Pub Date : 2009-10-23DOI: 10.1109/DEMPED.2009.5292773
Pinjia Zhang, Y. Duan, T. Habetler, B. Lu
Active thermal protection techniques have been proposed for the thermal protection of induction motors. By injecting dc signals, the dc model of induction motors can be used to estimate the stator winding resistance, and thus the average stator winding temperature. The injected dc signals may lead to magnetic saturation, which may degrade a motor's performance and increase heat dissipation in the motor. This paper presents a detailed analysis of the magnetic saturation caused by dc signal injection with its effects discussed. It is shown that the injected dc signal induces a varying magnetic saturation in each cycle. The effects of the magnetic saturation on the motor currents, the motor's thermal behavior and the estimation of the stator winding resistance and temperature are analyzed. A mathematical model of induction motor during dc signal injection is proposed with considerations of magnetic saturation. Such analysis is illustrated from finite-element simulation results and experimental results. It is shown that the magnetic saturation does not affect the performance of the stator resistance and temperature estimation, which proves the feasibility of these active thermal protection techniques under different load conditions.
{"title":"An analysis of magnetic saturation in induction motors during dc signal injection","authors":"Pinjia Zhang, Y. Duan, T. Habetler, B. Lu","doi":"10.1109/DEMPED.2009.5292773","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292773","url":null,"abstract":"Active thermal protection techniques have been proposed for the thermal protection of induction motors. By injecting dc signals, the dc model of induction motors can be used to estimate the stator winding resistance, and thus the average stator winding temperature. The injected dc signals may lead to magnetic saturation, which may degrade a motor's performance and increase heat dissipation in the motor. This paper presents a detailed analysis of the magnetic saturation caused by dc signal injection with its effects discussed. It is shown that the injected dc signal induces a varying magnetic saturation in each cycle. The effects of the magnetic saturation on the motor currents, the motor's thermal behavior and the estimation of the stator winding resistance and temperature are analyzed. A mathematical model of induction motor during dc signal injection is proposed with considerations of magnetic saturation. Such analysis is illustrated from finite-element simulation results and experimental results. It is shown that the magnetic saturation does not affect the performance of the stator resistance and temperature estimation, which proves the feasibility of these active thermal protection techniques under different load conditions.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125028824","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292785
G. Aroquiadassou, A. Mpanda-Mabwe, F. Betin, G. Capolino
This paper presents the simulation and experimental results of a 42V fault-tolerant six-phase induction machine (6PIM) with opened stator phases. The 6PIM has symmetrical 60 degrees displacement winding allowing fault-tolerant modes for an electric power steering (EPS) application. A Voltage Source Inverter (VSI) in closed-loop using a vector control feeds its. The 6PIM model is derived from the stator winding distribution on a conductor-by-conductor basis and the geometrical dimensions of the different slots. A case study by simulation and experimental tests on a six-phase squirrel-cage induction machine rating 90W, 14V, 50Hz, 2 poles is described and analyzed to validate the system performance in faulted modes. This paper presents also the torque ripple estimation in degraded mode using the dqO components.
{"title":"Six-phase induction machine drive model for fault-tolerant operation","authors":"G. Aroquiadassou, A. Mpanda-Mabwe, F. Betin, G. Capolino","doi":"10.1109/DEMPED.2009.5292785","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292785","url":null,"abstract":"This paper presents the simulation and experimental results of a 42V fault-tolerant six-phase induction machine (6PIM) with opened stator phases. The 6PIM has symmetrical 60 degrees displacement winding allowing fault-tolerant modes for an electric power steering (EPS) application. A Voltage Source Inverter (VSI) in closed-loop using a vector control feeds its. The 6PIM model is derived from the stator winding distribution on a conductor-by-conductor basis and the geometrical dimensions of the different slots. A case study by simulation and experimental tests on a six-phase squirrel-cage induction machine rating 90W, 14V, 50Hz, 2 poles is described and analyzed to validate the system performance in faulted modes. This paper presents also the torque ripple estimation in degraded mode using the dqO components.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125513969","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292753
M. Bertoluzzo, G. Buja, R. Keshri
The paper deals with the operation of a brushless DC drive during the phase commutation. At first, the various switching patterns that can be used to command the inverter are identified. It is demonstrated that the switching patterns are a combination of two basic commutation modes. For each mode, the current transients during the phase commutation are determined as well as two significant commutation-related quantities, namely the decay angle of the current in the outgoing phase and the maximum current excursion in the non-commutating phase. The results obtained for the two modes are then compared, showing that each switching pattern gives a brushless DC drive specific properties.
