This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating tra...This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.展开更多
This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the r...This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the rail foot.As a contactless method,EMATs could overcome some known limitations of conventional ultrasonic techniques,but require further validation.Differ-ent campaigns of experimental tests were performed,evaluating,by means of a probability of detection approach,the response of the technique to several artificial semi-elliptical flaws of increasing size and by considering two sensors characterized by different working frequencies.In contact,static tests allowed to assess the basic feasibility of the inspection technique and showed a linear response to defect size,saturating when defect width exceeded the rail web thickness.Dynamic tests allowed to introduce the effects of lift-off on signal responses.During all tests,the higher-frequency sensor outperformed the lower-frequency one.Finally,full-scale bogie tests on an indoor permanent track installation,comprehensive of defec-tive rails,confirmed the higher flaw detection rates of the higher-frequency sensor,with minimal detection failures despite occasional false alarms.EMATs showed encouraging results for in-motion rail inspection:with further technical development and optimization,this technique could enhance ultrasonic rail inspection by diagnostic trains.展开更多
In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of...In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of the antisymmetric Lamb wave is always dominated by out-of-plane components,using bias magnetic field perpendicular to plate surface is kind of inefficient.In this paper,the performance of both the normal bias magnetic field EMAT(NB-EMAT)and the parallel bias magnetic field EMAT(PB-EMAT)for transmitting and receiving A0 mode Lamb waves are thoroughly studied.The mechanisms of these two structures are elaborated.First,the finite element models of both structures are established.The magnetic fields of these two EMATs are numerically calculated and the results are compared with experiments.Then,the Lorentz force distributions excited by the two EMATs are compared to prove the feasibility of improving the excitation efficiency of MLC-EMAT by selecting the direction of bias magnetic field.Furthermore,the excitation efficiencies of NB-EMAT and PB-EMAT are quantitatively analyzed and compared in simulation software.Results show that the excitation efficiency of PB-EMAT is 108%higher than NB-EMAT.Finally,several groups of comparative experiments are conducted to verify the conclusion obtained through numerical calculation.Experimental results show that by simply replacing the tradition NB-EMAT with PB-EMAT,the excitation efficiency can be greatly increased by more than 50%.If PB-EMATs are used as both the receiver and transmitter,the excitation efficiency can be further increased by 113%.展开更多
Background:Breakpoint Cluster Region-Abelson(BCR::ABL1)fusion protein is essential in the pathogenesis of chronic myeloid leukemia(CML);however,the chronic-to-blast phase transformation remains elusive.We identified n...Background:Breakpoint Cluster Region-Abelson(BCR::ABL1)fusion protein is essential in the pathogenesis of chronic myeloid leukemia(CML);however,the chronic-to-blast phase transformation remains elusive.We identified novel kinesin light chain 2(KLC2)mutations in CML-myeloid blast phase patients.We aimed to examine the functional role of KLC2 mutations in leukemogenesis.Methods:To evaluate the biological role of KLC2 mutants(MT)in CML cells,we expressed KLC2-MT in different human CML cell lines harboring BCR::ABL1 and performed immunoblot,immunofluorescence,cell proliferation,differentiation,and apoptosis;Tyrosine kinase inhibitor(TKI)-drug activities;and clonogenic assays for in vitro functional analyses.We co-expressed KLC2-MT and BCR::ABL1 in mouse bone marrow cells(BMCs)to evaluate their clonogenic and self-renewal abilities ex vivo.Furthermore,we examined tumorigenic activity and drug efficacy in the K562 xenograft model.Results:KLC2-MT overexpression in BCR::ABL1-positive K562 and KU812 CML cells promoted cell proliferation and clonogenic potential,decreased imatinib sensitivity,and reduced apoptosis.Serial colony replating assays revealed that KLC2-MT and BCR::ABL1 co-expression enhanced the self-renewal ability of mouse BMCs with immature morphology.In the K562 xenograft model,KLC2-MT enhanced tumorigenic potential and diminished imatinib efficacy.Further studies reported that KLC2-MT augmented signal transducer and activator of transcription 3(STAT3)activation and nuclear accumulation in imatinib-treated CML cells.KLC2-WT and KLC2-MT interacted with mothers against decapentaplegic homolog 2(SMAD2);however,the latter impaired transforming growth factor-beta(TGF-β)–mediated SMAD2/3 activation while enhancing STAT3 phosphorylation.Conclusions:This study demonstrates the biological and functional importance of KLC2 mutation in CML cells,potentially enabling the development of better treatment strategies for CML patients carrying KLC2 mutations and providing enhanced understanding of the disease progression.展开更多
The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic t...The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.展开更多
Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a...Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.展开更多
A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and...A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and crosstalk just with a single conventional calibration approach. In this paper, a hybrid model comprising calibration matrix and SVM model for calibrating linearity and nonlinearity respectively is built up. The calibration matrix is determined by linear artificial neural network （ANN）, and the SVM is used to compensate for the nonlinear cross coupling among each dimension. A simulation of the calibration of a multi-dimensional sensor is conducted by the SVM hybrid calibration method, which is then utilized to calibrate a six-component force/torque transducer of wind tunnel balance. From the calibrating results, it can be indicated that the SVM hybrid calibration method has improved the calibration accuracy significantly without increasing data samples, compared with calibration matrix. Moreover, with the calibration matrix, the hybrid model can provide a basis for the design of transducers.展开更多
Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger ...Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger nonlinear effects that enable pumping and mixing of fluids,and moving particles without contact.However,the transition from signal processing to actuators comes with a range of challenges concerning power density and spatial resolution that have spurred exciting developments in solid-state acoustics and especially in IDT design.Assuming some familiarity with acoustofluidics,this paper aims to provide a tutorial for IDT design and characterization for the purpose of acoustofluidic actuation.It is targeted at a diverse audience of researchers in various fields,including fluid mechanics,acoustics,and microelectronics.展开更多
The measurements and analysis of deformation of engineering structures such as dams, bridges and high-rise buildings are important tasks for civil engineers. It is evident that, all civil engineering structures are su...The measurements and analysis of deformation of engineering structures such as dams, bridges and high-rise buildings are important tasks for civil engineers. It is evident that, all civil engineering structures are susceptible for deterioration over a period of time. Bridges in particular, deteriorate due to loading conditions, environmental changes, earth movement, material used during construction, age and corrosion of steel. Continuous monitoring of such structure is the most important aspect as it provides quantitative information, assesses the state of the structure, detects unsafe positions and proposes early safety measures to be taken before it can threaten the safety of vehicles, goods and human life. Despite government’s efforts to construct roads and highways, bridge deformation monitoring has not been given priority in most of African countries and ultimately causes some bridges to collapse unexpectedly. The purpose of this research is to integrate Global Positioning System (GPS) and Linear Variable Differential Transducers (LVDT) to monitor deformation of a bridge. The horizontal positions of reference and monitoring points were determined using Global Positioning System (GPS) while the vertical deflections, accelerations and strain were determined using Linear Variable Differential Transducers (LVDT). The maximum displacements obtained between zero and first epochs in x, y and z components were 0.798 m, at point LT08, 0.865 m at point BR13, and 0.56 m at point LT02 respectively. The maximum deflections for LVDT 1, 2 and 3 are 28.563 mm, 31.883 mm and 40.926 mm respectively. Finally, the correlation coefficient for the observations was 0.679 with standard deviations of 0.0168 and 0.0254 in x and y respectively. Our results identified some slight displacements in horizontal components at the bridge.展开更多
Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate dete...Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate detection and positioning,it will help to improve the accuracy and reliability of air-coupled ultrasonic Lamb wave detection,providing better technical support for the application and development of related fields.Because of the increased complexity of aircoupled signals,there is no definite theoretical formula to describe the mode changes of aircoupled signals,so the method based on blind separation has unique value.To address these challenges,the paper proposes a single-channel blind source separation(SCBSS)method.The effectiveness of this method is evaluated through simulations and experiments,demonstrating favorable separation results and efficient computational speed.This work first conducts an in-depth analysis of the signal characteristics of air-coupled ultrasonic non-destructive testing,and simulates the ultrasonic excitation conditions of air-coupled sensors through finite element software.The study of modal changes and multipath effects caused by the variation of the incidence angle of the ACT signal is carried out,and the situation of the Lamb wave signal excited by ACT at the receiving end is analyzed.By combining ACT with PZT signals,the ultrasonic signals of air-coupled Lamb waves are compared and studied,and their modal purification is carried out.展开更多
Photoacoustic microscopy(PAM),due to its deep penetration depth and high contrast,is playing an increasingly important role in biomedical imaging.PAM imaging systems equipped with conventional ultrasound transducers h...Photoacoustic microscopy(PAM),due to its deep penetration depth and high contrast,is playing an increasingly important role in biomedical imaging.PAM imaging systems equipped with conventional ultrasound transducers have demonstrated excellent imaging performance.However,these opaque ultrasonic transducers bring some constraints to the further development and application of PAM,such as complex optical path,bulky size,and difficult to integrate with other modalities.To overcome these problems,ultrasonic transducers with high optical transparency have appeared.At present,transparent ultrasonic transducers are divided into optical-based and acoustic-based sensors.In this paper,we mainly describe the acoustic-based piezoelectric transparent transducers in detail,of which the research advances in PAM applications are reviewed.In addition,the potential challenges and developments of transparent transducers in PAM are also demonstrated.展开更多
An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging app...An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.展开更多
In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers （EMATs）. With the modal expansion approach for wave...In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers （EMATs）. With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave＇s mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT＇s meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT＇s geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated （strengthened or restrained） by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.12474440).
