Pub Date : 2012-11-12DOI: 10.1109/ECCE.2012.6342673
S. Saarakkala, Marko Hinkkanen, Kai Zenger
This paper deals with model-based two-degrees-of-freedom (2DOF) speed control of two-mass systems. An analytic gain selection of a proportional integral (PI) type feedback controller is proposed. The gains are given as functions of system parameters and desired dominant closed-loop poles. An analytic design of a prefilter is given to complete the 2DOF structure, using the pole-zero distribution of the feedback loop. The prefilter design covers step, ramp, and parabolic reference tracking. The proposed 2DOF controller is evaluated by means of simulations and experiments. The experimental setup consists of two 4-kW servo motors coupled together with a toothed belt. It was found that the proposed controller gives good reference tracking for step and dynamic commands as well as robust and fast load-torque rejection.
{"title":"Speed control of two-mass mechanical loads in electric drives","authors":"S. Saarakkala, Marko Hinkkanen, Kai Zenger","doi":"10.1109/ECCE.2012.6342673","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342673","url":null,"abstract":"This paper deals with model-based two-degrees-of-freedom (2DOF) speed control of two-mass systems. An analytic gain selection of a proportional integral (PI) type feedback controller is proposed. The gains are given as functions of system parameters and desired dominant closed-loop poles. An analytic design of a prefilter is given to complete the 2DOF structure, using the pole-zero distribution of the feedback loop. The prefilter design covers step, ramp, and parabolic reference tracking. The proposed 2DOF controller is evaluated by means of simulations and experiments. The experimental setup consists of two 4-kW servo motors coupled together with a toothed belt. It was found that the proposed controller gives good reference tracking for step and dynamic commands as well as robust and fast load-torque rejection.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"3 1","pages":"1246-1253"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81655575","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342307
J. Asama, D. Kanehara, T. Oiwa, A. Chiba
A novel centrifugal pump has been developed that employs a bearingless motor with two-axis radial active positioning control. The structure of this motor is an extension of a hybrid of consequent-pole and homopolar-type bearingless motors. The passive stiffness has been enhanced. The test pump was fabricated and found to provide a maximum pump output of 1 W with a flow rate of 4 L/min against a head pressure of water of 1.5 m. An impeller with a shroud contributes to a significant reduction in axial impeller movement caused by axial fluid force. The rotor vibration is significantly smaller than the fluid gaps in the pump casing. In addition, significant torque ripple of the consequent-pole bearingless motor has no influence on the suspension performance. The experimental results demonstrate that the proposed consequent-pole bearingless motor is feasible and effective for a centrifugal pump.
{"title":"Performance investigation of a centrifugal pump with a consequent-pole bearingless motor","authors":"J. Asama, D. Kanehara, T. Oiwa, A. Chiba","doi":"10.1109/ECCE.2012.6342307","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342307","url":null,"abstract":"A novel centrifugal pump has been developed that employs a bearingless motor with two-axis radial active positioning control. The structure of this motor is an extension of a hybrid of consequent-pole and homopolar-type bearingless motors. The passive stiffness has been enhanced. The test pump was fabricated and found to provide a maximum pump output of 1 W with a flow rate of 4 L/min against a head pressure of water of 1.5 m. An impeller with a shroud contributes to a significant reduction in axial impeller movement caused by axial fluid force. The rotor vibration is significantly smaller than the fluid gaps in the pump casing. In addition, significant torque ripple of the consequent-pole bearingless motor has no influence on the suspension performance. The experimental results demonstrate that the proposed consequent-pole bearingless motor is feasible and effective for a centrifugal pump.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"6 1","pages":"3663-3669"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79700013","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342572
M. Savaghebi, J. Vasquez, Alireza Jalilian, Josep M. Guerrero, Tzung-Lin Lee
This paper presents a new control approach for voltage source inverters ended with LCL filters for microgrid applications. The control approach consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop. The virtual impedance is added in order to mitigate the voltage distortion after the output inductor and improve the load sharing among parallel inverters. A general case with a combined voltage harmonic and unbalance distortion is considered. In such a case, voltage distortion is mitigated by inserting capacitive virtual impedance for negative sequence of fundamental component as well as positive and negative sequences of main harmonic components. Furthermore, resistive virtual impedances are added at these components in order to provide a proper load sharing and make the overall system more damped. Simulation results are presented to demonstrate the effectiveness of the proposed control approach.
