Pub Date : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999692
D. Ignatyev, Hyo-Sang Shin, A. Tsourdos
The ability of the UAV to adapt to possible failures or changes in flight dynamics is crucial for its resilience. The paper proposes a two-layer fault detection procedure augmenting Incremental Controller (IC) designed for a fixed-wing UAV. IC benefits from recent advantages of the sensing technologies and uses angular accelerations and current control deflections to reduce the dependency on aircraft model. Nevertheless, control effectiveness is still required for its implementation. The elaborated two-layer fault detection scheme is capable to detect and localize possible failures and provide the IC with on-line estimations of control effectiveness. At the first layer, the system performs monitoring of possible failures. If a problem in one of the control direction is detected the algorithm initiates the second-layer identification determining the individual effectiveness of each control surface involved in this control direction. The effectiveness of the proposed fault detection technique is demonstrated with simulation of stuck in position and hardover of the aileron of a fixed-wing UAV.
{"title":"Two-layer Fault Detection for Incremental Flight Control of Fixed-wing UAV","authors":"D. Ignatyev, Hyo-Sang Shin, A. Tsourdos","doi":"10.1109/REDUAS47371.2019.8999692","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999692","url":null,"abstract":"The ability of the UAV to adapt to possible failures or changes in flight dynamics is crucial for its resilience. The paper proposes a two-layer fault detection procedure augmenting Incremental Controller (IC) designed for a fixed-wing UAV. IC benefits from recent advantages of the sensing technologies and uses angular accelerations and current control deflections to reduce the dependency on aircraft model. Nevertheless, control effectiveness is still required for its implementation. The elaborated two-layer fault detection scheme is capable to detect and localize possible failures and provide the IC with on-line estimations of control effectiveness. At the first layer, the system performs monitoring of possible failures. If a problem in one of the control direction is detected the algorithm initiates the second-layer identification determining the individual effectiveness of each control surface involved in this control direction. The effectiveness of the proposed fault detection technique is demonstrated with simulation of stuck in position and hardover of the aileron of a fixed-wing UAV.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127536963","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 : 2019-11-01DOI: 10.1109/reduas47371.2019.8999702
{"title":"RED UAS 2019 Author Index","authors":"","doi":"10.1109/reduas47371.2019.8999702","DOIUrl":"https://doi.org/10.1109/reduas47371.2019.8999702","url":null,"abstract":"","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"87 23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126301196","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999699
Young-Won Kim, Sang-Don Lee, Chang-hun Lee, Hyo-Sang Shin, A. Tsourdos
This paper aims to propose a nonlinear attitude controller for a drone system controlled by the control momentum gyros (CMGs). The dynamic modeling and the control mechanism of the considering system are first investigated. After that, based on the assumption of the timescale separation, the proposed controller is designed using the feedback linearization methodology. To make the resultant controller follow the three-loop structure, specific forms of the desired error dynamics are utilized in the design step. The characteristics of the proposed method are investigated through numerical simulations. The results show that the proposed controller can provide a good tracking performance against model uncertainties as well as model nonlinearities.
{"title":"A Nonlinear Attitude Controller for Drones with CMG (Control Momentum Gyro)","authors":"Young-Won Kim, Sang-Don Lee, Chang-hun Lee, Hyo-Sang Shin, A. Tsourdos","doi":"10.1109/REDUAS47371.2019.8999699","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999699","url":null,"abstract":"This paper aims to propose a nonlinear attitude controller for a drone system controlled by the control momentum gyros (CMGs). The dynamic modeling and the control mechanism of the considering system are first investigated. After that, based on the assumption of the timescale separation, the proposed controller is designed using the feedback linearization methodology. To make the resultant controller follow the three-loop structure, specific forms of the desired error dynamics are utilized in the design step. The characteristics of the proposed method are investigated through numerical simulations. The results show that the proposed controller can provide a good tracking performance against model uncertainties as well as model nonlinearities.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114944180","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999722
J. Cocoma-Ortega, L. Rojas-Perez, A. Cabrera-Ponce, J. Martínez-Carranza
In recent years Autonomous Drone Racing has become a significant challenge due to the problems involved in developing an algorithm for autonomous navigation. One of the major problems is the estimation of the camera pose; several approaches can be founded to achieve the estimation of the camera pose. In particular, it is possible to estimates the position based on specific object detection. However, object detection at the same time of navigation entails the problem of a blind spot area when the camera is closest to the object. We propose a methodology that overcomes the blind spot in autonomous navigation based on CNN gate detection to perform pose estimation with a stochastic algorithm for distance estimation. We achieve over 95 % in gate detection and a mean error of around 35 cm in 1D pose estimation into the blind spot zone.