文摘This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.
基金funded in the frame of the Joint Research Centre (JRC) Trasporti, established at Fondazione Politecnico di Milano, through contract C40/2019 “JRC Trasporti-Metodologie per l’ispezione delle rotaie nei riguardi della formazione di cricche”
文摘This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the rail foot.As a contactless method,EMATs could overcome some known limitations of conventional ultrasonic techniques,but require further validation.Differ-ent campaigns of experimental tests were performed,evaluating,by means of a probability of detection approach,the response of the technique to several artificial semi-elliptical flaws of increasing size and by considering two sensors characterized by different working frequencies.In contact,static tests allowed to assess the basic feasibility of the inspection technique and showed a linear response to defect size,saturating when defect width exceeded the rail web thickness.Dynamic tests allowed to introduce the effects of lift-off on signal responses.During all tests,the higher-frequency sensor outperformed the lower-frequency one.Finally,full-scale bogie tests on an indoor permanent track installation,comprehensive of defec-tive rails,confirmed the higher flaw detection rates of the higher-frequency sensor,with minimal detection failures despite occasional false alarms.EMATs showed encouraging results for in-motion rail inspection:with further technical development and optimization,this technique could enhance ultrasonic rail inspection by diagnostic trains.
基金supported by the Foundation of Guangxi Key Laboratory of Manufacturing System and Advanced Manufacturing Technology(No.17-259-05-005Z)Innovation Project of GUET Graduate Education(No.2025YCXS016)。
文摘In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of the antisymmetric Lamb wave is always dominated by out-of-plane components,using bias magnetic field perpendicular to plate surface is kind of inefficient.In this paper,the performance of both the normal bias magnetic field EMAT(NB-EMAT)and the parallel bias magnetic field EMAT(PB-EMAT)for transmitting and receiving A0 mode Lamb waves are thoroughly studied.The mechanisms of these two structures are elaborated.First,the finite element models of both structures are established.The magnetic fields of these two EMATs are numerically calculated and the results are compared with experiments.Then,the Lorentz force distributions excited by the two EMATs are compared to prove the feasibility of improving the excitation efficiency of MLC-EMAT by selecting the direction of bias magnetic field.Furthermore,the excitation efficiencies of NB-EMAT and PB-EMAT are quantitatively analyzed and compared in simulation software.Results show that the excitation efficiency of PB-EMAT is 108%higher than NB-EMAT.Finally,several groups of comparative experiments are conducted to verify the conclusion obtained through numerical calculation.Experimental results show that by simply replacing the tradition NB-EMAT with PB-EMAT,the excitation efficiency can be greatly increased by more than 50%.If PB-EMATs are used as both the receiver and transmitter,the excitation efficiency can be further increased by 113%.
