Pub Date : 2015-05-10DOI: 10.1109/IEMDC.2015.7409180
Ahmed Shehada, R. Krishnan
This paper studies the effects of operating a single-switch converter for a variable-speed switched reluctance machine (SRM) drive without the large DC-link capacitor. The converter is intended for only low-cost, high-volume applications with low performance requirements. Detailed simulations are carried out to analyze the effects of having and removing the dc link capacitor in the converter. Efficiency and input power factor are compared for both converters. Simulation results show that removing the dc link capacitor results in a slight increase in efficiency and input power factor. However, absence of the dc link capacitor results in a slight increase in the magnitude and frequency content of the torque ripple. The studied drive, without the dc link capacitor, presents a viable variable speed motor drive alternative to traditional brush DC drives and universal motors in the low-cost market where cost is a major consideration. Examples of such applications are vacuum cleaners and low-power residential and industrial fans.
{"title":"Low-cost single-switch variable-speed switched reluctance motor drive","authors":"Ahmed Shehada, R. Krishnan","doi":"10.1109/IEMDC.2015.7409180","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409180","url":null,"abstract":"This paper studies the effects of operating a single-switch converter for a variable-speed switched reluctance machine (SRM) drive without the large DC-link capacitor. The converter is intended for only low-cost, high-volume applications with low performance requirements. Detailed simulations are carried out to analyze the effects of having and removing the dc link capacitor in the converter. Efficiency and input power factor are compared for both converters. Simulation results show that removing the dc link capacitor results in a slight increase in efficiency and input power factor. However, absence of the dc link capacitor results in a slight increase in the magnitude and frequency content of the torque ripple. The studied drive, without the dc link capacitor, presents a viable variable speed motor drive alternative to traditional brush DC drives and universal motors in the low-cost market where cost is a major consideration. Examples of such applications are vacuum cleaners and low-power residential and industrial fans.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"26 1","pages":"981-985"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89339246","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409102
N. Ahmed, J. Washington, G. Atkinson, N. Baker, Lars Sjoberg
Modulated pole (transverse flux) machines are known for their torque density and can take advantage of mutual flux paths to further increase the torque density of this class of machine. This paper presents a retrospective design investigation into a combined phase machine conducted in order to reduce the harmonic content of the back EMF and the cogging torque of the machine; two common problems with modulated pole machines. A method is proposed and it is shown that by changing a simple geometry such as the tooth span, cogging torque, torque ripple and harmonic content can all be significantly reduced without a significant effect on the overall torque output.
{"title":"Reduction of cogging torque and back EMF harmonics in modulated pole machine by variations in tooth span","authors":"N. Ahmed, J. Washington, G. Atkinson, N. Baker, Lars Sjoberg","doi":"10.1109/IEMDC.2015.7409102","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409102","url":null,"abstract":"Modulated pole (transverse flux) machines are known for their torque density and can take advantage of mutual flux paths to further increase the torque density of this class of machine. This paper presents a retrospective design investigation into a combined phase machine conducted in order to reduce the harmonic content of the back EMF and the cogging torque of the machine; two common problems with modulated pole machines. A method is proposed and it is shown that by changing a simple geometry such as the tooth span, cogging torque, torque ripple and harmonic content can all be significantly reduced without a significant effect on the overall torque output.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"12 1","pages":"482-488"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87262302","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409290
M. Barzegaran, M. Kamruzzaman, Hazzaz Mahmud, O. Mohammed
This paper describes an investigation of a new control method for Sparse matrix converters (SMC) using Silicon Carbide (SiC) switches fed direct torque control (DTC) of permanent magnet synchronous motor (PMSM) drives. Using this control method, it is possible to combine the sparse matrix converters with VSI-DTC, which reduces the torque ripple, does not require rotational co-ordinate transformation, and no need to calculate duty cycle and ensure fixed switching frequency. Mathematical expressions for change rates of torque and flux of PMSM are derived as a function of SMC voltage vectors. Then, the SMC-fed DTC algorithm is implemented based on the VSI and SMC switching table. Some numerical simulation are carried out, showing the effectiveness of the proposed strategy in reducing torque ripple for SMC-based PMSM derives.
