Ultra-elongated depth of focus of plasmonic lenses with concentric elliptical slits under Gaussian beam illumination

In this paper, we discuss the influence of ratio of minor to major axis on the propagation property and focusing performance of a plasmonic lens with variant periodic concentric elliptical slits illuminating under a Gaussian beam. In order to analyse the influence theoretically, a finite-difference time-domain （FDTD） numerical algorithm is adopted for the computational numerical calculation and the design of the plasmonic structure. The structure is flanked with penetrated slits through a 200-nm metal film （Au） which is coated on a quartz substrate. Tunability of focusing capability of the plasmonic lenses is studied by tailoring the ratio. Our calculation results demonstrate that the ratio of the elliptical slits greatly affects the focusing capability of the lense. The plasmonic lenses with concentric elliptical slits illuminating under a Gaussian beam have ultra-elongated depth of focus. These results are very encouraging for the future study of the plasmonic lens-based applications.     

Depth‐integrated free‐surface flow with a two‐layer non‐hydrostatic formulation

This paper presents the derivation of a depth‐integrated wave propagation and runup model from a system of governing equations for two‐layer non‐hydrostatic flows. The governing equations are transformed into an equivalent, depth‐integrated system, which separately describes the flux‐dominated and dispersion‐dominated processes. The depth‐integrated system reproduces the linear dispersion relation within a 5 error for water depth parameter up to kd = 11, while allowing direct implementation of a momentum conservation scheme to model wave breaking and a moving‐waterline technique for runup calculation. A staggered finite‐difference scheme discretizes the governing equations in the horizontal dimension and the Keller box scheme reconstructs the non‐hydrostatic terms in the vertical direction. An semi‐implicit scheme integrates the depth‐integrated flow in time with the non‐hydrostatic pressure determined from a Poisson‐type equation. The model is verified with solitary wave propagation in a channel of uniform depth and validated with previous laboratory experiments for wave transformation over a submerged bar, a plane beach, and fringing reefs. Copyright © 2011 John Wiley & Sons, Ltd.     

Axial performance parameters developed for analytical design of center shaded filter in high aperture focusing system

In order to establish the explicit interrelation between the performance and structure parameters of a center shaded filter in high aperture focusing systems, approximate integral equations are proposed and further used to derive axial performance parameters, which are required for the evaluation of axial energy loss and focal depth extension. It has been derived that the axial intensity can be analytically expressed as a square of sinc function and the shaded angle of a center shaded filter can be explicitly calculated using either the expected Strehl ratio or axial gain. The developed axial performance parameters are proved through simulation to be precisely consistent with numerical evaluation results.     

Doping of nuclear tracks with fullerene solution

Latent nuclear tracks in polymers can occasionally be doped with fullerene solution. A new technique - ‘Fullerene Tracer Profiling’, FTP - allows us to verify the success of the doping procedure by determining the fullerene depth distribution along the tracks. The basic principle of FTP is described, and first examples are given. Fullerene solution is found to penetrate into ion tracks in polyimide, but not into tracks in polypropylene, or into unirradiated polyimide or polypropylene foils.     

Counting the onion

Iteratively computing and discarding a set of convex hulls creates a structure known as an “onion.” In this paper, we show that the expected number of layers of a convex hull onion for n uniformly and independently distributed points in a disk is Θ(n^2/3). Additionally, we show that in general the bound is Θ(n^2/(d+1)) for points distributed in a d‐dimensional ball. Further, we show that this bound holds more generally for any fixed, bounded, full‐dimensional shape with a nonempty interior. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004     

Escape factors for laser-plasmas

A method of parameterizing escape factors (transmission factors and net radiative brackets) for conditions typical of laser-produced plasmas is introduced. The assumptions of planar geometry, exponentially decreasing emissivity and absorption coefficient with distance with a step rise at a particular point, and spatially constant Doppler broadened line profiles have been made. The effect of velocity gradients in spectrally shifting the absorption and emission line profiles relative to each other is taken into account assuming linear velocity gradients with distance. A parameter R representing the ratio of the spatial scale-length of the absorption coefficient to the Doppler decoupling length is introduced. Fitting formulae for transmission factors and net radiative brackets are given which are valid for all R and all optical depths. In the limit of small R (large Doppler decoupling length), the escape factors asymptotically approach formulae developed originally by, for example, Holstein assuming negligible plasma velocities. For large R (small Doppler decoupling length), the escape factors have been shown to asymptotically approach the Sobolev approximation. The parameterized net radiative bracket has been used in the hydrodynamic and atomic physics code ‘EHYBRID’ for the calculation of the effect of radiation trapping on population densities in laser-produced plasmas. The output of the modified EHYBRID code has then been post processed using the parameterised transmission factors to simulate 123 Ne-like and 399 F-like germanium resonance line intensities emitted in typical X-ray laser experiments. We obtain an agreement between the simulated and experimental spectra.     

Neon Color Spreading Promoted by Motion Information

We conducted experiments to investigate the effects of head-motion and object-motion to produce a perception of neon color spreading. Our experimental results indicated that a two-dimensional motion of yellow patches promoted the color spreading. A horizontal head-motion with motion parallax and three-dimensional pictorial depth information together with changing the viewing point stimulated the color spreading even, more than the two-dimensional motion. Thus, motion signals appear to offer useful information for the formation of a subjective contour and/or to activate the filling-in effect needed to generate neon color spreading. We also tested whether there was a difference between the effects of vertical and horizontal motion parallaxes for neon color spreading and found that there was none. This suggests that vertical head motion provides information in depth and surface perception equivalent to horizontal head motion.     

Plane-chain coupling in YBa2Cu3O7: temperature dependence of the penetration depth

We have studied the penetration depth for a model of YBa₂Cu₃O₇ involving pairing, both in the CuO₂ planes and in the CuO chains. In this model pairing in the planes is due to an attractive interaction, while Coulomb repulsion induces in the chains an order parameter with opposite sign. Due to the anti-crossing produced by hybridization between planes and chains, one obtains a d-wave like order parameter which changes sign on a single sheet of the Fermi surface and has nodes in the gap. We find that our model accounts quite well for the anisotropy of the penetration depth and for the absolute values. We reproduce fairly well the whole temperature dependence for both the a- and the b-directions, including the linear dependence at low temperature. We use a set of parameters which are all quite reasonable physically. Our results for the c-direction are also satisfactory, although the situation is less clear both experimentally and theoretically.     

孔洞厚度对高功率微波脉冲耦合的影响

通过数值模拟研究了高功率微波脉冲与有限厚度孔洞的耦合过程，得出了孔洞厚度对高功率微波脉冲耦合的一些有用结果。     

STRESS AND DEFORMATION FIELDS ABOUT A LOCKED FAULT IN DEPTH

In this paper the stress and deformation fields about a locked fault in depth have been imitated using 3-dimensional finite element method and their time-space variation features have been analysed. The authors consider tentatively that the horizontal stresses about an active fault decrease slightly near the fault. The distributions of stress increasing and decreasing regions due to the locking of a fault are skew-symmetrical about the fault. The stresses about the locked region are increased in a larger range, where great elastic strain energy is accumulated and a stronger earthquake is more easily developed than at the ends of the fault. Reverse variations of crustal stress and deformation may be related to the different stages of the seismogeny of an earthquake focus.