高光谱图像光谱域噪声去除的经验模态分解方法

针对高光谱图像存在的光谱域噪声提出了基于经验模态分解的光谱域滤波方法(emp irical mode decomposi-tion based filter(EMDF)).首先基于光谱曲线二阶导数给出了光谱曲线噪声大小的判定,然后用EMDF方法进行逐像元滤波.在容易引入空间域噪声的光谱区间,以基于光谱导数的Savitzky-Golay滤波方法(derivative based savitz-ky-Golay filter(DSGF))进行替代,这样既抑制了空间域噪声的产生,也取得了较好的光谱域滤波效果.

光纤低相干干涉测量法的光谱域处理技术

使用低相干、宽带光源可以让光纤传感器系统获得高分辨率和大动态范围。光谱域处理技术在具有这种特点的光源下应运而生。该技术的特点是除了使用传感干涉仪以外,还必须用第二个处理干涉仪来提取所需的条纹图样信息。使用交叉的梳状谱也是其特点之一。使用这种技术的光纤传感器系统可以实现多种物理量的测量,而且其结构简单、成本低廉。

基于光谱色域最大化的喷墨打印墨量限制方法研究

为了在解决墨量超限问题的同时实现喷墨打印设备色彩再现色域的最大化,提出了一种基于多维非线性插值的墨量限制方法。以四类不同介质的墨水组合为研究对象,以特殊设计的墨量评判样本墨层铺展情况为判断依据,确定最大色域样本集,并利用分光光度计测量获取各样本在380～730nm波段的光谱反射率信息。通过主成分分析法对光谱数据进行降维处理,结合凸包算法,实现设备最大色域的数学建模表达及可视化分析。实验结果表明,本文提出的墨量限制算法,在解决喷墨打印墨量超限问题的同时,其光谱、色度及设备色空间的最大色域覆盖率皆大于95%,说明此方法在高保真色彩复制的墨量限制环节具有较为理想的表现。

加权视觉特性的PCA空间内光谱域映射模型

针对跨媒体光谱颜色复制过程中出现的设备光谱域不一致问题,在加权人眼视觉特性的主成分分析(PCA)光谱降维空间内构建了一种光谱域映射模型。利用标准色度观察者匹配函数构造权重系数,对高维光谱进行加权,采用PCA提取加权光谱的前三个主元,以构造低维加权PCA空间,在加权PCA空间内引入分区最大化色域边界描述算法描述设备光谱域,对超设备光谱域的颜色光谱进行裁切以映射到设备光谱域内。实验证明,新模型相比于常用的PCA空间内的光谱域映射模型而言,更能达到视觉感受的匹配,可以更为有效地解决设备光谱域不一致的问题。

基于点集模型的LabPQR空间光谱色域映射算法

目的针对色度色域映射中出现的同色异谱现象,提出一种基于点集模型的光谱域映射算法。方法以设备采样样本为基础,在LabPQR空间内构造色度色域和PQR色域,以此描述光谱色域;采用分级映射方法,在Lab和PQR等2个子空间内对目标光谱依次判断并进行映射。结果以munsell 1269个色块为检验样本进行试验,结果显示:提出算法色度误差为1.0779,光谱误差为5.12%。结论提出算法能够有效降低同色异谱现象,并拥有较高的光谱输出精度,映射之后的结果能够满足在多种光源下与目标的视觉匹配。

高光谱遥感图像光谱域去噪的小波变换方法

由于小波变换在时、频两域都具有表征信号局部特征的能力,对高光谱波谱维进行小波分解能够同时保留信号高频与低频信息,利于高光谱遥感光谱域噪声的去除。本文采用小波分解与重构法对高光谱遥感光谱域进行去噪,选择Symlet8小波基函数,应用离散小波分解对高光谱图像中提取的反射率光谱曲线进行小波分解,选择分解层数为2,在去除D1和D2高频分量后进行小波重构,得到去噪后的反射率光谱曲线,经去相关法计算的信噪比结果显示,高光谱图像质量得到一定提高。

