Lunar impact crater detection is crucial for lunar surface studies and spacecraft landing missions,yet deep learning still struggles with accurately detecting small craters,especially when relying on incomplete catalo...Lunar impact crater detection is crucial for lunar surface studies and spacecraft landing missions,yet deep learning still struggles with accurately detecting small craters,especially when relying on incomplete catalogs.In this work,we integrate Digital Elevation Model(DEM)data to construct a high-quality dataset enriched with slope information,enabling a detailed analysis of crater features and effectively improving detection performance in complex terrains and low-contrast areas.Based on this foundation,we propose a novel two-stage detection network,MSFNet,which leverages multi-scale adaptive feature fusion and multisize ROI pooling to enhance the recognition of craters across various scales.Experimental results demonstrate that MSFNet achieves an F1 score of 74.8%on Test Region1 and a recall rate of 87%for craters with diameters larger than 2 km.Moreover,it shows exceptional performance in detecting sub-kilometer craters by successfully identifying a large number of high-confidence,previously unlabeled targets with a low false detection rate confirmed through manual review.This approach offers an efficient and reliable deep learning solution for lunar impact crater detection.展开更多
The formation process of blasting craters and blasting fragments is simulated using the continuumdiscontinuum element method(CDEM),providing a reference for blasting engineering design.The calculation model of the bla...The formation process of blasting craters and blasting fragments is simulated using the continuumdiscontinuum element method(CDEM),providing a reference for blasting engineering design.The calculation model of the blasting funnel is established,and the formation and fragmentation effect of the blasting crater under different explosive burial depths and different explosive package masses are numerically simulated.The propagation law of the explosion stress wave and the formation mechanism of the blasting crater are studied,and the relationship between the rock-crushing effect and blasting design parameters is quantitatively evaluated.Comparing the results of numerical simulation with the results of field tests and theoretical calculations indicated that the three are consistent,which proves the accuracy of numerical simulation.The results showed that the area of the blasting crater rises with the increase of explosive package mass and explosive burial depth.Taking the proportion of broken blocks with particle size ranging from 0.01 to 0.1 m as the research object,it can be found that the proportion of broken blocks with an explosive burial depth of 0.62 to 1.12 m is 0.45 to 0.18 times that with an explosive burial depth of 0.5 m.The proportion of broken blocks with an explosive radius of 4 to 12 cm is 1.14 to 3.29 times that with an explosive radius of 2 cm.The quantitative analysis of the blasting effect and blasting design parameters provides guidance for the design of blasting engineering.展开更多
Landing spacecraft experience significant impact forces during landing,resulting in large deformation and failure in the soil surface,which severely affects landing safety and stability.This paper establishes a smooth...Landing spacecraft experience significant impact forces during landing,resulting in large deformation and failure in the soil surface,which severely affects landing safety and stability.This paper establishes a smoothed particle hydrodynamics(SPH)model based on the theory of soil elastoplastic constitutive relations to describe the process of a lander’s footpad impacting lunar regolith vertically.The model can provide engineering indices such as impact load and penetration depth,and illustrate the large deformation and crater characteristics of the regolith.A detailed analysis of the response of the footpad and lunar regolith during landing reveals that the process can be broadly divided into two stages of rapid penetration and oscillatory attenuation.Furthermore,there are significant similarities in the landing process under different landing velocities and footpad masses.The research investigates the large deformation and crater characteristics of the lunar regolith bed.The results demonstrate two failure modes in the regolith.Under the impact of a footpad with a smaller mass,the final failure surface of the regolith exhibits a bowl-shaped profile with a uniformly open mouth.In contrast,under the impact of a footpad with a larger mass,the final failure surface of the regolith presents an urn-shaped profile with a large abdomen and a small opening.However,the impact craters in both scenarios show a bowl-like distribution.In cases of high-velocity impacts,the impact crater exhibits obvious blocky spalling on its sides.The SPH model developed in this study can be applied to predict the large deformation and failure response of lunar soil under the impact of rigid structures as well as the impact load and penetration depth.It effectively predicts the dynamic response of the landing process,which is expected to provide a reference for engineering design.展开更多
Planetary surfaces,shaped by billions of years of geologic evolution,display numerous impact craters whose distribution of size,density,and spatial arrangement reveals the celestial body's history.Identifying thes...Planetary surfaces,shaped by billions of years of geologic evolution,display numerous impact craters whose distribution of size,density,and spatial arrangement reveals the celestial body's history.Identifying these craters is essential for planetary science and is currently mainly achieved with deep learning-driven detection algorithms.However,because impact crater characteristics are substantially affected by the geologic environment,surface materials,and atmospheric conditions,the performance of deep learning models can be inconsistent between celestial bodies.In this paper,we first examine how the surface characteristics of the Moon,Mars,and Earth,along with the differences in their impact crater features,affect model performance.Then,we compare crater detection across celestial bodies by analyzing enhanced convolutional neural networks and U-shaped Convolutional Neural Network-based models to highlight how geology,data,and model design affect accuracy and generalization.Finally,we address current deep learning challenges,suggest directions for model improvement,such as multimodal data fusion and cross-planet learning and list available impact crater databases.This review can provide necessary technical support for deep space exploration and planetary science,as well as new ideas and directions for future research on automatic detection of impact craters on celestial body surfaces and on planetary geology.展开更多
