee Adoption Of Information Systems Security Measures, Cynthia M. Jones, Richard V. Mccarthy, Leila Halawi, Bahaudin Mujtaba Jan 2010

Utilizing The Technology Acceptance Model To Assess The Employee Adoption Of Information Systems Security Measures, Cynthia M. Jones, Richard V. Mccarthy, Leila Halawi, Bahaudin Mujtaba

Publications

In this study, the factors that affect employee acceptance of information systems security measures were examined by extending the Technology Acceptance Model. Partial least squares structural equation modeling was applied to examine these factors. 174 valid responses from employees from companies in various industry segments in the United States and Canada were analyzed. The results of the statistical analysis indicate that subjective norm moderated by management support showed the strongest effect on intention to use information systems security measures.

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Anion Exchange Kinetics Of Nanodimensional Layered Metal Hydroxides: Use Of Isoconversional Analysis, Stephen Majoni, Jeanne Hossenlopp Jan 2010

Anion Exchange Kinetics Of Nanodimensional Layered Metal Hydroxides: Use Of Isoconversional Analysis, Stephen Majoni, Jeanne Hossenlopp

Chemistry Faculty Research and Publications

Anion exchange reactions of nanodimensional layered metal hydroxide compounds are utilized to create materials with targeted physical and chemical properties and also as a means for controlled release of intercalated anions. The kinetics of this important class of reaction are generally characterized by model-based approaches. In this work, a different approach based on isothermal, isoconversional analysis was utilized to determine effective activation energies with respect to extent of reaction. Two different layered metal hydroxide materials were chosen for reaction with chloride anions, using a temperature range of 30−60 °C. The concentrations of anions released into solution and the changes in …

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Isomerization As A Key Path To Molecular Products In The Gas-Phase Decomposition Of Halons, Aimable Kalume, Lisa George, Scott Reid Jan 2010

Isomerization As A Key Path To Molecular Products In The Gas-Phase Decomposition Of Halons, Aimable Kalume, Lisa George, Scott Reid

Chemistry Faculty Research and Publications

The decomposition of halons remains controversial concerning the branching between radical and molecular products. The latter channel, where it has been found, is presumed to occur via a constrained symmetric multicenter transition state. Isomerization pathways in the gas-phase chemistry of halons have rarely been considered, despite the fact that the iso-halons, which feature a halogen−halogen bond, are widely recognized as important reactive intermediates in condensed phases. In this Letter, detailed calculations and modeling of the unimolecular decomposition of several important halons, including CF2Cl2, CF2Br2, and CHBr3, reveal that isomerization is …

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Affinity Capillary Electrophoretic Study Of K+/Na+ Selectivity Of Hexaarylbenzene-Based Polyaromatic Receptor, Sille Ehala, Rajendra Rathore, Emanuel Makrlik, Petr Toman, Václav Kašička Jan 2010

Affinity Capillary Electrophoretic Study Of K+/Na+ Selectivity Of Hexaarylbenzene-Based Polyaromatic Receptor, Sille Ehala, Rajendra Rathore, Emanuel Makrlik, Petr Toman, Václav Kašička

Chemistry Faculty Research and Publications

Affinity capillary electrophoretic (ACE) study has proved the selectivity of hexaarylbenzene-based polyaromatic receptor (R) for K+ ion over Na+ ion. The apparent binding constants of the R complexes with K+ and Na+ ions were determined from the dependence of effective electrophoretic mobility of R on the concentration of the above alkali metal ions in the background electrolyte using a non-linear regression analysis. The apparent binding constants (Kb) of the K-R+ and Na–R+ complexes in methanolic medium were evaluated as log Kb = 3.20 ± 0.22 for the K–R+ complex, and log Kb≅−0.7 for the Na–R+ complex.

