载体姿态对海底混响时空相关特性的影响

讨论了载体姿态对海底混响时空相关特性的影响.考虑载体姿态对相关声呐信号发射的影响,推导理论时空相关函数,得到了时空相关特性与载体姿态之间的关系:载体在某一方向上的摇动越大,在该方向上的相关系数下降越快.将理论推导与仿真结果进行比较,发现在海底不存在大尺度起伏、表面粗糙度各向同性的情况下,二者的时空相关函数吻合得较好。实际海底通常具有大尺度起伏和各向异性的粗糙度,时空相关函数的形状不能由载体姿态和海底大尺度起伏完全确定,但海试数据证明了二者的联合影响。此外,讨论了载体姿态对载体垂向速度测量的影响。      

基于光学测量手段实时动态测量船体水平姿态

针对测量船传统实时水平测量方法精度较低（≥10.0″）的问题,引入了基于光学测量手段的动态实时船体水平姿态测量方法。采用＂光学编码精密测角＋惯性同步复示平台＋水平误差检测工具＂的设计模式,保证了跟踪的稳定性,提高了测量精度。实验结果表明：提出的方法可以提供比传统惯导系统更稳定、精度更高（纵摇5.37″,横摇3.60″）的船体水平姿态数据;可以作为一种普遍适用的运动载体精密水平测量监测手段,为运动载体实时提供高精度的水平基准信息,或用于运动载体惯导水平精度鉴定等。     

浅海波导中水平接收阵被动时反混响抑制方法研究

使用基于射线简正波异地混响理论建立的水平接收阵接收海底混响模型,提出了水平阵被动时反混响抑制方法。以水平接收阵接收回波信号的某一时刻作为开始,分别对其前一时刻和后一时刻的回波信号做时反算子分解获得两个混响子空间,将这两个混响子空间的平均作为该时刻的混响子空间的一个估计,然后利用投影处理来抑制该时刻接收信号中的混响成分。该方法可以在一定程度上克服由于海底粗糙引起的局部时间(距离)段内接收回波信号的不平稳性,使得估计得到的混响子空间更加接近真实混响子空间。因此,利用其进行被动时反混响抑制可以增强回波信混比,提高对目标的检测和方位估计能力。针对典型浅海波导环境开展的仿真验证了本文方法的有效性。      

浅海远程混响理论

本文从一定的混响模型出发,利用简正波理论讨论了浅海负梯度情况下由海底散射引起的远程混响问题。通过对简正波声场的分析,得到了由混响的空间积分表式转换为谱表式的条件,然后根据所得到的混响强度和自相关函数的谱表式,分析了有限带宽的调幅脉冲声的远程混响,所得结果便于对浅海远程混响作出预计。     

信源空间散布条件下的声呐目标滤波方法

基于密集多波束接收空间观测数据向量,定义了一个与信源空间分布参数相关的特征量-空间散布指数,并利用蒙特卡洛积分对不同信源散布角宽度、不同信噪比和不同噪声空间分布特性条件下的空间散布指数进行了建模与计算。在此基础上,形成了在分布式混响/噪声背景下检测目标回波信号的空间散布指数滤波方法。利用轻型AUV（Autonomous UnderwaterVehicle）水下航行器声呐获得的实验数据进行了验证,表明该方法可显著抑制了混响及流噪声干扰。该方法无需假设信源间彼此独立,对混响干扰具有良好的适应性;由于混响及流噪声成分被大部分滤除,显著提高了信号处理增益,在后续检测过程中避免了宽波束接收、旁瓣泄漏、主动声呐平台运动等因素引起的背景噪声的显著增加。      

Makarov势的Dirac方程的束缚态解

给出了Makarov型标量势与矢量势相等条件下的Dirac方程的束缚态解. Dirac方程的角向方程用因子分解方法求解，在得出角向波函数的过程中，自然地得到了属于同一本征值的不同角向波函数间的递推操作. 径向束缚态波函数用合流超几何函数表示，束缚态的能量方程可由径向波函数满足的边界条件得到. 关键词： Makarov势 Dirac方程 束缚态 因子分解方法     

