Pub Date : 2018-06-01DOI: 10.23919/IRS.2018.8448177
Xin Zhang, Hongbin Li, B. Himed
Passive radar detects and tracks targets of interest using non-cooperative illuminators of opportunity (IOs). This type of radar has become very popular nowadays since qualified IO sources are widely accessible. In this work, the target detection problem for passive multistatic radar is studied. The radar receivers observe not only noise-contaminated reflections of the IO signal but also non-negligible direct-path interference (DPI). We propose a generalized likelihood ratio test (GLRT) approach, where the estimation problem in the alternative hypothesis is solved by using an iterative method. The signal transmitted from the IO is treated as a deterministic but unknown process. A clairvoyant matched filtering detector is also provided to benchmark the detection performance by assuming the knowledge of the IO waveform. Numerical results show the effectiveness of our proposed detector when DPI is present.
{"title":"An Iterative Algorithm for Passive Detection with Direct-Path Interference","authors":"Xin Zhang, Hongbin Li, B. Himed","doi":"10.23919/IRS.2018.8448177","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448177","url":null,"abstract":"Passive radar detects and tracks targets of interest using non-cooperative illuminators of opportunity (IOs). This type of radar has become very popular nowadays since qualified IO sources are widely accessible. In this work, the target detection problem for passive multistatic radar is studied. The radar receivers observe not only noise-contaminated reflections of the IO signal but also non-negligible direct-path interference (DPI). We propose a generalized likelihood ratio test (GLRT) approach, where the estimation problem in the alternative hypothesis is solved by using an iterative method. The signal transmitted from the IO is treated as a deterministic but unknown process. A clairvoyant matched filtering detector is also provided to benchmark the detection performance by assuming the knowledge of the IO waveform. Numerical results show the effectiveness of our proposed detector when DPI is present.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123099732","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448071
P. Wellig, Peter J. Speirs, Christof Schuepbach, R. Oechslin, M. Renker, Urs Boeniger, H. Pratisto
Nowadays, unconventional Low Slow and Small (LSS) air threats pose serious challenges that cause deep concerns among military and civilian security organizations. Consequently, there is a high demand for robust and reliable counter small unmanned aerial vehicles (C-sUAV) solutions. However, traditional air defence systems may be unable to detect, identify and defeat some types of potentially hostile UAVs. Detection challenges such as small RCS values of air targets, unconventional flight patterns in low airspaces, terrain masking effects, or complex urban environments lead to high false alarm rates. Current C-sUAV systems in the market use improved radar components, originally either considered for VSHORAD (Very Short Air Defence) radar, battlefield radar, bird detection radar, perimeter surveillance radar, or high-resolution short-range radar. According to three NATO industrial advisory group (NIAG) studies [1]–[3], there is a strong need for improvement of the currently available C-sUAV systems and for the development of second generation robust and automated sense and warn systems. In addition, the evolution of advanced LSS air threats such as signature reduced drones or swarms as well as new scenarios [4] have to be considered in the development of the second generation. Therefore, many radar research activities on C-sUAV can be observed worldwide, for example research on passive radar, active multi-static radar, MIMO-radar, cognitive radar, or air-to-air radar. This article discusses current radar systems, challenges, and some radar research activities related to C-sUAV.
{"title":"Radar Systems and Challenges for C-UAV","authors":"P. Wellig, Peter J. Speirs, Christof Schuepbach, R. Oechslin, M. Renker, Urs Boeniger, H. Pratisto","doi":"10.23919/IRS.2018.8448071","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448071","url":null,"abstract":"Nowadays, unconventional Low Slow and Small (LSS) air threats pose serious challenges that cause deep concerns among military and civilian security organizations. Consequently, there is a high demand for robust and reliable counter small unmanned aerial vehicles (C-sUAV) solutions. However, traditional air defence systems may be unable to detect, identify and defeat some types of potentially hostile UAVs. Detection challenges such as small RCS values of air targets, unconventional flight patterns in low airspaces, terrain masking effects, or complex urban environments lead to high false alarm rates. Current C-sUAV systems in the market use improved radar components, originally either considered for VSHORAD (Very Short Air Defence) radar, battlefield radar, bird detection radar, perimeter surveillance radar, or high-resolution short-range radar. According to three NATO industrial advisory group (NIAG) studies [1]–[3], there is a strong need for improvement of the currently available C-sUAV systems and for the development of second generation robust and automated sense and warn systems. In addition, the evolution of advanced LSS air threats such as signature reduced drones or swarms as well as new scenarios [4] have to be considered in the development of the second generation. Therefore, many radar research activities on C-sUAV can be observed worldwide, for example research on passive radar, active multi-static radar, MIMO-radar, cognitive radar, or air-to-air radar. This article discusses current radar systems, challenges, and some radar research activities related to C-sUAV.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122804209","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 : 2018-06-01DOI: 10.23919/IRS.2018.8447961
Kaeye Dästner, Bastian von Haßler zu Roseneckh-Köhler, F. Opitz, Michael Rottmaier, Elke Schmid
Classical maritime surveillance systems are enhanced with disruptive elements comingf om big data and machine learning. Available receiver networks deliver a huge amount of worldwide maritime traffc data. The information includes the position as well as signifcant attributes of all vessels, which are equipped with AIS. The processing of this data lake with modern machine learning and big data techniques offer improved decision support for the user. This is especially the case, when AIS is not available and only sensor information, e.g., GMTI is gathered. New design concepts – e.g. the lambda architecture offer the modular integration of these new assets within existing surveillance systems.
