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Articles 61 - 85 of 85
Full-Text Articles in Physical Sciences and Mathematics
Generalized Neuron Based Secure Media Access Control Protocol For Wireless Sensor Networks, Raghavendra V. Kulkarni, Ganesh K. Venayagamoorthy, Abhishek V. Thakur, Sanjay Kumar Madria
Generalized Neuron Based Secure Media Access Control Protocol For Wireless Sensor Networks, Raghavendra V. Kulkarni, Ganesh K. Venayagamoorthy, Abhishek V. Thakur, Sanjay Kumar Madria
Electrical and Computer Engineering Faculty Research & Creative Works
Security plays a pivotal role in most applications of wireless sensor networks. It is common to find inadequately secure networks confined only to controlled environments. The issue of security in wireless sensor networks is a hot research topic for over a decade. This paper presents a compact generalized neuron (GN) based medium access protocol that renders a CSMA/CD network secure against denial-of-service attacks launched by adversaries. The GN enhances the security by constantly monitoring multiple parameters that reflect the possibility that an attack is launched by an adversary. Particle swarm optimization, a popular bio-inspired evolutionary-like optimization algorithm is used for …
A Proper Orthogonal Decomposition Approach To Approximate Balanced Truncation Of Infinite Dimensional Linear Systems, John R. Singler, Belinda A. Batten
A Proper Orthogonal Decomposition Approach To Approximate Balanced Truncation Of Infinite Dimensional Linear Systems, John R. Singler, Belinda A. Batten
Mathematics and Statistics Faculty Research & Creative Works
We extend a method for approximate balanced reduced order model derivation for finite dimensional linear systems developed by Rowley (Int. J. Bifur. Chaos Appl. Sci. Eng. 15(3) (2005), pp. 997-1013) to infinite dimensional systems. The algorithm is related to standard balanced truncation, but includes aspects of the proper orthogonal decomposition in its computational approach. The method can be also applied to nonlinear systems. Numerical results are presented for a convection diffusion system.
Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach
Effect Of Bacterial Adsorption On Low Frequency Electrical Properties Of Clean Quartz Sands And Iron-Oxide Coated Sands, Gamal Z. Abdel Aal, Estella A. Atekwana, Sylvia Radzikowski, Silvia Rossbach
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Low frequency electrical measurements (0.1-1000 Hz) were conducted to investigate the adsorption effect of Pseudomonas aeruginosa cells onto clean quartz sands and iron-oxide coated sands. The clean quartz sands showed a gradual increase in the microbial adsorption to mineral grains, concurrent with an increase of 13% in the imaginary conductivity component (σ″). However, iron-oxide coated sands (20-100% by weight) showed a rapid increase in microbial adsorption with σ″ reaching a maximum of 37% for the 80-100% iron coated sands. No significant changes were observed in the real conductivity component (σ′) due to microbial adsorption. A power law dependency was observed …
Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long
Influence Of The Rare-Earth Element On The Effects Of The Structural And Magnetic Phase Transitions In Cefeaso, Prfeaso And Ndfeaso, Michael A. Mcguire, Raphäel P. Hermann, Athena S. Sefat, Brian C. Sales, Rongying Jin, David Mandrus, Fernande Grandjean, Gary J. Long
Chemistry Faculty Research & Creative Works
We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron and antiferromagnetic ordering of rare-earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Mössbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is …
Accurate Retrieval Of Target Structures And Laser Parameters Of Few-Cycle Pulses From Photoelectron Momentum Spectra, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, J. Rauschenberger, M. F. Kling, C. D. Lin
Accurate Retrieval Of Target Structures And Laser Parameters Of Few-Cycle Pulses From Photoelectron Momentum Spectra, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, J. Rauschenberger, M. F. Kling, C. D. Lin
Physics Faculty Research & Creative Works