The development of guidance technology has made it possible for the earth penetration weapons(EPWs)to impact the target repeatedly at a close range. To investigative the damage of single and sequential strike induced ...The development of guidance technology has made it possible for the earth penetration weapons(EPWs)to impact the target repeatedly at a close range. To investigative the damage of single and sequential strike induced by the EPWs, experimental and numerical investigations are carried out in this paper.Firstly, a series of sequential explosion tests are conducted to provide the basic data of the crater size.Then, a numerical model is established to simulate the damage effects of sequential explosions using the meshfree method of Smoothed particle Galerkin. The effectiveness of numerical model is verified by comparison with the experimental results. Finally, based on dimensional analysis, several empirical formulas for describing the crater size are presented, including the conical crater diameter and the conical crater depth of the single explosion, the conical crater area and the joint depth of the secondary explosion. The formula for the single explosion expresses the relationship between the aspect ratio of the charge ranging from 3 to 7, the dimensionless buried depth ranging from 2 to 14 and the crater size. The formula for the secondary explosion expresses the relationship between the relative position of the two explosions and the crater size. All of data can provide reference for the design of protective structures.展开更多
Double-wall effusion cooling coupled with thermal barrier coating(TBC)is an important way of thermal protection for gas turbine vanes and blades of next-generation aero-engine,and formation of discrete crater holes by...Double-wall effusion cooling coupled with thermal barrier coating(TBC)is an important way of thermal protection for gas turbine vanes and blades of next-generation aero-engine,and formation of discrete crater holes by TBC spraying is an approved design.To protect both metal and TBC synchronously,a recommended geometry of crater is obtained through a fully automatic multi-objective optimization combined with conjugate heat transfer simulation in this work.The length and width of crater(i.e.,L/D and W/D)were applied as design variables,and the area-averaged overall effectiveness of the metal and TBC surfaces(i.e.,Φ_(av) and τ_(av))were selected as objective functions.The optimization procedure consists of automated geometry and mesh generation,conjugate heat transfer simulation validated by experimental data and Kriging surrogated model.The results showed that the Φ_(av) and τ_(av) are successfully increased respectively by 9.1%and 6.0%through optimization.Appropriate enlargement of the width and length of the crater can significantly improve the film coverage effect,since that the beneficial anti-CRVP is enhanced and the harmful CRVP is weakened.展开更多
Lunar Laser Ranging has extremely high requirements for the pointing accuracy of the telescopes used.To improve its pointing accuracy and solve the problem of insufficiently accurate telescope pointing correction achi...Lunar Laser Ranging has extremely high requirements for the pointing accuracy of the telescopes used.To improve its pointing accuracy and solve the problem of insufficiently accurate telescope pointing correction achieved by tracking stars in the all-sky region,we propose a processing scheme to select larger-sized lunar craters near the Lunar Corner Cube Retroreflector as reference features for telescope pointing bias computation.Accurately determining the position of the craters in the images is crucial for calculating the pointing bias;therefore,we propose a method for accurately calculating the crater position based on lunar surface feature matching.This method uses matched feature points obtained from image feature matching,using a deep learning method to solve the image transformation matrix.The known position of a crater in a reference image is mapped using this matrix to calculate the crater position in the target image.We validate this method using craters near the Lunar Corner Cube Retroreflectors of Apollo 15 and Luna 17 and find that the calculated position of a crater on the target image falls on the center of the crater,even for image features with large distortion near the lunar limb.The maximum image matching error is approximately 1″,and the minimum is only 0.47″,which meets the pointing requirements of Lunar Laser Ranging.This method provides a new technical means for the high-precision pointing bias calculation of the Lunar Laser Ranging system.展开更多
After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical ...After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.展开更多
Multi-channel wire electrical discharge machining(MC-WEDM)is an advanced and high-efficiency machining technology,but its material erosion mechanism remains unclear.In this study,dual-channel wire electrical discharge...Multi-channel wire electrical discharge machining(MC-WEDM)is an advanced and high-efficiency machining technology,but its material erosion mechanism remains unclear.In this study,dual-channel wire electrical discharge machining was utilized as a case study to investigate the impact of the plunging current on both the plasma characteristics and material erosion under complex discharge conditions.Force analysis was conducted on the charged particles in the plasma,revealing that the plunging current can influence the trajectory of the plasma by modifying the selfmagnetic field.The particle tracking method was employed to simulate the motion of electrons,revealing that in MC-WEDM,electrons exhibited a larger and more uniform distribution.The evolution of the plasma within a single-pulse discharge was observed using high-speed photography technology,and the discharge signals collected from different channels were analyzed.It was observed that the plasma in MC-WEDM experienced more intense back-and-forth sweeping on the workpiece surface,facilitating the ejection of molten metal from the molten pool.The oscillating plasma exhibits a larger processing area and a more uniform distribution of energy,resulting in the formation of larger and shallower discharge craters.Furthermore,the influence of the amplitude and time point of the plunging current on the volume and area of the discharge craters was summarized.Finally,MC-WEDM significantly reduced the occurrence of holes and micro-cracks and exhibited a thinner recast layer in the continuous discharge experiment.展开更多
