Using the hydrographic data obtained during two nearly simultaneous surveys in June 2015,we carried out semi-diagnostic calculations with the help of a finite element model and a modified inverse method,to study the c...Using the hydrographic data obtained during two nearly simultaneous surveys in June 2015,we carried out semi-diagnostic calculations with the help of a finite element model and a modified inverse method,to study the circulation in the northern South China Sea(NSCS)during the early summer of 2015.A number of new circulation features were found.(1)In most of the observation region,a large,basin-scale anticyclonic gyre appeared south of the 50-m isobath,which contained anticyclonic eddies.One anticyclonic eddy existed from the sea surface to 50-m depth,whose center showed no tilt,while the center of another eddy tilted eastward from the sea surface to 500-m depth.In the eastern part of the observation region,which is west of the Dongsha Islands,there was a sub-basin-scale cyclonic gyre containing a cyclonic eddy whose center tilted southward from the sea surface to 200-m depth.(2)There was a cross-continental slope current(CCSC)in the area southwest of the Dongsha Islands.Its volume transport was about 2.0×10^(6) m^(3)/s.(3)From the estimated order of magnitude of the stream function equation,the joint effect term of the baroclinity and relief(JEBAR)andβ-effect term are two important dynamic mechanisms affecting the variation of the circulation in the NSCS.(4)The JEBAR,as a transport-generating term,resulted in the dynamic mechanism determining the pattern of the depth-averaged flow across the contours of potential vorticity fH–1.Furthermore,we show that the negative values of the JEBAR were the most dominant dynamic mechanism,causing the CCSC southwest of the Dongsha Islands to deflect from the isobaths and veer toward the deep water.The CCSC around the Dongsha Islands was located further southwest during the early summer of 2015 than during the fall of 2005(revealed by a published study),which suggests that the location of the CCSC around the Dongsha Islands may vary with season.展开更多
Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau l...Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau lake Erhai,China using accuracy wind field observation,runoff data and monthly algae data during 2022–2023.The model successfully reproduced the circulation characteristics of Erhai under prevailing wind directions.The results showed that the lake flow velocity in Lake Erhai is higher in winter than in summer,with lower velocities near shore particularly in the northern and central parts of the lake.There is a negative correlation between algal biomass and flow velocity(FV)in different zones,with lower FV favoring the accumulation of algal biomass,particularly for Microcystis,Dolichospermum,and Peridinium.Additionally,due to buoyancy,cyanobacteria are highly affected by wind direction and tend to accumulate in downwind regions of the prevailing wind direction.This study demonstrates that wind-induced circulation is a crucial factor affecting the spatial distribution of dominant algae populations in shallow plateau lakes with weak hydrodynamic force.Further,the risk of bloom occurrence in Lake Erhai will be higher due to the background of global climate change and the lake’s wind speed decline.In conclusion,we suggest implementing targeted zoning measures to control algal blooms and establishing stricter regulations for nitrogen and phosphorus control to counterbalance the promotion of algal bloom accumulation in low-velocity zones caused by reduced wind speed.展开更多
Under the strategic framework of rural revitalization and agricultural modernization, Xinjiashan Specialty Coffee Base, located in Zaotang Village, Lujiang Town, Longyang District, Baoshan City, has been proactively i...Under the strategic framework of rural revitalization and agricultural modernization, Xinjiashan Specialty Coffee Base, located in Zaotang Village, Lujiang Town, Longyang District, Baoshan City, has been proactively investigating innovative models for agricultural development. Through extensive communication and collaboration, this base has established close partnerships with research institutions including Kunming University of Science and Technology, Baoshan University, and Yunnan Academy of Agricultural Sciences, with a commitment to thoroughly exploring the potential for resource recycling and ecological complementarity. An innovative four-in-one three-dimensional integrated planting system incorporating "coffee, bananas, green manure, and bees" has been implemented. Concurrently, technological and digital management strategies have been comprehensively integrated to improve planting efficiency. Under this model, the proportion of specialty coffee attains 71%, and the per-unit yield is 17% greater than that of the conventional planting model. This approach not only substantially enhances economic returns but also promotes the integrated development of ecological and social benefits, offering a valuable practical example and experiential reference for the specialty and sustainable advancement of the coffee industry in comparable regions.展开更多
Aerial surveys are dynamic and continuous processes,and there are different height distributions of the ground in the measurement area,which leads to problems such as overlapping measurement areas and inaccurate altit...Aerial surveys are dynamic and continuous processes,and there are different height distributions of the ground in the measurement area,which leads to problems such as overlapping measurement areas and inaccurate altitude correction during the survey process.Commonly used terrain correction methods are based on the concept of finite elementization of ground surface radioactive sources,using GPS coordinates,radar altitude,and ground elevation distribution information from aerial surveys,combined with the sourceless efficiency calibration method to construct a response matrix,which is then inverted for surface nuclide content.However,most of the sourceless efficiency calibration methods used are numerical calculations that consider the body detector as a point detector and do not consider the changes in intrinsic detection efficiency under different incident directions of gamma rays.Therefore,when the altitude of the measurement area varies significantly or the flight altitude of the aerial survey is relatively low,such sourceless efficiency calibration method calculations tend to have a large bias,which affects the accuracy of the terrain correction.To address the above problems,this study employs a novel sourceless efficiency calibration method based on the Boolean operation of the ray deposition process and simplifies the traditional body source measurement model to a surface source measurement model to achieve fast and accurate efficiency calibration.Then,through the discretization of the measurement process,the static measurement process is superposed as equivalent to the dynamic measurement process,and the dynamic measurement response matrix is built and optimized based on the calibration method.Finally,the PSO-MLEM algorithm was used to solve the dynamic measurement response matrix to achieve dynamic terrain correction of aerial survey data.Analysis of the Baiyun'ebo test area revealed that,after applying dynamic terrain correction,the inverted anomalies in uranium(eU),thorium(eTh),and potassium(K)concentrations were closer to ground measurements(within 5.72%-30.79%)and exhibited clearer anomaly boundaries compared to traditional height-based corrections.However,owing to the inherent statistical fluctuations and characteristics of matrix inversion,higher measurement values tend to absorb lower ones,potentially enlarging the anomalous regions.Nevertheless,the highanomaly regions after inversion largely coincided with the ground truth validation,demonstrating that the proposed method can effectively correct airborne gamma spectrometry data.展开更多
Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both g...Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both global and regional climates.This study assesses the performance of models participating in phase 6 of the Coupled Model Intercomparison Project in simulating interannual variability modes of Northern Hemisphere 500-hPa geopotential height during winter and summer,distinguishing predictable(potentially predictable on seasonal or longer timescales)and unpredictable(intraseasonal and essentially unpredictable at long range)components,using reanalysis data and a variance decomposition method.Although most models effectively capture unpredictable modes in reanalysis,their ability to reproduce dominant predictable modes-specifically the Pacific-North American pattern,Arctic Oscillation,and Western Pacific Oscillation in winter,and the East Atlantic and North Atlantic Oscillations in summer-varies notably.An optimal ensemble is identified to distinguish(a)predictable-external modes,dominated by external forcing,and(b)predictable-internal modes,associated with slow internal variability,during the historical period(1950-2014)and the SSP5-8.5 scenario(2036-2100).Under increased radiative forcing,the leading winter/summer predictable-external mode exhibits a more uniform spatial distribution,remarkably larger trend and annual variance,and enhanced height-sea surface temperature(SST)covariance under SSP5-8.5 compared to historical conditions.The dominant winter/summer predictable-internal modes also exhibit increased variance and height-SST covariance under SSP5-8.5,along with localized changes in spatial configuration.Minimal changes are observed in spatial distribution or variance for dominant winter/summer unpredictable modes under SSP5-8.5.This study,from a predictive perspective,deepens our understanding of model uncertainties and projected changes in circulations.展开更多
Summer rainfall in the Yangtze River basin(YRB)is favored by two key factors in the lower troposphere:the tropical anticyclonic anomaly over the western North Pacific and the extratropical northeasterly anomalies to t...Summer rainfall in the Yangtze River basin(YRB)is favored by two key factors in the lower troposphere:the tropical anticyclonic anomaly over the western North Pacific and the extratropical northeasterly anomalies to the north of the YRB.This study,however,found that approximately 46%of heavy rainfall events in the YRB occur when only one factor appears and the other is opposite signed.Accordingly,these heavy rainfall events can be categorized into two types:the extratropical northeasterly anomalies but tropical cyclonic anomaly(first unconventional type),and the tropical anticyclonic anomaly but extratropical southwesterly anomalies(second unconventional type).Anomalous water vapor convergence and upward motion exists for both types,but through different mechanisms.For the first type,the moisture convergence and upward motion are induced by a cyclonic anomaly over the YRB,which appears in the mid and lower troposphere and originates from the upstream region.For the second type,a mid-tropospheric cyclonic anomaly over Lake Baikal extends southward and results in southwesterly anomalies over the YRB,in conjunction with the tropical anticyclonic anomaly.The southwesterly anomalies transport water vapor to the YRB and lead to upward motion through warm advection.This study emphasizes the role of mid-tropospheric circulations in inducing heavy rainfall in the YRB.展开更多
The present study compares the Atlantic Meridional Overturning Circulation(AMOC)in the North Atlantic from two simulations by an oceanic general circulation model with 1°×1°and 0.1°×0.1°r...The present study compares the Atlantic Meridional Overturning Circulation(AMOC)in the North Atlantic from two simulations by an oceanic general circulation model with 1°×1°and 0.1°×0.1°resolution,respectively,which explores the sensitivity of AMOC to the resolution.The ocean model is the latest version of the LASG/IAP Climate System Model(LICOM3),and it is forced with atmospheric data from phase 2 of the Ocean Model Intercomparison Project(OMIP2).Comprehensive comparison between the two simulations indicates that the simulated AMOC is highly sensitive to the spatial resolution.The high-resolution model(LICOM-H)simulates a deeper mixed-layer depth(MLD),due to increased surface salinity,than that in the low-resolution model(LICOML)in the Labrador Sea,and it also has stronger AMOC strength(the maximum climatic mean AMOC from 1958 to 2018 is 23.4 Sv for LICOM-H and 21.2 Sv for LICOM-L)and larger variability of AMOC index(2.3 Sv for LICOM-H and 1.7 Sv for LICOM-L).These differences can mainly be attributed to two main dynamic processes that benefit from high resolution.Firstly,LICOM-H can simulate much stronger boundary currents(~0.6 m s^(-1))than LICOM-L(0.3 m s^(-1))in the upper ocean,which leads to saltier and warmer seawater being transported to the Labrador Sea,where it enhances deep convection.Secondly,in LICOM-H,the stronger variability of AMOC is related to the higher sensitivity of the MLD and transformation to the prescribed atmospheric forcing in the Labrador Sea.展开更多
Clouds play an important role in global atmospheric energy and water vapor budgets, and the low cloud simulations suffer from large biases in many atmospheric general circulation models. In this study, cloud microphys...Clouds play an important role in global atmospheric energy and water vapor budgets, and the low cloud simulations suffer from large biases in many atmospheric general circulation models. In this study, cloud microphysical processes such as raindrop evaporation and cloud water accretion in a double-moment six-class cloud microphysics scheme were revised to enhance the simulation of low clouds using the Global-Regional Integrated Forecast System(GRIST)model. The validation of the revised scheme using a single-column version of the GRIST demonstrated a reasonable reduction in liquid water biases. The revised parameterization simulated medium-and low-level cloud fractions that were in better agreement with the observations than the original scheme. Long-term global simulations indicate the mitigation of the originally overestimated low-level cloud fraction and cloud-water mixing ratio in mid-to high-latitude regions,primarily owing to enhanced accretion processes and weakened raindrop evaporation. The reduced low clouds with the revised scheme showed better consistency with satellite observations, particularly at mid-and high-latitudes. Further improvements can be observed in the simulated cloud shortwave radiative forcing and vertical distribution of total cloud cover. Annual precipitation in mid-latitude regions has also improved, particularly over the oceans, with significantly increased large-scale and decreased convective precipitation.展开更多
