Pub Date : 2013-03-17DOI: 10.1109/APEC.2013.6520770
Cong Li, Da Jiao, H. Mohan, F. Guo, Jin Wang
This paper discusses the modeling and application of Thermoelectric Cooling (TEC) in power electronics circuits. To investigate the benefits and challenges of using TEC, a comprehensive thermoelectric model which includes both power electronics circuit and TEC device is presented. With this model, the optimal operation range and dynamic base temperature control of power electronics switches are analyzed. The results show that with TEC, the base temperature of power electronics switches can maintain almost constant under different load conditions. Therefore, the switch lifetime and overall system reliability will be improved. Both simulation and experimental results are presented in this paper to verify the analysis.
{"title":"Thermoelectric Cooling for power electronics circuits: Modeling and applications","authors":"Cong Li, Da Jiao, H. Mohan, F. Guo, Jin Wang","doi":"10.1109/APEC.2013.6520770","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520770","url":null,"abstract":"This paper discusses the modeling and application of Thermoelectric Cooling (TEC) in power electronics circuits. To investigate the benefits and challenges of using TEC, a comprehensive thermoelectric model which includes both power electronics circuit and TEC device is presented. With this model, the optimal operation range and dynamic base temperature control of power electronics switches are analyzed. The results show that with TEC, the base temperature of power electronics switches can maintain almost constant under different load conditions. Therefore, the switch lifetime and overall system reliability will be improved. Both simulation and experimental results are presented in this paper to verify the analysis.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125392215","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520257
T. Sarkar, A. Challa, S. Sapp
Shielded-gate trench-MOSFETs yield superior performance compared to conventional gate trench devices by allowing higher doping density in the drift region and providing a `shielding effect' for the gate by placing an intermediate electrode between gate and drain. However, further design optimizations can be done for a shielded-gate trench-MOSFET to improve performance parameters particularly suited for next-generation high-frequency computing power supply applications and they have been outlined in this article. Channel length and threshold voltage optimization, substrate thinning and intrinsic gate resistance reduction (by layout enhancements) have been discussed along with their impact on device footprint reduction. Further, effects of these design optimizations on the power loss and efficiency of a high-frequency switching converter have been demonstrated through experimental characterizations.
{"title":"Enhanced shielded-gate trench MOSFETs for high-frequency, high-efficiency computing power supply applications","authors":"T. Sarkar, A. Challa, S. Sapp","doi":"10.1109/APEC.2013.6520257","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520257","url":null,"abstract":"Shielded-gate trench-MOSFETs yield superior performance compared to conventional gate trench devices by allowing higher doping density in the drift region and providing a `shielding effect' for the gate by placing an intermediate electrode between gate and drain. However, further design optimizations can be done for a shielded-gate trench-MOSFET to improve performance parameters particularly suited for next-generation high-frequency computing power supply applications and they have been outlined in this article. Channel length and threshold voltage optimization, substrate thinning and intrinsic gate resistance reduction (by layout enhancements) have been discussed along with their impact on device footprint reduction. Further, effects of these design optimizations on the power loss and efficiency of a high-frequency switching converter have been demonstrated through experimental characterizations.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126769222","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520428
Y. Jang, M. Jovanovic, J. M. Ruiz
A new three-phase, single-stage, isolated zero-voltage-switching (ZVS) rectifier that achieves less than 5% input-current total harmonic distortion (THD) and provides tightly regulated output voltage is introduced. The proposed circuit is obtained by integrating the three-phase, two-switch, ZVS, discontinuous-current-mode (DCM), boost power-factor-correction (PFC) rectifier with the ZVS full-bridge (FB) phase-shift dc/dc converter. The performance evaluation of the circuit was performed on a three-phase 1.8-kW prototype designed for the line-to-line voltage range of 180-264 VRMS and delivering a tightly regulated, selectable, dc output voltage from 220 V to 300 V.
