Pub Date : 2018-03-14DOI: 10.3997/2352-8265.20140224
Satoshi Fuse, H. Mikada, J. Takekawa
Recently, seismic processing techniques accommodate seismic anisotropy in the wave propagation phenomena for better imaging of subsurface structure and for more precise estimation of subsurface material parameters. After 30 years of research on seismic anisotropy, it has become well known that subsurface materials are more anisotropic than the foreseen. For example, shale rocks are anisotropic in the order around 30%, for which it is necessary to take the anisotropy into account for planning hydraulic fracturing. It is, however, difficult to estimate directly all of 21 independent parameters in the general elastic medium in the 3D Cartesian coordinate system, and a method to deal with seismic anisotropy for complex anisotropic materials has been waited for. In this research, we set model parameters as orientation and dip as well as 5 independent parameters instead of estimating 21 parameters directly under a hypothesis that the stable solution could be obtained. We attempt to estimate these parameters by full waveform strategy because azimuthal anisotropy influences the waveform. Low computational costs by efficient parameterization technique make it possible to work on 3D sonic logging model. Since one of the crucial problems of FWI is the predicted model would be possible to converge to local minimum as the number of parameters increases, the small number of unknowns in the proposed strategy could play a key role to deal with complex anisotropy. As a result, all elements come close to true values by full waveform inversion process. Our results suggest that the proposed parameterization strategy and FWI have an advantage over the conventional methods in terms of accuracy and stability.
{"title":"Estimation of seismic anisotropy with azimuth from sonic data by full waveform inversion","authors":"Satoshi Fuse, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140224","DOIUrl":"https://doi.org/10.3997/2352-8265.20140224","url":null,"abstract":"Recently, seismic processing techniques accommodate seismic anisotropy in the wave propagation phenomena for better imaging of subsurface structure and for more precise estimation of subsurface material parameters. After 30 years of research on seismic anisotropy, it has become well known that subsurface materials are more anisotropic than the foreseen. For example, shale rocks are anisotropic in the order around 30%, for which it is necessary to take the anisotropy into account for planning hydraulic fracturing. It is, however, difficult to estimate directly all of 21 independent parameters in the general elastic medium in the 3D Cartesian coordinate system, and a method to deal with seismic anisotropy for complex anisotropic materials has been waited for. In this research, we set model parameters as orientation and dip as well as 5 independent parameters instead of estimating 21 parameters directly under a hypothesis that the stable solution could be obtained. We attempt to estimate these parameters by full waveform strategy because azimuthal anisotropy influences the waveform. Low computational costs by efficient parameterization technique make it possible to work on 3D sonic logging model. Since one of the crucial problems of FWI is the predicted model would be possible to converge to local minimum as the number of parameters increases, the small number of unknowns in the proposed strategy could play a key role to deal with complex anisotropy. As a result, all elements come close to true values by full waveform inversion process. Our results suggest that the proposed parameterization strategy and FWI have an advantage over the conventional methods in terms of accuracy and stability.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85417883","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 : 2018-03-14DOI: 10.3997/2352-8265.20140225
M. Iwata, H. Mikada, J. Takekawa
Scale precipitation seriously damages all equipment in oil, gas and geothermal power plants. There have been lots of predictive analyses on scale growth from chemical perspectives based on reaction kinetics. However, the formation process of scale is very complex and there are some phenomena which cannot be explained by simple chemical considerations. One of them is the local scale deposition at the joint of piping structure, and its visualization was attempted by the lattice Boltzmann method (LBM) for a microscopic analysis on silica particle motion in a flow of geothermal fluid based on fluid dynamics. The Brownian motion and re-entrainment of fine particles have, however, not been taken into account in the dynamics and there remained the instability in the calculation at the early stage of scale growth in the overall macroscopic analysis. Although the previous work was a novel approach, it is clear that the completeness in the dynamics to silica particles has to be considered in the physical analysis of scaling phenomena. We therefore have introduced more elaborative calculation over the spatial scale from micrometers to millimeters with the Brownian random motion to dynamically describe the behavior of silica particles under the distribution in the sizes in fluid for both the adhesion to and the exfoliation from the wall surface. In study, result of new elaborative calculation to show how the Brownian motion influences the kinematic behavior of silica particles that lead us to a new expression of the scale deposition rate as a function of flow velocity. Next, as in the previous study, visualize a time sequence of the scale shape in a pipe with the macroscopic analysis using LBM coupled with the microscopic calculation. At this in order to increase the stability of the crystal growth, introduced a calculation that automatically complements the due to random scale
