Pub Date : 2016-05-26DOI: 10.1109/EFTF.2016.7477847
Szplet Ryszard, Rozyc Krzysztof, Kwiatkowski Pawel, Jachna Zbigniew
This paper presents the design, operation and test results of a Clocks Evaluation Subsystem (CES) developed for the EUREKA's research project called Legal Time Distribution System (LTDS). The main aim of the CES is to gather information about time drift of the tracked clocks, then to evaluate their stability, and finally to select the most stable one as a local reference clock. The CES contains three main functional blocks: 3-channel time interval counter [1], distribution amplifier and set of three local clock sources, i.e. low noise chip scale atomic clocks (LN CSAC, Microsemi).
{"title":"Local Clocks quality Evaluation Subsystem","authors":"Szplet Ryszard, Rozyc Krzysztof, Kwiatkowski Pawel, Jachna Zbigniew","doi":"10.1109/EFTF.2016.7477847","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477847","url":null,"abstract":"This paper presents the design, operation and test results of a Clocks Evaluation Subsystem (CES) developed for the EUREKA's research project called Legal Time Distribution System (LTDS). The main aim of the CES is to gather information about time drift of the tracked clocks, then to evaluate their stability, and finally to select the most stable one as a local reference clock. The CES contains three main functional blocks: 3-channel time interval counter [1], distribution amplifier and set of three local clock sources, i.e. low noise chip scale atomic clocks (LN CSAC, Microsemi).","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114496462","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 : 2016-05-26DOI: 10.1109/EFTF.2016.7477783
A. Bandura, P. Bogdanov, M. German
One of the ways to improve GLONASS performance is to increase the accuracy of GLONASS Time generation and its synchronization to Russian national time scale UTC(SU). This approach is planned to be realized by, first of all, increasing the accuracy of time scale comparisons between the Main and Reserved Central Synchronizers (CS) which are the basis for GLONASS Time generation and State Time and Frequency Reference (STFR) which is the basis for UTC(SU) generation as well as by increasing the accuracy of mutual comparisons between the Main and Reserved CSs. The paper presents the preliminary results of estimating the accuracy of CS-STFR time scale comparisons with using a new dual-frequency Time Transfer Unit TTU-1 developed at Russian Institute of Radionavigation and Time (RIRT) installed at both CSs and STFR and a new time receiver GTR-51 installed at STRF.
{"title":"Application of new time receivers in GLONASS","authors":"A. Bandura, P. Bogdanov, M. German","doi":"10.1109/EFTF.2016.7477783","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477783","url":null,"abstract":"One of the ways to improve GLONASS performance is to increase the accuracy of GLONASS Time generation and its synchronization to Russian national time scale UTC(SU). This approach is planned to be realized by, first of all, increasing the accuracy of time scale comparisons between the Main and Reserved Central Synchronizers (CS) which are the basis for GLONASS Time generation and State Time and Frequency Reference (STFR) which is the basis for UTC(SU) generation as well as by increasing the accuracy of mutual comparisons between the Main and Reserved CSs. The paper presents the preliminary results of estimating the accuracy of CS-STFR time scale comparisons with using a new dual-frequency Time Transfer Unit TTU-1 developed at Russian Institute of Radionavigation and Time (RIRT) installed at both CSs and STFR and a new time receiver GTR-51 installed at STRF.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131298360","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 : 2016-05-26DOI: 10.1109/EFTF.2016.7477784
L. Buczek, J. Kołodziej, P. Krehlik, M. Lipinski, L. Sliwczynski, A. Binczewski, W. Bogacki, P. Ostapowicz, M. Stroinski, K. Turza, P. Dunst, D. Lemański, J. Nawrocki, P. Nogas, W. Adamowicz, J. Igalson, T. Pawszak, J. Pieczerak, A. Czubla, M. Zawada
The OPTIME project creates an ultra-precise time and frequency signals dissemination system based on telecommunication networks. End users obtain access to these signals without incurring huge costs for the purchase of their own atomic clocks, and receive the service related to laboratories generating international atomic time scales, to which any precise time must be referred. This document describes the final stage of OPTIME project - which developed a self-calibrating, high precision dissemination system for time and frequency reference signals based on optical fiber links and ELSTAB devices developed at AGH University.