本文介绍了一种新型三相、单级、隔离式零电压开关（ZVS）整流器，其输入电流总谐波失真（THD）小于 5%，并能提供严格调节的输出电压。所提出的电路是通过将三相、双开关、ZVS、非连续电流模式（DCM）、升压功率因数校正（PFC）整流器与 ZVS 全桥（FB）移相直流/直流转换器集成而成。该电路的性能评估是在一个三相 1.8 千瓦原型上进行的，设计线对线电压范围为 180-264 VRMS，可提供 220 V 至 300 V 的严格调节、可选直流输出电压。
{"title":"The single-stage TAIPEI rectifier","authors":"Y. Jang, M. Jovanovic, J. M. Ruiz","doi":"10.1109/APEC.2013.6520428","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520428","url":null,"abstract":"A new three-phase, single-stage, isolated zero-voltage-switching (ZVS) rectifier that achieves less than 5% input-current total harmonic distortion (THD) and provides tightly regulated output voltage is introduced. The proposed circuit is obtained by integrating the three-phase, two-switch, ZVS, discontinuous-current-mode (DCM), boost power-factor-correction (PFC) rectifier with the ZVS full-bridge (FB) phase-shift dc/dc converter. The performance evaluation of the circuit was performed on a three-phase 1.8-kW prototype designed for the line-to-line voltage range of 180-264 VRMS and delivering a tightly regulated, selectable, dc output voltage from 220 V to 300 V.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126859926","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520662
D. Huwig, P. Wambsganss
Reducing power loss in wireless power receivers is important to avoid thermal design issues. Synchronous rectification is a suitable means for loss reduction. In this paper we propose a synchronous rectifier with a simple control scheme. A detailed analysis leads to a time-domain model which is used to perform a power loss analysis. Experimental verification shows that the predicted efficiency improvement agrees with measurement results.
{"title":"Digitally controlled synchronous bridge-rectifier for wireless power receivers","authors":"D. Huwig, P. Wambsganss","doi":"10.1109/APEC.2013.6520662","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520662","url":null,"abstract":"Reducing power loss in wireless power receivers is important to avoid thermal design issues. Synchronous rectification is a suitable means for loss reduction. In this paper we propose a synchronous rectifier with a simple control scheme. A detailed analysis leads to a time-domain model which is used to perform a power loss analysis. Experimental verification shows that the predicted efficiency improvement agrees with measurement results.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115455968","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520460
E. Reutzel, Rengeng Chen, S. Ragona, D. Jauregui
Accurate and lossless current sensing is a must for high performance multiphase buck converters used in the latest voltage regulation modules (VRMs). This paper presents a sync FET on-state resistance based approach for reconstructing a highly accurate inductor current signal that is immune to changes in operating conditions and temperature. This technique replaces DCR based sensing and can be used with any controller which requires inductor current information. The sense circuitry is built into the MOSFET driver, which in turn is co-packaged with the MOSFETs for reduced total footprint and ease of design. In addition, the accuracy that can be achieved with this technique is significantly better than the typical accuracy achieved with DCR sensing.
{"title":"An integrated current sense technique for multiphase buck converters to improve accuracy and reduce solution footprint","authors":"E. Reutzel, Rengeng Chen, S. Ragona, D. Jauregui","doi":"10.1109/APEC.2013.6520460","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520460","url":null,"abstract":"Accurate and lossless current sensing is a must for high performance multiphase buck converters used in the latest voltage regulation modules (VRMs). This paper presents a sync FET on-state resistance based approach for reconstructing a highly accurate inductor current signal that is immune to changes in operating conditions and temperature. This technique replaces DCR based sensing and can be used with any controller which requires inductor current information. The sense circuitry is built into the MOSFET driver, which in turn is co-packaged with the MOSFETs for reduced total footprint and ease of design. In addition, the accuracy that can be achieved with this technique is significantly better than the typical accuracy achieved with DCR sensing.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115586259","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520535
R. Greenwell, B. M. McCue, Leon M. Tolbert, B. Blalock, Syed K. Islam
High-temperature integrated circuits fill a need in applications where there are obvious benefits to reduced thermal management or where circuitry is placed away from temperature extremes. Examples of these applications include aerospace, automotive, power generation, and well-logging. This work focuses on automotive applications in which the growing demand for hybrid electric vehicles (HEVs), Plug-in-hybrids (PHEVs), and Fuel-cell vehicles (FCVs) has increased the need for high-temperature electronics that can operate at the extreme ambient temperatures that exist under the hood of these vehicles, which can be in excess of 150°C. Silicon carbide (SiC) and other wide-bandgap power switches that can function at these temperature extremes are now entering the market. To take full advantage of their potential, high-temperature capable circuits that can also operate in these environments are required.
