Turbulence-induced changes in degree of polarization,degree of coherence and spectrum of partially coherent electromagnetic beams

Based on a recently formulated unified theory of coherence and polarization, a method is described to study turbulence-induced changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic beams on propagation. The electromagnetic Gaussian Schell-model beam is taken as a typical example of partially coherent electromagnetic beams, and the closed-form expressions for the degree of polarization, the degree of coherence and the spectrum of electromagnetic Gaussian Schell-model beams propagating through atmospheric turbulence are derived in the quadratic approximation of Rytov＇s phase structure function. Some interesting results are obtained, which are illustrated by numerical examples and are explained in physics.

Effects of Hydrogen-bonding Interaction and Polarity on Emission Spectrum of Naphthalene-Triethylamine in Mixed Solvent

The effects of the protic and aprotic polar solvents on the emission spectrum of the naphthalene-triethyl-amine system in THF were studied under conditions of steady-state illumination. The fluorescence spectrum of the naphthalene-triethylamine system consists of two emission bands, the fluorescence band of naphthalene(band A, 329 nm) and the emission band of the exciplex(band B, 468 nm). The intensities of both the emission bands decrease with increasing the solvent polarity. The intensity of band B also decreases due to the hydrogen-bonding interaction between triethylamine and protic solvent, while that of band A increases. It is thus suggested that the quenching of naphthalene fluorescence by triethylamine in THF occurs through the charge transfer and electron transfer reactions. The spectral changes upon the increase of solvent polarity can be explained by the dependences of the equilibrium constant between exciplex and ion-pair and the rate constant for the electron transfer reaction from triethylamine to the excited naphthalene on the relative permittivity of solvent. It is shown that the formation of intermolecular hydrogen-bonding between triethylamine and protic solvent suppresses the quenching reaction by the decrease in free amine. Acetonitrile has only a polar effect and trichloroacetic acid only a hydrogen-bonding(or protonation) effect, while alcohols have both the effects. The effects of alcohols could be separated into the effects of solvent polarity and intermolecular hydrogen-bonding interaction quantitatively.

Near-field characteristics of highly non-paraxial subwavelength optical fields with hybrid states of polarization

The vectorial structure of an optical field with hybrid states of polarization （SOP） in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.

Oil spill detection by a support vector machine based on polarization decomposition characteristics

Marine oil spills have caused major threats to marine environment over the past few years.The early detection of the oil spill is of great significance for the prevention and control of marine disasters.At present,remote sensing is one of the major approaches for monitoring the oil spill.Full polarization synthetic aperture radarc SAR data are employed to extract polarization decomposition parameters including entropy（H） and reflection entropy（A）.The characteristic spectrum of the entropy and reflection entropy combination has analyzed and the polarization characteristic spectrum of the oil spill has developed to support remote sensing of the oil spill.The findings show that the information extracted from（1-A）×（1-H） and（1-H）×A parameters is relatively evident effects.The results of extraction of the oil spill information based on H×A parameter are relatively not good.The combination of the two has something to do with H and A values.In general,when H〉0.7,A value is relatively small.Here,the extraction of the oil spill information using（1-A）×（1-H） and（1-H）×A parameters obtains evident effects.Whichever combined parameter is adopted,oil well data would cause certain false alarm to the extraction of the oil spill information.In particular the false alarm of the extracted oil spill information based on（1-A）×（1-H） is relatively high,while the false alarm based on（1-A）×H and（1-H）×A parameters is relatively small,but an image noise is relatively big.The oil spill detection employing polarization characteristic spectrum support vector machine can effectively identify the oil spill information with more accuracy than that of the detection method based on single polarization feature.

