惠更斯对离心力公式的证明过程

惠更斯在1673年发表的《Horologium Oscillatorium》附录中提出了离心力的概念和计算方法,但没有给出相关的证明过程.在惠更斯去世之后的1703年,惠更斯对离心力计算公式的证明过程才被后人整理发表出来.本文主要介绍惠更斯的这个证明过程.     

磁场安培环路定理证明的新方法

大学物理中磁场的安培环路定理是学生重点掌握的内容之一,安培环路定理的证明也是必须要讲解的内容.现有的教材在证明环路不包围电流的情况时多采用圆心角的方法证明,本文给出了两种新的证明方法,此方法借用了环路中包围电流的环路积分结果,方法简单、明了,在国内广泛使用的教材中未见出现此证明方法.     

B92量子密钥分配协议的变形及其无条件安全性证明

分析了Shor和Preskill证明BB84量子密钥分配协议无条件安全性的方法,指出不能用ShorPreskill方法直接证明B92量子密钥分配协议的无条件安全性。同时借鉴ShorPreskill方法,引入一种将B92协议转化为BB84协议的变换,通过证明该变换过程不会泄漏密钥信息给窃听者,以此证明B92协议的无条件安全性.也解决了Lo等人提出的关于用ShorPreskill方法证明B92协议的困难 关键词： B92协议 CSS码 量子密钥分配 量子信息     

关于静电场中唯一性定理的证明

静电场中唯一性定理的证明一般都采用反证法,但出发点有所不同.有的利用格林公式,但大多数证明是首先人为构造一个函数,然后作面积分或体积分来证明.本文对唯一性定理的证明虽仍采用反证法,但从计算电势的差值解Φ=Φ′—Φ″所描述的静电场的能量 W_e 出发作推证,给出了较清晰的物理概念和较明确的物理意义,有利于教学.     

静电场描绘实验原理的简捷证明

静电场的描绘一般采用恒流电场模拟描绘,实验原理的证明和讲解是必要的,许多实验指导书上的证明过程不是过于繁琐就是不够清晰。提供了一种方法以供同行参考。     

关于第n布里渊区体积等于倒格子原胞体积的证明

通过证明Wigner-Seitz原胞的体积等于原胞体积,说明第一布里渊区体积等于倒格子原胞体积;对于第n布里渊区和第n-1布里渊区建立保长同胚映射证明两者体积相等.     

连续分布电荷体系电荷元的自能问题

连续分布电荷体系可分割为无穷多个电荷元,系统研究了电荷元的自能问题.利用均匀带电球体和均匀带电圆面的自能公式和夹逼定理,分两步严格证明了连续分布电荷体系电荷元的自能之和为零.第一步,证明自由电荷体系电荷元的自能之和为零;第二步,证明一般电荷体系电荷元的自能之和为零.因此,连续分布电荷体系的电场能就等于电荷元之间的相互作用能.     

等温线和绝热线不能 相交于两点的两种证法

在学习热学部分知识的过程中, 有这样一个命题是: 理想气体的p V 图上, 等温线和绝热线不能有两个 和两个以上的交点. 显然大家都知道这一命题是正确的. 且对于这一命题进行了证明. 笔者引用热力学第二定律及 其他方法对其进行了证明, 同样证明其命题的正确性     

静电场中电场力做功与路径无关推导方法的商榷

 1. 问题的提出
现行大学物理教材(吴百诗,《大学物理基础》;张三慧,《大学物理基础学》,以下均简称教材)在证明“静电场中电场力做功与路径无关”的结论时,思路是从库仑定律和叠加原理出发来证明电场力做功与路径无关,即先证明点电荷产生的电场中电场力对试验电荷做功(以下简称电场力做功)与路径无关,然后再证明任意带电体产生的电场中电场力做功与路径无关。在证明任意带电体产生的电场中电场力做功与路径无关时,教材认为任意带电体可分割为无数多个电荷元,每个电荷元可看成点电荷,根据叠加原理和点电荷产生的电场中电场力做功与路径无关的结论,任意带电体产生的电场中电场力做功与路径无关。这种推导方法的言下之意是,每个电荷元产生的场强dE 均可表达为1/(r²)的函数,而点电荷的电场中电场力做功与路径无关的结论通过简单的数学推导可以证明,因此,任意带电体的电场亦有此结论。     

实验探究培养物理科学思维核心素养

科学思维是核心素养的主要组成部分. 以往反射定律的证明和法线概念的建构过程过于粗略, 忽略了 逻辑推理的过程和科学思维能力的培养. 本文结合自制教具给出证明反射定律和建构法线概念的过程     

Simulations of measurements of fluorescence lifetimes using noise-modulated light

At the Pattern Recognition group at the Delft University of Technology, we are working on new ways to measure fluorescence lifetimes. There are two well-known ways to measure lifetimes; the phase method and the pulse method. In the phase method fluorescent material is stimulated by sinusoidally modulated light. The emitted fluorescent light will have the same modulation frequency, but there will be a phase shift between the excitation and the emission light. Measuring this phase shift will, after some simple calculation, give the lifetime of the fluorescent material. The second method is the pulse method. Short pulses of light are used to excite the material. The emitted light is detected, and from these measurements the decay curve of fluorescent light is determined. In our research we want to use a new method that may allow us to measure a mixture of lifetimes. We want to use excitation light that is modulated by a white noise signal. We are currently building an experimental setup for these measurements. We have been working on numerical and electrical simulations to investigate the properties of noise signals. Some results of these simulations are presented in this paper.     