We illustrate a new method of analyzing three-dimensional momentum images of high-energy photoelectrons generated by intense phase-stabilized few-cycle laser pulses. Using photoelectron momentum spectra that were obtained by velocity-map imaging of above-threshold ionization of xenon and argon targets, we show that the absolute carrier-envelope phase, the laser peak intensity, and pulse duration can be accurately determined simultaneously (with an error of a few percent). We also show that the target structure, in the form of electron-target ion elastic differential cross sections, can be retrieved over a range of energies. The latter offers the promise of using laser-generated electron spectra for …
Significant Seismic Anisotropy Beneath The Southern Lhasa Terrane, Tibetan Plateau, Stephen S. Gao, Kelly H. Liu
Significant Seismic Anisotropy Beneath The Southern Lhasa Terrane, Tibetan Plateau, Stephen S. Gao, Kelly H. Liu
Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works
Shear wave splitting measurements using teleseismic PKS, SKKS, and SKS phases recorded by station LSA on the southern part of the Lhasa Terrane of the Tibetan Plateau reveal significant azimuthal anisotropy with a splitting time of up to 1.5 s, a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy. In addition, systematic variations of the splitting parameters (fast polarization direction and splitting time) with the arriving azimuth of the seismic ray path are observed, suggesting a model of anisotropy that is more complicated than a single layer with horizontal axis of symmetry. The measurements are …
Virtual Resonant States In Two-Photon Decay Processes: Lower-Order Terms, Subtractions, And Physical Interpretations, Ulrich D. Jentschura
Virtual Resonant States In Two-Photon Decay Processes: Lower-Order Terms, Subtractions, And Physical Interpretations, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
We investigate the two-photon decay rate of a highly excited atomic state which can decay to bound states of lower energy via cascade processes. We show that a naïve treatment of the process, based on the introduction of phenomenological decay rates for the intermediate, resonant states, leads to lower-order terms which need to be subtracted in order to obtain the coherent two-photon correction to the decay rate. The sum of the lower-order terms is exactly equal to the one-photon decay rate of the initial state, provided the naïve two-photon decay rates are summed over all available two-photon channels. A quantum …
Recursive Algorithm For Arrays Of Generalized Bessel Functions: Numerical Access To Dirac-Volkov Solutions, Erik Lötstedt, Ulrich D. Jentschura
Recursive Algorithm For Arrays Of Generalized Bessel Functions: Numerical Access To Dirac-Volkov Solutions, Erik Lötstedt, Ulrich D. Jentschura
Physics Faculty Research & Creative Works
In the relativistic and the nonrelativistic theoretical treatment of moderate and high-power laser-matter interaction, the generalized Bessel function occurs naturally when a Schrödinger-Volkov and Dirac-Volkov solution is expanded into plane waves. For the evaluation of cross sections of quantum electrodynamic processes in a linearly polarized laser field, it is often necessary to evaluate large arrays of generalized Bessel functions, of arbitrary index but with fixed arguments. We show that the generalized Bessel function can be evaluated, in a numerically stable way, by utilizing a recurrence relation and a normalization condition only, without having to compute any initial value. We demonstrate …
Sequential And Direct Two-Photon Double Ionization Of D₂ At Flash, Y. H. Jiang, Artem Rudenko, Kai Uwe Kuhnel, Th. Ergler, S. Ludemann, Karl Zrost, Daniel Fischer, J. Perez-Torres, E. Plesiat, F. Martin, L. Foucar, J. Titze, Markus S. Schoffler, Reinhard Dorner, J. L. Sanz-Vicario, S. Dusterer, R. Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich
Sequential And Direct Two-Photon Double Ionization Of D₂ At Flash, Y. H. Jiang, Artem Rudenko, Kai Uwe Kuhnel, Th. Ergler, S. Ludemann, Karl Zrost, Daniel Fischer, J. Perez-Torres, E. Plesiat, F. Martin, L. Foucar, J. Titze, Markus S. Schoffler, Reinhard Dorner, J. L. Sanz-Vicario, S. Dusterer, R. Treusch, Claus Dieter Schroter, Robert Moshammer, Joachim Hermann Ullrich
Physics Faculty Research & Creative Works
Sequential and direct two-photon double ionization (DI) of D2 molecule is studied experimentally and theoretically at a photon energy of 38.8 eV. Experimental and theoretical kinetic energy releases of D++D+fragments, consisting of the contributions of sequential DI via the D2+(1sσg) state and direct DI via a virtual state, agree well with each other.
