基于PCA-BP多特征融合的油菜水分胁迫无损检测

针对油菜水分胁迫的无损探测,研究了利用冠层反射光谱、多光谱图像和冠层温度多信息融合对油菜含水率进行定量分析的方法.采用逐步回归法对含水率的多传感特征进行提取,通过测量分析冠-气温差,结合环境温湿度信息,获取了水分胁迫指数(CWSI)特征,并对光强影响进行了特征补偿.研究发现960,1 450,1 650 nm的光谱特征,560 nm处的可见光图像,960,810 nm处的近红外图像均值及960,810 nm图像比值特征与油菜含水率的相关性均较高.利用主成分分析法(PCA)对特征空间进行变换和降维,进而BP神经网络建立了油菜含水率的多传感特征预测模型.结果表明,该方法能够利用多信息的综合作用优势实现对油菜水分胁迫的定量分析,模型精度与单一检测方法相比有显著提高.     

基于偏最小二乘法的樟树叶片叶绿素含量高光谱估算

在BRDF测试系统环境下利用ASD便携式野外光谱仪采集樟树叶片光谱,并用UV2450-紫外可见分光光度计对观测叶片进行叶绿素含量测定.考虑到植物色素(叶绿素和类胡萝卜素)对叶片反射光谱的影响主要体现在可见光波段,选取400~900 nm范围波段光谱反射率与叶片叶绿素含量反演偏最小二乘法(PLS)模型,其中29个样本用于建模,10个样本用于验证,结果表明:当主成分个数为4时,PLS模型具有最佳的效果,4个主成分累计解释了99.91%的自变量信息和89.71%的因变量信息,此外,PLS模型能够充分利用高光谱信息,具有较高的精度和稳定性.通过与原始光谱和一阶导数光谱拟合的估测模型进行对比分析,得出PLS模型无论是从建模样本精度还是验证的误差方面均优于这两种传统的模型,适合于利用高光谱数据进行叶绿素含量的估测.     

基于可见/近红外光谱技术的新鲜茶叶叶片含水率快速测定

提出了利用可见/近红外光谱技术检测新鲜茶叶叶片中含水量的方法.首先采集350~2500nm波段范围内177个新鲜茶叶叶片的光谱反射率信息,作为X变量.将不同预处理后的光谱数据建立偏最小二乘(partial least squares,PLS)模型,再利用回归系数法(regression coefficients,RC)提取全波段光谱中的特征波长并建立基于特征波长的预测模型.结果显示,利用全谱段光谱信息建立的模型中,未经预处理建立的模型最优,建模集和预测集中决定系数(coefficient of determination,R~2)分别是0.9039和0.8856,均方根误差(root mean square error,RMSE)分别是0.0092和0.0120,剩余预测偏差(residual predictive deviation,RPD)是2.9659;基于特征波长的模型中,也是未经预处理建立的模型最优,建模集和预测集中R~2分别是0.9070和0.8199,RMSE分别是0.0107和0.0151,RPD是2.3701.结果表明,可见-近红外光谱技术结合特征波长提取进行新鲜茶叶叶片中含水率检测是可行的.     

基于连续统去除法的湿地松叶绿素含量高光谱估算模型

采用ASD野外光谱辐射仪在BRDF测试系统环境下对野外采集的湿地松叶片样本进行光谱测量,以获得湿地松的叶片光谱反射率,并利用UV2450-紫外可见分光光度计对湿地松叶片进行叶绿素含量测定.采用连续统去除法对光谱数据进行处理分析,计算波段深度(BD)、波深中心归一化(BNC)、波段面积归一化(BNA)、波段深度归一化指数(NBDI)和反射率差异比率(DRR(λi))等光谱特征参数,通过对湿地松叶片叶绿素含量与光谱特征参数的相关性分析,得到NBDI748,BNC749,BNA617,BNA748四个特征参量,与湿地松叶绿素含量建立估算模型并对模型进行精度检验.结果表明以BNA617为变量建立的光谱参量模型能够较好的估算湿地松叶绿素含量.     

