Pub Date : 2012-11-12DOI: 10.1109/ICELMACH.2012.6350193
T. Lin, L. Gong, Z. Zhu
This paper investigates the saliency in switched-flux permanent-magnet (SFPM) brushless AC (BLAC) motors. In order to use the method of high-frequency pulsating vector voltage carrier signal injection-based sensorless control techniques, the machine saliency is essential. However, the machine saliency behavior is complicated in real SFPM machines since it is dependent on the load condition. Furthermore, there may exhibit multiple saliencies due to the non-sinusoidal spatial distribution of machine reluctance. Saliency ratio and feasible region are usually used to describe the machine saliency level. It varies with fundamental excitation due to the magnetic saturation. Two simplified experimental procedures are employed for practical testing of saliency investigation in this paper, which could easily measure and obtain the machine saliency information without any knowledge of machine parameters. The experimental results show that the prototype machine has both primary and secondary (multiple saliencies) saliencies. The performance of rotor position estimation is implemented based on sensorless control at low and zero motor speed.
{"title":"Saliency investigation of switched-flux PM brushless AC machine for saliency-tracking-based sensorless control","authors":"T. Lin, L. Gong, Z. Zhu","doi":"10.1109/ICELMACH.2012.6350193","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350193","url":null,"abstract":"This paper investigates the saliency in switched-flux permanent-magnet (SFPM) brushless AC (BLAC) motors. In order to use the method of high-frequency pulsating vector voltage carrier signal injection-based sensorless control techniques, the machine saliency is essential. However, the machine saliency behavior is complicated in real SFPM machines since it is dependent on the load condition. Furthermore, there may exhibit multiple saliencies due to the non-sinusoidal spatial distribution of machine reluctance. Saliency ratio and feasible region are usually used to describe the machine saliency level. It varies with fundamental excitation due to the magnetic saturation. Two simplified experimental procedures are employed for practical testing of saliency investigation in this paper, which could easily measure and obtain the machine saliency information without any knowledge of machine parameters. The experimental results show that the prototype machine has both primary and secondary (multiple saliencies) saliencies. The performance of rotor position estimation is implemented based on sensorless control at low and zero motor speed.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"71 1","pages":"2238-2244"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84996896","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.2012.6349982
T. Bernardes, H. Grundling, H. Pinheiro
This paper proposes a new discrete-time sensor-less algorithm for current vector control of permanent magnet synchronous machines (PMSM). A discrete-time sliding mode current observer is proposed as well as the sliding and convergence conditions of the sliding mode are established. Then, an electric speed identification is proposed by using Lyapunov's direct method via a electromotive force (EMF) observer in the discrete-time domain. In addition, the stability of the proposed discrete-time observers is presented, and from them, the conditions to ensure convergence are derived. Therefore, the rotor position is identified directly of the observed EMF. Finally, experimental results are given to support the theoretical analysis as well as to demonstrate the good performance of the proposed discrete-time sensorless algorithm.
{"title":"Discrete time sliding mode observers for sensorless vector control of PMSM","authors":"T. Bernardes, H. Grundling, H. Pinheiro","doi":"10.1109/ICELMACH.2012.6349982","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349982","url":null,"abstract":"This paper proposes a new discrete-time sensor-less algorithm for current vector control of permanent magnet synchronous machines (PMSM). A discrete-time sliding mode current observer is proposed as well as the sliding and convergence conditions of the sliding mode are established. Then, an electric speed identification is proposed by using Lyapunov's direct method via a electromotive force (EMF) observer in the discrete-time domain. In addition, the stability of the proposed discrete-time observers is presented, and from them, the conditions to ensure convergence are derived. Therefore, the rotor position is identified directly of the observed EMF. Finally, experimental results are given to support the theoretical analysis as well as to demonstrate the good performance of the proposed discrete-time sensorless algorithm.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"63 1","pages":"893-899"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85015726","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.2012.6350150
T. Minav, L. Laurila, J. Pyrhonen
Electric drives offer effective means of directly controlling working machine hydraulic movements instead of using traditional valve control. This paper takes a step further and investigates the effect of the electric machine type applied in a direct electro hydraulic drive on the system efficiency of the electric energy recovery system of a hydraulic forklift. The control of the system is implemented directly with an electric motor drive without any control valves. A theoretical model is made and the model is verified by practical results. Permanent magnet motor and squirrel cage induction motor drives are compared. Finally, possible improvements of the efficiency in the suggested system are estimated.