基金supported by grants from the Ministry of Science and Technology,Taiwan(MOST108-2314-B-182-006,MOST109-2314-B-182-071:Lee-Yung Shih)the Ministry of Health and Welfare,Taiwan(MOHW110-TDU-B-212-134011:Lee-Yung Shih)+3 种基金Chang Gung Memorial Hospital(CMRPG3D1524,OMRPG3E0031:Lee-Yung Shih)the Grant-in-Aid for the Japan Society for the Promotion of Science(JSPS)KAKENHI(JP19H05656:Seishi Ogawa,22K16320:Yotaro Ochi)the Japan Agency for Medical Research and Development(AMED)(JP19cm0106501h0004,JP19ck0106250h0003:Seishi Ogawa)the Ministry of Education,Culture,Sports,Science and Technology of Japan(MEXT)(hp200138,hp210167:Seishi Ogawa)。
文摘Background:Breakpoint Cluster Region-Abelson(BCR::ABL1)fusion protein is essential in the pathogenesis of chronic myeloid leukemia(CML);however,the chronic-to-blast phase transformation remains elusive.We identified novel kinesin light chain 2(KLC2)mutations in CML-myeloid blast phase patients.We aimed to examine the functional role of KLC2 mutations in leukemogenesis.Methods:To evaluate the biological role of KLC2 mutants(MT)in CML cells,we expressed KLC2-MT in different human CML cell lines harboring BCR::ABL1 and performed immunoblot,immunofluorescence,cell proliferation,differentiation,and apoptosis;Tyrosine kinase inhibitor(TKI)-drug activities;and clonogenic assays for in vitro functional analyses.We co-expressed KLC2-MT and BCR::ABL1 in mouse bone marrow cells(BMCs)to evaluate their clonogenic and self-renewal abilities ex vivo.Furthermore,we examined tumorigenic activity and drug efficacy in the K562 xenograft model.Results:KLC2-MT overexpression in BCR::ABL1-positive K562 and KU812 CML cells promoted cell proliferation and clonogenic potential,decreased imatinib sensitivity,and reduced apoptosis.Serial colony replating assays revealed that KLC2-MT and BCR::ABL1 co-expression enhanced the self-renewal ability of mouse BMCs with immature morphology.In the K562 xenograft model,KLC2-MT enhanced tumorigenic potential and diminished imatinib efficacy.Further studies reported that KLC2-MT augmented signal transducer and activator of transcription 3(STAT3)activation and nuclear accumulation in imatinib-treated CML cells.KLC2-WT and KLC2-MT interacted with mothers against decapentaplegic homolog 2(SMAD2);however,the latter impaired transforming growth factor-beta(TGF-β)–mediated SMAD2/3 activation while enhancing STAT3 phosphorylation.Conclusions:This study demonstrates the biological and functional importance of KLC2 mutation in CML cells,potentially enabling the development of better treatment strategies for CML patients carrying KLC2 mutations and providing enhanced understanding of the disease progression.
基金supported by National Natural Science Foundation of China(Grant Nos.51075012,10772008)Beijing Municipal Natural Science Foundation of China(Grant No.1122005)
文摘The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.
基金Project(10974115) supported by the National Natural Science Foundation of China
文摘Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.
基金National Science Foundation of China(Grant No.10772142)National Natural Science Key Foundation of China(Grant No.10832002)the Fundamental Research Funds for the Central Universities
文摘A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and crosstalk just with a single conventional calibration approach. In this paper, a hybrid model comprising calibration matrix and SVM model for calibrating linearity and nonlinearity respectively is built up. The calibration matrix is determined by linear artificial neural network （ANN）, and the SVM is used to compensate for the nonlinear cross coupling among each dimension. A simulation of the calibration of a multi-dimensional sensor is conducted by the SVM hybrid calibration method, which is then utilized to calibrate a six-component force/torque transducer of wind tunnel balance. From the calibrating results, it can be indicated that the SVM hybrid calibration method has improved the calibration accuracy significantly without increasing data samples, compared with calibration matrix. Moreover, with the calibration matrix, the hybrid model can provide a basis for the design of transducers.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.12004078 and 61874033the State Key Lab of ASIC and Systems,the Science and Technology Commission of Shanghai Municipality Award/Grant Nos.22QA1400900 and 22WZ2502200Fudan University 2021MS001,2021MS002 and 2020KF006.
文摘Interdigitated transducers(IDTs)were originally designed as delay lines for radars.Half a century later,they have found new life as actuators for microfluidic systems.By generating strong acoustic fields,they trigger nonlinear effects that enable pumping and mixing of fluids,and moving particles without contact.However,the transition from signal processing to actuators comes with a range of challenges concerning power density and spatial resolution that have spurred exciting developments in solid-state acoustics and especially in IDT design.Assuming some familiarity with acoustofluidics,this paper aims to provide a tutorial for IDT design and characterization for the purpose of acoustofluidic actuation.It is targeted at a diverse audience of researchers in various fields,including fluid mechanics,acoustics,and microelectronics.
文摘The measurements and analysis of deformation of engineering structures such as dams, bridges and high-rise buildings are important tasks for civil engineers. It is evident that, all civil engineering structures are susceptible for deterioration over a period of time. Bridges in particular, deteriorate due to loading conditions, environmental changes, earth movement, material used during construction, age and corrosion of steel. Continuous monitoring of such structure is the most important aspect as it provides quantitative information, assesses the state of the structure, detects unsafe positions and proposes early safety measures to be taken before it can threaten the safety of vehicles, goods and human life. Despite government’s efforts to construct roads and highways, bridge deformation monitoring has not been given priority in most of African countries and ultimately causes some bridges to collapse unexpectedly. The purpose of this research is to integrate Global Positioning System (GPS) and Linear Variable Differential Transducers (LVDT) to monitor deformation of a bridge. The horizontal positions of reference and monitoring points were determined using Global Positioning System (GPS) while the vertical deflections, accelerations and strain were determined using Linear Variable Differential Transducers (LVDT). The maximum displacements obtained between zero and first epochs in x, y and z components were 0.798 m, at point LT08, 0.865 m at point BR13, and 0.56 m at point LT02 respectively. The maximum deflections for LVDT 1, 2 and 3 are 28.563 mm, 31.883 mm and 40.926 mm respectively. Finally, the correlation coefficient for the observations was 0.679 with standard deviations of 0.0168 and 0.0254 in x and y respectively. Our results identified some slight displacements in horizontal components at the bridge.
