Standard reference material 2036 near-infrared reflection wavelength standard

Standard Reference Material 2036 (SRM 2036) is a certified transfer standard intended for the verification and calibration of the wavelength/wavenumber scale of near-infrared (NIR) spectrometers operating in diffuse or trans-reflectance mode. SRM 2036 Near-Infrared Wavelength/Wavenumber Reflection Standard is a combination of a rare earth oxide glass of a composition similar to that of SRM 2035 Near-Infrared Transmission Wavelength/Wavenumber Standard and SRM 2065 Ultraviolet-Visible-Near-Infrared Transmission Wavelength/Wavenumber Standard, but is in physical contact with a piece of sintered poly(tetrafluoroethylene) (PTFE). The combination of glass contacted with a nearly ideal diffusely reflecting backing provides reflection-absorption bands that range from 15% R to 40% R. SRM 2036 is certified for the 10% band fraction air wavelength centroid location, (10%)B, of seven bands spanning the spectral region from 975 nm to 1946 nm. It is also certified for the vacuum wavenumber (10%)B of the same seven bands in the spectral region from 10 300 cm(-1) to 5130 cm(-1) at 8 cm(-1) resolution. Informational values are provided for the locations of thirteen additional bands from 334 nm to 804 nm.     

Two-color mixing for classifying agricultural products for safety and quality

We show that the chromaticness of the visual signal that results from the two-color mixing achieved through an optically enhanced binocular device is directly related to the band ratio of light intensity at the two selected wavebands. A technique that implements the band-ratio criterion in a visual device by using two-color mixing is presented here. The device will allow inspectors to identify targets visually in accordance with a two-wavelength band ratio. It is a method of inspection by human vision assisted by an optical device, which offers greater flexibility and better cost savings than a multispectral machine vision system that implements the band-ratio criterion. With proper selection of the two narrow wavebands, discrimination by chromaticness that is directly related to the band ratio can work well. An example application of this technique for the inspection of carcasses chickens of afficted with various diseases is given. An optimal pair of wavelengths of 454 and 578 nm was selected to optimize differences in saturation and hue in CIE LUV color space among different types of target. Another example application, for the detection of chilling injury in cucumbers, is given, here the selected wavelength pair was 504 and 652 nm. The novel two-color mixing technique for visual inspection can be included in visual devices for various applications, ranging from target detection to food safety inspection.     

Laser-induced fluorescence ratios of Cajanus cajan L. under the stress of cadmium and its correlation with pigment content and pigment ratios

Laser-induced fluorescence spectra were used to characterize the effect of cadmium on the pigment status of the leaves of Cajanus cajan L. Laser-induced fluorescence spectra of untreated as well as cadmium treated (0.01 mM, 0.10 mM, and 1.00 mM) Cajanus cajan L. were recorded using the 355 nm line of a Nd:YAG laser as the excitation source and a monochromator with an intensified charge-coupled device as a detector in the region 400-800 nm. The fluorescence intensity ratios (FIR) of control as well as treated Cajanus cajan L. have been calculated by evaluating curve fitted parameters using a Gaussian spectral function. In addition, some growth parameters, such as photosynthetic pigment content, were also measured. The 355 nm line of the laser-light-excited leaves not only showed a fluorescence emission in the red spectral region (650-800 nm), but also in the blue-green region (400-570 nm). The chlorophyll FIR F690/F740 strongly correlated with the photosynthetic pigment content (total chlorophyll and carotenoids) and its ratio. Consequently, a correlation was also seen between the ratio of the blue-green fluorescence F470/F540 and the photosynthetic pigment content. The results indicated that the plants treated with 0.01 mM of cadmium exhibited better growth, while higher concentrations of cadmium were hazardous for Cajanus cajan L.     

