Hamiltonian limit of the 3D Zamolodchikov model

A two-dimensional quantum Hamiltonian _N,M commuting with the layer-to-layer transfer matrix of the three-dimensional Zamolodchikov model is derived. This Hamiltonian is defined on a lattice ofN×M sites. The special casesN×2, 2×M, and 3×M are studied.This paper is dedicated to Cyril Domb.     

ZN-Graded Noncommutative Differential Calculus

We consider the algebra M _N (C) ofN × N matrices as a cyclic quantum plane.We also analyze the coaction of the quantum group F and the action of its dualquantum algebra H on it. Then we study the decomposition ofM _N (C) in termsof the quantum algebra representations. Finally, we develop the differential algebraof the cyclic group Z _N with d ^N = 0, where Z _N is viewed as the the subalgebraof diagonal N × N complex matrices, and treat the particularcase N = 3.     

Colorimetric Calibration of Video Cameras Using Two Color Constancy Models

Colorimetric calibration of color imaging devices is important to realize device independent color reproductions. However the calibration for digital or video cameras is difficult because a color image is acquired for unknown objects under various unknown illuminants. An experiment was carried out based on two computational color constancy models, the finite-dimensional linear model and the spectral sharpening model, to estimate colorimetric values using image data of a color chart captured by video camera. We estimated the colorimetric values by using a single reference reflectance with known spectral reflectance in a color chart under an unknown illuminant. The accuracy was evaluated by color differences in CIELAB color space and was compared on three different color charts under three different illuminants including a fluorescent lamp. It was confirmed that the two computational models do not require prior knowledge of illuminants and surfaces. The finite-dimensional linear model gave more accurate results than the spectral sharpening model in the simulations and experiments.     

Spectral switching-based fan-out architecture and information processing in free-space

In this paper, we elaborate different type of spectral switching techniques and spectral switching-based information processing (SSBIP) schemes. On the basis of theoretical, experimental and empirical studies carried out so far on spectral switching, we demonstrate novel type of interference-induced 1 × N (1 input N outputs) and 1 × N × M (1 input N × M outputs) spectral switching-based fan-out architectures for information transmission in free-space. In addition, a comprehensive analysis is presented to explore the feasibility of SSBIP scheme in contrast to the recent technological advancements. The spectral switching-based techniques are contrived ideas but might find potential applications in optical computing, state-of-the-art technique like SIMO (single-input multiple-output), free-space optical (FSO) interconnects and polychromatic light-based FSO communications.     

Theory of sparse random matrices and vibrational spectra of amorphous solids

The random matrix theory has been used for analyzing vibrational spectra of amorphous solids. The random dynamical matrix M = AA ^T with nonnegative eigenvalues ɛ = ω² has been investigated. The matrix A is an arbitrary square (N-by-N) real sparse random matrix with n nonzero elements in each row, mean values 〈A _ij 〉 = 0, and finite variance 〈A _ij ²〉 = V ². It has been demonstrated that the density of vibrational states g(ω) of this matrix at N, n ≫ 1 is described by the Wigner quarter-circle law with the radius independent of N. For n ≪ N, this representation of the dynamical matrix M = AA ^T makes it possible in a number of cases to adequately describe the interaction of atoms in amorphous solids. The statistics of levels (eigenfrequencies) of the matrix M is adequately described by the Wigner surmise formula and indicates the repulsion of vibrational terms. The participation ratio of the vibrational modes is approximately equal to 0.2–0.3 almost over the entire range of frequencies. The conclusions are in qualitative and, frequently, quantitative agreement with the results of numerical calculations performed by molecular dynamics methods for real amorphous systems.     

彩色视觉装置的颜色校正对比实验研究

鉴于利用彩色视觉装置进行在线测量是颜色测量在工业应用发展的趋势,而光源的光谱分布和相机响应函数与人眼的光谱响应曲线的不一致会严重影响测量的精确性,在人工D65光源和LED阵列光源照明下,利用相同的工业相机获取校正图片,采用多项式回归方法在与设备无关空间sRGB和CIEL*a*b*空间进行校正。实验结果显示在校正前平均色差分别为27.68E和16.09E,人工D65光源照明下获取的图片色差较小,校正后不同光源下获取图片的色度趋于一致,分别为2.56E和2.39E。采用sRGB颜色空间,在校正精度、校正步骤、图片显示等方面都要优于CIEL*a*b*空间。以一幅拍摄的实际图片校正为例,显示了色度校正对彩色装置的重要性。     