Depleted shergottites record unique information about the primary composition and differentiation of the mantle of Mars.Their petrology,geochemistry,and cosmic ray exposure and crystallization ages suggest that most o...Depleted shergottites record unique information about the primary composition and differentiation of the mantle of Mars.Their petrology,geochemistry,and cosmic ray exposure and crystallization ages suggest that most of them were excavated by a single young impact in the Amazonian-aged lava flows of the Tharsis and Elysium volcanic provinces.However,the difficulties of deriving consistent model ages for individual craters and inadequate evaluation of 3-7 km craters capable of ejecting martian meteorites have not been settled.Here we perform detailed geological investigations and crater statistics in patches of impact melt deposits for potential source craters of depleted shergottites with D>3 km,especially those in the Tharsis and Elysium volcanic provinces.By excluding the effect of heterogeneous textures across ejecta deposits,which hinder straightforward extraction of superposed production populations,our systematically updated model ages reveal that Chakpar crater at the northern flank of Ascraeus Mons is the best-fit candidate.The local context of this crater permits establishing a link between the meteorites and specific lava flows.The long-lived volcanic center here may experience an eruption and/or local deposition hiatus for about 1.8 billion years,and abundant subsurface water existed when the impact occurred at about 1.1 million years.展开更多
Ultrasonic-assisted micro-electro-discharge machining(EDM)has the potential to enhance processing responses such as material removal rate(MRR)and surface finish.To understand the reasons for this enhancement,the physi...Ultrasonic-assisted micro-electro-discharge machining(EDM)has the potential to enhance processing responses such as material removal rate(MRR)and surface finish.To understand the reasons for this enhancement,the physical mechanisms responsible for the individual discharges and the craters that they form need to be explored.This work examines features of craters formed by single discharges at various parameter values in both conventional and ultrasonic-assistedEDM of Ti6Al4V.High-speed imaging of the plasma channel is performed,and data on the individual discharges are captured in real-time.A 2D axisymmetric model using finite element software is established to model crater formation.On the basis of simulation and experimental results,a comparative study is then carried out to examine the effects of ultrasonic vibrational assistance on crater geometry.For every set ofEDM parameters,the crater diameter and depth from a single discharge are found to be higher in ultrasonic-assistedEDM than in conventionalEDM.The improved crater geometry and the reduced bulge formation at the crater edges are attributed to the increased melt pool velocity and temperature predicted by the model.展开更多
The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics(MD) simulations and experiments....The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics(MD) simulations and experiments.The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms,which has laser-induced high stress.However,under high fluence and short pulse width laser irradiation,the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film.In addition,Mg[0001] has higher pressure sensitivity and is more prone to ablation than Mg[0001].The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments.The results show that,under multiple pulsed laser irradiation,not only does the crater depth increase linearly with the pulse number,but also the quadratic term and constant term of the fitted crater profile curve increase linearly.展开更多
In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained...In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained. This article comprehensively analyzes the research achievements over the past 40 years of geology, geomorphology, seismic exploration, paleogeography, and oil and gas exploration in the Ordos Basin and Langshan. It recognizes that the northern part of the Ordos Basin experienced a meteorite impact in the Late Cretaceous period. The impact pushed the block northwest ward, subducting after colliding with igneous rocks in the north. This sudden event formed a clear arc-shaped mountain zone in the north and a wedge-shaped trench in front of the mountain. The chaotic layers, prolonged and continuous faults, and numerous thrust layers in the Langshan, a negative anomaly area in the center of the northern Ordos, abnormal orientation of crystalline basement structures in the north of Ordos, Moho uplift, and distribution of meteorite fragments in the northwest of Langshan, all of these geological phenomena support the occurrence of the meteorite impact event, forming the arc-shaped Langshan and the Trench.展开更多
The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological feat...The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological features of deposits within the impact crater using drilled sedimentary cores(23HIC01,20CR05,20CR09,and 20CR10),which consisted of an ascending order of impact breccias,lake sediments,and subaerial(e.g.,wetland)sediments.The impact breccia deposits in the 20CR05 and 23HIC01 cores contain shatter cones,which are a macroscopic indication of a meteorite impact.The overlying lake sediments were divided into three stages.The early stage of the post-impact lake environment corresponded to the lowermost lake sediments with frequent microfaults and slump-turbidite events.This stage is characterized by high calcite content of up to 13%.The middle stage showed a stable depositional environment,with silty to sandy lamination and bedding,and fewer microfaults.The final stage of the post-impact lake environment appears to have been very short and dramatic.This ended with the final slumping event,which appears to have been triggered by an abrupt outburst of lake water.This study demonstrates early post-impact lake sedimentation processes and crater instability in terms of soft-sediment deformation structures(e.g.,microfaults and slumps).展开更多
Impact craters are commonly found on the surface of planets, satellites, asteroids, and other solar system bodies. The applica- tion field of crater detection algorithm ranges from estimation of planetary surface age ...Impact craters are commonly found on the surface of planets, satellites, asteroids, and other solar system bodies. The applica- tion field of crater detection algorithm ranges from estimation of planetary surface age to autonomous landing on planets and advanced statistical analyses. this article introduced a method of passive image based crater autonomous detection. Candidate area, is defined as a small rectangular region including craters. The criterion to select a candidate area is there being one or a f...展开更多