According to the Mindlin plate theory and the first-order piston theory,this work obtains accurate closed-form eigensolutions for the flutter problem of three-dimensional(3D)rectangular laminated panels.The governing ...According to the Mindlin plate theory and the first-order piston theory,this work obtains accurate closed-form eigensolutions for the flutter problem of three-dimensional(3D)rectangular laminated panels.The governing differential equations are derived by the Hamilton's variational principle,and then solved by the iterative Separation-of-Variable(i SOV)method,which are applicable to arbitrary combinations of homogeneous Boundary Conditions(BCs).However,only the simply-support,clamped and cantilever panels are considered in this work for the sake of clarity.With the closed-form eigensolutions,the flutter frequency,flutter mode and flutter boundary are presented,and the effect of shear deformation and aerodynamic damping on flutter frequencies is investigated.Besides,the relation between panel energy and the work of aerodynamic load is discussed.The numerical comparisons reveal the following.(A)The flutter eigenvalues obtained by the present method are accurate,validated by the Finite Element Method(FEM)and the Galerkin method.(B)When the span-chord ratio is larger than 3,simplifying a 3D panel to 2D(two-dimensional)panel is reasonable and the relative differences of the flutter points predicted by the two models are less than one percent.(C)The reciprocal relationship between the mechanical energy of the panel and the work done by aerodynamic load is verified by using the present flutter eigenvalues and modes,further indicating the high accuracy of the present solutions.(D)The coupling of shear deformation and aerodynamic damping prevents frequency coalescing.展开更多
High-sulfur iron concentrates emit SO_(2)into the flue gas during pellet induration.To investigate the effect of the SO_(2)cycle on pellet quality in the grate-kiln process,sulfur balance analysis,thermodynamic calcul...High-sulfur iron concentrates emit SO_(2)into the flue gas during pellet induration.To investigate the effect of the SO_(2)cycle on pellet quality in the grate-kiln process,sulfur balance analysis,thermodynamic calculations,and pellet production experiments under simulated flue gas circulation conditions were conducted.The results indicated that SO_(2)circulation inhibited desulfurization and deteriorated pellet strength.SO_(2)absorption increased the pellet sulfur content to 0.70 wt.%during the downdraft drying phase,and the absorption could be aggravated by the moisture.The desulfurization rate of the preheating process was also decreased to 16.67%,resulting from the refractory sulfate generation.Sulfur content of the roasted pellets dropped to 0.13 wt.%because of the aluminosilicate generation.The finished pellet sulfur content further decreased to 0.08 wt.%due to the fresh air during the cooling process.Eventually,optimization measures were proposed when high-sulfur iron concentrates were used for oxidized pellet preparation.展开更多
Influenza A virus(IAV) has a wide host range,including wild birds,poultry,various mammals,and even humans(Xu et al.2024).Currently,two subtypes of canine influenza virus(CIV),H3N8 and H3N2,are primarily circulating in...Influenza A virus(IAV) has a wide host range,including wild birds,poultry,various mammals,and even humans(Xu et al.2024).Currently,two subtypes of canine influenza virus(CIV),H3N8 and H3N2,are primarily circulating in dogs.The H3N8 CIV was introduced from horses into dogs in 2004(Crawford et al.2005),while the H3N2 CIV originated from chickens in Asia in 2007(Song et al.2008).In China,H3N2 is the predominant CIV subtype,with a prevalence rate of up to 5.63% in the canine population,as reported by Chen et al.(2023).CIV infection typically manifests with symptoms such as coughing,sneezing,runny nose,and fever but is rarely fatal.However,co-infection with other pathogens(e.g.,Streptococcus,Mycoplasma or canine parainfluenza virus) can exacerbate symptoms and lead to lethal outcomes(Yondo et al.2023).展开更多
The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation （NPMOC） are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data....The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation （NPMOC） are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data. The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether. The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N, respectively, while the DTC and the subpolar cell are a weaker anticlockwise meridional cell between 3°N and 15°N and a weakest anticlockwise meridional cell between 35°N and 50°N, respectively. The DTC, the TC and the STC are all of very strong seasonal variations. As to the DTC, the southward transport is strongest in fall and weakest in spring. For the TC, the northward transport is strongest in winter and weakest in spring, while the southward transport is strongest in fall and weakest in spring, which is associated with the strong southward fiow of the DTC in fall. As the STC, the northward transport is strongest in winter and weakest in summer, while the southward transport is strongest in summer and weakest in spring. This seasonal difference may be associated with the DTC. The zonal wind stress and the east-west slope of sea level play important roles in the seasonal variations of the TC, the STC and the DTC.展开更多
The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results s...The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures: the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC.展开更多
A three-dimensional baroclinic shelf sea model’s numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a southward boundary cu...A three-dimensional baroclinic shelf sea model’s numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a southward boundary current exists along the east shore of the Indo-China Peninsula all year long. A cyclonic eddy (gyre) is formed by the current in the above sea areas except in the middle layer in spring, when an anticyclonic eddy exists on the eastern side of the current. In the deep layer, a large-scale anticyclonic eddy often exists in the sea areas between the Zhongsha Islands and west shore of southern Luzon Island. 2. In the middle layer in summer and autumn, and in the deep layer in autumn and winter, there is an anticyclonic eddy (gyre) in the northeastern SCS, while in the middle layer in winter and spring, and in the deep layer in spring and summer, there is a cyclonic one. 3. In the middle layer, there is a weak northeastward current in the Nansha Trough in spring and summer, while in autumn and winter it evolves into an anticyclonic eddy (gyre), which then spreads westward to the whole western Nansha Islands sea areas.展开更多
