基于同时的相对性对钟慢尺缩效应的再认识

同时的相对性、钟慢效应和尺缩效应是狭义相对论时空观的主要内容.鉴于同时性是时空测量的基础,本文从同时的相对性出发详述了对钟慢效应和尺缩效应的再认识:钟慢效应是运动时钟走时率变慢和校表问题的综合表现,其实质是同时的相对性在时间量度上的直接反映;尺缩效应的实质是同时的相对性在空间量度上的反映,也是不同观测者对同一客观事实的不同时空描述.     

狭义相对论中同时性的研究

本文对狭义相对论中＂同时性＂的基础和＂尺缩钟慢＂效应的本质进行了深入探讨.＂绝对同时＂和＂绝对静止＂一样是不存在的,＂同时＂和＂静止＂都具有相对性.以此为出发点,本文对一个不能直接应用＂尺缩钟慢＂效应解决的物理问题进行了深入研究.结果表明只要找到与正在发生的事件始终保持相对静止的惯性参考系,我们就可以引入＂固有时间＂的概念,再结合＂尺缩钟慢＂效应得到相应事件相对于地面参考系的时间变化规律.     

不同对流马赫数下光束畸变的实验研究

利用双曝光CCD相机成像技术,研究了小直径光束穿越可压缩混合层流场后所引起的气动光学效应.实验研究结果表明:在不同对流马赫数(Mc=0.17,0.45)下,光束投影(点扩散函数,PSF)发生了不同程度的变形和偏移.此外在不同对流马赫数下细光束投影都存在扩束、缩束和面积几乎不变的现象,但光束投影出现扩、缩束的概率不同.     

《从零学相对论》连载⑦ 第4讲 趣味运动学效应

§4.1尺缩效应和车库佯谬稍微接触过狭义相对论的人都听说过尺缩、钟慢等饶有兴味的效应.当你进一步听到"双生子悖论"和"车库悖论"时,除了觉得更加有趣之外,还会平添许多疑惑和不解.其实,只要思维清晰,利用洛伦兹变换就可把这些效应解释清楚.不过,对于某些问题(特别是"双子悖论"),在听完用洛伦兹变换的     

相对于动尺为静止的观测者如何理解“动尺缩”

相对于动尺为静止的观测者如何理解“动尺缩”徐子马文（北京机械工业学院北京１０００８５）（收稿日期：１９９５－１２－２９）设两个惯性参照系Ｓ与Ｓ′，坐标轴分别相互平行（Ｏｘ轴与Ｏｘ′重合），Ｓ′系相对于Ｓ系以速率ｕ向Ｏｘ′正向运动，Ｏ点和Ｏ′点重合时，...     

关于狭义相对论两种不同的长度测量方式

分析了"尺缩效应"的导出过程及其可能引起的误解,阐述了狭义相对论关于不同惯性系对同一物体长度测量的另一种观点,并对两种不同长度测量方式进行了比较.     

转塔气动光学效应时空特性

通过对相同马赫数、相近雷诺数、不同转塔口径(400mm和2000mm)的绕流流场模拟和气动光学效应进行分析,给出了不同发射方向时气动光学效应导致的光束倾斜角和光束质量因子的时间变化特性、统计特性以及时间相关特性。结果指出:多数场景下气动光学效应中平均流场效应占主要部分,平均流场效应的特征频率由绕流流场的特征频率决定。尺寸效应的研究表明:缩比实验可以有效模拟实际飞行状态下气动光学效应的统计特性,但无法准确模拟其时间相关特性。开展了前向发射时发射方向的优化选择,指出发射方向在中轴线上天顶角约为40°时,气动光学效应导致的波前畸变统计值和涨落值最小。分析了前向发射时发射口径的影响,指出发射光束半径增加会导致平均流场效应快速增加,但湍流效应基本不变。     

闵氏时空图在相对论教学中的应用

将闵科夫斯基二维时空图应用于大学物理课程中的相对论教学,直观地揭示了狭义相对论时空观以及"尺缩钟慢"效应与"同时的相对性"的内在联系.     