{"title":"Overcoming the Blind Spot in CNN-based Gate Detection for Autonomous Drone Racing","authors":"J. Cocoma-Ortega, L. Rojas-Perez, A. Cabrera-Ponce, J. Martínez-Carranza","doi":"10.1109/REDUAS47371.2019.8999722","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999722","url":null,"abstract":"In recent years Autonomous Drone Racing has become a significant challenge due to the problems involved in developing an algorithm for autonomous navigation. One of the major problems is the estimation of the camera pose; several approaches can be founded to achieve the estimation of the camera pose. In particular, it is possible to estimates the position based on specific object detection. However, object detection at the same time of navigation entails the problem of a blind spot area when the camera is closest to the object. We propose a methodology that overcomes the blind spot in autonomous navigation based on CNN gate detection to perform pose estimation with a stochastic algorithm for distance estimation. We achieve over 95 % in gate detection and a mean error of around 35 cm in 1D pose estimation into the blind spot zone.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132563474","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999707
Zhengjia Xu, I. Petrunin, A. Tsourdos, Mondal Sabyasachi, Alex A. Williamson
An intelligent and agile wireless communication scheme is a key factor in provision of efficient air-to-ground (A2G) communication for unmanned aerial vehicles (UAVs) operations. For this purpose we review and propose an architecture for aeronautical cognitive communication system (ACCS) that will be providing command, control and communication (C3) link between ground control stations (GCSs) and multiple UAVs utilizing cognitive radio (CR) concept. The factors reviewed and accounted for in the design process are the topology of cognitive detectors, connectivity between cognitive detector and control agency, connection with unmanned traffic management (UTM) system, data link requirements imposed by cognitive scheme, failure notification and recovery, etc. The proposed ACCS is suitable for supporting UAV operations and features a distributed non-communication architecture consisting of GCS network in the ground zone, hybrid data link with the static uplink and the flexible downlink, demonstrating a dynamic nature overall with the frequency handoff scheme generated periodically in accordance with current spectrum environment.
{"title":"Cognitive Communication Scheme for Unmanned Aerial Vehicle Operation","authors":"Zhengjia Xu, I. Petrunin, A. Tsourdos, Mondal Sabyasachi, Alex A. Williamson","doi":"10.1109/REDUAS47371.2019.8999707","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999707","url":null,"abstract":"An intelligent and agile wireless communication scheme is a key factor in provision of efficient air-to-ground (A2G) communication for unmanned aerial vehicles (UAVs) operations. For this purpose we review and propose an architecture for aeronautical cognitive communication system (ACCS) that will be providing command, control and communication (C3) link between ground control stations (GCSs) and multiple UAVs utilizing cognitive radio (CR) concept. The factors reviewed and accounted for in the design process are the topology of cognitive detectors, connectivity between cognitive detector and control agency, connection with unmanned traffic management (UTM) system, data link requirements imposed by cognitive scheme, failure notification and recovery, etc. The proposed ACCS is suitable for supporting UAV operations and features a distributed non-communication architecture consisting of GCS network in the ground zone, hybrid data link with the static uplink and the flexible downlink, demonstrating a dynamic nature overall with the frequency handoff scheme generated periodically in accordance with current spectrum environment.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114592663","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999680
Alex A. Williamson, S. Mondal, Zhengjia Xu, A. Tsourdos
This paper describes a solution to increase the efficiency of collecting agricultural ground truth data by the use of one or more off-the-shelf drones to autonomously collect high quality RGB image data at low level, through the incorporation of a bespoke smartphone application that receives routing path-planned location data in the form of Short Message Service (SMS) text messages.
