单模激光系统线性化近似适用范围的分析

采用线性化近似方法计算了具有实虚部关联的量子噪声和泵噪声驱动的单模激光损失模型的光强相对涨落,为了对线性化近似的适用范围进行详细的分析,分别讨论了量子噪声强度、泵噪声强度、量子噪声实虚部间关联系数对光强相对涨落的影响,得出在小噪声、远离阈值时,线性化近似适用范围扩大;小噪声、远离阈值且当量子噪声实虚部无关联时,线性化近似适用范围极大的结论.     

多参数分数Lévy过程局部时的存在性和联合连续性

首先引进了一类比Xiao和Zhang研究过的Gauss随机场更为一般的多参数Lévy过程.然后给出并证明了此过程的一种分解,并利用这一分解,证明了该过程的局部时的存在性和联合连续性.     

单向关闭两不同部件串联一部件冷贮备的三部件可修系统的可靠性

本文考虑单向关闭两个不同型部件串联和一个部件冷贮备的可修系统的可靠性.假设所有部件的寿命均为指数分布,修理时间为一般连续型分布.利用补充变量法,拉普拉斯变换和拉普拉斯-斯梯阶变换工具,研究系统的可用度,系统的可靠度以及系统在(0,t]内的故障频度.     

Nonlinear Optical Properties of Novel C60 Derivatives under Picosecond Laser Excitation

We investigate the third-order nonlinear optical properties of six novel fullerene derivatives under picosecond laser excitation by Z-scan technique. The experimental results reveal that all the derivatives have very large nonlinear absorption coefficient under 532 nm pulses excitation and great third-order nonlinear refraction index under 1064 nm pulses excitation. The molecular second hyperpolarizabilities are obtained from the experimental results.     

The molecular structure and analytical potential energy function of HCO （X^2A＇）

In this paper the equilibrium structure of HCO has been optimized by using density functional theory （DFT）/ B3P86 method and CC-PVTZ basis. It has a bent （Cs, X^2A＇） ground state structure with an angle of 124.4095 °. The vibronic frequencies and force constants have also been calculated. Based on the principles of atomic and molecular reaction statics, the possible electronic states and reasonable dissociation limits for the ground state of HCO molecule have been determined. The analytic potential energy function of HCO （X^2A＇） molecule has been derived by using the many-body expansion theory. The contour lines are constructed, which show the static properties of HCO （X^2A＇）, such as the equilibrium structure, the lowest energies, etc. The potential energy surface of HCO （X^2A＇） is reasonable and very satisfactory.     

He-HI复合物势能面及微分散射截面的理论研究

采用超分子单双迭代(包括非迭代三重激发)耦合簇理论CCSD(T)方法和由键函数3s3p2d1f组成的大基组, 计算得到了基态He-HI复合物相互作用的全程势能面. 该势能面上存在2个势阱, 分别对应于线性He-I-H和He-H-I构型, 势阱深度分别为4.473和2.996meV, He原子到HI分子质心的距离R分别为0.363和0.442nm. 使用Barker, Fisher和Watts提出的BFW势函数拟合计算得到的相互作用能数据, 获得了He原子与HI分子相互作用势的解析表达式. 在 关键词： He-HI复合物 势能面 微分散射截面     

一类Benney-Kawahara-Lin方程的孤波解

基于计算机代数系统,研究了一类Benney-Kawahara-Lin方程,利用行波变换法给出了它的一类孤波解,并分析了所得解的物理意义.     

Ab initio investigation of photoinduced non-thermal phase transition in β-cristobalite

Using the linear-response method, we investigate the phonon properties of β-cristobalite crystal under electronic excitation effect. We find that the transverse-acoustic phonon frequency becomes imaginary as the electron temperature is increased, which means that the lattice of β-cristobalite becomes unstable under intense laser irradiation. In addition, for the optic phonon mode, the LO(H)–TO(H) splitting disappears when the electronic temperature reaches a certain value,corresponding to the whole transverse-acoustic phonon branches becoming negative. It means that the electronic excitation destroys the macroscopic electric field of β-cristobalite. Based on the calculated phonon band structures, some thermodynamic properties are calculated as a function of temperature at different electronic temperatures. These investigations provide evidence that non-thermal melting takes place during a femtosecond pulse laser interaction with β-cristobalite.     

Electronic structure and optical properties of rutile RuO2 from first principles

The systematic trends of electrionic structure and optical properties of rutile (P42 /mnm) RuO2 have been calculated by using the plane-wave norm-conserving pseudopotential density functional theory (DFT) method within the generalised gradient approximation (GGA) for the exchange-correlation potential.The obtained equilibrium structure parameters are in excellent agreement with the experimental data.The calculated bulk modulus and elastic constants are also in good agreement with the experimental data and available theoretical calculations.Analysis based on electronic structure and pseudogap reveals that the bonding nature in RuO2 is a combination of covalent,ionic and metallic bonds.Based on a Kramers-Kronig analysis of the reflectivity,we have obtained the spectral dependence of the real and imaginary parts of the complex dielectric constant (ε1 and ε2,respectively) and the refractive index (n);and comparisons have shown that the theoretical results agree well with the experimental data as well.Meanwhile,we have also calculated the absorption coefficient,reflectivity index,electron energy loss function of RuO2 for radiation up to 30 eV.As a result,the predicted reflectivity index is in good agreement with the experimental data at low energies.     

Ultra broadband-flattened dispersion photonic crystal fiber for supercontinuum generation

We propose an improved design of photonic crystal fiber (PCF) with ultra broadband-flattened dispersion and ultra-low confinement loss in the telecommunication window.The design is considerably suitable for the generation of wideband supercontinuum spectrum.Numerical results reveal that the proposed PCF structure possesses a low dispersion of 0±1.5 ps/(nm·km) in the wavelengths ranging from 1.134 to 1.805 μm (approximately 700-nm bandwidth) with a confinement loss of less than 10 8 dB/km.In addition,a nonlinear coefficient greater than 11.47 (W·km) 1 and a dispersion slope of as low as 0.005694 ps/(nm 2 ·km) are obtained at 1.55-μm wavelength.Moreover,a symmetric flat supercontinuum spectrum with a 10-dB bandwidth of 190 nm is achieved in a 3-m-long fiber,verifying the excellent optical features of the innovative PCF.