The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to it...The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.展开更多
Intra-body communication (IBC) is a new,emerging,short-range and human body based communication methodology.It is a technique to network various devices on human body,by utilizing the conducting properties of human ti...Intra-body communication (IBC) is a new,emerging,short-range and human body based communication methodology.It is a technique to network various devices on human body,by utilizing the conducting properties of human tissues,suitable for currently fast developing Body area network (BAN)/Body sensor network (BSN).IBC is believed to have advantages in power consumption,electromagnetic radiation,interference from external electromagnetic noise,security,and restriction in spectrum resource.In this article,the authors develop two models,which are analytical and empirical approaches,for comparing the performance and accuracy of IBC on a human limb.Through in vivo experiment of five volunteers,both models basically match with the experimental result with equivalent circuit model superior than electromagnetic model in term of maximum error.展开更多
Sensing is the fundamental technique for sensor data acquisition in monitoring the operation condition of the machinery,structures,and manufacturing processes.In this paper,we briefly discuss the general idea and adva...Sensing is the fundamental technique for sensor data acquisition in monitoring the operation condition of the machinery,structures,and manufacturing processes.In this paper,we briefly discuss the general idea and advances of various new sensing technologies,including multiphysics sensing,smart materials and metamaterials sensing,microwave sensing,fiber optic sensors,and terahertz sensing,for measuring vibration,deformation,strain,acoustics,temperature,spectroscopic,etc.Based on the observations from the state of the art,we provide comprehensive discussions on the possible opportunities and challenges of these new sensing technologies so as to steer future development.展开更多
To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The u...To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The uncertainty of measurement is analyzed using grey system theory, and the defects of the grey evaluation model of measurement uncertainty (GEMU) are studied. We then establish an improved grey evaluation model of measurement uncertainty (IGEMU). Simulations show that the precision of IGEMU is greater than that of GEMU, and that sample size has only a small effect on the precision of IGEVU. In particular, IGEMU is applied to evaluating measurement uncertainty for small sample size and measurement data from an unknown distribution. The measurement uncertainty of total profile deviation, which is measured by the CNC gear measuring center, can be evaluated by a combination of IGEMU and the Monte Carlo method.展开更多
Parallel manipulators for the machine tool industry have been studied extensively for various industrial applications. However, limited useful workspace areas, the poor mobility, and design difficulties of more compl...Parallel manipulators for the machine tool industry have been studied extensively for various industrial applications. However, limited useful workspace areas, the poor mobility, and design difficulties of more complex parallel manipulators have led to more interest in parallel manipulators with less than six degrees of freedom (DoFs). Several parallel mechanisms with various numbers and types of degrees of freedom are described in this paper, which can be used in parallel kinematics machines, motion simulators, and industrial robots.展开更多
As a nondestructive testing technique,terahertz time-domain spectroscopy technology is commonly used to measure the thickness of ceramic coat in thermal barrier coatings(TBCs).However,the invisibility of ceramic/therm...As a nondestructive testing technique,terahertz time-domain spectroscopy technology is commonly used to measure the thickness of ceramic coat in thermal barrier coatings(TBCs).However,the invisibility of ceramic/thermally grown oxide(TGO)reflective wave leads to the measurement failure of natural growth TGO whose thickness is below 10μm in TBCs.To detect and monitor TGO in the emergence stage,a time of flight(TOF)improved TGO thickness measurement method is proposed.A simulative investigation on propagation characteristics of terahertz shows the linear relationship between TGO thickness and phase shift of feature wave.The accurate TOF increment could be acquired from wavelet soft threshold and cross-correlation function with negative effect reduction of environmental noise and system oscillation.Thus,the TGO thickness could be obtained efficiently from the TOF increment of the monitor area with different heating times.The averaged error of 1.61μm in experimental results demonstrates the highly accurate and robust measurement of the proposed method,making it attractive for condition monitoring and life prediction of TBCs.展开更多
