I. INTRODUCTION It has become a very important subject to investigate the acoustic nonlinearity parameter B/A in biological media since 1980. Experimental evidence indicates that there are nonlinear phenomena under bi...I. INTRODUCTION It has become a very important subject to investigate the acoustic nonlinearity parameter B/A in biological media since 1980. Experimental evidence indicates that there are nonlinear phenomena under biological frequencies and intensities. B/A is one of the ba-展开更多
Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured ...Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured data away from the edge of a geometric discontinuity. Photoelastic data are hybridized with complex variable/mapping techniques to calculate photoelastic stress-field around a circular hole or an elliptical hole in plates under uniaxial tensile loading. This method determines full-field stresses in perforated finite tensile plates containing either a circular or an elliptical hole. The second one is a fringe phase shift method to separate isochromatics and isoclinics from photoelastic fringes of a circular disk under diametric compression by use of phase shift method. Digitally determined isochromatics and isoclinics are agreed well with those of manual measurements.展开更多
In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calcula...In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calculates the scattering phase shift instead of scattering matrix elements in order to simplify the calculation. As an illustration, this method is used to calculate the broadening and shift coefficients of the absorption lines of alkali metal atom Rb, as it collides with buffer gas He and Ar, in a temperature range from 150 K to 800 K. With a comparison with other calculations and experiment measurements, the reasonable agreements in all cases demonstrate the validity and simplicity of this method.展开更多
The complex Red River fault zone(RRFZ), which is situated in the southwestern region of China and separates the Indochina plate and South China blocks, has diverse seismic activities in different segments. To reveal t...The complex Red River fault zone(RRFZ), which is situated in the southwestern region of China and separates the Indochina plate and South China blocks, has diverse seismic activities in different segments. To reveal the detailed geometric characteristics of the RRFZ at different sections and to better understand the seismogenic environment, in 2022 and 2023 we deployed 7 seismic dense linear arrays, consisting of 574 nodal stations, across the RRFZ in the northern and southern segments near the towns Midu, Gasa, Zhega,Dazhai, Xinzhai, and Taoyuan. The linear arrays, which extend from 2.4 to 12.5 km in length with station intervals ranging between 40 and140 m, recorded seismic ambient noise for approximately one month. Using the extended range phase shift method, we extract the phase velocity dispersion curves of the Rayleigh waves between 0.9 and 10 Hz, which are then used to invert for the high resolution shearwave velocity structures across the RRFZ beneath the linear arrays. The key findings are:(1) the 7 imaged sections of the RRFZ exhibit quite similar structures, with higher velocities on the SW side and lower velocities on the NE side;the velocity variation is consistent with the surface geological structures along the RRFZ;(2) the shear-wave velocities on the SW side of the RRFZ at the northern Midu section and southern Gasa-Dazhai sections are generally higher than their counterparts in the southern Xinzhai-Taoyuan sections, which reflects lithological variations from the marble-dominated Paleoproterozoic Along basement to the gneiss dominated Paleoproterozoic Qingshuihe basement;(3) from the northern Midu section to the southern region where the RRFZ intersects with the Xiaojiang Fault, the major faults of the RRFZ exhibit a consistent high-angle, NE-dipping structure;(4) the low shear-wave velocities immediately to the NE of the velocity boundary may indicate a faulted zone due to long-term shearing, where excessive amplifications of ground motions could occur. This study provides new insights into the characteristics of the shallow structures of the RRFZ.展开更多
