Pub Date : 2022-10-11DOI: 10.1109/spawda.2016.7830054
Thomas R. Shrput
{"title":"List of invited plenary talks","authors":"Thomas R. Shrput","doi":"10.1109/spawda.2016.7830054","DOIUrl":"https://doi.org/10.1109/spawda.2016.7830054","url":null,"abstract":"","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128764722","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7829951
S. Zhai, Yongchen Wang, Bo Geng, Hong-chao Xu, Shi-feng Huang
The 1–3 orthotropic polymer/cement based piezoelectric composite(OPCM) fabricated using PZT-51 as functional part and epoxy resin/cement as matrix via twice cutting-filling methods was to be used as acoustic emission (AE) sensors. The acoustic emission signals were collected by pencil lead-break as signal source on the concrete surface and the linear location test of signal source was carried by AE technique. The results showed that the values of signal amplitude and voltage both varied from distance and angle, it reached the maximum along the direction of 0° and 180°, which exhibited the OPCM an excellent orthotropic property. The attenuation curve showed a trend that signals of amplitude and voltage decreased sharply in near field region and reduced steadily in far field area. The OPCM used as sensors could receive each signal in the process of liner location, and the positioning accuracy could reach above 95%, which provide a basic for the OPCM to carry out health monitoring of civil engineering with AE technique.
{"title":"Study on the 1–3 orthotropic polymer/cement based piezoelectric composite","authors":"S. Zhai, Yongchen Wang, Bo Geng, Hong-chao Xu, Shi-feng Huang","doi":"10.1109/SPAWDA.2016.7829951","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7829951","url":null,"abstract":"The 1–3 orthotropic polymer/cement based piezoelectric composite(OPCM) fabricated using PZT-51 as functional part and epoxy resin/cement as matrix via twice cutting-filling methods was to be used as acoustic emission (AE) sensors. The acoustic emission signals were collected by pencil lead-break as signal source on the concrete surface and the linear location test of signal source was carried by AE technique. The results showed that the values of signal amplitude and voltage both varied from distance and angle, it reached the maximum along the direction of 0° and 180°, which exhibited the OPCM an excellent orthotropic property. The attenuation curve showed a trend that signals of amplitude and voltage decreased sharply in near field region and reduced steadily in far field area. The OPCM used as sensors could receive each signal in the process of liner location, and the positioning accuracy could reach above 95%, which provide a basic for the OPCM to carry out health monitoring of civil engineering with AE technique.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121031737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7829976
Zhengqiu Xie, C. Kwuimy, Wenbin Huang
Energy harvesting from human motion faces with challenges including low-frequency and non-harmonic excitation. This paper presents a novel impact-excited energy harvesting system using a bilayer structure which is composed of a buckled piezoelectric beam and a rubber plate with a certain spatial separation. When the rubber plate is excited by the low frequency human gait impulse, it would touch the buckled piezoelectric beam and trigger the snap-through vibration of the beam through the up-conversion mechanism. The electromechanical response of the proposed nonlinear energy harvesting system under the standard low-frequency and non-harmonic gait excitation is studied by numerical simulations. The influences of the geometrical and physical parameters including the mechanical properties of the materials, separation distance of the bilayer structure and the excitation parameters are examined respectively. The appearances of the chaotic and periodic responses of the energy harvesting systems with different physical parameters are illustrated by the phase portraits, and time-domain images. Compared with intrawell and chaotic oscillations, high energy periodic interwell vibrations are demonstrated to greatly improve the energy harvesting performance. The results of the parameter analysis can be used to optimize the energy harvesting structure.
