共查询到19条相似文献,搜索用时 140 毫秒
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化学计量学用于解析黄连上清片的高效液相色谱指纹图谱 总被引:3,自引:2,他引:3
采用高效液相色谱获得黄连上清片的色谱指纹图谱,利用基于主成分分析的投影判别法分析实验结果,并用反传人工神经网络对未知样品进行预报。结果表明,不同厂家生产的黄连上清片存在显著差异,主成分分析投影判别法能对样品进行正确分类,从而建立了识别不同厂家黄连上清片的方法,能有效地控制中药黄连上清片的质量。此外,主成分分析还用于优化反传人工神经网络,统计多次预报的结果,表明经过优化的反传人工神经网络能对未知样品的来源进行准确预报。 相似文献
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限于传统涂敷敏感膜的声表面波(SAW)气敏传感器存在成膜困难和选择性差、重复性差以及再生性差等问题,本研究提出一种基于压电基底表面气体气液相转换效应机理的瑞利波传感器。首先建立了挥发性有机气体(VOCs)液相凝聚体薄层负载下的SAW波传模型,并仿真计算了其波传频散和波传衰减。然后在此基础上开发了一种基于瑞利声表面波传感器和气相色谱(GC)分离柱的便携式气体检测系统。最后实验论证了方案的可行性,初步的实验结果表明该系统具有分析时间短、选择性好、灵敏度高(可检测ppb浓度的混合VOCs)以及成本低等优势,因此其在痕量挥发性有机气体检测和分析应用上有良好的潜力和前景。 相似文献
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近年来以煤为原料制备获得碳纳米管已经在实验室中得以实现,这开拓了碳纳米管低成本制备的途径。然而,煤基碳纳米管中氮、硅等原子掺杂对于碳管结构和功能性质影响的研究仍然相对较少。本研究使用基于第一性原理的自洽场晶体轨道法对硅、氮原子掺杂的(6,6)碳管进行研究。探讨硅、氮原子掺杂对碳纳米管电子性质和杨氏模量的影响。研究发现,氮原子和硅原子取代掺杂缺陷的形成在能量上是不利的,尤其对于硅掺杂。能带结构的计算表明,氮掺杂碳管显示金属导电性,而硅掺杂碳管发生了金属/半导体性质的转变,为半导体。杨氏模量的结果暗示,氮掺杂可以增强煤基碳管的力学性能。 相似文献
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应用半经验量子化学AM1法获得18种3-芳氧基-6-氯哒嗪化合物的优势构象,再用AM1法和分子图形学技术获得其电子结构参数和几何结构参数,然后采用多元线性回归分析(MLR)和人工神经网络误差反传算法(BP)将这些参数和化合物对油菜的抑制活性相关联.MLR和BP建模的复相关系数(R2)、去一法(LOO)交互检验复相关系数(R2cv)分别为0.840,0.743和0.889,0.733,表明所建市的QSAR模型的稳定性和预测能力良好.结果表明,苯环上应尽量避免大体积取代基的引入,在2号位引入的取代基可稍大些;在苯环2、4、6位引入供电子基团、3位引入吸电子基团可提高化合物的除草活性,所建模型可为哒嗪类除草剂的设计合成提供理论指导. 相似文献
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Identification and pattern recognition analysis of Chinese liquors by doped nano ZnO gas sensor array 总被引:2,自引:0,他引:2
Qinyi Changsheng Shunping Aihua Bailin Lin Zhongbao 《Sensors and actuators. B, Chemical》2005,110(2):370-376
In this paper, ZnO nanoparticles were prepared by the renovated hybrid induction and laser heating. The sensitivities of gas sensors can be greatly improved by doping MnO2, TiO2 and Co2O3. Five different Chinese liquors, namely, Baiyunbian, Beijing Erguotou, Red Star Erguotou, Zhijiangdaqu and Jianliliangjiu, alcohol and diluted alcohol (forged liquor) were measured. Though the main ingredient is alcohol in liquors, Chinese liquors mainly differ from their flavour types, which rely on their trace components. Flavour type of liquors is a very important factor in Chinese liquor identification. Principal component analysis incorporating with discriminant analysis (PCA-DA), back-propagation artificial neural network (BP-ANN) and learning vector quantization (LVQ) were compared for their classification ability. The accuracy of PCA-DA, BP-ANN and LVQ in terms of predicting tested samples was 76.8, 71.4 and 89.3%, respectively. The LVQ is the most suitable pattern recognition algorithm in present experiment. This work shows the potential application of the gas sensor arrays for monitoring the quality of Chinese liquors. 相似文献
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人体呼气中的丙酮含量可作为糖尿病的标志物.为实现无创糖尿病诊断,设计以金属氧化物半导体气敏传感器阵列为核心的人工嗅觉系统,对完成痕量丙酮的快速检测具有重要意义.通过多个气体流量控制器MFC(Mass Flow Controller)分别配制出模拟糖尿病患者呼气样本(30×10-6丙酮)与另两种干扰气体样本(30×10-6乙醇样本、15×10-6丙酮与15×10-6乙醇混合样本)进行实验,基于BP神经网络算法对3种气体定性识别,并通过主成分分析PCA(Principal Component Analysis)算法对原始的高维特征子集进行降维优化.实验表明:PCA与BP算法相结合,可降低BP神经网络的复杂性、减少预测的误差,同时能够解决单个气体传感器交叉敏感问题,进而提高对气体的选择性.对痕量丙酮样本与另两种干扰气体样本进行分析识别,识别的结果显示:对3种样本的识别准确率为91%.该研究为准确识别糖尿病标志物实现无创诊断技术提供了理论指导. 相似文献
