A GPR survey at Muweilah in the United Arab Emirates capably identified archaeological features such as walls and floors to a depth of several metres. Surveying conditions were favourable with sand cover allowing good radar penetration and strong reflections from targets. A feature of this work is that three-dimensional migrations of two dense data sets provided plan view slices at 10 cm intervals, in a manner which mirrors the excavation methodology employed by archaeologists. Presented also are problems and limitations encountered throughout the survey and subsequent data processing. It is conjectured that data quality is significantly improved when the area is flattened and de-vegetated prior to surveying. Although much of the interpretation is subject to ground-truthing, the preliminary analysis is extremely encouraging. It is observed however, that interpretation is complex and ambiguous if undertaken in isolation. Reliance on a conceptual archaeological model, a combination of other geophysical approaches, and ongoing ground-truthing are thus strongly recommended.
{"title":"3D imaging of an Iron Age archaeological site: GPR analysis at Muweilah, United Arab Emirates (UAE)","authors":"R. Evangelista, P. Magee, E. Wedepohl","doi":"10.1117/12.462203","DOIUrl":"https://doi.org/10.1117/12.462203","url":null,"abstract":"A GPR survey at Muweilah in the United Arab Emirates capably identified archaeological features such as walls and floors to a depth of several metres. Surveying conditions were favourable with sand cover allowing good radar penetration and strong reflections from targets. A feature of this work is that three-dimensional migrations of two dense data sets provided plan view slices at 10 cm intervals, in a manner which mirrors the excavation methodology employed by archaeologists. Presented also are problems and limitations encountered throughout the survey and subsequent data processing. It is conjectured that data quality is significantly improved when the area is flattened and de-vegetated prior to surveying. Although much of the interpretation is subject to ground-truthing, the preliminary analysis is extremely encouraging. It is observed however, that interpretation is complex and ambiguous if undertaken in isolation. Reliance on a conceptual archaeological model, a combination of other geophysical approaches, and ongoing ground-truthing are thus strongly recommended.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130773113","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}
Ground penetrating radar (GPR) has been widely used for the detection and location of buried objects. However, the detection method is often subjected to operator's interpretation due to large quantities of data and undesired clutter and noise. Such a detection method is neither reliable nor efficient.
{"title":"Automatic GPR target detection and clutter reduction using neural network","authors":"H. Youn, Chi-Chih Chen","doi":"10.1117/12.462229","DOIUrl":"https://doi.org/10.1117/12.462229","url":null,"abstract":"Ground penetrating radar (GPR) has been widely used for the detection and location of buried objects. However, the detection method is often subjected to operator's interpretation due to large quantities of data and undesired clutter and noise. Such a detection method is neither reliable nor efficient.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127478568","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}
Railway is nowadays considered as the most ecological and economical alternative to cars and planes; on the other hand, in order to be really competitive, trains have to go faster and faster on safe tracks that allows an high velocity. From this point of view, speedy track construction is just as important as periodic maintenance and methods of the past (such as coring and visual inspection) are not longer able to provide helpful information especially because too slow and, often, too expensive. Therefore, the use of a Ground Penetrating Radar can be thought as a suitable and economical alternative to the other survey methods. In this paper is presented a GPR equipment especially designed for inspecting and verifying railroad tracks in a reliable and effective way, without interruption of regular traffic.
{"title":"Customized GPR system for railroad track verification","authors":"G. Manacorda, D. Morandi, A. Sarri, G. Staccone","doi":"10.1117/12.462265","DOIUrl":"https://doi.org/10.1117/12.462265","url":null,"abstract":"Railway is nowadays considered as the most ecological and economical alternative to cars and planes; on the other hand, in order to be really competitive, trains have to go faster and faster on safe tracks that allows an high velocity. From this point of view, speedy track construction is just as important as periodic maintenance and methods of the past (such as coring and visual inspection) are not longer able to provide helpful information especially because too slow and, often, too expensive. Therefore, the use of a Ground Penetrating Radar can be thought as a suitable and economical alternative to the other survey methods. In this paper is presented a GPR equipment especially designed for inspecting and verifying railroad tracks in a reliable and effective way, without interruption of regular traffic.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115856055","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}
Subsurface imaging techniques have been discussed with MUSIC algorithm to locate point reflectors. Generally, a radar signal received by a spatial array must be decorrelate as pre-processing for the MUSIC algorithm. Since most of decorrelation techniques are based on a plane wave incidence model, it is difficult to apply the decorrelation technique for the radar targets around the near field of the array. In this report, we introduce a new decorrelation technique with transmitting and receiving array for targets near the array and apply the MUSIC algorithm for estimation of the 2D position of the point targets in crosshole tomographic measurement. Simulation results show that this method has much higher resolution and accuracy than the conventional diffraction stack method. Moreover, we discuss the relationship between the S/N ratio and the geometrical separation.
