Image forces for a point-like dipole near a plane metal surface: An account of the spatial dispersion of dielectric permittivity

Image-force energy profiles were calculated for a constant point-like dipole located in a dispersionless semi-infinite medium adjacent to a medium with the spatial dispersion of its dielectric permittivity. Three models for the substrate were considered: classical (dispersionless), Thomas–Fermi (classical, but taking non-local screening effects into account), and Schulze–Unger (the approximation to the quantum–mechanical non-local Lindhard dependence, reproducing short-range spatial asymptotics correctly). The results obtained taking into account the non-local character of charge-carrier screening differ drastically from those obtained in the classical limit. Hence, classical electrostatics is inadequate, when being applied to analyze the dipole energy at the interface between two polarizable media. In particular, non-local screening results in finite values of the dipole image force energies at the interfaces.     

On dynamic image potential

Self consistent calculations for the dynamic image potential are carried out, taking the finite acceleration of the incoming charge into account. Results indicate that the effect of the inclusion of acceleration is rather small, and the simpler self consistent approach neglecting the acceleration and using a local speed approximation seems to be adequate. Our theoretical framework also provides a mathematical justification of the latter simpler approach which was earlier employed by Ray and Mahan in an ad hoc manner.     

On the measurements of particles by imaging methods: Theoretical and Experimental Aspects

Imaging techniques in particle sizing have always been important. Nevertheless, owing to the progress in CCD cameras, these techniques have found new potential which strongly depends on the capability to describe the image formation. Based on a combination of the generalized Lorenz-Mie theory and the diffraction theory, the image characteristics are described, taking into account the beam size, particle location, direction of observation and collecting optics characteristics. In the case of forward detection, a finite coherence is introduced and the results are compared with those obtained by a convolution approach, with the point spread function assumed to be Gaussian. Then some experimental results are displayed which underline the improvement achieved in particle size measurement.     

Zernike-basis expansion of the fractional and radial Hilbert phase masks

The linear Hilbert phase mask or transform has found applications in image processing and spectroscopy. An optical version of the fractional Hilbert mask is considered here, comprising an imaging system with a circular, unobscured pupil in which a variable phase delay is introduced into one half of the pupil, split bilaterally.The radial Hilbert phase mask is also used in image processing and to produce optical vortices which have applications in optical tweezers and the detection of exoplanets.We subjected the fractional and radial Hilbert phase masks to Zernike function expansion in order to compute the image plane electromagnetic field distribution using Nijboer-Zernike theory. The Zernike functions form an orthogonal basis on the unit circle. The complex-valued Zernike expansion coefficients for these two phase masks were derived for use in the context of the Extended Nijboer-Zernike (ENZ) theory of image formation. The ENZ approach is of interest in that it allows a greater range of defocus to be dealt with, provides a simple means of taking a finite source size into account and has been adapted to high Numerical Aperture (NA) imaging applications.Our image plane results for the fractional Hilbert mask were verified against a numerical model implemented in the commercial optical design and analysis code, Zemax^®. It was found that the Nijboer-Zernike result converged to the Zemax^® result from below as the number of Zernike terms in the expansion was increased.     

凸优化耦合传感器模式噪声的图像伪造检测

现有的图像伪造检测算法主要是借助局部像素与恒虚警率来决策真伪,且忽略了源图像的强烈空间相关性,使算法鲁棒性不佳,难以检测微小尺寸伪造。对此,根据成像传感器的独特随机特性,设计传感器模式噪声检测思想;并提出了凸优化机制耦合传感器模式噪声的图像伪造检测算法。基于光响应非均匀性噪声,联合马尔可夫随机场与贝叶斯规则,设计传感器模式噪声;并构造最佳图像标记像素的先验概率模型;嵌入贝叶斯规则,代替恒虚警率,考虑源图像的强烈空间依赖性,联合整个图像像素,确定最大概率标记像素映射;设计凸优化机制,将图像伪造检测转换为凸问题,提高算法检测效率。并分析了不同伪造区域尺寸对算法检测的影响。仿真结果表明：与当前图像伪造检测算法相比,本文算法具备更好的接收机工作特征;以及更高的检测精度与检测效率。     

Signature of the ground-state topology in the low-temperature dynamics of spin glasses

We numerically address the issue of how the ground-state topology is reflected in the finite temperature dynamics of the +/-J Edwards-Anderson spin glass model. In this system a careful study of the ground-state configurations allows us to classify spins into two sets: solidary and nonsolidary spins. We show that these sets quantitatively account for the dynamical heterogeneities found in the mean flipping time distribution at finite low temperatures. The results highlight the relevance of taking into account the ground-state topology in the analysis of the finite temperature dynamics of spin glasses.     

Finite grade pheromone ant colony optimization for image segmentation

By combining the decision process of ant colony optimization (ACO) with the multistage decision process of image segmentation based on active contour model (ACM), an algorithm called finite grade ACO (FACO) for image segmentation is proposed. This algorithm classifies pheromone into finite grades and updating of the pheromone is achieved by changing the grades and the updated quantity of pheromone is independent from the objective function. The algorithm that provides a new approach to obtain precise contour is proved to converge to the global optimal solutions linearly by means of finite Markov chains. The segmentation experiments with ultrasound heart image show the effectiveness of the algorithm. Comparing the results for segmentation of left ventricle images shows that the ACO for image segmentation is more effective than the GA approach and the new pheromone updating strategy appears good time performance in optimization process.     

