Pub Date : 2018-08-01DOI: 10.1109/CCTA.2018.8511380
Vincent A. Looijen, M. Heertjes
For synchronization of high-precision motion stages, in particular a wafer and a reticle stage combination of an industrial wafer scanner, a centralized controller is optimized using both time- and frequency-domain data. The resulting multi-variable controller, which is designed using a sequential loop closing approach, transmits both the error from wafer-to-reticle as well as from reticle-to-wafer stage. The controller is designed to minimize the synchronization error occurring between the otherwise decentralized control loops of both stage systems. The controller tuning is performed using off-line particle swarm optimization and combines time-domain performance specifications with frequency-domain robustness constraints. The optimized controller demonstrates improved synchronization performance which follows from measurement results obtained from an industrial wafer scanner.
{"title":"Robust Synchronization of Motion in Wafer Scanners Using Particle Swarm Optimization","authors":"Vincent A. Looijen, M. Heertjes","doi":"10.1109/CCTA.2018.8511380","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511380","url":null,"abstract":"For synchronization of high-precision motion stages, in particular a wafer and a reticle stage combination of an industrial wafer scanner, a centralized controller is optimized using both time- and frequency-domain data. The resulting multi-variable controller, which is designed using a sequential loop closing approach, transmits both the error from wafer-to-reticle as well as from reticle-to-wafer stage. The controller is designed to minimize the synchronization error occurring between the otherwise decentralized control loops of both stage systems. The controller tuning is performed using off-line particle swarm optimization and combines time-domain performance specifications with frequency-domain robustness constraints. The optimized controller demonstrates improved synchronization performance which follows from measurement results obtained from an industrial wafer scanner.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125843459","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511567
M. Ruf
In this paper, a new hybrid time-optimal flexible-joint trajectory planning algorithm is introduced. Time-optimal rigid-body trajectories contain sudden changes of acceleration, which can result in violation of constraints when applied to flexible robotic manipulators. The abrupt acceleration changes are replaced by a smooth time-optimal switching strategy, which is based on the solution of a two-mass oscillator two-point boundary-value problem. It is designed such that the two-mass oscillator's flexible modes are not excited. In between the transitions, a multi-axis rigid-body model is used. This combination of flexible and rigid-body models allows to design a computationally very efficient trajectory planning algorithm, which considers multi-axis dynamics as well as some important inherent flexibilities.
{"title":"Near Time-Optimal Flexible-Joint Trajectory Planning Algorithm for Robotic Manipulators","authors":"M. Ruf","doi":"10.1109/CCTA.2018.8511567","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511567","url":null,"abstract":"In this paper, a new hybrid time-optimal flexible-joint trajectory planning algorithm is introduced. Time-optimal rigid-body trajectories contain sudden changes of acceleration, which can result in violation of constraints when applied to flexible robotic manipulators. The abrupt acceleration changes are replaced by a smooth time-optimal switching strategy, which is based on the solution of a two-mass oscillator two-point boundary-value problem. It is designed such that the two-mass oscillator's flexible modes are not excited. In between the transitions, a multi-axis rigid-body model is used. This combination of flexible and rigid-body models allows to design a computationally very efficient trajectory planning algorithm, which considers multi-axis dynamics as well as some important inherent flexibilities.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123109065","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511551
M. Glück, J. Pott, O. Sawodny
In the last decades, large telescopes have been planned and built to explore the universe for fainter objects than ever before. Presently, the largest telescope for optical wavelengths, the Extremely Large Telescope (ELT), is constructed with a primary mirror of 39 m diameter. In order to reduce the total weight of the telescope and due to the enormous size, the optics are mounted on lightweight constructions, which are very sensitive to wind excitations. Therefore, telescope optics and their control have to be considered in the design of the next generation ELT's, where a good vibration compensation is required. To achieve the diffraction limit of the ELT, its optical path is equipped with a deformable mirror and a plane tiptilt mirror for correction. Due to the atmospheric turbulences and structural vibrations, the compensation mirrors can reach their stroke and frequency limitations. Without considering these limitations in the control system the telescope instruments cannot fully reach its optimal performance. Therefore, we propose a solution based on Model Predictive Control (MPC), which can control the mirrors in an optimal way under given constraints. In this paper a model of the Adaptive Optics system, the MPC controller design and an integral control concept for comparison are presented. As a result the residual tip-tilt error can be reduced over a larger frequency range with an MPC controller when considering input constraints.
