Pub Date : 2007-06-04DOI: 10.1109/WDDC.2007.4339398
D. Humphreys, M. Harper, P. Roberts
We describe a new sampling-oscilloscope based technique to measure the AM and PM components of a modulated RF signal. The method uses in-phase and quadrature referencing to simultaneously demodulate the RF signal and correct the instrument timebase nonlinearities. Preliminary results show a dynamic range of > 80 dB and agreement of better than 1% with existing methods was achieved for a 100 MHz carrier signal amplitude modulated at 20 kHz with a 50% modulation depth.
{"title":"Preliminary results for a traceable amplitude modulation measurement technique using in-phase and quadrature referencing","authors":"D. Humphreys, M. Harper, P. Roberts","doi":"10.1109/WDDC.2007.4339398","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339398","url":null,"abstract":"We describe a new sampling-oscilloscope based technique to measure the AM and PM components of a modulated RF signal. The method uses in-phase and quadrature referencing to simultaneously demodulate the RF signal and correct the instrument timebase nonlinearities. Preliminary results show a dynamic range of > 80 dB and agreement of better than 1% with existing methods was achieved for a 100 MHz carrier signal amplitude modulated at 20 kHz with a 50% modulation depth.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127815449","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339397
M. Ferrara, M. Kupferschmid, G. Coxson
Low aperiodic-autocorrelation peak sidelobe levels (PSLs) relate to enhanced range resolution for binary-phase-coded radar and communication waveforms. Typical methods to identify the minimum-attainable PSL for a given code length N require exhaustive calculations whose computational burden grows exponentially with N. In this project, exact PSL histograms were determined for computationally practical lengths. These histograms may lead to ways to estimate PSL distributions for computationally impractical lengths. Plots of the lower four moments for N between 1 and 45 showed that the moments can be approximated closely by aNk. Histograms for N = 45 were compared to a binomially-distributed PSL PDF model based on statistically independent sidelobes. The independent-sidelobe model agreed closely with truth for middle-to high-PSL values, and only varied significantly from truth for PSLs one or two units away from the lowest achievable PSL. Future work will examine ways to develop the PDF from the moments accurately enough to estimate minimum PSL for a given N, and ways to account for sidelobe dependence in the probabilistic model.
{"title":"The peak sidelobe distribution for binary codes","authors":"M. Ferrara, M. Kupferschmid, G. Coxson","doi":"10.1109/WDDC.2007.4339397","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339397","url":null,"abstract":"Low aperiodic-autocorrelation peak sidelobe levels (PSLs) relate to enhanced range resolution for binary-phase-coded radar and communication waveforms. Typical methods to identify the minimum-attainable PSL for a given code length N require exhaustive calculations whose computational burden grows exponentially with N. In this project, exact PSL histograms were determined for computationally practical lengths. These histograms may lead to ways to estimate PSL distributions for computationally impractical lengths. Plots of the lower four moments for N between 1 and 45 showed that the moments can be approximated closely by aNk. Histograms for N = 45 were compared to a binomially-distributed PSL PDF model based on statistically independent sidelobes. The independent-sidelobe model agreed closely with truth for middle-to high-PSL values, and only varied significantly from truth for PSLs one or two units away from the lowest achievable PSL. Future work will examine ways to develop the PDF from the moments accurately enough to estimate minimum PSL for a given N, and ways to account for sidelobe dependence in the probabilistic model.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130025478","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339422
M. Hussain
Ultrawideband impulse radio communication is based on the classical principles of pulse time modulation conveniently used for baseband transmission. In this paper, we present the principles of impulse waveform design, impulse time modulation for information transmission process, period-staggering modulation scheme for multiple access applications, and M-ary impulse modulation. Periodic and orthogonal non-sinusoidal impulse waveforms are generated in terms of the periodic and orthogonal sinusoidal waveforms. The conventional analog and digital modulation schemes that are based on the use of sinusoidal carrier waveforms are applied to nonsinusoidal impulse waveforms. As illustrative examples, M-ary impulse modulation schemes are described, i.e., M-ary phase shift keying (M-PSK) and M-ary frequency shift keying (M-FSK). The design of a linear FM "chirp" impulse waveform for radar applications is presented too.