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Tricarbonylrhenium(I) And Manganese(I) Complexes Of 2-(Pyrazolyl)-4-Toluidine, Brendan J Liddle, Sarath Wanniarachchi, Sergey V. Lindeman, James R. Gardinier Jan 2010

Tricarbonylrhenium(I) And Manganese(I) Complexes Of 2-(Pyrazolyl)-4-Toluidine, Brendan J Liddle, Sarath Wanniarachchi, Sergey V. Lindeman, James R. Gardinier

Chemistry Faculty Research and Publications

A series of tricarbonyl rhenium(I) and manganese(I) complexes of the electroactive 2-(pyrazolyl)-4-toluidine ligand, H(pzAnMe), has been prepared and characterized including by single crystal X-ray diffraction studies. The reactions between H(pzAnMe) and M(CO)5Br afford fac-MBr(CO)3[H(pzAnMe)] (M = Mn, 1a; Re, 1b) complexes. The ionic species {fac-M(CH3CN)(CO)3[H(pzAnMe)]}(PF6) (M = Mn, 2a; Re, 2b) were prepared by metathesis of 1a or 1b with TlPF6 in acetonitrile. Complexes 1a and 1b partly ionize to {M(CH3CN)(CO)3[H(pzAnMe)]+ …

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Fluid Budget Of Metasedimentary Rocks From A Tertiary Accretionary Prism And Connections To Seismicity, Olympic Peninsula, Northwest Washington State, Holly Makena Macfadden Rotman Jan 2010

Fluid Budget Of Metasedimentary Rocks From A Tertiary Accretionary Prism And Connections To Seismicity, Olympic Peninsula, Northwest Washington State, Holly Makena Macfadden Rotman

All Master's Theses

Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow …

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Radiographic Imagery Of A Variable Density 3d Object, Justin Stottlemyer Jan 2010

Radiographic Imagery Of A Variable Density 3d Object, Justin Stottlemyer

Undergraduate Journal of Mathematical Modeling: One + Two

The purpose of this project is to develop a mathematical model to study 4D (three spatial dimensions plus density) shapes using 3D projections. In the model, the projection is represented as a function that can be applied to data produced by a radiation detector. The projection is visualized as a three-dimensional graph where x and y coordinates represent position and the z coordinate corresponds to the object's density and thickness. Contour plots of such 3D graphs can be used to construct traditional 2D radiographic images.

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Selective Fluorescence Detection Of Cysteine And N-Terminal Cysteine Peptide Residues, Soojin Lim, Jorge O. Escobedo, Mark Lowry, Xiangyang Xu, Robert M. Strongin Jan 2010

Selective Fluorescence Detection Of Cysteine And N-Terminal Cysteine Peptide Residues, Soojin Lim, Jorge O. Escobedo, Mark Lowry, Xiangyang Xu, Robert M. Strongin

Chemistry Faculty Publications and Presentations

A new fluorogenic fluorescein derivative containing an α,β-unsaturated aldehyde moiety produces a selective fluorescent signal enhancement in the presence of cysteine or peptides containing N-terminal cysteine residues. The mechanism is based on synergistic covalent and supramolecular interactions.

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Nir Dyes For Bioimaging Applications, Jorge O. Escobedo, Oleksandr Rusin, Soojin Lim, Robert M. Strongin Jan 2010

Nir Dyes For Bioimaging Applications, Jorge O. Escobedo, Oleksandr Rusin, Soojin Lim, Robert M. Strongin

Chemistry Faculty Publications and Presentations

Fluorescent dyes based on small organic molecules that function in the near infra red (NIR) region are of great current interest in chemical biology. They allow for imaging with minimal autofluorescence from biological samples, reduced light scattering and high tissue penetration. Herein, examples of ongoing NIR fluorophore design strategies as well as their properties and anticipated applications relevant to the bioimaging are presented.