{"title":"Model Predictive Control of Multi-Mirror Adaptive Optics Systems","authors":"M. Glück, J. Pott, O. Sawodny","doi":"10.1109/CCTA.2018.8511551","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511551","url":null,"abstract":"In the last decades, large telescopes have been planned and built to explore the universe for fainter objects than ever before. Presently, the largest telescope for optical wavelengths, the Extremely Large Telescope (ELT), is constructed with a primary mirror of 39 m diameter. In order to reduce the total weight of the telescope and due to the enormous size, the optics are mounted on lightweight constructions, which are very sensitive to wind excitations. Therefore, telescope optics and their control have to be considered in the design of the next generation ELT's, where a good vibration compensation is required. To achieve the diffraction limit of the ELT, its optical path is equipped with a deformable mirror and a plane tiptilt mirror for correction. Due to the atmospheric turbulences and structural vibrations, the compensation mirrors can reach their stroke and frequency limitations. Without considering these limitations in the control system the telescope instruments cannot fully reach its optimal performance. Therefore, we propose a solution based on Model Predictive Control (MPC), which can control the mirrors in an optimal way under given constraints. In this paper a model of the Adaptive Optics system, the MPC controller design and an integral control concept for comparison are presented. As a result the residual tip-tilt error can be reduced over a larger frequency range with an MPC controller when considering input constraints.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"s3-22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130098841","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511593
Kazuhiko Takahashi
In this study, a simple recurrent neural network is designed for controlling nonlinear systems. All signals and parameters of the network are quaternion numbers, and the network is trained with a real-time recurrent learning algorithm. The control system is composed of a feedforward-feedback controller based on a recurrent quaternion neural network and a feedback controller to reconcile the plant output with the desired output. A feedback error learning method is used for the online training of the feedforward-feedback controller. The numerical simulations of controlling discrete-time nonlinear plants are conducted to evaluate the characteristics of the recurrent quaternion neural network-based controller. Simulation results show the feasibility and the effectiveness of the proposed controller.
{"title":"Remarks on Feedforward-Feedback Controller Using Simple Recurrent Quaternion Neural Network","authors":"Kazuhiko Takahashi","doi":"10.1109/CCTA.2018.8511593","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511593","url":null,"abstract":"In this study, a simple recurrent neural network is designed for controlling nonlinear systems. All signals and parameters of the network are quaternion numbers, and the network is trained with a real-time recurrent learning algorithm. The control system is composed of a feedforward-feedback controller based on a recurrent quaternion neural network and a feedback controller to reconcile the plant output with the desired output. A feedback error learning method is used for the online training of the feedforward-feedback controller. The numerical simulations of controlling discrete-time nonlinear plants are conducted to evaluate the characteristics of the recurrent quaternion neural network-based controller. Simulation results show the feasibility and the effectiveness of the proposed controller.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126857195","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}
In this paper, we propose a novel path-following controller design method for the rigid body attitude dynamics. We first consider a trajectory-tracking problem and design a tracking control Lyapunov function (T-CLF). Then we design a path-following control Lyapunov function (PF-CLF) based on the minimum projection method and the designed T-CLF. Moreover, we construct a discontinuous state feedback controller for the path-following problem based on the PF-CLF. The effectiveness of the proposed method is confirmed by a numerical example of a multicopter.
{"title":"Path-Following Control of Rigid Body Attitude by Using Minimum Projection Method","authors":"Seiya Nomura, Yasuyuki Satoh, Hisakazu Nakamura, Kiyotaka Kato","doi":"10.1109/CCTA.2018.8511603","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511603","url":null,"abstract":"In this paper, we propose a novel path-following controller design method for the rigid body attitude dynamics. We first consider a trajectory-tracking problem and design a tracking control Lyapunov function (T-CLF). Then we design a path-following control Lyapunov function (PF-CLF) based on the minimum projection method and the designed T-CLF. Moreover, we construct a discontinuous state feedback controller for the path-following problem based on the PF-CLF. The effectiveness of the proposed method is confirmed by a numerical example of a multicopter.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"157 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126901210","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511557
Y. Yoon, Eric N. Johnson, L. Ren
Multirotors are one of the most popular types of small unmanned aircraft systems today with applications in many areas including but not limited to aerial photography, transport, military, surveillance, agriculture, and leisure. Autonomous flight controls is one of the key enabler technologies for their popularity and growing applications. Many studies about the flight controls for multirotors have enhanced the control performance, but we still have rooms to improve in tracking accuracy and efficiency. This paper presents an autonomous flight control method for multirotors based on a simple input-output linearization coupled with nested saturation. We choose an unconventional, alternative output of the multirotor flight control system, which leads to reducing computational cost regarding Lie algebra when we linearize the system dynamics. Then we stabilize the linearized system with nested saturation with real poles of our own choice. Given the desired output through the outer loop PID controller, the results of the simulations show that the error dynamics regarding the outputs are stabilized exponentially fast.
