Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative cont...Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative contributions to the overall evolution of rifting margins and possible roles in the formation of microcontinent are still elusive.Here,we use coupled geodynamic and surface processes numerical modeling to assess the extent to which surface processes may determine the formation of microcontinent during lithospheric stretching in presence or absence of a mantle plume underneath.Our modeling results indicate that fast extension rates and hillslope(i.e.,diffusion)erosion promote ridge jump events and therefore the formation of microcontinents.On the contrary,efficient fluvial erosion and far-reaching sediment transport(i.e.,stream power erosion)inhibits ridge jump events and the formation of microcontinents.The ridge jump event and overall evolution in our numerical models is consistent with the shift from the Mascarene Ridge to the Carlsberg Ridge that determined the formation of the Seychelles microcontinent.We therefore speculate that hillslope erosion,rather than fluvial erosion,was predominant during the formation of the Seychelles,a possible indication of overall dry local climate conditions.展开更多
The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for...The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for the first time a suite of columnar basalts from the Mesoarchean Coorg Block in the Southern Granulite Terrain(SGT)of India and characterize these rocks through field,petrological,geo-chemical,and isotope geochronological studies.The basalts show porphyritic texture with phenocrysts of pyroxene and plagioclase embedded in fine groundmass.Geochemical data reveal tholeiitic flood basalt affinity with affinities of plume-related magmatism.The zircon U-Pb data of the rocks yield a weighted mean age of 137 Ma,thus corresponding to the Valanginian Age of the Early Cretaceous Period.We suggest the possible geochemical affinity of the studied rocks Kerguelen plume basalts which provide new insights into magmatism associated with the final stages of East Gondwana rifting.展开更多
A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associate...A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.展开更多
The existing deep-sea sediment plume tests are mostly under small-scale static water and rarely under large-scale flowing water conditions.In this study,large-scale tank experiments of flowing water were designed and ...The existing deep-sea sediment plume tests are mostly under small-scale static water and rarely under large-scale flowing water conditions.In this study,large-scale tank experiments of flowing water were designed and conducted to investigate the morphological characteristics and concentration evolution of the sediment plumes under different discharge rates(Q)and initial sediment concentrations(c).Viscosity tests,resuspension tests and free settling tests of the sediment solution with different c values were performed to reveal the settling mechanism of the plume diffusion process.The results show that the plume diffusion morphology variation in flowing water has four stages and the plume concentration evolution has three stages.The larger the Q,the smaller the initial incidence angle at the discharge outlet,the larger the diffusion range,the poorer the stability and the more complicated the diffusion morphology.The larger the c,the larger the settling velocity,the faster the formation of high-concentration accumulation zone,the better the stability and the clearer the diffusion boundary.The research results could provide experimental data for assessing the impact of deep-sea mining on the ocean environment.展开更多
The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and alti...The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and altitude control.In this study,an ionic liquid electrospray thruster with a 100-tip emitter configuration is tested primarily to examine the difference in performance of the thruster at different angles with time-of-flight(TOF)mass spectrometry tests.In the experiment,it was measured that the half-angle of the thruster plume angle emission was in the range of−60 degrees to+65 degrees.Accordingly,the measurement range was set from−50 degrees to+50 degrees,with an interval of 10 degrees.Relative to the results of the 0 degree current curve,the positive mode is relatively homogeneous at all angles of the operating mode.In the negative mode,for n 2 ions,the negative angle region accounts for a larger proportion and the positive angle region accounts for a smaller proportion,which makes a significant difference to the specific impulse of the two regions.The range of the specific impulse at different angles is 3776-4401 s under the typical working condition of+2.5 kV.Under−2.5 kV,the range of the specific impulse at different angles is 3309-4654 s.This research quantifies the angular performance variations of the ionic liquid electrospray thruster,offering valuable data to improve its design and operational reliability for precise propulsion and altitude control in satellite applications.展开更多
Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Xizang.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137...Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Xizang.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.展开更多
Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et ...Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.展开更多
Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the c...Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.展开更多
A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(...A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.展开更多
Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the poten...Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.展开更多