Quantifying metarefraction with confocal lenslet arrays

METATOYs can change the direction of light in ways that appear to, but do not actually, contravene the laws of wave optics. This direction change applies only to part of the transmitted light beam; the remainder gets re-directed differently. For a specific example, namely confocal pairs of rectangular lenslet arrays with no dead area between lenslets, we calculate here the fractions of power of a uniform-intensity light beam incident from a specific (but arbitrary) direction that get re-directed in different ways, and we derive an equation describing this redirection. This will facilitate assessment of the suitability of METATOYs for applications such as solar concentration. Finally, we discuss similarities between the multiple refraction of light at the lenslet arrays and multiple refraction and reflection of cold atoms at a barrier in the presence of the light fields.     

对PECVD制备碳纳米管的研究和探讨

高纯度和高产率的制备碳纳米管是碳纳米管研究的一个重点。目前制备碳纳米管的方法有电弧法、激光蒸发法、化学气相沉积法(又称CVD法)和模板法等。本文主要介绍采用PECVD化学气相沉积法制备碳纳米管,并对该种方法制备碳纳米管进行了系统的研究和探讨。     

多光刀三维轮廓快速测量方法研究

提出了一种三维自由曲面多光刀快速测量方案,阐述了此方法的测量原理,讨论了多光刀阵列的实现方法,分析了影响其测试精度的主要因素.提出了采用虚拟网格标定法对各光刀分别进行标定,以及运用光刀编码的方法实现对复杂自由曲面测量的方法,结果表明:该方法是一种快速有效的三维轮廓测量方法.     

Femtosecond laser pulses for surface-profile metrology

We discuss two ways to use femtosecond pulsed lasers as a new interferometric light source for enhanced precision surface-profile metrology. First, a train of ultrafast laser pulses yields repeated low temporal coherence, which allows unequal-path scanning interferometry, which is not feasible with white light, to be performed. Second, the high spatial coherence of femtosecond pulsed lasers enables large-sized optics to be tested in nonsymmetric configurations with relatively small-sized reference surfaces. These two advantages are verified experimentally with Fizeau and Twyman-Green type scanning interferometers.     

用于ICF的新型单色退偏器

 设计了一种三元结构的双折射型退偏器,将两个这样的退偏器组合使用（两退偏器光轴成45°）对单色线偏光进行退偏,无论是用洛匈棱镜和红外感光卡对退偏效果进行观察,还是用偏振分析仪对退偏光束进行偏振分析,所得的结果表明退偏效果很好,且退偏效果对入射线偏光的偏振方向不敏感。     

非致冷焦平面热成像技术

简要介绍了三种非致冷红外探测器的技术途径和发展现状。从系统原理提出ＵＦＰＡ热像仪的设计概念以及必须解决的几个关键技术。分析ＵＦＰＱ的性能极限和系统的性能水平,并与第一代轻型热像仪的ＭＲＴＤ曲线进行比较。     

Features of neodymium laser epilation

The efficiency and features of the use of the Nd:YAG laser for epilation in comparison with ruby, alexandrite, diode lasers and a broadband light source were studied. Procedures for calculating the temperature distribution of the hair follicle over the entire depth of its position in the skin and temperatures of undesirable heating of surrounding skin regions under exposure to Nd:YAG laser radiation were developed. The heating temperature of hair follicles with black, brown, and light hair was calculated. The heating temperature of follicles of biological tissues for patients with light, swarthy, and dark skin was calculated. The ranges of the neodymium laser applicability to hair and skin colors during epilation procedures were determined. The ways of optimization of the output radiation parameters (pulse energy and duration, light spot sizes) for removing variously colored hair of patients with various skin phototypes were directed. The ways of epilation technology improvement (active skin cooling, injection of special dyes into hair follicles, and others) were proposed.     

光束“尺缩效应”的探讨

推导出在沿着或垂直于光束运动的参照系中,光束的长度和宽度的变化规律。并且得出以光速运动的几何尺度,在不同的参照系中也有着和光束相同的变化规律。我们比较了这种光束的"尺缩效应"与一般物体尺缩效应的不同之处,最后又推导出光束的体积在不同参照系中的变化公式。