{"title":"High-temperature SOI-based gate driver IC for WBG power switches","authors":"R. Greenwell, B. M. McCue, Leon M. Tolbert, B. Blalock, Syed K. Islam","doi":"10.1109/APEC.2013.6520535","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520535","url":null,"abstract":"High-temperature integrated circuits fill a need in applications where there are obvious benefits to reduced thermal management or where circuitry is placed away from temperature extremes. Examples of these applications include aerospace, automotive, power generation, and well-logging. This work focuses on automotive applications in which the growing demand for hybrid electric vehicles (HEVs), Plug-in-hybrids (PHEVs), and Fuel-cell vehicles (FCVs) has increased the need for high-temperature electronics that can operate at the extreme ambient temperatures that exist under the hood of these vehicles, which can be in excess of 150°C. Silicon carbide (SiC) and other wide-bandgap power switches that can function at these temperature extremes are now entering the market. To take full advantage of their potential, high-temperature capable circuits that can also operate in these environments are required.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114478827","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520186
N. Sukesh, M. Pahlevaninezhad, P. Jain
A novel Zero Voltage Switching (ZVS) approach to improve the efficiency of a single-stage grid connected flyback inverter is proposed in this paper. The proposed scheme eliminates the need for any additional auxiliary circuits to achieve soft-switching. ZVS of the primary switch is realized by allowing negative current from the grid-side through bidirectional switches placed on the secondary side of the transformer. The negative current discharges the MOSFET's output capacitor thereby allowing ZVS turn-on of the primary switch. Therefore, the switching losses of the bi-directional switches are negligible. In order to optimize the amount of reactive current required to achieve ZVS, a variable frequency control scheme is implemented over the line cycle. A 250W prototype was implemented to validate the proposed scheme. Experimental results confirm the feasibility and superior performance of the converter compared to the conventional flyback inverter.
{"title":"Novel scheme for Zero Voltage Switching of single stage photovoltaic micro-inverter","authors":"N. Sukesh, M. Pahlevaninezhad, P. Jain","doi":"10.1109/APEC.2013.6520186","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520186","url":null,"abstract":"A novel Zero Voltage Switching (ZVS) approach to improve the efficiency of a single-stage grid connected flyback inverter is proposed in this paper. The proposed scheme eliminates the need for any additional auxiliary circuits to achieve soft-switching. ZVS of the primary switch is realized by allowing negative current from the grid-side through bidirectional switches placed on the secondary side of the transformer. The negative current discharges the MOSFET's output capacitor thereby allowing ZVS turn-on of the primary switch. Therefore, the switching losses of the bi-directional switches are negligible. In order to optimize the amount of reactive current required to achieve ZVS, a variable frequency control scheme is implemented over the line cycle. A 250W prototype was implemented to validate the proposed scheme. Experimental results confirm the feasibility and superior performance of the converter compared to the conventional flyback inverter.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116814362","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520282
Han Peng, V. Pala, T. Chow, M. Hella
A 100 MHz DC-DC converter for RF power amplifier modules employing polar modulation is presented. A resonant low side gate driver and phase shedding/segmentation in the output stage are used for light load efficiency improvement. The proposed two-phases four-segments flip chip DC-DC converter is implemented in 0.5 μm AlGaAs/GaAs p-HEMT technology and occupies 2.5×2 mm2 for the two segments. An efficiency improvement of 5% is achieved at 4.5 V to 1 V conversion using the resonant low side gate driver. The peak efficiency at 4.5 V/3.3 V and 2 A output current is 85% with the peak value maintained as the load current changes from 0.2 A to 2.8 A under phase shedding/segmentation.