Industrial activities, through the human-induced release of Green House Gas (GHG) emissions, have beenidentified as the primary cause of global warming. Accurate and quantitative monitoring of these emissions isessent...Industrial activities, through the human-induced release of Green House Gas (GHG) emissions, have beenidentified as the primary cause of global warming. Accurate and quantitative monitoring of these emissions isessential for a comprehensive understanding of their impact on the Earth’s climate and for effectively enforcingemission regulations at a large scale. This work examines the feasibility of detecting and quantifying industrialsmoke plumes using freely accessible geo-satellite imagery. The existing systemhas so many lagging factors such aslimitations in accuracy, robustness, and efficiency and these factors hinder the effectiveness in supporting timelyresponse to industrial fires. In this work, the utilization of grayscale images is done instead of traditional colorimages for smoke plume detection. The dataset was trained through a ResNet-50 model for classification and aU-Net model for segmentation. The dataset consists of images gathered by European Space Agency’s Sentinel-2 satellite constellation from a selection of industrial sites. The acquired images predominantly capture scenesof industrial locations, some of which exhibit active smoke plume emissions. The performance of the abovementionedtechniques and models is represented by their accuracy and IOU (Intersection-over-Union) metric.The images are first trained on the basic RGB images where their respective classification using the ResNet-50model results in an accuracy of 94.4% and segmentation using the U-Net Model with an IOU metric of 0.5 andaccuracy of 94% which leads to the detection of exact patches where the smoke plume has occurred. This work hastrained the classification model on grayscale images achieving a good increase in accuracy of 96.4%.展开更多
Laser powder bed fusion(LPBF)is a highly dynamic and complex physical process,and single-track de-fects tend to accumulate into non-negligible internal defects of parts.The nickel-based superalloy single track was fab...Laser powder bed fusion(LPBF)is a highly dynamic and complex physical process,and single-track de-fects tend to accumulate into non-negligible internal defects of parts.The nickel-based superalloy single track was fabricated by LPBF,and its plume and spattering behavior were monitored in situ and recorded in real time based on image recognition and tracking in this study.The relationship among laser energy density,melt flow,plume and spattering behavior during LPBF was discussed.Volumetric energy density had limitations as a design parameter for LPBF.However,we found that plume and spattering behavior can be used as real-time design parameters for the processing of LPBF parts and implemented the initial velocity statistics for LPBF single-track spattering based on the centroid extraction algorithm.The influ-ence of melt flow evolution paths on the spattering and plume behavior in three different melting modes was revealed,and a shift in plume behavior was found in the overlap region of the additive substrate.This study provides a new method for obtaining statistics of spattering-related physical quantities in the melting mode,which is beneficial for the development of processing methods to mitigate the instability of the LPBF process.展开更多
The present investigation centers on the impact of viscous dissipation and ohmic heating on the plume generated by a line heat source under the impact of an aligned magnetic field.In this study,the flow model is adapt...The present investigation centers on the impact of viscous dissipation and ohmic heating on the plume generated by a line heat source under the impact of an aligned magnetic field.In this study,the flow model is adapted to incorporate ohmic heating and viscous dissipation by including the respective terms in the energy equation.A mathematical model is formulated as a system of coupled partial differential equations to analyze the flow problem.Subsequently,a numerical solution is derived with stream function formulation for the system of coupled partial differential equations,which transmutes it into ordinary differential equations.To achieve this,the numerical properties of the problem are established through the utilization of the Shooting method in tandem with the MATLAB tool bvp4c.The graphical representations of both missing and specified boundary conditions depict the effects of the magnetic parameter,viscous dissipation variable,magnetic force parameter,Prandtl number,and magnetic Prandtl number.These are accompanied by a discussion of their respective physical implications.The observed results claimed that the velocity,current density,and temperature distribution decrease for enhancing magnetic parameters.Meanwhile,the skin friction and magnetic flux drop while the heat transfer rate increases with an increment in magnetic parameters.These fluid flow and heat transfer characteristics were observed to decrease for increasing viscous dissipation.The current work is novel in incorporating ohmic heating viscous dissipation in energy equations coupled with Max-well and magnetic induction equations.展开更多