Spectral decomposition at a complex laser polarization configuration

We study the role of laser polarization in the diamagnetic spectrum for the transition from the ground state to the highly excited Rydberg states through a single photon absorption. For simplicity, one usually polarizes the irradiation laser to the selected main quantum axis, which is along the applied external electric or magnetic field. The transition selection rule is simply expressed as Am = O, which corresponds to the π transition. When the polarization is circularly polarized around the main axis, the σ＋ or σ- transition occurs, corresponding to the selection rule of △m = 1 or △m = - 1, respectively. A slightly more complex case is that the laser is linearly polarized perpendicular to the main axis. The numerical calculation shows that we can decompose the transition into the sum of σ＋ and σ- transitions, it is noted as the σ transition. For the more complex case in which the laser is linearly polarized with an arbitrary angle with respect to the main axis, we have to decompose the polarization into one along the main axis and the other one perpendicular to the main axis. They correspond to π and σ transitions, respectively. We demonstrate that these transitions in the diamagnetic spectrum and the above spectral decomposition well explain the experimentally observed spectra.

Signal processing method of a novel polarized array radar seeker

This paper proposes a novel polarized radar seeker based on the polarized antenna array. A fully polarized signal processing method for the proposed radar seeker is studied under the environments with electromagnetic interferences. A dual polarized antenna array is employed to transmit and receive the radar signals. The instantaneous polarization signal processing technique is used to detect and recognize the targets. The direction of arrival （DOA） of the target is measured through the spatial spectrum with high resolution for the polarized array radar seeker system. The fully polarized signal model of the polarized array radar seeker is formulated and a specific signal processing algorithm is expounded. The theoretical research and numerical simulation results demonstrate that the proposed radar seeker has good performances in target detection and electronic warfare. The research results can provide an effective technical approach to develop and research the new generation radar seeker.

海洋油膜偏振反射特性仿真与测试

为了海洋溢油的检测与识别,在偏振特性建模中综合考虑天空的偏振辐射、油膜表面的动态反射、接收探测器的姿态和性能,进行全数字仿真,开展外场动态水面的实测,进行油膜偏振半实物仿真,最后对海洋溢油进行了偏振测试与分析。试验结果表明:在区分油品方面,汽油和水的强度差值为29.33%,线偏振度差值为0.97%,二者结合可较好的分辨溢油。

Electron acceleration by tightly focused radially polarized few-cycle laser pulses

Within the framework of plane-wave angular spectrum analysis of the electromagnetic field structure, a solution valid for tightly focused radially polarized few-cycle laser pulses propagating in vacuum is presented. The resulting field distribution is significantly different from that based on the paraxial approximation for pulses with either small or large beam diameters. We compare the electron accelerations obtained with the two solutions and find that the energy gain obtained with our new solution is usually much larger than that with the paraxial approximation solution.

基于界面电荷极化特性的变压器油纸绝缘寿命预测方法研究

准确预测变压器油纸绝缘寿命对于保障电力系统安全稳定运行具有重要意义。根据微观介电响应机制剖析界面极化与油纸绝缘老化的内在机理联系,并基于混合极化模型——一种在扩展德拜模型基础上引入界面极化支路的等效电路拓扑,探究界面电荷极化特性在油纸绝缘寿命预测中的应用。首先,分析温升过程中频谱特性变化背后蕴含的普适弛豫极化规律,基于混合极化模型重构回复电压极化谱。结合温度对主时间常数和模型参数的影响规律,提出一种单一温度测试下的油纸绝缘活化能计算方法,通过界面极化电容构建出频温平移因子。其次,剖析介质损耗因数随老化加深的变化规律,探究损耗峰偏移现象与界面极化弛豫时间的内在联系,凝练全新表征油纸绝缘聚合度含量的频域特征参量——界面极化支路极点Ph2。最后,联合界面极化支路极点Ph2、频温平移因子和损失累积动力学方程构建油纸绝缘寿命预测模型,并将不同运行年限变压器现场实测数据代入模型验证实效性,为油纸绝缘寿命预测提供了一种新思路。

基于IKNN和LOF的变压器回复电压数据清洗方法研究

基于回复电压极化谱提取特征参量是目前广泛应用的变压器油纸绝缘状态评估方法,但极化谱易受工况干扰、人工失误等因素影响而出现特征数据异常的情况,严重降低评估准确性。针对上述问题,该文提出了一种基于局部离群因子(LOF)和改进K最近邻(IKNN)的回复电压数据清洗方法。首先,选取回复电压极化谱的回复电压极大值Urmax、初始斜率Sr与主时间常数tcdom作为老化特征参量,并基于LOF算法对非标准极化谱中的异常特征量数据进行识别与筛除。其次,利用模糊C均值(FCM)聚类算法减小噪声点对KNN算法的干扰,并通过加权欧氏距离标度突出各特征量间的关联性,进而构建出基于IKNN的数据填补模型架构以实现特征缺失数据的填补。最后,代入多组实测数据验证所提数据清洗方法的实效性。结果表明,数据清洗后的状态评估准确率相较于原有数据上升了50%左右,有效提高了变压器回复电压数据质量,为准确感知变压器运行状况奠定坚实的基础。

