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51.
The structure of the title adduct comprises a phenanthroline derivative 2-phenyl-imidazo[4,5-f]1,10-phenanthroline and a methanol.The composition of the crystalline adduct was characterized as C19H12N4.CH3OH.It belongs to orthorhombic system,space group Pna21 with a=1.3693(4)nm,b=2.2988(7)nm,c=0.51338(15)nm,V=1.6160(8)nm^3.Z=4,and final R1=0.0423.wR2=0.1012 .Crystal structure shows that all the 19 carbon atoms and 4 nitrogen atoms are coplanar.The bond length data indicated that a very extensive conjugation system was formed.This conjugation makes the compound being a potentially excellent energy transformer used for luminescent materials. 相似文献
52.
Hongyong Zhao 《Journal of Mathematical Analysis and Applications》2003,282(2):437-443
The paper is devoted to the invariant set and periodic attractor for nonautonomous functional differential systems. Some sufficient criteria of the invariant set and periodic attractor are derived. Particularly, we have provided an estimate on existence range of periodic attractor by using the properties of nonnegative matrices and differential inequality technique. 相似文献
53.
A new method based on anion exchange resin separation and graphite furnace atomic absorption spectrometry (GFAAS) detection
is proposed for the determination of inorganic tin species. The result showed that Sn(IV) was quantitatively retained on the
resin when [HCl] = 9.0 mol · L−1, but Sn(II) could not be adsorbed on the resin under the same condition. Thus, a separation of Sn(II) and Sn(IV) has been
realized. When the concentration of NaOH solution was between 2.0–7.0 mol · L−1, Sn(IV) that adsorbed on the resin could be eluated from the resin completely. Meanwhile, under the atmosphere and the nitrogen
states, the translation between Sn(II) and Sn(IV) was investigated. Under the optimal conditions, the detection limit of Sn(IV)
is 0.40 μg · L−1 with RSD of 2.3% (n = 5, c = 2.0 μg · L−1). The proposed method was applied to the speciation analysis of tin in different water samples and the recovery of total
Sn was in the range of 98.7–101.7%. In order to verify the accuracy of the method, a certified reference water sample was
analyzed and the results obtained were in good agreement with the certified value. 相似文献
54.
Ji-hong SU & Yi-cai ZHAO LMAM Department of Mathematics Jinan University Guangzhou China 《中国科学A辑(英文版)》2007,50(4):495-502
Let X be a smooth projective variety of dimension 2k-1 (k≥3) over the complex number field. Assume that fR: X→Y is a small contraction such that every irreducible component Ei of the exceptional locus of fR is a smooth subvariety of dimension k. It is shown that each Ei is isomorphic to the k-dimensional projective space Pk, the k-dimensional hyperquadric surface Qk in Pk 1, or a linear Pk-1-bundle over a smooth curve. 相似文献
55.
In this paper, we establish a theorem on the distribution of primes in quadratic progressions on average. 相似文献
56.
In this paper, we consider a queueing system in which there are two exponential servers, each having his own queue, and arriving
customers will join the shorter queue. Based on the results given in Flatto and McKean, we rewrite the formula for the probability
that there are exactlyk customers in each queue, wherek = 0, 1,…. This enables us to present an algorithm for computing these probabilities and then to find the joint distribution
of the queue lengths in the system. A program and numerical examples are given. 相似文献
57.
为解决高等师范院校物理专业学生的知识结构和实际能力与社会需要明显不相适应的矛盾,我们对四年制物理专业的课程结构进行了全面改革。改革后,毕业生不仅能胜任普通中学或职业中学(职业中专)的教学,而且有能力参与厂矿企业的技术工作,具有更广泛的适应性和更强的竞争力。 相似文献
58.
本文对星载光学系统遮光罩消杂光结构的优化设计做了初步探讨。提出了遮光罩和挡光环消杂光设计的基本原则。给出了一种二级遮光罩结构寸的优化设计方法和一种遮光罩内壁上挡光环位置优化设计方法,并对一级和二级遮光罩进行了初步的分析比较。 相似文献
59.
用漫反射红外光谱和光声红外光谱研究了金属羰基化合物(CpFe(CO)2)2Cp=η^5-C5H5与酸性,中性和碱性Al2O3及TiO2的相互作用,结果表明,在Al2O3表面生成的洗生物种类及浓度与Al2O3的酸碱度明显相关,在酸性Al2O3表面,主要存在衍生物(CpFe(CO)2Fe-H-Fe(CO2Cp)^+及少量的CpFe(CO)2(-O-);在中性Al2O3表面存在的CpFe(CO)2(-O 相似文献
60.
苯并噻唑重氮氨基偶氮苯与汞(Ⅱ)的显色反应及其应用 总被引:26,自引:2,他引:24
报道了新试剂苯并噻唑重氮氨基偶氮苯的合成及其与汞(Ⅱ)的显色反应,在TritonX-100存在下弱碱性介质中,试剂与汞形成2:1的橙红色络合物,最大吸收波长位于520nm处,表观摩尔吸光系数为1.51×10^5L.mol^-1.cm^-1。汞量在0~1.2mg/L范围内遵守比尔定律,直接应用于废水中微量汞的测定,结果满意。 相似文献