Pub Date : 2014-11-24DOI: 10.1109/NAPS.2014.6965372
Titiksha Joshi, G. Heydt, R. Ayyanar
A project on high penetration of solar photovoltaic resources in a power distribution system is described. The photovoltaic resources energize pulse width modulated inverters to interface with the 60 Hz distribution system. The inverter currents have high frequency components (these are not `harmonics', but they are artifacts of the pulse width modulation and generally they are in the 2.0 kHz range and higher). Residential (i.e., `roof top') PV resources are generally relegated to the 5 kW range or less, while `utility scale' PV in the range of 400 kW or more has been used. Modeling of the distribution feeder appropriate for high frequency studies is discussed and simulation results from high frequency power flow are presented. The distribution system is an actual system in the Western United States, and instrumented measurements are available.
{"title":"High frequency spectral components in distribution voltages and currents due to photovoltaic resources","authors":"Titiksha Joshi, G. Heydt, R. Ayyanar","doi":"10.1109/NAPS.2014.6965372","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965372","url":null,"abstract":"A project on high penetration of solar photovoltaic resources in a power distribution system is described. The photovoltaic resources energize pulse width modulated inverters to interface with the 60 Hz distribution system. The inverter currents have high frequency components (these are not `harmonics', but they are artifacts of the pulse width modulation and generally they are in the 2.0 kHz range and higher). Residential (i.e., `roof top') PV resources are generally relegated to the 5 kW range or less, while `utility scale' PV in the range of 400 kW or more has been used. Modeling of the distribution feeder appropriate for high frequency studies is discussed and simulation results from high frequency power flow are presented. The distribution system is an actual system in the Western United States, and instrumented measurements are available.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115805260","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965353
A. Nagarajan, R. Ayyanar
This paper demonstrates the application of a graph search algorithm for the network reduction of the distribution feeder. The purpose behind the network-reduction is to develop a reduced distribution system to facilitate the dynamic analysis of the feeders with high penetration of PV generators. Dynamic analysis requires modeling of the distribution feeders in the electromagnetic transient programs for understanding the transients. Performing the transient analysis on large distribution feeders with high PV penetration is time intensive and impracticable. To aid this purpose a network-reduction algorithm for the distribution feeder is proposed in this paper. The objective is to develop a reduced distribution system to support the study of long-term transients of the PV inverters such as - interaction with other control devices (capacitor banks and PV generators), cloud transients, and voltage flicker. This paper proposes a novel network-reduction technique, based on a network-flow procedure, which is referred to as Minimum Spanning Tree (MST) with additional capabilities. The network reduction proposed in this paper selectively retains the laterals and additionally accommodates the reactive power generation from the cable capacitance to the loads. The proposed algorithm will serve as an interface for modeling the feeder from the GIS database to the transient analysis tool.
{"title":"Application of Minimum Spanning Tree algorithm for network reduction of distribution systems","authors":"A. Nagarajan, R. Ayyanar","doi":"10.1109/NAPS.2014.6965353","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965353","url":null,"abstract":"This paper demonstrates the application of a graph search algorithm for the network reduction of the distribution feeder. The purpose behind the network-reduction is to develop a reduced distribution system to facilitate the dynamic analysis of the feeders with high penetration of PV generators. Dynamic analysis requires modeling of the distribution feeders in the electromagnetic transient programs for understanding the transients. Performing the transient analysis on large distribution feeders with high PV penetration is time intensive and impracticable. To aid this purpose a network-reduction algorithm for the distribution feeder is proposed in this paper. The objective is to develop a reduced distribution system to support the study of long-term transients of the PV inverters such as - interaction with other control devices (capacitor banks and PV generators), cloud transients, and voltage flicker. This paper proposes a novel network-reduction technique, based on a network-flow procedure, which is referred to as Minimum Spanning Tree (MST) with additional capabilities. The network reduction proposed in this paper selectively retains the laterals and additionally accommodates the reactive power generation from the cable capacitance to the loads. The proposed algorithm will serve as an interface for modeling the feeder from the GIS database to the transient analysis tool.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125541495","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965403
Shamina Hossain, Hao Zhu, T. Overbye
The detection and location of high impedance faults has historically been a difficult endeavor due to the low currents produced. However, the recent advent of distributed voltage monitoring devices, enabling access to fast-sampled, expansive voltage measurements throughout a distribution network, can ease this task. This paper considers the potential to use these distribution level devices to detect and locate such faults. A simulation-based method is proposed that compares a measured voltage profile, obtained from the devices, and simulated voltage profiles at various locations using a power system simulation software. The simulation locations are intelligently selected using the Golden section search and possible fault impedance values are iterated through for each location. The L1-norm is used to compare the two profiles, with the lowest error norm representing the best match - the most likely fault location and impedance.