In Earth’s mantle,gravity instabilities initiated by density inversion lead to upwelling of hot materials as plumes.This study focuses upon the ascent dynamics of plumes to provide an explanation of the periodic mult...In Earth’s mantle,gravity instabilities initiated by density inversion lead to upwelling of hot materials as plumes.This study focuses upon the ascent dynamics of plumes to provide an explanation of the periodic multiple eruption events in large igneous provinces(LIP)and hotspots.We demonstrate that depending on physical conditions,plumes can either ascend in a continuous process with a single,large head trailing into a long slender tail,or alternatively,they ascend in a pulsating fashion producing multiple inaxis heads.Based on the Volume of Fluid(VOF)method,we performed computational fluid dynamics(CFD)simulations to constrain the thermo-mechanical conditions that decide the continuous versus pulsating dynamics.The simulations suggest the density(ρ^(*))and the viscosity(R)ratios of the ambient to the plume and the influx rates(Re)are the prime factors in controlling the ascent dynamics.The simulations could also predict thermal events near the surface causing eruption periodically as pulses.The pulsating plume model explains the multiple eruption events in different LIPs and our simulation results predict that variation in the temperature of the source layer can cause a range of timescale for this periodicity.展开更多
This paper presents a computational model of simulating a deep-sea hydrothermal plume based on a Lagrangian particle random walk algorithm. This model achieves the efficient process to calculate a numerical plume deve...This paper presents a computational model of simulating a deep-sea hydrothermal plume based on a Lagrangian particle random walk algorithm. This model achieves the efficient process to calculate a numerical plume developed in a fluid-advected environment with the characteristics such as significant filament intermittency and significant plume meander due to flow variation with both time and location. Especially, this model addresses both non-buoyant and buoyant features of a deep-sea hydrothermal plume in three dimensions, which significantly challenge a strategy for tracing the deep-sea hydrothermal plume and localizing its source. This paper also systematically discusses stochastic initial and boundary conditions that are critical to generate a proper numerical plume. The developed model is a powerful tool to evaluate and optimize strategies for the tracking of a deep-sea hydrothermal plume via an autonomous underwater vehicle （AUV）.展开更多
Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Ch...Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.展开更多
Aim To investigate the effects of the incident orientation on the microwave attenuation. Methods Attenuation allowing microwave signal transmitting in an oblique or vertical direction through the solid propellant ex...Aim To investigate the effects of the incident orientation on the microwave attenuation. Methods Attenuation allowing microwave signal transmitting in an oblique or vertical direction through the solid propellant exhaust plume was computed, and the experiments were performed utilizing a lab scale solid rocket motor with a fully expanded nozzle. Results The predicted results accord well with the experimental results. Conclusion The microwave attenuation in the oblique path is greater than that in the vertical path.展开更多
Recent space geodetic and gravimetric studies have given indications that the Earth’s radius is increasing at 0.1-0.4 mm yr-1 at present. Seismic studies have also shown that earthquakes alone could be causing the ra...Recent space geodetic and gravimetric studies have given indications that the Earth’s radius is increasing at 0.1-0.4 mm yr-1 at present. Seismic studies have also shown that earthquakes alone could be causing the radius to increase at 0.011-0.06 mm yr-1. Deep mantle plumes provide a geophysical context within which such radial expansion, if confirmed, could possibly be explained. Both theory and observation suggest that these rising plumes more readily penetrate the 670 km barrier than do subducting slabs moving in the opposite direction towards the core-mantle boundary. If so, there would be a net flow of mass from the deep lower mantle into the upper mantle. Due to the lower pressures in the upper mantle,the excess mass of plume materials reaching there would transform to minerals with lower densities than they had at the mantle base. An increase in the mantle volume and the Earth’s radius would therefore be implied. Using previously published data for the African superplume. it is estimated that this mechanism could cause the Earth’s radius to increase at rates of 0.02-0.3 mm yr-1, similar to the rates possibly indicated in the present studies. This mechanism could also explain the very large range in current estimates of mantle plume heat and volume fluxes. A possible energy source for this plumedriven mode of expansion is discussed.展开更多
Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been ...Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.展开更多
An improved near far field divided coupled method was established to investigate the electromagnetic properties of mildly overexpanded and underexpanded rocket exhaust plumes. Firstly, axisymmetric Navier Stokes eq...An improved near far field divided coupled method was established to investigate the electromagnetic properties of mildly overexpanded and underexpanded rocket exhaust plumes. Firstly, axisymmetric Navier Stokes equations incorporated with k ε two equation turbulence models were solved using time dependent approach to calculate the pressure of the near filed. Secondly, parabolized axisymmetric Navier Stokes equations incorporated with finite rate chemical kinetics models were marching on the detailed pressure map of the near field. The termination of the near field would yield the initial line for the far field. In addition, in the far field, the spatial marching method was directly used under the constant pressure condition, but considering more complicated chemically reacting process. Finally, the electromagnetic parameters of the whole plume were calculated with the electron conductive model. The calculated results of the overexpanded and underexpanded rocket exhaust plume were discussed. The predicted microwave attenuation accorded with the experimental results. This improved method is feasible for calculating the microwave attenuation characteristics of mildly non fully expanded rocket exhaust plumes.展开更多
