Evaluation of multiple surface irradiance-based clear sky detection methods at Xianghe—A heavy polluted site on the North China Plain

Surface irradiance measurements with high temporal resolution can be used to detect clear skies,which is a critical step for further study,such as aerosol and cloud radiative effects.Twenty-one clear-sky detection(CSD)methods are assessed based on five years of 1-min surface irradiance data at Xianghe—a heavily polluted station on the North China Plain.Total-sky imager(TSI)discrimination results corrected by manual checks are used as the benchmark for the evaluation.The performance heavily relies on the criteria adopted by the CSD methods.Those with higher cloudy-sky detection accuracy rates produce lower clear-sky accuracy rates,and vice versa.A general tendency in common among all CSD methods is the detection accuracy deteriorates when aerosol loading increases.Nearly all criteria adopted in CSD methods are too strict to detect clear skies under polluted conditions,which is more severe if clear-sky irradiance is not properly estimated.The mean true positive rate(CSD method correctly detects clear sky)decreases from 45%for aerosol optical depth(AOD)≤0.2%to 6%for AOD>0.5.The results clearly indicate that CSD methods in a highly polluted region still need further improvements.

A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection

To dates,most ship detection approaches for single-pol synthetic aperture radar（SAR） imagery try to ensure a constant false-alarm rate（CFAR）.A high performance ship detector relies on two key components：an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm.First,a novel nonparametric sea surface distribution estimation method is developed based on n-order Bézier curve.To estimate the sea surface distribution using n-order Bézier curve,an explicit analytical solution is derived based on a least square optimization,and the optimal selection also is presented to two essential parameters,the order n of Bézier curve and the number m of sample points.Next,to validate the ship detection performance of the estimated sea surface distribution,the estimated sea surface distribution by n-order Bézier curve is combined with a cell averaging CFAR（CA-CFAR）.To eliminate the possible interfering ship targets in background window,an improved automatic censoring method is applied.Comprehensive experiments prove that in terms of sea surface estimation performance,the proposed method is as good as a traditional nonparametric Parzen window kernel method,and in most cases,outperforms two widely used parametric methods,K and G0 models.In terms of computation speed,a major advantage of the proposed estimation method is the time consuming only depended on the number m of sample points while independent of imagery size,which makes it can achieve a significant speed improvement to the Parzen window kernel method,and in some cases,it is even faster than two parametric methods.In terms of ship detection performance,the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors,resolutions and sea surface homogeneities and obtains a leading performance on the test dataset.

Laser ultrasonic technique for surface defects detection of 6061 aluminum alloy

In order to estimate and detect the surface defect depth of metals, the transmission method of laser ultrasonic surface waves is used in this work. The laser ultrasonic detection platform taking use of thermoelastic mechanism as acoustic signal excitation method and interference receiver as acoustic signal receiver method was built, by which B-scan images of detected specimens with surface defects were collected to establish the relationship between the transmission coefficient and depth of the surface defect. Experimental results show that the amplitude of transmitted acoustic signal is related to the depth of surface defect. At last, a fitted curve of transmission coefficient using measured experimental data is obtained to estimate depth of surface defect on the 6061 aluminum alloy. Furthermore, a surface defect depth of 0.3 mm is estimated by the fitting curve with an estimated error of 16%. Therefore, a experimental method using the transmission method by laser ultrasonic is presented in this paper.

Impact of climate change and human activities on the spatiotemporal dynamics of surface water area in Gansu Province, China

Understanding the dynamics of surface water area and their drivers is crucial for human survival and ecosystem stability in inland arid and semi-arid areas.This study took Gansu Province,China,a typical area with complex terrain and variable climate,as the research subject.Based on Google Earth Engine,we used Landsat data and the Open-surface Water Detection Method with Enhanced Impurity Control method to monitor the spatiotemporal dynamics of surface water area in Gansu Province from 1985 to 2022,and quantitatively analyzed the main causes of regional differences in surface water area.The findings revealed that surface water area in Gansu Province expanded by 406.88 km2 from 1985 to 2022.Seasonal surface water area exhibited significant fluctuations,while permanent surface water area showed a steady increase.Notably,terrestrial water storage exhibited a trend of first decreasing and then increasing,correlated with the dynamics of surface water area.Climate change and human activities jointly affected surface hydrological processes,with the impact of climate change being slightly higher than that of human activities.Spatially,climate change affected the'source'of surface water to a greater extent,while human activities tended to affect the'destination'of surface water.Challenges of surface water resources faced by inland arid and semi-arid areas like Gansu Province are multifaceted.Therefore,we summarized the surface hydrology patterns typical in inland arid and semi-arid areas and tailored surface water'supply-demand'balance strategies.The study not only sheds light on the dynamics of surface water area in Gansu Province,but also offers valuable insights for ecological protection and surface water resource management in inland arid and semi-arid areas facing water scarcity.