衍射扭曲高斯-谢尔模型光束在远场的光谱移动和光谱开关

从部分相干光的传输理论出发,研究了被光阑衍射扭曲高斯-谢尔模型光束远场的光谱变化规律。结果表明,扭曲高斯-谢尔模型光束在远场也会出现光谱移动和光谱开关效应。与衍射高斯-谢尔模型光束情况相比,光谱移动和光谱开关效应不仅与光束空间相关性、截断参量和源光谱谱宽有关,光束的扭曲因子也会对衍射扭曲高斯-谢尔模型光束远场的光谱移动和光谱开关效应产生影响。通过数值计算结果详细讨论了光束扭曲因子影响衍射扭曲高斯-谢尔模型远场光谱的规律。     

竞争非局域非线性向列相液晶中亮孤子

针对热效应的非局域程度和分子取向效应的非局域程度不等的情况,利用JUNG P S等提出的模型研究了具有竞争非局域非线性效应的向列相液晶中的亮孤子特性.通过变分法得到光束振幅、宽度、啁啾和位相等参数随传输距离的变化规律,即光束振幅和宽度与入射光的功率息息相关,光束宽度随热非局域程度增加单调递减,随热非线性系数增加单调递增.在此基础上给出和入射光束功率密切相关的势能函数.利用势能函数预言了入射光束功率越大亮孤子宽度越小.通过解变分方程组可得,入射光功率为4或8时,光束宽度均随传输距离周期性震荡.这两个震荡趋势有明显的区别,功率为4时光束传输过程中宽度始终大于或等于初始宽度,功率为8时光束传输过程中宽度始终小于或等于初始宽度.该变化规律与数值仿真结论一致.     

Finite-size image isochronism

Classical imaging tautochronism implies zero light transit-time variation over paths, connecting the point source with its image point. For a certain imaging class the variation is shown to be zero over two-dimensional objects and corresponding images. The area-isochronous imaging is surely important for pico and subpicosecond photography.     

Use of local fuzzy variance to extract the scattered regions of spatial stray light influence in hyperspectral images

Spatial stray light is a phenomenon caused by scattering of photons from target objects, and it is generated within and among adjacent objects. The intensity and radiometric composition of spatial stray light depends on the light source properties and chemical and physical properties of the objects being imaged. A special kind of region exists in hyperspectral images, referred to as the “scattered region” of spatial stray light, which can be regarded as a boundary between different objects or between an object and background. In this study, local fuzzy variance was used to extract the regions, in which spatial stray light may have significant influence. The proposed method was applied to three data sets: synthetic array data and two hyperspectral imaging datasets (1: plastic card and 2: maize kernels from three inbred lines). Using local fuzzy variance method, scattered regions of spatial stray light could be extracted and visual inspection of data sets demonstrated the effectiveness and sensitivity of the proposed method.     

LIGHT SCATTERING AND INFRARED RADIATION OF SPATIAL OBJECTS

In this paper, the characteristic of light scattering and infrared radiation of spatial objects are discussed. The spectral distribution of solar, sky and earth background radiation is given. Based on theories of heat transfer, background radiation and the law of energy conservation, the thermal balance equation for spatial objects can be obtained. With the equation solved and thermal meshwork method, the variation of the thermal equilibrium temperature and radiation power with height is discussed under the conditions of different time zone and altitude.     

