Pub Date : 2010-05-01DOI: 10.1109/TMAG.2009.2038482
L. Wu, Z.Q. Zhu, J. Chen, Z. Xia, G. Jewell
The split ratio has been optimized for the maximum torque density when the airgap flux density is fixed in existing papers. However, the airgap flux density can vary with the split ratio significantly in interior permanent magnet (IPM) machines due to flux focusing. Therefore, an optimal airgap flux density may exist, together with the optimal split ratio, for the maximum torque in IPM machines. This paper analytically optimizes the airgap flux density and split ratio individually, as well as the global optimum in terms of the torque density in the fractionalslot IPM machines with non-overlapping windings. In addition, the influence of pole-slot combination and tooth-tips on the optimal split ratio and airgap flux density is discussed. The analytical result is verified by the finite element analysis. It shows that the optimal split ratio reduces with the increase of the airgap flux density, and the preferred airgap flux density is around 0.5–0.7 times of maximum flux density in the stator teeth when the rare earth permanent magnets are employed.
{"title":"Optimal split ratio in fractional-slot interior permanent magnet machines with non-overlapping windings","authors":"L. Wu, Z.Q. Zhu, J. Chen, Z. Xia, G. Jewell","doi":"10.1109/TMAG.2009.2038482","DOIUrl":"https://doi.org/10.1109/TMAG.2009.2038482","url":null,"abstract":"The split ratio has been optimized for the maximum torque density when the airgap flux density is fixed in existing papers. However, the airgap flux density can vary with the split ratio significantly in interior permanent magnet (IPM) machines due to flux focusing. Therefore, an optimal airgap flux density may exist, together with the optimal split ratio, for the maximum torque in IPM machines. This paper analytically optimizes the airgap flux density and split ratio individually, as well as the global optimum in terms of the torque density in the fractionalslot IPM machines with non-overlapping windings. In addition, the influence of pole-slot combination and tooth-tips on the optimal split ratio and airgap flux density is discussed. The analytical result is verified by the finite element analysis. It shows that the optimal split ratio reduces with the increase of the airgap flux density, and the preferred airgap flux density is around 0.5–0.7 times of maximum flux density in the stator teeth when the rare earth permanent magnets are employed.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126190594","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075415
Hassan M. Kamel, Hany. M. Hasanien, H. E. A. Ibrahim
The paper presents a fuzzy logic controller (FLC) for permanent magnet synchronous motor (PMSM). The fuzzy logic controller is used for speed control of this type of motors. The dynamic response of (PMSM) with the proposed controller is studied during the starting process and under different load disturbances. The effectiveness of the proposed fuzzy logic controller is compared with that of the conventional PI controller. The proposed controller is used in order to overcome the nonlinearity problem of PMSM.
{"title":"Speed control of permanent magnet synchronous motor using fuzzy logic controller","authors":"Hassan M. Kamel, Hany. M. Hasanien, H. E. A. Ibrahim","doi":"10.1109/IEMDC.2009.5075415","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075415","url":null,"abstract":"The paper presents a fuzzy logic controller (FLC) for permanent magnet synchronous motor (PMSM). The fuzzy logic controller is used for speed control of this type of motors. The dynamic response of (PMSM) with the proposed controller is studied during the starting process and under different load disturbances. The effectiveness of the proposed fuzzy logic controller is compared with that of the conventional PI controller. The proposed controller is used in order to overcome the nonlinearity problem of PMSM.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115276126","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075409
T. Schoenen, A. Krings, D. van Treek, R. D. De Doncker
In hybrid and electrical vehicles the electric components have to be optimized to their limits. The voltage which is delivered by a high-voltage battery should be used fully by the machine. This paper describes the influence of the dc-link voltage on the efficiency and the operating limits of the electric system. For the optimal usage of the dc-link voltage, the converter control has to be extended to the six-step mode. This paper starts with a short introduction describing the electrical components of the developed hybrid vehicle. Afterwards the restrictions due to the voltage limit of the high voltage battery are analyzed. A field oriented control (FOC) is chosen to achieve a high performance control system. However, the field oriented control is not capable to fully utilize the available dc-link voltage. As will be shown it is possible to improve the control strategy of the electrical machine. Especially in applications with limited dc-link voltage and high power density, the new control strategy leads to a better utilization and a higher efficiency of the electrical system.
