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Articles 1 - 30 of 2228

Full-Text Articles in Electromagnetics and Photonics

Suppression Of Magnetostructural Transition On Gdsige Thin Film After Thermal Cyclings, A. L. Pires, J. H. Belo, I. T. Gomes, Ravi L. Hadimani, Deborah L. Schlagel, Thomas A. Lograsso, David C. Jiles, A. M. L. Lopes, J. P. Araújo, A. M. Pereira Jan 2018

Suppression Of Magnetostructural Transition On Gdsige Thin Film After Thermal Cyclings, A. L. Pires, J. H. Belo, I. T. Gomes, Ravi L. Hadimani, Deborah L. Schlagel, Thomas A. Lograsso, David C. Jiles, A. M. L. Lopes, J. P. Araújo, A. M. Pereira

Ravi L Hadimani

The influence of thermal cycling on the microstructure, magnetic phase transition and magnetic entropy change of a Gd5Si1.3Ge2.7 thin film up to 1000 cycles is investigated. The authors found that after 1000 cycles a strong reduction of the crystallographic phase responsible for the magnetostructural transition (Orthorhombic II phase) occurs. This is attributed to chemical disorder, caused by the large number of expansion/compression cycles that the Orthorhombic II phase undergoes across the magnetostructural transition. The suppression of the magnetostructural transition corresponds to a drastic decrease of the thin film magnetic entropy change. These results reveal the importance of ...


Annealing Influence On The Magnetostructural Transition In Gd5si1.3ge2.7 Thin Films, A. L. Pires, J. H. Belo, I. T. Gomes, R. L. Hadimani, David C. Jiles, L .Fernandes, P. B. Tavares, J. P. Araújo, A. M. L. Lopes, A. M. Pereira Jan 2018

Annealing Influence On The Magnetostructural Transition In Gd5si1.3ge2.7 Thin Films, A. L. Pires, J. H. Belo, I. T. Gomes, R. L. Hadimani, David C. Jiles, L .Fernandes, P. B. Tavares, J. P. Araújo, A. M. L. Lopes, A. M. Pereira

Ravi L Hadimani

Due to the emerging cooling possibilities at the micro and nanoscale, such as the fast heat exchange rate, the effort to synthesize and optimize the magnetocaloric materials at these scales is rapidly growing. Here, we report the effect of different thermal treatments on Gd5Si1.3Ge2.7 thin film in order to evaluate the correlation between the crystal structure, magnetic phase transition and magnetocaloric effect. For annealing temperatures higher than 773 K, the samples showed a typical paramagnetic behavior. On the other hand, annealing below 773 K promoted the suppression of the magnetostructural transition at 190 K, while the magnetic transition ...


Magnetic Interaction And Electronic Transport In La0.4bi0.6mn0.5ti0.5o3 Manganite, Vijaylakshmi Dayal, Punith Kumar V., Ravi L. Hadimani, E. A. Balfour, H. Fu, David C. Jiles Jan 2018

Magnetic Interaction And Electronic Transport In La0.4bi0.6mn0.5ti0.5o3 Manganite, Vijaylakshmi Dayal, Punith Kumar V., Ravi L. Hadimani, E. A. Balfour, H. Fu, David C. Jiles

Ravi L Hadimani

We report magnetic interactions and electronic transport properties in La0.4Bi0.6Mn0.5Ti0.5O3 perovskite manganite synthesized using solid-state route. After characterizing the samples structurally, the systematic investigations of magnetic and electrical transport behaviors have been undertaken. It has been observed that at low temperatures near TC, the sample is magnetically frustrated leading to the second-order magnetic transition. A justification for the observed magnetic behavior has been explained based on Arrott's plot study. The resistivity as a function of temperature in the absence and the presence of applied magnetic field suggests semiconducting nature of the sample. The conduction of ...


Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock Dec 2017

Generalized Ellipsometry On Complex Nanostructures And Low-Symmetry Materials, Alyssa Mock

Theses, Dissertations, and Student Research from Electrical & Computer Engineering

In this thesis, complex anisotropic materials are investigated and characterized by generalized ellipsometry. In recent years, anisotropic materials have gained considerable interest for novel applications in electronic and optoelectronic devices, mostly due to unique properties that originate from reduced crystal symmetry. Examples include white solid-state lighting devices which have become ubiquitous just recently, and the emergence of high-power, high-voltage electronic transistors and switches in all-electric vehicles. The incorporation of single crystalline material with low crystal symmetry into novel device structures requires reconsideration of existing optical characterization approaches. Here, the generalized ellipsometry concept is extended to include applications for materials with ...


Free-Space Measurements Of Dielectrics And Three-Dimensional Periodic Metamaterials, Clifford E. Kintner Dec 2017

Free-Space Measurements Of Dielectrics And Three-Dimensional Periodic Metamaterials, Clifford E. Kintner

Theses and Dissertations

This thesis presents the free-space measurements of a periodic metamaterial structure. The metamaterial unit cell consists of two dielectric sheets intersecting at 90 degrees. The dielectric is a polyetherimide-based material 0.001” thick. Each sheet has a copper capacitively-loaded loop (CLL) structure on the front and a cut-wire structure on the back. Foam material is used to support the unit cells. The unit cell repeats 40 times in the x-direction, 58 times in the y-direction and 5 times in the z-direction. The sample measures 12” × 12” × 1” in total. We use a free-space broadband system comprised of a pair of ...


Modeling And Simulation Of Iii-Nitride-Based Solar Cells Using Nextnano®, Malak Refaei Dec 2017

Modeling And Simulation Of Iii-Nitride-Based Solar Cells Using Nextnano®, Malak Refaei

Theses and Dissertations

Nextnano³ software is a well-known package for simulating semiconductor band-structures at the nanoscale and predicting the general electronic structure. In this work, it is further demonstrated as a viable tool for the simulation of III-nitride solar cells. In order to prove this feasibility, the generally accepted solar cell simulation package, PC1D, was chosen for comparison. To critique the results from both PC1D and Nextnano3, the fundamental drift-diffusion equations were used to calculate the performance of a simple p-n homojunction solar cell device analytically. Silicon was picked as the material for this comparison between the outputs of the two simulators as ...


Recursive Non-Local Means Filter For Video Denoising, Redha A. Ali, Russell C. Hardie Dec 2017

Recursive Non-Local Means Filter For Video Denoising, Redha A. Ali, Russell C. Hardie

Electrical and Computer Engineering Faculty Publications

In this paper, we propose a computationally efficient algorithm for video denoising that exploits temporal and spatial redundancy. The proposed method is based on non-local means (NLM). NLM methods have been applied successfully in various image denoising applications. In the single-frame NLM method, each output pixel is formed as a weighted sum of the center pixels of neighboring patches, within a given search window.

The weights are based on the patch intensity vector distances. The process requires computing vector distances for all of the patches in the search window. Direct extension of this method from 2D to 3D, for video ...


Speckle Effects In Target-In-The-Loop Laser Beam Projection Systems, Mikhail Vorontsov Dec 2017

Speckle Effects In Target-In-The-Loop Laser Beam Projection Systems, Mikhail Vorontsov

Electro-Optics and Photonics Faculty Publications

In target-in-the-loop laser beam projection scenarios typical of remote sensing, directed energy, and adaptive optics applications, a transmitted laser beam propagates through an optically inhomogeneous medium toward a target, scatters off the target’s rough surface, and returns back to the transceiver plane. Coherent beam scattering off the randomly rough surface results in strong speckle modulation in the transceiver plane. This speckle modulation has been a long-standing challenge that limits performance of remote sensing, active imaging, and adaptive optics techniques. Using physics-based models of laser beam scattering off a randomly rough surface, we show that received speckle-field spatial and temporal ...


