Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects,...Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects, and this study evaluates an advanced on-vehicle AE detection approach using bone-conduct sensors—a solution to improve upon previous AE methods of using on-rail sensor installations, which required extensive, costly on-rail sensor networks with limited effectiveness. In response to these challenges, the study specifically explored bone-conduct sensors mounted directly on the vehicle rather than rails by evaluating AE signals generated by the interaction between rails and the train’s wheels while in motion. In this research, a prototype detection system was developed and tested through initial trials at the Nevada Railroad Museum using a track with pre-damaged welding defects. Further testing was conducted at the Transportation Technology Center Inc. (rebranded as MxV Rail) in Colorado, where the system’s performance was evaluated across various defect types and train speeds. The results indicated that bone-conduct sensors were insufficient for detecting AE signals when mounted on moving vehicles. These findings highlight the limitations of contact-based methods in real-world applications and indicate the need for exploring improved, non-contact approaches.展开更多
Chemical oxygen demand(COD)is an important criterion for detecting the emission of pollutants and judging the quality of water.This paper improves the absorption spectrum compensation model for COD and turbidity mixed...Chemical oxygen demand(COD)is an important criterion for detecting the emission of pollutants and judging the quality of water.This paper improves the absorption spectrum compensation model for COD and turbidity mixed solution in the dual-wavelength spectral method based on the Lambert-Beer law additive principle.It compensates for the influence of turbidity on the absorption coefficient of the COD solution at 355 nm by the absorption spectrum coefficient of the mixed solution at 623 nm.This paper establishes a linear relationship model between the absorbance difference of the mixed solution at 355 nm and 623 nm and COD.The experimental determination coefficient R2 of the model is 0.98335,with a relative error of 3.5%and an average error of 0.7 mg/L.The design of the model is simple and easy to systematize,which is of strong significance for practical application.展开更多
This work first investigated the detection of slags,slag pool liquid level,and slag accumulation height in laboratory scale based on acoustic emission(AE)detection,and further tried the feasibility of this method in a...This work first investigated the detection of slags,slag pool liquid level,and slag accumulation height in laboratory scale based on acoustic emission(AE)detection,and further tried the feasibility of this method in an industrial scale coal gasifier.Results show that the energy and variance of acoustic signals can realize the accurate detection of large slag(criterion:E>1.5 E0,S>1.2 S0),and the average relative error is only 0.28%.The acoustic energy in the frequency range of 20–40 k Hz is defined as the characteristic energy,which can realize the accurate detection of slag accumulation height and slag pool liquid level,and the average relative error is only 3.94%.Furthermore,AE detection also realize accurate detection of large slag in an industrial scale gasifier and the acoustic signals at slag screen can be used to realize the early warning of the slag collapse(5 h earlier).展开更多
Most reported fluorescent probes have limitations in practical applications in living systems due to the strong autofluorescence background,construction of probes with near-infrared（NIR） fluorescence emission is an ...Most reported fluorescent probes have limitations in practical applications in living systems due to the strong autofluorescence background,construction of probes with near-infrared（NIR） fluorescence emission is an accessible approach for addressing this challenge.We here designed a NIR fluorescent probe for monitoring the endogenous production of H2S in living cells.The designed probe showed significant NIR fluorescence turn-on response to H2S with high selectivity,enabling the sensitive detection H2S.Importantly,the probe could be applied in monitoring the endogenous production of H2S in raw 264.7 macrophages.This study showed that fluvastatin can promote the activity of cystathionineγ-lyase（CSE） for generation H2S.展开更多
Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical m...Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical module and an optical channel formed by two ideal InGaN/GaN light-emitting diodes(LEDs)with transmit-receive characteristics.As an emitter,the InGaN/GaN device(5 mm×4 mm)exhibits electroluminescence at 469 nm with an on-voltage of 2.33 V.As a receiver,the response spectrum of InGaN/GaN devices spans from 350 to 480 nm,featuring a peak at 390 nm,rise time of~68.4 ms,and falling edge of~61.0 ms.The PDMS film can transform the force into deformation data and influence the signals in the optical receiver.The drive current,the gap between the emitter and receiver,and distance between the LED and PDMS mechanical module all significantly influence the receiver photocurrent.Distinct from the integrated design,our PDMS-assisted force sensing model uses discrete structures to allow signal intensity optimization.The finite element simulation and experimental results indicate that force of the designed PDMS film exhibits a linear relationship with z-axis displacement and photocurrent from 0 to 0.7 mm.The findings reveal that when the PDMS film height is 1.5 mm and the distance between the emitter and receiver is near,the photocurrent is higher.Meanwhile,Ag film with a thickness of 100 nm considerably enhances the photocurrent response and signal stability in the sensing channel.Finally,a weight measurement demonstration is employed to demonstrate force sensing.The system resolution is 1.23μA/N,and the measurement range is 0 to 0.7 N.展开更多
The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Mag...The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions)satellite detectors ICE(Internet Communications Engine),IAP(In Application Programming),and ISL(Interior Switching Link).In this paper,we take the 12 May 2008 Wenchuan earthquake as an example,use the spatial gridding method to construct the background field over the epicenter,analyze the background characteristics of very low frequency(VLF)electric field components,low-energy particle parameters,and plasma parameters,and define the perturbation intensity index of each parameter before the earthquake to extract each parameter anomaly in both space and time dimensions.The results show that the background values of some ionospheric parameters in the Wenchuan area are related to spatial distribution.Moreover,anomalous enhancement of low-frequency electric field power spectral density,H+concentration,He+concentration and ion concentration with different intensities and anomalous weakening of ion temperature were extracted in the fifteen days before the Wenchuan earthquake.After filtering the data to exclude external interference,such as solar activity,this paper concludes that there is some connection between these anomalies and the Wenchuan earthquake.展开更多
Otoacoustic emissions (OAEs) has been considered as an excellent objective tool in clinics for diagnosing hearing loss. The signal-to-noise ratio (SNR) and correlation coefficient of OAEs are very important for the pu...Otoacoustic emissions (OAEs) has been considered as an excellent objective tool in clinics for diagnosing hearing loss. The signal-to-noise ratio (SNR) and correlation coefficient of OAEs are very important for the purpose of diagnosis. An adaptive signal enhancer (ASE) based on the Least Mean Square (LMS) algorithm is presented to detect transient evoked OAEs (TEOAEs). The TEOAEs detection results from 106 ears show that ASE reaches better estimation of TEOAEs than a conventional ensemble averaging (EA) technique. With the ASE, the improvement of SNR was increased faster than that with the EA and the number of sweeps required can be markedly reduced. The detection time with ASE could be shortened by about 50% in comparison with that of EA.展开更多
The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inner cracks in rail. In order to obtain the features of Acoustic Emission （AE） sour...The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inner cracks in rail. In order to obtain the features of Acoustic Emission （AE） sources of inner cracks in rail, AE sources with different types, depths and propagation distances are examined for crack in rail. The finite element method is utilized to model the rail with cracks and the results of experiment demonstrate the effectiveness of this model. Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of crack AE sources. The results illustrate that the intensity ratio among AE modes can identify the AE source types and the AE sources with different frequencies in rail. There are uniform AE mode features existing in the AE signals from AE sources in rail web, however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes. Different AE source types have the different propagation features in rail. It is helpful to understand the rail cracks and detect the rail cracks based on the AE technique.展开更多
The bonded distributed feedback（DFB） fiber laser（FL） acoustic emission sensor and the intensity response of the DFB-FL to external acoustic emissions are investigated. The dynamic sensitivity of the DFB-FL is cali...The bonded distributed feedback（DFB） fiber laser（FL） acoustic emission sensor and the intensity response of the DFB-FL to external acoustic emissions are investigated. The dynamic sensitivity of the DFB-FL is calibrated by a referenced piezoelectric receiver. In the DFB-FL we used here, the minimum detectable signal is2 × 10^（-6）m∕s at 5 kHz. Using wavelet packet technology, the collected signals are analyzed, which confirms that an intensity-modulated DFB-FL sensor can be used to detect acoustic emission signals.展开更多
