Impact of Atmospheric Transmittance and NLTE Correction on Simulation of High Spectral Infrared Atmospheric Sounder onboard FY-3E

With the launch of the first civilian early-morning orbit satellite Fengyun-3E(FY-3E),higher demands are placed on the accuracy of radiative transfer simulations for hyperspectral infrared data.Therefore,several key issues are investigated in the paper.First,the accuracy of the fast atmospheric transmittance model implemented in the Advanced Research and Modeling System(ARMS)has been evaluated with both the line-by-line radiative transfer model(LBLRTM)and the actual satellite observations.The results indicate that the biases are generally less than 0.25 K when compared to the LBLRTM,while below 1.0 K for the majority of the channels when compared to the observations.However,during both comparisons,significant biases are observed in certain channels.The accuracy of Hyperspectral Infrared Atmospheric Sounder-II(HIRAS-II)onboard FY-3E is comparable to,and even superior to that of the Cross-track Infrared Sounder(CrIS)onboard NOAA-20.Furthermore,apodization is a crucial step in the processing of hyperspectral data in that the apodization function is utilized as the instrument channel spectral response function to produce the satellite channel-averaged transmittance.To further explore the difference between the apodized and unapodized simulations,Sinc function is adopted in the fast transmittance model.It is found that the use of Sinc function can make the simulations fit the original satellite observations better.When simulating with apodized observations,the use of Sinc function exhibits larger deviations compared to the Hamming function.Moreover,a correction module is applied to minimize the impact of Non-Local Thermodynamic Equilibrium(NLTE)in the shortwave infrared band.It is verified that the implementation of the NLTE correction model leads to a significant reduction in the bias between the simulation and observation for this band.

DETERMINATION OF GASEOUS COMPOSITION IN THE MIDDLE ATMOSPHERE BY USING HIGH SPECTRAL RESOLUTION METHODS

One of the crucial problems in study on the middle atmosphere is to determine the concentration and distribution of some trace gases.In this aspect,sounding methods with high spectral resolution have been developed by many scientists.Some major trace gases and their spectral characteristics,space-borne limb method for determination of trace gases in the middle atmosphere are introduced,requirements for used methods and instruments,development and challenge encountered by sounding of trace gases with high spectral resolution are discussed in this paper.

Focused Wave Properties Based on A High Order Spectral Method with A Non-Periodic Boundary

In this paper, a numerical model is developed based on the High Order Spectral （HOS） method with a non-periodic boundary. A wave maker boundary condition is introduced to simulate wave generation at the incident boundary in the HOS method. Based on the numerical model, the effects of wave parameters, such as the assumed focused amplitude, the central frequency, the frequency bandwidth, the wave amplitude distribution and the directional spreading on the surface elevation of the focused wave, the maximum generated wave crest, and the shifting of the focusing point, are numerically investigated. Especially, the effects of the wave directionality on the focused wave properties are emphasized. The numerical results show that the shifting of the focusing point and the maximum crest of the wave group are dependent on the amplitude of the focused wave, the central frequency, and the wave amplitude distribution type. The wave directionality has a definite effect on multidirectional focused waves. Generally, it can even out the difference between the simulated wave amplitude and the amplitude expected from theory and reduce the shifting of the focusing points, implying that the higher order interaction has an influence on wave focusing, especially for 2D wave. In 3D wave groups, a broader directional spreading weakens the higher nonlinear interactions.

Re-study on Recurrence Period of Stokes Wave Train with High Order Spectral Method

Owing to the Benjamin-Feir instability, the Stokes wave train experiences a modulation-demodulation process, and presents a recurrence characteristics. Stiassnie and Shemer researched the unstable evolution process and provided a theoretical formulation for the recurrence period in 1985 on the basis of the nonlinear cubic Schrodinger equation （NLS）. However, NLS has limitations on the narrow band and the weak nonlinearity. The recurrence period is re-investigated in this paper by using a highly efficient High Order Spectral （HOS） method, which can be applied for the direct phase- resolved simulation of the nonlinear wave train evolution. It is found that the Stiassnie and Shemer＇s formula should be modified in the cases with most unstable initial conditions, which is important for such topics as the generation mechanisms of freak waves. A new recurrence period formula is presented and some new evolution characteristics of the Stokes wave train are also discussed in details.

