对数似然图像分割的快速主动轮廓跟踪算法

针对跟踪目标尺度变化问题,提出了基于灰度对数似然图像分割的快速主动轮廓跟踪算法。改进的主动轮廓跟踪算法将根据以目标与背景的颜色差异而建立的对数似然图对图像进行阈值分割和数学形态学处理,再将Kalman滤波器结合到主动轮廓跟踪算法进行目标跟踪。改进的主动轮廓跟踪算法对目标分割准确,轮廓特征显著,跟踪效果稳定,算法能很好地适应跟踪目标尺度变化。通过Kalman滤波器对目标位置点的预测减少了主动轮廓跟踪算法收敛的迭代次数,使算法的运算效率提高了33%左右。     

Quantum Dynamics of Entanglement and Single Excitation Transfer in LH1-RC-Type Trimer

In this paper, we study quantum dynamics of entanglement and single excitation transfer (SET) in an LH1-RC-type trimer which can describe a basic unit cell in the LH1-RC complex in the photosynthetic process. It is shown that there exists a sudden change of entanglement at the critic point of quantum phase transition (QPT) of the system at low temperatures, the entanglement sudden change caused by the QPT is suppressed at higher temperatures. We investigate the influence of environment on entanglement and SET. We show the generation of the dephasing-assisted entanglement between a donor and an acceptor and the existence of the steady-state entanglement, and demonstrate the entanglement transfer from donor-donor entanglement to donor-acceptor entanglement in the dynamic evolution. We reveal the close relation between the SET probability and donor-acceptor entanglement. Especially, we find that the SET probability is proportional to the amount of donor-acceptor entanglement under certain conditions.     

物理教育研究评估

科学的定性及定量评估方法是物理教育研究重要的研究手段.目前国际通用的教育评估测试,根据测试目标的不同,可分为多种类型:学习内容调查、学习态度调查和科学分析能力调查等.我们已将本文中介绍的部分评估测试应用于国际教育研究领域.     

多种通信手段在遇险救生体系中的应用研究

我国海域辽阔,各类船只的水上航行和作业安全密切关系到生命和财产的安全,需要可靠保障。由于海上险情发生的随机性和突发性,岸上险情监视力量必须全时、全天候地开设险情通信通道,接收海上遇险对象的遇险呼救信号并及时对遇险信息进行处理。因此,岸基必须建设遇险救生信息系统并规定必要的信息传输流程,保障险情报知通信的顺利完成。文章简要分析了目前海上救生的通信现状,对常用通信手段进行了分析与介绍,并提出了一种整合各通信手段的设计方法,实现了多种通信手段的综合使用以及统一调度,大幅提升险情信息的传输和处理效率,提高险情信息的保密性,为救援工作提供了精确可靠的问责手段。     

Perturbation to Lie-Mei Symmetry and Adiabatic Invariants for Birkhoffian Systems

Based on the concept of adiabatic invariant, the perturbation to Lie-Mei symmetry and adiabatic invariants for Birkhoffian systems are studied. The definition of the perturbation to Lie-Mei symmetry for the system is presented, and the criterion of the perturbation to Lie-Mei symmetry is given. Meanwhile, the Hojman adiabatic invariants and the Mei adiabatic invariants for the perturbed system are obtained.     

Geometric and Electronic Properties of SrCoO2.5: An LSDA+U Study

The geometric and electronic properties of SrCoO_2.5 have been studied using the local-spin density approximation together with the Hubbard method. The geometric optimization shows that the energy of a unit supercell for SrCoO_2.5 with the space group Pnma is at least 1.37eV lower than the others, so we infer that the Pnma structure is the ground state of SrCoO_2.5 at low temperature. The electronic band structure calculations demonstrate that the paramagnetic ordering SrCoO_2.5 at high temperature has the character of an indirect band gap semi-conductor, while the antiferromagnetic ordering SrCoO_2.5 at low temperature has the character of a conductor. The magnetism calculation shows that the magnetic moment of Co is 2.96μ_B, comparable with the experimental measurement at the liquid nitrogen temperature, i.e. 3.30±0.5μ_B.     

Generation and Modulation of Phase Difference of Output Intensities in a Feedback Nd:YAG Laser with an Extracavity Waveplate Rotated

External anisotropic feedback effects on the phase difference behaviour of output intensities in a microchip Nd：YAG laser are presented. By rotating a quarter wave plate placed in the external cavity, the angle between laser initial polarization direction and o-axis of the wave plate is tuned from -45°to 45°, which results in variable extra-cavity birefringence along two orthogonal detection directions. With only one optical path and one wave plate, laser intensities of the two orthogonal directions, both modulated by the external cavity length, are output with a tunable phase difference, which can be continuously changed from zero to twice as large as that of the waveplate. Experimental results as well as a theoretical analysis based on Fabry-Perot cavity equivalent model and the refractive index ellipsoid, are presented. The potential applications of this phenomenon are also discussed.     

燃煤飞灰物理化学特性及其润湿机理研究

以小龙潭电厂燃煤飞灰及其不同粒径范围的分级灰为对象,采用X射线荧光光谱、X射线衍射、离子色谱、Zeta电位、扫描电镜等实验方法研究了飞灰的物理化学特征.同时采用沉降实验、表面张力实验研究了三种不同润湿剂对飞灰的润湿性能.研究发现,溶液对飞灰的润湿能力不仅取决于其气液界面张力,还与飞灰的组成、表面电位以及形貌特征密切相关.亲水性物质含量的增加,颗粒表面电荷与润湿剂分子间的静电吸引,颗粒表面的棱角孔隙等均可以促进其润湿;温度越高飞灰润湿性能越好,且温度对飞灰润湿过程影响较大,温度较高(60℃)时润湿剂种类及浓度对飞灰润湿过程的影响不明显.     

HL-2M偏滤器CFC/CuCrZr靶板的非晶钎焊工艺研究

在采用商用的STEMET-1101非晶钎料、温度为710~750°C的真空钎焊下,对CFC/OFC(氯氟烃/无氧铜)复合块与CuCrZr(铬锆铜)的钎焊进行了研究。首先,通过X-射线衍射(XRD)和差式扫描量热分析对钎料的结构和熔化行为进行了表征;然后,通过光学显微镜、电子探针微分析和拉伸试验等方法对焊缝的组织形貌、元素成分分布、相结构和力学性能进行了分析;最后,通过高热负荷装置对CFC/OFC/CuCrZr钎焊模块的热疲劳性能进行测试。结果表明,在710~750°C钎焊温度内焊缝由Cu固溶体、(Cu, Ni)3P和Ni(Cu ,Cr)2P金属间化合物组成,焊缝平整无裂纹;特别是在750°C/15min情况下,抑制了焊缝金属间化合物的连续分布,OFC/CuCrZr的焊接强度大于OFC的抗拉强度,CuCrZr/CuCrZr的结合强度为210MPa,并呈现部分韧性断裂。在750°C/15min情况下制备的CFC/Cu/CuCrZr模块可以承受1000次7MW·m^-2的循环热负荷。