{"title":"Machine Learning Techniques for Enhancing Maritime Surveillance Based on GMTI Radar and AIS","authors":"Kaeye Dästner, Bastian von Haßler zu Roseneckh-Köhler, F. Opitz, Michael Rottmaier, Elke Schmid","doi":"10.23919/IRS.2018.8447961","DOIUrl":"https://doi.org/10.23919/IRS.2018.8447961","url":null,"abstract":"Classical maritime surveillance systems are enhanced with disruptive elements comingf om big data and machine learning. Available receiver networks deliver a huge amount of worldwide maritime traffc data. The information includes the position as well as signifcant attributes of all vessels, which are equipped with AIS. The processing of this data lake with modern machine learning and big data techniques offer improved decision support for the user. This is especially the case, when AIS is not available and only sensor information, e.g., GMTI is gathered. New design concepts – e.g. the lambda architecture offer the modular integration of these new assets within existing surveillance systems.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122936758","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 : 2018-06-01DOI: 10.23919/IRS.2018.8447993
T. Thayaparan, Y. Ibrahim, John Polak, R. Riddolls
OTHRs have recently been making a comeback in Canada, as the need for accurate long-range tracking becomes more important, and less-expensive, ground based radars are once again being considered for more effective long-range surveillance of Canadian airspace. Ray-tracing is a powerful tool and is especially useful in applications requiring a detailed knowledge of radio wave propagation through the ionosphere. In this study, methodologies are developed to determine feasible radar parameters such as operating frequencies, elevation angles, and absorption for OTHR operation using a 3-dimensional ray-tracing technique. Results suggest that a 3-dimensional ray-tracing technique can be used to provide the basis for the way ahead in exploring OTHR applications in Canada.
{"title":"Over-The-Horizon Radar (OTHR) In Canada","authors":"T. Thayaparan, Y. Ibrahim, John Polak, R. Riddolls","doi":"10.23919/IRS.2018.8447993","DOIUrl":"https://doi.org/10.23919/IRS.2018.8447993","url":null,"abstract":"OTHRs have recently been making a comeback in Canada, as the need for accurate long-range tracking becomes more important, and less-expensive, ground based radars are once again being considered for more effective long-range surveillance of Canadian airspace. Ray-tracing is a powerful tool and is especially useful in applications requiring a detailed knowledge of radio wave propagation through the ionosphere. In this study, methodologies are developed to determine feasible radar parameters such as operating frequencies, elevation angles, and absorption for OTHR operation using a 3-dimensional ray-tracing technique. Results suggest that a 3-dimensional ray-tracing technique can be used to provide the basis for the way ahead in exploring OTHR applications in Canada.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129158868","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448231
A. Lazarov, C. Kabakchiev, C. Minchev, I. Garvanov
The aim of the study is imaging of moving objects, asteroids illuminated by continuous coherent wideband signals illuminated by pulsars. As pulsars are placed on hundreds of light years from the Earth, objects crossing pulsars’ emission beams are considered as second sources of electromagnetic waves, carrying object’s shape and velocity information that ca be extracted by application pulsar emission-based inverse aperture synthesis. Inverse synthetic aperture radar (ISAR) scenario, geometry and kinematics are analytically described. Models of pulsar signals and ISAR signals secondary emitted by asteroids are suggested White Gaussian noise of high level is added to the ISAR signal in order to approach scenario to reality. Two-dimensional fast Fourier transform for image extraction is applied To verify mathematical model and imaging algorithms numerical experiments are carried out.