{"title":"Waveform design and modulation schemes for impulse communications and radar","authors":"M. Hussain","doi":"10.1109/WDDC.2007.4339422","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339422","url":null,"abstract":"Ultrawideband impulse radio communication is based on the classical principles of pulse time modulation conveniently used for baseband transmission. In this paper, we present the principles of impulse waveform design, impulse time modulation for information transmission process, period-staggering modulation scheme for multiple access applications, and M-ary impulse modulation. Periodic and orthogonal non-sinusoidal impulse waveforms are generated in terms of the periodic and orthogonal sinusoidal waveforms. The conventional analog and digital modulation schemes that are based on the use of sinusoidal carrier waveforms are applied to nonsinusoidal impulse waveforms. As illustrative examples, M-ary impulse modulation schemes are described, i.e., M-ary phase shift keying (M-PSK) and M-ary frequency shift keying (M-FSK). The design of a linear FM \"chirp\" impulse waveform for radar applications is presented too.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"313 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122538511","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339440
D. Gray, R. Fry
The noise radar concept is extended to an array of K transmit antenna and M receive antenna. When independent noise sources are transmitted from each antenna the approach may be viewed as a special case of MIMO radar. Two transmission approaches, termed element space (ES) and beam space (BS), are considered together with both conventional and MVDR beamforming on receive.
{"title":"MIMO noise radar — element and beam space comparisons","authors":"D. Gray, R. Fry","doi":"10.1109/WDDC.2007.4339440","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339440","url":null,"abstract":"The noise radar concept is extended to an array of K transmit antenna and M receive antenna. When independent noise sources are transmitted from each antenna the approach may be viewed as a special case of MIMO radar. Two transmission approaches, termed element space (ES) and beam space (BS), are considered together with both conventional and MVDR beamforming on receive.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122431590","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339415
D. Fuhrmann
This paper considers the problem of choosing the optimal linear measurement for the estimation of a state vector X in a Bayesian context where the prior distribution for X is multivariate Gaussian. The motivation for this comes from waveform-agile active sensing systems that have the capability of choosing transmit or illumination waveforms in real time. The measurement is characterized by a measurement matrix B with an energy constraint along each row. Qualitatively, the optimal solution applies the available transmit energy to each of the eigenmodes of the prior covariance of X, such that more energy is applied to modes with higher prior variance, in an attempt to bring the posterior variances down to a small common value. The allocation of the energy along the various eigenmodes requires the solution of a straightforward waterfilling problem.
{"title":"One-step optimal measurement selection for linear gaussian estimation problems","authors":"D. Fuhrmann","doi":"10.1109/WDDC.2007.4339415","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339415","url":null,"abstract":"This paper considers the problem of choosing the optimal linear measurement for the estimation of a state vector X in a Bayesian context where the prior distribution for X is multivariate Gaussian. The motivation for this comes from waveform-agile active sensing systems that have the capability of choosing transmit or illumination waveforms in real time. The measurement is characterized by a measurement matrix B with an energy constraint along each row. Qualitatively, the optimal solution applies the available transmit energy to each of the eigenmodes of the prior covariance of X, such that more energy is applied to modes with higher prior variance, in an attempt to bring the posterior variances down to a small common value. The allocation of the energy along the various eigenmodes requires the solution of a straightforward waterfilling problem.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116753884","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339370
L. Landi, R. Adve
Distributed aperture radars represent an interesting solution for target detection in environments affected by ground clutter. Due to the large distances between array elements, both target and interfering sources are in the near field of the antenna array. As a consequence the characterization of both the target and the clutter is complicated, combining bistatic and monostatic configurations. Using orthogonal signaling the receivers can treat the incoming signals independently solving separately bistatic problems instead of the initial multistatic problem. Recent works have demonstrated the benefits of the use of frequency diversity space time adaptive processing for distributed aperture radars. This paper modifies the waveform diversity signal model, resorting to a time orthogonal signaling scheme, which does not present the coherence loss exhibited by frequency diversity.