The influences of intense magnetic pinch effect caused by electromagnetic field with high frequency on discharge channel expansion and plasma configuration change are discussed. The change of Lorentz force exerting on...The influences of intense magnetic pinch effect caused by electromagnetic field with high frequency on discharge channel expansion and plasma configuration change are discussed. The change of Lorentz force exerting on charged particles in discharge channel is calculated under the electromagnetic field with high frequency. Through the theoretical analysis and experimental study, the forming process of discharge channel is conjectured. And it is considered that the changes of discharge channel, such as the decrease of diameter and increase of energy density, coming from the intense magnetic pinch effect in high frequency electromagnetic field, are the main reasons for a series of special phenomena on the machined surface in micro EDM.展开更多
The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularl...The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6Al-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth（KT） and average flank wear width（VB） firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50% and 55%,respectively.Under the given conditions,the optimum hydrogen content is 0.26%.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.展开更多
This paper presents a method for the automatic adjustment of the laser defocusing amount in micro-laser-induced breakdown spectroscopy. A microscopic optical imaging system consisting of a CCD camera and a 20× ob...This paper presents a method for the automatic adjustment of the laser defocusing amount in micro-laser-induced breakdown spectroscopy. A microscopic optical imaging system consisting of a CCD camera and a 20× objective lens was adopted to realize the method. The real-time auto-focusing of the system was achieved by detecting the effective pixels of the light spot generated by the laser pointer. The focusing accuracy of the method could achieve 3 μm. The element concentrations of Mn and Ni in low-alloy steels were analyzed at a crater diameter of about 35 μm using the presented method. After using the presented method, the determination coefficients of Mn and Ni both exceeded 0.997, with the root-mean-square errors being 0.0133 and 0.0395, respectively. Scanning analysis was performed on the inclined plane and the curved surface by means of focusing control and non-focusing control. Ten characteristic spectral lines of Fe were selected as the analysis lines. With the focusing control, the average relative standard deviations obtained on the inclined plane and curved surface were both less than 5%, and much less than the values without focusing control, 14.6% and 40.39%.展开更多
Permian Kaipaileicike （开派雷兹克） volcanic rocks approximately 0-200 m thick are drilled in the Tahe （塔河） field. The distribution of volcanic rocks and their potential to form hydrocarbon reservoirs are discuss...Permian Kaipaileicike （开派雷兹克） volcanic rocks approximately 0-200 m thick are drilled in the Tahe （塔河） field. The distribution of volcanic rocks and their potential to form hydrocarbon reservoirs are discussed based on the integrated interpretation of log and 3D seismic data. The volcanic rocks, mainly consisting of dacites and basalts, are sandwiched between the Lower Triassic and Lower Carboniferous and bounded by top and bottom unconformities. The dacites accumulated in a mound shape around volcanic craters, whereas the basalts are deposited in tabular or trough-fill ge- ometries. Permian volcanic craters mainly located at the northwest corner of the Tahe field are identi- fied from volcanic rock thickening, occurrence of volcanic breccias, structural arch of the top Permian, seismic attribute anomalies, and fault （piercing conduit） reflections. Along the northwest wing of a Carboniferous salt dome, a stratigraphic trap is formed by a northeast updip pinch-out of Permian volcanic rock. Oil indications within the trap are found in numerous wells. The reservoir volcanic rocks are mainly of the fracture-pore pattern and covered by the caprock of a Lower Triassic mudstone. The hydrocarbon reservoir, which can potentially be a medium-sized oil pool, is connected to Camhrian-Ordovician source rocks through normal faults along the salt dome boundary.展开更多
The wavelength dependence of laser induced breakdown spectroscopy （LIBS） in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength las...The wavelength dependence of laser induced breakdown spectroscopy （LIBS） in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square （PLS） model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.展开更多
基金National Natural Science Foundation of China(12103020,12363009)Natural Science Foundation of Jiangxi Province(20224BAB211011)+1 种基金Open Project Program of State Key Laboratory of Lunar and Planetary Sciences(Macao University of Science and Technology)(Macao FDCT grant No.002/2024/SKL)Youth Talent Project of Science and Technology Plan of Ganzhou(2022CXRC9191,2023CYZ26970)。
文摘Lunar impact crater detection is crucial for lunar surface studies and spacecraft landing missions,yet deep learning still struggles with accurately detecting small craters,especially when relying on incomplete catalogs.In this work,we integrate Digital Elevation Model(DEM)data to construct a high-quality dataset enriched with slope information,enabling a detailed analysis of crater features and effectively improving detection performance in complex terrains and low-contrast areas.Based on this foundation,we propose a novel two-stage detection network,MSFNet,which leverages multi-scale adaptive feature fusion and multisize ROI pooling to enhance the recognition of craters across various scales.Experimental results demonstrate that MSFNet achieves an F1 score of 74.8%on Test Region1 and a recall rate of 87%for craters with diameters larger than 2 km.Moreover,it shows exceptional performance in detecting sub-kilometer craters by successfully identifying a large number of high-confidence,previously unlabeled targets with a low false detection rate confirmed through manual review.This approach offers an efficient and reliable deep learning solution for lunar impact crater detection.
基金funded by the National Natural Science Foundation of China(Program Nos.52379128,52209162)Natural Science Foundation of Hubei Province of China(Program Nos.2023AFA048,2023AFB657)+3 种基金Hubei Provincial Key Laboratory of Construction and Management in Hydropower Engineering(Program Nos.2023KSD03,2023KSD04)Natural Science Research of Jiangsu Higher Education Institutions of China(Program No.21KJB580001)Educational Commission of Hubei Province of China(Program No.T2020005)the Young Top-Notch Talent Cultivation Program of Hubei Province.
