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Dynamics of converging laser-created plasmas in semicylindrical cavities studied using soft x-ray laser interferometry

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Physical Review E 2007年第4期76卷 046402-046402页

作者： Mike Purvis Jonathan Grava Jorge Filevich Mario C. Marconi James Dunn Stephen J. Moon Vyacheslav N. Shlyaptsev Elizabeth Jankowska Jorge J. Rocca NSF ERC for Extreme Ultraviolet Science and Technology and Department of Electrical and Computer Engineering Colorado State University Fort Collins Colorado 80523 USA Department of Physics Colorado State University Fort Collins Colorado 80523 USA Lawrence Livermore National Laboratory Livermore California 94551 USA Department of Applied Science University of California Davis-Livermore Livermore California 94551 USA Wroclaw University of Technology Wroclaw Poland

The evolution of dense aluminum and carbon plasmas produced by laser irradiation of 500−μm-diam semicylindrical targets was studied using soft x-ray laser interferometry. Plasmas created heating the cavity walls with 120−ps—duration optical laser pulses of ∼1×1012Wcm−2 peak intensity were observed to expand and converge on axis to form a localized high-density plasma region. Electron density maps were measured using a 46.9−nm-wavelength tabletop capillary discharge soft x-ray laser probe in combination with an amplitude division interferometer based on diffraction gratings. The measurements show that the plasma density on axis exceeds 1×1020cm−3. The electron density profiles are compared with simulations conducted using the hydrodynamic code HYDRA, which show that the abrupt density increase near the axis is dominantly caused by the convergence of plasma generated at the bottom of the groove during laser irradiation.

关键词： Plasmas

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High light-extraction efficiency in GaInN light-emitting diode with pyramid reflector

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Proceedings of SPIE - The International Society for Optical engineering 2007年 6486卷

作者： Xi, J.-Q. Luo, Hong Kim, Jong Kyu Schubert, E.F. Future Chips Constellation Rensselaer Polytechnic Institute 110 8th Street Troy NY 12180 United States Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute 110 8th Street Troy NY 12180 United States Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute 110 8th Street Troy NY 12180 United States

ISBN: (纸本)0819465992;9780819465993

A GaInN light-emitting diode (LED) that employs a new type of reflector consisting of an array of SiO2 pyramids and a reflective Ag layer is demonstrated to have enhanced light extraction compared to GaInN LEDs with a planar Ag reflector. Ray tracing simulations reveal that the pyramid reflector provides 14.1% enhancement in extraction efficiency. Consistent with the simulation, it is experimentally demonstrated that the GaInN LED employing the pyramid-patterned Ag reflector shows 13.9% higher light-output compared to the LED with a planar Ag reflector. In addition, the GaInN LED with pyramid reflector shows uniform light intensity due to current spreading beneath the SiO2 pyramid pattern. The enhancement is attributed to the appearance of an additional escape cone for light extraction, enabled by the change in direction of light rays reflected by the 3-dimensional pyramid reflector.

关键词： Light emitting diodes

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Molecular dynamic simulation of heat pulse propagation in multiwall carbon nanotubes

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Physical Review B 2007年第15期76卷 155424-155424页

作者： Taejin Kim Mohamed A. Osman Cecilia D. Richards David F. Bahr Robert F. Richard Material Science Program Washington State University Pullman Washington 99164-4620 USA Department of Physics Washington State University Pullman Washington 99164-2814 USA School of Electrical Engineering and Computer Science Washington State University Pullman Washington 99164-2752 USA School of Mechanical and Materials Engineering Washington State University Pullman Washington 99164-2920 USA

