Harmonic Retrieval in Colored ARMA Noise

We propose a new approach to harmonic retrieval in colored ARMA noise. A suitable filter is first used to remove all the sharp power spectrum peaks of the noisy observed process, then some kinds of cross correlation is employed to identify the noise characteristics. After filtering the noisy observed process with the identified noise characteristics again, SVD-TLS method can be applied to retrieve the harmonics. The proposed approach can be used to retrieve real-valued harmonic signals in colored ARMA noise with no restrictions on the phase coupling of harmonics and the distribution of the noise. Simulation examples show its effectiveness.

NEW APPROACH TO HARMONIC RETRIEVAL IN NOISE

This paper addresses the harmonic retrieval problem in non-Gaussian ARMA noise. A hybrid ESPRIT approach using second-and third-order statistics is proposed. First, third-order statistics are used to identify the AR part of the non-Gaussian noise process, then the noisy measurements are filtered by AR polynomial, finally, the harmonic signal parameters are estimated. Simulation examples show the effectiveness and high resolution of the new approach.

Harmonic Retrieval Embedded in Hybrid Colored Noise: a Novel Pisarenko Method Based on Cross high order Cumulant

Spectral estimation method is an effective method in the case of parameter estimation of sinusoid signal in noises.It always applies cross spectral estimation theory and high order self spectral estimation methods up to now.Yule Walker equation based on cross fourth order cumulant is developed and Pisarenko method is provided in this paper.Simulation results show that the method is effective to retrieve sinusoid signal frequencies from hybrid colored noises and has good performance.

Atomic coherent states as energy eigenstates of a Hamiltonian describing a two-dimensional anisotropic harmonic potential in a uniform magnetic field

In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states ｜τ） in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state 〈η｜ representation of the state ｜τ）.

Feasibility of a novel beamforming algorithm via retrieving spatial harmonics

This paper introduces an algorithm for beamforming systems by the aid of multidimensional harmonic retrieval(MHR).This algorithm resolves problems,removes limitations of sampling and provides a more robust beamformer.A new sample space is created that can be used for estimating weights of a new beamforming called spatial-harmonics retrieval beamformer(SHRB).Simulation results show that SHRB has a better performance,accuracy,and applicability and more powerful eigenvalues than conventional beamformers.A simple mathematical proof is provided.By changing the number of harmonics,as a degree of freedom that is missing in conventional beamformers,SHRB can achieve more optimal outputs without increasing the number of spatial or temporal samples.We will demonstrate that SHRB offers an improvement of 4 dB in signal to noise ratio(SNR) in bit error rate(BER) of 10~(-4) over conventional beamformers.In the case of direction of arrival(DOA) estimation,SHRB can estimate the DOA of the desired signal with an SNR of-25 dB,when conventional methods cannot have acceptable response.

An improved wind retrieval algorithm for the HY-2A scatterometer

Since January 2012,the National Satellite Ocean Application Service has released operational wind products from the HY-2A scatterometer(HY2-SCAT),using the maximum-likelihood estimation(MLE) method with a median filter. However,the quality of the winds retrieved from HY2-SCAT depends on the sub-satellite cross-track location,and poor azimuth separation in the nadir region causes particularly low-quality wind products in this region. However,an improved scheme,i.e.,a multiple solution scheme(MSS) with a two-dimensional variational analysis method(2DVAR),has been proposed by the Royal Netherlands Meteorological Institute to overcome such problems. The present study used the MSS in combination with a 2DVAR technique to retrieve wind data from HY2-SCAT observations. The parameter of the empirical probability function,used to indicate the probability of each ambiguous solution being the "true" wind,was estimated based on HY2-SCAT data,and the 2DVAR method used to remove ambiguity in the wind direction. A comparison between MSS and ECMWF winds showed larger deviations at both low wind speeds(below 4 m/s) and high wind speeds(above 17 m/s),whereas the wind direction exhibited lower bias and good stability,even at high wind speeds greater than 24 m/s. The two HY2-SCAT wind data sets,retrieved by the standard MLE and the MSS procedures were compared with buoy observations. The RMS error of wind speed and direction were 1.3 m/s and 17.4°,and 1.3 m/s and 24.0° for the MSS and MLE wind data,respectively,indicating that MSS wind data had better agreement with the buoy data. Furthermore,the distributions of wind fields for a case study of typhoon Soulik were compared,which showed that MSS winds were spatially more consistent and meteorologically better balanced than MLE winds.