{"title":"Autonomous Flight Control for Multirotors by a Simple Input-Output Linearization with Nested Saturation","authors":"Y. Yoon, Eric N. Johnson, L. Ren","doi":"10.1109/CCTA.2018.8511557","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511557","url":null,"abstract":"Multirotors are one of the most popular types of small unmanned aircraft systems today with applications in many areas including but not limited to aerial photography, transport, military, surveillance, agriculture, and leisure. Autonomous flight controls is one of the key enabler technologies for their popularity and growing applications. Many studies about the flight controls for multirotors have enhanced the control performance, but we still have rooms to improve in tracking accuracy and efficiency. This paper presents an autonomous flight control method for multirotors based on a simple input-output linearization coupled with nested saturation. We choose an unconventional, alternative output of the multirotor flight control system, which leads to reducing computational cost regarding Lie algebra when we linearize the system dynamics. Then we stabilize the linearized system with nested saturation with real poles of our own choice. Given the desired output through the outer loop PID controller, the results of the simulations show that the error dynamics regarding the outputs are stabilized exponentially fast.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129070993","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511588
K. Chernyshov
An alternative approach to define the anisotropic norm of random vectors is proposed, based on a symmetric Tsallis divergence measure constructed within the present paper. The consideration is motivated by a definition available in the literature, which is based on Kullback-Leibler divergence and, thus, being non-symmetric, what, at least from a theoretical point of view, stimulates to consider some other possibilities in this field.
{"title":"The Anisotropic Norm of Random Vectors: Defining via a Symmetric Tsallis Divergence","authors":"K. Chernyshov","doi":"10.1109/CCTA.2018.8511588","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511588","url":null,"abstract":"An alternative approach to define the anisotropic norm of random vectors is proposed, based on a symmetric Tsallis divergence measure constructed within the present paper. The consideration is motivated by a definition available in the literature, which is based on Kullback-Leibler divergence and, thus, being non-symmetric, what, at least from a theoretical point of view, stimulates to consider some other possibilities in this field.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131233076","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511523
Maryam Abdollahi
In this paper, the problem of simultaneous sensor and actuator fault detection, isolation and estimation (FDIE) for nonlinear Euler-Lagrange (EL) systems is addressed. First, an output redefinition and a state coordinate transformation are employed that do not use any a priori knowledge about the system nonlinearities to decouple the system into two subsystems where each subsystem is only affected by either a sensor or an actuator fault. Then, two separate sliding mode observers (SMO) are employed to estimate sensor and actuator faults corresponding to these subsystems. Simulation results are provided for an Autonomous Underwater Vehicle (AUV) that is modeled by EL equations. The results demonstrate the capabilities and benefits as well as the performance of our proposed FDIE approach as compared to the existing results in the literature.
{"title":"Simultaneous Sensor and Actuator Fault Detection, Isolation and Estimation of Nonlinear Euler-Lagrange Systems Using Sliding Mode Observers","authors":"Maryam Abdollahi","doi":"10.1109/CCTA.2018.8511523","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511523","url":null,"abstract":"In this paper, the problem of simultaneous sensor and actuator fault detection, isolation and estimation (FDIE) for nonlinear Euler-Lagrange (EL) systems is addressed. First, an output redefinition and a state coordinate transformation are employed that do not use any a priori knowledge about the system nonlinearities to decouple the system into two subsystems where each subsystem is only affected by either a sensor or an actuator fault. Then, two separate sliding mode observers (SMO) are employed to estimate sensor and actuator faults corresponding to these subsystems. Simulation results are provided for an Autonomous Underwater Vehicle (AUV) that is modeled by EL equations. The results demonstrate the capabilities and benefits as well as the performance of our proposed FDIE approach as compared to the existing results in the literature.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121181107","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511605
T. Kigezi, J. Dunne
Reconstruction of engine in-cylinder pressure with observers in conventional engines has extensively been studied in the literature. The subject however remains unaddressed for Free-piston Engines (FPEs). An in-cylinder pressure observer suitable for FPEs is developed in this paper. The observer reconstructs in-cylinder pressure from measured piston position and net heat release rate. Observer development starts by examining the commonly adopted high gain observer for nonlinear systems, showing its limitations in a numerical FPE case study. A newly developed sliding mode observer that overcomes these limitations is then proposed. The proposed observer has a finite-time converging error, making it suitable for applications requiring accurate and real-time pressure estimation. Effectiveness of the observer is analytically proven and verified by simulation. The proposed observer is finally generalized into a large family of sliding mode observers.