The propagation of heat pulses in zigzag and armchair double wall nanotubes (DWNTs) has been investigated using molecular dynamics simulations. It is found that the leading heat wave packets in zigzag (9,0)∕(18,0) and armchair (5,5)∕(10,10) DWNTs move with the speed of longitudinal acoustic (LA) phonon modes. The intensities of the leading heat wave packets in outer and inner shells in DWNTs were found to be five to seven times larger than that of the corresponding single wall nanotubes (SWNTs). The heat energy carried by the leading heat wave packets in zigzag DWNT was about four and five times more than those in armchair DWNT shells. Within the leading LA wave packet, the strain in the inner shell of the DWNTs is stronger than the strain in the outer shell and considerably larger than strain in the corresponding SWNTs. The regions with the largest strain coincide with the regions of high kinetic temperatures within the LA mode wave packets. The higher energy of the LA mode waves in DWNT shells compared to SWNT is attributed to the presence of higher strain fields in DWNTs compared to individual SWNTs. The higher strain in the inner shell of DWNT compared to the outer shell accounts for the three to five times higher kinetic energy of leading wave packets in inner shells compared to those in outer shells. The induced strain fields in zigzag DWNT are distributed over a wider region compared to armchair DWNT, and the strains in inner and outer shells of zigzag DWNT are out phase by 180°.

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Oscillator models and collective motion

IEEE Control Systems Magazine

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IEEE Control Systems Magazine 2007年第4期27卷 89-105页

作者： Paley, Derek A. Leonard, Naomi Ehrich Sepulchre, Rodolphe Grünbaum, Daniel Parrish, Julia K. Princeton University Department of Mechanical and Aerospace Engineering Princeton NJ 08544 United States Department of Mechanical and Aerospace Engineering Program in Applied and Computational Mathematics Princeton University Princeton NJ 08544 United States Department Electrical Engineering and Computer Science University of Liège Liège Belgium School of Oceanography Department of Biology University of Washington Seattle WA United States Biology Department School of Aquatic and Fishery Sciences University of Washington Seattle WA United States

A description of the so called "particles with coupled oscillator dynamics" (PCOD) is presented which is used to model, analyze and synthesize collective motion. An oscillator model with spatial dynamics is presented to help describe how to design steering control laws while it is being used to study biological collectives. Lastly, both engineering and biological analysis were described.

关键词： Oscillators (mechanical)

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Comparison of modeled and observed microwave emissivities of water surfaces in the presence of breaking waves and foam

Comparison of modeled and observed microwave emissivities of...

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IEEE International Symposium on Geoscience and Remote Sensing (IGARSS)

作者： S. Padmanabhan S. C. Reising W. E. Asher V. Raizer P. W. Gaiser Department of Electrical and Computer Engineering Colorado State University Fort Collins CO USA Applied Physics Laboratory University of Washington Seattle WA USA Zel Technologies Limited Liability Company Fairfax VA USA Remote Sensing Division Naval Research Laboratory Inc. WA USA

Wind speed has been retrieved reliably from SSM/I microwave radiometric measurements since 1990 with a precision of better than 2 m/s. However, operational requirements of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) dictate retrieval of the ocean surface wind vector, i.e. both speed and direction. This requires improved understanding and forward modeling of the physical processes governing ocean surface microwave emissivity. Although the microwave brightness temperature over the ocean exhibits a relatively strong dependence on wind speed, the dependence on wind direction with respect to the azimuthal angle of observation is at most a few Kelvin peak-to-peak. Although it is known that breaking waves and foam significantly affect the microwave emission of the ocean surface at 6.8, 10.8, 19 and 37 GHz, the effect of foam on the azimuthal dependence of sea surface emissivity is not well understood. This understanding is critical to improve forward models to achieve the accuracy required for ocean surface wind vector retrievals. Recently, electromagnetic modeling of the emissivity of foam generated by breaking waves has been improved by considering the vertical and horizontal heterogeneity of thick layers of foam at the ocean- atmosphere interface [1]. In this work, we compare foam emissivities both calculated using this model with those inferred from microwave brightness temperature measurements performed during the Polarimetric Observations of the Emissivity of Whitecaps Experiment (POEWEX'04).