{"title":"Autonomous collection of ground truth data by unmanned aerial vehicles instructed using SMS text messages","authors":"Alex A. Williamson, S. Mondal, Zhengjia Xu, A. Tsourdos","doi":"10.1109/REDUAS47371.2019.8999680","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999680","url":null,"abstract":"This paper describes a solution to increase the efficiency of collecting agricultural ground truth data by the use of one or more off-the-shelf drones to autonomously collect high quality RGB image data at low level, through the incorporation of a bespoke smartphone application that receives routing path-planned location data in the form of Short Message Service (SMS) text messages.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"256 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133372575","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999723
E. Bond, B. Crowther, B. Parslew
High-performance multirotor drones optimised for speed and agility present a significant and increasing challenge to current counter-drone systems based on jamming or physical interdiction. Existing jamming technology requires sustained visual line of sight targets and is most effective in countering threats from relatively slow and RF compliant videography drones. Physical interdiction using nets is again only suitable for low-speed interception. Small vehicles based on commercially available consumer drone technology with a mass of less than 1 kg and package size of 15 cm can achieve flight speeds in excess of 70 m/s and can accelerate at up to 15g, and are sufficiently inexpensive as to be considered disposable. Custom flight control systems bypass geofence restrictions and the wide availability of high power radio links greatly exceeding OFCOM limits significantly reduces the range over which commercial jamming systems are effective. Static acceleration performance is maximised simply by decreasing the power loading and decreasing the disc loading and is approximately independent of the size (mass) of the vehicle. Maximisation of top speed is more complex, requiring identification of an optimal disc loading that balances thrust against rotor drag. Top speed is also affected by area/volume scaling meaning that larger vehicles with the same power to weight ratio and disc loading generally have less drag and hence higher top speed. Consumer technology for very high thrust to weight ratio variants of larger multirotor drones is currently not readily available. However, 10 kg drones with a top speed of 100 m/s and static acceleration of 20 g are foreseeable in the next 5 years.
{"title":"The Rise Of High-Performance Multi-Rotor Unmanned Aerial Vehicles - How worried should we be?","authors":"E. Bond, B. Crowther, B. Parslew","doi":"10.1109/REDUAS47371.2019.8999723","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999723","url":null,"abstract":"High-performance multirotor drones optimised for speed and agility present a significant and increasing challenge to current counter-drone systems based on jamming or physical interdiction. Existing jamming technology requires sustained visual line of sight targets and is most effective in countering threats from relatively slow and RF compliant videography drones. Physical interdiction using nets is again only suitable for low-speed interception. Small vehicles based on commercially available consumer drone technology with a mass of less than 1 kg and package size of 15 cm can achieve flight speeds in excess of 70 m/s and can accelerate at up to 15g, and are sufficiently inexpensive as to be considered disposable. Custom flight control systems bypass geofence restrictions and the wide availability of high power radio links greatly exceeding OFCOM limits significantly reduces the range over which commercial jamming systems are effective. Static acceleration performance is maximised simply by decreasing the power loading and decreasing the disc loading and is approximately independent of the size (mass) of the vehicle. Maximisation of top speed is more complex, requiring identification of an optimal disc loading that balances thrust against rotor drag. Top speed is also affected by area/volume scaling meaning that larger vehicles with the same power to weight ratio and disc loading generally have less drag and hence higher top speed. Consumer technology for very high thrust to weight ratio variants of larger multirotor drones is currently not readily available. However, 10 kg drones with a top speed of 100 m/s and static acceleration of 20 g are foreseeable in the next 5 years.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126136276","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999672
Fausto Fanin, Ju-Hyeon Hong
There has been a recent surge in interest regarding small Unmanned Aerial Vehicles (UAV) that operate in indoor environments. A crucial part of such platforms is the navigation system that allows them to navigate in Global Navigation Satellite System (GNSS) denied environments. The two objectives of this work were to develop an Optical Flow (OF) based method for navigation and a high-fidelity simulation for testing and verification. This paper presents the Visual-Inertial Navigation System (VINS) developed that utilises sparse and dense Optical Flow patterns within an Extended Kalman Filter (EKF) framework for autonomous navigation in GNSS denied environments. The principal novelty is the use of dense Optical Flow measurements to estimate the velocity of the UAV.