{"title":"Energy harvesting from human motion by impact-excited bistable buckled beams","authors":"Zhengqiu Xie, C. Kwuimy, Wenbin Huang","doi":"10.1109/SPAWDA.2016.7829976","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7829976","url":null,"abstract":"Energy harvesting from human motion faces with challenges including low-frequency and non-harmonic excitation. This paper presents a novel impact-excited energy harvesting system using a bilayer structure which is composed of a buckled piezoelectric beam and a rubber plate with a certain spatial separation. When the rubber plate is excited by the low frequency human gait impulse, it would touch the buckled piezoelectric beam and trigger the snap-through vibration of the beam through the up-conversion mechanism. The electromechanical response of the proposed nonlinear energy harvesting system under the standard low-frequency and non-harmonic gait excitation is studied by numerical simulations. The influences of the geometrical and physical parameters including the mechanical properties of the materials, separation distance of the bilayer structure and the excitation parameters are examined respectively. The appearances of the chaotic and periodic responses of the energy harvesting systems with different physical parameters are illustrated by the phase portraits, and time-domain images. Compared with intrawell and chaotic oscillations, high energy periodic interwell vibrations are demonstrated to greatly improve the energy harvesting performance. The results of the parameter analysis can be used to optimize the energy harvesting structure.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"105 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124821207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7829988
Taotao Zhang, Yi-nan Zhou
Exact dynamic analysis of 2–2 cement-based piezoelectric actuator is presented based on the theory of piezo-elasticity in this article with considering ambient temperature. The temperature field considered is assumed to be of uniform distribution over the plate surface. The solution of the piezoelectric composite under sinusoidal electric signal was obtained by using displacement method. The effects of amplitude and frequency of the electric signal, ambient temperature and some material coefficients of piezoelectric material are simulated and discussed. The solutions are compare with the numerical results, and good agreements are found. The results obtained in this present investigation provide a theoretical method for applying the cement based piezoelectric composite in civil engineering.
{"title":"Dynamic analysis of 2–2 cement based piezoelectric composite actuator with considering ambient temperatures","authors":"Taotao Zhang, Yi-nan Zhou","doi":"10.1109/SPAWDA.2016.7829988","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7829988","url":null,"abstract":"Exact dynamic analysis of 2–2 cement-based piezoelectric actuator is presented based on the theory of piezo-elasticity in this article with considering ambient temperature. The temperature field considered is assumed to be of uniform distribution over the plate surface. The solution of the piezoelectric composite under sinusoidal electric signal was obtained by using displacement method. The effects of amplitude and frequency of the electric signal, ambient temperature and some material coefficients of piezoelectric material are simulated and discussed. The solutions are compare with the numerical results, and good agreements are found. The results obtained in this present investigation provide a theoretical method for applying the cement based piezoelectric composite in civil engineering.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114911209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7830022
Long-cheng Li, Sheng-qiang Zhou
In this paper, a piezoelectric actuator combined the longitudinal vibration transducer with the travelling wave ring has been proposed. After analysis of the transducer working mode frequency and amplitude under different pre-tightening force, the relationship of the pre-tightening force to transducer vibration characteristics was found. According to the three characteristics of work mode shape, the work modes of piezoelectric actuator were identified from the modes acquired by ADPL programming, and the structural parameter optimization design of the actuator was studied under ANSYS environment. Finally, a prototype was fabricated on the basis of the optimization design scheme in which the size parameters (P1, P2, P3, P5) were 3.15 mm, 2.2 mm, 0.57 mm, 34.9 mm respectively, and the bolt pre-tightening force was 7Nm. The experimental result of the prototype was consistent with the simulation analysis.
{"title":"Analysis and optimization of a piezoelectric actuator combined the longitudinal vibration transducer with the travelling wave ring","authors":"Long-cheng Li, Sheng-qiang Zhou","doi":"10.1109/SPAWDA.2016.7830022","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7830022","url":null,"abstract":"In this paper, a piezoelectric actuator combined the longitudinal vibration transducer with the travelling wave ring has been proposed. After analysis of the transducer working mode frequency and amplitude under different pre-tightening force, the relationship of the pre-tightening force to transducer vibration characteristics was found. According to the three characteristics of work mode shape, the work modes of piezoelectric actuator were identified from the modes acquired by ADPL programming, and the structural parameter optimization design of the actuator was studied under ANSYS environment. Finally, a prototype was fabricated on the basis of the optimization design scheme in which the size parameters (P1, P2, P3, P5) were 3.15 mm, 2.2 mm, 0.57 mm, 34.9 mm respectively, and the bolt pre-tightening force was 7Nm. The experimental result of the prototype was consistent with the simulation analysis.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115077822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7829947
Jie Xu, Yang Dou, Shu-Yu Lin
Based on the electromechanical equivalent circuit method, with the consideration of mechanical loss and dielectric loss, input electrical impedance equation and electroacoustic efficiency equation are obtained. Sandwich piezoelectric transducers of both symmetrical and asymmetrical structure are analyzed. Characteristic parameters of effective electromechanical coupling coefficient, mechanical quality factor and electroacoustic efficiency are optimized. Resonance/anti-resonance frequency is measured and effective electromechanical coupling coefficient is calculated. It is found that the experimental results are in good agreement with the analytical results.
