To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D lea...To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.展开更多
A segmented predictor-corrector method is proposed for hypersonic glide vehicles to address the issue of the slow computational speed of obtaining guidance commands using the traditional predictor-corrector guidance m...A segmented predictor-corrector method is proposed for hypersonic glide vehicles to address the issue of the slow computational speed of obtaining guidance commands using the traditional predictor-corrector guidance method.Firstly,an altitude-energy profile is designed,and the bank angle is derived analytically as the initial iteration value for the predictor-corrector method.The predictor-corrector guidance method has been improved by deriving an analytical form for predicting the range-to-go error,which greatly accelerates the iterative speed.Then,a segmented guidance algorithm is proposed.The above analytically predictor-corrector guidance method is adopted when the energy exceeds an energy threshold.When the energy is less than the threshold,the equidistant test method is used to calculate the bank angle command,which ensures guidance accuracy as well as computational efficiency.Additionally,an adaptive guidance cycle strategy is applied to reduce the computational time of the reentry guidance trajectory.Finally,the accuracy and robustness of the proposed method are verified through a series of simulations and Monte-Carlo experiments.Compared with the traditional integral method,the proposed method requires 75%less computation time on average and achieves a lower landing error.展开更多
To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composite...To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composites using Zr_(2)Cu as the filler.The microstructure,mechanical properties,and ablation properties of the Zr_(2)Cu packed composites were analyzed.Results show that during Zr_(2)Cu impregnation,the melt efficiently fills the large pores of the composites and is converted to ZrCu due to a partial reaction of zirconium with carbon.This results in an increase in composite density from 1.91 g/cm^(3)to 2.24 g/cm^(3)and a reduction in open porosity by 27.35%.Additionally,the flexural strength of Zr_(2)Cu packed C/C-SiC-ZrC composites is improved from 122.78±8.09 MPa to 135.53±5.40 MPa.After plasma ablation for 20 s,the modified composites demonstrate superior ablative resistance compared to PIP C/C-SiC-ZrC,with mass ablation and linear ablation rates of 2.77×10^(−3)g/s and 2.60×10^(−3)mm/s,respectively.The“selftranspiration”effect of the low-melting point copper-containing phase absorbs the heat of the plasma flame,further reducing the ablation temperature and promoting the formation of refined ZrO_(2)particles within the SiO_(2)melting layer.This provides more stable erosion protection for Zr_(2)Cu packed C/C-SiC-ZrC composites.展开更多
BACKGROUND Depression,anxiety,and insomnia were found out that were significant relevance to the mental health impact of the coronavirus disease 2019(COVID-19)lock-down.AIM To examine the interrelationships among perc...BACKGROUND Depression,anxiety,and insomnia were found out that were significant relevance to the mental health impact of the coronavirus disease 2019(COVID-19)lock-down.AIM To examine the interrelationships among perceived severity,anxiety,depression,insomnia,and sense of security in Chinese community residents during the COVID-19 lockdown period.METHODS Participants were selected using simple random sampling from four large gated communities in Chengdu,China.All participants were invited to complete a survey that included the Perceived Severity Questionnaire,Security Question-naire,Patient Health Questionnaire-9,Generalized Anxiety Disorder 7-item,and Insomnia Severity Index-7.In total,568 valid questionnaires were gathered.Co-rrelation analysis and structural equation models were used to explore the rela-RESULTS The observed prevalence rates of anxiety,depression,and insomnia among residents during lockdown were 27.5%,17.6%,and 16.0%,respectively.Correlation analysis showed that both perceived severity and sense of security were positively correlated with anxiety,depression,and insomnia[Pearson’s r was perceived severity and anxiety r=0.44(P<0.01);with depression r=0.48(P<0.01);with insomnia r=0.43(P<0.01);security with anxiety r=-0.65(P<0.01);with depression r=-0.65(P<0.01);with insomnia r=-0.53(P<0.01)].Structural equation modeling and bootstrap tests revealed that sense of security acted as a significant mediator in the relationship between perceived severity and emotional and sleep disorders(anxiety,depression,and insomnia).CONCLUSION This study demonstrates that sense of security is a significant predictor of emotional and sleep disorders(namely,depression,anxiety,and insomnia)among residents during the COVID-19 lockdown,with sense of security acting as a mediating factor.These findings suggest that mental health interventions for Chinese community residents during lockdowns may benefit from developing community-based educational programs to reduce perceived severity and ensuring the stable supply of essential resources and promoting social support networks to enhance the sense of security.展开更多
