现今的地球物理勘探观测精度要求越来越高,采集数据动辄达PB级,如何对PB级的海量数据进行质控与管理成为了新的挑战。本文提出了地震采集实时质量控制(RTQC,Real Time QC)、模块流程化工序、软件实现等方法。该方法在中东某20万道级数...现今的地球物理勘探观测精度要求越来越高,采集数据动辄达PB级,如何对PB级的海量数据进行质控与管理成为了新的挑战。本文提出了地震采集实时质量控制(RTQC,Real Time QC)、模块流程化工序、软件实现等方法。该方法在中东某20万道级数字检波器三维项目中成功应用,通过实际验证和基础数据分析证明了该质控与管理方法的实用性,为类似地震勘探项目PB级地震数据的数据管理提供了可借鉴思路。展开更多
The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstruct...The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.展开更多
Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be preve...Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be prevented effectively by establishing fire airflow control system. In this work, the 5th belt roadway of Kongzhuang coal mine was taken as the object of investigation, where geometrical models of this roadway were established firstly. Then, based on mathematical model of fire smoke flow, the CO volume fraction, smoke density distribution, air temperature and pollutant velocity vector in the roadway before and after taking airflow control measures were simulated by using Fluent software. It can be known from the simulation that with the normal ventilation status in 5th belt roadway, the countercurrent of smoke does not happen when a fire occurs; the roadway's section is almost filled with CO at 10 m downstream from the fire source, and with air velocity getting stable gradually, the CO concentration reaches about 15 %. After taking airflow control measures, the effect range of temperature field which are harmful to the miners decreases from 69 m to 30 m; and the distance of the roadway fully filled with CO is 5 m farther than that before taking measures. Finally, according to the numerical simulation results and the actual condition of the belt roadway, the warning and automatic remote airflow control system with short-circuit method for the 5th belt roadway was designed to guarantee the safety production.展开更多
The FLAC3D software was used to simulate and analyze numerically the displacement, stress and plastic zone distribu-tion characteristics of a large span intersection in a deep soft rock roadway after the surrounding r...The FLAC3D software was used to simulate and analyze numerically the displacement, stress and plastic zone distribu-tion characteristics of a large span intersection in a deep soft rock roadway after the surrounding rock was excavated. Our simula-tion results show that there are two kinds of dominating factors affecting roadway stability at points of intersection, one is the angle between horizontal stress and axial direction of the roadway and the other are the angles at the points of intersection. These results are based on a study we carried out as follows: first, we analyzed the failure mechanism of a large span intersection and then we built a mechanical model of a rock pillar at one of the points of intersection. At the end of this analysis, we obtained the failure characteristics of the critical parts on the large span intersection. Given these failure characteristics, we proposed a new supporting method, i.e., a Double-Bolt Control Technology (DBCT). By way of numerical simulation, DBCT can effectively control the deformation of the surrounding rock at the points of intersection in roadways.展开更多
Segment sectional model tests are carried out to investigate the wind loading on middle pylon of Taizhou Bridge, which has complicated three-dimensional flow due to its feature of double columns. Through the force mea...Segment sectional model tests are carried out to investigate the wind loading on middle pylon of Taizhou Bridge, which has complicated three-dimensional flow due to its feature of double columns. Through the force measuring tests, aerodynamic force coefficients of every segment of the pylon columns have been obtained. It is found that the tested aerodynamic force coefficients are much smaller than those given by codes. The interference effects of aerodynamic force coefficients between columns of pylon are discussed. The results show that the interference effect is the most evident when the yaw angle is about 30 ° from transverse direction. This kind of interference effect can be described as diminutions in transverse aerodynamic force coefficients and magnifications in longitudinal aerodynamic force coefficients of downstream columns.展开更多
For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously u...For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.展开更多
