Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-wa...Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.展开更多
Background Migration,a widespread ecological phenomenon,significantly influences the spatial and temporal distributions of organisms by altering community structure and shaping food web dynamics and ecosystem function...Background Migration,a widespread ecological phenomenon,significantly influences the spatial and temporal distributions of organisms by altering community structure and shaping food web dynamics and ecosystem functioning.In marine ecosystems,a combination of biotic and abiotic factors shapes species behaviors,reproductive patterns,and phenological traits,ultimately driving seasonal adaptive migrations across habitats.Throughout this process,shifts in species composition and resource density can not only modify the structure of trophic networks but may also lead to functional changes within the ecosystem.However,our understanding of how the adaptive migration of fish at relatively fine temporal scales in subtropical coastal waters affects food webs remains limited.This study employs regional-scale ecosystem survey and high-resolution trophic interaction data,constructing a comprehensive metaweb and seasonal subnetworks of the Beibu Gulf ecosystem,while applying topological network analysis and energy flux modeling to quantify how adaptive fish migration reshapes food web structure and energy flow dynamics.Results We found that the adaptive migration of fish in the Beibu Gulf enhanced connectivity between regions and caused community boundaries to shift northward along environmental isoclines,which results in the increased structural similarity of subnetwork among these regions.Simultaneously,this migration altered the community structure of fish within regions and led to spatial and temporal variability in fish species diversity and biomass.Although the increase in fish species diversity increased the complexity of the subnetworks,it did not fundamentally alter the topology of the subnetworks within the region or diminish the modularity of reconnected networks.Changes in species biomass transformed energy flux pathways in the northern Gulf from two pathways,which are dominated by benthic detritivore flows and pelagic phytoplanktivorous flows,to a single pathway that is predominantly reliant on benthic detritivore flows,whereas the energy flux pathways in the southern Gulf exhibited the opposite trend.These results suggest that natural boundaries formed between submodules,the trophic structure within these modules,and the consistency of the topological roles of certain super-generalist fish species contribute to the stability of the food web structure in the Beibu Gulf.Furthermore,changes in species biomass may have altered the relative utilization of resources by consumers across different habitats or the relative availability of these resources to consumers,and thereby affects the intensity of interactions between consumers and prey and potentially alters the pathways of energy flux transfer.Conclusions Our study examined the effects of seasonal environmental changes on fish migration and their subsequent impact on the structure and function of food webs in subtropical coastal waters.This research offers new perspectives on how global climate change may drive species migration,trigger food web reorganization,and induce cascading effects.Furthermore,the findings provide compelling evidence for prioritizing the monitoring of supergeneralist fish species and adopting food web structural indicators in marine ecosystem management.展开更多
Dielectric degradation typically originates from local defects.The resulting electric field concentration accelerates defect growth.Suppressing field distortion arising from such local weaknesses has long been a major...Dielectric degradation typically originates from local defects.The resulting electric field concentration accelerates defect growth.Suppressing field distortion arising from such local weaknesses has long been a major challenge in electrical insulation.In this work,we incorporated the voltage stabiliser anthrone(ET)into cross-linked polyethylene(XLPE).This design enables fielddriven adaptive migration and charge trapping,thereby dynamically regulating local electric fields.Space charge analysis reveals that ET captures charge and creates a reverse electric field.This process inhibits charge injection and transport,significantly reduces internal field distortion and results in a negative electric field coefficient effect.Notably,at 110 kV/mm the distortion ratio decreases from 118.6%in XLPE to only 0.05%in ET/XLPE,a reduction by more than 2000 times.These findings highlight the critical role of voltage stabilisers in enhancing dielectric reliability.展开更多
文摘Gaussian beam migration （GBM） is an effec- tive and robust depth seismic imaging method, which overcomes the disadvantage of Kirchhoff migration in imaging multiple arrivals and has no steep-dip limitation of one-way wave equation migration. However, its imaging quality depends on the initial beam parameters, which can make the beam width increase and wave-front spread with the propagation of the central ray, resulting in poor migration accuracy at depth, especially for exploration areas with complex geological structures. To address this problem, we present an adaptive focused beam method for shot-domain prestack depth migration. Using the infor- mation of the input smooth velocity field, we first derive an adaptive focused parameter, which makes a seismic beam focused along the whole central ray to enhance the wave- field construction accuracy in both the shallow and deep regions. Then we introduce this parameter into the GBM, which not only improves imaging quality of deep reflectors but also makes the shallow small-scale geological struc- tures well-defined. As well, using the amplitude-preserved extrapolation operator and deconvolution imaging condi- tion, the concept of amplitude-preserved imaging has been included in our method. Typical numerical examples and the field data processing results demonstrate the validity and adaptability of our method.