{"title":"Time-orthogonal-waveform-space-time adaptive processing for distributed aperture radars","authors":"L. Landi, R. Adve","doi":"10.1109/WDDC.2007.4339370","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339370","url":null,"abstract":"Distributed aperture radars represent an interesting solution for target detection in environments affected by ground clutter. Due to the large distances between array elements, both target and interfering sources are in the near field of the antenna array. As a consequence the characterization of both the target and the clutter is complicated, combining bistatic and monostatic configurations. Using orthogonal signaling the receivers can treat the incoming signals independently solving separately bistatic problems instead of the initial multistatic problem. Recent works have demonstrated the benefits of the use of frequency diversity space time adaptive processing for distributed aperture radars. This paper modifies the waveform diversity signal model, resorting to a time orthogonal signaling scheme, which does not present the coherence loss exhibited by frequency diversity.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121168704","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339451
S. Gumas, B. Himed
In this paper, a new signal processing approach referred to as simultaneous range-Doppler (SRDreg) is presented. It applies fractional Fourier transforms in a manner that yields projections and slices of the cross-ambiguity function (CAF). Waveform diversity (WD) techniques often require extensive processing resources, thus precluding WD from smaller, more mobile systems, or applications with limited resources. By employing SRDreg, the feasibility of WD in these applications is greatly increased. The projection and slice processing is used to detect targets and estimate their unambiguous range and Doppler in the CAF range-Doppler space. SRDreg detects peaks of the CAF in a processor-efficient manner, thereby reducing the computational load associated with traditional approaches since computing the entire CAF is avoided. The number of required operations is reduced to O(Nlog2(N)) as opposed to O(N2log2(N)). Since SRD* processing load is insensitive to waveform modulation and coding, orthogonal waveforms can be exploited to confer temporal, spatial, and spectral diversity to a sensor system, without incurring any processing penalty. Fundamentally, SRDreg offers waveform flexibility and increased processing efficiency, which can be applied to broaden the scope of applicability of WD to sensor systems.
{"title":"Computationally efficient waveform diversity","authors":"S. Gumas, B. Himed","doi":"10.1109/WDDC.2007.4339451","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339451","url":null,"abstract":"In this paper, a new signal processing approach referred to as simultaneous range-Doppler (SRDreg) is presented. It applies fractional Fourier transforms in a manner that yields projections and slices of the cross-ambiguity function (CAF). Waveform diversity (WD) techniques often require extensive processing resources, thus precluding WD from smaller, more mobile systems, or applications with limited resources. By employing SRDreg, the feasibility of WD in these applications is greatly increased. The projection and slice processing is used to detect targets and estimate their unambiguous range and Doppler in the CAF range-Doppler space. SRDreg detects peaks of the CAF in a processor-efficient manner, thereby reducing the computational load associated with traditional approaches since computing the entire CAF is avoided. The number of required operations is reduced to O(Nlog2(N)) as opposed to O(N2log2(N)). Since SRD* processing load is insensitive to waveform modulation and coding, orthogonal waveforms can be exploited to confer temporal, spatial, and spectral diversity to a sensor system, without incurring any processing penalty. Fundamentally, SRDreg offers waveform flexibility and increased processing efficiency, which can be applied to broaden the scope of applicability of WD to sensor systems.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121734510","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339392
J. Yi, Young-Jin Byun
This paper proposes a new method to select optimal pulse repetition frequency (PRF) sets for use in tracking mode of medium PRF airborne pulsed-Doppler radar. Neural networks algorithm is used to map from engagement variables to the optimal PRF set. On-line computation during flight can be made real-time after off-line training of the neural network. The training sets for the neural network need to be generated by selecting optimal PRF set for the possible engagement scenarios from which range-Doppler clutter map is calculated to check the decodability and detectability for all PRF candidates. The PRF sets generated by the method must guarantee the maximum detectability inside the target tracking window as well as maintaining good decodability. Simulation result shows that the proposed method has much better range-Doppler detection performance compared to the previous algorithms by applying different optimal PRF set to different engagement scenarios and target positions.
{"title":"Real-time PRF selection for medium PRF airborne pulsed-doppler radars in tracking phase","authors":"J. Yi, Young-Jin Byun","doi":"10.1109/WDDC.2007.4339392","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339392","url":null,"abstract":"This paper proposes a new method to select optimal pulse repetition frequency (PRF) sets for use in tracking mode of medium PRF airborne pulsed-Doppler radar. Neural networks algorithm is used to map from engagement variables to the optimal PRF set. On-line computation during flight can be made real-time after off-line training of the neural network. The training sets for the neural network need to be generated by selecting optimal PRF set for the possible engagement scenarios from which range-Doppler clutter map is calculated to check the decodability and detectability for all PRF candidates. The PRF sets generated by the method must guarantee the maximum detectability inside the target tracking window as well as maintaining good decodability. Simulation result shows that the proposed method has much better range-Doppler detection performance compared to the previous algorithms by applying different optimal PRF set to different engagement scenarios and target positions.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116547890","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339446
S. P. Sira, A. Papandreou-Suppappola, D. Morrell, D. Cochran
The detection and tracking of small targets on the ocean surface is a challenging problem due to low signal-to-clutter ratio (SCR) that results from low grazing angles and high sea state. Recent advances in sensing technologies have enabled waveform-agile schemes that tailor the sensor waveform to match the overall sensing objective. In this paper, we propose a methodology to dynamically adapt the transmitted waveform to improve the tracking performance for scenarios characterized by heavy sea clutter. Employing the compound-Gaussian model for sea clutter, we develop an algorithm for online design of a phase-modulated waveform that improves the SCR in a range bin of interest. A particle Alter tracker uses the measurements obtained by this waveform to estimate the target state. We present a simulation study to demonstrate that our scheme leads to improved tracking performance.