{"title":"Effect of driving electric machine type on the system efficiency of an industrial forklift","authors":"T. Minav, L. Laurila, J. Pyrhonen","doi":"10.1109/ICELMACH.2012.6350150","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350150","url":null,"abstract":"Electric drives offer effective means of directly controlling working machine hydraulic movements instead of using traditional valve control. This paper takes a step further and investigates the effect of the electric machine type applied in a direct electro hydraulic drive on the system efficiency of the electric energy recovery system of a hydraulic forklift. The control of the system is implemented directly with an electric motor drive without any control valves. A theoretical model is made and the model is verified by practical results. Permanent magnet motor and squirrel cage induction motor drives are compared. Finally, possible improvements of the efficiency in the suggested system are estimated.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"10 1","pages":"1964-1970"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81912946","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.2012.6350070
Masahiro Hori, Mamoru Kimura, A. Komura, D. Kori, S. Masuda, Takayuki Koizumi
This paper describes our work in developing a 2.4-MW permanent magnet generator (PMG) for a diesel electric propulsion system. The PMG was designed by using a design method combining electromagnetic field analysis, stress analysis, and thermal and fluid analysis. Several generator characteristics were verified in examinations of a 2.4-MW PMG prototype.
{"title":"Study on permanent magnet generator for diesel electric propulsion system","authors":"Masahiro Hori, Mamoru Kimura, A. Komura, D. Kori, S. Masuda, Takayuki Koizumi","doi":"10.1109/ICELMACH.2012.6350070","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350070","url":null,"abstract":"This paper describes our work in developing a 2.4-MW permanent magnet generator (PMG) for a diesel electric propulsion system. The PMG was designed by using a design method combining electromagnetic field analysis, stress analysis, and thermal and fluid analysis. Several generator characteristics were verified in examinations of a 2.4-MW PMG prototype.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"24 1","pages":"1457-1462"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81923929","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.2012.6349997
Zengcai Qu, Toni Tuovinen, M. Hinkkanen
This paper deals with the modeling of the magnetic saturation in synchronous reluctance motors (SyRMs). The saturation is modeled by means of analytical expressions, which can be easily embedded in dynamic equivalent-circuit models. A modified power function - proposed in this paper - can take into account the cross saturation between the orthogonal windings, it is physically consistent, and the number of its parameters is small. The function can be used in real-time control applications and in computer simulations. The model fits well to the experimentally measured inductances of a 6.7-kW SyRM. As an application example, the proposed saturation model was implemented in a full-order observer of a motion-sensorless drive, and experimental results are shown.
{"title":"Inclusion of magnetic saturation in dynamic models of synchronous reluctance motors","authors":"Zengcai Qu, Toni Tuovinen, M. Hinkkanen","doi":"10.1109/ICELMACH.2012.6349997","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349997","url":null,"abstract":"This paper deals with the modeling of the magnetic saturation in synchronous reluctance motors (SyRMs). The saturation is modeled by means of analytical expressions, which can be easily embedded in dynamic equivalent-circuit models. A modified power function - proposed in this paper - can take into account the cross saturation between the orthogonal windings, it is physically consistent, and the number of its parameters is small. The function can be used in real-time control applications and in computer simulations. The model fits well to the experimentally measured inductances of a 6.7-kW SyRM. As an application example, the proposed saturation model was implemented in a full-order observer of a motion-sensorless drive, and experimental results are shown.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"313 1","pages":"994-1000"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79697423","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.2012.6349920
M. J. Picazo-Ródenas, R. Royo, J. Antonino-Daviu, J. Roger-Folch
This paper proposes a methodology for the computation of the energy balance and heating curves of an induction motor taking as a basis the information provided by the application of the infrared thermography. Moreover, use of infrared thermography data to diagnose rotor bar failures is preliminarily studied. In the paper, a 1.1 kW induction motor is tested. Thermography images of the chassis temperature are captured at each second during the whole startup transient, from standstill till steady-state, by using an infrared camera connected to a laptop computer fitted with an acquisition and analysis program. A model based on the calculation of the heat losses by convection and radiation through the frame of the machine is developed. It uses the geometrical dimensions as well as temperature values obtained from the thermography images. The developed model enables studying any motor configuration and operating conditions by just varying thermal and geometry parameters. Finally, a preliminary study relying on the possible use of Thermography data for diagnosis of rotor failures is carried out. Experimental data corresponding to a healthy machine and a machine with broken bars are analysed and compared. This methodology will be the baseline for further complex failure diagnosis in electric motors.
