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应用小波和小波包变换对傅里叶变换衰减全反射红外光谱(FTIR/ATR)进行去噪处理,以提高苯丙酮尿症(PKU)筛查模型的性能。首先优化小波和小波包变换的参数,然后分别对原始光谱(OS)、9点平滑光谱(9S)和一阶微分9点平滑光谱(1D9S)进行去噪处理,以均方根误差(RMSE)、平均相对误差(MRE)、预测准确率(Acc)等为指标,考察小波和小波包变换对模型性能的影响。结果与变换前相比,模型性能均有所提高,其中小波变换以1D9S+sym12处理结果为最优,而小波包变换以1D9S+sym1为最优;Acc全部提高为100%。 相似文献
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小波变换用于不同晶型聚丙烯红外特征峰的鉴别 总被引:5,自引:0,他引:5
本文运用小波变换研究了α晶相和β晶相聚丙烯的很相似的傅里叶变换红外特征光谱。经过小波变换后,这两种晶相聚丙烯的吸收光谱有显著的差别。结果表明聚丙烯的晶相可通过对其红外光谱进行小波变换而鉴别。 相似文献
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小波变换用于植物激素重叠色谱峰中组分的定量分析 总被引:12,自引:3,他引:12
根据小波变换将信号按频率大小分解的性质,作者提出了一种用小波变换直接提取重叠色谱峰中单一组分信息的方法,并将其应用于植物激素混和体系重叠峰的解析与定量分析。结果表明:单组分的色谱信号经小波变换分解后仍能保持原有的线性关系,用小波变换从重叠信号中提取的单一组分信息也具有良好的线性关系。 相似文献
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小波包变换潜变量回归分辨重叠的紫外光谱 总被引:1,自引:1,他引:0
采用小波包变换潜变量回归(WPLVR)方法,同时测定联苯、苯酚和邻苯二酚。该法结合小波包变换和潜变量回归改进除噪质量。通过最佳化,选择了小波函数及小波包分解水平(L)。编制了两个程序PWPLVR和PFTLVR进行WPLVR和付立叶变换潜变量回归(FTLVR)法计算。试验结果表明WPLVR法是成功的且优于FTLVR法。 相似文献
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小波包变换潜变量回归同时测定三组分混合物 总被引:2,自引:0,他引:2
采用小波包变换潜变量回归 (WPLVR)方法 ,同时测定水杨酸甲酯(MSA)、邻苯二甲酸二丁酯 (DBP)和邻苯二甲酸氢钾 (PHP)。该法结合小波包变换和潜变量回归改进除噪质量。通过最佳化 ,选择了小波函数及小波包分解水平 (L)。编制了两个程序 (PWPLVR)和 (PFTLVR)进行WPLVR和付立叶变换潜变量回归 (FTLVR)法计算。实验结果表明WPLVR法是成功的且优于FTLVR法。 相似文献
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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. 相似文献
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A class of excitable media described by the Fitzhugh-Nagumo equation is investigated. Based on the stable and self adaptive theory, the error between the systems grid variables and the standard sampling of the periodical signal or constant signal was feed back into the system both globally and locally. When the controller was then shut off, automatically, the whole system became homogeneous. Additionally, the scheme was tested under noisy conditions. The numerical simulations results demonstrate its effectiveness. The system reached a homogeneous state and a spiral wave was converted into a target wave, resulting in a wonderful pattern emerging using a different controller. The scheme proved robust in resisting the effects of noise. 相似文献
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K. Ueberreiter 《Colloid and polymer science》1982,260(1):37-45
Viscosity measurements have been made of water-solvent and water-polymer solutions in a temperature range of 20–60 centigrades. A medium structure temperatureT
0 was calculated from the Vogel-equation. Water has a structure temperature of 140–150 K, its decrease indicates structure breakage, an increase structure promotion. Pyridine, dioxane, dimethylformamide and urea are structure breakers. This is explained by a shift of the equilibrium — bonded water molecules — nonbonded — to the right. Acetone shows hydrophobic bonding in the same concentration range of 0–10 mole % as the normal alcohols. They are quasifree liquids-structure temperature zero-in the pure state. This is explained by hydrogen bridged dimer formation with the exception of tert-butanol. Its 3 methylgroups sterically prevent dimer formation and cause structuring. Adding urea to methanol-water solutions breaks water structure according to urea concentration but extends the hydrophobic bonding maximum over the whole diagram. Glucose-water solutions have a minimum in the structure temperature diagram. Its left side indicates waterstructure breakage, its right side formation of a new structure forced upon water by the sugar. The equilibrium can be formulated: Waterlike bonded-nonbonded-hetero (solvent)-like bonded, Ribose also shows this minimum but after a short range of heterobondedness the structure is completely broken to nonbondedness.The polymers dextrane and polyvinylpyrrolidone are strong waterstructure breakers. Dextrane much stronger than PVP, it breaks to nonbondedness while PVP maintains a certain structuring, perhaps indicating heterobonding at higher concentrations. Polyacrylamide is a strong structurebreaker. It resembles urea in this sense. Perhaps the solvationwater structure of the NH2 groups is very different from pure waterstructure. Polyacrylicacid breaks waterstructure completely, if sodiumchloride is added waterstructure is rebuilt again. The