斜角入射沉积法制备渐变折射率薄膜的折射率分析

斜角入射沉积法是一种制备薄膜的新颖方法，它可以用来制备渐变折射率薄膜．本文首先探讨了膜料的沉积入射角为α，薄膜柱状生长倾斜角为β时的薄膜的填充系数；之后利用drude理论，分析研究了斜角入射沉积法制备渐变折射率薄膜的折射率与薄膜的入射角和生长方向的关系．

In-situ synthesis of AlN powders and composite AlN powders with yttrium addition

Using Al-Mg and Al-Mg-Y alloys as raw materials and nitrogen as gas reactants, AIN powders and composite AIN powders by in-situ synthesis method were prepared. AIN lumps prepared by the nitriding of Al-Mg and Al-Mg-Y alloys have porous microstructure, which is favorable for pulverization. They have high purity, containing 1.23 % (mass fraction) oxygen impurity, and consisted of AIN single phase . The average particle size of AIN powders is 6.78 mum. Composite AlN powders consist of AlN phases and rare, earth oxide Y2O3 phase. The distribution of particle size of AIN powders shows two peaks. In view, of packing factor, AIN powders with such size distribution can easily be sintered to high density.

Tight intermolecular packing through supramolecular interactions in crystals of cyano substituted oligo(para-phenylene vinylene): a key factor for aggregation-induced emission

Strong supramolecular interactions, which induced tight packing and rigid molecules in crystals of cyano substituent oligo(para-phenylene vinylene) (CN-DPDSB), are the key factor for the high luminescence efficiency of its crystals; opposite to its isolated molecules in solution which have very low luminescence efficiency.

Dynamic stress intensity factor of a functionally graded material under antiplane shear loading

The dynamic response of a finite crack in an unbounded Functionally Graded Material (FGM) subjected to an antiplane shear loading is studied in this paper. The variation of the shear modulus of the functionally graded material is modeled by a quadratic increase along the direction perpendicular to the crack surface. The dynamic stress intensity factor is extracted from the asymptotic expansion of the stresses around the crack tip in the Laplace transform plane and obtained in the time domain by a numerical Laplace inversion technique. The influence of graded material property on the dynamic intensity factor is investigated. It is observed that the magnitude of dynamic stress intensity factor for a finite crack in such a functionally graded material is less than in the homogeneous material with a property identical to that of the FGM crack plane.

Computer Simulation Of Random Sphere Packing In An Arbitrarily Shaped Container

Most simulations of random sphere packing concern a cubic or cylindric container with periodic boundary, containers of other shapes are rarely studied. In this paper, a new relaxation algorithm with pre-expanding procedure for random sphere packing in an arbitrarily shaped container is presented. Boundaries of the container are simulated by overlapping spheres which covers the boundary surface of the container. We find 0.4 similar to 0.6 of the overlap rate is a proper value for boundary spheres. The algorithm begins with a random distribution of small internal spheres. Then the expansion and relaxation procedures are performed alternately to increase the packing density. The pre-expanding procedure stops when the packing density of internal spheres reaches a preset value. Following the pre-expanding procedure, the relaxation and shrinking iterations are carried out alternately to reduce the overlaps of internal spheres. The pre-expanding procedure avoids the overflow problem and gives a uniform distribution of initial spheres. Efficiency of the algorithm is increased with the cubic cell background system and double link data structure. Examples show the packing results agree well with both computational and experimental results. Packing density about 0.63 is obtained by the algorithm for random sphere packing in containers of various shapes.

Stress intensity factor histories of a steadily propagating crack under 3-D combined mode traction

Elastodynamic stress intensity factor histories of an unbounded solid containing a semi-infinite plane crack that propagates at a constant velocity under 3-D time-independent combined mode loading are considered. The fundamental solution, which is the response of point loading, is obtained. Then, stress intensity factor histories of a general loading system are written out in terms of superposition integrals. The methods used here are the Laplace transform methods in conjunction with the Wiener-Hopf technique.