{"title":"Parameters optimization of the sandwich piezoelectric transducer","authors":"Jie Xu, Yang Dou, Shu-Yu Lin","doi":"10.1109/SPAWDA.2016.7829947","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7829947","url":null,"abstract":"Based on the electromechanical equivalent circuit method, with the consideration of mechanical loss and dielectric loss, input electrical impedance equation and electroacoustic efficiency equation are obtained. Sandwich piezoelectric transducers of both symmetrical and asymmetrical structure are analyzed. Characteristic parameters of effective electromechanical coupling coefficient, mechanical quality factor and electroacoustic efficiency are optimized. Resonance/anti-resonance frequency is measured and effective electromechanical coupling coefficient is calculated. It is found that the experimental results are in good agreement with the analytical results.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122698644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7830044
Zi-bo Jiang
3-Inch diameter PMN-PT ingots were grown along [001] direction using Vertical Gradient Freeze (VGF) method. Wafers are sliced, sequentially numbered and tested for the study of property distribution along the ingot, and samples from the same wafer were studied for in-wafer uniformity. As a result, [001] grown and poled PMN-PT crystals typically have electromechanical coupling coefficient k33 higher than 0.91, and free relative permittivity between 4,600 and 7,500, varying monotonically along the ingot, due to PT composition segregation. In-wafer free relative permittivity variation coefficient is measured within 2%, due to sufficient agitation during growth. It is also shown that piezoelectric properties saturate around 350 kV/mm for PMN-0.29PT and 250 kV/mm for PMN-0.31PT, respectively. Both PMN-0.29PT and PMN-0.31PT experience property degradation due to over-poling over 1300 kV/mm, and PMN-0.31PT is more susceptible to over-poling due to closer vicinity to the Morphotropic Phase Boundary (MPB). It is thought that over-poling is a field-induced phase transition and such transition is found reversible by annealing at certain elevated temperatures.
{"title":"Property uniformity and poling behavior of PMN-PT crystal grown by vertical gradient freeze method","authors":"Zi-bo Jiang","doi":"10.1109/SPAWDA.2016.7830044","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7830044","url":null,"abstract":"3-Inch diameter PMN-PT ingots were grown along [001] direction using Vertical Gradient Freeze (VGF) method. Wafers are sliced, sequentially numbered and tested for the study of property distribution along the ingot, and samples from the same wafer were studied for in-wafer uniformity. As a result, [001] grown and poled PMN-PT crystals typically have electromechanical coupling coefficient k33 higher than 0.91, and free relative permittivity between 4,600 and 7,500, varying monotonically along the ingot, due to PT composition segregation. In-wafer free relative permittivity variation coefficient is measured within 2%, due to sufficient agitation during growth. It is also shown that piezoelectric properties saturate around 350 kV/mm for PMN-0.29PT and 250 kV/mm for PMN-0.31PT, respectively. Both PMN-0.29PT and PMN-0.31PT experience property degradation due to over-poling over 1300 kV/mm, and PMN-0.31PT is more susceptible to over-poling due to closer vicinity to the Morphotropic Phase Boundary (MPB). It is thought that over-poling is a field-induced phase transition and such transition is found reversible by annealing at certain elevated temperatures.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124004853","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7830008
Jing Gong, Hong-bin He, Wei-jun Lin
Due to the influence of the manufacturing process and usage environment of the transducer, when the transducer works for a long time, the resonant frequency will drift. So it is necessary to have frequency automatic tracking device in the power ultrasonic supply. Traditional frequency automatic tracking devices have disadvantages of small tracking range, great error and so on. This paper introduces a new kind of power ultrasonic supply based on MCU. It will introduce the design of wave generator, power amplifier and matching network in detail. And it demonstrates a new method of frequency tracking to solve the problem caused by the transducer frequency drift and ensure the output efficiency of the transducer.
