基于拉格朗日拟序结构的吕宋海峡表层水交换研究

黑潮通过吕宋海峡入侵南海呈现明显的瞬态特征。以往的研究通常将黑潮在吕宋海峡附近的流态分为几种不同类型。本文基于表层地转流计算得到的有限时间李雅普诺夫指数场（FTLE）,展示了拉格朗日视角下的吕宋海峡上层水交换特征。从FTLE场提取的拉格朗日拟序结构（LCSs）很好地识别了吕宋海峡附近的典型流态和旋涡活动。此外,这些LCSs还揭示了吕宋海峡周围复杂的输运路径和流体域,这些特征得到了卫星跟踪浮标轨迹的验证,且从流速场中是无法直接识别的。FTLE场显示,吕宋海峡附近表层水体的输运形态主要可分为四类。其中,黑潮直接向北流动的“跨越”形态和顺时针旋转的“流套”形态的发生频次明显高于直接进入南海的黑潮分支“渗入”形态和南海水流出至太平洋的“外流”形态。本文还进一步分析了黑潮在吕宋海峡处的涡旋脱落事件,突出强调了LCSs在评估涡旋输运方面的重要性。反气旋涡旋的脱落个例表明,这些涡旋主要源自黑潮“流套”,涡旋脱落之前可有效地俘获黑潮水。LCS所指示的输运通道信息有助于预测最终被反气旋涡所挟卷水体在上游的位置。而在气旋涡的形成过程中,LCS的分布特征表明,大部分气旋涡并未与黑潮水的输运路径相连通。因此,气旋涡对从太平洋到南海的上层水交换的贡献较小。     

有限尺度李雅普诺夫指数与海表温度梯度相关性的初步分析

为了探究海表温度和海面高度之间的瞬时相关性,介绍了一种卫星测高数据的拉格朗日分析指数--有限尺度李雅普诺夫指数(Finite Size Lyapunov Exponent,FSLE),以黑潮延伸体区域的涡旋和南大西洋的亚南极锋为例,通过对观测、模式结果和融合产品结果的分析,探讨了该指数与海表温度梯度(Sea Surface Temperature Gradient,SSTG)之间的相关性。比较FSLE图像和SSTG图像发现,FSLE与SSTG均呈丝状结构,对海洋表层水体结构描述具有一致性,尤其在温度梯度大和地转流强的区域更为一致。二者的一致性要远好于其他常用方式,比如全流速、OW参数涡旋识别方法和Winding-Angle涡旋识别方法。不同区域FSLE与SSTG之间的相关性表现不同,黑潮延伸体区域相关系数存在显著的季节变化,而南大西洋亚南极锋区域季节内变化突出。     

边带分离型超导SIS接收机本振耦合噪声研究

超导SIS (Superconductor-Insulator-Superconductor)接收机因极低的接收机噪声温度成为毫米波和亚毫米波段射电天文观测的首选.本振系统耦合噪声也是接收机噪声的一部分,在多年的天文观测中,发现本振耦合噪声无法完全忽略,对天文观测的灵敏度有一定影响.采用两个不同种类的信号发生器作为本振系统初级信号源,测试了超导SIS接收机的噪声温度,发现信号发生器输出的基底噪声能够耦合到接收机内部,从而增加接收机噪声强度.分析研究了本振系统热噪声和信号发生器基底噪声对接收机噪声的影响.通过在信号发生器输入端加入窄带滤波器滤除其基底噪声,消除了信号发生器基底噪声引入的接收机噪声,降低了接收机的整体噪声,提高了望远镜的灵敏度.     

结合BM3D和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法

提出了一种基于三维块匹配（BM3D）和多级非线性加权平均中值滤波的遥感影像混合噪声去噪方法,使用coief3小波和sym2小波替换传统三维块匹配算法中的bior1.5和hear参数,将三维块匹配算法和多级非线性加权平均中值滤波相结合以提高算法对混合噪声的去噪能力。进行一个仿真对比试验和一个真实遥感影像去噪试验,试验表明,本文提出的方法在遥感影像混合噪声去噪方面效果要优于传统混合噪声去噪方法。     

顾及水陆差异的高分五号影像条带去除

高分五号搭载的可见光短波红外高光谱相机,能获取精细的地物光谱信息,具有十分广泛的应用前景。但高光谱卫星遥感数据往往无法避免条带噪声的干扰,进行条带去除是数据预处理中不可缺少的步骤。传统方法往往对地物的异质性与丰富的细节纹理考虑不足,导致条带不能被彻底地消除。为此,本文提出了一种顾及水陆差异的影像条带去除方法,采用水体与陆地区别统计的策略,解决条带噪声在异质区域的统计特征差异问题,并结合优化统计和一维变分滤波技术实现水陆区域参考统计特征的精确估计,最终基于矩匹配方法分别实现条带去除。实验结果表明:无论是真实实验还是模拟实验,本文提出的算法相较于传统条带去除算法,能更加稳健地去除数据条带噪声,还原地表真实辐射信息;在模拟实验中,本文算法处理结果的峰值信噪比(PSNR)达到46.58,且平均绝对误差(MAE)仅有11.56,均明显优于用于比较的3种传统算法,且算法执行效率也具备优势,能够更好地适用于高分五号大数据量的处理需求。     

