Pub Date : 2020-10-11DOI: 10.1109/ECCE44975.2020.9236024
Zeljko Jankovic, P. Murthy, Lixiang Wei, A. Nasiri
This paper proposes a Dynamic Discontinuous PWM (DDPWM) strategy for Grid Tied Inverter applications utilizing 2 level Voltage Source Inverters (VSIs). DDPWM is a version of Generalized DPWM (GDPWM) optimized for usage with full range of operating power factor values and without need for current feedback signals, such that it provides minimal switching loss. Switching and Conduction Loss expressions are derived, simulated and analyzed for individual transistors and diodes inside inverter module. Simplified thermal model based on available datasheet parameters is presented and used for evaluation of thermal performance of semiconductor devices under DDPWM across full range of power factor and modulation index values. It is demonstrated that high modulation index and low power factor values produce highest overall module losses, but that the individual device temperatures are dependent on module forward and switching characteristics, as well as thermal resistances. Experimental setup is implemented to evaluate thermal performance of DDPWM.
{"title":"Dynamic Discontinuous PWM for Grid-tied Inverter Applications","authors":"Zeljko Jankovic, P. Murthy, Lixiang Wei, A. Nasiri","doi":"10.1109/ECCE44975.2020.9236024","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9236024","url":null,"abstract":"This paper proposes a Dynamic Discontinuous PWM (DDPWM) strategy for Grid Tied Inverter applications utilizing 2 level Voltage Source Inverters (VSIs). DDPWM is a version of Generalized DPWM (GDPWM) optimized for usage with full range of operating power factor values and without need for current feedback signals, such that it provides minimal switching loss. Switching and Conduction Loss expressions are derived, simulated and analyzed for individual transistors and diodes inside inverter module. Simplified thermal model based on available datasheet parameters is presented and used for evaluation of thermal performance of semiconductor devices under DDPWM across full range of power factor and modulation index values. It is demonstrated that high modulation index and low power factor values produce highest overall module losses, but that the individual device temperatures are dependent on module forward and switching characteristics, as well as thermal resistances. Experimental setup is implemented to evaluate thermal performance of DDPWM.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"75 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115663549","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9236028
L. Bu, Y. Fujimoto
In this paper, a robust position control system was designed specifically for the RotLin Machine, a radialgap magnetic-screw type direct-drivable linear actuator. The RotLin Machine, as a 2-mass system, is insufficient in accuracy and robustness. To ensure system accuracy under load side disturbance, firstly, a load force estimator with a similar structure of Disturbance Observer (DOB) was designed based on a spring force estimation. Secondly, a deflection compensator, which can adjust the rotor angle according to load side disturbance and thereby ensure accuracy of position control, was designed. Besides, to further enhance response speed against a sudden change load force, a feedback loop with an adjustable parameter was designed inside of speed control loop. Under an appropriate parameter design, this inner loop reacts to load force sudden change before outer loops and thus increase response speed. Finally, the proposed system was tested comparing with the conventional system in both simulation and experiment. The results show superiority of the proposed control system in robustness and accuracy over the conventional system.
{"title":"A Robust Position Control System Based on Load Force Observer for RotLin Machine","authors":"L. Bu, Y. Fujimoto","doi":"10.1109/ECCE44975.2020.9236028","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9236028","url":null,"abstract":"In this paper, a robust position control system was designed specifically for the RotLin Machine, a radialgap magnetic-screw type direct-drivable linear actuator. The RotLin Machine, as a 2-mass system, is insufficient in accuracy and robustness. To ensure system accuracy under load side disturbance, firstly, a load force estimator with a similar structure of Disturbance Observer (DOB) was designed based on a spring force estimation. Secondly, a deflection compensator, which can adjust the rotor angle according to load side disturbance and thereby ensure accuracy of position control, was designed. Besides, to further enhance response speed against a sudden change load force, a feedback loop with an adjustable parameter was designed inside of speed control loop. Under an appropriate parameter design, this inner loop reacts to load force sudden change before outer loops and thus increase response speed. Finally, the proposed system was tested comparing with the conventional system in both simulation and experiment. The results show superiority of the proposed control system in robustness and accuracy over the conventional system.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"191 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123049876","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235921
M. Carbonieri, W. Soong, A. Mahmoudi, S. Kahourzade, N. Bianchi
This paper proposes several methods to compare the overload performance of different types of synchronous machines for electric traction applications. An ideal model to predict the performance of the motor at high overload condition is introduced. In the simplified analytical saturation model, the saturation flux linkage is a parameter. This allows the performance prediction as a function of three normalized parameters: magnet flux linkage, unsaturated inductance and saliency ratio.The other main part of the work concerns the machines analysis using the finite element approach. Models with different levels of accuracy and generality show the possibility of reducing the number of simulations in the d- and q-axis currents plane to obtain the full performance prediction. Machines with different level of cross saturation are considered to test the proposed models.Simulation results of the studied approaches are compared with the prediction obtained from the full machine mapping using finite element analysis, in which a large number of evenly spaced points in the (id,iq) plane are analyzed to derive the working characteristics.