ANGULAR SPECTRUM PROPERTY OF SPONTANEOUS EMISSION IN A TWO-DIMENSIONAL UNDULATOR FREE-ELECTRON LASER

The angular spectrum of spontaneous emission in a two-dimensional undulator free-electron laser is analyzed theoretically. Numerical calculation shows that the 3-th harmonic spontaneous emission power density can be greatly enhanced by using a two-dimensional undulator, for which l=s, so the harmonic number can be selected by selecting l. Therefore, the higher harmonic operation of a free-electron laser can be realized selectively.

Modulation of the second-harmonic generation in MoS_(2) by graphene covering

Nonlinear optical frequency mixing,which describes new frequencies generation by exciting nonlinear materials with intense light field,has drawn vast interests in the field of photonic devices,material characterization,and optical imaging.Investigating and manipulating the nonlinear optical response of target materials lead us to reveal hidden physics and develop applications in optical devices.Here,we report the realization of facile manipulation of nonlinear optical responses in the example system of MoS_(2) monolayer by van der Waals interfacial engineering.We found that,the interfacing of monolayer graphene will weaken the exciton oscillator strength in MoS_(2) monolayer and correspondingly suppress the second harmonic generation(SHG)intensity to 30%under band-gap resonance excitation.While with off-resonance excitation,the SHG intensity would enhance up to 130%,which is conjectured to be induced by the interlayer excitation between MoS_(2) and graphene.Our investigation provides an effective method for controlling nonlinear optical properties of two-dimensional materials and therefore facilitates their future applications in optoelectronic and photonic devices.

THEORETICAL ANALYSES AND NUMERICAL EXPERIMENTS FOR TWO-DIMENSIONAL WIND RETRIEVALS FROM SINGLE-DOPPLER DATA

Based on variational adjoint methods,theoretical analyses and numerical experiments are performed for retrievals of two-dimensional winds and related parameters from single-Doppler radar data in polar coordinates.In the method,the reflectivity conservation equation is used as the governing equation and the mass continuity equation as a weak constraint.At the same time,the stable functional of regularization and background field are also introduced in the cost functional.Based on the ideal experiments with artificial data,real two-dimensional wind fields are retrieved with low-altitude data from the Nanjing Doppler Radar Station,and the results are encouraging and promising.

混合色噪声背景下谐波恢复:一种可消除谱估计伪峰的互谱SVD-LS方法

扩阶特征方程方法由于可以有效地提高谐波恢复的谱分辨率及噪声抑制能力 ,因而被大多数谐波恢复方法所普遍采用 .但由此而产生的谱估计伪峰却严重干扰着谐波谱峰的判别 .本文依据对正弦谐波信号的扩阶互相关函数矩阵的特征分析 ,提出消除这种谱估计伪峰的理论及方法 .仿真结果表明本文所提出的互谱SVD LS方法可完全消除谱估计伪峰 。

一种三维模型形状检索描述符

为了解决基于关键字的搜索方式不能准确查找三维模型的问题,对三角网格形式的三维模型提出一种基于内容的模型搜索算法.首先将模型中的三角网格再次划分,增加形状函数的维度,定义了一种新的三维模型形状函数,以提高形状函数的准确性;然后确定三维模型的极轴,将三维模型绕任意轴的旋转转换为绕极轴旋转,增强了球面调和方法提取的形状描述符旋转不变性;最后根据形状描述符之间的欧氏距离来度量三维模型的相似程度.实验结果表明,该算法适用于基于内容的三维模型搜索,并且在准确性和时效性方面都令人满意.

