Pub Date : 2007-05-03DOI: 10.1109/IEMDC.2007.383688
A. Sharaf, E. Elbakush, I.H. Alias, H. Okumus
This paper presents a switched mode model of a permanent magnet DC motor drive with a robust control scheme. The switched mode simulation model is developed for a using the Matlab/Simulink GUI environment. The model is based on the switching/pulsing sequence of the DC-DC chopper converter, which is used to supply controlled variable DC armature voltage to the motor. As the modulated DC voltage is applied to the motor, the energy stored in armature winding and rotating armature inertia is varied and need to be included in the model. In order to operate the motor at specified speed level with the required electrical torque for different load excursions, the DC-DC chopper converter is dynamically controlled by the General Predictive Speed Controller (GPC). The GPC is used as the main speed regulator due to its inherent ability to handle parameter variations and sudden excursions as an adaptive controller in nature. The performance of the GPC Scheme is validated by comparing the digital simulation results with those of obtained using the classical PI speed controller.
{"title":"A Switched Mode Simulation Model for a PMDC Motor Scheme Controlled by Predictive Dynamic Controller","authors":"A. Sharaf, E. Elbakush, I.H. Alias, H. Okumus","doi":"10.1109/IEMDC.2007.383688","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383688","url":null,"abstract":"This paper presents a switched mode model of a permanent magnet DC motor drive with a robust control scheme. The switched mode simulation model is developed for a using the Matlab/Simulink GUI environment. The model is based on the switching/pulsing sequence of the DC-DC chopper converter, which is used to supply controlled variable DC armature voltage to the motor. As the modulated DC voltage is applied to the motor, the energy stored in armature winding and rotating armature inertia is varied and need to be included in the model. In order to operate the motor at specified speed level with the required electrical torque for different load excursions, the DC-DC chopper converter is dynamically controlled by the General Predictive Speed Controller (GPC). The GPC is used as the main speed regulator due to its inherent ability to handle parameter variations and sudden excursions as an adaptive controller in nature. The performance of the GPC Scheme is validated by comparing the digital simulation results with those of obtained using the classical PI speed controller.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126999174","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.383697
H. Okumus, M. Aktas
Hysteresis band control is one of the simplest and most popular techniques used in direct torque control (DTC) of induction machine drives. However the conventional fixed band hysteresis control has a variable switching frequency which causes serious problems in DTC. In this paper, the adaptive hysteresis band control strategy is proposed, where the hysteresis band is controlled in real time as variation of applied voltage vectors. Thereby reducing the torque ripple whilst maintaining a constant torque switching frequency. The proposed adaptive hysteresis band control technique is verified by simulations. The system is first simulated by MATLAB and tested by hardware in the loop. Then, it is implemented based on a TMS320C6711, 32-bit fixed point digital signal processor. Experimental results prove the feasibility of the proposed strategy as compared with the conventional method.
{"title":"Direct Torque Control of Induction Machine Drives Using Adaptive Hysteresis Band for Constant Switching Frequency","authors":"H. Okumus, M. Aktas","doi":"10.1109/IEMDC.2007.383697","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383697","url":null,"abstract":"Hysteresis band control is one of the simplest and most popular techniques used in direct torque control (DTC) of induction machine drives. However the conventional fixed band hysteresis control has a variable switching frequency which causes serious problems in DTC. In this paper, the adaptive hysteresis band control strategy is proposed, where the hysteresis band is controlled in real time as variation of applied voltage vectors. Thereby reducing the torque ripple whilst maintaining a constant torque switching frequency. The proposed adaptive hysteresis band control technique is verified by simulations. The system is first simulated by MATLAB and tested by hardware in the loop. Then, it is implemented based on a TMS320C6711, 32-bit fixed point digital signal processor. Experimental results prove the feasibility of the proposed strategy as compared with the conventional method.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128040630","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.382698
R. Leidhold, P. Mutschler
The Magnetic Equivalent Circuit (MEC) method is investigated for modeling the synchronous-linear-motor characteristics used by sensorless methods. The characteristics of interest are the magnetic saliencies due to the saturation that the secondary flux produces in the primary, and saliencies modification due to the load. They are not represented in the standard Fundamental-Wave model, and the usual tool for analyzing them is the Finite Element Analysis (FEA). Nevertheless, as the FEA models require extremely high computation time for dynamic simulations, the use of MEC is proposed to be used in this paper. The MEC is derived from the motor geometry, magnetic characteristics of the involved materials, and the winding arrangement. Consequently, with this model, a sensorless method can be analyzed and simulated for a given motor design before its prototype is build. In order to test the model, the injection of a high-frequency alternating voltage, as used in some sensorless methods, is simulated with the proposed model as well as implemented experimentally. The obtained results show agreement between them, demonstrating that the model is viable for analysis of sensorless methods.
