(Ce,Gd,Mn)MgB5O10磷光体的合成及其发光

本文采用固相反应的方法合成了一系列(Ce,Gd,Mn)MgB5O10磷光体。观察到合成温度、灼烧时间、原料配比对磷光体的形成和发光亮度有重要影响。X射线衍射分析表明,磷光体结构与LaMgB5O10相同,属单斜晶系、空间群P21/c。用EPR确定了磷光体中锰离子为二价。测定了(Ce0.2La0.2)MgB5O10,(Gd0.7La0.3)MgB5O10,(Mn0.05La0.95)MgB5O10,(Ce0.2Mn0.05La0.75)MgB5O10,(Gd0.95Mn0.05)MgB5O10、(Ce0.2Gd0.8)MgB5O10和(Ce0.2Gd0.75Mn0.05)MgB5O15等磷光体的光谱。根据光谱数据讨论了(Ce0.2Gd0.75Mn0.05)MgB5O10磷光体中能量传递过程为:Ce3+→Mn2+,Gd3+→Mn2+以及Ce3+→Gd3+→Mn2+,其中Ce3+离子可将能量高效地传递给Gd3+,Gd3+离子起着中间体的作用。     

Liquid phase epitaxial growth and optical property of flower-like ZnO nanosheets on Zinc foil

Large scale flower-like ZnO nanosheets have been synthesized on Zinc foil by a simple hydrothermal method. Their morphology and microstructures were characterized and analyzed by X-ray spectroscopy (XRD), field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HRTEM). The as-synthesized flower-like nanosheets are hexagonal phase single crystal with 200-300 nm in width, 50 nm in thickness. The growth process follows the liquid phase epitaxial growth mechanism. In this approach, the ZnO buffer is used as substrate for the growth of flower-like ZnO nanosheets. The growth direction of the nanosheets is the preferential [0 0 0 1] growth direction of ZnO. The photoluminescence spectrum of the sample exhibits only a sharp and strong UV emission centered at 386 nm, which indicates that the flower-like ZnO nanosheets on Zn foil are of good optical property.     

利用最小调整法求解特殊的二维0-1规划

具有特殊约束的二维0-1规划的实际应用广泛,在解法中多是应用传统算法,或是在它基础上进行改进,但是此类解法计算繁琐不易推广.针对这种情形,本文引入最小调整法处理此类问题,并将其与传统算法进行对比,充分展示了该方法的优越性,呈现出灵活、方便、简单、易行的特点.通过举例验证了方法的有效性.     

Orthorhombic B2CN crystal synthesized by high pressure and temperature

B_0.54C_0.28N_0.18 precursor powder with turbostratic structure was prepared by using melamine and boric acid. The precursor was transformed into orthorhombic B₂CN under definite high pressure and temperature conditions. The composition of the orthorhombic B₂CN powder is B_0.47C_0.23N_0.30. Its lattice parameters are a=0.4776 nm, b=0.4585 nm and c=0.3629 nm. A strong absorption band from 1088 to 1385 cm⁻¹ of orthorhombic B₂CN was observed by infrared measurement. In the photoluminescence (PL) spectrum of orthorhombic B₂CN powder measured at room temperature, a broad peak corresponding to its band-edge emission centers at 374 nm.     

Deprojection technique for galaxy cluster considering the point spread function

We present a new method for the analysis of Abell 1835 observed by XMM-Newton. The method is a combination of the Direct Demodulation technique and deprojection. We eliminate the effects of the point spread function (PSF) with the Direct Demodulation technique. We then use a traditional deprojection technique to study the properties of Abell 1835. Compared to only using a deprojection method, the central electron density derived from this method increases by 30%, while the temperature profile is similar.

     

Hyperbranched polymers generated from oxyanionic vinyl polymerization of commercially available methacrylate inimers

Hyperbranched polymethacrylates were prepared by means of oxyanionic vinyl polymerization of commercially available monomers, including hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol) methacrylate (PEG‐MA). Hyperbranched polymethacrylates with high molecular weight were obtained with the complex of potassium hydride and 18‐crown‐6 as the initiator. The effect of 18‐crown‐6 is very important, and only oligomer can be obtained in the polymerization without 18‐crown‐6. The molecular structure of the hyperbranched polymers was confirmed with ¹H NMR and ¹³C NMR spectra. The ratio of initiator to monomer significantly affects the architecture of the resultant polymers. When the ratio of initiator to monomer equals 1 in the oxyanionic vinyl polymerization of HEMA, the degree of branching of the resulting polymer was calculated to be around 0.49. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3502–3509, 2005     

Chemical Components from Leontopodium Nanum

Phytochemical investigation of the whole plant of Leontopodium nanum afforded a new coumarin named leontonanin ( 1 ), together with six known compounds, umbelliferone ( 2 ), 3,4′, 7‐trihydroxyflavone ( 3 ), oleanolic acid ( 4 ), β‐sitosterol ( 5 ), daucosterol ( 6 ) and stearic acid ( 7 ). The structure of compound ( 1 ) was elucidated by spectroscopic methods including 2D‐NMR techniques.     

On the index of finite determinacy of vector fields with resonances

In this paper we study normal forms for a class of germs of 1-resonant vector fields on R^n with mutually different eigenvalues which may admit extraneous resonance relations. We give an estimation on the index of finite determinacy from above as well as the essentially simplified polynomial normal forms for such vector fields. In the case that a vector field has a zero eigenvalue, the result leads to an interesting corollary, a linear dependence of the derivatives of the hyperbolic variables on the central variable.     

信息技术与大学数学课程整合的方式与理论探讨

信息技术与大学数学课程整合正成为当前我国信息技术教育乃至整个教育信息化进程中的一个热点问题,探讨其整合的方式及理论基础是非常必要的.本文首先结合大学数学案例探讨了整合的三种方式:动态的课堂演示型、单机的数学实验型和全交互的网络教学型,其次探讨了整合所依据的四种理论:传播理论、建构主义理论、教学设计理论和系统理论,最后提出了自己对信息技术与大学数学课程整合的一些思考.