Improvement of X-Band Polarization Radar Melting Layer Recognition by the Bayesian Method and ITS Impact on Hydrometeor Classification

Using melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasUsing melting layer(ML)and non-melting layer(NML)data observed with the X-band dual linear polarization Doppler weather radar(X-POL)in Shunyi,Beijing,the reflectivity(ZH),differential reflectivity(ZDR),and correlation coefficient(CC)in the ML and NML are obtained in several stable precipitation processes.The prior probability density distributions(PDDs)of the ZH,ZDR and CC are calculated first,and then the probabilities of ZH,ZDR and CC at each radar gate are determined(PBB in the ML and PNB in the NML)by the Bayesian method.When PBB>PNB the gate belongs to the ML,and when PBB<PNB the gate belongs to the NML.The ML identification results with the Bayesian method are contrasted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.ted under the conditions of the independent PDDs and joint PDDs of the ZH,ZDR and CC.The results suggest that MLs can be identified effectively,although there are slight differences between the two methods.Because the values of the polarization parameters are similar in light rain and dry snow,it is difficult for the polarization radar to distinguish them.After using the Bayesian method to identify the ML,light rain and dry snow can be effectively separated with the X-POL observed data.

Practical calibration method for instantaneous polarization radar systems utilizing a metal sphere

A practical calibration method is proposed for instantaneous polarization radar systems.The method only needs one measurement by using a metal sphere.The distortions of system and the actual polarization scattering matrix（PSM）of target can be obtained.First,an instantaneous polarization radar system is presented.The system can obtain PSM by a single pulse echo.The dual-polarization antenna can transmit and receive two orthogonal polarization waves.The multilayer micro-strip patch antenna is adopted for this kind of radar system.Second,based on the multi-port network theory,the operation and system errors of instantaneous polarization radar system are analyzed.By making assumption on the cross-talk factors of antenna,distortion matrices of R and Tare derived.Finally,the calibration method based on instantaneous polarization measurement is introduced.Simulation results show the performance of this calibration method.The values of calibrated PSM are in agreement with the actual ones after calibration.

An element-free Galerkin method for ground penetrating radar numerical simulation

An element-free Galerkin method(EFGM) is used to solve the two-dimensional(2D) ground penetrating radar(GPR)modelling problems, due to its simple pre-processing, the absence of elements and high accuracy. Different from element-based numerical methods, this approach makes nodes free from the elemental restraint and avoids the explicit mesh discretization. First, we derived the boundary value problem for the 2D GPR simulation problems. Second, a penalty function approach and a boundary condition truncated method were used to enforce the essential and the absorbing boundary conditions, respectively. A three-layered GPR model was used to verify our element-free approach. The numerical solutions show that our solutions have an excellent agreement with solutions of a finite element method(FEM). Then, we used the EFGM to simulate one more complex model to show its capability and limitations. Simulation results show that one obvious advantage of EFGM is the absence of element mesh, which makes the method very flexible. Due to the use of MLS fitting, a key feature of EFM, is that both the dependent variable and its gradient are continuous and have high precision.

RADAR CROSS-SECTION COMPUTATIONS OF ARBITRARILY COMPLICATED TARGETS BY APPLYING THE PANEL METHOD

The present paper deals with the method for the radar cross-section (RCS)computations of arbitrarily complicated targets based on the work by D. Klement et al.(1988).This method is convenient in use, fast in operation and precise in calculating RCS of a complicatedtarget. With this method, the RCS of classic scatterers, for example, a cone and a cylinder, arecomputed with the result of good agreement with experimental data. Furthermore, the RCS’of an aircraft model at various attitudes are calculated with the result of good agreement withexperimental data also.

Efficient Calculation of the Radar Cross Section at the Interior Resonance by the Inverse Power Method

It is well known that the incorrect results will be given using either the electric or magnetic field integral equation to calculate the radar cross section (RCS) of a closed body at the interior resonance. In this paper, an effective iterative technique is used to correct the calculated surface current density from the electric field integral equation. The radar cross section is computed for an infinite conducting circular cylinder at the interior resonance, and the obtained results are in good agreement with the analytical results. The backscattering cross section of an infinite triangular cylinder in the vicinity of a resonant frequency is also calculated. It is shown that the presence method is efficient and accurate.

