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2017

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Articles 1411 - 1440 of 1463

Full-Text Articles in Physics

Proton--Proton And Proton--Antiproton Differential Elastic Cross Sections Modeling At High And Ultra-High Energies Using A Hybrid Computing Paradigm, Elsayed Eldahshan Jan 2017

Proton--Proton And Proton--Antiproton Differential Elastic Cross Sections Modeling At High And Ultra-High Energies Using A Hybrid Computing Paradigm, Elsayed Eldahshan

Turkish Journal of Physics

This work presents a hybrid computing technique for modeling the differential elastic cross section of both proton--proton ``pp'' and proton--antiproton ``pp(bar)'' collisions from high to ultra-high energy regions (from 13.9 GeV to 14 TeV) as a function of the center-of-mass energy ``s'' squared and four momentum transfer squared ``t''. We proposed a genetic algorithm (GA) and support vector regression (SVR) hybrid techniques to calculate and predict the ``differential elastic cross section'' of both ``pp'' and ``pp(bar)''. Our proposed GA-SVR hybrid model shows a good match to the available experimental data, as well as predicting the latest and future ``TOTEM'' experiments …

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Magnetized Strange Quark Matter In Reconstructed $F(R,T)$ Gravity For Bianchi I And V Universes With Cosmological Constant, Can Aktaş Jan 2017

Magnetized Strange Quark Matter In Reconstructed $F(R,T)$ Gravity For Bianchi I And V Universes With Cosmological Constant, Can Aktaş

Turkish Journal of Physics

In this article, we have investigated the behaviors of magnetized strange quark matter distributions for Bianchi I and V universes in reconstructed $f?eft( R,T \right)=\alpha_{1}R+\alpha_{2}f_{3}(T)$ gravity (here $\alpha_{1}$ and $\alpha_{2}$ are constants; $f_{3}(T)$ is an arbitrary function of $T)$. To get solutions of the field equations we have used a deceleration parameter and the equation of state for strange quark matter. The new represented $f(R,T)$ model includes two models of Harko et al. and transforms to general relativity. When $t\to ınfty $, we get the dark energy model ($p=-\rho )$ in reconstructed $f?eft( R,T \right)=\alpha _{1}R+\alpha_{2}f_{3}(T)$ gravity. However, we obtain …

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Optical Visible Wavelength Region Selective Reflector Design For Photovoltaic Cells Using Photonic Crystal, Veysel Korkmaz, Ali̇ Çeti̇n Jan 2017

Optical Visible Wavelength Region Selective Reflector Design For Photovoltaic Cells Using Photonic Crystal, Veysel Korkmaz, Ali̇ Çeti̇n

Turkish Journal of Physics

In this study, we have proposed an optical broadband angular reflector having a band selective feature and high reflectivity rate for photovoltaic implementations by using a photonic crystal structure made of two different dielectric layers. This paper presents new and useful information about a reflector that was designed by using a periodic structure composed of two Si based layers for the visible range in the solar spectrum region. The system has been adjusted in such a way that it could cover a wide wavelength area between the photonic band gaps at nearly λ ≈ 300-800 nm. We have tested the …

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Deconvolution Analysis Of Thermoluminescent Glow Curves In Various Commercial Dosimeters Using Two Different Approaches In The Framework Of The One-Trap, One-Recombination Model, Eren Şahi̇ner Jan 2017

Deconvolution Analysis Of Thermoluminescent Glow Curves In Various Commercial Dosimeters Using Two Different Approaches In The Framework Of The One-Trap, One-Recombination Model, Eren Şahi̇ner

Turkish Journal of Physics

This paper reports kinetic analysis on the thermoluminescence (TL) glow peaks of various widespread luminescence dosimeters. A common general order kinetic (GOK) approximation and a relatively recently suggested Lambert W-function equation were used. The activation energies and the order of kinetic parameters are the main subjects of the present study. According to the results of this study, the activation energies of the main dosimetric peaks are estimated as 2.05 $\pm $ 0.11, eV, 1.23 $\pm $ 0.05 eV, and 1.11 $\pm $ 0.06 eV for LiF based dosimeters (TLD100, TLD600, TLD700), Al$_{2}$O$_{3}$:C (TLD500), and BeO dosimeters, respectively. Moreover, a number …

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Monte Carlo Simulation Of A Medical Linear Accelerator For Filtered And Fff Systems, Çağri Yazğan, Yi̇ği̇t Çeçen Jan 2017