Comprehensive Assessment and Analysis of National Surface Meteorological Observation Stations: A Case Study of Hebei Province

With the rapid development of China s economic construction and the rapid advancement of urban-rural integration construction, meteorological detection environment has been damaged repeatedly, which seriously affects the representativeness, accuracy, and comparability of meteorological data, so it is urgent to protect meteorological detection environment. Based on the investigation and evaluation method of detection environment of national ground meteorological observation stations and high-altitude meteorological observation stations, satellite remote sensing data, and climate analysis method, the evaluation method of detection environment and meteorological data was improved to comprehensively assess the detection environment and meteorological data of stations. After the evaluation results were compared with the results of the survey and evaluation in 2013, it is found that the new assessment method maintains the continuity of detection environment assessment and can objectively reflect the changes of the station detection environment. The research on the method and standard for the evaluation of detection environment and data analysis of meteorological stations provides a scientific basis for the establishment of detection environmental protection plans by stations at all levels, and provides technical support for the scientific and rational adjustment of station network by administrative departments at all levels.

Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.

Dark-field detection method of shallow scratches on the super-smooth optical surface based on the technology of adaptive smoothing and morphological differencing

In recent years, modern optical processing technologies, such as single point diamond turning, ion beam etching, and magneto-theological finishing, arc getting break- throughs. Machining precisions of super-smooth optics have also been significantly improved. However, with increasing demands for the optical surface quality,

A sparse representation method for image-based surface defect detection

In this paper, an efficient sparse representation-based method is presented for detecting surface defects. The proposed method uses the sparse degree of coefficient in the redundant dictionary for checking whether the test image is defective or not, and the binary representation of the defective images is obtained, according to the global coefficient feature. Owing to the requirements for the efficiency and detecting quality, the block proximal gradient operator is introduced to speed up the online dictionary learning. Considering the correlation among the testing samples, prior knowledge is applied in the orthogonal-matching-pursuit sparse representation algorithm to improve the speed of sparse coding. Experimental results demonstrate that the proposed detection method can effectively detect and extract the defects of the surface images, and has broad applicability.

提高钢板表面缺陷检出率的分割新方法

文中针对传统图像分割方法难以准确分割钢板表面小目标缺陷的问题,提出了一种基于二维灰度直方图反向投影的缺陷分割新方法。该方法无需手工标注大量缺陷样本,利用图像的二维灰度直方图反向投影,提取小目标缺陷轮廓。当图像不具备明显双峰效应时,排除背景像素的干扰,将缺陷轮廓图像进行形态学处理和二值化,实现目标缺陷与背景像素的准确分割。实验结果表明,所提方法在钢板表面缺陷数据集上分割精确度综合评价指标达到92.45%,优于其他先进检测方法。同时搭建实验平台,结果显示在模拟工程实验中所提方法能够准确分割多种缺陷。

表面增强拉曼光谱法在食品安全检测中的应用研究进展

近年来国内外频发的食品安全事件使得公众对食品安全问题的关注度不断提高,快速、灵敏、可靠地评估食品质量与安全的能力在食品行业中十分重要,因此开发满足食品安全需求的高性能检测技术势在必行。表面增强拉曼光谱(surface-enhanced Raman spectroscopy,SERS)具有高特异性、高灵敏度、无损检测、可实现多重检测等优异性能,在食品安全检测领域得到广泛应用,并取得了令人瞩目的进展。本文介绍了SERS技术的理论基础,总结了增强SERS信号强度的活性基底,综述了基于SERS方法的食品安全检测应用研究进展,讨论了其未来发展趋势与前景,旨在为研究人员根据具体食品安全检测应用需求选择合适的SERS方法提供建议。

