一种时间相关吸收光谱技术分析新方法

时间相关吸收光谱技术，如腔衰荡光谱技术(CRDS)和腔衰减相移光谱技术(CAPS)，是近三十几年发展起来的一类新型吸收光谱检测技术，它具有探测灵敏度高、响应速度快、不受光源强度起伏变化影响等优点。传统的吸收光谱技术都是基于Lambert-Beer定律，如直接吸收光谱技术(DAS)、波长调制光谱技术(WMS)和腔增强吸收光谱技术(CEAS)等，这类光谱技术在探测物质微弱吸收的时候一旦遇到较强的背景光信号就变得难以测量，而且光源的不稳定性也会对检测带来一定的限制。时间相关吸收光谱技术由于其不受光源强度起伏变化的特点，在很大程度上能够弥补传统吸收光谱技术所存在的缺陷，但其也有自身的局限性。首先在理论上，CRDS和CAPS这两种时间相关吸收光谱技术并不统一，而且在现有光谱理论下，Pulse-CRDS在应用时使用的脉冲光源的脉宽必须远小于谐振腔本身的时间常数，对于长脉宽的脉冲光或者反射率低(小于99.9%)的腔体，现有理论将不再适用；CAPS在应用时光源调制信号必须是周期性的正弦信号或者方波信号，对于其他类型的周期调制信号或者非周期性信号，现有理论并没有涉及。针对上述提到的时间相关吸收光谱技术的局限性，提出了一种新的分析时间相关吸收光谱技术的方法，即利用一阶传递函数，将谐振腔视为一阶传感系统，对时间相关吸收光谱技术理论进行统一解释，在公式推导上证明新方法下的推导结果和现有理论结果的一致性。针对Pulse-CRDS，以高斯脉冲光为例，给出一阶传感理论下的透射光强表达式，并对一系列不同的脉冲宽度γ、谐振腔时间常数τ_real以及从输出信号中拟合而得的时间常数τ_anal进行了模拟仿真。经过分析比较后发现，当γ<0.3τ_real时，τ_anal和τ_real的偏差小于1%；当γ>0.3τ_real时，τ_anal和τ_real的偏差渐渐变大，将不再满足实验条件。为了使Pulse-CRDS在长脉宽脉冲光下也能应用，本文给出了修正函数，使得在脉宽大于腔衰荡时间0.3倍的情况下，经过修正补偿后，衰荡时间的误差小于1%。对于CAPS系统，搭建相应实验平台，LED中心波长选用405 nm，使用方波调制信号，测量不同频率下的入射参考信号与探测信号的相位差和探测信号峰-峰值，通过由一阶传递函数推导而得的相频特性和幅频特性，拟合得到时间常数τ，结果分别为7.24和7.25 μs，残差范围分别为[-0.01, 0.02]和[-0.02, 0.025]，两者结果基本一致。实验结果验证了一阶传感系统理论完全适用于时间相关光谱的信号分析，并且一阶传感系统理论还使得时间相关光谱技术的理论得到了统一。     

Determination of Young's modulus of epoxy coated polyethylene micro-cantilever using phase-shift shadow moiré method

Young′s moduli of various epoxy coated polyethylene terephthalate (PET) micro-cantilevers were determined from the deflection results obtained using the phase-shift shadow moiré (PSSM) method. The filler materials for epoxy coatings were aluminum and graphite powders that were mixed with epoxy at various percentages. Young′s moduli were calculated from theory based on the deflection results. The PET micro-cantilever coated with aluminum-epoxy coating showed increasing value of Young′s modulus when the ratios of the aluminum-epoxy were increased. The graphite-epoxy coating on the PET micro-cantilever also showed the same trend. The experimental results also show that Young′s modulus of the graphite-epoxy coating is higher than aluminum-epoxy coating in comparison at the same mixing ratio.     

三电平大功率并联逆变电源在EAST系统中的应用

针对EAST超导托卡马克装置中的等离子体位移快控电源大电流快速响应的要求，采用三电平结合移相PWM多重化技术，实现多组变流器并联运行，提高了变流器的等效开关频率控制性能，从而改善了电流波形品质。分析了快控电源系统的设计方案和控制方法，并针对移相PWM多重化技术，采用Matlab进行了仿真，验证了设计思想。实验结果表明，该系统设计方案合理、控制策略有效，具备良好的大电流输出和快速响应能力。     

干涉型复合腔激光束相干合成中分束器的相移特性研究

分析了采用分束器构建干涉型复合腔进行激光束相干合成的过程与原理.利用分束器的特征矩阵研究了分束时产生的反射与透射相移,得到了两束相干光经过分束器分束后进行相干叠加时相移满足的普适关系,从相移的角度解释了分束器一侧发生相长干涉时另一侧必然发生相消干涉这一现象.比较了分束器与光纤耦合器在激光束相干合成应用中的一些特性,并验证了所得相移关系式的正确性.     

Phase-shift analysis of electric conductance through nanostructure bridges

We present our theoretical studies of electric conductance through nanostructure bridges. A simple expression of the electric conductance is obtained by using the phase-shift analysis. The phase-shifts are given by solving the characteristic equation obtained by extending the method applied to the single impurity problem in the metal. It is shown that the importance of the effect due to multiple orbitals in nanostructures. The conductance of the chain consisting atoms with sp_z character such as Al is given.     