To obtain the platform s big data analytics support,manufacturers in the traditional retail channel must decide whether to use the direct online channel.A retail supply chain model and a direct online supply chain mod...To obtain the platform s big data analytics support,manufacturers in the traditional retail channel must decide whether to use the direct online channel.A retail supply chain model and a direct online supply chain model are built,in which manufacturers design products alone in the retail channel,while the platform and manufacturer complete the product design in the direct online channel.These two models are analyzed using the game theoretical model and numerical simulation.The findings indicate that if the manufacturers design capabilities are not very high and the commission rate is not very low,the manufacturers will choose the direct online channel if the platform s technical efforts are within an interval.When the platform s technical efforts are exogenous,they positively influence the manufacturers decisions;however,in the endogenous case,the platform s effect on the manufacturers is reflected in the interaction of the commission rate and cost efficiency.The manufacturers and the platform should make synthetic effort decisions based on the manufacturer s development capabilities,the intensity of market competition,and the cost efficiency of the platform.展开更多
Simulated outgoing longwave radiation (OLR) outputs by two versions of the grid-point atmospheric general circulation model (GAMIL) were analyzed to assess the influences of improvements in cloud microphysics and ...Simulated outgoing longwave radiation (OLR) outputs by two versions of the grid-point atmospheric general circulation model (GAMIL) were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation (MJO) and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the M30, Kelvin, equatorial Rossby (ER), mixed Rossby-gravity (MRG), and inertio-gravity (1G) waves. The performances of different versions of the GAMIL model (version 1.0 (GAMIL1.0) and version 2.0 (GAMIL2.0)) were evalu- ated by comparing the power spectrum distributions of these waves among GAMIL 1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1-3, suggesting that GAMILI.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model's performance.展开更多
Based on the IDP data from the French DEMETER satellite,global distribution is shown,which corresponds to three precipitation zones:the aural precipitation zone,the mid-high latitude precipitation zone and the South A...Based on the IDP data from the French DEMETER satellite,global distribution is shown,which corresponds to three precipitation zones:the aural precipitation zone,the mid-high latitude precipitation zone and the South Atlantic precipitation zone.Then the Chili earthquake with M8.8 which occurred on February 27,2010 is taken as an example.The IDP fluxes from repeat orbits are compared and the results show that there is a clear enhancement on February 26,2010,just one day ahead of the Chili earthquake.In the south zone with L=2.1~2.7,the flux on February 26 is higher than that on previous days.However in the north zone with L=2.1~2.7,there is no clear change during the day but great enhancement during the night,which is close to the time of the earthquake.At the same time,the flux on February 26 near the equator is far lower than that on previous days.展开更多
The particle size and shape measured by image analysis is helpful to discuss the human health effects of particulate beside the aerodynamic scale. To explore the size and shape features of particle suspended in the ro...The particle size and shape measured by image analysis is helpful to discuss the human health effects of particulate beside the aerodynamic scale. To explore the size and shape features of particle suspended in the road environment, this research selected 12 bus stations as the sampling sites along the main road in the air polluted city Shijiazhuang, China, where a Car-Free Campaign had been carried out. We hung 2 slides covered with a layer of petroleum jelly to collect suspending particles for 24 hours at each sampling site, and measured the particles size and shape parameters with the Particle Size Analyzer of CIS-50. The results show that the average particle size by the equivalent area diameter is around 10 μm, the size distributions are multi-modal with wide span, demonstrating that coarse dust suspended on road derived from several particle sources. Most of the particles suspended are square or square-like in shape with rugged border. Compared the samples of ordinary days and of the Car-Free day, the size and shape features vary little, inferring the ineffective results for the particle control of the Campaign. There is certain relationship between particle size and shape. The number percent of PMs-E (particulate matter with equivalent area diameter beneath 5 pro) is positively correlative with the number percent of particles of square or square-like shape, and negatively correlative with that of round or round-like shape. This relationship pattern in the road environment is contrary to the situations in the upper atmosphere, inferring different transportation and source emission mechanism influences.展开更多
