Pub Date : 2021-08-31DOI: 10.1109/UComms50339.2021.9598084
A. Pottier, P. Bouvet, P. Forjonel
This paper presents a study of Multiuser Multiple Input Multiple Output (MU-MIMO) as a multi-access method for underwater acoustic communications. Traditional multi-access schemes such as Time Division Multiple Access (TDMA) suffer from limited data rates due to an inefficient sharing of communication resources. In a MU-MIMO systems, each user can be viewed by the receiver as an input of a conventional MIMO channel. The receiver can then exploit the spatial diversity to decode the input streams of each users. Achievable rates of MU-MIMO with Successive Interference Cancellation (SIC) are studied in a first place, and compared with single user and TDMA theoretical performance. The theoretical rates are computed on channels sounded at-sea for a two-user configuration so as to evaluate what gains can be expected from the MU-MIMO approach. Finally, comparisons with the effective rates obtained from simulations of full modulation and demodulation stages using measured channels and the underWater AcousTic channEl Replay benchMARK (WATERMARK) are provided.
{"title":"Performance evaluation of Multi-User MIMO Underwater Acoustic Communications","authors":"A. Pottier, P. Bouvet, P. Forjonel","doi":"10.1109/UComms50339.2021.9598084","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598084","url":null,"abstract":"This paper presents a study of Multiuser Multiple Input Multiple Output (MU-MIMO) as a multi-access method for underwater acoustic communications. Traditional multi-access schemes such as Time Division Multiple Access (TDMA) suffer from limited data rates due to an inefficient sharing of communication resources. In a MU-MIMO systems, each user can be viewed by the receiver as an input of a conventional MIMO channel. The receiver can then exploit the spatial diversity to decode the input streams of each users. Achievable rates of MU-MIMO with Successive Interference Cancellation (SIC) are studied in a first place, and compared with single user and TDMA theoretical performance. The theoretical rates are computed on channels sounded at-sea for a two-user configuration so as to evaluate what gains can be expected from the MU-MIMO approach. Finally, comparisons with the effective rates obtained from simulations of full modulation and demodulation stages using measured channels and the underWater AcousTic channEl Replay benchMARK (WATERMARK) are provided.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125831808","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598109
Christophe Bernard, P. Bouvet, A. Pottier, P. Forjonel
This article presents a new multiple access technique for underwater acoustic communication in the framework of AUV fleet. The multiuser scheme is based on a set of orthogonal waveforms built by combining 2 types of HFM signals allowing at the reception side very simple matched filter based decoding. The proposed multiuser technique provides good resilience against multiuser interference while keeping robustness against underwater acoustic channel impairments like Doppler shift. The implementation of this protocol for the underwater acoustic scenario is described, and performance are analysed and compared against conventional TDMA and CDMA techniques over replayed experimental channels for up to 5 AUVs acting as mobile nodes.
{"title":"Multiple access acoustic communication in underwater mobile networks","authors":"Christophe Bernard, P. Bouvet, A. Pottier, P. Forjonel","doi":"10.1109/UComms50339.2021.9598109","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598109","url":null,"abstract":"This article presents a new multiple access technique for underwater acoustic communication in the framework of AUV fleet. The multiuser scheme is based on a set of orthogonal waveforms built by combining 2 types of HFM signals allowing at the reception side very simple matched filter based decoding. The proposed multiuser technique provides good resilience against multiuser interference while keeping robustness against underwater acoustic channel impairments like Doppler shift. The implementation of this protocol for the underwater acoustic scenario is described, and performance are analysed and compared against conventional TDMA and CDMA techniques over replayed experimental channels for up to 5 AUVs acting as mobile nodes.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130675081","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598038
Jacob Rudander, Thor HusØy, P. Orten, P. V. van Walree
The performance of a coherent receiver depends on accurate Doppler estimation. This paper presents a Doppler estimator intended for single-carrier data streaming. It is based on a coarse estimate found via a small bank of shifted replicas, followed by a correction step. The cross-ambiguity function phase difference between two binary pseudo-noise training sequences, embedded in the start of the frame, is used to find the correction factor. The Doppler estimator was implemented in an FPGA and evaluated in three horizontal very high frequency (250 kHz) shallow water channels. The results show satisfactory real-time performance in the range of $pm 2$ m/s.