{"title":"Visual Inertial Navigation for a Small UAV Using Sparse and Dense Optical Flow","authors":"Fausto Fanin, Ju-Hyeon Hong","doi":"10.1109/REDUAS47371.2019.8999672","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999672","url":null,"abstract":"There has been a recent surge in interest regarding small Unmanned Aerial Vehicles (UAV) that operate in indoor environments. A crucial part of such platforms is the navigation system that allows them to navigate in Global Navigation Satellite System (GNSS) denied environments. The two objectives of this work were to develop an Optical Flow (OF) based method for navigation and a high-fidelity simulation for testing and verification. This paper presents the Visual-Inertial Navigation System (VINS) developed that utilises sparse and dense Optical Flow patterns within an Extended Kalman Filter (EKF) framework for autonomous navigation in GNSS denied environments. The principal novelty is the use of dense Optical Flow measurements to estimate the velocity of the UAV.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123780588","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999720
Joonwon Choi, Yeongho Song, Seunghan Lim, H. Oh
It is well known that the V-shape formation of fixed-wing aerial vehicles can contribute to saving fuel consumption from its induced drag reduction. Although it has been widely adopted on various flight missions, the conventional formation method of forming a single V-formation has issues on robustness and scalability if large number of agents are involved. In this paper, we propose a decentralized and scalable approach capable of generating separated multiple V-shape formations for the undirected time-varying networked agents. Using a variation of the multi-consensus algorithm, a flock of agents can be divided into the desired number of subgroups regardless of the subgroup network topology if the algebraic connectivity of the entire flock is maintained. Numerical simulation results are provided to show the feasibility of the proposed formation control.
{"title":"Decentralized Multiple V-Formation Control in Undirected Time-Varying Network Topologies","authors":"Joonwon Choi, Yeongho Song, Seunghan Lim, H. Oh","doi":"10.1109/REDUAS47371.2019.8999720","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999720","url":null,"abstract":"It is well known that the V-shape formation of fixed-wing aerial vehicles can contribute to saving fuel consumption from its induced drag reduction. Although it has been widely adopted on various flight missions, the conventional formation method of forming a single V-formation has issues on robustness and scalability if large number of agents are involved. In this paper, we propose a decentralized and scalable approach capable of generating separated multiple V-shape formations for the undirected time-varying networked agents. Using a variation of the multi-consensus algorithm, a flock of agents can be divided into the desired number of subgroups regardless of the subgroup network topology if the algebraic connectivity of the entire flock is maintained. Numerical simulation results are provided to show the feasibility of the proposed formation control.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129935310","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 : 2019-11-01DOI: 10.1109/REDUAS47371.2019.8999674
A. G. Eguíluz, J. P. Rodríguez-Gómez, J. Paneque, P. Grau, J.R. Martínez de Dios, A. Ollero
The development of perception systems for bio-inspired flapping wing robots, or ornithopters, is very challenging due to their fast flying maneuvers and the high amount of vibrations and motion blur originated by the wing flapping. Visual sensors have been widely used in aerial robot perception due to their size, weight, and energy consumption capabilities. This paper analyzes the issues and challenges for vision sensors onboard ornithopter robots. Two visual sensors are evaluated: a monocular camera and an event-based camera. First, the pros and cons of integrating different sensors on flapping wing robots are studied. Second, the paper experimentally evaluates the impact of wing flapping frequency on both sensors using experiments with the ornithopter developed in the EU-funded GRIFFIN ERC project.
{"title":"Towards flapping wing robot visual perception: Opportunities and challenges","authors":"A. G. Eguíluz, J. P. Rodríguez-Gómez, J. Paneque, P. Grau, J.R. Martínez de Dios, A. Ollero","doi":"10.1109/REDUAS47371.2019.8999674","DOIUrl":"https://doi.org/10.1109/REDUAS47371.2019.8999674","url":null,"abstract":"The development of perception systems for bio-inspired flapping wing robots, or ornithopters, is very challenging due to their fast flying maneuvers and the high amount of vibrations and motion blur originated by the wing flapping. Visual sensors have been widely used in aerial robot perception due to their size, weight, and energy consumption capabilities. This paper analyzes the issues and challenges for vision sensors onboard ornithopter robots. Two visual sensors are evaluated: a monocular camera and an event-based camera. First, the pros and cons of integrating different sensors on flapping wing robots are studied. Second, the paper experimentally evaluates the impact of wing flapping frequency on both sensors using experiments with the ornithopter developed in the EU-funded GRIFFIN ERC project.","PeriodicalId":351115,"journal":{"name":"2019 Workshop on Research, Education and Development of Unmanned Aerial Systems (RED UAS)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117047889","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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