Solving multi-object radar cross section based on wide-angle parabolic equation method

Based on a Pade approximation, a wide-angle parabolic equation method is introduced for computing the multiobject radar cross section （RCS） for the first time. The method is a paraxial version of the scalar wave equation, which solves the field by marching them along the paraxial direction. Numerical results show that a single wide-angle parabofic equation run can compute multi-object RCS efficiently for angles up to 45 ° . The method provides anew and efficient numerical method for computation electromagnetics.

堤坝蚁巢综合物探技术研究进展

通过梳理不同时期土石坝蚁巢的类型与规模,阐述了蚁巢的结构特点及成灾模式,总结了蚁巢物探的物性基础;着重介绍了直流电阻率法、探地雷达技术、地震勘探法等在蚁巢探测中的应用现状,从成果维度、探测效率、工作强度、探查精度等视角论述了探测方法的适用条件,指出现有物探技术还不能有效支撑蚁巢的高精度、高效率、立体化探测,并提出了普查-详查-治理-监控的蚁患综合物探服务架构。立足于蚁巢探查技术的客观需要,提出未来蚁巢物探技术应聚焦研制蚁巢发育阶段的1∶1病害物理模拟装置及隐患图谱,研发适应堤坝地形的蚁巢探测装备及正反演算法,构建堤坝蚁害常态化巡查体系及时移电阻率监控系统。

基于几何的星载探测雷达组网空中目标高度估计算法

星载探测雷达具有全球覆盖、全天候、全天时、不易受到攻击等优点,在预警防御系统中具有巨大潜力。单个星载探测雷达由于俯仰角误差过大,导致其不具备空中目标高度估计能力;准确的目标高度估计对改善目标定位精度及威胁估计能力等具有重要意义。考虑多部星载探测雷达组网,提出了一种基于几何的空中目标高度估计方法,并通过仿真验证方法的有效性。通过仿真比较了雷达探测区域不同位置目标高度估计精度的差别,为组网雷达系统设计等提供技术支撑。

改进雷达图法在高校宿舍火灾风险评估中的应用

由于高校宿舍人员高度密集,一旦发生火灾其极易造成严重后果,因此高校宿舍火灾问题亟待重视。为合理评估该风险,首先,借助文献从人、物、环境、管理四方面建立评价指标体系及评价量表;其次,运用合作博弈法将主观赋权结果和客观赋权结果相结合以对评价指标进行组合赋权;随后,将指标权重集转换成各指标轴夹角并计算各指标取值;最后,将经火灾风险雷达图平均周长与同面积圆周长之比为短板系数进行修正的雷达图平均面积作为评价特征量建立高校宿舍火灾风险评价方法。该方法可避免人为赋权的主观性且能以图形形式直观显示出风险管控环节中的薄弱环节。最后以某一实例验证了该评价方法的有效可行性,可为高校宿舍火灾风险评价提供新的思路。

高铁运营隧道岩溶探测及处置方案研究

随着我国高速铁路的快速发展,高铁运营安全越来越重要。当暴雨、地震、人为扰动等原因导致地质灾害发生时,如何准确、快速地探明地质灾害对既有隧道的影响情况,是治理铁路病害的关键所在。文章结合某高铁隧道泄水洞涌泥涌砂病害探测实例,基于施工迅速、操作方便、不影响运营为原则,提出了“地质调查与勘探结合、地面与地下相结合、纵向与横向结合”的综合探测方法,以地面大地电磁宏观探测结果为指导,在既有正洞边墙采用地质雷达法和瞬变电磁法辅助探测,在泄水洞掌子面采用弹性波法和瞬变电磁法进行超前地质预报,进行多方向多尺度的综合探测与分析,最后通过超前水平钻进行验证。通过该方法体系,宏观上准确、快速地查明了地质病害的影响范围,为病害整治解决方案提供依据。

探地雷达法在水工隧洞衬砌隐蔽缺陷检测中的应用

水工隧洞衬砌施工过程中易产生隐蔽性缺陷,危害隧洞的安全稳定运行,因此同步开展检测对保证施工质量具有重要作用。探地雷达法属于当前较为先进的混凝土质量原位检测技术,根据该方法基础原理和数据采集及处理方法,以新疆某水利枢纽为例分析研究该方法在中孔溢洪洞衬砌质量检测中的具体应用,结果表明,探地雷达法可通过研究电磁波在衬砌结构体内传播特征对隐蔽性缺陷进行无损、经济、高效检测,可为指导后续处理方案设计提供科学的数据服务和决策支持。