{"title":"Experimental evaluation of an FPGA based Real-Time Doppler estimator","authors":"Jacob Rudander, Thor HusØy, P. Orten, P. V. van Walree","doi":"10.1109/UComms50339.2021.9598038","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598038","url":null,"abstract":"The performance of a coherent receiver depends on accurate Doppler estimation. This paper presents a Doppler estimator intended for single-carrier data streaming. It is based on a coarse estimate found via a small bank of shifted replicas, followed by a correction step. The cross-ambiguity function phase difference between two binary pseudo-noise training sequences, embedded in the start of the frame, is used to find the correction factor. The Doppler estimator was implemented in an FPGA and evaluated in three horizontal very high frequency (250 kHz) shallow water channels. The results show satisfactory real-time performance in the range of $pm 2$ m/s.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114352538","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598132
Mohammadreza Alimadadi, M. Stojanovic, P. Closas
We consider a network of distributed underwater sensors whose task is to monitor the movement of objects across an area. The sensors measure the strength of signals emanated by the objects and convey the measurements to the local fusion centers. Multiple fusion centers are deployed to cover an arbitrarily large area. The fusion centers communicate with each other to achieve consensus on the estimated locations of the moving objects. We introduce two efficient methods for data fusion of distributed partial estimates when delay in communication is not negligible. We concentrate on the minimum mean squared error (MMSE) global estimator, and evaluate the performance of these fusion methods in the context of multiple-object tracking via extended Kalman filtering. Numerical results show the superior performance compared to the case when delay is ignored.
{"title":"Delay-Tolerant Data Fusion for Underwater Acoustic Tracking Networks","authors":"Mohammadreza Alimadadi, M. Stojanovic, P. Closas","doi":"10.1109/UComms50339.2021.9598132","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598132","url":null,"abstract":"We consider a network of distributed underwater sensors whose task is to monitor the movement of objects across an area. The sensors measure the strength of signals emanated by the objects and convey the measurements to the local fusion centers. Multiple fusion centers are deployed to cover an arbitrarily large area. The fusion centers communicate with each other to achieve consensus on the estimated locations of the moving objects. We introduce two efficient methods for data fusion of distributed partial estimates when delay in communication is not negligible. We concentrate on the minimum mean squared error (MMSE) global estimator, and evaluate the performance of these fusion methods in the context of multiple-object tracking via extended Kalman filtering. Numerical results show the superior performance compared to the case when delay is ignored.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"395 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132847827","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598050
E. Erstorp, P. Sigray, J. Kuttenkeuler
In this study, we present the first iteration of DPower, an energy conserving method for use in underwater acoustic networks. The method encompasses a straightforward transmission power calibration procedure and adaptive power level selection. The method was evaluated in combination with DFlood, a known and validated constrained flooding protocol developed for underwater applications. Simulations of a network with given prerequisites have shown that, with an acceptable increase in packet loss, the presented method can dramatically reduce the energy consumption and thus improve the life-time of networks.
{"title":"An Adaptive Transmission Power Controller for Flooding-based Underwater Network Protocols","authors":"E. Erstorp, P. Sigray, J. Kuttenkeuler","doi":"10.1109/UComms50339.2021.9598050","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598050","url":null,"abstract":"In this study, we present the first iteration of DPower, an energy conserving method for use in underwater acoustic networks. The method encompasses a straightforward transmission power calibration procedure and adaptive power level selection. The method was evaluated in combination with DFlood, a known and validated constrained flooding protocol developed for underwater applications. Simulations of a network with given prerequisites have shown that, with an acceptable increase in packet loss, the presented method can dramatically reduce the energy consumption and thus improve the life-time of networks.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"426 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115612217","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598036
A. Jarrot, Andriy Gelman, Gloria Choi, A. Speck, G. Strunk, Arnaud Croux, T. Osedach, Stephane Vannuffelen, S. Ossia, Jack Vincent, S. Grall, Guillaume Eudeline
Service providers for subsea inspection, maintenance, and repair (IMR) generally utilize remotely operated tethered vehicles (ROVs) to inspect and to intervene on underwater infrastructure. The cost of these operations can be considerable due to the need of deploying a large surface vessel and a highly skilled crew to support the IMR campaign. This work describes a novel multi-agent autonomous system comprising an autonomous underwater vehicle (AUV) and unmanned surface vessel (USV) incorporating a proprietary high-bandwidth acoustic communication system capable of video transmission to the surface with effective data rates in excess of 100 kbps at 2 km. Real-time data stream transmission from the AUV was demonstrated at a depth of 840 m as well as a shallow water test in which the video stream of a World War 2 fighter plane wreck was transmitted to the surface.
