认知不确定二维声场的响应特性数值分析

针对声学参数存在认知不确定性的问题,为实现认知不确定声场声压响应的预测。提出了解决二维认知不确定声场的有限元法(Evidence Theory-based Finite Element Method,ETFEM),引入证据理论,采用焦元和基本可信度的概念来描述认知不确定参数,基于摄动法的区间分析技术,推导了认知不确定声场声压响应的标准差、期望求解公式。为验证本文方法的可行性。以认知不确定参数下的二维管道声场模型和某轿车二维声腔模型为例进行了数值计算,对比离散随机变量得到认知不确定参数的声场分析结果和相应的随机声场所得分析结果,研究表明:该方法能够有效的处理认知不确定参数下的二维声场,为工程问题中噪声预测提供可靠的分析模型。     

高功率激光装置输出光束相对光谱功率测量方法

针对SILEX-I超短超强脉冲激光装置输出光束光谱分布的精密测量问题,采用脉冲激光相对光谱功率来评价光谱分布,以溴钨灯为标准光源开展相对光谱功率测量方法的研究,获得相对光谱功率的理论计算公式。以SP2760光栅光谱仪作为光谱测量设备在SILEX-I激光装置上进行了光谱分布测量的验证实验,并给出了不确定度评定,获得了扩展相对不确定度1.7%的测量精度。测量结果显示,相对光谱功率分布与光栅光谱仪的原始光谱响应值分布具有显著的差异,可以更加准确地反映输出脉冲的光谱分布。     

Photoluminescence of an Yb3+/Al3+-codoped microstructured optical fibre

An Yb 3+ /Al 3+-codoped microstructured optical fibre is prepared based on photonic crystal fibre technology.The characteristic spectra of preforms and fibres are experimentally investigated.The results show that under a 971 nm excitation,besides the known infrared fluorescence luminescence around 1050 nm,a blue luminescence peak at 486 nm is obtained.Moreover,an unexpected emission peak at 730 nm is also observed.The photoluminescence mechanism of an Yb 3+ /Al 3+-codoped microstructured optical fibre is discussed.The emission peak at 486 nm is attributed to the cooperative upconversion resulting from pairs of Yb 3+ ions,and the emission peak around 730 nm is ascribed to the stimulated Raman scattering because of nonlinear effects of microstructured optical fibre.The Yb 3+ /Al 3+-codoped microstructured optical fibre is promising for varieties of applications from laser printing and optical recording to cancer treatments,such as photodynamic therapy.     

EXCITON ENERGY OF THE InAs/GaAs SELF-ASSEMBLED QUANTUM DOT IN A SEMICONDUCTOR MICROCAVITY

We report on the theoretical study of the interaction of the quantum dot (QD) exciton with the photon waveguide models in a semiconductor microcavity. The InAs/GaAs self-assembled QD exciton energies are calculated in a microcavity. The calculated results reveal that the electromagnetic field reduces the exciton energies in a semiconductor microcavity. The effect of the electromagnetic field decreases as the radius of the QD increases. Our calculated results are useful for designing and fabricating photoelectron devices.     

新型在线近红外分析系统用于工业醋酸生产的实时监测

醋酸生产过程的实时在线监控一直是困扰醋酸生产安全和质量控制的关键技术难题。传统的在线色谱分析方法由于其固有的缺点无法满足实时在线监测要求。以SupNIR-4510在线近红外分析仪为核心,设计实现的新型在线近红外分析系统可现场在线分析醋酸反应釜中各组分含量的实时变化,该系统可实现实时在线分析。实验室模型和现场试用均证实该系统稳定性好、准确性高,较好地解决了醋酸安全、稳定生产的关键技术难题。     

气动加热下高温陶瓷材料的表观辐射特性

建立了气动加热下高温陶瓷材料表面的辐射模型,采用控制容积法结合蒙特卡罗法模拟了不同条件下材料的温度分布与表观发射率、在分析等温条件下光学厚度、散射反照率、基底发射率和折射率对表观发射影响的基础上,考察了气动热流和散射反照率对材料内温度场与表观发射率的影响.结果表明,随着气动加热热流和散射反照率的增加,高温陶瓷材料内温度升高,表现发射率减小.     