Elastodynamic stress intensity factor history for a semi-infinite crack under three-dimensional transient loading

The dynamic stress intensity factor history for a semi-infinite crack in an otherwise unbounded elastic body is analyzed. The crack is subjected to a pair of suddenly-applied point loadings on its faces at a distance L away from the crack tip. The exact expression for the mode I stress intensity factor as a function of time is obtained. The method of solution is based on the direct application of integral transforms, the Wiener-Hopf technique and the Cagniard-de Hoop method. Due to the existence of the characteristic length in loading this problem was long believed a knotty problem. Some features of the solutions are discussed and graphical result for numerical computation is presented.

A new method of measuring the waveguide dispersion factor and the thermo-optic coefficient of long-period fiber gratings

Based on the Mach-Zehnder effect between the core mode and the cladding modes, the interference fringes are formed by a pair of cascaded long-period fiber gratings (CLPFGs). Theoretical analyses show that the spectral spacing and the wavelength of these fringes are functions of the waveguide dispersion factor gamma, which is a characterizing parameter to LPFG and with theoretical and applicational significance. By measuring the characteristics of the transmission spectra of CLPFGs, the absolute value of gamma can be obtained. At the same time, the thermo-optic coefficient of effective refractive index difference between core and cladding modes, p, can also be obtained by measured the temperature sensitivity of these fringes. In the experiments, \gamma\ and mu were measured by this method to be 0.874 and 4.08 x 10(-5) degreesC(-1), respectively, for LPFGs with period of 450 mum and with a HE14 resonant peak at 1554 nm. (C) 2004 Elsevier B.V. All rights reserved.

Anomalous scattering factor determined by semicircle fitting near the K-absorption edge of Ge

It is shown that the locus of the f' + if '' plot in the complex plane, f' being determined from measured f '' by using the dispersion relation, looks like a semicircle very near the absorption edge of Ge. The semicircular locus is derived from a quantum theory of X-ray resonant scattering when there is a sharp isolated peak in f '' just above the K-absorption edge. Using the semicircular behavior, an approach is proposed to determine the anomalous scattering factors in a crystal by fitting known calculated values based on an isolated-atom model to a semicircular focus. The determined anomalous scattering factors f' show excellent agreement with the measured values just below the absorption edge. In addition, the phase determination of a crystal structure factor has been considered by using the semicircular behavior.

Far-field intensity distribution and M-2 factor of hollow Gaussian beams

The far-field intensity distribution of hollow Gaussian beams was investigated based on scalar diffraction theory. An analytical expression of the M-2 factor of the beams was derived on the basis of the second-order moments. Moreover, numerical examples to illustrate our analytical results are given. (c) 2005 Optical Society of America.

Effects of oxygen partial pressure on packing density and laser damage threshold of TiO2 thin films

TiO2 films are deposited by electron beam evaporation as a function of oxygen partial pressure. The packing density, refractive index, and extinction coefficient all decrease with the increase of pressure, which also induces the change of the film's microstructure, such as the increase of voids and H2O concentration in the film. The laser-induced damage threshold (LIDT) of the film increases monotonically with the rise of pressure in this experiment. The porous structure and low nonstoichiometric defects absorption contribute to the film's high LIDT. The films prepared at the lowest and the highest pressure show nonstoichiometric and surface-defects-induced damage features, respectively.(C) 2007 American Institute of Physics.

Far-field intensity distribution, M-2 factor of beams generated by Gaussian mirror resonator

We investigated M-2 factor and far-field distribution of beams generated by Gaussian mirror resonator. And we found usable analytical expressions of the M2 factor and the far-field distribution intensity with respect to variation of diffraction parameters. Particular attention was paid to the parameters such as mirror spot size and reflectance of the Gaussian mirror. (c) 2006 Elsevier GrnbH. All rights reserved.