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Full-Text Articles in Engineering
Characterization Of Wireless Communications Networks Using Machine Learning And 3d Electromagnetic Wave Propagation Simulations, Margaret Mary Rooney
Characterization Of Wireless Communications Networks Using Machine Learning And 3d Electromagnetic Wave Propagation Simulations, Margaret Mary Rooney
Dissertations, Theses, and Masters Projects
In this work, we employ machine learning, signal identification, and signal classification to infer network processes governing packet transmission in dense, non-cooperative wireless networks. We exploit signal features in radio frequency (RF) transmissions to generate fingerprints that can enable the characterization of transmission events in a non-cooperative cognitive radio network or in a cognitive adaptive electronic attack scenario. In these situations, we have anticipated a need to depend heavily on identifying RF features that correspond to the way in which devices access spectrum channels and to the interactions of transmitted signals with the devices' surroundings. We develop improved signal processing …
Optical Control Of Ultrafast Spin -Wave Relaxation By Magnetic Anisotropy In A Ferromagnet, Kevin James Smith
Optical Control Of Ultrafast Spin -Wave Relaxation By Magnetic Anisotropy In A Ferromagnet, Kevin James Smith
Dissertations, Theses, and Masters Projects
This thesis presents an investigation of the damping of spin waves in ferromagnetic Au(3 nm)/Ni(10 nm)/MgO(001) thin films using the time-resolved Magneto-optical Kerr Effect (TR-MOKE) and ferromagnetic resonance (FMR) techniques. In the optical measurements, a 150 fs, 800 nm laser beam pulse is split into pump and probe components. The pump pulse, containing most of the beam energy, thermally excites coherent spin precession. The weaker probe pulse, time-delayed by a variable beam path, captures the magnetization dynamics via the polar MOKE effect, and oscillations are observed as a function of external field amplitude and direction. The extracted precession frequency is …
Optical Characterization Of Ferromagnetic Heterostructure *Interfaces And Thin Films, Haibin Zhao
Optical Characterization Of Ferromagnetic Heterostructure *Interfaces And Thin Films, Haibin Zhao
Dissertations, Theses, and Masters Projects
This thesis presents optical characterizations of interfaces in ferromagnetic heterostructures and thin films used for spin polarized electronic devices. In these experiments, femtosecond laser spectroscopies are exploited to investigate the interface magnetization reversal, spin precession, and band offset, which are crucial in determining the performances of spintronic devices.;First, magnetization-induced second-harmonic-generation (MSHG) is applied to study interface magnetism in a hybrid structure containing a noncentrosymmetric semiconductor---Fe/AlGaAs. The reversal process of Fe interface layer magnetization is compared with the bulk magnetization reversal. In Fe/AlGaAs (001), the interface magnetization is found to be decoupled from the bulk magnetization based on the different switching …
Studies Of Energy Recovery Linacs At Jefferson Laboratory: 1 Gev Demonstration Of Energy Recovery At Cebaf And Studies Of The Multibunch, Multipass Beam Breakup Instability In The 10 Kw Fel Upgrade Driver, Christopher D. Tennant
Studies Of Energy Recovery Linacs At Jefferson Laboratory: 1 Gev Demonstration Of Energy Recovery At Cebaf And Studies Of The Multibunch, Multipass Beam Breakup Instability In The 10 Kw Fel Upgrade Driver, Christopher D. Tennant
Dissertations, Theses, and Masters Projects
An energy recovering linac (ERL) offers an attractive alternative for generating intense electron beams by approaching the operational efficiency of a storage ring while maintaining the superior beam quality typical of a linear accelerator. Two primary physics challenges exist in pushing the frontier of ERL performance. The first is energy recovering a high energy beam while demonstrating operational control of two coupled beams in a common transport channel. The second is controlling the high average current effects in ERLs, specifically a type of beam instability called multipass beam breakup (BBU). This work addresses each of these issues.;A successful 1 GeV …
Ultrafast Laser Spectroscopy Of Half -Metallic Chromium Dioxide, Hailong Huang
Ultrafast Laser Spectroscopy Of Half -Metallic Chromium Dioxide, Hailong Huang
Dissertations, Theses, and Masters Projects
This thesis presents ultrafast laser pump-probe differential transmission experiments on epitaxial CrO2 (110). The experiments were conducted at the wavelengths of 600 nm, 800 nm and 1200 nm, corresponding to the transition energies of 2 eV, 1.5 eV and 1 eV respectively. The wavelength dependent results, comparing with linear optical absorption, revealed the electronic structure of the material. The experimental results also showed polarization dependence of the probe beams. This is attributed to the electronic orbital anisotropy.;Temperature dependence was observed in the pump-probe experiments. The ultrafast transmission data show similar temperature dependence as ultrafast MOKE (Magneto-Optical Kerr Effect) data. A …