The subduction channel is defined as a planar to wedge-like area of variable size,internal structure and composition,which forms between the upper and lower plates during slab subduction into the mantle.The materials ...The subduction channel is defined as a planar to wedge-like area of variable size,internal structure and composition,which forms between the upper and lower plates during slab subduction into the mantle.The materials in the channel may experience complex pressure,temperature,stress and strain evolution,as well as strong fluid and melt activity.A certain amount of these materials may subduct to and later exhume from>100 km depth,forming high to ultra-high pressure rocks on the surface as widely discovered in nature.Rock deformation in the channel is strongly assisted by metamorphic fluids activities,which change composition and mechanical properties of rocks and thus affect their subduction and exhumation histories.In this study,we investigate the detailed structure and dynamics of both oceanic and continental subduction channels,by conducting highresolution petrological-thermomechanical numerical simulations taking into account fluid and melt activities.The numerical results demonstrate that subduction channels are composed of a tectonic rock melange formed by crustal rocks detached from the subducting slab and the hydrated mantle rocks scratched from the overriding plate.These rocks may either extrude sub-vertically upward through the mantle wedge to the crust of the upper plate,or exhume along the subduction channel to the surface near the suture zone.Based on our numerical results,we first analyze similarities and differences between oceanic and continental subduction channels.We further compare numerical models with and without fluid and melt activity and demonstrate that this activity results in strong weakening and deformation of overriding lithosphere.Finally,we show that fast convergence of orogens subjected to fluid and melt activity leads to strong deformation of the overriding lithosphere and the topography builds up mainly on the overriding plate.In contrast,slow convergence of such orogens leads to very limited deformation of the overriding lithosphere and the mountain building mainly occurs on the subducting plate.展开更多
Based on the auroral electron/ion precipitation boundary database observed by the DMSP satellites during 1984–2009, the characteristics of the nightside equatorial boundaries of the electron precipitation(B1E) and ...Based on the auroral electron/ion precipitation boundary database observed by the DMSP satellites during 1984–2009, the characteristics of the nightside equatorial boundaries of the electron precipitation(B1E) and the ion precipitation(B1I) in the Northern/Southern Hemispheres(NH/SH) are statistically investigated. The results show: That most of the boundaries are located between magnetic latitude(MLAT) of 60°–70° with the mean MLAT for B1E/B1 I to be 64.30°N/63.22°N and 64.48°S/63.26°S in the NH and SH, respectively, indicating that B1 E and B1 I in both hemispheres are located in conjugated magnetic field lines with B1 E ~1.2° poleward of B1I; that the MLAT of B1 E and B1 I in both hemispheres shift to lower MLAT(from ~70° to ~55°) as geomagnetic activity increases; that MLAT of both B1 E and B1 I and their differences slowly decrease from dusk to midnight with some difference in both hemispheres during different levels of geomagnetic activities; that B1 E and B1 I in both hemisphere decrease linearly with Kp and exponentially with Dst, AE, and SYM-H, respectively, demonstrating that auroral particle precipitation is closely related with geomagnetic activity; that in different magnetic local time(MLT) sectors, the changing rates of the boundaries with Kp are different, and the rates of B1 E are generally larger than that of B1 I, implying that the difference between B1 E and B1 I reduce with increasing geomagnetic activity. Compared with previous studies, the statistical results based on the long-term large database in this paper can well reflect the properties of the equatorial boundaries of auroral precipitation and may be used for physical modeling or space weather forecasting in future.展开更多
文摘现今的地球物理勘探观测精度要求越来越高,采集数据动辄达PB级,如何对PB级的海量数据进行质控与管理成为了新的挑战。本文提出了地震采集实时质量控制(RTQC,Real Time QC)、模块流程化工序、软件实现等方法。该方法在中东某20万道级数字检波器三维项目中成功应用,通过实际验证和基础数据分析证明了该质控与管理方法的实用性,为类似地震勘探项目PB级地震数据的数据管理提供了可借鉴思路。
基金Project (2016YFB1200602-11) supported by National Key R&D Plan of China
文摘The influence of enlarged section parameters on pressure transients of high-speed train passing through a tunnel was investigated by numerical simulation.The calculation results obtained by the structured and unstructured grid and the experimental results of smooth wall tunnel were verified.Numerical simulation studies were conducted on three tunnel enlarged section parameters,the enlarged section distribution along circumferential direction,the enlarged section area and the enlarged section distribution along tunnel length direction.The calculation results show that the influence of the different enlarged section distributions along tunnel circumferential direction on pressure transients in the tunnel is basically consistent.There is an optimal enlarged section area for the minimum value of the pressure variation amplitude and the average pressure variation in the tunnel.The law of the pressure variation amplitude and the average pressure variation of the enlarged section distribution along tunnel length direction are obtained.
