722 research outputs found

    Adaptive multibeam phased array design for a Spacelab experiment

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    The parametric tradeoff analyses and design for an Adaptive Multibeam Phased Array (AMPA) for a Spacelab experiment are described. This AMPA Experiment System was designed with particular emphasis to maximize channel capacity and minimize implementation and cost impacts for future austere maritime and aeronautical users, operating with a low gain hemispherical coverage antenna element, low effective radiated power, and low antenna gain-to-system noise temperature ratio

    Study on successive superconducting transitions in Ta2_{2}S2_{2}C from electrical resistivity and nonlinear AC magnetic susceptibility

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    Ta2_{2}S2_{2}C compound undergoes superconducting transitions at Tcl=3.60±0.02T_{cl} = 3.60 \pm 0.02 K and Tcu=9.0±0.2T_{cu} = 9.0 \pm 0.2 K. The nature of successive superconducting transitions has been studied from electrical resistivity, linear and nonlinear AC magnetic susceptibilities. The resistivity ρ\rho at HH = 0 shows a local maximum near TcuT_{cu}, a kink-like behavior around TclT_{cl}, and reduces to zero at below T0T_{0} = 2.1 K. The lnT\ln T dependence of ρ\rho is observed at HH = 50 kOe at low temperatures, which is due to two-dimensional weak-localization effect. Below TcuT_{cu} a two-dimensional superconducting phase occurs in each TaC layer. The linear and nonlinear susceptibilities χ1\chi_{1}^{\prime\prime}, χ3\chi_{3}^{\prime}, χ5\chi_{5}^{\prime}, and χ7\chi_{7}^{\prime} as well as the difference δχ\delta\chi (=χFCχZFC= \chi_{FC} - \chi_{ZFC}) between the FC and ZFC susceptibilities, start to appear below 6.0 K, the onset temperature of irreversibility. A drastic growth of the in-plane superconducting coherence length below 6.0 K gives rise to a three-dimensional superconducting phase below TclT_{cl}, through interplanar Josephson couplings between adjacent TaC layers. The oscillatory behavior of χ3\chi_{3}^{\prime\prime}, χ5\chi_{5}^{\prime\prime}, and χ7\chi_{7}^{\prime\prime} below TclT_{cl} is related to the nonlinear behavior arising from the thermally activated flux flow.Comment: 11 pages, 10 figures, Physical Review B (accepted for publication

    Focal Plane Detector System of SHARAQ Spectrometer

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    International audienceThis report describes the basic performance of the detector system installed in the final momentum-dispersive focal plane of the SHARAQ spectrometer

    Fluctuating-friction molecular motors

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    We show that the correlated stochastic fluctuation of the friction coefficient can give rise to long-range directional motion of a particle undergoing Brownian random walk in a constant periodic energy potential landscape. The occurrence of this motion requires the presence of two additional independent bodies interacting with the particle via friction and via the energy potential, respectively, which can move relative to each other. Such three-body system generalizes the classical Brownian ratchet mechanism, which requires only two interacting bodies. In particular, we describe a simple two-level model of fluctuating-friction molecular motor that can be solved analytically. In our previous work [M.K., L.M and D.P. 2000 J. Nonlinear Opt. Phys. Mater. vol. 9, 157] this model has been first applied to understanding the fundamental mechanism of the photoinduced reorientation of dye-doped liquid crystals. Applications of the same idea to other fields such as molecular biology and nanotechnology can however be envisioned. As an example, in this paper we work out a model of the actomyosin system based on the fluctuating-friction mechanism.Comment: to be published in J. Physics Condensed Matter (http://www.iop.org/Journals/JPhysCM
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