布莱克特对威耳逊云室的改进及相关研究

简述了布莱克特的生平,回顾了他对威耳逊云室的改进及利用威耳逊云室所做的证明原子核人工转变、验证正电子的存在和对宇宙射线的研究工作,分析了他成功的因素.     

威耳逊云室的发明和霍秉权的改进

英国物理学家C．T．R．威耳逊是云室的发明者，中国物理学家霍秉权对云室做了重要改进．文章在介绍威耳逊发明云室工作的基础上，着重分析了霍秉权对云室的改进工作及其意义．     

量子多体系统的线性张量重正化群方法

文章简述了数值重正化群方法的历史发展,包括威耳逊（Wilson）的数值重正化群算法,S.R.White的密度矩阵重正化群方法,以及近期迅速发展的处理强关联量子系统的几种张量网络态与张量网络算法.在此基础上,文章重点介绍了作者最近提出的用于研究量子多体系统热力学性质的线性张量重正化群方法,以及该方法在一维和二维量子系统中的应用.     

威耳逊的临界点相变的重正化群理论

临界现象的研究进展缓慢,６０年代实验方面的发展使人们相继建立了几个标度理论及普适性理论,并提出了标度变换概念,威耳逊一直从事量子场论的研究,对相变理论也很关注,对迹些唯象理论不满,他把量子场论中的重正化群概念应用到相变理论中,并运用标度律和普适性概念,建立了临界点的重点重正化群理论,提供了研究临界点现象的系统方法。     

云雾室、核乳胶与气泡室

 现代高能粒子物理学的发展,是以高能加速器与探测技术的发展作为基础的。云雾室、核乳胶与气泡室是3种原理相关、设计精巧、生动直观的探测器,在物理学史上曾发挥重要作用。云雾室简称云室,是英国物理学家本·尼维斯(ＢｅｎＮｅｖｉｓ)于1895年发明的,据说1894年9月威耳逊在苏格兰最高山峰本尼维斯山顶上,注意到当太阳照耀在围绕着山顶的云雾时,太阳、山顶以及人投在云雾上的影子周围出现了彩色的光环。这给了他很大的启示,并试图在实验室中进行模拟。1895年初,他在自己的实验室,利用湿空气膨胀来制造云雾,立刻就发现了许多有趣的现象,由此导致了云室的产生。     

内耗研究的历史评述

通过介绍几位在内耗领域的先驱研究者:C.Zener,葛庭燧,P.G.Bordoni ,J.L.Snoek,评述了内耗研究的进展.也介绍了日本研究者的相关工作.     

我是怎样喜欢上物理的

 我从小学起,就比较喜欢数学,上初中以后,有了物理课,也就自然而然地对物理产生了浓厚的兴趣.而我真正迷上物理,还是高二的事.高二时,我们开设了选修课,我选学了物理实验.虽然每周只有一个下午的选修课,但它却使我一下发现了一个新天地.主持选修课的刘滨生老师很重视对实验设计的训练,特别突出了实验中严谨、细致作风的培养.也许正是这种严谨、细致的要求,恰恰与我沉稳、耐心的性格相符.因此,我在实验中能够比较得心应手,从中获得了很大的乐趣.这时,我才真正领会到了学物理的快乐.     

钙钛矿锰氧化物La0.7Sr0.3MxMn1-xO3(M=Cr,Fe)的巨磁电阻效应与磁性

研究了溶胶 -凝胶法制备氧化物巨磁电阻材料的工艺 ,制备了La0 .7Sr0 .3 CrxMn1-xO3 (x =0 ,0 .10 ,0 .15 )和La0 .7Sr0 .3 FexMn1-xO3 (x =0 .0 5 ,0 .10 ,0 .16 )两系列的单相钙钛矿锰氧化物多晶样品 ,并研究了Cr ,Fe替代La0 .7Sr0 .3 MnO3 中部分Mn后对其结构、磁性和巨磁电阻性质的影响 .观察到La0 .7Sr0 .3 Cr0 .15Mn0 .85O3 和La0 .7Sr0 .3 Fe0 .0 5Mn0 .95O3 两个样品的电阻 温度曲线都出现了双峰 .定性讨论了可能产生双峰的机制 .随Cr(或Fe)替代量的增加 ,材料的居里温度很快下降 ,铁磁性减弱 ,导电性降低 ,巨磁电阻效应增强 .但与Fe掺杂相比 ,相同数量的Cr掺杂对材料的影响要小 .     

半导体激光器光谱的聚类分析

本文提出了分析半导体激光器光谱分布差异的聚类算法.首先,介绍了聚类分析的有关概念和原理,接着给出了分析光谱差异的算法.该算法具有较强的有效性和通用性.最后,给出了一个具体应用.     

单个量子态的操纵和测量:2012年诺贝尔物理学奖述评

塞尔日.阿罗什和大卫.维因兰德获得了2012年诺贝尔物理学奖.他们独立地发展了突破性的实验方法,成功地实现了对单个量子态的测量和控制,由此展示了量子世界的基本特性.同时促进了基于量子技术的量子信息和原子钟的发展.     

