网络环境下的物理实验教学模式

目前网络环境下的物理实验教学新模式主要有物理实验专题网站、实验教学网络管理、实验类网络课程及远程控制物理实验.本文简要介绍了各个模式的特点及实施方法.     

猜想M(2k,k+1)=3k-1+[(k-1)/2]的反例

Brualdi与Jung在[1]中研究了一类具有固定线和k的n×n矩阵上的最大跳跃数M(n,k),并提出猜想M(2k, k + 1) = 3k - 1 + [(k-1)/2].本文给出了这一猜想的两个反例．     

Structural evolution in amorphous silicon and germanium thin films.

The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method.     

On crepant resolution of some hypersurface singularities and a criterion for UFD

In this article, we find some diagonal hypersurfaces that admit crepant resolutions. We also give a criterion for unique factorization domains.

     

Three New Polyoxygenated Steroids from Two Species of the South China Sea Gorgonian Muricella flexuosa and Menella verrucosa Brundin

Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds.     

A finite model property for RMImin

It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI _min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI _min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

1+1/2对转涡轮叶排轴向间距对性能影响的研究

木文对1+1/2对转涡轮中轴向间距影响进行了初步研究。对不同轴向间距叶栅流场进行了大量时间精确模拟。研究表明,1+1/2对转涡轮高低压转叶间轴向间距成为追求高效率的制约因素,轴向间距为高压转叶喉部宽度是关键点。因此有关小轴向间距下强激波/叶排干扰的研究应该加强。     

两种方法制备ITO薄膜的红外特性分析

比较了用电束加热蒸发法和直流磁控溅射法制备的氧化锡铟(ITO)薄膜在红外波段的光学特性实验发现,通过直流磁控溅射在常温下制备的ITO薄膜在红外波段折射率稳定、消光系数小,比电子束加热蒸发制备的膜有较高的透过率在波长1550nm附近的透过率可达86%以上,消光系数约为004,方电阻最低为100Ω/□.     

Effects of B′-site transition metal on the properties of double perovskites Sr2FeMO6 (M=Mo, W): B′ 4d-5d system

The crystal structure, magnetic and magnetotransport properties of the variation of B′-site transition metal in Sr₂FeMO₆ (M=Mo, W) with double perovskites structure have been investigated systematically. Measurements of magnetization vs. temperature at H=5 T show that Sr₂FeMoO₆ is a ferromagnet and Sr₂FeWO₆ is an antiferromagnet with T_N∼35 K. Additionally, the large magnetoresistance ratio (MR) of ∼22% (H=3 T) at room temperature (RT) was observed in the Sr₂FeWO₆ compound. However, the Sr₂FeMoO₆ compound did not show any significant MR even at high fields and RT (MR∼1%; H=3 T and 300 K). The implications of these findings are supported by band structure calculations to explain the interaction between the 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions.