Pub Date : 2012-06-02DOI: 10.1109/IPEMC.2012.6258890
O. H. Abdalla, Minxiao Han
This paper presents a cascaded H-bridge multilevel converter for application in variable-speed pump storage. Most of the results are related the performance of the inverter voltage, rotor currents and speed when the 6kV wound router induction machine is fed by 11 level H bridge inverter. Multi carrier phase shift modulation is used to obtain 11 level phase voltage. The phase shift transformer is used to feed the rectifier side of the H-Bridge cascaded multi-level converter to reduce the total harmonic distortion of the current motor. A simulation model based on the PS IM software program is used.
{"title":"Variable speed pumped storage based on the use of H-bridge cascaded multilevel converter","authors":"O. H. Abdalla, Minxiao Han","doi":"10.1109/IPEMC.2012.6258890","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6258890","url":null,"abstract":"This paper presents a cascaded H-bridge multilevel converter for application in variable-speed pump storage. Most of the results are related the performance of the inverter voltage, rotor currents and speed when the 6kV wound router induction machine is fed by 11 level H bridge inverter. Multi carrier phase shift modulation is used to obtain 11 level phase voltage. The phase shift transformer is used to feed the rectifier side of the H-Bridge cascaded multi-level converter to reduce the total harmonic distortion of the current motor. A simulation model based on the PS IM software program is used.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"117 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124202139","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259024
Xiao-Fei He, Zhiliang Zhang, Xin Li
For an interleaved flyback micro-inverter, the efficiency at heavy load is mainly determined by the conduction loss and switching loss of the semiconductor switches and magnetic components, whereas the efficiency at light load is primarily determined by the frequency-dependent losses such as the MOSFET driving loss, the turn-off loss and the transformer core loss. To shield one phase is an effective method to reduce the frequency-dependent loss and to minimize the overall loss during wide range. In this paper, both Boundary Conduction Mode (BCM) and Discontinuous Conduction Mode (DCM) control strategies are investigated for the flyback micro-inverters. Then 2Φ DCM and 1Φ DCM control methods are investigated and a hybrid control method is proposed to minimize the overall loss depending on different load current to achieve high efficiency in wide load range. The experimental results verified the benefits of the proposed hybrid control method.
{"title":"An optimal control method for photovoltaic grid-connected interleaved flyback micro-inverters to achieve high efficiency in wide load range","authors":"Xiao-Fei He, Zhiliang Zhang, Xin Li","doi":"10.1109/IPEMC.2012.6259024","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259024","url":null,"abstract":"For an interleaved flyback micro-inverter, the efficiency at heavy load is mainly determined by the conduction loss and switching loss of the semiconductor switches and magnetic components, whereas the efficiency at light load is primarily determined by the frequency-dependent losses such as the MOSFET driving loss, the turn-off loss and the transformer core loss. To shield one phase is an effective method to reduce the frequency-dependent loss and to minimize the overall loss during wide range. In this paper, both Boundary Conduction Mode (BCM) and Discontinuous Conduction Mode (DCM) control strategies are investigated for the flyback micro-inverters. Then 2Φ DCM and 1Φ DCM control methods are investigated and a hybrid control method is proposed to minimize the overall loss depending on different load current to achieve high efficiency in wide load range. The experimental results verified the benefits of the proposed hybrid control method.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123533148","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259305
Wu Jian, Hu Zhihao, X. Dianguo, Hua Ke
With the extensive use of power quality compensator and wind power generation system, various voltage sag generators (VSG) have been designed to achieve the performance test of power quality compensator and satisfy the requirement of low voltage ride through (LVRT) experiment of wind power system. Two methods to simulate the sag of grid voltage are proposed, one is to use autotransformer regulator and switches, and the other one is based on the topology of power electronic device. Both of them have been analyzed on their work principles and topology in detail. Then, on the basis of the result, experimental prototype is built for functional verification. Experimental results make out that the autotransformer regulator based VSG has simple structure, but it fails to achieve the phase angle jump and needs electronic switches to take place of contactor to avoid the control delay; the power electronic based VSG is more flexible that it can produce various voltage faults with controllable amplitude, phase and duration time. Moreover, the power electronic based VSG has a transient process with smooth transition.
