OBJECTIVE To investigate a new noninvasive method for calculating left ventricular diastolic time constant(Tau) through a continuous-wave aortic regurgitation Doppler spectrum.METHODS According to ultrasound guidance,...OBJECTIVE To investigate a new noninvasive method for calculating left ventricular diastolic time constant(Tau) through a continuous-wave aortic regurgitation Doppler spectrum.METHODS According to ultrasound guidance, twenty-four animal models(beagles) of aortic regurgitation and acute ischemic left ventricular diastolic dysfunction were created. The left ventricular diastolic function was manipulated with dobutamine or esmolol and fifty-nine hemodynamic stages were achieved. Raw audio signals of the continuous-wave Doppler spectra were collected, and new aortic regurgitation Doppler spectra were built after reprocessing by a personal computer. The updating time of the spectral line was 0.3 ms. The new Doppler spectra contour line was automated using MATLAB(MATrix LABoratory, MathWorks, Natick, MA, USA), and two time intervals,(t2–t1) and(t3–t1) were measured on the ascending branch of the aortic regurgitation Doppler spectrum. Then, the two time intervals were substituted into Bai's equations, and Doppler-derived Tau(Tau-D)was resolved and compared with catheter-derived Tau(Tau-c).RESULTS There is no significant difference between Tau-D and Tau-c(45.95 ± 16.90 ms and 46.81 ± 17.31 ms, respectively;P >0.05). Correlation analysis between Tau-c and Tau-D suggested a strong positive relationship(r = 0.97, P = 0.000). A Bland-Altman plot of Tau-c and Tau-D revealed fair agreement.CONCLUSIONS This new calculation method is simple, convenient, and shows a strong positive relationship and fair agreement with the catheter method.展开更多
The second-order small slope approximation(SSA2) method is introduced to study the Doppler characteristics from time-evolving sea surfaces.Simulation results show better agreement between the SSA2 model and the numeri...The second-order small slope approximation(SSA2) method is introduced to study the Doppler characteristics from time-evolving sea surfaces.Simulation results show better agreement between the SSA2 model and the numerical method for both vertical and horizontal polarizations,meaning that SSA2 gives a satisfactory prediction of the spectral difference between two polarizations;while such discrepancy cannot be captured using the lowest-order SSA(SSA1) model.In particular,the Doppler shifts and spectral widths for different incident angles,wind directions and polarizations are analyzed,demonstrating correct variations with respect to such parameters.Those observations prove that the SSA2 provides an efficient and relatively fast tool for sea surface Doppler spectral analysis.展开更多
An iterative physical optics(IPO) model is proposed to solve extra large scale electric electromagnetic(EM) scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward...An iterative physical optics(IPO) model is proposed to solve extra large scale electric electromagnetic(EM) scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation(Fa FFA) in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle(LGA).展开更多
用迭代法对湮没辐射的Doppler展宽谱去卷职,获取湮没辐射的本征分布。用高斯—牛顿法将本征分布拟合为一个高斯函数(心电子贡献)和抛物线函数(传导电子贡献)之和。从本征分布和抛物线函致可以算出电子的动量分布信息和估测费米能。用纯G...用迭代法对湮没辐射的Doppler展宽谱去卷职,获取湮没辐射的本征分布。用高斯—牛顿法将本征分布拟合为一个高斯函数(心电子贡献)和抛物线函数(传导电子贡献)之和。从本征分布和抛物线函致可以算出电子的动量分布信息和估测费米能。用纯Ge探测器测量了Al、Ag、Cu、Co、Ni、Sa、In、Mo、W、Zr,Ti、Ge、Si等13种材料的多普勒展宽谱,算出它们的动量分布和费米能,显示各种材料的动量分布明显不同,由实验测得的费米能值与由自由电子气模型计算的理论值很好符合。对Fe Si B非晶和晶态合金的研究表明:两者的动量分布差异甚小,但费米能略有不同。展开更多
基金supported by the National Natural Science Foundation of China (No.81771833)the Beijing Natural Science Foundation (No.7172209)。
