Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both o...Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both on the interface positions and the total fluid volume keeping. Though one more step of the interpolations is added in the procedure, there is no significant increase in total machine time spent.展开更多
This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Re...This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model （MM5）.Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau （TP）,where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries （LLB） westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.展开更多
In this paper, radial basis functions are used to obtain the solution of evolution equations which appear in variational level set method based image segmentation. In this method, radial basis functions are used to in...In this paper, radial basis functions are used to obtain the solution of evolution equations which appear in variational level set method based image segmentation. In this method, radial basis functions are used to interpolate the implicit level set function of the evolution equation with a high level of accuracy and smoothness. Then, the original initial value problem is discretized into an interpolation problem. Accordingly, the evolution equation is converted into a set of coupled ordinary differential equations, and a smooth evolution can be retained. Compared with finite difference scheme based level set approaches, the complex and costly re-initialization procedure is unnecessary. Numerical examples are also given to show the efficiency of the method.展开更多
In view of the serious reactive power loss in the rural network, improved ant colony optimization algorithm （ACOA） was used to optimize the reactive power compensation for the rural distribution system. In this stud...In view of the serious reactive power loss in the rural network, improved ant colony optimization algorithm （ACOA） was used to optimize the reactive power compensation for the rural distribution system. In this study, the traditional ACOA was improved in two aspects： one was the local search strategy, and the other was pheromone mutation and re-initialization strategies. The reactive power optimization for a county＇s distribution network showed that the improved ACOA was practicable.展开更多
In this paper, we present a novel region-based active contour model based on global in-tensity fitting energy in a variational level set framework. Meanwhile, an internal energy term is in-troduced, and it forces the ...In this paper, we present a novel region-based active contour model based on global in-tensity fitting energy in a variational level set framework. Meanwhile, an internal energy term is in-troduced, and it forces the level set function to be close to a signed distance function. Image global information utilized efficiently makes the proposed model insensitive to noise, and the introduced penalty term can avoid the costly re-initialization for the evolving level set function, which not only speeds up the contour evolvement, but also improves accuracy of the final contour. Comparisons with other classical region-based models, such as Chan-Vese model and Region-Scalable Fitting (RSF) model, show the advantages of our model in terms of efficiency and accuracy. Moreover, the model is robust to noise.展开更多
As relics of ancient ocean lithosphere,ophiolites are the most important petrological evidence for marking the sutures and also play a key role in reconstructing plate configuration.They also provide valuable windows ...As relics of ancient ocean lithosphere,ophiolites are the most important petrological evidence for marking the sutures and also play a key role in reconstructing plate configuration.They also provide valuable windows for studying crustal accretion and mantle processes occurring at modem ocean ridges.Abundant ophiolites are distributed along the Yarlung-Tsangpo suture and represent the relics of ocean lithosphere of the Neo-Tethys.They are characterized by an incomplete litho-stratigraphy,of which the mantle section is much thicker than the crustal section.Ocean crustal rocks outcropped in the Yarlung-Tsangpo ophiolites are much thinner than normal ocean crusts(~7 km)or even absent.Tectonic settings from which the Yarlung-Tsangpo ophiolites originated remain highly controversial,although an origin of the supra-subduction zone is prevailing.Moreover,their incomplete litho-stratigraphy has been commonly attributed to tectonic dismemberment during the late-stage emplacement after their formation.Nevertheless,such an incompleteness resembles the ocean lithosphere generated at modem ultraslow spreading ridges,such as the Southwest Indian Ridge(SWIR).In this paper,we present several lines of evidence that support the formation of the Yarlung-Tsangpo ophiolites at ultraslow spreading ridges,during which detachment faults were developed.This suggests that the Yarlung-Tsangpo ophiolites might represent the ocean core complexes(OCC)in the Neo-Tethys Ocean.The OCC with high topography in the seafloor were clogged in the trench and preserved as ophiolites through Indo-Eurasia collision.The clogging resulted in the demise of an old subduction and a new subduction was re-initiated beneath the clogged OCC.展开更多
The metamorphic sole located beneath ophiolites preserves critical information about the formation and subsequent obduction of ophiolites.A typical metamorphic sole consists of an assemblage of high-temperature-low-pr...The metamorphic sole located beneath ophiolites preserves critical information about the formation and subsequent obduction of ophiolites.A typical metamorphic sole consists of an assemblage of high-temperature-low-pressure(high T/P)metamorphic rocks,including amphibolites and garnet pyroxenites.The metamorphic grades range from greenschist facies to high-grade amphibolite and granulite facies,indicating formation under high geothermal gradients(>25℃/km).A synthesis of studies on globally exposed metamorphic soles and their corresponding ophiolites reveals that the protoliths of most mafic metamorphic soles share similar geochemical signatures with the mafic oceanic crust of the overlying ophiolites.Moreover,the crystallization ages of the protoliths and the formation ages of