{"title":"Reproduction of complicated scale form in pipe systems from hydrodynamic perspectives","authors":"M. Iwata, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140225","DOIUrl":"https://doi.org/10.3997/2352-8265.20140225","url":null,"abstract":"Scale precipitation seriously damages all equipment in oil, gas and geothermal power plants. There have been lots of predictive analyses on scale growth from chemical perspectives based on reaction kinetics. However, the formation process of scale is very complex and there are some phenomena which cannot be explained by simple chemical considerations. One of them is the local scale deposition at the joint of piping structure, and its visualization was attempted by the lattice Boltzmann method (LBM) for a microscopic analysis on silica particle motion in a flow of geothermal fluid based on fluid dynamics. The Brownian motion and re-entrainment of fine particles have, however, not been taken into account in the dynamics and there remained the instability in the calculation at the early stage of scale growth in the overall macroscopic analysis. Although the previous work was a novel approach, it is clear that the completeness in the dynamics to silica particles has to be considered in the physical analysis of scaling phenomena. We therefore have introduced more elaborative calculation over the spatial scale from micrometers to millimeters with the Brownian random motion to dynamically describe the behavior of silica particles under the distribution in the sizes in fluid for both the adhesion to and the exfoliation from the wall surface. In study, result of new elaborative calculation to show how the Brownian motion influences the kinematic behavior of silica particles that lead us to a new expression of the scale deposition rate as a function of flow velocity. Next, as in the previous study, visualize a time sequence of the scale shape in a pipe with the macroscopic analysis using LBM coupled with the microscopic calculation. At this in order to increase the stability of the crystal growth, introduced a calculation that automatically complements the due to random scale","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87738471","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 : 2018-03-14DOI: 10.1130/ABS/2018AM-322722
Anooja Thomas, K. Purkayastha, B. Yadav
Hydraulic redistribution (HR) refers to the mechanism by which passive movement of water takes place from wetter soil layers to drier root-zone via plant roots, driven by the moisture gradient. Likewise, Soil moisture stress that occurs in one part of the root zone can be compensated for by enhanced extraction from the other wetter parts through root compensation mechanism (RCM) under varying soil moisture conditions. A numerical model is developed in this study to understand the effect of these root water uptake mechanisms in multi-layered soil profile through coupled soil-water-root zone system. The governing equations of water flow in soil and root biomass are solved numerically using implicit finite difference method coupled with an iterative technique. Modeling of HR requires a sink/source term that allows flow of water in both directions, i.e. from soil to root and vice versa. For this a realistic non-linear function of root density distribution is incorporated in the soil moisture flow equation for simulating the rate of water removal with and without considering the HR and RCM mechanisms. The model was first tested for a barren layered soil profile before applying it to a rain-fed wheat (Triticum aestivum) plot using a dynamic root growth model. Model predicted soil-moisture parameters, i.e. moisture depletion, moisture profile at different depths, and the water uptake rate by plants. The model results indicate that in favourable soil moisture conditions, the water uptake is higher in the region close to ground surface as compared to the mid or lower region of the root zone. However after meeting the transpiration demand during the day time, moisture stress is developed in the upper soil profile which is compensated by water uptake from the lower wet layers due to HR mechanism during the night time. Results also show that under favorable soil moisture conditions, plants extract water at the maximum rate according to the root distribution pattern and when the moisture stress is developed in a part of root zone, the diminished water uptake rate in the water scarce region is compensated for by an enhanced water uptake from the surrounding wetter zones. An underestimation of root water uptake in wet soil zone and slight overestimation in dry soil part has been observed during dry days when the RCM is not considered. This shows that the optimal availability of water in some part of root zone and little moisture stress in top soil layers can significantly reduce the amount of evaporation without significantly affecting the water uptake by plants and, therefore, the plant growth. Thus, the developed hydraulic redistribution model can be used for planning better irrigation scheduling and practices particularly in the water scarce arid and semi-arid regions having deep vadose zone. The model can also be integrated with a transport equation to predict the solute uptake by plants and for accurate quantification of solute load to underlying groundwat
{"title":"Soil Moisture Modeling using Hydraulic Redistribution and Root Compensation Mechanisms of Plants in Stratified Vadose Zone","authors":"Anooja Thomas, K. Purkayastha, B. Yadav","doi":"10.1130/ABS/2018AM-322722","DOIUrl":"https://doi.org/10.1130/ABS/2018AM-322722","url":null,"abstract":"Hydraulic redistribution (HR) refers to the mechanism by which passive movement of water takes place from wetter soil layers to drier root-zone via plant roots, driven by the moisture gradient. Likewise, Soil moisture stress that occurs in one part of the root zone can be compensated for by enhanced extraction from the other wetter parts through root compensation mechanism (RCM) under varying soil moisture conditions. A numerical model is developed in this study to understand the effect of these root water uptake mechanisms in multi-layered soil profile through coupled soil-water-root zone system. The governing equations of water flow in soil and root biomass are solved numerically using implicit finite difference method coupled with an iterative technique. Modeling