杉木综纤维素和木质素的近红外光谱法测定

用近红外光谱法对杉木中综纤维素和木质素含量进行了快速测定。用常规湿化学方法测定了48个杉木木材样品的综纤维素和木质素,用近红外光谱仪采集相应的光谱,进行二阶微分处理和平滑预处理后,用偏最小二乘法和完全交互验证方式建立相应预测模型。综纤维素校正模型和预测模型的相关系数分别为0.96和0.93;预测标准误差分别为0.39和0.50;木质素校正模型和预测模型的相关系数分别为0.99和0.90;预测标准误差分别为0.10和0.28。结果表明,近红外光谱法可以快速分析木材中综纤维素和木质素含量。     

我们为什么提出建造环形正负电子对撞机

<正>一、粒子物理和标准模型自从20世纪30年代物理学家建立了原子模型之后,人类对亚原子和更深层次物质结构、相互作用和自然规律的实验、理论的探索和研究揭示了自然界基本粒子的存在和他们的特性,以及由这些基本粒子组成的各类介子,重子,原子,分子和它们形成的丰富和多样的自然物质世界。粒子物理硕果累累,标准模型在过去50多年得到发展和实验验证,成为一套能够全面解释已知粒子物理实验现象     

第十七届中国国际激光·光电子及光显示产品展览会全国光学元件及光学仪器产业发展论坛

本次产业发展论坛拟组织特邀报告、大会交流报告和产品、样品宣展等系列推广和市场活动，届时将邀请工业和信息化部、科技部以及航空航天集团的相关司局和部门前来作报告和指导。热忱欢迎广大光学行业的科技人员、工程技术人员和企业管理人员积极撰写论文，到会交流，展示最新产品以及研究成果和在光学元器件应用、开发及生产实践中所取得的宝贵经验和成绩。     

现代物理学及其应用

 现代科学技术是生产力的一个重要因素,而现代物理学则是现代科学技术的基础.19世纪中期电磁感应现象的发现和电磁理论的发展,为电能的开发应用和电气化奠定了基础;19世纪末电磁波和电子的发现和研究,开创了无线电电子学的新时代;20世纪初期量子论、相对论量子力学和原子核物理的创立和发展,不但引起了物理学自身的革命,开始了微观、高速和高能领域的研究,而且也为半导体、激光和原子核能等新技术的开发应用提供了启迪的根据和明确的途径.物理学为什么具有这样的作用呢?物理学的现状和未来又是怎样和将会怎样发展呢?     

主动声呐信息过程的实验研究——声呐信号综合分析仪在信道研究和声呐设计中的应用

本文介绍声呐信号综合分析仪(简称SZY)在主动声呐信道特性的实时测量和声呐设计中的应用原理和方法,并给出部分实验结果.内容包括:1.声呐信号分析:相关、模糊度和谱以及随机数据的统计测量;2.主动声呐信道(水声传输信道、目标散射和混响)特性的测量:时变谱和时变相关、时空相干性和散射函数;3.声呐检测和最佳设计:定位、跟踪、波形设计和信道匹配.     

估测田间烟叶色素含量的光谱模型研究

田间烟叶色素含量的光谱无损快速测量,对烟草营养生长期的营养诊断与长势监测、成熟期的烟叶品质评判具有重要的生产指导意义。该研究的目的是利用烟叶田间光谱估测烟叶的叶绿素和类胡萝卜素含量。研究采集了营养生长期和成熟期烟叶田间反射光谱,测量了样品烟叶的色素含量,利用支持向量机(SVM)和光谱指数法,对营养生长期和成熟期烟叶样品用分期建模和混合建模两种方法建立色素含量估测模型,并对模型的预测性能进行比较。研究结果表明,分期建模和混合建模对于烟叶色素含量的估测效果差异不显著。对于叶绿素含量,SVM和光谱指数法均有较好的估测效果;对于类胡萝卜素含量,SVM方法比光谱指数法具有更高的估测精度。采用SVM方法对烟叶样品的叶绿素含量分期建模得到的估测决定系数和均方根误差分别为0.862 9和0.015 5,对叶绿素含量混合建模得到的估测决定系数和均方根误差分别为0.898 5和0.012 3;采用SVM方法对烟叶样品类胡萝卜素含量分期建模得到的估测决定系数和均方根误差分别为0.873 0和0.002 4,对类胡萝卜素含量混合建模得到的估测决定系数和均方根误差分别为0.852 7和0.002 4。该研究的创新点是通过支持向量机和光谱指数法采用分期建模以及混合建模的方式建立了烟叶样品色素含量的估测模型,为烟草田间生产的质量控制、烟叶的采收品质保证提供科学依据和技术支持。     

