This investigation aimed at improving the performance of Taylor’s dispersion analysis for the fast and accurate measurement of diffusion coefficient of a minute solute in various solvents. The investigation was carri...This investigation aimed at improving the performance of Taylor’s dispersion analysis for the fast and accurate measurement of diffusion coefficient of a minute solute in various solvents. The investigation was carried out on a capillary electrophoresis instrument by monitoring the UV absorption peak of a solute pulse and calculating the diffusion coefficient by peak efficiency. With L-phenylalanine as a main testing solute, some key factors were afterward disclosed including especially the capillary size, carrier flow velocity, injection volume and capillary conditioning. Peak tailing, large volume of sample injection and slow migration were found to underestimate the diffusion coefficient while very fast migration and high sample concentration caused overestimation. At a moderate flow velocity of 0.1―1 cm/s with a capillary of 72.44 μm I.D.×60 cm (50 cm effective) maintained at 25℃, the diffusion coefficient of aqueous L-phenylalanine was determined, giving a value of 7.02×10-6 cm2/s with error <2% and relative standard deviation <0.2% (n=3). The method was shown to be applicable to the measurement of various samples such as aqueous phenylalanine, acetone, phenol, toluene and benzene, and nonaqueous benzene (in ethanol or 1-butanol).展开更多
This paper presents an approach to calculate dispersion penalty for VSR-1 optical links.Based on parameters of a specific VSR-1 link,dispersion penalties are computed for various modal dispersion bandwidths respective...This paper presents an approach to calculate dispersion penalty for VSR-1 optical links.Based on parameters of a specific VSR-1 link,dispersion penalties are computed for various modal dispersion bandwidths respectively.The worst-case eye closure is expressed numerically by using the signal waveform at time 0,and the signal waveform is obtained in frequency domain through FFT algorithm.By this approach,the dispersion penalty is determined by the shape of transfer functions of the various components in the links.To simplify the derivation of multimode fiber link transfer function,a Gaussian form of normalized impulse response is used.This calculation approach can be used to estimate the worst-case dispersion penalty of VSR-1 links in the link budget analysis.展开更多
This paper presents a robust color image hiding method based on YCbCr color system in discrete cosine transform （DOT） domain,which can hide a secret color image behind a public color cover image and is compatible wi...This paper presents a robust color image hiding method based on YCbCr color system in discrete cosine transform （DOT） domain,which can hide a secret color image behind a public color cover image and is compatible with the international image compression standard of JPEG. To overcome the grave distortion problem in the restored secret image,this paper proposes a new embedding scheme consisting of reasonable partition of a pixel value and sign embedding. Moreover, based on human visual system （HVS） and fuzzy theory,this paper also presents a fuzzy classification method for DOT sub-blocks to realize the adaptive selection of embedding strength. The experimental results show that the maximum distortion error in pixel value for the extracted secret image is ±1. And the color cover image can provide good quality after embedding large amount of data.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20435030 and 20628507)Chinese Academy of Sciences and the Ministry of Science and Technology (Grant No. 2002CB713803)
文摘This investigation aimed at improving the performance of Taylor’s dispersion analysis for the fast and accurate measurement of diffusion coefficient of a minute solute in various solvents. The investigation was carried out on a capillary electrophoresis instrument by monitoring the UV absorption peak of a solute pulse and calculating the diffusion coefficient by peak efficiency. With L-phenylalanine as a main testing solute, some key factors were afterward disclosed including especially the capillary size, carrier flow velocity, injection volume and capillary conditioning. Peak tailing, large volume of sample injection and slow migration were found to underestimate the diffusion coefficient while very fast migration and high sample concentration caused overestimation. At a moderate flow velocity of 0.1―1 cm/s with a capillary of 72.44 μm I.D.×60 cm (50 cm effective) maintained at 25℃, the diffusion coefficient of aqueous L-phenylalanine was determined, giving a value of 7.02×10-6 cm2/s with error <2% and relative standard deviation <0.2% (n=3). The method was shown to be applicable to the measurement of various samples such as aqueous phenylalanine, acetone, phenol, toluene and benzene, and nonaqueous benzene (in ethanol or 1-butanol).
基金Supported by"863"Hi-Tech Research and Development Program(2005AA311030) and the National Natural Science Foundationof China(Grant No.60502005)
文摘This paper presents an approach to calculate dispersion penalty for VSR-1 optical links.Based on parameters of a specific VSR-1 link,dispersion penalties are computed for various modal dispersion bandwidths respectively.The worst-case eye closure is expressed numerically by using the signal waveform at time 0,and the signal waveform is obtained in frequency domain through FFT algorithm.By this approach,the dispersion penalty is determined by the shape of transfer functions of the various components in the links.To simplify the derivation of multimode fiber link transfer function,a Gaussian form of normalized impulse response is used.This calculation approach can be used to estimate the worst-case dispersion penalty of VSR-1 links in the link budget analysis.
基金This workis partially supported by National Science Foundation(Grant No.A0324676)
文摘This paper presents a robust color image hiding method based on YCbCr color system in discrete cosine transform （DOT） domain,which can hide a secret color image behind a public color cover image and is compatible with the international image compression standard of JPEG. To overcome the grave distortion problem in the restored secret image,this paper proposes a new embedding scheme consisting of reasonable partition of a pixel value and sign embedding. Moreover, based on human visual system （HVS） and fuzzy theory,this paper also presents a fuzzy classification method for DOT sub-blocks to realize the adaptive selection of embedding strength. The experimental results show that the maximum distortion error in pixel value for the extracted secret image is ±1. And the color cover image can provide good quality after embedding large amount of data.