{"title":"Overload Performance Prediction of PM and Synchronous Reluctance Machines for Traction Applications","authors":"M. Carbonieri, W. Soong, A. Mahmoudi, S. Kahourzade, N. Bianchi","doi":"10.1109/ECCE44975.2020.9235921","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235921","url":null,"abstract":"This paper proposes several methods to compare the overload performance of different types of synchronous machines for electric traction applications. An ideal model to predict the performance of the motor at high overload condition is introduced. In the simplified analytical saturation model, the saturation flux linkage is a parameter. This allows the performance prediction as a function of three normalized parameters: magnet flux linkage, unsaturated inductance and saliency ratio.The other main part of the work concerns the machines analysis using the finite element approach. Models with different levels of accuracy and generality show the possibility of reducing the number of simulations in the d- and q-axis currents plane to obtain the full performance prediction. Machines with different level of cross saturation are considered to test the proposed models.Simulation results of the studied approaches are compared with the prediction obtained from the full machine mapping using finite element analysis, in which a large number of evenly spaced points in the (id,iq) plane are analyzed to derive the working characteristics.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121788961","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}
High frequency sinusoidal pulsating voltage injection has been one of the best solutions in low speed for sensorless control. In the process of HF voltage injection, position signal demodulation plays a key role. Conventional sinusoidal demodulation is widely used. However, it has an intrinsic defect, which leads to the necessity of low-pass filter ( LPF ) to eliminate the high frequency ripple in estimated position. Thus, the cube of HF current in q-axis is used as the position signal carrier. This process of nonlinear demodulation, which means nonlinear reaching law, is used to obtain the position deviation from HF current response. Experimental results conform the advantages of proposed method.
{"title":"Position Sensorless Control of PMSM Drives Based on HF Sinusoidal Pulsating Voltage Injection","authors":"Jiali Liu, Yongchang Zhang, Haitao Yang, Wenjia Shen","doi":"10.1109/ECCE44975.2020.9236162","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9236162","url":null,"abstract":"High frequency sinusoidal pulsating voltage injection has been one of the best solutions in low speed for sensorless control. In the process of HF voltage injection, position signal demodulation plays a key role. Conventional sinusoidal demodulation is widely used. However, it has an intrinsic defect, which leads to the necessity of low-pass filter ( LPF ) to eliminate the high frequency ripple in estimated position. Thus, the cube of HF current in q-axis is used as the position signal carrier. This process of nonlinear demodulation, which means nonlinear reaching law, is used to obtain the position deviation from HF current response. Experimental results conform the advantages of proposed method.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116640355","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235672
Joon-Hee Lee, S. Sul
This paper proposes a method to compensate for the nonlinearity of an inverter, which generally exists regardless of PWM schemes. The nonlinearity originates from the on-state voltage drop of the semiconductor switches and the dead time effect. The effect of the dead time to the control of the inverter has a strong dependency on PWM scheme because the dead time effects occur only at the switching instant of the inverter and the switching is solely decided by PWM scheme. Thus, for the accurate compensation of the nonlinearity, the effect of the dead time should be analyzed with different PWM schemes. The proposed method considers the difference of dead time effect according to different PWM schemes, namely Continuous PWM and Discontinuous PWM. In addition, to implement the proposed method, a new nonlinearity effect identification is introduced, which can separate the on-state voltage drop from the dead-time effect. Several experimental tests are carried out to verify the validity of the proposed method.