{"title":"Application of music algorithm for imaging point reflectors near transmitting and receiving array","authors":"T. Miwa, I. Arai","doi":"10.1117/12.462235","DOIUrl":"https://doi.org/10.1117/12.462235","url":null,"abstract":"Subsurface imaging techniques have been discussed with MUSIC algorithm to locate point reflectors. Generally, a radar signal received by a spatial array must be decorrelate as pre-processing for the MUSIC algorithm. Since most of decorrelation techniques are based on a plane wave incidence model, it is difficult to apply the decorrelation technique for the radar targets around the near field of the array. In this report, we introduce a new decorrelation technique with transmitting and receiving array for targets near the array and apply the MUSIC algorithm for estimation of the 2D position of the point targets in crosshole tomographic measurement. Simulation results show that this method has much higher resolution and accuracy than the conventional diffraction stack method. Moreover, we discuss the relationship between the S/N ratio and the geometrical separation.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121798009","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}
The clutter caused by scattering from a rough air-ground interface is analyzed numerically. The simulations have been done using Monte-Carlo approach. An ensemble of surface profiles with the desired probability distribution and autocorrelation spectrum is simulated numerically. For each realization of the interface profile the scattered field has been calculated by a deterministic approach. Averaging of the scattered filed over ensemble of the surface realizations has been done numerically. Statistical properties of the scattered field have been analyzed. It has been found that the magnitude of the surface clutter caused by reasonably smooth surfaces can exceed easily the mean value of the ground reflection. Furthermore it is demonstrated that if the magnitude of the surface clutter is considerably less than the mean value of the ground reflection then the correlation function of the reflected field coincides with the correlation function of the rough surface.
{"title":"Numerical analysis of surface clutter in GPR scenarios","authors":"A. Yarovoy","doi":"10.1117/12.462286","DOIUrl":"https://doi.org/10.1117/12.462286","url":null,"abstract":"The clutter caused by scattering from a rough air-ground interface is analyzed numerically. The simulations have been done using Monte-Carlo approach. An ensemble of surface profiles with the desired probability distribution and autocorrelation spectrum is simulated numerically. For each realization of the interface profile the scattered field has been calculated by a deterministic approach. Averaging of the scattered filed over ensemble of the surface realizations has been done numerically. Statistical properties of the scattered field have been analyzed. It has been found that the magnitude of the surface clutter caused by reasonably smooth surfaces can exceed easily the mean value of the ground reflection. Furthermore it is demonstrated that if the magnitude of the surface clutter is considerably less than the mean value of the ground reflection then the correlation function of the reflected field coincides with the correlation function of the rough surface.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"45 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122151093","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}
S. Kuroda, H. Nakazato, S. Nihira, M. Hatakeyama, M. Takeuchi, Masato Asano, Y. Todoroki, Michiaki Konno
Continuous monitoring by time-lapse and repetitive measurements using cross-hole geo-radar was conducted to investigate soil moisture distribution and migration beneath infiltration pit for artificial groundwater recharge. This monitoring enabled us to clarify the infiltration process from the infiltration pit into the vadose zone in a quantitative, nondestructive, and noninvasive way. The infiltration pit was 2.0 x 2.0 m square and 2.3 m deep between 2 boreholes in gravel soil. The groundwater table was at about —10 m. We monitored the veitical distribution of electromagnetic wave traveltime beneath the infiltration pit by repetitive measurements using cross-hole geo-radar profiling with zero-offset gathering. Traveltime was distinctly retarded from the upper layer to the deeper one after ponding of the pit. The downward retardation velocity of the infiltration rate into the soil was estimated at8 x 10-2cm/s. The estimated values for water content and water seepage rate in the soil were almost coincident with the directly measured values. In our case of an infiltration pit test, cross-hole geo-radar monitoring was an efficient, noninvasive method for visualizing the infiltration process and estimating water migration properties of the soil on a macro scale.
