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971.
Yiming Bi Qiong Xie Silong Peng Liang Tang Yong Hu Jie Tan Yuhui Zhao Changwen Li 《Analytica chimica acta》2013
A new ensemble learning algorithm is presented for quantitative analysis of near-infrared spectra. The algorithm contains two steps of stacked regression and Partial Least Squares (PLS), termed Dual Stacked Partial Least Squares (DSPLS) algorithm. First, several sub-models were generated from the whole calibration set. The inner-stack step was implemented on sub-intervals of the spectrum. Then the outer-stack step was used to combine these sub-models. Several combination rules of the outer-stack step were analyzed for the proposed DSPLS algorithm. In addition, a novel selective weighting rule was also involved to select a subset of all available sub-models. Experiments on two public near-infrared datasets demonstrate that the proposed DSPLS with selective weighting rule provided superior prediction performance and outperformed the conventional PLS algorithm. Compared with the single model, the new ensemble model can provide more robust prediction result and can be considered an alternative choice for quantitative analytical applications. 相似文献
972.
The photo-Ritter reaction of five arylmethyl bromides can occur in acetonitrile to give acetamides. The intermediates, carbocations, which are formed from subsequent electron transfer between the radical pairs generated from initial homolytic cleavage of the C–Br bond, are trapped by acetonitrile, and subsequent hydrolysis generates the corresponding acetamides. 相似文献
973.
In this paper, we mainly study a family of unbounded non-hyperbolic domains in $$\mathbb {C}^{n+m}$$, called Fock–Bargmann–Hartogs domains $$D_{n,m}(\mu )$$ ($$\mu >0$$) which are defined as a Hartogs type domains with the fiber over each $$z\in \mathbb {C}^{n}$$ being a ball of radius $$e^{-\frac{\mu }{2} {\Vert z\Vert }^{2}}$$. The purpose of this paper is twofold. Firstly, we obtain necessary and sufficient conditions for Rawnsley’s $$\varepsilon $$-function $$\varepsilon _{(\alpha ,g)}(\widetilde{w})$$ of $$\big (D_{n,m}(\mu ), g(\mu ;\nu )\big )$$ to be a polynomial in $$\Vert \widetilde{w}\Vert ^2$$, where $$g(\mu ;\nu )$$ is a Kähler metric associated with the Kähler potential $$\nu \mu {\Vert z\Vert }^{2} -\ln (e^{-\mu {\Vert z\Vert }^{2}}-\Vert w\Vert ^2)$$. Secondly, using above results, we study the Berezin quantization on $$D_{n,m}(\mu )$$ with the metric $$\beta g(\mu ;\nu )$$$$(\beta >0)$$. 相似文献
974.
Ziru Liu Jiameng Qu Fan Ke Haotian Zhang Yiwen Zhang Qian Zhang Qing Li Kaishun Bi Huarong Xu 《Molecules (Basel, Switzerland)》2022,27(9)
The excessive expression of reactive oxygen species is closely connected to many diseases. Considerable studies have demonstrated dandelion as well as its ingredients exhibited antioxidant activity. However, specific material basis reflecting the antioxidant activity has not been comprehensively investigated. In this study, a spectrum–effect relationship study on dandelion between fingerprinting and antioxidant activity was analyzed in detail, while a UHPLC quantification method developed and completely validated for simultaneous determination of active ingredients in dandelion. With the establishment of dandelion fingerprints of different regions, 24 common peaks were characterized. The classic FRAP method and ABTS methods were then used to detect their antioxidant activity. Partial least squares regression analysis, bivariate correlation analysis and grey correlation method were used to accomplish the spectrum–effect relationship. Eventually, the ingredients with antioxidant activity which could be considered as candidate quality markers of dandelion were discovered through spectrum–effect relationship analysis. The six compounds including caftaric acid, chlorogenic acid, caffeic acid, chicoric acid, isochlorogenic acid A, and isochlorogenic acid C were quantitatively determined. The developed UHPLC assay method was accurate, precise, and reliable. The study has elucidated the antioxidant material basis of dandelion and provided a scientific basis for the quality control of dandelion. 相似文献
975.