Analysis Of The Joint Impact Of Atmospheric Turbulence And Refractivity On Laser Beam Propagation, Victor A. Kulikov, Mikhail Vorontsov Nov 2017

Analysis Of The Joint Impact Of Atmospheric Turbulence And Refractivity On Laser Beam Propagation, Victor A. Kulikov, Mikhail Vorontsov

Electro-Optics and Photonics Faculty Publications

A laser beam propagation model that accounts for the joint effect of atmospheric turbulence and refractivity is introduced and evaluated through numerical simulations. In the numerical analysis of laser beam propagation, refractive index inhomogeneities along the atmospheric propagation path were represented by a combination of the turbulence-induced random fluctuations described in the framework of classical Kolmogorov turbulence theory and large-scale refractive index variations caused by the presence of an inverse temperature layer. The results demonstrate that an inverse temperature layer located in the vicinity of a laser beam’s propagation path may strongly impact the laser beam statistical characteristics including ...


Combating Ground Reflection For Wireless Sensors, Ashutosh Tadkase, Nagarjun Srinivasan, Robert A. Iannucci Oct 2017

Combating Ground Reflection For Wireless Sensors, Ashutosh Tadkase, Nagarjun Srinivasan, Robert A. Iannucci

Bob Iannucci

Low-power sensing and communication technologies have evolved to the point where it is feasible to install intelligent, wirelessly-connected sensors pervasively on roadways to enable precise, real-time monitoring of traffic flows. Efficient operation of the sensing, computing and communications subsystems in these devices offers the possibility of battery lifetimes comparable to replacement cycles for normal raised pavement markers, making install-and-forget sensing a practical reality. But such unobtrusive mounting on the road surface brings with it an inherent problem. Data signals sent from the wireless devices in these sensors suffer from the effect of ground reflection which distort the antenna’s pattern ...


Spatial Division Multiplexing Using Ince-Gaussian Beams, Sahil Sakpal Aug 2017

Spatial Division Multiplexing Using Ince-Gaussian Beams, Sahil Sakpal

Electrical Engineering Theses and Dissertations

In space division multiplexing (SDM) the spatial modes of a multimode optical fiber are used as individual data channels. SDM gives another degree of freedom over wavelength for increasing data transmission rates. As a result, SDM is a potential solution for more than 400Gbit/s requirements in data centers where scaling data transmission rates with parallel single mode optical fibers is currently ubiquitous. However, due to mode coupling, i.e., spatial modes exchange of power, SDM may require multiple inputs multiple output digital signal processing (MIMO-DSP) to mitigate resulting mode crosstalk, the cost and complexity of which may be prohibited ...


Gui For Mri-Compatible Neural Stimulator And Recorder, Soo Han Soon, Nishant Babaria, Ranajay Mandal, Zhongming Liu Aug 2017

Gui For Mri-Compatible Neural Stimulator And Recorder, Soo Han Soon, Nishant Babaria, Ranajay Mandal, Zhongming Liu

The Summer Undergraduate Research Fellowship (SURF) Symposium

Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) are useful tools to analyze brain activities given active stimulation. However, the electromagnetic noise from the MRI distorts the brain signal recording and damages the subject with excessive heat generated on the electrodes attached to the skin. MRI-compatible recording and stimulation systems previously developed at LIBI lab were capable of removing the electromagnetic noise during the imaging process. Previously, the hardware systems had required the integrative software that could control both circuits simultaneously and enable users to easily change recording and stimulation parameters. Graphical user interface (GUI) programmed with computer language informed ...