A three-dimensional density field associated with mesoscaie unstable waves generated by the 3-D, primitive-equation model (Wang and Ikeda, 1996) is provided to the quasi-geostrophic pressure tendency and ω-equations,...A three-dimensional density field associated with mesoscaie unstable waves generated by the 3-D, primitive-equation model (Wang and Ikeda, 1996) is provided to the quasi-geostrophic pressure tendency and ω-equations, and to the (ageostrophic) Q-vector equation. Diagnostic analyses, analogous to the approaches in meteorology: ω-equation and Q-vector method, are for the first time developed to examine the mesoscaie dynamical processes and mechanisms of the unstable waves propagating in the mid-latitude ocean. The weaknesses and strengths of these two diagnostic approaches are evaluated and compared to the model results. The Q-vector method is then recommended to diagnose the vertical motion associated with the mesoscaie dynamics from a hydrographic CTD (conductivity-temperature-depth) array, while the quasi-geostrophic equations produce some small-scale features (errors) in the diagnosed fields.展开更多
The hydrodynamic characteristics of a rigid, single, circular cylinder in a three dimensional, incompressible, uniform cross flow were calculated using the large-eddy simulation method of CFX5. Solutions to the three ...The hydrodynamic characteristics of a rigid, single, circular cylinder in a three dimensional, incompressible, uniform cross flow were calculated using the large-eddy simulation method of CFX5. Solutions to the three dimensional N-S equations were obtained by the finite volume method. The focus of this numerical simulation was to research the characteristics of pressure distribution （drag and litt forces） and vortex tubes at high Reynolds numbers. The results of the calculations showed that the forces at every section in the spanwise direction of the cylinder were symmetrical about the middle section and smaller than the forces calculated in two dimensional cases. Moreover, the flow around the cylinder obviously presents three dimensional characteristics.展开更多
During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to dril...During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to drilling fluids is the most common method for controlling lost circulation.Among these,granular LCMs are widely used,but the application frequency of flaky LCMs has been increasing annually due to their unique morphology.However,the migration and plugging behavior of flaky LCMs within fractures,and the mechanisms enhancing the pressure-bearing capacity of the plugging zone are not well understood.Therefore,this study conducted visual plugging experiments and dynamic fracture plugging experiments to evaluate the plugging mode and pressure-bearing capacity of the plugging slurry with various particle sizes and concentrations of flaky LCMs.The experimental results demonstrate that the fracture plugging process can be divided into four stages:uniform flow stage of the plugging slurry,formation and development stage of the bridging area,formation and development stage of the plugging area,and pressure-bearing stage of the plugging zone.The inclusion of flaky LCMs notably reduces the duration of stages 1 and 2,while simultaneously increasing the proportion of the plugging zone and enhancing its surface porosity.Flaky LCMs reduce the effective fracture width through“interception”and“co-bridging”modes,thus improving plugging zone formation efficiency.Appropriate particle size and concentration of flaky LCMs increase the area and length of the plugging zone.This reduces the fracture width increment caused by injection pressure and enhances frictional force between the plugging zone and fracture surface,thereby improving the pressure-bearing capacity of the plugging zone.However,excessively high concentrations of flaky LCMs result in decreased structural stability of the plugging zone,and excessively large particle sizes increase the risk of plugging outside fracture inlet.The recommended concentration of flaky LCMs in the plugging slurry is 2%–3%,with a particle size 1.2 to 1.5 times that of the bridging granular LCMs and not exceeding twice the fracture width.This study provides a theoretical foundation for selecting LCMs and designing plugging formulations for field applications.展开更多
The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic...The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.展开更多
To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D lea...To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.展开更多
基金The Joint Project of Guangxi-Provincial and China-National Natural Science Foundations under contract No.U20A20104the National Basic Research Program of China under contract No.2014CB441501+2 种基金the National Natural Science Foundation of China under contract Nos 41830540 and 42076216the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)under contract No.311020003the Project of State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,Ministry of Natural Resources,under contract Nos SOEDZZ2101 and SOEDZZ2003.
文摘Using the hydrographic data obtained during two nearly simultaneous surveys in June 2015,we carried out semi-diagnostic calculations with the help of a finite element model and a modified inverse method,to study the circulation in the northern South China Sea(NSCS)during the early summer of 2015.A number of new circulation features were found.(1)In most of the observation region,a large,basin-scale anticyclonic gyre appeared south of the 50-m isobath,which contained anticyclonic eddies.One anticyclonic eddy existed from the sea surface to 50-m depth,whose center showed no tilt,while the center of another eddy tilted eastward from the sea surface to 500-m depth.In the eastern part of the observation region,which is west of the Dongsha Islands,there was a sub-basin-scale cyclonic gyre containing a cyclonic eddy whose center tilted southward from the sea surface to 200-m depth.(2)There was a cross-continental slope current(CCSC)in the area southwest of the Dongsha Islands.Its volume transport was about 2.0×10^(6) m^(3)/s.(3)From the estimated order of magnitude of the stream function equation,the joint effect term of the baroclinity and relief(JEBAR)andβ-effect term are two important dynamic mechanisms affecting the variation of the circulation in the NSCS.(4)The JEBAR,as a transport-generating term,resulted in the dynamic mechanism determining the pattern of the depth-averaged flow across the contours of potential vorticity fH–1.Furthermore,we show that the negative values of the JEBAR were the most dominant dynamic mechanism,causing the CCSC southwest of the Dongsha Islands to deflect from the isobaths and veer toward the deep water.The CCSC around the Dongsha Islands was located further southwest during the early summer of 2015 than during the fall of 2005(revealed by a published study),which suggests that the location of the CCSC around the Dongsha Islands may vary with season.