文摘The formation process of blasting craters and blasting fragments is simulated using the continuumdiscontinuum element method(CDEM),providing a reference for blasting engineering design.The calculation model of the blasting funnel is established,and the formation and fragmentation effect of the blasting crater under different explosive burial depths and different explosive package masses are numerically simulated.The propagation law of the explosion stress wave and the formation mechanism of the blasting crater are studied,and the relationship between the rock-crushing effect and blasting design parameters is quantitatively evaluated.Comparing the results of numerical simulation with the results of field tests and theoretical calculations indicated that the three are consistent,which proves the accuracy of numerical simulation.The results showed that the area of the blasting crater rises with the increase of explosive package mass and explosive burial depth.Taking the proportion of broken blocks with particle size ranging from 0.01 to 0.1 m as the research object,it can be found that the proportion of broken blocks with an explosive burial depth of 0.62 to 1.12 m is 0.45 to 0.18 times that with an explosive burial depth of 0.5 m.The proportion of broken blocks with an explosive radius of 4 to 12 cm is 1.14 to 3.29 times that with an explosive radius of 2 cm.The quantitative analysis of the blasting effect and blasting design parameters provides guidance for the design of blasting engineering.
基金funded by the National Natural Science Foundation of China(Nos.12172057 and 12032005).
文摘Landing spacecraft experience significant impact forces during landing,resulting in large deformation and failure in the soil surface,which severely affects landing safety and stability.This paper establishes a smoothed particle hydrodynamics(SPH)model based on the theory of soil elastoplastic constitutive relations to describe the process of a lander’s footpad impacting lunar regolith vertically.The model can provide engineering indices such as impact load and penetration depth,and illustrate the large deformation and crater characteristics of the regolith.A detailed analysis of the response of the footpad and lunar regolith during landing reveals that the process can be broadly divided into two stages of rapid penetration and oscillatory attenuation.Furthermore,there are significant similarities in the landing process under different landing velocities and footpad masses.The research investigates the large deformation and crater characteristics of the lunar regolith bed.The results demonstrate two failure modes in the regolith.Under the impact of a footpad with a smaller mass,the final failure surface of the regolith exhibits a bowl-shaped profile with a uniformly open mouth.In contrast,under the impact of a footpad with a larger mass,the final failure surface of the regolith presents an urn-shaped profile with a large abdomen and a small opening.However,the impact craters in both scenarios show a bowl-like distribution.In cases of high-velocity impacts,the impact crater exhibits obvious blocky spalling on its sides.The SPH model developed in this study can be applied to predict the large deformation and failure response of lunar soil under the impact of rigid structures as well as the impact load and penetration depth.It effectively predicts the dynamic response of the landing process,which is expected to provide a reference for engineering design.
基金funded by the National Natural Science Foundation of China(12363009 and 12103020)Natural Science Foundation of Jiangxi Province(20224BAB211011)+1 种基金Youth Talent Project of Science and Technology Plan of Ganzhou(2022CXRC9191 and 2023CYZ26970)Jiangxi Province Graduate Innovation Special Funds Project(YC2024-S529 and YC2023-S672).
文摘Planetary surfaces,shaped by billions of years of geologic evolution,display numerous impact craters whose distribution of size,density,and spatial arrangement reveals the celestial body's history.Identifying these craters is essential for planetary science and is currently mainly achieved with deep learning-driven detection algorithms.However,because impact crater characteristics are substantially affected by the geologic environment,surface materials,and atmospheric conditions,the performance of deep learning models can be inconsistent between celestial bodies.In this paper,we first examine how the surface characteristics of the Moon,Mars,and Earth,along with the differences in their impact crater features,affect model performance.Then,we compare crater detection across celestial bodies by analyzing enhanced convolutional neural networks and U-shaped Convolutional Neural Network-based models to highlight how geology,data,and model design affect accuracy and generalization.Finally,we address current deep learning challenges,suggest directions for model improvement,such as multimodal data fusion and cross-planet learning and list available impact crater databases.This review can provide necessary technical support for deep space exploration and planetary science,as well as new ideas and directions for future research on automatic detection of impact craters on celestial body surfaces and on planetary geology.
文摘The development of guidance technology has made it possible for the earth penetration weapons(EPWs)to impact the target repeatedly at a close range. To investigative the damage of single and sequential strike induced by the EPWs, experimental and numerical investigations are carried out in this paper.Firstly, a series of sequential explosion tests are conducted to provide the basic data of the crater size.Then, a numerical model is established to simulate the damage effects of sequential explosions using the meshfree method of Smoothed particle Galerkin. The effectiveness of numerical model is verified by comparison with the experimental results. Finally, based on dimensional analysis, several empirical formulas for describing the crater size are presented, including the conical crater diameter and the conical crater depth of the single explosion, the conical crater area and the joint depth of the secondary explosion. The formula for the single explosion expresses the relationship between the aspect ratio of the charge ranging from 3 to 7, the dimensionless buried depth ranging from 2 to 14 and the crater size. The formula for the secondary explosion expresses the relationship between the relative position of the two explosions and the crater size. All of data can provide reference for the design of protective structures.