AOTF高光谱成像系统的标定及性能测试

提出了一套声光可调谐滤光器高光谱成像系统的标定及性能测试方法,并针对研制的高光谱成像系统原理样机进行了实验验证.结果表明:所提方法可以较为完整、准确地验证系统的光谱域及空间域特性;经过光谱图像平场校正可明显改善系统响应的非均匀性;通过自动控制相机曝光时间及像元增益的方式逐波段进行光谱灵敏度校正,可以提高系统的信噪比;采用改变相机曝光时间并测定系统响应的方式验证系统的光谱线性度,较传统方法更为方便,且可有效节约测试成本.该方法同样适用于基于液晶可调谐滤光器等的高光谱成像系统.

基于高光谱影像的SG滤波算法的研究

高光谱遥感是当前遥感技术发展前沿,已经被成功应用于农业、水利、交通等许多领域.高光谱遥感影像中不仅存在空间域噪声而且存在光谱域噪声,传统的图像滤波只能对图像空间域噪声进行处理,而不能去除光谱域噪声.为了改变这种状况,本文提出了一种Savitzky-Golay(SG)滤波改进算法,诊断光谱域噪声.本文主要以航空高光谱遥感数据为研究对象,基于最小二乘的SG滤波求取反射率光谱的二阶导数,然后对影像进行噪声去除,该方法在保证有效去除光谱域噪声的同时,保留高光谱图像的大部分的细微特征.与其他不同的光谱域噪声滤波方法进行对比,实验证明本文的滤波方法是一种较为有效的手段.

地塞米松玻璃体内植入剂在特发性黄斑前膜玻璃体手术中的应用

目的比较特发性黄斑前膜患者玻璃体手术联合与不联合玻璃体腔地塞米松玻璃体内植入剂注药术后视网膜黄斑区超微结构与视功能变化。方法收集2019年1月至2022年12月接受手术治疗的特发性黄斑前膜患者94例(94只眼)。按术毕时是否联合玻璃体腔内注射地塞米松玻璃体内植入剂将患者分为注药组59例(59只眼)和对照组35例(35只眼)。2组患者行玻璃体切除术剥除黄斑前膜及内界膜,术后随访>12个月。观察2组患者手术前后最佳矫正视力(BCVA)、黄斑中心凹厚度、异常中心凹内层厚度的变化情况。结果患者术前及术后1、3、6、12个月最佳矫正视力(LogMAR)分别为0.71±0.14、0.62±0.15、0.51±0.16、0.48±0.29、0.36±0.20,注药组和对照组术后最佳矫正视力LogMAR视力均较术前明显提高(Waldχ^(2)=3428.83,P<0.001;Waldχ^(2)=445.67,P<0.001)。在术后3、6、12个月,2组间最佳矫正视力差异有统计学意义(Waldχ^(2)=8.31,P=0.004;Waldχ^(2)=11.31,P=0.001;Waldχ^(2)=22.54,P<0.001)。黄斑中心凹视网膜厚度分别为(472.64±69.69)、(423.68±83.56)、(380.08±104.98)、(319.55±95.83)、(294.55±104.88)μm,差异有统计学意义(Waldχ^(2)=1322.92,P<0.001)。在术后3、6、12个月,2组间黄斑中心凹厚度差异有统计学意义(Waldχ^(2)=12.47,P<0.001;Waldχ^(2)=21.15,P<0.001;Waldχ^(2)=28.88,P<0.001)。异常中心凹内层厚度分别为(189.87±38.22)、(164.05±40.17)、(142.08±47.80)、(112.51±52.87)、(91.49±53.25)μm,差异有统计学意义(Waldχ^(2)=969.82,P<0.001)。在术后3、6、12个月,2组间异常中心凹内层厚度差异有统计学意义(Waldχ^(2)=11.25,P=0.001;Waldχ^(2)=15.93,P<0.001;Waldχ^(2)=11.98,P=0.001)。结论特发性黄斑前膜患者术毕时玻璃体腔注射地塞米松玻璃体内植入剂可以辅助于黄斑超微结构和视功能的恢复。

