视频监控中若干关键问题的研究

随着网络带宽、计算机处理能力和存储容量的迅速提高，以及各种视频信息处理技术的出现，全程数字化、网络化的视频监控系统优势愈发明显。其高度的开放性、集成性和灵活性为视频监控系统和设备的整体性能提升创造了必要的条件；同时也为整个安防产业的发展提供了更加广阔的发展空间，崭新的应用模式和市场机遇不断涌现。视频监控系统过程向着大型、连续、综合化发展，形成了复杂监控过程，监测控制的要求越来越高，需要更高性能的系统和采用更优秀的控制手段，面临着不能用传统方法解决的新问题。本文概述了目前视频监控中面临的挑战，简要介绍了与视频监控相关的研究领域和研究现状，研究了视频监控中若干亟待解决的问题，主要取得了以下几个方面的研究成果： 第一，提出了基于AdaBoost的改进的人脸检测算法，针对AdaBoost算法的训练速度慢的问题，提出了基于阈值控制的训练方法；同时研究了AdaBoost算法人脸检测方法，利用肤色模型检测人脸区域，并对颜色模型进行了光照补偿。实验结果表明本文的算法具有较好的检测结果。 第二，提出了基于Canny算法的一般目标检测算法，提出了改进的Canny边缘检测算法，研究了Canny算法中噪声抑制的方法，采用改进中心加权的MTM算法有效的抑制噪声。针对Canny检测算法中阈值设置的问题，提出改进的Canny阈值补偿的方法。实验结果表明，改进的Canny算法相比原算法具有更好的目标检测性能。 第三，提出了一种基于均值漂移（Mean Shift）的改进的目标跟踪算法，通过搜索窗口带宽的计算，加权背景信息以及卡尔曼滤波器建模改进了跟踪算法，避免了均值漂移算法中的一些关键问题。对比实验结果表明，本文的改进方法相比原算法具有较好的性能。 第四，研究了视频监控中基于可扩展视频编码(SVC)的技术。首先讨论了视频监控中采用可扩展视频编码(SVC)的优势，探讨了视频监控中采用可扩展视频编码(SVC)的框架。然后针对于视频质量评估问题，设计并实现了基于可扩展视频编码(SVC)的视频质量评估系统Evalvid-SVC，研究了基于可扩展视频编码(SVC)的视频质量评估。 第五，研究并实现了视频数据安全传输技术。提出了基于Diameter的统一认证方案。任何用户想要获取视频资源，都必须通过AAA子系统的认证和授权，授予合法用户以特定的方式使用资源。另外，为了保证监控数据从监控前端安全地传送到视频监控客户端，本文提出了一种有效的保证视频数据安全传输的方案。设计的数据加密算法应用DES算法对前端设备采集到的音视频数据进行加密，并通过定时更新和RSA加密的方式保护和传输DES密钥。

基于融合模板的均值移动头部跟踪算法

针对被跟踪头部目标特征状态随时间变化而与参考模板不匹配的问题,提出一种基于融合参考模板的均值移动算法,即将被跟踪目标在不同状态下所呈现出的不同特征使用采样的方法进行融合,如将头部跟踪过程中正面的肤色信息和后面的发色信息进行融合,从而形成一个包含不同特征的参考模板.在跟踪过程中,使用该融合模板可以有效地克服由被跟踪目标特征变化导致跟踪失败而不能实现头部连续跟踪的问题.通过头部跟踪实验可以看出,该算法实现了复杂环境下的具有360°旋转的头部跟踪,并且在一定程度上提高了跟踪精度.