{"title":"Maximum DC-link voltage utilization for optimal operation of IPMSM","authors":"T. Schoenen, A. Krings, D. van Treek, R. D. De Doncker","doi":"10.1109/IEMDC.2009.5075409","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075409","url":null,"abstract":"In hybrid and electrical vehicles the electric components have to be optimized to their limits. The voltage which is delivered by a high-voltage battery should be used fully by the machine. This paper describes the influence of the dc-link voltage on the efficiency and the operating limits of the electric system. For the optimal usage of the dc-link voltage, the converter control has to be extended to the six-step mode. This paper starts with a short introduction describing the electrical components of the developed hybrid vehicle. Afterwards the restrictions due to the voltage limit of the high voltage battery are analyzed. A field oriented control (FOC) is chosen to achieve a high performance control system. However, the field oriented control is not capable to fully utilize the available dc-link voltage. As will be shown it is possible to improve the control strategy of the electrical machine. Especially in applications with limited dc-link voltage and high power density, the new control strategy leads to a better utilization and a higher efficiency of the electrical system.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115674074","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075418
A. Tariq, C. Niño, E. Strangas
This paper presents a faster and simpler approach for the calculation of iron and magnet losses of an IPMSM than Finite Element Analysis. It uses large elements and takes into account the magnetic saturation and magnet eddy currents. The machine is represented by its magnetic equivalent circuit, consisting of non-linear and constant reluctance elements and flux sources. Solution of non-linear magnetic circuit is obtained by an iterative method. The results allow the calculation of losses and efficiency of the machine. Owing to the approximations used in the formulation of the magnetic equivalent circuit, this method is less accurate but faster than non-linear transient magnetic FEM, and is more useful for the comparison of different machine designs during design optimization process.
{"title":"A novel numerical method for the calculation of iron and magnet losses of IPMSMs","authors":"A. Tariq, C. Niño, E. Strangas","doi":"10.1109/IEMDC.2009.5075418","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075418","url":null,"abstract":"This paper presents a faster and simpler approach for the calculation of iron and magnet losses of an IPMSM than Finite Element Analysis. It uses large elements and takes into account the magnetic saturation and magnet eddy currents. The machine is represented by its magnetic equivalent circuit, consisting of non-linear and constant reluctance elements and flux sources. Solution of non-linear magnetic circuit is obtained by an iterative method. The results allow the calculation of losses and efficiency of the machine. Owing to the approximations used in the formulation of the magnetic equivalent circuit, this method is less accurate but faster than non-linear transient magnetic FEM, and is more useful for the comparison of different machine designs during design optimization process.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124396729","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075206
W. Abu-Elhaija
When operating three phase induction motor with single phase supply the motor behavior becomes complicated, owing to the emergence of negative and zero sequence components in winding currents. This paper analyzes the behavior of small rating three phase induction motor connected to one phase supply taking into account the variation of rotor resistance with slip for different stator connections. The proper capacitor required for canceling negative sequence component of stator winding voltages is dependent on the rotor resistance and slip values and this capacitance differ for each connection.
{"title":"Effect of variable slip rotor impedance on the performance of singly excited three phase induction motor","authors":"W. Abu-Elhaija","doi":"10.1109/IEMDC.2009.5075206","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075206","url":null,"abstract":"When operating three phase induction motor with single phase supply the motor behavior becomes complicated, owing to the emergence of negative and zero sequence components in winding currents. This paper analyzes the behavior of small rating three phase induction motor connected to one phase supply taking into account the variation of rotor resistance with slip for different stator connections. The proper capacitor required for canceling negative sequence component of stator winding voltages is dependent on the rotor resistance and slip values and this capacitance differ for each connection.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124438089","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075378
M. Comanescu, T. Batzel
The paper discusses the problem of rotor position estimation for the nonsalient permanent magnet synchronous motor (PMSM) and presents two reduced order observers that are based on the machine's model in the stationary reference frame. The first observer estimates the machine's stator flux linkages and then computes the rotor fluxes and the rotor position. The second observer estimates the back emfs of the PMSM and allows for direct calculation of the rotor angle. Both methods are developed under the assumption that the speed of the motor is known (the motor's speed is an input into the observers). The observers are designed in the framework of nonlinear control; their stability and rate of convergence is discussed. The methods proposed are directly applicable to rotor position estimation for sensorless nonsalient PMSM drives.