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The Population Of Sap And Tsap Isomers In Cyclen-Based Lanthanide(Iii) Chelates Is Substantially Affected By Solvent, Kyle J. Miller, Ali A. Saherwala, Benjamin C. Webber, Yunkou Wu, A. Dean Sherry, Mark Woods Jan 2010

The Population Of Sap And Tsap Isomers In Cyclen-Based Lanthanide(Iii) Chelates Is Substantially Affected By Solvent, Kyle J. Miller, Ali A. Saherwala, Benjamin C. Webber, Yunkou Wu, A. Dean Sherry, Mark Woods

Chemistry Faculty Publications and Presentations

The square antiprism/twisted square antiprism ratio in LnDOTA-tetraamide chelates is a critical parameter in governing water-exchange kinetics and ultimately the utility of a chelate as a PARACEST MRI contrast agent. In LnDOTA-tetraamide chelates with tertiary amides, this ratio and the rate of interconversion between these two structural isomers are found to be dramatically dependent upon the solvent and possibly other local environmental factors.

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Polymeric Paracest Mri Contrast Agents As Potential Reporters For Gene Therapy, Yunkou Wu, Christiane E. Carney, Michael Denton, Elaine Hart, Piyu Zhao, Daniel N. Streblow, A. Dean Sherry, Mark Woods Jan 2010

Polymeric Paracest Mri Contrast Agents As Potential Reporters For Gene Therapy, Yunkou Wu, Christiane E. Carney, Michael Denton, Elaine Hart, Piyu Zhao, Daniel N. Streblow, A. Dean Sherry, Mark Woods

Chemistry Faculty Publications and Presentations

Gene therapy is a potentially powerful treatment approach that targets molecular remedies for disease. Among other challenges it remains difficult to monitor gene delivery and its downstream metabolic consequences. Approaches to MRI gene reporters have been reported but few have the potential for translation beyond isolated cell systems. Herein, we report a polycationic polymer MRI contrast agent that binds to DNA in a ratio of one monomer unit per phosphate group of DNA. Significantly, this binding event diminishes the MR contrast signal from the agent itself potentially providing a platform for imaging delivery and release of a gene into cells …

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Determination Of Autoregressive Model Orders For Seizure Detection, Serap Aydin Jan 2010

Determination Of Autoregressive Model Orders For Seizure Detection, Serap Aydin

Turkish Journal of Electrical Engineering and Computer Sciences

In the present study, a step-wise least square estimation algorithm (SLSA), implemented in a Matlab package called as ARfit, has been newly applied to clinical data for estimation of the accurate Auto-Regressive (AR) model orders of both normal and ictal EEG series where the power spectral density (PSD) estimations are provided by the Burg Method. The ARfit module is found to be usefull in comparison to a large variety of traditional methods such as Forward Prediction Error (FPE), Akaike's Information Criteria (AIC), Minimum Description Lenght (MDL), and Criterion of Autoregressive Transfer function (CAT) for EEG discrimination. According to tests, the …

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P2p Collaborative Filtering With Privacy, Ci̇han Kaleli̇, Hüseyi̇n Polat Jan 2010

P2p Collaborative Filtering With Privacy, Ci̇han Kaleli̇, Hüseyi̇n Polat

Turkish Journal of Electrical Engineering and Computer Sciences

With the evolution of the Internet and e-commerce, collaborative filtering (CF) and privacy-preserving collaborative filtering (PPCF) have become popular. The goal in CF is to generate predictions with decent accuracy, efficiently. The main issue in PPCF, however, is achieving such a goal while preserving users' privacy. Many implementations of CF and PPCF techniques proposed so far are centralized. In centralized systems, data is collected and stored by a central server for CF purposes. Centralized storage poses several hazards to users because the central server controls users' data. In this work, we investigate how to produce naïve Bayesian classifier (NBC)-based recommendations …

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Experimental Studies Of A Scaled-Down Tsr-Based Svc And Tcr-Based Svc Prototype For Voltage Regulation And Compensation, Ayetül Gelen, Tankut Yalçinöz Jan 2010

