Chen＇s technique of computing synthetic seismograms, which decomposes every vector with a set of basis of orthogonality and completeness before applying the Luco-Apsel-Chen （LAC） generalized reflection and transmis...Chen＇s technique of computing synthetic seismograms, which decomposes every vector with a set of basis of orthogonality and completeness before applying the Luco-Apsel-Chen （LAC） generalized reflection and transmission coefficients method, is confirmed to be efficient in dealing with elastic waves in multi-layered media and accurate in any frequency range. In this article, we extend Chen＇s technique to the computation of coupled seismic and electromagnetic （EM） waves in layered porous media. Expanding the involved mechanical and electromagnetic fields by a set of scalar and vector wave-function basis, we obtain the fundamental equations which are subsequently solved by using a recently developed version of the LAC generalized reflection and transmission coefficients method. Our approach and corresponding program is validated by reciprocity tests. We also show a numerical example of a two-layer model with an explosion source. The P-to-EM conversion waves radiated from the interface may have potential application.展开更多
Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring ...Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring and remote operation,offering users high level of safety,convenience and comfort.Moreover,noncontact sensing is ideal to maximize the immersive user experience in the human–machine interaction(HMI),eliminating interference to human activities and mechanical fatigue to the sensor,simultaneously.Herein,we report a self-powered flexible sensor integrated with irradiation cross-linked polypropylene(IXPP)piezoelectret film for noncontact sensing,featuring multi-functions to detect mechanical signals transmitted through solid,liquid and gaseous media and would facilitate their versatile practical applications.The folded-structure configuration of the sensor facilitates the improvement of the noncontact sensing sensitivity.For solid media,such as the rectangular wooden stick used in this study,the sensor can detect mechanical stimulus exerted at a distance of 100 cm.A system detection sensitivity up to 57 pC/kPa with a low detection limit of 0.6 kPa is achieved at a noncontact distance of 10 cm.Even when partly or completely immersed in water,the sensor effectively traces movement signals of human bodies underwater,demonstrating great advantages for non-inductive aquatic fitness training monitoring.Furthermore,due to the low acoustic impedance of piezoelectret film,speech recognition through gaseous medium is also achieved.We further introduce application demonstrations of the developed film sensors to monitor exercise postures and physiological signals without direct contact between human body and the sensor,displaying great potential to be incorporated into future smart electronics.This study commendably expands the application scope of piezoelectret materials,which will have profound implications for exploring novel intelligent human–machine interactions.展开更多
基金supported by the Natural R&D Special Fund for Public Welfare Industry(No.200808069)National Natural Science Foundation of China(Nos.40974038,40774028 and 40821062)
文摘Chen＇s technique of computing synthetic seismograms, which decomposes every vector with a set of basis of orthogonality and completeness before applying the Luco-Apsel-Chen （LAC） generalized reflection and transmission coefficients method, is confirmed to be efficient in dealing with elastic waves in multi-layered media and accurate in any frequency range. In this article, we extend Chen＇s technique to the computation of coupled seismic and electromagnetic （EM） waves in layered porous media. Expanding the involved mechanical and electromagnetic fields by a set of scalar and vector wave-function basis, we obtain the fundamental equations which are subsequently solved by using a recently developed version of the LAC generalized reflection and transmission coefficients method. Our approach and corresponding program is validated by reciprocity tests. We also show a numerical example of a two-layer model with an explosion source. The P-to-EM conversion waves radiated from the interface may have potential application.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.62201392,12174061 and 12374451).
文摘Mechanical signal capture without physical contact has emerged as a highly promising research field and attracted tremendous attention due to its prosperous applications in household medical care,lifestyle monitoring and remote operation,offering users high level of safety,convenience and comfort.Moreover,noncontact sensing is ideal to maximize the immersive user experience in the human–machine interaction(HMI),eliminating interference to human activities and mechanical fatigue to the sensor,simultaneously.Herein,we report a self-powered flexible sensor integrated with irradiation cross-linked polypropylene(IXPP)piezoelectret film for noncontact sensing,featuring multi-functions to detect mechanical signals transmitted through solid,liquid and gaseous media and would facilitate their versatile practical applications.The folded-structure configuration of the sensor facilitates the improvement of the noncontact sensing sensitivity.For solid media,such as the rectangular wooden stick used in this study,the sensor can detect mechanical stimulus exerted at a distance of 100 cm.A system detection sensitivity up to 57 pC/kPa with a low detection limit of 0.6 kPa is achieved at a noncontact distance of 10 cm.Even when partly or completely immersed in water,the sensor effectively traces movement signals of human bodies underwater,demonstrating great advantages for non-inductive aquatic fitness training monitoring.Furthermore,due to the low acoustic impedance of piezoelectret film,speech recognition through gaseous medium is also achieved.We further introduce application demonstrations of the developed film sensors to monitor exercise postures and physiological signals without direct contact between human body and the sensor,displaying great potential to be incorporated into future smart electronics.This study commendably expands the application scope of piezoelectret materials,which will have profound implications for exploring novel intelligent human–machine interactions.
