被动虚拟阵列的CRB界及最大似然估计方法研究

针对利用机载运动平台对窄带微波信号进行侦测的背景,研究了被动虚拟阵列（PASA）对窄带微波信号的参数估计性能。在考虑方向角、频率和幅度均为未知参数的条件下,推导了方向角估计的克拉美劳界（CRB）的表达式,同时给出了PASA合成孔径长度的选取方案。另外,本文给出了PASA对方位角估计的最大似然（ML）估计算法。研究表明,随着合成孔径长度和信噪比的增加,ML估计误差可以很快地收敛于CRB,但存在阈值效应。计算机仿真结果验证了本文研究结果的正确性。     

TDDFT方法研究两个基于Michael反应的氰离子传感器的不同传感机理

利用含时密度泛函方法计算了两个具有类似结构的传感器分子a和b的氰离子传感机理. 结果证实,传感器分子a在基态和S₁态下有着类似的几何构型. 在质子性溶剂水中,氰离子能与传感器分子a发生Michael加成反应,水溶液提供质子,促使最终的α,β-加成产物的生成. 而此加成产物在S₁态下会发生构型变化,导致荧光的猝灭. 传感器分子b的S₁态与基态构型相比发生了构型扭转,并且在非质子性溶剂乙腈中,也可以与氰离子发生Michael加成反应. 由于乙腈     

Photocatalytic performance of ZnO:Fe array films under sunlight irradiation

ZnO:Fe array thin films were prepared by the hydrothermal method using the sol-gel grown film as a seed layer. The samples were characterized by X-ray diffraction (XRD), ultraviolet/visible absorption spectra (UV-vis) and scanning electron microscopy (SEM). The photocatalytic activities of the prepared samples were investigated for the photodegradation of methylene blue (MB) under sunlight irradiation. The results show that the lattice constant a and the cell volume of ZnO:Fe film increase due to the substitution of Fe for Zn. The absorption edge of Fe-doped ZnO displays a red shift with a significant absorption between 600 and 700 nm. The ZnO:Fe array film is composed of disk particles with uniformity and compactness. Doping Fe ions enhances the photodegradation rate of ZnO array film for MB. 1.5% Fe doped ZnO sample exhibits the highest activity under irradiation time of 4 h. Its degradation rate increases about 1.6 times compared to the undoped ZnO.     

Time and direction of arrival detection and filtering for imaging in strongly scattering random media

We study detection and imaging of small reflectors in heavy clutter, using an array of transducers that emits and receives sound waves. Heavy clutter means that multiple scattering of the waves in the heterogeneous host medium is strong and overwhelms the arrivals from the small reflectors. Building on the adaptive time-frequency filter of [Borcea et al, SIIMS 2011;4(3)], we propose a robust method for detecting the direction of arrival of the direct echoes from the small reflectors, and suppressing the unwanted clutter backscatter. This improves the resolution of imaging. We illustrate the performance of the method with realistic numerical simulations in a non-destructive testing setup.     

COMPRESSED SPEECH SIGNAL SENSING BASED ON THE STRUCTURED BLOCK SPARSITY WITH PARTIAL KNOWLEDGE OF SUPPORT

Structural and statistical characteristics of signals can improve the performance of Compressed Sensing (CS).Two kinds of features of Discrete Cosine Transform (DCT) coefficients of voiced speech signa...     

Two Nickel(II) Coordination Polymers Based on Tri(p‐carboxyphenyl) phosphane Oxide with Highly Selectively and Sensitively Detection of Acetone

Two nickel(II) coordination polymers, namely, {[Ni_1/2(TPO)_1/3(bib)_1/2(H₂O)] · H₂O}_n ( 1 ), and [Ni(HTPO)(bpy)(H₂O)₂]_n ( 2 ), were assembled from tripodal ligand of tripodal tri(p‐carboxyphenyl) phosphane oxide (H₃TPO) and two N‐donors [bib = 1,4‐bis(imidazolyl)benzene, and bpy = 4,4′‐bipyridine]. Their structures were determined by single‐crystal X‐ray diffraction analysis and further characterized by elemental analysis, IR spectra, powder X‐ray diffraction (PXRD), and thermogravimetric analysis (TGA). Structural analysis reveals that complex 1 is an interestingly 3D (3,4)‐connected {10³}₂{10⁶}₃ net, whereas complex 2 is a 1D polymeric chain, which was further expanded into a 3D supramolecular structure through hydrogen bonds. Luminescent sensing measurements show two nickel CPs can selectively and sensitively detect for acetone from normal solvents (DMF, DMA, DMSO, MeOH, EtOH, CH₃CN, H₂O, and N‐butanol).     

用退火型神经网络估计多个非相干源的迭加正弦信号参量＊

基于模拟退火方法和线性规划神经网络,本文提出了一种新的参数估计方法——退火型神经网络计算方法,并将其应用于进行叠加正弦信号参量的估计,通过构造相应的模拟电路系统,该方法可获得估计问题的实时解。模拟实验结果显示了该神经网络方法进行平面波到达方向估计与跟踪的优良性能。     

基于SMI－CMA联合自适应算法的性能分析

恒模算法(CMA)被广泛地应用到盲自适应波束形成中，除了传输信号波形具有恒定的包络外．CMA不需要先验知识。基于SMI—CMA算法的恒模(CM)阵列级联的结构，由SMI算法决定CMA的初始权向量．系统可以分离多个同信道信源，在干扰信号较强时，仍有稳定的SINR输出，具有较好的收敛速度。仿真结果也证明了SMI—CMA算法具有较强的稳健型和较快的收敛速度。     

一种计入互耦的线阵方向图综合方法

本文在前人的基础上,继续对天线阵的综合技术进行了研究,充分利用了经典综合技术成熟、简便的优点以及数值算法快捷、方便等特点,提出了一种简便的天线阵综合方法。具体思想是:首先采用现有的综合算法在不考虑互耦的情况下对天线进行综合,然后再利用本文的算法补偿互耦所造成的影响,从而完成综合。     

Design of Scannable Non‐uniform Planar Array Structure for Maximum Side‐Lobe Reduction

In this letter, we propose a novel design scheme for an optimal non‐uniform planar array geometry in view of maximum side‐lobe reduction. This is implemented by a thinned array using a genetic algorithm. We show that the proposed method can maintain a low side‐lobe level without pattern distortion during beam steering.