{"title":"Evaluation of Sensorless Methods for Synchronous-Linear-Motors by using a Magnetic Equivalent Circuit based Model","authors":"R. Leidhold, P. Mutschler","doi":"10.1109/IEMDC.2007.382698","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.382698","url":null,"abstract":"The Magnetic Equivalent Circuit (MEC) method is investigated for modeling the synchronous-linear-motor characteristics used by sensorless methods. The characteristics of interest are the magnetic saliencies due to the saturation that the secondary flux produces in the primary, and saliencies modification due to the load. They are not represented in the standard Fundamental-Wave model, and the usual tool for analyzing them is the Finite Element Analysis (FEA). Nevertheless, as the FEA models require extremely high computation time for dynamic simulations, the use of MEC is proposed to be used in this paper. The MEC is derived from the motor geometry, magnetic characteristics of the involved materials, and the winding arrangement. Consequently, with this model, a sensorless method can be analyzed and simulated for a given motor design before its prototype is build. In order to test the model, the injection of a high-frequency alternating voltage, as used in some sensorless methods, is simulated with the proposed model as well as implemented experimentally. The obtained results show agreement between them, demonstrating that the model is viable for analysis of sensorless methods.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132560090","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.382780
A. Haddoun, M. Benbouzid, D. Diallo, R. Abdessemed, J. Ghouili, K. Srairi
This paper presents system analysis, modeling and simulation of an EV with two independent rear wheel drives. The traction control system is designed to guarantee the EV dynamics and stability in case of no differential gears. Using two electrics in-wheel motors give the possibility to have a torque and speed control in each wheel. This control level improves the EV stability and the safety. The proposed traction control system uses the vehicle speed, which is different from wheels speed characterized by slip in the driving mode, an input. In this case, a generalized neural network algorithm is proposed to estimate the vehicle speed. In terms of the analysis and the simulations carried out, the conclusion can be drawn that the proposed system is feasible. Simulation results on a test vehicle propelled by two 37-kW induction motors showed that the proposed control approach operates satisfactorily.
{"title":"Analysis, Modeling and Neural Network Traction Control of an Electric Vehicle without Differential Gears","authors":"A. Haddoun, M. Benbouzid, D. Diallo, R. Abdessemed, J. Ghouili, K. Srairi","doi":"10.1109/IEMDC.2007.382780","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.382780","url":null,"abstract":"This paper presents system analysis, modeling and simulation of an EV with two independent rear wheel drives. The traction control system is designed to guarantee the EV dynamics and stability in case of no differential gears. Using two electrics in-wheel motors give the possibility to have a torque and speed control in each wheel. This control level improves the EV stability and the safety. The proposed traction control system uses the vehicle speed, which is different from wheels speed characterized by slip in the driving mode, an input. In this case, a generalized neural network algorithm is proposed to estimate the vehicle speed. In terms of the analysis and the simulations carried out, the conclusion can be drawn that the proposed system is feasible. Simulation results on a test vehicle propelled by two 37-kW induction motors showed that the proposed control approach operates satisfactorily.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133347147","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.383640
M. Drif, A. Cardoso
Detection of broken rotor bars has long been an important but difficult job in the detection area of motor faults. The characteristic frequency components of a faulted rotor in the stator current spectrum are very close to the power frequency component but by far less in amplitude, which brings about great difficulty for accurate detection. In this paper a new detection method based on the instantaneous phase-angle signature analysis is proposed for the diagnosis of rotor cage faults in operating three-phase induction motors. For that purpose, a mathematical model based on the winding function approach is used in order to simulate this type of fault and experimental tests are carried out on an induction motor with several faulty rotors. Simulation and experimental results are presented to show the merits of this novel approach for the detection of cage induction motor broken rotor bars.
