Rapid surface-to-volume ratio and tortuosity measurement using Difftrain

Analysis of diffusion measurements as a function of observation time (Delta), to calculate surface-to-volume ratios (S/V) and tortuosities (kappa), is a useful tool in the characterisation of porous media using NMR. However, using conventional pulsed field gradient (PFG) measurements, this requires long total experiment times (typically hours). Here, we show how the rapid diffusion measurement pulse sequence, Difftrain, can be used to provide the required experimental data much more rapidly (typically within minutes) with a consequential reduction in total experiment time of typically over an order of magnitude. Several novel modifications to the Difftrain pulse sequence are also presented to tailor it to this particular application; these include a variable delay between echoes (to ensure optimal echo position with respect to Delta) and a variable tip angle for the refocusing pulse (to ensure optimal use of available signal). Difftrain is applied to measure both S/V and kappa for a model glass bead pack; excellent agreement is found with both a conventional PFG measurement and with a bulk gravimetric measurement of S/V.     

Optical signal-to-noise ratio measurement by optical homodyne tomography

An all-fiber optical homodyne tomography setup is introduced that measures the optical signal-to-noise ratio through reconstruction of the photon statistics. The scheme described has been conceived for applications to optical communications. In particular, the signal-to-noise ratio has been evaluated at lambda= 1.55 microm as a function of the received power. From the experimental data, in the case of optically amplified signals, the amplifier noise figure can be estimated.     

A complex image reconstruction algorithm for real-time measurement of transient field

Optical CT is now expanding into reconstruction from few views or limited-view range projection considering the economy and practicality. To solve the conflict of velocity and precision, which are two main aims that image reconstruction algorithm pursued, an innovative complex image reconstruction algorithm for real-time measurement of transient field is proposed. This method reconstructs computerized tomography (CT) image firstly by frequency spectrum approach reconstruction technique (FSART) and then by modified simultaneous algebraic reconstruction technique (MSART) and can give a fast and precise reconstruction to complicated transient field.     

基于噪声追踪的二值时频掩蔽到浮值掩蔽的泛化算法

虽然浮值掩蔽比二值掩蔽有更好的语音分离效果,但是由于理想浮值掩蔽难以直接估计,现有的语音分离系统通常以理想二值掩蔽估计作为计算目标。我们提出了一个二值掩蔽到浮值掩蔽的泛化算法。由于实现浮值掩蔽估计的关键在于噪声能量追踪,我们首先采用指数分布刻画以混合谱和噪声能量以混合能量及二值掩蔽为观测的条件分布。其次,采用高斯马尔柯夫条件随机场刻画噪声估计在连续几帧内的关联。最后,采用马尔柯夫链-蒙特卡洛计算噪声能量最小均方误差估计并进一步计算浮值掩蔽。实验表明,相比于基于二值掩蔽估计的常规算法,我们所提出的算法在信噪比增益和客观感知质量两方面都有显著提高。     

A measurement of the ratio of the nucleon structure function in copper and deuterium

Results are presented on the ratios of the nucleon structure function in copper to deuterium from two separate experiments. The data confirm that the nucleon structure function,F ₂, is different for bound nucleons than for the quasi-free ones in the deuteron. The redistribution in the fraction of the nucleon's momentum carried by quarks is investigated and it is found that the data are compatible with no integral loss of quark momenta due to nuclear effects.Supported by Bundesministerium für Forschung und Technologie     

回旋电子束横纵速度比测试技术

摘要:通过对回旋电子束形成的电位和电场分布,推导出电子束横纵速度比测量的计算式.提出将电子束作传输线内导体等效,采用陶瓷电容分压器来测量速度比的方法.介绍了该测量装置的设计和加工工艺,及陶瓷电容分压器的标定方法和结果分析,并介绍了初步的原理性实验结果.该测试方法装置简单,测试电子束横纵速度比时不会破坏电子束的特性,能够...     