基金financially supported by the National Science Foundation of China(No.41920104010)the China Postdoctoral Science Foundation(No.2024M762767)+3 种基金the Fundamental Research Funds for the Central University,CHD(No.300102264104)by the Postdoctoral Fellowship Program of CPSF(No.GZC20241444)supported by Fondazione Cariplo and Fondazione CDP(No.2022-1546_001)by the Italian Ministry of Education,MUR(Project Dipartimenti di Eccellenza,TECLA,Department of Earth and Environmental Sciences,University of Milano-Bicocca)。
文摘Mantle plumes and surface erosion and sediment deposition affect the modes of continental lithospheric rupturing in extensional tectonic settings,modulating the evolution of rifting margins.However,their relative contributions to the overall evolution of rifting margins and possible roles in the formation of microcontinent are still elusive.Here,we use coupled geodynamic and surface processes numerical modeling to assess the extent to which surface processes may determine the formation of microcontinent during lithospheric stretching in presence or absence of a mantle plume underneath.Our modeling results indicate that fast extension rates and hillslope(i.e.,diffusion)erosion promote ridge jump events and therefore the formation of microcontinents.On the contrary,efficient fluvial erosion and far-reaching sediment transport(i.e.,stream power erosion)inhibits ridge jump events and the formation of microcontinents.The ridge jump event and overall evolution in our numerical models is consistent with the shift from the Mascarene Ridge to the Carlsberg Ridge that determined the formation of the Seychelles microcontinent.We therefore speculate that hillslope erosion,rather than fluvial erosion,was predominant during the formation of the Seychelles,a possible indication of overall dry local climate conditions.
基金supported by the“Startup Grant for the University Teachers”of the University of Kerala.
文摘The role of mantle plume in the final stages of rifting of the East Gondwana crustal fragments remains equivocal with only limited evidence so far reported from the southern part of Peninsular India.Here,we report for the first time a suite of columnar basalts from the Mesoarchean Coorg Block in the Southern Granulite Terrain(SGT)of India and characterize these rocks through field,petrological,geo-chemical,and isotope geochronological studies.The basalts show porphyritic texture with phenocrysts of pyroxene and plagioclase embedded in fine groundmass.Geochemical data reveal tholeiitic flood basalt affinity with affinities of plume-related magmatism.The zircon U-Pb data of the rocks yield a weighted mean age of 137 Ma,thus corresponding to the Valanginian Age of the Early Cretaceous Period.We suggest the possible geochemical affinity of the studied rocks Kerguelen plume basalts which provide new insights into magmatism associated with the final stages of East Gondwana rifting.
基金supported by grant D86-RALMI23CIVIE_01 awarded by the Italian Ministry of University and Research under the Program for Young Researchers“Rita Levi Montalcini”.
文摘A wide northeast-trending belt of intraplate alkaline volcanism,exhibiting similar geochemical characteristics,stretches from the Eastern Atlantic Ocean to the Cenozoic rift system in Europe.Its formation is associated with both passive and active mechanisms,but it remains a source of ongoing debate among geoscientists.Here,we show that seismic whole-mantle tomography models consistently identify two extensive low-velocity anomalies beneath the Canary Islands(CEAA)and Western-Central Europe(ECRA)at mid-mantle depths,merging near the core-mantle boundary.These low-velocity features are interpreted as two connected broad plumes originating from the top of the African LLSVP,likely feeding diapir-like upwellings in the upper mantle.The CEAA rises vertically,whereas the ECRA is tilted and dissipates at mantle transition zone depths,possibly due to the interaction with the cold Alpine subducted slab,which hinders its continuity at shallower depths.While plate-boundary forces are considered the primary drivers of rifting,the hypothesis that deep mantle plumes play a role in generating volcanic activity provides a compelling explanation for the European rift-related alkaline volcanism,supported by geological,geophysical,and geochemical evidence.
基金supported by the Major Project of Hunan Natural Science Foundation,China(No.2021JC0010)the National Natural Science Foundation of China(No.51274251)。
文摘The existing deep-sea sediment plume tests are mostly under small-scale static water and rarely under large-scale flowing water conditions.In this study,large-scale tank experiments of flowing water were designed and conducted to investigate the morphological characteristics and concentration evolution of the sediment plumes under different discharge rates(Q)and initial sediment concentrations(c).Viscosity tests,resuspension tests and free settling tests of the sediment solution with different c values were performed to reveal the settling mechanism of the plume diffusion process.The results show that the plume diffusion morphology variation in flowing water has four stages and the plume concentration evolution has three stages.The larger the Q,the smaller the initial incidence angle at the discharge outlet,the larger the diffusion range,the poorer the stability and the more complicated the diffusion morphology.The larger the c,the larger the settling velocity,the faster the formation of high-concentration accumulation zone,the better the stability and the clearer the diffusion boundary.The research results could provide experimental data for assessing the impact of deep-sea mining on the ocean environment.