Origami mechanisms are extensively employed in various engineering applications due to their exceptional folding performance and deformability.The key to designing origami mechanisms lies in the design of the creases....Origami mechanisms are extensively employed in various engineering applications due to their exceptional folding performance and deformability.The key to designing origami mechanisms lies in the design of the creases.The crease design is often derived from experience and inspiration,so it is crucial to have a systematic approach to crease design.In this paper,a novel synthesis approach based on graph theory is proposed,which effectively addresses the challenge of designing the creases in origami mechanisms.The essence of this method lies in the acquisition of the double symmetrical crease pattern through the directed graph product operation of two subgraphs.The crease pattern can be simplified by employing a technique that eliminates certain creases while preserving the non-isomorphism and symmetry of the pattern.An improved mixed-integer linear programming model is developed to achieve an automatic distribution of the peak_valley creases of the origami.The proposed method ultimately generates 12 unique double symmetrical crease patterns.The new method proposed in this paper,through systematic design,significantly improves the efficiency of mechanism design while opening up broad prospects for exploring new mechanism structures,thereby greatly expanding its application potential in cutting-edge fields such as aerospace engineering and intelligent robots.展开更多
Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by in...Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by inherent structural instability and ambiguous structure-kinetics correlation.In this study,Fe NCN crystallites with selectively exposed(002)and{010}facets were precisely engineered and synthesized.Notably,the sodium storage kinetics and electrochemical performance of Fe NCN exhibit facet-dependent variations.Polyhedral-Fe NCN(P-Fe NCN)dominated by{010}facets exhibited a pseudocapacitance-driven storage mechanism and delivered exceptional rate capability(372 m Ah/g at5 A/g)and long cyclability(95.8%capacity retention after 300 cycles at 0.5 A/g).In contrast,sheet-like Fe NCN(S-Fe NCN)with predominant(002)facet exposure displayed diffusion-limited kinetics due to sluggish ion diffusion rate.Crucially,time-resolved operando XRD analysis and DFT simulation bridge this performance gap to mechanistic origins:Fe NCN as an intercalation-conversion type anode,the solid-state diffusion is the rate-determining step during charge/discharge process.Active{010}facets possess numerous broad hexagonal tunnels,coupled with a low diffusion barrier of 0.168 e V along{010}directions.This unique architectural configuration enables rapid sodium-ion transport,thereby shifting the diffusioncontrolled kinetics to intercalation-pseudocapacitive behavior.This discovery establishes active facet exposure as a storage kinetic switch,offering a generalized paradigm for optimizing the rate performance and stability of sodium-ion batteries.展开更多
A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper con...A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper conflict-free k-coloring.The PCF chromatic number of a graph G,denoted by χ_(pcf)(G),is the minimum k such that G is PCF k-colorable.Caro et al conjectured that for a connected graph G with maximum degreeΔ≥3,χ_(pcf)(G)≤Δ+1.One case in this conjecture,a connected graph with maximum degree 3 is PCF 4-colorable,can be derived from the result of Liu and Yu.Jiménez et al stated that the upper bound of PCF chromatic number of a graph G is max{5,x(G)}without a proof.In this paper,we give new proofs of the two results above and derive that for a connected graph G with maximum degreeΔ≥3,its complete subdivision is PCF(Δ+1)-colorable.展开更多
In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concer...In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concerns with the detection capabilities rather than coverage performance. To establish the relationship between these two aspects, the reconnaissance processes of normal stochastic targets are considered and the mathematic models of detection processes are built. The indicators of coverage performance are used to evaluate the detection probability and expectation of detection time delay, which are important factors in reconnaissance constellation estimation viewed from military intelligence discipline. The conclusions confirmed by the final simulation will be useful in LEO reconnaissance constellation design, optimization and evaluation.展开更多
The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to...The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to manifest the corrosion resistance of the 2195 Al-Li alloy in practical propellant tanks filled with N2O4, the alloy was soaked in 30% nitric acid solution, an accelerating corrosion environment, to test its corrosion behavior. Scanning electron microscopy(SEM) and transmission electron microscopy(TEM)were used to characterize microstructure and corrosion morphology of the alloy. Focused ion beam(FIB),combined with SEM, was used to demonstrate localized corrosion features and the propagation of corrosion pathways beneath the alloy surface. It was found that the corrosion network was formed with most intergranular corrosion and sparse intragranular corrosion. Additionally, the distribution and number of intermetallic particles influenced the localized corrosion degree and the direction of corrosion pathways. Aggregated particles made corrosion pathways continuously and caused more severe corrosion. The results from this work were valid and useful to corrosion prevention and protection for storage safety on propellant tanks in N_(2)O_(4).展开更多
