Pub Date : 2015-04-12DOI: 10.1109/FCS.2015.7138842
Xiangwei Zhu, H. Gong, G. Sun, K. Liang
High-precision time synchronization is a basic element in some areas of aeronautical engineering, such as satellite navigation and deep space exploration. It is more accurate and stable to use the optical fibers while performing time frequency transfer than using other media such as GNSS common view and two-way satellite time frequency transfer. The frequency transfer is the main focus of the current research in optical fiber time frequency transfer. However, there is little study on time transfer, and the accuracy of time transfer is commonly in nanosecond level. In this paper, a two way time transfer method based on spread spectrum ranging is studied. For the proposed method, the accuracy is improved and extra links for data check are not needed any more. The designing schemes and the implementation progress of the engineering prototype are presented. The experimental results indicate that the time synchronization uncertainty is less than 30ps by use of the proposed method when the optical fiber transmission distance is within 2km.
{"title":"The research progress of two way time synchronization with fiber based on spread spectrum signal","authors":"Xiangwei Zhu, H. Gong, G. Sun, K. Liang","doi":"10.1109/FCS.2015.7138842","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138842","url":null,"abstract":"High-precision time synchronization is a basic element in some areas of aeronautical engineering, such as satellite navigation and deep space exploration. It is more accurate and stable to use the optical fibers while performing time frequency transfer than using other media such as GNSS common view and two-way satellite time frequency transfer. The frequency transfer is the main focus of the current research in optical fiber time frequency transfer. However, there is little study on time transfer, and the accuracy of time transfer is commonly in nanosecond level. In this paper, a two way time transfer method based on spread spectrum ranging is studied. For the proposed method, the accuracy is improved and extra links for data check are not needed any more. The designing schemes and the implementation progress of the engineering prototype are presented. The experimental results indicate that the time synchronization uncertainty is less than 30ps by use of the proposed method when the optical fiber transmission distance is within 2km.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82268285","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138949
Bo Wang, Xi Zhu, Yu Bai, C. Gao, Lijun Wang
We present two RF frequency dissemination methods (active and passive phase fluctuation compensation) for branching network. For the active one, the phase noise compensation function placed at the client site. One transmitting module hence can be linked with multiple client sites. For the passive one, without any phase control on the disseminated rf signals or usages of active feedback loop, the highly stable reference radio frequency signal can be delivered to several remote sites simultaneously and independently.
{"title":"Actively and passively compensated RF frequency disseminations on branching fiber network","authors":"Bo Wang, Xi Zhu, Yu Bai, C. Gao, Lijun Wang","doi":"10.1109/FCS.2015.7138949","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138949","url":null,"abstract":"We present two RF frequency dissemination methods (active and passive phase fluctuation compensation) for branching network. For the active one, the phase noise compensation function placed at the client site. One transmitting module hence can be linked with multiple client sites. For the passive one, without any phase control on the disseminated rf signals or usages of active feedback loop, the highly stable reference radio frequency signal can be delivered to several remote sites simultaneously and independently.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87834589","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138811
D. Gaied, M. Khairy, M. Atef, A. Ahmed, M. Shadoufa, A. Hassanein, O. El-Aassar, M. Gamal, A. El-Sayed, A. Badawy, A. Adel, M. Erfan, N. Sinoussi, A. Helmy
This work presents a highly stable monolithic integrated CMOS LC-based frequency reference. The frequency reference is based on a Self-Compensated Oscillator (SCO) architecture where the LC tank operates at a specific phase Phi-NULL where frequency sensitivity versus temperature is minimum. A new compensation technique is applied over Phi-Null to further optimize frequency stability and extend the temperature range. The new technique is based on an analog approach and induces a minimum impact on oscillator phase noise, current consumption and die area. Utilizing this technique, the temperature range has been extended to (-40-105°C) with a ±40ppm frequency stability. Achieved performance makes it possible for the SCO to be introduced to automotive applications where crystals suffer vibration induced stability issues.