Effect Of Dlk1 And Rtl1 But Not Meg3 Or Meg8 On Muscle Gene Expression In Callipyge Lambs, Jolena N. Fleming-Waddell, Gayla R. Olbricht, Tasia M. Taxis, Jason D. White, Tony Vuocolo, Bruce A. Craig, Ross L. Tellam, Mike K. Neary, Noelle E. Cockett, Christopher A. Bidwell
Effect Of Dlk1 And Rtl1 But Not Meg3 Or Meg8 On Muscle Gene Expression In Callipyge Lambs, Jolena N. Fleming-Waddell, Gayla R. Olbricht, Tasia M. Taxis, Jason D. White, Tony Vuocolo, Bruce A. Craig, Ross L. Tellam, Mike K. Neary, Noelle E. Cockett, Christopher A. Bidwell
Mathematics and Statistics Faculty Research & Creative Works
Callipyge sheep exhibit extreme postnatal muscle hypertrophy in the loin and hindquarters as a result of a single nucleotide polymorphism (SNP) in the imprinted DLK1-DIO3 domain on ovine chromosome 18. The callipyge SNP up-regulates the expression of surrounding transcripts when inherited in cis without altering their allele-specific imprinting status. The callipyge phenotype exhibits polar overdominant inheritance since only paternal heterozygous animals have muscle hypertrophy. Two studies were conducted profiling gene expression in lamb muscles to determine the down-stream effects of over-expression of paternal allele-specific DLK1 and RTL1 as well as maternal allele-specific MEG3, RTL1AS and MEG8, using Affymetrix bovine expression …
A Finite Element Splitting Extrapolation For Second Order Hyperbolic Equations, Xiaoming He, Tao Lü
A Finite Element Splitting Extrapolation For Second Order Hyperbolic Equations, Xiaoming He, Tao Lü
Mathematics and Statistics Faculty Research & Creative Works
Splitting extrapolation is an efficient technique for solving large scale scientific and engineering problems in parallel. This article discusses a finite element splitting extrapolation for second order hyperbolic equations with time-dependent coefficients. This method possesses a higher degree of parallelism, less computational complexity, and more flexibility than Richardson extrapolation while achieving the same accuracy. By means of domain decomposition and isoparametric mapping, some grid parameters are chosen according to the problem. The multiparameter asymptotic expansion of the d-quadratic finite element error is also established. The splitting extrapolation formulas are developed from this expansion. An approximation with higher accuracy on a …
Infinite-Randomness Quantum Critical Points Induced By Dissipation, Thomas Vojta, Chetan Kotabage, Jose A. Hoyos
Infinite-Randomness Quantum Critical Points Induced By Dissipation, Thomas Vojta, Chetan Kotabage, Jose A. Hoyos
Physics Faculty Research & Creative Works
We develop a strong-disorder renormalization group to study quantum phase transitions with continuous O(N) symmetry order parameters under the influence of both quenched disorder and dissipation. For Ohmic dissipation, as realized in Hertz's theory of the itinerant antiferromagnetic transition or in the superconductor-metal transition in nanowires, we find the transition to be governed by an exotic infinite-randomness fixed point in the same universality class as the (dissipationless) random transverse-field Ising model. We determine the critical behavior and calculate key observables at the transition and in the associated quantum Griffiths phase. We also briefly discuss the cases of super-Ohmic and sub-Ohmic …
Infinite-Randomness Critical Point In The Two-Dimensional Disordered Contact Process, Thomas Vojta, A. Farquhar, J. Mast
Infinite-Randomness Critical Point In The Two-Dimensional Disordered Contact Process, Thomas Vojta, A. Farquhar, J. Mast
Physics Faculty Research & Creative Works
We study the nonequilibrium phase transition in the two-dimensional contact process on a randomly diluted lattice by means of large-scale Monte Carlo simulations for times up to 1010 and system sizes up to 8000×8000 sites. Our data provide strong evidence for the transition being controlled by an exotic infinite-randomness critical point with activated (exponential) dynamical scaling. We calculate the critical exponents of the transition and find them to be universal, i.e., independent of disorder strength. The Griffiths region between the clean and the dirty critical points exhibits power-law dynamical scaling with continuously varying exponents. We discuss the generality of our …