基金Project supported by Joint Innovative Center for Safe and Effective Mining Technology and Equipment of Coal Resources of Shandong Province,ChinaProject supported by Taishan Scholar Program of Shandong Province,China+2 种基金Project(2014JQJH106)supported by Shandong University of Science and Technology Research Fund,ChinaProject(LAK2012-1)supported by Science and Technology Development Program of Safety Production of Shandong Province,ChinaProject(2012ZHTD06)supported by Science Research Innovative Group of College of Mining and Safety Engineering of Shandong University of Science and Technology,China
文摘Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be prevented effectively by establishing fire airflow control system. In this work, the 5th belt roadway of Kongzhuang coal mine was taken as the object of investigation, where geometrical models of this roadway were established firstly. Then, based on mathematical model of fire smoke flow, the CO volume fraction, smoke density distribution, air temperature and pollutant velocity vector in the roadway before and after taking airflow control measures were simulated by using Fluent software. It can be known from the simulation that with the normal ventilation status in 5th belt roadway, the countercurrent of smoke does not happen when a fire occurs; the roadway's section is almost filled with CO at 10 m downstream from the fire source, and with air velocity getting stable gradually, the CO concentration reaches about 15 %. After taking airflow control measures, the effect range of temperature field which are harmful to the miners decreases from 69 m to 30 m; and the distance of the roadway fully filled with CO is 5 m farther than that before taking measures. Finally, according to the numerical simulation results and the actual condition of the belt roadway, the warning and automatic remote airflow control system with short-circuit method for the 5th belt roadway was designed to guarantee the safety production.
基金Financial supports for this work, provided by the Major Program of the National Natural Science Foundation of China (No.50490270)the National Basic Research Program of China (973) (No. 2006CB202200) the Innovation Term Project of Ministry of Education of China (No.IRT0656), are gratefully acknowledged
文摘The FLAC3D software was used to simulate and analyze numerically the displacement, stress and plastic zone distribu-tion characteristics of a large span intersection in a deep soft rock roadway after the surrounding rock was excavated. Our simula-tion results show that there are two kinds of dominating factors affecting roadway stability at points of intersection, one is the angle between horizontal stress and axial direction of the roadway and the other are the angles at the points of intersection. These results are based on a study we carried out as follows: first, we analyzed the failure mechanism of a large span intersection and then we built a mechanical model of a rock pillar at one of the points of intersection. At the end of this analysis, we obtained the failure characteristics of the critical parts on the large span intersection. Given these failure characteristics, we proposed a new supporting method, i.e., a Double-Bolt Control Technology (DBCT). By way of numerical simulation, DBCT can effectively control the deformation of the surrounding rock at the points of intersection in roadways.
基金National Science and Technology Support Program of China ( No. 2009BAG15B01)Key Pro-grams for Science and Technology Development of Chinese Transportation Industry ( No. 2008-353-332-190 )National Science Foundation( No. 51008233)
文摘Segment sectional model tests are carried out to investigate the wind loading on middle pylon of Taizhou Bridge, which has complicated three-dimensional flow due to its feature of double columns. Through the force measuring tests, aerodynamic force coefficients of every segment of the pylon columns have been obtained. It is found that the tested aerodynamic force coefficients are much smaller than those given by codes. The interference effects of aerodynamic force coefficients between columns of pylon are discussed. The results show that the interference effect is the most evident when the yaw angle is about 30 ° from transverse direction. This kind of interference effect can be described as diminutions in transverse aerodynamic force coefficients and magnifications in longitudinal aerodynamic force coefficients of downstream columns.
基金supportedin part by Natural Science Foundation under grant No.91338108,91438206Co-innovation Laboratory of Aerospace Broadband Network Technology
文摘For digital channelized frequency division multiple access based satellite communication(SATCOM) systems,it is a challenging but critical issue to improve the transponder power and spectrum efficiency simultaneously under limited and non-linear high-power amplifier conditions.In this paper,different from the traditional link supportability designs aiming at minimizing the total transponder output power,a maximal sum Shannon capacity optimization objective is firstly raised subject to link supportability constraints.Furthermore,an efficient multilevel optimization(MO) algorithm is proposed to solve the considered optimization problem in the case of single link for each terminal.Moreover,in the case of multiple links for one terminal,an improved MO algorithm involving Golden section and discrete gradient searching procedures is proposed to optimize power allocation over all links.Finally,several numerical results are provided to demonstrate the effectiveness of our proposals.Comparison results show that,by the MO algorithm,not only all links' supportability can be guaranteed but also a larger sum capacity can be achieved with lower complexity.