基金supported by the National Key R&D Program of China(Nos.2020YFC2201103 and 2022YFB4601300)National Natural Science Foundation of China(No.U22B20120)+1 种基金the Program of Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology(No.LabASP-2024-09)the Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘The ionic liquid electrospray thruster is a microminiature thruster that can be applied on a micro or nano-satellite,and its highly energy-efficient,compact,modular system can be used for both main propulsion and altitude control.In this study,an ionic liquid electrospray thruster with a 100-tip emitter configuration is tested primarily to examine the difference in performance of the thruster at different angles with time-of-flight(TOF)mass spectrometry tests.In the experiment,it was measured that the half-angle of the thruster plume angle emission was in the range of−60 degrees to+65 degrees.Accordingly,the measurement range was set from−50 degrees to+50 degrees,with an interval of 10 degrees.Relative to the results of the 0 degree current curve,the positive mode is relatively homogeneous at all angles of the operating mode.In the negative mode,for n 2 ions,the negative angle region accounts for a larger proportion and the positive angle region accounts for a smaller proportion,which makes a significant difference to the specific impulse of the two regions.The range of the specific impulse at different angles is 3776-4401 s under the typical working condition of+2.5 kV.Under−2.5 kV,the range of the specific impulse at different angles is 3309-4654 s.This research quantifies the angular performance variations of the ionic liquid electrospray thruster,offering valuable data to improve its design and operational reliability for precise propulsion and altitude control in satellite applications.
基金supported by National Science Foundation of China(42102059 and 92055202)the China Geological Survey(DD20221817 and DD20190057)+1 种基金the basic scientific research funding in CAGS(J2204)the Second Tibetan Plateau Scientific Expedition and Research(2019QZKK0702).
文摘Two suites of mafic dykes,T1193-A and T1194-A,outcrop in Gyangze area,southeast Xizang.They are in the area of Comei LIP and have indistinguishable field occurrences with two other dykes in Gyangze,T0902 dyke with 137.7±1.3 Ma zircon age and T0907 dyke with 142±1.4 Ma zircon age reported by Wang YY et al.(2016),indicating coeval formation time.Taking all the four diabase dykes into consideration,two different types,OIB-type and weak enriched-type,can be summarized.The“OIB-type”samples,including T1193-A and T0907 dykes,show OIB-like geochemical features and have initial Sr-Nd isotopic values similar with most mafic products in Comei Large Igneous Provinces(LIP),suggesting that they represent melts directly generated from the Kerguelen mantle plume.The“weak enriched-type”samples,including T1194-A and T0902 dykes,have REEs and trace element patterns showing withinplate affinity but have obvious Nb-Ta-Ti negative anomalies.They show uniform lowerεNd(t)values(−6‒−2)and higher 87Sr/86Sr(t)values(0.706‒0.709)independent of their MgO variation,indicating one enriched mantle source.Considering their closely spatial and temporal relationship with the widespread Comei LIP magmatic products in Tethyan Himalaya,these“weak enriched-type”samples are consistent with mixing of melts from mantle plume and the above ancient Tethyan Himalaya subcontinental lithospheric mantle(SCLM)in different proportions.These weak enriched mafic rocks in Comei LIP form one special rock group and most likely suggest large scale hot mantle plume-continental lithosphere interaction.This process may lead to strong modification of the Tethyan Himalaya lithosphere in the Early Cretaceous.
文摘Plume-lithosphere interactions are key in the coupling of deep Earth and surface processes,impacting deformation and evolution of sedimentary basins and continental topography at different spatial scales(Cloetingh et al.,2022,2023).The North Atlantic region is a prime example of the interaction between plate tectonic movements and thermal instabilities in the Earth's mantle.The opening of the Labrador Sea/Baffin Bay and the North Atlantic,the widespread volcanism and the localized uplift of the topography in Greenland and the North Atlantic are traditionally attributed to the thermal effect of the Iceland mantle plume.