Monte Carlo Simulation Of A Medical Linear Accelerator For Filtered And Fff Systems, Çağri Yazğan, Yi̇ği̇t Çeçen

Turkish Journal of Physics

In order to simulate radiation transport, various algorithms, codes, and programs have been developed. In this study Monte Carlo N-particle code is used to simulate a medical electron linear accelerator gantry for research purposes. Detailed geometry of the LINAC head and water phantom are modeled and simulated for calculations. Analyses are made for filtered and flattening filter-free (FFF) systems. Percent depth dose and dose profile measurements are calculated with Monte Carlo simulations and compared with experimental and theoretical values for quality assurance of the model. Flux, dose, and spectrum analyses are performed for filtered and FFF systems separately. In this …

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Elastic Scattering Analysis Of $^{12}$C+$^{24}$Mg By Wkb Method, Orhan Bayrak Jan 2017

Elastic Scattering Analysis Of $^{12}$C+$^{24}$Mg By Wkb Method, Orhan Bayrak

Turkish Journal of Physics

We present the elastic scattering analysis of the $^{12}$C+$^{24}$Mg system by using the WKB approximation method within the framework of the barrier-internal wave decomposition over a wide range of energy from E$_{lab}$ = 16 MeV to 24.0 MeV. The results obtained are good agreement with the quantum mechanical (QM) calculation and experimental data.

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Calculation Of The Frequency Shifts And Damping Constant For The Raman Modes (A$_{1g}$, B$_{1})$ Near The Tetragonal-Cubic Transition In Srtio$_{3}$, Ali̇ Ki̇raci, Hasan Hami̇t Yurtseven Jan 2017

Calculation Of The Frequency Shifts And Damping Constant For The Raman Modes (A$_{1g}$, B$_{1})$ Near The Tetragonal-Cubic Transition In Srtio$_{3}$, Ali̇ Ki̇raci, Hasan Hami̇t Yurtseven

Turkish Journal of Physics

Raman shifts of the soft mode A$_{1g}$ and the B$_{1}$ mode are calculated at various pressures at room temperature for the cubic-tetragonal transition (P$_{C}$ = 9.5 GPa) in SrTiO$_{3}$. This calculation is performed using the observed volume data through the mode Grüneisen parameters of A$_{1g}$ and B$_{1}$, which vary with pressure, by fitting to the experimental wavenumbers in this crystalline system. Calculated Raman shifts are then used as order parameters to predict the pressure dependence of the damping constant and the inverse relaxation time for the cubic-tetragonal transition in SrTiO$_{3}$. Our predictions from the pseudospin-phonon coupling and the energy fluctuation …

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Synthesis Of Ni-Fe Thin Films By Electrochemical Deposition Technique And Characterization Of Their Microstructures And Surface Morphologies, Umut Saraç, Mali̇k Kaya, Mevlana Celaletti̇n Baykul Jan 2017

Synthesis Of Ni-Fe Thin Films By Electrochemical Deposition Technique And Characterization Of Their Microstructures And Surface Morphologies, Umut Saraç, Mali̇k Kaya, Mevlana Celaletti̇n Baykul

Turkish Journal of Physics

Microstructural features and surface morphologies of Ni-Fe thin films fabricated by the electrochemical deposition technique have been experimentally studied. Ni-Fe thin films have been deposited under different deposition potentials and FeSO$_{4}$ concentrations. Energy dispersive X-ray measurements demonstrate that the Fe content decreases (increases) as the deposition potential (FeSO$_{4}$ concentration) is enhanced. All of the produced films exhibit an anomalous codeposition behavior. The effects of deposition potential and FeSO$_{4}$ concentrations on the degree of anomalous codeposition have been also characterized. X-ray diffraction studies reveal that the films have face-centered cubic crystallographic structures with [111] preferred crystallographic orientation regardless of the applied …

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Quark Shapes Of Most Modern Parton Distribution Functions, Hasan Oğul Jan 2017

Quark Shapes Of Most Modern Parton Distribution Functions, Hasan Oğul

Turkish Journal of Physics

Parton distribution functions (PDFs) describe the internal structure of the proton and are necessary inputs to almost all theory predictions of hadron colliders. One way to do a precise measurement of a PDF is to measure the lepton charge asymmetry of W boson where u$\bar{d}\to W^{+}$ and $d\bar{u}\to W^{-}$. Therefore, u, d, $\bar{u}$, and $\bar{d}$ quark shapes of the most modern PDF models (NNPDF3.1, NNPDF3.0, CT14, MMHT2014, and HERAPDF2.0) are inspected using the APFEL online cluster in this paper. The ratio of $d$ to $u$ is further investigated since the charge asymmetry is sensitive to the value of $d$ over …