{"title":"High-speed underwater acoustic communication for multi-agent supervised autonomy","authors":"A. Jarrot, Andriy Gelman, Gloria Choi, A. Speck, G. Strunk, Arnaud Croux, T. Osedach, Stephane Vannuffelen, S. Ossia, Jack Vincent, S. Grall, Guillaume Eudeline","doi":"10.1109/UComms50339.2021.9598036","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598036","url":null,"abstract":"Service providers for subsea inspection, maintenance, and repair (IMR) generally utilize remotely operated tethered vehicles (ROVs) to inspect and to intervene on underwater infrastructure. The cost of these operations can be considerable due to the need of deploying a large surface vessel and a highly skilled crew to support the IMR campaign. This work describes a novel multi-agent autonomous system comprising an autonomous underwater vehicle (AUV) and unmanned surface vessel (USV) incorporating a proprietary high-bandwidth acoustic communication system capable of video transmission to the surface with effective data rates in excess of 100 kbps at 2 km. Real-time data stream transmission from the AUV was demonstrated at a depth of 840 m as well as a shallow water test in which the video stream of a World War 2 fighter plane wreck was transmitted to the surface.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127393224","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598062
R. Diamant, P. Casari, S. Tomasin
We propose a method to let a source and a destination agree on a key that remains secret to a potential eavesdropper in an underwater acoustic network (UWAN). We generate the key from the propagation delay measured over a set of multihop routes: this harvests the randomness in the UWAN topology and turns the slow sound propagation in the water into an advantage for the key agreement protocol. Our scheme relies on a route discovery handshake. During this process, all intermediate relays accumulate message processing delays, so that both the source and the destination can compute the actual propagation delays along each route, and map this information to a string of bits. Finally, via a secret key agreement from the information-theoretic security framework, we obtain an equal set of bits at the source and destination, which is provably secret to a potential eavesdropper located away from both nodes. Our simulation results show that, even for small UWANs of 4 nodes, we obtain 11 secret bits per explored topology, and that the protocol is insensitive to an average node speed of up to 0.5 m/s.
{"title":"Topology-based Secret Key Generation for Underwater Acoustic Networks","authors":"R. Diamant, P. Casari, S. Tomasin","doi":"10.1109/UComms50339.2021.9598062","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598062","url":null,"abstract":"We propose a method to let a source and a destination agree on a key that remains secret to a potential eavesdropper in an underwater acoustic network (UWAN). We generate the key from the propagation delay measured over a set of multihop routes: this harvests the randomness in the UWAN topology and turns the slow sound propagation in the water into an advantage for the key agreement protocol. Our scheme relies on a route discovery handshake. During this process, all intermediate relays accumulate message processing delays, so that both the source and the destination can compute the actual propagation delays along each route, and map this information to a string of bits. Finally, via a secret key agreement from the information-theoretic security framework, we obtain an equal set of bits at the source and destination, which is provably secret to a potential eavesdropper located away from both nodes. Our simulation results show that, even for small UWANs of 4 nodes, we obtain 11 secret bits per explored topology, and that the protocol is insensitive to an average node speed of up to 0.5 m/s.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"875 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114149514","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598122
P. V. van Walree, M. Colin
A channel sounding and communications experiment was performed in the Oslofjord in April/May 2019, where 8 bottom units were deployed in a network configuration. Five units were equipped with a software-defined acoustic modem operating in the 4–8 kHz band, programmed to transmit probe signals and communication packets. All transmitted signals were recorded by all units over 35 unique horizontal links and 5 vertical links. Measured power delay profiles are used to predict receiver output SNR, examining the effect of ambient noise, reverberation of previously transmitted packets, and the packet's own reverberation. It is shown that modem performance is limited by the own reverberation, and that the mean prediction error is below 3 dB when this reverberation is taken into account.