{"title":"Waveform-agile tracking in heavy sea clutter","authors":"S. P. Sira, A. Papandreou-Suppappola, D. Morrell, D. Cochran","doi":"10.1109/WDDC.2007.4339446","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339446","url":null,"abstract":"The detection and tracking of small targets on the ocean surface is a challenging problem due to low signal-to-clutter ratio (SCR) that results from low grazing angles and high sea state. Recent advances in sensing technologies have enabled waveform-agile schemes that tailor the sensor waveform to match the overall sensing objective. In this paper, we propose a methodology to dynamically adapt the transmitted waveform to improve the tracking performance for scenarios characterized by heavy sea clutter. Employing the compound-Gaussian model for sea clutter, we develop an algorithm for online design of a phase-modulated waveform that improves the SCR in a range bin of interest. A particle Alter tracker uses the measurements obtained by this waveform to estimate the target state. We present a simulation study to demonstrate that our scheme leads to improved tracking performance.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127556450","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 : 2007-06-04DOI: 10.1109/WDDC.2007.4339453
S. Welstead
Frequency diversity in linear frequency modulated (LFM) waveforms can introduce unintended range shifts among receive radars in a distributed environment. This can make it difficult to predict where interference will occur in those receive radars, particularly when multipath is considered. This paper introduces the concept of interference region in range-frequency space to characterize the interference levels at a receive radar caused by waveforms transmitted from different radars in a distributed architecture. Linear frequency modulated (LFM) stretch-processed waveforms provide wide bandwidth and high range resolution while imposing only modest demands on the digital processing capabilities of a radar system. For this reason they are the waveform family of choice for many current wideband radar systems, including synthetic aperture radar (SAR) systems. However, LFM waveforms do not easily lend themselves to applications that require orthogonality, such as distributed radar architectures. The widespread use of these waveforms and the processing advantages they provide make it worthwhile to examine schemes for their use in a distributed environment. The paper uses interference region analysis to assess the effectiveness of frequency diversity, upchirp-downchirp diversity and chirp slope mismatch using LFM stretch-processed waveforms in a distributed environment.
{"title":"Characterization of diversity approaches for LFM stretch-processed waveforms","authors":"S. Welstead","doi":"10.1109/WDDC.2007.4339453","DOIUrl":"https://doi.org/10.1109/WDDC.2007.4339453","url":null,"abstract":"Frequency diversity in linear frequency modulated (LFM) waveforms can introduce unintended range shifts among receive radars in a distributed environment. This can make it difficult to predict where interference will occur in those receive radars, particularly when multipath is considered. This paper introduces the concept of interference region in range-frequency space to characterize the interference levels at a receive radar caused by waveforms transmitted from different radars in a distributed architecture. Linear frequency modulated (LFM) stretch-processed waveforms provide wide bandwidth and high range resolution while imposing only modest demands on the digital processing capabilities of a radar system. For this reason they are the waveform family of choice for many current wideband radar systems, including synthetic aperture radar (SAR) systems. However, LFM waveforms do not easily lend themselves to applications that require orthogonality, such as distributed radar architectures. The widespread use of these waveforms and the processing advantages they provide make it worthwhile to examine schemes for their use in a distributed environment. The paper uses interference region analysis to assess the effectiveness of frequency diversity, upchirp-downchirp diversity and chirp slope mismatch using LFM stretch-processed waveforms in a distributed environment.","PeriodicalId":142822,"journal":{"name":"2007 International Waveform Diversity and Design Conference","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125986587","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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