Retrieval of column-averaged volume mixing ratio of CO_2 with ground-based high spectral resolution solar absorption

The total column-averaged volume mixing ratio of atmospheric carbon dioxide(XCO2)has been retrieved with high spectral resolution solar absorption data obtained from ground-based Fourier transform spectrometer(FTS)measurements at Xichong,a coastal site in the district of Shenzhen in southern China.Based on differential optical absorption spectroscopy(DOAS)theory,the XCO2was retrieved by finding the best match of observed high spectral resolution solar absorption data and monochromatic radiation transfer model calculations.The averaged XCO2in the whole observation period was about 394.9 ppm.The uncertainty of the retrieval was estimated to be 2.0 ppm(0.51%)by comparing retrievals at two bands.The preliminary results show that XCO2retrieved by this method can be used to validate satellite remote sensing of XCO2:

Review:Recent Development of High⁃Order⁃Spectral Method Combined with Computational Fluid Dynamics Method for Wave⁃Structure Interactions

The present paper reviews the recent developments of a high⁃order⁃spectral method(HOS)and the combination with computational fluid dynamics(CFD)method for wave⁃structure interactions.As the numerical simulations of wave⁃structure interaction require efficiency and accuracy,as well as the ability in calculating in open sea states,the HOS method has its strength in both generating extreme waves in open seas and fast convergence in simulations,while computational fluid dynamics(CFD)method has its advantages in simulating violent wave⁃structure interactions.This paper provides the new thoughts for fast and accurate simulations,as well as the future work on innovations in fine fluid field of numerical simulations.

3-D simulations of freak waves based on high-order spectral method

Three-dimensional ( 3-D) directional wave focusing is one of the mechanisms that contribute to the generation of freak waves. To simulate and analyze this phenomenon,a 3-D wave focusing model is proposed based on the enhanced high-order spectral method,which solves the fully nonlinear potential flow equations with a free surface within periodic unbounded 3-D domains. The numerical model is validated against a fifth-order Stokes solution for regular waves. Laboratory-scale freak waves are observed with wave components having equal amplitudes. Investigations of the appearance and propagation of freak-wave events in a 3-D open wavefield defined by a directional wave spectrum are then realized.

Spectral redshift of high-order harmonics by adding a weak pulse in the falling part of the trapezoidal laser pulse

We investigate the spectral redshift of high-order harmonics of the H_2~＋（D_2~＋） molecule by numerically solving the non-Born–Oppenheimer time-dependent Schr ¨odinger equation（TDSE）. The results show that the spectral redshift of highorder harmonics can be observed by adding a weak pulse in the falling part of the trapezoidal laser pulses. Comparing with the H_2~＋ molecule, the shift of high-order harmonic generation（HHG） spectrum for the D_2~＋ molecule is more obvious.We employ the spatial distribution in HHG and time-frequency analysis to illustrate the physical mechanism of the spectral redshift of high-order harmonics.

High dynamic synchronization algorithm based on cyclic spectral density

A new high dynamic synchronization algorithm using cyclic spectral density was presented according to the theories of cyclic spectral density and its anti-interface and anti-noise properties.The closed forms of frequency error and phase error were obtained,and their performances were analyzed.The in-phase signal throw costas loop was normalized to obtain a cosine signal.Cyclic spectral density of the cosine signal of was computed to obtain the frequency error and the phase error and then results were put into NCO to synchronize.Finally,the performance of the presented algorithms was compared with the conventional algorithms by virtue of simulations,and the simulation results proved the correctness and the superiority of the new algorithms.

High-precision solution to the moving load problem using an improved spectral element method

In this paper, the spectral element method(SEM)is improved to solve the moving load problem. In this method, a structure with uniform geometry and material properties is considered as a spectral element, which means that the element number and the degree of freedom can be reduced significantly. Based on the variational method and the Laplace transform theory, the spectral stiffness matrix and the equivalent nodal force of the beam-column element are established. The static Green function is employed to deduce the improved function. The proposed method is applied to two typical engineering practices—the one-span bridge and the horizontal jib of the tower crane. The results have revealed the following. First, the new method can yield extremely high-precision results of the dynamic deflection, the bending moment and the shear force in the moving load problem.In most cases, the relative errors are smaller than 1%. Second, by comparing with the finite element method, one can obtain the highly accurate results using the improved SEM with smaller element numbers. Moreover, the method can be widely used for statically determinate as well as statically indeterminate structures. Third, the dynamic deflection of the twin-lift jib decreases with the increase in the moving load speed, whereas the curvature of the deflection increases.Finally, the dynamic deflection, the bending moment and the shear force of the jib will all increase as the magnitude of the moving load increases.