UHF波段无源雷达低仰角波瓣分裂现象分析及校正方法

针对低频段无源雷达低仰角远程预警探测时波瓣分裂影响俯仰向探测空域覆盖的问题,提出了一种波瓣分裂校正方法.首先分析了波瓣分裂形成原因和影响因素;然后基于阵列流型拟合思想,提出了一种利用最小二乘法求解变换矩阵的校正方法;最后通过仿真分析了角度量化间隔、角度变换区间对校正误差的影响,验证了校正方法的有效性.这对改进基于数字广播电视信号的无源雷达性能提供了参考.

雷达图法综合评价抗线虫大豆品种(系)农艺性状

为筛选出综合性状优良的抗线虫大豆品种(系),以2020-2021年抗线虫大豆品种(系) 11个主要农艺性状的5点试验数据均值为评价指标,利用雷达图法进行综合评价分析。结果表明,百粒重最大、单株粒重最高、SCN指数与倒伏级别最低的品系为17-665,其综合评价和产量数据排名均为第1,说明该品系抗病性、抗倒性、丰产性较其他品种(系)突出;产量排名第2位(2020年)和第4位(2021年)的品系为17-555,因SCN指数偏高,单株粒重低,其他性状中等偏上,在综合评价分析中排名均较产量排名下降;而2年产量排名第8位的品系为17-474,倒伏级别最低,单株荚数、单株粒数及百粒重较高,综合性状较好,在综合评价分析中排名第3位(2020年)和第2位(2021年);各农艺性状表现较差的品系17-388产量及综合评价排名均为第10位;对照品种齐农5号在2年5点试验中产量与综合评价排名较小,说明在不同年际间、不同试验地点齐农5号表现稳定,适宜作为黑龙江省大豆区域试验对照品种。

基于电磁波的煤岩识别技术研究进展

将电磁波应用于煤岩识别中,可有效提高煤岩界面分辨能力。结合煤岩界面模型,阐述了运用电磁波技术进行煤岩识别的原理;介绍了γ射线法、雷达探测法、太赫兹信号法、电子共振法、X射线法和红外热成像法6种具体的煤岩识别方法,分析了各方法的原理,对各方法的优缺点及煤矿井下适用性进行了对比,并结合实际工业应用分析了各方法的研究现状。γ射线法在探测距离上具有显著优势,但存在放射性问题,基本被淘汰;雷达探测法具有识别准确的优点,但由于其信号衰减严重,探测距离短,目前一般应用于薄煤层测厚;太赫兹信号法探测距离短,只有在井下环境组成稳定时才能应用;电子共振法信号衰减严重,探测距离较短且难度较大,所以目前矿井基本摒弃;X射线法穿透性强,成像较清晰,但危害性极大;红外热成像法中,主动红外激励法需耗费大量时间对煤岩进行激励,且在处于高瓦斯的矿井环境中,存在极大的安全隐患;截割闪温法虽耗时较短,但对于截齿多、排布复杂的情况很难实现有效的煤岩识别。指出电磁波回波信息决定着电磁波煤岩识别的准确性,后续应对其进行深层次挖掘。

滇中引水工程隧洞综合超前地质预报分析及应用

针对隧洞施工过程中不同工程地质条件下何种超前地质预报方法预测更为准确、更为适用和单一方法精确度不够、适用性不强的问题,分别介绍了基于地震波法的长距离隧洞超前地质预报技术和基于电磁法的中、短距离隧洞超前地质预报技术原理及特点,依据其工作原理、工作方式、预报距离等特点,探讨了不同超前地质预报方法的优、缺点及其最适用的工作场景,总结出一套实用性强的综合超前地质预报流程。依托滇中引水工程大理Ⅱ段两个隧洞的工程实例,利用所提出的综合超前地质预报流程,分别介绍了结合长距离的隧道地震预报(TSP)法、中短距离的瞬变电磁法和探地雷达法对断层破碎带和裂隙水等不良地质体的综合预报研究。首先,通过长距离预报方法对地质灾害危险程度进行分级、识别高危地段,再通过短距离预报方法对不良地质体进行更精确的识别与定位,综合分析3种超前地质预报方法的地球物理响应特征,可以推断出不良地质体的类型及其空间分布特征;其次,通过探地雷达探测溶蚀波场特征的案例分析,可以推断出溶蚀的物性特征、规模及其空间分布特征。预报结果与隧洞掌子面开挖揭示的结果基本一致,验证了3种超前地质预报方法预报隧洞不良地质体的可靠性,也证实了所提出的综合超前地质预报流程的实用性,有助于指导物探工作者对不良地质体进行更精确的预报,确保隧洞施工安全。