{"title":"Inverter Nonlinearity Compensation of Discontinuous PWM Considering Voltage Drop of Power Semiconductor and Dead Time Effect","authors":"Joon-Hee Lee, S. Sul","doi":"10.1109/ECCE44975.2020.9235672","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235672","url":null,"abstract":"This paper proposes a method to compensate for the nonlinearity of an inverter, which generally exists regardless of PWM schemes. The nonlinearity originates from the on-state voltage drop of the semiconductor switches and the dead time effect. The effect of the dead time to the control of the inverter has a strong dependency on PWM scheme because the dead time effects occur only at the switching instant of the inverter and the switching is solely decided by PWM scheme. Thus, for the accurate compensation of the nonlinearity, the effect of the dead time should be analyzed with different PWM schemes. The proposed method considers the difference of dead time effect according to different PWM schemes, namely Continuous PWM and Discontinuous PWM. In addition, to implement the proposed method, a new nonlinearity effect identification is introduced, which can separate the on-state voltage drop from the dead-time effect. Several experimental tests are carried out to verify the validity of the proposed method.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116893885","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235780
Abbas Hassan, A. Bazzi
This paper presents open-circuit fault analysis and diagnosis of a four-phase interleaved dc-dc power converter. The converter operation mode is first discussed in healthy condition. All fault cases are analyzed and discussed. A reconfiguration method is proposed for fault mitigation at level of the interleaved converter. Results are shown to validate the proposed reconfiguration method, where the converter’s output voltage is maintained at the desired value irrespective of which switch fails.
{"title":"Open-Circuit Fault Reconfiguration of Multiphase Interleaved DC-DC Converter","authors":"Abbas Hassan, A. Bazzi","doi":"10.1109/ECCE44975.2020.9235780","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235780","url":null,"abstract":"This paper presents open-circuit fault analysis and diagnosis of a four-phase interleaved dc-dc power converter. The converter operation mode is first discussed in healthy condition. All fault cases are analyzed and discussed. A reconfiguration method is proposed for fault mitigation at level of the interleaved converter. Results are shown to validate the proposed reconfiguration method, where the converter’s output voltage is maintained at the desired value irrespective of which switch fails.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"191 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117166479","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235651
Vu Le, Xiu Yao, Chad Miller, Tsao-Bang Hung
Series dc arc fault detection and localization in the modern power electronics system that comprises multiple loads is a difficult task due to the arcing noise cross-talk. The arcing noises can propagate to the adjacent loads and mistrigger the detector units. This paper proposes a master controller to compare all the Random Forest (RF) based detector units’ predicted class probabilities for arc fault detection and localization. The predicted probability comes from one of the RF’s attributes, where the largest probability becomes the final decision. The master controller also sends out a control signal to create synchronization between detectors. This step arranges the detectors to monitor all input currents simultaneously, and provide predicted probability correlation accurately. The master controller capability was emulated and verified using an experimental testbed of two parallel- connected constant power loads.
{"title":"Series Arc Fault Detection and Localization in DC Distribution Based on Master Controller","authors":"Vu Le, Xiu Yao, Chad Miller, Tsao-Bang Hung","doi":"10.1109/ECCE44975.2020.9235651","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235651","url":null,"abstract":"Series dc arc fault detection and localization in the modern power electronics system that comprises multiple loads is a difficult task due to the arcing noise cross-talk. The arcing noises can propagate to the adjacent loads and mistrigger the detector units. This paper proposes a master controller to compare all the Random Forest (RF) based detector units’ predicted class probabilities for arc fault detection and localization. The predicted probability comes from one of the RF’s attributes, where the largest probability becomes the final decision. The master controller also sends out a control signal to create synchronization between detectors. This step arranges the detectors to monitor all input currents simultaneously, and provide predicted probability correlation accurately. The master controller capability was emulated and verified using an experimental testbed of two parallel- connected constant power loads.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127138700","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235774
Cheng Xue, L. Ding, Y. Li
Model predictive control (MPC) with a long predictive horizon can offer significant benefits, especially for a power converter with high-order filters, such as virtual-impedance based active damping loop that can be eliminated. In this article, the continuous-control-set model predictive control (CCS-MPC) with a long prediction horizon is investigated for the grid-connected current-source converter (CSC). The cost function in multi-variable form is designed, which ensures power command tracking and LC filter resonance suppression simultaneously. The optimized control law is generated by a modulator to obtain a constant switching frequency. The single MPC loop can replace conventional multiloop control with reduced complexity and simplified tuning process. Simulation and experimental results show that the long horizon MPC for CSC can achieve satisfactory performance as well as improved robustness for the variation of system parameters.