{"title":"Use of infrared thermography for computation of heating curves and preliminary failure detection in induction motors","authors":"M. J. Picazo-Ródenas, R. Royo, J. Antonino-Daviu, J. Roger-Folch","doi":"10.1109/ICELMACH.2012.6349920","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349920","url":null,"abstract":"This paper proposes a methodology for the computation of the energy balance and heating curves of an induction motor taking as a basis the information provided by the application of the infrared thermography. Moreover, use of infrared thermography data to diagnose rotor bar failures is preliminarily studied. In the paper, a 1.1 kW induction motor is tested. Thermography images of the chassis temperature are captured at each second during the whole startup transient, from standstill till steady-state, by using an infrared camera connected to a laptop computer fitted with an acquisition and analysis program. A model based on the calculation of the heat losses by convection and radiation through the frame of the machine is developed. It uses the geometrical dimensions as well as temperature values obtained from the thermography images. The developed model enables studying any motor configuration and operating conditions by just varying thermal and geometry parameters. Finally, a preliminary study relying on the possible use of Thermography data for diagnosis of rotor failures is carried out. Experimental data corresponding to a healthy machine and a machine with broken bars are analysed and compared. This methodology will be the baseline for further complex failure diagnosis in electric motors.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"68 1","pages":"525-531"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81848008","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.2012.6349972
F. Mapelli, A. Bezzolato, D. Tarsitano
Field Oriented Control (FOC) based induction motor drive is a good choice for electric vehicles especially if we consider its low cost, due to the absence of permanent magnets. The control algorithm needs a good motor state variables estimation, such as a proper flux orientation, to assure full torque and power performances. Usually observers or estimators are adopted, but good results are strongly parameters dependent. In the induction machine control one of the most important parameter is the rotor resistance, that is temperature-dependent and therefore time-varying. The paper shows and compares three different Model Reference Adaptive System (MRAS) rotor resistance estimation methods, based on total active power, reactive power and motor torque. The algorithms have been studied by means of a rotor resistance uncertain of estimation based sensitivity analysis for different load and speed operating conditions. A simulation analysis has been proposed since the algorithm has been defined in order to operate under dynamic conditions, the typical situation during an electric vehicle drive cycle. A simple non linear variable structure MRAS has been adopted for assuring a good rotor resistance estimation convergence. Full theoretical analysis are reported for all the proposed methods.
{"title":"A rotor resistance MRAS estimator for induction motor traction drive for electrical vehicles","authors":"F. Mapelli, A. Bezzolato, D. Tarsitano","doi":"10.1109/ICELMACH.2012.6349972","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349972","url":null,"abstract":"Field Oriented Control (FOC) based induction motor drive is a good choice for electric vehicles especially if we consider its low cost, due to the absence of permanent magnets. The control algorithm needs a good motor state variables estimation, such as a proper flux orientation, to assure full torque and power performances. Usually observers or estimators are adopted, but good results are strongly parameters dependent. In the induction machine control one of the most important parameter is the rotor resistance, that is temperature-dependent and therefore time-varying. The paper shows and compares three different Model Reference Adaptive System (MRAS) rotor resistance estimation methods, based on total active power, reactive power and motor torque. The algorithms have been studied by means of a rotor resistance uncertain of estimation based sensitivity analysis for different load and speed operating conditions. A simulation analysis has been proposed since the algorithm has been defined in order to operate under dynamic conditions, the typical situation during an electric vehicle drive cycle. A simple non linear variable structure MRAS has been adopted for assuring a good rotor resistance estimation convergence. Full theoretical analysis are reported for all the proposed methods.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"50 1","pages":"823-829"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80577155","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.2012.6350216
N. Freire, J. Estima, A. Cardoso
The widespread use of electric drives has led to an increasing interest in their condition monitoring and fault diagnostics. Regarding power switch open-circuit fault diagnosis, the proposed voltage-based approaches require additional hardware, increasing the system cost. Thus, the industry acceptance may be low. Therefore, this paper proposes a new voltage-based approach for open-circuit faults diagnosis in voltage source inverters with space vector modulation (SVM) feeding permanent magnet synchronous motors (PMSM) without additional sensors, by employing a flux observer based on the machine current model, which allows to estimate the motor terminal voltages. The diagnostic method uses the average values of the errors between the reference and the estimated voltages. Its implementation in a direct torque controlled (DTC) PMSM drive implies a minimum additional computational effort, because the flux observer is usually already available. Several experimental results are presented for a DTC as well as for a vector controlled PMSM drive.