关键词： Surface waves Sea surface Ocean temperature Wind speed Microwave measurements Sea measurements Brightness temperature Atmospheric modeling Microwave radiometry Velocity measurement

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Dispersion Characteristics of TE Waves in Beam-Loaded Corrugated Waveguides with Losses

Dispersion Characteristics of TE Waves in Beam-Loaded Corrug...

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32nd International Conference on Infrared and Millimeter Waves, and 15th International Conference on Terahertz Electronics (IRMMW-THz 2007), part 1

作者： George P. Latsas Ioannis G. Tigelis John L. Vomvoridis Faculty of Physics Department of Applied Physics National and Kapodistrian University of Athens Athens Greece School of Electrical and Computer Engineering Division of Electromagnetics National and Technical University of Athens Athens Greece

A universal method based on an eigenfunction expansion and the linearized Vlasov equation is used to study the dispersion relation and the field distributions of TE modes for beam-loaded circumferentially corrugated waveguides at the small-signal regime. The possible interaction regions are studied and the growth rate of the emerging modes is presented for geometries with and without losses. The effect of the losses is examined, whereas the possibility of the evolution of TE modes in a lossy structure like a gyrotron beam tunnel is discussed.

关键词： Corrugated waveguides Cyclotron resonance Gyrotrons

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Crystallographic Study of Mixtures La1+xBa2−xCu3Oy (x=0,0.2,0.4,0.6) after annealing at 860°C

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AIP Conference Proceedings 2007年第1期899卷 657-657页

作者： A. Stergiou S. Yilmaz C. Stergiou 1Department of Physics Laboratory of Applied Physics Aristotle University of Thessaloniki Greece 2Department of Electrical & Computer Engineering Aristotle University of Thessaloniki Greece

Four powder mixtures with chemical formula La1+xBa2−xCu3Oy was prepared. The mixtures were heated in free atmosphere, at temperature 850°C for 60h and then at 860°C for 40h. XRD measurements were obtained with CuKa radiation. The samples were characterized with the help of the PDF and refined, using the Rietveld’s “Powder Profile Analysis”. Four phases, same for all the samples, were found: (La,Ba)2CuO4, BaCuO2, LaBa2Cu3O7−d, and BaCO3. The percentages of the tour phases are changed, as the x quantity increases, and varied from 38, 25, 18, 19%, for x=0, to 69, 14, 7, 10%, for x=0.6, respectively.

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Crystallographic Study of Mixture CeBa1.8Pb0.2Cu3Oy in the Range of 860°C to 940 °C

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AIP Conference Proceedings 2007年第1期899卷 656-656页

A powder mixture with chemical formula CeBa1.8Pb0.2Cu3Oy was prepared. The mixture was heated in free atmosphere, at temperatures 860°C to 940°C, for 24 to 72h. The samples were measured by X‐Ray powder diffraction with CuKa radiation. Each sample was characterized with the help of the PDF and refined, using the Rietveld’s “Powder Profile Analysis”. The first sample (860°C) was identified with the phases: Ba2CeBiO6, CuO and BaCuO2, while all the remaining samples (870°C–940°C) with the phases Ba2CePbO6, CuO and CeO2. The phases Ba2CeBiO6 and Ba2CePbO6 are the main phases with analogous chemical types, but different symmetry. The phase CuO is common in all the samples, while from the remaining phases the BaCuO2 appears only in the first sample and the CeO2 in all, except the first one. The quantity 0.2 of Pb is distributed in the Ba positions, substituting a part of these. The percentages of phases are about 82%, 10% and 8% for the first sample and for all the remaining about 85%, 8% and 7%, respectively with above serious.

