Pub Date : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350324
C. Stuebig, B. Ponick
Innovation in the area of electromobility relies primarily on the performance of the electrical drive system of the automobile. Motor concepts used in electromobility mostly consist of three-phase electrical machines like induction machines (IM) or permanent magnet synchronous machines (PMSM). Both machine designs rely on a rotating three-phase magnetic field in the air gap of the motor which is the result of the superimposed alternating fields of three phase currents. A knowledge of the underlying principles of electromagnetic field theory is a must for designers of all kinds of motors, especially for the highly utilized motors used in automobile applications. Students frequently express difficulties in understanding the basic theory of electromagnetic fields in rotating electrical machines. To further their understanding of the theory involved, an experimental motor has been developed. Using this motor, students have to design and implement different winding schemes. The motor design is kept simple, using basic technology such as a laminated stator core, simple coils and a rudimentary squirrel cage rotor. The experiment helps students to comprehend electromagnetic field theory with special consideration of electrical machines and is highly praised by students for its practical orientation.
{"title":"Practical experiment for students: Winding an induction machine","authors":"C. Stuebig, B. Ponick","doi":"10.1109/ICELMACH.2012.6350324","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350324","url":null,"abstract":"Innovation in the area of electromobility relies primarily on the performance of the electrical drive system of the automobile. Motor concepts used in electromobility mostly consist of three-phase electrical machines like induction machines (IM) or permanent magnet synchronous machines (PMSM). Both machine designs rely on a rotating three-phase magnetic field in the air gap of the motor which is the result of the superimposed alternating fields of three phase currents. A knowledge of the underlying principles of electromagnetic field theory is a must for designers of all kinds of motors, especially for the highly utilized motors used in automobile applications. Students frequently express difficulties in understanding the basic theory of electromagnetic fields in rotating electrical machines. To further their understanding of the theory involved, an experimental motor has been developed. Using this motor, students have to design and implement different winding schemes. The motor design is kept simple, using basic technology such as a laminated stator core, simple coils and a rudimentary squirrel cage rotor. The experiment helps students to comprehend electromagnetic field theory with special consideration of electrical machines and is highly praised by students for its practical orientation.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79362453","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350174
M. Rosyadi, S. Muyeen, R. Takahashi, J. Tamura
In this paper design and analysis of the grid side converter controller for Permanent Magnet Synchronous Generator (PMSG) based variable speed wind generator connected to a grid through LCL filter are presented. Since utilization of the LCL filter in output of the converter can lead to stability problem due to resonance at high frequency, determination of the controller parameters should be carefully designed. In this study, a simple dynamic model of the LCL filter is developed in order to analyze the performance of the control system easily. By using the bode diagram and step response of the system, the combination of gain controller and damping resistance parameters can be selected. The proposed method has been implemented on the grid side controller design for 2.5 MW PMSG based variable speed wind generator. The simulation results show that the proposed method is very useful and good response performance of the control system can be achieved.
{"title":"New controller design for PMSG based wind generator with LCL-filter considered","authors":"M. Rosyadi, S. Muyeen, R. Takahashi, J. Tamura","doi":"10.1109/ICELMACH.2012.6350174","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350174","url":null,"abstract":"In this paper design and analysis of the grid side converter controller for Permanent Magnet Synchronous Generator (PMSG) based variable speed wind generator connected to a grid through LCL filter are presented. Since utilization of the LCL filter in output of the converter can lead to stability problem due to resonance at high frequency, determination of the controller parameters should be carefully designed. In this study, a simple dynamic model of the LCL filter is developed in order to analyze the performance of the control system easily. By using the bode diagram and step response of the system, the combination of gain controller and damping resistance parameters can be selected. The proposed method has been implemented on the grid side controller design for 2.5 MW PMSG based variable speed wind generator. The simulation results show that the proposed method is very useful and good response performance of the control system can be achieved.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85645873","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350314
M. V. D. Giet, K. Kasper, R. D. Doncker, K. Hameyer
Acoustic noise and vibration of electrical machines becomes increasingly relevant. The determination of equivalent mechanical material parameters of electrical steel is therefore necessary to bound the computational costs of the structural dynamic simulation to practical levels. An analytical model based on fundamental laws of mixture is compared to three different experimental approaches to from test objects. The following approaches are reviewed and compared: Static pressure test, ultrasonic measurements and the fitting of eigenfrequencies between measurement and Finite Element analysis. The forced vibration spectra show good agreement for the FEM fit and the ultrasonic approach. It verified that the FEM fit gives physically correct values.