Measurements of cavity ringdown spectroscopy of acetone in the ultraviolet and near-infrared spectral regions: potential for development of a breath analyzer

We report a study on the cavity ringdown spectroscopy of acetone in both the ultraviolet (UV) and the near-infrared (NIR) spectral regions to explore the potential for development of a breath analyzer for disease diagnostics. The ringdown spectrum of acetone in the UV (282.4-285.0 nm) region is recorded and the spectrum is in good agreement with those obtained by other spectral techniques reported in the literature. The absorption cross-section of the C-H stretching overtone of acetone in the NIR (1632.7-1672.2 nm) is reported for the first time and the maximum absorption cross-section located at 1666.7 nm is 1.2 x 10(-21) cm(2). A novel, compact, atmospheric cavity with a cavity length of 10 cm has been constructed and implemented to investigate the technical feasibility of the potential instrument size, optical configuration, and detection sensitivity. The detection limit of such a mini cavity employing ringdown mirrors of reflectivity of 99.85% at 266 nm, where acetone has the strongest absorption, is approximately 1.5 ppmv based on the standard 3 criteria. No real breath gas samples are used in the present study. Discussions on the detection sensitivity and background spectral interferences for the instrument development are presented. This study demonstrates the potential of developing a portable, sensitive breath analyzer for medical applications using the cavity ringdown spectral technique.     

间歇升温处理对苹果贮藏品质的影响

目的研究苹果在长期低温贮藏期内容易发生冷害和品质下降等问题。方法以“红富士”苹果为实验材料,该品种最适宜的贮藏温度为−1~0℃,设定此试验在−1℃贮藏环境下对苹果进行间歇升温处理,探究此方法对苹果贮藏期间品质的影响。设置对照组CK(−1℃)恒温贮藏,3组间歇升温处理T1(5℃)、T2(10℃)、T3(20℃)在−1℃贮藏条件下每隔30 d重复升温24 h后再转回−1℃下继续贮藏,通过指标测定研究其贮藏期间品质的变化规律。结果苹果长期低温贮藏会产生冷害现象,贮藏结束时T2处理组冷害指数仅为0.14,明显低于CK组,果实仍具有良好的货架品质。质量损失率、硬度、色差L*及饱和度C值改变量均为最小,有效抑制了多酚氧化酶(PPO)活性,丙二醛(MDA)含量变化比CK组低0.191 nmol/g。结论综合比较间歇升温对苹果贮藏期间规避冷害、保持品质的效果大小依次为T2>T1>CK>T3,表明间歇式升温10℃时效果最佳。间歇升温处理可以起到规避冷害的作用,有利于“红富士”苹果的长期贮藏保鲜。     

A Self-consistent Calculation and an Anisotropic Wavelength Cutoff Energy of Spin-wave Spectrum in Magnetic Tunnel Junctions

Temperature dependence of tunnel magnetoresistance (TMR) ratio, resistance, and coercivity from 4.2 K to room temperature (RT), applied de bias voltage dependence of the TMR ratio and resistances at 4.2 K and RT, tunnel current I and dynamic conductance dI/dV as functions of the de bias voltage at 4.2 K, and inelastic electron tunneling (IET) spectroscopy, d(2)I/dV(2) versus V, at 4.2 K for a tunnel junction of Ta(5 nm)/Ni79Fe21(25 nm)/Ir22Mn78(12 nm)/Co75Fe25(4 nm)/Al(0.8 nm)-oxide/Co75Fe25(4 nm)/Ni79Fe21(25 nm)/Ta(5 nm) were systematically investigated. High TMR ratio of 59.2% at 4.2 K and 41.3% at RT were observed for this junction after annealing at 275℃ for an hour. The temperature dependence of TMR ratio and resistances from 4.2 to 300 K at 1.0 mV bias and the de bias voltage dependence of TMR ratio at 4.2 K from 0 to 80 mV can be evaluated by a comparison of self-consistent calculations with the experimental data based on the magnon-assisted inelastic excitation model and theory. An anisotropic wavelength cutoff energy of spin-wave spectrum in magnetic tunnel junctions (MTJs) was suggested, which is necessary for self-consistent calculations, based on a series of IET spectra observed in the MTJs.     