{"title":"Selective harmonic virtual impedance for voltage source inverters with LCL filter in microgrids","authors":"M. Savaghebi, J. Vasquez, Alireza Jalilian, Josep M. Guerrero, Tzung-Lin Lee","doi":"10.1109/ECCE.2012.6342572","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342572","url":null,"abstract":"This paper presents a new control approach for voltage source inverters ended with LCL filters for microgrid applications. The control approach consists of voltage and current inner control loops in order to fix the filter capacitor voltage and a virtual impedance loop. The virtual impedance is added in order to mitigate the voltage distortion after the output inductor and improve the load sharing among parallel inverters. A general case with a combined voltage harmonic and unbalance distortion is considered. In such a case, voltage distortion is mitigated by inserting capacitive virtual impedance for negative sequence of fundamental component as well as positive and negative sequences of main harmonic components. Furthermore, resistive virtual impedances are added at these components in order to provide a proper load sharing and make the overall system more damped. Simulation results are presented to demonstrate the effectiveness of the proposed control approach.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"348 1","pages":"1960-1965"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79703746","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342157
Sehwan Kim, J. Seok
This paper proposes a voltage-limited finite-settling-step direct torque and flux control (FSS-DTFC) method with a constant switching frequency for torque-controlled interior permanent-magnet synchronous motors (IPMSMs). The proposed control law dynamically scales voltage vectors on the hexagonal voltage boundary to ensure maximum torque capabilities at given operating conditions, while simultaneously regulating the stator flux linkage magnitude under flux-weakening operation. Instead of evaluating control performance based on intuitive voltage selection rule, this paper focuses on developing a discrete time function of the rate of change of an air-gap torque for facilitating optimal voltage vector choices. Then, this analytical solution leads to optimal voltage modification at each time step with respect to the available inverter voltage. The voltage-limited FSS-DTFC approach has potential advantages of achieving fastest transient torque trajectories and direct manipulation of the stator flux linkage while exploiting maximum voltage excitation.
{"title":"Wide-speed direct torque and flux control of torque-controlled IPMSM drives","authors":"Sehwan Kim, J. Seok","doi":"10.1109/ECCE.2012.6342157","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342157","url":null,"abstract":"This paper proposes a voltage-limited finite-settling-step direct torque and flux control (FSS-DTFC) method with a constant switching frequency for torque-controlled interior permanent-magnet synchronous motors (IPMSMs). The proposed control law dynamically scales voltage vectors on the hexagonal voltage boundary to ensure maximum torque capabilities at given operating conditions, while simultaneously regulating the stator flux linkage magnitude under flux-weakening operation. Instead of evaluating control performance based on intuitive voltage selection rule, this paper focuses on developing a discrete time function of the rate of change of an air-gap torque for facilitating optimal voltage vector choices. Then, this analytical solution leads to optimal voltage modification at each time step with respect to the available inverter voltage. The voltage-limited FSS-DTFC approach has potential advantages of achieving fastest transient torque trajectories and direct manipulation of the stator flux linkage while exploiting maximum voltage excitation.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"35 1","pages":"3993-3999"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84386455","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342601
A. S. Andrade, L. Barros, E. D. da Silva, C. Jacobina
This paper investigates the digital implementation of a modulation strategy that can completely remove the low-frequency voltage oscillation, which appears in the neutral point, for all the operating points and for any kind of loads. The implementation is based on a hybrid modulation technique that produces low switching losses and is simple to implement. Losses, average switching frequency, and performance in terms of voltage balance and low frequency neutral point oscillation, THD, and WTHD are investigated. Simulation and experimental results confirm the feasibility of the approach.