一种检测弱磁场的光纤传感器的研究与仿真

提出一种基于表面等离子共振的光子晶体光纤传感器,用于实时检测弱磁场强度变化。光子晶体光纤表面覆盖氮化硅和银薄膜,实现表面等离子共振,传感器外侧的磁流体用于感知磁场变化。针对磁场强度检测,基于折射率性能指标归纳了磁场与传感器性能指标。有限元方法的仿真结果表明,在80 Oe~1000 Oe磁场强度范围内,传感器波长灵敏度可达0.55 nm·Oe^(-1);此外,幅度灵敏度、分辨力、检测限、品质因数和拟合度分别达到了-0.107 Oe^(-1)、1.8×10^(-2)Oe、3.3×10^(-2)Oe~2·nm^(-1)、6.73×10^(-2)Oe^(-1)和0.99117。该传感器具备制作工艺简单、易于制造的特点,可以预见其在磁场检测的广阔前景。

掺氢天然气管道氢损伤管外漏磁检测机构设计

掺氢天然气管道受氢损伤等因素影响,容易产生缺陷进而导致管道失效,因此需要定期对掺氢管道进行检查。通过对掺氢管道的主要缺陷产生机制和缺陷特征进行分析,得到主要的缺陷形式,设计一种针对掺氢管道氢损伤的管外漏磁检测机构对管道进行缺陷检测,利用Maxwell进行漏磁检测仿真模拟,采用响应面法建立检测探头各参数与轴向漏磁曲线峰谷差值、吸附力和成本之间的函数,得到探头的结构参数最优组合。最后搭建实验台,利用单组探头进行单通道的漏磁检测。结果表明:与未优化结构对比,优化后管外缺陷检测效果提高26.2%,管内缺陷检测效果提升11%,探头与管壁吸附力降低56.7%,探头成本降低14%,检测效果得到提升;优化探头不仅能检测到已成型的比较明显的掺氢管道缺陷,也可以在缺陷形成早期管壁损失达到整体壁厚40%时将其检测出来。缺陷检测实验验证了文中设计方案的可行性。

蔗渣纤维乳化沥青吸附机制

为了探索蔗渣纤维与沥青吸附机制的问题,通过BET(Brunauer-Emmet-Teller, BET)比表面积检测法、挂篮吸附实验以及棒状薄层色谱-氢火焰离子探测实验(thin-layer chromatography with flame ionization detection, TLC-FID),研究改性前后蔗渣纤维的孔隙结构特性、改性蔗渣纤维对沥青组分的吸附性能的影响,以及不同改性蔗渣纤维掺量对吸附过程的影响,并结合吸附动力学模型进行理论验证分析吸附机理。实验结果表明:蔗渣纤维具有大孔与狭缝孔结构,改性后蔗渣纤维的表面积略有增加,总孔体积、微孔面积与体积增加幅度较大,分别达到241%、170%和276%;达到吸附平衡后,饱和分质量分数降低5.77%、芳香分质量分数增加20.75%、胶质质量分数降低29.37%,以及沥青质质量分数降低5.66%,说明改性蔗渣纤维最易吸附的沥青组分为胶质;随着改性蔗渣纤维掺量的增加,吸附率从15.25%增加至34.16%,而单位平衡吸附量从4.827减小至2.162;实验采用准一级、准二级吸附动力学模型,其中准二级动力学模型拟合效果更好,模型预测单位平衡吸附量q_e(3.247)更接近实验测得的q_e(3.098);胶质的吸附过程是由外向内的,驱动力不足以及吸附点位的数量影响使得吸附达到平衡。

煤矿采掘面隐患排查治理效果评价研究

基于袁店二井煤矿生产,全面的隐患排查治理对于避免事故发生、提高矿井生产效率和优化矿井安全管理而言有重要的作用。为预防事故发生,消除安全隐患,建立了评价指标体系,利用AHP法确定各级指标的权重,结合煤矿现场实际情况,由三位专家现场打分,利用TOPSIS法构造评价矩阵,计算出影响煤矿采掘面隐患排查治理效果指标的综合得分,得到6个一级指标下影响隐患排查治理效果最显著的6个二级指标,并提出相应的治理效果评价体系,该体系适用于常规煤矿采掘面的隐患排查及治理。

基于传感器感知信息的船舶底面结构变形检测研究

以及时发现船舶底面结构变形,确保船舶在良好状态下运行为目的,研究基于传感器感知信息的船舶底面结构变形检测方法。该方法使用不锈钢封装光纤光栅传感器后,选择8路光纤,在每路光纤上连接若干光纤光栅传感器,然后将8路光纤布设在船舶底面结构上,通过每路光纤上连接的光纤光栅传感器感知船舶底面结构光栅信号,再通过非平衡M-Z干涉法对光纤光栅传感器光栅信号进行解调,得到船舶底面结构应变信息,以其为基础同时结合光纤光栅传感器感知应变状态方程,建立多感知信息融合的变形检测模型,求解该模型后得到船舶底面结构变形检测结果。实验表明:该方法可准确感知船舶底面结构应变信息,且传感器信号零漂波动较小,同时可有效实现船舶底面结构变形检测,应用效果较佳。