Earth's Heat Source -- The Sun, Oliver Manuel
Earth's Heat Source -- The Sun, Oliver Manuel
Chemistry Faculty Research & Creative Works
The Sun encompasses planet Earth, supplies the heat that warms it, and even shakes it. The United Nation's Intergovernmental Panel on Climate Change (IPCC) assumed that solar influence on Earth's climate is limited to changes in solar irradiance and adopted the consensus opinion of a hydrogen-filled Sun - the Standard Solar Model (SSM). They did not consider the alternative solar model and instead adopted another consensus opinion: Anthropogenic greenhouse gases play a dominant role in climate change. The SSM fails to explain the solar wind, solar cycles, and the empirical link of solar surface activity with Earth's changing climate. The …
Coulomb-Field-Induced Conversion Of A High-Energy Photon Into A Pair Assisted By A Counterpropagating Laser Beam, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Coulomb-Field-Induced Conversion Of A High-Energy Photon Into A Pair Assisted By A Counterpropagating Laser Beam, Erik Lotstedt, Ulrich D. Jentschura, Christoph H. Keitel
Physics Faculty Research & Creative Works
The laser-induced modification of a fundamental process of quantum electrodynamics, the conversion of a high-energy gamma photon in the Coulomb field of a nucleus into an electron-positron pair, is studied theoretically. Although the employed formalism allows for the general case where the gamma photon and laser photons cross at an arbitrary angle, we here focus on a theoretically interesting and numerically challenging setup, where the laser beam and gamma photon counterpropagate and impinge on a nucleus at rest. For a peak laser field smaller than the critical Schwinger field and gamma photon energy larger than the field-free threshold, the total …
Kinetic Energy Release Distributions For C⁺₂ Emission From Multiply Charged C₆₀ And C₇₀ Fullerenes, Henrik Cederquist, Nicole Haag, Zoltan Berenyi, Peter Reinhed, Daniel Fischer, M. Gudmundsson, Birgitta W. Johansson, Torsten Schmidt, Henning Zettergren
Kinetic Energy Release Distributions For C⁺₂ Emission From Multiply Charged C₆₀ And C₇₀ Fullerenes, Henrik Cederquist, Nicole Haag, Zoltan Berenyi, Peter Reinhed, Daniel Fischer, M. Gudmundsson, Birgitta W. Johansson, Torsten Schmidt, Henning Zettergren
Physics Faculty Research & Creative Works
We present asystematic study of experimental kinetic energy release distributions for the asymmetric fission processes Cq+60 C(iq-1<)+70+ C+2 and C q+70 C(q-1)+60+ C+ 2 for mother ions incharge states q 4-8 produced incollisions with slow highly charged ions. Somewhat to our surprise, we find that the KERD for asymmetric fission from Cq+60 are considerably wider and have larger most likely values than the Cq+70 distributions inthe corresponding charge states when q > 4.
Electron Angular Distributions In He Single Ionization Impact By H₂⁺ Ions At 1 Mev, Shaofeng Zhang, J. Suske, Daniel Fischer, K. U. Kuehnel, Siegbert Hagmann, Alexander B. Voitkiv, B. Najjari, Achim Krauss, Robert Moshammer, Joachim Hermann Ullrich, Xinwen Ma
Electron Angular Distributions In He Single Ionization Impact By H₂⁺ Ions At 1 Mev, Shaofeng Zhang, J. Suske, Daniel Fischer, K. U. Kuehnel, Siegbert Hagmann, Alexander B. Voitkiv, B. Najjari, Achim Krauss, Robert Moshammer, Joachim Hermann Ullrich, Xinwen Ma
Physics Faculty Research & Creative Works
For the first time we investigated in a kinematically complete experiment the ionization of helium in collisions with H2+-molecular ions at 1 MeV. Using two separate detectors, the orientation of the projectile H2+-molecular ions was determined at the instance of the collision. The electron angular distribution was measured by a "Reaction Microscope". The observed structures are found in agreement with theoretical calculations, indicating that the ionized electron of He shows a slight preferential emission direction parallel to the molecular axis.