{"title":"OPTIME - final release","authors":"L. Buczek, J. Kołodziej, P. Krehlik, M. Lipinski, L. Sliwczynski, A. Binczewski, W. Bogacki, P. Ostapowicz, M. Stroinski, K. Turza, P. Dunst, D. Lemański, J. Nawrocki, P. Nogas, W. Adamowicz, J. Igalson, T. Pawszak, J. Pieczerak, A. Czubla, M. Zawada","doi":"10.1109/EFTF.2016.7477784","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477784","url":null,"abstract":"The OPTIME project creates an ultra-precise time and frequency signals dissemination system based on telecommunication networks. End users obtain access to these signals without incurring huge costs for the purchase of their own atomic clocks, and receive the service related to laboratories generating international atomic time scales, to which any precise time must be referred. This document describes the final stage of OPTIME project - which developed a self-calibrating, high precision dissemination system for time and frequency reference signals based on optical fiber links and ELSTAB devices developed at AGH University.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"191 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134495297","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 : 2016-05-24DOI: 10.1109/EFTF.2016.7477782
Y. Stadnik, V. Flambaum
We propose new schemes for the direct detection of low-mass dark matter with atomic clock and laser interferometry experiments. Dark matter, which consists of low-mass bosons, can readily form an oscillating classical field that survives to reside in the observed galactic dark matter haloes if these particles have sufficiently low mass and are sufficiently feebly interacting. We have recently shown that the interaction of an oscillating classical dark matter field φ with Standard Model fields via quadratic-in- φ couplings produces both a `slow' cosmological evolution and oscillating variations in the fundamental constants. Oscillating variations in the fundamental constants produce oscillating shifts in the transition frequencies of atomic clocks and other related systems, which can be used as high-precision probes to search for dark matter. Using recent atomic dysprosium spectroscopy data, we have derived limits on the quadratic interaction of φ with the photon that improve on existing constraints by up to 15 orders of magnitude. We have also proposed the use of laser and maser interferometry, in which a photon wavelength is compared with the interferometer arm length, as a novel high-precision platform to search for dark matter, with effects due to the variation of the electromagnetic fine-structure constant on alterations in the accumulated phase enhanced by up to 13 orders of magnitude.
{"title":"Searching for dark matter with atomic clocks and laser interferometry","authors":"Y. Stadnik, V. Flambaum","doi":"10.1109/EFTF.2016.7477782","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477782","url":null,"abstract":"We propose new schemes for the direct detection of low-mass dark matter with atomic clock and laser interferometry experiments. Dark matter, which consists of low-mass bosons, can readily form an oscillating classical field that survives to reside in the observed galactic dark matter haloes if these particles have sufficiently low mass and are sufficiently feebly interacting. We have recently shown that the interaction of an oscillating classical dark matter field φ with Standard Model fields via quadratic-in- φ couplings produces both a `slow' cosmological evolution and oscillating variations in the fundamental constants. Oscillating variations in the fundamental constants produce oscillating shifts in the transition frequencies of atomic clocks and other related systems, which can be used as high-precision probes to search for dark matter. Using recent atomic dysprosium spectroscopy data, we have derived limits on the quadratic interaction of φ with the photon that improve on existing constraints by up to 15 orders of magnitude. We have also proposed the use of laser and maser interferometry, in which a photon wavelength is compared with the interferometer arm length, as a novel high-precision platform to search for dark matter, with effects due to the variation of the electromagnetic fine-structure constant on alterations in the accumulated phase enhanced by up to 13 orders of magnitude.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128241284","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 : 2016-05-12DOI: 10.1109/EFTF.2016.7477770
B. Fang, I. Dutta, D. Savoie, B. Venon, C. L. Garrido Alzar, R. Geiger, A. Landragin
We report the operation of a cold-atom inertial sensor in a joint interrogation scheme, where we simultaneously prepare a cold-atom source and operate an atom interferometer in order to eliminate dead times. Noise aliasing and dead times are consequences of the sequential operation which is intrinsic to cold-atom atom interferometers. Both phenomena have deleterious effects on the performance of these sensors. We show that our continuous operation improves the short-term sensitivity of atom interferometers, by demonstrating a record rotation sensitivity of 100 nrad.s-1/√(Hz) in a cold-atom gyroscope of 11 cm2 Sagnac area. We also demonstrate a rotation stability of 1 nrad.s-1 after 104 s of integration, improving previous results by an order of magnitude. We expect that the continuous operation will allow cold-atom inertial sensors with long interrogation time to reach their full sensitivity, determined by the quantum noise limit.