of HR requires a sink/source term that allows flow of water in both directions, i.e. from soil to root and vice versa. For this a realistic non-linear function of root density distribution is incorporated in the soil moisture flow equation for simulating the rate of water removal with and without considering the HR and RCM mechanisms. The model was first tested for a barren layered soil profile before applying it to a rain-fed wheat (Triticum aestivum) plot using a dynamic root growth model. Model predicted soil-moisture parameters, i.e. moisture depletion, moisture profile at different depths, and the water uptake rate by plants. The model results indicate that in favourable soil moisture conditions, the water uptake is higher in the region close to ground surface as compared to the mid or lower region of the root zone. However after meeting the transpiration demand during the day time, moisture stress is developed in the upper soil profile which is compensated by water uptake from the lower wet layers due to HR mechanism during the night time. Results also show that under favorable soil moisture conditions, plants extract water at the maximum rate according to the root distribution pattern and when the moisture stress is developed in a part of root zone, the diminished water uptake rate in the water scarce region is compensated for by an enhanced water uptake from the surrounding wetter zones. An underestimation of root water uptake in wet soil zone and slight overestimation in dry soil part has been observed during dry days when the RCM is not considered. This shows that the optimal availability of water in some part of root zone and little moisture stress in top soil layers can significantly reduce the amount of evaporation without significantly affecting the water uptake by plants and, therefore, the plant growth. Thus, the developed hydraulic redistribution model can be used for planning better irrigation scheduling and practices particularly in the water scarce arid and semi-arid regions having deep vadose zone. The model can also be integrated with a transport equation to predict the solute uptake by plants and for accurate quantification of solute load to underlying groundwat","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"95 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79263853","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 : 2018-03-14DOI: 10.3997/2352-8265.20140231
J. Takekawa, H. Mikada
We developed a novel method for simulating brittle failure of rock based on the combination of the moving particle semi-implicit (MPS) and the discrete element methods (DEM). The MPS method is a kind of particle methods, and can simulate behavior of continuous bodies without going through a calibration process. On the other hand, DEM is used to calculate collision of fragments after macroscopic failure. This strategy can simulate deformation behavior of rock in not only pre-failure but also post-failure behavior in a seamless manner. We evaluate the effectiveness of the proposed method using a numerical experiment. Our experiment consists of a brittle sphere and a steel plate. The sphere collides with the plate with a certain speed. The failure criterion is only applied to particles constitute the brittle sphere. We compare the failure pattern of the brittle sphere with that of a laboratory experiment. Our result shows excellent agreement with the laboratory result. This indicates that the proposed method could be an alternative to the conventional numerical methods for simulating discontinuous behavior of brittle materials.
{"title":"Numerical simulation of brittle failure of rock using MPS method and DEM","authors":"J. Takekawa, H. Mikada","doi":"10.3997/2352-8265.20140231","DOIUrl":"https://doi.org/10.3997/2352-8265.20140231","url":null,"abstract":"We developed a novel method for simulating brittle failure of rock based on the combination of the moving particle semi-implicit (MPS) and the discrete element methods (DEM). The MPS method is a kind of particle methods, and can simulate behavior of continuous bodies without going through a calibration process. On the other hand, DEM is used to calculate collision of fragments after macroscopic failure. This strategy can simulate deformation behavior of rock in not only pre-failure but also post-failure behavior in a seamless manner. We evaluate the effectiveness of the proposed method using a numerical experiment. Our experiment consists of a brittle sphere and a steel plate. The sphere collides with the plate with a certain speed. The failure criterion is only applied to particles constitute the brittle sphere. We compare the failure pattern of the brittle sphere with that of a laboratory experiment. Our result shows excellent agreement with the laboratory result. This indicates that the proposed method could be an alternative to the conventional numerical methods for simulating discontinuous behavior of brittle materials.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"2009 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83355875","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}
{"title":"Estimation of thermal resistance of soil around underground power transmission line using geophysical surveys","authors":"Koichi Suzuki","doi":"10.3124/segj.71.1","DOIUrl":"https://doi.org/10.3124/segj.71.1","url":null,"abstract":"","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74982125","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 : 2018-03-14DOI: 10.5194/EGUSPHERE-EGU21-1448
O. Girina, D. Melnikov, A. Manevich, A. Nuzhdaev, E. Petrova
Strong explosive eruptions of volcanoes are the most dangerous for aircraft because they can produce in a few hours or days to the atmosphere and the stratosphere till several cubic kilometers of volcanic ash and aerosols. Ash plumes and the clouds, depending on the power of the eruption, the strength and wind speed, can travel thousands of kilometers from the volcano for several days, remaining hazardous to aircraft, as the melting temperature of small particles of ash below the operating temperature of jet engines.