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Applying A Self-Feedback Method To Control Chaos In The Buck Converter, Mei Mei Jia Jan 2017

Applying A Self-Feedback Method To Control Chaos In The Buck Converter, Mei Mei Jia

Turkish Journal of Physics

Chaos exists in the Buck converter due to the switching action of the controlled switch and this nonlinear phenomenon results in unreliable working performances. Hence, this paper uses a self-feedback control method with two adjustable parameters to suppress the chaotic behavior in the Buck converter. First, the self-feedback control method is presented by introducing a generic second-order chaotic system. Then, from the perspective of transfer functions obtained in terms of the piecewise linear model of the controlled Buck converter, effects of controller's parameters on system performances are discussed. On the basis of the Jacobian matrix of the discrete iterative mapping …

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Simulation Study On Jleic High Energy Bunched Electron Cooling, H. Zhang, Y. Roblin, Y. Zhang, Ya. Derbenev, S. Benson, R. Li, J. Chen, H. Huang, L. Luo Jan 2017

Simulation Study On Jleic High Energy Bunched Electron Cooling, H. Zhang, Y. Roblin, Y. Zhang, Ya. Derbenev, S. Benson, R. Li, J. Chen, H. Huang, L. Luo

Mathematics & Statistics Faculty Publications

In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as …

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Multiplicative Noise Removal With A Sparsity-Aware Optimization Model, Jian Lu, Lixin Shen, Chen Xu, Yuesheng Xu Jan 2017

Multiplicative Noise Removal With A Sparsity-Aware Optimization Model, Jian Lu, Lixin Shen, Chen Xu, Yuesheng Xu

Mathematics & Statistics Faculty Publications

Restoration of images contaminated by multiplicative noise (also known as speckle noise) is a key issue in coherent image processing. Notice that images under consideration are often highly compressible in certain suitably chosen transform domains. By exploring this intrinsic feature embedded in images, this paper introduces a variational restoration model for multiplicative noise reduction that consists of a term reflecting the observed image and multiplicative noise, a quadratic term measuring the closeness of the underlying image in a transform domain to a sparse vector, and a sparse regularizer for removing multiplicative noise. Being different from popular existing models which focus …

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Manifestations Of Classical Physics In The Quantum Evolution Of Correlated Spin States In Pulsed Nmr Experiments, Martin K. Ligare Jan 2017

Manifestations Of Classical Physics In The Quantum Evolution Of Correlated Spin States In Pulsed Nmr Experiments, Martin K. Ligare

Faculty Journal Articles

Multiple-pulse NMR experiments are a powerful tool for the investigation of mole- cules with coupled nuclear spins. The product operator formalism provides a way to understand the quantum evolution of an ensemble of weakly coupled spins in such experiments using some of the more intuitive concepts of classical physics and semi- classical vector representations. In this paper I present a new way in which to inter- pret the quantum evolution of an ensemble of spins. I recast the quantum problem in terms of mixtures of pure states of two spins whose expectation values evolve identi- cally to those of classical …

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Resonant Excitation Spectroscopy And Photon Statistics Of Self-Assembled Semiconductor Quantum Dots, Disheng Chen Jan 2017

Resonant Excitation Spectroscopy And Photon Statistics Of Self-Assembled Semiconductor Quantum Dots, Disheng Chen

Graduate Theses, Dissertations, and Problem Reports (ETD)

Light-matter interactions in semiconductor nanostructures have attracted significant research interest because of both fundamental physics questions and practical concerns. Epitaxially grown quantum dots (QDs), with their narrow emission linewidths and atom-like density of states in a solid state system, are archetypical elements of study and are potentially useful for many applications, such as on-demand single photon emitters [1,2], efficient entangled photon-pair sources [3,4], and cavity quantum electrodynamics (QED) research [5–11]. Most experiments employ resonant or near-resonant excitation to directly interact with the bound states, which enables high excitation efficiency, precise control of quantum states, and minimal disturbance of the local …

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Study Of Nano-Bio Interfaces In Nano-Bio Conjugates: Nanoparticles Of Zinc Oxide (Zno) And Biomolecules Of Glucose, Cytosine, And Thymine, Bithi Paul Jan 2017

Study Of Nano-Bio Interfaces In Nano-Bio Conjugates: Nanoparticles Of Zinc Oxide (Zno) And Biomolecules Of Glucose, Cytosine, And Thymine, Bithi Paul

