Pub Date : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571066
Gabriel Baraban, Siddharth Kothiyal, Marin Kobilarov
This work considers autonomous fruit picking using an aerial grasping robot by tightly integrating vision-based perception and control within a learning framework. The architecture employs a convolutional neural network (CNN) to encode images and vehicle state information. This encoding is passed into a sub-task classifier and associated reference waypoint generator. The classifier is trained to predict the current phase of the task being executed: Staging, Picking, or Reset. Based on the predicted phase, the waypoint generator predicts a set of obstacle-free 6-DOF waypoints, which serve as a reference trajectory for model-predictive control (MPC). By iteratively generating and following these trajectories, the aerial manipulator safely approaches a mock-up goal fruit and removes it from the tree. The proposed approach is validated in 29 flight tests, through a comparison to a conventional baseline approach, and an ablation study on its key features. Overall, the approach achieved comparable success rates to the conventional approach, while reaching the goal faster.
{"title":"Perception-Based UAV Fruit Grasping Using Sub-Task Imitation Learning","authors":"Gabriel Baraban, Siddharth Kothiyal, Marin Kobilarov","doi":"10.1109/AIRPHARO52252.2021.9571066","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571066","url":null,"abstract":"This work considers autonomous fruit picking using an aerial grasping robot by tightly integrating vision-based perception and control within a learning framework. The architecture employs a convolutional neural network (CNN) to encode images and vehicle state information. This encoding is passed into a sub-task classifier and associated reference waypoint generator. The classifier is trained to predict the current phase of the task being executed: Staging, Picking, or Reset. Based on the predicted phase, the waypoint generator predicts a set of obstacle-free 6-DOF waypoints, which serve as a reference trajectory for model-predictive control (MPC). By iteratively generating and following these trajectories, the aerial manipulator safely approaches a mock-up goal fruit and removes it from the tree. The proposed approach is validated in 29 flight tests, through a comparison to a conventional baseline approach, and an ablation study on its key features. Overall, the approach achieved comparable success rates to the conventional approach, while reaching the goal faster.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122769820","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571037
Goran Vasiljević, Dean Martinovic, M. Orsag, S. Bogdan
This paper presents the method for the localization and grabbing of the long straight conductor based only on the magnetic field generated by the alternating current flowing through the conductor. The method uses two magnetometers mounted on the robot arm end-effector for localization. This location is then used to determine needed robot movement in order to grab the conductor. The method was tested in the laboratory conditions using the Schunk LWA 4P 6-axis robot arm.
{"title":"Grabbing power line conductors based on the measurements of the magnetic field strength","authors":"Goran Vasiljević, Dean Martinovic, M. Orsag, S. Bogdan","doi":"10.1109/AIRPHARO52252.2021.9571037","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571037","url":null,"abstract":"This paper presents the method for the localization and grabbing of the long straight conductor based only on the magnetic field generated by the alternating current flowing through the conductor. The method uses two magnetometers mounted on the robot arm end-effector for localization. This location is then used to determine needed robot movement in order to grab the conductor. The method was tested in the laboratory conditions using the Schunk LWA 4P 6-axis robot arm.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132626962","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571029
A. Suárez, Honorio Romero, Rafael Salmoral, J. A. Acosta, Jesús Zambrano, A. Ollero
This paper presents an aerial manipulation robot intended to conduct the installation of clip-type bird diverters on power lines, consisting of a multirotor platform equipped with a high force linear actuator and a clamp mechanism that holds the device until it is exerted on the cable. The installation mechanism has been specifically designed for a particular model of bird flight diverter that is extensively employed on the Spanish power grid. The paper analyzes the risks involved in this operation and describes the approach followed in the validation of the aerial robot, from the installation in indoor testbed, to representative outdoor scenario, and preliminary flight tests on a 15 kV power line to identify possible malfunctions on the platform due to the electrostatic discharge.