Metamaterials(MMs)have become increasingly prominent in terahertz flexible devices.However,bending deformation often alters the structure of the unit,which affects the response performance and stability of MMs.Here,a ...Metamaterials(MMs)have become increasingly prominent in terahertz flexible devices.However,bending deformation often alters the structure of the unit,which affects the response performance and stability of MMs.Here,a metal-aperture metamaterial(MA-MM)utilizing the strong coupling effect induced by two resonance modes is innovatively proposed to address the mentioned limitations.Specifically,it is found that the coupling state between multiple resonance modes remains consistent at different bending angles.Under these circumstances,the generated Rabi splitting peak presents stable response performance even under low resonance intensity caused by excessive deformation.The experimental results demonstrate that despite the amplitude of two resonant peaks decreasing significantly by 87.6%,the Q-factor of the Rabi splitting only reduced by 14.8%.Furthermore,armed with the response mode of the Rabi splitting being unaffected by plasma excitation range,the designed MA-MMs are able to maintain constant Q-factors and frequencies on curved surfaces of varying sizes.These findings exhibit the characteristics of electromagnetic response for multi-mode resonance-coupled MAMMs on different curved surfaces,presenting a novel design approach for terahertz flexible functional devices.展开更多
Multifunctionality,interference-free signal readout,and quantum effect are important considerations for flexible sensors equipped within a single unit towards further miniaturization.To address these criteria,we prese...Multifunctionality,interference-free signal readout,and quantum effect are important considerations for flexible sensors equipped within a single unit towards further miniaturization.To address these criteria,we present the slotted carbon nanotube(CNT)junction features tunable Fano resonance driven by flexoelectricity,which could serve as an ideal multimodal sensory receptor.Based on extensive ab initio calculations,we find that the effective Fano factor can be used as a temperature-insensitive extrinsic variable for sensing the bending strain,and the Seebeck coefficient can be used as a strain-insensitive intrinsic variable for detecting temperature.Thus,this dual-parameter permits simultaneous sensing of temperature and strain without signal interference.We further demonstrate the applicability of this slotted junction to ultrasensitive chemical sensing which enables precise determination of donor-type,acceptor-type,and inert molecules.This is due to the enhancement or counterbalance between flexoelectric and chemical gating.Flexoelectric gating would preserve the electron–hole symmetry of the slotted junction whereas chemical gating would break it.As a proof-of-concept demonstration,the slotted CNT junction provides an excellent quantum platform for the development of multistimuli sensation in artificial intelligence at the molecular scale.展开更多
基金National Natural Science Foundation of China(Grant Nos.52275096,52005108,52275523)Fuzhou-Xiamen-Quanzhou National Independent Innovation Demonstration Zone High-end Equipment Vibration and Noise Detection and Fault Diagnosis Collaborative Innovation Platform ProjectFujian Provincial Major Research Project(Grant No.2022HZ024005)。
文摘The use of terahertz time-domain spectroscopy(THz-TDS)for the nondestructive testing and evaluation(NDT&E)of materials and structural systems has attracted significant attention over the past two decades due to its superior spatial resolution and capabilities of detecting and characterizing defects and structural damage in non-conducting materials.In this study,the THz-TDS system is used to detect,localize and evaluate hidden multi-delamination defects(i.e.,a three-level multi-delamination system)in multilayered GFRP composite laminates.To obtain accurate results,a wavelet shrinkage de-noising algorithm is used to remove the noise from the measured time-of-flight(TOF)signals.The thickness and location of each delamination defect in the z-direction(i.e.,through-the-thickness direction)are calculated from the de-noised TOF signals considering the interaction between the pulsed THz waves and the different interfaces in the GFRP composite laminates.A comparison between the actual and the measured thickness values of the delamination defects before and after the wavelet shrinkage denoising process indicates that the latter provides better results with less than 3.712%relative error,while the relative error of the non-de-noised signals reaches 16.388%.Also,the power and absorbance levels of the THz waves at every interface with different refractive indices in the GFRP composite laminates are evaluated based on analytical and experimental approaches.The present study provides an adequate theoretical analysis that could help NDT&E specialists to estimate the maximum thickness of GFRP composite materials and/or structures with different interfaces that can be evaluated by the THz-TDS.Also,the accuracy of the obtained results highlights the capabilities of the THz-TDS for the NDT&E of multilayered GFRP composite laminates.