Graduate Theses/Dissertations

Nano conjugates, composites of inorganic nanomaterials and bio molecules such as DNA, RNA and proteins, establish a sequence of wide varieties of nano-bio boundaries. The formation of these boundaries strongly depends on bio physicochemical reaction of biomolecules coated on the surface of nanomaterials. I am investigating various nano-bio conjugates consisting of zinc oxide (ZnO) nanoparticles with simple biomolecules including glucose and the nitrogenous bases of DNA such as cytosine and thymine. All nano-bio conjugates were fabricated using a standard bio-chemical synthesis process. Structural, physical, bio-chemical interface properties of nano-bio composites were probed using X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence …

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A Review Of The Recommendations Governing Quality Assurance Of Ultrasound Systems Used For Guidance In Prostate Brachytherapy, Andrea Jane Doyle, Deirdre King, Jacinta Browne Jan 2017

A Review Of The Recommendations Governing Quality Assurance Of Ultrasound Systems Used For Guidance In Prostate Brachytherapy, Andrea Jane Doyle, Deirdre King, Jacinta Browne

Articles

Ultrasound guided brachytherapy for the treatment of prostate cancer has become a routine treatment option, due to many benefits including patient recovery and dose localisation [1]; however it is not clear whether the standards which govern the image quality for these systems are adequate. Upon review of the recommended standards for ultrasound systems used in prostate brachytherapy procedures, the recommended tests do not appear to be specific to the clinical application of ultrasound guided prostate brachytherapy. Rather they are generic and similar to those recommended for other clinical applications such as general abdominal scanning [2]. Furthermore, there is growing evidence …

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Broadband Acoustic Measurement Of The Agar-Based Tissue Mimicking Material: A Longitudinal Study, A. Rabell-Montiel, Jacinta Browne, S. D. Pye, T. A. Anderson, C. Moran Jan 2017

Broadband Acoustic Measurement Of The Agar-Based Tissue Mimicking Material: A Longitudinal Study, A. Rabell-Montiel, Jacinta Browne, S. D. Pye, T. A. Anderson, C. Moran

Articles

Commercially available ultrasound quality assurance test phantoms rely on the long-term acoustic stability of the tissue-mimicking-material (TMM). Measurement of the acoustic properties of the TMM can be technically challenging, and it is important to ensure its stability. The standard technique is to film-wrap samples of TMM and to measure the acoustic properties in a water bath. In this study, a modified technique was proposed whereby the samples of TMM are measured in a preserving fluid that is intended to maintain their characteristics. The acoustic properties were evaluated using a broadband pulse-echo substitution technique over the frequency range 4.5–50 MHz at …

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Evaluation Of The Effect Of Plasma Treatment Frequency On The Activation Of Polymer Particles, Hisham Abourayana, Vladimir Milosavljevic, Peter Dobbyn, Denis Dowling Jan 2017

Evaluation Of The Effect Of Plasma Treatment Frequency On The Activation Of Polymer Particles, Hisham Abourayana, Vladimir Milosavljevic, Peter Dobbyn, Denis Dowling

Articles

This study investigates the influence of treatment frequency (1–150 kHz) on the atmospheric plasma activation of both silicone and polyethylene terephthalate (PET) particles. These polymer particles with diameters in the range 3–5 mm, were treated using either helium or helium/oxygen gas mixtures, in a barrel atmospheric plasma system. The level of polymer particles activation was monitored using water contact angle measurements. The effect of plasma treatment frequency on barrel heating was monitored using an infrared thermographic camera, the maximum barrel temperature after 15 min treatment was found to be 98 °C at a frequency of 130 kHz. Optical emission spectroscopy …

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Advancing Vibrational Spectroscopy For Cellular And Sub Cellular Analysis: Raman Spectroscopy As An In Vitro Chemotherapeutic Screeening And Assessment Protocol, Zeineb Farhane Jan 2017

Advancing Vibrational Spectroscopy For Cellular And Sub Cellular Analysis: Raman Spectroscopy As An In Vitro Chemotherapeutic Screeening And Assessment Protocol, Zeineb Farhane

Doctoral

Vibrational spectroscopy, including Raman micro-spectroscopy, has attracted considerable attention over the last few years, as a powerful, non-invasive tool for clinical applications, especially in cancer diagnosis, in vivo and ex vivo. As a molecular fingerprinting technique with optical resolution, Raman micro-spectroscopy is able to monitor biochemical processes, drug uptake, efficacy and mode of action and mechanisms of interaction of chemotherapeutic drugs at a subcellular level. In vitro applications may be more strategically achievable, and can help guide drug design and discovery, and eventually evaluate To this end, different lung cell lines were used and Raman micro-spectroscopy was coupled to valuable …