沿面放电光脉冲发展特征与临界击穿判据研究

绝缘沿面放电是引起高压开关柜中滑闪及电弧击穿的主要原因和前期阶段,准确有效地对绝缘异常爬电进行监测、跟踪和预警对保障设备安全运行非常关键。该文通过试验研究强垂直分量绝缘爬电的光脉冲阶段特征,并提出基于多波段光谱辐射强度信息的放电发展阶段划分方法和临界击穿判据,从而建立基于多波段光谱强度比值的放电跟踪预警方法。首先,搭建多波段单光子试验系统,采用自制多波段光学传感装置对沿面放电发展全过程跟踪测量,获得表征放电发展过程光谱比率的统计参量;其次,借助模糊聚类算法和支持向量机,构建放电发展临界特征空间边界,并对放电严重程度进行量化评估,结果表明该方法对放电阶段的正判率达到96.9%以上;最后,确立基于光谱比率的放电危险性主动预警逻辑,并开发了放电光脉冲跟踪预警系统,为开关柜放电和弧光监测的创新应用提供了参考。

基于荧光素的高选择性Hg^(2+)荧光探针的合成及其光谱性质研究

以荧光素、水合肼及费舍尔氏醛制备了一种新颖的Hg^(2+)荧光探针,其分子结构通过核磁及质谱进行了表征。该探针在金属离子中能够特异性识别Hg^(2+),可应用于对Hg^(2+)的检测。在生命科学及环境科学领域对于Hg^(2+)的准确、快速的实时监测备受关注,本研究在此方面具有潜在的应用价值。

AlGaAs光电阴极表面清洗技术研究

针对高Al组分AlGaAs光电阴极设计了不同清洗方法,通过XPS对不同清洗条件下的材料表面元素成分进行了测试分析,并结合SEM和高倍显微镜对光电阴极材料表面缺陷进行了分析研究。在超高真空腔体中进行了透射式AlGaAs光电阴极及其像增强管的制备,测试了器件的光谱响应曲线和图像质量。结果表明,采用H_(2)SO_(4)/H_(2)O_(2)/H_(2)O溶液和HCl/H_(2)O溶液的化学清洗工艺,结合等离子体物理清洗工艺,可有效去除AlGaAs表面的氧化物、有机颗粒和杂质C,提升器件的光谱灵敏度和图像质量。

基于5 kHz平面激光诱导荧光的射流火焰局部熄火时空特性分析

基于高频光学测量手段研究射流火焰局部熄火的分布特性,对于分析燃烧场不稳定性机理有重要意义。建立5 kHz的平面激光诱导荧光测量系统,对高速射流火焰开展实验研究,并获得火焰结构的动态发展过程;将双边滤波、竖直滑窗局部自适应阈值等图像处理方法引入平面激光诱导荧光图像的预处理,在局部断裂结构数量特征的基础上,提取局部断裂结构长度和空间位置等特征;基于上述特征深入解析局部熄火的时空分布特性,进一步完善高频平面激光诱导荧光诊断与分析方法。研究表明:双边滤波算法处理后,图像峰值信噪比为34.3 dB,结构相似度为0.93,噪声水平显著降低,获得了较好的去噪效果;使用竖直滑窗局部自适应方法进行图像分割的F1分数达到93.30%;断裂结构累计数量随时间线性增加,当射流马赫数由0.5增至1.6时,单侧图像断裂结构的每秒累计数量从790.7增至9 217.2,并且局部熄火频率与射流马赫数呈指数关系;断裂结构主要分布区域为火焰臂及上侧中央燃料区。本研究进一步拓展了高频平面激光诱导荧光技术的应用能力,证明了高频平面激光诱导荧光技术用于局部熄火时空分布特性研究的可行性。