基金Supported by the National Natural Science Foundation of China(Nos.92360306,52222504 and 52241502).
文摘Due to the complexity and faintness of the detection wave patterns obtained by aircoupled transducers,if it is possible to effectively separate the various modes and obtain nondispersive signals for more accurate detection and positioning,it will help to improve the accuracy and reliability of air-coupled ultrasonic Lamb wave detection,providing better technical support for the application and development of related fields.Because of the increased complexity of aircoupled signals,there is no definite theoretical formula to describe the mode changes of aircoupled signals,so the method based on blind separation has unique value.To address these challenges,the paper proposes a single-channel blind source separation(SCBSS)method.The effectiveness of this method is evaluated through simulations and experiments,demonstrating favorable separation results and efficient computational speed.This work first conducts an in-depth analysis of the signal characteristics of air-coupled ultrasonic non-destructive testing,and simulates the ultrasonic excitation conditions of air-coupled sensors through finite element software.The study of modal changes and multipath effects caused by the variation of the incidence angle of the ACT signal is carried out,and the situation of the Lamb wave signal excited by ACT at the receiving end is analyzed.By combining ACT with PZT signals,the ultrasonic signals of air-coupled Lamb waves are compared and studied,and their modal purification is carried out.
基金supported by Guangdong Province Introduction of Innovative R&D Team(2016ZT06G375)National Natural Science Foundation of China(11804059,62205070 and 11664011).
文摘Photoacoustic microscopy(PAM),due to its deep penetration depth and high contrast,is playing an increasingly important role in biomedical imaging.PAM imaging systems equipped with conventional ultrasound transducers have demonstrated excellent imaging performance.However,these opaque ultrasonic transducers bring some constraints to the further development and application of PAM,such as complex optical path,bulky size,and difficult to integrate with other modalities.To overcome these problems,ultrasonic transducers with high optical transparency have appeared.At present,transparent ultrasonic transducers are divided into optical-based and acoustic-based sensors.In this paper,we mainly describe the acoustic-based piezoelectric transparent transducers in detail,of which the research advances in PAM applications are reviewed.In addition,the potential challenges and developments of transparent transducers in PAM are also demonstrated.
基金supported by the National Science Council of the Republic China (No.NSC 98-2221-E-468-023)
文摘An improved model for ultrasonic transducers is proposed. By considering only the first symmetric mode, each layer is represented as an acoustical transmission line in modeling of bulk wave transducers. In imaging applications, wide bandwidth and short time duration are required. The approach we have used consists of impedance matching the front face of the piezoelectric transducer to the propagating medium with a quarter wavelength impedance matching layer and inserting an nnmatching quarter wavelength acoustical layer between the rear face and backing material. A heavy backing would degrade the wide-band phenomena, but show a time duration shorter than 0.5 μs for imaging applications. PSPICE code of the controlled source model is implemented to precisely predict the performance of the matched transducers such as impedance, insertion loss, bandwidth and duration of the impulse response. Good agreement between the simulation and experimental results has been achieved.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474361 and 11274388)
文摘In this paper, we describe a modal expansion approach for the analysis of the selective generation of ultrasonic Lamb waves by electromagnetic acoustic transducers （EMATs）. With the modal expansion approach for waveguide excitation, an analytical expression of the Lamb wave＇s mode expansion coefficient is deduced, which is related to the driving frequency and the geometrical parameters of the EMAT＇s meander coil, and lays a theoretical foundation for exactly analyzing the selective generation of Larnb waves with EMATs. The influences of the driving frequency on the mode expansion coefficient of ultrasonic Lamb waves are analyzed when the EMAT＇s geometrical parameters are given. The numerical simulations and experimental examinations show that the ultrasonic Lamb wave modes can be effectively regulated （strengthened or restrained） by choosing an appropriate driving frequency of EMAT, with the geometrical parameters given. This result provides a theoretical and experimental basis for selectively generating a single and pure Lamb wave mode with EMATs.