Terrestrial gamma-ray flashes(TGFs)are high-energy emissions in thunderstorms that were discovered first by satellite-based and then by ground-based gamma-ray detectors with photon energy up to tens of Me V.TGFs are a...Terrestrial gamma-ray flashes(TGFs)are high-energy emissions in thunderstorms that were discovered first by satellite-based and then by ground-based gamma-ray detectors with photon energy up to tens of Me V.TGFs are a natural highenergy phenomenon associated with lightning discharges that frequently occur during thunderstorms.However,their production mechanisms and associated processes are still unclear.TGF studies have already been a research spotlight in the atmospheric electricity and high-energy atmosphere research areas.In this paper,we review recent research progresses on TGF studies in the past decade,including TGF detection,the relationship between TGFs and lightning processes,and thunderstorm activities.Several unsolved important scientific questions are discussed.Results suggest that upward TGFs observed by satellite-based detectors are closely connected with the development of in-cloud upward negative leaders.They are usually generated in milliseconds of the initiation of upward negative leaders and may produce a kind of distinct radio emissions because of the generation and propagation of huge amounts of high-energy electrons.By contrast,its counterpart,i.e.,downward TGFs observed by ground-based gamma-ray detectors,is associated with different types of lightning processes,such as downward negative or upward positive leaders,the initial continuing current stage of rocket-triggered lightning flashes return stroke processes.Because of limited observations,how these downward TGFs are generated is still unclear.Benefiting from the development of state-of-the-art instruments with high temporal and spatial resolutions,new insights into the processes and mechanisms of TGFs will be achieved with coordinated observations from satellite-based and ground-based measurements.展开更多
Featured with light emission and detection coexistence phenomenon,nitride-based multiple-quantum-well(MQW)diodes integrated chip has been proven to be an attractive structure for application prospects in variousfields...Featured with light emission and detection coexistence phenomenon,nitride-based multiple-quantum-well(MQW)diodes integrated chip has been proven to be an attractive structure for application prospects in variousfields such as lighting,sensing,optical communication,and otherfields.However,most of the recent reports are based on planar structures.Three-dimensional(3D)structures are endowed with extra advantages in direction,polarization,and absorption modulation and may pioneer a new way to make the same thing over and over again with interesting properties.In this paper,we designed and fabricated a singlecantilever InGaN/GaN MQW diode with warped 3D microstructure via standard microfabrication technology.Experimental results indicate that the strain architecture of the multi-layer materials is the key principle for the self-warped device.The planar structure will bear greater compressive stress while the warped beam part has less stress,which results in differences in the optical and electrical performance.The strain-induced band bending highly influences the emission and detection properties,while the warped structure will introduce direction selectivity to the 3D device.As an emitter,3D structures exhibit a directional emission with lower turn-on voltage,higher capacitance,increased luminous intensity,higher external quantum efficiency(EQE),high–3 dB bandwidth,and redshifted peak wavelength.Besides,it can serve as an emitter for directional-related optical communication.As a receiver,3D structures have lower darkcurrent,higher photocurrent,and red-shifted response spectrum and also show directional dependence.Thesefindings not only deepen the understanding of the working principle of the singlecantilever GaN devices but also provide important references for device performance optimization and new applications in visible light communication(VLC)technology.展开更多
文摘Rail defects can pose significant safety risks in railway operations, raising the need for effective detection methods. Acoustic Emission (AE) technology has shown promise for identifying and monitoring these defects, and this study evaluates an advanced on-vehicle AE detection approach using bone-conduct sensors—a solution to improve upon previous AE methods of using on-rail sensor installations, which required extensive, costly on-rail sensor networks with limited effectiveness. In response to these challenges, the study specifically explored bone-conduct sensors mounted directly on the vehicle rather than rails by evaluating AE signals generated by the interaction between rails and the train’s wheels while in motion. In this research, a prototype detection system was developed and tested through initial trials at the Nevada Railroad Museum using a track with pre-damaged welding defects. Further testing was conducted at the Transportation Technology Center Inc. (rebranded as MxV Rail) in Colorado, where the system’s performance was evaluated across various defect types and train speeds. The results indicated that bone-conduct sensors were insufficient for detecting AE signals when mounted on moving vehicles. These findings highlight the limitations of contact-based methods in real-world applications and indicate the need for exploring improved, non-contact approaches.