{"title":"Pulse width modulation for reduction of power losses in three-phase neutral point clamped inverters","authors":"A. S. Andrade, L. Barros, E. D. da Silva, C. Jacobina","doi":"10.1109/ECCE.2012.6342601","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342601","url":null,"abstract":"This paper investigates the digital implementation of a modulation strategy that can completely remove the low-frequency voltage oscillation, which appears in the neutral point, for all the operating points and for any kind of loads. The implementation is based on a hybrid modulation technique that produces low switching losses and is simple to implement. Losses, average switching frequency, and performance in terms of voltage balance and low frequency neutral point oscillation, THD, and WTHD are investigated. Simulation and experimental results confirm the feasibility of the approach.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"48 1","pages":"1746-1752"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85121841","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342244
A. Solomon, Jianfeng Li, A. Castellazzi, M. Johnson
An application oriented integration concept for half-bridge switch assembly has been developed based on the latest generation Infineon Technologies 70um thin IGBTs and diodes, rated at 200A/600V. This paper addresses the thermo-mechanical simulation to optimize the designed assembly along with three different cylinderical bump shapes for reducing the stress and creep strain development in the solder joints. The simulation results show that effect of the bump shape on thermal performance is negligible, however thin hollow cylinder type can reduce the creep strain accumulation in the solder joints as compared to solid and thick cylinder bumps. A preliminary experimental test was also carried out and the functionality of the assembly was demonstrated.
{"title":"Integrated half-bridge switch using 70µm thin devices and hollow interconnects","authors":"A. Solomon, Jianfeng Li, A. Castellazzi, M. Johnson","doi":"10.1109/ECCE.2012.6342244","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342244","url":null,"abstract":"An application oriented integration concept for half-bridge switch assembly has been developed based on the latest generation Infineon Technologies 70um thin IGBTs and diodes, rated at 200A/600V. This paper addresses the thermo-mechanical simulation to optimize the designed assembly along with three different cylinderical bump shapes for reducing the stress and creep strain development in the solder joints. The simulation results show that effect of the bump shape on thermal performance is negligible, however thin hollow cylinder type can reduce the creep strain accumulation in the solder joints as compared to solid and thick cylinder bumps. A preliminary experimental test was also carried out and the functionality of the assembly was demonstrated.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"151 1","pages":"4254-4261"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85384568","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342282
A. De, S. Roy, S. Bhattacharya
In this paper, a comparative study on AC-Link™ Topology and a conventional solid state transformer (TIPS) has been shown. Alongside, as a building block, a comparative device level design study has been shown for 6.5kV Si-IGBT/SiC JBS diode, 6.5kV Si-IGBT/Si-PiN Diode and 10kV SiC-MOSFET/SiC-JBS Diode for a zero voltage/current transition and hard switched condition for medium voltage application. It is shown that soft switching yields a considerable reduction of losses for all devices. A low voltage hardware device test prototype has been built and tested. The main motive of the paper is to make a fair judgment on the two topologies with accurate device testing. This is further extended to the maximum attainable frequency analysis, corresponding efficiency comparison, frequency transfer capability and various other topology based comparisons.
{"title":"Efficiency Comparison of AC-Link and TIPS (SST) Topologies based on accurate device models","authors":"A. De, S. Roy, S. Bhattacharya","doi":"10.1109/ECCE.2012.6342282","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342282","url":null,"abstract":"In this paper, a comparative study on AC-Link™ Topology and a conventional solid state transformer (TIPS) has been shown. Alongside, as a building block, a comparative device level design study has been shown for 6.5kV Si-IGBT/SiC JBS diode, 6.5kV Si-IGBT/Si-PiN Diode and 10kV SiC-MOSFET/SiC-JBS Diode for a zero voltage/current transition and hard switched condition for medium voltage application. It is shown that soft switching yields a considerable reduction of losses for all devices. A low voltage hardware device test prototype has been built and tested. The main motive of the paper is to make a fair judgment on the two topologies with accurate device testing. This is further extended to the maximum attainable frequency analysis, corresponding efficiency comparison, frequency transfer capability and various other topology based comparisons.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"77 1","pages":"3862-3868"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80215403","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342268
D. Martin, E. Santi
By injecting a small signal pseudo-random binary sequence (PRBS) based injection sequence, chosen for its wideband spectral content, into the inverter's PWM control signal and utilizing digital network analyzer techniques, an accurate estimation of the output impedance can be obtained without external equipment. This knowledge can then be leveraged to tune the inverter's digital deadbeat controllers for optimal performance, i.e. reaching the desired reference in n switching cycles, where n is the order of the system.