文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间...文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间,从而达到提升图像质量和深度测量精度的效果。在运动模糊测试平台上对改善效果进行一系列测试。结果表明,该方法能显著提高ToF相机在动态场景下的深度图像质量,在测试装置转速为100~200 r/min内时,由运动模糊产生的错误像素数减少百分比可达35%以上,最高可达41.46%。通过实验验证,基于增益标定的ToF相机运动模糊矫正方法能有效提升图像质量和深度信息的准确性,展现了其在动态环境下的广泛应用潜力。展开更多
针对串联谐振型双有源桥(dual active bridges,简称DAB)双向直流变换器,该文提出一种基于变频控制的电流峰值优化控制策略.首先,利用时域分析法获得双有源桥变换器中峰值电感电流和传输功率的归一化解析式;然后,将所构建时域模型与传统...针对串联谐振型双有源桥(dual active bridges,简称DAB)双向直流变换器,该文提出一种基于变频控制的电流峰值优化控制策略.首先,利用时域分析法获得双有源桥变换器中峰值电感电流和传输功率的归一化解析式;然后,将所构建时域模型与传统基波分析法的计算结果进行比较,并推导出软开关范围且对死区时间进行分析.最后,通过仿真实验验证了时域分析结果和电流峰值优化策略.仿真结果表明,在不同功率等级下所提优化控制策略相对于现有定频控制能有效地降低电流峰值.展开更多
This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe ana...This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.展开更多
Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper p...Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.展开更多
Measured differential phase shift ΦDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ΦDP data has direct impact on specific differential phase shift KDP estimation, and subsequ...Measured differential phase shift ΦDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ΦDP data has direct impact on specific differential phase shift KDP estimation, and subsequently, the KDP-based rainfall estimation. Over the past decades, many ΦDP de-noising methods have been developed; however, the de-noising effects in these methods and their impact on KDP-based rainfall estimation lack comprehensive comparative analysis. In this study, simulated noisy ΦDP data were generated and de-noised by using several methods such as finite-impulse response（FIR）, Kalman, wavelet,traditional mean, and median filters. The biases were compared between KDP from simulated and observedΦDP radial profiles after de-noising by these methods. The results suggest that the complicated FIR, Kalman,and wavelet methods have a better de-noising effect than the traditional methods. After ΦDP was de-noised,the accuracy of the KDP-based rainfall estimation increased significantly based on the analysis of three actual rainfall events. The improvement in estimation was more obvious when KDP was estimated with ΦDP de-noised by Kalman, FIR, and wavelet methods when the average rainfall was heavier than 5 mm h-1.However, the improved estimation was not significant when the precipitation intensity further increased to a rainfall rate beyond 10 mm h-1. The performance of wavelet analysis was found to be the most stable of these filters.展开更多
基金Project supported by the National Natural Science Foundation of China
文摘I. INTRODUCTION It has become a very important subject to investigate the acoustic nonlinearity parameter B/A in biological media since 1980. Experimental evidence indicates that there are nonlinear phenomena under biological frequencies and intensities. B/A is one of the ba-
文摘Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured data away from the edge of a geometric discontinuity. Photoelastic data are hybridized with complex variable/mapping techniques to calculate photoelastic stress-field around a circular hole or an elliptical hole in plates under uniaxial tensile loading. This method determines full-field stresses in perforated finite tensile plates containing either a circular or an elliptical hole. The second one is a fringe phase shift method to separate isochromatics and isoclinics from photoelastic fringes of a circular disk under diametric compression by use of phase shift method. Digitally determined isochromatics and isoclinics are agreed well with those of manual measurements.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11405077 and 11575073)
文摘In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calculates the scattering phase shift instead of scattering matrix elements in order to simplify the calculation. As an illustration, this method is used to calculate the broadening and shift coefficients of the absorption lines of alkali metal atom Rb, as it collides with buffer gas He and Ar, in a temperature range from 150 K to 800 K. With a comparison with other calculations and experiment measurements, the reasonable agreements in all cases demonstrate the validity and simplicity of this method.
