辐照导致钨表面的溅射现象的理论研究

采用基于量子力学的分子动力学方法,模拟了高能粒子辐照导致钨表面的溅射和结构损伤.结果显示,当PKA能量高于200 eV且入射角度大于65°时开始产生溅射原子,当入射角度在45°-65°之间时,钨表面因受辐照而导致的空位数目最少.因此,当PKA入射角度取在45°-65°之间时,可以有效地降低辐照导致的钨表面的结构损伤.还发现钨表面含有间隙原子时会加剧表面原子溅射,而包含空位原子且PKA取在空位附近时则会抑制表面原子的溅射.     

High power terahertz quantum cascade laser

We present high power terahertz quantum laser at about 3 THz based on bound-to-continuum active region design. At 10 K, corrected by the collection efficiency, the maximum peak power of 137 mW is obtained in pulsed mode. What＇s more, we firstly introduce Inonolithically integrated THz quantum cascade laser （QCL） array and the maximum peak power increased to 218 mW after correction. In total, the array shows better performance than single device, implying cheerful prospect.     

First-principles study on the optical properties for CsI crystal with a pair of V_(Cs)~(1-)-V_I~(1+)

The electronic structures and optical properties of both the perfect CsI crystal and the crystal containing a pair of V_(Cs)~1-V_1~(1+) are calculated using CASTEP code with the lattice structure optimized.The calculated results indicate that the optical symmetry of the CsI crystal coincides with the lattice structure geometry of the CsI crystal.The absorption spectrum of the CsI crystal containing a pair of V_(Cs)~(1-)-V_1~(1+) also does not occur in the visible and near-ultraviolet range.It reveals tha...     

圆波导TE01模激励器设计及实验研究

对比分析了几种可输出圆波导TE₀₁模激励器的仿真设计结果。结果表明,利用行波功分结构实现矩形波导TE₁₀模到4路矩形波导TE₁₀模的等幅同相功分,进而合成转换成圆波导TE₀₁模的转换过程,可在较宽的频带范围内,实现圆波导TE₀₁模的高效激励。以中心频率9.40 GHz仿真设计的圆波导TE₀₁模激励器,在中心频率上的传输效率超过99.9%;在9.08~9.61 GHz的频率范围内,传输效率大于99%。实验测量结果表明,所加工激励器在较宽的频带范围内,传输损耗优于-0.2 dB,与仿真结果的差异主要来自于波导壁面的欧姆损耗和波同转换结构;器件工作频带内平坦特性良好,有利于开展测量工作。     

Structural transition of FeSe under high pressure

The density functional calculations of the energy band structure and density of state for the tetragonal PbO-type phase α-FeSe and hexagonal NiAs-type phase β-FeSe are reported in this paper. The structural phase transition from tetragonal to hexagonal FeSe under high pressure is investigated, it is found that the calculated transition pressure for the α → β phase transformation is 8.5 GPa. Some fluctuations in the transition pressure maybe occurred by different external factors such as temperature and stress condition. There is about 17% volume collapse accompanying the α → β phase transformation.     

利用模拟退火遗传算法实现图像阈值分割

本文提出了一种利用模拟退火算法和遗传算法相结合的图像阈值分割算法,试验结果表明该算法增强了算法的全局收敛性,加快了算法的收敛速度,提高了图像阈值分割的效率.     

硅基二氧化钒相变薄膜电学特性研究

本文以原子层沉积超薄氧化铝(Al₂ O₃)为过渡层, 采用射频反应磁控溅射法在硅半导体基片上制备了颗粒致密并具有(011)择优取向的二氧化钒(VO₂)薄膜. 该薄膜具有显著的绝缘体–金属相变特性, 相变电阻变化超过3 个数量级, 热滞回线宽度约为6℃. 基于VO₂薄膜构建了平面二端器件并测试了不同温度下I-V曲线, 观测到超过2个数量级的电流跃迁幅度, 显示了优越的电致相变特性. 室温下电致相变阈值电压为8.6 V, 电致相变弛豫电压宽度约0.1 V. 随着温度升高到60℃, 其电致相变所需要的阈值电压减小到2.7 V. 本实验制备的VO₂薄膜在光电存储、开关、太赫兹调控器件中具有广泛的应用价值.     

新题征展(25)第7题的别解及推广

贵刊 2 0 0 1年第 12期新题征展 (2 5 )第 7题是2 0 0 0年春季京皖高考题的改编题 ,是培养学生整体思维品质与细心演算习惯的一道好题 .我们再提供这道题的另外 4种解法并把结论推广到一般情况 .原题　如图 1,过原点 O作抛物线 y2 =2 px(p >0 )的两条互相垂直的弦 OA、OB,再作∠ AOB的平分线交 AB于 C,求 C点的轨迹方程 .解法 1　设 A(2 pt2 ,2 pt) ,C(x,y)则 k OA =1t,　 k OB =- t≠ 0 ,直线 OB的方程为 y =- tx (t≠ 0 ) ,代入 y2 =2 px得 B点坐标 (2 pt2 ,- 2 pt) ,图 1则　 | OA| =(2 p t2 ) 2 (2 pt) 2 =2 p| t| t2 1,|…     

Modeling capacitance voltage characteristic of TiW/p-InP Schottky barrier diode

The capacitance-voltage(C-V) characteristic of the TiW/p-InP Schottky barrier diodes(SBDs) is analyzed considering the effects of the interface state(N_(ss)), series resistance(R_s), and deep level defects. The C-V of the Schottky contact is modeled based on the physical mechanism of the interfacial state and series resistance effect. The fitting coefficients α andβ are used to reflect the N_(ss) and R_s on the C-V characteristics, respectively. The α decreases with the increase of frequency,while β increases with the increase of frequency. The capacitance increases with the increase of α and the decrease of β.From our model, the peak capacitance and its position can be estimated. The experimental value is found to be larger than the calculated one at the lower voltage. This phenomenon can be explained by the effect of deep level defects.     

含哌嗪酰胺类杨梅素衍生物的合成及生物活性

以杨梅苷、哌嗪和各种芳香酸为原料,通过甲基化保护羟基和脱苷形成选择性单一的杨梅素中间体,然后以三步取代反应连接哌嗪和芳香酸,合成了13个新型含哌嗪酰胺类杨梅素衍生物.采用四甲基偶氮唑盐(MTT)比色法测试了化合物对人类乳腺癌细胞(MDA-MB-231)体外增殖的抑制活性.结果表明,大多数含哌嗪酰胺的杨梅素衍生物对MDA-MB-231细胞表现出较好的抑制活性.当浓度为1μmol/L时,化合物4a和4i的抑制活性均高于阳性对照药盐酸表阿霉素;当浓度为10μmol/L时,化合物4h和4i的抑制活性高达86.7%和83.6%.