{"title":"Cold-atom inertial sensor without deadtime","authors":"B. Fang, I. Dutta, D. Savoie, B. Venon, C. L. Garrido Alzar, R. Geiger, A. Landragin","doi":"10.1109/EFTF.2016.7477770","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477770","url":null,"abstract":"We report the operation of a cold-atom inertial sensor in a joint interrogation scheme, where we simultaneously prepare a cold-atom source and operate an atom interferometer in order to eliminate dead times. Noise aliasing and dead times are consequences of the sequential operation which is intrinsic to cold-atom atom interferometers. Both phenomena have deleterious effects on the performance of these sensors. We show that our continuous operation improves the short-term sensitivity of atom interferometers, by demonstrating a record rotation sensitivity of 100 nrad.s-1/√(Hz) in a cold-atom gyroscope of 11 cm2 Sagnac area. We also demonstrate a rotation stability of 1 nrad.s-1 after 104 s of integration, improving previous results by an order of magnitude. We expect that the continuous operation will allow cold-atom inertial sensors with long interrogation time to reach their full sensitivity, determined by the quantum noise limit.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114635379","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 : 2016-05-01DOI: 10.1109/FCS.2016.7546783
Magnus Danielson, F. Vernotte, E. Rubiola
The Ω preprocessing was introduced to improve phase noise rejection by using a least square algorithm. The associated variance is the PVAR which is more efficient than MVAR to separate the different noise types. However, unlike AVAR and MVAR, the decimation of PVAR estimates for multi-τ analysis is not possible if each counter measurement is a single scalar. This paper gives a decimation rule based on two scalars, the processing blocks, for each measurement. For the Ω preprocessing, this implies the definition of an output standard as well as hardware requirements for performing high-speed computations of the blocks.
{"title":"Memory-efficient high-speed algorithm for multi-τ PDEV analysis","authors":"Magnus Danielson, F. Vernotte, E. Rubiola","doi":"10.1109/FCS.2016.7546783","DOIUrl":"https://doi.org/10.1109/FCS.2016.7546783","url":null,"abstract":"The Ω preprocessing was introduced to improve phase noise rejection by using a least square algorithm. The associated variance is the PVAR which is more efficient than MVAR to separate the different noise types. However, unlike AVAR and MVAR, the decimation of PVAR estimates for multi-τ analysis is not possible if each counter measurement is a single scalar. This paper gives a decimation rule based on two scalars, the processing blocks, for each measurement. For the Ω preprocessing, this implies the definition of an output standard as well as hardware requirements for performing high-speed computations of the blocks.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130554995","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 : 2016-04-26DOI: 10.1109/EFTF.2016.7477809
J. McGilligan, Rachel Elvin, P. Griffin, E. Riis, A. Arnold
Laser cooled atomic samples have resulted in profound advances in precision metrology [1], however the technology is typically complex and bulky. In recent publications we described a micro-fabricated optical element, that greatly facilitates miniaturisation of ultra-cold atom technology [2], [3], [4], [5]. Portable devices should be feasible with accuracy vastly exceeding that of equivalent room-temperature technology, with a minimal footprint. These laser cooled samples are ideal for atomic clocks. Here we will discuss the implementation of our micro-fabricated diffractive optics towards building a robust, compact cold atom clock.
{"title":"Utilising diffractive optics towards a compact, cold atom clock","authors":"J. McGilligan, Rachel Elvin, P. Griffin, E. Riis, A. Arnold","doi":"10.1109/EFTF.2016.7477809","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477809","url":null,"abstract":"Laser cooled atomic samples have resulted in profound advances in precision metrology [1], however the technology is typically complex and bulky. In recent publications we described a micro-fabricated optical element, that greatly facilitates miniaturisation of ultra-cold atom technology [2], [3], [4], [5]. Portable devices should be feasible with accuracy vastly exceeding that of equivalent room-temperature technology, with a minimal footprint. These laser cooled samples are ideal for atomic clocks. Here we will discuss the implementation of our micro-fabricated diffractive optics towards building a robust, compact cold atom clock.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"172 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132247393","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 : 2016-04-18DOI: 10.1109/EFTF.2016.7477833
T. Dunker, H. Hauglin, Ole Petter Rønningen
We analyze noise properties of time series of frequency data from different counting modes of a Keysight 53230A frequency counter. We use a 10MHz reference signal from a passive hydrogen maser connected via phase-stable Huber+Suhner Sucoflex 104 cables to the reference and input connectors of the counter. We find that the high resolution gap-free (“CONT”) frequency counting process imposes long-term correlations in the output data, resulting in a modified Allan deviation MDEV~ τ-1/2-characteristic of random walk phase noise. Equally important, the CONT mode results in a frequency bias. In contrast, the counter's undocumented raw continuous mode (“RCON”) yields unbiased frequency stability estimates with white phase noise characteristics, MDEV~ τ-3/2, and of a magnitude consistent with the counters 20 ps single-shot resolution. Furthermore, we demonstrate that a 100-point running average filter in conjunction with the RCON mode yields resolution enhanced frequency estimates with flicker phase noise characteristics, MDEV~ τ-1. For instance, the counter's built-in moving-average function can be used. The improved noise characteristics of the averaged RCON mode versus the CONT mode imply that the former mode yields frequency estimates with improved confidence for a given measurement time.