{"title":"Distribution high impedance fault location using localized voltage magnitude measurements","authors":"Shamina Hossain, Hao Zhu, T. Overbye","doi":"10.1109/NAPS.2014.6965403","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965403","url":null,"abstract":"The detection and location of high impedance faults has historically been a difficult endeavor due to the low currents produced. However, the recent advent of distributed voltage monitoring devices, enabling access to fast-sampled, expansive voltage measurements throughout a distribution network, can ease this task. This paper considers the potential to use these distribution level devices to detect and locate such faults. A simulation-based method is proposed that compares a measured voltage profile, obtained from the devices, and simulated voltage profiles at various locations using a power system simulation software. The simulation locations are intelligently selected using the Golden section search and possible fault impedance values are iterated through for each location. The L1-norm is used to compare the two profiles, with the lowest error norm representing the best match - the most likely fault location and impedance.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"506 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130019072","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965389
Yue Zhang, M. Beaudin, H. Zareipour, D. Wood
Solar Photovoltaic power production has grown significantly over the past few years. California ISO is the first system operator in North America to make the data for aggregated system-level solar power production across its territory available on a regular basis. In this paper, we demonstrate the application of three well-established forecasting models to 24-hour-ahead prediction of solar power at the system level. The models investigated in this paper include Auto Regressive Integrated Moving Average (ARIMA), Radial Basis Function Neural Network (RBFNN), and Least Squares Support Vector Machine (LS-SVM). Numerical results and discussions are provided based on California ISO solar power data.
{"title":"Forecasting Solar Photovoltaic power production at the aggregated system level","authors":"Yue Zhang, M. Beaudin, H. Zareipour, D. Wood","doi":"10.1109/NAPS.2014.6965389","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965389","url":null,"abstract":"Solar Photovoltaic power production has grown significantly over the past few years. California ISO is the first system operator in North America to make the data for aggregated system-level solar power production across its territory available on a regular basis. In this paper, we demonstrate the application of three well-established forecasting models to 24-hour-ahead prediction of solar power at the system level. The models investigated in this paper include Auto Regressive Integrated Moving Average (ARIMA), Radial Basis Function Neural Network (RBFNN), and Least Squares Support Vector Machine (LS-SVM). Numerical results and discussions are provided based on California ISO solar power data.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128434444","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965415
A. Esmaeilian, M. Kezunovic
Several major blackouts were caused by distance relay mis-operation. Distance relay mis-operation may occur following a large disturbance in the system causing power swing and out-of-step conditions. If an on-line fault analysis tool is able to detect power swing or out-of-step conditions and indicate mis-operation of relays, the operator may be notified to switch back the healthy transmission lines tripped due to relay mis-operation. A new automated fault analysis tool comprising fault detection, classification and location has been developed and its performance under various power swing and out-of-step conditions is reported. The test results indicate that the fault analysis tool performs better than distance relay under power swing and out of-step conditions and can be used as a tool to verify distance relay operation in practical circumstances. The simulations have been performed using IEEE118 bus test system modeled in ATP software.
{"title":"Evaluation of fault analysis tool under power swing and out-of-step conditions","authors":"A. Esmaeilian, M. Kezunovic","doi":"10.1109/NAPS.2014.6965415","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965415","url":null,"abstract":"Several major blackouts were caused by distance relay mis-operation. Distance relay mis-operation may occur following a large disturbance in the system causing power swing and out-of-step conditions. If an on-line fault analysis tool is able to detect power swing or out-of-step conditions and indicate mis-operation of relays, the operator may be notified to switch back the healthy transmission lines tripped due to relay mis-operation. A new automated fault analysis tool comprising fault detection, classification and location has been developed and its performance under various power swing and out-of-step conditions is reported. The test results indicate that the fault analysis tool performs better than distance relay under power swing and out of-step conditions and can be used as a tool to verify distance relay operation in practical circumstances. The simulations have been performed using IEEE118 bus test system modeled in ATP software.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125781073","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965412
J. Valdez, Xun Zhang, Jackeline Abad Torres, Sandip Roy
This paper explores real-time fault location in a power transmission network using measurements of transients from sparsely-placed synchrophasors. The fault-location problem is abstracted to a statistical hypothesis-testing or detection problem, wherein the linearized dynamical models corresponding to different fault conditions must be distinguished in the face of fault-clearing and measurement uncertainty. A maximum a posteriori probability (MAP) detector is constructed. A strategy for real-time implementation of the fault-locator is discussed, which is based on pre-computation of detector parameters using state-estimator and contingency-analysis data, along with on-line collection of synchrophrasor data and implementation of the hypothesis test. Numerical case studies of the 11-Bus two area power system verify that the proposed fault-location algorithm can locate a faulted line accurately and quickly.