荧光寿命的正弦调制测量法及分析

设计并制作了光强调制度和频率可调的发光二极管驱动电路,应用这种激励源激发荧光样品Eu2L'3·nH2O(L'=C4H4O4),测量了激发光和Eu3 离子的5D0-7F2发射光的波形.实验得到的数据用按照相位法测量荧光寿命的原理用非线性最小平方曲线拟合,得到Eu3 离子激发态5D0的寿命约为0.680ms.讨论了光源调制中的高次谐波分量对测量结果的影响以及寿命具有一定分布的多指数衰减体系的测量和处理方式,提出应用傅里叶级数展开处理数据的修正方法,以扩大相位法测量荧光寿命的适用范围,得到更准确的荧光寿命值.     

Modified Fourier-transform method for phase-shift calibration

A fast convergent algorithm to accurately measure phase-shift for phase shifter is proposed. In the presence of a spatial carrier frequency, an error function in the Fourier-domain is introduced and then the unknown phase-shift between two phase-shifted fringe patterns is determined by minimization of the error function with the help of a golden section search approach. Compared with the conventional Fourier-transform method, the modified method proposed in the paper is more immune to random noise and hence can give a more accurate result. The translation curve of a liquid-crystal spatial light modulator is also experimentally calibrated.     

Multi-time scale characterization of acoustic droplet vaporization and payload release of phase-shift emulsions using high-speed microscopy

Acoustic droplet vaporization (ADV) is the phase-transitioning of perfluorocarbon emulsions, termed phase-shift emulsions, into bubbles using focused ultrasound. ADV has been utilized in many biomedical applications. For localized drug release, phase-shift emulsions with a bioactive payload can be incorporated within a hydrogel to yield an acoustically-responsive scaffold (ARS). The dynamics of ADV and associated drug release within hydrogels are not well understood. Additionally, emulsions used in ARSs often contain high molecular weight perfluorocarbons, which is unique relative to other ADV applications. In this study, we used ultra-high-speed brightfield and fluorescence microscopy, at frame rates up to 30 million and 0.5 million frames per second, respectively, to elucidate ADV dynamics and payload release kinetics in fibrin-based ARSs containing phase-shift emulsions with three different perfluorocarbons: perfluoropentane (PFP), perfluorohexane (PFH), and perfluorooctane (PFO). At an ultrasound excitation frequency of 2.5 MHz, the maximum expansion ratio, defined as the maximum bubble diameter during ADV normalized by the initial emulsion diameter, was 4.3 ± 0.8, 4.1 ± 0.6, and 3.6 ± 0.4, for PFP, PFH, PFO emulsions, respectively. ADV yielded stable bubble formation in PFP and PFH emulsions, though the bubble growth rate post-ADV was three orders of magnitudes slower in the latter emulsion. Comparatively, ADV generated bubbles in PFO emulsions underwent repeated vaporization/recondensation or fragmentation. Different ADV-generated bubble dynamics resulted in distinct release kinetics in phase-shift emulsions carrying fluorescently-labeled payloads. The results provide physical insight enabling the modulation of bubble dynamics with ADV and hence release kinetics, which can be used for both diagnostic and therapeutic applications of ultrasound.     

Computing circadian rhythmic patterns and beyond: introduction to a new non-Fourier analysis

We introduce a new computational approach for recognizing and analyzing rhythmic dynamics hidden in lengthy recording of animal’s locomotive activity. This recoding is presented in a form of event-time series, and termed actogram in biological rhythm literature. Upon an actogram, we lay out the construction of our computational approach, called hierarchical segmentation (HS) approach, on a platform based on 3-level-coding algorithm with detailed heuristic ideas and statistical explanation. Our HS approach is then demonstrated to objectively compute and identify a series of phase-markers, which in turn partition the whole actogram into a series of circadian rhythmic cycles of varying lengths. Among these rhythmic cycles, common waveform pattern is also extracted as the chief characteristic of recognizing individual circadian dynamics, and period is calculated as the averaged length of the series of rhythmic cycles. Also we demonstrate how to measure the essential ingredients of rhythmic dynamics: phase-shifts due to Zeitgeber and their information contents, through simple linear regression analysis on subseries of phase-markers before and after Zeitgeber. Along our development explicit contrasts are made to explain the shortcomings of periodogram or Fourier transform based spectrum analysis which rigidly determines rhythmic cycles with equal length, and in general ignores the waveform identification completely. We then show a new construction for the phase response curve (PRC) with confidence band. This construction is proved to be critical for biologists who endeavor to make unbiased inferences on circadian rhythm. Examples of real data analysis on actogram of German cockroach are realistically illustrated. Beyond as being an alternative, we conclude that our computational approach can deliver viable non-Fourier rhythmic pattern recognition on circadian rhythms.     

相控阵多普勒计程仪的相控波束接收方案

相控阵多普勒计程仪具有基阵体积小，且无需进行声速补偿等优点，本在讨论相控阵多普勒计程仪原理的基础上，提出了相控接收和宽带系统移相的方案，并通过试验验证了实际设计制作的相控接收系统的可行性。