近红外光谱法快速分析葛根中的有效成分

本文应用近红外光谱技术建立了快速检测葛根中有效成分的方法。研究了优化分析葛根总异黄酮、葛根素和大豆苷含量数学模型的各种条件，包括建模样品集的选择、化学值的定标、测量的方法及条件等，结果表明：建模样品集的化学值（又称真值）与近红外预测值的相关系数分别为：葛根总异黄酮r=0.975，葛根素r=0.984，大豆苷r=0.966；检验样品集的化学值与近红外预测值的相关系数分别为：0.982,0.975和0．981。说明所建模型具有实际应用价值。     

棉籽油分含量近红外无损检测分析模型与应用

棉花是一种重要的油料作物。建立快速、无损检测棉花种子含油量的方法,对于棉花油分育种工作中的材料鉴定、筛选具有重要意义。利用近红外光谱仪采集118份不同油分含量棉花种籽的近红外漫反射光谱,结合化学方法测定验证,建立了棉籽油分含量快速无损检测的近红外模型。光谱预处理方法采用一阶导数＋多元散射校正(MSC),光谱范围5 446～8 848 cm-1,主成分维数为5,以基本覆盖陆地棉棉籽含油量范围的106份试验材料为校正样品集,利用偏最小二乘法(PLS)建立了棉籽仁油分含量近红外反射光谱(NIR)校正模型。校正模型决定系数R2=0.975,校正标准差SEC=0.67。用外部验证样品集进行外部验证,对所建模型的实际预测能力进行检验。结果表明,油分含量预测值与化学值相关系数r=0.978,预测结果误差范围0.1%～1.7%,建立的模型具有很好的预测性。利用建立的模型对784份育种材料进行了油分含量预测,结果显示,该模型应用可以加快棉花育种材料的油分鉴定。     

土壤金属元素近红外光谱定量校正模型适应性初步研究

为研究土壤金属元素近红外光谱定量校正模型适应性,采用近红外光谱结合偏最小二乘算法,针对风干土壤中的K,As,Hg,Cu,Zn,Pb,Cr,Cd元素,在剔除异常值后,建立定量校正模型;并对风干、烘干处理的外部验证集样品分别预测上述元素含量。结果表明,风干外部验证集样品的预测值-参考值相关系数皆大于相应烘干外部验证集样品的预测值-参考值相关系数;风干外部验证集各元素的预测值-参考值均具有显著的相关关系,烘干外部验证集中K,Hg,Cr的预测值-参考值之间不具有显著的相关关系。对土壤金属元素近红外光谱定量校正模型的适应性进行了初步研究,可为土壤中金属元素快速定量监测方法以及农产品产地环境监测等提供一定的参考。     

近红外漫反射光谱法测定黄芩中总黄酮及黄芩苷的含量

文章建立了近红外漫反射光谱技术快速测定中药黄芩中主要活性成分黄芩苷和总黄酮含量的方法.对黄芩苷含量在12.24%～21.34%,总黄酮含量在16.08%～26.52%范围内的61个不同产地的黄芩,选择在8 000～4 000 cm-1范围内的近红外吸收光谱,采用偏最小二乘算法(PLS)比较不同光谱预处理方法建市的校正模型,结果表明一阶导数和最小最大归一化的数据预处理方法分别为黄芩苷和总黄酮最优预处理建模方法.黄芩苷校正集相关系数(r)为0.902 4,校正集标准偏差(SEC)为1.01,预测集标准偏差(SEP)为0.876 4;总黄酮校正集相关系数(r)为0.952 7,校正集标准偏差(SEC)为0.785,预测集标准偏差(SEP)为0.521 1,该方法快速简便,适合于黄芩中主要活性成分的快速分析.     

近红外光谱用于杉木木材强度分等的研究

利用近红外光谱技术对木材强度分等进行了研究.选择 1000～1400 nm波段,结合偏最小二乘法,在木材强度和近红外光谱数据间建立了校正模型,校正模型的相关系数(r)为0.89,校正标准误差(SEC)为6.30 MPa.利用校正模型对35个未知样品的强度进行预测,根据近红外预测值和实测值分别对木材样品进行分等,A级预测...     