基金Anhui Provincial Natural Science Foundation of China(2108085ME176)the Natural Science Foundation of China(52276043)。
文摘Double-wall effusion cooling coupled with thermal barrier coating(TBC)is an important way of thermal protection for gas turbine vanes and blades of next-generation aero-engine,and formation of discrete crater holes by TBC spraying is an approved design.To protect both metal and TBC synchronously,a recommended geometry of crater is obtained through a fully automatic multi-objective optimization combined with conjugate heat transfer simulation in this work.The length and width of crater(i.e.,L/D and W/D)were applied as design variables,and the area-averaged overall effectiveness of the metal and TBC surfaces(i.e.,Φ_(av) and τ_(av))were selected as objective functions.The optimization procedure consists of automated geometry and mesh generation,conjugate heat transfer simulation validated by experimental data and Kriging surrogated model.The results showed that the Φ_(av) and τ_(av) are successfully increased respectively by 9.1%and 6.0%through optimization.Appropriate enlargement of the width and length of the crater can significantly improve the film coverage effect,since that the beneficial anti-CRVP is enhanced and the harmful CRVP is weakened.
基金funded by Natural Science Foundation of Jilin Province(20220101125JC)the National Natural Science Foundation of China(12273079).
文摘Lunar Laser Ranging has extremely high requirements for the pointing accuracy of the telescopes used.To improve its pointing accuracy and solve the problem of insufficiently accurate telescope pointing correction achieved by tracking stars in the all-sky region,we propose a processing scheme to select larger-sized lunar craters near the Lunar Corner Cube Retroreflector as reference features for telescope pointing bias computation.Accurately determining the position of the craters in the images is crucial for calculating the pointing bias;therefore,we propose a method for accurately calculating the crater position based on lunar surface feature matching.This method uses matched feature points obtained from image feature matching,using a deep learning method to solve the image transformation matrix.The known position of a crater in a reference image is mapped using this matrix to calculate the crater position in the target image.We validate this method using craters near the Lunar Corner Cube Retroreflectors of Apollo 15 and Luna 17 and find that the calculated position of a crater on the target image falls on the center of the crater,even for image features with large distortion near the lunar limb.The maximum image matching error is approximately 1″,and the minimum is only 0.47″,which meets the pointing requirements of Lunar Laser Ranging.This method provides a new technical means for the high-precision pointing bias calculation of the Lunar Laser Ranging system.
基金supported by the Key Research Program of the Institute of Geology and Geophysics,CAS(Nos.IGGCAS-202102 and IGGCAS-201904)the National Natural Science Foundation of China(No.42230111)the CAS Key Technology Talent Program。
文摘After landing in the Utopia Planitia,Tianwen-1 formed the deepest landing crater on Mars,approximately 40 cm deep,exposing precious information about the mechanical properties of Martian soil.We established numerical models for the plume-surface interaction(PSI)and the crater formation based on Computational Fluid Dynamics(CFD)methods and the erosion model modified from Roberts’Theory.Comparative studies of cases were conducted with different nozzle heights and soil mechanical properties.The increase in cohesion and internal friction angle leads to a decrease in erosion rate and maximum crater depth,with the cohesion having a greater impact.The influence of the nozzle height is not clear,as it interacts with the position of the Shock Diamond to jointly control the erosion process.Furthermore,we categorized the evolution of landing craters into the dispersive and the concentrated erosion modes based on the morphological characteristics.Finally,we estimated the upper limits of the Martian soil’s mechanical properties near Tianwen-1 landing site,with the cohesion ranging from 2612 to 2042 Pa and internal friction angle from 25°to 41°.
基金Supported by the National Natural Science Foundation of China(No.51275098)National Natural Science Foundation of China(No.52375416)Natural Science Foundation of Guangdong Province(No.2023A1515012028).
文摘Multi-channel wire electrical discharge machining(MC-WEDM)is an advanced and high-efficiency machining technology,but its material erosion mechanism remains unclear.In this study,dual-channel wire electrical discharge machining was utilized as a case study to investigate the impact of the plunging current on both the plasma characteristics and material erosion under complex discharge conditions.Force analysis was conducted on the charged particles in the plasma,revealing that the plunging current can influence the trajectory of the plasma by modifying the selfmagnetic field.The particle tracking method was employed to simulate the motion of electrons,revealing that in MC-WEDM,electrons exhibited a larger and more uniform distribution.The evolution of the plasma within a single-pulse discharge was observed using high-speed photography technology,and the discharge signals collected from different channels were analyzed.It was observed that the plasma in MC-WEDM experienced more intense back-and-forth sweeping on the workpiece surface,facilitating the ejection of molten metal from the molten pool.The oscillating plasma exhibits a larger processing area and a more uniform distribution of energy,resulting in the formation of larger and shallower discharge craters.Furthermore,the influence of the amplitude and time point of the plunging current on the volume and area of the discharge craters was summarized.Finally,MC-WEDM significantly reduced the occurrence of holes and micro-cracks and exhibited a thinner recast layer in the continuous discharge experiment.