{"title":"Fast fault location in power transmission networks using transient signatures from sparsely-placed synchrophasors","authors":"J. Valdez, Xun Zhang, Jackeline Abad Torres, Sandip Roy","doi":"10.1109/NAPS.2014.6965412","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965412","url":null,"abstract":"This paper explores real-time fault location in a power transmission network using measurements of transients from sparsely-placed synchrophasors. The fault-location problem is abstracted to a statistical hypothesis-testing or detection problem, wherein the linearized dynamical models corresponding to different fault conditions must be distinguished in the face of fault-clearing and measurement uncertainty. A maximum a posteriori probability (MAP) detector is constructed. A strategy for real-time implementation of the fault-locator is discussed, which is based on pre-computation of detector parameters using state-estimator and contingency-analysis data, along with on-line collection of synchrophrasor data and implementation of the hypothesis test. Numerical case studies of the 11-Bus two area power system verify that the proposed fault-location algorithm can locate a faulted line accurately and quickly.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122596906","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965479
Yin Yao, Wenzhong Gao
In this paper, a stochastic model of plug-in hybrid electric vehicle (PHEV) is developed in Matlab to investigate its impact on distribution transformer. Two types of PHEVs are included in this model, sedan and SUV. These two types of PHEV share the same charging schedule, but possess different charging characteristics. Charging power, Full-charge time for example. If dumb charging method (V0G) is applied, that will surely result in a load peak in the evening. From the simulation results, it is proven that this scale of load peak will lead to the increase of loss of life (LOL) of distribution transformer. To mitigate the load peak, particle swarm optimization method is performed to reschedule the charging pattern of each PHEV. Eventually, the LOL of distribution transformer is minimized with smoother charging load curve after optimization.
{"title":"Relieving the pressure of electric vehicle battery charging on distribution transformer via particle swarm optimization method","authors":"Yin Yao, Wenzhong Gao","doi":"10.1109/NAPS.2014.6965479","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965479","url":null,"abstract":"In this paper, a stochastic model of plug-in hybrid electric vehicle (PHEV) is developed in Matlab to investigate its impact on distribution transformer. Two types of PHEVs are included in this model, sedan and SUV. These two types of PHEV share the same charging schedule, but possess different charging characteristics. Charging power, Full-charge time for example. If dumb charging method (V0G) is applied, that will surely result in a load peak in the evening. From the simulation results, it is proven that this scale of load peak will lead to the increase of loss of life (LOL) of distribution transformer. To mitigate the load peak, particle swarm optimization method is performed to reschedule the charging pattern of each PHEV. Eventually, the LOL of distribution transformer is minimized with smoother charging load curve after optimization.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122710819","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965368
Meng Yen Shih, Arturo Conde Enríquez
As Smart Grid concept is employed in the electric power system, network load flow and topologyis changingintensively to meet the best generation-demand balancing point. These changes must be accounted for the protection devices in order to enhance their performance. The coordination of directional overcurrent relays is most commonly studied based on fixed network operation and topology within a mesh power system. But the sub-transmission and distribution systems constantly operate differently in order to satisfy the variety of load demand levels throughout the day and year. Hence, if the setting of directional overcurrent relays (DOCRs) change according to the different operations of the system, then relay operation time and sensitivity can both be enhanced. This can potentially improve the protection performance in Smart Grid system. Therefore, the study is carried out based on the comparison among three coordination approaches: conventional (fixed settings), discrete (changing setting groups), and continuous or real time (dynamic settings).