泰山一次强雹暴微物理特征双偏振雷达和雨滴谱观测分析

为了研究雹暴的微物理特征,利用双偏振雷达和雨滴谱仪探测资料,结合粒子相态分类算法,对2020年6月1日发生在泰山的一次降雹天气进行了分析,获得了雹暴云影响泰山站时附近区域雷达参量、水凝物粒子、降水粒子谱分布特征。研究表明:雹暴云前缘开始影响泰山站时,反射率因子(ZH)梯度大值区紧邻泰山站,与差分反射率(ZDR)弧位置大致重合,此处主要为大滴粒子,由上空霰粒子融化形成;雨滴谱为双峰结构,对降水贡献较大的为2~3 mm粒子。当雹暴云主体影响泰山站时,其前侧径向出现三体散射,上空出现悬垂回波,泰山站附近区域主要识别为雹粒子;泰山站南侧出现有界弱回波,该处辐合升运动增强,被ZDR大值半环绕,主要分布大滴与雹粒子,夹杂霰与湿雪粒子;归一化等高频率(CFAD)显示冰相过程增强;-10℃层以下雹粒子主要由-10~0℃层的霰粒子凇附上升气流携带的大滴与中小雨粒子形成,这些粒子无法下落碰并形成尺寸较大的降水粒子,雨滴谱变为单峰结构,对降水贡献最大的为14~16 mm粒子。雹暴云主体离开泰山站,CFAD显示冰相过程减弱,冰晶凇附过冷云滴转化成霰的效率降低,泰山站上空识别出大量的冰晶与干雪粒子,出现层状云降水特征;雨滴谱再次变为双峰结构,第二峰值为2~3 mm粒子,对降水贡献最大。

基于多策略融合粒子群算法的油纸绝缘参数辨识

针对粒子群优化算法收敛速度较慢、易陷入局部最优、收敛结果不够稳定等问题,本文从初始种群、边界处理、惯性权重三个方面对传统粒子群算法进行改进,提出多策略融合粒子群算法(MSF-PSO),并通过测试函数证明了MSF-PSO可大幅提高计算速度和计算效率。将MSF-PSO应用于变压器油纸绝缘介电响应的德拜等效电路参数辨识中,计算结果表明,与其他粒子群优化算法相比,该算法获得的回复电压极化谱能更好地与现场测试获得的回复电压极化谱相吻合,进一步验证了本文所提改进算法的准确性,可为诊断变压器油纸绝缘设备老化情况提供参考。

雨滴谱数据在S波段双偏振天气雷达数据质量评估中的应用

结合T-Matrix方法和雨滴谱仪数据反演双偏振参量,设计了一种雨滴谱反演评估方法(雨滴谱法),利用其反演结果可对双偏振天气雷达数据进行评估。将此方法应用于不同类型降水过程的雷达偏振参量数据质量评估,结果表明:满足微雨条件时,雨滴谱法与传统的微雨滴法均能有效监测由雷达系统误差导致的观测偏差,且评估结果十分接近;不满足微雨条件时,雨滴谱法评估的不同类型降水过程的雷达数据质量与满足微雨条件下的评估结果十分接近,客观证明了系统调整后雷达运行良好、数据质量稳定;不同雨强(R)情况下,雨滴谱法的评估结果具有一致性。10 mm·h^(-1)≤R<20 mm·h^(-1)时,雷达观测的数据质量最为稳定。该雨滴谱法适用范围广,可动态评估双偏振雷达偏振参量质量,有助于雷达调整和数据校正。

