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?     

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。     

EAST中央控制系统

描述了EAST中央控制系统和EAST虚拟合作实验室系统的体系结构和各个部分的主要功能和设计思想。EAST中央控制系统主要功能是协调统一各个控制、诊断、采集子系统,为各个子系统提供统一的控制接口。EAST中央控制系统制定和规范了与各分控系统之间的通信协议,加强了对各分控系统的控制,统一和规范了控制数据的发布和控制参数的设置。系统按照功能模块设计和实施,有效地提高了系统的升级和扩展能力。     

GaN基半导体新热点:从半导体照明到功率电子器件

Ⅲ族氮化物(又称GaN基)宽禁带半导体属于新兴的第三代半导体体系,在短波长光电子器件和功率电子器件领域具有重大应用价值。过去10多年,以蓝光和白光LED为核心的半导体照明技术和产业飞速发展,形成了对国家经济和人民生活产生显著影响的高技术产业。近年来GaN基功率电子器件受到了学术界和产业界的高度重视,形成了新的研发和产业化热点。首先介绍了半导体照明技术和产业的发展历程和现状,分析了当前GaN基LED芯片技术面临的关键科学和技术问题;然后重点介绍了GaN基微波功率器件和电力电子器件的发展历程和动态,包括微波功率器件已经取得的突破性进展和产业化现状,电力电子器件相对Si和SiC同类器件的优势和劣势,并对GaN基功率电子器件当前面临的关键科学和技术挑战进行了较详细的分析。     

从规律中找规律——凸透镜成像规律的理解和应用

凸透镜成像规律这一重点和难点一直困扰着很多师生,对这个规律的理解和应用也较为生硬和枯燥.其实这规律中还有规律,焦点可分虚实像,二倍焦距可分像的大小,像的放大和缩小也是全方位的,物和像的移动是同方向的.     

HG-ICP-AES法测定多金属矿区人发中的汞和砷

应用ICP-2070型等离子体发射光谱仪和氢化物发生技术,采用HNO₃-HClO₄酸消解体系,建立了生物样品中痕量汞和砷的氢化物发生-等离子体发射光谱检测法(HG-ICP-AES法)。在选定的实验条件下,Hg和As的检测限分别达到0.6和0.8 ng·mL-1,且分析稳定性较好,能满足生物样品中痕量Hg和As的检测要求。对人发、大米和茶叶等国家标准物质中Hg和As的含量进行对照测定,检测结果与推荐值一致,测定结果的RSD均在5%左右。与此同时,应用本法实测了湘西多金属矿区人发中Hg和As的含量,发现该矿区发Hg和发As平均含量为1.290和1.865 μg·g-1,分别为对照的3.59倍和2.44倍。表明湘西矿区人群Hg和As暴露危害严重,须引起相关部门重视。     

我们为什么提出建造环形正负电子对撞机

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。     

殚思求火种,深情寄木铎——祝贺黄祖洽院士75岁生日

 今年10月2日是我们的老所长和现任名誉所长黄祖洽院士的75岁生日,我和中国物理学界的朋友们一道向这位著名的核物理和理论物理学家,中国核武器理论研究和设计的功臣表示热烈的祝贺。     

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。     

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。     

应用数字散斑投影测量纸页厚度

传统的纸张厚度测量方法只能测量纸页某一点厚度, 该类方法会因为纸张厚度全场分布不匀带来测量误差。针对该问题, 提出利用数字散斑投影的纸页厚度检测方法, 向待测纸页投射散斑图案, 并构建散斑投影的实验测量系统, 通过三维数字图像相关的算法处理, 得到纸页的形貌以及厚度。实验表明, 对纸张厚度名义值为0.180 mm的实验样品进行测量, 结果为0.177 mm, 对该方法进行重复实验, 测得的相对误差小于4%, 而且该方法能够直观地显示纸页的全场分布。此外, 提出的纸页厚度测量方法具有结构简单、非接触式测量、全场测量等优点, 为纸页生产中的厚度检测提供了新思路。     