{"title":"Material parameters for the structural dynamic simulation of electrical machines","authors":"M. V. D. Giet, K. Kasper, R. D. Doncker, K. Hameyer","doi":"10.1109/ICELMACH.2012.6350314","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350314","url":null,"abstract":"Acoustic noise and vibration of electrical machines becomes increasingly relevant. The determination of equivalent mechanical material parameters of electrical steel is therefore necessary to bound the computational costs of the structural dynamic simulation to practical levels. An analytical model based on fundamental laws of mixture is compared to three different experimental approaches to from test objects. The following approaches are reviewed and compared: Static pressure test, ultrasonic measurements and the fitting of eigenfrequencies between measurement and Finite Element analysis. The forced vibration spectra show good agreement for the FEM fit and the ultrasonic approach. It verified that the FEM fit gives physically correct values.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77054192","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350202
A. Aktaibi, M. Rahman
This paper presents a successful implementation of d-q axis and wavelet packet transform based hybrid technique for protection of power transformers. This characterization helps to develop an improved differential relay to detect and discriminate internal faults from inrush currents in power transformers. This hybrid method provides accurate information with only one level of the wavelet packet transform (WPT) of the d-q components of the differential current for power transformer protection. A real-time experiment has been carried out for different normal and abnormal operating conditions such as magnetizing inrush and internal incipient faults for different cases of loading to test the efficacy of the proposed algorithm. The experimental results show the efficiency and reliability of the proposed technique.
{"title":"A novel technique for differential protection of power transformers","authors":"A. Aktaibi, M. Rahman","doi":"10.1109/ICELMACH.2012.6350202","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350202","url":null,"abstract":"This paper presents a successful implementation of d-q axis and wavelet packet transform based hybrid technique for protection of power transformers. This characterization helps to develop an improved differential relay to detect and discriminate internal faults from inrush currents in power transformers. This hybrid method provides accurate information with only one level of the wavelet packet transform (WPT) of the d-q components of the differential current for power transformer protection. A real-time experiment has been carried out for different normal and abnormal operating conditions such as magnetizing inrush and internal incipient faults for different cases of loading to test the efficacy of the proposed algorithm. The experimental results show the efficiency and reliability of the proposed technique.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77141815","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350269
Y. Kano, T. Kosaka, N. Matsui, M. Fujitsuna
We present the design of a saliency-based sensorless drive interior permanent magnet synchronous motor (IPMSM) for a traction drive in hybrid electric vehicles (HEVs), and we introduce the sensorless safety operation region (SSOR), which accounts for cross-coupling magnetic saturation and harmonics of inductance distributions. The SSOR defines a working point under the maximum torque per ampere (MTPA) trajectory in which the motor can perform sensorless operation with a guaranteed performance in the steady state. The reliability of the SSOR was verified by experiments using two prototypes. The influence of the IPM motor geometry on the SSOR was then examined. Consequently, the design guidelines were established to obtain a suitable motor geometry that can maximize the torque capability and the stability during the sensorless drive. Under the restricted specifications of dimensions and requirements, the 100 Nm-10 kW 12-pole, 18-slot IPMSM is optimally designed for the target traction drive in HEVs. The validity of the proposed design was verified using a MATLAB/SIMULINK-based dynamic simulator.