{"title":"Passive Aperture Synthesis Using Pulsar’s Emissions","authors":"A. Lazarov, C. Kabakchiev, C. Minchev, I. Garvanov","doi":"10.23919/IRS.2018.8448231","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448231","url":null,"abstract":"The aim of the study is imaging of moving objects, asteroids illuminated by continuous coherent wideband signals illuminated by pulsars. As pulsars are placed on hundreds of light years from the Earth, objects crossing pulsars’ emission beams are considered as second sources of electromagnetic waves, carrying object’s shape and velocity information that ca be extracted by application pulsar emission-based inverse aperture synthesis. Inverse synthetic aperture radar (ISAR) scenario, geometry and kinematics are analytically described. Models of pulsar signals and ISAR signals secondary emitted by asteroids are suggested White Gaussian noise of high level is added to the ISAR signal in order to approach scenario to reality. Two-dimensional fast Fourier transform for image extraction is applied To verify mathematical model and imaging algorithms numerical experiments are carried out.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121028549","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448267
Ieda Pscheidt, S. Trömel
Previous studies suggested that organization of clouds in clusters can modify the mean state of the atmosphere. The increase in outgoing longwave radiation can result in a negative feedback on the surface temperature. This raised the question whether convective organizations can also impact the climate and how climate predictions are affected by the current negligence of such representation in the climate models. Since recent studies show diverging results regarding the question whether convective clouds have a tendency to organize in clusters, our goal in this study is to investigate how convection and precipitation cores organize in a typical mid latitude region. We identified and characterized convection in reflectivity fields of C-band radar composites for Germany every 30 minutes from April to September in the years 2014 and 2015. The identified objects are characterized by means of organization indices which provide information on the spatial arrangements, the number of objects, their shapes and the rainfall produced. The climatology of organization indices indicate some degree of organization in about 98 % of the time. In the remaining 2 % of the time the objects are either random or regularly arranged in space. Organized spatial arrangements presented a larger amount of rainfall than the random and the regular arrangements. This is associated with the fact that more precipitation cores prevail in organizations than in non-organized arrangements.
{"title":"Characteristics of Convective Organizations in Radar Measurements","authors":"Ieda Pscheidt, S. Trömel","doi":"10.23919/IRS.2018.8448267","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448267","url":null,"abstract":"Previous studies suggested that organization of clouds in clusters can modify the mean state of the atmosphere. The increase in outgoing longwave radiation can result in a negative feedback on the surface temperature. This raised the question whether convective organizations can also impact the climate and how climate predictions are affected by the current negligence of such representation in the climate models. Since recent studies show diverging results regarding the question whether convective clouds have a tendency to organize in clusters, our goal in this study is to investigate how convection and precipitation cores organize in a typical mid latitude region. We identified and characterized convection in reflectivity fields of C-band radar composites for Germany every 30 minutes from April to September in the years 2014 and 2015. The identified objects are characterized by means of organization indices which provide information on the spatial arrangements, the number of objects, their shapes and the rainfall produced. The climatology of organization indices indicate some degree of organization in about 98 % of the time. In the remaining 2 % of the time the objects are either random or regularly arranged in space. Organized spatial arrangements presented a larger amount of rainfall than the random and the regular arrangements. This is associated with the fact that more precipitation cores prevail in organizations than in non-organized arrangements.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116965868","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 : 2018-06-01DOI: 10.23919/IRS.2018.8447962
M. Bączyk, Bartosz Dzikowski, P. Samczyński, K. Kulpa
This paper presents the system development of wideband and multistatic passive radar demonstrator built with custom-off-the-shelf (COTS) components. The main goal of this work was to build the system which would allow for a high resolution and multistatic imaging with the use of the passive inverse synthetic aperture radar (ISAR) technic. In this paper a detailed description of the system design and a thorough analysis of system requirements for the multistatic radar imaging are shown. Also, the system validation with aircrafts illuminated by the Digital Video Broadcasting-Terrestrial (DVB-T) transmitters of opportunity used as the targets is presented.