the ophiolitic crust are generally consistent,and the timing of metamorphism is either contemporaneous to or slightly younger than the crystallization age.These features suggest that shortly after the formation of ophiolites(typically within<10 Myr),a rapid geodynamic transition from seafloor spreading to subduction occurred.Therefore,the metamorphic sole serves as a key petrological archive for recording the subduction initiation at former mid-ocean ridges.By summarizing recent research progress on the Yarlung-Tsangpo ophiolites and their metamorphic soles in Tibetan Plateau,we propose a model of“subduction re-initiation at mid-ocean ridges”.In this model,the Neo-Tethyan Ocean experienced ultra-slow spreading between 130 and 120 Ma,leading to the formation of oceanic core complexes along detachment faults.Subsequently,the cessation of earlier subduction to the north triggered new subduction initiation along the detachment fault near the ridge axis.As a result,oceanic lithologies underwent metamorphism under relatively high geothermal gradients(25–30℃/km),forming the metamorphic soles.Eventually,the metamorphic soles and the associated oceanic core complexes were preserved together as the Yarlung-Tsangpo ophiolite-metamorphic sole assemblage.Comparative studies with classic global ophiolites suggest that this“subduction re-initiation”model provides a reasonable explanation for the geological relationship between ophiolites and their metamorphic soles,offering a broadly applicable framework for understanding the formation and emplacement of ophiolites.展开更多
In this paper we present a selective segmentation model using a dual level set variational formulation.Our variational model aims to segment all objects with one level set function(global)and the selected object,which...In this paper we present a selective segmentation model using a dual level set variational formulation.Our variational model aims to segment all objects with one level set function(global)and the selected object,which is the closest to the geometric constraints(markers),with another level set(local).It is a combination of edge detection,markers distance function and active contour without edges.Experimental results show that our model is more robust than previous work.展开更多
文摘Re-initialization procedure in level-set interface capturing method were investigated. The algorithm accomplishes the re-initialization step through locking the interface positions. Better accuracy was obtained both on the interface positions and the total fluid volume keeping. Though one more step of the interpolations is added in the procedure, there is no significant increase in total machine time spent.
基金supported by the funding of the Key Program of the Chinese Academy of Sciences (Grant No.KZCX2-YW-328)the National Key Basic Research Program (2005CB422003)+1 种基金National Science Foundation Center of China (NSFC) (40871001)the US JPL Grant No. 1278492,NOAA Grant Nos NA07OAR4310226 and NA08OAR4310591
文摘This study investigates the capability of the dynamic downscaling method （DDM） in an East Asian climate study for June 1998 using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research non-hydrostatic Mesoscale Model （MM5）.Sensitivity experiments show that MM5 results at upper atmospheric levels cannot match reanalyses data,but the results show consistent improvement in simulating moisture transport at low levels.The downscaling ability for precipitation is regionally dependent.During the monsoon season over the Yangtze River basin and the pre-monsoon season over North China,the DDM cannot match observed precipitation.Over Northwest China and the Tibetan Plateau （TP）,where there is high topography,the DDM shows better performance than reanalyses.Simulated monsoon evolution processes over East Asia,however,are much closer to observational data than reanalyses.The convection scheme has a substantial impact on extreme rainfall over the Yangtze River basin and the pre-monsoon over North China,but only a marginal contribution for Northwest China and the TP.Land surface parameterizations affect the locations and pattern of rainfall bands.The 10-day re-initialization in this study shows some improvement in simulated precipitation over some sub-regions but with no obvious improvement in circulation.The setting of the location of lateral boundaries （LLB） westward improves performance of the DDM.Including the entire TP in the western model domain improves the DDM performance in simulating precipitation in most sub-regions.In addition,a seasonal simulation demonstrates that the DDM can also obtain consistent results,as in the June case,even when another two months consist of no strong climate/weather events.
基金Project supported by the National Natural Science Foundation of China (Grant No.11101454)the Educational Commission Foundation of Chongqing City,China (Grant No.KJ130626)the Program of Innovation Team Project in University of Chongqing City,China (Grant No.KJTD201308)
文摘In this paper, radial basis functions are used to obtain the solution of evolution equations which appear in variational level set method based image segmentation. In this method, radial basis functions are used to interpolate the implicit level set function of the evolution equation with a high level of accuracy and smoothness. Then, the original initial value problem is discretized into an interpolation problem. Accordingly, the evolution equation is converted into a set of coupled ordinary differential equations, and a smooth evolution can be retained. Compared with finite difference scheme based level set approaches, the complex and costly re-initialization procedure is unnecessary. Numerical examples are also given to show the efficiency of the method.
基金Supported by China Postdoctoral Science Foundation(20090460873)
文摘In view of the serious reactive power loss in the rural network, improved ant colony optimization algorithm （ACOA） was used to optimize the reactive power compensation for the rural distribution system. In this study, the traditional ACOA was improved in two aspects： one was the local search strategy, and the other was pheromone mutation and re-initialization strategies. The reactive power optimization for a county＇s distribution network showed that the improved ACOA was practicable.