{"title":"Development of an In-Cylinder Pressure Observer for Free-Piston Engines","authors":"T. Kigezi, J. Dunne","doi":"10.1109/CCTA.2018.8511605","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511605","url":null,"abstract":"Reconstruction of engine in-cylinder pressure with observers in conventional engines has extensively been studied in the literature. The subject however remains unaddressed for Free-piston Engines (FPEs). An in-cylinder pressure observer suitable for FPEs is developed in this paper. The observer reconstructs in-cylinder pressure from measured piston position and net heat release rate. Observer development starts by examining the commonly adopted high gain observer for nonlinear systems, showing its limitations in a numerical FPE case study. A newly developed sliding mode observer that overcomes these limitations is then proposed. The proposed observer has a finite-time converging error, making it suitable for applications requiring accurate and real-time pressure estimation. Effectiveness of the observer is analytically proven and verified by simulation. The proposed observer is finally generalized into a large family of sliding mode observers.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121378233","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 : 2018-08-01DOI: 10.1109/CCTA.2018.8511450
A. Pajares, E. Schuster
Tokamaks are toroidal devices in which a plasma is confined by means of helical magnetic fields with the purpose of obtaining energy from nuclear fusion reactions. The safety factor, $q$, measures the pitch of the helical magnetic field lines in a tokamak. Active control of the $q$ profile (i.e., spatial shape) is needed due to its relationship with plasma performance, steady-state operation, and magneto-hydrodynamic stability. However, the responses of some plasma magnitudes, such as the electron temperature, are difficult to model and introduce a high level of uncertainty in the model used for $q$-profile control design. Control algorithms that are robust against such model uncertainties must be developed in order to ensure successful q-profile regulation. In this work, a nonlinear, robust $q$-profile controller is designed using feedback linearization and nonlinear damping techniques. The controller makes use of plasma current modulation, neutral beam injection, electron-cyclotron heating & current drive, and electron density modulation as actuation methods. A simulation study is carried out for a DIII-D scenario to test the controller's performance under the presence of electron temperature uncertainties.
{"title":"Nonlinear Robust Safety Factor Profile Control in Tokamaks via Feedback Linearization and Nonlinear Damping Techniques","authors":"A. Pajares, E. Schuster","doi":"10.1109/CCTA.2018.8511450","DOIUrl":"https://doi.org/10.1109/CCTA.2018.8511450","url":null,"abstract":"Tokamaks are toroidal devices in which a plasma is confined by means of helical magnetic fields with the purpose of obtaining energy from nuclear fusion reactions. The safety factor, $q$, measures the pitch of the helical magnetic field lines in a tokamak. Active control of the $q$ profile (i.e., spatial shape) is needed due to its relationship with plasma performance, steady-state operation, and magneto-hydrodynamic stability. However, the responses of some plasma magnitudes, such as the electron temperature, are difficult to model and introduce a high level of uncertainty in the model used for $q$-profile control design. Control algorithms that are robust against such model uncertainties must be developed in order to ensure successful q-profile regulation. In this work, a nonlinear, robust $q$-profile controller is designed using feedback linearization and nonlinear damping techniques. The controller makes use of plasma current modulation, neutral beam injection, electron-cyclotron heating & current drive, and electron density modulation as actuation methods. A simulation study is carried out for a DIII-D scenario to test the controller's performance under the presence of electron temperature uncertainties.","PeriodicalId":358360,"journal":{"name":"2018 IEEE Conference on Control Technology and Applications (CCTA)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128685263","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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