回旋电子束横纵速度比测试技术

通过对回旋电子束形成的电位和电场分布,推导出电子束横纵速度比测量的计算式。提出将电子束作传输线内导体等效,采用陶瓷电容分压器来测量速度比的方法。介绍了该测量装置的设计和加工工艺,及陶瓷电容分压器的标定方法和结果分析,并介绍了初步的原理性实验结果。该测试方法装置简单,测试电子束横纵速度比时不会破坏电子束的特性,能够做到在回旋管运行时在线测量,实时监测电子束质量。     

一种测量功率超声振动系统振速比的简单方法

本文提出了一种测量功率超声振动系统中振动速度比的简单方法。与传统的测量方法相比,本方法将力学量转变为电学量的测量,将绝对测量变成了相对测量,降低了对实验设备的要求,有利于提高测试精度。     

Precise measurement of the depolarization ratio from photoacoustic Raman spectroscopy

A new method for the accurate determination of the Raman depolarization ratio is reported with an improved setup for photoacoustic Raman spectroscopy (PARS). The precise measurement is achieved by measuring the dependence of the acoustic signal intensity on the cross‐angle between the polarizations of two incident laser beams. We demonstrate this sensitive and simple method with several gaseous molecules, such as CH₄ and H₂. The measured results of depolarization ratios agree well with the theoretical values with an upper error limit of ± 0.005, which is comparable to that with polarization‐resolved CARS spectroscopy. Copyright © 2007 John Wiley & Sons, Ltd.     

大气后向散射比对风速测量的影响

采用同时测量Rayleigh散射和Mie散射混合信号的多普勒频移的单边缘技术,探测低空中（b值的变化,导致测量结果有很大的误差。详细分析了Rb值的变化对风速测量灵敏度及测量结果的影响,并做出了在不同Rb值情况下的风速测量校正曲线。结果表明：随着Rb值的增大,风速测量灵敏度有升高的趋势;随着Rb值偏差的增大,测量的风速误差有增大的趋势;同时,在相同的Rb值偏差情况下,随着径向风速的增大,测量的风速误差也有相应的增大。     

大气后向散射比对风速测量的影响

 采用同时测量Rayleigh散射和Mie散射混合信号的多普勒频移的单边缘技术,探测低空中（<12 km）的大气风速。由于大气后向散射比R_b值的变化,导致测量结果有很大的误差。详细分析了Rb值的变化对风速测量灵敏度及测量结果的影响,并做出了在不同Rb值情况下的风速测量校正曲线。结果表明：随着R_b值的增大,风速测量灵敏度有升高的趋势;随着Rb值偏差的增大,测量的风速误差有增大的趋势;同时,在相同的R_b值偏差情况下,随着径向风速的增大,测量的风速误差也有相应的增大。     

Spectral measurement of acceptor-to-donor extinction coefficient ratio in living cells

This report presents a simple method named as sp-ECR to determine the molar extinction coefficient ratio (γ(λ_ex)) of acceptor-to-donor in living cells at excitation wavelength λ_ex, which is closely associated with the acceptor cross-excitation, the hardest issue of FRET quantification. sp-ECR determines γ(λ_ex) by spectrally unmixing the emission spectrum of a donor–acceptor tandem construct under λ_ex excitation without any additional references, such that this method can be performed under optimal imaging condition. We used sp-ECR to measure the γ(458) of Venus/Cerulean in living HepG2 cells on a confocal microscope, and the measured values were consistent with those obtained by lux-FRET method. We also used sp-ECR to measure the γ(458) values of Venus/Cerulean and YFP/CFP as well as YFP/GFP, the commonly used FRET FPs pairs in other two kinds of cancer cell lines on the confocal microscope, and found that the extinction coefficients of FPs depended on cell lines. After predetermining the γ(458) of Venus to ECFP, we used sp-ECR method to monitor the staurosporine (STS)-induced dynamical caspase-3 activation in single live A549 cells expressing SCAT3 by spectrally resolving the absolute FRET efficiency of SCAT3, and found that STS-induced caspase-3 activation in single cells is a very rapid process within 20 min.     

First measurement of the Λ→nγ branching ratio

In an experiment performed at the CERN-SPS charged hyperon beam, we have observed the radiative decay Λ→nγ, using well identified Λ from the decays of Ο^? of 116 GeV/c momentum. Neutrons and photons from the Λ decays were observed in liquid argon and lead glass detectors. From a sample of 31 candidates, containing an estimated background of 7.3 events, the decay branching ratio was measured to be Γ(Λ→nγ)/Γ(Λ→all)=(1.02±0.33)×10^?3.     