基于探地雷达的杂散电流环境下混凝土损伤检测研究

因走行轨不能对地完全绝缘,地铁运行时会产生杂散电流,导致混凝土中的钢筋发生电化学腐蚀。由于电化学腐蚀的持续发生,腐蚀产物累积在钢筋表面周围,从而对混凝土产生膨胀应力,导致混凝土开裂脱落,因此有必要对杂散电流影响严重区域的钢筋混凝土结构进行检测。该文首先基于多物理场法对钢筋混凝土的电化学腐蚀进行二维瞬态仿真研究,得到与实际混凝土结构相近似的腐蚀损伤图;进而对得到的损伤图进行探地雷达数值正演模拟检测。研究结果表明,在钢筋混凝土发生电化学腐蚀的过程中,钢筋直径的减小和腐蚀产物厚度的增加对探地雷达检测信号影响较小,因膨胀应力而产生的混凝土裂缝对探地雷达检测信号的影响起主要作用。

依托雷达兵战术专业教室的想定作业课程“四步”教学法

为提高想定作业课程教学效果和人才培养质量,根据指挥专业毕业期班学员特点,提出基于雷达兵战术专业教室的想定作业课程“四步”教学法.该教学法以作战任务为牵引,以雷达兵战术专业教室为支撑,规范了想定作业教学的组织实施流程和方法,提升了信息化教学水平,突出学员核心指挥能力的培养.教学实践表明,该教学法效果明显,为指挥专业其他课程教学改革提供了借鉴.

浅层地震反射波法及地质雷达法在地下防空洞探测的应用研究

由于早期人防工程相关资料的缺失,形成若干盲区。本文采用浅层地震反射波法及地质雷达法对浙江宁波地区的地下防空洞盲区进行定位探测,分析其满水和抽水后状态下进行无损检测的可行性。结果表明,结合两种方法的应用可基本实现对防空洞埋深定位探测,抽干水后状态下的反射信号更为清晰。在现场勘测应用时,应减少环境干扰,优选测试分析参数并验证结果。

基于雷达传感器的非接触式睡眠呼吸检测系统设计

为解决当前接触式睡眠呼吸监测系统操作复杂、影响睡眠质量的问题,设计了一种非接触式睡眠呼吸检测系统。硬件系统以STM32G431VBT6单片机为核心,设计了信号调理与采集电路、WiFi通信电路,采用K-LC5雷达传感器采集用户睡眠过程中的呼吸信号。软件系统采用数字滤波算法对雷达传感器采集的胸腔位移信号进行处理,从中提取呼吸信号,并基于能量法进行呼吸暂停判定。测试结果表明,所设计系统能有效检测出睡眠状态下的呼吸状态,呼吸率的测试准确率达到了94.44%以上。

基于InSAR技术的大跨桥梁温度变形监测研究

以国内某高速铁路钢拱桥为研究对象,选取2017—2018年期间59幅C波段Senti⁃nel-1号雷达卫星影像,利用PS-InSAR技术处理影像获得桥梁的视线向(Line of Sight,LOS)位移,根据SAR成像空间几何关系解算出支座的纵向位移.研究结果表明:支座纵向位移的时空特性与实际桥梁结构相符合,验证了PS-InSAR技术观测桥梁结构位移的可行性.建立支座纵向位移与温度的线性相关模型,并与结构健康监测系统的实测结果进行对比.两者吻合良好,相对误差控制在10%以内,验证了PS-InSAR测量桥梁结构位移的可靠性.利用有限元模拟温度作用下桥梁支座的位移变化,并与PS-InSAR位移时间序列进行对比.两者趋势基本一致,LOS向位移误差在[-10,10]mm,验证了PS-InSAR测量桥梁结构位移的准确性.