{"title":"Sensorless-oriented design of concentrated-winding IPM motors for HEV drive application","authors":"Y. Kano, T. Kosaka, N. Matsui, M. Fujitsuna","doi":"10.1109/ICELMACH.2012.6350269","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350269","url":null,"abstract":"We present the design of a saliency-based sensorless drive interior permanent magnet synchronous motor (IPMSM) for a traction drive in hybrid electric vehicles (HEVs), and we introduce the sensorless safety operation region (SSOR), which accounts for cross-coupling magnetic saturation and harmonics of inductance distributions. The SSOR defines a working point under the maximum torque per ampere (MTPA) trajectory in which the motor can perform sensorless operation with a guaranteed performance in the steady state. The reliability of the SSOR was verified by experiments using two prototypes. The influence of the IPM motor geometry on the SSOR was then examined. Consequently, the design guidelines were established to obtain a suitable motor geometry that can maximize the torque capability and the stability during the sensorless drive. Under the restricted specifications of dimensions and requirements, the 100 Nm-10 kW 12-pole, 18-slot IPMSM is optimally designed for the target traction drive in HEVs. The validity of the proposed design was verified using a MATLAB/SIMULINK-based dynamic simulator.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81008360","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350154
N. Benyahia, N. Benamrouche, T. Rekioua
This paper presents a study of proton exchange membrane (PEM) fuel cell modules for small ship applications. The advantages of modules architecture are related to an increased fault tolerance and high power ratings achieved through power segmentation. The main weak point of fuel cells is slow dynamics. However, the very fast power response and high specific power of a supercapacitor complement the slower power output of the PEM fuel cell to produce the compatibility and performance characteristics needed by the load. A supercapacitor offers an additional flexibility to prevent starvation phenomena, improve performance and increase lifetime. To verify the proposed principle, an emulator system is realized with a dSPACE for the PEM fuel cell.
{"title":"Modeling, design and simulation of fuel cell modules for small marine applications","authors":"N. Benyahia, N. Benamrouche, T. Rekioua","doi":"10.1109/ICELMACH.2012.6350154","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350154","url":null,"abstract":"This paper presents a study of proton exchange membrane (PEM) fuel cell modules for small ship applications. The advantages of modules architecture are related to an increased fault tolerance and high power ratings achieved through power segmentation. The main weak point of fuel cells is slow dynamics. However, the very fast power response and high specific power of a supercapacitor complement the slower power output of the PEM fuel cell to produce the compatibility and performance characteristics needed by the load. A supercapacitor offers an additional flexibility to prevent starvation phenomena, improve performance and increase lifetime. To verify the proposed principle, an emulator system is realized with a dSPACE for the PEM fuel cell.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85896653","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6351842
K. Nakamura, O. Ichinokura
This paper describes a super-multipolar permanent magnet reluctance generator (PMRG) for small-scale renewable energy generation. The numbers of stator and rotor poles of the PMRG are 72 and 96 respectively, in order to be directly connected to the turbine without a gear box. The rated power of the designed PMRG is about 1.0 kW at 100 rpm. The PMRG has two features for reducing torque ripple; the first one is a two-stacked structure, namely, one rotor is shifted by 180 deg. in electrical angle from the other rotor; the second one is that the rotor pole-tips are cut off so that the torque waveform consists of only odd-harmonics. In such a structure, the torque ripple of the PMRG can be reduced drastically. In this paper, first, the shape of rotor pole-tips is optimized by two-dimensional finite element method (2D-FEM) coupled with a general purpose optimization program. Next, the load characteristics of the PMRG obtained from 3D-FEM are indicated. Finally, the measured characteristics of the developed 72/96-pole PMRG are described.
{"title":"Super-multipolar permanent magnet reluctance generator designed for small-scale renewable energy generation","authors":"K. Nakamura, O. Ichinokura","doi":"10.1109/ICELMACH.2012.6351842","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6351842","url":null,"abstract":"This paper describes a super-multipolar permanent magnet reluctance generator (PMRG) for small-scale renewable energy generation. The numbers of stator and rotor poles of the PMRG are 72 and 96 respectively, in order to be directly connected to the turbine without a gear box. The rated power of the designed PMRG is about 1.0 kW at 100 rpm. The PMRG has two features for reducing torque ripple; the first one is a two-stacked structure, namely, one rotor is shifted by 180 deg. in electrical angle from the other rotor; the second one is that the rotor pole-tips are cut off so that the torque waveform consists of only odd-harmonics. In such a structure, the torque ripple of the PMRG can be reduced drastically. In this paper, first, the shape of rotor pole-tips is optimized by two-dimensional finite element method (2D-FEM) coupled with a general purpose optimization program. Next, the load characteristics of the PMRG obtained from 3D-FEM are indicated. Finally, the measured characteristics of the developed 72/96-pole PMRG are described.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84152940","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6349893
I. Erceg, D. Sumina, M. Vrazic
The availability of a hydropower plant is very important. During the last few decades intermittent operation has increased, and power plants designed for base electrical energy production became the ones that cover peak power needs. This lead to greater strains on the stator package. Power generators are often very robust and can endure these new operating conditions but sometimes with reduced lifetime of stator package. Often, the main problem is a generator's cooling system. Older synchronous generators often have cooling system control with very rough steps. This paper describes such a generator, its problems and presents a possible solution for cooling system control.