{"title":"An experimental research on comparison of two kinds of voltage sag generators","authors":"Wu Jian, Hu Zhihao, X. Dianguo, Hua Ke","doi":"10.1109/IPEMC.2012.6259305","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259305","url":null,"abstract":"With the extensive use of power quality compensator and wind power generation system, various voltage sag generators (VSG) have been designed to achieve the performance test of power quality compensator and satisfy the requirement of low voltage ride through (LVRT) experiment of wind power system. Two methods to simulate the sag of grid voltage are proposed, one is to use autotransformer regulator and switches, and the other one is based on the topology of power electronic device. Both of them have been analyzed on their work principles and topology in detail. Then, on the basis of the result, experimental prototype is built for functional verification. Experimental results make out that the autotransformer regulator based VSG has simple structure, but it fails to achieve the phase angle jump and needs electronic switches to take place of contactor to avoid the control delay; the power electronic based VSG is more flexible that it can produce various voltage faults with controllable amplitude, phase and duration time. Moreover, the power electronic based VSG has a transient process with smooth transition.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114321706","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259203
Weixing Li, Xiaoming Mou, Yuebin Zhou, C. Marnay
Owing to the increasing prevalence for DC home appliances and distributed energy resources, the concept of a DC home microgrid is attracting considerable attention. This paper is to investigate voltage standards for DC home microgrids. First, a DC home microgrid configuration is proposed. All home loads are divided into five groups for separate connection to a common DC bus. An alternative path is designed to supply the high-power load groups through the public AC grid with less power conversion stages, when local sources are deficient. Second, voltage levels and wire cross-sections for different load groups are discussed, according to line thermal limits, power losses, and voltage drops. The results show that, if 120 volts is chosen for the DC bus, higher voltage standard over 120 volts could not bring loss savings for load groups. It can also be concluded that, 24 V DC could be a standard only for extra-low power appliances in a small house or single room, because of big losses; instead, 48 V DC may be better suitable for lighting and low-power appliances, especially when most of them could be working on 48 V DC in future.
{"title":"On voltage standards for DC home microgrids energized by distributed sources","authors":"Weixing Li, Xiaoming Mou, Yuebin Zhou, C. Marnay","doi":"10.1109/IPEMC.2012.6259203","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259203","url":null,"abstract":"Owing to the increasing prevalence for DC home appliances and distributed energy resources, the concept of a DC home microgrid is attracting considerable attention. This paper is to investigate voltage standards for DC home microgrids. First, a DC home microgrid configuration is proposed. All home loads are divided into five groups for separate connection to a common DC bus. An alternative path is designed to supply the high-power load groups through the public AC grid with less power conversion stages, when local sources are deficient. Second, voltage levels and wire cross-sections for different load groups are discussed, according to line thermal limits, power losses, and voltage drops. The results show that, if 120 volts is chosen for the DC bus, higher voltage standard over 120 volts could not bring loss savings for load groups. It can also be concluded that, 24 V DC could be a standard only for extra-low power appliances in a small house or single room, because of big losses; instead, 48 V DC may be better suitable for lighting and low-power appliances, especially when most of them could be working on 48 V DC in future.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"33 7-8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116476488","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259180
Xinlong Liu, R. Wang, Xueguang Zhang, Dianguo Xu
This paper analyses the theory of variable pitch wind turbines, and according to the works of various parts of the wind turbine, establishes the mathematical model of the aerodynamic part, the drive part, the operative part and the whole unit. An algorithm is proposed to allow the generator to track the maximum power points of the wind turbine system when the wind speed is below the rated value and control the pitch angle to keep the output active power under the rated power when the wind speed is above the rated value by the gain scheduling PD controller. The proposed algorithm has been simulated in the main controller of SIMATIC MICROBOX PC, and good control results are achieved.