基金supported by The Science and Technology Development Fund of Macao under grant 014/2007/A1,063/2009/A and 024/2009/A1the Research Committee of the University of Macao under Grants UL012/09-Y1/EEE/VMI01/FST,RG077/09-10S/ VMI/FST,RG075/07-08S/10T/VMI/FST,and RG072/09-10S/ MPU/FSTthe Funds of Fujian Provincial Department of Science & Technology as 2007Y0024,2007T0009,2007I0018 and 2008J1005
文摘Intra-body communication (IBC) is a new,emerging,short-range and human body based communication methodology.It is a technique to network various devices on human body,by utilizing the conducting properties of human tissues,suitable for currently fast developing Body area network (BAN)/Body sensor network (BSN).IBC is believed to have advantages in power consumption,electromagnetic radiation,interference from external electromagnetic noise,security,and restriction in spectrum resource.In this article,the authors develop two models,which are analytical and empirical approaches,for comparing the performance and accuracy of IBC on a human limb.Through in vivo experiment of five volunteers,both models basically match with the experimental result with equivalent circuit model superior than electromagnetic model in term of maximum error.
基金The work in Section III was supported by the National Science Foundation of China(NSFC)(Nos.52275116,52105112)The work in Section IV was supported by the National Science Foundation of China(NSFC)(Nos.52275117,12127801).
文摘Sensing is the fundamental technique for sensor data acquisition in monitoring the operation condition of the machinery,structures,and manufacturing processes.In this paper,we briefly discuss the general idea and advances of various new sensing technologies,including multiphysics sensing,smart materials and metamaterials sensing,microwave sensing,fiber optic sensors,and terahertz sensing,for measuring vibration,deformation,strain,acoustics,temperature,spectroscopic,etc.Based on the observations from the state of the art,we provide comprehensive discussions on the possible opportunities and challenges of these new sensing technologies so as to steer future development.
基金supported by the National Natural Science Foundation of China (Grant Nos. 61108052 and 61108073)the Technology Program of the Educational Office of Hei Longjiang Province in China (Grant No.11553016)
文摘To evaluate measurement uncertainty for small sample size and measurement data from an unknown distribution, we propose a grey evaluation method of measurement uncertainty based on the grey relation coefficient. The uncertainty of measurement is analyzed using grey system theory, and the defects of the grey evaluation model of measurement uncertainty (GEMU) are studied. We then establish an improved grey evaluation model of measurement uncertainty (IGEMU). Simulations show that the precision of IGEMU is greater than that of GEMU, and that sample size has only a small effect on the precision of IGEVU. In particular, IGEMU is applied to evaluating measurement uncertainty for small sample size and measurement data from an unknown distribution. The measurement uncertainty of total profile deviation, which is measured by the CNC gear measuring center, can be evaluated by a combination of IGEMU and the Monte Carlo method.
基金Supported by the National "973" Program of China( No.G19980 30 6 0 7
文摘Parallel manipulators for the machine tool industry have been studied extensively for various industrial applications. However, limited useful workspace areas, the poor mobility, and design difficulties of more complex parallel manipulators have led to more interest in parallel manipulators with less than six degrees of freedom (DoFs). Several parallel mechanisms with various numbers and types of degrees of freedom are described in this paper, which can be used in parallel kinematics machines, motion simulators, and industrial robots.
基金the National Natural Science Foundation of China(Grant Nos.52275096,51905102)the Fujian Provincial Science and Technology Project,China(Grant No.2019I0004)+2 种基金the State Key Laboratory of Mechanical Systems and Vibration,China(Grant No.MSV-2018-07)the Shanghai Natural Sciences Fund,China(Grant No.18ZR1414200)the China Postdoctoral Science Foundation(Grant No.2019M662226).