{"title":"A design of intelligent power ultrasonic supply","authors":"Jing Gong, Hong-bin He, Wei-jun Lin","doi":"10.1109/SPAWDA.2016.7830008","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7830008","url":null,"abstract":"Due to the influence of the manufacturing process and usage environment of the transducer, when the transducer works for a long time, the resonant frequency will drift. So it is necessary to have frequency automatic tracking device in the power ultrasonic supply. Traditional frequency automatic tracking devices have disadvantages of small tracking range, great error and so on. This paper introduces a new kind of power ultrasonic supply based on MCU. It will introduce the design of wave generator, power amplifier and matching network in detail. And it demonstrates a new method of frequency tracking to solve the problem caused by the transducer frequency drift and ensure the output efficiency of the transducer.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"147 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114642316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-10-01DOI: 10.1109/SPAWDA.2016.7829979
Lan Yang, Hao Chen, Xiuming Wang, L. Tang
Nowadays many logging communication systems adapt the Orthogonal Frequency Division Multiplexing (OFDM) for the implementation of high transmission rate. In order to realize higher rate, adaptive bit allocation is proposed, which is based on signal-to-noise ratio (SNR). SNR is a significant evaluation parameter for the channel quality in the communication systems. In this paper, we derive a SNR estimation method for the logging cable channel. Simulation results show that the proposed algorithm is available to obtain relatively accurate measurements of SNR. On the basis of measurements, we assign the bits for sub-channels by a simplified bit allocation method. Compared with fixed bit allocation, this method improves the transmission rate.
{"title":"SNR estimation and bit allocation applied in logging telemetry equipment","authors":"Lan Yang, Hao Chen, Xiuming Wang, L. Tang","doi":"10.1109/SPAWDA.2016.7829979","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7829979","url":null,"abstract":"Nowadays many logging communication systems adapt the Orthogonal Frequency Division Multiplexing (OFDM) for the implementation of high transmission rate. In order to realize higher rate, adaptive bit allocation is proposed, which is based on signal-to-noise ratio (SNR). SNR is a significant evaluation parameter for the channel quality in the communication systems. In this paper, we derive a SNR estimation method for the logging cable channel. Simulation results show that the proposed algorithm is available to obtain relatively accurate measurements of SNR. On the basis of measurements, we assign the bits for sub-channels by a simplified bit allocation method. Compared with fixed bit allocation, this method improves the transmission rate.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132251100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The traditional one-dimensional (1D) electromechanical impedance model simplifies the PZT as a thin bar, only considering the vibration in the axial direction, and the vibrations in other two directions are neglected. In this study, the vibrations of the PZT patch in x and z directions are taken into account to model the electromechanical coupling interaction between the PZT transducer and the host structure. The corresponding admittance formula is derived and a free vibration experiment of the PZT patch is carried out to verify the proposed two-dimensional (2D) electromechanical impedance model. It can be found that the proposed model is effective by comparing the theoretical formula and the experimental results.
{"title":"A two-dimensional electromechanical impedance model and experimental verification of a PZT transducer","authors":"Dansheng Wang, Xiao-meng Zhou, Hong-yuan Song, Hong-ping Zhu","doi":"10.1109/SPAWDA.2016.7830001","DOIUrl":"https://doi.org/10.1109/SPAWDA.2016.7830001","url":null,"abstract":"The traditional one-dimensional (1D) electromechanical impedance model simplifies the PZT as a thin bar, only considering the vibration in the axial direction, and the vibrations in other two directions are neglected. In this study, the vibrations of the PZT patch in x and z directions are taken into account to model the electromechanical coupling interaction between the PZT transducer and the host structure. The corresponding admittance formula is derived and a free vibration experiment of the PZT patch is carried out to verify the proposed two-dimensional (2D) electromechanical impedance model. It can be found that the proposed model is effective by comparing the theoretical formula and the experimental results.","PeriodicalId":243839,"journal":{"name":"2016 Symposium on Piezoelectricity, Acoustic Waves, and Device Applications (SPAWDA)","volume":"159 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134296593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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