{"title":"Gain scheduling PD controller for variable pitch wind turbines","authors":"Xinlong Liu, R. Wang, Xueguang Zhang, Dianguo Xu","doi":"10.1109/IPEMC.2012.6259180","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259180","url":null,"abstract":"This paper analyses the theory of variable pitch wind turbines, and according to the works of various parts of the wind turbine, establishes the mathematical model of the aerodynamic part, the drive part, the operative part and the whole unit. An algorithm is proposed to allow the generator to track the maximum power points of the wind turbine system when the wind speed is below the rated value and control the pitch angle to keep the output active power under the rated power when the wind speed is above the rated value by the gain scheduling PD controller. The proposed algorithm has been simulated in the main controller of SIMATIC MICROBOX PC, and good control results are achieved.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128087899","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6258907
X. Qu, Siu-Chung Wong, C. Tse, Zai-jun Wu
Advanced techniques in light-emitting-diode (LED) light sources allow LED lighting to appear in more and more applications. Besides providing the constant driving current source, LED ballast is usually isolated for safety specifications and dimmed for energy saving. Normally, LED ballast is designed with transformer for isolation and external circuits for dimming, increasing the challenges and complexity of the ballast design. To overcome the above limitations, this paper proposed a non-electrical dimming method based on a contactless transformer, taking full use of the transformer parasitical parameters to transfer energy by resonance. By adjusting the transformer air gap mechanically, the parameters in the resonance tank will change sensitively, which can be used for dimming control without additional components and control. In some extreme conditions, the proposed ballast provides a total environmentally-shield secondary enclosure with contactless transformer. Analysis, design example and prototype verification are given for the LED ballast and dimming control.
{"title":"Contactless electronic ballast for high brightness LED lamps with mechanical dimming method","authors":"X. Qu, Siu-Chung Wong, C. Tse, Zai-jun Wu","doi":"10.1109/IPEMC.2012.6258907","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6258907","url":null,"abstract":"Advanced techniques in light-emitting-diode (LED) light sources allow LED lighting to appear in more and more applications. Besides providing the constant driving current source, LED ballast is usually isolated for safety specifications and dimmed for energy saving. Normally, LED ballast is designed with transformer for isolation and external circuits for dimming, increasing the challenges and complexity of the ballast design. To overcome the above limitations, this paper proposed a non-electrical dimming method based on a contactless transformer, taking full use of the transformer parasitical parameters to transfer energy by resonance. By adjusting the transformer air gap mechanically, the parameters in the resonance tank will change sensitively, which can be used for dimming control without additional components and control. In some extreme conditions, the proposed ballast provides a total environmentally-shield secondary enclosure with contactless transformer. Analysis, design example and prototype verification are given for the LED ballast and dimming control.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"171 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115939828","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259110
Daqing Wang, Tao Meng, H. Ben, Yan Liu
Power factor correctin technique is an effect active to eliminate the harmonic pollution of power system. A single-stage power factor corrector basic on clamptive technique is presented in this paper. PFC and AC/DC power conversion is manipulated in one stage circuit. Due to the adoption of high frequency transformer, the electrical isolation between input and output sides can be realized. The voltage stress of each switch is reduced due to the active clamp circuit. By using soft-switching techniques, the bridge devices and the clamp switch could achieve ZVS (Zero-Voltage-Switching). Because of the characteristic of the structure, there is big current peak in the input inductor when the corrector starting-up. The scheme of soft starting-up is introduced, which made the starting-up process smoothly. Experimental results show that this converter has a good effect.
{"title":"Single-stage full-bridge PFC converter basic on clamptive technique and its starting-up scheme","authors":"Daqing Wang, Tao Meng, H. Ben, Yan Liu","doi":"10.1109/IPEMC.2012.6259110","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259110","url":null,"abstract":"Power factor correctin technique is an effect active to eliminate the harmonic pollution of power system. A single-stage power factor corrector basic on clamptive technique is presented in this paper. PFC and AC/DC power conversion is manipulated in one stage circuit. Due to the adoption of high frequency transformer, the electrical isolation between input and output sides can be realized. The voltage stress of each switch is reduced due to the active clamp circuit. By using soft-switching techniques, the bridge devices and the clamp switch could achieve ZVS (Zero-Voltage-Switching). Because of the characteristic of the structure, there is big current peak in the input inductor when the corrector starting-up. The scheme of soft starting-up is introduced, which made the starting-up process smoothly. Experimental results show that this converter has a good effect.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131387068","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}
A novel flux damping control strategy of DFIG based on grid voltage oriented is proposed in this paper. The transient DC flux component will emerge in DFIG stator because of the voltage changed by grid fault, which makes the output power fluctuate and the electromagnetic torque vibrate. In serious conditions, over voltage and current will be induced in the generator rotor. So it is necessary to adopt the flux damping control strategy to eliminate the DC flux component in stator. Firstly the influence on electromagnetic relationship caused by grid fault is analyzed based on the DFIG model. The stability of DFIG grid voltage vector oriented control strategy is also analyzed. The principle of the proposed flux damping control strategy is introduced in details. The effects of the rotor side converter's rate and the generator operation state are considered. Finally, the availability of proposed control strategy is verified by simulation results. The transient DC flux component can be eliminated quickly and the stability of control system is improved, so this method is helpful to achieve the LVRT (low voltage ride through) operation of DFIG system.
