时间逆转成像技术具有定位准确和操作简单之特点,本文将其运用于混凝土结构损伤的检测.通过提取各换能器单元的发射信号和损伤散射信号构建超声波传播的传递矩阵然后对其进行奇异值分解,获得包含损伤信息的奇异向量;采用多重信号分类(mu...时间逆转成像技术具有定位准确和操作简单之特点,本文将其运用于混凝土结构损伤的检测.通过提取各换能器单元的发射信号和损伤散射信号构建超声波传播的传递矩阵然后对其进行奇异值分解,获得包含损伤信息的奇异向量;采用多重信号分类(multiple signal classification,MUSIC)算法,分别基于数值模拟数据和实验实测数据对混凝土结构内部损伤进行成像,实现了准确的损伤定位,并将成像结果与偏移成像法进行对比.此工作探索了将时间逆转成像技术应用于混凝土结构内部损伤实际工程检测可行性,为无损检测技术人员定性或定量分析混凝土结构的内部缺陷提供理论参考.展开更多
In this paper, we present a new method to determine the relative permittivity of periodic stratified media using the iterative time-reversal method. Based on transmission line theory, the focal peak value of iterative...In this paper, we present a new method to determine the relative permittivity of periodic stratified media using the iterative time-reversal method. Based on transmission line theory, the focal peak value of iterative time-reversal electro- magnetic waves, which contain information about the periodic stratified medium, is computed in pulse-echo mode. Using the relationship between the focal peak value and the relative permittivity of the periodic stratified medium, the relative permittivity can be obtained by measuring the focal peak value. Numerical simulations are conducted, and the results demonstrate the feasibility of the proposed approach to the measurement of the relative permittivity of a periodic stratified medium.展开更多
The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of ...The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions：（i） along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;（ii） opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.展开更多
针对空空时间反转多信号分类(time reversal multiple signal classification,TR-MUSIC)抗噪性能差而难以实现对复杂随机介质影响下目标的聚焦成像,以及空空多态数据矩阵的获取较为复杂等问题,提出基于空频分解的时间反转成像新方法,即...针对空空时间反转多信号分类(time reversal multiple signal classification,TR-MUSIC)抗噪性能差而难以实现对复杂随机介质影响下目标的聚焦成像,以及空空多态数据矩阵的获取较为复杂等问题,提出基于空频分解的时间反转成像新方法,即空频TR-MUSIC。该方法利用天线阵列采集的散射场回波信号建立空频多态数据矩阵,对该矩阵进行奇异值分解得到噪声子空间向量,从而实现对目标的成像。基于完全散射场数据的成像函数包含多个子矩阵的贡献,具有统计特性。仿真结果表明,无论是在自由空间中还是在随机介质背景下,空频TR-MUSIC的成像效果均优于传统的空空TR-MUSIC,具有较好的分辨率和定位精度。即使在信噪比为10 dB的高斯白噪声影响下,也能实现对目标的准确成像。展开更多
文摘时间逆转成像技术具有定位准确和操作简单之特点,本文将其运用于混凝土结构损伤的检测.通过提取各换能器单元的发射信号和损伤散射信号构建超声波传播的传递矩阵然后对其进行奇异值分解,获得包含损伤信息的奇异向量;采用多重信号分类(multiple signal classification,MUSIC)算法,分别基于数值模拟数据和实验实测数据对混凝土结构内部损伤进行成像,实现了准确的损伤定位,并将成像结果与偏移成像法进行对比.此工作探索了将时间逆转成像技术应用于混凝土结构内部损伤实际工程检测可行性,为无损检测技术人员定性或定量分析混凝土结构的内部缺陷提供理论参考.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61071031,61107018,and 61201089)the Research Fund for the Doctoral Program of Higher Education of China(Grant Nos.20100185110021 and 20120185130001)+2 种基金the Program for Changjiang Scholars and Innovation Team in University,China(Grant No.IRT1113)the Natural Science Foundation of the Higher Education Institutions of Anhui Province(Grant No.KJ2013Z287)Fundamental Research Fund for the Central Universities(Grant No.ZYGX2011YB018)
文摘In this paper, we present a new method to determine the relative permittivity of periodic stratified media using the iterative time-reversal method. Based on transmission line theory, the focal peak value of iterative time-reversal electro- magnetic waves, which contain information about the periodic stratified medium, is computed in pulse-echo mode. Using the relationship between the focal peak value and the relative permittivity of the periodic stratified medium, the relative permittivity can be obtained by measuring the focal peak value. Numerical simulations are conducted, and the results demonstrate the feasibility of the proposed approach to the measurement of the relative permittivity of a periodic stratified medium.
基金Project supported by the National Natural Science Foundation of China(Grant No.61378083)the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China(Grant No.2011DFA12220)+1 种基金the Major Research Plan of National Natural Science Foundation of China(Grant No.91123030)the Natural Science Foundation of Shaanxi Province of China(Grant Nos.2010JS110 and2013SZS03-Z01)
文摘The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions：（i） along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value;（ii） opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity.The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.