{"title":"A CMOS LC-based frequency reference with ±40ppm stability from −40°C to 105°C","authors":"D. Gaied, M. Khairy, M. Atef, A. Ahmed, M. Shadoufa, A. Hassanein, O. El-Aassar, M. Gamal, A. El-Sayed, A. Badawy, A. Adel, M. Erfan, N. Sinoussi, A. Helmy","doi":"10.1109/FCS.2015.7138811","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138811","url":null,"abstract":"This work presents a highly stable monolithic integrated CMOS LC-based frequency reference. The frequency reference is based on a Self-Compensated Oscillator (SCO) architecture where the LC tank operates at a specific phase Phi-NULL where frequency sensitivity versus temperature is minimum. A new compensation technique is applied over Phi-Null to further optimize frequency stability and extend the temperature range. The new technique is based on an analog approach and induces a minimum impact on oscillator phase noise, current consumption and die area. Utilizing this technique, the temperature range has been extended to (-40-105°C) with a ±40ppm frequency stability. Achieved performance makes it possible for the SCO to be introduced to automotive applications where crystals suffer vibration induced stability issues.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77465438","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138888
A. Mikhail
For efficient performance of a single-state selection system when using Majorana method, it's extremely important to know how eventual angle of rotation for atom's spin depends on a total magnetic field in a region between selection magnets. As it was shown in previous work, the angle of rotation for spinor F = 1 greatly depends on a transverse (in regard to the hydrogen beam axis z) displacement of the point where total field is zero. In this work, for the first time, the dependence of single-state selection system performance (or H-maser's output power) on the currents of the transverse coils, that are placed at the region between magnets, is experimentally obtained. On the dependence, the angles of rotation for spinor that are equal to 0, π/2, π under corresponding quantity of the currents, i. e. transverse coordinates of the zero field, are explicitly determined. The optimal values of the currents, when the maximum of the single-state selection efficiency (the angle of rotation is equal π) is achieved, are defined. Moreover, the operation of the single-state selection system is confirmed by exploration of the H-maser's power curve and also by double resonance method. The relative amount of the operating atoms in the beam, that defines single-state selection system efficiency, is approximately 70%.
{"title":"Majorana atomic transition research in H-maser's magnetic state selection region","authors":"A. Mikhail","doi":"10.1109/FCS.2015.7138888","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138888","url":null,"abstract":"For efficient performance of a single-state selection system when using Majorana method, it's extremely important to know how eventual angle of rotation for atom's spin depends on a total magnetic field in a region between selection magnets. As it was shown in previous work, the angle of rotation for spinor F = 1 greatly depends on a transverse (in regard to the hydrogen beam axis z) displacement of the point where total field is zero. In this work, for the first time, the dependence of single-state selection system performance (or H-maser's output power) on the currents of the transverse coils, that are placed at the region between magnets, is experimentally obtained. On the dependence, the angles of rotation for spinor that are equal to 0, π/2, π under corresponding quantity of the currents, i. e. transverse coordinates of the zero field, are explicitly determined. The optimal values of the currents, when the maximum of the single-state selection efficiency (the angle of rotation is equal π) is achieved, are defined. Moreover, the operation of the single-state selection system is confirmed by exploration of the H-maser's power curve and also by double resonance method. The relative amount of the operating atoms in the beam, that defines single-state selection system efficiency, is approximately 70%.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90089676","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}
A new time transfer modem for two-way satellite time and frequency transfer (TWSTFT) has been developed recently at Beijing Institute of Radio Metrology and Measurement (BIRMM). The DSSS and BPSK modulation techniques are used to generate a PRN signal. A FFT fast parallel algorithm is applied to achieve fast acquisition of the PRN modulated receiving signal. A 2nd order FLL assisted 3rd order PLL is designed to keep both of the performance of loop dynamic stress and carrier phase tracking accuracy, and a 2nd order DLL is used to track and measure the code phase. A short baseline TWSTFT experiment was done with two 1.2 m VSAT earth stations and a commercial geosynchronous orbit communication satellite to evaluate the modem's performance. The result shows very low noise with the standard deviation (1 σ) equal to 0.13 ns at a 2.5 MChip/s code rate.