{"title":"A novel flux damping control strategy of DFIG based on voltage vector oriented","authors":"Hongbin Ma, Xueguang Zhang, Xinlong Liu, Dianguo Xu","doi":"10.1109/IPEMC.2012.6259181","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259181","url":null,"abstract":"A novel flux damping control strategy of DFIG based on grid voltage oriented is proposed in this paper. The transient DC flux component will emerge in DFIG stator because of the voltage changed by grid fault, which makes the output power fluctuate and the electromagnetic torque vibrate. In serious conditions, over voltage and current will be induced in the generator rotor. So it is necessary to adopt the flux damping control strategy to eliminate the DC flux component in stator. Firstly the influence on electromagnetic relationship caused by grid fault is analyzed based on the DFIG model. The stability of DFIG grid voltage vector oriented control strategy is also analyzed. The principle of the proposed flux damping control strategy is introduced in details. The effects of the rotor side converter's rate and the generator operation state are considered. Finally, the availability of proposed control strategy is verified by simulation results. The transient DC flux component can be eliminated quickly and the stability of control system is improved, so this method is helpful to achieve the LVRT (low voltage ride through) operation of DFIG system.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"147 8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129995181","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6258952
Ning He, Dehong Xu, Ye Zhu, Jun Zhang, G. Shen, Yangfan Zhang, Jie Ma, Changjin Liu
A novel control method, named Weighted Average Current control (WACC) is proposed for damping control of three-phase grid inverter with LCL-filter. With WACC, three-phase current control of the grid inverter can be decoupled under synchronous rotating frame (SRF). Besides the system transfer function is degraded from the 6th order system to the 1st order one. Consequently, the control loop gain and bandwidth can be increased. Therefore the current control of the grid system is able to be optimized easily for higher power quality and good dynamics. WACC is verified with the experiment on a 30kW three-phase grid inverter prototype.
{"title":"Weighted Average Current control in three-phase grid inverter with LCL-filter","authors":"Ning He, Dehong Xu, Ye Zhu, Jun Zhang, G. Shen, Yangfan Zhang, Jie Ma, Changjin Liu","doi":"10.1109/IPEMC.2012.6258952","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6258952","url":null,"abstract":"A novel control method, named Weighted Average Current control (WACC) is proposed for damping control of three-phase grid inverter with LCL-filter. With WACC, three-phase current control of the grid inverter can be decoupled under synchronous rotating frame (SRF). Besides the system transfer function is degraded from the 6th order system to the 1st order one. Consequently, the control loop gain and bandwidth can be increased. Therefore the current control of the grid system is able to be optimized easily for higher power quality and good dynamics. WACC is verified with the experiment on a 30kW three-phase grid inverter prototype.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130115504","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 : 2012-06-02DOI: 10.1109/IPEMC.2012.6259087
Li Ning, W. Yue, Liangcheng Su, Liao YuFei, Wang Zhao-an
In this paper, direct power control strategy used in three-level neutral point clamped (NPC) converters is discussed. With the theory of instantaneous power, it gets the deep relations between power (active power and reactive power) and space voltage vectors. After the analysis, considering the special issues in three-level NPC converters, such as the excessive dv/dt and fluctuation of neutral point potential, a direct power control (DPC) strategy for three-level NPC converters is proposed. Simulation results show the correctness of the new DPC control strategy.
{"title":"Direct power control strategy used in three-level NPC converters","authors":"Li Ning, W. Yue, Liangcheng Su, Liao YuFei, Wang Zhao-an","doi":"10.1109/IPEMC.2012.6259087","DOIUrl":"https://doi.org/10.1109/IPEMC.2012.6259087","url":null,"abstract":"In this paper, direct power control strategy used in three-level neutral point clamped (NPC) converters is discussed. With the theory of instantaneous power, it gets the deep relations between power (active power and reactive power) and space voltage vectors. After the analysis, considering the special issues in three-level NPC converters, such as the excessive dv/dt and fluctuation of neutral point potential, a direct power control (DPC) strategy for three-level NPC converters is proposed. Simulation results show the correctness of the new DPC control strategy.","PeriodicalId":236136,"journal":{"name":"Proceedings of The 7th International Power Electronics and Motion Control Conference","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130147437","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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