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Advancing Vibrational Spectroscopy For Cellular And Sub Cellular Analysis: Raman Spectroscopy As A Novel In Vitro Nanotoxicological Assessment Protocol, Esen Efeoglu Jan 2017

Advancing Vibrational Spectroscopy For Cellular And Sub Cellular Analysis: Raman Spectroscopy As A Novel In Vitro Nanotoxicological Assessment Protocol, Esen Efeoglu

Doctoral

This work is designed to establish a ‘High content Nanotoxicological Screening method’ using in vitro Raman microspectroscopy. The undeniable increase of nanotechnology based products has brought challenges in terms of determining their toxicological properties. Considering the total time and cost of screening nanomaterials by conventional methods, the need for a rapid, label-free technique which will provide a wide range of information on multiple parameters is unquestionable. This study investigated the applicability of Raman microspectroscopy as a High Content Screening technique to clarify cell-nanoparticle interaction by determining the localisation of the nanoparticles and consequent effects in these localised areas in terms …

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Pilot Investigation Into The Use Of An Anthropomorphic Breast Sonography Phantom As A Training And Assessment Tool, Jacinta Browne, Louise Cannon, Ronan Mcdermott, Max Ryan, Andrew J. Fagan Jan 2017

Pilot Investigation Into The Use Of An Anthropomorphic Breast Sonography Phantom As A Training And Assessment Tool, Jacinta Browne, Louise Cannon, Ronan Mcdermott, Max Ryan, Andrew J. Fagan

Articles

A device for the training and quantitative assessment of the competency of trainee radiologists in the technically challenging area of breast sonography was developed and evaluated. Currently, suitable commercially available devices are lacking, and there is a growing realization that the reliance on direct exposure to patients for learning may not represent best practice from either the trainees' or patients' perspective. Three devices (PI, PII and PIII) were designed to produce very realistic sonographic images of breast morphology with a range of embedded pathologies. The pilot evaluation used a case study research design to evaluate the role of the anthropomorphic …

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Thermal And Waveguide Optimization Of Broad Area Quantum Cascade Laser Performance, Matthew Suttinger Jan 2017

Thermal And Waveguide Optimization Of Broad Area Quantum Cascade Laser Performance, Matthew Suttinger

Electronic Theses and Dissertations

Quantum Cascade Lasers are a novel source of coherent infrared light, unique in their tunability over the mid-infrared and terahertz range of frequencies. Advances in bandgap engineering and semiconductor processing techniques in recent years have led to the development of highly efficient quantum cascade lasers capable of room temperature operation. Recent work has demonstrated power scaling with broad area quantum cascade lasers by increasing active region width beyond the standard ~10 ?m. Taking into account thermal effects caused by driving a device with electrical power, an experimentally fitted model is developed to predict the optical power output in both pulsed …

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Charge And Spin Transport In Low-Dimensional Materials, Amin Ahmadi Jan 2017

Charge And Spin Transport In Low-Dimensional Materials, Amin Ahmadi

Electronic Theses and Dissertations

My research has been focused on two main areas. First, electronic transports in chiral carbon nanotubes in the presence of charged adatoms. To study such systems we employed recursive Greens function technique to evaluate the conductance using the Landauer formula. Comparing with the experimental data, we determined the effective amplitude and the range of scattering potentials. In addition, using a similar approach we explained qualitatively an unusual conductance feature in a metallic carbon nanotube. The second part of my study was concerned to the dynamical spin injection and spin currents in low-dimensional materials. We have developed an atomistic model to …

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System For Metal Coated Fiber Fabrication, Da Zhang Jan 2017

System For Metal Coated Fiber Fabrication, Da Zhang

Electronic Theses and Dissertations

For many specific applications, such as sensors, aerospace, chemical industry, deep-well oil-field industry, metal-coated fiber shows strong abilities to satisfy people's requirement. With in-line coating technology, we are able to coat Aluminum on the fibers. Using electromagnetic induction, we can easily heat an electrically conducting thing such as a metal with the eddy current. This process is defined as Induction heating. And we will melt the Aluminum by this induction heating during drawing the fibers on the tower. Introduce the fiber tower system. The drawing process of in-line technology is formed of the following steps: Position, Melting, Forming into fibers, …