基金Supported by the State Key Program of National Natural Science of China (No. 61003134, 60736008)the National Natural Science Foundation of China (No. 60803082)the Key Program of Natural Science of Beijing (No.4081002)
文摘In this paper, we present a novel region-based active contour model based on global in-tensity fitting energy in a variational level set framework. Meanwhile, an internal energy term is in-troduced, and it forces the level set function to be close to a signed distance function. Image global information utilized efficiently makes the proposed model insensitive to noise, and the introduced penalty term can avoid the costly re-initialization for the evolving level set function, which not only speeds up the contour evolvement, but also improves accuracy of the final contour. Comparisons with other classical region-based models, such as Chan-Vese model and Region-Scalable Fitting (RSF) model, show the advantages of our model in terms of efficiency and accuracy. Moreover, the model is robust to noise.
基金the National Science Fund for Distinguished Young Scholars(Grant No.42025201)。
文摘As relics of ancient ocean lithosphere,ophiolites are the most important petrological evidence for marking the sutures and also play a key role in reconstructing plate configuration.They also provide valuable windows for studying crustal accretion and mantle processes occurring at modem ocean ridges.Abundant ophiolites are distributed along the Yarlung-Tsangpo suture and represent the relics of ocean lithosphere of the Neo-Tethys.They are characterized by an incomplete litho-stratigraphy,of which the mantle section is much thicker than the crustal section.Ocean crustal rocks outcropped in the Yarlung-Tsangpo ophiolites are much thinner than normal ocean crusts(~7 km)or even absent.Tectonic settings from which the Yarlung-Tsangpo ophiolites originated remain highly controversial,although an origin of the supra-subduction zone is prevailing.Moreover,their incomplete litho-stratigraphy has been commonly attributed to tectonic dismemberment during the late-stage emplacement after their formation.Nevertheless,such an incompleteness resembles the ocean lithosphere generated at modem ultraslow spreading ridges,such as the Southwest Indian Ridge(SWIR).In this paper,we present several lines of evidence that support the formation of the Yarlung-Tsangpo ophiolites at ultraslow spreading ridges,during which detachment faults were developed.This suggests that the Yarlung-Tsangpo ophiolites might represent the ocean core complexes(OCC)in the Neo-Tethys Ocean.The OCC with high topography in the seafloor were clogged in the trench and preserved as ophiolites through Indo-Eurasia collision.The clogging resulted in the demise of an old subduction and a new subduction was re-initiated beneath the clogged OCC.
基金financially supported by the National Science Fund for Distinguished Young Scholars(Grant No.42025201)the National Science Foundation of China(Grant No.42272055)the Key Research Program of the Institute of Geology and Geophysics,CAS(Grant No.IGGCAS-202202)。
文摘The metamorphic sole located beneath ophiolites preserves critical information about the formation and subsequent obduction of ophiolites.A typical metamorphic sole consists of an assemblage of high-temperature-low-pressure(high T/P)metamorphic rocks,including amphibolites and garnet pyroxenites.The metamorphic grades range from greenschist facies to high-grade amphibolite and granulite facies,indicating formation under high geothermal gradients(>25℃/km).A synthesis of studies on globally exposed metamorphic soles and their corresponding ophiolites reveals that the protoliths of most mafic metamorphic soles share similar geochemical signatures with the mafic oceanic crust of the overlying ophiolites.Moreover,the crystallization ages of the protoliths and the formation ages of the ophiolitic crust are generally consistent,and the timing of metamorphism is either contemporaneous to or slightly younger than the crystallization age.These features suggest that shortly after the formation of ophiolites(typically within<10 Myr),a rapid geodynamic transition from seafloor spreading to subduction occurred.Therefore,the metamorphic sole serves as a key petrological archive for recording the subduction initiation at former mid-ocean ridges.By summarizing recent research progress on the Yarlung-Tsangpo ophiolites and their metamorphic soles in Tibetan Plateau,we propose a model of“subduction re-initiation at mid-ocean ridges”.In this model,the Neo-Tethyan Ocean experienced ultra-slow spreading between 130 and 120 Ma,leading to the formation of oceanic core complexes along detachment faults.Subsequently,the cessation of earlier subduction to the north triggered new subduction initiation along the detachment fault near the ridge axis.As a result,oceanic lithologies underwent metamorphism under relatively high geothermal gradients(25–30℃/km),forming the metamorphic soles.Eventually,the metamorphic soles and the associated oceanic core complexes were preserved together as the Yarlung-Tsangpo ophiolite-metamorphic sole assemblage.Comparative studies with classic global ophiolites suggest that this“subduction re-initiation”model provides a reasonable explanation for the geological relationship between ophiolites and their metamorphic soles,offering a broadly applicable framework for understanding the formation and emplacement of ophiolites.
文摘In this paper we present a selective segmentation model using a dual level set variational formulation.Our variational model aims to segment all objects with one level set function(global)and the selected object,which is the closest to the geometric constraints(markers),with another level set(local).It is a combination of edge detection,markers distance function and active contour without edges.Experimental results show that our model is more robust than previous work.