Electronic structure and ultraviolet spectra of p-C_(6)H_(4)-C_(20)

Geometry optimization of p-C_(6)H_(4)-connected cyclo[20]carbon(p-C_(6)H_(4)-C_(20))was carried out at M062X/6-311G(d,p)level,three kinds of bond orders(Mayer,Laplacian,and Wiberg),electron-hole distributions,localized orbital locators(LOL),and infrared(IR)spectrum were also performed at the same level.Based on TD-DFT M062X/6-311G(d,p)method,the first 20 excited states and ultraviolet(UV)spectra of p-C_(6)H_(4)-C_(20) were calculated.Calculation results of π-electron delocalization analyses prove thatπ-electron delocalization of p-C_(6)H_(4)-C_(20) is more likely to occur on shorter C-C bonds rather than longer C-C bonds,and inside/outside of the ring plane rather than above/below the ring plane.Two absorption peaks of p-C_(6)H_(4)-C_(20) locate at about 319 nm and 236 nm,respectively.

眼前节OCT在闭合性眼外伤患者中的应用（英文）

目的:比较光谱域光学相干断层扫描(SD-OCT)和裂隙灯生物显微镜对闭合性眼球损伤患者眼前节病变的检测能力。方法:这是一项观察性横断面研究。2010-01/2015-07,在惠州市中心人民医院连续招募了16名闭合性眼球损伤患者。所有患者均行完整的眼科检查,包括视力评估、非接触眼压测量和裂隙灯生物显微镜检查。采用SD-OCT检查所有损伤眼的前段。两名患者双侧眼外伤,接受双侧SD-OCT检查。记录角膜、虹膜、前房和晶状体的OCT表现,并与裂隙灯生物显微镜检查结果进行比较。结果:所纳入的18眼均合并前房积血,且前房积血至少占前房容积的三分之一。16眼在裂隙灯生物显微镜和OCT检查中发现角膜水肿和角膜上皮损伤。OCT检查检出Descemet膜脱离(n=7),房角退缩(n=6),晶状体半脱位(n=3)和虹膜根部离断(n=3)。结论:SD-OCT能鉴别闭式眼球损伤的特征,而在裂隙灯生物显微镜下则看不到这些特征。在闭合性眼球损伤中,SD-OCT可能优于临床检查。

Determination of 2 Amides Pesticide Residues in Agricultural Products by Terahertz Time-domain Spectroscopy

[Objective] The aim was to explore the application of terahertz （THz） technique in pesticide recognition and residue determination. [Method] THz far-infrared spectral characteristics of 2 herbicides （butachlor and metolachlor） were measured by THz time-domain spectroscopy （THz-TDS） under conditions of room temperature and nitrogen,meanwhile their refractive index and absorption coefficient between 0.2 and 2.2 THz were calculated by using models based on Fresenl equations. [Result] The 2 pesticides both had a series of different characteristic absorption peaks between 0.2 and 2.2 THz,respectively. Their molecular structures were similar,but there were great difference in absorption and refractive index spectrum between them. [Conclusion] THz-TDS technique is feasible to detect pesticide residues,especially there is a greater advantage in identifying the structure of similar substances.

Experimental measurements of water content in crude oil emulsions by terahertz time-domain spectroscopy

We measured the water content （0.01% 0.25% w/w） in crude oil emulsions using terahertz time-domain spectroscopy （THz-TDS）. To improve the precision and range of the measurements, we used 1 and 10 mm thick quartz cells. The experiments were performed at 20 ℃ and the THz wave was transmitted vertically to the samples and detected on the other side. The experimental results suggest linear relation for the THz absorption coefficient and the water content of the crude oil emulsions in the observed range. The linear dependence facilitates high-precision measurements of the water content of crude oil. This suggests the potential of THz-TDS in determining the water concentration in crude oil and borehole fluid identification.