基金supported by the Youth Project of National Natural Science Foundation of China(No.61505145)the Tianjin Science and Technology Commissioner Project(No.20YDTPJC02010)+1 种基金the Tianjin Municipal Education Commission(No.2021KJ003)the Tianjin Zhonghuan Tianjia Electronics Company(No.HX20193)。
文摘Chemical oxygen demand(COD)is an important criterion for detecting the emission of pollutants and judging the quality of water.This paper improves the absorption spectrum compensation model for COD and turbidity mixed solution in the dual-wavelength spectral method based on the Lambert-Beer law additive principle.It compensates for the influence of turbidity on the absorption coefficient of the COD solution at 355 nm by the absorption spectrum coefficient of the mixed solution at 623 nm.This paper establishes a linear relationship model between the absorbance difference of the mixed solution at 355 nm and 623 nm and COD.The experimental determination coefficient R2 of the model is 0.98335,with a relative error of 3.5%and an average error of 0.7 mg/L.The design of the model is simple and easy to systematize,which is of strong significance for practical application.
基金the support and encouragement of The National Science Fund for Distinguished Young(21525627)the Science Fund for Creative Research Groups of National Natural Science Foundation of China(61621002)。
文摘This work first investigated the detection of slags,slag pool liquid level,and slag accumulation height in laboratory scale based on acoustic emission(AE)detection,and further tried the feasibility of this method in an industrial scale coal gasifier.Results show that the energy and variance of acoustic signals can realize the accurate detection of large slag(criterion:E>1.5 E0,S>1.2 S0),and the average relative error is only 0.28%.The acoustic energy in the frequency range of 20–40 k Hz is defined as the characteristic energy,which can realize the accurate detection of slag accumulation height and slag pool liquid level,and the average relative error is only 3.94%.Furthermore,AE detection also realize accurate detection of large slag in an industrial scale gasifier and the acoustic signals at slag screen can be used to realize the early warning of the slag collapse(5 h earlier).
基金financial support by the National Natural Science Foundation of China (Nos. 21190033, 21372083, 21572039)National 973 Program (No. 2013CB733700)
文摘Most reported fluorescent probes have limitations in practical applications in living systems due to the strong autofluorescence background,construction of probes with near-infrared（NIR） fluorescence emission is an accessible approach for addressing this challenge.We here designed a NIR fluorescent probe for monitoring the endogenous production of H2S in living cells.The designed probe showed significant NIR fluorescence turn-on response to H2S with high selectivity,enabling the sensitive detection H2S.Importantly,the probe could be applied in monitoring the endogenous production of H2S in raw 264.7 macrophages.This study showed that fluvastatin can promote the activity of cystathionineγ-lyase（CSE） for generation H2S.
基金supported by the Natural Science Foundation of Jiangsu Province(BK20210593)the National Natural Science Foundation of China(62204127,62404040)the Fundamental Research Funds for the Central Universities(No.NS2022096).