only waterstructure promoting polymer is natural gelatine. Perhaps this structure is different from pure water or the watermolecule equilibrium is shifted towards bondedness. The structure temperatures of pure polyethyleneglycoles show a minimum with increasing molecular weight. The high structure temperature of the small chains is explained by long chain assoziates formation through hydrogen bridging. This liquid of long assoziate chains is structured and has a high structure temperature. With increasing molecular weight ringformation instead of linear assoziation becomes possible. These neutral rings form a free liquid. Long chains again have a linear structure and the structure temperature increases at higher molecular weights. Existence of linear chain assoziation of low molecular PEGs is proved with their breakage by adding the chain terminating methanol.Dedicated to Prof. Dr. F. H. Müller.Herrn Chemotechniker D. Ziegler möchte ich für die sorgfältige Durchführung der Messungen sehr danken.Dem Verband der Chemischen Industrie danke ich sehr für die Ermöglichung der Arbeit. 相似文献
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W. Li M. Wang Z. H. Li X. F. Shang H. Wang Y. W. Wang Y. B. Xu 《Russian Journal of Electrochemistry》2007,43(11):1279-1283
The lithium-ion-conducting inorganic solid electrolytes in the oxide systems Li2O-SiO2-P2O5 and Li2O-TiO2-SiO2-P2O5 were prepared by the solid-state reaction, and the electrolyte pellet made by cold-pressing method had diameter of 13 mm
and was about 1 mm thick. Phase identification and surface morphology of the products were carried out by X-ray diffraction
and scanning electron microscopy. Ionic conductivity of the pellets was investigated through ac impedance. The results show
that the adding of other cations can improve the ionic conductivity of the solid electrolyte, and the sintering temperature
and duration can influence the ionic conductivity. The maximum ionic conductivity in the samples is 9.9 × 10−4 S/cm in the Li2O-TiO2-SiO2-P2O5 system.
Original Russian Text ? W. Li, M. Wang, Z.H. Li, X.F. Shang, H. Wang, Y.W. Wang, Y.B. Xu, 2007, published in Elektrokhimiya,
2007, Vol. 43, No. 11, pp. 1341–1345. 相似文献
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Shu-FengLi Xin-LinYang Wen-QiangHuang 《高分子科学》2005,(2):197-202
Monodisperse crosslinked poly(chloromethylstyrene-co-divinylbenzene) (poly(CMSt-co-DVB)) microspheres were prepared by distillation-precipitation copolymerization of chloromethylstyrene (CMSt) and divinylbenzene (DVB) in neat acetonitrile. The polymer particles had clean surfaces due to the absence of any added stabilizer. The size of the particles ranges from 2.59 μm to 3.19 μm and with mono-dispersity around 1.002-1.014. The effects of monomer feed in copolymerization on the microsphere formation were described. The polymer microspheres were characterized by SEM and chlorinity elemental analysis. 相似文献
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Colloidal dispersions of uniform spherical particles of cadmium phosphate, nickel basic phosphate, and manganese (II) phosphate were prepared by aging at elevated temperatures metal salt solutions and phosphoric acid or sodium dihydrogen phosphate in the presence of urea and sodium dodecyl sulfate. Uniform spheres were obtained only if urea and the surfactant were added within a given range of concentrations.The spherical particles were amorphous as prepared. Cadmium phosphate and nickel basic phosphate particles crystallized when calcined at appropriate temperatures. Manganese (II) phosphate particles underwent a phase transformation to crystalline plate-like solids when aged in doubly distilled water at room temperature.Supported by NFS grant CHE-8619509.Part of M. S. Thesis by L.L.S. 相似文献