{"title":"CCS-MPC with Long Predictive Horizon for Grid-Connected Current Source Converter","authors":"Cheng Xue, L. Ding, Y. Li","doi":"10.1109/ECCE44975.2020.9235774","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235774","url":null,"abstract":"Model predictive control (MPC) with a long predictive horizon can offer significant benefits, especially for a power converter with high-order filters, such as virtual-impedance based active damping loop that can be eliminated. In this article, the continuous-control-set model predictive control (CCS-MPC) with a long prediction horizon is investigated for the grid-connected current-source converter (CSC). The cost function in multi-variable form is designed, which ensures power command tracking and LC filter resonance suppression simultaneously. The optimized control law is generated by a modulator to obtain a constant switching frequency. The single MPC loop can replace conventional multiloop control with reduced complexity and simplified tuning process. Simulation and experimental results show that the long horizon MPC for CSC can achieve satisfactory performance as well as improved robustness for the variation of system parameters.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127271589","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9235922
Xicai Pan, S. Pan, Jinwu Gong, X. Zha
The cascaded H-bridge (CHB) multilevel inverter is considered as one of the most suitable configurations for large-scale photovoltaic (PV) plants. However, power mismatch problem will easily happen when solar irradiation is uneven. The current work on power mismatch elimination focuses predominantly on voltage regulation, which cannot cope with severe power imbalance scenarios. In order to address this problem, in this paper, a parallel control strategy is proposed to eliminate power mismatch by power sharing between inverters. Since the power mismatch elimination strategy changes from voltage regulation to circulating current regulation, it can accommodate most imbalance cases without voltage overmodulation. Simulation results validated the effectiveness of the proposed strategy.
{"title":"A Parallel Control Strategy for Power Mismatch Elimination of Photovoltaic Grid-Connected Cascaded H-Bridge Multilevel Inverter","authors":"Xicai Pan, S. Pan, Jinwu Gong, X. Zha","doi":"10.1109/ECCE44975.2020.9235922","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9235922","url":null,"abstract":"The cascaded H-bridge (CHB) multilevel inverter is considered as one of the most suitable configurations for large-scale photovoltaic (PV) plants. However, power mismatch problem will easily happen when solar irradiation is uneven. The current work on power mismatch elimination focuses predominantly on voltage regulation, which cannot cope with severe power imbalance scenarios. In order to address this problem, in this paper, a parallel control strategy is proposed to eliminate power mismatch by power sharing between inverters. Since the power mismatch elimination strategy changes from voltage regulation to circulating current regulation, it can accommodate most imbalance cases without voltage overmodulation. Simulation results validated the effectiveness of the proposed strategy.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124908107","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 : 2020-10-11DOI: 10.1109/ECCE44975.2020.9236417
Haiwei Cai
A high speed traction induction machine usually requires large rotor electrical time constant for high efficiency, which leads to unacceptably long transient response time in finite element analysis during machine design stage. To reduce the transient time, this paper proposes ramping up the magnitude of stator current excitation in finite element model from zero to full magnitude gradually, such that the DC component in rotor flux and torque can be greatly suppressed. The implementation of proposed method is very simple and it does not rely on machine parameters. Its performance is tested by a two-dimensional finite element model of an example induction machine. The result shows that the proposed method can significantly reduce the finite element calculation time.
{"title":"A Fast Calculation Method for Steady State Performance of High Speed Traction Induction Machine by Finite Element Analysis","authors":"Haiwei Cai","doi":"10.1109/ECCE44975.2020.9236417","DOIUrl":"https://doi.org/10.1109/ECCE44975.2020.9236417","url":null,"abstract":"A high speed traction induction machine usually requires large rotor electrical time constant for high efficiency, which leads to unacceptably long transient response time in finite element analysis during machine design stage. To reduce the transient time, this paper proposes ramping up the magnitude of stator current excitation in finite element model from zero to full magnitude gradually, such that the DC component in rotor flux and torque can be greatly suppressed. The implementation of proposed method is very simple and it does not rely on machine parameters. Its performance is tested by a two-dimensional finite element model of an example induction machine. The result shows that the proposed method can significantly reduce the finite element calculation time.","PeriodicalId":433712,"journal":{"name":"2020 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124934256","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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