激光除漆频率对LIBS准确性影响研究

验证激光诱导击穿光谱(Laser-Induced Breakdown Spectroscopy,LIBS)技术在千赫兹级激光条件下检测准确性对LIBS技术应用于大区域、高效率激光除漆过程监测具有重要意义。本文采用高频(kHz级)1064nm红外脉冲光纤激光器清洗飞机蒙皮漆层,结合能谱仪测试结果及原子光谱数据库数据,研究千赫兹激光对LIBS光谱谱峰波长和峰值强度的影响,并验证LIBS技术在千赫兹级激光除漆过程中的准确性。结果表明千赫兹谱峰较赫兹谱峰波长位置向蓝光区域偏移,偏移量不大于0.18nm。380nm~425nm范围内的谱峰完全消失,425nm~550nm范围内的谱峰信噪比下降。能谱仪测试结果与赫兹级LIBS光谱协同验证了千赫兹级激光条件下LIBS技术检测效果的准确性。表明在大区域、高效率飞机蒙皮激光除漆过程中,LIBS技术可用于除漆过程监测。本研究可为千赫兹级激光除漆过程LIBS监测提供参考。

High-Order Spectral Stochastic Finite Element Analysis of Stochastic Elliptical Partial Differential Equations

This study presents an experiment of improving the performance of spectral stochastic finite element method using high-order elements. This experiment is implemented through a two-dimensional spectral stochastic finite element formulation of an elliptic partial differential equation having stochastic coefficients. Deriving this spectral stochastic finite element formulation couples a two-dimensional deterministic finite element formulation of an elliptic partial differential equation with generalized polynomial chaos expansions of stochastic coefficients. Further inspection of the performance of resulting spectral stochastic finite element formulation with adopting linear and quadratic (9-node or 8-node) quadrilateral elements finds that more accurate standard deviations of unknowns are surprisingly predicted using quadratic quadrilateral elements, especially under high autocorrelation function values of stochastic coefficients. In addition, creating spectral stochastic finite element results using quadratic quadrilateral elements is not unacceptably time-consuming. Therefore, this study concludes that adopting high-order elements can be a lower-cost method to improve the performance of spectral stochastic finite element method.

数字经济赋能乡村振兴研究热点与趋势——基于CiteSpace的可视化分析

数字经济是信息通信技术应用与发展所创造的新生产物,已成为全球经济发展和社会进步的重要源动力。在国家推进“数字经济赋能乡村振兴”的大背景之下,本文采用CiteSpace软件对2000—2022年中国知网(CNKI)所收录的CSSCI来源期刊有关“数字经济赋能乡村振兴”研究505篇文献,根据研究热点、聚类变化和演进趋势等特征分别进行了关键词共现、聚类分析、时间区图和时间线图等知识图谱的绘制。结合对知识图谱的分析和文献梳理,对数字化转型背景下我国乡村领域的研究现状和研究内容、热点问题、演进脉络及研究趋势等进行了深入分析,并对数字经济赋能乡村振兴的实践提出了三点对策建议:加快乡村信息化转型,开创城乡经济融合的新格局及孵化创新乡村产业模式,以期为乡村振兴数字经济领域研究提供参考。

基于谱线-高阶累积量的调制识别研究与实现

已发表的调制识别算法大多基于单一特征参数,识别种类较少,且往往很难在实际系统中布署。提出了一种基于谱线-高阶累积量的数字调制识别算法,该算法利用载波频率估计、符号速率估计、定时恢复、噪声功率估计等前处理手段,结合信号功率谱、二次方谱、四次方谱中的离散谱线和四阶归一化高阶累积量,可识别2ASK、4ASK、8ASK、2FSK、4FSK、8FSK、BPSK、QPSK、8PSK、OQPSK、MSK、16QAM、32QAM、64QAM、128QAM、256QAM 16种数字调制信号。基于该算法,设计并实现了一种数字调制识别处理系统,可实时识别上述16种调制信号。结果表明,该实时系统对大部分调制信号的识别准确率可达到99%以上,对8PSK、32QAM、128QAM等调制信号的识别准确率可达到94%以上。

太阳塔高分辨率光谱观测系统研制与实验教学应用

该文以推进实测天文课程教学改革与提升天文实验教学质量为目标,对太阳塔硬件基础设施进行重新设计与系统优化,研制了一套太阳塔高分辨率光谱观测系统。该系统满足太阳光球、色球层特征谱线的高分辨观测需求,可达到研究太阳黑子和耀斑特性的观测精度。开放式的光路设计与模块化实验平台有助于学生将光学理论与天文实践相结合。文章设计“定标汞灯的光谱拍摄与谱线证认”和“太阳高分辨率光谱拍摄与谱线证认”两个实操型创新实验,从多重视角增进学生开展有关太阳科研的兴趣。实验将实践教学与科学研究充分结合,有效推动了天文实验类课程的教学改革。