可录型光盘(CD-R)中染料膜层的光谱性质和光学特性

本文利用光在多层膜介质中的传播模型,计算了可录型光盘（ＣＤ Ｒ）中染料媒体的光学特性．表明在适合于ＣＤ Ｒ光盘记录的７８０ｎｍ波长处,由于多层膜中光的干涉作用,样品反射率随薄膜的厚度变化发生振荡．振荡的幅度和周期依赖于染料薄膜的复数折射率（ｎ＋ｉｋ）．当记录介质层的复数折射率在２．１＋ｉ０．０２至２．８＋ｉ０．１２之间时,能够满足ＣＤ Ｒ光盘对染料介质的要求．通过对三种菁染料薄膜的光谱性质分析及光学参数的模拟计算,证实了该方法用于染料薄膜光学特性研究的合理性．并为选择适合于光记录的染料薄膜的厚度范围提供了简便的方法     

Soliton squeezing generated in an all-fiber contiguration

We experimentally demonstrate amplitude squeezed soliton utilizing intensity-dependent self-phase modulation in an asymmetric Sagnac interferometer.The system.whose components are connected via ferrule connector/physical connection(FC/PC)fiber connectors,constitutes all-fiber configuration to generate squeezed soliton.Soliton amplitude reduction measured by homodyne detection is near 4.0 dB below the shot-noise level.Optimal squeezing fields in both simple and compact all-fiber configuration are obtained.     

Monte-Carlo simulation of a compact gamma-ray detector using wavelength-shifting fibers coupled to a YAP scintillation crystal

The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes.An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area.With this gamma-ray detector,the gamma camera is small and flexible and has larger effective field of view and low cost.Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray,and a spatial resolution of 3.6 mm FWHM is obtained,b)a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained.Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout.However,since the very low photoelectron levels,it is very important to use a photon counting device with good single photo-electron response to readout the WSFs.     

Integrated Density of States for Ergodic Random Schrödinger Operators on Manifolds

We consider the Riemannian universal covering of a compact manifold M = X/ and assume that is amenable. We show the existence of a (nonrandom) integrated density of states for an ergodic random family of Schrödinger operators on X.     

High-order accurate dissipative weighted compact nonlinear schemes

Based on the method deriving dissipative compact linear schemes (DCS), novel high-order dissipative weighted compact nonlinear schemes (DWCNS) are developed. By Fourier analysis,the dissipative and dispersive features of DWCNS are discussed. In view of the modified wave number, the DWCNS are equivalent to the fifth-order upwind biased explicit schemes in smooth regions and the interpolations at cell-edges dominate the accuracy of DWCNS. Boundary and near boundary schemes are developed and the asymptotic stabilities of DWCNS on both uniform and stretching grids are analyzed. The multi-dimensional implementations for Euler and Navier-Stokes equations are discussed. Several numerical inviscid and viscous results are given which show the good performances of the DWCNS for discontinuities capturing, high accuracy for boundary layer resolutions, good convergent rates (the root-mean-square of residuals approaching machine zero for solutions with strong shocks) and especially the damping effect on the spudous oscillations which were found in the solutions obtained by TVD and ENO schemes.     

Nontransitive quasi-uniformities in the Pervin quasi-proximity class

We show that each topological space that does not admit a unique quasi-uniformity possesses a Pervin quasi-proximity class containing at least nontransitive members.

     

Normality and paracompactness of the Fell topology

Let be a Hausdorff topological space and the hyperspace of all closed nonempty subsets of . We show that the Fell topology on is normal if and only if the space is Lindelöf and locally compact. For the Fell topology normality, paracompactness and Lindelöfness are equivalent.

     

Four-Dimensional Compact Projective Planes with a Solvable Collineation Group

We consider a four-dimensional compact projective plane whose collineation group is six-dimensional and solvable with a nilradical N isomorphic to Nil×R, where Nil denotes the three-dimensional, simply connected, non-Abelian, nilpotent Lie group. We assume that fixes a flag p W, acts transitively on and fixes no point in the set W\p. Under these conditions, we will prove that either contains a three-dimensional group of elations or acts doubly transitively on .     

Countably compact extensions of topological spaces

We study the question whether a topological space X with a property $\text{P}$ can be embedded in a countably compact space X? with the same property $\text{P}$.