文摘Force sensing provides a crucial physical-electrical channel within sensing technology.This study showcases the fabrication and characterization of force sensors by integrating a polydimethylsiloxane(PDMS)mechanical module and an optical channel formed by two ideal InGaN/GaN light-emitting diodes(LEDs)with transmit-receive characteristics.As an emitter,the InGaN/GaN device(5 mm×4 mm)exhibits electroluminescence at 469 nm with an on-voltage of 2.33 V.As a receiver,the response spectrum of InGaN/GaN devices spans from 350 to 480 nm,featuring a peak at 390 nm,rise time of~68.4 ms,and falling edge of~61.0 ms.The PDMS film can transform the force into deformation data and influence the signals in the optical receiver.The drive current,the gap between the emitter and receiver,and distance between the LED and PDMS mechanical module all significantly influence the receiver photocurrent.Distinct from the integrated design,our PDMS-assisted force sensing model uses discrete structures to allow signal intensity optimization.The finite element simulation and experimental results indicate that force of the designed PDMS film exhibits a linear relationship with z-axis displacement and photocurrent from 0 to 0.7 mm.The findings reveal that when the PDMS film height is 1.5 mm and the distance between the emitter and receiver is near,the photocurrent is higher.Meanwhile,Ag film with a thickness of 100 nm considerably enhances the photocurrent response and signal stability in the sensing channel.Finally,a weight measurement demonstration is employed to demonstrate force sensing.The system resolution is 1.23μA/N,and the measurement range is 0 to 0.7 N.
文摘The pre-earthquake ionospheric anomalies in Wenchuan,China(21°-41°N,93°-113°E)are studied and analyzed using the summer nighttime data from 2005 to 2008 measured by DEMETER(Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions)satellite detectors ICE(Internet Communications Engine),IAP(In Application Programming),and ISL(Interior Switching Link).In this paper,we take the 12 May 2008 Wenchuan earthquake as an example,use the spatial gridding method to construct the background field over the epicenter,analyze the background characteristics of very low frequency(VLF)electric field components,low-energy particle parameters,and plasma parameters,and define the perturbation intensity index of each parameter before the earthquake to extract each parameter anomaly in both space and time dimensions.The results show that the background values of some ionospheric parameters in the Wenchuan area are related to spatial distribution.Moreover,anomalous enhancement of low-frequency electric field power spectral density,H+concentration,He+concentration and ion concentration with different intensities and anomalous weakening of ion temperature were extracted in the fifteen days before the Wenchuan earthquake.After filtering the data to exclude external interference,such as solar activity,this paper concludes that there is some connection between these anomalies and the Wenchuan earthquake.
基金This work was supported by the National Natural Science Foundation of China (No.39870212)
文摘Otoacoustic emissions (OAEs) has been considered as an excellent objective tool in clinics for diagnosing hearing loss. The signal-to-noise ratio (SNR) and correlation coefficient of OAEs are very important for the purpose of diagnosis. An adaptive signal enhancer (ASE) based on the Least Mean Square (LMS) algorithm is presented to detect transient evoked OAEs (TEOAEs). The TEOAEs detection results from 106 ears show that ASE reaches better estimation of TEOAEs than a conventional ensemble averaging (EA) technique. With the ASE, the improvement of SNR was increased faster than that with the EA and the number of sweeps required can be markedly reduced. The detection time with ASE could be shortened by about 50% in comparison with that of EA.
基金supported by the China Scholarship Council,the National Natural Science Foundation of China(61171197,61201307,61371045)the Innovation Funds of Harbin Institute of Technology(Grant IDGA18102011)the Promotive Research Fund for Excellent Young and Middle-Aged Scientisits of Shandong Province(BS2010DX001)
文摘The safety of rail is very important for the development of high speed railway, and it is necessary to investigate the features of inner cracks in rail. In order to obtain the features of Acoustic Emission （AE） sources of inner cracks in rail, AE sources with different types, depths and propagation distances are examined for crack in rail. The finite element method is utilized to model the rail with cracks and the results of experiment demonstrate the effectiveness of this model. Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of crack AE sources. The results illustrate that the intensity ratio among AE modes can identify the AE source types and the AE sources with different frequencies in rail. There are uniform AE mode features existing in the AE signals from AE sources in rail web, however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes. Different AE source types have the different propagation features in rail. It is helpful to understand the rail cracks and detect the rail cracks based on the AE technique.