基金The National Natural Science Foundation of China(No.72071039)the Foundation of China Scholarship Council(No.202106090197)。
文摘To obtain the platform s big data analytics support,manufacturers in the traditional retail channel must decide whether to use the direct online channel.A retail supply chain model and a direct online supply chain model are built,in which manufacturers design products alone in the retail channel,while the platform and manufacturer complete the product design in the direct online channel.These two models are analyzed using the game theoretical model and numerical simulation.The findings indicate that if the manufacturers design capabilities are not very high and the commission rate is not very low,the manufacturers will choose the direct online channel if the platform s technical efforts are within an interval.When the platform s technical efforts are exogenous,they positively influence the manufacturers decisions;however,in the endogenous case,the platform s effect on the manufacturers is reflected in the interaction of the commission rate and cost efficiency.The manufacturers and the platform should make synthetic effort decisions based on the manufacturer s development capabilities,the intensity of market competition,and the cost efficiency of the platform.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW- Q11-04)the National Basic Research Program of China (2011 CB403505 and 2010CB950402)the National Natural Science Foundation of China (40975052)
文摘Simulated outgoing longwave radiation (OLR) outputs by two versions of the grid-point atmospheric general circulation model (GAMIL) were analyzed to assess the influences of improvements in cloud microphysics and convective parameterization schemes on the simulation of the Madden-Julian oscillation (MJO) and other tropical waves. The wavenumber-frequency spectral analysis was applied to isolate dominant modes of convectively coupled equatorial waves, including the M30, Kelvin, equatorial Rossby (ER), mixed Rossby-gravity (MRG), and inertio-gravity (1G) waves. The performances of different versions of the GAMIL model (version 1.0 (GAMIL1.0) and version 2.0 (GAMIL2.0)) were evalu- ated by comparing the power spectrum distributions of these waves among GAMIL 1.0, GAMIL2.0, and observational data. GAMIL1.0 shows a weak MJO signal, with the maximum variability occurring separately at wavenumbers 1 and 4 rather than being concentrated on wavenumbers 1-3, suggesting that GAMILI.0 could not effectively capture the intraseasonal variability. However, GAMIL2.0 is able to effectively reproduce both the symmetric and anti-symmetric waves, and the significant spectra of the MJO, Kelvin, and MRG waves are in agreement with observational data, indicating that the ability of GAMIL2.0 to simulate the MJO and other tropical waves is enhanced by improving the cloud microphysics and convective parameterization schemes and implying that such improvements are crucial to further improving this model's performance.
基金sponsored by the Special Scientific Research.Fund of Earthquake Public Welfare Prefession of China(201008007),CEA(02092408)the Sino-Italy Cooperation Project(2009DFA21480)
文摘Based on the IDP data from the French DEMETER satellite,global distribution is shown,which corresponds to three precipitation zones:the aural precipitation zone,the mid-high latitude precipitation zone and the South Atlantic precipitation zone.Then the Chili earthquake with M8.8 which occurred on February 27,2010 is taken as an example.The IDP fluxes from repeat orbits are compared and the results show that there is a clear enhancement on February 26,2010,just one day ahead of the Chili earthquake.In the south zone with L=2.1~2.7,the flux on February 26 is higher than that on previous days.However in the north zone with L=2.1~2.7,there is no clear change during the day but great enhancement during the night,which is close to the time of the earthquake.At the same time,the flux on February 26 near the equator is far lower than that on previous days.
基金This research was supported by the Nature Science Foundation of Hebei Province (D2005000176) and the Construction Projects of Key Disciplines in University of Hebei Province, China. The authors would like to thank the support of the Environment Monitoring Center of Shijiazhuang city, China.
文摘The particle size and shape measured by image analysis is helpful to discuss the human health effects of particulate beside the aerodynamic scale. To explore the size and shape features of particle suspended in the road environment, this research selected 12 bus stations as the sampling sites along the main road in the air polluted city Shijiazhuang, China, where a Car-Free Campaign had been carried out. We hung 2 slides covered with a layer of petroleum jelly to collect suspending particles for 24 hours at each sampling site, and measured the particles size and shape parameters with the Particle Size Analyzer of CIS-50. The results show that the average particle size by the equivalent area diameter is around 10 μm, the size distributions are multi-modal with wide span, demonstrating that coarse dust suspended on road derived from several particle sources. Most of the particles suspended are square or square-like in shape with rugged border. Compared the samples of ordinary days and of the Car-Free day, the size and shape features vary little, inferring the ineffective results for the particle control of the Campaign. There is certain relationship between particle size and shape. The number percent of PMs-E (particulate matter with equivalent area diameter beneath 5 pro) is positively correlative with the number percent of particles of square or square-like shape, and negatively correlative with that of round or round-like shape. This relationship pattern in the road environment is contrary to the situations in the upper atmosphere, inferring different transportation and source emission mechanism influences.
