Energetics of carbon and nitrogen impurities and their interactions with vacancy in vanadium

We studied the energetic behaviors of interstitial and substitution carbon(C)/nitrogen(N) impurities as well as their interactions with the vacancy in vanadium by first-principles simulations. Both C and N impurities prefer the octahedral site(O-site). N exhibits a lower formation energy than C. Due to the hybridization between vanadium-d and N/C-p, the N-p states are located at the energy from-6.00 e V to-5.00 e V, which is much deeper than that from-5.00 e V to-3.00 e V for the C-p states. Two impurities in bulk vanadium, C–C, C–N, and N–N can be paired up at the two neighboring Osites along the 111 direction and the binding energies of the pairs are 0.227 e V, 0.162 e V, and 0.201 e V, respectively.Further, we find that both C and N do not prefer to stay at the vacancy center and its vicinity, but occupy the O-site off the vacancy in the interstitial lattice in vanadium. The possible physical mechanism is that C/N in the O-site tends to form a carbide/nitride-like structure with its neighboring vanadium atoms, leading to the formation of the strong C/N–vanadium bonding containing a covalent component.     

空气电晕辐照对聚酯薄膜表面组成及形貌的影响

分析了聚酯薄膜经空气电晕等离子体辐照处理后,其表面组成和形貌的变化。 结果表明,聚酯薄膜表面的活性基团在亲水环境中更倾向于迁移至表面,而不是向次表面或者基材本体内迁移。 薄膜表面C=O和O-H的引入量随电晕辐照强度的增加而增大,XPS结果表明,C-O、C=O和O-C=O的总含量增大,O1s谱图中新峰的结合能为532.49 eV,对应于聚酯薄膜表面过氧化物的-O-O-键。 原子力显微镜研究表明,聚酯薄膜经电晕辐照后,表面形成离散的球状颗粒,表面粗糙度变化范围在10 nm左右。     

Self-Organized Micro-Columns and Nano-Spheres Generated by Pulsed Laser Ablation of Ti/A1 Alloy in Water

Dense arrays of micro-columns are formed on the surface of Ti-AI alloy by cumulative nanosecond pulsed laser ablation in water. The fabric-like structure characterized by Ti-A1 nano-spheres absorbed on micro-duster in liquid is most likely responsible for the occurrence of laser micro-etching and localized melting, resulting in continuous deepening of micro-holes and the formation of micro-columns. Laser induced plasma spectroscopy is carried out to reveal the effect of micro-columns on subsequent pulse laser ablation. The intensity of spectral lines from Ti ions by additional laser ablation of the modified spot is higher than that created over a smooth surface. These results suggest that the micro-columns lead to an enhanced absorption of the following laser energy. The proposed results and relevant discussions are of importance for the development of light-trapping coatings on a metal surface.     

YBCO半导体薄膜及Bolometer特性

就Si为衬底的钇钡铜氧(分子式：Y₁Ba₂Cu₃O_7-δ ,δ≥05,简称YBCO)薄膜的半导体性质,及用于红外测辐射热计(Bolometer)的探 测性能进行了研究.通过测定温度电阻系数(TCR)和霍尔(Hall)系数,并采用XRD、拉曼散射 光谱等手段分析了YBCO半导体薄膜的微观结构和光谱响应特性,认为该薄膜是非制冷红外焦 平面的新型探测元材料. 关键词： YBCO半导体薄膜 测辐射热计 温度电阻系数     

由复映射z←z~α十c(α<0)所构造的广义M-集的研究

阐述了构造复映射z←zα＋c（α＜0）所产生的广义Mandelbrot-集（简称M-集或M-分形图）的逃逸时间算法．通过改变参数a，作出了一系列有趣的分形图．这些分形图为若干卫星群环绕中央恒星的星群结构．定量地研究了恒星和卫星群的几何结构，并对a取非整数时分形图的结构特点和卫星群胚胎出现的原因进行了分析．最后给出几点结论．     

Monte Carlo Simulation on Energy Deposition of Low-Energy Electrons in Liquid Water

A Monte Carlo approach to simulate the transport and energy deposition of low energy electrons (E0≤10keV) in liquid water is presented. The elastic scattering of electrons is described by Mott cross section, which is derived from the relativistic wave equation of Dirac. The inelastic scattering model of electrons is based on the dielectric response theory with exchange effect included. A new method of sampling various inelastic scattering events is proposed in the simulation. Using the approach stated, the spatial distribution of inelastic scattering events and energy deposition of electrons in liquid water are computed and the results are compared with other theoretical studies.     

透镜到靶材的距离对脉冲激光诱导等离子体的影响机理研究

采用高功率抽运调Q激光器分别在真空和空气中烧蚀Ti-Al合金靶材激发等离子体,研究了在不同气体压强下透镜到靶材的距离对等离子体参数的影响机理对于焦距为111mm的聚焦透镜,当透镜到靶材距离小于透镜焦距时,随着距离逐渐接近焦距,真空和空气中电子温度、电子密度和谱线强度均逐渐增强.当透镜到靶材距离大于透镜焦距时,真空中,电子温度和电子密度仍然继续升高,而谱线强度却变化不大.空气中,等离子体参数却有不同的演化特性:等离子体的电子温度、电子密度和谱线强度在透镜到靶材距离为107 mm时达到最大值,当距离继续增大时,均呈现出迅速下降的趋势,当透镜到靶材距离大于112mm时,电子温度和电子密度又有明显上升,特征谱线强度却大幅下降.     

Silicon micro-hemispheres with periodic nanoscale rings produced by the laser ablation of single crystalline silicon

We describe the fabrication of silicon micro-hemispheres by adopting the conventional laser ablation of single crystalline silicon in the vacuum condition without using any catalysts or additives. The highly oriented structures of silicon micro-hemispheres exhibit many periodic nanoscale rings along their outer surfaces. We consider that the self-organized growth of silicon micro-structures is highly dependent on the laser intensity and background air medium. The difference between these surface modifications is attributed to the amount of laser energy deposited in the silicon material and the consequent cooling velocity.     

名优白酒质量指纹专家鉴别系统

利用气相色谱法分析了中国名白酒(茅台、泸州老窖、五粮液、汾酒、董酒等)中的34种主要挥发性香味化学物质,根据这些香味化学物质之间的量比关系提出了中国名白酒的“质量指纹”是决定名白酒香型及质量特征的观点。建立了一套完整的名白酒质量指纹库。一次色谱分析可定量检测白酒中多种酯、醇、醛、酸并确定出它们之间的量比关系,通过计算机专家鉴别系统的自动分析,不仅能鉴别白酒的真伪,还能确定白酒的优劣。     

光电信息工程实验教学的思考与改革

面对急剧变化的世界,工程知识本身的有效期变得越来越短,社会对学生各种素质的要求越来越高。如何定位大学工程教育本身的角色?如何在光电工程实验教学中培养社会对学生所提出的各种要求?结合对这些问题的思考,讨论了光电信息工程专业实验教学所面临的挑战,以及为应对这些挑战所进行的教学改革实践。