Stokes shift spectroscopy pilot study for cancerous and normal prostate tissues

Stokes shift spectroscopy (S3) is an emerging approach toward cancer detection. The goal of this paper is to evaluate the diagnostic potential of the S3 technique for the detection and characterization of normal and cancerous prostate tissues. Pairs of cancerous and normal prostate tissue samples were taken from each of eight patients. Stokes shift spectra were measured by simultaneously scanning both the excitation and emission wavelengths while keeping a fixed wavelength interval Δλ=20 nm between them. The salient features of this technique are the highly resolved emission peaks and significant spectral differences between the normal and cancerous prostate tissues, as observed in the wavelength region of 250 to 600 nm. The Stokes shift spectra of cancerous and normal prostate tissues revealed distinct peaks around 300, 345, 440, and 510 nm, which are attributed to tryptophan, collagen, NADH, and flavin, respectively. To quantify the spectral differences between the normal and cancerous prostate tissues, two spectral ratios were computed. The findings revealed that both ratio parameters R1=I297/I345 and R2=I307/I345 were excellent diagnostic ratio parameters giving 100% specificity and 100% sensitivity for distinguishing cancerous tissue from the normal tissue. Our results demonstrate that S3 is a sensitive and specific technique for detecting cancerous prostate tissue.     

Optical properties of hot-pressed B4C in the extreme ultraviolet

Hot-pressed B(4)C is found to have a high normal reflectance in the extreme-UV spectral region above 49 nm. This reflectance is comparable with or higher than chemical-vapor-deposited SiC in the spectral region from 49 to 92 nm. Reflectance measurements as a function of the angle of incidence yielded the optical constants of B(4)C in the spectral range 49-121.6 nm.     

猕猴桃挤压损伤高光谱快速检测研究

目的 探究猕猴桃挤压损伤较优的快速无损判别方法。方法 利用高光谱成像系统获得所有猕猴桃的高光谱图像,并提取猕猴桃损伤区域以及完好无损区域的光谱反射率;运用多元散射校正方法对原始反射光谱进行预处理,并运用主成分分析对光谱数据降维;比较并分析Fisher判别分析方法以及简化的K最近邻(Simplified K Nearest Neighbor,SKNN)模式识别方法对猕猴桃挤压损伤的判别效果。结果 在710~850 nm和960~1 030 nm这2个波段内,猕猴桃损伤区域的平均光谱反射率与完好无损区域的平均光谱反射率存在较明显差异;采用主成分分析从256个全波段中筛选了前5个主成分作为新变量,识别模型的检测效率得到了提升;构建的SKNN和Fisher模型对预测集中样本的正确识别率均为93.3%,从SKNN识别模型的混淆矩阵中得出,预测集中仅有2个样本出现误判,并且SKNN模型对校正集中样本的正确识别率高于Fisher模型。结论 在判别猕猴桃挤压损伤时,SKNN识别模型具有相对较好的判别效果。     

干混工艺对PVC搪塑制品中纳米颗粒分布和性能的影响

通过增加室温混合阶段并优化关键工艺参数的方式改进了聚氯乙烯(PVC)搪塑粉料的传统混料工艺,针对粒径60~80nm的活性CaCO_3和粒径100~120nm的金红石型钛白粉等纳米颗粒,对比研究了新混料工艺和传统混料工艺对无机纳米颗粒均匀分散的影响,并定量分析了在室温混合阶段的不同工艺参数下PVC搪塑粉料的流动性和搪塑制品的力学性能及热稳定性。结果表明:优化后的干混工艺不仅有效提高了搪塑表皮中纳米颗粒分散均匀性和搪塑粉料的流动性,而且明显改善了搪塑表皮的断裂伸长率、热稳定性和耐热挥发损失性。     

Spectral reflectance of silicon photodiodes

A precision spectrometer was used to measure the spectral reflectance of a silicon photodiode over the wavelength range from 250 to 850 nm. The results were compared with the corresponding values predicted by a model based on thin-film Fresnel formulas and the known refractive indices of silicon and silicon dioxide. The good agreement at the level of 2 x 10(-3) in the visible wavelength range verifies that the reflection model can be used for accurate extrapolation of the spectral reflectance and responsivity of silicon photodiode devices. In addition, characterization of the photodiode reflectance in the ultraviolet region improves the accuracy of the spectral irradiance measurements when filter radiometers based on trap detectors are used.     

