空间目标TLE天基光学混合状态SPKF拟合方法

针对天基光学监视应用中空间目标两行轨道根数拟合估计问题,通过引入UT变换和混合状态空间,将简化的常规摄动预测模型嵌入跟踪滤波过程,提出两行轨道根数拟合估计的天基光学混合状态Sigma点卡尔曼滤波方法.仿真结果表明,该方法可利用仅测角观测资料实现对空间碎片等非合作目标的两行轨道根数序贯滤波拟合估计.     

基于天基光学测角的高轨空间目标轨道确定

受到距离和观测条件等因素的影响,地基设施对高轨空间目标的观测能力有限,但天基观测设施可以有效突破地基设施的观测局限,从而提高对高轨空间目标的观测效率和精度.基于此,结合当前天基测量技术的现状,研究基于天基光学测角的高轨空间目标轨道确定方法,包括初始轨道确定方法和轨道改进方法.针对观测量类型对轨道确定结果的影响,推导直接利用天基观测角度的轨道改进方法,以及基于天基观测方向矢量的轨道改进方法.利用仿真数据和实测数据对两种改进方法进行比较.研究结果表明,基于天基观测方向矢量解算得到的高轨目标轨道精度相对较高,可为我国空间态势感知体系的建设提供有益借鉴.     

基于改进Phong模型的天基光学观测GEO目标姿态估计方法

针对于缺少基于天基光学观测的空间目标姿态估计的问题,提出将无味卡尔曼滤波应用于基于天基光学观测的地球同步轨道目标姿态估计中.以光学横截面积代替星等作为观测量,提高观测方程的线性化水平,实现观测方程的简化;同时建立基于改进Phong模型的光学横截面积观测模型,在提高观测方程描述能力的同时,以角度作为模型的输入,极大地简化了计算,增强了实时性.最后,以贴敷聚酰亚胺薄膜及朗伯体材质的长方体为例,对比分析了姿态估计情况,验证了所提方法的有效性;并进一步对正六棱柱、正八棱柱进行了姿态估计.     

空间目标天基光学观测的序列图像仿真方法

利用STK和OpenGL,提出了一种能体现空间目标天基光学观测系统真实成像距离和系统性能的序列图像仿真方法。首先建立空间目标的三维模型和轨道模型,利用STK预测目标卫星和观测卫星的相对几何关系,然后在分析相机针孔成像和OpenGL透视投影成像模型关系的基础上,通过设置OpenGL的有关参数生成了包含目标和成像系统信息在内的目标仿真图像,最后生成运动空间目标近距离光学观测的二维图像序列,可为天基空间目标识别研究提供数据基础。     

基于TracePro的空间目标光学散射特性建模与仿真EI北大核心CSCD

为给空间目标光学探测与识别提供数据支持,建立了基于TracePro的空间目标光学散射特性计算模型.以空间目标天基红外系统为例,综合考虑目标的结构特性、材料特性、背景特性及轨道特性,通过TracePro中建立几何模型、设定材质、设定光源、计算光线路径等环节,对目标光学散射特性进行仿真分析.结果表明,目标的光谱辐照度曲线与太阳一致.镜反射时,目标的等效光谱反射率曲线与砷化镓电池片一致,随着目标旋转,目标的等效光谱反射率曲线趋向于与包覆材料一致,而后保持不变.为空间目标光学散射特性研究思路提供了借鉴.     

基于TracePro的空间目标光学散射特性建模与仿真

为给空间目标光学探测与识别提供数据支持,建立了基于TracePro的空间目标光学散射特性计算模型.以空间目标天基红外系统为例,综合考虑目标的结构特性、材料特性、背景特性及轨道特性,通过TracePro中建立几何模型、设定材质、设定光源、计算光线路径等环节,对目标光学散射特性进行仿真分析.结果表明,目标的光谱辐照度曲线与太阳一致.镜反射时,目标的等效光谱反射率曲线与砷化镓电池片一致,随着目标旋转,目标的等效光谱反射率曲线趋向于与包覆材料一致,而后保持不变.为空间目标光学散射特性研究思路提供了借鉴.     