{"title":"The 2020 Activity of Kamchatkan Volcanoes and Danger to Aviation","authors":"O. Girina, D. Melnikov, A. Manevich, A. Nuzhdaev, E. Petrova","doi":"10.5194/EGUSPHERE-EGU21-1448","DOIUrl":"https://doi.org/10.5194/EGUSPHERE-EGU21-1448","url":null,"abstract":"Strong explosive eruptions of volcanoes are the most dangerous for aircraft because they can produce in a few hours or days to the atmosphere and the stratosphere till several cubic kilometers of volcanic ash and aerosols. Ash plumes and the clouds, depending on the power of the eruption, the strength and wind speed, can travel thousands of kilometers from the volcano for several days, remaining hazardous to aircraft, as the melting temperature of small particles of ash below the operating temperature of jet engines.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81092478","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}
As East African countries face increasing destruction of natural forests and diminishing stocks of forest plantations, and as poverty alleviation continues to be a major development goal, academic and practical attention is being paid to farm forestry undertaken by smallholders growing softwood. However, there are few detailed examinations of the softwood timber value chain in these countries. The present study discusses signs of premature harvesting in the farm forestry in the Mount Meru area of northern Tanzania, and examines the economic significance of timber sawing and marketing for softwood farmers from the perspective of rural timber traders on whom timber yard retailers in urban and trading centers rely greatly for access to information on rural timber availability. As reflected in rural timber traders’ transaction strategies, premature harvesting was found usually to be a result of poverty, or less frequently as a way of maximizing income for farmers with access to sufficient land for woodlots; thus, the sale of premature trees is not necessarily disadvantageous to farmers. However, it was also found that the sale of small-diameter trees negatively affects the farmers’ share of sales proceeds from mature trees, especially if these mature trees are sold in small quantity and are put together with small-diameter trees in a tree set for a single transaction. Moreover, farmers do not organize themselves into producer organizations under the current individualized production and processing. Although smallholder forestry certainly generates income from outside rural areas in the rapidly urbanizing regional economy, careful investigations are needed as to how the sales proceeds are distributed among the different rural participants in these transactions.
{"title":"Economic significance of premature harvesting for farm forestry smallholders in the Mount Meru area, Tanzania","authors":"Gen Ueda","doi":"10.14989/230162","DOIUrl":"https://doi.org/10.14989/230162","url":null,"abstract":"As East African countries face increasing destruction of natural forests and diminishing stocks of forest plantations, and as poverty alleviation continues to be a major development goal, academic and practical attention is being paid to farm forestry undertaken by smallholders growing softwood. However, there are few detailed examinations of the softwood timber value chain in these countries. The present study discusses signs of premature harvesting in the farm forestry in the Mount Meru area of northern Tanzania, and examines the economic significance of timber sawing and marketing for softwood farmers from the perspective of rural timber traders on whom timber yard retailers in urban and trading centers rely greatly for access to information on rural timber availability. As reflected in rural timber traders’ transaction strategies, premature harvesting was found usually to be a result of poverty, or less frequently as a way of maximizing income for farmers with access to sufficient land for woodlots; thus, the sale of premature trees is not necessarily disadvantageous to farmers. However, it was also found that the sale of small-diameter trees negatively affects the farmers’ share of sales proceeds from mature trees, especially if these mature trees are sold in small quantity and are put together with small-diameter trees in a tree set for a single transaction. Moreover, farmers do not organize themselves into producer organizations under the current individualized production and processing. Although smallholder forestry certainly generates income from outside rural areas in the rapidly urbanizing regional economy, careful investigations are needed as to how the sales proceeds are distributed among the different rural participants in these transactions.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"76 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79638337","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 : 2018-01-01DOI: 10.1007/978-3-319-77359-9_11
M. Ohori
{"title":"Estimation of Empirical Green’s Tensor Spatial Derivative Elements: A Preliminary Study Using Strong Motion Records in Southern Fukui Prefecture, Japan","authors":"M. Ohori","doi":"10.1007/978-3-319-77359-9_11","DOIUrl":"https://doi.org/10.1007/978-3-319-77359-9_11","url":null,"abstract":"","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"1 1","pages":"253-262"},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88208254","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}
Y. Imanishi, Kazunari Nawa, Y. Tamura, H. Ikeda, R. Honda, T. Okuda, M. Okubo
{"title":"Combined Use of a Superconducting Gravimeter and Scintrex Gravimeters for Hydrological Correction of Precise Gravity Measurements: A Superhybrid Gravimetry","authors":"Y. Imanishi, Kazunari Nawa, Y. Tamura, H. Ikeda, R. Honda, T. Okuda, M. Okubo","doi":"10.1007/1345_2018_31","DOIUrl":"https://doi.org/10.1007/1345_2018_31","url":null,"abstract":"","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"133 1","pages":"1-6"},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79664755","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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