基金supported by the National Basic Research Program of China(Grant No.2015CB856106)the National Natural Science Foundation of China(Grant Nos.41304071,41425010)+2 种基金China Geological Survey Project(Grant No.12120114057301)the start-up research fund from the Institute of Geology of CAGSthe National‘Qian-Ren’Program for young scholars to ZHLI
文摘The subduction channel is defined as a planar to wedge-like area of variable size,internal structure and composition,which forms between the upper and lower plates during slab subduction into the mantle.The materials in the channel may experience complex pressure,temperature,stress and strain evolution,as well as strong fluid and melt activity.A certain amount of these materials may subduct to and later exhume from>100 km depth,forming high to ultra-high pressure rocks on the surface as widely discovered in nature.Rock deformation in the channel is strongly assisted by metamorphic fluids activities,which change composition and mechanical properties of rocks and thus affect their subduction and exhumation histories.In this study,we investigate the detailed structure and dynamics of both oceanic and continental subduction channels,by conducting highresolution petrological-thermomechanical numerical simulations taking into account fluid and melt activities.The numerical results demonstrate that subduction channels are composed of a tectonic rock melange formed by crustal rocks detached from the subducting slab and the hydrated mantle rocks scratched from the overriding plate.These rocks may either extrude sub-vertically upward through the mantle wedge to the crust of the upper plate,or exhume along the subduction channel to the surface near the suture zone.Based on our numerical results,we first analyze similarities and differences between oceanic and continental subduction channels.We further compare numerical models with and without fluid and melt activity and demonstrate that this activity results in strong weakening and deformation of overriding lithosphere.Finally,we show that fast convergence of orogens subjected to fluid and melt activity leads to strong deformation of the overriding lithosphere and the topography builds up mainly on the overriding plate.In contrast,slow convergence of such orogens leads to very limited deformation of the overriding lithosphere and the mountain building mainly occurs on the subducting plate.
基金supported by the National Basic Research Program of China(Grant Nos.2012CB957800,2011CB811400)the National Hi-Tech Research and Development Program of China(Grant No.2010AA121000)the National Natural Science Foundation of China(Grant Nos.41274147,41204102)
文摘Based on the auroral electron/ion precipitation boundary database observed by the DMSP satellites during 1984–2009, the characteristics of the nightside equatorial boundaries of the electron precipitation(B1E) and the ion precipitation(B1I) in the Northern/Southern Hemispheres(NH/SH) are statistically investigated. The results show: That most of the boundaries are located between magnetic latitude(MLAT) of 60°–70° with the mean MLAT for B1E/B1 I to be 64.30°N/63.22°N and 64.48°S/63.26°S in the NH and SH, respectively, indicating that B1 E and B1 I in both hemispheres are located in conjugated magnetic field lines with B1 E ~1.2° poleward of B1I; that the MLAT of B1 E and B1 I in both hemispheres shift to lower MLAT(from ~70° to ~55°) as geomagnetic activity increases; that MLAT of both B1 E and B1 I and their differences slowly decrease from dusk to midnight with some difference in both hemispheres during different levels of geomagnetic activities; that B1 E and B1 I in both hemisphere decrease linearly with Kp and exponentially with Dst, AE, and SYM-H, respectively, demonstrating that auroral particle precipitation is closely related with geomagnetic activity; that in different magnetic local time(MLT) sectors, the changing rates of the boundaries with Kp are different, and the rates of B1 E are generally larger than that of B1 I, implying that the difference between B1 E and B1 I reduce with increasing geomagnetic activity. Compared with previous studies, the statistical results based on the long-term large database in this paper can well reflect the properties of the equatorial boundaries of auroral precipitation and may be used for physical modeling or space weather forecasting in future.