基金supported by the Open Research Fund of Key Laboratory for Lake Pollution Control of the Ministry of Ecology and Environment(No.2024HPYKFZD04)the Fundamental Research Funds for the Central Publicinterest Scientific Institution(No.2025YSKY-04)the National Natural Science Foundation of China(Nos.U1902207 and 42207265).
文摘Wind-induced circulation is the main form of lake flow for shallow lakes and plays an important role in algae population distribution.This study constructed a three-dimensional hydrodynamic model(EFDC)of the plateau lake Erhai,China using accuracy wind field observation,runoff data and monthly algae data during 2022–2023.The model successfully reproduced the circulation characteristics of Erhai under prevailing wind directions.The results showed that the lake flow velocity in Lake Erhai is higher in winter than in summer,with lower velocities near shore particularly in the northern and central parts of the lake.There is a negative correlation between algal biomass and flow velocity(FV)in different zones,with lower FV favoring the accumulation of algal biomass,particularly for Microcystis,Dolichospermum,and Peridinium.Additionally,due to buoyancy,cyanobacteria are highly affected by wind direction and tend to accumulate in downwind regions of the prevailing wind direction.This study demonstrates that wind-induced circulation is a crucial factor affecting the spatial distribution of dominant algae populations in shallow plateau lakes with weak hydrodynamic force.Further,the risk of bloom occurrence in Lake Erhai will be higher due to the background of global climate change and the lake’s wind speed decline.In conclusion,we suggest implementing targeted zoning measures to control algal blooms and establishing stricter regulations for nitrogen and phosphorus control to counterbalance the promotion of algal bloom accumulation in low-velocity zones caused by reduced wind speed.
文摘Under the strategic framework of rural revitalization and agricultural modernization, Xinjiashan Specialty Coffee Base, located in Zaotang Village, Lujiang Town, Longyang District, Baoshan City, has been proactively investigating innovative models for agricultural development. Through extensive communication and collaboration, this base has established close partnerships with research institutions including Kunming University of Science and Technology, Baoshan University, and Yunnan Academy of Agricultural Sciences, with a commitment to thoroughly exploring the potential for resource recycling and ecological complementarity. An innovative four-in-one three-dimensional integrated planting system incorporating "coffee, bananas, green manure, and bees" has been implemented. Concurrently, technological and digital management strategies have been comprehensively integrated to improve planting efficiency. Under this model, the proportion of specialty coffee attains 71%, and the per-unit yield is 17% greater than that of the conventional planting model. This approach not only substantially enhances economic returns but also promotes the integrated development of ecological and social benefits, offering a valuable practical example and experiential reference for the specialty and sustainable advancement of the coffee industry in comparable regions.
基金supported by the National Key Research and Development Program(No.2022YFC2807400)the National Natural Science Foundation of China(Nos.12265003 and 12205044)。
文摘Aerial surveys are dynamic and continuous processes,and there are different height distributions of the ground in the measurement area,which leads to problems such as overlapping measurement areas and inaccurate altitude correction during the survey process.Commonly used terrain correction methods are based on the concept of finite elementization of ground surface radioactive sources,using GPS coordinates,radar altitude,and ground elevation distribution information from aerial surveys,combined with the sourceless efficiency calibration method to construct a response matrix,which is then inverted for surface nuclide content.However,most of the sourceless efficiency calibration methods used are numerical calculations that consider the body detector as a point detector and do not consider the changes in intrinsic detection efficiency under different incident directions of gamma rays.Therefore,when the altitude of the measurement area varies significantly or the flight altitude of the aerial survey is relatively low,such sourceless efficiency calibration method calculations tend to have a large bias,which affects the accuracy of the terrain correction.To address the above problems,this study employs a novel sourceless efficiency calibration method based on the Boolean operation of the ray deposition process and simplifies the traditional body source measurement model to a surface source measurement model to achieve fast and accurate efficiency calibration.Then,through the discretization of the measurement process,the static measurement process is superposed as equivalent to the dynamic measurement process,and the dynamic measurement response matrix is built and optimized based on the calibration method.Finally,the PSO-MLEM algorithm was used to solve the dynamic measurement response matrix to achieve dynamic terrain correction of aerial survey data.Analysis of the Baiyun'ebo test area revealed that,after applying dynamic terrain correction,the inverted anomalies in uranium(eU),thorium(eTh),and potassium(K)concentrations were closer to ground measurements(within 5.72%-30.79%)and exhibited clearer anomaly boundaries compared to traditional height-based corrections.However,owing to the inherent statistical fluctuations and characteristics of matrix inversion,higher measurement values tend to absorb lower ones,potentially enlarging the anomalous regions.Nevertheless,the highanomaly regions after inversion largely coincided with the ground truth validation,demonstrating that the proposed method can effectively correct airborne gamma spectrometry data.