{"title":"Experimental Evaluation of Aerial Manipulation Robot for the Installation of Clip Type Bird Diverters: Outdoor Flight Tests","authors":"A. Suárez, Honorio Romero, Rafael Salmoral, J. A. Acosta, Jesús Zambrano, A. Ollero","doi":"10.1109/AIRPHARO52252.2021.9571029","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571029","url":null,"abstract":"This paper presents an aerial manipulation robot intended to conduct the installation of clip-type bird diverters on power lines, consisting of a multirotor platform equipped with a high force linear actuator and a clamp mechanism that holds the device until it is exerted on the cable. The installation mechanism has been specifically designed for a particular model of bird flight diverter that is extensively employed on the Spanish power grid. The paper analyzes the risks involved in this operation and describes the approach followed in the validation of the aerial robot, from the installation in indoor testbed, to representative outdoor scenario, and preliminary flight tests on a 15 kV power line to identify possible malfunctions on the platform due to the electrostatic discharge.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133642161","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571042
Ulrico Celentano, Marko Kauppinen, J. Röning
Unmanned aerial vehicles (UAV) can help in improving safety and decreasing costs in the inspection of industrial plants such as oil and gas pipings. UAV-based inspection brings endurance requirements and safety constraints to the inspection system as a whole. This article focuses on the ground support segment of the HYFLIERS inspection systems and more particularly it looks at effectively and efficiently supporting the inspection data flow and at competent and safe power supply.
{"title":"Ground Support for Drone-based Industrial Inspections","authors":"Ulrico Celentano, Marko Kauppinen, J. Röning","doi":"10.1109/AIRPHARO52252.2021.9571042","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571042","url":null,"abstract":"Unmanned aerial vehicles (UAV) can help in improving safety and decreasing costs in the inspection of industrial plants such as oil and gas pipings. UAV-based inspection brings endurance requirements and safety constraints to the inspection system as a whole. This article focuses on the ground support segment of the HYFLIERS inspection systems and more particularly it looks at effectively and efficiently supporting the inspection data flow and at competent and safe power supply.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"215 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122686194","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571024
Lorena Calvente, J. Acosta, A. Ollero
This paper presents a folding mechanism for ornithopter's wings. The mechanism has been implemented using rods and joints to replicate wing performance of animal flight. In this sense, bio-inspiration has been the baseline of the design but hard requirements as lightweight and integration with the current platform have also been considered. The final specifications of volume ratio folded/unfolded of 1/3 and additional mass < 100 g/wing with respect to the current structure, make this concept quite promising. Moreover, unlike most of the existent creations, it is intended to allow control of the folding while perching. Bench experiments demonstrate its performance and compatibility with the prototype platform.
{"title":"Design and Manufacture of the Wing Folding Mechanism for a Bioinspired Ornithopter","authors":"Lorena Calvente, J. Acosta, A. Ollero","doi":"10.1109/AIRPHARO52252.2021.9571024","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571024","url":null,"abstract":"This paper presents a folding mechanism for ornithopter's wings. The mechanism has been implemented using rods and joints to replicate wing performance of animal flight. In this sense, bio-inspiration has been the baseline of the design but hard requirements as lightweight and integration with the current platform have also been considered. The final specifications of volume ratio folded/unfolded of 1/3 and additional mass < 100 g/wing with respect to the current structure, make this concept quite promising. Moreover, unlike most of the existent creations, it is intended to allow control of the folding while perching. Bench experiments demonstrate its performance and compatibility with the prototype platform.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122094381","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571026
V. Sumathy, D. Ghose
A robust adaptive non-linear controller for a quadcopter manipulator system, used in applications in constrained narrow corridors, is proposed in this paper. The aerial robot considered comprises a three degree of freedom manipulator attached to the aerial vehicle's center of gravity at the bottom. During tasks that involve constrained environments like corridors, the controller should provide efficient control inputs to traverse with minimum trajectory tracking error, disturbance rejection, and stability. External disturbances such as wind, noise, and other factors and unmodeled non-linearities within the model affect the system in real-time applications and degrade its performance. To achieve stability and minimize trajectory tracking error, a novel robust augmented adaptive torque control law is developed for the system, which combines a feedback linearization controller with a model reference adaptive controller. The integrated system has a coupled uncertain non-linear dynamics. The adaptive mechanism's update law is derived using the SPR-Lyapunov approach and then modified with a Γ-projection operator to ensure that the estimates are bounded. In addition, the designed controller with projection-based adaptive law is implemented on the unified plant dynamics and evaluated using MATLAB and ROS/Gazebo simulations. A real-time task scenario is developed in ROS/Gazebo, with two rooms connected by a small corridor as the environment and ArUco marks on the walls serving as targets.