基于高光谱图像技术的番茄叶片氮素营养诊断

通过提取番茄叶片高光谱图像的灰度、纹理特征将高光谱数据立方体转化成二维特征曲线,再利用特征选择方法 CFS对所有波长进行筛选,确定灰度特征的特征波长:549,669,742,830 nm和纹理特征的特征波长:482,684 nm.每个样本共有12个特征变量,对这12个变量进行主成分分析,提取9个主成分因子作为模型的输入向量,采用支持向量机建立番茄氮素营养水平诊断模型,得到4个梯度氮素水平(N1,N2,N3,N4)番茄叶片的正确识别率为96%,88%,92%,92%.研究结果表明高光谱图像技术对番茄氮素营养水平具有较好的诊断作用.     

基于近红外光谱特性分析的花生含水率检测

以花生检测国家标准GB/T 5497为基础，采用近红外光谱检测技术对花生含水率是否达标进行检测. 实验配制了30个不同含水率的花生样本，其中18个样本含水率达到国家标准，12个未达标，将样本分为训练集和测试集，通过近红外实验获取不同含水率的花生对不同波长光的吸收情况，将采集的数据作为BP神经网络的输入参数，在训练集对神经网络进行学习和训练，然后采用该模型，对测试集花生含水率是否达标进行测试. 实验表明，基于近红外光谱技术和神经网络的识别方法可全部正确识别测试集样本.     

台湾相思树叶片叶绿素含量的高光谱参量模型研究

在BRDF测试系统环境下利用ASD便携式野外光谱仪采集台湾相思树叶片光谱,并用UV2450-紫外可见分光光度计对观测叶片进行叶绿素含量测定.采用原始光谱、导数光谱技术及连续统去除法对光谱数据进行分析,得到估算台湾相思树叶绿素含量的光谱特征参数(DV575、BNA726、BNC726).结合实测叶绿素含量数据,构建台湾相思树叶片叶绿素含量的光谱参量模型.结果表明DV575与BNC726两参量构建模型估测精度较高,其中用一阶导数光谱变量估测精度最高,均达到83%以上.     

锶胁迫条件下生菜光谱效应特征

锶（Sr）胁迫条件下生菜的反射光谱特征会发生明显改变。通过室内生菜水培试验，获取了36个不同生长期、6个不同锶浓度胁迫的生菜叶片400～950 nm波段区间的生化参数信息（叶绿素含量、细胞结构、叶片金属含量）和反射光谱信息，利用光谱技术并结合数学统计方法研究了生菜叶片7个光谱特征参数与实测叶片锶元素含量之间的相关性，优选了较敏感光谱特征参数，建立了其与生菜叶片锶含量的线性回归模型。结果表明，锶胁迫生菜叶片叶绿素含量呈先上升后下降的规律，细胞结构差异不明显。锶胁迫生菜叶片反射光谱直观上无规律，通过采用光谱技术方法分析得出锶胁迫生菜叶片的红边波段位置先“红移”再“蓝移”，红谷波段位置则“红移”，植被指数B4/B3比值先升高后降低，红边归一化植被指数（NDVI）值随着锶浓度的升高而降低。相关性及线性回归模型分析表明红边波段位置与叶片锶含量显著相关。本文为下一步基于光谱特征的叶片重金属含量反演模型的构建提供了较好的数据源和基础理论。     

基于介电特性的青萝卜干燥品质预测模型

以青萝卜为实验物料,利用网络分析仪,采用同轴探头法测量了在16～3 500 MHz的频率范围内,湿基含水率为15%～93.20%,物料温度为(36±1)℃的青萝卜的介电常数ε'和介质损耗因子ε".分析了频率、含水率、糖度、密度与介电特性的关系,建立了915 MHz和2 450 MHz下介电特性与含水率、糖度、密度的关联模型,检验了基于介电特性预测含水率、糖度、密度的可行性.结果表明:在16～3 500 MHz频率段内,介电常数ε'和介质损耗因子ε"随着频率的增大而减小.介电常数ε'随着含水率的增大而增大,介质损耗因子ε"在湿基含水率为15%～60%时,随着含水率的增大而增大,之后随着含水率的增大而降低.糖度与含水率呈负相关.可用二元一次方程描述含水率、糖度、密度与介电特性的关系,对模型进行方差分析,各模型的决定系数均大于0.92,P值小于0.05,表明所得基于介电特性预测干燥过程中青萝卜的含水率、糖度、密度的模型是准确的.     