基金supported by the National 863 Program of China(No.2014AA093406)the Youth Innovation Promotion Association of CAS(No.2016106)+1 种基金the Project of Observation Instrument Development for Integrated Geophysical Field of China Mainland(No.Y201606)the Key Project of Hebei Educational Committee(No.BJ2016048)
文摘The bonded distributed feedback（DFB） fiber laser（FL） acoustic emission sensor and the intensity response of the DFB-FL to external acoustic emissions are investigated. The dynamic sensitivity of the DFB-FL is calibrated by a referenced piezoelectric receiver. In the DFB-FL we used here, the minimum detectable signal is2 × 10^（-6）m∕s at 5 kHz. Using wavelet packet technology, the collected signals are analyzed, which confirms that an intensity-modulated DFB-FL sensor can be used to detect acoustic emission signals.
基金supported by the National Key Research and Development Program of China(Grant No.2017YFC1501500)the Basic Research Fund of the Chinese Academy of Meteorological Sciences(Grants Nos.2020R004&2021Z003)the Chinese Meridian Project and the International Partnership Program of Chinese Academy of Sciences(Grant No.183311KYSB20200003)。
文摘Terrestrial gamma-ray flashes(TGFs)are high-energy emissions in thunderstorms that were discovered first by satellite-based and then by ground-based gamma-ray detectors with photon energy up to tens of Me V.TGFs are a natural highenergy phenomenon associated with lightning discharges that frequently occur during thunderstorms.However,their production mechanisms and associated processes are still unclear.TGF studies have already been a research spotlight in the atmospheric electricity and high-energy atmosphere research areas.In this paper,we review recent research progresses on TGF studies in the past decade,including TGF detection,the relationship between TGFs and lightning processes,and thunderstorm activities.Several unsolved important scientific questions are discussed.Results suggest that upward TGFs observed by satellite-based detectors are closely connected with the development of in-cloud upward negative leaders.They are usually generated in milliseconds of the initiation of upward negative leaders and may produce a kind of distinct radio emissions because of the generation and propagation of huge amounts of high-energy electrons.By contrast,its counterpart,i.e.,downward TGFs observed by ground-based gamma-ray detectors,is associated with different types of lightning processes,such as downward negative or upward positive leaders,the initial continuing current stage of rocket-triggered lightning flashes return stroke processes.Because of limited observations,how these downward TGFs are generated is still unclear.Benefiting from the development of state-of-the-art instruments with high temporal and spatial resolutions,new insights into the processes and mechanisms of TGFs will be achieved with coordinated observations from satellite-based and ground-based measurements.
基金supported by the Natural Science Foundation of Jiangsu Province(No.BK20210593)the National Natural Science Foundation of China(No.62204127)Open Fund of Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education NJ2024001.
文摘Featured with light emission and detection coexistence phenomenon,nitride-based multiple-quantum-well(MQW)diodes integrated chip has been proven to be an attractive structure for application prospects in variousfields such as lighting,sensing,optical communication,and otherfields.However,most of the recent reports are based on planar structures.Three-dimensional(3D)structures are endowed with extra advantages in direction,polarization,and absorption modulation and may pioneer a new way to make the same thing over and over again with interesting properties.In this paper,we designed and fabricated a singlecantilever InGaN/GaN MQW diode with warped 3D microstructure via standard microfabrication technology.Experimental results indicate that the strain architecture of the multi-layer materials is the key principle for the self-warped device.The planar structure will bear greater compressive stress while the warped beam part has less stress,which results in differences in the optical and electrical performance.The strain-induced band bending highly influences the emission and detection properties,while the warped structure will introduce direction selectivity to the 3D device.As an emitter,3D structures exhibit a directional emission with lower turn-on voltage,higher capacitance,increased luminous intensity,higher external quantum efficiency(EQE),high–3 dB bandwidth,and redshifted peak wavelength.Besides,it can serve as an emitter for directional-related optical communication.As a receiver,3D structures have lower darkcurrent,higher photocurrent,and red-shifted response spectrum and also show directional dependence.Thesefindings not only deepen the understanding of the working principle of the singlecantilever GaN devices but also provide important references for device performance optimization and new applications in visible light communication(VLC)technology.