{"title":"Reduced order observers for rotor position estimation of nonsalient PMSM","authors":"M. Comanescu, T. Batzel","doi":"10.1109/IEMDC.2009.5075378","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075378","url":null,"abstract":"The paper discusses the problem of rotor position estimation for the nonsalient permanent magnet synchronous motor (PMSM) and presents two reduced order observers that are based on the machine's model in the stationary reference frame. The first observer estimates the machine's stator flux linkages and then computes the rotor fluxes and the rotor position. The second observer estimates the back emfs of the PMSM and allows for direct calculation of the rotor angle. Both methods are developed under the assumption that the speed of the motor is known (the motor's speed is an input into the observers). The observers are designed in the framework of nonlinear control; their stability and rate of convergence is discussed. The methods proposed are directly applicable to rotor position estimation for sensorless nonsalient PMSM drives.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116969385","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075230
M. Chomat, L. Schreier, J. Bendl
Electric drives may be negatively affected by non-standard conditions in the power network such as voltage unbalance, which may arise in three-phase power networks. The unbalance can be caused by a failure in the network or by unbalanced load in the vicinity of the affected drive. Unsymmetrical voltages at the input of a voltage source inverter cause pulsations in the DC-link voltage when not properly taken care of. This may result in reduced power capabilities of the drive. The paper deals with the methods to address this problem and with the limitations placed on the drive when operated from the unbalanced voltage supply. Influence of circuit parameters on the operating regions and their constraints are particularly dealt with.
{"title":"Influence of circuit parameters on operating regions of PWM rectifier under unbalanced voltage supply","authors":"M. Chomat, L. Schreier, J. Bendl","doi":"10.1109/IEMDC.2009.5075230","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075230","url":null,"abstract":"Electric drives may be negatively affected by non-standard conditions in the power network such as voltage unbalance, which may arise in three-phase power networks. The unbalance can be caused by a failure in the network or by unbalanced load in the vicinity of the affected drive. Unsymmetrical voltages at the input of a voltage source inverter cause pulsations in the DC-link voltage when not properly taken care of. This may result in reduced power capabilities of the drive. The paper deals with the methods to address this problem and with the limitations placed on the drive when operated from the unbalanced voltage supply. Influence of circuit parameters on the operating regions and their constraints are particularly dealt with.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"114 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117211067","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075416
T. Raminosoa, C. Gerada, Nazri Othman
The necessary reliability of a safety critical drive system is often partly achieved by using fault tolerant electrical machines. Although there are various degrees as to what types of faults and to the duration the machine has to tolerate, these generally include open and short circuit winding faults. There are numerous published literatures on the design of fault tolerant machines as well as on control algorithms used to maintain drive operation with an incurred fault. This paper is set to look at the effects of various fault tolerant control methods on the losses in three and five phase surface mount Permanent Magnet (PM) machines when in fault tolerant operation in order to be able to choose the correct rating for such conditions.
{"title":"Rating issues in fault tolerant PMSM","authors":"T. Raminosoa, C. Gerada, Nazri Othman","doi":"10.1109/IEMDC.2009.5075416","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075416","url":null,"abstract":"The necessary reliability of a safety critical drive system is often partly achieved by using fault tolerant electrical machines. Although there are various degrees as to what types of faults and to the duration the machine has to tolerate, these generally include open and short circuit winding faults. There are numerous published literatures on the design of fault tolerant machines as well as on control algorithms used to maintain drive operation with an incurred fault. This paper is set to look at the effects of various fault tolerant control methods on the losses in three and five phase surface mount Permanent Magnet (PM) machines when in fault tolerant operation in order to be able to choose the correct rating for such conditions.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117255790","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075195
B. Nikbakhtian, S. Talebi, P. Niazi, H. Toliyat
In this paper, a general analytical model for permanent magnet assisted synchronous reluctance machine with ‘N’ barrier, including space harmonics using winding function is being developed. Flux densities in the air gap, in the cutouts, and in the flux barriers are found. Back-EMF developed by the permanent magnets using winding function is derived. Equations for the d-axis and the q-axis inductances are also obtained. Electromagnetic torque is finally derived using the co-energy method. The developed analytical model results are supported by finite element analysis (FEA). Once the model is verified, then it is much faster to make changes to the geometrical dimensions and determine their effects on the torque, inductances, etc than FEA . The developed analytical model highlights the contributions of the reluctance variations and permanent magnets on the developed torque. An interactive software has been written in Matlab environment for ‘N’ flux barrier. Simulation results are obtained in the Ansoft/Maxwell environment for four flux barriers per pole. These results are supported by the experimental results obtained from a laboratory test bed.