Terahertz spectrum clustering of traditional Chinese medicine based on first derivative characteristics

In order to deal with the unclear absorption peak caused by the absorption peak overlap of traditional Chinese medicine(TCM)and other mixtures,a method of three unsupervised clustering algorithms as K-means,K-medoids and Fuzzy C-means(FCM)combined with the first derivative characteristics of terahertz absorption spectrum,is proposed to perform the terahertz spectra clustering of Sanchi and other three kinds of TCM compared with their easily-confused products(ECPs).These three unsupervised clustering methods complement the scope of the supervised learning classification method.The first derivative of the spectrum could amplify the difference in the absorption coefficient with different substances,so that the obvious absorption peak can be revealed.Experiments shows that these three clustering algorithms can achieve good results by combining the origin absorption coefficient with its first-order derivative as the characteristic data,and among which K-means does the best with the accuracy of95.32%.Compared with pure absorption coefficient data clustering,the accuracy in this study has been significantly improved,especially for the non-absorption-peak TCM classification.And the accuracy of K-means algorithm is improved by5.38%.Besides,clustering algorithms in this study have strong anti-interference ability to the error data.

Tourism sectorization opportunity spectrum model and space partition of tourism urbanization area:a case of the Mayangxi ecotourism area,Fujian province,China

Nowadays, tourism has become an increasingly significant driving force of modern urbanization in China. However, it has caused varieties of problems, such as resource unreasonable utilization, society unfair play, and environment pollution, etc. Thus, the establishment of an efficient and sustainable space partition model for tourism urbanization, from the geographical perspective, is highly necessary and urgent. Herein, a new evaluation model of tourist town space, referred to as Tourism Sectorization Opportunity Spectrum(TSOS), is established on the relationships between productionliving-ecology spaces. TSOS is a kind of quantitative evaluation model involving such factors as urban living area, ecological conservation area and the tourism industry. Furthermore, the analysis of quantitative production-living-ecology spatial overlap has been utilized for space division in a tourism urbanization area. This paper, using both the TSOS model and GIS technology, analyzes the spatial restructure of the Mayangxi ecotourism area. Theresult demonstrates that tourism industrial space takes the Shanchong Village as a core which shows a pattern of local regional agglomeration and a fuzzy edge extending along the entire Mayangxi River. The urban living area should be consolidated in the Shili village with the supporting facilities and living space for tourism. In addition, Tianzhu Mountain forest park should be the key environmental protection area. The case study on the Mayangxi ecotourism area verifies that the TSOS model has strong operability. Therefore, TSOS model provides a scientific foundation for the space reconstruction of new urbanization area, and an effective tool for optimizing the space partition of a tourism urbanization area.

REGIONAL FEATURES OF LONG-TERM SST VARIATION IN THE WESTERN PACIFIC WARM POOL AREA

The main features of SST interannual and long term variations in the Western Pacific Warm Pool area were studied by using regression analysis, running t test and spectral analysis methods based on monthly mean SST data in the Pacific during 1950-1998. The results showed that the SST inter annual and long term variations in the Western Pacific Warm Pool area had evident regional features. There were significant differences in variation range, phase, period, occurrence time of abrupt variation between SST in the eastern area (east of 160°E) and SST in the western area (west of 160°E).

Evaluation of Spectral Scale Effects in Estimation of Vegetation Leaf Area Index Using Spectral Indices Methods

Spectral index methodology has been widely used in Leaf Area Index(LAI) retrieval at different spatial scales. There are differences in the spectral response of different remote sensors and thus spectral scale effect generated during the use of spectral indices to retrieve LAI. In this study, PROSPECT, leaf optical properties model and Scattering by Arbitrarily Inclined Layers(SAIL) model, were used to simulate canopy spectral reflectance with a bandwidth of 5 nm and a Gaussian spectral response function was employed to simulate the spectral data at six bandwidths ranging from 10 to 35 nm. Additionally, for bandwidths from 5 to 35 nm, the correlation between the spectral index and LAI, and the sensitivities of the spectral index to changes in LAI and bandwidth were analyzed. Finally, the reflectance data at six bandwidths ranging from 40 to 65 nm were used to verify the spectral scale effect generated during the use of the spectral index to retrieve LAI. Results indicate that Vegetation Index of the Universal Pattern Decomposition(VIUPD) had the highest accuracy during LAI retrieval. Followed by Normalized Difference Vegetation Index(NDVI), Modified Simple Ratio Indices(MSRI) and Triangle Vegetation Index(TVI), although the coefficient of determination R^2 was higher than 0.96, the retrieved LAI values were less than the actual value and thus lacked validity. Other spectral indices were significantly affected by the spectral scale effect with poor retrieval results. In this study, VIUPD, which exhibited a relatively good correlation and sensitivity to LAI, was less affected by the spectral scale effect and had a relatively good retrieval capability. This conclusion supports a purported feature independent of the sensor of this model and also confirms the great potential of VIUPD for retrieval of physicochemical parameters of vegetation using multi-source remote sensing data.