依据几何光学和非成像光学理论,提出了一种基于大尺寸近焦点非球面透镜的大功率LED均匀光源设计方法。在该方法中,首先根据选定参数的LED通过几何光学理论初步设计非球面透镜参数,然后在ZEMAX软件中对非球面透镜参数进行基于评价函数的优化,得到焦距76.79 mm、直径为200 mm的非球面透镜。将非球面透镜导入TRACEPRO软件建模并进行光线追迹仿真,根据仿真结果获得最优透镜参数进行加工和下一步实验。实验结果表明:均匀照明系统可以在60 cm处实现发散角±8.53°的均匀照明,光斑均匀性达到95.82%。 相似文献
976.
新型农村养老保险制度是一项面向农村的影响深远的重要民生工程。本文基于农业农村部每年对约350个县(村)2万户农户的固定观察数据,从居民消费的角度评估新农保政策的影响。研究发现,新农保政策对居民消费有显著的促进作用,参与新农保使居民消费支出提高4%,2009年折合户均消费可以增加700元,折算新农保项目财政支出带来的消费支出系数为1.86,远远高于平均的边际消费倾向0.36;新农保缴费额度每增加1倍,农户消费支出提高约5.9%。机制检验表明,收入效应和预期效应都会使新农保促进居民消费,而预期的影响尤其重要。此外,新农保政策对户主年龄较大的家庭、户主受教育程度较高的家庭、家庭收入相对较低的家庭的消费促进作用更强。本文的研究表明,新农保政策的实施不但有利于农村社会保障体系的完善,也有利于降低未来预期不确定性,提高农村居民消费水平。 相似文献
977.
Kurochkin N. S. Savinov S. A. Bi Dongxue Sychev V. V. Eliseev S. P. Gritsienko A. V. 《Journal of Russian Laser Research》2021,42(6):713-720
Journal of Russian Laser Research - The color centers in nanodiamonds are promising candidates for the fabrication of stable room-temperature sources of single photons. We investigate the... 相似文献
978.
979.
Yong Yang Shaopeng Liu Shuang Li Dr. Zhaohong Liu Dr. Peiqiu Liao Paramasivam Sivaguru Ying Lu Jiaojiao Gao Prof. Xihe Bi 《Angewandte Chemie (International ed. in English)》2023,62(4):e202214519
The construction of allylic quaternary sp3-carbon centers has long been a formidable challenge in transition-metal-catalyzed alkyl-allyl coupling reactions due to the severe steric hindrance. Herein, we report an effective carbene strategy that employs well-defined vinyl-N-triftosylhydrazones as a versatile allylating reagent to enable direct assembly of these medicinally desirable structural elements from low-cost alkane feedstocks. The reaction exhibited excellent site selectivity for tertiary C−H bonds, broad scope (>60 examples and >20 : 1:0 r. r.) and good efficiency, even on a gram-scale, making it a convenient alternative to the well-known Trost–Tsuji allylation reaction for the formation of alkyl–allyl bonds. Combined experimental and computational studies were employed to unravel the mechanism and origin of site- and chemoselectivity of the reaction. 相似文献
980.
A sensitive and robust on-line LC/MS method was developed for quantitative determination of linoleic acid,docosahexaenoic acid and docosanoic acid from edible oil samples.The oil samples were dissolved in chloroform-isopropyl alcohol(20:80,v:v)solution and the three fatty acids were separated by HPLC with a C4 column using 10 mmol/L ammonium acetate-isopropyl alcohol-acetonitrile(20:40:40,v:v:v)mobile phase in isocratic elution.Electrospray ionization mass spectrometry with the selected ion recording monitoring was used to detect and quantify the fatty acid.The calibration curves were linear in the range of 10.00–5000 pg/mL for linoleic acid and docosanoic acid,and 1.000–500.0 pg/mL for docosahexaenoic acid.The limit of detection was 2.0 pg/mL for linoleic acid,3.0 pg/mL for docosanoic acid,and 0.20 pg/mL for docosahexaenoic acid.The results showed that the method described in this paper could be utilized for rapid determination of three fatty acids at picogram levels in edible oils. 相似文献