应力作用下吸附过渡金属原子的蓝磷单层中的拓扑转变

本文通过第一性原理计算方法研究了被第四B族过渡金属吸附原子(Cr,Mo,W)修饰的蓝磷单层的电子结构性质,发现Cr修饰的蓝磷单层为磁性半金属,而Mo或W修饰的蓝磷单层为半导体,其带隙均小于0.2 eV. 对Mo或W修饰的蓝磷单层施加双轴压应力使得带隙先闭合再打开,且在此过程中发生了能带反转的现象,说明Mo或W修饰的蓝磷单层发生了拓扑转变. Mo和W修饰的蓝磷单层的拓扑转变压应力分别为-5.75%和-4.25%,其拓扑绝缘带隙分别为94 meV和218 meV. 如此大的拓扑绝缘带隙意味着在较高温度条件下有可能在蓝磷单层中通过吸附过渡金属原子实现拓扑绝缘态.     

基于数字全息及离散余弦变换的图像数字水印技术

提出了一种以数字全息和离散余弦变换为基础的数字水印技术,实现了在原始图像中嵌入数字全息水印。考虑到数字全息图的不可撕毁性,使得数字全息水印本身就具有良好的抗剪切能力,并且与传统的二维灰度水印相比嵌入的信息更多。数字全息图通过傅里叶变换全息的方法获得,为了提高抗有损压缩能力,在数字全息水印嵌入过程中采用了基于(JPEG模型和分解离散余弦变换(DCT)系数的方法。实验表明,通过该算法获得的数字全息水印对JPEG有损压缩和剪切等图像处理操作均有很好的稳健性,并且采用密钥加强了水印的安全性。因此该算法能成为数字多媒体产品版权保护的有效方案。     

三个简谐振动合成的拍现象和实验仪

在三个简谐振动合成的拍现象进行理论分析基础上,提出了一种能够准确演示三个简谐振动拍现象的实验仪器,对进行的演示和计算机仿真比较,所给结果正确,并比传统演示手段更加直观,演示内容更加丰富.     

磁控溅射制备Y2O3-TiO2薄膜形貌的研究

室温下采用射频磁控溅射法,在硅衬底上制备了Y₂O₃-TiO₂氧化物复合薄膜.利用XRD(X-ray diffraction)和AFM( atomic force microscopy)分析观察了退火前后样品的物相、形貌等变化,讨论了致密薄膜的生长机理.实验发现,溅射功率越大,薄膜的平整度和致密度越好.对热处理前后样品的结晶结构和表面形貌的分析结果显示,在本实验参数范围内,随着溅射功率的增大,更多的Y₂O_{3关键词： 2}O₃-TiO₂薄膜')" href="#">Y₂O₃-TiO₂薄膜 表面形貌 原子力显微镜 磁控溅射     

宽覆盖高分辨率机载相机光学系统设计

针对机载相机广域高效航拍作业需求,采用新型级联光学成像结构,设计了一种宽覆盖高分辨率机载相机光学系统.该系统由对称前置同心物镜和中继转像透镜阵列组成,对称前置同心物镜获取剩余像差均匀的宽视场曲面像,中继转像透镜阵列对该曲面像进行视场细分、剩余像差校正及中继成像.所设计的机载相机光学系统焦距为60 mm、F数为3.4、视...     

Rotational energy transfer in the NO A 2Σ+(v' = 0) state with He and Ar

Rotational energy transfer cross sections are determined for NO (A ²Σ⁺, v' = 0, N' = 0, 7, and 15) +He and NO (A ²Σ⁺, v' = 0, N' = 0) +Ar by the two-color, double-resonance ionization method. Rotational jumps up to ΔN' = 8 take place as a single collision event. The cross sections determined are discussed in terms of the IOS and ECS scaling laws.     

Lif study of the I2+F → IF+I reaction: population of the v' = 0 level of IF

We have attempted to detect the v' =0 level in IF molecules produced by the reactive collision I₂+F → IF+I under crossed-beam conditions. The signal that we have observed is shown to be due to a background IF vapour. This is an important result as it settles a controversy concerning the energy disposal in this reaction.     

High-resolution infrared spectrum of the fundamental band of LiCl at a temperature of 830°C

High-resolution Fourier transform spectra of ⁶LiCl and ⁷LiCl have been recorded at 830°C. A total of 2522 lines have been measured at 0.006 cm⁻¹ resolution in the 500- to 730-cm⁻¹ region. The data for all four isotopic species have been fit with a standard deviation of 0.00027 cm⁻¹ using 19 isotopically invariant rovibrational constants including five Δ_ij correction terms to the usual Dunham Y_ij terms. Comparison is made with the constants derived from a direct fit of the observed transitions to a Dunham potential function with only 13 coefficients including for Δ correction terms. The gas phase band center for the v = 1–0 transition of ⁷Li³⁵Cl is 634.0753(7) cm⁻¹.     

Interaction of dimethyltin sulfide with 1,2-dibromoethane. Crystal structure of the dimethyltin dibromide /1,4-dithiane complex.

Reaction between trimeric dimethyltin sulfide and 1,2-dibromoethane of 140°C results in a complex of dimethyltin dibromide with 1,4-dithiane formulated as: Me₂SnBr₂ · SC₂H₄C₂H₄S · Me₂SnBr₂. X-ray analysis of the crystal structure of this complex has been performed.     

分光光度法测定方酸

研究了方酸与FeCl3体系显色反应的最佳条件,建立了分光光度法测定方酸的方法.在pH2.1的HCl-HAc溶液中,有色络合物在505nm处有最大吸收,方酸含量在0.05-1.0mmol/L范围内呈良好的线性关系,其线性相关系数为0.9995,检出限为0.005mmol/L.该方法仪器简单,操作方便,应用于样品中方酸的测定结果令人满意.