基金Supported by Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (2019BT02H594)Sanya Technology Innovation Special Project (2022KJCX08)。
文摘Offshore carbon dioxide(CO_(2)) storage is an effective method for reducing greenhouse gas emissions. However, when using traditional seismic wave methods to monitor the migration of sequestration CO_(2) plumes, the characteristics of wave velocity changes tend to become insignificant beyond a certain limit. In contrast, the controllable source electromagnetic method(CSEM) remains highly sensitive to resistivity changes. By simulating different CO_(2) plume migration conditions, we established the relevant models and calculated the corresponding electric field response characteristic curves, allowing us to analyze the CSEM's ability to monitor CO_(2) plumes. We considered potential scenarios for the migration and diffusion of offshore CO_(2) storage, including various burial depths, vertical extension diffusion, lateral extension diffusion,multiple combinations of lateral intervals, and electric field components. We also obtained differences in resistivity inversion imaging obtained by CSEM to evaluate its feasibility in monitoring and to analyze all the electric field(Ex, Ey, and Ez) response characteristics. CSEM has great potential in monitoring CO_(2) plume migration in offshore saltwater reservoirs due to its high sensitivity and accuracy. Furthermore, changes in electromagnetic field response reflect the transport status of CO_(2) plumes, providing an important basis for monitoring and evaluating CO_(2)transport behavior during storage processes.
基金supported by National Natural Science Foundation of China(Nos.12375250,11875121,51977057 and 11805013)the Natural Science Foundation of Hebei Province(Nos.A2020201025 and A2022201036)+3 种基金Hebei Province Optoelectronic Information Materials Laboratory Performance Subsidy Fund Project(No.22567634H)Funds for Distinguished Young Scientists of Hebei Province(No.A2012201045)the Natural Science Interdisciplinary Research Program of Hebei University(Nos.DXK201908 and DXK202011)the Post-graduate’s Innovation Fund Project of Hebei University(No.HBU2022bs004)。
文摘A remote plasma,also referred to as a plasma plume(diffuse or filamentary),is normally formed downstream of an atmospheric pressure plasma jet.In this study,a diffuse plume is formed by increasing the bias voltage(U_(b))applied to the downstream electrode of an argon plasma jet excited by a negatively pulsed voltage.The results indicate that the plume is filamentary when U_(b)is low,which transits to the diffuse plume with increasing U_(b).The discharge initiated at the rising edge of the pulsed voltage is attributed to the diffuse plume,while that at the falling edge contributes to the filament in the plume.For the diffuse plume,the discharge intensity decreases with the increasing oxygen content(C_o).Fast photography reveals that the diffuse plume results from a negative streamer,which has a dark region near the nozzle with C_o=0%.However,the dark region is absent with C_o=0.5%.From the optical emission spectrum,the electron density,electron excitation temperature,gas temperature,and oxygen atom concentration are investigated.
基金supported by the National Natural Science Foundation of China(Nos.52225107,U2106224,U1906234,51822904,and U1706223)the Fundamental Research Funds for the Central Universities(No.202041004)
文摘Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.
文摘Industrial activities, through the human-induced release of Green House Gas (GHG) emissions, have beenidentified as the primary cause of global warming. Accurate and quantitative monitoring of these emissions isessential for a comprehensive understanding of their impact on the Earth’s climate and for effectively enforcingemission regulations at a large scale. This work examines the feasibility of detecting and quantifying industrialsmoke plumes using freely accessible geo-satellite imagery. The existing systemhas so many lagging factors such aslimitations in accuracy, robustness, and efficiency and these factors hinder the effectiveness in supporting timelyresponse to industrial fires. In this work, the utilization of grayscale images is done instead of traditional colorimages for smoke plume detection. The dataset was trained through a ResNet-50 model for classification and aU-Net model for segmentation. The dataset consists of images gathered by European Space Agency’s Sentinel-2 satellite constellation from a selection of industrial sites. The acquired images predominantly capture scenesof industrial locations, some of which exhibit active smoke plume emissions. The performance of the abovementionedtechniques and models is represented by their accuracy and IOU (Intersection-over-Union) metric.The images are first trained on the basic RGB images where their respective classification using the ResNet-50model results in an accuracy of 94.4% and segmentation using the U-Net Model with an IOU metric of 0.5 andaccuracy of 94% which leads to the detection of exact patches where the smoke plume has occurred. This work hastrained the classification model on grayscale images achieving a good increase in accuracy of 96.4%.
基金Defense Industrial Technology Development Program(No.JCKY2019205A002)National Science and Technology Major Project(Nos.J2019-IV-0012-0080,J2019-VII-0004-0144,and Y2022-VII-0007).
