In the past few years, support vector machines (SVMs) have been applied to many fields, such as pattern recognition and data mining, etc. However there still exist some problems to be solved. One of them is that the S...In the past few years, support vector machines (SVMs) have been applied to many fields, such as pattern recognition and data mining, etc. However there still exist some problems to be solved. One of them is that the SVM is very sensitive to outliers or noises because of over-fitting problem. In this paper, a fuzzy support vector regression (FSVR) method is presented to deal with this problem. Strategies based on k nearest neighbor (kNN) and support vector data description (SVDD) are adopted to set the fuzzy membership values of data points in FSVR.The proposed FSVR soft sensor models based on kNN and SVDD are employed to predict the concentration of 4-carboxy-benzaldehyde (4-CBA) in purified terephthalic acid (PTA) oxidation process. Simulation results indicate that the proposed method indeed reduces the effect of outliers and yields higher accuracy.展开更多
The crystal structure of the title compound C16H18NO2+·C7H7SO3-·2H2O, (C23H29NSO7, Mr=463.53) has been determined by single-crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system wi...The crystal structure of the title compound C16H18NO2+·C7H7SO3-·2H2O, (C23H29NSO7, Mr=463.53) has been determined by single-crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system with space group P21/n, a=8.101(1), b=8.958(2), c=33.281(5)?,β= 94.910(1)(, V=2406.3(7)?3, Z=4, Dc=1.279g/cm3, μ=0.176mm-1, F(000)=984, final R=0.0409, and Rw=0.0860 for 4401 independent reflections. The result shows that in the crystal structure of the title compound the planar cations have two configurations with equal occupation ratio and are antiparally packed through π…π interactions. Similar packing energies in A and B are probably the main factor that leads to the disorder structure.展开更多
For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups,...For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.展开更多
Aim To investigate the chemical constituents of Piper wallichii. Methods Five compounds were isolated by silica gel column chromatography and Sephadex LH-20 gel column chromatography, and the structures of compounds w...Aim To investigate the chemical constituents of Piper wallichii. Methods Five compounds were isolated by silica gel column chromatography and Sephadex LH-20 gel column chromatography, and the structures of compounds were identified by spectral analysis. Result Five compounds were identified as piperlonguminine （trans, trans） （1）, 4-hydroxy-3,5-dimethoxy-benzoic acid （2）, galgravin （3）, β-sitosterol （4）, and daucosterol （5）. Conclusion Five compounds were isolated from Piper wallichii for the first time, and compounds 1 -3 were isolated from this genus far the first time.展开更多
Seven novel fluorescent coumarin derivatives were synthesized from 7-diethylamino-4-chloro-3-formyl-coumarin. The spectra of absorption, excitation and emission were dependent not only on the structures and also on th...Seven novel fluorescent coumarin derivatives were synthesized from 7-diethylamino-4-chloro-3-formyl-coumarin. The spectra of absorption, excitation and emission were dependent not only on the structures and also on the concentration of dyes. The PPP-MO predictions can only be consistent with the spectra in dilute solutions.展开更多
Molecularly imprinted polymers(MIPs)for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule.Polymers of va...Molecularly imprinted polymers(MIPs)for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule.Polymers of varying composition were prepared using different monomers(4-vinylpyridine,methacrylic acid,and acrylamide),ethylene glycol dimethacrylate as the cross-linker,2,2-azobis(2-methylpropinitrile)as the initiator,and different porogen solvents(ethanol,acetone/methanol,and acetonitrile).The best polymer was obtained when 4-vinylpyridine was used as the monomer and acetone/methanol(3:2)as the porogen solvent,whereas the template:-monomer:-cross-linker ratio was 1:4:20.The imprinting factor of the selected MIPs for esculetin was 3.77.The polymers were evaluated according to their selective recognition properties for esculetin and structurally-related compounds(esculin,scopoletin,coumarin,and 7-methoxycoumarin).Chemical and morphological characterizations of the polymers were investigated by FTIR and scanning electron microscope,which confirmed a high degree of polymerization.Surface area,pore volume,and pore size of the polymer were investigated by Brunauer-Emmett-Teller analysis.MIPs were also successfully used as solid-phase adsorbent materials for the extraction of esculetin from tobacco leaves.Esculetin contents in dried tobacco leaves were found to be(9.27±0.17)μg g-1.展开更多
基金National Key Technologies Research and Development Program in the 10th five-year plan，国家杰出青年科学基金
文摘In the past few years, support vector machines (SVMs) have been applied to many fields, such as pattern recognition and data mining, etc. However there still exist some problems to be solved. One of them is that the SVM is very sensitive to outliers or noises because of over-fitting problem. In this paper, a fuzzy support vector regression (FSVR) method is presented to deal with this problem. Strategies based on k nearest neighbor (kNN) and support vector data description (SVDD) are adopted to set the fuzzy membership values of data points in FSVR.The proposed FSVR soft sensor models based on kNN and SVDD are employed to predict the concentration of 4-carboxy-benzaldehyde (4-CBA) in purified terephthalic acid (PTA) oxidation process. Simulation results indicate that the proposed method indeed reduces the effect of outliers and yields higher accuracy.