Extensions Of Effective-Medium Theory Of Transport In Disordered Systems, V. M. Kenkre, Z. Kalay, Paul Ernest Parris
Extensions Of Effective-Medium Theory Of Transport In Disordered Systems, V. M. Kenkre, Z. Kalay, Paul Ernest Parris
Physics Faculty Research & Creative Works
The effective-medium theory of transport in disordered systems, whose basis is the replacement of spatial disorder by temporal memory, is extended in several practical directions. Restricting attention to a one-dimensional system with bond disorder for specificity, a transformation procedure is developed to deduce explicit expressions for the memory functions from given distribution functions characterizing the system disorder. It is shown how to use the memory functions in the Laplace domain forms in which they first appear, and in the time domain forms which are obtained via numerical inversion algorithms, to address time evolution of the system beyond the asymptotic domain …
Emission Of Low-Energy Photons By Electrons At Electron-Positron And Electron-Ion Colliders With Dense Bunches, Ulrich D. Jentschura, G. L. Kotkin, V. G. Serbo
Emission Of Low-Energy Photons By Electrons At Electron-Positron And Electron-Ion Colliders With Dense Bunches, Ulrich D. Jentschura, G. L. Kotkin, V. G. Serbo
Physics Faculty Research & Creative Works
Usually, the emission of low-energy photons in electron-positron (or electron-ion) bunch collisions is calculated with the same approach as for synchrotron radiation (beamstrahlung). However, for soft photons (Eγ
Phonon Confinement Effects In The Raman Spectrum Of Nanodiamond, Sebastian Osswald, Vadym Mochalin, Mickaël Havel, Gleb N. Yushin, Yury G. Gogotsi
Phonon Confinement Effects In The Raman Spectrum Of Nanodiamond, Sebastian Osswald, Vadym Mochalin, Mickaël Havel, Gleb N. Yushin, Yury G. Gogotsi
Chemistry Faculty Research & Creative Works
Nanodiamonds (ND) exhibit unique properties due to their small size and high surface-to-volume ratio compared to bulk diamonds. A reduction in crystal size also affects ND Raman spectra. The confinement of optical phonons in nanocrystals (<10 nm) results in asymmetrically broadened Raman lines, which are shifted toward lower wavenumbers. The phonon confinement model (PCM) relates the observed changes in the Raman spectra to the crystal size and can be used for size characterization at the nanoscale. While the PCM was successfully applied to a variety of materials including Si and BN, results remained unsatisfactory in the case of ND. In order to improve the agreement between the predictions of the model and experimental Raman spectra of ND, effects such as crystal size distribution, lattice defects, and the energy dispersion of the phonon modes were taken into consideration and incorporated into the PCM. This work has shown that phonon wave vectors from small vibrational domains lead to a broad shoulder peak at ~1250 cm-1, that is often observed in the Raman spectrum of ND.
Unified Treatment Of Even And Odd Anharmonic Oscillators Of Arbitrary Degree, Ulrich D. Jentschura, Andrey Surzhykov, Jean Zinn-Justin
Unified Treatment Of Even And Odd Anharmonic Oscillators Of Arbitrary Degree, Ulrich D. Jentschura, Andrey Surzhykov, Jean Zinn-Justin
Physics Faculty Research & Creative Works
We present a unified treatment, including higher-order corrections, of anharmonic oscillators of arbitrary even and odd degree. Our approach is based on a dispersion relation which takes advantage of the [script P][script T] symmetry of odd potentials for imaginary coupling parameter, and of generalized quantization conditions which take into account instanton contributions. We find a number of explicit new results, including the general behavior of large-order perturbation theory for arbitrary levels of odd anharmonic oscillators, and subleading corrections to the decay width of excited states for odd potentials, which are numerically significant.