基金supported by the Regional Innovation Development Joint Fund Project of the National Natural Science Foundation of China(U20A2087)the Shiptime Sharing Project of National Natural Science Foundation of China(42249911)
文摘Background Migration,a widespread ecological phenomenon,significantly influences the spatial and temporal distributions of organisms by altering community structure and shaping food web dynamics and ecosystem functioning.In marine ecosystems,a combination of biotic and abiotic factors shapes species behaviors,reproductive patterns,and phenological traits,ultimately driving seasonal adaptive migrations across habitats.Throughout this process,shifts in species composition and resource density can not only modify the structure of trophic networks but may also lead to functional changes within the ecosystem.However,our understanding of how the adaptive migration of fish at relatively fine temporal scales in subtropical coastal waters affects food webs remains limited.This study employs regional-scale ecosystem survey and high-resolution trophic interaction data,constructing a comprehensive metaweb and seasonal subnetworks of the Beibu Gulf ecosystem,while applying topological network analysis and energy flux modeling to quantify how adaptive fish migration reshapes food web structure and energy flow dynamics.Results We found that the adaptive migration of fish in the Beibu Gulf enhanced connectivity between regions and caused community boundaries to shift northward along environmental isoclines,which results in the increased structural similarity of subnetwork among these regions.Simultaneously,this migration altered the community structure of fish within regions and led to spatial and temporal variability in fish species diversity and biomass.Although the increase in fish species diversity increased the complexity of the subnetworks,it did not fundamentally alter the topology of the subnetworks within the region or diminish the modularity of reconnected networks.Changes in species biomass transformed energy flux pathways in the northern Gulf from two pathways,which are dominated by benthic detritivore flows and pelagic phytoplanktivorous flows,to a single pathway that is predominantly reliant on benthic detritivore flows,whereas the energy flux pathways in the southern Gulf exhibited the opposite trend.These results suggest that natural boundaries formed between submodules,the trophic structure within these modules,and the consistency of the topological roles of certain super-generalist fish species contribute to the stability of the food web structure in the Beibu Gulf.Furthermore,changes in species biomass may have altered the relative utilization of resources by consumers across different habitats or the relative availability of these resources to consumers,and thereby affects the intensity of interactions between consumers and prey and potentially alters the pathways of energy flux transfer.Conclusions Our study examined the effects of seasonal environmental changes on fish migration and their subsequent impact on the structure and function of food webs in subtropical coastal waters.This research offers new perspectives on how global climate change may drive species migration,trigger food web reorganization,and induce cascading effects.Furthermore,the findings provide compelling evidence for prioritizing the monitoring of supergeneralist fish species and adopting food web structural indicators in marine ecosystem management.
基金supported by the National Natural Science Foundation of China(Grant 52037009).
文摘Dielectric degradation typically originates from local defects.The resulting electric field concentration accelerates defect growth.Suppressing field distortion arising from such local weaknesses has long been a major challenge in electrical insulation.In this work,we incorporated the voltage stabiliser anthrone(ET)into cross-linked polyethylene(XLPE).This design enables fielddriven adaptive migration and charge trapping,thereby dynamically regulating local electric fields.Space charge analysis reveals that ET captures charge and creates a reverse electric field.This process inhibits charge injection and transport,significantly reduces internal field distortion and results in a negative electric field coefficient effect.Notably,at 110 kV/mm the distortion ratio decreases from 118.6%in XLPE to only 0.05%in ET/XLPE,a reduction by more than 2000 times.These findings highlight the critical role of voltage stabilisers in enhancing dielectric reliability.
