33,492 research outputs found

    Ultra-high resolution Fourier domain optical coherence tomography for resolving thin layers in painted works of art

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    While OCT has been applied to the non-invasive examination of the stratigraphy of paint layers in recent years, it has been recognized that the resolutions of commercially available OCT cannot compete in depth resolution with conventional microscopic examination of cross-sections of paint samples. It is necessary to achieve resolutions better than 3 microns to resolve the thinnest layers of paint and varnish. In this paper, we demonstrate a Fourier domain ultrahigh resolution OCT at 810nm with depth resolution of 1.8μm in air (or 1.2μm in varnish or paint)

    Properties of nano-graphite ribbons with zigzag edges -- Difference between odd and even legs --

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    Persistent currents and transport properties are investigated for the nano-graphite ribbons with zigzag shaped edges with paying attention to system length LL dependence. It is found that both the persistent current in the isolated ring and the conductance of the system connected to the perfect leads show the remarkable LL dependences. In addition, the dependences for the systems with odd legs and those with even legs are different from each other. On the persistent current, the amplitude for the cases with odd legs shows power-low behavior as LNL^{-N} with NN being the number of legs, whereas the maximum of it decreases exponentially for the cases with even legs. The conductance per one spin normalized by e2/he^2/h behaves as follows. In the even legs cases, it decays as L2L^{-2}, whereas it reaches to unity for LL \to \infty in the odd legs cases. Thus, the material is shown to have a remarkable property that there is the qualitative difference between the systems with odd legs and those with even legs even in the absence of the electron-electron interaction.Comment: 4 pagaes, 8 figures, LT25 conference proceeding, accepted for publication in Journal of Physics: Conference Serie

    Supersonic airplane design optimization method for aerodynamic performance and low sonic boom

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    This paper presents a new methodology for the optimization of supersonic airplane designs to meet the dual design objectives of low sonic boom and high aerodynamic performance. Two sets of design parameters are used on an existing High Speed Civil Transport (HSCT) configuration to maximize the aerodynamic performance and minimize the sonic boom under the flight track. One set of the parameters perturbs the camber line of the wing sections to maximize the lift-over-drag ratio (L/D). A preliminary optimization run yielded a 3.75 percent improvement in L/D over a baseline low-boom configuration. The other set of parameters modifies the fuselage area to achieve a target F-function. Starting from an initial configuration with strong bow, wing, and tail shocks, a modified design with a flat-top signature is obtained. The methods presented can easily incorporate other design variables and objective functions. Extensions to the present capability in progress are described
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