{"title":"Alternative coordination approaches for implementation in Smart Grid","authors":"Meng Yen Shih, Arturo Conde Enríquez","doi":"10.1109/NAPS.2014.6965368","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965368","url":null,"abstract":"As Smart Grid concept is employed in the electric power system, network load flow and topologyis changingintensively to meet the best generation-demand balancing point. These changes must be accounted for the protection devices in order to enhance their performance. The coordination of directional overcurrent relays is most commonly studied based on fixed network operation and topology within a mesh power system. But the sub-transmission and distribution systems constantly operate differently in order to satisfy the variety of load demand levels throughout the day and year. Hence, if the setting of directional overcurrent relays (DOCRs) change according to the different operations of the system, then relay operation time and sensitivity can both be enhanced. This can potentially improve the protection performance in Smart Grid system. Therefore, the study is carried out based on the comparison among three coordination approaches: conventional (fixed settings), discrete (changing setting groups), and continuous or real time (dynamic settings).","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123161831","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965388
Hung-Ming Chou, K. Butler-Purry
Because of the slow expansion of distribution systems, fast growth of load, and increased penetration level of distribution generation (DG), voltage stability becomes an important issue for the proper operation of distribution systems. In this work modal analysis technique was extended to three-phase unbalanced distribution systems to analyze voltage stability problem. Netwon-Raphson algorithm with power mismatch in polar representation was adopted to find the three-phase power flow solution, and its Jacobian matrix was used for three-phase modal analysis technique. This technique was applied to IEEE 13-node test feeder. Several case studies were performed to investigate the impact of unbalance loading degree and DG power output on voltage stability problem. It was found that both would influence not only the maximum loadability of the system but also the location of the weak buses, weak branches and suitable locations to provide reactive power support.
{"title":"Investigation of voltage stability in three-phase unbalanced distribution systems with DG using modal analysis technique","authors":"Hung-Ming Chou, K. Butler-Purry","doi":"10.1109/NAPS.2014.6965388","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965388","url":null,"abstract":"Because of the slow expansion of distribution systems, fast growth of load, and increased penetration level of distribution generation (DG), voltage stability becomes an important issue for the proper operation of distribution systems. In this work modal analysis technique was extended to three-phase unbalanced distribution systems to analyze voltage stability problem. Netwon-Raphson algorithm with power mismatch in polar representation was adopted to find the three-phase power flow solution, and its Jacobian matrix was used for three-phase modal analysis technique. This technique was applied to IEEE 13-node test feeder. Several case studies were performed to investigate the impact of unbalance loading degree and DG power output on voltage stability problem. It was found that both would influence not only the maximum loadability of the system but also the location of the weak buses, weak branches and suitable locations to provide reactive power support.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114071412","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 : 2014-11-24DOI: 10.1109/NAPS.2014.6965381
Bo Chen, K. Butler-Purry, A. Goulart, D. Kundur
Numerous innovative smart grid technologies are deployed in modern power systems, making a power system a typical cyber-physical system (CPS). The increasing coupling between a physical power system and its communication network requires a smart grid simulator to run in a cyber-physical environment for cyber security research. In addition, smart grid technologies introduce numerous access points to the communication network, making cyber security a big concern in smart grid planning and operation. In this paper, a simple real time CPS test bed, implemented in RTDS and OPNET, is discussed. The setup of the test bed is introduced. Results of a case study simulated in the test bed to study the impact of cyber attacks on system transient stability are presented. The simple test bed was capable of accurately modelling a smart grid while providing user-friendly modeling experience.
{"title":"Implementing a real-time cyber-physical system test bed in RTDS and OPNET","authors":"Bo Chen, K. Butler-Purry, A. Goulart, D. Kundur","doi":"10.1109/NAPS.2014.6965381","DOIUrl":"https://doi.org/10.1109/NAPS.2014.6965381","url":null,"abstract":"Numerous innovative smart grid technologies are deployed in modern power systems, making a power system a typical cyber-physical system (CPS). The increasing coupling between a physical power system and its communication network requires a smart grid simulator to run in a cyber-physical environment for cyber security research. In addition, smart grid technologies introduce numerous access points to the communication network, making cyber security a big concern in smart grid planning and operation. In this paper, a simple real time CPS test bed, implemented in RTDS and OPNET, is discussed. The setup of the test bed is introduced. Results of a case study simulated in the test bed to study the impact of cyber attacks on system transient stability are presented. The simple test bed was capable of accurately modelling a smart grid while providing user-friendly modeling experience.","PeriodicalId":421766,"journal":{"name":"2014 North American Power Symposium (NAPS)","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114433545","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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