基金funded by the National Natural Science Foundation of China(Grant Nos.42241108,423B2205,42273040,62227901)the Strategic Priority Research Program of Chinese Academy of Science(Grant No.XDB41000000)。
文摘Depleted shergottites record unique information about the primary composition and differentiation of the mantle of Mars.Their petrology,geochemistry,and cosmic ray exposure and crystallization ages suggest that most of them were excavated by a single young impact in the Amazonian-aged lava flows of the Tharsis and Elysium volcanic provinces.However,the difficulties of deriving consistent model ages for individual craters and inadequate evaluation of 3-7 km craters capable of ejecting martian meteorites have not been settled.Here we perform detailed geological investigations and crater statistics in patches of impact melt deposits for potential source craters of depleted shergottites with D>3 km,especially those in the Tharsis and Elysium volcanic provinces.By excluding the effect of heterogeneous textures across ejecta deposits,which hinder straightforward extraction of superposed production populations,our systematically updated model ages reveal that Chakpar crater at the northern flank of Ascraeus Mons is the best-fit candidate.The local context of this crater permits establishing a link between the meteorites and specific lava flows.The long-lived volcanic center here may experience an eruption and/or local deposition hiatus for about 1.8 billion years,and abundant subsurface water existed when the impact occurred at about 1.1 million years.
基金support from the Department of Science and Technology (DST),Government of India (Grant No.ECR/DST/2017/000918)the Indian Institute of Technology Ropar for providing financial support under an ISIRD grant (F.No.9-282/2017IITRPR/705).
文摘Ultrasonic-assisted micro-electro-discharge machining(EDM)has the potential to enhance processing responses such as material removal rate(MRR)and surface finish.To understand the reasons for this enhancement,the physical mechanisms responsible for the individual discharges and the craters that they form need to be explored.This work examines features of craters formed by single discharges at various parameter values in both conventional and ultrasonic-assistedEDM of Ti6Al4V.High-speed imaging of the plasma channel is performed,and data on the individual discharges are captured in real-time.A 2D axisymmetric model using finite element software is established to model crater formation.On the basis of simulation and experimental results,a comparative study is then carried out to examine the effects of ultrasonic vibrational assistance on crater geometry.For every set ofEDM parameters,the crater diameter and depth from a single discharge are found to be higher in ultrasonic-assistedEDM than in conventionalEDM.The improved crater geometry and the reduced bulge formation at the crater edges are attributed to the increased melt pool velocity and temperature predicted by the model.
文摘The micro-ablation processes and morphological evolution of ablative craters on single-crystal magnesium under subpicosecond laser irradiation are investigated using molecular dynamics(MD) simulations and experiments.The simulation results exhibit that the main failure mode of single-crystal Mg film irradiated by a low fluence and long pulse width laser is the ejection of surface atoms,which has laser-induced high stress.However,under high fluence and short pulse width laser irradiation,the main damage mechanism is nucleation fracture caused by stress wave reflection and superposition at the bottom of the film.In addition,Mg[0001] has higher pressure sensitivity and is more prone to ablation than Mg[0001].The evolution equation of crater depth is established using multi-pulse laser ablation simulation and verified by experiments.The results show that,under multiple pulsed laser irradiation,not only does the crater depth increase linearly with the pulse number,but also the quadratic term and constant term of the fitted crater profile curve increase linearly.
文摘In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained. This article comprehensively analyzes the research achievements over the past 40 years of geology, geomorphology, seismic exploration, paleogeography, and oil and gas exploration in the Ordos Basin and Langshan. It recognizes that the northern part of the Ordos Basin experienced a meteorite impact in the Late Cretaceous period. The impact pushed the block northwest ward, subducting after colliding with igneous rocks in the north. This sudden event formed a clear arc-shaped mountain zone in the north and a wedge-shaped trench in front of the mountain. The chaotic layers, prolonged and continuous faults, and numerous thrust layers in the Langshan, a negative anomaly area in the center of the northern Ordos, abnormal orientation of crystalline basement structures in the north of Ordos, Moho uplift, and distribution of meteorite fragments in the northwest of Langshan, all of these geological phenomena support the occurrence of the meteorite impact event, forming the arc-shaped Langshan and the Trench.
基金supported by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources(GP2022-006[24-3111-3]and GP2022-005[24-3807])。
文摘The recently confirmed Hapcheon impact crater in Korea is a complex impact structure 7 km in diameter,with clear rims and impact-driven underground lacustrine sedimentary features.We investigated the lithological features of deposits within the impact crater using drilled sedimentary cores(23HIC01,20CR05,20CR09,and 20CR10),which consisted of an ascending order of impact breccias,lake sediments,and subaerial(e.g.,wetland)sediments.The impact breccia deposits in the 20CR05 and 23HIC01 cores contain shatter cones,which are a macroscopic indication of a meteorite impact.The overlying lake sediments were divided into three stages.The early stage of the post-impact lake environment corresponded to the lowermost lake sediments with frequent microfaults and slump-turbidite events.This stage is characterized by high calcite content of up to 13%.The middle stage showed a stable depositional environment,with silty to sandy lamination and bedding,and fewer microfaults.The final stage of the post-impact lake environment appears to have been very short and dramatic.This ended with the final slumping event,which appears to have been triggered by an abrupt outburst of lake water.This study demonstrates early post-impact lake sedimentation processes and crater instability in terms of soft-sediment deformation structures(e.g.,microfaults and slumps).