{"title":"An analytical model for an N-flux barrier per pole permanent magnet-assisted synchronous reluctance motor","authors":"B. Nikbakhtian, S. Talebi, P. Niazi, H. Toliyat","doi":"10.1109/IEMDC.2009.5075195","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075195","url":null,"abstract":"In this paper, a general analytical model for permanent magnet assisted synchronous reluctance machine with ‘N’ barrier, including space harmonics using winding function is being developed. Flux densities in the air gap, in the cutouts, and in the flux barriers are found. Back-EMF developed by the permanent magnets using winding function is derived. Equations for the d-axis and the q-axis inductances are also obtained. Electromagnetic torque is finally derived using the co-energy method. The developed analytical model results are supported by finite element analysis (FEA). Once the model is verified, then it is much faster to make changes to the geometrical dimensions and determine their effects on the torque, inductances, etc than FEA . The developed analytical model highlights the contributions of the reluctance variations and permanent magnets on the developed torque. An interactive software has been written in Matlab environment for ‘N’ flux barrier. Simulation results are obtained in the Ansoft/Maxwell environment for four flux barriers per pole. These results are supported by the experimental results obtained from a laboratory test bed.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121039772","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 : 2009-05-03DOI: 10.1109/IEMDC.2009.5075394
H. M. Mzungu, M. Manyage, M. A. Khan, P. Barendse, T. Mthombeni, P. Pillay
This paper investigates the application of international induction machine efficiency testing standards in South Africa (SA). Motorized systems in SA account for up to 60% of the total electricity consumption. Recent power crisis in SA has accelerated the need for motor efficiency optimization. The applications of minimum energy performance standards (MEPS) to increase motor efficiency have become the norm around the world. Most electric motors in South Africa are still being rewound, with no consideration for the potential loss of efficiency and the most-likely increase in energy consumption. The status of motor rewinds is not good. Efficiency testing is underway at the University of Cape Town Machine Laboratory (UCTML) to investigate the impact of rewinding on motor efficiency in SA. As one of a very few testing labs, the power quality and instrumentation accuracy limits required in the standards were difficult to achieve. The result of this was errors and poor repeatability in testing. An alternative MG-set was used to create a supply that conforms to the standards. The impact of motor rewinding in SA is presented in this paper. It was found that procedures such as uncontrolled burnout temperatures result in efficiency drops of up to 4% at 25–50% loading points and up to 2% at rated loading points.
{"title":"Application of induction machine efficiency testing standards in South Africa","authors":"H. M. Mzungu, M. Manyage, M. A. Khan, P. Barendse, T. Mthombeni, P. Pillay","doi":"10.1109/IEMDC.2009.5075394","DOIUrl":"https://doi.org/10.1109/IEMDC.2009.5075394","url":null,"abstract":"This paper investigates the application of international induction machine efficiency testing standards in South Africa (SA). Motorized systems in SA account for up to 60% of the total electricity consumption. Recent power crisis in SA has accelerated the need for motor efficiency optimization. The applications of minimum energy performance standards (MEPS) to increase motor efficiency have become the norm around the world. Most electric motors in South Africa are still being rewound, with no consideration for the potential loss of efficiency and the most-likely increase in energy consumption. The status of motor rewinds is not good. Efficiency testing is underway at the University of Cape Town Machine Laboratory (UCTML) to investigate the impact of rewinding on motor efficiency in SA. As one of a very few testing labs, the power quality and instrumentation accuracy limits required in the standards were difficult to achieve. The result of this was errors and poor repeatability in testing. An alternative MG-set was used to create a supply that conforms to the standards. The impact of motor rewinding in SA is presented in this paper. It was found that procedures such as uncontrolled burnout temperatures result in efficiency drops of up to 4% at 25–50% loading points and up to 2% at rated loading points.","PeriodicalId":148263,"journal":{"name":"2009 IEEE International Electric Machines and Drives Conference","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121336406","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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