基于混合粒子滤波的水下小目标跟踪

针对水下小目标粒子滤波估计过程中“粒子贫化”引起的估计性能下降,提出了混合粒子滤波算法。该算法在常规粒子滤波算法基础上,在每一步迭代估计过程中进行量测的再次随机采样,以丰富随机粒子多样性,缓解水下小目标状态估计过程中的“粒子贫化”的影响。对算法进行了仿真分析,并将该方法用于水下小目标探测实验的数据处理,结果表明,相比于常规的粒子滤波算法,所提出的混合粒子滤波得到了误差更小且稳定的状态估计结果,有效地改善水下小目标跟踪的精度和稳健性。     

天基光电望远镜空间多目标成像模拟技术研究

提出了一种天基光电望远镜对空间多目标成像的模拟方法。首先由卫星轨道参数向量和三维矩阵变换得到卫星在地心赤道坐标系中的坐标矩阵,然后再通过平移、旋转和比例等变换得到卫星及恒星在望远镜中的坐标矩阵,最后即可得到总模拟图。设计了一种应用在天基光电望远镜上的空间多目标成像模拟数据库,并为数据库提供了几种基本的维护管理功能。给出了该数据库的基本设计方法和目标数据实例,提供了1000余颗卫星的相关轨道参数。计算机模拟了天基光电望远镜对空间多目标的成像。仿真结果表明,该方法可有效地模拟天基光电望远镜对空间多目标的成像。     

基于概率假设密度滤波的中段弹道目标群红外多传感器组跟踪方法

分析低轨光学星座对中段弹道目标群进行组跟踪的必要性,提出了一种红外多传感器对中段弹道目标群的组跟踪新方法.该方法以概率假设密度滤波对目标群进行像平面跟踪,剔除杂波、估计目标状态和个数;以图像配准方法调整帧间目标状态估计,提高像平面目标跟踪稳定性;最后依据像平面目标跟踪结果提取目标群在像平面的质心量测,运用不敏卡尔曼滤波...     

空间目标天基光学监视平台的参数仿真分析

利用天基光学系统对空间目标进行监视是重要而有效的手段之一。以在轨运行的低轨卫星为研究对象,对天基光学平台的观察方向、升交点赤经和真近点角等参数进行了优化设置。通过分析可知,观察方向指向左和指向右时可以监视更多的目标,升交点赤经选取在0°、270°和315°对空间目标的监视效果较好,而卫星被截获的概率与真近点角的变化关系并不密切,因此真近点角可以任意选取。根据参数优化结果,以卫星仿真工具包STK(Satellite Tool Kit)为平台,对空间目标天基光学监视平台的轨道参数进行了仿真。     

二能级原子的混态SU(2)压缩

本文采用时间演化算符方法研究混态下二能级原子的SU(2)压缩行为,得出有光场相互作用下的混态原子的压缩比一般纯态原子算符的SU(2)压缩还要深,而且处于准基态下比在准激发态下的压缩要深得多的新结果。通过数值计算,讨论了原子能级布居的统计几率与压缩的关系。     

Radon transforms of the Wigner operator on hyperplanes

The generalization of tomographic maps to hyperplanes is considered. We find that the Radon transform of the Wigner operator in multi-dimensional phase space leads to a normally ordered operator in binomial distribution---a mixed-state density operator. Reconstruction of the Wigner operator is also feasible. The normally ordered form and the Weyl ordered form of the Wigner operator are used in our derivation. The operator quantum tomography theory is expressed in terms of some operator identities, with the merit of revealing the essence of the theory in a simple and concise way.     

倒谱本征空间结构化高斯混合模型语音转换方法

针对非平行语料非联合训练条件下的语音转换,提出一种基于倒谱本征空间结构化高斯混合模型的方法。提取说话人语音倒谱特征参数之后,根据其散布矩阵计算本征向量构造倒谱本征空间并训练结构化高斯混合模型SGMM-ES(Structured Gaussian Mixture Model in Eigen Space)。源和目标说话人各自独立训练的SGMM-ES根据全局声学结构AUS(Acoustical Universal Structure)原理进行匹配对准,最终得到基于倒谱本征空间的短时谱转换函数。实验结果表明,转换语音的目标说话人平均识别率达到95.25%,平均谱失真度为1.25,相对基于原始倒谱特征空间的SGMM方法分别提高了0.8%和7.3%,而ABX和MOS测评表明转换性能非常接近于传统平行语料方法。这一结果说明采用倒谱本征空间结构化高斯混合模型进行非平行语料条件下的语音转换是有效的。      