Two Senior Projects: 2.4 Ghz, 40% Efficiency Radio Frequency Amplifier, Ieee Design Contest, & Design And Implementation Of A Software Costas Loop For Audio Frequencies, Robert J. Tong Aug 2017

Two Senior Projects: 2.4 Ghz, 40% Efficiency Radio Frequency Amplifier, Ieee Design Contest, & Design And Implementation Of A Software Costas Loop For Audio Frequencies, Robert J. Tong

Electrical Engineering

How to Read this Document:

This document combines two senior project reports. The first senior project documents designing a class AB RF amplifier. The second, discusses the design and implementation of a software Costas loop for audio frequencies. The first report begins on the next page, while the Costas loop report starts on page 24. The two reports are orthogonal from one another. It is not a prerequisite to read the RF amplifier report before reading the Costas loop report. This document is merely two reports combined into one document. The second report, about the Costas loop, was written as ...


Optimization Of Miniaturized Resonant Microwave Cavities For Use In Q-Thrusters, Joshua Steven Pennington Aug 2017

Optimization Of Miniaturized Resonant Microwave Cavities For Use In Q-Thrusters, Joshua Steven Pennington

Theses and Dissertations

A gedankenexperiment was considered to compare a hypothetical thruster that used no reaction mass to propulsion methods currently in use. A brief discussion of previous research work done on closed resonant cavity thrust devices was conducted. Using the previous work as a template, a simulation plan was devised. Computational models of resonant microwave cavities were constructed and investigated using COMSOL software. These COMSOL simulations were verified against known analytical solutions using Matlab software as a computational tool. Multiphysics simulations were created to study the microwave heating environment of the resonant cavities. From the COMSOL study outputs, the electromagnetic field magnitude ...


Si-Based Germanium Tin Semiconductor Lasers For Optoelectronic Applications, Sattar H. Sweilim Al-Kabi Aug 2017

Si-Based Germanium Tin Semiconductor Lasers For Optoelectronic Applications, Sattar H. Sweilim Al-Kabi

Theses and Dissertations

Silicon-based materials and optoelectronic devices are of great interest as they could be monolithically integrated in the current Si complementary metal-oxide-semiconductor (CMOS) processes. The integration of optoelectronic components on the CMOS platform has long been limited due to the unavailability of Si-based laser sources. A Si-based monolithic laser is highly desirable for full integration of Si photonics chip. In this work, Si-based germanium-tin (GeSn) lasers have been demonstrated as direct bandgap group-IV laser sources. This opens a completely new avenue from the traditional III-V integration approach. In this work, the material and optical properties of GeSn alloys were comprehensively studied ...


Laser-Assisted Metal Organic Chemical Vapor Deposition Of Gallium Nitride, Hossein Rabiee Golgir Jul 2017

Laser-Assisted Metal Organic Chemical Vapor Deposition Of Gallium Nitride, Hossein Rabiee Golgir

Theses, Dissertations, and Student Research from Electrical & Computer Engineering

Due to its unique properties, gallium nitride is of great interest in industry applications including optoelectronics (LEDs, diode laser, detector), high power electronics, and RF and wirelss communication devices. The inherent shortcomings of current conventional deposition methods and the ever-increasing demand for gallium nitride urge extended efforts for further enhancement of gallium nitride deposition. The processes of conventional methods for gallium nitride deposition, which rely on thermal heating, are inefficient energy coupling routes to drive gas reactions. A high deposition temperature (1000-1100 °C) is generally required to overcome the energy barriers to precursor adsorption and surface adatom migration. However, there ...


Microwave Interferometry Diagnostic Applications For Measurements Of Explosives, Loren A. Kline Jul 2017

Microwave Interferometry Diagnostic Applications For Measurements Of Explosives, Loren A. Kline

Master's Theses and Project Reports

Microwave interferometry (MI) is a Doppler based diagnostic tool used to measure the detonation velocity of explosives, which has applications to explosive safety. The geometry used in existing MI experiments is cylindrical explosives pellets layered in a cylindrical case. It is of interest to Lawrence Livermore National Labs to measure additional geometries that may be overmoded, meaning that the geometries propagate higher-order transverse electromagnetic waves. The goal of my project is to measure and analyze the input reflection from a novel structure and to find a good frequency to use in an experiment using this structure. Two methods of determining ...


