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 Ehsan Khatami (22)
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Articles 1  30 of 95
FullText Articles in Physics
Fast SuperResolution With Affine Motion Using An Adaptive Wiener Filter And Its Application To Airborne Imaging, Russell C. Hardie, Kenneth J. Barnard, Raúl Ordóñez
Fast SuperResolution With Affine Motion Using An Adaptive Wiener Filter And Its Application To Airborne Imaging, Russell C. Hardie, Kenneth J. Barnard, Raúl Ordóñez
Raúl Ordóñez
Fast nonuniform interpolation based superresolution (SR) has traditionally been limited to applications with translational interframe motion. This is in part because such methods are based on an underlying assumption that the warping and blurring components in the observation model commute. For translational motion this is the case, but it is not true in general. This presents a problem for applications such as airborne imaging where translation may be insufficient. Here we present a new Fourier domain analysis to show that, for many image systems, an affine warping model with limited zoom and shear approximately commutes with the point spread function ...
FiniteTemperature Superconducting Correlations Of The Hubbard Model, Ehsan Khatami, Richard T. Scalettar, Rajiv R.P. Singh
FiniteTemperature Superconducting Correlations Of The Hubbard Model, Ehsan Khatami, Richard T. Scalettar, Rajiv R.P. Singh
Ehsan Khatami
Geometry Dependence Of The Sign Problem In Quantum Monte Carlo Simulations, V. I. Iglovikov, Ehsan Khatami, R. T. Scalettar
Geometry Dependence Of The Sign Problem In Quantum Monte Carlo Simulations, V. I. Iglovikov, Ehsan Khatami, R. T. Scalettar
Ehsan Khatami
Nuclear Proliferation And Testing: A Tale Of Two Treaties, Pierce S. Corden, David Hafemeister
Nuclear Proliferation And Testing: A Tale Of Two Treaties, Pierce S. Corden, David Hafemeister
David W. Hafemeister
Despite progress in reducing stockpiles after the end of the Cold War, the disturbing actions of some nations could spread nuclear weapon capabilities and enlarge existing arsenals.
Magnetic Correlations And Pairing In The 1/5Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Magnetic Correlations And Pairing In The 1/5Depleted Square Lattice Hubbard Model, Ehsan Khatami, Rajiv R.P. Singh, Warren E. Pickett, Richard T. Scalettar
Ehsan Khatami
We study the singleorbital Hubbard model on the 1/5depleted squarelattice geometry, which arises in such diverse systems as the spingap magnetic insulator CaV4O9 and orderedvacancy iron selenides, presenting new issues regarding the origin of both magnetic ordering and superconductivity in these materials. We find a rich phase diagram that includes a plaquette singlet phase, a dimer singlet phase, a Néel and a blockspin antiferromagnetic phase, and stripe phases. Quantum Monte Carlo simulations show that the dominant pairing correlations at half filling change character from d wave in the plaquette phase to extended s wave upon transition to the Néel ...
LinkedCluster Expansion For The Green's Function Of The InfiniteU Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
LinkedCluster Expansion For The Green's Function Of The InfiniteU Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
Ehsan Khatami
FiniteTemperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol
FiniteTemperature Properties Of Strongly Correlated Fermions In The Honeycomb Lattice, Baoming Tang, Thereza Paiva, Ehsan Khatami, Marchos Rigol
Ehsan Khatami
We study finitetemperature properties of strongly interacting fermions in the honeycomb lattice using numerical linkedcluster expansions and determinantal quantum Monte Carlo simulations. We analyze a number of thermodynamic quantities, including the entropy, the specific heat, uniform and staggered spin susceptibilities, shortrange spin correlations, and the double occupancy at and away from half filling. We examine the viability of adiabatic cooling by increasing the interaction strength for homogeneous as well as for trapped systems. For the homogeneous case, this process is found to be more efficient at finite doping than at half filling. That, in turn, leads to an efficient adiabatic ...
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John B. Geddes
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John B. Geddes
Brian Storey
When a ﬂuid comprised of multiple phases or constituents ﬂows through a network, nonlinear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the ﬂow of blood through the microcirculation, the ﬂow of picoliter droplets through microﬂuidic devices, the ﬂow of magma through lava tubes, and twophase ﬂow in refrigeration systems. While the existence of nonlinear phenomena in a network with many interconnections containing ﬂuids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian ﬂuids in laminar ﬂow ...
