A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT). In this paper, one goal of the simulation is to compute ultrasonic field radiated b...A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT). In this paper, one goal of the simulation is to compute ultrasonic field radiated by arbitrary transducers into pieces under examination. The other simulates a testing experiment. The simulation approach is based on the model for the computation of the ultrasonic field in isotropic media radiated from actual NDT transducers. After the field is known, remaining to be modeled is the interaction between this field and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchhoff’s diffraction approximations theory applied to elastodynamics. We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous. The simulating results demonstrate that the model in ultrasonic NDT of welds is practical in further research and useful in optimizing testi展开更多
With the increase of communication frequency,terahertz(THz)communication technology has been an important research feld;particularly the terahertz modulator is becoming one of the core devices in THz communication sys...With the increase of communication frequency,terahertz(THz)communication technology has been an important research feld;particularly the terahertz modulator is becoming one of the core devices in THz communication system.Te modulation performance of a THz communication system depends on the characterization of THz modulator.THz modulators based on diferent principles and materials have been studied and developed.However,they are still on the way to practical application due to low modulation speed,narrow bandwidth,and insufcient modulation depth.Terefore,we review the research progress of THz modulator in recent years and evaluate devices critically and comprehensively.We focus on the working principles such as electric,optical,optoelectrical,thermal,magnetic,programmable metamaterials and nonlinear modulation methods for THz wave with semiconductors,metamaterials,and 2D materials(such as graphene,molybdenum disulfde,and tungsten disulfde).Furthermore,we propose a guiding rule to select appropriate materials and modulation methods for specifc applications in THz communication.展开更多
基金supported by the Doctoral Degree Fund of Xi’an Jiaotong University
文摘A computer simulation technique for ultrasonic propagation is utilized for the simulation of ultrasonic nondestructive testing (NDT). In this paper, one goal of the simulation is to compute ultrasonic field radiated by arbitrary transducers into pieces under examination. The other simulates a testing experiment. The simulation approach is based on the model for the computation of the ultrasonic field in isotropic media radiated from actual NDT transducers. After the field is known, remaining to be modeled is the interaction between this field and the scatters (defect) and the echo structure. The model of beam-defect interaction is based on the Kirchhoff’s diffraction approximations theory applied to elastodynamics. We assumed that the incident wave fronts on the defect are plane in the case of a focused immersed transducer and material is isotropic and homogeneous. The simulating results demonstrate that the model in ultrasonic NDT of welds is practical in further research and useful in optimizing testi
基金The work was fnancially supported by Te National Key R.&D.Plan of China(2016YFB0402700,2017YFB0405400)The National Natural Science Foundation of China(61774175,61674146,and 61875140)+4 种基金The National Natural Science Foundation of China(Key Program:61634006)The Opened Fund of the State Key Laboratory of Integrated Optoelectronics(No.IOSKL2017KF12)the Key Program of Natural Science Foundation of Beijing(4181001)The Leading Project of Youth Academic Team@Minzu University of China(Sensor and Microsystem:317201929)Young and Middle-Aged Talents Training Program of State Ethnic Afairs Commission.
文摘With the increase of communication frequency,terahertz(THz)communication technology has been an important research feld;particularly the terahertz modulator is becoming one of the core devices in THz communication system.Te modulation performance of a THz communication system depends on the characterization of THz modulator.THz modulators based on diferent principles and materials have been studied and developed.However,they are still on the way to practical application due to low modulation speed,narrow bandwidth,and insufcient modulation depth.Terefore,we review the research progress of THz modulator in recent years and evaluate devices critically and comprehensively.We focus on the working principles such as electric,optical,optoelectrical,thermal,magnetic,programmable metamaterials and nonlinear modulation methods for THz wave with semiconductors,metamaterials,and 2D materials(such as graphene,molybdenum disulfde,and tungsten disulfde).Furthermore,we propose a guiding rule to select appropriate materials and modulation methods for specifc applications in THz communication.