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Picosecond Yb-Doped Fiber Amplifier, Weibin Zhu Jan 2017

Picosecond Yb-Doped Fiber Amplifier, Weibin Zhu

Electronic Theses and Dissertations

Due to its versatility, rare earth doped fiber amplifier (RDFA) has attracted a lot of researchers worldwide in recent years. Depends on different kinds of rare earth ion, RDFA can be categorized into neodymium doped fiber amplifier (NDFA), erbium doped fiber amplifier (EDFA), thulium doped fiber amplifier (TDFA), and so forth. Among many kinds of RDFA, the ytterbium doped fiber amplifier (YDFA) has received even more interest, especially in high power application, mainly because of its broad gain bandwidth and high conversion efficiency which are due to its relatively simple electronic structure. The purpose of this research is to study …

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Quantification Of Non-Stoichiometry And Impurities In Transparent Yag Ceramics By Laser-Induced Breakdown Spectroscopy (Libs), Sudeep Pandey Jan 2017

Quantification Of Non-Stoichiometry And Impurities In Transparent Yag Ceramics By Laser-Induced Breakdown Spectroscopy (Libs), Sudeep Pandey

Electronic Theses and Dissertations

Transparent ceramics are an important class of optical materials with applications in street-lighting, high-strength windows, electro- and magneto-optical isolators, high-power laser gain media and nuclear radiation detectors. Compared to single-crystal growth, ceramic processing enables size scalability, near net-shape forming and prevents issues associated with dopant segregation and inhomogeneity, such as stress-induced birefringence and wavefront distortions. The fabrication of high optical grade ceramics by route of powder sintering, relies on a controlled set of techniques preventing the formation of scattering centers (pores and secondary phases) and harmful point defects (color centers, charge-carrier trapping sites). This thesis work investigates a novel approach …

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Predictive Modeling Of Functional Materials For Catalytic And Sensor Applications, Takat Rawal Jan 2017

Predictive Modeling Of Functional Materials For Catalytic And Sensor Applications, Takat Rawal

Electronic Theses and Dissertations

The research conducted in my dissertation focuses on theoretical and computational studies of the electronic and geometrical structures, and the catalytic and optical properties of functional materials in the form of nano-structures, extended surfaces, two-dimensional systems and hybrid structures. The fundamental aspect of my research is to predict nanomaterial properties through ab-initio calculations using methods such as quantum mechanical density functional theory (DFT) and kinetic Monte Carlo simulation, which help rationalize experimental observations, and ultimately lead to the rational design of materials for the electronic and energy-related applications. Focusing on the popular single-layer MoS2, I first show how its hybrid …

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Photothermal Lensing In Mid-Infrared Materials, Justin Cook Jan 2017

Photothermal Lensing In Mid-Infrared Materials, Justin Cook

Electronic Theses and Dissertations

A thorough understanding of laser-materials interactions is crucial when designing and building optical systems. An ideal test method would probe both the thermal and optical properties simultaneously for materials under large optical loads where detrimental thermal effects emerge. An interesting class of materials are those used for infrared wavelengths due to their wide spectral transmission windows and large optical nonlinearities. Since coherent sources spanning the mid-wave and long-wave infrared wavelength regions have only become widely available in the past decade, data regarding their thermal and optical responses is lacking in literature. Photothermal Lensing (PTL) technique is an attractive method for …

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Filament Wavefront Evolution, Daniel Thul Jan 2017

Filament Wavefront Evolution, Daniel Thul

Electronic Theses and Dissertations

Filamentation is a complex process that gives rise to many nonlinear interactions. However, the fundamentals of filament formation and propagation can be explained in terms of two dominant mechanisms: Kerr self-focusing and plasma defocusing. The first to occur, self-focusing, is responsible for an increase in irradiance through beam collapse. This process requires sufficient initial peak power, on the order of gigawatts for near infrared beams in air. Plasma defocusing then arrests the collapse process once the irradiance reaches the ionization threshold of the medium. These two processes balance each other in an extended plasma channel known as a filament. A …

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Growth And Doping Of Mos2 Thin Films For Electronic And Optoelectronic Applications, Hussain Abouelkhair Jan 2017

Growth And Doping Of Mos2 Thin Films For Electronic And Optoelectronic Applications, Hussain Abouelkhair

Electronic Theses and Dissertations

MoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning electron microscope images revealed the growth of microdomes of MoS2 on top of a smooth MoS2 film. These microdomes are very promising as a broadband omnidirectional light trap …

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