基于高光谱的法国梧桐和毛白杨叶片叶绿素含量反演模型研究

利用ASD便携式野外光谱仪和SPAD-502叶绿素计,实测了落叶阔叶树法国梧桐(Platanus orientalis L)和毛白杨(Populus tomentosa Carr)叶片的高光谱反射率与叶片绿度,并对原始光谱反射率及一阶导数光谱与叶片绿度进行了相关分析;采用导数光谱数据敏感波段建立了叶绿素含量估算模型,法国梧桐和毛白杨模型的确定性系数R2分别为0.7791和0.6858;采用相关系数较大的波段作为BP和RBF人工神经网络模型的输入变量,分别进行了叶绿素含量的估算,结果表明,BP和RBF神经网络模型预测效果均良好,在预测精度上,RBF略优于BP神经网络模型.     

近红外图像纹理分析叶片含水率的初步研究

利用水分子对９６０ｎｍ附近的近红外光有较强的吸收这一特性,通过图像处理技术中的纹理分析方法,对三种作物（苞菜、青菜及生菜）叶片的近红外图像进行纹理分析,找寻图像的纹理特征量与叶片的干基含水率之间的关系,为应用图像处理技术获取作物生理信息作初步的研究采用纹理分析的直方图统计特征法、灰度—梯度共生矩阵法分别对叶片的近红外图像求出各自的特征量特征量与叶片干基含水率之间的线性关系不仅和特征量有关,而且和拍摄图像时的实验因素（如摄像头的工作距离、光圈、光强等）有关灰度—梯度共生矩阵法还取决于梯度图像灰度级的数目     

水分胁迫下非气孔因素对葡萄叶片光合作用的影响

水分胁迫使葡萄叶片Chl、Car含量下降,Pn、Gs下降,Ci先降后升,SOD、POD、CAT活性先升后降,O2-.、H2O2含量增高;水分胁迫下葡萄幼苗叶片的Pn与其Chl、O2-.、H2O2、Gs间均呈显著相关。表明水分胁迫对葡萄光合速率的影响除受气孔因素限制之外,在胁迫后期由活性氧代谢失调所诱导的非气孔因素成为限制光合速率的主导因子。     

Study on the biomass change derived from the hyperspectral data of cotton leaves in canopy under moisture stress

In this study, an ASD spectrometer made in USA is used to derive the hyperspectral data of cotton leaves in canopy in north Xinjiang. The integral area variables of red edge are used to estimate the total nitrogen (TN) content in cotton leaves in canopy. The first order differential of reflective spectra is carried out. The analysis methods based on the spectral position variables are derived from the first order differential spectral data. The analysis on the correlation between the integral area of red edge (SDr, regarded as the independent variable) and the TN content (regarded as the function) is carried out, and the correlation mathematical model between the integral area of red edge and the TN content in canopy leaves of cotton varieties named as Xinluzao No.6 is developed. The analysis on the correlation between the chlorophyll content and the TN content in single cotton leaves in canopy growing under the irrigation with different water volumes is carried out. The results show that there is a significant positive correlation between the chlorophyll content and the TN content (R = 0.8723, n = 39), and the data of chlorophyll content can be used to estimate the TN content in single cotton leaves; the correlation between the integral area variable of red edge and the TN content in cotton leaves in canopy is significant, their correlation coefficient is 0.7394 (n = 40), the TN contents in canopy leaves of cotton varieties named as Xinluzao No. 6 and No. 8 can be accurately estimated by using the developed model, and their RMSE values are 0.3859 and 0.4272 respectively. After researching, it is considered that there is an applying potential to use the integral area variables of red edge for estimating the TN content in cotton leaves in canopy, and the mathematical model developed with the third-side area variables has a high applying value in deriving the TN content in crop canopy. It is also considered that it is feasible to recognize the moisture stress suffered by cotton plants by researching the shift and change extent of red edge, and the key is to develop the corresponding rational recognition index system.

     

A feasibility study on diagnosing wheat water status using spectral reflectance

A total of 110 wheat leaf samples were collected in the field and their spectral reflectances were measured with a spectroradiometer in laboratory. After a spectral normalizing technique, the spectral absorption feature parameters such as the absorption depth and area, were extracted from each leaf spectrum. The relative water content (RWC) was measured for samples. The experimental results indicated that the spectral absorption depth and area of wheat leaves at 1 450 nm were correlated with their RWC. So we can diagnose wheat water status by using their spectral reflectances. Furthermore, we discuss the possibility of developing new instruments based on the analysis of the spectroradiometer data for non-destructive and instantaneous measurement of the wheat water status in the field.     