The Search For Quantum Critical Scaling In A Classical System, Jagat Lamsal, John Gaddy, Marcus Petrovic, Wouter Montfrooij, Thomas Vojta
The Search For Quantum Critical Scaling In A Classical System, Jagat Lamsal, John Gaddy, Marcus Petrovic, Wouter Montfrooij, Thomas Vojta
Physics Faculty Research & Creative Works
Order-disorder phase transitions in magnetic metals that occur at zero temperature have been studied in great detail. Theorists have advanced scenarios for these quantum critical systems in which the unusual response can be seen to evolve from a competition between ordering and disordering tendencies, driven by quantum fluctuations. Unfortunately, there is a potential disconnect between the real systems that are being studied experimentally, and the idealized systems that theoretical scenarios are based upon. Here we discuss how disorder introduces a change in morphology from a three-dimensional system to a collection of magnetic clusters, and we present neutron scattering data on …
Isotope Shifts In Dielectronic Recombination: From Stable To In-Flight-Produced Nuclei, Carsten Brandau, S. Kozhedub, Alfred K. Muller, Dietrich Bernhardt, Stefan Bohm, Fritz J. Bosch, Daniel Boutin, Fred John Currell, Christina Dimopoulou, Bernhard Franzke, Alexandre Gumberidze, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Heinz Jurgen Kluge, S. Kozhedub, Reiner Krucken, Yu A. Litvinov, Fritz Nolden, Brian E. O'Rourke, Regina Reuschl, Stefan Schippers, Vladimir M. Shabaev, Uwe Spillmann, Zbigniew Stachura
Isotope Shifts In Dielectronic Recombination: From Stable To In-Flight-Produced Nuclei, Carsten Brandau, S. Kozhedub, Alfred K. Muller, Dietrich Bernhardt, Stefan Bohm, Fritz J. Bosch, Daniel Boutin, Fred John Currell, Christina Dimopoulou, Bernhard Franzke, Alexandre Gumberidze, Zoltan Harman, Ulrich D. Jentschura, Christoph H. Keitel, Heinz Jurgen Kluge, S. Kozhedub, Reiner Krucken, Yu A. Litvinov, Fritz Nolden, Brian E. O'Rourke, Regina Reuschl, Stefan Schippers, Vladimir M. Shabaev, Uwe Spillmann, Zbigniew Stachura
Physics Faculty Research & Creative Works
The study of isotope shifts and hyperfine effects in dielectronic recombination (DR) resonance spectra strikes a conceptually new path for investigations of nuclear properties such as charge radius, spin, magnetic moment of nuclei or lifetimes of long-lived excited nuclear states. A series of DR experiments with heavy three-electron ions (Li-like) was performed at the heavy-ion storage ring ESR of the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany. In a pilot experiment the two stable isotopes A=142 and A=150 of neodymium ANd57+ were investigated. From the displacement of DR resonances the isotope shifts δE142,150(2s - 2Pl/2) …
Quantitative Rescattering Theory For Nonsequential Double Ionization Of Atoms By Intense Laser Pulses, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, C. D. Lin
Quantitative Rescattering Theory For Nonsequential Double Ionization Of Atoms By Intense Laser Pulses, Samuel Micheau, Zhangjin Chen, Anh-Thu Le, C. D. Lin
Physics Faculty Research & Creative Works
Laser-induced electron recollisions are fundamental to many strong field phenomena in atoms and molecules. Using the recently developed quantitative rescattering theory, we demonstrate that the nonsequential double ionization (NSDI) of atoms by lasers can be obtained quantitatively in terms of inelastic collisions of the target ions with the free returning electrons where the latter are explicitly given by a spectrum-characterized wave packet. Using argon atoms as target, we calculated the NSDI yield including contributions from direct (e,2e) electron-impact ionization and electron-impact excitation accompanied by subsequent field ionization. We further investigate the dependence of total NSDI on the carrier-envelope phase of …
An Improved Upfc Control For Oscillation Damping, Jagannathan Sarangapani, Mariesa Crow, Jianjun Guo
An Improved Upfc Control For Oscillation Damping, Jagannathan Sarangapani, Mariesa Crow, Jianjun Guo
Electrical and Computer Engineering Faculty Research & Creative Works
This paper proposes a new control approach for a unified power flow controller (UPFC) for power system oscillation damping. This control is simple to implement, yet is valid over a wide range of operating conditions. It is also effective in the presence of multiple modes of oscillation. The proposed control is implemented in several test systems and is compared against a traditional PI control.