海量图像检索算法的核心问题是如何对特征进行有效的编码以及快速的检索.局部集聚向量描述(Vector of locally aggregated descriptors,VLAD)算法因其精确的编码方式以及较低的特征维度,取得了良好的检索性能.然而VLAD算法在编码过程中...海量图像检索算法的核心问题是如何对特征进行有效的编码以及快速的检索.局部集聚向量描述(Vector of locally aggregated descriptors,VLAD)算法因其精确的编码方式以及较低的特征维度,取得了良好的检索性能.然而VLAD算法在编码过程中并没有考虑到局部特征的角度信息,VLAD编码向量维度依然较高,无法支持实时的海量图像检索.本文提出一种在VLAD编码框架中融合重力信息的角度编码方法以及适用于海量图像的角度乘积量化快速检索方法.在特征编码阶段,利用前端移动设备采集的重力信息实现融合特征角度的特征编码方法.在最近邻检索阶段将角度分区与乘积量化子分区相结合,采用改进的角度乘积量化进行快速近似最近邻检索.另外本文提出的基于角度编码的图像检索算法可适用于主流的词袋模型及其变种算法等框架.在GPS及重力信息标注的北京地标建筑(Beijing landmark)数据库、Holidays数据库以及SUN397数据库中进行测试,实验结果表明本文算法能够充分利用匹配特征在描述符以及几何空间的相似性,相比传统的VLAD以及协变局部集聚向量描述符(Covariant vector of locally aggregated descriptors,CVLAD)算法精度有明显提升.展开更多
A investigation of the properties of the bound states of D^- centers confined in a parabolic quantum dot has been performed for the case with the presence of a perpendicular magnetic field. Calculations are carried ou...A investigation of the properties of the bound states of D^- centers confined in a parabolic quantum dot has been performed for the case with the presence of a perpendicular magnetic field. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. The binding energies of the ground and some bound-excited states are obtained as a function of the applied magnetic field strength. Detailed calculations of the binding energies for a number of low-lying states show that for field strength less than B = 2.1 T, the D center confined in a quantum dot possesses two bound states, for 2.1 〈 B 〈 2.4 T, there exist three bound states, etc. Further relevant characteristics of the D- center quantum dots in magnetic fields are provided.展开更多
基金supported by National Natural Science Foundation of China under Grant No. 10775035
文摘A investigation of the properties of the bound states of D^- centers confined in a parabolic quantum dot has been performed for the case with the presence of a perpendicular magnetic field. Calculations are carried out by using the method of numerical diagonalization of Hamiltonian matrix within the effective-mass approximation. The binding energies of the ground and some bound-excited states are obtained as a function of the applied magnetic field strength. Detailed calculations of the binding energies for a number of low-lying states show that for field strength less than B = 2.1 T, the D center confined in a quantum dot possesses two bound states, for 2.1 〈 B 〈 2.4 T, there exist three bound states, etc. Further relevant characteristics of the D- center quantum dots in magnetic fields are provided.