基金supported by the National Natural Science Foundation of China(Grant Nos.U2342210 and 42275043)the National Institute of Natural Hazards,Ministry of Emergency Management of China(Grant Nos.J2223806,ZDJ2024-25 and ZDJ2025-34)。
文摘Climate models are essential for understanding past,present,and future changes in atmospheric circulation,with circulation modes providing key sources of seasonal predictability and prediction uncertainties for both global and regional climates.This study assesses the performance of models participating in phase 6 of the Coupled Model Intercomparison Project in simulating interannual variability modes of Northern Hemisphere 500-hPa geopotential height during winter and summer,distinguishing predictable(potentially predictable on seasonal or longer timescales)and unpredictable(intraseasonal and essentially unpredictable at long range)components,using reanalysis data and a variance decomposition method.Although most models effectively capture unpredictable modes in reanalysis,their ability to reproduce dominant predictable modes-specifically the Pacific-North American pattern,Arctic Oscillation,and Western Pacific Oscillation in winter,and the East Atlantic and North Atlantic Oscillations in summer-varies notably.An optimal ensemble is identified to distinguish(a)predictable-external modes,dominated by external forcing,and(b)predictable-internal modes,associated with slow internal variability,during the historical period(1950-2014)and the SSP5-8.5 scenario(2036-2100).Under increased radiative forcing,the leading winter/summer predictable-external mode exhibits a more uniform spatial distribution,remarkably larger trend and annual variance,and enhanced height-sea surface temperature(SST)covariance under SSP5-8.5 compared to historical conditions.The dominant winter/summer predictable-internal modes also exhibit increased variance and height-SST covariance under SSP5-8.5,along with localized changes in spatial configuration.Minimal changes are observed in spatial distribution or variance for dominant winter/summer unpredictable modes under SSP5-8.5.This study,from a predictive perspective,deepens our understanding of model uncertainties and projected changes in circulations.
基金supported by the National Natural Science Foundation of China(Grant No.42275041)the Hainan Province Science and Technology Special Fund(Grant No.SOLZSKY2025006).
文摘Summer rainfall in the Yangtze River basin(YRB)is favored by two key factors in the lower troposphere:the tropical anticyclonic anomaly over the western North Pacific and the extratropical northeasterly anomalies to the north of the YRB.This study,however,found that approximately 46%of heavy rainfall events in the YRB occur when only one factor appears and the other is opposite signed.Accordingly,these heavy rainfall events can be categorized into two types:the extratropical northeasterly anomalies but tropical cyclonic anomaly(first unconventional type),and the tropical anticyclonic anomaly but extratropical southwesterly anomalies(second unconventional type).Anomalous water vapor convergence and upward motion exists for both types,but through different mechanisms.For the first type,the moisture convergence and upward motion are induced by a cyclonic anomaly over the YRB,which appears in the mid and lower troposphere and originates from the upstream region.For the second type,a mid-tropospheric cyclonic anomaly over Lake Baikal extends southward and results in southwesterly anomalies over the YRB,in conjunction with the tropical anticyclonic anomaly.The southwesterly anomalies transport water vapor to the YRB and lead to upward motion through warm advection.This study emphasizes the role of mid-tropospheric circulations in inducing heavy rainfall in the YRB.
基金supported by the National Natural Science Foundation of China [grant number 92358302]。
文摘The present study compares the Atlantic Meridional Overturning Circulation(AMOC)in the North Atlantic from two simulations by an oceanic general circulation model with 1°×1°and 0.1°×0.1°resolution,respectively,which explores the sensitivity of AMOC to the resolution.The ocean model is the latest version of the LASG/IAP Climate System Model(LICOM3),and it is forced with atmospheric data from phase 2 of the Ocean Model Intercomparison Project(OMIP2).Comprehensive comparison between the two simulations indicates that the simulated AMOC is highly sensitive to the spatial resolution.The high-resolution model(LICOM-H)simulates a deeper mixed-layer depth(MLD),due to increased surface salinity,than that in the low-resolution model(LICOML)in the Labrador Sea,and it also has stronger AMOC strength(the maximum climatic mean AMOC from 1958 to 2018 is 23.4 Sv for LICOM-H and 21.2 Sv for LICOM-L)and larger variability of AMOC index(2.3 Sv for LICOM-H and 1.7 Sv for LICOM-L).These differences can mainly be attributed to two main dynamic processes that benefit from high resolution.Firstly,LICOM-H can simulate much stronger boundary currents(~0.6 m s^(-1))than LICOM-L(0.3 m s^(-1))in the upper ocean,which leads to saltier and warmer seawater being transported to the Labrador Sea,where it enhances deep convection.Secondly,in LICOM-H,the stronger variability of AMOC is related to the higher sensitivity of the MLD and transformation to the prescribed atmospheric forcing in the Labrador Sea.
基金National Natural Science Foundation of China(42375153,42105153,42205157)Development of Science and Technology at Chinese Academy of Meteorological Sciences(2023KJ038)。
文摘Clouds play an important role in global atmospheric energy and water vapor budgets, and the low cloud simulations suffer from large biases in many atmospheric general circulation models. In this study, cloud microphysical processes such as raindrop evaporation and cloud water accretion in a double-moment six-class cloud microphysics scheme were revised to enhance the simulation of low clouds using the Global-Regional Integrated Forecast System(GRIST)model. The validation of the revised scheme using a single-column version of the GRIST demonstrated a reasonable reduction in liquid water biases. The revised parameterization simulated medium-and low-level cloud fractions that were in better agreement with the observations than the original scheme. Long-term global simulations indicate the mitigation of the originally overestimated low-level cloud fraction and cloud-water mixing ratio in mid-to high-latitude regions,primarily owing to enhanced accretion processes and weakened raindrop evaporation. The reduced low clouds with the revised scheme showed better consistency with satellite observations, particularly at mid-and high-latitudes. Further improvements can be observed in the simulated cloud shortwave radiative forcing and vertical distribution of total cloud cover. Annual precipitation in mid-latitude regions has also improved, particularly over the oceans, with significantly increased large-scale and decreased convective precipitation.