Multi-domain High-Resolution Platform for Integrated Spectroscopy and Microscopy Characterizations

In recent decades,materials science has experienced rapid development and posed increasingly high requirements for the characterizations of structures,properties,and performances.Herein,we report on our recent establishment of a multi-domain(energy,space,time)highresolution platform for integrated spectroscopy and microscopy characterizations,offering an unprecedented way to analyze materials in terms of spectral(energy)and spatial mapping as well as temporal evolution.We present several proof-of-principle results collected on this platform,including in-situ Raman imaging(high-resolution Raman,polarization Raman,low-wavenumber Raman),time-resolved photoluminescence imaging,and photoelectrical performance imaging.It can be envisioned that our newly established platform would be very powerful and effective in the multi-domain high-resolution characterizations of various materials of photoelectrochemical importance in the near future.

Spectral Domain Optical Coherence Tomography of Vogt-Koyanagi-Harada Disease: Novel Findings and New Insights into the Pathogenesis

Objective To provide novel spectral domain optical coherence tomography (SD OCT) findings of Vogt-Koyanagi-Harada (VKH) disease as well as new insights into the pathogenesis of this disease. Methods Detailed SD OCT and fluorescein angiography (FA) findings of 18 consecutive VKH patients (11 women and 7 men) from December 2007 to April 2009 who were in acute uveitic stage at presentation were reviewed. All the patients had been followed up for at least 6 months with reevaluation(s) of SD OCT performed in 10 patients. Results Intraretinal cysts were found to be located in various layers of the outer retina. In addition to the photoreceptor layer, they could also be found between the outer plexiform layer and the outer nuclear layer, or spanning the external limiting membrane. On FA, intraretinal cysts could be hypofluorescent, normofluorescent, or hyperfluorescent. Some intraretinal cysts had a characteristic FA pattern, in which a small round hypofluorescent area was surrounded by a ring of hyperfluorescence (donut-shaped dye pooling). Subretinal fibrinoid deposit appeared in acute uveitic stage in two severe VKH patients and seemed to develop from subretinal exudates and evolved into typical subretinal fibrosis. Gradual transfiguration/migration and progressive proliferation/pigmentation of the subretinal fibrinoid deposit/subretinal fibrosis was observed in one patient. Conclusions Intraretinal cysts could form in various layers of the outer retina and may result from extension of choroidal inflammation. Subretinal fibrosis may develop from subretinal exudates in VKH patients and may cause substantial visual impairment.

Parallel Spectral-Domain Optical Coherence Tomography for Non-Scattering Object Imaging

The parallel spectral-domain optical coherence tomography（PSDOCT） is described for highspeed optical coherence tomography（OCT） without lateral scanning. In this setup, the self-elimination of auto-correlation（AC） interference algorithm was used for eradicating the AC interference and ghost images. However, when performed in free space OCT, this algorithm still generated a weak DC component. The algorithm was improved by adding the background intensity part to compensate for the mutual interference between object and reference arms. The results demonstrate that the DC component can be eradicated. Compared with conventional QCT and complex Fourier-domain optical coherence to- mography, the advantages of PSDOCT with the improved algorithm in free space are that it has no moving parts to generate consecutive phase shift, the structure of the object can be reconstructed immediately and automatically, and the speed is approximately 16 times faster than those of the other two in the same case.