Electronic Spectral Properties Of The TwoDimensional InfiniteU Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
Electronic Spectral Properties Of The TwoDimensional InfiniteU Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
Ehsan Khatami
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John Geddes
Laminar Flow Of Two Miscible Fluids In A Simple Network, Casey Karst, Brian Storey, John Geddes
John B. Geddes
When a ﬂuid comprised of multiple phases or constituents ﬂows through a network, nonlinear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the ﬂow of blood through the microcirculation, the ﬂow of picoliter droplets through microﬂuidic devices, the ﬂow of magma through lava tubes, and twophase ﬂow in refrigeration systems. While the existence of nonlinear phenomena in a network with many interconnections containing ﬂuids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian ﬂuids in laminar ﬂow ...
A Short Introduction To Numerical LinkedCluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol
A Short Introduction To Numerical LinkedCluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol
Ehsan Khatami
FluctuationDissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol
FluctuationDissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol
Ehsan Khatami
We examine the validity of fluctuationdissipation relations in isolated quantum systems taken out of equilibrium by a sudden quench. We focus on the dynamics of trapped hardcore bosons in onedimensional lattices with dipolar interactions whose strength is changed during the quench. We find indications that fluctuationdissipation relations hold if the system is nonintegrable after the quench, as well as if it is integrable after the quench if the initial state is an equilibrium state of a nonintegrable Hamiltonian. On the other hand, we find indications that they fail if the system is integrable both before and after quenching.
Workshop Addresses Aviation Community, Jennifer Meehan, Joseph Kunches
Workshop Addresses Aviation Community, Jennifer Meehan, Joseph Kunches
Jennifer (Jinni) Meehan
No abstract provided.
Effect Of Particle Statistics In Strongly Correlated TwoDimensional Hubbard Models, Ehsan Khatami, Marcos Rigol
Effect Of Particle Statistics In Strongly Correlated TwoDimensional Hubbard Models, Ehsan Khatami, Marcos Rigol
Ehsan Khatami
The Second Annual Space Weather Community Operations Workshop: Advancing Operations Into The Next Decade, Jennifer Meehan, Jared Fulgham, Kent Tobiska
The Second Annual Space Weather Community Operations Workshop: Advancing Operations Into The Next Decade, Jennifer Meehan, Jared Fulgham, Kent Tobiska
Jennifer (Jinni) Meehan
No abstract provided.
Incommensurate Spin Fluctuations In HighTransition Temperature Superconductors, Barrett Wells, Young Lee, Marc Kastner, Rebecca Christianson, Robert Birgeneau, Kazuyoshi Yamada, Yasuo Endoh, Gen Shirane
Incommensurate Spin Fluctuations In HighTransition Temperature Superconductors, Barrett Wells, Young Lee, Marc Kastner, Rebecca Christianson, Robert Birgeneau, Kazuyoshi Yamada, Yasuo Endoh, Gen Shirane
Rebecca J. Christianson
Neutron scattering experiments have revealed a fascinating interplay between the hole doping, the spin fluctuations, and the superconductivity of the cuprate superconductors. Recently, electrochemical techniques have been used to produce large single crystals of La2CuO4+ y, which has mobile oxygen dopants. Staging behavior of the excess oxygen has been demonstrated, and the lowenergy spin fluctuations in stage 6 La2CuO4+ y have been measured. The spin fluctuations are incommensurate with the lattice and have spatial, energy, and temperature dependencies very much like those in La2− xSrxCuO4, with similar high transition temperature. This establishes the universality of the incommensurate spin fluctuations among ...