北京无线电计量测量研究所研制了一种新型的卫星时频双向传输时间调制解调器(TWSTFT)。采用DSSS和BPSK调制技术产生PRN信号。采用FFT快速并行算法实现了PRN调制接收信号的快速采集。为了保证环动应力性能和载波相位跟踪精度，设计了二阶FLL辅助三阶锁相环，并利用二阶DLL跟踪和测量码相位。在两个1.2 m VSAT地面站和一颗商业地球同步轨道通信卫星上进行了短基线TWSTFT实验，以评估调制解调器的性能。结果表明，在2.5 MChip/s的码率下，噪声极低，标准差(1 σ)为0.13 ns。
{"title":"A new modem for two way satellite time and frequency transfer","authors":"shengkang zhang, Xueyun Wang, Haifeng Wang, Hongbo Wang, Yuan Yuan, K. Feng","doi":"10.1109/FCS.2015.7138834","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138834","url":null,"abstract":"A new time transfer modem for two-way satellite time and frequency transfer (TWSTFT) has been developed recently at Beijing Institute of Radio Metrology and Measurement (BIRMM). The DSSS and BPSK modulation techniques are used to generate a PRN signal. A FFT fast parallel algorithm is applied to achieve fast acquisition of the PRN modulated receiving signal. A 2nd order FLL assisted 3rd order PLL is designed to keep both of the performance of loop dynamic stress and carrier phase tracking accuracy, and a 2nd order DLL is used to track and measure the code phase. A short baseline TWSTFT experiment was done with two 1.2 m VSAT earth stations and a commercial geosynchronous orbit communication satellite to evaluate the modem's performance. The result shows very low noise with the standard deviation (1 σ) equal to 0.13 ns at a 2.5 MChip/s code rate.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1109/FCS.2015.7138834","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72446982","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138797
Gobong Choi, Y. Yong
In this paper, we introduce a novel design length extension vibratory gyroscope to detect the angular velocity rotation about z-axis. The proposed gyroscope is a new type of a gyroscope which utilizes a length extension mode as a driving mode and a flexure mode as a sensing mode to detect the Coriolis force generated by the rotation of the system. The gyroscope was designed and gyro-characteristics were simulated using COMSOL, finite element method (FEM) software. Quartz and langatate crystals are used for gyroscopes and compared. The driving frequencies and sensing frequencies of each gyroscope are obtained by optimizing the geometries of the each gyroscope using eigenfrequency analyses. Frequency response analyses were performed to simulate the gyro-characteristics of the gyroscopes which subjected to the angular velocity about z-axis. The results show that the length extension gyroscope can be used as a gyro-sensor. Moreover, we find that langatate crystals are more suitable materials for higher precision piezoelectric gyro-sensors than quartz crystal.
{"title":"Design of a novel length extension vibratory gyroscope","authors":"Gobong Choi, Y. Yong","doi":"10.1109/FCS.2015.7138797","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138797","url":null,"abstract":"In this paper, we introduce a novel design length extension vibratory gyroscope to detect the angular velocity rotation about z-axis. The proposed gyroscope is a new type of a gyroscope which utilizes a length extension mode as a driving mode and a flexure mode as a sensing mode to detect the Coriolis force generated by the rotation of the system. The gyroscope was designed and gyro-characteristics were simulated using COMSOL, finite element method (FEM) software. Quartz and langatate crystals are used for gyroscopes and compared. The driving frequencies and sensing frequencies of each gyroscope are obtained by optimizing the geometries of the each gyroscope using eigenfrequency analyses. Frequency response analyses were performed to simulate the gyro-characteristics of the gyroscopes which subjected to the angular velocity about z-axis. The results show that the length extension gyroscope can be used as a gyro-sensor. Moreover, we find that langatate crystals are more suitable materials for higher precision piezoelectric gyro-sensors than quartz crystal.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72608873","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138907
C. Gao, Bian-Hong Wang, X. Zhu, T. Li, L. J. Wang
Using fiber based frequency dissemination system, we are building Beijing regional time and frequency network. Currently, Tsinghua University (THU), the Changping site of National Institute of Metrology (NIM-Changping) and Beijing Institute of Radio Measurement (BIRM) have been linked and synchronized via the fiber network. The frequency signals of three hydrogen masers, two placed in NIM, one in BRIM are transferred to Tsinghua University, and compared with the local hydrogen maser. By this remote comparison, the absolute frequency stability of each clock as well as the correlations between the two clocks in NIM are measured and studied.
{"title":"Investigating the correlation between hydrogen-maser clocks in the same place","authors":"C. Gao, Bian-Hong Wang, X. Zhu, T. Li, L. J. Wang","doi":"10.1109/FCS.2015.7138907","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138907","url":null,"abstract":"Using fiber based frequency dissemination system, we are building Beijing regional time and frequency network. Currently, Tsinghua University (THU), the Changping site of National Institute of Metrology (NIM-Changping) and Beijing Institute of Radio Measurement (BIRM) have been linked and synchronized via the fiber network. The frequency signals of three hydrogen masers, two placed in NIM, one in BRIM are transferred to Tsinghua University, and compared with the local hydrogen maser. By this remote comparison, the absolute frequency stability of each clock as well as the correlations between the two clocks in NIM are measured and studied.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79258223","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138960
Kensuke Sakamoto, T. Omori, J. Kushibiki, S. Matsuda, K. Hashimoto
This paper describes evaluation of stiffnesses of SiO2 thin films when the anisotropy in elasticity is taken into account. The authors measured the propagation direction θ dependence of the water-loaded surface acoustic waves (SAW) velocity, and tried to estimate stiffnesses of SiO2 films from the measured θ dependence. The result indicates that SiO2 films possess the strong 6mm anisotropy. Namely, stiffnesses normal to the surface are significantly lager than those along the surface. This anisotropy may be induced during the deposition or caused by variation of film properties in the thickness direction.