一种基于偏振解析的三维表面重建方法

提出用解析反射光偏振图像来重建透明物体表面形状的原理及实现方法。从物体表面反射的光具有一定的偏振特性,偏振特性的不同反映了物体的形状和反射特性的不同,这两者之间存在一种必然的联系。通过分析物体表面反射光的偏振分布,可以得到物体的表面形状。依据菲涅耳反射公式,推导出偏振度与物体表面法线间的函数关系,据此构建相应算法,对由CCD照相机拍得的被测物体的偏振灰度图像进行处理,重建出被测物体的表面形状。实验结果证明提出的方法是实用且有效的。     

The wavelength sensitivity of back-scattering

The effect of wavelength variations on the backscattering of laser light from contoured or shaped objects is analyzed. In order to consider remote sensing by frequency-scan means, equations are derived for the transforms of the signal field and its intensity and for the correlation functions appropriate in the study of rough objects. In these expressions, interesting dependences upon object shape, roughness, and orientation are found. In experiments using roughened plates and spheres illuminated by a tunable dye laser, good agreement with theory is observed.     

A method for measuring two-dimensional refractive index distribution with the total internal reflection of p-polarized light and the phase-shifting interferometry

Based on the total internal reflection of p-polarized light and the phase-shifting interferometry, an alternative method for measuring the two-dimensional refractive index distribution of a material is presented. The p-polarized light is incident on the boundary between a right-angle prism and a tested material. When the total internal reflection occurs at the boundary, and the p-polarized light has a phase variation. It depends on the refractive index of the tested material. Firstly, the two-dimensional phase variation distribution of the p-polarized light at the boundary is measured by the four-step phase shifting interferometric technique. Then, substituting the data into the special equations derived from Fresnel equations, the two-dimensional refractive index distribution of the tested material can be obtained.     

基于线偏振光反射率测量介质折射率的研究

研究线偏振光的振幅反射率与介质折射率的关系,提出一种测量介质材料折射率的方法。文中从菲涅耳公式出发,推导出各向同性介质的线偏振光反射率与折射率的关系式,给出基于线偏振光反射率测定介质折射率的原理。设计实验方案,在不同入射角情况,定出线偏振光p方向和s方向两种线偏振光在玻璃表面的反射率,得到线偏振光振幅反射率随入射角变化的实验曲线。依此实验数据得出材料的折射率。结果表明,测出的介质材料的折射率与理论值相符,所采取的测定方案可行。     

Variation of the plasma oscillation eigenfrequencies in metal nanoparticles upon their attachment to dielectric micro-objects

The possibilities of studying the structure of micro-objects by measuring optical characteristics of metal nanoparticles attached to them are analyzed. Approximate expressions describing variation of the plasmon dipole oscillation frequencies of a spherical nanoparticle depending on its position with respect to different objects are derived in the framework of a perturbative approach. Special attention is paid to the case of intrusion of a nanoparticle into a spherical object. Possible application of intrusion of nanoparticles into an object is discussed.     

The Use of Micro-Fading Spectrometry to Evaluate the Light Fastness of Materials in Oxygen-Free Environments

The use of inert gases for displaying sensitive objects and for the treatment of artifacts infected with bio-deteriorating agents is a current practice in many cultural institutions around the world. However, some artifacts may also experience color changes as a result of exposure to light in these reducing environments. Therefore, it becomes essential to evaluate the light stability of an object under anoxic conditions prior to its exhibition. This study dealt with the development of a procedure based on micro-fading spectroscopy to determine the light fastness of materials when exposed to an argon atmosphere. The efficacy of this method has been tested using turmeric/silk and Prussian blue/silk systems. Evaluation of color changes in real time have demonstrated that the approach provides an efficient way of detecting any potential variation occurring as a result of long-term anoxic display in a museum environment.     

Theory of reflection and absorption of light by low-dimensional semiconductor objects in a strong magnetic field under monochromatic and pulsed excitations

The theoretical principles of reflection and absorption of light by low-dimensional semiconductor objects (quantum wells, quantum wires, quantum dots) under monochromatic and pulsed excitations with an arbitrary pulse shape are developed. A semiconductor object can be placed in a strong constant magnetic field. The normal incidence of light on a quantum well whose width can be comparable to the light wavelength and for which the number of levels of electronic excitations can be arbitrary is considered as an example. An integral equation similar to the Dyson equation is derived for the Fourier components of the electric fields. The solutions to this equation are given for a number of special cases.