In this paper,a large-sized ingot of Mg–9Gd–3Y–1.5Zn–0.5Zr(wt%) alloy with a diameter of 600 mm was successfully prepared by the semi-continuous casting method.The alloy was subsequently annealed at a relatively l...In this paper,a large-sized ingot of Mg–9Gd–3Y–1.5Zn–0.5Zr(wt%) alloy with a diameter of 600 mm was successfully prepared by the semi-continuous casting method.The alloy was subsequently annealed at a relatively low temperature of 430°C for 12 h as a homogenization treatment.The microstructure and room-temperature mechanical properties of the alloy were investigated systematically.The results show that the as-cast alloy contained a mass of discontinuous lamellar-shaped 18 R long-period stacking ordered(LPSO) phases with a composition of Mg10 Zn Y and an α-Mg matrix,along with net-shaped Mg5(Y,Gd) eutectic compounds at the grain boundaries.Most of the eutectic compounds dissolved after the homogenization treatment.Moreover,the amount and dimensions of the lamellar-shaped LPSO phase obviously increased after the homogenization treatment.The structure of the phase transformed into 14H-type LPSO with composition Mg12Zn(Y,Gd).The mechanical properties of the heat-treated large-sized alloy ingot are uniform.The ultimate tensile strength(UTS) and tensile yield strength(TYS) of the alloy reached 207.2 MPa and 134.8 MPa,respectively,and the elongation was 3.4%.The high performances of the large-sized alloy ingot after the homogenization treatment is attributed to the strengthening of the α-Mg solid solution and to the plentiful LPSO phase distributed over the α-Mg matrix.展开更多
A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impac...A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.展开更多
This paper studies a multi-unmanned aerial vehicle(UAV)enabled wireless communication system,where multiple UAVs are employed to communicate with a group of ground terminals(GTs)in the presence of potential jammers.We...This paper studies a multi-unmanned aerial vehicle(UAV)enabled wireless communication system,where multiple UAVs are employed to communicate with a group of ground terminals(GTs)in the presence of potential jammers.We aim to maximize the throughput overall GTs by jointly optimizing the UAVs’trajectory,the GTs’scheduling and power allocation.Unlike most prior studies,we consider the UAVs’turning and climbing angle constraints,the UAVs’three-dimensional(3D)trajectory constraints,minimum UAV-to-UAV(U2U)distance constraint,and the GTs’transmit power requirements.However,the formulated problem is a mixed-integer non-convex problem and is intractable to work it out with conventional optimization methods.To tackle this difficulty,we propose an efficient robust iterative algorithm to decompose the original problem be three sub-problems and acquire the suboptimal solution via utilizing the block coordinate descent(BCD)method,successive convex approximation(SCA)technique,and S-procedure.Extensive simulation results show that our proposed robust iterative algorithm offers a substantial gain in the system performance compared with the benchmark algorithms.展开更多
Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment,just like natural living beings.And the smart design could efficiently improve the performance of a robot...Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment,just like natural living beings.And the smart design could efficiently improve the performance of a robotic leg.Inspired by the simplified human leg structure,we present a 3-DOF robotic leg—OmniLeg,that is capable of making omnidirectional legged locomotion while keeping constant posture of the foot.Additionally,the concentrated drive mode,in which all the motor actuators are installed in the torso and do not move with the leg,minimizes the inertia of the robotic leg.In this paper,the modular design,the kinematics model,the structural analysis,the workspace,and the performance evaluation of the OmniLeg are discussed.Furthermore,we build a prototype based on the proposed design,and the precision of it is verified by the error calibration experiment which is conducted by tracking the trajectory of the prototype’s endpoint.Then,we present an OmniLeg-based single legged mobile robot.The capability of omnidirectional legged locomotion of the OmniLeg is demonstrated by the experiments.展开更多
This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%HNO3.The microstructure was observed and determined by the scanning electron microscopy and the ...This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%HNO3.The microstructure was observed and determined by the scanning electron microscopy and the transmission electron microscopy.The typical corrosion features,i.e.,regular or irregular corrosion pits and sub/intergranular corrosion,were investigated,and the role of stress were analyzed.The statistical results of the number and area of corrosion pits in various sizes were studied using an improved image processing method.Experimental results demonstrate that stress affects the intergranular corrosion or sub-intergranular corrosion of the alloy most,and promotes them to evolve into cracks under stress corrosion.Stress also plays a role in accelerating corrosion severity of certain corrosion feature.The number of corrosion pits with an area of 0–50μm~2 can be seen as an index to reflect the degree of corrosion.Besides,a corrosion phenomenon,i.e.,the pit bottom in the site with the maximum stress locally suffering from no severe corrosion,was observed and discussed.展开更多
Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomne...Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.展开更多
Aimed at improving the real-time performance of guidance instruction generation,an analytical hypersonic reentry guidance framework is presented.The key steps of the novel guidance framework are the parameterization o...Aimed at improving the real-time performance of guidance instruction generation,an analytical hypersonic reentry guidance framework is presented.The key steps of the novel guidance framework are the parameterization of reentry guidance problems and the optimization of parameters.First,a quintic polynomial function of energy was designed to describe the altitude profile.Then,according to the altitude-energy profile,the altitude,velocity,flight path angle,and bank angle were obtained analytically,which naturally met the terminal constraints.In addition,the angle of the attack profile was determined using the velocity parameter.The swarm intelligent optimization algorithms were used to optimize the parameters.The path constraints were enforced by the penalty function method.Finally,extensive simulations were carried out in both nominal and dispersed cases,and the simulation results showed that the proposed guidance framework was effective,high-precision,and robust in different scenarios.展开更多