Structures And Incommensurate Spin Excitations In Excess OxygenDoped La2cuo4+Y, Robert Birgeneau, Rebecca Christianson, Yasuo Endoh, Marc Kastner, Young Lee, Gen Shirane, Barrett Wells, Kazuyoshi Yamada
Structures And Incommensurate Spin Excitations In Excess OxygenDoped La2cuo4+Y, Robert Birgeneau, Rebecca Christianson, Yasuo Endoh, Marc Kastner, Young Lee, Gen Shirane, Barrett Wells, Kazuyoshi Yamada
Rebecca J. Christianson
Over the past decade, we have studied in detail the lowenergy spin fluctuations in :a2−xSrxCuO4 for xbetween 0 and 0.18. Our experiments, as well as those by others, have revealed a fascinating interplay between the hole doping, the static and dynamic spin fluctuations and superconductivity. Recently, using electrochemical techniques, we have learned how to produce large single crystals of La2CuO4+y which are relatively homogenous. In this latter system, the dopants are characterized by annealed rather than quenched disorder. Furthermore, we have demonstrated staging behavior of the excess oxygen analogous to staging in intercalated graphite. We have now ...
A Reduced Model Of Cavitation Physics For Use In Sonochemistry, Brian Storey, Andrew Szeri
A Reduced Model Of Cavitation Physics For Use In Sonochemistry, Brian Storey, Andrew Szeri
Brian Storey
Sonochemistry involves focusing acoustic energy through cavitation bubbles to increase chemical activity. The violent bubble collapses lead to temperatures of several thousand kelvin, which drive chemical reactions. In previous work, we gave a detailed computational model of a single bubble collapse, taking into account phase change, mass diffusion, heat diffusion and chemical reactions. All of these phenomena are important in determining the conditions at collapse. The present work involves development of a much simpler model that includes all the physics relevant to the determination of the reaction products. Comparisons with the more detailed computations are made; the reduced model is ...
Water Vapour, Sonoluminescence And Sonochemistry, Brian Storey, Andrew Szeri
Water Vapour, Sonoluminescence And Sonochemistry, Brian Storey, Andrew Szeri
Brian Storey
Sonoluminescence is the production of light from acoustically forced bubbles; sonochemistry is a related chemical processing technique. The two phenomena share a sensitive dependence on the liquid phase. The present work is an investigation of the fate and consequences of water vapour in the interior of strongly forced argon micro–bubbles. Due to the extreme nonlinearity of the volume oscillations, excess water vapour is trapped in the bubble during a rapid inertial collapse. Water vapour is prevented from exiting by relatively slow diffusion and non–equilibrium condensation at the bubble wall. By reducing the compression heating of the mixture and ...
Temperature Distribution In An Oscillatory Flow With A Sinusoidal Wall Temperature, Eduardo Ramos, Brian Storey, Fernando Sierra, Raul Zuniga, Andriy Avramenko
Temperature Distribution In An Oscillatory Flow With A Sinusoidal Wall Temperature, Eduardo Ramos, Brian Storey, Fernando Sierra, Raul Zuniga, Andriy Avramenko
Brian Storey
The temperature field generated by an oscillatory boundary layer flow in the presence of a wall with a sinusoidal temperature distribution is analyzed. A linear perturbation method is used to find closed form analytical solutions for the temperature field when the amplitude of the velocity oscillation is small. The analytical solutions only consider longtime behavior when the temperature fields oscillate with the frequency of the flow. The structure of the equation that governs the temperature correction due to convection is similar to that of diffusive waves with the solution consisting of traveling or standing waves. The temperature distribution is also ...
Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev
Double Layer In Ionic Liquids: Overscreening Versus Crowding, Martin Z. Bazant, Brian D. Storey, Alexei A. Kornyshev
Brian Storey
We develop a simple LandauGinzburgtype continuum theory of solventfree ionic liquids and use it to predict the structure of the electrical double layer. The model captures overscreening from shortrange correlations, dominant at small voltages, and steric constraints of finite ion sizes, which prevail at large voltages. Increasing the voltage gradually suppresses overscreening in favor of the crowding of counterions in a condensed inner layer near the electrode. This prediction, the ion profiles, and the capacitancevoltage dependence are consistent with recent computer simulations and experiments on roomtemperature ionic liquids, using a correlation length of order the ion size.
Mixture Segregation Within Sonoluminescence Bubbles, Brian D. Storey, Andrew J. Szeri
Mixture Segregation Within Sonoluminescence Bubbles, Brian D. Storey, Andrew J. Szeri
Brian Storey
This paper concerns a relaxation of the assumption of uniform mixture composition in the interior of sonoluminescence bubbles. Intense temperature and pressure gradients within the bubble drive relative mass diffusion which overwhelms diffusion driven by concentration gradients. This thermal and pressure diffusion results in a robust compositional inhomogeneity in the bubble which lasts several orders of magnitude longer than the temperature peak or light pulse at the main collapse of the bubble. This effect has important consequences for control of sonoluminescence, gas dynamics, sonochemistry, and the physics of light production.
Nonextensive Statistical Mechanics For Rotating QuasiTwoDimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Nonextensive Statistical Mechanics For Rotating QuasiTwoDimensional Turbulence, Sunghwan Jung, Brian Storey, Julien Aubert, Harry Swinney
Brian Storey
We have conducted experiments on an asymmetrically forced quasitwodimensional turbulent flow in a rapidly rotating annulus. Assuming conservation of potential enstrophy and energy, we maximize a nonextensive entropy function to obtain the azimuthally averaged vorticity as a function of radial position. The predicted vorticity profile is in good accord with the observations. A nonextensive formalism is appropriate because longrange correlations between smallscale vortices give rise to large coherent structures in the turbulence. We also derive probability distribution functions for the vorticity from both extensive and nonextensive entropies, and we find that the prediction from nonextensive theory is in better accord ...
Radiation Dose Distributions In Three Dimensions From Tomographic Optical Density Scanning Of Polymer Gels: Ii. Optical Properties Of The Bang Polymer Gel, Yevgeniya Zastavker, Marek Maryanski, John Gore
Radiation Dose Distributions In Three Dimensions From Tomographic Optical Density Scanning Of Polymer Gels: Ii. Optical Properties Of The Bang Polymer Gel, Yevgeniya Zastavker, Marek Maryanski, John Gore
Yevgeniya V. Zastavker
A newly developed method of radiation dosimetry makes use of the optical properties of polymer gels. The doseresponse mechanism relies on the production of lightscattering polymer microparticles in the gel at each site of radiation absorption. The scattering produces an attenuation of transmitted light intensity that is directly related to the dose and independent of dose rate. For the BANG polymer gel (bis, acrylamide, nitrogen, and gelatin) the shape of the doseresponse curve depends on the fraction of the crosslinking monomer in the initial mixture and on the wavelength of light. At 500 nm the attenuation coefficient (μ) increases by ...
SelfAssembly Of Helical Ribbons, Yevgeniya V. Zastavker, Neer Asherie, Aleksey Lomakin, Jayanti Pande, Joanne M. Donovan, Joel M. Schnur, George B. Benedek
SelfAssembly Of Helical Ribbons, Yevgeniya V. Zastavker, Neer Asherie, Aleksey Lomakin, Jayanti Pande, Joanne M. Donovan, Joel M. Schnur, George B. Benedek
Yevgeniya V. Zastavker
The selfassembly of helical ribbons is examined in a variety of multicomponent enantiomerically pure systems that contain a bile salt or a nonionic detergent, a phosphatidylcholine or a fatty acid, and a steroid analog of cholesterol. In almost all systems, two different pitch types of helical ribbons are observed: high pitch, with a pitch angle of 54 ± 2°, and low pitch, with a pitch angle of 11 ± 2°. Although the majority of these helices are righthanded, a small proportion of lefthanded helices is observed. Additionally, a third type of helical ribbon, with a pitch angle in the range 30–47 ...
Dynamical Signature Of The MottHubbard Transition In Ni(S,Se)(2), Yevgeniya Zastavker, Anke Husmann, Deborah Jin, Thomas Rosenbaum, X Yao, J Honig
Dynamical Signature Of The MottHubbard Transition In Ni(S,Se)(2), Yevgeniya Zastavker, Anke Husmann, Deborah Jin, Thomas Rosenbaum, X Yao, J Honig
Yevgeniya V. Zastavker
The transition metal chalcogenide Ni(S,Se)2 is one of the few highly correlated, MottHubbard systems without a strong firstorder structural distortion that normally cuts off the critical behavior at the metalinsulator transition. The zerotemperature (T) transition was tuned with pressure, and significant deviations were found near the quantum critical point from the usual T1/2 behavior of the conductivity characteristic of electronelectron interactions in the presence of disorder. The transport data for pressure and temperature below 1 kelvin could be collapsed onto a universal scaling curve.