基于冠层辐射传输模型的地表反射率光谱重建方法

针对基于多光谱数据有限光谱信息重建地表反射率光谱的病态求解难题,提出一种基于冠层辐射传输物理机理并充分考虑像元异质性的地表反射率光谱重建方法,该方法假设混合像元由植被和土壤两种地物类型组成,利用冠层辐射传输模型构造端元光谱查找表,进而通过组分比例因子估算实现基于多光谱图像的高光谱地表反射率模拟。以Landsat ETM+多光谱图像为例的地表反射率超光谱重建验证实验结果表明,模拟的反射率光谱能够较好的反映不同地物特征信息。进一步地,利用模拟的地表反射率拟合Landsat ETM+图像和MODIS图像,各波段模拟图像与实际观测图像之间具有较高的相关系数(Landsat: 0.90~0.99, MODIS: 0.74~0.85),进一步验证了该方法的可行性。     

Compression Properties of Finite Nuclear Matter at Zero and Finite Temperatures with the Skyrme Force SKM

By taking into account the finite-size effect rationally in the framework of the Hartree-Fock theory, compression properties at zero and finite temperatures of finite nuclear matter are investigated with the Skyrme force SKM^*. Energies of the isoscalar giant monopole resonance of nuclei at zero temperature calculated are found to be in agreement with experimental and empirical values.     

Recursive method for opacity expansion at finite temperature

Using a reaction operator approach, we derive the multiple-scattering induced gluon number distribution function to all orders in powers of opacity at finite temperature. The detailed balance effect is analyzed by taking into account both gluon emission and absorption in a thermal medium. We also calculate virtual corrections and show that the infrared divergence cancels out in the gluon distribution function at finite temperature.     

Recursive method for opacity expansion at finite temperature

Using a reaction operator approach,we derive the multiple-scattering induced gluon number distribution function to all orders in powers of opacity at finite temperature.The detailed balance effect is analyzed by taking into account both gluon emission and absorption in a thermal medium.We also calculate virtual corrections and show that the infrared divergence cancels out in the gluon distribution function at finite temperature.     

一种边缘提取的图像分割方法

图像分析技术从广义上来讲 ,是指从图像中提取有用的数据或其它信息。图像分割是图像分析技术的重要手段 ,在前人的理论基础上经过实验提出了一种边缘提取的图像分割方法———行扫描空间带通滤波法。该方法在电视图像的自动跟踪识别中取得了很好的效果 ,是一种较为可取的图像分割方法     

An expression of QED thermodynamic potential in strong magnetic fields at finite temperature and density

With the closed path Green function approach and taking into account the one-loop polarization only, a closed expression for the thermodynamic potential of two dimensional QED in strong magnetic fields at finite temperature and density is derived.     

Chiral Bag Model at Finite Temperature

By taking the thermodynamical contributions of the pion mesons cloud outside the bag into account,the chiral bag model is extended to finite temperature.The temperature dependence of the radius of the chiral bag and the critical temperature of quark deconfinement are given.     

Image composition with color harmonization

Image matting and color transfer are combined to achieve image composition. Firstly, digital matting is used to pull out the region of interest. Secondly, taking color harmonization into account, color transfer techniques are introduced in pasting the region onto the target image. Experimental results show that the proposed approach generates visually pleasing composite images.     

Morphological stability of two-dimensional new phase precipitate located at the grain boundary

The diffusion growth of two-dimensional new phase precipitate located at the grain boundary of a finite thickness is considered taking into account diffusion fluxes of impurity atoms from the bulk of a grain depth to the grain boundary. The stability of the growing precipitate of a relatively small radius to small random perturbations of its shape is analyzed taking into account the surface kinetics of the impurity atoms on the grain boundary-precipitate interface. The threshold radii of the precipitate are found, above which the amplitude of the shape distortion and the amplitude of the relative shape deformation of the precipitate rise.     

Development and trial of a new method of image enhancement for ultrasonic medical diagnostics

The subject of this work is the problem of separation of noise from informative texture elements taking into account special features of the ultrasonic image. A mathematical model is developed that describes statistical and spectral properties of different elements of image texture. A noise-suppression procedure based on the developed mathematical model is implemented. The method passed clinical trials that proved its efficiency.     

Effects of finite temperatures,valence bands and energy gaps on the indirect exchange interaction in intrinsic semiconductors

The indirect exchange interaction between localized magnetic moments via virtual excitations from the valence band in intrinsic semiconductors is calculated taking into account the temperature, energy gaps, finite valence bands and effective masses. The inclusion of finite temperature effects changes significantly the phase and magnitude of the oscillations. For small gap semiconductors the oscillatory character and the possibility of ferro-magnetic as well as anti-ferromagnetic coupling are obtained. The exchange interaction oscillates with temperature suggesting interesting applications of this model.     

Quantum Recoil Effects of Spontaneous Emission on Disentanglement

By taking into account spatial degrees of freedom of atoms, we study theinternal-state disentanglement dynamics of two atoms interacting with avacuum multi-mode noise field. We show that the complete internal-statedisentanglement of the two atoms, caused due to the atomic spontaneousemission can be achieved in a finite time.