Evolution of Spiral Waves under Modulated Electric Fields

Spirals generated from the excitable media within the Barkley model is investigated under the gradient electric fields by a numerical simulation. The spiral drift and spiral break up are observed when the amplitude of the electric fields is modulated by a constant signal or a chaotic signal. It is also verified that, even in the presence of the white noise, the whole system can reach homogeneous states after the spiral breakup, by using an adaptive strategy.     

Cu-Ni包套MgB2带应力效应研究

使用电测量方法测量了用粉末套管(PIT)工艺制备的Cu-Ni包套MgB2单芯带的弹性模量E,其值与Cu及其合金的弹性模量为同一量级,还证实了在带中存在着压缩预应力.我们研究了该带在4.2K,0.5～4T磁场下弯曲成不同曲率时的Ic-B特性曲线,并且计算相应曲率时的最大应变和应力.弯曲实验显示该带材对应力较为敏感,必须改进工艺并实施机械强化.     

SiO-Au法制备硅纳米线

在低真空的CVD系统中直接热蒸发SiO粉末并以金为催化剂在硅衬底上制备出大量长达几十微米的硅纳米线(SiNWs), 通过X 射线衍射谱(XRD)、场发射扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、选区电子衍射仪(SAED)和Raman光谱等技术对硅纳米线进行形貌及结构分析. 实验结果表明, 在不同生长温度下制备得到的硅纳米线质量不同, 其中在700 ℃温区生长的硅线质量最好; 与晶体硅Raman的一级散射特征峰(TO)520.3 cm−1相比, 纳米硅线的Raman特征峰(TO)红移至514.8 cm−1.     

惠更斯次波法在遥感图像去云和云影中的应用

针对在遥感图像中有云和云影的区域无法获取信息的情况，提出一种对遥感图像局域增强的新方法，即采用惠更斯次波法寻找遥感图像中有云覆盖的区域和有云阴影的区域，进而采用邻域平均法，将有云覆盖的区域和云阴影区域与大尺寸的平滑卷积核进行卷积得到具有较宽的渐变边缘，再对原图像中有云覆盖的区域和云阴影区域的亮度进行补偿，从而获得原图中被云覆盖的区域和云阴影区域的信息。这种半自动提取地物的方法，对在有云和有云影的遥感图像中提取地物信息具有辅助作用。     

Au5Si2/Si Heterojunction Nanowires Formed by Combining SiO Evaporation with Vapour--Liquid--Solid Mechanism

Crystalline AusSi2/Si heterojunetion nanowires （AusSi2/SiNWs） are obtained by thermal evaporating SiO pow- ders on thick gold-coated silicon substrates in a low vacuum system. Structure analysis of the produced AusSh/Si heterojunetions is performed by employing a transmission electron microscope （TEM） and a selected area electric diffraetometer. The chemical compositions axe studied by a energy-dispersive x-ray spectroscope attached to the TEM. A two-step growth model is proposed to describe the formation of the AusSi2/SiNWs. During the first step, crystalline SiNWs are formed via a growth mechanism combining the oxide-assisted growth process with the vapour-liquid-solid model at relatively high temperature. In the second step, the temperature decreases and one segment of the preformed SiNWs reacts with the remnant Au to form single crystalline AusSi2 nanowires by a solid-liquid-solid process. The present work should be useful for the future synthesis and research of high-quality gold silicide nanowires and microelectronic devices based on the nanowires.     

二维完全阻挫Josephson结阵列的非平衡态相变

在短时动力学标度方法的框架下, 研究了二维完全阻挫Josephson 结阵列在外加电流时的非平衡态相变-Ising 型相变. 采用电阻分流结动力学, 分别求出了临界温度TC , 静态临界指数2β/υ、υ和动态临界指数z.