{"title":"Cross-hole georadar monitoring for moisture distribution and migration in soil beneath an infiltration pit: a case study of an artificial groundwater recharge test in Niigata, Japan","authors":"S. Kuroda, H. Nakazato, S. Nihira, M. Hatakeyama, M. Takeuchi, Masato Asano, Y. Todoroki, Michiaki Konno","doi":"10.1117/12.462258","DOIUrl":"https://doi.org/10.1117/12.462258","url":null,"abstract":"Continuous monitoring by time-lapse and repetitive measurements using cross-hole geo-radar was conducted to investigate soil moisture distribution and migration beneath infiltration pit for artificial groundwater recharge. This monitoring enabled us to clarify the infiltration process from the infiltration pit into the vadose zone in a quantitative, nondestructive, and noninvasive way. The infiltration pit was 2.0 x 2.0 m square and 2.3 m deep between 2 boreholes in gravel soil. The groundwater table was at about —10 m. We monitored the veitical distribution of electromagnetic wave traveltime beneath the infiltration pit by repetitive measurements using cross-hole geo-radar profiling with zero-offset gathering. Traveltime was distinctly retarded from the upper layer to the deeper one after ponding of the pit. The downward retardation velocity of the infiltration rate into the soil was estimated at8 x 10-2cm/s. The estimated values for water content and water seepage rate in the soil were almost coincident with the directly measured values. In our case of an infiltration pit test, cross-hole geo-radar monitoring was an efficient, noninvasive method for visualizing the infiltration process and estimating water migration properties of the soil on a macro scale.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116784430","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 we present the electric field integral equation (EFIE) method for the analysis of transient metallic antennas above a lossy half-space. This formulation is suitable for the analysis of a wide class of metallic GPR antennas that does not contain any dielectric material. Ground influence is properly taken into account by the Green's function for layered media. The EFIE is solved numerically by the method of moments using the well-known Rao-Wilton-Glisson basis function. For GPR antennas, the free-space Green's function is replaced by the dyadic Green's function for layered media. The time-domain solution for transient antennas is obtained using Fourier transform method and a time-window technique. By using time window to remove reflections from antenna open ends, the solution for transient antennas is obtained. To speed up computations, several approaches are used, which include the exploitation of antenna symmetry, a special treatment for integration over singularity, and an interpolation method to expedite the evaluation of Sommerfeld integrals. We have found that those approaches allow rapid and accurate computations for obtaining the time-domain solution. Good agreement between the computation and measurement of the input impedance of a wire dipole and a wire bow-tie antenna is obtained.
{"title":"Electric-field integral equation model for transient GPR antennas","authors":"A. A. Lestari, A. Yarovoy, L. Ligthart","doi":"10.1117/12.462192","DOIUrl":"https://doi.org/10.1117/12.462192","url":null,"abstract":"In this paper we present the electric field integral equation (EFIE) method for the analysis of transient metallic antennas above a lossy half-space. This formulation is suitable for the analysis of a wide class of metallic GPR antennas that does not contain any dielectric material. Ground influence is properly taken into account by the Green's function for layered media. The EFIE is solved numerically by the method of moments using the well-known Rao-Wilton-Glisson basis function. For GPR antennas, the free-space Green's function is replaced by the dyadic Green's function for layered media. The time-domain solution for transient antennas is obtained using Fourier transform method and a time-window technique. By using time window to remove reflections from antenna open ends, the solution for transient antennas is obtained. To speed up computations, several approaches are used, which include the exploitation of antenna symmetry, a special treatment for integration over singularity, and an interpolation method to expedite the evaluation of Sommerfeld integrals. We have found that those approaches allow rapid and accurate computations for obtaining the time-domain solution. Good agreement between the computation and measurement of the input impedance of a wire dipole and a wire bow-tie antenna is obtained.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116917449","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}
GPR is considered ineffectual in penetrating silty soils. Capillary tension appears to move the interstitial water dielectric relaxation frequency near the GPR range. If hydrocarbons relieve the tension, then GPR attenuation rates should decrease. We profiled these rates across a partly contaminated quartz silt diamicton at an inactive fuel terminal in Haines, Alaska. We calculated the rates from the signal amplitude decay within a series of 400-MHz moveout surveys recorded along a single transect. We sampled the hydrocarbon content along the transect and on the wall of a trench we excavated beside it, along with water content, density and resistivity. The silt was saturated and generally at 50-80 ohm-m. The ground impedance loading brought the antenna pulse center frequency down to near 200 MHz. The rates ranged from 5 to 8 dB/m in the contaminated zone and about 10 to 15 dB/m in the uncontaminated zone. The resistivities account for the contamination rates, but a dielectric relaxation centered near 1-2 GHz, using a simple mixing model, is required to account for those in the uncontaminated zone. Hydrocarbon soil analysis suggests that the threshold level for the attenuation effect is not higher than about 1000 ppm. We suggest GPR offset surveys for assessing contamination zones.