Isothermal depolarization currents measurements of cement mortar during the hardening process. Commentaries on previous work

In this short paper the experimental results after the application of the Isothermal Depolarization Current Technique on cement mortar samples during the hardening process are presented and discussed. Specifically, the electrical current relaxation phenomena and parameters are analyzed in order to provide a more general empirical law to fit similar experimental tests. This is a follow-up of the discussion made in a previous work while herein a preprocessing is applied on the experimental data in order to remove the background level of the depolarization current. The new results lead to more accurate and consistent values for the m factor that corresponds to the long depolarization times describing the flip-flop mechanisms.     

Eliashberg theory for disordered superconductors. I. Tunneling into three-dimensional systems

We consider the effect of changes in the Coulomb interaction due to the diffusive nature of propagation of the electron density fluctuations in three dimensional weakly disordered strong coupling superconductor on the low temperature tunneling density of states. Our results are completely consistent with the experimental finding of a negligible Coulomb effect in disordered A-15Nb–Sn.     

基于FTIR-SVM的西洋参与籽播参的分类研究

支持向量机(SVM)是根据统计理论提出的一种新的学习算法。文章以40个西洋参样品为实验材料,通过FTIR-SVM建立了西洋参样品与籽播参识别的模型。对学习训练集中的30个样品模型识别率为100%,对10个预测样品的识别准确率为90%。研究结果表明,FTIR-SVM可以用于中药西洋参与籽播参的区别。     

Gas phase diagnostics by laser-induced gratings I. theory

Electrostriction and collisional thermalization of absorbed laser energy are the two dominant mechanisms leading to the formation of laser-induced gratings (LIGs) in the gas phase. In this article the results of the theoretical investigations that have been achieved in the past ten years at the Paul Scherrer Institute on this issue are summarized and yield a comprehensive understanding of the underlying physical concepts. Furthermore, a study of the influence of various parameters, such as the alignment and the spatial intensity profile of the beams on the generated electrostrictive and thermal signal is presented for the first time to the authors’ knowledge. The variations of the refractive index responsible for the appearance of laser-induced gratings have been theoretically described by solving the linearized hydrodynamic equations. The contributions from electrostriction, as well as from instantaneous and slow relaxation of the absorbed radiation energy into heat is obtained. These expressions are employed for analysis of experimental data presented in the companion paper [1] which is devoted to the application of the technique for diagnostic purposes in the gas phase. Much effort has been undertaken in order to allow a straightforward physical interpretation of the experimental findings of the expressions presented here.     

Femtosecond filamentation in air at low pressures. Part II: Laboratory experiments

We present experimental studies of filamentation of a femtosecond laser pulse in air at low pressures. The evolution of the filament has been studied by measuring along the propagation axis the conductivity and the sub-THz emission from the plasma channel. We show experimentally that the filamentation process occurs at pressures as low as 0.2 atm in agreement with numerical simulations. Experimental and numerical results [A. Couairon, M. Franco, G. Méchain, T. Olivier, B. Prade, A. Mysyrowicz, Opt. Commun., submitted for publication] are compared and the possible sources of discrepancy are discussed.     

Instability of layered quantum liquids: 5. Collective modes at low density

We calculate the plasmon dispersion of electron superlattices by taking into account many-body effects via the local-field correction. For small electron density we find a weak roton structure in the dispersion of optical plasmons. Landau damping is strongly enhanced by many-body effects, especially for acoustical plasmons. We compare with experimental results of high-T _c superconductors. Some experiments are suggested.     

Infrared laser based on the principle of melt crystallization or vapor condensation. Why not?

The paper discusses a possibility of new effects in quantum electronics: amplification of certain frequency infrared beams in supersaturated vapors or super-cooled melts as well as design of infrared lasers based on a new type of pumping. The basis of these effects is the existence of characteristic infrared radiation accompanying phase transitions of the first order, especially crystallization and condensation. Experimental results of the author and other researchers concerning characteristic infrared emission detection during crystallization from the melt of some substances (alkali halides, sapphire, tellurium, ice, etc.) are presented, as well as condensation of water vapor. The author has critically analyzed these experimental data in terms of correspondence to the theoretical models. The last ones are based on the assumption that the particle (atom, molecule or cluster), during transition from higher energetic level (vapor or melt) to the lower energetic level (crystal), emits one or more photons depending on the latent energy of the transition. Based on the experimental data, the author postulates a transparency window appearance for the characteristic radiation in the substances where first-order phase transitions take place.     

Reconstruction of systems with delayed feedback: II. Application

We apply a recently proposed method for the analysis of time series from systems with delayed feedback to experimental data generated by a laser. The method allows estimating the delay time with an error of the order of the sampling interval, while an approach based on the peaks of either the autocorrelation function, or the time delayed mutual information would yield systematically larger values. We reconstruct rather accurately the equations of motion and, in turn, estimate the Lyapunov spectrum even for high dimensional attractors. By comparing models constructed for different “embedding dimensions” with the original data, we are able to find the minimal faithful model. For short delays, the results of our procedure have been cross-checked using a conventional Takens time-delay embedding. For large delays, the standard analysis is inapplicable since the dynamics becomes hyperchaotic. In such a regime we provide the first experimental evidence that the Lyapunov spectrum, rescaled according to the delay time, is independent of the delay time itself. This is in full analogy with the independence of the system size found in spatially extended systems. Received 17 December 1999     

利用ASP．NET实现物理实验数据处理

利用ASP．NET语言编制了一个物理实验数据处理系统。该系统界面友好,通过最小二乘法能够自动处理输入的实验数据,拟合出曲线,分析误差,输出曲线图形,适合在实验教学中使用。