Conductance of Graphene Nanoribbon Junctions and the Tight Binding Model

Planar carbon-based electronic devices, including metal/semiconductor junctions, transistors and interconnects, can now be formed from patterned sheets of graphene. Most simulations of charge transport within graphene-based electronic devices assume an energy band structure based on a nearest-neighbour tight binding analysis. In this paper, the energy band structure and conductance of graphene nanoribbons and metal/semiconductor junctions are obtained using a third nearest-neighbour tight binding analysis in conjunction with an efficient nonequilibrium Green's function formalism. We find significant differences in both the energy band structure and conductance obtained with the two approximations.     

Multi-scale cross entropy analysis for inclined oil–water two-phase countercurrent flow patterns

The flow of an oil–water two-phase fluid in an inclined pipe exhibits fundamentally different behaviors to that of a vertical two-phase flow, especially the flow commonly presents complex countercurrent flow structure due to the influence of gravity. The understanding of inclined oil–water flow is of important significance for flow measurement and production optimization. We using multi-scale cross entropy (MSCE) analysis investigate the nonlinear dynamics of inclined water-dominated oil–water two-phase flow patterns which are Dispersion oil-in-water-Pseudoslugs (D O/W PS), Dispersion oil-in-water-Countercurrent (D O/W CT) and Transitional Flow (TF). We find that the rate of low-scale cross entropy can effectively identify flow patterns, and the high-scale cross entropy can represent their long-range dynamics. The research results show that the multi-scale cross entropy analysis can be a helpful tool for revealing nonlinear dynamics of inclined oil–water two-phase flow in terms of microscopic and macroscopic views.     

预处理浸泡对聚酰亚胺重离子微孔膜蚀刻的影响

聚酰亚胺(Polyimide,PI)膜是一种新型的有机膜,具有耐高温、耐强酸和耐辐射等特性,用其制备的重离子微孔膜可以用于电池隔膜和放射性废气过滤等特殊领域。应用中国原子能科学研究院HI-13串列加速器产生的重离子束32S离子轰击25?m的PI薄膜,再对薄膜进行化学蚀刻处理,使由重离子辐照损伤产生的径迹形成微孔。为改善微孔质量,在化学蚀刻前采用具有强氧化性溶液对PI膜进行预处理浸泡,系统分析了常温下采用高锰酸钾和双氧水两种溶液浸泡不同时间对PI膜化学蚀刻的影响。实验结果显示,预处理浸泡可明显加快PI膜的径迹蚀刻速率,缩短蚀刻时间,减小微孔的锥角和提高PI重离子微孔膜的蚀刻质量。     

Thin silicon oxide films on N-type 4H-SiC prepared by scanning frequency anodization method

The effect of selective anodization on SiC in direct voltage superimposed with alternative voltage of scanning frequencies has been investigated. Compared with the gate oxides grown with direct voltage or alternative voltage of a constant frequency, the oxide charge and the interface state density of the sample with scanning frequencies are significantly reduced. It is suggested that the bulk traps and interface traps in the oxides can be compensated during the scanning frequency anodization process since the scanning frequencies are in close proximity to the response times of interface states.     

分布损耗回旋行波管线性分析与稳定性研究

研究了分布损耗材料导电特性的下降能够增强回旋行波管注-波互作用段对电磁波的衰减,提高了绝对不稳定性振荡的起振电流和竞争模式回旋返波振荡的起振长度;但同时减小了回旋行波管的线性增长率及其轴向功率和高频场增益.给出了石墨乳涂敷圆波导结构回旋行波管工作参数,采用电子束电流,I_0=10A、注-波互作用段长度L=10cm时的设计结果,在兼顾功率和增益的条件下,能够有效抑制不稳定性,保证其稳定工作.     

Resistive switching in Rose Bengal and other Xanthene molecules is a molecular phenomenon

There has been a debate on the mechanism of resistive switching in Rose Bengal and other Xanthene class molecules. While some authors proposed that the switching was due to an oxide layer at the Rose Bengal/Aluminum interface, some inferred the switching as an extrinsic effect like filament formation. We show results from Rose Bengal and other Xanthene class molecules on doped Si. Conductance switching in such monolayers induced by Pt/Ir tip of a scanning tunneling microscope (STM) in a non-contact mode shows that resistive switching in these molecules, initially reported by us in 2003 (in thin films), is indeed a molecular phenomenon.     

真空系统设计的程序化

在真空系统的设计中,一般涉及到流态判别、流导、泵的抽速和系统的压力等参数。在流导计算中又涉及到不同的管道长度和管道形状,其应用的流导公式不同。有时要反复尝试各种参数使设计的真空系统满足使用要求,使得计算过程非常繁琐。本文介绍了一种真空系统设计的应用程序,可计算常用的20℃空气气体下的流导、差分管参数或系统两端压力等参数,还给出了应用实例。     

聚合物离子径迹化学蚀刻过程的数值分析

介绍了聚合物材料离子径迹化学蚀刻过程的电导监测技术及相应的数据分析方法,针对理论假设与实际蚀刻过程不符的情况,详细考虑了径迹穿孔时间分布、孔形以及微孔中蚀刻液电导率随蚀刻时间变化等因素,建立了相应的径迹蚀刻模型,并通过数值计算研究了各种因素对径迹蚀刻过程中电导测量结果的影响,获得了有关离子径迹微观结构、微孔中蚀刻液电导率随孔径的变化以及径迹蚀刻速率比对孔形影响的信息.     

电导式相关流量计应用于油井井下流量测量

本文提出了一种新型的电导相关流量计,其敏感元件采用两个电导传感器,该流量能够应用于高含水油井的油水两相流流量测量,在多相流动实验装置上进行的实验表明,该流量计测量的流速范围宽,线性好,该流量计已经在大庆油田进行现场试验,使用该流量计在井下测量的油水的总流量与地面计量结果对比良好。