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In this work, we propose the use of the neural gas (NG), a neural network that uses an unsupervised Competitive Hebbian Learning (CHL) rule, to develop a reverse engineering process. This is a simple and accurate method to reconstruct objects from point clouds obtained from multiple overlapping views using low-cost sensors. In contrast to other methods that may need several stages that include downsampling, noise filtering and many other tasks, the NG automatically obtains the 3D model of the scanned objects. To demonstrate the validity of our proposal we tested our method with several models and performed a study of the neural network parameterization computing the quality of representation and also comparing results with other neural methods like growing neural gas and Kohonen maps or classical methods like Voxel Grid. We also reconstructed models acquired by low cost sensors that can be used in virtual and augmented reality environments for redesign or manipulation purposes. Since the NG algorithm has a strong computational cost we propose its acceleration. We have redesigned and implemented the NG learning algorithm to fit it onto Graphics Processing Units using CUDA. A speed-up of 180× faster is obtained compared to the sequential CPU version. 相似文献
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六个由贵金属Au,Cu,Pt做添加剂的SnO2气体传感器构成了微气体传感器阵列.首先研究了这六只传感器对挥发性有机化合物(VOCs)敏感特性,本文中的VOCs 指VOCsmixture和甲醛(HCHO)气体,其中VOCsmixture是10 ppm甲苯、1 ppm丙酮、5 ppm α-派烯和10 ppm乙醇的混合气.然后采用BP神经网络对所获得的传感器信号进行了分析、识别.结果显示微气体传感器阵列与BP神经网络相结合不仅能有效地识别低浓度的单成分VOCsmixture和甲醛气体,而且也能有效地识别两元气体中的VOCsmixture和甲醛气体. 相似文献
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电子鼻模式识别算法的比较研究 总被引:14,自引:4,他引:10
文中比较了k-近邻法、线性判别分析、反向传播人工神经网络、概率神经网、学习向量量化以及自组织映射6种电子鼻模式识别算法的分类能力.采用了1个定量指标(识别精度)和4个定性指标(运算速度、训练速度、内存容量、抗干扰能力)对不同算法进行了系统比较.研究表明基于神经网络的模式识别算法比基于统计理论的模式识别算法具有更高的识别精度.如果同时考虑定性指标,当训练速度要求不高时,宜采用学习向量量化算法;能满足内存需求前提下,优先推荐采用概率神经网算法.对于选择性高的信号,采用线性判别分析可以达到最佳效果. 相似文献
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Francisco A.A. Souza Rui Araújo Tiago Matias Jérôme Mendes 《Journal of Process Control》2013,23(10):1371-1378
The paper proposes a new method for variable selection for prediction settings and soft sensors applications. The new variable selection method is based on the multi-layer perceptron (MLP) neural network model, where the network is trained a single time, maintaining low computational cost. The proposed method was successfully applied, and compared with four state-of-the-art methods in one artificial dataset and three real-world datasets, two publicly available datasets (Box–Jenkins gas furnace and gas mileage), and a dataset of a problem where the objective is to estimate the fluoride concentration in the effluent of a real urban water treatment plant (WTP). The proposed method presents similar or better approximation performance when compared to the other four methods. In the experiments, among all the five methods, the proposed method selects the lowest number of variables and variables-delays pairs to achieve the best solution. In soft sensors applications having a lower number of variables is a positive factor for decreasing implementation costs, or even making the soft sensor feasible at all. 相似文献