文摘Laser powder bed fusion(LPBF)is a highly dynamic and complex physical process,and single-track de-fects tend to accumulate into non-negligible internal defects of parts.The nickel-based superalloy single track was fabricated by LPBF,and its plume and spattering behavior were monitored in situ and recorded in real time based on image recognition and tracking in this study.The relationship among laser energy density,melt flow,plume and spattering behavior during LPBF was discussed.Volumetric energy density had limitations as a design parameter for LPBF.However,we found that plume and spattering behavior can be used as real-time design parameters for the processing of LPBF parts and implemented the initial velocity statistics for LPBF single-track spattering based on the centroid extraction algorithm.The influ-ence of melt flow evolution paths on the spattering and plume behavior in three different melting modes was revealed,and a shift in plume behavior was found in the overlap region of the additive substrate.This study provides a new method for obtaining statistics of spattering-related physical quantities in the melting mode,which is beneficial for the development of processing methods to mitigate the instability of the LPBF process.
基金supported by the National Foreign Expert Project-Foreign Youth Talent Program Fund No.QN2023001001Beijing Natural Science Foundation Project-Foreign Scholar Program Fund No.IS23046/ZW001A00202301+1 种基金National Natural Science Foundation of China(NSFC)Fund No.12202019Beijing PostdoctoralResearch Activities Fund No.Q6001A00202301.
文摘The present investigation centers on the impact of viscous dissipation and ohmic heating on the plume generated by a line heat source under the impact of an aligned magnetic field.In this study,the flow model is adapted to incorporate ohmic heating and viscous dissipation by including the respective terms in the energy equation.A mathematical model is formulated as a system of coupled partial differential equations to analyze the flow problem.Subsequently,a numerical solution is derived with stream function formulation for the system of coupled partial differential equations,which transmutes it into ordinary differential equations.To achieve this,the numerical properties of the problem are established through the utilization of the Shooting method in tandem with the MATLAB tool bvp4c.The graphical representations of both missing and specified boundary conditions depict the effects of the magnetic parameter,viscous dissipation variable,magnetic force parameter,Prandtl number,and magnetic Prandtl number.These are accompanied by a discussion of their respective physical implications.The observed results claimed that the velocity,current density,and temperature distribution decrease for enhancing magnetic parameters.Meanwhile,the skin friction and magnetic flux drop while the heat transfer rate increases with an increment in magnetic parameters.These fluid flow and heat transfer characteristics were observed to decrease for increasing viscous dissipation.The current work is novel in incorporating ohmic heating viscous dissipation in energy equations coupled with Max-well and magnetic induction equations.
基金UD would like to thank the Department of Science and TechnologyGovernment of India for funding through INSPIRE-FACULTY award(DST/INSPIRE/04/2016/001582)NM is thankful to Department of Science and Technology,Government of India for J.C.Bose Fellowship award.
文摘In Earth’s mantle,gravity instabilities initiated by density inversion lead to upwelling of hot materials as plumes.This study focuses upon the ascent dynamics of plumes to provide an explanation of the periodic multiple eruption events in large igneous provinces(LIP)and hotspots.We demonstrate that depending on physical conditions,plumes can either ascend in a continuous process with a single,large head trailing into a long slender tail,or alternatively,they ascend in a pulsating fashion producing multiple inaxis heads.Based on the Volume of Fluid(VOF)method,we performed computational fluid dynamics(CFD)simulations to constrain the thermo-mechanical conditions that decide the continuous versus pulsating dynamics.The simulations suggest the density(ρ^(*))and the viscosity(R)ratios of the ambient to the plume and the influx rates(Re)are the prime factors in controlling the ascent dynamics.The simulations could also predict thermal events near the surface causing eruption periodically as pulses.The pulsating plume model explains the multiple eruption events in different LIPs and our simulation results predict that variation in the temperature of the source layer can cause a range of timescale for this periodicity.
基金supported by the National Natural Science Foundation of China(Grant Nos.61075085 and 41106085)Program of the State Key Laboratory of Robotics(Grant No.2009-Z03)
文摘This paper presents a computational model of simulating a deep-sea hydrothermal plume based on a Lagrangian particle random walk algorithm. This model achieves the efficient process to calculate a numerical plume developed in a fluid-advected environment with the characteristics such as significant filament intermittency and significant plume meander due to flow variation with both time and location. Especially, this model addresses both non-buoyant and buoyant features of a deep-sea hydrothermal plume in three dimensions, which significantly challenge a strategy for tracing the deep-sea hydrothermal plume and localizing its source. This paper also systematically discusses stochastic initial and boundary conditions that are critical to generate a proper numerical plume. The developed model is a powerful tool to evaluate and optimize strategies for the tracking of a deep-sea hydrothermal plume via an autonomous underwater vehicle （AUV）.