Creeping instability in YBCO ceramics under non-isothermal superconducting transition

A high number of normal-superconductor transitions of sintered YBCO samples have been monitored by AC susceptibility measurements simultaneously in three different regions of samples, in the presence of strong thermal gradient. With this method, different accidental mesoscopic vortex structure instabilities have not only been observed but also located. Even if local magnetothermal instabilities of oscillatory nature (f=0.1–0.02 Hz) appear in strong thermal gradient fields, their evolution remains localized. However, when such instabilities appear in superposed temperature and electric (DC) potential gradient fields, they travel together with the mixed-state zone (v=0.06–0.1 mms⁻¹) along the macroscopic specimen. The interaction of transport currents with shielding current instabilities of the mixed-state — modifying some percolative network paths — can be considered as a possible macroscopic scenario for the traveling instabilities.     

Construction of an optimal witness for unknown two-qubit entanglement

Whether entanglement in a state can be detected, distilled, and quantified without full state reconstruction is a fundamental open problem. We demonstrate a new scheme encompassing these three tasks for arbitrary two-qubit entanglement, by constructing the optimal entanglement witness for polarization-entangled mixed-state photon pairs without full state reconstruction. With better efficiency than quantum state tomography, the entanglement is maximally distilled by newly developed tunable polarization filters and quantified by the expectation value of the witness, which equals the concurrence. This scheme is extendible to multiqubit Greenberger-Horne-Zeilinger entanglement.     

轴对称流场干涉条纹折射率的模拟计算

提出一种获取流场干涉条纹折射率分布的新方法。该方法首先采用不等间隔的环带分割轴对称流场,使折射率变化大的地方获得的数据点密,然后通过对Abel变换进行离散数值计算来获取流场的折射率分布。通过模拟轴对称流场的实时全息干涉条纹证明了该方法不仅简单易行,而且所获取的折射率分布精度高。     

Pure state condition for the semi-classical Wigner function

The Wigner function W(p,q) is a symmetrized Fourier transform of the density matrix ρ(q₁,q₂), representing quantum-mechanical states or their statistical mixture in phase space. Identification of these two alternatives in the case of density matrices depends on the projection identity ρ² = ρ; its Wigner correspondence is the pure state condition. This criterion is applied to the Wigner functions obtained from standard semiclassical wave functions, determining as pure states those whose classical invariant tori satisfy the generalized Bohr-Sommerfeld conditions. Superpositions of eigenstates are then examined and it is found that the Wigner function corresponding to Gaussian random wave functions are smoothed out in the manner of mixed-state Wigner functions. Attention is also given to the pure-state condition in the case where an angular coordinate is used.     

Entanglement production in quantized chaotic systems

Quantum chaos is a subject whose major goal is to identify and to investigate different quantum signatures of classical chaos. Here we study entanglement production in coupled chaotic systems as a possible quantum indicator of classical chaos. We use coupled kicked tops as a model for our extensive numerical studies. We find that, in general, chaos in the system produces more entanglement. However, coupling strength between two subsystems is also a very important parameter for entanglement production. Here we show how chaos can lead to large entanglement which is universal and describable by random matrix theory (RMT). We also explain entanglement production in coupled strongly chaotic systems by deriving a formula based on RMT. This formula is valid for arbitrary coupling strengths, as well as for sufficiently long time. Here we investigate also the effect of chaos on the entanglement production for the mixed initial state. We find that many properties of the mixed-state entanglement production are qualitatively similar to the pure state entanglement production. We however still lack an analytical understanding of the mixed-state entanglement production in chaotic systems.     

Secondary quantization of the Dirac free field in hypercomplex system of numbers

The method of secondary quantization of the Dirac free field is developed in the formalism of a hypercomplex system of numbers, generalizing the Clifford algebra to state space analogously to its generalization to distorted space. Then, after conversion to a new basis, it is shown that, taking account of the projection operators, the bases of Fermi algebra — creation and annihilation operators — may be taken as the new basis. Writing the solution of the Dirac free equation in the new basis, the physically observed field values are written in terms of secondary-quantization operators. The adjustable Dirac-field function is calculated in the same formalism.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 93–97, October, 1989.