涡旋光束与相位全息光栅不对准时的衍射特性研究

研究了涡旋光束与相位全息光栅不对准时衍射光束的解析特性.利用理论推导的方法得出涡旋光束经相位全息光栅接收后一阶衍射光束的解析表达式.然后通过仿真分析分别得出在发生正常对准、横向偏移、角向倾斜及横向偏移和角向倾斜两者同时出现时衍射光束的质心偏移特性和中心强度变化特性.研究表明: 拉盖尔-高斯光束经相位全息光栅衍射后得到的光场表达式为合流超几何函数形式.光束与相位全息光栅间的不对准会引起衍射光束质心的偏移,而且光束质心的偏移量随入射光束偏移距离和偏离角的增加而增加,与入射光束的偏移方向和方位角无关.角向倾斜时 关键词： 拉盖尔-高斯光束 相位全息光栅 横向偏移 角向倾斜     

船舶运动状态下风速风向测量补偿与数字仿真

为了研究船舶运动状态下的风速风向精确测量,设计了一种船舶风速风向动态测量及误差补偿的数字仿真系统。通过对船舶航行状态下的风速风向测量原理进行分析,建立了船舶平面运动的相对风速风向和真风风速风向的解算模型,并根据船舶空间运动的风速风向测量及其误差补偿算法,对船舶横摇、纵摇状态下的风速风向的动态测量和误差补偿进行了数字仿真。数字仿真结果表明,该方法能够消除船舶航行时的运动姿态对风速风向测量带来的影响,为船舶的操纵控制和航行安全提供了精确和可靠的风速风向数据信息。     

相关测速声呐底混响时空相关函数与载体俯仰角的关系

由于载体在运动过程中存在姿态的变化,不考虑载体姿态的理论相关函数会影响相关声呐的测速精确度。考虑载体俯仰角对发射信号海底照射区域的影响,引入不同权重的多阶贝塞尔函数,得到改进后的理论相关函数。同时,根据相关测速声呐发射参数,给出了基于FOM模型的海底回波仿真。仿真结果表明,改进的理论相关函数将相关声呐的测速误差降至1%以下。载体的俯仰角对时空相关函数产生影响。考虑载体俯仰角的理论相关函数更贴近实际情况,与仿真结果的相关系数吻合的较好,能够更加准确的估计载体速度。      

用于混响中信号检测的空时预白化处理器

提出了一种新型的空时预白化处理器用于抑制混响,它是基于二维自回归模型的。这种处理器将接收到的数据从空间和时间上联合进行处理,进而分离目标回波和混响。这种方法较传统的从空间和时间上分别进行处理的方法能够更有效的抑制混响。通过与传统的一维自回归预白化处理器相比较,使用空时预白化处理器后的检测效果提高了约9~11 dB。      

Microscopic basis for Fick's law for self-diffusion

We investigate self-diffusion in a classical fluid composed of two species which are distinguished through the color of their particles, either black or white, but are identical as regards their mechanical properties. Disregarding color the fluid is in thermal equilibrium. We show that if a single test particle in the one-component fluid moves asymptotically as Brownian motion, then the color density and current in certain classes of nonequilibrium states are related, on the appropriate macroscopic scale, through Fick's law, and the former is governed by the diffusion equation. If in addition several test particles move asymptotically as independent Brownian motions, then the colored fluid is, on a macroscopic scale, in local equilibrium with parameters governed by the solution of the diffusion equation.Part of this work was done while both authors were at IHES, Bures-sur-Yvette, France.Supported in part by NSF Grant No. PHY 78-15920-02.Supported by a Heisenberg fellowship of the Deutsche Forschungsgemeinschaft.     

Convolution identities for quasiprobabilities for Bose functions

We present identities relating the equations of motion of various quasiprobabilities for quantum oscillators. These identities turn out useful for checking the consistency of approximations made in constructing the equations of motion with the basic Bose commutator. Moreover, our identities allow to identify the quasiprobability distributions which have the easiest-to-solve equations of motion.     

Requirements for Optical Systems for Virtual Displays

Currently, there are many types of virtual displays and new types arise every year. However, their vast majority appear technically inapplicable because they are inconsistent with a number of key factors related to the eye physiology. In this paper, we present the general requirements for optical systems of virtual displays, taking into account human eye physiology.     