用于3D模型检索的扩展距离球面调和表达

使用光线投射方法对3D模型定义了一个对应的球函数———扩展距离球函数,然后引入了球面调和分析方法,构造了一种对于平移、缩放和旋转变换具有不变性的特征向量,并用于基于形状的3D模型检索中·与基于向径方法结合,提高了检索的效果,扩大了应用范围·

相位法估计信号源数

针对高频地波雷达用谐波恢复在频域进行目标检测时 ,无法有效确定信号源数的问题 ,提出了一种利用回波的相位确定信号源数的方法 .阐述了该方法的理论根据和信号的处理过程 。

1.653μm处甲烷分子谐波探测技术研究

谐波探测被广泛应用于激光光谱技术中,利用它可以提高探测灵敏度。利用1.653μm的分布反馈式(DFB)二极管激光器作为光源,建立了一套可调谐半导体激光吸收光谱(TDLAS)甲烷探测装置。该装置利用由2块圆形柱面镜构成的光学多通池增加吸收光程,提高探测灵敏度。吸收池基长为15cm,在112次反射情况下,有效吸收光程达到16.8m,实现甲烷0.60×10-6(2s采样时间)的探测极限,可应用于实际大气甲烷的痕量探测。

混合色噪声下:可消除谱估计伪峰的多正弦信号频率估计互谱奇异值分解方法

本文依据对正弦谐波信号的扩阶互相关函数矩阵的特征分析 ,提出消除扩阶方程产生的谱估计伪峰的理论及方法。仿真结果表明本文所提出的互谱奇异值 -整体最小二乘法 (SVD LS)可完全消除谱估计伪峰 。

谐波恢复的互高阶累计量Hankel矩阵法

本文将状态空间模型与互高阶累计量结合在一起 ,首次提出了基于状态空间模型谐波恢复的互高阶累计量的Hankel矩阵分解法 .该方法清晰地展现了谐波恢复问题的实质 ,充分利用状态空间模型所具有的灵活性、方便性 ,为解决谐波恢复问题提供了一条全新的思路 ,是一种短数据条件下的高精度算法 .仿真结果表明 ,该方法在混合色噪声和很低信噪比条件下谱估计的分辨率、稳定性及对混合色噪声的抑制等方面均明显优于自高阶谱估计方法 .

乘性和加性噪声中复谐波恢复的乘积型循环统计量方法

本文提出了乘积型循环统计量的概念,利用这一概念讨论了乘性和加性平稳噪声条件下的谐波恢复问题。首先从理论上证明了循环均值的样本估计误差服从零均值渐近正态分布,提出采用乘积型循环均值来抑制噪声,并给出了基于乘积型循环统计量的谐波估计的具体方法,仿真实验验证了该算法的有效性。

乘性和加性噪声中谐波恢复的循环统计量方法

本文从循环平衡的观点出发来研究乘性和加性噪声中的谐波恢复问题.首先，在一定条件下建立了一般复过程的有限长付里叶变换的大样本性质．然后，得到了任意阶循环矩的样本估计关于循环频率的一致收敛速度．对于乘性和加性噪声中的谐波信号，建立了一、二、三阶循环矩样本估计的统计性质．在此基础上，分别提出了基于不同阶循环矩的谐波分最个数和频率的估计方法，并得到了估计的强相容性质和强收敛速度，最后给出了模拟实验结果．

基于状态空间模型谐波恢复的Tls-Hankel法

将状态空间模型与互高阶累计量相结合,充分利用状态空间模型具有的灵活性、方便性,提出基于状态空间模型谐波恢复的互高阶累计量的Tls-Hankel矩阵分解法,为解决谐波恢复问题提供了一条新的思路。仿真结果表明,在混合色噪声和很低信噪比条件下,该方法在谱估计的分辨率、稳定性及对混合色噪声的抑制等方面均明显优于自高阶谱估计方法。

累量域谐波恢复方法(英文)

累量域谐波恢复算法 ,通常假定谐波初相在 [-π,π]区间上均匀分布 ,而且大量的仿真实验沿用相关域的分析方法 ,假定谐波数目为二 ,其振幅几乎相等 .本文在对实际信号模型分析的基础上 ,从理论上得出了初相确定、谐波数目较多和信号动态范围比较大时累量自身及累量域参数估计方法的一些特点 ,指出了现有谐波恢复和基于三阶累量的噪声预滤波算法在理论和实际信号处理中的缺陷 ,并对大动态范围信号谐波恢复算法作了改进 ,使其理论更加完善。