基金support of the National Natural Science Foundation of China(No.12172023)。
文摘According to the Mindlin plate theory and the first-order piston theory,this work obtains accurate closed-form eigensolutions for the flutter problem of three-dimensional(3D)rectangular laminated panels.The governing differential equations are derived by the Hamilton's variational principle,and then solved by the iterative Separation-of-Variable(i SOV)method,which are applicable to arbitrary combinations of homogeneous Boundary Conditions(BCs).However,only the simply-support,clamped and cantilever panels are considered in this work for the sake of clarity.With the closed-form eigensolutions,the flutter frequency,flutter mode and flutter boundary are presented,and the effect of shear deformation and aerodynamic damping on flutter frequencies is investigated.Besides,the relation between panel energy and the work of aerodynamic load is discussed.The numerical comparisons reveal the following.(A)The flutter eigenvalues obtained by the present method are accurate,validated by the Finite Element Method(FEM)and the Galerkin method.(B)When the span-chord ratio is larger than 3,simplifying a 3D panel to 2D(two-dimensional)panel is reasonable and the relative differences of the flutter points predicted by the two models are less than one percent.(C)The reciprocal relationship between the mechanical energy of the panel and the work done by aerodynamic load is verified by using the present flutter eigenvalues and modes,further indicating the high accuracy of the present solutions.(D)The coupling of shear deformation and aerodynamic damping prevents frequency coalescing.
基金supported by the Science and Technology Innovation Program of Hunan Province(Nos.2023RC1025 and 2024RC3022)the Technology Special Program Project of China Minmetals Corporation(No.2021ZXA04)the Major Scientific Research Projects of Inner Mongolia Baotou Steel Union Co.,Ltd.(No.HKF202300356).
文摘High-sulfur iron concentrates emit SO_(2)into the flue gas during pellet induration.To investigate the effect of the SO_(2)cycle on pellet quality in the grate-kiln process,sulfur balance analysis,thermodynamic calculations,and pellet production experiments under simulated flue gas circulation conditions were conducted.The results indicated that SO_(2)circulation inhibited desulfurization and deteriorated pellet strength.SO_(2)absorption increased the pellet sulfur content to 0.70 wt.%during the downdraft drying phase,and the absorption could be aggravated by the moisture.The desulfurization rate of the preheating process was also decreased to 16.67%,resulting from the refractory sulfate generation.Sulfur content of the roasted pellets dropped to 0.13 wt.%because of the aluminosilicate generation.The finished pellet sulfur content further decreased to 0.08 wt.%due to the fresh air during the cooling process.Eventually,optimization measures were proposed when high-sulfur iron concentrates were used for oxidized pellet preparation.
基金supported by the National Key Research and Development Program of China (2021YFD1800200)the National Natural Science Foundation of China (32170539)。
文摘Influenza A virus(IAV) has a wide host range,including wild birds,poultry,various mammals,and even humans(Xu et al.2024).Currently,two subtypes of canine influenza virus(CIV),H3N8 and H3N2,are primarily circulating in dogs.The H3N8 CIV was introduced from horses into dogs in 2004(Crawford et al.2005),while the H3N2 CIV originated from chickens in Asia in 2007(Song et al.2008).In China,H3N2 is the predominant CIV subtype,with a prevalence rate of up to 5.63% in the canine population,as reported by Chen et al.(2023).CIV infection typically manifests with symptoms such as coughing,sneezing,runny nose,and fever but is rarely fatal.However,co-infection with other pathogens(e.g.,Streptococcus,Mycoplasma or canine parainfluenza virus) can exacerbate symptoms and lead to lethal outcomes(Yondo et al.2023).
基金Supported by the National Basic Research Development Program of China(973 Program)under contract Nos 2007CB816002,2007CB816005the innovative key project of Chinese Academy of Sciences under contract No.KZCXZ-YW-201
文摘The three-dimensional structure and the seasonal variation of the North Pacific meridional overturning circulation （NPMOC） are analyzed based on the Simple Ocean Data Assimilation data and Argo profiling float data. The NPMOC displays a multi-cell structure with four cells in the North Pacific altogether. The TC and the STC are a strong clockwise meridional cell in the low latitude ocean and a weaker clockwise meridional cell between 7°N and 18°N, respectively, while the DTC and the subpolar cell are a weaker anticlockwise meridional cell between 3°N and 15°N and a weakest anticlockwise meridional cell between 35°N and 50°N, respectively. The DTC, the TC and the STC are all of very strong seasonal variations. As to the DTC, the southward transport is strongest in fall and weakest in spring. For the TC, the northward transport is strongest in winter and weakest in spring, while the southward transport is strongest in fall and weakest in spring, which is associated with the strong southward fiow of the DTC in fall. As the STC, the northward transport is strongest in winter and weakest in summer, while the southward transport is strongest in summer and weakest in spring. This seasonal difference may be associated with the DTC. The zonal wind stress and the east-west slope of sea level play important roles in the seasonal variations of the TC, the STC and the DTC.
基金supported by the National Basic Research Program of China(973 Program,Grant No.2012CB417404)
文摘The decadal variability of the North Atlantic thermohaline circulation(THC) is investigated within a three-dimensional ocean circulation model using the conditional nonlinear optimal perturbation method. The results show that the optimal initial perturbations of temperature and salinity exciting the strongest decadal THC variations have similar structures: the perturbations are mainly in the northwestern basin at a depth ranging from 1500 to 3000 m. These temperature and salinity perturbations act as the optimal precursors for future modifications of the THC, highlighting the importance of observations in the northwestern basin to monitor the variations of temperature and salinity at depth. The decadal THC variation in the nonlinear model initialized by the optimal salinity perturbations is much stronger than that caused by the optimal temperature perturbations, indicating that salinity variations might play a relatively important role in exciting the decadal THC variability. Moreover, the decadal THC variations in the tangent linear and nonlinear models show remarkably different characteristics, suggesting the importance of nonlinear processes in the decadal variability of the THC.