Figure of merit for spectrometers for EDXRF

How should one select the best detector for a particular measurement in energy dispersive X‐ray fluorescence (EDXRF)? How should one select the optimum system configuration, i.e. the best shaping time and beam current? Manufacturers provide a variety of specifications, such as energy resolution and maximum count rate, but these are indirectly related to the end use of an EDXRF instrument, the measurement and detection limit of the measured elemental concentrations. We suggest in this paper using the time required to achieve a given statistical uncertainty as a figure of merit. We derive scaling rules for this figure of merit based on conventional specifications, including energy resolution, peaking time, maximum count rate, detector area, and intrinsic efficiency. These scaling rules also include the peak to background ratio of a photopeak and the number of overlapping peaks. We then show how this figure of merit can be used to select the optimum detector and spectrometer configuration for specific applications and compare the results to data obtained with typical systems. Copyright © 2012 John Wiley & Sons, Ltd.     

内窥镜校正中棋盘格标志点自动提取方法

为了解决具有大畸变内窥镜标定的标志点提取困难和人工参与较多等问题,提出了一种简单快速准确的棋盘格标志点提取方法。该方法是采用粗提取和优化来完成棋盘格标志点的提取的:首先利用高斯滤波去除图像噪声,并计算两次图像的梯度特征,利用梯度极值约束得到粗提取的角点;然后利用棋盘格标志点的对称特点消除噪声点的影响,并得到优化的角点位置。实验结果表明,该方法简单易行,计算量小,不需要人工干预即可获得全部标志点,反投影误差小于0.2pixel。     

Memory for pitch versus memory for loudness

The decays of pitch traces and loudness traces in short-term auditory memory were compared in forced-choice discrimination experiments. The two stimuli presented on each trial were separated by a variable delay (D); they consisted of pure tones, series of resolved harmonics, or series of unresolved harmonics mixed with lowpass noise. A roving procedure was employed in order to minimize the influence of context coding. During an initial phase of each experiment, frequency and intensity discrimination thresholds [P(C) = 0.80] were measured with an adaptive staircase method while D was fixed at 0.5 s. The corresponding physical differences (in cents or dB) were then constantly presented at four values of D: 0.5, 2, 5, and 10 s. In the case of intensity discrimination, performance (d') markedly decreased when D increased from 0.5 to 2 s, but was not further reduced when D was longer. In the case of frequency discrimination, the decline of performance as a function of D was significantly less abrupt. This divergence suggests that pitch and loudness are processed in separate modules of auditory memory.     

溶剂化的热力学集团展开理论

把二元溶液的过剩内能（ｅｘｃｅｓｓ ｅｎｅｒｇｙ）分成溶剂－溶剂、溶剂－溶质及溶质－溶质相互作用部分。利用集团展开方法给出了二元溶液在正则系综的配分函数的表达式，利用该表达式得到了溶质的偏摩尔内能（ｐａｒｔｉａｌ ｍｏｌａｒ ｅｎｅｒｇｙ）和偏摩尔熵（ｐａｒｔｉａｌ ｍｏｌａｒ ｅｎｔｒｏｐｙ）的表达式。在无限稀溶液情形，过剩偏摩尔内能的溶剂－溶剂部分又称重组织内能（ｒｅｏｒｇａｎｉｚａｔｉｏｎ ｅｎｅｒｇｙ），它反映了溶质存在时对其周围溶剂分子之间的相互作用能的影响。研究表明，在溶质的粒子数密度相对较大时，溶质分子之间的相互作用将影响过过剩偏摩尔内能的溶剂－溶剂部分，对于稀溶液，过氧偏摩尔内能的溶剂－溶剂部分与溶质的摩尔分数成线性关系。对低蜜度二元溶液，溶质的过剩偏摩尔内能和过剩偏摩尔熵也与溶质的摩尔分数成线     

Expressions for third-order aberration theory for holographic images

Expressions for third-order aberration in the reconstructed wave front of point objects are established by Meier. But Smith, Neil Mohon, Sweatt independently reported that their results differ from that of Meier. We found that coefficients for spherical aberration, astigmatism, tally with Meier’s while coefficients for distortion and coma differ.     

Map for Simultaneous Measurements for a Quantum Logic

In this paper we will study a function of simultaneous measurements for quantum events (s-map) which will be compared with the conditional states on an orthomodular lattice as a basic structure for quantum logic. We will show the connection between s-map and a conditional state. On the basis of the Rényi approach to the conditioning, conditional states, and the independence of events with respect to a state are discussed. Observe that their relation of independence of events is not more symmetric contrary to the standard probabilistic case. Some illustrative examples are included.