改进的等效半空间法及瑞雷波频散曲线反演

层状模型的理论频散曲线表明,层状模型表面瑞雷波同一频率对应的相速度具有多值特点,这就是所谓的瑞雷波多阶性. 面波的多阶性导致了实测频散曲线的复杂性,当地层中存在软弱夹层时这一问题尤为突出,从而给实测频散曲线的解释带来了困难. 本文从工程实用的角度出发,根据等效半空间理论,提出了一种计算理论频散曲线的新算法——改进的等效半空间法,避开了面波多阶性这一复杂问题. 由此方法计算得到的面波相速度并不同于某个具体阶数的面波,而是对多阶面波的综合反映. 按照改进的等效半空间法编制了拟合反演程序,并在工程中进行了运用,取得较好的效果.     

一种新的实时电磁逆散射方法

为解决介质圆柱体逆散射问题,提出一种新的在线逆散射方法,通过支持向量机将逆散射问题转化成一个回归估计问题. 该方法可应用于各种逆散射方面, 尤其是目标的几何与电磁参数重构和埋地目标探测. 文中首次将支持向量机方法应用到该领域,设置多个散射场的观测点,通过提取散射场的不同信息作为样本信息训练支持向量机, 建立了介质圆柱体的逆散射模型, 利用该模型重构了介质圆柱体的电磁参数,同时探测了埋地位置. 数值结果显示了该方法的有效性和准确性,为目标的实时逆散射研究提供了一种有效方法.     

SH波入射时多个半圆形沉积谷地附近浅埋圆形孔洞的动力分析

本文采用辅助函数的思想,利用复变函数和多级坐标的方法给出了SH波入射条件下多个半圆形沉积谷地附近浅埋圆形孔洞动力分析问题的解答。将整个求解区域分割成两部分来处理,区域I为多个半圆形沉积谷地,区域II为浅埋圆形孔洞附近带半圆形凹陷的半无限弹性空间。在区域I和II中分别构造位移解,并在二个区域的“公共边界”上实施位移应力的连续条件,建立求解该问题的无穷代数方程组。最后,本文给出了算例和数值结果,并对其进行了讨论。     

一种新的用于极化SAR图像船只检测的散射相似性测度

本文提出了一种新的用于极化合成孔径雷达（SAR）海上船只目标检测的测度。首先利用散射相似性参数研究船只与海杂波散射机制的差异。基于这些差异,提出了一种新的船只检测测度,该测度能够有效区分船只目标和海杂波。然后提出了利用核密度估计（KDE）方法对该测度进行建模的方法。基于统计模型,实现了自适应恒虚警率（CFAR）的检测方案。本文利用多景C波段RADARSAT-2极化SAR（Pol-SAR）数据上进行实验,系统分析了所提出测度的海杂波拟合性能与船只检测性能,并与两个经典的极化测度进行了比较,实验和比较结果证明了所提的测度的可行性。     

Analysis on the effect of salinity in underwater wireless optical communication

Abstract

This article deals with the effect of salinity variation on underwater wireless optical communication (UWOC). Effect of different concentration of salt on underwater optical communication has been carried out experimentally in terms of received power at different link lengths. Based on the analysis of experimental data, a mathematical model has been proposed to describe the saline water channel. A simulation study is performed for different data rates and link lengths. It is seen that with increased salinity the attenuation is higher and the UWOC system performance degrades with higher data rate and increased link length.     

Monitoring regional sea ice of the Bohai Sea by SSM/I scattering index

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溢油乳化过程C波段微波散射特性实验研究

本文基于水槽溢油观测实验,研究溢油乳化过程中表面散射特性的变化。利用全极化C波段微波散射计和矢量网络分析仪等测量设备对易发生乳化反应沥青含量小于3%的原油（A型油）、油田中开采出的新鲜原油（B型油）和经过脱水去杂质处理的工业原油（C型油）进行观测。文中详细分析了在C波段微波下乳化油膜与平静水面的后向散射差异,以及油膜乳化过程对后向散射的影响,结果显示在低风速、无浪的条件下（最大波高低于3mm）,原油的乳化反应可通过表面粗糙度和自身介电常数的变化来调制雷达后向散射,并且这两种方式中表面粗糙度的影响占主导地位。对比B型和C型原油在乳化状态和未乳化状态下的表面后向散射,结果显示在各状态下B型油膜表面后向散射均大于C型油,且在VV、HH、HV/VH极化方式下两者后向散射平均差异分别为2.19 dB、2.63 dB、2.21 dB,在20%油膜含水率的乳化状态下差异较未乳化状态时小,平均差异分别为0.98 dB、1.49 dB、1.5 dB,结果表明不同类型油种间由于成分和油膜属性的不同会在一定程度上导致油膜表面粗糙度存在差异,影响油膜表面后向散射。     

Improvement in the calculation of anti-Stokes energy transfer and experimental justification based on Er0.01YbxY1 - 0.01 - xVO4 crystal

The improvement on the calculation of anti-Stokes energy transfer rate is studied in the present work. The additional proportion coefficient between Stokes and anti-Stokes light intensities of quantum Raman scattering theory as compared with the classical Raman theory is introduced to successfully describe the anti-Stokes energy transfer. The theoretical formula for the improvement on the calculation of anti-Stokes energy transfer rate is derived for the first time in this study. The correctness of introducing coefficient exp{ΔE / kT} from well-known Raman scatter theory is demonstrated also. Moreover, the experimental lifetime measurement in Er_0.01Yb_xY_{1 - 0.01 - x}VO₄ crystal is performed to justify the validity of our important improvement in the original phonon-assisted energy transfer theory for the first time.     

An interconnect width and spacing optimization model considering scattering effect

As the feature size of the CMOS integrated circuit continues to shrink, the more and more serious scattering effect has a serious impact on interconnection performance, such as delay and bandwidth. Based on the impact of the scattering effect on latency and bandwidth, this paper first presents the quality-factor model which optimises latency and bandwidth effectively with the consideration of the scattering effect. Then we obtain the analytical model of line width and spacing with application of curve-fitting method. The proposed model has been verified and compared based on the nano-scale CMOS technology. This optimisation model algorithm is simple and can be applied to the interconnection system optimal design of nano-scale integrated circuits.     

Brillouin scattering study on elastic and piezoelectric properties of laser irradiated ZnO single crystals

Brillouin light scattering technique can be successfully used to determine the whole set of elastic and piezoelectric constants of a ZnO single crystal irradiated by different laser energy densities, into a micron range (radiation layer thickness). It is found that the scattering intensity, the linewidth and the Brillouin scattering shift of acoustic phonons are all strongly dependent on laser energy density. Based on the sound propagation equations and these results, the directional dependences of the compressional and shear moduli of the irradiated ZnO sample in the (001) plane are investigated. It is found that under an appropriate laser condition, 248 nm KrF excimer laser irradiation can significantly improve the surface quality and increase the elastic properties of ZnO single crystal. This procedure has potential applications in the fabrication of ZnO-based surface acoustic wave and optic-electronic devices.