Land-ocean interaction in modern delta formation and development: A case study of the Pearl River delta,China

The distinctive characteristics of the modern Pearl River delta formation and development are divided phases, diversity and imbalance in spatial and temporal. The delta was moving seaward gradually in a long period after the last Holocene glacial stage and the ancient drowned Pearl River estuary was predominated by tide. The delta was expanding quickly since fluvial force was turned to be leading status about 2500 years ago. The sediment grain size was changing longitudinally from coarser to finer. As well as the finer sediment may be reworked and redistributed shoreward by tidal current nearby the river mouth. And the fluvial-dominated delta is developed by the mutual deposition reflected in the vertical direction. According to the spatial difference of land-ocean interaction, the main body of the Pearl River delta which is the fluvial-dominated and protruding seaward is coupled with or concomitant with the estuaries and tide-dominated deltas which are adjoined to both sides of the main part like two wi     

掺杂超晶格量子阱的沟道效应与沟道辐射

 分析了超晶格量子阱的沟道效应和沟道辐射,利用正弦平方势描述了掺杂超晶格量子阱沟道粒子的运动行为,并在经典力学框架内,把粒子的运动方程化为摆方程。用Jacobian椭圆函数和椭圆积分解析地给出了系统的解和粒子运动周期,导出了量子阱沟道辐射的辐射强度和辐射能量。结果表明,对于能量为100 MeV左右的电子,辐射能量可达keV量级（X能区）。指出了用量子阱沟道辐射作为X激光或γ激光的可能性。     

基于一致性测度的非线性扩散图像消噪算法

以各向异性扩散模型为基础,分析了现有扩散消噪算法在处理斑点噪声时性能不稳定和汁算复杂的不足,提出了一种新的扩散方向估计算法:利用四个方向带状区域灰度的方差值作为图像的局部方向测度,引入常规与对角积分图实现方差的快速计算,每个像素点的扩散量由邻域八像素与该点的差值以及相应的方向权系数决定,给出了相应的扩散函数及其计算方法.实验表明该方法适应能力强,在消除噪声同时很好地保护了纹理细节,而且迭代次数少,运算速度快.     

Thickness dependent manipulation of uniaxial magnetic anisotropy in Fe-thin films by oblique deposition

The uniaxial magnetic anisotropy of obliquely deposited Fe(001)/Pd film on MgO(001) substrate is investigated as a function of deposition angle and film thickness. The values of incidence angle of Fe flux relative to surface normal of the substrate are 0°, 45°, 55°, and 70°, respectively. In-situ low energy electron diffraction is employed to investigate the surface structures of the samples. The Fe film thicknesses are determined to be 50 ML, 45 ML, 32 ML, and 24 ML(1 ML = 0.14 nm) by performing x-ray reflectivity on the grown samples, respectively. The normalized remanent magnetic saturation ratio and coercivity are obtained by the longitudinal surface magneto-optical Kerr effect. Here, the magnetic anisotropy constants are quantitatively determined by fitting the anisotropic magnetoresistance curves under different fields.These measurements show four-fold cubic anisotropy in a large Fe film thickness(50 ML) sample, but highly in-plane uniaxial magnetic anisotropies in thin films(24 ML and 32 ML) samples. In the obliquely deposited Fe films, the coercive fields and the uniaxial magnetic anisotropies(UMAs) increase as the deposition angle becomes more and more tilted. In addition, the UMA decreases with the increase of the Fe film thickness. Our work provides the possibility of manipulating uniaxial magnetic anisotropy, and paves the way to inducing UMA by oblique deposition with smaller film thickness.     

PS/MWNT复合材料界面上的化学反应性

利用悬浮聚合法制备了可溶于甲苯的聚苯乙烯／多壁碳纳米管（PS／MWNT）复合材料,通过透射电镜观察到MWNT完全或部分被PS包裹。拉曼光谱分析表明,复合材料中MWNT的两个特征峰D峰和G峰的位置均发生了红移,且D峰的强度及ID／IG值也较MWNT明显增大。凝胶渗透色谱测得复合材料的分子量相对于纯PS的分子量有较大幅度提高。同时比较共混法与悬浮聚合法制得的复合材料在甲苯中的溶解性。可以认为悬浮聚合法制备复合材料的过程中,MWNT参与了PS的聚合反应,与PS形成了化学键从而完全或部分地被PS包裹。     

Numerical simulation and experimental validation of direct current air corona discharge under atmospheric pressure

Air corona discharge is one of the critical problems associated with high-voltage equipment. Investigating the corona mechanism plays a key role in enhancing the electrical insulation performance. An improved self-consistent multi-component two-dimensional plasma hybrid model is presented for the simulation of a direct current atmospheric pressure corona discharge in air. The model is based on plasma hydrodynamic and chemical models, and includes 12 species and 26 reactions. In addition, the photoionization effect is introduced into the model. The simulation on a bar-plate electrode configuration with an inter-electrode gap of 5.0 mm is carried out. The discharge voltage– current characteristics and the current density distribution predicted by the hybrid model agree with the experimental measurements. In addition, the dynamics of volume charged species generation, discharge current waveform, current density distribution at an electrode, charge density, electron temperature, and electric field variations are investigated in detail based on the model. The results indicate that the model can contribute valuable insights into the physics of an air plasma discharge.     

超声成像中基于特征空间的前后向最小方差波束形成

针对最小方差(MV)波束形成在算法稳健性和超声成像对比度方面存在的缺点,提出一种将特征空间法和前后向空间平滑法融合用于最小方差波束形成的超声成像方法。首先用前后向空间平滑取代传统的前向空间平滑,得到更精确的协方差矩阵;然后计算最优加权向量,并将该向量投影到由协方差矩阵特征空间构造的信号子空间中;最后利用投影所获得的向量与阵元数据进行运算得到成像回波数据。为了验证算法的有效性,对医学成像中常用的点目标和斑目标进行了成像实验。仿真结果表明:所提出的方法不依赖于对角加载参数的选取,在保持MV算法高分辨率的同时,还有效提高图像的对比度和算法的稳健性。      

含查尔酮结构的光敏性二胺合成

含查尔酮结构的光敏性二胺合成;二氨基苯基丙烯酮;羟醛缩合     

石墨电极直接电氧化合成D-阿拉伯糖

本文报道采用石墨电极直接电氧化Ｄ＿葡萄糖酸钠（ＮａＧＬ）合成Ｄ＿阿拉伯糖研究结果．研究了葡萄糖酸钠浓度、电解电压、温度及电解液组成对电流效率和合成产率的影响。同时指出采用液体电解池进行恒电位电解,其效果比恒电流电解法更好     

Journal of Chemical Education 中关于化学批判性思维的文献分析

通过对1987年到2019年在Journal of Chemical Education上出版的所有以“Critical Thinking”为主题的文献进行内容分析,将这些文献分为5个类别,并从每一个类别中选择最具有代表性的一篇文献作为实例,从实验的过程分析、主动学习教学法、课程设置方案、纠正教科书错误、分析网络信息等5个维度提供了发展批判性思维能力的路径。最后总结了目前国际化学教育关于批判性思维的研究现状和趋势。