Development of electrostatic paper separation and feed mechanism

A new paper separation and feed mechanism is proposed to realize a highly reliable paper handling system for printers and copiers. The paper-separation system consisted of a pair of parallel electrodes and a paper pile between the electrodes. Electrostatic separation of a piece of paper was possible from the top of the pile when the applied voltage exceeded the threshold needed to generate an electrostatic force larger than the weight of the paper. The threshold voltage was on the order of several kilovolts, and it agreed with the numerical value calculated using the finite element method (FEM) for the electrostatic field. Based on these basic investigations, a prototype mechanism for paper separation and feeding was constructed. It consisted of a roller-type separation electrode coated with an insulating film, a biased charger roller in contact with the separation roller to charge the insulating film on the separation roller, a ground electrode, and a paper pile situated between the electrodes. When an electrostatic field was applied between the biased charger roller and the ground electrode on which the paper pile was mounted, only the top sheet of paper separated, adhering electrostatically to the roller. The sheet was then fed rotating the separation roller. Using this system, reliable paper separation and feed was realized and a feed speed over 600 mm/s was demonstrated.     

纳米SiO_2掺杂对有水环境下间位芳纶绝缘纸性能影响的研究

为了进一步了解SiO_2纳米粒子掺杂对有水环境下间位芳纶绝缘纸性能的影响以及有、无水环境下芳纶绝缘纸性能的变化,本文利用分子动力学的方法建立了有水存在的芳纶分子模型、经SiO_2纳米掺杂后的芳纶分子模型以及无水参与的芳纶分子模型,研究了SiO_2纳米掺杂和水分对芳纶绝缘纸在玻璃转化温度、均方位移及力学模量方面的影响.研究结果表明,水分的存在使得芳纶绝缘纸的玻璃转化温度由原先的549 K降为523 K,在此基础上进行纳米SiO_2掺杂后玻璃转化温度可以由523 K提升到530 K.与无水环境芳纶绝缘纸的均方位移相对比可以发现,水分的存在在一定程度上提高了芳纶分子的链运动进而削弱了绝缘纸的热稳定性,而SiO_2纳米改性可以减弱水分对芳纶绝缘纸的这种不利影响.改性后的绝缘纸在有水环境下的力学性能得以提升,通过对比有、无水环境下芳纶绝缘纸的力学模量可以发现,一定水分的加入反而使得绝缘纸的力学性能得到了一定的提升.最后对所得模拟结果进行了理论分析,为提升芳纶绝缘纸的性能提供了有益的参考.     

Imaging anisotropic elastic properties of an orthotropic paper sheet using photorefractive dynamic holography

An important material property in the paper industry is the anisotropic stiffness distribution due to the fibrous microstructure of paper and to processing procedures. Ultrasonic methods offer a means of determining the stiffness of sheets of paper from the anisotropic propagation characteristics of elastic Lamb waves along the machine direction and the cross direction. That is, along and perpendicular to the direction of paper production. Currently, piezoelectric ultrasonic methods are employed in the industry to measure the elastic polar diagram of paper through multiple contacting measurements made in all directions. This paper describes a new approach utilizing the INEEL Laser Ultrasonic Camera to provide a complete image of the elastic waves traveling in all directions in the plane of the paper sheet. This approach is based on optical dynamic holographic methods that record the out of plane ultrasonic motion over the entire paper surface simultaneously without scanning. The full-field imaging technique offers great potential for increasing the speed of the measurement and it ultimately provides a substantial amount of information concerning local property variations and flaws in the paper. This report shows the success of the method and the manner in which it yields the elastic polar diagram for the paper from the dispersive flexural or antisymmetric Lamb wave.     

微生物培养法推断纸张的相对生产时间

利用微生物培养法检测两种制浆方式的纸张,观察随着生产时间的不同,纸张上细菌和霉菌数量上的变化,根据其纸张上细菌和霉菌的变化规律,推断纸张的相对生产时间。该方法利用现代生物技术,对文件制成时间的检验提供一种新的思路和方法。     

The logical quantization of algebraic groups

In a previous paper we introduced a highly abstract framework within which the theory of manuals initiated by Foulis and Randall is to be developed. The framework enabled us in a subsequent paper to quantize the notion of a set. Following these lines, this paper is devoted to quantizing algebraic groups viewed from Grothendieck's functorial standpoint.     