基金Project (51175095) supported by the National Natural Science Foundation of ChinaProjects (10251009001000001,9151009001000020) supported by the Natural Science Foundation of Guangdong Province,ChinaProject (20104420110001) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Classification of plume and spatter images was studied to evaluate the welding stability. A high-speed camera was used to capture the instantaneous images of plume and spatters during high power disk laser welding. Characteristic parameters such as the area and number of spatters, the average grayscale of a spatter image, the entropy of a spatter grayscale image, the coordinate ratio of the plume centroid and the welding point, the polar coordinates of the plume centroid were defined and extracted. Karhunen-Loeve transform method was used to change the seven characteristics into three primary characteristics to reduce the dimensions. Also, K-nearest neighbor method was used to classify the plume and spatter images into two categories such as good and poor welding quality. The results show that plume and spatter have a close relationship with the welding stability, and two categories could be recognized effectively using K-nearest neighbor method based on Karhunen-Loeve transform.
文摘Aim To investigate the effects of the incident orientation on the microwave attenuation. Methods Attenuation allowing microwave signal transmitting in an oblique or vertical direction through the solid propellant exhaust plume was computed, and the experiments were performed utilizing a lab scale solid rocket motor with a fully expanded nozzle. Results The predicted results accord well with the experimental results. Conclusion The microwave attenuation in the oblique path is greater than that in the vertical path.
文摘Recent space geodetic and gravimetric studies have given indications that the Earth’s radius is increasing at 0.1-0.4 mm yr-1 at present. Seismic studies have also shown that earthquakes alone could be causing the radius to increase at 0.011-0.06 mm yr-1. Deep mantle plumes provide a geophysical context within which such radial expansion, if confirmed, could possibly be explained. Both theory and observation suggest that these rising plumes more readily penetrate the 670 km barrier than do subducting slabs moving in the opposite direction towards the core-mantle boundary. If so, there would be a net flow of mass from the deep lower mantle into the upper mantle. Due to the lower pressures in the upper mantle,the excess mass of plume materials reaching there would transform to minerals with lower densities than they had at the mantle base. An increase in the mantle volume and the Earth’s radius would therefore be implied. Using previously published data for the African superplume. it is estimated that this mechanism could cause the Earth’s radius to increase at rates of 0.02-0.3 mm yr-1, similar to the rates possibly indicated in the present studies. This mechanism could also explain the very large range in current estimates of mantle plume heat and volume fluxes. A possible energy source for this plumedriven mode of expansion is discussed.
基金supported by ARC grants IH130200012 and DP130101946supported by the National Science Foundation under award EAR-1645775undertaken with the assistance of resources from the National Computational Infrastructure(NCI),which is supported by the Australian Government。
文摘Anomalous topographic swells and Cenozoic volcanism in east Africa have been associated with mantle plumes.Several models involving one or more fixed plumes beneath the northeastward migrating African plate have been suggested to explain the space-time distribution of magmatism in east Africa.We devise paleogeographically constrained global models of mantle convection and,based on the evolution of flow in the deepest lower mantle,show that the Afar plume migrated southward throughout its lifetime.The models suggest that the mobile Afar plume provides a dynamically consistent explanation for the spatial extent of the southward propagation of the east African rift system(EARS),which is difficult to explain by the northeastward migration of Africa over one or more fixed plumes alone,over the last≈45 Myr.We further show that the age-progression of volcanism associated with the southward propagation of EARS is consistent with the apparent surface hotspot motion that results from southward motion of the modelled Afar plume beneath the northeastward migrating African plate.The models suggest that the Afar plume became weaker as it migrated southwards,consistent with trends observed in the geochemical record.
文摘An improved near far field divided coupled method was established to investigate the electromagnetic properties of mildly overexpanded and underexpanded rocket exhaust plumes. Firstly, axisymmetric Navier Stokes equations incorporated with k ε two equation turbulence models were solved using time dependent approach to calculate the pressure of the near filed. Secondly, parabolized axisymmetric Navier Stokes equations incorporated with finite rate chemical kinetics models were marching on the detailed pressure map of the near field. The termination of the near field would yield the initial line for the far field. In addition, in the far field, the spatial marching method was directly used under the constant pressure condition, but considering more complicated chemically reacting process. Finally, the electromagnetic parameters of the whole plume were calculated with the electron conductive model. The calculated results of the overexpanded and underexpanded rocket exhaust plume were discussed. The predicted microwave attenuation accorded with the experimental results. This improved method is feasible for calculating the microwave attenuation characteristics of mildly non fully expanded rocket exhaust plumes.