{"title":"On temporal correlations in high-resolution frequency counting","authors":"T. Dunker, H. Hauglin, Ole Petter Rønningen","doi":"10.1109/EFTF.2016.7477833","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477833","url":null,"abstract":"We analyze noise properties of time series of frequency data from different counting modes of a Keysight 53230A frequency counter. We use a 10MHz reference signal from a passive hydrogen maser connected via phase-stable Huber+Suhner Sucoflex 104 cables to the reference and input connectors of the counter. We find that the high resolution gap-free (“CONT”) frequency counting process imposes long-term correlations in the output data, resulting in a modified Allan deviation MDEV~ τ-1/2-characteristic of random walk phase noise. Equally important, the CONT mode results in a frequency bias. In contrast, the counter's undocumented raw continuous mode (“RCON”) yields unbiased frequency stability estimates with white phase noise characteristics, MDEV~ τ-3/2, and of a magnitude consistent with the counters 20 ps single-shot resolution. Furthermore, we demonstrate that a 100-point running average filter in conjunction with the RCON mode yields resolution enhanced frequency estimates with flicker phase noise characteristics, MDEV~ τ-1. For instance, the counter's built-in moving-average function can be used. The improved noise characteristics of the averaged RCON mode versus the CONT mode imply that the former mode yields frequency estimates with improved confidence for a given measurement time.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131848140","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 : 2016-04-04DOI: 10.1109/EFTF.2016.7477831
Tomás Bagala, Adam Fibich, V. Stofanik
In this paper we introduce long-term frequency stability improvement of Oven Controlled Crystal Oscillator (OCXO) using Chip Scale Atomic Clock (CSAC). Compared to OCXO, the main disadvantage of the CSAC is their higher phase noise; however the CSAC features with better long-term frequency stability, much lower power consumption and much faster warm-up.
{"title":"Long-term frequency stability improvement of OCXO using CSAC","authors":"Tomás Bagala, Adam Fibich, V. Stofanik","doi":"10.1109/EFTF.2016.7477831","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477831","url":null,"abstract":"In this paper we introduce long-term frequency stability improvement of Oven Controlled Crystal Oscillator (OCXO) using Chip Scale Atomic Clock (CSAC). Compared to OCXO, the main disadvantage of the CSAC is their higher phase noise; however the CSAC features with better long-term frequency stability, much lower power consumption and much faster warm-up.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124276982","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 : 2016-04-04DOI: 10.1109/EFTF.2016.7477836
F. A. Khan, A. Yousaf, L. Reindl
This paper presents a proof of concept of continuous level monitoring and build-up detection by developing an innovative capacitive E-fields approach “Glocal” (global and local). The change in the sensitivity of the sensor to detect the build-up on the sensor probe is increased by using local E-fields. An initial prototype sensor with a length of 89.5 mm is developed and tested on various fluids. Finite element method (FEM) analysis is also performed in order to investigate the sensitivity of the proposed sensor in liquids with various dielectric constants. An analytical model is also presented which estimates the electric field strength between the capacitive elements as a function of level for a single segment.
{"title":"Build-up detection and level monitoring by using capacitive glocal technique","authors":"F. A. Khan, A. Yousaf, L. Reindl","doi":"10.1109/EFTF.2016.7477836","DOIUrl":"https://doi.org/10.1109/EFTF.2016.7477836","url":null,"abstract":"This paper presents a proof of concept of continuous level monitoring and build-up detection by developing an innovative capacitive E-fields approach “Glocal” (global and local). The change in the sensitivity of the sensor to detect the build-up on the sensor probe is increased by using local E-fields. An initial prototype sensor with a length of 89.5 mm is developed and tested on various fluids. Finite element method (FEM) analysis is also performed in order to investigate the sensitivity of the proposed sensor in liquids with various dielectric constants. An analytical model is also presented which estimates the electric field strength between the capacitive elements as a function of level for a single segment.","PeriodicalId":184222,"journal":{"name":"2016 European Frequency and Time Forum (EFTF)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121256844","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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