浓度序列对基于双异步正交样品设计构建的二维异步谱峰信噪比的影响

双异步正交样品设计(DAOSD)是通过对样品体系施加浓度的微扰,诱导光谱信号产生动态变化,并通过数学处理研究样品中物质间相互作用的二维相关光谱方法。提高二维谱图的信噪比对于谱图中交叉峰的分辨乃至物质间相互作用的考察有着十分重要的意义。通过计算机模拟考察了DAOSD构建二维相关光谱的方法中样品浓度序列对光谱行为影响。结果表明,在溶液数量较少的情况下,通过改变样品的浓度和组合顺序,可以有效提高交叉峰的信噪比,从而得到更高质量的二维谱图。     

Effect of active control on optimal structures in wall turbulence

The effect of active control imposed at the wall on optimal structures in wall turbulence is studied by using a linear transient growth model.When the detection plane of the control is located in the buffer layer,the influence of the control on the transient growth of large scale motion becomes negligible as Reynolds number increases.However,if the control signal is detected at the plane located in the logarithm region,the transient growth at large scale can be greatly suppressed.New peak values of transient growth resulting from the strong blowing and suction on the wall exist.The study indicates that a proper selection of control imposed on the wall can suppress the large scale motion in the logarithmic region.     

Chemical synthesis and characterization of manganese oxide coated Ni particles

Nanosized Ni particles with an average diameter of about 8 nm were prepared by reducing of NiCl 2 with sodium borohydride (NaBH 4 ) in aqueous solution. By moderate annealing in protective atmosphere, the composite grew up to be 15-20 nm particles. Both of the as-prepared and annealed Ni particles were coated by a layer of manganese oxide via decomposition reaction in aqueous KMnO4 solution. Hysteresis loops of as-prepared samples show a large increase in the magnetization with decreasing temperature and an unsaturated component at high magnetic field. In contrast, the ferromagnetic characteristics of annealed one are much stronger with large magnetization and coercivity. The thermomagnetic curves verified the coexistence of ferromagnetic Ni and antiferromangetic Mn oxide phases. But there exists no exchange bias behavior in the samples, even though the interface structure between the ferromagnetic Ni core and the antiferromagnetic manganese oxides has been distinctly formed. The absence of exchange bias probably originates from the weak ferromagnetic characteristic of Ni cores.     

泊松逆高斯回归模型的贝叶斯统计推断

本文研究泊松逆高斯回归模型的贝叶斯统计推断.基于应用Gibbs抽样,Metropolis-Hastings算法以及Multiple-Try Metropolis算法等MCMC统计方法计算模型未知参数和潜变量的联合贝叶斯估计,并引入两个拟合优度统计量来评价提出的泊松逆高斯回归模型的合理性.若干模拟研究与一个实证分析说明方...     

利用可调谐的混沌Fabry-Perot激光器实现波分复用无源光网络的断点检测

波分复用无源光网络具有支路多、节点密的特征,为精确定位各支路的断点,提出了一种基于可调谐混沌Fabry-Perot激光器的检测方法.将光反馈多纵模Fabry-Perot半导体激光器作为混沌光源,在改变反馈光光波模式的条件下输出波长可调谐的混沌激光.以探测光的波长标记各被测支路,将探测信号和携带延时信息的回波信号进行互相关运算,根据相关曲线峰值的位置即可完成定位.分析了可调谐混沌源的特性,并以1×4的波分复用无源光网络为例,进行了初步的实验验证,结果表明该方法可以精确定位光网络支路中连接点及断点的位置,空间分辨率达4 cm,且与探测距离无关.     

THERMODYNAMIC ANALYSIS AND FORMATION ENTHALPY CALCULATION OF OXYGEN VACANCY DEFECT IN DOPED LITHIUM NIOBATE CRYSTALS

Based on the thermodynamic analysis of oxygen vacancy defects in lithium niobate (LiNbO₃ (LN)) and the data of thermogravimetric experiment, the formation enthalpies of congruent and several rare-earth (RE) doped LN crystals have been calculated. It was found that the formation enthalpy of oxygen vacancies can be decreased evidently by doping with valence-changeable RE ions. The experimental results were discussed and a new reduction process for photorefractive LN crystals at a relatively low temperature was proposed, and the reduction-treated crystals showed good effect in practical use.     

KLiSO4单晶的电学性质

我们证实了KLiSO₄为Li离子导体。通过测定样品中的电位分布,确定其载流子为间隙Li离子和Li空位。其电流弛豫在一定时域内遵从负幂次衰减规律。与之对应,在一定频域内存在与频率成负幂次关系的介电色散。在相变温度附近,本底电流、直流电导率和表观介电常数除发生跃变外还出现一个尖锐的小峰。此峰只有在变温速率较慢时才能观察到,表明该相变具有弛豫过程。 关键词：     

卷云短波红外辐射特性

 采用离散纵标法耦合大气分子吸收,模拟计算了卷云大气的反射特性。研究了在短波波段卷云辐射性质随波长、卷云光学厚度、卷云有效尺度、云高和卷云中冰晶粒子形状等的变化关系,分析了卷云对大气红外背景辐射的影响。结果表明：在2.7 μm的水汽强吸收带上,卷云的出现明显增强了该波段的大气背景辐射,反射率随光学厚度和云高增大而增大。     

SiO2∶Sm粉体：溶胶-凝胶法制备及特殊荧光性能

采用溶胶-凝胶法制备SiO2:Sm粉体,通过TG-DSC、FTIR、MAS-NMR、PL对材料的结构和性能进行测试表征.FTIR分析显示样品位于960 cm-1的吸收峰归属于Si-O-Sm键的变形振动,29Si MAS-NMR证实Sm3+进入SiO2网络结构.在380 nm入射光激发下样品产生除Sm3+特征发光以外的蓝绿荧光,对不同Sm3+掺量样品荧光性能进行对比分析,结果表明这种特殊的荧光发射与Si-O-Sm键的形成有关.     

多线性分数次积分算子一般框架下的交换子的有界性——献给陆善镇教授75华诞

对任意给定的正整数m,Z^＋×{1,...,m}的任意一个有限子集S,定义一般化的多线性分数次积分算子的交换子Iα,→b,S（f）（x）=∫（Rn）^m ∏（i,j）∈S（bi（x）-bi（yj））/（｜x-y1｜＋…＋｜x-ym｜）^mn-α∏（j=1→m）fj（yj）d→y,其中d→y=dy1…dym.此框架下的交换子包含了以往研究的各类分数次积分算子的交换子,并蕴含了多线性背景下新的交换子形式.在上述非常一般框架下,本文给出带多重A→p,q权的多线性分数次积分算子的交换子Iα,→b,S（→f）的加权强型（L^p1（ω1）×···×L^pm（ωm）,L^q（ν→ωq））估计和加权弱型端点估计.本文还得到更一般核条件下的上述结果.