Detection of point-like scatterers using one type of scattered elastic waves

In this paper, we are concerned with the detection of point-like obstacles using elastic waves. We show that one type of waves, either the P or the S scattered waves, is enough for localizing the points. We also show how the use of S incident waves gives better resolution than the P waves. These affirmations are demonstrated by several numerical examples using a MUSIC type algorithm.     

一种改进的微弱NQR信号检测算法

核四极矩共振（NQR）是一种固态射频谱分析技术,可用于检测高危险爆炸物. 然而NQR信号本身非常弱,并且易受线圈的热噪声和外部射频干扰的影响,低信噪比限制了NQR的实际应用. 该文提出一种改进的微弱NQR信号检测算法. 首先利用Hankel矩阵方式下奇异值分解的方法,有效地抑制射频干扰和噪声,并将NQR信号分离出来. 然后提出了一种基于MUSIC谱估计的非线性最小二乘检测器,它既保证了高的频率分辨率,又大大降低了运算量. 仿真数据和实测数据结果表明该算法的有效性.     

The application of MUSIC algorithm in spectrum reconstruction and interferogram processing

Three different methods of spectrum reproduction and interferogram processing are discussed and contrasted in this paper. Especially, the nonparametric model of MUSIC (multiple signal classification) algorithm is firstly brought into the practical spectrum reconstruction processing. The experimental results prove that this method has immensely improved the resolution of reproduced spectrum, and provided a better math model for super advanced resolving power in spectrum reconstruction. The usefulness and simplicity of the technique will lead the interference imaging spectrometers to almost every field into which the spectroscopy has ventured and into some where it has not gone before.     

OSMAR2000基于MUSIC的超分辨率海洋表面流算法

为了解决OSMAR2000以小天线阵实现中远距离的海洋表面流探测,同时实现高的角分辨率的问题,提出了OSMAR2000基于MUSIC的超分辨率海洋表面流算法。该算法首先通过预处理从海洋回波中分离包含海流信息的一阶回波,然后针对其中可分辨的每一个Doppler频移（对应海洋表面径向流速）上的信号,采用MUSIC算法求其多个存在方位。阐述了MUSIC算法应用于高频地波雷达海洋表面流遥感的理论基础、处理过程和实测信号的处理结果。     

激光微加工制作的微光纤珐-珀加速度传感器

将157nm激光微加工制作的微光纤珐-珀腔贴于悬臂梁结构构成加速度传感器。通过设计特定的悬臂梁结构和FFT方法,该加速度传感器的分辨率约为1．13mg／HZ1/2。通过采用MUSIC算法处理信号,信噪比可提高45dB,系统分辨率约为3．56×10^-2μg／Hz1/2。该微光纤珐一珀传感器具有可批量制作、成本低、抗高温、量程灵活等优点,有望应用于石油勘探、地震测量等领域中。     

采用便携式天线的近海海洋表面流探测

针对高频地波雷达天线阵通常十分庞大的问题，根据海洋回波理论，利用单个到达角海洋回波进行雷达通道幅度相位的自校准，应用适合便携式天线系统的信源估计方法，采用MUSIC(MUltiple Slgnal C1assification)算法反演海流信息，研究了交叉环／单极子天线在高频地波雷达近海海洋表面流探测中的应用，将探测结果与采用相控阵接收的高频地波雷达OSMAR2000的探测结果进行对比，径向流速平均偏差为1．3cm／s,说明近海海洋表面流探测采用便携式的小天线可取得与传统相控阵相同的效果.     

Smart Antenna for Indoor Millimeter Wave Communication

The following paper introduces a smart antenna system with MUSIC algorithm for indoor millimeter wave communication. The smart antenna system separates main transmission paths towards receiver by antenna array. Maximal-ratio combination (MRC) of the separated transmission paths provides nearly optimal performance of receiver. Multipath distortion and noise can be greatly reduced by the system.     

Adsorption of Ions on Zirconium Oxide Surfaces from Aqueous Solutions at High Temperatures

Surface titrations were carried out on suspensions of monoclinic ZrO₂ from 25 to 290 °C slightly above saturation vapor pressure at ionic strengths of 0.03, 0.1 and 1.0 mol⋅kg⁻¹(NaCl). A typical increase in surface charge was observed with increasing temperature. There was no correlation between the radius of the cations, Li⁺, Na⁺, K⁺ and (CH₃)₄N⁺, and the magnitude of their association with the surface. The combined results were treated with a 1-pK_a MUSIC model, which yielded association constants for the cations (and chloride ion at low pH) at each temperature. The pH of zero-point-charge, pH_zpc, decreased with increasing temperature as found for other metal oxides, reaching an apparent minimum value of 4.1 by 250 °C. Batch experiments were performed to monitor the concentration of LiOH in solutions containing suspended ZrO₂ particles from 200 to 360 °C. At 350 and 360 °C, Li⁺ and OH⁻ ions were almost totally adsorbed when the pressure was lowered to near saturation vapor pressure. This reversible trend has implications not only to pressure-water reactor, PWR, operations, but is also of general scientific and other applied interest. Additional experiments probed the feasibility that boric acid/borate ions adsorb reversibly onto ZrO₂ surfaces at near-neutral pH conditions as indicated in earlier publications. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

基于Group Lasso的多重信号分类声源 定位优化算法*

多重信号分类算法因其抑制噪声能力强、计算速度快等优点,在声源定位领域得到广泛应用。但该算法在中低频段分辨率及聚焦性能较差。针对该问题,提出一种基于Group Lasso的多重信号分类优化算法。该算法将多重信号分类算法输出值作为初始值,并在Group Lasso算法组间计算时对目标信号进行稀疏、在组内计算时对该组信号进行平滑及阈值截断。仿真结果表明:该优化算法在中低频段可明显提高多重信号分类算法分辨率,同时改善因扫描位置与声源面位置不重合引起的聚焦性能下降问题。     

Near field imaging of small isotropic and extended anisotropic scatterers

In this paper, we consider two time-harmonic inverse scattering problems of reconstructing penetrable inhomogeneous obstacles from near field measurements. First, we appeal to the Born approximation for reconstructing small isotropic scatterers via the MUSIC algorithm. Some numerical reconstructions using the MUSIC algorithm are provided for reconstructing the scatterer and piecewise constant refractive index using a Bayesian method. We then consider the reconstruction of an anisotropic extended scatterer by a modified linear sampling method and the factorization method applied to the near field operator. This provides a rigorous characterization of the support of the anisotropic obstacle in terms of a range test derived from the measured data. Under appropriate assumptions on the material parameters, the derived factorization can be used to determine the support of the medium without a priori knowledge of the material properties.