{"title":"Rotor Cage Fault Diagnostics in Three-Phase Induction Motors, by the Instantaneous Phase-Angle Signature Analysis","authors":"M. Drif, A. Cardoso","doi":"10.1109/IEMDC.2007.383640","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383640","url":null,"abstract":"Detection of broken rotor bars has long been an important but difficult job in the detection area of motor faults. The characteristic frequency components of a faulted rotor in the stator current spectrum are very close to the power frequency component but by far less in amplitude, which brings about great difficulty for accurate detection. In this paper a new detection method based on the instantaneous phase-angle signature analysis is proposed for the diagnosis of rotor cage faults in operating three-phase induction motors. For that purpose, a mathematical model based on the winding function approach is used in order to simulate this type of fault and experimental tests are carried out on an induction motor with several faulty rotors. Simulation and experimental results are presented to show the merits of this novel approach for the detection of cage induction motor broken rotor bars.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"496 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133953272","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.382783
Yuchen Lu, H. Hess, B.K. Johnson
An innovative optimized space vector modulation method (OSVM) for 3ϕ-3ϕ matrix converter is proposed in this paper. This modulation method maximizes the modulability of reference vectors. It is a direct modulation method. The solution of OSVM immediately tells the modulability of reference vectors. An efficient algorithm for OSVM is provided and tested through simulations. Comparison with the conventional SVM methods is performed. Simulation results show the validity and the performance of OSVM.
{"title":"An Optimized Space-Vector Modulation Method for 3ϕ-3ϕ Matrix Converter","authors":"Yuchen Lu, H. Hess, B.K. Johnson","doi":"10.1109/IEMDC.2007.382783","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.382783","url":null,"abstract":"An innovative optimized space vector modulation method (OSVM) for 3ϕ-3ϕ matrix converter is proposed in this paper. This modulation method maximizes the modulability of reference vectors. It is a direct modulation method. The solution of OSVM immediately tells the modulability of reference vectors. An efficient algorithm for OSVM is provided and tested through simulations. Comparison with the conventional SVM methods is performed. Simulation results show the validity and the performance of OSVM.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"242 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132127441","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.382803
Amr Amin, M. I. Korfally, A. Sayed, O. Hegazy
In this paper, applying field orientation based on Particle Swarm Optimization (PSO) controls the speed of two-asymmetrical windings induction motor. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point. In addition, the electro-magnetic torque is also improved while maintaining a fast dynamic response. In this research, a novel approach is used to evaluate the optimal rotor flux level. This approach is based on Particle Swarm Optimization (PSO). PSO method is a member of the wide category of Swarm Intelligence methods (SI). This research presents two speed control strategies. These are field- oriented controller (FOC) and FOC based on PSO.. The results have demonstrated that the FOC based on PSO method saves more energy than the conventional FOC method.
{"title":"Swarm Intelligence-Based Controller of Two-Asymmetric Windings Induction Motor","authors":"Amr Amin, M. I. Korfally, A. Sayed, O. Hegazy","doi":"10.1109/IEMDC.2007.382803","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.382803","url":null,"abstract":"In this paper, applying field orientation based on Particle Swarm Optimization (PSO) controls the speed of two-asymmetrical windings induction motor. The maximum efficiency of the motor is obtained by the evaluation of optimal rotor flux at any operating point. In addition, the electro-magnetic torque is also improved while maintaining a fast dynamic response. In this research, a novel approach is used to evaluate the optimal rotor flux level. This approach is based on Particle Swarm Optimization (PSO). PSO method is a member of the wide category of Swarm Intelligence methods (SI). This research presents two speed control strategies. These are field- oriented controller (FOC) and FOC based on PSO.. The results have demonstrated that the FOC based on PSO method saves more energy than the conventional FOC method.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134127580","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.383649
Izaskun Sarasola, Javier Poza, Miguel A. Rodriguez, Gonzalo Abad
In this paper, a direct torque control strategy for the brushless doubly fed machine is presented. The classical direct torque control strategy for brushless doubly fed machines has been developed, obtaining the voltage vector table. The vector voltage table has been developed analyzing the flux and torque derivatives for each voltage vector as a function of control winding flux angle. Two types of simulations have been done, one for an ideal case and the other for a practical implementation. Simulation results show the effectiveness of the proposed control algorithm.