文摘A three-dimensional baroclinic shelf sea model’s numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a southward boundary current exists along the east shore of the Indo-China Peninsula all year long. A cyclonic eddy (gyre) is formed by the current in the above sea areas except in the middle layer in spring, when an anticyclonic eddy exists on the eastern side of the current. In the deep layer, a large-scale anticyclonic eddy often exists in the sea areas between the Zhongsha Islands and west shore of southern Luzon Island. 2. In the middle layer in summer and autumn, and in the deep layer in autumn and winter, there is an anticyclonic eddy (gyre) in the northeastern SCS, while in the middle layer in winter and spring, and in the deep layer in spring and summer, there is a cyclonic one. 3. In the middle layer, there is a weak northeastward current in the Nansha Trough in spring and summer, while in autumn and winter it evolves into an anticyclonic eddy (gyre), which then spreads westward to the whole western Nansha Islands sea areas.
文摘A three-dimensional density field associated with mesoscaie unstable waves generated by the 3-D, primitive-equation model (Wang and Ikeda, 1996) is provided to the quasi-geostrophic pressure tendency and ω-equations, and to the (ageostrophic) Q-vector equation. Diagnostic analyses, analogous to the approaches in meteorology: ω-equation and Q-vector method, are for the first time developed to examine the mesoscaie dynamical processes and mechanisms of the unstable waves propagating in the mid-latitude ocean. The weaknesses and strengths of these two diagnostic approaches are evaluated and compared to the model results. The Q-vector method is then recommended to diagnose the vertical motion associated with the mesoscaie dynamics from a hydrographic CTD (conductivity-temperature-depth) array, while the quasi-geostrophic equations produce some small-scale features (errors) in the diagnosed fields.
文摘The hydrodynamic characteristics of a rigid, single, circular cylinder in a three dimensional, incompressible, uniform cross flow were calculated using the large-eddy simulation method of CFX5. Solutions to the three dimensional N-S equations were obtained by the finite volume method. The focus of this numerical simulation was to research the characteristics of pressure distribution （drag and litt forces） and vortex tubes at high Reynolds numbers. The results of the calculations showed that the forces at every section in the spanwise direction of the cylinder were symmetrical about the middle section and smaller than the forces calculated in two dimensional cases. Moreover, the flow around the cylinder obviously presents three dimensional characteristics.
基金support from the National Natural Science Foundation of China(Grant No.52274009).
文摘During drilling operations in deep fractured tight gas reservoirs,lost circulation of working fluid frequently occurs due to the formationʼs low pressure-bearing capacity.Adding lost circulation materials(LCMs)to drilling fluids is the most common method for controlling lost circulation.Among these,granular LCMs are widely used,but the application frequency of flaky LCMs has been increasing annually due to their unique morphology.However,the migration and plugging behavior of flaky LCMs within fractures,and the mechanisms enhancing the pressure-bearing capacity of the plugging zone are not well understood.Therefore,this study conducted visual plugging experiments and dynamic fracture plugging experiments to evaluate the plugging mode and pressure-bearing capacity of the plugging slurry with various particle sizes and concentrations of flaky LCMs.The experimental results demonstrate that the fracture plugging process can be divided into four stages:uniform flow stage of the plugging slurry,formation and development stage of the bridging area,formation and development stage of the plugging area,and pressure-bearing stage of the plugging zone.The inclusion of flaky LCMs notably reduces the duration of stages 1 and 2,while simultaneously increasing the proportion of the plugging zone and enhancing its surface porosity.Flaky LCMs reduce the effective fracture width through“interception”and“co-bridging”modes,thus improving plugging zone formation efficiency.Appropriate particle size and concentration of flaky LCMs increase the area and length of the plugging zone.This reduces the fracture width increment caused by injection pressure and enhances frictional force between the plugging zone and fracture surface,thereby improving the pressure-bearing capacity of the plugging zone.However,excessively high concentrations of flaky LCMs result in decreased structural stability of the plugging zone,and excessively large particle sizes increase the risk of plugging outside fracture inlet.The recommended concentration of flaky LCMs in the plugging slurry is 2%–3%,with a particle size 1.2 to 1.5 times that of the bridging granular LCMs and not exceeding twice the fracture width.This study provides a theoretical foundation for selecting LCMs and designing plugging formulations for field applications.
基金supported by the National Natural Science Foundation of China(42250101,42250102)the Macao Foundation.
文摘The movement of global ocean circulation in the Earth’s main magnetic field generates a measurable induced magnetic field(about 2 nT at geomagnetic satellite altitudes).However,this ocean circulation-induced magnetic field has not been previously estimated or incorporated into geomagnetic field models,potentially causing leakage into the core field model.Here,we present a method to account for the circulation-induced magnetic field during geomagnetic field modeling.First,a forward model of the circulation-induced magnetic field is constructed by numerically solving electromagnetic induction equations based on a realistic ocean circulation model.Then,this forward model is subtracted from the observed data.Finally,the core and lithospheric fields,magnetospheric and Earth’s mantle-induced fields,and the ocean tide-induced magnetic field are co-estimated.Applying our method to over 20 years of MSS-1,Swarm,CryoSat-2,and CHAMP satellite magnetic data,we derive a new multisource geomagnetic field model(MGFM).We find that incorporating a forward model of the circulation-induced magnetic field marginally improves the fit to the data.Furthermore,we demonstrate that neglecting the circulation-induced magnetic field in geomagnetic field modeling results in leakage into the core field model.The highlights of the MGFM model include:(i)a good agreement with the widely used CHAOS model series;(ii)the incorporation of magnetic fields induced by both ocean tides and circulation;and(iii)the suppression of leakage of the circulation-induced magnetic field into the core field model.
文摘To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.