空间盘绕型声学超材料的亚波长拓扑谷自旋态

声子晶体的Dirac线性色散关系,使其具有奇特的声拓扑特性,在声波控制领域具有良好的应用前景.目前,声子晶体的拓扑边缘态主要基于Bragg散射所产生的能带结构,难以实现低频声波的受拓扑保护单向边缘传输.本文引入空间盘绕结构,设计了具有C_(3v)对称性的空间盘绕型声学超材料,并研究其布里渊区高对称点(K/K'点)的亚波长Dirac锥形线性色散.接着,通过旋转打破空间盘绕型声学超材料的镜像对称性,使其Dirac简并锥裂开而产生亚波长拓扑相变和亚波长拓扑谷自旋态.最后,采用拓扑相位互逆的声学超材料构造拓扑界面,实现声拓扑谷自旋传输.空间盘绕型声学超材料的亚波长Dirac线性色散与亚波长拓扑谷自旋态突破了声子拓扑绝缘体的几何尺寸限制,为声拓扑稳健传输在低频段的应用提供理论基础.     

PM567-Doped solid dye lasers based on PMMA

Polymers are a kind of attractive hosts for laser dyes due to their high transparency in both pumping and lasing ranges and superior optical homogeneity. In this paper solid dye samples based on polymethyl methacrylate (PMMA) doped with different concentrations of 1, 3, 5, 7, 8 -pentamethyl-2, 6-diethylpyrromethene-BF$_{2 }$ (PM567) are prepared. The absorption, fluorescence and lasing spectra of the samples are obtained. Wide absorption and fluorescence bands are obtained and a red shift of the maxima of the lasing emission spectra is observed. With the second-harmonic generation of Q-switched Nd:YAG laser (532\,nm, $\sim $20\,ns) pumping the samples longitudinally, the slope efficiencies of the samples are obtained. There is an optimal dye concentration for the highest slope efficiency when the pumping energy is lower than some typical value ($\sim $250\,mJ), and the highest slope efficiency 35.6{\%} is obtained in the sample with a dye concentration of $2\times10^{ - 4}$\,mol/L. Pumping the samples at a rate of 10Hz with a pulse energy as high as 200\,mJ (the fluence is 0.2\,J/cm$^{2})$, the output energy drops to one-half of its initial value after approximate 15500 pulses and the normalized photostability is 5.17\,GJ/mol. A kind of solid dye laser which could have some applications is built.     

Role of highest occupied molecular orbitals in molecular field-free alignment by a femtosecond pulse

This paper studies the molecular rotational excitation and field-free spatial alignment in a nonresonant intense laser field numerically and analytically by using the time-dependent Schr?dinger equation. The broad rotational wave packets excited by the femtosecond pulse are defined in conjugate angle space, and their coefficients are obtained by solving a set of coupled linear equations. Both single molecule orientation angles and an ensemble of O₂ and CO molecule angular distributions are calculated in detail. The numerical results show that, for single molecule highest occupied molecular orbital (HOMO) symmetry σ tends to have a molecular orientation along the laser polarization direction and the permanent dipole moment diminishes the mean of the orientation angles; for an ensemble of molecules, angular distributions provide more complex and additional information at times where there are no revivals in the single molecule plot. In particular, at the revival peak instant, with the increase of temperature of the molecular ensemble, the anisotropic angular distributions with respect to the laser polarization direction of the π _g orbital gradually transform to the symmetrical distributions regarding the laser polarization vector and for two HOMO configurations angular distributions of all directions are confined within a smaller angle when the temperature of the molecular ensemble is higher.     

TEXONO低能中微子实验中的CsI(T1)晶体探测器

TEXONO合作组首次采用CsI(T1)晶体测量反应堆中微子的能量、通量和反常磁矩,描述了实验的基本原理,探测器结构及其性能.