Using the quantitative error probability density method we studied the S/N ratio of alternately sampled signals digitized by a 4-channel A/D. A complete expression for the S/N ratio of a 4-channel A/D non-uniform samp...Using the quantitative error probability density method we studied the S/N ratio of alternately sampled signals digitized by a 4-channel A/D. A complete expression for the S/N ratio of a 4-channel A/D non-uniform sampling signal was deduced. First we obtained an expression for the S/N ratio of a 1-channel A/D uniform sampling signal when the sampling frequency was equal to or greater than 2 times the frequency of the sampled signal. Based on the S/N ratio of a 2-channel A/D,alternating,non-uniform sampling signal,we analyzed the distribution of quantitative error using the quantitative error probability density method and the distribution convolution formula. From this the S/N ratio expression of a 4-channel A/D sampling signal was deduced. The simulation result shows that the deduced expression is correct.展开更多
The polarization-resolved laser-induced breakdown spectroscopy （PRLIBS） technique, which can significantly reduce the polarized emission from laser plasma by placing a polarizer in front of the detector, is a powerf...The polarization-resolved laser-induced breakdown spectroscopy （PRLIBS） technique, which can significantly reduce the polarized emission from laser plasma by placing a polarizer in front of the detector, is a powerful tool to improve the line-to-continuum ratio in LIBS applications. It is shown that the continuum emission from the plasma produced through ablating an Al sample by nanosecond laser pulses is much more polarized than the discrete line emission with the singlepulse PRLIBS technique. The effects of laser fluence and detection angle on the Al polarization spectrum are systematically explored experimentally. The calculated result of the polarization spectrum as a function of laser fluence shows that it is in agreement with the experimental observations.展开更多
CHCA as a matrix facilitates the ionization of proteins and peptides in a matrix-assisted laser desorption/ionization(MALDI) time-of-flight(TOF) mass spectrometer. The matrix itself also ionizes and so do its adducts....CHCA as a matrix facilitates the ionization of proteins and peptides in a matrix-assisted laser desorption/ionization(MALDI) time-of-flight(TOF) mass spectrometer. The matrix itself also ionizes and so do its adducts. Matrix clusters and adducts interfere with peptide ionization and peptide mass spectrum interpretation, especially at low sample concentrations and within m/z 500-1 000 range. These matrix adducts, especially within m/z 500-1 000, are significantly reduced with addition of ammonium citrate, ammonium sulfate, ammonium benzoate, ammonium bicarbonate, ammonium citrate and potassium dihydrogen phosphate to the matrix and the samples were deposited onto the MALDI target. The reduction of matrix adducts improves peptide ionization and signal-to-noise ratio, which enhances the reliability of database searching.展开更多
本文提出了一种新的资料处理方法——速度谱约束(Constraints of Velocity Spectrum,CVS)。该方法首先对叠前CMP道集进行速度分析,拾取有效信号速度,经过动校正后利用横向滤波技术将校平后的信号和未校平的噪声分离;再进行反动校;再次...本文提出了一种新的资料处理方法——速度谱约束(Constraints of Velocity Spectrum,CVS)。该方法首先对叠前CMP道集进行速度分析,拾取有效信号速度,经过动校正后利用横向滤波技术将校平后的信号和未校平的噪声分离;再进行反动校;再次进行速度分析拾取干扰波速度,经过动校正后将校平的干扰波与未校平的有效信号分离,对分离的有效信号利用干扰波速度反动校后再利用有效信号速度动校正;最后进行水平叠加。该方法在提高资料信噪比的同时有效地提高了横向和纵向分辨率,且具有很好的保真度。展开更多
基金Projects 07KJZ11 supported by the President Fund of Xuzhou Medical School07KJB310117 by the Education Department of Jiangsu Province
文摘Using the quantitative error probability density method we studied the S/N ratio of alternately sampled signals digitized by a 4-channel A/D. A complete expression for the S/N ratio of a 4-channel A/D non-uniform sampling signal was deduced. First we obtained an expression for the S/N ratio of a 1-channel A/D uniform sampling signal when the sampling frequency was equal to or greater than 2 times the frequency of the sampled signal. Based on the S/N ratio of a 2-channel A/D,alternating,non-uniform sampling signal,we analyzed the distribution of quantitative error using the quantitative error probability density method and the distribution convolution formula. From this the S/N ratio expression of a 4-channel A/D sampling signal was deduced. The simulation result shows that the deduced expression is correct.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60978014, 11074027, 61178022, 11274053, and 11211120156)the Fundsfrom Science and Technology Department of Jilin Province, China (Grant Nos. 20090523, 20100521, 20100168, and 20111812)Funds from Education Department of Jilin Province
文摘The polarization-resolved laser-induced breakdown spectroscopy （PRLIBS） technique, which can significantly reduce the polarized emission from laser plasma by placing a polarizer in front of the detector, is a powerful tool to improve the line-to-continuum ratio in LIBS applications. It is shown that the continuum emission from the plasma produced through ablating an Al sample by nanosecond laser pulses is much more polarized than the discrete line emission with the singlepulse PRLIBS technique. The effects of laser fluence and detection angle on the Al polarization spectrum are systematically explored experimentally. The calculated result of the polarization spectrum as a function of laser fluence shows that it is in agreement with the experimental observations.
文摘CHCA as a matrix facilitates the ionization of proteins and peptides in a matrix-assisted laser desorption/ionization(MALDI) time-of-flight(TOF) mass spectrometer. The matrix itself also ionizes and so do its adducts. Matrix clusters and adducts interfere with peptide ionization and peptide mass spectrum interpretation, especially at low sample concentrations and within m/z 500-1 000 range. These matrix adducts, especially within m/z 500-1 000, are significantly reduced with addition of ammonium citrate, ammonium sulfate, ammonium benzoate, ammonium bicarbonate, ammonium citrate and potassium dihydrogen phosphate to the matrix and the samples were deposited onto the MALDI target. The reduction of matrix adducts improves peptide ionization and signal-to-noise ratio, which enhances the reliability of database searching.
文摘本文提出了一种新的资料处理方法——速度谱约束(Constraints of Velocity Spectrum,CVS)。该方法首先对叠前CMP道集进行速度分析,拾取有效信号速度,经过动校正后利用横向滤波技术将校平后的信号和未校平的噪声分离;再进行反动校;再次进行速度分析拾取干扰波速度,经过动校正后将校平的干扰波与未校平的有效信号分离,对分离的有效信号利用干扰波速度反动校后再利用有效信号速度动校正;最后进行水平叠加。该方法在提高资料信噪比的同时有效地提高了横向和纵向分辨率,且具有很好的保真度。