{"title":"Field study of GPR attenuation rates in natural and contaminated silt","authors":"S. Arcone, A. Delaney","doi":"10.1117/12.462306","DOIUrl":"https://doi.org/10.1117/12.462306","url":null,"abstract":"GPR is considered ineffectual in penetrating silty soils. Capillary tension appears to move the interstitial water dielectric relaxation frequency near the GPR range. If hydrocarbons relieve the tension, then GPR attenuation rates should decrease. We profiled these rates across a partly contaminated quartz silt diamicton at an inactive fuel terminal in Haines, Alaska. We calculated the rates from the signal amplitude decay within a series of 400-MHz moveout surveys recorded along a single transect. We sampled the hydrocarbon content along the transect and on the wall of a trench we excavated beside it, along with water content, density and resistivity. The silt was saturated and generally at 50-80 ohm-m. The ground impedance loading brought the antenna pulse center frequency down to near 200 MHz. The rates ranged from 5 to 8 dB/m in the contaminated zone and about 10 to 15 dB/m in the uncontaminated zone. The resistivities account for the contamination rates, but a dielectric relaxation centered near 1-2 GHz, using a simple mixing model, is required to account for those in the uncontaminated zone. Hydrocarbon soil analysis suggests that the threshold level for the attenuation effect is not higher than about 1000 ppm. We suggest GPR offset surveys for assessing contamination zones.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114935743","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 heterogeneous sub-surface environments, the evaluation of GPR sections is complicated by the influence of near-field effects, antenna radiation patterns, velocity variations and surveying inconsistencies. Section interpretation can be exceedingly difficult, even with advanced processing methods, and therefore mathematical modelling has become an increasingly popular addition to traditional techniques. The Finite-Difference Time-Domain method (FDTD) is the most common, but to be of practical use the modelling scheme must incorporate realistic antenna configurations, complex sub-surface geometries and accurate material property descriptions. These additional components add computational complexity to the models and, at present, most single processor FDTD schemes are only capable of modelling relatively basic three-dimensional data sets in practical time scales. Modern parallel computing techniques have the potential to overcome these limitations by spreading the computational demand across a number of processors (or individual PC's). These PC 'cluster' machines provide the necessary computational power required to model more complex GPR problems in realistic time-scales. Consequently, the scope and run-time of current GPR FDTD modelling applications can be improved making them an accessible and affordable aid to GPR interpretation.
{"title":"Mathematical modeling of ground-penetrating radar: parallel computing applications","authors":"N. Cassidy, G. Tuckwell","doi":"10.1117/12.462292","DOIUrl":"https://doi.org/10.1117/12.462292","url":null,"abstract":"In heterogeneous sub-surface environments, the evaluation of GPR sections is complicated by the influence of near-field effects, antenna radiation patterns, velocity variations and surveying inconsistencies. Section interpretation can be exceedingly difficult, even with advanced processing methods, and therefore mathematical modelling has become an increasingly popular addition to traditional techniques. The Finite-Difference Time-Domain method (FDTD) is the most common, but to be of practical use the modelling scheme must incorporate realistic antenna configurations, complex sub-surface geometries and accurate material property descriptions. These additional components add computational complexity to the models and, at present, most single processor FDTD schemes are only capable of modelling relatively basic three-dimensional data sets in practical time scales. Modern parallel computing techniques have the potential to overcome these limitations by spreading the computational demand across a number of processors (or individual PC's). These PC 'cluster' machines provide the necessary computational power required to model more complex GPR problems in realistic time-scales. Consequently, the scope and run-time of current GPR FDTD modelling applications can be improved making them an accessible and affordable aid to GPR interpretation.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122665817","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}
GPR applications to historical buildings have been cautiously increasing in recent years. The investigation of the wooden structural elements in historical buildings is essential to plan the restoration works. We discuss three case histories where 2D and 3D GPR surveys were executed to solve problems posed by restorers. The first survey was carried out to locate the beams of a wooden floor in a two hundred years old house in Pescate (Italy). The second survey was carried out in a stone masonry house of the 19th century in Lecco (Italy) to investigate the beam-wall connection. The third survey was carried out in a five hundred years old church in Busto Arsizio (Italy) to detect all the wooden elements. In this case some beams were totally hidden inside the brick and stone walls.
{"title":"GPR investigations to reconstruct the geometry of the wooden structures in historical buildings","authors":"M. Lualdi, L. Zanzi","doi":"10.1117/12.462260","DOIUrl":"https://doi.org/10.1117/12.462260","url":null,"abstract":"GPR applications to historical buildings have been cautiously increasing in recent years. The investigation of the wooden structural elements in historical buildings is essential to plan the restoration works. We discuss three case histories where 2D and 3D GPR surveys were executed to solve problems posed by restorers. The first survey was carried out to locate the beams of a wooden floor in a two hundred years old house in Pescate (Italy). The second survey was carried out in a stone masonry house of the 19th century in Lecco (Italy) to investigate the beam-wall connection. The third survey was carried out in a five hundred years old church in Busto Arsizio (Italy) to detect all the wooden elements. In this case some beams were totally hidden inside the brick and stone walls.","PeriodicalId":256772,"journal":{"name":"International Conference on Ground Penetrating Radar","volume":"169 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2002-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124902573","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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