基于移动窗口-迭代遗传算法的近红外光谱波长选择方法

光谱样本数据常会受到环境噪声和其它组分的干扰,应作波长选择,以提高分析精度.近红外光谱谱区宽,搜索空间过大,难以直接采用遗传算法进行波长选择.为此本研究提出先用移动窗口偏最小二乘法(MWPLS)从宽谱区中初选出信息区间,再采用改进的迭代遗传算法(IGA)从中选出最优的信息子区间.MWPLS用移动窗口沿全谱区扫描,对信息区间的定位效果好,而IGA将顾及光谱数据的连续相关特性,运行多轮GA,并以上轮选择结果平滑处理后作为先验知识支持下轮的种群初始化.由此选出的连续相邻的波长点作为自变量,进行PLS建模,既可显著地简化模型,又保留一定的数据冗余,模型的稳健性好,分析精度高.将其用于小麦水分的近红外分析,效果良好,预测性能明显优于其它方法.     

最小角回归算法(LAR)结合采样误差分布分析(SEPA)建立稳健的近红外光谱分析模型

结合采样误差分布分析(SEPA)框架和最小角回归(LAR)算法,提出了一种SEPA-LAR变量逐步筛选方法用于波长选择,并建立了稳健的近红外光谱分析模型。利用蒙特卡洛采样(MCS)获得多个数据集划分建立多个模型,对光谱各变量(波长)在所有模型的LAR系数进行统计分析,按其回归系数绝对值总和由大到小排序,选择排序靠前的波长建立偏最小二乘(PLS)模型,以未参与SEPA-LAR和建模的独立验证集对该模型进行评价。将玉米湿度、柴油密度以及奶酪脂肪的近红外光谱数据用于SEPA-LAR的性能检验,独立验证集的预测均方根误差(RMSEP)分别为0.001 44%(湿度指标)、0.001 58 g/mL(密度指标)以及1.13 g/100 g(脂肪含量指标)。结果表明,相较于竞争自适应重加权采样法(CARS),该方法具有更优异的稳定性;相较于移动窗口偏最小二乘(MWPLS)以及蒙特卡洛无信息变量消除(MCUVE)方法,该方法选择的变量更少,预测误差更低,预测性、可解释性和稳定性更优异。     

近红外光谱结合遗传算法快速检测红曲菌固态发酵生物量

该文研究了近红外光谱技术在红曲菌固态发酵生物量快速检测方面的应用。共采集了4个批次80个样本的光谱,采用氨基葡萄糖法测定生物量。为降低模型的复杂度和提高模型的预测性能,研究了遗传算法(Genetic Algorithm,GA)的光谱谱区选择方法,并建立所优选光谱变量的预测红曲菌固态发酵生物量的PLS模型。为说明遗传算法优选光谱变量的可行性,另外分别建立了全谱和相关系数法两种波长选择方法下的PLS定量模型,比较分析了3种方法所获模型的预测能力,并对GA方法优选的光谱波段信息与菌体成分中含氢基团的对应吸收进行分析。结果表明,遗传算法能在降低模型复杂度的同时提高模型的预测性能,其建模结果为Rc=0.998 3,RMSECV=3.580 2,Rp=0.993 1,RMSEP=3.643 7,参与建模的数据点由全谱的1 457个减少到585个,且模型预测精度相比FS-PLS模型提高了11.55%。研究表明近红外光谱技术结合遗传算法所建的PLS预测模型能够实现红曲菌固态发酵生物量的快速检测,从而为进一步实现在线发酵过程优化控制提供依据。     

遗传算法在绿茶叶近红外光谱分析中波长选择的应用

利用遗传算法提取茶叶的近红外吸收特征波长,研究建立了绿茶水分和氨基酸的近红外光谱分析模型,并对波长选择前后模型进行了比较分析.结果表明:经遗传算法波长选择后,简化了分析模型,有效地减小了不相关或非线性变量的干扰,模型的稳健性增强.     

基于遗传算法结合神经网络的航空润滑油粘度近红外光谱分析

研究了基于遗传算法(GA)的波长选择方法结合反向传播神经网络(BP-ANN)建模用于在用航空润滑油-40℃运动粘度的近红外光谱分析。采集样品光谱经均值中心化和SavitzkyGolay平滑求导法预处理后,通过分段组合建模初选最优波段,利用遗传算法进一步筛选了对粘度预测敏感的波长点建模。该波长选择方法与相关系数法相比,所建模型预测准确度高。在建模采用的非线性BP-ANN法中,先通过主成分分析(PCA)分解光谱数据,将得分矩阵输入3层神经网络训练,通过参数优化建立最优模型。所建模型对8个在用油进行分析,各预测值与标准值的相对误差均低于2%,并且经t检验不存在显著性差异,模型预测能力较强,应用于在用润滑油质量的快速分析效果好,为油品在线监控提供了参考。     

应用遗传算法和PLS的近红外光谱预测玉米中淀粉含量的研究

以普通玉米籽粒为试验材料,在应用遗传算法结合偏最小二乘回归法对近红外光谱数据进行特征波长选择的基础上,应用偏最小二乘回归法建立了特征波长测定玉米籽粒中淀粉含量的校正模型．试验结果表明,基于11个特征波长所建立的校正模型,其校正误差（RMSEC）、交叉检验误差（RMSECV）和预测误差（RMSEP）分别为0.30％、0.35％和0.27％,校正数据集和独立的检验数据集的预测值与实际测定值之间的相关系数分别达到0.9279和0.9390,与全光谱数据所建立的预测模型相比,在预测精度上均有所改善,表明应用遗传算法和PLS进行光谱特征选择,能获得更简单和更好的模型,为玉米籽粒中淀粉含量的近红外测定和红外光谱数据的处理提供了新的方法与途径．     

近红外波长选择结合偏最小二乘法测定混胺中微量水分

对混胺的近红外波长范围进行选择并结合偏最小二乘法建立微量水分的定量分析模型,通过配对t检验(α=0.05)验证校正模型预测的准确性.首先对混胺的性质和其近红外吸收信息进行分析,采用二阶微分(差分宽度为4nm)对光谱进行预处理.研究波长范围对微量水分测定的影响并确定了建模的最佳波长区间为940 ～ 965 nm.采用偏最...     

小波多尺度分段直接校正法用于近红外光谱模型传递的研究

分段直接校正(PDS)算法是目前最常用的近红外光谱模型传递方法,但它在对整个谱区进行校正时,始终依赖大小不变的传递窗口.为了提高传递效果,本研究在PDS基础上提出了一种新的算法--小波多尺度分段直接校正法(WMPDS),用于混胺的近红外光谱模型传递,并详细讨论了模型的传递参数和传递结果.本算法首先对混胺的近红外光谱进行...     

叠加多元校正分析

基于多模型(模型融合)建模的思想,开发了两种新的叠加多元校正分析算法:叠加PCR(PLS)多元校正分析和叠加移动窗口PCR(PLS)多元校正分析。与一般的多模型建模方法不同的是其通过赋予光谱数据中的不同部分不同权重叠加子多元校正模型。因此,其可以通过权重调节或选择变量。在消除光谱数据中常见的冗余信息的同时,避免信息遗漏的缺点,并最终提高模型的稳健性,简化了模型。对于这两个新的算法,尽管其具体步骤不同,但仍取得了相似的预测结果。本文通过两套近红外光谱文献数据计算验证了这两个新方法的优越性。     

自适应蚁群优化算法的近红外光谱特征波长选择方法

为提高近红外光谱预测模型的精度和适用性,同时简化模型,提出了自适应蚁群优化偏最小二乘法优选特征波长的方法,建立不同产地苹果可溶性固形物含量混合分析模型。收集山东、陕西和新疆的富士苹果,采集3800~14000 cm"1范围的近红外光谱,并对其重要品质指标可溶性固形物含量进行测定。利用蚁群算法启发式全局搜索的特点,结合蒙特卡罗轮盘赌随机选择机制,优选苹果可溶性固形物含量的近红外光谱特征波长,然后用偏最小二乘法建立分析模型。与全光谱偏最小二乘模型和遗传偏最小二乘模型相比,蚁群优化算法选择的波长数最少,模型预测能力最强,预测的相关系数R和预测均方根误差RMSEP分别为0.9708和0.5144。研究结果表明,自适应蚁群优化算法可以有效选择近红外光谱特征波长,提高模型的稳健性和适用性。     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.     

Copper-catalyzed multicomponent reactions of 2-iodoanilines,benzylamines, and elemental sulfur toward 2-arylbenzothiazoles

A relatively cheap copper salt-catalyzed, three-component approach providing 2-arylbenzothiazoles in good to excellent yields from readily available 2-iodoanilines, benzylamines, and sulfur powder is reported. This methodology allows preparation of various classes of 2-arylbenzothiazoles and provides a general, reliable approach.