Drying Characteristics-Property Correlationships in Gas-Fired Infrared Drying of Paper Obtained by Diffuse Reflectance FT-IR Spectroscopy

Introduction

Infrared (IR) drying of paper in a pilot scale has been investigated by several researchers in the past [1–3]. Both high-intensity electric heating and medium-intensity gas heating are now being used industrially either to preheat wet paper before conventional steam drying [1] or as a moisture-profile corrector just before paper sizing press [2]. Our own investigation [3] on the use of radiant energy from a gas-fired IR radiator have revealed that the drying efficiency of IR radiation is influenced by the nature of association of water molecules with cellulose in wet paper. Depending on the total moisture content of a paper, the free and bound moisture contents of paper will vary in wet paper sheet. Our previous study [3] has also confirmed that it is possible to remove free moisture more efficiently using gas-fired IR emitter operated at 1373 K rather than as 1223 K. It is reported that besides emitter temperature, the efficiency of drying also depends on the location of the emitter. In general, the efficiency is high if the emitter is installed near the preheating zone and the efficiency changes in the following order: falling rate < constant rate < preheating. Pikulik [4] compared the efficiency of hot gas impinging drying with conventional steam drying emphasizing the paper properties. The properties of a high-intensity hot gas-dried paper has been reported to be better than those of conventionally steam dried paper. An immediate quality improvement in terms of reduced moisture steaks and superior resistance to paper embrittleness was also observed when installing a high-intensity infrared drying system [5,6].     

Characterization of mineral paper by air-coupled ultrasonic spectroscopy

A novel technology in the paper industry makes possible to produce paper by using a mineral powder and a polymer instead of cellulose fibers. This new product is called mineral paper, it presents some potential environmental advantages compared with conventional paper, while it exhibit a similar appearance and properties. The purpose of this work is to determine the possibilities of an air-coupled ultrasonic technique using wide band signals and spectral analysis to study this kind of materials. As no direct contact nor coupling fluids between the paper and the transducers is required, this technique is specially well suited to this problem. It also offers good perspectives for the development of a on-line quality control system. A through transmission technique (0.15-2.3 MHz) is employed and Fourier analysis is performed to obtain both magnitude and phase spectra of the transmission coefficient. Properties in the thickness direction as well as in the paper plane has been determined by the excitation and analysis of thickness and plate resonances at several incident angles and different directions within the paper plane. Different paper grades (from 140 to 480 g/m²) have been studied. Very high attenuation coefficients and very low propagation velocities (and hence elastic constant) have been obtained for most cases, this can be explained by considering the large porosity of this material (up to 50%) and the microstructure: a mixture of solid grains with a resin with a relatively large fraction of air-filled pores. Measurements show that unlike conventional cellulose machine made paper this material is transversely isotropic (isotropic in the paper plane) and that the degree of anisotropy (when in-plane directions are compared with the thickness direction) largely depends on the level of resin impregnation.     

Change in the optical properties of paper when exposed to the magnetic component of a high-frequency electromagnetic field

We have used laser Stokes polarimetry to study changes in the structure of paper for offset printing when exposed to a high-frequency electromagnetic field. We have shown that the effect of a high-frequency electromagnetic field on paper appears as a decrease in the structural ordering of the material and a change in the shape of the indicatrix of the reflected radiation power from an He-Ne laser at the wavelength 632.8 nm, a decrease in the bidirectional reflection and transmission coefficients of the paper. We have established that when the force lines of the magnetic component of the high-frequency electromagnetic field are oriented perpendicular to the plane of the sheet of paper, we observe a more substantial decrease in the anisotropy in the surface layer and within the interior (the volume) of the paper than when the lines of force are oriented parallel to the plane of the paper. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 421–426, July–August, 2007.     

Estimation of curl in paper using a combination of shape measurement and least-squares modelling

Curl is a quality problem that makes paper less suitable for printing. A paper sheet that has structural variations in its thickness such as gradients of fibre orientation, density and filler content, will curl and hence assume a cylindrical shape when its humidity content is changed. We propose a method to measure curl that can be used for automated analysis of the paper quality. The shape of the curled paper is measured using a stereoscopic camera system, which is capable of viewing a random pattern that is projected onto the specimen. The shape of the object is found by calculating the perspective difference in the camera set-up using digital image correlation. The quality parameters that are searched for are the magnitude of curl, which is defined as the inverse of the radius of curvature and the orientation of the curled paper. These parameters are estimated by performing a least-squares fit of a cylindrical shape to the three-dimensional measurement data. The least-squares model is non-linear and an iterative technique based on the Gauss–Newton algorithm is used.