Experimental Studies Of A Scaled-Down Tsr-Based Svc And Tcr-Based Svc Prototype For Voltage Regulation And Compensation, Ayetül Gelen, Tankut Yalçinöz

Turkish Journal of Electrical Engineering and Computer Sciences

In this paper, prototypes of two shunt flexible AC transmission system (FACTS) devices, a thyristor switched reactor (TSR)-based static VAr compensator (SVC) and a thyristor controlled reactor (TCR)-based static VAr compensator- have been developed. The design and testing of both a TSR-based SVC and a TCR-based SVC are accomplished in the Power Systems Research Laboratory of Nigde University. The TSR-based SVC and TCR-based SVC devices are studied in three-bus and single machine infinite bus systems for three-phase static load conditions. The effects of TSR-based SVC and TCR-based SVC devices on load voltages are also analyzed. Experimental results show that significant …

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Robust Multimedia Watermarking: Hidden Markov Model Approach For Video Sequences, Ersi̇n Elbaşi Jan 2010

Robust Multimedia Watermarking: Hidden Markov Model Approach For Video Sequences, Ersi̇n Elbaşi

Turkish Journal of Electrical Engineering and Computer Sciences

Because of the large amount of frames, similarity between frames and temporal attacks (frame dropping, frame averaging, frame swapping etc.), the process for video watermarking is more difficult than that for image watermarking. Current image watermarking methods are limited to solve all these difficulties. We propose a novel video watermarking system based on the Hidden Markov Model (HMM). This novel watermarking scheme splits the video sequences into a Group of Pictures (GOP) with HMM. Portions of the binary watermark are embedded into each GOP with a wavelet domain watermarking algorithm. The embedding process is the standard additive algorithm [1] in …

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The Effect Of Heat On The Metallurgical Structure And B-H Characteristic Of (Stator) Armature With Iron-Silicon Alloy In Electric Machines, Fevzi̇ Kentli̇, Ümi̇t Kemaletti̇n Terzi̇ Jan 2010

The Effect Of Heat On The Metallurgical Structure And B-H Characteristic Of (Stator) Armature With Iron-Silicon Alloy In Electric Machines, Fevzi̇ Kentli̇, Ümi̇t Kemaletti̇n Terzi̇

Turkish Journal of Electrical Engineering and Computer Sciences

Coils in electric machines are varnished for insulation after winding. These varnished coils are formed in stiff construction in slots. Under heavy-duty operating conditions, all or part of some coils may be burnt or broken. Thermal method is one of several ways to remove the defective coils. In this method, current is passed through the defective coils by an autotransformer (variac) until all the varnish of the coils is burned. If all the coils are out of order, the varnish is burned by replacing the stator or armature in a burning room. Consequently, defective coils in the stator (armature) slots …

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Nonlinear Dynamic Analysis Of Mitral Valve Doppler Signals: Surrogate Data Analysis, Esma Uzunhi̇sarcikli Jan 2010

Nonlinear Dynamic Analysis Of Mitral Valve Doppler Signals: Surrogate Data Analysis, Esma Uzunhi̇sarcikli

Turkish Journal of Electrical Engineering and Computer Sciences

In our study, the nonlinear dynamics of mitral valve Doppler signals from 32 healthy and 28 patients with mitral valve stenosis was evaluated using by the computation of Lyapunov exponents, correlation dimension values and surrogate data analysis. Two chaotic features are compared for healthy and patient subjects. It was found that the largest Lyapunov exponent and correlation dimension values derived from patient subjects were larger than that of healthy subjects (\rho < 0.005). Surrogate data analysis was performed to determine the chaotic dynamics of Doppler signals. It was observed that the original and surrogate data have similar spectral features. Receiver operating characteristic (ROC) curves were used to evaluate the nonlinearity character Area Under the curve (AUC) values were obtained as 0.99 and 0.978 for the largest Lyapunov exponent and correlation dimension values, respectively. According to these results, Doppler signals have a nonlinear dynamic property and the largest Lyapunov exponent. Correlation dimension features can be used to detect the change in blood flow velocity of patients with mitral valve stenosis.

