多面转镜激光器扫频光学相干层析成像系统的全光谱重采样方法

在多面转镜激光器扫频光学相干层析成像系统中,激光器存在着输出光谱错位与扫频范围波动的问题.目前的重采样方法中,普遍利用互相关运算校正光谱错位,并进行大范围的截取,保证扫频范围的一致性,但这会导致成像信噪比与分辨率的降低.本文用马赫-曾德尔干涉仪(MZI)采集到的干涉信号对扫频范围波动的问题进行了详细的测量与分析,其中干涉信号的解缠相位曲线的非随机性和平行性,表明该类激光器输出光谱的波长分布具备一致性.在此基础上,提出了一种用最长扫频范围的MZI干涉信号,对样品干涉信号进行时域光谱对齐、然后进行一对多插值的重采样方法.实验与分析表明,该方法利用了所有的光谱信号,保证了样品干涉信号的能量利用率,能有效提高图像的信噪比与分辨率.     

Langevin dynamic simulation of hysteresis in a field-swept Landau potential

Numerical simulations are done of Langevin dynamics for a uniform-orderparameter, field-swept Landau model,= –|a/2|m ²+|b/4|m ⁴–mh(t) , to study hysteresis effects. The field is swept at a constant rateh(t)=h(0)+ht. The stochastic jump values of the field {h_J from an initially prepared metastable minimumm(0) are recorded, on passage to a global minimum m(). The results are: (a) The mean jump¯h _J(h) increases (hysteresis loop widens) with h, confirming a previous theoretical criterion based on rate competition between field-sweep and inverse mean first-passage time (FPT); (b) The broad jump distribution(h _J,h) is related to intrinsically large FPT fluctuations ( ²–²)/ ² O(1), and can be quantitatively understood. Possible experimental tests of the ideas are indicated.     

Time-domain sweeplets for acoustic measurements

This paper proposes new types of time-domain generated sine sweeps for impulse response measurements. A general time-domain analytical formulation method, combined with numeric phase alignment and frequency-domain inverse filtering is presented. It is applied to derive three new families of controllable spectrum sine sweeps called sweeplets, capable of matching 1/f^β background noises, producing finite band defocusing and single frequency focusing shapes. Mathematical properties concentrating on practical control of the signal shapes are examined. Effects of various perturbations, such as stationary and transient background noise, harmonic distortion and finite length are presented. Applicability of the proposed method is experimentally verified by a room acoustic measurement example.     

Ultrasonically assisted synthesis of barium stannate incorporated graphitic carbon nitride nanocomposite and its analytical performance in electrochemical sensing of 4-nitrophenol

We describe the ultrasonic assisted preparation of barium stannate-graphitic carbon nitride nanocomposite (BSO-gCN) by a simple method and its application in electrochemical detection of 4-nitrophenol via electro-oxidation. A bath type ultrasonic cleaner with ultrasonic power and ultrasonic frequency of 100 W and 50 Hz, respectively, was used for the synthesis of BSO-gCN nanocomposite material. The prepared BSO-gCN nanocomposite was characterized by employing several spectroscopic and microscopic techniques such as X-ray diffraction, X-ray photoelectron spectroscopy, fourier transform infra-red, field emission scanning electron microscopy, and high resolution transmission electron microscopy, to unravel the structural and electronic features of the prepared nanocomposite. The BSO-gCN was drop-casted on a pre-treated glassy carbon electrode (GCE), and their sensor electrode was utilized for electrochemical sensing of 4-nitrophenol (4-NP). The BSO-gCN modified GCE exhibited better electrochemical sensing behavior than the bare GCE and other investigated electrodes. The electroanalytical parameters such as charge transfer coefficient (α = 0.5), the rate constant for electron transfer (k_s = 1.16 s⁻¹) and number of electron transferred were calculated. Linear sweep voltammetry (LSV) exhibited increase in peak current linearly with 4-NP concentration in the range between 1.6 and 50 μM. The lowest detection limit (LoD) was calculated to be 1 μM and sensitivity of 0.81 μA μM⁻¹ cm⁻²_. A 100-fold excess of various ions, such as Ca²⁺, Na⁺, K⁺, Cl⁻, I⁻, CO₃²⁻, NO₃, NH₄⁺ and SO₄²⁻ did not able to interfere with the determination of 4-NP and high sensitivity for detecting 4-NP in real samples was achieved. This newly developed BSO-gCN could be a potential candidate for electrochemical sensor applications.     