基于直方图插值的均值移动小尺寸目标跟踪算法

小尺寸目标跟踪是视觉跟踪中的难题。该文首先指出了均值移动小尺寸目标跟踪算法中的两个主要问题:算法跟踪中断和丢失跟踪目标。然后,论文给出了相应的解决方法。对传统Parzen窗密度估计法加以改进,并用于对候选目标区域的直方图进行插值处理,较好地解决了算法跟踪中断问题。论文采用Kullback-Leibler距离作为目标模型和候选目标之间的新型相似性度量函数,并推导了其相应的权值和新位置计算公式,提高了算法的跟踪精度。多段视频序列的跟踪实验表明,该文提出的算法可以有效地跟踪小尺寸目标,能够成功跟踪只有6×12个像素的小目标,跟踪精度也有一定提高。

基于直方图处理和新型相似性度量函数的小尺寸目标跟踪算法

小尺寸目标跟踪是视觉跟踪中的难题。本文使用均值移动算法跟踪小尺寸目标。论文首先分析了基于均值移动的小尺寸目标跟踪算法的两个主要问题:跟踪算法中断和跟踪目标丢失。然后,论文在这两个方面对小尺寸目标跟踪算法进行改进。给出了一种新的直方图单元编号方法,使包含目标颜色分量的直方图单元分布得更为集中紧凑。当候选目标与目标模型不匹配时,给出一种平滑算法来处理候选目标的直方图。论文提出一种新的相似性度量函数,推导了相应的权值计算公式,在此基础上建立了基于均值移动的目标跟踪算法。多段真实场景视频序列的跟踪实验表明,本文提出的算法可以有效地跟踪小尺寸目标,跟踪精度也有一定提高。

Improved BCS-type pairing for the relativistic mean-field theory

A density-dependent delta interaction (DDDI) is proposed in the formalism of BCS-type pairing correlations for exotic nuclei whose Fermi surfaces are close to the threshold of the unbound state. It provides the possibility to pick up those states whose wave functions are concentrated in the nuclear region by making the pairing matrix elements state dependent. On this basis, the energy level distributions, occupations, and ground-state properties are self-consistently studied in the RMF theory with deformation. Calculations are performed for the Sr isotopic chain. A good description of the total energy per nucleon, deformations, two-neutron separation energies and isotope shift from the proton drip line to the neutron drip line is found. Especially, by comparing the single-particle structure from the DDDI pairing interaction with that from the constant pairing interaction for a very neutron-rich nucleus it is demonstrated that the DDDI pairing method improves the treatment of the pairing in the continuum.

Properties and structure of N = Z nuclei within relativistic mean field theory

The axially deformed relativistic mean field theory with the force NLSH has been performed in the blocked BCS approximation to investigate the proper-ties and structure of N=Z nuclei from Z=20 to Z=48. Some ground state quantities such as binding energies, quadrupole deformations, one/two-nucleon separation energies, root-mean-squaxe (rms) radii of charge and neutron, and shell gaps have been calculated. The results suggest that large deformations can be found in medium-heavy nuclei with N=Z=38-42. The charge and neutron rms radii increase rapidly beyond the magic number N=Z=28 until Z=42 with increasing nucleon number, which is similar to isotope shift, yet beyond Z=42, they decrease dramatically as the structure changes greatly from Z=42 to Z=43. The evolution of shell gaps with proton number Z can be clearly observed. Besides the appearance of possible new shell closures, some conventional shell closures have been found to disappear in some region. In addition, we found that the Coulomb interaction is not strong enough to breakdown the shell structure of protons in the current region.

The relationship between chemical bond properties and Stokes shift of Eu2+ in some silicate host lattices

The covalency of each bond in divalent europium doped hosts CaSiO3, SrSiO3, BaSiO3, Sr2LiSiO4F, Ba5SiO4Cl6 and Ba5SiO4Br6 were calculated by using the complicate crystal chemical bond theory. The relationship between the Stokes shift and the bond properties of Eu2+ in these crystals was discussed. The result demonstrates that, in the isostructural crystals that being doped with Eu2+, there is a more precise connection between the magnitude of Stokes shift and the mean covalency of the dopant site.