Remote-sensing technique for determination of the volume absorption coefficient of turbid water

We use remote-sensing reflectance from particulate R(rs) to determine the volume absorption coefficient a of turbid water in the 400 < lambda < 700-nm spectral region. The calculated and measured values of a(lambda) show good agreement for 0.5 < a < 10 (m(-1)). To determine R(rs) from a particulate, we needed to make corrections for remote-sensing reflectance owing to surface roughness S(rs). We determined the average spectral distribution of S(rs) from the difference in total remote-sensing reflectance measured with and without polarization. The spectral shape of S(rs) showed an excellent fit to theoretical formulas for glare based on Rayleigh and aerosol scattering from the atmosphere.     

Ultraviolet Spectral Irradiance Scale Comparison: 210 nm to 300 nm

Comparison of the irradiances from a number of ultraviolet spectral irradiance standards, based on different physical principles, showed agreement to within their combined standard uncertainties as assigned to them by NIST. The wavelength region of the spectral irradiance comparison was from 210 nm to 300 nm. The spectral irradiance sources were: an electron storage ring, 1000 W quartz-halogen lamps, deuterium arc lamps, and a windowless argon miniarc.     

Two-dimensional infrared spectroscopy and principal component analysis studies on a new azobenzene derivative supramolecular system based on hydrogen bonds

Infrared (IR) spectra of a supramolecular assembly with an azobenzene derivative and intermolecular hydrogen bonds have been measured in the temperature range from 30 to 200 degrees C to investigate heat-induced structural changes and thermal stability. Principal component analysis (PCA) and two kinds of two-dimensional (2D) correlation spectroscopy, variable-variable (VV) 2D and sample-sample (SS) 2D spectroscopy, have been employed to analyze the observed temperature-dependent spectral variations. The PCA and SS 2D correlation analyses have demonstrated that the complete decoupling of hydrogen bonds in the supramolecular assembly occurs between 110 and 115 degrees C, which is in good agreement with the results of a differential scanning calorimetry (DSC) study for the heating process. The PCA of the IR spectra in the region of 3600-3100 cm(-1) has illustrated that there are at least four principal components for the different NH2 and CONH species in the present supramolecular system. The VV 2D correlation spectroscopy study has provided information about the structure and strength of hydrogen bonds of NH2 and CONH groups and their temperature-dependent variations. The different species of hydrogen-bonded NH2 and CONH groups in the supramolecular system can be clarified by the VV 2D correlation analysis. The VV 2D correlation analysis has also revealed the specific order of the temperature-induced changes in the hydrogen bonds of NH2 and CONH groups.     

Frequency-modulation spectroscopy with blue diode lasers

Frequency-modulation spectroscopy provides ultrasensitive absorption measurements. The technique is especially adaptable to diode lasers, which can be modulated easily, and has been used extensively in the near-infrared and infrared spectral regions. The availability of blue diode lasers now means that the accessible wavelength region can be increased. We successfully demonstrate wavelength-modulation spectroscopy and two-tone frequency-modulation spectroscopy for the weak second resonance line of potassium at 404.8 nm and for the transition at 405.8 nm in lead, starting from the thermally populated 6(p)(2 3)P(2) metastable level. Information on the modulation parameters is obtained with a fitting procedure. Experimental signal-to-noise ratios at different absorption levels are compared with theoretical signal-to-noise ratios and show good agreement. Detection sensitivities of 2 x 10(-6) and 5 x 10(-6) for wavelength and two-tone frequency-modulation spectroscopy, respectively, for a 120-Hz bandwidth are demonstrated.     