针对调频引信的窄带扫频式干扰优化方法

扫频式干扰是调频体制引信的主要威胁之一,但其干扰效果具有一定随机性。为了提高其干扰效率,在理论分析扫频式干扰作用下调频引信失效机理的基础上,提出了一种针对单通道调频多普勒引信的窄带扫频式干扰优化方法,可以获取最优的扫频频率步进点数,并依此进行非等间隔频率步进的窄带扫频式干扰。仿真与实测结果表明,该方法可以提高扫频式干扰的干扰效率,同时该方法也可以为成功干扰采用多通道等抗干扰措施的调频引信提供理论设计依据。     

光学条纹相机时间扫描性能应用

对相机全屏扫速性能进行了系统分析,发现基于相机整体的平均扫速及扫速非线性处理扫描时间的传统方法不能反映相机空间畸变现象,并且扫速非线性放大了数据处理不确定度,从而降低了相机应用价值。建立了一套基于全屏扫速及扫速不确定度的扫描时间精细处理方法,它自洽消除了相机的空间畸变和扫速非线性的系统性影响。开展了理论分析和验证实验,结果表明:精细处理方法很容易使扫描时间数据处理相对不确定度降低到1%以内,显著提高了条纹相机时间扫描精度和应用可靠性。     

电偏转扫描法测量高电荷态ECR源发射度

成功地研制了一套适合于低能离子束流发射度测量的电偏转扫描探测器.对该探测器的原理和结构作了较详细的描述,并给出该探测器对兰州近代物理研究所高电荷态ECR源LECR3引出离子束流发射度的测量结果.典型结果为:在引出高压为15.97kV,引出束流为190μA时,O⁴⁺水平发射度(x方向)为137πmm·mrad,垂直发射度(y方向)为120πmm·mrad(包括90%束流).最后,对测量结果作了一些分析和讨论.     

Spin-spin coupling edition in chiral liquid crystal NMR solvent

The application of the G-SERFph pulse sequence is presented on enantiomeric mixtures dissolved in a chiral liquid crystal. It aims at editing, within one single 2D spectrum, every proton coupling which is experienced by a given proton site in the molecule, and leads to real phased T-edited spectroscopy (T=J+2D). This NMR experiment is based on the combination of homonuclear semi-selective refocusing techniques with a spatial frequency encoding of the sample. This approach, which consists in handling selectively each coupling in separate cross sections of the sample, is applied to the visualization of enantiomers dissolved in a chiral liquid crystalline phase. Advantages and limits of this methodology are widely discussed.     

用于双光子激发荧光寿命显微成像的高重复频率皮秒扫描相机

建立了一台基于新研制的高重复频率皮秒扫描相机的双光子激发荧光寿命显微成像系统,重点介绍所研制的高重复频率皮秒扫描相机。为了在高时间分辨力的同时扩大时间测量范围,实现大面积两维空间高时间分辨取样测量,从而提高采样速率和更有效地发挥扫描相机的作用,设计和研制了一种大面积、高时间分辨力扫描变像管和一种重复频率高达1MHz的斜坡电压扫描电路。基于上述关键部件所研制的扫描相机具有重复频率高、扫描速度可调、时间分辨力高、工作面积大、非线性低、触发晃动小等优点。用钛宝石飞秒激光器作为激光脉冲源,通过脉冲提取器将76MHz的高重复频率降低为1MHz,采用可调延时器和标准具对扫描相机的时间分辨力、扫描速度和非线性进行标定。该系统的时间分辨力达到6.5ps,非线性为2.60%,可测量的时间范围从十几皮秒到几十纳秒。测量了若丹明6G和香豆素314两种标准荧光染料的荧光寿命,取得了与参考文献一致的实验结果。     

Distinction between stepwise and concerted mechanisms in reductive cleavage reactions—use of voltammetric current function in the analysis of non-linear kinetic laws

A systematic way of distinguishing stepwise and concerted mechanisms in reductive cleavage reactions has been formulated involving current function analysis of the voltammetric data. The electrochemical reductive cleavage of the carbon-iodine bond in 1,3-dichloro-2-iodobenzene has been analyzed from a mechanistic point of view to illustrate the methodology. 1,3-Dichloro-2-iodobenzene undergoes an initial stepwise electron transfer obeying quadratic activation-driving force relationship. The current function analysis yields the reorganization energy for the reduction of 1,3-dichloro-2-iodobenzene and the results have been verified independently using convolution potential sweep voltammetry.