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A Review Of High Frequency Surface Wave Radar For Detection And Tracking Of Ships, Tony Ponsford, Jian Wang Jan 2010

A Review Of High Frequency Surface Wave Radar For Detection And Tracking Of Ships, Tony Ponsford, Jian Wang

Turkish Journal of Electrical Engineering and Computer Sciences

In today's resource-driven economy, maritime nations are claiming economic borders that extend beyond the continental shelf or the 200 nautical mile (nm) Exclusive Economic Zone (EEZ). However, claiming such large economic area places responsibilities on the parent nation to exercise jurisdiction through surveillance and enforcement. The requirement to see beyond the horizon has long been a goal of maritime security forces. Today, this is largely dependent on cooperative vessels voluntarily communicating their intentions to local shore-side authorities, as well as on those vessel sightings reported by patrollers. Recent advances in technology provide maritime nations with options to provide more systematic …

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Implementation Of Method For Operating Multiple High Frequency Surface Wave Radars On A Common Carrier Frequency, Ryan Riddolls Jan 2010

Implementation Of Method For Operating Multiple High Frequency Surface Wave Radars On A Common Carrier Frequency, Ryan Riddolls

Turkish Journal of Electrical Engineering and Computer Sciences

The increasing use of High Frequency Surface Wave Radar (HFSWR) for the surveillance of coastal regions is faced with the problem of limited channel availability in the electromagnetic spectrum. Thus, there is a need for multiple radars to share a common frequency channel. Proof-of-concept work is presented here for a method to operate multiple radar systems on a common carrier frequency. A review is provided of an existing concept where a common waveform is modulated by tones varying by a few hertz across the different radars. The signals from the different radars are separated by either pulse-domain filtering or Doppler …

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Propagation Modeling And Path Loss Prediction Tools For High Frequency Surface Wave Radars, Gökhan Apaydin, Levent Sevgi̇ Jan 2010

Propagation Modeling And Path Loss Prediction Tools For High Frequency Surface Wave Radars, Gökhan Apaydin, Levent Sevgi̇

Turkish Journal of Electrical Engineering and Computer Sciences

Propagation modeling and simulation approaches for the use of High Frequency Surface Wave Radar (HFSWR) are discussed. HFSWR uses vertically polarized surface waves along multi-mixed paths in the lower HF band (3 MHz - 15 MHz). Various numerical propagators are reviewed with an early analytical model. Split Step Fast Fourier Transformation, finite- difference, and finite-element solutions of the well-known one-way, forward propagation Parabolic Equation (PE) model are presented. MATLAB-based numerical propagation prediction tools based on these models are listed. Tests and comparisons among these analytical and numerical tools are given for some canonical surface wave propagation scenarios. The Millington effect …

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Antenna Systems With Beam Forming And Beam Steering Capabilities For Hf Skywave Radars, Çağatay Uluişik Jan 2010

Antenna Systems With Beam Forming And Beam Steering Capabilities For Hf Skywave Radars, Çağatay Uluişik

Turkish Journal of Electrical Engineering and Computer Sciences

Radiation characteristics of linearly phased, periodic, planar dipole arrays, which can be used as transmitting/receiving antenna systems for HF skywave radars, are investigated. Rectangular, triangular and trapezoidal arrays are proposed in obtaining different beam shapes in the desired directions. Beam steering is achieved by adjusting the inter-element phase increments coherently. The effects of vertical array-tilt with a desired take-off angle (TOA) \alpha are presented by a number of radiation pattern examples. The ground effect is investigated using the image theory by assuming the Earth's surface as perfectly electric conductor (PEC). Radiated fields are obtained using Floquet wave representations plus the …

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