Simulation study on terahertz vibrational absorption in liquid crystal compounds

The terahertz (THz) spectrum absorptions of nematic liquid crystal (LC) material, i.e. N-(p-methoxybenzylidene)-p-butylaniline (MBBA), and its relevant compounds are simulated in this paper by using the density functional theory (DFT) method. A strong absorptive frequency is located at 3.65 THz for the MBBA, which is in agreement with experimental data found in the literature. The result suggests that the DFT method is effective for dealing with the anisotropic nematic LC compounds.     

Ultrafast multiplex CARS investigation of vibrational characteristics in chloroform and PMMA

This paper demonstrates the femtosecond time-resolved coherent anti-Stokes Raman scattering by using folded BOXCARS geometry where an ultrashort broadband coherent white light continuum was used as Stokes pulse, and carries out the non-contact detection at long distance. The CARS signal is so easy to be detected that it can be seen even by nude eye. The C--H bonds of chloroform or PMMA were detected and the vibration modes belonging to the side chain and the main chain in PMMA were also compared. Their vibrational characteristics involved decay process and quantum beating were discussed. This modified CARS experimental technique could make up the deficiency of traditional CARS technique.     

合肥光源逐圈束流位置监测系统中的定时系统

定时系统是合肥光源逐圈束流位置监测和相空间测量系统中的重要组成部分，其主要目的是为数据采集卡提供与环内电子束团同步的时钟信号。该系统包含高速ECL时钟成形、分频电路、程控延时电路、控制模块等部分。可实现延时范围0～220ns，最小延时步距0.5ns，调整精度0.1ns，时钟抖动小于200ps。系统控制软件基于客户/服务器结构，操作灵活、方便。     

测试温度对nc—Si：H膜光致发光特性的影响

利用常规等离子体化学气相沉积（ＰＥＣＶＤ）工艺制备了ｎｃ－Ｓｉ：Ｈ膜，并对其光致发光（ＰＬ）特性从１０－２５０Ｋ温度范围内进行了变温测量，实验结果指出，随着测试温度升高，ＰＬ峰值能量发生了５４ｍｅＶ的红移，ＰＬ强度在Ｔ〉８０Ｋ后呈指数下降趋势，ＰＬ峰值能量的红移起因于带隙收缩，而ＰＬ强度的减弱则是由于非辐射复合起了主导作用。     

Comparison of Proton Shower Developments in the BGO Calorimeter of the Dark Matter Particle Explorer between GEANT4 and FLUKA Simulations

The DArk Matter Particle Explorer(DAMPE) is a satellite-borne detector for high-energy cosmic rays and y-rays. To fully understand the detector performance and obtain reliable physical results, extensive simulations of the detector are necessary. The simulations are particularly important for the data analysis of cosmic ray nuclei, which relies closely on the hadronic and nuclear interactions of particles in the detector material. Widely adopted simulation softwares include the GEANT4 and FLUKA,...     

远距离三原子量子纠缠特性与其应用

三原子分别被束缚在用光纤环形连接单侧泄漏微光学腔场中,在微腔中输入激光驱动场和施加局域激光场,利用输入-输出技术及绝热近似理论,推导出一维Ising链模型的有效哈密顿量,该哈密顿量表明该系统会诱导出三原子中的任意两原子纠缠及三原子纠缠,用伴随数(concurrence)度量两原子纠缠,用内禀纠缠度量三原子纠缠,通过数值计算,给出两原子和三原子纠缠随时间演化曲线,通过适当调控激光驱动场和局域激光场,在远距离三原子中任意两原子实现未知量子态的隐形传送。     

基于无人机多光谱图像的土壤水分检测方法研究

以表层土壤为对象,探究土壤的多光谱反射率与土壤水分含量相关性,进行基于无人机多光谱图像的土壤水分含量预测模型方法的探究。选取中国农业大学通州实验站为研究区域,实地采集试验田的土壤样本100组,按照一定梯度配制土壤含水量,配成的土壤含水率为10%~50%之间,土壤含量的真实值采用土壤烘干法进行测定。多光谱相机灵巧便捷,可搭载在无人机上对土壤进行监测。将RedEdged-M型多光谱相机搭载在Phantom 3型无人机上,选择阳光充足的采集环境,实时采集土壤样本的多光谱图像,建立土壤多光谱信息与水分含量之间的模型。利用处理光谱数据的ENVI5.3软件提取土壤样本多光谱信息,以多光谱相机自带的标准白板反射率为100%,计算出土壤样本在蓝、绿、红、红边、近红外五个波段的光谱反射率。采用BP神经网络算法、支持向量机算法、偏最小二乘算法分别建立基于无人机多光谱图像的土壤水分含量的预测模型。以80组土壤样本数据作为训练集,建立基于多光谱图像的土壤水分含量预测模型。采用莱文贝格-马夸特算法对BPNN进行改进,提高了其训练速度,当网络结构为5-10-1时,训练效果最好,本文选择该网络结构;SVM采取高斯核函数,当参数为0.56时,模型效果最好。本研究采用归一化均方根误差(NRMSE)和决策系数(R 2)对三种土壤水分含量的预测模型进行定量对比。以20组土壤样本数据作为测试集,结果可知,基于BP神经网络土壤水分含量预测模型的NRMSE为0.268,R 2为0.872;基于支持向量机的土壤水分含量预测模型的NRMSE为0.298,R 2为0.821;基于偏最小二乘土壤水分含量预测模型的NRMSE为0.316,R 2为0.789。对三种模型分析可知,基于BPNN的土壤水分含量预测模型效果均较好。结果可知,土壤的光谱反射率与含水率间存在较密切的相关性,将多光谱相机搭载在无人机上可以对土壤水分含量进行有效的实时监测,对监测土壤墒情提供技术支持和理论支撑。     

测试温度对nc-Si∶H膜光致发光特性的影响

利用常规等离子体化学气相沉积（ＰＥＣＶＤ）工艺制备了ｎｃ－Ｓｉ∶Ｈ膜，并对其光致发光（ＰＬ）特性从１０～２５０Ｋ温度范围内进行了变温测量．实验结果指出，随着测试温度升高，ＰＬ峰值能量发生了５４ｍｅＶ的红移，ＰＬ强度在Ｔ＞８０Ｋ后呈指数下降趋势．ＰＬ峰值能量的红移起因于带隙的收缩，而ＰＬ强度的减弱则是由于非辐射复合起了主导作用．     

用“观察——归纳”法学习幂函数图象

学习幂函数图象必须解决两大问题 :一是会作任意幂函数的图象 ;二是会由图象观察幂函数的性质 .但这历来是同学们学习的难点 .为此 ,我们介绍一种“观察———归纳”的方法 .1　观察“单”函数图象归纳“类”函数图象1.1　作出下列函数的图象 :① ｙ =ｘ2 ,② ｙ =ｘ3,③ ｙ =ｘ32 ,④ ｙ =ｘ12 ,⑤ ｙ =ｘ13 ,⑥ ｙ =ｘ23 ,⑦ ｙ =ｘ- 12 ,⑧ ｙ =ｘ- 2 ,⑨ ｙ =ｘ- 1.(Ａ)　　　　　 (Ｂ)　　　　　 (Ｃ)(Ｄ)　　　　　 (Ｅ)　　　　　 (Ｆ)(Ｇ)　　　　　 (Ｈ)　　　　　 (Ｉ)图 1　幂函数的代表函数的图象　　其中①—⑨分别对应图象 (…