文摘The crystal structure of the title compound C16H18NO2+·C7H7SO3-·2H2O, (C23H29NSO7, Mr=463.53) has been determined by single-crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system with space group P21/n, a=8.101(1), b=8.958(2), c=33.281(5)?,β= 94.910(1)(, V=2406.3(7)?3, Z=4, Dc=1.279g/cm3, μ=0.176mm-1, F(000)=984, final R=0.0409, and Rw=0.0860 for 4401 independent reflections. The result shows that in the crystal structure of the title compound the planar cations have two configurations with equal occupation ratio and are antiparally packed through π…π interactions. Similar packing energies in A and B are probably the main factor that leads to the disorder structure.
文摘For the production of reactive polyurethane cross-linkinger and curing agents, 2, 4-diisocyanate toluene （TDI） terpolymer, which possesses the rigid structures of hexatomic ring and three reactive functional groups, was synthesized and characterized by the Fourier transform infrared （FFIR）, the gel permeation chromatography （GPC） and the chemical analysis methods. The reaction conditions were studied and optimized. A tracking research on the polymerization process of TDI was taken by using the GPC. The formation processes of the terpolymer, oligomers and higher-polymers were also dealt with. Results show that the TDI terpolymer can be prepared in the presence of Cat-3 catalyst and at the reaction temperature of （60 ±2）℃. The reaction time is short, its outcomes have narrow molecular weights distribution, namely molecular weights from 530 to 550, Mw/Mn =1.10, and the mass fraction of NCO is （25. 0 ± 0. 5）%. With the reaction time prolonging, however, TDI can be further higher-polymedzed to form higher-polymers. Benzoyl chloride （0. 4%, mass fraction）, as the stabilizing agent, can effectively inhibit the occurrence of higher-polymerization. The obtained TDI terpolymer can be stable for more than half a year.
文摘Aim To investigate the chemical constituents of Piper wallichii. Methods Five compounds were isolated by silica gel column chromatography and Sephadex LH-20 gel column chromatography, and the structures of compounds were identified by spectral analysis. Result Five compounds were identified as piperlonguminine （trans, trans） （1）, 4-hydroxy-3,5-dimethoxy-benzoic acid （2）, galgravin （3）, β-sitosterol （4）, and daucosterol （5）. Conclusion Five compounds were isolated from Piper wallichii for the first time, and compounds 1 -3 were isolated from this genus far the first time.
基金Supported by the State Key Laboratory of Dyes and Surfactants Fine Chemicals.
文摘Seven novel fluorescent coumarin derivatives were synthesized from 7-diethylamino-4-chloro-3-formyl-coumarin. The spectra of absorption, excitation and emission were dependent not only on the structures and also on the concentration of dyes. The PPP-MO predictions can only be consistent with the spectra in dilute solutions.
基金supported by the Yunnan Green Tobacco Production Research(2011YN01)the China Equipment and Education Resources System(CERS-1-75)
文摘Molecularly imprinted polymers(MIPs)for solid-phase extraction and pre-concentration of esculetin have been successfully prepared by the bulk polymerization method using esculetin as a template molecule.Polymers of varying composition were prepared using different monomers(4-vinylpyridine,methacrylic acid,and acrylamide),ethylene glycol dimethacrylate as the cross-linker,2,2-azobis(2-methylpropinitrile)as the initiator,and different porogen solvents(ethanol,acetone/methanol,and acetonitrile).The best polymer was obtained when 4-vinylpyridine was used as the monomer and acetone/methanol(3:2)as the porogen solvent,whereas the template:-monomer:-cross-linker ratio was 1:4:20.The imprinting factor of the selected MIPs for esculetin was 3.77.The polymers were evaluated according to their selective recognition properties for esculetin and structurally-related compounds(esculin,scopoletin,coumarin,and 7-methoxycoumarin).Chemical and morphological characterizations of the polymers were investigated by FTIR and scanning electron microscope,which confirmed a high degree of polymerization.Surface area,pore volume,and pore size of the polymer were investigated by Brunauer-Emmett-Teller analysis.MIPs were also successfully used as solid-phase adsorbent materials for the extraction of esculetin from tobacco leaves.Esculetin contents in dried tobacco leaves were found to be(9.27±0.17)μg g-1.