{"title":"Auto tuning of digital deadbeat controllers for high performance AC voltage sources using wide bandwidth impedance identification","authors":"D. Martin, E. Santi","doi":"10.1109/ECCE.2012.6342268","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342268","url":null,"abstract":"By injecting a small signal pseudo-random binary sequence (PRBS) based injection sequence, chosen for its wideband spectral content, into the inverter's PWM control signal and utilizing digital network analyzer techniques, an accurate estimation of the output impedance can be obtained without external equipment. This knowledge can then be leveraged to tune the inverter's digital deadbeat controllers for optimal performance, i.e. reaching the desired reference in n switching cycles, where n is the order of the system.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"12 1","pages":"4085-4092"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75852465","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342752
K. Kobravi, R. Iravani, H. Kojori
This paper describes the main requirements and challenges regarding the application of a Matrix Converter (MC) for aerospace power conversion. The challenges are reviewed in terms of (i) the input-filter (and output-filter) design, (ii) the selection of semiconductor switches and commutation-strategy, and (iv) the PWM strategy. The aerospace application of the MC requires operation at an input-frequency of 360Hz to 800Hz. The required output-frequency is either 400Hz to operate as a power supply or variable frequency of a few Hz up to 1200 Hz for drive applications such as fans and air compressors. Operation at 800Hz input-frequency imposes restrictions on the selection of the input-filter component values. These restrictions require the MC to operate at a high switching-frequency. Consequently, the switches, commutation strategy, and PWM strategy should be selected properly to enable MC operation at the higher switching-frequency. This paper uses MOSFET switches and demonstrates suitable commutation and modulation-strategies that enable a MOSFET-based MC to properly operate at around a switching-frequency of 40kHz, single-sided or 20kHz, double-sided.
{"title":"A review and implementation of Matrix-Converter for aerospace application","authors":"K. Kobravi, R. Iravani, H. Kojori","doi":"10.1109/ECCE.2012.6342752","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342752","url":null,"abstract":"This paper describes the main requirements and challenges regarding the application of a Matrix Converter (MC) for aerospace power conversion. The challenges are reviewed in terms of (i) the input-filter (and output-filter) design, (ii) the selection of semiconductor switches and commutation-strategy, and (iv) the PWM strategy. The aerospace application of the MC requires operation at an input-frequency of 360Hz to 800Hz. The required output-frequency is either 400Hz to operate as a power supply or variable frequency of a few Hz up to 1200 Hz for drive applications such as fans and air compressors. Operation at 800Hz input-frequency imposes restrictions on the selection of the input-filter component values. These restrictions require the MC to operate at a high switching-frequency. Consequently, the switches, commutation strategy, and PWM strategy should be selected properly to enable MC operation at the higher switching-frequency. This paper uses MOSFET switches and demonstrates suitable commutation and modulation-strategies that enable a MOSFET-based MC to properly operate at around a switching-frequency of 40kHz, single-sided or 20kHz, double-sided.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"99 1","pages":"698-705"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82463413","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 : 2012-11-12DOI: 10.1109/ECCE.2012.6342571
A. Paquette, D. Divan
This paper discusses the need for power quality microgrids to provide 1/4 cycle response to compete with existing power quality products by offering similar performance. However, providing 1/4 cycle response in distributed line-interactive microgrids is difficult due to the challenge of force commutating the static switch. Seamless islanding adds significant cost to microgrids, and to avoid adding unnecessary cost, the main value propositions for microgrids are analyzed. Requirements and characteristics are described for microgrids designed for each of the three value propositions: reliability, energy arbitrage, and power quality. Sample designs are compared for an example case, along with a discussion on the role of energy storage in microgrids.
{"title":"Design considerations for microgrids with energy storage","authors":"A. Paquette, D. Divan","doi":"10.1109/ECCE.2012.6342571","DOIUrl":"https://doi.org/10.1109/ECCE.2012.6342571","url":null,"abstract":"This paper discusses the need for power quality microgrids to provide 1/4 cycle response to compete with existing power quality products by offering similar performance. However, providing 1/4 cycle response in distributed line-interactive microgrids is difficult due to the challenge of force commutating the static switch. Seamless islanding adds significant cost to microgrids, and to avoid adding unnecessary cost, the main value propositions for microgrids are analyzed. Requirements and characteristics are described for microgrids designed for each of the three value propositions: reliability, energy arbitrage, and power quality. Sample designs are compared for an example case, along with a discussion on the role of energy storage in microgrids.","PeriodicalId":6401,"journal":{"name":"2012 IEEE Energy Conversion Congress and Exposition (ECCE)","volume":"1 1","pages":"1966-1973"},"PeriodicalIF":0.0,"publicationDate":"2012-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83430811","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：