超高压和热杀菌对草莓浊汁及清汁品质的影响

研究超高压(常温下,550MPa,处理5min)、热处理(中心温度90℃,处理1min)及高温短时杀菌(110℃,处理8.6s)对草莓浊汁和清汁品质的影响。结果表明:(1)经超高压处理后,草莓浊汁的黏度、果胶含量和浊度无显著变化,悬浮稳定性显著增加;而热处理和高温短时杀菌处理后,浊汁的黏度和果胶含量显著减小,浊度增大,悬浮稳定性降低,但高温短时杀菌组好于热处理组;(2)草莓浊汁和清汁经超高压处理后Vc分别损失11.09%和13.59%,而热烫结合超高压处理后分别损失7.75%和10.73%;热处理和高温短时杀菌组浊汁和清汁中Vc的损失率高于超高压组,分别为28.86%~38.89%和20.38%~29.02%;(3)超高压处理对草莓浊汁和清汁的单体花色苷、聚合色度及总酚含量、DPPH和FRAP抗氧化活性没有显著影响;热处理和高温短时杀菌处理后草莓浊汁中的花色苷总量分别损失了3.89%~4.63%和7.46%~8.02%,而清汁中分别损失了5.97%~6.02%和8.09%~9.20%;聚合色度和聚合色度百分比增加,总酚含量无显著变化,抗氧化活性显著降低;(4)超高压处理对草莓浊汁和清汁的亮度L*、红值a*、黄值b*、彩度C*及色调角hab均没有显著影响;而热处理和高温短时杀菌处理使L*值和a*值均显著减小。     

电子间的吸引与排斥

 吸引和排斥作为特定的哲学范畴,专指无机界事物相互作用中两种相反因素的对立统一关系,是对接近和分离、收缩和膨胀、化合和化分、吸收和发射、引力和斥力、聚合和裂变等特殊矛盾运动所作的科学概括。显然吸引和排斥不是单一的、不变的;它是作为无机界的基本矛盾来把握的。     

大功率微波真空电子器件的应用

 大功率微波真空电子器件具有工作频率高、峰值和平均功率大等特点,已广泛应用于微波电子系统,在科学研究和国民经济方面的应用越来越广泛。在科学研究方面,它主要应用在高能粒子加速器和可控热核聚变加热装置等大型科学装置上,主要包括高峰值功率速调管、连续波和长脉冲高功率速调管和高功率回旋管等器件。在国民经济方面,则主要应用于天气雷达、导航雷达、医用和工业辐照加速器、电视广播和通信等微波电子系统,主要包括大功率脉冲和连续波速调管、分布作用速调管、行波管、磁控管和感应输出管等。为此,介绍了这些微波真空电子器件的技术现状、共性技术问题和发展趋势。     

分布式传感光纤应变和温度同时标定方法

为了实现分布式传感光纤应变和温度响应系数的快速准确标定,提出了应变和温度同时标定法.利用恒温装置控制传感光纤和金属管的温度,利用金属管的线性热膨胀对缠绕其上的分布式传感光纤施加应变,通过恒温装置中的松弛传感光纤补偿金属管上传感光纤的温度,共同实现应变和温度的同时、快速、准确标定.利用恒温水浴和不锈钢管进行了单模裸纤布里渊频移应变和温度响应系数的标定实验,应变标定跨度620με,温度标定范围35~75℃,得到单模裸纤布里渊频移的应变和温度响应系数分别为0.048 MHz/με和1.06 MHz/℃.结果表明该方法可用于小直径分布式传感光纤的应变和温度同时标定.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.