{"title":"Brushless DC drive operation during phase commutation under various switching patterns","authors":"M. Bertoluzzo, G. Buja, R. Keshri","doi":"10.1109/DEMPED.2009.5292753","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292753","url":null,"abstract":"The paper deals with the operation of a brushless DC drive during the phase commutation. At first, the various switching patterns that can be used to command the inverter are identified. It is demonstrated that the switching patterns are a combination of two basic commutation modes. For each mode, the current transients during the phase commutation are determined as well as two significant commutation-related quantities, namely the decay angle of the current in the outgoing phase and the maximum current excursion in the non-commutating phase. The results obtained for the two modes are then compared, showing that each switching pattern gives a brushless DC drive specific properties.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125765499","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292804
B. Trajin, M. Chabert, J. Régnier, J. Faucher
This paper deals with mechanical fault monitoring in induction machines from stator current measurements. The considered faults lead to amplitude and/or phase modulations of the measured stator current. The different faults can be characterized by their time-frequency signatures via the Wigner distribution. The time-frequency representations apply to complex signals that may be obtained through the Hubert transform of the real measured signal. In case of high frequency modulations, it can not be taken advantage of the time frequency signatures. This study proposes an alternative complex signal representation for modulated stator currents. The so-called space vector is obtained through the Concordia transform. From three stator current measurements, the Concordia transform builds a complex vector which conveniently carries the information about phase and amplitude modulations. This paper applies and compares the Wigner distribution computed with the Hilbert and Concordia transforms in case of simulated and experimental signals with various modulation frequency ranges.
{"title":"Wigner distribution for the diagnosis of high frequency amplitude and phase modulations on stator currents of induction machine","authors":"B. Trajin, M. Chabert, J. Régnier, J. Faucher","doi":"10.1109/DEMPED.2009.5292804","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292804","url":null,"abstract":"This paper deals with mechanical fault monitoring in induction machines from stator current measurements. The considered faults lead to amplitude and/or phase modulations of the measured stator current. The different faults can be characterized by their time-frequency signatures via the Wigner distribution. The time-frequency representations apply to complex signals that may be obtained through the Hubert transform of the real measured signal. In case of high frequency modulations, it can not be taken advantage of the time frequency signatures. This study proposes an alternative complex signal representation for modulated stator currents. The so-called space vector is obtained through the Concordia transform. From three stator current measurements, the Concordia transform builds a complex vector which conveniently carries the information about phase and amplitude modulations. This paper applies and compares the Wigner distribution computed with the Hilbert and Concordia transforms in case of simulated and experimental signals with various modulation frequency ranges.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129625752","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292764
M. Dobriceanu, A. Bitoleanu, M. Popescu, E. Subţirelu, Octavian Dan Dobriceanu
The paper describes medium voltage electrical stations in which there is going to be implemented an automated monitoring system formed of local data acquisition, protection and control equipments mounted at the level of each cell within the electrical stations. This monitoring system is based on software packages for data acquisition, storing, data transmission and processing, monitoring and analysis. Tasks entailing the protection of operating plant, supervision of the system, detection and provision of measured values and messages for cases of operation, recording and evaluating measured values and messages for disturbances, control and locking functions as well as various possibilities of communication are to be mentioned here as being of great importance. In this way, the system is to help the human factor in taking optimal decisions in monitoring the electrical stations, by offering adequate information in a specific format. The internal modular set-up of hardware and software permits flexible inclusion of extensions and customers requirements according to needs.