Recursive Non-Local Means Filter For Video Denoising With Poisson-Gaussian Noise, Redha A. Almahdi, Russell C. Hardie Jun 2017

Recursive Non-Local Means Filter For Video Denoising With Poisson-Gaussian Noise, Redha A. Almahdi, Russell C. Hardie

Russell C. Hardie

In this paper, we describe a new recursive Non-Local means (RNLM) algorithm for video denoising that has been developed by the current authors. Furthermore, we extend this work by incorporating a Poisson-Gaussian noise model. Our new RNLM method provides a computationally efficient means for video denoising, and yields improved performance compared with the single frame NLM and BM3D benchmarks methods. Non-Local means (NLM) based methods of denoising have been applied successfully in various image and video sequence denoising applications. However, direct extension of this method from 2D to 3D for video processing can be computationally demanding. The RNLM approach takes ...


On The Simulation And Mitigation Of Anisoplanatic Optical Turbulence For Long Range Imaging, Russell C. Hardie, Daniel A. Lemaster Jun 2017

On The Simulation And Mitigation Of Anisoplanatic Optical Turbulence For Long Range Imaging, Russell C. Hardie, Daniel A. Lemaster

Russell C. Hardie

We describe a numerical wave propagation method for simulating long range imaging of an extended scene under anisoplanatic conditions. Our approach computes an array of point spread functions (PSFs) for a 2D grid on the object plane. The PSFs are then used in a spatially varying weighted sum operation, with an ideal image, to produce a simulated image with realistic optical turbulence degradation. To validate the simulation we compare simulated outputs with the theoretical anisoplanatic tilt correlation and differential tilt variance. This is in addition to comparing the long- and short-exposure PSFs, and isoplanatic angle. Our validation analysis shows an ...


Analysis Of Various Classification Techniques For Computer Aided Detection System Of Pulmonary Nodules In Ct, Barath Narayanan Narayanan, Russell C. Hardie, Temesguen Messay Jun 2017

Analysis Of Various Classification Techniques For Computer Aided Detection System Of Pulmonary Nodules In Ct, Barath Narayanan Narayanan, Russell C. Hardie, Temesguen Messay

Russell C. Hardie

Lung cancer is the leading cause of cancer death in the United States. It usually exhibits its presence with the formation of pulmonary nodules. Nodules are round or oval-shaped growth present in the lung. Computed Tomography (CT) scans are used by radiologists to detect such nodules. Computer Aided Detection (CAD) of such nodules would aid in providing a second opinion to the radiologists and would be of valuable help in lung cancer screening. In this research, we study various feature selection methods for the CAD system framework proposed in FlyerScan. Algorithmic steps of FlyerScan include (i) local contrast enhancement (ii ...


Comparing Multiple Turbulence Restoration Algorithms Performance On Noisy Anisoplanatic Imagery, Michael Armand Rucci, Russell C. Hardie, Alexander J. Dapore Jun 2017

Comparing Multiple Turbulence Restoration Algorithms Performance On Noisy Anisoplanatic Imagery, Michael Armand Rucci, Russell C. Hardie, Alexander J. Dapore

Russell C. Hardie

In this paper, we compare the performance of multiple turbulence mitigation algorithms to restore imagery degraded by atmospheric turbulence and camera noise. In order to quantify and compare algorithm performance, imaging scenes were simulated by applying noise and varying levels of turbulence. For the simulation, a Monte-Carlo wave optics approach is used to simulate the spatially and temporally varying turbulence in an image sequence. A Poisson-Gaussian noise mixture model is then used to add noise to the observed turbulence image set. These degraded image sets are processed with three separate restoration algorithms: Lucky Look imaging, bispectral speckle imaging, and a ...