文摘As a nondestructive testing technique,terahertz time-domain spectroscopy technology is commonly used to measure the thickness of ceramic coat in thermal barrier coatings(TBCs).However,the invisibility of ceramic/thermally grown oxide(TGO)reflective wave leads to the measurement failure of natural growth TGO whose thickness is below 10μm in TBCs.To detect and monitor TGO in the emergence stage,a time of flight(TOF)improved TGO thickness measurement method is proposed.A simulative investigation on propagation characteristics of terahertz shows the linear relationship between TGO thickness and phase shift of feature wave.The accurate TOF increment could be acquired from wavelet soft threshold and cross-correlation function with negative effect reduction of environmental noise and system oscillation.Thus,the TGO thickness could be obtained efficiently from the TOF increment of the monitor area with different heating times.The averaged error of 1.61μm in experimental results demonstrates the highly accurate and robust measurement of the proposed method,making it attractive for condition monitoring and life prediction of TBCs.
基金National Natural Science Foundation of China(52275096,72304127)Fujian Provincial Major Research Project(2022HZ024005)+1 种基金Science and Technology Planning Project of Fuzhou(2022-P-022)Natural Science Foundation of Fujian Province(2022J01071).
文摘Metamaterials(MMs)have become increasingly prominent in terahertz flexible devices.However,bending deformation often alters the structure of the unit,which affects the response performance and stability of MMs.Here,a metal-aperture metamaterial(MA-MM)utilizing the strong coupling effect induced by two resonance modes is innovatively proposed to address the mentioned limitations.Specifically,it is found that the coupling state between multiple resonance modes remains consistent at different bending angles.Under these circumstances,the generated Rabi splitting peak presents stable response performance even under low resonance intensity caused by excessive deformation.The experimental results demonstrate that despite the amplitude of two resonant peaks decreasing significantly by 87.6%,the Q-factor of the Rabi splitting only reduced by 14.8%.Furthermore,armed with the response mode of the Rabi splitting being unaffected by plasma excitation range,the designed MA-MMs are able to maintain constant Q-factors and frequencies on curved surfaces of varying sizes.These findings exhibit the characteristics of electromagnetic response for multi-mode resonance-coupled MAMMs on different curved surfaces,presenting a novel design approach for terahertz flexible functional devices.
基金supported by the Natural Science Foundation of China(Grant nos.41877499,21771017,and 42072163)the Natural Science Foundation of Shandong Province(Grant nos.ZR2019BA003 and ZR201807100384)+2 种基金the Ocean University of China(Grant no.3002000-861901206002)X.Shi acknowledges the Natural Science Foundation of Hebei Province of China(no.A2021201001)the Advanced Talents Incubation Program of the Hebei University(521000981390).
文摘Multifunctionality,interference-free signal readout,and quantum effect are important considerations for flexible sensors equipped within a single unit towards further miniaturization.To address these criteria,we present the slotted carbon nanotube(CNT)junction features tunable Fano resonance driven by flexoelectricity,which could serve as an ideal multimodal sensory receptor.Based on extensive ab initio calculations,we find that the effective Fano factor can be used as a temperature-insensitive extrinsic variable for sensing the bending strain,and the Seebeck coefficient can be used as a strain-insensitive intrinsic variable for detecting temperature.Thus,this dual-parameter permits simultaneous sensing of temperature and strain without signal interference.We further demonstrate the applicability of this slotted junction to ultrasensitive chemical sensing which enables precise determination of donor-type,acceptor-type,and inert molecules.This is due to the enhancement or counterbalance between flexoelectric and chemical gating.Flexoelectric gating would preserve the electron–hole symmetry of the slotted junction whereas chemical gating would break it.As a proof-of-concept demonstration,the slotted CNT junction provides an excellent quantum platform for the development of multistimuli sensation in artificial intelligence at the molecular scale.
