Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengths

Gigacycle fatigue behaviors of two SNCM439 steels with different tensile strengthes were experimentally studied by rotating bending tests,to investigate the effects of the tensile strength obtained by different heat treatment processes on very high cycle fatigue failure mechanisms.The material with higher tensile strength of 1 710 MPa exhibited typical gigacycle fatigue failure characteristics,whereas one with lower tensile strength of 1 010 MPa showed only traditional fatigue limit during the tests and no gigacycle failure could be found even when the specimen ran up to more than 10 8 cycles.Metallographic and fractographic analysis were carried out by an optical microscope (OM) and scanning electron microscope (SEM).It showed two different crack initiation mechanisms that for the specimen with lower tensile strength the crack prefers surface initiation and for that with higher strength the crack initiates from subsurface inclusions revealed by a fish-eye like microstructure.     

Effects of disordered interchain interactions on polaron dynamics in semiconducting polymers

Polaron dynamics in a system of two randomly coupled polymer chains is simulated using a nonadiabatic evolution method. The simulations are performed within the framework of the Su-Schrieffer-Heeger model modified to include disordered interchain interactions and an external electric field. By analysing the polaron velocity statistically, we find that the polaron motion is determined by the competition between the electric field and the disordered interchain interactions. Polaron dynamics are classified into two types, weak-coupling dynamics and strong-coupling dynamics. It is found that the strength of interchain interactions is the dominant factor controlling charge propagation in weak-coupling dynamics, whereas the effects of disorder are dominant in strong-coupling dynamics. The charge carriers tend to have higher mobility for stronger interchain coupling, and interchain coupling disorder can be favorable for charge transport depending on the coupling strength and the electric field.     

氧化锌和氧化钛纳米树热液合成的研究进展

本文简要介绍了近年来多枝纳米结构材料的研究进展,概述了氧化锌和氧化钛纳米树阵列的热液合成和反应机理,探讨性地展望了多枝纳米树阵列的研究和应用前景.     

Homotopic mapping method of solitary wave solutions for generalized complex Burgers equation

A class of generalized complex Burgers equation is considered. First, a set of equations of the complex value functions are solved by using the homotopic mapping method. The approximate solution for the original generalized complex Burgers equation is obtained. This method can find the approximation of arbitrary order of precision simply and reliably.     

Effect of the mesons σ* and Φ and the variety of U(N)Σ on the transition density of hyperon stars

The effect of the mesons σ* and φ and the variety of U(N)Σ on the transition density of hyperon stars is examined within the framework of relativistic mean field theory for the baryon octet {n,p,∧,∑-,∑0,∑+,Ξ- and Ξ0} system.It is found that,compared with that without considering the mesons δ* and φ,the transition density of hyperon stars decreases,the critical baryon density that hyperons Σ-,Σ0,Ξ+,Ξ- and Ξ0 appears to decrease too,but for A the effect is not obvious.As U(N)Σ goes up,the critical baryon density of Σ+,Σ0 and Σ- increases,that of Ξ0 decreases and that of A and Ξ- is fixed.In addition,it is found that the variety of U(N)Σ almost does not influence the transition density.     

Dynamics of an Ultracold Bose Gas in Funnel-Shaped Potential

In this paper we develop a variational theory to study the dynamic properties of ultracold Bose gas in a funnel external potential. We obtain one-dimensional nonlinear equation which describes the dynamics of transverse tight confined bosonic gas from three-dimension to one-dimension, and find one-dimensional s-wave scattering length which depends on the shape of transverse confining potential. If the funnel trapping potential is strong enough at zero temperature, all transverse excitations are frozen. We find the dynamic equation which describes the Tonks-Girardeau gas and present a qualitative analysis of the experimental accessibility of the Tonks Girardeau gas with funnel-trapped alkalic atoms.     

实现多准位相匹配的一维非周期和无周期光学超晶格的设计方法——自调整方法

文章作者提出了一种实现多准位相匹配的-维光学超晶格的新的设计方法--自调整方法,详细介绍了用自调整方法设计非周期光学超晶格和无周期光学超晶格的流程,并对结果进行了分析.数值模拟结果表明,自调整方法是一种高效灵活的专用于设计-维光学超晶格的优化算法,与其他优化算法相比,自调整方法能在更短的时间内搜索出更理想的优化结果.此外,自调整方法的优化结果不依赖于参数的设置和初始化条件,运行方便.     

超声射流冷却S2自由基激光诱导荧光激发谱

在超声射流条件下.采用SF6/Ar(～10%)混合气束脉冲直流放电方法产生S2自由基,观测了32S2自由基在30000～35500 cm-1波段的激光诱导荧光激发谱.通过对所观测到的40多个振动谱带的归属,确定其中28个谱带为s2自由基B3∑μ一X3∑-g跃迁的(v'=1-9,0),(v'=1-8,1),(v'=1-7,2)和(v'=2-5,3)四个谱带序列.通过对所获谱带的转动分析,得到更为丰富的S2自由基B3∑-μ-X3∑-g跃迁谱带的转动光谱常数和更为精确的B3∑-μ电子态的平衡分子常数:Te,щe,щXe,Be,ae和Re.另外,还测得所有观测到的谱带的寿命,进一步丰富了S2自由基学∑-μ-X2∑-g跃迁谱带的光谱信息.     

对称单负介质包层平面波导的模式特征

系统研究了负μ材料(MNG)作为包层的对称三层平板波导的传输特性. 研究发现,这种波导既支持快波的传播,又支持TE₀,TE₁模式的慢波传输. 其模式特性不同于左手介质波导和传统介质波导,导模存在的模折射率范围要比它们的大. MNG波导的TE₀快波模缺失,且TE_m模(m>1)的传播常数大于TM_m模的传播常数. TE_m模具有双模特征,且与波导的结构参数密切相关,导致波导中的净能流出现负值. 关键词： 单负介质 平板波导 快波与慢波 传播常数     

Fabrication of Two-Dimensional Photonic Crystals with Controlled Defects by Combination of Holographic Lithography and Two-Photon Polymerization

A new ternary photopolymer system is used in fabricating photonic crystals （PhCs） with controlled defects by combination of single-photon and two-photon photopolymerization. The former process can produce PhCs in one-step recording with a low-power （tens mW） continuous-wave laser at 532nm, while the latter can create desired defects. The preparation of the material, the optical setup and the preliminary experimental results are given. Compared with other methods, this approach is much more accessible and convenient for use of visible light and has advantages of making PhCs in a large scale quickly and economicaJly and introducing any defects exactly, especially for three-dimensional structures.