Anti-plane analysis on a finite crack in a one-dimensional hexagonal quasicrystal strip

The anti-plane fracture problem for a finite crack in a one-dimensional hexagonal quasicrystal strip is analyzed. By using Fourier transforms, the mixed boundary value problems are reduced to the dual integral equations. The solution of the dual integral equations is then expressed by the complete elliptic integrals of the first and the third kinds. The expressions for stress, strains, displacements and field intensity factors of the phonon and phason fields near the crack tip are obtained exactly. The path-independent integral derived by a conservation law equals the energy release rate, which can be used as a fracture criterion for a mode III fracture problem.     

Viewing the effective k-space coverage of MR images: phantom experiments with fast Fourier transform

The purpose of this experimental study was to evaluate whether the effective k-space coverage of MR images can in principle be viewed after multidimensional Fourier transform back to k-space.     

Simulated Raman spectra of four tetraphenylbutadiene polymorphs

We report a combined experimental and theoretical investigation on the Raman spectra of the polymorphs α, β, γ, and δ of 1,1,4,4‐tetraphenyl‐1,3‐butadiene (TPB), in the region of the intramolecular modes. The interpretation of the polarized spectra is supported by ab‐initio calculations for the isolated molecules and by lattice dynamics calculations for the crystals. The calculations reproduce the peculiar, and surprisingly large, differences among the spectra of the various polymorphs. The phenyl groups of 1,1,4,4‐tetraphenyl‐1,3‐butadiene may arrange themselves around the butadiene skeleton in 2 stable conformers, which have either inversion (C_i) or 2‐fold (C₂) symmetry and therefore exhibit intramolecular vibrations with quite different Raman selection rules and spectra. The compound forms 4 crystalline polymorphs (α, β, γ, and δ) with different combinations of C_i and C₂ conformers, and correspondingly different intramolecular spectra. The theoretical calculations provide a quantitative analysis of the various spectra.     

高斯型光谱设计在飞秒激光放大器中消除增益窄化效应的研究

本文主要从增益窄化效应入手,通过理论分析并结合数据模拟说明了高斯型光谱设计在消除增益窄化效应方面的重要作用,导出了确定调制参量的较为适用的关系式,为实际的实验系统提供了一种可行的设计依据.     

羰基振动频率的理论计算模拟

分子中具有红外活性的两个原子间的振动频率与化学键的力常数及折合质量有关,本工作将力常数和折合质量的比值表砂与理论计算结果中原子的电荷,化学键的键长和键级等住处的函数,由此建立起理论计算与实难验光谱频率之间的联系,结果显示:理论计算结果与实验测定频率之间具有较好的线性关系,表明了本工作所做的探讨索对红外谱图谱峰的归属和解析具有进一步研究的意义.     

Calculation of the light intensity distribution reflected by a planar corner-cube retroreflector array with the size of centimeter and above

The light intensity distribution (LID) reflected by a planar corner-cube retroreflector array with the size of centimeter and above (PCCRA) is calculated based on the Collins formula, coordinate transformation matrixes and vector algebra. The expression can be used for the PCCRAs with different parameters and different complex optical systems described by ABCD matrix. The expression indicates that the LID of a PCCRA is much different from a single corner-cube retroreflector (CCR) with equivalent aperture. Computer simulations are applied to explain the expression clearly. The results show that the LID of the PCCRA is more homogeneous than the single CCR with equivalent aperture under circumstances of both normal incident light and oblique incident light. In addition, the expression is proved by comparing the simulation result of the PCCRA only comprising a single CCR and the previous experimental result.     

Precise measurement of the micron-scale spot of ultrashort laser pulse based on film scanning

A novel and precise micron-scale nanosecond laser spot measurement based on film-scanning method is presented. The method can be used to measure the spot size, beam profile, and intensity distribution of the pulse.     

金属样品在激光微光源中发射强度的研究

通过对金属样品表面覆盖涂层或改变其表面光洁度的方法，减少样品表面对激光束的反射，增大金属样品在激光微光源中的发射强度，有利于降低光谱分析的检测限。     

Representation theorems for probability functions satisfying spectrum exchangeability in inductive logic

We prove de Finetti style representation theorems covering the class of all probability functions satisfying spectrum exchangeability in polyadic inductive logic and give an application by characterizing those probability functions satisfying spectrum exchangeability which can be extended to a language with equality whilst still satisfying that property.