Invariant set and attractor of nonautonomous functional differential systems

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.     

Speciation Analysis of Inorganic Tin (Sn(II)/Sn(IV)) by Graphite Furnace Atomic Absorption Spectrometry Following Ion-Exchange Separation

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.     

On structure of small contractions of odd dimensional projective varieties

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.     

Primes in quadratic progressions on average

In this paper, we establish a theorem on the distribution of primes in quadratic progressions on average.     

A numerically stable algorithm for two server queue models

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.     

高等师范学校物理专业课程结构改革研究

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。     

Hybrid organosilazane/organosilylamine telechelic oligomers—I. Two-dimensional NMR spectroscopy characterization of dimethylsilylethylenediamine oligomers

The detailed characterization of multifunctional hybrid organosilazane/organosilylamine telechelic oligomers by IR and ¹H, ¹³C and ²⁹Si NMR spectroscopy in one and two dimenions has been undertaken. The specific multifunctional oligomers, comprising NH/NH₂ or SiCl functionalities depending on the monomer feed-ratio, were prepared from mono- and di-functionally reacted dichlorodimethylsilane (DDS) and mono-, di-, tri- and tetra-functionally reacted ethylenediamine (EDA). Varying the feed-ratio afforded control of the microstructures of the oligomers and the preparation of oligomers with, in some cases, conterminously located silicon–chlorine (SiCl) groups. The combination of the NMR methods with the IR technique has enabled the detailed microstructural characterization of the oligomers and the identification of the functionalities therein. This approach and the knowledge gained from the DDS/EDA system has been applied to the microstructural characterization of other hybrid organosilazane/silylamine preceramic telechelic oligomers.     

金属羰基化合物（CpFe（CO）2）2与金属氧化物表面作用的傅里叶变…

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