{"title":"Robust Adaptive Non-Linear Control Design for an Aerial Robot with In-Door Application in Constrained Corridors","authors":"V. Sumathy, D. Ghose","doi":"10.1109/AIRPHARO52252.2021.9571026","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571026","url":null,"abstract":"A robust adaptive non-linear controller for a quadcopter manipulator system, used in applications in constrained narrow corridors, is proposed in this paper. The aerial robot considered comprises a three degree of freedom manipulator attached to the aerial vehicle's center of gravity at the bottom. During tasks that involve constrained environments like corridors, the controller should provide efficient control inputs to traverse with minimum trajectory tracking error, disturbance rejection, and stability. External disturbances such as wind, noise, and other factors and unmodeled non-linearities within the model affect the system in real-time applications and degrade its performance. To achieve stability and minimize trajectory tracking error, a novel robust augmented adaptive torque control law is developed for the system, which combines a feedback linearization controller with a model reference adaptive controller. The integrated system has a coupled uncertain non-linear dynamics. The adaptive mechanism's update law is derived using the SPR-Lyapunov approach and then modified with a Γ-projection operator to ensure that the estimates are bounded. In addition, the designed controller with projection-based adaptive law is implemented on the unified plant dynamics and evaluated using MATLAB and ROS/Gazebo simulations. A real-time task scenario is developed in ROS/Gazebo, with two rooms connected by a small corridor as the environment and ArUco marks on the walls serving as targets.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123360445","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 : 2021-10-01DOI: 10.1109/airpharo52252.2021.9571062
{"title":"AIRPHARO 2021 Venue","authors":"","doi":"10.1109/airpharo52252.2021.9571062","DOIUrl":"https://doi.org/10.1109/airpharo52252.2021.9571062","url":null,"abstract":"","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124500425","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 : 2021-10-01DOI: 10.1109/AIRPHARO52252.2021.9571059
M. Salvago, F. J. Pérez-Gran, J. Parra, M. A. Trujillo, A. Viguria
This work describes the methodology for detecting pipes and their pose in refineries inspection using Unmanned Aerial Vehicles (UAV s) for remote Ultrasonic Testing (UT). Segmentation techniques such as the Hough Transform and its variations, and Random Sample Consensus have been widely used. This paper is therefore focused on the development of an efficient computer vision algorithm to detect the position and orientation of the pipes in order to land on them autonomously to perform the inspection, by using 3D point cloud information from depth cameras. Applying a methodology based on Random Sample Consensus and point cloud pre-processing to fasten the algorithm performance has led to robust estimations of the pipes and their poses in an indoor testbed using a realistic environment, allowing the autonomous landing and the subsequent inspection.
{"title":"Robust and Efficient Pose Estimation of Pipes for Contact Inspection using Aerial Robots","authors":"M. Salvago, F. J. Pérez-Gran, J. Parra, M. A. Trujillo, A. Viguria","doi":"10.1109/AIRPHARO52252.2021.9571059","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571059","url":null,"abstract":"This work describes the methodology for detecting pipes and their pose in refineries inspection using Unmanned Aerial Vehicles (UAV s) for remote Ultrasonic Testing (UT). Segmentation techniques such as the Hough Transform and its variations, and Random Sample Consensus have been widely used. This paper is therefore focused on the development of an efficient computer vision algorithm to detect the position and orientation of the pipes in order to land on them autonomously to perform the inspection, by using 3D point cloud information from depth cameras. Applying a methodology based on Random Sample Consensus and point cloud pre-processing to fasten the algorithm performance has led to robust estimations of the pipes and their poses in an indoor testbed using a realistic environment, allowing the autonomous landing and the subsequent inspection.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126796500","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 : 2021-09-01DOI: 10.1109/AIRPHARO52252.2021.9571055
Jonathon E. Slightam, Daniel R. McArthur, S. Spencer, S. Buerger
The broad dissemination of unmanned aerial vehicles (UAV s), specifically quadrotor aircraft, has accelerated their successful use in a wide range of industrial, military, and agricultural applications. Research in the growing field of aerial manipulation (AM) faces many challenges but may enable the next generation of UAV applications. The physical contact required to perform AM tasks results in dynamic coupling with the environment, which may lead to instability with devastating consequences for a UAV in flight. Considering these concerns, this work seeks to determine whether off-the-shelf flight controllers for quadrotor UAV s are suitable for AM applications by investigating the passivity and coupled-stability of quad rotors using generic cascaded position-attitude (CPA) and PX4 flight controllers. Using a planar 3-degree of freedom (DOF) linearized state-space model and two high fidelity 6-DOF models with the CPA and PX4 closed-loop flight controllers, passivity is analyzed during free flight, and stability is analyzed when the UAV is coupled to environments with varying degrees of stiffness. This analysis indicates that quadrotors using the CPA and PX4 flight controllers are non-passive (except for the PX4 controller in the vertical direction with certain vehicle parameters) and may become unstable when the UAV is coupled with environments of certain stiffnesses. Similarities between the results from the linearized 3-DOF model and nonlinear 6-DOF models in the passivity analysis suggest that using an analytical, linear approach is sufficient and potentially useful for vehicle geometry and controller design to improve stability for AM applications.