{"title":"Evaluation of elastic properties of SiO2 thin films by ultrasonic microscopy","authors":"Kensuke Sakamoto, T. Omori, J. Kushibiki, S. Matsuda, K. Hashimoto","doi":"10.1109/FCS.2015.7138960","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138960","url":null,"abstract":"This paper describes evaluation of stiffnesses of SiO2 thin films when the anisotropy in elasticity is taken into account. The authors measured the propagation direction θ dependence of the water-loaded surface acoustic waves (SAW) velocity, and tried to estimate stiffnesses of SiO2 films from the measured θ dependence. The result indicates that SiO2 films possess the strong 6mm anisotropy. Namely, stiffnesses normal to the surface are significantly lager than those along the surface. This anisotropy may be induced during the deposition or caused by variation of film properties in the thickness direction.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73586923","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 : 2015-04-12DOI: 10.1109/FCS.2015.7138860
H. Wang, G. Iyanu
We report the results of a three-clock, cascade synchronization experiment, in which a crystal oscillator clock is slaved to a Rb atomic clock while the Rb clock is independently slaved to a Cs reference clock. The Cs clock in the experiment is calibrated against a GPS receiver. With such a cascade scheme and a real-time linear regression algorithm, we are able to precisely synchronize the digitally-tuned space clock with the Cs clock within 50 ns with an averaged residual frequency offset of 5 × 10-13. This cascade synchronization technique has also significantly reduced the two space clocks' long-term frequency drift to 1.7 × 10-14 per day and 2.5 × 10-13 per day for the Rb clock and the crystal oscillator clock, respectively.
{"title":"Precise cascade synchronization of two digitally tuned space clocks to UTC (GPS)","authors":"H. Wang, G. Iyanu","doi":"10.1109/FCS.2015.7138860","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138860","url":null,"abstract":"We report the results of a three-clock, cascade synchronization experiment, in which a crystal oscillator clock is slaved to a Rb atomic clock while the Rb clock is independently slaved to a Cs reference clock. The Cs clock in the experiment is calibrated against a GPS receiver. With such a cascade scheme and a real-time linear regression algorithm, we are able to precisely synchronize the digitally-tuned space clock with the Cs clock within 50 ns with an averaged residual frequency offset of 5 × 10-13. This cascade synchronization technique has also significantly reduced the two space clocks' long-term frequency drift to 1.7 × 10-14 per day and 2.5 × 10-13 per day for the Rb clock and the crystal oscillator clock, respectively.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85250966","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}
In this paper, the elastic, piezoelectric, and dielectric constants of Ca3TaGa3Si2O14 (CTGS) single crystals were fully characterized from room temperature to 800°C according to IEEE standard methods. The sensitivity and stability of the temperature sensors based on CTGS crystals were also investigated. One of the elastic stiffness constants-c11E shows the highest temperature sensitivity. The results of the repeated measurements of X-cut square-plate resonator sample indicate its excellent stability through the entire measurement temperature range.
{"title":"Characterization and temperature sensor application of Ca3TaGa3Si2O14 crystals","authors":"Hongfei Zu, Huiyan Wu, Qing-Ming Wang, Quan-ming Lin, Yanqing Zheng","doi":"10.1109/FCS.2015.7138897","DOIUrl":"https://doi.org/10.1109/FCS.2015.7138897","url":null,"abstract":"In this paper, the elastic, piezoelectric, and dielectric constants of Ca<sub>3</sub>TaGa<sub>3</sub>Si<sub>2</sub>O<sub>14</sub> (CTGS) single crystals were fully characterized from room temperature to 800°C according to IEEE standard methods. The sensitivity and stability of the temperature sensors based on CTGS crystals were also investigated. One of the elastic stiffness constants-c<sub>11</sub><sup>E</sup> shows the highest temperature sensitivity. The results of the repeated measurements of X-cut square-plate resonator sample indicate its excellent stability through the entire measurement temperature range.","PeriodicalId":57667,"journal":{"name":"时间频率公报","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2015-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91148569","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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