基金Innovation Fund for Graduate Student of Jiangsu (CX07B_113z)Innovation Fund for Ph.D. of Nanjing University of Aeronautics and Astronautics (BCXJ07-06)
文摘Impact craters are commonly found on the surface of planets, satellites, asteroids, and other solar system bodies. The applica- tion field of crater detection algorithm ranges from estimation of planetary surface age to autonomous landing on planets and advanced statistical analyses. this article introduced a method of passive image based crater autonomous detection. Candidate area, is defined as a small rectangular region including craters. The criterion to select a candidate area is there being one or a f...
基金Supported by the National Natural Science Foundation of China(50635040)~~
文摘The influences of intense magnetic pinch effect caused by electromagnetic field with high frequency on discharge channel expansion and plasma configuration change are discussed. The change of Lorentz force exerting on charged particles in discharge channel is calculated under the electromagnetic field with high frequency. Through the theoretical analysis and experimental study, the forming process of discharge channel is conjectured. And it is considered that the changes of discharge channel, such as the decrease of diameter and increase of energy density, coming from the intense magnetic pinch effect in high frequency electromagnetic field, are the main reasons for a series of special phenomena on the machined surface in micro EDM.
基金supported by National Natural Science Foundation of China (Grant No. 50775115)
文摘The influence of hydrogen contents on the tool wear has been mainly focused on the flank wear of the common tool,and the influence of hydrogen contents on the rake crater wear（main wear type） of the tool,particularly for the fine granular material tool,has been less investigated comprehensively.In this paper,for the purpose of researching the influence of hydrogen contents on tool wear,the titanium alloy Ti-6Al-4V is hydrogenated at 800 ℃ by thermohydrogen treatment technology and the turning experiments are carried out by applying uncoated WC-Co cemented carbide tool.The three-dimensional video microscope is used to take photos and measure tool wear.The results show that both of crater wear depth（KT） and average flank wear width（VB） firstly decreases and then increases with the increasing of hydrogen content.The maximum reducing amplitude of KT and VB is about 50% and 55%,respectively.Under the given conditions,the optimum hydrogen content is 0.26%.It is considered that the reduction of cutting temperature is an important factor for improving tool wear after the Ti-6Al-4V alloy is properly hydrogenated.Furthermore,the reasons of hydrogen effect on the tool wear are chiefly attributed to comprehensive effect of hydrogen contents on microstructure,physical properties and dynamic mechanical properties of the Ti-6Al-4V alloy.The proposed research provides the basic data for evaluating the machinability of hydrogenation Ti-6Al-4V alloy,and promotes practical application of thermohydrogen treatment technology in titanium alloys.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFF0106202)National Natural Science Foundation of China (Grant No. 61473279)+1 种基金the Key Research Program of Frontier Sciences, CAS (Grant No. QYZDJ-SSW-JSC037)the Youth Innovation Promotion Association, CAS
文摘This paper presents a method for the automatic adjustment of the laser defocusing amount in micro-laser-induced breakdown spectroscopy. A microscopic optical imaging system consisting of a CCD camera and a 20× objective lens was adopted to realize the method. The real-time auto-focusing of the system was achieved by detecting the effective pixels of the light spot generated by the laser pointer. The focusing accuracy of the method could achieve 3 μm. The element concentrations of Mn and Ni in low-alloy steels were analyzed at a crater diameter of about 35 μm using the presented method. After using the presented method, the determination coefficients of Mn and Ni both exceeded 0.997, with the root-mean-square errors being 0.0133 and 0.0395, respectively. Scanning analysis was performed on the inclined plane and the curved surface by means of focusing control and non-focusing control. Ten characteristic spectral lines of Fe were selected as the analysis lines. With the focusing control, the average relative standard deviations obtained on the inclined plane and curved surface were both less than 5%, and much less than the values without focusing control, 14.6% and 40.39%.
基金supported by the SINOPEC Forward Looking Project (No. YPH08114)the National Key Project of China(No. 2011zx05001-003)
文摘Permian Kaipaileicike （开派雷兹克） volcanic rocks approximately 0-200 m thick are drilled in the Tahe （塔河） field. The distribution of volcanic rocks and their potential to form hydrocarbon reservoirs are discussed based on the integrated interpretation of log and 3D seismic data. The volcanic rocks, mainly consisting of dacites and basalts, are sandwiched between the Lower Triassic and Lower Carboniferous and bounded by top and bottom unconformities. The dacites accumulated in a mound shape around volcanic craters, whereas the basalts are deposited in tabular or trough-fill ge- ometries. Permian volcanic craters mainly located at the northwest corner of the Tahe field are identi- fied from volcanic rock thickening, occurrence of volcanic breccias, structural arch of the top Permian, seismic attribute anomalies, and fault （piercing conduit） reflections. Along the northwest wing of a Carboniferous salt dome, a stratigraphic trap is formed by a northeast updip pinch-out of Permian volcanic rock. Oil indications within the trap are found in numerous wells. The reservoir volcanic rocks are mainly of the fracture-pore pattern and covered by the caprock of a Lower Triassic mudstone. The hydrocarbon reservoir, which can potentially be a medium-sized oil pool, is connected to Camhrian-Ordovician source rocks through normal faults along the salt dome boundary.
基金supported by National Natural Science Foundation of China(No.51276100)National Basic Research Program of China(973 Program)(No.2013CB228501)
文摘The wavelength dependence of laser induced breakdown spectroscopy （LIBS） in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square （PLS） model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.