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Lattice Boltzmann Algorithms for Fluid Turbulence

Lattice Boltzmann Algorithms for Fluid Turbulence

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DoD High Performance Computing Modernization program Users Group

作者： G. Vahala J. Yepez M. Soe L. Vahala S. Ziegeler Department of Physics The College of William and Mary Williamsburg VA USA U.S. Air Force Research Laboratory MA USA US Air Force Research Laboratory (AFRL) Hanscom Field MA Department of Mathematics and Science Rogers State University Claremore OK USA Department of Electrical & Computer Engineering Old Dominion University Norfolk VA USA High Performance Computing Modernization Program Mississippi State University MS

Lattice Boltzmann algorihms are a mesoscopic representation of nonlinear continuum physics (like Navier-Stokes, magnetohydro dynamics (MHD), Gross- Pitaevskii equations) which are ideal for parallel supercomputers because they transform the difficult nonlinear convective macroscopic derivatives into purely local moments of distribution functions. The macroscopic nonlinearities are recovered by relaxation distribution functions in the collision operator whose dependence on the macroscopic velocity is algebraically nonlinear and thus purely local. Unlike standard computational fluid dynamics codes, there is no loss in parallelization in handling arbitrary geometric boundaries, e.g., using bounce-back rules from kinetic theory. By encoding detailed balance into the collision operator through the introduction of discrete H-function, the lattice Boltzmann algorithm can be made unconditionally stable for arbitrary high Reynolds numbers. It is shown that this approach is a special case of a quantum lattice Boltzmann algorithm that entangles local qubits through unitary collision operators and which is ideally parallelized on quantum computer architectures. Here we consider turbulence simulations using 2,048 PEs on a 1,6003-spatial grid. A connection is found between the rate of change of enstrophy and the onset of laminar-to- turbulent flows.

关键词： Lattice Boltzmann methods Magnetohydrodynamics Distribution functions Quantum computing Quantum entanglement physics Fluid dynamics Navier-Stokes equations Nonlinear equations Supercomputers

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Decision Fusion of Circulating Markers for Breast Cancer Detection in Premenopausal Women

Decision Fusion of Circulating Markers for Breast Cancer Det...

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IEEE Symposium on Bioinformatics and Bioengineering (BIBE)

作者： Jonathan L. Jesneck Sayan Mukherjee Loren W. Nolte Anna E. Lokshin Jeffrey R. Marks Joseph Lo Duke Advanced Imaging Labs Institute for Genome Sciences and Policy Department of Computer Science Duke University USA Department of Electrical and Computer Engineering Division of Hematology/Oncology University of Pittsburgh School of Medicine Pittsburgh PA USA Division of Hematology/Oncology University of Pittsburgh Cancer Institute Pittsburgh PA USA Division of Hematology/Oncology University of Pittsburgh Cancer Institute Pittsburgh PA Institute for Genome Sciences and Policy Department of Experimental Surgery Medical Center Duke University USA Department of Experimental Surgery Duke University Medical Center Medical Physics Graduate Program Duke University Durham NC USA

Current mammographic screening for breast cancer is less effective for younger women. To complement mammography for premenopausal women, we investigated the feasibility screening test using 98 blood serum proteins. Because the data set was very noisy and contained only weak features, we used a classifier designed for noisy data: decision fusion. Decision fusion outperformed both a support vector machine (SVM) and linear regression with forward stepwise feature selection on all three two-class classification tasks: normal tissue vs. cancer, normal tissue vs. benign lesions, and benign lesions vs. cancer. Decision fusion detected cancer moderately well (AUC=0.84 on normal vs. cancer), demonstrating promise as a screening tool. Decision fusion also detected benign lesions similarly well (AUC=0.83 on normal vs. benign lesions) and was the only classifier to achieve any success in separating benign from malignant lesions (AUC=0.64 on benign vs. cancer). The classification results suggest that the assayed proteins are more indicative of a secondary effect, such as immune response, rather than specific for breast cancer. In conclusion, the decision fusion classifier demonstrated some promise in detecting breast lesions and outperformed other classifiers, especially for the very noisy classification problem of distinguishing benign from malignant lesions.

关键词： Breast cancer Cancer detection Lesions Proteins Support vector machines Support vector machine classification Mammography Testing Blood Linear regression

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