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71.
JunHu Ma HeQing Yang YuZhe Song Li Li XiaoLi Xie RuiNi Liu LinFang Wang 《中国科学E辑(英文版)》2009,52(5):1264-1272
Large-scale oriented ZnO nanocone arrays were directly grown on zinc substrate through a hydro-thermal reaction of Zn foil with aqueous butylamine solution(3 mol/L) at 100—180 ℃ for 12 h.The syn-thesized products were characterized with X-ray diffraction,Raman spectrum,scanning electron mi-croscopy and transmission electron microscopy.The results showed that the ZnO nanocones were single crystalline with the wurtzite structure and grown along the [0001] direction.The diameter of nanocones is decreased with ... 相似文献
72.
XU Bin WU ZhenSen WU Jian & XUE Kun School of Science Xidian University Xi’an China State Key Laboratory of Electromagnetic Environment China Research Institute of Radiowave Propagation Beijing 《中国科学E辑(英文版)》2009,52(4):1112-1116
The electron velocity distribution function and the incoherent scatter spectra during ionospheric heating in low ionosphere
region are presented with consideration of the elastic collision between electrons and neural particles and the excitation
of rotation energy level. The effects of pump frequency and electric fields on the spectra are discussed. With the increase
of electric field, the non-Maxwellian feature is enhanced, and with the increase of heating frequency, the non-Maxwellian
feature is weakened. The non-Maxwellian factor will bring a large error in ionosphere parameters, which must be considered
in the inversion.
Supported by the National Natural Science Foundation of China (Grant No. 40310223), the National Key Laboratory of Electromagnetic
Environment (LEME), and National Key Technologies R&D Program of China (Grant No. 2006BAB18B06) 相似文献
73.
74.
AgPb2B2V3O12 (B = Mg, Zn) ceramics with low sintering temperature were synthesized via the conventional solid-state reaction route. Rietveld refinements of the X-ray diffraction patterns confirm cubic symmetry with space group . The number of observed vibrational modes and those predicted by group theoretical calculations also confirm the space group. At the optimum sintering temperature of 750°C/4 hours, AgPb2Mg2V3O12 has a relative permittivity of 23.3 ± 0.2, unloaded quality factor () of 26 900 ± 500 GHz (), and temperature coefficient of resonant frequency of 19.3 ± 1 ppm/°C, while AgPb2Zn2V3O12 has the corresponding values of 26.4 ± 0.2, 28 400 ± 500 GHz () and –18.4 ± 1 ppm/°C at 590°C/4 hours. Microwave dielectric properties of a few reported garnets and Pb2AgB2V3O12 (B = Mg, Zn) ceramics were correlated with their intrinsic characteristics such as the Raman shifts as well as width of A1g Raman bands. Higher quality factor was obtained for lower full width at half-maxima (FWHMs) values of A1g modes. The increase in B-site bond valence contributes to high and low |τf| with the substitution of Zn2+ by Mg2+. Furthermore, the high ionic polarizability and unit cell volume with Zn2+substitution contribute to increased relative permittivity. 相似文献
75.
Raman spectroscopy studies of concentrated vanadium redox battery positive electrolytes 总被引:3,自引:0,他引:3
Spectroscopic changes in highly concentrated vanadium(V)-sulfate solutions to be used in the vanadium redox battery are consistent with the presence of more than one V(V)-sulfate species. The results of Raman spectroscopy indicate that the major species in highly acidic conditions are VO2SO4
–, VO2(SO4)2
3–, VO2(HSO4)2
–, VO3
–, V(V) dimers with V2O3
4+ and V2O4
2+ central units. The nature and amount of these species depends upon the V(V) and total sulfate concentrations as well as on S to V and H+ to V ratios in the positive half-cell electrolyte. V(V) forms V2O3
4+, VO2(SO4)2
3– and their copolymer species at higher total sulfate concentrations, which tends to stabilize the vanadium (V) positive electrolyte in the vanadium redox battery. The V(V) and V(IV) species show the least interaction with each other. Ageing of concentrated V(V) solutions at elevated temperature (50 °C) produces decomposition of species causing formation of V2O5 precipitates with a decrease in the amount of vanadium polymer. 相似文献
76.
