The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses o...The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses on a LDPC encoded slow frequency hopping (SFH) communication system with partial-band interference. Firstly, a modified soft- decision algorithm based on the utilization of interference information is proposed, and its performance is compared with some other soft-decision methods. Secondly, with numerical simulation, the influence of code rate, code length and the number of symbols per hops on the performance of the system with partial band noise interference is illustrated and examined in detail. Considering the great influence of hops per symbol on the performance, interleaver should be used and its influence on the performance is further examined by simulation. Finally, some constructive advises for the design of LDPC coded SFH system are given. Simulation results show that, with a reasonable design, the SFH system with LDPC code could achieve a desirable performance.展开更多
Most giant porphyry-skarn Cu-Au ore systems are associated with either the metasomatic mantle wedge,formed by the dehydration of subducting oceanic crust,or the melting of Cu-rich juvenile lower crust.The ore-forming ...Most giant porphyry-skarn Cu-Au ore systems are associated with either the metasomatic mantle wedge,formed by the dehydration of subducting oceanic crust,or the melting of Cu-rich juvenile lower crust.The ore-forming parent rocks are typically depleted adakites.In contrast,parent rocks in intracontinental Cu-Au ore systems exhibit enriched isotopic compositions,yet their formation mechanisms and deep processes remain unclear.To address this,our study focuses on the central Yangtze River ore belt(CYROB)and adjacent areas.By compiling regional petrological and chronological data,we conducted multi-isotope tracing and Hf isotope mapping,integrated with regional seismic velocity tomography and magnetotelluric detection results,to reconstruct the lithospheric architecture and its evolutionary processes.Our findings indicate that the CYROB underwent significant crustal accretion during the Meso-and Neo-proterozoic,forming a juvenile crust.In the Late Mesozoic,the crust experienced polygenetic reworking,through two distinct periods(156–136 Ma and 136–120 Ma).During the transition from the Late Jurassic to the Early Cretaceous(156–140 Ma),in the area near and north of the Gaotan fault,lithospheric delamination in an extensional setting facilitated mantle convection and partial melting of enriched lithospheric mantle.This process modified the pre-existing juvenile lower crust,leading to the formation of adakites with slightly negativeεHf values(-5 to 0)and associated porphyry-skarn Cu-Au deposits.Concurrently,ascent of adakitic magma occasionally incorporated W-rich middle-to-upper crustal materials,enriching the melts in W and forming localized small-to medium-sized skarn W deposits.During 140–136 Ma,with the continued relaxation of lithospheric stress,a more intense modification of the lower crust by enriched mantle occurred west of Anqing and north of Qingyang.This led to the formation of adakic magmas with strongly negativeεHfvalues(-24 to-8)and related skarn Cu-Fe deposits.To the south of the Jiangnan fault,where the crust was deeper,mantle convection induced the remelting of Proterozoic reworked crust,releasing W and Mo into crust-derived melts,ultimately forming a series of large-and medium-sized porphyry-skarn W-Mo deposits.During the late period(136–120 Ma),progressive lithospheric extension triggered large-scale lithospheric delamination and oblique asthenospheric upwelling from the southeast to the northwest,further modifying the lower crust.The remelting of reworked crust with input from depleted mantle materials,led to the formation of extensive alkali-rich granitic batholiths.This study demonstrates that,under the extensional regime of the Late Mesozoic,the polygenic reworking of juvenile crust and the remelting of previously reworked crust—driven by ongoing lithosphere-scale delamination and asthenospheric upwelling—played a key role in controlling the temporal and spatial distribution of metal ore systems in the CYROB and adjacent areas.展开更多
文摘The application of Low Density Parity Check (LDPC) code in the anti-interference systems has drawn an increasing attention, due to its admiring performance which is very close to the theory limit. This paper focuses on a LDPC encoded slow frequency hopping (SFH) communication system with partial-band interference. Firstly, a modified soft- decision algorithm based on the utilization of interference information is proposed, and its performance is compared with some other soft-decision methods. Secondly, with numerical simulation, the influence of code rate, code length and the number of symbols per hops on the performance of the system with partial band noise interference is illustrated and examined in detail. Considering the great influence of hops per symbol on the performance, interleaver should be used and its influence on the performance is further examined by simulation. Finally, some constructive advises for the design of LDPC coded SFH system are given. Simulation results show that, with a reasonable design, the SFH system with LDPC code could achieve a desirable performance.
基金jointly funded by the National Key Technologies Research and Development Program(Grant Nos.2019YFA0708603,2023YFF0804203)the China Geological Survey(Grant No.DD20243510)+2 种基金the Scientific Research Fund Project of BGRIMM Technology Group(Grant No.JTKY202427822)the National Natural Science Foundation of China(Grant No.42073042)the Basic Scientific Research Fund of the Institute of Geology,Chinese Academy of Geological Sciences(Grant No.J2402)。
文摘Most giant porphyry-skarn Cu-Au ore systems are associated with either the metasomatic mantle wedge,formed by the dehydration of subducting oceanic crust,or the melting of Cu-rich juvenile lower crust.The ore-forming parent rocks are typically depleted adakites.In contrast,parent rocks in intracontinental Cu-Au ore systems exhibit enriched isotopic compositions,yet their formation mechanisms and deep processes remain unclear.To address this,our study focuses on the central Yangtze River ore belt(CYROB)and adjacent areas.By compiling regional petrological and chronological data,we conducted multi-isotope tracing and Hf isotope mapping,integrated with regional seismic velocity tomography and magnetotelluric detection results,to reconstruct the lithospheric architecture and its evolutionary processes.Our findings indicate that the CYROB underwent significant crustal accretion during the Meso-and Neo-proterozoic,forming a juvenile crust.In the Late Mesozoic,the crust experienced polygenetic reworking,through two distinct periods(156–136 Ma and 136–120 Ma).During the transition from the Late Jurassic to the Early Cretaceous(156–140 Ma),in the area near and north of the Gaotan fault,lithospheric delamination in an extensional setting facilitated mantle convection and partial melting of enriched lithospheric mantle.This process modified the pre-existing juvenile lower crust,leading to the formation of adakites with slightly negativeεHf values(-5 to 0)and associated porphyry-skarn Cu-Au deposits.Concurrently,ascent of adakitic magma occasionally incorporated W-rich middle-to-upper crustal materials,enriching the melts in W and forming localized small-to medium-sized skarn W deposits.During 140–136 Ma,with the continued relaxation of lithospheric stress,a more intense modification of the lower crust by enriched mantle occurred west of Anqing and north of Qingyang.This led to the formation of adakic magmas with strongly negativeεHfvalues(-24 to-8)and related skarn Cu-Fe deposits.To the south of the Jiangnan fault,where the crust was deeper,mantle convection induced the remelting of Proterozoic reworked crust,releasing W and Mo into crust-derived melts,ultimately forming a series of large-and medium-sized porphyry-skarn W-Mo deposits.During the late period(136–120 Ma),progressive lithospheric extension triggered large-scale lithospheric delamination and oblique asthenospheric upwelling from the southeast to the northwest,further modifying the lower crust.The remelting of reworked crust with input from depleted mantle materials,led to the formation of extensive alkali-rich granitic batholiths.This study demonstrates that,under the extensional regime of the Late Mesozoic,the polygenic reworking of juvenile crust and the remelting of previously reworked crust—driven by ongoing lithosphere-scale delamination and asthenospheric upwelling—played a key role in controlling the temporal and spatial distribution of metal ore systems in the CYROB and adjacent areas.