{"title":"A voltage-based approach for open-circuit fault diagnosis in voltage-fed SVM motor drives without extra hardware","authors":"N. Freire, J. Estima, A. Cardoso","doi":"10.1109/ICELMACH.2012.6350216","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350216","url":null,"abstract":"The widespread use of electric drives has led to an increasing interest in their condition monitoring and fault diagnostics. Regarding power switch open-circuit fault diagnosis, the proposed voltage-based approaches require additional hardware, increasing the system cost. Thus, the industry acceptance may be low. Therefore, this paper proposes a new voltage-based approach for open-circuit faults diagnosis in voltage source inverters with space vector modulation (SVM) feeding permanent magnet synchronous motors (PMSM) without additional sensors, by employing a flux observer based on the machine current model, which allows to estimate the motor terminal voltages. The diagnostic method uses the average values of the errors between the reference and the estimated voltages. Its implementation in a direct torque controlled (DTC) PMSM drive implies a minimum additional computational effort, because the flux observer is usually already available. Several experimental results are presented for a DTC as well as for a vector controlled PMSM drive.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"22 2 1","pages":"2378-2383"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75797194","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.2012.6349859
M. Galea, C. Gerada, T. Hamiti
This paper considers the design and analysis of a field wound, flux switching motor where both the field and the armature windings are placed on the stator. Different machine topoogies and slot-segment combinations are considered in an attempt to obtain high torque density and fault tolerant performances such as those required in the aerospace industry. The highly demanding application in terms of torque density results in an outer rotor approach being selected. Optimisation with respect to machine geometry is addressed analytically and validated through finite element simulations.
{"title":"Design considerations for an outer rotor, field wound, flux switching machine","authors":"M. Galea, C. Gerada, T. Hamiti","doi":"10.1109/ICELMACH.2012.6349859","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6349859","url":null,"abstract":"This paper considers the design and analysis of a field wound, flux switching motor where both the field and the armature windings are placed on the stator. Different machine topoogies and slot-segment combinations are considered in an attempt to obtain high torque density and fault tolerant performances such as those required in the aerospace industry. The highly demanding application in terms of torque density results in an outer rotor approach being selected. Optimisation with respect to machine geometry is addressed analytically and validated through finite element simulations.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"13 1","pages":"171-176"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75870760","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.2012.6350133
C. Debruyne, S. Derammelaere, J. Desmet, L. Vandevelde
Induction machines have nearly reached their maximum efficiency. In order to further increase the efficiency of electrical machines the use of permanent magnets in combination with the robust design of the induction machine is being extensively researched. Many experimental designs have been suggested in literature, but recently these Line Start Permanent Magnet Machines have also become commercially available in a power range to 10kW. It is commonly known that the induction from the magnets is function of the temperature of the permanent magnet. As a consequence, this temperature dependency of induction will affect almost every electrical quantity of the machine, including current, torque and efficiency. In this paper, the efficiency of an off-the-shelf 4kW three phase Line Start Permanent Magnet Machine is evaluated in function of the ambient temperature by practical measurement. A detailed loss evaluation is given to explain the results.
{"title":"Temperature dependency of the efficiency of Line Start Permanent Magnet Machines","authors":"C. Debruyne, S. Derammelaere, J. Desmet, L. Vandevelde","doi":"10.1109/ICELMACH.2012.6350133","DOIUrl":"https://doi.org/10.1109/ICELMACH.2012.6350133","url":null,"abstract":"Induction machines have nearly reached their maximum efficiency. In order to further increase the efficiency of electrical machines the use of permanent magnets in combination with the robust design of the induction machine is being extensively researched. Many experimental designs have been suggested in literature, but recently these Line Start Permanent Magnet Machines have also become commercially available in a power range to 10kW. It is commonly known that the induction from the magnets is function of the temperature of the permanent magnet. As a consequence, this temperature dependency of induction will affect almost every electrical quantity of the machine, including current, torque and efficiency. In this paper, the efficiency of an off-the-shelf 4kW three phase Line Start Permanent Magnet Machine is evaluated in function of the ambient temperature by practical measurement. A detailed loss evaluation is given to explain the results.","PeriodicalId":6309,"journal":{"name":"2012 XXth International Conference on Electrical Machines","volume":"6 1","pages":"1846-1853"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82465838","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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