{"title":"Modification of synchronous generator cooling system control","authors":"I. Erceg, D. Sumina, M. Vrazic","doi":"10.1109/ICELMACH.2012.6349893","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349893","url":null,"abstract":"The availability of a hydropower plant is very important. During the last few decades intermittent operation has increased, and power plants designed for base electrical energy production became the ones that cover peak power needs. This lead to greater strains on the stator package. Power generators are often very robust and can endure these new operating conditions but sometimes with reduced lifetime of stator package. Often, the main problem is a generator's cooling system. Older synchronous generators often have cooling system control with very rough steps. This paper describes such a generator, its problems and presents a possible solution for cooling system control.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82378728","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6349888
M. Petrinić, S. Car, A. Elez
Periodical changes in the magnetic field of a synchronous generator, and its mechanical or electrical unbalances, have effect on the armature voltage, current and electromagnetic forces. Determination of these values during the design stage of a machine gives insight in its possible operation problems, and enables their easier prevention. Quantities of interest can be determined by using the finite element method calculations. However, in order to obtain data that correspond to real working conditions of a machine, simulations of different operation points have to be done. The procedure described here provides algorithm for determination of synchronous generator load condition parameters. It relates to symmetrical 3-phase load, it is based on physically measurable values, and can be universally used on any synchronous generator with field winding. This method was applied on a 34 MVA generator and the obtained results show good agreement with the measured data.
{"title":"Iterative procedure for determination of synchronous generator load point using finite element method","authors":"M. Petrinić, S. Car, A. Elez","doi":"10.1109/ICELMACH.2012.6349888","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349888","url":null,"abstract":"Periodical changes in the magnetic field of a synchronous generator, and its mechanical or electrical unbalances, have effect on the armature voltage, current and electromagnetic forces. Determination of these values during the design stage of a machine gives insight in its possible operation problems, and enables their easier prevention. Quantities of interest can be determined by using the finite element method calculations. However, in order to obtain data that correspond to real working conditions of a machine, simulations of different operation points have to be done. The procedure described here provides algorithm for determination of synchronous generator load condition parameters. It relates to symmetrical 3-phase load, it is based on physically measurable values, and can be universally used on any synchronous generator with field winding. This method was applied on a 34 MVA generator and the obtained results show good agreement with the measured data.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82573527","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 : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350156
M. N. Ansari, A. K. Singh, P. Kumar
Electric vehicle (EV) application requires motor used in the drivetrain to be highly efficient, compact in size and of high power density. A unique and novel means to achieve the above motor features is using dual rotor motor (DRM). This paper presents the various possible structures of DRM. The analytical model of hybrid induction motor (IM) - permanent magnet motor (PM) based DRM is presented. Analytical model is framed to determine the steady state performance of DRM. DRM performance is also cross verified using FEM and compared with a conventional IM and PM of the same dimensions. It is observed for a given motor size, hybrid DRM gives increased power output. Hybrid DRM thus has higher power density highly suited for EV application.
{"title":"Performance analysis of a hybrid dual rotor motor for electric vehicle application","authors":"M. N. Ansari, A. K. Singh, P. Kumar","doi":"10.1109/ICELMACH.2012.6350156","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350156","url":null,"abstract":"Electric vehicle (EV) application requires motor used in the drivetrain to be highly efficient, compact in size and of high power density. A unique and novel means to achieve the above motor features is using dual rotor motor (DRM). This paper presents the various possible structures of DRM. The analytical model of hybrid induction motor (IM) - permanent magnet motor (PM) based DRM is presented. Analytical model is framed to determine the steady state performance of DRM. DRM performance is also cross verified using FEM and compared with a conventional IM and PM of the same dimensions. It is observed for a given motor size, hybrid DRM gives increased power output. Hybrid DRM thus has higher power density highly suited for EV application.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81353869","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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