基于场景自适应收敛非均匀性校正方法

收敛问题是基于场景非均匀性校正算法的一个共性问题,提出了一个能够自适应收敛的非均匀性校正算法,该算法的一个特点是只对非均匀性空间频率的高频部分进行处理,详细论述了该处理的优点,同时还提出了一个控制收敛速度的因子,使得算法的收敛速度根据场景的动态范围自动调整,这将很大程度的改善基于场景非均匀性校正算法收敛特性,最后通过实...     

稀疏性正则化的图像泊松去噪算法

去除医学、天文图像中的泊松噪声是一个重要问题,基于图像在过完备字典下的稀疏表示,在BayesianMAP框架下建立了稀疏性正则化的图像泊松去噪凸变分模型,采用负log的泊松似然函数作为模型的数据保真项,模型中非光滑的正则项约束图像表示系数的稀疏性,并附加非负件约束,保证去噪图像的非负性.基于分裂Bregman方法,提出...     

指数掺杂透射式GaAs光电阴极表面光电压谱研究

通过求解一维稳态少数载流子扩散方程,推导了指数掺杂和均匀掺杂的透射式GaAs光电阴极表面光电压谱理论方程。利用金属有机化学气相沉积(MOCVD)外延生长了发射层厚度相同、掺杂结构不同的两款透射式阴极材料。通过表面光电压谱实验测试和理论拟合发现指数掺杂结构在发射层厚度和后界面复合速率相同的情况下能够有效提高阴极电子扩散长度,这主要由于内建电场能够促使光生电子通过扩散和电场漂移两种方式向表面运动,从而最终提升阴极的发射效率和表面光电压谱。利用能带计算公式和电子散射理论对这两种不同结构材料的表面光电压谱进行了详细分析。     

基于矩量法有限厚度耦合带线电容的提取

该文运用矩量法（MoM）提取了位于均匀介质中有限厚度耦合带线的单位长度电容和电感。基于矩量法理论编写了算法程序,并计算和分析了几种有代表性的耦合带线,诸如垂直宽边耦合带线、水平宽边耦合带线以及非对称侧边耦合带线等,与现有文献计算结果相比,吻合度较好,其平均误差小于2%,同时也给出了内导体带为其他厚度时的电容值。研究结果表明,所编写的算法程序具有较强的适用性和准确性,为此类耦合电路的设计和分析提供了参考数据。     

A parametric study on supersonic/hypersonic flutter behavior of aero-thermo-elastic geometrically imperfect curved skin panel

In this paper, the effect of the system parameters on the flutter of a curved skin panel forced by a supersonic/hypersonic unsteady flow is numerically investigated. The aeroelastic model investigated includes the third-order piston theory aerodynamics for modeling the flow-induced forces and the Von Kármán non-linear strain-displacement relation in conjunction with the Kirchhoff plate hypothesis for the panel structural modeling. Structural non-linearities are considered and are due to the non-linear coupling between out-of-plane bending and in-plane stretching. The effects of thermal degradation and Kelvin??s model of structural damping independent on time and temperature are also considered. The aero-thermo-elastic governing equations are developed from the geometrically imperfect non-linear theory of infinitely long two-dimensional curved panels. Computational analysis and discussion of the finding along with pertinent conclusions are presented.     

Preparation, characterization, and fluorescence properties of well-dispersed core–shell CdS/carbon nanoparticles

The core–shell CdS-carbon (CdS/C) nanoparticles were synthesized for the first time via a facile pyrolysis approach of bis(β-mercaptoethanol)-cadmium(II) as a single-source precursor. After using acid treatment method, well-dispersed and homogeneous core–shell CdS/C nanoparticles were obtained. The morphology, structure, and properties of CdS/C nanoparticles were investigated by X-ray diffraction (XRD), Raman spectra, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy. Most of the prepared nanoparticles presented core–shell structures with core diameter of ~10 nm and shell thickness of ~4 nm. The CdS core belonged to hexagonal crystal system. The carbon shell was employed as a good dispersion medium to form well-dispersed small sized CdS particles. XRD and XPS results revealed that there is an interaction between CdS core and carbon shell. Fluorescence measurement showed that the monodispersed CdS-carbon nanoparticles exhibit remarkable fluorescence enhancement effect compared with that of the pristine CdS nanoparticles, which indicates the prepared nanoparticles are a promising photoresponsive material.     

Poly(vinylidene fluoride)/poly(methyl methacrylate)/TiO2 blown films: preparation and surface study

Blown films of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) blends and PVDF/PMMA/TiO₂ composites were prepared by melting-extrusion for the first time. The crystalline structure and surface morphology PVDF/PMMA (DFMA) blown films were investigated using differential scanning calorimeter (DSC), atomic force microscope (AFM), and X-ray diffractometry (XRD). PVDF/PMMA/TiO₂ blown films were further prepared and underwent surface treatment. The results show that PVDF/PMMA/TiO₂ blown films present good mechanical properties, and acrylic acid surface-grafted films exhibit good adhesion capability and long-lasting hydrophilicity, making them attractive as encapsulation materials.     

Preparation,thermostability, and spectroscopic properties of Rhodamine 6G intercalated titanoniobate nanocomposite

Rhodamine 6G (R6G), a well-known fluorescent dye, has been intercalated into layered potassium titanoniobate (KTiNbO₅) through a guest–guest exchange method by using propylammonium titanoniobate (PrNH₃ ⁺-TiNbO₅) as a precursor. The synthesis process, the structure and morphology characterizations for lamellar nanocomposite have been investigated by means of XRD, FTIR, and SEM. The thermostability of R6G⁺-TiNbO₅ nanocomposite is discussed on the basis of thermogravimetric and calorimetric techniques. Absorption and fluorescence techniques are applied to study the photoresponse of R6G in hybrid film. The results indicate that R6G⁺ cations in thin film are highly fluorescent even at a high dye concentration, which may be due to the formation of J-dimers within the confined galleries.     

Effects of annealing treatment on the ratcheting behavior of extruded AZ31B magnesium alloy under asymmetrical uniaxial cyclic loading

The objective of this investigation is to study the effects of annealing treatment on the ratcheting behavior of extruded AZ31B magnesium alloy. First, the microstructures and monotonic tensile properties of the extruded and annealed alloys were assessed. The results showed that the grain size increased slightly with increasing annealing time until an annealing time of 6 h after which abnormal grain growth happened. Accordingly, the ultimate tensile strength of the Mg alloy decreased with increasing annealing time, while the tensile yield strength and elongation percentage of the Mg alloy increased with annealing time until the annealing time reached 2 h. The cyclic softening/hardening behavior of the annealed AZ31B Mg alloy was similar to that of the extruded alloy: first an apparent cyclic softening was observed, then a cyclic hardening occurred, and finally a stable state was reached. The annealing treatment delayed the occurrence of the cyclic hardening. It was also shown that the effects of the annealing time on the ratcheting strain of the Mg alloy depended of the loading path.     

卷边Z型钢梁防止畸变屈曲的加固措施研究

采用有限元软件ABAQUS对卷边Z型钢梁进行线弹性畸变屈曲分析,针对其畸变屈曲模态,在沿梁的长度方向加设一定数量的连杆或隔板来防止畸变屈曲的发生.通过有限元对加固后的Z型钢梁进行分析,比较各种加固措施,提出有效的加固方法.