Thermoelastic And Photoelastic Full-Field Stress Measurement, Deonna Faye Woolard
Thermoelastic And Photoelastic Full-Field Stress Measurement, Deonna Faye Woolard
Dissertations, Theses, and Masters Projects
Photoelasticity is an optical technique that measures the difference of the principal stresses plus the principal stress direction. A complementary technique is thermoelasticity which measures the sum of the principal stresses. Combining these two full-field, non-contact nondestructive evaluation techniques allows the individual stress components to be measured. One of the main difficulties in merging these two measurement systems is in identifying an appropriate surface coating. Thermoelasticity demands a highly emissive surface, while photoelasticity requires a thick, stress-birefringent, transparent coating with a retro-reflective backing. Two coatings have been identified that can be used for combined thermoelastic and photoelastic stress measurements: PMMA …
The Projector Basis Method For Electronic Band Structure Calculations, Christopher Haas
The Projector Basis Method For Electronic Band Structure Calculations, Christopher Haas
Dissertations, Theses, and Masters Projects
Over the last several decades, two methods have emerged as the standard tools for the calculation of electronic band structures. These methods, the Car-Parinello plane wave method and the linear augmented plane wave method (LAPW), each have strengths and weaknesses in different regimes of physical problems. The Car-Parinello algorithm is ideal for calculations with soft pseudopotentials and large numbers of atoms. The LAPW method, on the other hand, easily handles all-electron and hard-core pseudopotential calculations with a small number of atoms. The projector basis method, presented here, is a hybrid mixed basis method which allows the calculation of moderately large …
A Theoretical Investigation Of Electromagnetic Waves Obliquely Incident Upon A Plasma Slab, Calvin Thomas Swift
A Theoretical Investigation Of Electromagnetic Waves Obliquely Incident Upon A Plasma Slab, Calvin Thomas Swift
Dissertations, Theses, and Masters Projects
No abstract provided.
Investigation Of A Two-Dimensional Negative Resistance Oscillator, Leo Rogon
Investigation Of A Two-Dimensional Negative Resistance Oscillator, Leo Rogon
Dissertations, Theses, and Masters Projects
No abstract provided.
Nonlinear Response Of An Oscillating Discharge To Very High Frequency Signals, Daniel Burnley Raiford
Nonlinear Response Of An Oscillating Discharge To Very High Frequency Signals, Daniel Burnley Raiford
Dissertations, Theses, and Masters Projects
No abstract provided.
Thick Target Bremsstrahlung Production, Donald I. Mcree
Thick Target Bremsstrahlung Production, Donald I. Mcree
Dissertations, Theses, and Masters Projects
No abstract provided.
Bimodal-Cavity Measurement Of The Microwave Faraday Effect In A Gaseous Magnetoplasma, Maurice Terrell Raiford
Bimodal-Cavity Measurement Of The Microwave Faraday Effect In A Gaseous Magnetoplasma, Maurice Terrell Raiford
Dissertations, Theses, and Masters Projects
No abstract provided.
Some Considerations Of An Axial Arc In A Radial Magnetic Field, Philip Brockman
Some Considerations Of An Axial Arc In A Radial Magnetic Field, Philip Brockman
Dissertations, Theses, and Masters Projects
No abstract provided.
A Technique For Measuring The Electrical Conductivity Of Moving Conductors, Joseph Norwood
A Technique For Measuring The Electrical Conductivity Of Moving Conductors, Joseph Norwood
Dissertations, Theses, and Masters Projects
No abstract provided.
Some Physical Properties Of An Axial Electric Arc In A Radial Magnetic Field, Robert Norris Rigby
Some Physical Properties Of An Axial Electric Arc In A Radial Magnetic Field, Robert Norris Rigby
Dissertations, Theses, and Masters Projects
No abstract provided.
A Study Of Luminous-Shock Fronts In An Electromagnetic Shock Tube, James Franklin Roach
A Study Of Luminous-Shock Fronts In An Electromagnetic Shock Tube, James Franklin Roach
Dissertations, Theses, and Masters Projects
No abstract provided.
Vhf Oscillations In A Penning Gauge, Robert Newman Dennis
Vhf Oscillations In A Penning Gauge, Robert Newman Dennis
Dissertations, Theses, and Masters Projects
No abstract provided.
Angle Sensitivity Of A Silicon Cell Solar Sensor, Paul R. Spencer
Angle Sensitivity Of A Silicon Cell Solar Sensor, Paul R. Spencer
Dissertations, Theses, and Masters Projects
No abstract provided.
Angle Sensitivity Of A Silicon Cell Solar Sensor Application Of Electromagnetic Radiation Pressure For Plasma Acceleration, Theodore Morin
Angle Sensitivity Of A Silicon Cell Solar Sensor Application Of Electromagnetic Radiation Pressure For Plasma Acceleration, Theodore Morin
Dissertations, Theses, and Masters Projects
No abstract provided.
Some Special Electrical Measurements, Charles Anthony Marciano
Some Special Electrical Measurements, Charles Anthony Marciano
Dissertations, Theses, and Masters Projects
No abstract provided.