Changes in the power spectrum of electrical signals in maize leaf induced by osmotic stress

To quantify the characteristics of the power spectrum of plant electrical signals, we defined the following concepts:spectral edge frequency (SEF), spectral center frequency (SCF), power index (PI) and power spectral entropy (PSE). These parameters were used to examine and quantify changes in the power spectrum of electrical signals in maize leaves under osmotic stress. In the absence of osmotic stress, the SEF of the electrical signal in maize leaves was approx. 0.2 Hz and the SCF was approx. 0.1 Hz. The electrical signal in maize leaves was mainly a slow wave signal with a frequency of 0-0.1 Hz. After 2 h osmotic stress, the SEF and SCF of the electrical signal increased to higher frequencies. The proportion of the fast wave frequency also increased to 0.1-0.2 Hz, resulting in a dramatic increase in PSE. We also found that the changes in PSE and SCF were significantly correlated during osmotic stress. We propose that the changes in the PSE and SCF in maize leaves can be used as a sensitive signal indicating water deficit in leaf cells under osmotic stress. Thus, measurement of SCF or PSE of electrical signals in maize leaves could be used to develop early warning and rapid diagnosis techniques for the water demands of plants.     

水分胁迫对蚕豆（Vicia faba L.）叶片水分状况的影响

两个蚕豆品种经水分胁迫,蚕豆叶片的含水量,叶片相对含水量（RWC）降低,水分饱和亏缺（WDS）明显增大,主要是自由水含量减少而致,香珠豆的气孔调节能力强,RWC,自由水下降幅度小,保水能力强,抗旱性强,经离体叶片失水速率实验也证明了这一点。     

葡萄力学模型的研究及对压缩载荷的响应分析

根据葡萄结构特点,以二维问题为研究对象,建立了葡萄力学模型.提出了用数值模拟与实验相结合确定模型力学参数和用线性拟合实验数据确定物体刚度的方法.用有限元方法和MATLAB计算软件研究了葡萄压缩时内压改变量、压缩外力、压缩变形量和皮的应力之间的关系,给出了关系曲线图.得出了葡萄在压缩情况下,总体变形量与压缩外力、内压改变量和皮的应力的关系是非线性关系.但葡萄内压改变量与压缩外力和皮的应力的关系以及皮应力与压缩外力的关系是近似的线性关系.葡萄体积改变量随压缩外力的增加而成线性的增加.葡萄首先在不受力的表皮破裂等5点结论.图6,表2,参8.     

In situ hyperspectral data analysis for pigment content estimation of rice leaves

Analyses of the correlation between hyperspectral reflectance and pigment content including chlorephyll-a, chlorephyll-b and carotenoid of leaves in different sites of rice were reported in this paper. The hyperspectral reflectance of late rice during the whole growing season was measured using a Spectroradiometer with spectral range of 350 - 1050 nm and resolution of 3 nm. The chlorophyll-a, chlorephyll-b and carotenoid contents in rice leaves in rice fields to which different levels of nitrogen were applied were measured. The chlorephyll-a content of upper leaves was well correlated with the spectral variables. However, the correlation between both chlorephyll-b and careteniod and the spectral variables was far from that of chlorophyll-a. The potential of hyperspectral reflectance measurement for estimating chlorophyll-a of upper leaves was evaluated using univariate correlation and multivariate regression analysis methods with different types of predictors. This study showed that the most suitable estimated model of chlorephyll-a of upper leaves was obtained by using some hyperspectral variables such as SDr , SDb and their integration.     

SA与高温锻炼对高温逆境下葡萄幼苗叶片钙离子水平的影响

为研究SA与高温锻炼（HA）对高温逆境下葡萄细胞中钙含量的影响,用原子吸收光谱法对其叶片中的可溶性钙及结合态钙含量进行了测定.结果表明：高温胁迫促进幼叶细胞中可溶性钙和总钙含量的增加,随着胁迫时间的延长,可溶性钙的增幅变大而总钙含量的增幅变小;经SA与HA分别处理后,可溶性钙和总钙含量的变化表现出同步性,并且它们都可以不同程度地缓减高温胁迫下钙含量的增加,以维持细胞中钙离子水平的稳定;特别是经HA处理后,可溶性钙含量的变化更加明显,各处理中的可溶性钙含量甚至都低于对照中的钙离子水平.所以从这个层面上说SA与HA对于提高葡萄抗热性的效果是一致的,但与SA相比,HA处理后的作用更为明显.