{"title":"Electrical stations real-time monitoring using combined protection and control systems","authors":"M. Dobriceanu, A. Bitoleanu, M. Popescu, E. Subţirelu, Octavian Dan Dobriceanu","doi":"10.1109/DEMPED.2009.5292764","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292764","url":null,"abstract":"The paper describes medium voltage electrical stations in which there is going to be implemented an automated monitoring system formed of local data acquisition, protection and control equipments mounted at the level of each cell within the electrical stations. This monitoring system is based on software packages for data acquisition, storing, data transmission and processing, monitoring and analysis. Tasks entailing the protection of operating plant, supervision of the system, detection and provision of measured values and messages for cases of operation, recording and evaluating measured values and messages for disturbances, control and locking functions as well as various possibilities of communication are to be mentioned here as being of great importance. In this way, the system is to help the human factor in taking optimal decisions in monitoring the electrical stations, by offering adequate information in a specific format. The internal modular set-up of hardware and software permits flexible inclusion of extensions and customers requirements according to needs.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124203333","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292775
P. M. de la Barrera, M. Curti, Guillermo R. Bossio, G. García, J. Solsona
A non-destructive method to analyze stator core faults on induction motors is presented and developed in the present work. It allows generating entirely reversible faults of different magnitudes. The quantification of fault severity was performed through the stator core interlaminar insulation test and through no-load test. The obtained experimental results show the feasibility of the method and the detectability of generated faults, which makes it a useful method to develop new diagnosis strategies.
{"title":"Experimental generation and quantification of stator core faults on induction motors","authors":"P. M. de la Barrera, M. Curti, Guillermo R. Bossio, G. García, J. Solsona","doi":"10.1109/DEMPED.2009.5292775","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292775","url":null,"abstract":"A non-destructive method to analyze stator core faults on induction motors is presented and developed in the present work. It allows generating entirely reversible faults of different magnitudes. The quantification of fault severity was performed through the stator core interlaminar insulation test and through no-load test. The obtained experimental results show the feasibility of the method and the detectability of generated faults, which makes it a useful method to develop new diagnosis strategies.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"160 8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129014996","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292757
C. Bianchini, F. Immovilli, M. Cocconcelli, R. Rubini, A. Bellini
Electric linear motors are spreading in industrial automation, because they allow for direct drive applications with very high dynamic performances, reliability and flexibility in trajectory generation. The moving part of the motor is linked to the fixed part by means of linear bearings. As in many other electric machines, bearings represents one of the most vulnerable part because they are prone to wear and contamination. In case of linear roller bearings this issue is even more critical as the rail cannot be easily fully enclosed and protected from environmental contamination, unlike the radial rotating bearing counterpart. This paper presents a diagnostic method based on vibration analysis to recognize the signature frequency of the fault.
{"title":"Fault diagnosis of linear bearings in brushless AC linear motors","authors":"C. Bianchini, F. Immovilli, M. Cocconcelli, R. Rubini, A. Bellini","doi":"10.1109/DEMPED.2009.5292757","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292757","url":null,"abstract":"Electric linear motors are spreading in industrial automation, because they allow for direct drive applications with very high dynamic performances, reliability and flexibility in trajectory generation. The moving part of the motor is linked to the fixed part by means of linear bearings. As in many other electric machines, bearings represents one of the most vulnerable part because they are prone to wear and contamination. In case of linear roller bearings this issue is even more critical as the rail cannot be easily fully enclosed and protected from environmental contamination, unlike the radial rotating bearing counterpart. This paper presents a diagnostic method based on vibration analysis to recognize the signature frequency of the fault.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114367384","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292762
M. Orkisz, M. Wnek, P. Joerg, Klaus Ruetten, E. Jellum
Variable speed drives are becoming the method of choice for powering AC motors in many industrial applications. They allow for flexible speed control, substantial energy savings, and reduced stress during motor start-up, all of which lead to lower lifecycle costs for the shaft line. Modern drives, in order to perform their controlling function, are equipped with sensors, hardware and software to measure or compute a number of signals (for example, current, torque, speed, frequency, power, flux, etc.). This data is available and can be used for diagnostic purposes. These signals can be analyzed for their spectral content, used for monitoring the operating point, for examining cyclic processes, etc. The data is freely available, but the format, quality and quantity are determined by the hardware. Furthermore, variable speed drives change the output frequency to follow desired process parameters. This work presents selected methods for handling these difficulties and turning them to our advantage. Some examples of these methods application to industrial data are presented. These results prove that a variable speed drive can be a valuable source of diagnostic data not only for the drive itself, but also for the entire driven process.