基于同色异谱黑理论的非线性复合模型光谱重建研究

同色异谱现象是光谱反射率重建与颜色再现中的一个重要问题。采用三基色CCD相机采集CIE标准光源D65下的颜色样品信号,建立非线性复合模型,使用主成分分析结合神经网络的方法(PCA-NET)改进基于同色异谱黑理论的R矩阵算法,对标准Munsell色卡光谱重建进行研究。在保证给定照明条件下的色度精度同时,对光谱重建的结果进行了实验评价和讨论。实验结果表明,在给定的照明条件下,PCA-NET算法能够准确的拟合相机输出信号与主成分系数之间的非线性关系, 将其代替线性算法应用于R矩阵算法中时,测试集的平均均方根值是未改进R矩阵算法的0.76,平均标准差是R矩阵算法的0.85,可有效提高光谱反射率的重建精度。改进后的R矩阵算法具有精度较高、操作简单易实现的特点, 可用于对重建色度精度及光谱精度均要求较高的领域。     

基于光源相对光谱功率分布的颜色真值获取方法

嫦娥三号全景相机具有彩色成像模式,在发射前需先进行彩色定标,样本真值的获取是彩色定标的前提。传统方法获取的颜色真值在色差值和视觉感知上都与实际值存在明显的偏差。若直接采用该颜色值作为真值进行彩色定标,影响定标后的色差大小和定标校正后颜色的人眼视觉感知效果。为探索更好的颜色真值获取方法,利用实验室内测得的D65定标光源的相对光谱功率分布,重新定义了转换矩阵中的白点坐标,然后基于CIE颜色计算公式,根据格拉斯曼颜色混合定律,对XYZ与sRGB颜色空间之间的转换矩阵进行了修正,提高了样本真值获取的准确度。另外利用修正后的转换矩阵对sRGB空间的三刺激值曲线进行了重新计算,对标准转换值偏离实际值的原因进行了分析。通过地面试验验证,相对于传统样本真值获取方法,利用该真值获取方法定标后A,B两相机的色差值分别降低了0.8和0.73;定标矩阵校正在轨图像时,色差分别降低了26.50%和34.47%,且校正后的颜色与人眼的视觉感知效果更接近。     

A non-standard auxiliary integrating sphere and correction method for the realization of diffuse reflectance

To realize spectral diffuse reflectance scale in 0/d geometric condition at National Institute of Metrology in China (NIM), a facility based on a non-standard auxiliary integrating sphere method with special structure has been built up and a correction method for the influence on the thickness of PTFE (polytetrafluoroethylene) coating at the port of auxiliary integrating sphere is mainly discussed. The uncertainty of spectral diffuse reflectance in NIM is approximately 0.25% (k = 2) in 380–800 nm. This facility has been used to establish China diffuse reflectance scales in the VIS–NIR part of the spectrum. This system and correction method presented in this paper can be easily implemented on most commercial spectrophotometers with a lower cost.     

Recovery of Surface Reflectances Using Video Camera Image Signals under Unknown Illuminations

Estimation of surface spectral reflectance functions and colorimetric values of object colors was carried out for the image data captured by video camera under unknown illuminations. The estimation method is based on the finite-dimensional linear model of illuminants and surfaces using a single reference reflectance with known surface spectral reflectance in a scene. Experimental results showed that recovered surface spectral reflectance functions are the almost same for different illuminations. This method is useful for the colorimetric calibration of the devices, since any set of orthonormal basis vectors to represent illuminations and any set of eigen vectors derived from principal component analysis on the data set of a color chart to express surfaces of different objects can be applied to the estimation. The recovered surface reflectances were evaluated by color differences in CIE L*a*b* color space.     

Reflectance fluctuations in an absorbing random waveguide

We study the statistics of the reflectance (the ratio of reflected and incident intensities) of an N-mode disordered waveguide with weak absorption g per mean free path. Two distinct regimes are identified. The regime γ N ²≫1 shows universal fluctuations. With increasing length L of the waveguide, the variance of the reflectance changes from the value 2/15N ², characteristic for universal conductance fluctuations in disordered wires, to another value 1/8N ², characteristic for chaotic cavities. The weak-localization correction to the average reflectance performs a similar crossover from the value 1/3N to 1/4N. In the regime γ N ²≫1, the large-L distribution of the reflectance R becomes very wide and asymmetric, P(R)∝(1−R)⁻² for R≪1−γN. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 4, 289–293 (25 August 1996) Published in English in the original Russian journal. Edited by J. R. Anderson.     

Color image encryption using spatial bit-level permutation and high-dimension chaotic system

This paper proposes a bit-level permutation and high-dimension chaotic map to encrypt color image. Firstly, convert the plain color image of size (M × N) into a grayscale image of size (M × 3N), then transform it into a binary matrix, and permute the matrix at bit-level by the scrambling mapping generated by piecewise linear chaotic map (PWLCM). Secondly, use Chen system to confuse and diffuse the red, green and blue components simultaneously. Experiment results and security analysis not only show that the scheme can achieve good encryption result, but also that the key space is large enough to resist against common attack.     