{"title":"100 MHz, 85% efficient integrated AlGaAs/GaAs supply modulator for RF power amplifier modules","authors":"Han Peng, V. Pala, T. Chow, M. Hella","doi":"10.1109/APEC.2013.6520282","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520282","url":null,"abstract":"A 100 MHz DC-DC converter for RF power amplifier modules employing polar modulation is presented. A resonant low side gate driver and phase shedding/segmentation in the output stage are used for light load efficiency improvement. The proposed two-phases four-segments flip chip DC-DC converter is implemented in 0.5 μm AlGaAs/GaAs p-HEMT technology and occupies 2.5×2 mm2 for the two segments. An efficiency improvement of 5% is achieved at 4.5 V to 1 V conversion using the resonant low side gate driver. The peak efficiency at 4.5 V/3.3 V and 2 A output current is 85% with the peak value maintained as the load current changes from 0.2 A to 2.8 A under phase shedding/segmentation.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129495613","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520741
Cheng-Nan Wu, Yaow-Ming Chen, Yang-Lin Chen
The objective of this paper is to propose a high-precision control strategy for the primary-side regulated flyback converter. The primary-side regulated flyback converter with universal input voltage is widely used for low-cost and low power applications such as the LED lighting with constant output currents. However, the conventional primary-side regulation method suffers from the drawback of current inaccuracy and the LED may be easily damaged. Therefore, a high-precision primary-side regulation strategy for the flyback converter with constant output current is proposed. In this paper, the cause of the output current inaccuracy is discussed and the operation principle of the proposed high-precision current control for the primary-side regulated flyback converter is introduced. Hardware experimental measurements are presented to verify the performance of the proposed control strategy.
{"title":"High-precision constant output current control for primary-side regulated flyback converters","authors":"Cheng-Nan Wu, Yaow-Ming Chen, Yang-Lin Chen","doi":"10.1109/APEC.2013.6520741","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520741","url":null,"abstract":"The objective of this paper is to propose a high-precision control strategy for the primary-side regulated flyback converter. The primary-side regulated flyback converter with universal input voltage is widely used for low-cost and low power applications such as the LED lighting with constant output currents. However, the conventional primary-side regulation method suffers from the drawback of current inaccuracy and the LED may be easily damaged. Therefore, a high-precision primary-side regulation strategy for the flyback converter with constant output current is proposed. In this paper, the cause of the output current inaccuracy is discussed and the operation principle of the proposed high-precision current control for the primary-side regulated flyback converter is introduced. Hardware experimental measurements are presented to verify the performance of the proposed control strategy.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128407339","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 : 2013-03-17DOI: 10.1109/APEC.2013.6520233
M. Pahlevaninezhad, P. Das, G. Moschopoulos, P. Jain
This paper presents a novel approach to control a boost PFC AC/DC converter without using any current sensors. Due to the particular structure of the boost PFC AC/DC converter, sensorless control of the converter is very challenging. As illustrated in this paper, the converter loses its observability for some operating points. This is the reason that the sensorless control of the boost PFC entails special attentions. A very simple and practical senseless scheme is proposed in this paper, which is able to accurately estimate the inductor current for the entire operating range of the converter. In addition, a very simple and practical closed-loop control approach is proposed in order to improve the transient response of the single-phase boost PFC converter. This approach eliminates the need for filtering double frequency ripple from the output voltage, which allows increasing the bandwidth of the external voltage loop. Simulation and experimental results validate the feasibility of the proposed technique and confirm its superior performance compared to the conventional control system.
{"title":"Sensorless control of a boost PFC AC/DC converter with a very fast transient response","authors":"M. Pahlevaninezhad, P. Das, G. Moschopoulos, P. Jain","doi":"10.1109/APEC.2013.6520233","DOIUrl":"https://doi.org/10.1109/APEC.2013.6520233","url":null,"abstract":"This paper presents a novel approach to control a boost PFC AC/DC converter without using any current sensors. Due to the particular structure of the boost PFC AC/DC converter, sensorless control of the converter is very challenging. As illustrated in this paper, the converter loses its observability for some operating points. This is the reason that the sensorless control of the boost PFC entails special attentions. A very simple and practical senseless scheme is proposed in this paper, which is able to accurately estimate the inductor current for the entire operating range of the converter. In addition, a very simple and practical closed-loop control approach is proposed in order to improve the transient response of the single-phase boost PFC converter. This approach eliminates the need for filtering double frequency ripple from the output voltage, which allows increasing the bandwidth of the external voltage loop. Simulation and experimental results validate the feasibility of the proposed technique and confirm its superior performance compared to the conventional control system.","PeriodicalId":256756,"journal":{"name":"2013 Twenty-Eighth Annual IEEE Applied Power Electronics Conference and Exposition (APEC)","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124555565","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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