N掺杂对α-石墨炔表面吸附H_2O,H,O和OH的电子性质和磁性的影响

石墨炔是一种新型的二维(2D)碳的同素异形体,炔键单元的高活性使其在小分子吸附方面相比石墨烯更具优势.本文基于密度泛函理论(DFT),研究了H_2O和H、O及OH分别在原始的和掺杂了N原子的α-石墨炔上的相互作用.研究结果表明,N掺杂和小分子吸附能够改变α-石墨炔的电子结构和磁性. N原子掺杂后α-石墨炔对小分子的吸附能力明显增强. H、O原子和OH吸附在N原子掺杂体系前后表现出明显的磁性差异:H原子和OH吸附在纯净的α-石墨炔上体系显示磁性,N原子掺杂后,磁性消失;而O原子则是吸附在纯净的α-石墨炔上未表现出磁性,N原子掺杂后,体系出现磁性.此外,α-石墨炔对水分子的吸附作用较弱,受范德瓦耳斯作用影响较大,属于物理吸附.本研究将为α-石墨炔中N杂质检测以及α-石墨炔基气体传感器的设计研究提供新的思路.     

基于遗传算法的多车体机器人路径规划方法

带拖车的移动机器人系统是一种复杂的多车体系统,在不同的转弯角度下所需的路径宽度也不同,其路径规划是个难题;在给出带拖车轮式移动机器人稳态和暂态过程运动学方程的基础上,推导得出了多车体移动机器人在最大转弯情况下所需的最大路径宽度,并将之定义为等效尺寸;应用遗传算法,提出了基于等效尺寸的多车体移动机器人的路径规划方法;首先通过等效尺寸的多步障碍扩张,对障碍物的临近区域和狭窄通道进行可行性约束的分析;然后应用遗传算法进行全局的路径规划,将路径的长度和宽度综合在适应度函数之中;在一定程度上,多车体移动机器人的路径规划问题得到解决;文章通过建立三维网格化地图,对障碍物的临近区域和狭窄的瓶颈通道区域进行了可行性约束的描述,遗传算法在较复杂的环境中实现了良好的避障,并得到了相对较短的有效路径。     

Detection H2S mixed with natural gas using hollow-core photonic bandgap fiber

An optical fiber gas sensor using hollow-core photonic bandgap fiber as a gas cell is proposed to detect H₂S mixed with natural gas. This sensor is advantageous for eliminating instability of light source, impact of thermal zero drift, and zero shift of photoelectric device. The gas sensing probe of configuration is using two shorter pieces of hollow-core photonic bandgap fiber (HC-PBF) with the same overall length instead of one long piece of HC-PBF to improve the system response. The experimental dates indicate that a minimum detectivity of 10 ppm for the system configuration was estimated.     

Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography

Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work, we used this method to construct nanostructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was investigated. The Pt-Cu-Cu _x O-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The I–V curves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices. Supported by the National Natural Science Foundation of China (Grant No. 90306010), the Program for New Century Excellent Talents in University of China (Grant No. NCET-04-0653), the National Basic Research Program of China (Grant No. 2007CB616911), and the Science and Technology Department of Henan Province (Grant No. 072300420100)     

强幂零根与半素模类

本文就Szasz在[1]中提出的第20个公开问题作了一些讨论,得到了强幂零根的若干结果,并利用半素模类对强幂零根作了刻划。     

旋风除尘器阻力计算的新方法

本文根据旋风除尘器内部流场的理想模型,通过伯努里方程导出了旋风除尘器阻力计算的新公式,经实验表明该公式比其它计算式具有更简单、更精确的特点.     

瞬态场研究的时间步进法与共轭梯度法

本文以任意形状细导线散射问题为例讨论了时间步进法与共轭梯度法及其在瞬态场问题研究中的应用,我们发现了这两种方法之间的联系,并对Rao等人提出的改进型共轭梯度法做了进一步简化.数值计算结果与相关文献结果吻合很好.