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Review of Scientific Instruments : High-density, high-temperature ...

By: V. O. Lorenz, X. Dai, H. Green, T. R. Asnicar, and S. T. Cundiff

Description: We present a vapor cell design that enables resonant optical spectroscopy in high-density, high-temperature alkali metal vapors. Optical access is provided via reflection from the interface between the vapor and a sapphire window. The cell resists corrosion from the highly reactive alkali vapors, in our case, potassium, up to 800 °C (number densities up to 1019 cm−3). The cells maintain their integrity for an average of 100 h above 500 °C with about 10 heating/cooling cycles.

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Journal of Mathematical Physics : On the divine clockwork: The spe...

By: Richard Durran, Andrew Neate, Aubrey Truman, and Feng-Yu Wang

Description: The correspondence limit of the atomic elliptic state in three dimensions is discussed in terms of Nelson’s stochastic mechanics. In previous work we have shown that this approach leads to a limiting Nelson diffusion, and here we discuss in detail the invariant measure for this process and show that it is concentrated on the Kepler ellipse in the plane z = 0. We then show that the limiting Nelson diffusion generator has a spectral gap; thereby proving that i...

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Chaos : Winnerless competition principle and prediction of the tra...

By: Valentin Afraimovich, Irma Tristan, Ramon Huerta, and Mikhail I. Rabinovich

Description: Predicting the evolution of multispecies ecological systems is an intriguing problem. A sufficiently complex model with the necessary predicting power requires solutions that are structurally stable. Small variations of the system parameters should not qualitatively perturb its solutions. When one is interested in just asymptotic results of evolution (as time goes to infinity), then the problem has a straightforward mathematical image involving simple attrac...

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Journal of Applied Physics : Optical properties of m-plane GaN qua...

By: Julien Renard, Benoit Amstatt, Catherine Bougerol, Edith Bellet-Amalric, Bruno Daudin et al

Description: We have studied the optical properties of m-plane GaN/AlN quantum dots and quantum wires. The photoluminescence, both on an ensemble of nanostructures and on single nanostructures, shows a strong degree of linear polarization perpendicular to the c-axis. Time-resolved photoluminescence evidences the strong reduction in the quantum confined Stark effect. Temperature dependence measurements suggest a difference in nonradiative processes between quantum dots and quantum wires.

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Journal of Mathematical Physics : Symmetry, full symmetry groups, ...

By: Biao Li, Wang-Chuan Ye, and Yong Chen

Description: The Lie symmetry algebra of a generalized Davey–Stewartson (GDS) system is obtained. The general element of this algebra depends on eight arbitrary functions of time, which has a Kac–Moody–Virasoro loop algebra structure and is isomorphic to that of the standard integrable Davey–Stewartson equations under certain conditions imposed on parameters and arbitrary functions. Then based on the symmetry group direct method proposed by Lou and Ma [J. Phys. A 38, L12...

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Applied Physics Letters : Low temperature diffusion length of exci...

By: Naoyuki Ino and Naoki Yamamoto

Description: Monochromatic cathodoluminescence (CL) images of threading dislocations in GaN epitaxial layers were observed using a transmission electron microscopy combined with CL system. The carrier diffusion lengths were derived from the free exciton emission intensity profile of the dislocation contrast in the CL images. The carrier diffusion lengths in Si-doped and Mg-doped GaN were nearly the same and shorter than that in undoped GaN in the temperature range from 2...

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Journal of Applied Physics : Fourier transform infrared spectrosco...

By: G. Scardera, T. Puzzer, G. Conibeer, and M. A. Green

Description: A correlation between bonding changes in silicon-rich silicon nitride films, subjected to high temperature annealing under N2 ambient, and the formation of silicon nanocrystals is presented. The postannealing appearance of a shoulder between 1000 and 1100 cm−1 in the Fourier transform infrared (FTIR) spectra of silicon-rich silicon nitride films is attributed to a reordering in the films toward an increased SiN4 bonding configuration resulting from the preci...

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Applied Physics Letters : Bandgap engineering by tuning particle s...

By: M. B. Sahana, C. Sudakar, G. Setzler, A. Dixit, J. S. Thakur et al

Description: We report the structural and optical properties of xSnO2–yFe2O3 nanocrystalline composite thin films. SnO2 and Fe2O3 exhibit strong phase separation instability and their particle size and crystallinity are tunable by changing their composition and annealing temperature. The bandgap for these composites continuously increases from 2.3 to 3.89 eV. We discuss the increasing bandgap values in terms of the quantum confinement effect manifested by the decreasing ...

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Journal of Applied Physics : Selective transmittance of linearly p...

By: Viktor Leontyev, Nicholas G. Wakefield, Kyrylo Tabunshchyk, Jeremy C. Sit, Michael J. Brett et al

Description: Columnar thin films exhibiting linear polarization selectivity have been theoretically investigated and fabricated using the glancing angle deposition (GLAD) technique. The film structure employed an s-shaped columnar morphology that may be either smoothly bent or composed of discrete segments. Finite-difference time-domain and frequency-domain methods have been used to model these thin film structures numerically. Simulation results have yielded optimal geo...

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The Journal of Chemical Physics : A noniterative perturbative trip...

By: Prashant U. Manohar and Anna I. Krylov

Description: A noniterative N 7 triples correction for the equation-of-motion coupled-cluster method with single and double substitutions (CCSD) is presented. The correction is derived by second-order perturbation treatment of the similarity-transformed CCSD Hamiltonian. The spin-conserving variant of the correction is identical to the triples correction of Piecuch and co-workers [Mol. Phys. 104, 2149 (2006) ] derived within method-of-moments framework and is not size in...