提高飞秒超强激光对比度测量动态范围的一种新方法

普克尔盒(Pockelscell)和格兰棱镜以一定方式组合使用时能对超强激光脉冲的主脉冲进行消光而不会削弱预脉冲的强度,利用这一特性,文章作者设计搭建了一套高动态范围的激光纳秒对比度测量系统,利用该方法将对比度在ns量程内的动态测量范围提高了3个量级,并实验测得了2.95×10-8的纳秒对比度.     

遗传算法在椭圆偏振测量中的应用

详细介绍了椭圆偏振法测量的基本原理和椭偏函数方程的建立 ,将遗传算法引入到椭偏法测试薄膜的折射率和厚度的计算中 ,改善了计算的收敛性并提高收敛速度。给出了计算程序流程图 ,重点分析了各遗传算子的设计。     

用于三维测量的快速相位解包裹算法

减少条纹投影轮廓术的条纹图数量一直是本领域的研究热点。传统的时间相位解包裹算法,一般需要额外的条纹信息来确定条纹级次,导致条纹图数量过多。提出一种用于三维测量的快速相位解包裹算法,只需要N步标准相移正弦条纹图,就可以完成绝对相位的计算。首先,利用标准相移算法计算包裹相位和消除背景的掩膜;然后,直接利用包裹相位和掩膜,根据连通域标记算法计算条纹级次,进而求得绝对相位。该方法最少只需3幅条纹图,就可以完成三维测量,数据处理速度快。计算机仿真和实验结果验证了该方法的有效性和鲁棒性。     

基于后验概率度量的粒子滤波跟踪算法研究

 针对遮挡、光照变化、尺度变化等复杂环境中的视觉跟踪问题,提出一种基于后验概率度量的粒子滤波跟踪算法。由于后验概率指标与Bhattacharyya系数指标相比具有更强的峰值特性,采用后验概率指标作为相似性度量函数,通过粒子的更新、推广、观测、估计等步骤实现跟踪算法。通过对实际视频图像序列进行目标跟踪实验,实验结果表明:传统算法只有约50%的图像能够实现尺度自适应,而本文算法采用传统算法25%的粒子就能够收敛逼近目标的真实轨迹,达到更强的抗遮挡能力,90%以上的图像序列都能够实现良好的尺度自适应效果。     

基于图像透光率的粉尘浓度测量算法研究

为了实时在线监测颗粒物料在装卸和运输过程中所产生粉尘的浓度,提高粉尘浓度测量结果的精确性与可靠性,提出了一种基于图像透光率特征值计算的粉尘浓度测量算法。通过搭建粉尘浓度视觉测量实验平台,采集粉尘图像,再提取粉尘图像的透光率特征,以暗通道理论为基础,结合图像饱和度与亮度信息对粉尘图像透光率值进行计算,并采用多项式拟合的方式建立了粉尘浓度与图像透光率之间的映射关系,实现了粉尘浓度的高效率、高精度测量。研究结果表明：该算法不仅能有效地测量出粉尘浓度,且平均相对误差仅为7.77%,精确度得到有效提高,测量范围更大。     

Standardization for oxygen isotope ratio measurement - still an unsolved problem

Numerous organic and inorganic laboratory standards were gathered from nine European and North American laboratories and were analyzed for their delta(18)O values with a new on-line high temperature pyrolysis system that was calibrated using Vienna standard mean ocean water (VSMOW) and standard light Antartic precipitation (SLAP) internationally distributed reference water samples. Especially for organic materials, discrepancies between reported and measured values were high, ranging up to 2 per thousand. The reasons for these discrepancies are discussed and the need for an exact and reliable calibration of existing reference materials, as well as for the establishment of additional organic and inorganic reference materials is stressed. Copyright 1999 John Wiley & Sons, Ltd.     

Direct measurement of the phi(1020) leptonic branching ratio

The process e(+)e(-)-->mu(+)mu(-) has been studied by the SND detector at the VEPP-2M e(+)e(-) collider in the phi(1020)-resonance energy region. The measured effective phi meson leptonic branching ratio B(phi-->l(+)l(-)) identical with square root of B(phi-->e(+)e(-))B(phi-->mu(+)mu(-))] = (2.89 +/- 0.10 +/- 0.06) x 10(-4) agrees well with the Particle Data Group value B(phi-->e(+)e(-)) = (2.91 +/- 0.07) x 10(-4), confirming mu-e universality. Without additional assumption of mu-e universality the branching ratio B(phi-->mu(+)mu(-)) = (2.87 +/- 0.20 +/- 0.14) x 10(-4) was obtained.