近红外光谱法快速测定植物油中脂肪酸含量

应用近红外光谱技术建立了快速测定植物油中4种脂肪酸含量的方法。应用气相色谱法测定52个植物油样品中棕榈酸(C16：0)、硬脂酸(C18：0)、油酸(C18：1)和亚油酸(C18：2)的含量作为其化学值(真值)。建模集样品数为41,检验集样品数为11,通过对模型的优化,结果表明建模样品集脂肪酸的化学值(真值)与近红外预测值的相关系数r分别为：r(C16：0)=0.891,r(C18：0)=0.837,r(C18：1)=0.982,r(C18：2)=0.971。检验样品集脂肪酸的化学值与近红外预测值的相关系数分别为0.921,0.891,0.946和0.949。实验结果表明气相色谱法测得的植物油中四种脂肪酸含量与近红外预测值之间存在较好的线性关系。应用近红外光谱法测定植物油中主要脂肪酸的含量是可行的。该方法既快速、方便,又可进行同一样品的多组分分析,有很好的应用前景。     

不确定度评估在中药近红外定量分析中的应用

采集六一散混合过程中样品近红外光谱,建立甘草酸含量近红外(NIR)偏最小二乘(PLS)定量模型。结果校正集相关系数r_cal=0.998 5,RMSEC=0.044 0 mg·g-1,预测集r_val=0.947 4,RMSEP=0.124 mg·g-1,表明近红外光谱法可作为六一散混合过程中甘草酸含量的快速测定方法。在定量模型建立的基础上,设计验证试验,采用由Liao等提出的基于蒙特卡罗仿真的方法,估计β-容度-γ-置信容许区间,并计算NIR定量分析不确定度,绘制不确定度轮廓。结果表明甘草酸含量高于1.56 mg·g-1时,测量不确定度在可接受范围(λ=±20%)内,表明所建不确定度评估方法可有效评价不同浓度水平下的甘草酸含量NIR定量模型的准确性和可靠性,可为其他中药NIR定量分析方法的不确定度评估提供借鉴。     

短波近红外光谱法同时定量分析水溶液中葡萄糖、果糖和蔗糖

用通用紫外-可见分光光度计的短波近红外光谱区域(800～1 100 nm),测量了葡萄糖、果糖和蔗糖混合水溶液的近红外光谱,并用偏最小二乘方法建立了同时定量分析水溶液中葡萄糖、果糖和蔗糖的模型。用正交设计法配制了25个校正集样品和9个预测集样品,通过对校正集样品的建模和对预测集样品的检验,结果良好。对浓度范围分别在12.23～61.14 mg·mL-1,12.50～62.50 mg·mL-1,12.09～60.44 mg·mL-1的葡萄糖、果糖和蔗糖水溶液,校正集的相对标准偏差分别为1.43%,4.51%和1.59%,预测集的相对标准偏差分别为3.40%,3.73%和2.80%。该方法对同时定量分析多组分体系,具有简便、快速价廉、易于推广应用等优点。     

六味地黄丸指纹图谱的近红外光谱分析方法的建立

建立了一种近红外光谱测定六味地黄丸指纹图谱的方法。应用毛细管电泳法建立六味地黄丸指纹图谱,计算其相似度,同时测定其近红外光谱,建立六味地黄丸指纹图谱相似度与近红外光谱之间的数学模型。通过对模型的优化,建模集样品的相关系数(r)、校正标准差和平均相对误差分别为0.9046,0.058和6.12%,表明六味地黄丸指纹图谱相似度实测值与预测值之间有较好的线性关系。研究结果表明以基于指纹图谱的近红外光谱法用于六味地黄丸的质量控制具有可行性。     

基于遗传算法的安溪铁观音品质快速评价研究

为探究一种快速无损的安溪铁观音品质评价方法,利用遗传算法(GA)对茶样的近红外光谱特征波长进行筛选,结合偏最小二乘(PLS),建立全谱段的PLS定量模型与GA-PLS模型。结果表明,傅里叶变换近红外(FT-NIR)全谱段光谱在经过平滑+二阶导数+归一化处理后,PLS模型预测性能最高,建模结果为：校正集相关系数R_C=0.921,校正集均方根误差RMSEC=0.543,验证集相关系数R_P=0.913,验证集均方根误差RMSEP=0.665。选用近红外光谱6 670～4 000 cm-1谱区,采用遗传算法进行特征波长筛选,参与建模数据点数从1 557缩减到408个。优选波段后,GA-PLS建模结果为：校正集相关系数R_C=0.959,校正集均方根误差RMSEC=0.413,验证集相关系数R_P=0.940,验证集均方根误差RMSEP=0.587。可见,GA-PLS模型的校正集和验证集的预测结果均优于全谱段PLS模型。结果说明,在传统的近红外光谱技术结合化学计量学方法的建模基础上,加入遗传算法进行波长筛选,能有效提高模型预测能力,实现方法学的创新研究,且GA-PLS品质评价模型具有较强的参考和推广价值,为提高我国茶叶品质的检测技术水平提供新的方法借鉴。     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.