云南地区GPS基准站噪声模型分析

以云南地区陆态网27个全球定位系统(GPS)基准站在2011-2017年不同时间跨度的观测数据为例,使用赤池信息量和贝叶斯信息量估计准则(AIC/BIC)对解算结果进行分析,从而确定其最优有色噪声模型.结果表明,不同时间跨度基准站各坐标分量上噪声特性主要体现为白+闪烁噪声(WN+FN)、幂律噪声(PL)模型组合.部分基准站在北向和垂向的最优噪声模型会随着观测时间的累积而改变,PL模型所占比例有所下降,WN+FN模型所占比例有所上升.当时间跨度大于5 a时,基准站噪声模型的稳定性显著提高.随着坐标时间序列积累时长的增加,未知噪声分量出现的可能性也相应提高.     

Stochastic Response Analysis of Piled Offshore Platform Excited by Stationary Filtered White Noise

In this paper,the analysis method of stochastic response of piled offshore platform excited bystationary filtered white noise is presented.With this method,the strong ground motion is considered asthree direction stationary filtered white noise process,the theoretic solutions of three special integrationequations are derived with the residue theorem,and the expression of response nodal displacements andmember forces of offshore platform excited by the stationary filtered white noise is put forward.Thestochastic response of a piled offshore platform excited by the stationary filtered white noise,which is lo-cated 114.3m in water depth,is computed.The results are compared with those obtained with the re-sponse spectrum analysis method and the stationary white noise model analysis method,and the corre-sponding conclusion is drawn.     

小波变换压制噪声在单道地震资料处理中的应用

海洋区域地质调查中,单道地震勘探以其高分辨率、方便快捷等优点成为揭示浅地层地质构造的重要手段之一.结合前人研究成果并出于保护信号的完整性,对低频部分的噪声采用带通滤波进行滤除,而对高频信号中的随机噪声采用小波阈值去噪方法进行压制处理.在小波阈值去噪过程中,通过比较选用最佳小波基函数sym5对地震剖面进行三层小波分解.结果表明:两种阈值去噪方法在带通滤波的基础上进一步提升了剖面的质量,使得反射层面变得连续可追踪.软阈值去噪滤掉了剖面上的较多信息,去噪效果较为彻底,硬阈值去噪则保留了较多的细节信息.     

多极化SAR溢油探测影响因素分析研究

Polarimetric synthetic aperture radar(SAR) oil spill detection parameters conformity coefficient(μ), Muller matrix parameters(|C|, B_0), the eigenvalues of simplified coherency matrix(λ_(nos)) and the influence of SAR observing parameters, ocean environment and noise level are investigated. Radarsat-2 data are used to make systematic analysis of polarimetric parameters for different incidences, wind speeds, noise levels and the ocean phenomena(oil slick and look likes). The influence of the SAR observing parameters, the ocean environment and the noise level on the typical polarimetric SAR parameter conformity coefficient has been analyzed. The results indicate that conformity coefficient cannot be simply used for oil spill detection, which represents the image signal to the noise level to some extent. When the signals are below the noise level for the oil slick and the look likes, the conformity coefficients are negative; while the signals above the noise level corresponds to positive conformity coefficients. For dark patches(low wind and biogenic slick) with the signal below the noise,polarization features such as conformity coefficient cannot separate them with oil slick. For the signal above the noise, the oil slick, the look likes(low wind and biogenic slick) and clean sea all have positive conformity coefficients, among which, the oil slick has the smallest conformity coefficient, the look likes the second, and the clean sea the largest value. For polarimetric SAR data oil spill detection, the noise plays a significant role. So the polarimetric SAR data oil spill detection should be carried out on the basis of noise consideration.     

Faithful quantum secure direct communication protocol against collective noise

An improved quantum secure direct communication (QSDC) protocol is proposed in this paper. Blocks of entangled photon pairs are transmitted in two steps in which secret messages are transmitted directly. The single logical qubits and unitary operations under decoherence free subspaces are presented and the generalized Bell states are constructed which are immune to the collective noise. Two steps of qubit transmission are used in this protocol to guarantee the security of communication. The security of the protocol against various attacks are discussed.