基金funded by the National Key Research and Development Project of China (Grant No. 2021YFC3000600)the China Earthquake Science Experiment Field-Cross-fault Observation Array-Red River Fault Scientific Drilling Project Geophysical Prospecting Site Selection Project+2 种基金Anhui Province Science and Technology Breakthrough Plan Project (Key Project,202423l10050030)the Earthquake Science and Technology Spark Program of the China Earthquake Administration (XH23020YA)the Anhui Mengcheng National Geophysical Observatory Joint Open Fund (MENGO-202307)。
文摘The complex Red River fault zone(RRFZ), which is situated in the southwestern region of China and separates the Indochina plate and South China blocks, has diverse seismic activities in different segments. To reveal the detailed geometric characteristics of the RRFZ at different sections and to better understand the seismogenic environment, in 2022 and 2023 we deployed 7 seismic dense linear arrays, consisting of 574 nodal stations, across the RRFZ in the northern and southern segments near the towns Midu, Gasa, Zhega,Dazhai, Xinzhai, and Taoyuan. The linear arrays, which extend from 2.4 to 12.5 km in length with station intervals ranging between 40 and140 m, recorded seismic ambient noise for approximately one month. Using the extended range phase shift method, we extract the phase velocity dispersion curves of the Rayleigh waves between 0.9 and 10 Hz, which are then used to invert for the high resolution shearwave velocity structures across the RRFZ beneath the linear arrays. The key findings are:(1) the 7 imaged sections of the RRFZ exhibit quite similar structures, with higher velocities on the SW side and lower velocities on the NE side;the velocity variation is consistent with the surface geological structures along the RRFZ;(2) the shear-wave velocities on the SW side of the RRFZ at the northern Midu section and southern Gasa-Dazhai sections are generally higher than their counterparts in the southern Xinzhai-Taoyuan sections, which reflects lithological variations from the marble-dominated Paleoproterozoic Along basement to the gneiss dominated Paleoproterozoic Qingshuihe basement;(3) from the northern Midu section to the southern region where the RRFZ intersects with the Xiaojiang Fault, the major faults of the RRFZ exhibit a consistent high-angle, NE-dipping structure;(4) the low shear-wave velocities immediately to the NE of the velocity boundary may indicate a faulted zone due to long-term shearing, where excessive amplifications of ground motions could occur. This study provides new insights into the characteristics of the shallow structures of the RRFZ.
文摘文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间,从而达到提升图像质量和深度测量精度的效果。在运动模糊测试平台上对改善效果进行一系列测试。结果表明,该方法能显著提高ToF相机在动态场景下的深度图像质量,在测试装置转速为100~200 r/min内时,由运动模糊产生的错误像素数减少百分比可达35%以上,最高可达41.46%。通过实验验证,基于增益标定的ToF相机运动模糊矫正方法能有效提升图像质量和深度信息的准确性,展现了其在动态环境下的广泛应用潜力。
文摘针对串联谐振型双有源桥(dual active bridges,简称DAB)双向直流变换器,该文提出一种基于变频控制的电流峰值优化控制策略.首先,利用时域分析法获得双有源桥变换器中峰值电感电流和传输功率的归一化解析式;然后,将所构建时域模型与传统基波分析法的计算结果进行比较,并推导出软开关范围且对死区时间进行分析.最后,通过仿真实验验证了时域分析结果和电流峰值优化策略.仿真结果表明,在不同功率等级下所提优化控制策略相对于现有定频控制能有效地降低电流峰值.
基金Project supported by the National Natural Sciences Foundation of China (No. 10572102).
文摘This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.
文摘Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.
基金Supported by the National Natural Science Foundation of China(41375038)China Meteorological Administration Special Public Welfare Research Fund(GYHY201306040 and GYHY201306075)Jiangshu Province Meteorological Administration Beijige Open Research Fund(BJG201201)
文摘Measured differential phase shift ΦDP is known to be a noisy unstable polarimetric radar variable, such that the quality of ΦDP data has direct impact on specific differential phase shift KDP estimation, and subsequently, the KDP-based rainfall estimation. Over the past decades, many ΦDP de-noising methods have been developed; however, the de-noising effects in these methods and their impact on KDP-based rainfall estimation lack comprehensive comparative analysis. In this study, simulated noisy ΦDP data were generated and de-noised by using several methods such as finite-impulse response（FIR）, Kalman, wavelet,traditional mean, and median filters. The biases were compared between KDP from simulated and observedΦDP radial profiles after de-noising by these methods. The results suggest that the complicated FIR, Kalman,and wavelet methods have a better de-noising effect than the traditional methods. After ΦDP was de-noised,the accuracy of the KDP-based rainfall estimation increased significantly based on the analysis of three actual rainfall events. The improvement in estimation was more obvious when KDP was estimated with ΦDP de-noised by Kalman, FIR, and wavelet methods when the average rainfall was heavier than 5 mm h-1.However, the improved estimation was not significant when the precipitation intensity further increased to a rainfall rate beyond 10 mm h-1. The performance of wavelet analysis was found to be the most stable of these filters.
