Synthesis, Crystal Structure and Luminescent Properties of a Novel 2D Sheet Cd(Ⅱ) Coordination Polymer [Cd(Cpna)(Py)]n

A coordination polymer, [Cd(cpna)(py)]n(H2cpna = 5-(2-carboxylphenyl) nicotic acid, py = pyridine) 1 has been hydrothermally synthesized and characterized by elemental analysis, IR, TG, fluorescence spectra and single-crystal X-ray diffraction. Colorless crystals crystallize in the monoclinic system, space group P21/c with a = 8.589(2), b = 13.047(3), c = 14.940(4) , β = 96.001(2)°, V = 1664.9(7) 3 , C18H12CdN2O4 , Mr = 432.70, Dc = 1.726 g/cm 3 , F(000) = 856, Z = 4, μ(MoKα) = 1.337 mm -1 , the final R = 0.0396 and wR = 0.0891 for 2422 observed reflections (I > 2σ(I)). Complex 1 exhibits a two-dimensional (2D) sheet structure, which further builds a three-dimensional (3D) supramolecular architecture via C-H···O hydrogen-bonding interactions.     

Torsion of an elastic space with a semi-infinite conical crack

The axisymmetric problem of stress concentration near a conical crack in an infinite elastic space with a rotation center is addressed. The problem is reduced to an integro-differential equation. Its exact solution is obtained. An expression for the stress intensity factor in crack neighborhood is derived and numerically analyzed for different positions of the rotation center and the crack opening angles __________ Translated from Prikladnaya Mekhanika, Vol. 43, No. 2, pp. 99–107, February 2007. For the centenary of the birth of G. N. Savin.     

Heteropoly acids of the Keggin type with N-substituted β-amminoethylphosphonic acids as coordinate center

Organophosphorus-heteropolytungstic acids of 1 : 12 of P/W ratio, with N-substituted 2-amminoethylphosphonic acids R2R'N+CH2CH2PO3H- (R = R' = H; R = Me, R' = H; R = R' = Me; R = H, R' = Me2CH; R = H , R' = CH3(CH2)2CH2) as coordinate centers were prepared, and characterized by means of elemental analysis, IR, UV spectroscopy, TG and DSC thermal analysis. The results indicate that these organophosphorous-HPAs possess Keggin type structure, and their stoichiometric formulation is R2R'N+CH2CH2PO3H - ·W12O36 ·nH2O. The organic side chain with the ammino-group R2R'N+CH2CH2- and the phosphono-group-PO3H- participate altogether in the formation of the primary structure of the heteropoly anion. In other words, the entirety of each compound R2R'N+CH2CH2PO3H- is as the core or coordinate center of the heteropoly anions. The number of crystal water in the HPA was affected obviously by the N-substituents of the organo-phosphonic acids.     

On Central Elements in the Universal Enveloping Algebras of the Orthogonal Lie Algebras

We present an analogy of the famous formula that the square of the Pfaffian is equal to the determinant for an alternating matrix for the case where the entries are the generators of the orthogonal Lie algebras. This identity clarifies the relation between the two sets of central elements in the enveloping algebra of the orthogonal Lie algebras. We employ systematically the exterior calculus for the proof.     

声空化物理化学综合法制备发光多孔硅薄膜的微结构与发光特性

声空化所引发的特殊的物理、化学环境为制备高效发光的多孔硅薄膜提供了一条重要的途径.实验结果表明，声化学处理对于改善多孔硅的微结构，提高发光效率和发光稳定性都是一项非常有效的技术.超声波加强阳极电化学腐蚀制备发光多孔硅薄膜，比目前通用的常规方法制备的样品显示出更优良的性质.这种超声的化学效应源于声空化，即腐蚀液中气泡的形成、生长和急剧崩溃，在多孔硅的腐蚀过程中，孔中的氢气泡，由于超声波的作用增加了逸出比率和塌缩，有利于孔沿垂直方向的腐蚀. 关键词： 声空化方法 微结构 发光特性 多孔硅     

Decay of ESR nutation signals fromE′1 centers in quartz

Decay of time-dependent nutation signals from E′₁ centers in crystalline quartz is investigated at room temperature. ESR-nutation signals were excited in the single-photon mode and were shaped by Zeeman field pulses. It is found that the decay of this signal follows an exponential law with a rate Λ substantially smaller than 1/T₂ (T₂ being the transverse relaxation time) and increases with the amplitude of the acting ultrahigh-frequency field B₁. It is shown with the use of the Bloch equations that the intergral decay rate of nutations in an inhomogeneously broadened two-level system depends on the ratio of B₁ to the linewidth and increases nonlinearly with increasing B₁. The observed quantitative disagreement between the experimentally observed nutation decay with Bloch's theory is explained by the stochasticity of conditions of the resonant interaction of radiation with a system of spins. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 213–219, March–April, 1999.     

温度和浓度对分散在SiO_2中Y_2O_3∶Eu~(3+)纳米材料发光的影响

讨论了分散在SiO2中的Y2O3∶Eu纳米发光材料在不同浓度和不同灼烧温度下光谱的变化规律,在室温紫外激光波长激发下不同灼烧温度下样品的发射光谱。从光谱上看到在一定浓度下随着灼烧温度的升高发光变强,而且在一定温度下随浓度提高发光变强。尤其在5D0→7F0跃迁谱线的强度明显高于5D0→7F2的电偶极跃迁强度,并分析了原因。探讨了合理的掺杂浓度和灼烧温度,并测量了Y2O3∶Eu质量分数为5%时,灼烧温度在1300℃时的激发光谱和格位选择激发光谱。样品平均粒径50nm,得到在不同波长激发下的5D0→7F1和5D0→7F2选择激发光谱。分析认为Eu3+存在着4种格位,并对其进行了初步的分析讨论。     

A robust fuzzy k-means clustering model for interval valued data

Summary  In this paper a robust fuzzy k-means clustering model for interval valued data is introduced. The peculiarity of the proposed model is the capability to manage anomalous interval valued data by reducing the effects of such outliers in the clustering model. In the interval case, the concept of anomalous data involves both the center and the width (the radius) of an interval. In order to show how our model works the results of a simulation experiment and an application to real interval valued data are discussed.     

关于有限群的不可约特征标个数的一个结果

本文研究了一般的非交换有限群G的阶与不可约特征标个数的比值与群G结构之间的关系.通过群G阶的最小素因子和G的换位子群的阶的最小素因子,得出了这个比值的下界,并确定了达到下界的一个充分必要条件.     

钨酸铅晶体中与铅空位有关的电子结构和色心模型研究

根据密度泛函理论对钨酸铅晶体中铅空位周围的晶格进行了结构优化，计算得到铅空位周围的晶格结构、电子态密度分布和偏振吸收光谱；计算结果表明钨酸铅晶体中铅空位的两价负电性是通过铅空位周围的氧共同抓获两个空穴来维持局部电中性的，即铅空位周围形成的色心模型为［O₂^3--V_Pb^2--O₂^3-］，不同的氧离子抓获空穴方式不同形成不同的色心，对应不同的吸收带；根据吸收带的偏振性质，提出了各个 关键词： 钨酸铅晶体 色心模型 电子结构 偏振特性