一种基于单色测量的迷彩色光谱反射比测量计算方法

提出一种基于单色测量的迷彩色光谱反射比的测量计算方法。这种方法根据单色光通量的计算方法推导得出,以单色块反射比的测量为基础,根据单色块光谱反射比和各单色在迷彩样品中所占面积,可计算出迷彩样品的光谱反射比。通过实地测量实验进行对比验证,证明了此计算方法具有一定的可行性。     

斜光束对校正滤色器校正精度的影响

当用测色仪器按照国际照明委员会规定的条件测量物体颜色时 ,若样品与探测器之间的距离不够大 ,则斜光束会透过校正滤色器而被探测器接收 ,这时对应探测器某点校正滤色器的当量透射比可以用修正计算式求得。以“Y”校正滤色器为例 ,从计算结果和实验说明了斜光束对校正滤色器透射比的影响。     

Multiplexed fiber optic sensors matrix demodulated by a white light interferometric Mach–Zehnder interrogator

A multiplexed white light interferometric fiber optic sensors matrix system was designed and demonstrated. In this system, a Mach–Zehnder optical path interrogating technique is used to demodulate each sensor of the sensors matrix. The sensors matrix consists of M×N sensing elements linked by a 1×M star coupler. The multiplexing capacity of the sensing scheme has been analyzed and an experimental result with a 2×2 sensors matrix was presented.     

空间分辨漫反射的高阶参量灵敏度

光源附近的空间分辨漫反射与散射介质的高阶光学参量有关.为了研究高阶参量对漫反射的影响，定义了二阶参量灵敏度和三阶参量灵敏度，它们表示了由于高阶参量变化导致漫反射变化的相对量.从P₃近似理论出发，推导了二阶参量灵敏度和三阶参量灵敏度的解析表示，并进行了数值分析和比较.研究表明，在大于一个输运平均自由程的非漫射近似区域，反射率随二阶光学参量增加而增加，其灵敏度随着空间变化，并在小于两个输运平均自由程内出现极大值；相比之下，三阶光学参量对漫反射率的影响可以忽略. 关键词： 漫反射 3近似')" href="#">P₃近似 灵敏度     

A novel blind color images watermarking based on SVD

Since the color image watermark has more bit information, it is a challenging problem to design a robust and blind color watermarking scheme for copyright protection. In this paper, a blind watermarking scheme based on singular value decomposition (SVD) is proposed. By analyzing the orthogonal matrix U via SVD, it is found that there exists a strong similarity correlation between the second row first column element and the third row first column element. Hence, this paper utilizes this property for image watermarking. Firstly, the 4 × 4 non-overlapping pixels block of each component in color host image is processed by SVD. And then, the color watermark is embedded by slightly modifying the value of the second row first column element and the third row first column one of U matrix, and the modified relation can be utilized to extract watermark. Experimental results, compared with the related existing methods, show that the proposed color image scheme has stronger robustness against most common attacks such as image compression, filtering, cropping, noise adding, blurring, scaling and sharpening et al.     

Dihyperons in chiral color dielectric model

The mass of the dibaryon having spin, parityJ ^π = 0⁺, isospinI = 0 and strangeness—2 is computed using chiral color dielectric model. The bare wave function is constructed as a product of two color-singlet three-quark clusters and then it is properly antisymmetrized by considering appropriate exchange operators for spin, flavor and color. Color magnetic energy due to gluon exchange, meson self energy and energy correction due to center of mass motion are computed. The calculation shows that the mass of the particle is 80 to 160 MeV less than twice λ mass.     

Transformation Operators for Sturm-Liouville Operators with Singular Potentials

We construct transformation operators for Sturm-Liouville operators with singular potentials from the space W ⁻¹ ₂(0,1) and show that these transformation operators naturally appear during factorisation of Fredholm operators of a special form. Some applications to the spectral analysis of Sturm-Liouville operators with singular potentials under consideration are also given. This revised version was published online in July 2006 with corrections to the Cover Date.     

Observing many-body effects on lepton pair production from low mass enhancement and flow at RHIC and LHC energies

The ρ spectral function at finite temperature calculated using the real-time formalism of thermal field theory is used to evaluate the low mass dilepton spectra. The analytic structure of the ρ propagator is studied and contributions to the dilepton yield in the region below the bare ρ peak from the different cuts in the spectral function are discussed. The space-time integrated yield shows significant enhancement in the region below the bare ρ peak in the invariant mass spectra. It is argued that the variation of the inverse slope of the transverse mass (M _T ) distribution can be used as an efficient tool to predict the presence of two different phases of the matter during the evolution of the system. The sensitivities of the effective temperature obtained from the slopes of the M _T spectra to the medium effects are studied.