{"title":"Passivity Analysis of Quadrotor Aircraft for Physical Interactions","authors":"Jonathon E. Slightam, Daniel R. McArthur, S. Spencer, S. Buerger","doi":"10.1109/AIRPHARO52252.2021.9571055","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571055","url":null,"abstract":"The broad dissemination of unmanned aerial vehicles (UAV s), specifically quadrotor aircraft, has accelerated their successful use in a wide range of industrial, military, and agricultural applications. Research in the growing field of aerial manipulation (AM) faces many challenges but may enable the next generation of UAV applications. The physical contact required to perform AM tasks results in dynamic coupling with the environment, which may lead to instability with devastating consequences for a UAV in flight. Considering these concerns, this work seeks to determine whether off-the-shelf flight controllers for quadrotor UAV s are suitable for AM applications by investigating the passivity and coupled-stability of quad rotors using generic cascaded position-attitude (CPA) and PX4 flight controllers. Using a planar 3-degree of freedom (DOF) linearized state-space model and two high fidelity 6-DOF models with the CPA and PX4 closed-loop flight controllers, passivity is analyzed during free flight, and stability is analyzed when the UAV is coupled to environments with varying degrees of stiffness. This analysis indicates that quadrotors using the CPA and PX4 flight controllers are non-passive (except for the PX4 controller in the vertical direction with certain vehicle parameters) and may become unstable when the UAV is coupled with environments of certain stiffnesses. Similarities between the results from the linearized 3-DOF model and nonlinear 6-DOF models in the passivity analysis suggest that using an analytical, linear approach is sufficient and potentially useful for vehicle geometry and controller design to improve stability for AM applications.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129266512","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 : 2021-08-27DOI: 10.1109/AIRPHARO52252.2021.9571032
Yash Vyas, Mike Allenspach, Christian Lanegger, R. Siegwart, M. Tognon
An approach to model and estimate human walking kinematics in real-time for Physical Human-Robot Interaction is presented. The human gait velocity along the forward and vertical direction of motion is modelled according to the Yoyo-model. We designed an Extended Kalman Filter (EKF) algorithm to estimate the frequency, bias and trigonometric state of a biased sinusoidal signal, from which the kinematic parameters of the Yoyo-model can be extracted. Quality and robustness of the estimation are improved by opportune filtering based on heuristics. The approach is successfully evaluated on a real dataset of walking humans, including complex trajectories and changing step frequency over time.
{"title":"Modelling and Estimation of Human Walking Gait for Physical Human-Robot Interaction","authors":"Yash Vyas, Mike Allenspach, Christian Lanegger, R. Siegwart, M. Tognon","doi":"10.1109/AIRPHARO52252.2021.9571032","DOIUrl":"https://doi.org/10.1109/AIRPHARO52252.2021.9571032","url":null,"abstract":"An approach to model and estimate human walking kinematics in real-time for Physical Human-Robot Interaction is presented. The human gait velocity along the forward and vertical direction of motion is modelled according to the Yoyo-model. We designed an Extended Kalman Filter (EKF) algorithm to estimate the frequency, bias and trigonometric state of a biased sinusoidal signal, from which the kinematic parameters of the Yoyo-model can be extracted. Quality and robustness of the estimation are improved by opportune filtering based on heuristics. The approach is successfully evaluated on a real dataset of walking humans, including complex trajectories and changing step frequency over time.","PeriodicalId":415722,"journal":{"name":"2021 Aerial Robotic Systems Physically Interacting with the Environment (AIRPHARO)","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128335447","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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