多尺度电磁联合方法在贵州某磷矿深部岩溶探测中的应用

随着新能源行业的迅猛发展以及粮食需求的不断增多,深部磷矿资源开采迫在眉睫。贵州作为磷矿资源大省,品位高、矿层厚,具有很高的开采价值。但该地区呈现典型的喀斯特地貌特征,可溶岩总面积达12.88万km^(2),约占全省总面积的73%。开采过程中极易发生井喷、突泥等地质灾害,严重影响工程进度与开发成本,甚至造成人员伤亡。因此,探明地下岩溶发育情况对于磷矿开采工作十分重要。结合研究区地质条件以及磷矿埋藏深的特点,本文综合运用扩频激电法和可控源电磁法进行岩溶探测。两种方法优势互补,相互印证,通过对反演得到的电阻率剖面图进行定性分析,准确地圈定出岩溶发育区,为下一步磷矿开采工作提供参考,同时也为岩溶发育地区的物探工作提供有益的参考和借鉴。

基于太赫兹时域光谱系统的双折射率晶体非接触式表征方法

晶体的各向异性探测技术正逐渐向非接触和非破坏性方法发展。太赫兹辐射由于其对许多介电材料的大穿透深度和非电离特性,在各向异性材料的双折射研究中具有广阔的前景。石英、蓝宝石、液晶以及含有亚波长结构的超材料等都表现出太赫兹双折射,作为偏振功能器件中的常用材料,其参数测量对于太赫兹器件研发具有重要意义。材料双折射率的提取往往依赖光轴方向和晶体厚度等先验参数。材料的光轴方向表征其各向异性的优先方向,对于已知光轴取向的晶体,可以根据经验选择合适的琼斯向量,而在实际应用中,只要选择探测太赫兹波的线偏振方向、光轴、探测轴。可以很容易地测量出寻常光和非常光,并直接从时域信号中计算出各自的折射率。对于光轴方向未知的材料,需要旋转样品以不同的方位角进行测量。双折射率的提取依赖于材料厚度的确定,通过游标卡尺或千分尺所得测量值与真实值存在较大差异,容易在样品表面造成划痕。无论是旋转样品还是厚度测量,人为操作都会为双折射率表征引入不确定性。基于透射式太赫兹时域光谱系统(THz-TDS)开发了一种双折射晶体光轴方向和晶片厚度的非接触式测量方法,不依赖于晶体先验参数,即可获取晶体完整的折射率。通过控制样品旋转配合光学延迟线动作实现光轴自动定位,利用传递函数迭代逼近算法提取晶体厚度和完整的折射率。为验证该方法,选择了在太赫兹波段具有双折射特性的(10-10)取向蓝宝石晶体进行测量,准确地提取了晶体在0.3~1.5 THz频率范围的平均寻常光折射率3.39±0.02,非常光折射率3.08±0.02,双折射率-0.31±0.02,并绘制了吸收谱。结果证明,所建立的测量方法避免了人工操作引起的样品损坏和定位误差,提高了双折射晶体太赫兹频段材料参数的测量速度、稳定性和精确度,对偏振敏感太赫兹测量技术及其应用具有重要意义。

基于机器学习的SIP数据砂岩型铀矿氧化-还原带识别研究

砂岩型铀矿成矿过程中,氧化-还原作用是实现铀富集成矿的重要作用之一,有效圈定深部氧化-还原过渡带范围能够对指示深部找矿提供重要线索。频谱激电法(SIP)利用氧化-还原带岩石电化学特性差异,基于柯尔-柯尔(Cole-Cole)模型可反演获得地下介质多个复电阻率参数。采用该参数特征组合开展改进的Kmeans聚类,通过无监督机器学习算法实现数据结果自动分类,从而达到划分砂岩型铀矿氧化-还原分带的目的。经验证地层分带识别结果与钻探剖面验证情况一致性较好,表明Kmeans++法能够有效识别SIP结果数据中蕴含的砂岩型铀矿氧化-还原分带信息,为铀矿勘探缩小找矿范围,指示下一步找矿方向提供参考。