Accurate retrieval of region of interest for estimating point spread function and image deblurring

Extraction of an optimal region of interest (ROI) is crucial in many image processing applications, such as estimation of the point spread function (PSF) and blind deconvolution (BD). Although the amount of publications on PSF and BD is quite extensive; however, the work on ROI estimation has not received much attention. Existing methods which used heuristic models are not only time-consuming but also computationally expensive. In this paper, we proposed a new ROI retrieval scheme based on image partitioning and entropy measurement feedback. This method has low computation cost since it contains no matrix operations. Comprehensive experiments on real and synthetic datasets revealed that the proposed method is competitive when compared with existing search techniques, averaging at 26.1?dB, 0.46 and 1.44 on peak signal-to-noise ratio, universal image quality index and error ratio scales, respectively. On average, the proposed method takes less than 10?s to retrieve the ROI which is significantly faster compared to established solution.     

镶嵌在SiO2薄膜中的锗纳米晶粒的光致发光

采用６３０ｎｍ波长的激发光在室温下对镶嵌有锗纳米晶的ＳｉＯ２薄膜进行了光致姚研究。在室温下观察到了由于双光子吸收而导致的蓝色荧光峰。按照量子限域理论对所观察到的峰的特征进行了讨论。     

Wavelengths of spectral lines in mercury pencil lamps

The wavelengths of 19 spectral lines in the region 253-579 nm emitted by Hg pencil-type lamps were measured by Fourier-transform spectroscopy. Precise calibration of the spectra was obtained with wavelengths of (198)Hg as external standards. Our recommended values should be useful aswavelength-calibration standards for moderate-resolution spectrometers at an uncertainty level of 0.0001 nm.     

基于高光谱技术的花椰菜农药残留检测

目的 为了快速、无损地检测花椰菜上的农药残留,采用高光谱成像技术分别对花椰菜上是否含有苏云金杆菌、高效氯氰菊酯和虫螨茚虫威等3种农药进行无损检测研究,并且跟踪研究检测效果最好的农药安全间隔期。方法 对含有农药和不含农药的花椰菜样本进行高光谱成像处理,提取感兴趣区域的光谱数据。剔除前后20个波段的原始光谱数据,以降低噪声的影响,针对剩余216个波段(950~1 666 nm)的数据分别采用卷积平滑(S–G)、多元散射校正(MSC)和变量标准化(SNV)等3种算法对光谱数据进行优化。为了提高判别运行速率,采用竞争性自适应重加权算法(CARS)提取3种农药光谱数据的特征波长,并建立偏最小二乘法(PLS)判别模型。结果 基于SNV优化后的PLS模型对花椰菜上3种农药的识别准确率相对最高,其中虫螨茚虫威农药样本的测试效果相对最好,识别率为100%,随后对该农药进行了连续7 d的检测,其结果符合农药的消散规律。结论 将高光谱图像技术应用于花椰菜的农药残留检测具有很好的应用前景。     

基于独立成分分析的掌纹识别

本文研究了独立成分分析(ICA)两种不同的结构ICA I和ICAII在掌纹识别中的应用.为了提高识别准确性和可靠性,该方法首先对掌纹图像进行预处理,提取掌纹感兴趣(ROI)区域进行特征提取和匹配.为了减少计算量,运用ICA算法之前,先采用主成分分析(PCA)算法去除掌纹图像的二阶统计特征相关性,其余的高阶统计特征由ICA分离.对于PolyU掌纹图像库,基于ICA模型的预测误差平方和(SPE)小于PCA,而且重构的原始图像优于PCA.为了比较两种算法识别性能,本丈分别用PCA、ICA I、ICAII提取特征掌纹子空间,然后将待识别图像投影到低维子空间上,最后用余弦距离进行掌纹匹配.实验结果表明,ICA算法两种结构的识别率均高于PCA,ICAII在性能上优于ICA I.