文摘OBJECTIVE To investigate a new noninvasive method for calculating left ventricular diastolic time constant(Tau) through a continuous-wave aortic regurgitation Doppler spectrum.METHODS According to ultrasound guidance, twenty-four animal models(beagles) of aortic regurgitation and acute ischemic left ventricular diastolic dysfunction were created. The left ventricular diastolic function was manipulated with dobutamine or esmolol and fifty-nine hemodynamic stages were achieved. Raw audio signals of the continuous-wave Doppler spectra were collected, and new aortic regurgitation Doppler spectra were built after reprocessing by a personal computer. The updating time of the spectral line was 0.3 ms. The new Doppler spectra contour line was automated using MATLAB(MATrix LABoratory, MathWorks, Natick, MA, USA), and two time intervals,(t2–t1) and(t3–t1) were measured on the ascending branch of the aortic regurgitation Doppler spectrum. Then, the two time intervals were substituted into Bai's equations, and Doppler-derived Tau(Tau-D)was resolved and compared with catheter-derived Tau(Tau-c).RESULTS There is no significant difference between Tau-D and Tau-c(45.95 ± 16.90 ms and 46.81 ± 17.31 ms, respectively;P >0.05). Correlation analysis between Tau-c and Tau-D suggested a strong positive relationship(r = 0.97, P = 0.000). A Bland-Altman plot of Tau-c and Tau-D revealed fair agreement.CONCLUSIONS This new calculation method is simple, convenient, and shows a strong positive relationship and fair agreement with the catheter method.
基金supported by the National Natural Science Foundation of China (40771133)
文摘The second-order small slope approximation(SSA2) method is introduced to study the Doppler characteristics from time-evolving sea surfaces.Simulation results show better agreement between the SSA2 model and the numerical method for both vertical and horizontal polarizations,meaning that SSA2 gives a satisfactory prediction of the spectral difference between two polarizations;while such discrepancy cannot be captured using the lowest-order SSA(SSA1) model.In particular,the Doppler shifts and spectral widths for different incident angles,wind directions and polarizations are analyzed,demonstrating correct variations with respect to such parameters.Those observations prove that the SSA2 provides an efficient and relatively fast tool for sea surface Doppler spectral analysis.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60578018, 10434080 and 10374062）, by the Key Scientific Program of Education Ministry of China （Grant No 204019）, and by the Research Funds for Youth Academic Leaders of Shanxi Province, China.
基金supported by the National Natural Science Foundation of China(61372033)
文摘An iterative physical optics(IPO) model is proposed to solve extra large scale electric electromagnetic(EM) scattering from randomly rough surfaces. In order to accelerate the convergence of the IPO model, the forward-backward methodology and its modification with underrelaxation iteration are developed to simulate the rough surface scattering; the local iteration methodology and the fast far field approximation(Fa FFA) in the matrix-vector product are proposed to reduce greatly the computational complexity. These techniques make Monte Carlo simulations possible. Thus, the average Doppler spectra of backscattered signals obtained from the simulations are compared for different incident angles and sea states. In particular, the simulations show a broadening of the Doppler spectra for a more complicated sea state at a low grazing angle(LGA).
文摘用迭代法对湮没辐射的Doppler展宽谱去卷职,获取湮没辐射的本征分布。用高斯—牛顿法将本征分布拟合为一个高斯函数(心电子贡献)和抛物线函数(传导电子贡献)之和。从本征分布和抛物线函致可以算出电子的动量分布信息和估测费米能。用纯Ge探测器测量了Al、Ag、Cu、Co、Ni、Sa、In、Mo、W、Zr,Ti、Ge、Si等13种材料的多普勒展宽谱,算出它们的动量分布和费米能,显示各种材料的动量分布明显不同,由实验测得的费米能值与由自由电子气模型计算的理论值很好符合。对Fe Si B非晶和晶态合金的研究表明:两者的动量分布差异甚小,但费米能略有不同。
