新型纳米羟基磷灰石晶体复合抗菌剂的制备

以纳米羟基磷灰石为载体,聚乙烯醇为有机抗菌组分,铜离子和锌离子为无机抗菌组分,在一定条件下制备了有机/无机复合抗菌剂.运用XRD、IR和SEM等现代分析方法对复合抗菌剂中抗菌成分与载体的结合方式进行了分析、形貌进行了观测,并对其抗菌性和安全性能进行研究.结果表明,在聚乙烯醇含量为2.8;,铜离子和锌离子含量分别为10;和15;时,制备有机/无机复合抗菌剂具有优异的抗菌性能和安全性.     

A penny-shaped interface crack between a functionally graded piezoelectric layer and a homogeneous piezoelectric layer

The problem of a penny-shaped interface crack between a functionally graded piezoelectric layer and a homogeneous piezoelectric layer is investigated. The surfaces of the composite structure are subjected to both mechanical and electrical loads. The crack surfaces are assumed to be electrically impermeable. Integral transform method is employed to reduce the problem to a Fredholm integral equation of the second kind. The stress intensity factor, electric displacement intensity factor and energy release rate are derived, some typical numerical results are plotted graphically. The effects of electrical loads, material nonhomogeneity and crack configuration on the fracture behaviors of the cracked composite structure are analyzed in detail.     

一步法制备BN/Si复合团簇结构

以球磨的B/BN混合物为原料,采用一步法在蘸有催化剂的硅片上合成了大量BN纳米刺包裹在Si纳米或微米线上的复合团簇结构.EDS和SAED表明外层的纳米刺是六方BN多晶,里面包裹的Si纳米或微米线则是立方的Si单晶.实验结果表明合成温度对BN/Si复合结构形成有重要影响,只有在1250 ℃以上的温度才会生成BN /Si复合团簇结构,另外只有当硅片与样品接触时才会形成复合产物.PL光谱显示复合产物在360 nm的激发下,其发光峰在303 nm(4.1 eV)和423 nm(2.93 eV)处.     

PROPAGATION BEHAVIORS OF SHEAR HORIZONTAL WAVES IN PIEZOELECTRIC-PIEZOMAGNETIC PERIODICALLY LAYERED STRUCTURES

This paper investigates shear horizontal （SH） waves propagating in a periodically layered structure that consists of piezoelectric （PE） layers perfectly bonded with piezomagnetic （PM） layers alternately. The explicit dispersion relations are derived for the two cases when the propagation directions of SH waves are normal to the interface and parallel to the interface, respectively. The asymptotic expressions for dispersion relations are also given when the wave number is extremely small. Numerical results for stop band effect and phase velocity are presented for a periodic system of alternating BaTiO3 and Terfenol-D layers. The influence of volume fraction on stop band effect and dispersion behaviors is discussed and revealed.     

Bi2Te3纳米晶溶剂热合成及表征

采用溶剂热方法,在水合肼溶剂中通过添加适量表面活性剂十二烷基硫酸钠(SDS),在180 ℃下反应10 h后成功地制备了不同形貌的纯相Bi2Te3纳米晶,包括纳米颗粒、纳米棒和花瓣状纳米片.用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能量色散谱仪(EDS)对产物进行了表征,探讨了表面活性剂用量和温度对产物形貌的影响,提出了可能的形成机理.     

Branching ratio of rare decay B0(Bs)→γνν

The three-body decay B⁰(B_s)→γνν can occur via penguin and box diagrams in the Standard Model (SM). These channels are useful to determine the decay constant f_B (f_Bs) and B (B_s) meson wave function. Using the B meson wave function determined in hadronic B (B_s) decays, we calculate and get the branching ratio of order 10^－9 and 10^－8 for B⁰ and B_s decay, respectively. They agree with previous calculations.     

Fracture behavior of a bonded magneto-electro-elastic rectangular plate with an interface crack

In this paper the anti-plane problem for an interface crack between two dissimilar magneto-electro-elastic plates subjected to anti-plane mechanical and in-plane magneto-electrical loads is investigated. The interface crack is assumed to be either magneto-electrically impermeable or permeable, and the position of the interface crack is arbitrary. The finite Fourier transform method is employed to reduce the mixed boundary-value problem to triple trigonometric series equations. The dislocation density functions and proper replacement of the variables are introduced to reduce these series equations to a standard Cauchy singular integral equation of the first kind. The resulting integral equation together with the corresponding single-valued condition is approximated as a system of linear algebra equations which can be easily solved. Field intensity factors and energy release rates are determined numerically and discussed in detail. Numerical results show the effects of crack configuration and loading combination parameters on the fracture behaviors of crack tips according to energy release rate criterion. The study of this problem is expected to have applications to the investigation of dynamic fracture properties of magneto-electro-elastic materials with cracks.     

Nuclear parton distribution functions and energy-loss effect in the Drell-Yan reaction off nuclei

The energy-loss effect in nuclear matter is another nuclear effect apart from the nuclear effects on the parton distribution as in deep inelastic scattering process. The quark energy loss can be measured best by the nuclear dependence of the high energy nuclear Drell-Yan process. By means of two typical kinds of quark energy-loss parametrization and the different sets of nuclear parton distribution functions, we present an analysis of the E866 experiments on the nuclear dependence of Drell-Yan lepton pair production resulting from the bombardment of Be, Fe and W targets by 800 GeV protons at Fermilab. It is found that the quark energy loss in cold nuclei is strongly dependent on the used nuclear parton distribution functions. The further prospects of using relatively low energy protons incident on nuclear targets are presented by combining the quark energy-loss rate determined from a fit to the E866 nuclear-dependent ratios versus x ₁, with the nuclear parton distribution functions given from lA deep inelastic scattering (DIS) data. The experimental study of the relatively low energy nuclear Drell-Yan process can give valuable insight in the energy loss of the fast quark propagating through cold nuclei and help to pin down nuclear parton distribution functions.Received: 8 September 2004, Revised: 18 October 2004, Published online: 11 January 2005PACS: 24.85. + p, 13.85.Qk, 25.40.-h, 25.75.Nq     

气垫导轨实验中极限法测速度的分析与讨论

对线性外推法测气轨上滑块的瞬时速度实验进行理论分析,给出了-v-δt和-v-δs函数、其表达的物理意义及实验需满足的条件.     

Hyers–Ulam stability of Sahoo–Riedel’s point

In this paper, we construct a counter example to show that “Theorem” of Hyers–Ulam Stability of Flett’s Point in [M. Das, T. Riedel, P.K. Sahoo, Hyers-Ulam stability of Flett’s points, Applied Mathematics Letters. 16 (3) (2003), 269–271] is incorrect. At the same time, we give the correct theorem and generalize it.