黔西北垭都铅锌矿区岩矿石电性特征与激电找矿实践

研究区位于北西向垭都—蟒洞构造带中部,区内铜矿山、海坝和篾匠冲3个矿段发现零星铅锌氧化矿、硫化矿、硫铁矿和多个褐铁矿体,其中海贝矿段曾通过物探TEM发现较大铅锌氧化矿体,其成矿条件与临区猪拱塘超大型铅锌矿床相似,分析深部找矿潜力巨大,因地形、信号干扰和物探方法勘探深度的局限性,后期找矿进展缓慢。本文总结分析了该区以往找矿勘查存在的难点,结合研究区地质背景特征,系统对岩(矿)石进行物性测量和分析发现,硫化矿石在频率0.1~10 Hz表现为高相位高极化率异常,异常强度大,与地层差异凸显,能有效压制地层带来干扰异常;在此基础上设计长周期大极距激电扫面探测,引入η/ρ绘制等值线平面异常进行异常划分,有效压制了高阻高极化异常,发现了不同强度的低阻高极化异常13个,对其中条带状(6)号中高极化低阻异常进行扩频激电法双边三极测深验证显示,深部YC74-1板状高极化率异常明显,异常位于高低电阻率密集接触带,极化率异常强度大,与围岩差异明显,推断该异常由深部硫化矿引起。钻孔验证发现深部隐伏硫铁矿体,矿体直接产出F_(0)断层破碎带中,赋矿围岩为二叠系栖霞组灰岩—泥盆系高坡场组白云质灰岩,矿体真厚3.33~12.47 m,平均厚7.65 m,Ts:17.32%~42.57%,Ts平均:28.54%,矿体埋深310.50~472.18 m。其中ZK74-2钻孔深度692.38 m见细脉状铅锌硫化矿,矿体真厚4.00 m。找矿实践证明,根据系统的电性测试结果,合理设计激电不同装置组合探测,可以在该区硫化矿的勘查中获得较好找矿效果。

扩频激电法(SSIP)找矿效果分析——以湖南省永州市零陵区东湘桥锰矿床勘查为例

本文在充分研究勘查区地质背景的基础上,首次采用扩频激电法在祁零盆地开展锰矿资源的探测。通过双边三极测深反演结果分析,发现了一条较连续的相对高极化异常带,异常带强度与围岩相差10倍,突出而稳定;电阻率反演结果则表现为“U”型盆状高阻基底包裹低阻的特征,推测其高极化异常带由地下矿床引起;而高阻盆底包裹低阻则指示地层受向斜构造控制,与已知的向斜构造一致。经钻探勘探,发现2条较为连续的锰矿矿脉,厚0.9~2.8 m,品位9.3%~15.2%,与黄铁矿成伴生关系,一同赋存于灰岩中。通过SSIP实验成果以及钻探验证情况,得出视极化率异常与矿脉揭露深度、形态轮廓十分吻合,视电阻率异常较好地反应矿区地层展布信息,扩频激电法在碳酸锰矿产资源勘查方面的有效性得到验证。

2024年2月我国两次大范围雨雪冰冻天气对比

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固体氧化物燃料电池(SOFC)是一个不透明的实体,有时被称为“黑盒子”,动力学过程在其运行中发挥着关键作用。对电池内部的动力学过程进行深入研究,可以促进电池的精确诊断,并推动电池机理研究的进步。弛豫时间分布(DRT)技术是近年来备受瞩目的一种方法,可以有效地评估SOFC系统中的电化学特性。然而,传统的DRT分析技术中,由于正则化参数选择的问题,会使DRT结果出现伪峰和表示不对称现象,这干扰了时域分析中时间常数识别的稳定性和准确性。基于最佳参数自动确定的DRT技术,通过不同物理参数(SOFC阴极厚度、反应温度、进气流量)条件下动力学过程的特性差异对电化学阻抗的时域信息进行了分析,将DRT得出的四个高峰分别总结为:P1的欧姆极化、P2的活化极化、P3的浓差极化、P4的物理吸附和气体扩散。通过判断各个峰所代表的物理意义进一步发现:阴极厚度的增加会导致电催化层厚度的相应增加,如果电催化层厚度超过17μm的临界厚度,就会导致迁移电阻的活化极化显著降低。