{"title":"Direct Torque Control for Brushless Doubly Fed Induction Machines","authors":"Izaskun Sarasola, Javier Poza, Miguel A. Rodriguez, Gonzalo Abad","doi":"10.1109/IEMDC.2007.383649","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383649","url":null,"abstract":"In this paper, a direct torque control strategy for the brushless doubly fed machine is presented. The classical direct torque control strategy for brushless doubly fed machines has been developed, obtaining the voltage vector table. The vector voltage table has been developed analyzing the flux and torque derivatives for each voltage vector as a function of control winding flux angle. Two types of simulations have been done, one for an ideal case and the other for a practical implementation. Simulation results show the effectiveness of the proposed control algorithm.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134417547","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.383681
C. Baguley, U. Madawala
Three-phase cage induction motors can be started on single-phase supply lines by field aligned starting (FAS) with minimal inrush currents. FAS is a technique that generates a high impulse-like torque to start a motor independent of the mains supply, before connecting the already spinning motor to the mains to operate in a standard Steinmetz connection. A dynamic model and parameter estimation method for FAS have previously been presented and experimentally validated. As the starting performance of FAS is largely governed by the values of a small number of key variables, this paper utilizes the dynamic model to investigate both the functionality and the impact of these variables on the starting performance. The results of the investigation suggest that the proper choice variable values is critical to a successful FAS design, and that the FAS model could effectively be used as a design aid to achieve improved FAS starting performance.
{"title":"Investigations into Performance Aspects of Field Aligned Starting","authors":"C. Baguley, U. Madawala","doi":"10.1109/IEMDC.2007.383681","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383681","url":null,"abstract":"Three-phase cage induction motors can be started on single-phase supply lines by field aligned starting (FAS) with minimal inrush currents. FAS is a technique that generates a high impulse-like torque to start a motor independent of the mains supply, before connecting the already spinning motor to the mains to operate in a standard Steinmetz connection. A dynamic model and parameter estimation method for FAS have previously been presented and experimentally validated. As the starting performance of FAS is largely governed by the values of a small number of key variables, this paper utilizes the dynamic model to investigate both the functionality and the impact of these variables on the starting performance. The results of the investigation suggest that the proper choice variable values is critical to a successful FAS design, and that the FAS model could effectively be used as a design aid to achieve improved FAS starting performance.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"91 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131889729","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 : 2007-05-03DOI: 10.1109/IEMDC.2007.383546
Seok-Hee Han, Thomas M. Jahns, W. Soong
A new magnetic circuit model is presented for an interior permanent magnet (IPM) synchronous machine, using a machine with three-phase distributed stator windings and three layers of flux barriers in the rotor as an example topology. The model accounts for: i) the effects of cross-coupled magnetic saturation caused by the salient rotor; ii) variation of magnetic saturation levels in the iron rotor bridges that are key elements of the unitary rotor laminations; iii) the effects of stator lamination slots on the airgap mmf distribution; and iv) the local variation of airgap permeance due to the stator slotting and the relative position of the rotor with respect to the stator. As a result of these features, the new model is capable of significantly improving the accuracy of electromagnetic performance predictions for aggressively-designed IPM machines compared to previously-available magnetic circuit models. Comparisons with finite-element analysis and measurement results are provided showing that the new model is much faster while delivering appealing accuracy compared to the FE method.
{"title":"A Magnetic Circuit Model for an IPM Synchronous Machine Incorporating Moving Airgap and Cross-Coupled Saturation Effects","authors":"Seok-Hee Han, Thomas M. Jahns, W. Soong","doi":"10.1109/IEMDC.2007.383546","DOIUrl":"https://doi.org/10.1109/IEMDC.2007.383546","url":null,"abstract":"A new magnetic circuit model is presented for an interior permanent magnet (IPM) synchronous machine, using a machine with three-phase distributed stator windings and three layers of flux barriers in the rotor as an example topology. The model accounts for: i) the effects of cross-coupled magnetic saturation caused by the salient rotor; ii) variation of magnetic saturation levels in the iron rotor bridges that are key elements of the unitary rotor laminations; iii) the effects of stator lamination slots on the airgap mmf distribution; and iv) the local variation of airgap permeance due to the stator slotting and the relative position of the rotor with respect to the stator. As a result of these features, the new model is capable of significantly improving the accuracy of electromagnetic performance predictions for aggressively-designed IPM machines compared to previously-available magnetic circuit models. Comparisons with finite-element analysis and measurement results are provided showing that the new model is much faster while delivering appealing accuracy compared to the FE method.","PeriodicalId":446844,"journal":{"name":"2007 IEEE International Electric Machines & Drives Conference","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133597336","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：