Recursive Non-Local Means Filter For Video Denoising, Redha A. Ali, Russell C. Hardie Jun 2017

Recursive Non-Local Means Filter For Video Denoising, Redha A. Ali, Russell C. Hardie

Russell C. Hardie

In this paper, we propose a computationally efficient algorithm for video denoising that exploits temporal and spatial redundancy. The proposed method is based on non-local means (NLM). NLM methods have been applied successfully in various image denoising applications. In the single-frame NLM method, each output pixel is formed as a weighted sum of the center pixels of neighboring patches, within a given search window. The weights are based on the patch intensity vector distances. The process requires computing vector distances for all of the patches in the search window. Direct extension of this method from 2D to 3D, for video ...


Block Matching And Wiener Filtering Approach To Optical Turbulence Mitigation And Its Application To Simulated And Real Imagery With Quantitative Error Analysis, Russell C. Hardie, Michael Armand Rucci, Barry K. Karch, Alexander J. Dapore Jun 2017

Block Matching And Wiener Filtering Approach To Optical Turbulence Mitigation And Its Application To Simulated And Real Imagery With Quantitative Error Analysis, Russell C. Hardie, Michael Armand Rucci, Barry K. Karch, Alexander J. Dapore

Russell C. Hardie

We present a block-matching and Wiener filtering approach to atmospheric turbulence mitigation for long-range imaging of extended scenes. We evaluate the proposed method, along with some benchmark methods, using simulated and real-image sequences. The simulated data are generated with a simulation tool developed by one of the authors. These data provide objective truth and allow for quantitative error analysis. The proposed turbulence mitigation method takes a sequence of short-exposure frames of a static scene and outputs a single restored image. A block-matching registration algorithm is used to provide geometric correction for each of the individual input frames. The registered frames ...


Simulation Of Anisoplanatic Imaging Through Optical Turbulence Using Numerical Wave Propagation With New Validation Analysis, Russell C. Hardie, Jonathan D. Power, Daniel A. Lemaster, Douglas R. Droege, Szymon Gladysz, Santasri Bose-Pillai Jun 2017

Simulation Of Anisoplanatic Imaging Through Optical Turbulence Using Numerical Wave Propagation With New Validation Analysis, Russell C. Hardie, Jonathan D. Power, Daniel A. Lemaster, Douglas R. Droege, Szymon Gladysz, Santasri Bose-Pillai

Russell C. Hardie

We present a numerical wave propagation method for simulating imaging of an extended scene under anisoplanatic conditions. While isoplanatic simulation is relatively common, few tools are specifically designed for simulating the imaging of extended scenes under anisoplanatic conditions. We provide a complete description of the proposed simulation tool, including the wave propagation method used. Our approach computes an array of point spread functions (PSFs) for a two-dimensional grid on the object plane. The PSFs are then used in a spatially varying weighted sum operation, with an ideal image, to produce a simulated image with realistic optical turbulence degradation. The degradation ...


Differential Tilt Variance Effects Of Turbulence In Imagery: Comparing Simulation With Theory, Daniel A. Lemaster, Russell C. Hardie, Szymon Gladysz, Matthew D. Howard, Michael Armand Rucci, Matthew E. Trippel, Jonathan D. Power, Barry K. Karch Jun 2017

Differential Tilt Variance Effects Of Turbulence In Imagery: Comparing Simulation With Theory, Daniel A. Lemaster, Russell C. Hardie, Szymon Gladysz, Matthew D. Howard, Michael Armand Rucci, Matthew E. Trippel, Jonathan D. Power, Barry K. Karch

Russell C. Hardie

Differential tilt variance is a useful metric for interpreting the distorting effects of turbulence in incoherent imaging systems. In this paper, we compare the theoretical model of differential tilt variance to simulations. Simulation is based on a Monte Carlo wave optics approach with split step propagation. Results show that the simulation closely matches theory. The results also show that care must be taken when selecting a method to estimate tilts.


Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles Jun 2017

Second Order Phase Transition Temperature Of Single Crystals Of Gd5si1.3ge2.7 And Gd5si1.4ge2.6, Ravi L. Hadimani, Yevgen Melikhov, Deborah L. Schlagel, Thomas A. Lograsso, Kevin W. Dennis, R. William Mccallum, David C. Jiles

Thomas A. Lograsso

Gd5(Six Ge 1−x)4 has mixed phases in the composition range 0.32 < x < 0.41, which have not been widely studied. In this paper, we have synthesized and indexed single crystal samples of Gd5Si1.3 Ge 2.7 and Gd5Si1.4 Ge 2.6. We have investigated the first order and second orderphase transition temperatures of these samples using magnetic moment vs. temperature andmagnetic moment vs. magnetic field at different temperatures. We have used a modified Arrott plot technique that was developed and reported by us previously to determine the “hidden” second order phase transition temperature of ...


Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo Jun 2017

Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo

Thomas A. Lograsso

Magnetic refrigeration based on the magnetocaloric effect is one of the best alternatives to compete with vapor-compression technology. Despite being already in its technology transfer stage, there is still room for optimization, namely, on the magnetic responses of the magnetocaloric material. In parallel, the demand for different magnetostrictive materials has been greatly enhanced due to the wide and innovative range of technologies that emerged in the last years (from structural evaluation to straintronics fields). In particular, the Gd5(Six Ge1−x)4 compounds are a family of well-known alloys that present both giant magnetocaloric and colossal magnetostriction effects. Despite their ...


A Graph-Based Formulation For Computational Characterization Of Bulk Heterojunction Morphology, Olga Wodo, Srikanta Tirthapura, Sumit Chaudhary, Baskar Ganapathysubramanian Jun 2017

A Graph-Based Formulation For Computational Characterization Of Bulk Heterojunction Morphology, Olga Wodo, Srikanta Tirthapura, Sumit Chaudhary, Baskar Ganapathysubramanian

Srikanta Tirthapura

To improve the efficiency of organic solar cells, it is essential to understand the role of morphology and to tailor fabrication process to get desired morphologies. In this context, a comprehensive set of computational tools to quantify and classify the 2D/3D heterogeneous internal structure of thin films is invaluable. We present a graph-based framework to efficiently compute a broad suite of physically meaningful morphology descriptors. These morphology descriptors are further classified according to the physical subprocesses within OSCs – photon absorption, exciton diffusion, charge separation, and charge transport. This approach is motivated by the equivalence between a discretized 2D/3D ...


Computational Eddy-Current Probe Model For Composites, Metals And Semiconductors, L. David Sabbagh, John R. Bowler, Harold A. Sabbagh Jun 2017

Computational Eddy-Current Probe Model For Composites, Metals And Semiconductors, L. David Sabbagh, John R. Bowler, Harold A. Sabbagh

John R. Bowler

A comprehensive computer code for research and design studies in electromagnetic NDE is now at an advanced stage of development. It has the capability of predicting the impedance characteristics of fully three-dimensional eddy-current probes in the presence of metals, semiconductors and advanced composites. By using a combination of the conjugate gradient method applied to a matrix and fast Fourier transform techniques, the resulting algorithm is both efficient in CPU time and has modest storage requirements. The theoretical model was presented in [1].


Eddy Current Probe Impedances Due To Interaction With Advanced Composites, John R. Bowler, Harold A. Sabbagh, L. David Sabbagh Jun 2017

Eddy Current Probe Impedances Due To Interaction With Advanced Composites, John R. Bowler, Harold A. Sabbagh, L. David Sabbagh

John R. Bowler

Electromagnetic fields in uniaxial conductors have been studied in order to examine the induced current distributions excited by external alternating current sources. The problem is motivated by the need to evaluate eddy current testing techniques for the inspection of composites such as graphite-epoxy or boron-epoxy. In particular it is important to understand how eddy currents behave in anisotropic materials, especially uniaxial conductors in which the conductivity in the axial direction may be several hundred times greater than the transverse conductivity [1].