地表水污染状态实时监测与污染物特征分布研究

在广东省黄冈河流域,由于亚热带季风气候和大量降雨导致的土壤侵蚀,地表水污染成为一个严重问题。为降低损失,文章实施了实时监测并分析污染物特征分布。首先,对地理、气候、地表水利用及污染现状进行了深入分析;然后,利用地表水微波检测法进行实时监测;最后,基于监测结果,采用单因子指数评价法对地表水污染物特征分布进行了分析。结果表明,文章研究成功实现了实时监测,并展示良好的污染物特征分布分析能力,为地表水污染防治提供有力保障。

拉普拉斯金字塔变换算法的光学元件表面疵病检测

为了解决由于光学元件表面疵病造成光的散射、反射或透射现象,影响光学系统成像质量的问题,设计了基于多光谱技术的光学元件表面疵病检测方法。采集光学元件表面疵病的多光谱图像。采用拉普拉斯金字塔变换算法融合光学元件表面疵病的多光谱图像,利用帧差法对两幅光学元件多光谱图像相减处理,获取光学元件表面疵病的二值图像特征,标记光学元件多光谱图像融合结果的连通区域,利用图像连通区域的长宽比等参数,检测光学元件表面疵病的种类、数量、大小。实验结果表明,该方法有效检测光学元件的麻点、划痕、破点等不同类型的表面疵病,表面疵病尺寸检测精度最高为98.15%。

采煤工作面地下水分布变化的综合物探应用研究

浅埋煤层上覆含水层的分布状态是影响煤层开采的重要因素。针对宁夏某煤矿开采工作面煤层厚度大、埋深浅的特点,开展了高密度电阻率、核磁共振、微动探测的综合物探方法,对煤层上覆含水层的分布状态进行了探测研究。综合探测结果显示:(1)高密度电阻率法可以快速、高效地划分岩层及采空区异常;(2)地面核磁共振法能够对高密度电阻率法划分的异常含水特性进行评价;(3)微动探测方法视横波速度能够很好地识别地层与冒落带、裂隙带发育特征。综合物探反演解释,能够降低单一方法引起的多解性,较准确地辨识浅埋煤层采动中工作面上覆地下水分布状态和地层特征,为探究采煤引起的生态问题提供地球物理依据。

基于空间插值与SVM的地表径流水质多传感器融合检测

在地表径流水质检测中,不同类型传感器数据冗余,导致水质检测结果准确性受限且灵敏度较低,由此设计了基于空间插值与SVM的地表径流水质多传感器融合检测。首先,构建世界坐标系与空间变异函数,分析地表径流空间变异特征,全面获取地表径流的水体样本数据;其次,依据水质分布情况,构造出空间插值的连续数据曲面,缩短数据间隔距离,通过融合连续数据曲面,得到具有空间性、实时性和多源性的准确水质参数数据;然后,构建SVM算法寻找最优超平面,划分高灵敏性分隔水质参数数据,解析相应的水质参数并进行表征,得到地表径流水质多传感器融合检测结果。由实验结果可知,地表径流水质检测结果的综合评价值在0.5以下,检出限结果最高仅为28.6 mg/L,最低能够达到22.2 mg/L。水质检测灵敏度较高,满足了地表径流水质管理工作的现实需求。

多尺度信息融合的船舶外板检测三维标志点识别方法

针对船舶外板开展数字化检测技术研究对提升船舶外板智能制造水平具有重要意义;为解决船舶外板检测参考点坐标获取问题,提出了一种识别三维标志点的方法,可在船舶外板数字化检测过程中为实测点云和模型点云的匹配提供参考坐标信息;该方法针对船舶外板结构特点和形面测量需求,设计三维标志点的几何结构;此外,结合三维标志点自身多种特征和周边结构差异化特征,将标志点多种尺度信息进行融合,实现对标志点的精准识别;最后通过标志点测量数据计算对应船舶外板上定位点的三维坐标;通过试验验证了所提出的方法在三维标志点识别方面具有准确性高、定位精准的优点,将大幅提升船舶外板数字化检测的效率。