{"title":"In-situ performance prediction of a coherent acoustic modem","authors":"P. V. van Walree, M. Colin","doi":"10.1109/UComms50339.2021.9598122","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598122","url":null,"abstract":"A channel sounding and communications experiment was performed in the Oslofjord in April/May 2019, where 8 bottom units were deployed in a network configuration. Five units were equipped with a software-defined acoustic modem operating in the 4–8 kHz band, programmed to transmit probe signals and communication packets. All transmitted signals were recorded by all units over 35 unique horizontal links and 5 vertical links. Measured power delay profiles are used to predict receiver output SNR, examining the effect of ambient noise, reverberation of previously transmitted packets, and the packet's own reverberation. It is shown that modem performance is limited by the own reverberation, and that the mean prediction error is below 3 dB when this reverberation is taken into account.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131955960","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598094
Fabian Steinmetz, Bernd-Christian Renner
Micro Autonomous Underwater Vehicles (μAUVs) and Underwater Wireless Sensor Networks (UWSNs) enable diverse underwater applications in ports and other shallow inshore waters. During the past, several acoustic underwater modems were developed, which have typical communication ranges of a few kilometers. Opposed to that, there is a growing demand of short-range communication (less than a kilometer) for the mentioned applications. This paper discusses the requirements of different acoustic communication devices and motivates the need of short-range and very shallow-water soundings. Typical observations of long-range channels do not apply. Afterwards, soundings in two locations are discussed. The soundings indicates quite different behavior and illustrates the diversity of acoustic transmission channels. Based on our findings, new modulation schemes can be developed.
{"title":"From the Long-Range Channel in the Ocean to the Short-Range and Very Shallow-Water Acoustic Channel in Ports and Harbors","authors":"Fabian Steinmetz, Bernd-Christian Renner","doi":"10.1109/UComms50339.2021.9598094","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598094","url":null,"abstract":"Micro Autonomous Underwater Vehicles (μAUVs) and Underwater Wireless Sensor Networks (UWSNs) enable diverse underwater applications in ports and other shallow inshore waters. During the past, several acoustic underwater modems were developed, which have typical communication ranges of a few kilometers. Opposed to that, there is a growing demand of short-range communication (less than a kilometer) for the mentioned applications. This paper discusses the requirements of different acoustic communication devices and motivates the need of short-range and very shallow-water soundings. Typical observations of long-range channels do not apply. Afterwards, soundings in two locations are discussed. The soundings indicates quite different behavior and illustrates the diversity of acoustic transmission channels. Based on our findings, new modulation schemes can be developed.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115738701","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 : 2021-08-31DOI: 10.1109/UComms50339.2021.9598012
Toby Schneider, H. Schmidt, S. Randeni
Complex vehicle missions (such as under-ice operations) require balancing the various competing uses of the acoustic channel. We present an integrated communications and navigation system, where a single synchronized digital communication packet is used to both provide tracking and data to the operator. In response, a navigation correction is telemetered to the vehicle. This system was deployed and operating during the ICEX20 experiment in the Beaufort Sea in March 2020. The variability of acoustic propagation with depth in the Beaufort Sea imposes a challenge to ensure reliable connectivity between the vehicle and the topside operators (in this case, via ice buoys). In the context of this under-ice system, where the ice buoys have multiple receiver and transmitter depths, we explore a self-adapting network that uses oceanographic and propagation modeling to predict the expected optimal receiver depth layer and transmitter hydrophone.
{"title":"Self-Adapting Under-Ice Integrated Communications and Navigation Network","authors":"Toby Schneider, H. Schmidt, S. Randeni","doi":"10.1109/UComms50339.2021.9598012","DOIUrl":"https://doi.org/10.1109/UComms50339.2021.9598012","url":null,"abstract":"Complex vehicle missions (such as under-ice operations) require balancing the various competing uses of the acoustic channel. We present an integrated communications and navigation system, where a single synchronized digital communication packet is used to both provide tracking and data to the operator. In response, a navigation correction is telemetered to the vehicle. This system was deployed and operating during the ICEX20 experiment in the Beaufort Sea in March 2020. The variability of acoustic propagation with depth in the Beaufort Sea imposes a challenge to ensure reliable connectivity between the vehicle and the topside operators (in this case, via ice buoys). In the context of this under-ice system, where the ice buoys have multiple receiver and transmitter depths, we explore a self-adapting network that uses oceanographic and propagation modeling to predict the expected optimal receiver depth layer and transmitter hydrophone.","PeriodicalId":371411,"journal":{"name":"2021 Fifth Underwater Communications and Networking Conference (UComms)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121967630","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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