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ZnO films were deposited on glass substrates by gas discharge reaction evaporation. The influences of substrate temperature on the surface morphology, crystal structure and electric properties of ZnO films were studied by scanning electron microscopy, atomic force microscopy, X-ray diffraction spectroscopy and complex impedance spectroscopy. The results show that the films with dense and amorphous structure and lower grain boundary resistance were deposited at room temperature. When the substrate temperature is higher than 50 ℃, the films with certain c-axis orientation can be deposited. With the increase of the substrate temperature, the preferential orientation of ZnO films along c-axis is augmented, the tensile stress along c-axis orientation decreases and the grain boundary resistance increases in a marked degree. When the substrate temperature is higher than 100 ℃, the increasing trend of the preferential orientation of ZnO films along c-axis slows down. ZnO films possess high preferential c-axis orientation and best crystalline quality at 180-200 ℃. These possess a smooth surface, symmetrical grain dimension (i.e. 30-40 nm), inerratic crystal shape, less tensile stress and 0.965 epitaxial degree along the c-axis direction. Here the grain boundary effect increases and the grain boundary resistance is evidently more than that of the films deposited at room temperature. The mechanism by which substrate temperature affects crystal structure and grain boundary properties were also discussed. 相似文献
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Theoretical studies on the α- and β-forms nitroguanidine were carried out using ab initio theoretical methods, at the MP2/6-31G(d,p) level. The predicted geometrical parameters were in good agreement with the available theoretical values, which calculated by other author. The three C-N bond lengths in α-form nitroguanidine were different, the longest bond length was 1.430 A, the shortest was 1.283 A. But they were almost similar in β-form, the longest was 1.375 A, the shortest was 1.322 A. Therefore there were conjugative effects in β-form but not in α-form. The calculated results also show that the β-form is stable with respect to the α-form from energetically, lower 28.16 kJ/mol corrected with zero point vibrational energy. The transition-state for the unimolecular isomerization was conformed by the IRC calculation. The calculated energy barrier for the direct intramolecular hydrogen atom transfer isomerization process was 132.95 kJ/mol. The isomerization reaction, exothermal reaction, is a typical intramolecular hydrogen atom synfacial transfer reaction. Rate constants of the isomerization reaction were evaluated within the temperature range of 200-1773 K by the classical transition state theory. The rate constant was 1.99×10-11 s-1 and the equilibrium constant was 1.00×105 at 298 K. With the temperature increasing, the equilibrium value decayed and the reaction process was more difficult. 相似文献
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FiveBetula species,B. pendula, B. browicziana, B. medwediewii, B. litwinowii, andB. recurvata, were collected from different parts of Turkey. The leaves of these species were hydrodistilled to yield the consequent essential oils. The essential oil compositions were investigated by GC/MS. 14-Hydroxy--caryophyllene was the main constituent in the oil ofB. pendula. 14-Hydroxy-4,5-dihydro--caryophyllene, a new compound, was identified as the main constituent in the oils ofB. browicziana, B. litwinowii, and B. recurvata. In the oil ofB. medwediewii methyl salicylate was the main compound. Various phytopathogenic fungi were studied by the agar tube dilution technique to test the antifungal activities of the essential oils at 400 g/ml concentration. The essential oils showed strong antifungal activity againstCephalosporium aphidicola, Drechslera sorokinianse, Fusarium solani, andRhizoctonia cerealis.Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 126–130, March–April, 2000. 相似文献
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Using CD-measurements the influence of nonionic surfactants (dodecyl polyoxyethylene, ethoxylated para tert. octyl phenol, commercial nonionic WON 100 and octyl diethyl phosphinoxid) on the secondary structure of gelatin in aqueous solutions was investigated. At surfactant concentrations smaller than the c.m.c. the triple helical content of the gelatin is increased. At concentrations exceeding the c.m.c. the triple helical content decreases. Chain reversals of the peptide chains after the destruction of the triple helical structure were shown to appear in acidic environment at 298 K. This destruction is reversible by rechilling the solution. 相似文献