The convection during NaClO3 crystal growth observed by the phase shift interferometer

An optical diagnostic system consisting of the Mach-Zehnder interferometer with the phase shift device and an image processor has been developed for the study of the kinetics of the crystal growing process. The dissolution and crystallization process of NaClO3 crystal has been investigated. The concentration distributions around a growing and dissolving crystal have been obtained by using phase-shift of four-steps theory for the interpretation of the interferograms. The convection (a plume flow) has been visualized and analyzed in the process of the crystal growth. The experiment demonstrates that the buoyancy convection dominates the growth rate of the crystal growing face on the ground-based experiment.

Control of Mean and Fluctuating Forces on a Circular Cylinder at High Reynolds Numbers

A narrow strip is used to control mean and fluctuating forces on a circular cylinder at Reynolds numbers from 2.0 x 10(4) to 1.0 x 10(5). The axes of the strip and cylinder are parallel. The control parameters are strip width ratio and strip position characterized by angle of attack and distance from the cylinder. Wind tunnel tests show that the vortex shedding from both sides of the cylinder can be suppressed, and mean drag and fluctuating lift on the cylinder can be reduced if the strip is installed in an effective zone downstream of the cylinder. A phenomenon of mono-side vortex shedding is found. The strip-induced local changes of velocity profiles in the near wake of the cylinder are measured, and the relation between base suction and peak value in the power spectrum of fluctuating lift is studied. The control mechanism is then discussed from different points of view.

Growth of zero-mean-shear turbulent-mixed layer with suspended particles in a 2-layer fluid system

The growth behaviour of zero-mean-shear turbulent-mixed layer containing suspended solid particles has been studied experimentally and analysed theoretically in a two-layer fluid system. The potential model for estimating the turbulent entrainment rate of the mixed layer has also been suggested, including the results of the turbulent entrainment for pure two-layer fluid. The experimental results show that the entrainment behaviour of a mixed layer with the suspended particles is well described by the model. The relationship between the entrainment distance and the time, and the variation of the dimensionless entrainment rate E with the local Richardson number Ri1 for the suspended particles differ from that for the pure two-layer fluid by the factors-eta-1/5 and eta-1, respectively, where eta = 1 + sigma-0-DELTA-rho/DELTA-rho-0.

Red-shift conical emission by femtosecond pulses at low input power

Red-shift conical emission (CE) is observed by femtosecond laser pulse propagating in BK7 at a low input power (compared to those input powers for generation of blue-shift CE). With the increasing input power the blue-shift CE begins to appear whereas the red-shift CE ring (902 nm in our experiment) disappears accompanied by the augment of the central white spot size synchronously. The disappearing of red-shift CE in our experiment is explained such that the increase of axial intensity is much higher than that of ring emission and the augment of the central white spot size with the increasing input laser power.

Pondermotive shift of photoelectron spectra in intense laser field

In a recent experimental work on the excess photon detachment (EPD) of H- ions [Phys. Rev. Lett. 87 (2001) 243001] it has been found that the ponderomotive shift of each EPD peak increases with the order of the EPD channel. By using a nonperturbative quantum scattering theory, we obtain the kinetic energy spectra for the differential detachment rate along the laser polarization for several laser intensities. It is demonstrated that higher order EPD peaks are produced mainly at relatively higher laser intensities. By calculating the overall EPD spectra with varying laser intensities, it is found that the ponderomotive shift of each EPD peak increases with the order of the EPD channel. Our calculations are in good agreement with the experimental observation. It is found that different EPD channels occur mainly when the laser field reaches some values, thus the intensity distribution of the laser field is responsible for the varying ponderomotive shifts.

Red shift and broadening of backward harmonic radiation from electron oscillations driven by femtosecond laser pulse

The characteristics of backward harmonic radiation due to electron oscillations driven by a linearly polarized fs laser pulse are analysed considering a single electron model. The spectral distributions of the electron's backward harmonic radiation are investigated in detail for different parameters of the driver laser pulse. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width the broadening of the high harmonic radiations can be controlled.