TensionInduced Straightening Transition Of SelfAssembled Helical Ribbons, Yevgeniya V. Zastavker, Brice Smith, George B. Benedek
TensionInduced Straightening Transition Of SelfAssembled Helical Ribbons, Yevgeniya V. Zastavker, Brice Smith, George B. Benedek
Yevgeniya V. Zastavker
Helical ribbons with pitch angles of either 11° or 54° selfassemble in a wide variety of quaternary surfactantphospholipid/fatty acidsterolwater systems. By elastically deforming these helices, we examined their response to uniaxial forces. Under sufficient tension, a low pitch helix reversibly separates into a straight domain with a pitch angle of 90° and a helical domain with a pitch angle of 16.5°. Using a newly developed continuum elastic free energy model, we have shown that this phenomenon can be understood as a first order mechanical phase transition.
Performance Characteristics Of Nanocrystalline Diamond Vacuum Field Emission Transistor Array, S Hsu, W Kang, J Davidson, J Huang, David Kerns
Performance Characteristics Of Nanocrystalline Diamond Vacuum Field Emission Transistor Array, S Hsu, W Kang, J Davidson, J Huang, David Kerns
David V. Kerns
Nitrogenincorporated nanocrystalline diamond (ND) vacuum field emission transistor (VFET) with selfaligned gate is fabricated by mold transfer microfabrication technique in conjunction with chemical vapor deposition (CVD) of nanocrystalline diamond on emitter cavity patterned on silicononinsulator (SOI) substrate. The fabricated NDVFET demonstrates gatecontrolled emission current with good signal amplification characteristics. The dc characteristics of the NDVFET show welldefined cutoff, linear, and saturation regions with low gate turnon voltage, high anode current, negligible gate intercepted current, and large dc voltage gain. The ac performance of the NDVFET is measured, and the experimental data are analyzed using a modified small signal circuit model ...
Oxygen Line Mapping Of Sn 1006 With Suzaku, Aya Bamba, Hiroya Yamaguchi, Katsuji Koyama, Junko Hiraga, Stephen Holt, John Hughes, Hideaki Katagiri, Jun Kataoka, Satoru Katsuda, Shunji Kitamoto, Motohide Kokubun, Hironori Matsumoto, Emi Miyata, Koji Mori, Hiroshi Nakajima, Masanobu Ozaki, Robert Petre, Akiko Sekiguchi, Tadayuki Takahashi, Takaaki Tanaka, Yukikatsu Terada, Hiroshi Tomida, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Yasunobu Uchiyama, Masaru Ueno, Shin Watanabe
Oxygen Line Mapping Of Sn 1006 With Suzaku, Aya Bamba, Hiroya Yamaguchi, Katsuji Koyama, Junko Hiraga, Stephen Holt, John Hughes, Hideaki Katagiri, Jun Kataoka, Satoru Katsuda, Shunji Kitamoto, Motohide Kokubun, Hironori Matsumoto, Emi Miyata, Koji Mori, Hiroshi Nakajima, Masanobu Ozaki, Robert Petre, Akiko Sekiguchi, Tadayuki Takahashi, Takaaki Tanaka, Yukikatsu Terada, Hiroshi Tomida, Yohko Tsuboi, Masahiro Tsujimoto, Hiroshi Tsunemi, Yasunobu Uchiyama, Masaru Ueno, Shin Watanabe
Stephen Holt
SN1006 is one of the supernova remnants (SNRs) with relatively lowtemperature electrons, considering the young age of just 1000 years. We carried out SN1006 mapping observations with the Xray Imaging Spectrometers (XIS) and the Hard Xray Detector (HXD) onboard Suzaku, the fifth Japanese Xray satellite. Thanks to the excellent spectral resolution of XIS in the soft Xray band, Hlike and Helike oxygen emission lines were clearly detected, and we could make a map of the line intensity, and as well as a flux and the photon index of nonthermal component. We found that these parameters have spatial dependences from region ...
Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio M. GarcíaGarcía