{"title":"Direct torque control of permanent magnet synchronous machine using Sparse matrix converter with SiC switches","authors":"M. Barzegaran, M. Kamruzzaman, Hazzaz Mahmud, O. Mohammed","doi":"10.1109/IEMDC.2015.7409290","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409290","url":null,"abstract":"This paper describes an investigation of a new control method for Sparse matrix converters (SMC) using Silicon Carbide (SiC) switches fed direct torque control (DTC) of permanent magnet synchronous motor (PMSM) drives. Using this control method, it is possible to combine the sparse matrix converters with VSI-DTC, which reduces the torque ripple, does not require rotational co-ordinate transformation, and no need to calculate duty cycle and ensure fixed switching frequency. Mathematical expressions for change rates of torque and flux of PMSM are derived as a function of SMC voltage vectors. Then, the SMC-fed DTC algorithm is implemented based on the VSI and SMC switching table. Some numerical simulation are carried out, showing the effectiveness of the proposed strategy in reducing torque ripple for SMC-based PMSM derives.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"2 1","pages":"1683-1688"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87250504","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409177
S. Odhano, A. Cavagnino, R. Bojoi, Alberto Tenconi
In this paper, a magnetizing characteristic identification method for an induction machine at standstill is proposed. The technique is based on machine testing with a single-phase ac supply generated through a standard inverter. This type of test strategy is available in the literature, however, it has been used for parameter identification at a single current level thus ignoring the effects of magnetic saturation. To reproduce accurately the magnetizing curve, the test current level must be varied in order to trace the entire curve. The method presented here takes care of the magnetic saturation and estimates the magnetizing curve for complete current range of the machine. The proposed scheme does not require any external supply, measurement or data acquisition system and works at standstill thus avoiding the need to isolate the machine from its load or to block the rotor. This strategy is suitable for self-commissioning of induction motor drives and for sensorless control applications as well.
{"title":"Induction motor magnetizing characteristic identification at standstill with single-phase tests conducted through the inverter","authors":"S. Odhano, A. Cavagnino, R. Bojoi, Alberto Tenconi","doi":"10.1109/IEMDC.2015.7409177","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409177","url":null,"abstract":"In this paper, a magnetizing characteristic identification method for an induction machine at standstill is proposed. The technique is based on machine testing with a single-phase ac supply generated through a standard inverter. This type of test strategy is available in the literature, however, it has been used for parameter identification at a single current level thus ignoring the effects of magnetic saturation. To reproduce accurately the magnetizing curve, the test current level must be varied in order to trace the entire curve. The method presented here takes care of the magnetic saturation and estimates the magnetizing curve for complete current range of the machine. The proposed scheme does not require any external supply, measurement or data acquisition system and works at standstill thus avoiding the need to isolate the machine from its load or to block the rotor. This strategy is suitable for self-commissioning of induction motor drives and for sensorless control applications as well.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"13 1","pages":"960-966"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85324052","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409069
Xuezhou Wang, T. Strous, D. Lahaye, H. Polinder, J. Ferreira
Brushless doubly-fed induction machines (BDFIM) have great potential as variable-speed generators in larger-scale wind turbines. Undesired space harmonics exist because the special rotor needs to couple both two stator windings which with different pole-pair numbers and different frequencies. These rich space harmonics lead to a bigger torque ripple comparing to the normal induction machine. This paper makes use of 2D multi-slice finite element (FE) method to study the effect of the rotor skew on the performance of the BDFIM in the cases without and with saturation. The results show the torque ripple is reduced significantly by skewing the rotor both in those two situations. But the rotor skew has negligible influence on the harmonics due to the saturation effect. Furthermore, the rotor skew has little influence on the total amount of losses. However, based on the simulation results, it redistributes the core losses along the axial direction in the BDFIM.
