Investigation of Kinematics of the Portevin-Le Chatelier Deformation Bands with Dynamic Digital Speckle Pattern Interferometry

The Portevin-Le Chatelier (PLC) effect with typical temporal instabilities in the recorded stress is closely associated with local inhomogeneities of deformation. By employing the dynamic digital speckle pattern interferometry technology, the characterizations for the PLC deformation bands of type A (continuous propagation along the specimen), type B (“hopping“ propagation along the specimen) and type C (random nucleation in the sample) were distinctly clarified. The corresponding positions of deformation bands were traced throughout the whole tensile process. By systemic experiments, the range of the applied strain rates for each type of bands existing was investigated respectively. The evolution of the band velocity (for types A and B) was also statistically investigated and qualitatively interpreted.     

诺贝尔物理学奖得主知识交流网络结构研究

将诺贝尔物理学奖得主作为结点，在有知识交流的两位得主间添加一条连接，由此得到诺贝尔物理学奖得主知识交流网络。本文对此网络的结构特征进行研究，结果表明该网络的结构具有一般社会网络共有的Seale-free、度协调、负相关特征，而直径较一般社会网络大，聚集系数则明显较小。     

超快速COSY类2DNMR实验弛豫假峰的抑制

在脉冲梯度场基础上研究了进一步缩短ＣＯＳＹ类２ＤＮＭＲ实验数据采集时间的新方法．利用主动屏蔽梯度场线圈的梯度场恢复时间仅为１００μｓ数量级这一特点，提出一类基于脉冲梯度场消除弛豫假峰的脉冲序列．并以ＤＱＦ－ＣＯＳＹ脉冲序列为例加以验证．实验结果表明：采用文中的方法，取序列重复时间远小于Ｔ＿１和Ｔ＿２是切实可行的；梯度场技术能很好地抑制弛豫假蜂以达到２ＤＮＭＫ数据的快速采集．     

三元系SrGa2S4：Ce蓝色发光材料

制备了可用于蓝色TFEL的粉末发光材料SrGa2S4:Ce,并对其晶体结构进行了X射线衍射分析,测量并研究了其激发光谱和发射光谱,同时研究了Ce3+浓度的变化对SrGa2S4:Ce的激发光谱、发射光谱、色纯度及发光强度的影响,结果表明SrGa2S4:Ce可发射纯蓝色光,色纯度极佳,实现其高效率的、纯蓝色发射的最佳Ce3+浓度为3～4mol%。     

EFFECTS OF BANDGAP SHRINKAGE IN FEMTOSECOND ABSORPTION SATURATION MEASUREMENTS OF GaAs FILM

Using CPM dye laser and self-mode-locked Ti sapphire laser as pump-probe optical sources, the effects of bandfilling and bandgap shrinkage on the femtosecond absorption saturation spectra of GaAs film have been studied, For exciting photon energy of 1.97eV and carrier density of 1×10¹⁸cm^-3, an optical-induced absorption increase is observed and is attributed to bandgap shrinkage, The dependence of the absorption coefficient change on the carrier temperature and the carrier densities is discussed.     

相空间中脑电近似熵和信息熵的计算

提出一种基于相空间重构脑电信号来计算脑电近似熵和信息熵的新方法．实验计算结果表明，癫痫患者脑电和正常人脑电的近似熵和信息熵随相空间嵌入维数的变化有明显的不同．     

Hausdroff公式的自动代数展开及其应用

报道了用代数语言REDUCE模拟Hausdroff公式叠代展开过程的计算机程序SIMHAUS.并通过实例叙述了用SIMHAUS程序处理自旋体系在复杂哈密顿作用下的计算机辅助分析过程,为有关这方面的脉冲序列的分析和设计提供了一种新方法.     

一种基于时空变换和压缩感知的磁共振螺旋采样的图像重建算法

螺旋采样磁共振快速成像在功能性成像、并行成像和动态成像等领域发挥着越来越重要的作用.螺旋采样图像重建的传统算法是用核函数将螺旋状分布的k空间数据插值到均匀网格中,再利用傅里叶变换和最小二乘法进行重建.但是基于网格化的算法对核函数过于依赖,在网格化过程中产生难以避免的误差.该文提出了基于时空变换和压缩感知的l1范数的最优化模型和重建算法.时空变换矩阵描述了空间上的磁共振图像与采集到的时域信号间的关系,使得算法直接使用采集到的数据作为保真约束项,避免了网格化过程产生的误差.此外,基于图像处理单元的并行计算被用来提高时空变换矩阵的运算速度,使得算法具有较强的应用价值.     

Solvent Suppression in Intermolecular Magnetic Resonance Spectra Multiple-Quantum Coherence Nuclear with Only z-axis Gradients

The solvent peak in the intermolecular multiple-quantum coherence spectra can be suppressed by either applying pulse field gradients or spinning sample along the magic angle direction （φ = 54.7）. However, these two methods also suppress the signals of the solute. We design two pulse sequences with only z-axis gradients to suppress the solvent peak without reducing the intensity of solute signals. Compared to the former pulse sequence, the latter pulse sequence is insensitive to the imperfection of pulse flip angles. When the flip angles of the second pulse sequence are purposely deviated 1/10 from the optimal values, the solvent peak is still weak. Theoretical expressions, experimental observations and computer simulations demonstrate that the two methods can be used to effectively suppress solvent peak in intermolecular multiple-quantum coherence spectra.     

二极管整流器的演示实验

高三物理课第五章电子管整流器一节的教材比较抽象,学生不容易理解,有如下几个难点: 1.二极电子管具有单向导电性,学生对此缺乏具体了解,实际意义更体会不深刻。2.当加在二极电子管上的板压一定时,改变灯丝电压,板流改变。当灯丝电压一定时,改变板压,板流也跟着改变。学生对此很难具体