Calcium‐containing poly(urethane‐ester)s (PUEs) were prepared by reacting diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)2] and hydroxyl‐terminated poly(1,4‐butylene glutarate) [HTPBG1000], using di‐n‐butyltin‐dilaurate as catalyst. About six calcium‐containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)2:HTPBG1000:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4, and 1:3:4. Two blank PUEs were synthesized by the reaction of HTPBG1000 with diisocyanate (HMDI or TDI). The polymers were characterized by IR, 1H NMR, Solid state 13C‐CP‐MAS NMR, TGA, DSC, XRD, solubility, and viscosity studies. The Tg value of PUEs increases with increase in the calcium content and decreases with increase in soft segment content. The viscosity of the calcium‐containing PUEs increases with increase in the soft segment content and decreases with increase in the calcium content. X‐ray diffraction patterns of the polymers show that the HMDI‐based polymers are partially crystalline and TDI‐based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium‐containing PUEs based on HMDI shows that with increase in the calcium content of polymer, modulus (g′ and g″) increases at any given temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1720–1727, 2006 相似文献
77.
采用常规的Sol-gel工艺合成了In^3 掺杂的多孔SiO2干凝胶,In^3 离子作为间隙离子存在于SiO2网络中,展示了一种新颖的发光现象,改变了多孔SiO2干凝胶的发射光谱。这种掺杂的多孔SiO2干凝胶的激发和发射光谱均由2个带组成,短波长的发光峰在440nm(λex=380nm),其相对荧光强度约是未掺杂的多孔SiO2干凝胶的4倍;长波长的发光峰(In^3 离子在多孔SiO2干凝胶的特征发射)在600nm(λex=476nm),其相对荧光强度约是In^3 掺杂ZnS纳米晶的10倍。由此可以看出:掺杂的多孔SiO2干凝胶是一种高效的发光材料。 相似文献
78.
Masao Tomikawa Frank W. Harris Stephen Z. D. Cheng Edward Galentier 《Reactive and Functional Polymers》1996,30(1-3):101-107
A series of new, substituted pyromellitic dianhydrides were synthesized from 1,2,4,5-tetramethylbenzene. New soluble rigid-rod polyimides were obtained from the dianhydrides and 2,2′-bis(trifluoromethyl)-4,4′-biphenyl (PFMB) in phenolic solvents in the presence of isoquinoline as a catalyst. The polyimides are soluble in N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), m-cresol and other solvents, in spite of having no bending in their rigid structures.
UV irradiation changed color of the polyimide solutions and also their viscosity. We observed new absorbance in the 700-nm region and an ESR signal by UV irradiation. The new visible absorbance and the ESR signal are derived from the same origin. They are attributed to the anion radical of the diimide moiety in the polyimide as deduced from the hyper fine structure of the ESR signal. In addition, UV irradiation diminishes the solution viscosity. 相似文献
79.
Gas chromatography, coupled gas chromatography-mass spectrometry (electron impact mode and chemical ionization with methane as reactant gas), gas chromatography-infrared spectroscopy, and derivatization techniques were used to identity 53 compounds in the interdigital secretion of the red hartebeest, Alcelaphus buselaphus caama. These compounds included alkanes, isoalkanes, alcohols, ketones, carboxylic acids, oxiranes, furanoid linalool oxides, and a large number of branched and unbranched saturated and unsaturated aldehydes. The secretion probably plays a role in demarcation of territories by dominant bulls. 相似文献
80.
有效的甄别、掌握空间碎片的状态,是合理利用太空资源和在轨航天器规避风险的前提,为了安全、持续地开发和利用空间资源,基于散射光谱,使用夹角余弦和欧式距离嵌入K临近法(KNN-AC-ED),并与经典的朴素贝叶斯分类器作为对比,对实验室测得的空间碎片中常用的四种材质进行分类识别。分类识别的结果显示,KNN-AC-ED法比经典的朴素贝叶斯分类器总体分类精度高4%。研究表明:朴素贝叶斯分类器需要提取每个光谱曲线的三个特征,而特征提取费时费力;KNN-AC-ED法利用光谱线型和强度两种信息,不仅全面的反应了光谱的信息,且计算相对更快捷。通过对空间碎片常用材质的分类,为进一步研究空间碎片的尺寸、材质等信息提供一定的借鉴意义。 相似文献