{"title":"Effects of rotor skew on the performance of brushless doubly-fed induction machine","authors":"Xuezhou Wang, T. Strous, D. Lahaye, H. Polinder, J. Ferreira","doi":"10.1109/IEMDC.2015.7409069","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409069","url":null,"abstract":"Brushless doubly-fed induction machines (BDFIM) have great potential as variable-speed generators in larger-scale wind turbines. Undesired space harmonics exist because the special rotor needs to couple both two stator windings which with different pole-pair numbers and different frequencies. These rich space harmonics lead to a bigger torque ripple comparing to the normal induction machine. This paper makes use of 2D multi-slice finite element (FE) method to study the effect of the rotor skew on the performance of the BDFIM in the cases without and with saturation. The results show the torque ripple is reduced significantly by skewing the rotor both in those two situations. But the rotor skew has negligible influence on the harmonics due to the saturation effect. Furthermore, the rotor skew has little influence on the total amount of losses. However, based on the simulation results, it redistributes the core losses along the axial direction in the BDFIM.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"69 Suppl 4 1","pages":"260-265"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91162965","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409065
H. Nakane, T. Kosaka, N. Matsui
This paper presents design studies on hybrid excitation flux switching motor (HEFSM) that can compete with an interior permanent magnet synchronous motor (IPMSM) installed on TOYOTA PRIUS-2010. A stator of the HEFSM consists of not only laminated core and three-phase armature windings, but also field excitation coils and permanent magnets as field mmf sources. This machine makes it possible to vary its field flux by combining the two different mmf sources and thus, the name is capped by "hybrid excitation" as a variable field flux motor. The first trial manufacturing of HEFSM has been built for tests to assess its drive performances. Based on analysis of the test results, design refinements on the first test motor are examined to make the second trial manufacturing. Various experimental test results using the second test motor demonstrate that drive performances of the HEFSM are comparable to those of the PRIUS's IPMSM.
{"title":"Design studies on hybrid excitation flux switching motor with high power and torque densities for HEV applications","authors":"H. Nakane, T. Kosaka, N. Matsui","doi":"10.1109/IEMDC.2015.7409065","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409065","url":null,"abstract":"This paper presents design studies on hybrid excitation flux switching motor (HEFSM) that can compete with an interior permanent magnet synchronous motor (IPMSM) installed on TOYOTA PRIUS-2010. A stator of the HEFSM consists of not only laminated core and three-phase armature windings, but also field excitation coils and permanent magnets as field mmf sources. This machine makes it possible to vary its field flux by combining the two different mmf sources and thus, the name is capped by \"hybrid excitation\" as a variable field flux motor. The first trial manufacturing of HEFSM has been built for tests to assess its drive performances. Based on analysis of the test results, design refinements on the first test motor are examined to make the second trial manufacturing. Various experimental test results using the second test motor demonstrate that drive performances of the HEFSM are comparable to those of the PRIUS's IPMSM.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"168 1","pages":"234-239"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89427182","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409210
V. Bilyi, D. Gerling
This paper presents the design of a high-performance 14-pole, 12-slot interior permanent magnet synchronous machine with flux barriers inside the stator iron core and fractional-slot concentrated windings. This work focuses on electromagnetic, mechanical and thermal aspects of the machine design. The specific goal of this work was to design an electrical machine, which will have a small size, high power-to-weight ratio, high efficiency, especially at part-load operating points, and high speed capability for traction drive applications. Therefore the unconventional stator design is used. The proposed machine design was compared with the conventional one, concerning the magnetic saturation, spectrum of the magneto-motive force and produced torque. To ensure the high speed capability of the motor, the numerical structural analysis of the rotor is shown. Temperature behavior inside of the designed motor at steady-state operating point is shown.
{"title":"Design of high-efficiency interior permanent magnet synchronous machine with stator flux barriers and single-layer concentrated windings","authors":"V. Bilyi, D. Gerling","doi":"10.1109/IEMDC.2015.7409210","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409210","url":null,"abstract":"This paper presents the design of a high-performance 14-pole, 12-slot interior permanent magnet synchronous machine with flux barriers inside the stator iron core and fractional-slot concentrated windings. This work focuses on electromagnetic, mechanical and thermal aspects of the machine design. The specific goal of this work was to design an electrical machine, which will have a small size, high power-to-weight ratio, high efficiency, especially at part-load operating points, and high speed capability for traction drive applications. Therefore the unconventional stator design is used. The proposed machine design was compared with the conventional one, concerning the magnetic saturation, spectrum of the magneto-motive force and produced torque. To ensure the high speed capability of the motor, the numerical structural analysis of the rotor is shown. Temperature behavior inside of the designed motor at steady-state operating point is shown.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"39 1","pages":"1177-1183"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76590646","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409067
Alejandro J. Pina, S. Paul, R. Islam, Longya Xu
During the mass production of surface-mounted permanent magnet motors the rotor and stator geometrical dimensions usually deviate from their nominal values due to manufacturing tolerances which impact machine performance. One such common tolerance can be noticed in the placement of the permanent magnets on the rotor surface which creates new orders of cogging torque. Finite element models can be used to analyze the cogging generated due to the asymmetry in the magnet placement. However, it is time consuming to study the effect of imbalance of each magnet numerically since periodicity and symmetry conditions cannot be used to reduce the model. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against a finite element model and also with experimental results.