{"title":"Wideband Multistatic Passive Radar Demonstrator for ISAR Imaging Using COTS Components","authors":"M. Bączyk, Bartosz Dzikowski, P. Samczyński, K. Kulpa","doi":"10.23919/IRS.2018.8447962","DOIUrl":"https://doi.org/10.23919/IRS.2018.8447962","url":null,"abstract":"This paper presents the system development of wideband and multistatic passive radar demonstrator built with custom-off-the-shelf (COTS) components. The main goal of this work was to build the system which would allow for a high resolution and multistatic imaging with the use of the passive inverse synthetic aperture radar (ISAR) technic. In this paper a detailed description of the system design and a thorough analysis of system requirements for the multistatic radar imaging are shown. Also, the system validation with aircrafts illuminated by the Digital Video Broadcasting-Terrestrial (DVB-T) transmitters of opportunity used as the targets is presented.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117200178","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448118
Simon Bækkegaard, Jeppe Blixenkrone-Møller, J. Larsen, Lars W. Jochumsen
We study the performance of a Recurrent Neural Network (RNN) for target classification using kinematic data from vessels sailing in Danish waters.We use data obtained from the Automatic Identification System (AIS) to get labelled data for supervised learning as a proof of concept for later use on 2D radar tracks. The RNN classifier was trained for five classes on five days of AIS data, and tested on data from a separate day. We used five-fold cross validation, achieving a classification accuracy of 78.3%. The results are compared with a random forest classifier using the same dataset. The RNN classifier achieved a classification accuracy 1.9 percent-points higher than the random forest classifier, showing that RNNs have good potential for target classification using kinematic data.
{"title":"Target Classification Using Kinematic Data and a Recurrent Neural Network","authors":"Simon Bækkegaard, Jeppe Blixenkrone-Møller, J. Larsen, Lars W. Jochumsen","doi":"10.23919/IRS.2018.8448118","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448118","url":null,"abstract":"We study the performance of a Recurrent Neural Network (RNN) for target classification using kinematic data from vessels sailing in Danish waters.We use data obtained from the Automatic Identification System (AIS) to get labelled data for supervised learning as a proof of concept for later use on 2D radar tracks. The RNN classifier was trained for five classes on five days of AIS data, and tested on data from a separate day. We used five-fold cross validation, achieving a classification accuracy of 78.3%. The results are compared with a random forest classifier using the same dataset. The RNN classifier achieved a classification accuracy 1.9 percent-points higher than the random forest classifier, showing that RNNs have good potential for target classification using kinematic data.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116217625","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448017
H. Bloecher, J. Dickmann
Due to the application of automotive radar technology in non-automotive applications and the increasing number of vehicles equipped with radar, the need of protecting automotive radar against these interference sources increases, in particular due to the upcoming highly automated and autonomous vehicle operation. The contribution reviews the situation and its boundary conditions, and outlines different approaches of probable technical and non-technical countermeasures.
{"title":"Automotive Radar Sensor Interference – Thread and probable Countermeasures","authors":"H. Bloecher, J. Dickmann","doi":"10.23919/IRS.2018.8448017","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448017","url":null,"abstract":"Due to the application of automotive radar technology in non-automotive applications and the increasing number of vehicles equipped with radar, the need of protecting automotive radar against these interference sources increases, in particular due to the upcoming highly automated and autonomous vehicle operation. The contribution reviews the situation and its boundary conditions, and outlines different approaches of probable technical and non-technical countermeasures.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"124 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115824937","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 : 2018-06-01DOI: 10.23919/IRS.2018.8448257
K. Kulpa, M. Bączyk, J. Misiurewicz, M. Malanowski, D. Gromek
The paper presents the limitations in application of CLEAN based clutter cancelation method in mobile airborne passive radar. As the ground clutter is Doppler spread due to the platform motion it is necessary to clean not only the direct signal and time shifted replicas of illuminated signals but also Doppler and time shifted copies of the reference signal originated by clutter return. The paper discuss the maximum clutter cancelation range and maximum Doppler spread.
{"title":"Limits of Ground Clutter CLEAN Based Cancelation in Mobile PCL Radar","authors":"K. Kulpa, M. Bączyk, J. Misiurewicz, M. Malanowski, D. Gromek","doi":"10.23919/IRS.2018.8448257","DOIUrl":"https://doi.org/10.23919/IRS.2018.8448257","url":null,"abstract":"The paper presents the limitations in application of CLEAN based clutter cancelation method in mobile airborne passive radar. As the ground clutter is Doppler spread due to the platform motion it is necessary to clean not only the direct signal and time shifted replicas of illuminated signals but also Doppler and time shifted copies of the reference signal originated by clutter return. The paper discuss the maximum clutter cancelation range and maximum Doppler spread.","PeriodicalId":436201,"journal":{"name":"2018 19th International Radar Symposium (IRS)","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115936077","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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