{"title":"Selected data analysis techniques for equipment monitoring using drive's control signals","authors":"M. Orkisz, M. Wnek, P. Joerg, Klaus Ruetten, E. Jellum","doi":"10.1109/DEMPED.2009.5292762","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292762","url":null,"abstract":"Variable speed drives are becoming the method of choice for powering AC motors in many industrial applications. They allow for flexible speed control, substantial energy savings, and reduced stress during motor start-up, all of which lead to lower lifecycle costs for the shaft line. Modern drives, in order to perform their controlling function, are equipped with sensors, hardware and software to measure or compute a number of signals (for example, current, torque, speed, frequency, power, flux, etc.). This data is available and can be used for diagnostic purposes. These signals can be analyzed for their spectral content, used for monitoring the operating point, for examining cyclic processes, etc. The data is freely available, but the format, quality and quantity are determined by the hardware. Furthermore, variable speed drives change the output frequency to follow desired process parameters. This work presents selected methods for handling these difficulties and turning them to our advantage. Some examples of these methods application to industrial data are presented. These results prove that a variable speed drive can be a valuable source of diagnostic data not only for the drive itself, but also for the entire driven process.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125675585","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292766
A. Berdinyazov, F. Camci, M. Sevkli, S. Baskan
Maintenance is an inevitable reality in industry. Maintenance of a system usually involves maintenance of multiple components with multiple failure modes, each of which may require different maintenance policy (i.e., corrective (CM), preventive (PM), or condition based maintenance (CBM)). A maintenance policy may be best for one component and the worst for the other (CM may be best for a very cheap and non-critical component and the worst for a critical one). This paper presents an economical analysis method that identifies the best maintenance policy for a failure mode and/or component of a system.
{"title":"Economic analysis of maintenance policies for a system","authors":"A. Berdinyazov, F. Camci, M. Sevkli, S. Baskan","doi":"10.1109/DEMPED.2009.5292766","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292766","url":null,"abstract":"Maintenance is an inevitable reality in industry. Maintenance of a system usually involves maintenance of multiple components with multiple failure modes, each of which may require different maintenance policy (i.e., corrective (CM), preventive (PM), or condition based maintenance (CBM)). A maintenance policy may be best for one component and the worst for the other (CM may be best for a very cheap and non-critical component and the worst for a critical one). This paper presents an economical analysis method that identifies the best maintenance policy for a failure mode and/or component of a system.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123801213","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 : 2009-10-23DOI: 10.1109/DEMPED.2009.5292803
K. Wilson
We describe a new method for detecting characteristic bearing fault signatures from accelerometer vibration data based on a probabilistic model of the fault signal generation process. It is common to assume that single-point bearing defects cause periodic disturbances in bearing vibration signals, but this assumption may not be valid in practice. Our new method is less sensitive to departures from periodicity, such as fault disturbance amplitude and timing variations, than standard spectral or autocorrelation-based approaches. We demonstrate the utility of our method by distinguishing among inner race, outer race, and rolling element faults in a bearing fault test rig. Our method is significantly better than standard techniques at detecting rolling element (ball) faults.
{"title":"Probabilistic inter-disturbance interval estimation for bearing fault diagnosis","authors":"K. Wilson","doi":"10.1109/DEMPED.2009.5292803","DOIUrl":"https://doi.org/10.1109/DEMPED.2009.5292803","url":null,"abstract":"We describe a new method for detecting characteristic bearing fault signatures from accelerometer vibration data based on a probabilistic model of the fault signal generation process. It is common to assume that single-point bearing defects cause periodic disturbances in bearing vibration signals, but this assumption may not be valid in practice. Our new method is less sensitive to departures from periodicity, such as fault disturbance amplitude and timing variations, than standard spectral or autocorrelation-based approaches. We demonstrate the utility of our method by distinguishing among inner race, outer race, and rolling element faults in a bearing fault test rig. Our method is significantly better than standard techniques at detecting rolling element (ball) faults.","PeriodicalId":405777,"journal":{"name":"2009 IEEE International Symposium on Diagnostics for Electric Machines, Power Electronics and Drives","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121085522","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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