{"title":"Effect of radial asymmetry of magnets in surface-mounted permanent magnet motors on cogging torque","authors":"Alejandro J. Pina, S. Paul, R. Islam, Longya Xu","doi":"10.1109/IEMDC.2015.7409067","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409067","url":null,"abstract":"During the mass production of surface-mounted permanent magnet motors the rotor and stator geometrical dimensions usually deviate from their nominal values due to manufacturing tolerances which impact machine performance. One such common tolerance can be noticed in the placement of the permanent magnets on the rotor surface which creates new orders of cogging torque. Finite element models can be used to analyze the cogging generated due to the asymmetry in the magnet placement. However, it is time consuming to study the effect of imbalance of each magnet numerically since periodicity and symmetry conditions cannot be used to reduce the model. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against a finite element model and also with experimental results.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"283 1","pages":"247-253"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76835573","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409288
J. W. Jiang, B. Bilgin, Brock Howey, A. Emadi
This paper studies a design optimization procedure for switched reluctance motors (SRMs) using a Genetic Algorithm (GA). A multi-objective optimization method has been employed in the optimization of current commutation angles for priority operating points and over the entire operating range of the machine. Criteria of optimal control, which are maximizing output average torque and minimizing the root mean square value of net torque ripple, have been used in the optimization problem. A decision-making algorithm has been investigated to choose a solution from the optimal Pareto-front with finite optimal points. Five SRM design candidates have been selected and studied. The optimized motor performance at the priority operating points has been used to compare between different designs. Finally, a motor design that satisfies all design requirements has been characterized over its entire operating envelope based on turn-on and turn-off angles.
{"title":"Design optimization of switched reluctance machine using genetic algorithm","authors":"J. W. Jiang, B. Bilgin, Brock Howey, A. Emadi","doi":"10.1109/IEMDC.2015.7409288","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409288","url":null,"abstract":"This paper studies a design optimization procedure for switched reluctance motors (SRMs) using a Genetic Algorithm (GA). A multi-objective optimization method has been employed in the optimization of current commutation angles for priority operating points and over the entire operating range of the machine. Criteria of optimal control, which are maximizing output average torque and minimizing the root mean square value of net torque ripple, have been used in the optimization problem. A decision-making algorithm has been investigated to choose a solution from the optimal Pareto-front with finite optimal points. Five SRM design candidates have been selected and studied. The optimized motor performance at the priority operating points has been used to compare between different designs. Finally, a motor design that satisfies all design requirements has been characterized over its entire operating envelope based on turn-on and turn-off angles.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"47 1","pages":"1671-1677"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78403704","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 : 2015-05-10DOI: 10.1109/IEMDC.2015.7409312
C. Lechner, E. Schmidt
The paper discusses design, manufacturing and testing of a prototype permanent magnet synchronous machine for the application in an electric driven racing car. Very high performance and low mass of these machines are achieved by using a Halbach magnet array with a novel segmentation technology for reducing the eddy currents, high performance FeCo stator sheets as well as a fractional slot stator winding build of tooth coils. The final design of these 40 kW / 30 Nm machines yields a total mass of only 3.95 kg. The operating range is up to 18000 rpm with a nominal speed of 12600 rpm.
{"title":"Lightweight design and prototyping of high performance permanent magnet synchronous machines for an electric driven racing car","authors":"C. Lechner, E. Schmidt","doi":"10.1109/IEMDC.2015.7409312","DOIUrl":"https://doi.org/10.1109/IEMDC.2015.7409312","url":null,"abstract":"The paper discusses design, manufacturing and testing of a prototype permanent magnet synchronous machine for the application in an electric driven racing car. Very high performance and low mass of these machines are achieved by using a Halbach magnet array with a novel segmentation technology for reducing the eddy currents, high performance FeCo stator sheets as well as a fractional slot stator winding build of tooth coils. The final design of these 40 kW / 30 Nm machines yields a total mass of only 3.95 kg. The operating range is up to 18000 rpm with a nominal speed of 12600 rpm.","PeriodicalId":6477,"journal":{"name":"2015 IEEE International Electric Machines & Drives Conference (IEMDC)","volume":"5 1","pages":"1826-1830"},"PeriodicalIF":0.0,"publicationDate":"2015-05-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75174517","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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