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The Journal of Chemical Physics : Molecular dynamics simulation of...

By: Hossein Eslami, Farkhondeh Mozaffari, Jalil Moghadasi, and Florian Müller-Plathe

Description: A method for the simulation of fluids confined between surfaces is developed. The molecular dynamics, with coupling to an external bath, simulation method of Berendsen et al. [J. Chem. Phys. 81, 3684 (1984) ] is extended for this purpose. We keep the temperature and the parallel component of pressure fixed and change the box length in the perpendicular direction with respect to the confining surfaces to archive equilibrium. The simulation is easy to perform,...

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Chaos : Dynamical parameter identification from a scalar time series

By: Dongchuan Yu and Fang Liu

Description: If a drive system with unknown parameters represents “reality” and the response system a “computational model,” the unidirectional coupling can be used to change model parameters, as well as the model state, such that both systems synchronize with each other and model parameters coincide with their true values of “reality.” Such a parameter identification method is called adaptive synchronization (also autosynchronization) method and is widely used in the li...

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Review of Scientific Instruments : Measurement of shock wave unste...

By: D. Estruch, N. J. Lawson, D. G. MacManus, K. P. Garry, and J. L. Stollery

Description: A new method to measure shock wave unsteadiness is presented. Time-resolved visualizations of the flow field under investigation are obtained using a high-speed schlieren optical system and the motion of the shock wave is determined by means of digital image processing. Information on the shock’s unsteadiness is subsequently derived with Fourier analysis. A sample study on shock unsteadiness in a shock-wave/turbulent boundary-layer interaction with separatio...

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Physics of Fluids : History force on an asymmetrically rotating bo...

By: Sukalyan Bhattacharya

Description: Experimental evidence shows that suspended particles preferentially migrate away from confining boundaries due to the effect of a shear flow. In this paper, we consider an asymmetric particle in Poiseuille flow and determine an inertial lift force which can contribute to the particle migration. Under the influence of Poiseuille flow in a slit pore, an arbitrary particle undergoes periodic rotation which is described by Jeffery’s orbit [ G. Jeffery, Proc. R. ...

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Applied Physics Letters : Dielectric properties of Ba0.5Sr0.5TiO3/...

By: Niandeng Xiong, Shuwen Jiang, Yanrong Li, Lefan Tan, and Ruguan Li

Description: The Ba0.5Sr0.5TiO3(BST)/SiN bilayered thin films with a SiN layer serving as a buffer layer between the top electrode and the BST layer have been prepared onto Pt-coated c-plane sapphire substrates. The dielectric measurements show that the loss tangent has been significantly lowered. The dielectric properties of the BST/SiN bilayered thin films are strongly dependent on the SiN thickness. The BST/SiN bilayered thin films at a SiN/BST thickness ratio of 0.2 ...

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Journal of Applied Physics : Optically driven fluid flow along arb...

By: Franz M. Weinert and Dieter Braun

Description: We show how fluid can be moved by a laser scanning microscope. Selected parts of a fluid film are pumped along the path of a moving warm spot which is generated by the repetitive motion of an infrared laser focus. With this technique, we remotely drive arbitrary two-dimensional fluid flow patterns with a resolution of 2 μm. Pump speeds of 150 μm/s are reached in water with a maximal temperature increase in the local spot of 10 K. Various experiments confirm ...

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Chaos : Synchronization of a class of chaotic systems with fully u...

By: M. Roopaei and M. Zolghadri Jahromi

Description: In this paper, an adaptive sliding mode control method for synchronization of a class of chaotic systems with fully unknown parameters is introduced. In this method, no knowledge of the bounds of parameters is required in advance and the parameters are updated through an adaptive control process. We use our proposed method to synchronize two chaotic gyros, which has been the subject of intense study during the recent years for its application in the navigati...

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Review of Scientific Instruments : A method for removing surfactan...

By: J. Kou and J. R. Saylor

Description: The study of heat, mass, and momentum transport across an air/water interface is an aspect of fluid mechanics where the presence of surfactant monolayers can play a significant role. Experimental studies of air/water transport typically require a method for cleaning the air/water interface so that it is free from any contaminating surfactant monolayer. This may be for the sake of running an experiment under clean surface conditions, or to clean the surface p...

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Physics of Fluids : Numerical study of the Guderley and Vasilev re...

By: Andrea Defina, Francesca Maria Susin, and Daniele Pietro Viero

Description: We present high-resolution numerical solutions of the depth-averaged two-dimensional inviscid shallow water equations which provide new information on shock reflection configuration within the von Neumann paradox conditions. The computed flow field and shock wave patterns close to the triple point for the Guderley and the Vasilev reflections confirm the four-wave theory. We suggest that the most likely Guderley reflection model is a four-wave pattern with a ...

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Journal of Mathematical Physics : The calculation of the bilinear ...

By: Ji-jun Ao and Achilaltu Wang

Description: The formula of the bilinear Boltzmann integral operator of gas mixtures is obtained. With the use of Bobylev’s transform it can be carried out much easier and an extended formula of more general validity is obtained. The formula can give the eigenvalues and the eigenfunctions of the bilinear Boltzmann integral operator of a gas mixture, which is essential to the solution of the Boltzmann equation.

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