A consensus-distributed fault-tolerant(CDFT)control law is proposed for a class of leader-following multi-vehicle cooperative attack(MVCA)systems in this paper.In particular,the switching communication topologies,stoc...A consensus-distributed fault-tolerant(CDFT)control law is proposed for a class of leader-following multi-vehicle cooperative attack(MVCA)systems in this paper.In particular,the switching communication topologies,stochastic multi-hop timevarying delays,and actuator faults are considered,which may lead to system performance degradation or on certain occasions even cause system instability.Firstly,the estimator of actuator faults for the following vehicle is designed to identify the actuator faults under a fixed topology.Then the CDFT control protocol and trajectory following error are derived by the relevant content of Lyapunov stability theory,the graph theory,and the matrix theory.The CDFT control protocol is proposed in the same manner,where a more realistic scenario is considered,in which the maximum trajectory following error and information on the switching topologies during the cooperative attack are available.Finally,numerical simulation are carried out to indicate that the proposed distributed fault-tolerant(DFT)control law is effective.展开更多
Based on the experimental analysis and theoretical calculation, the self-propagating high temperature synthesis of TiB2/Fe composite was studied. The experimental results show that the interfacial between TiB2 and Fe ...Based on the experimental analysis and theoretical calculation, the self-propagating high temperature synthesis of TiB2/Fe composite was studied. The experimental results show that the interfacial between TiB2 and Fe was smooth and clear, and the composite bending strength increased with the addition of Fe, however, the hardness decreased accordingly. The thermodynamics of the composites preparation process was calculated. The calculation results show that the primary chemical reaction was the reaction between Ti and B. The extra B can react with Fe, producing the brittle phase Fe2 B. By increasing Ti, the production of Fe2B will decrease and a few of Ti-Fe intermetallic compound will be produced by the reaction between Ti and Fe in the composites. Finally, according to the Merzhanov condition of the adiabatic system, it is concluded that the Fe content must be selected between 16.3% and 54.3% by the thermodynamics temperature of reaction calculation.展开更多
The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on simultaneously.This study aims to investigate the low-velocity impact response and infrared radiation c...The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on simultaneously.This study aims to investigate the low-velocity impact response and infrared radiation characteristics of the glass fiber reinforced thermoplastic polypropylene and carbon fiber reinforced thermosetting epoxy resin laminates wildly used in the aircraft industry.The impact tests were conducted at five energy levels.Characterization parameters such as impact load,displacement,and absorbed energy were measured.The damage evolution and damage modes of the laminates were analyzed through active and passive thermography,ultrasonic C-scan,and optical microscope.The results indicate that Thermosets(TS)laminates exhibit better impact resistance,while Thermoplastics(TP)laminates show higher delamination ductility,and the maximum contact force of TP laminates is much smaller than that of the TS laminates under lowvelocity impacts,but the low bending stiffness and low ductility of the TP matrix cause the difference in energy absorption level between the two not significant.The temperature characteristic changes of passive infrared thermography heat maps could characterize the damage mode of the laminates.The correlation between the heat maps and the impact characteristic curves is explained;the fluctuation of the impact characteristic curves is directly related to the hot spot characteristics changes of the heat maps.More frequent curve fluctuations correspond to a larger and brighter hot spot on the heat map,which peaks at the maximum impact load after the impact force versus time curve fluctuation cutoff point,the maximum center displacement of the impact force versus displacement curve,and the maximum absorbed energy of the absorbed energy versus time curve.展开更多
Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improv...Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improved processing precision,the data need to be edge-padded to the length required by the fast Fourier transform algorithm.For conventional vertical derivative conversion of potential fi eld data(PFD),only vertical derivative conversion is considered,or interpolation,border padding,and vertical derivative conversion are executed independently.In this paper,these three steps are considered uniformly,and a vertical derivative conversion method for irregular-range PFD based on an improved projection onto convex sets method is proposed.The cutoff wavenumber of the filter used in the proposed method is determined by fractal model fi tting of the radial average power spectrum(RAPS)of the potential fi eld.Theoretical gravity models and real aeromagnetic data show the following:(1)The fitting of the RAPS with a fractal model can separate useful signals and noise reasonably.(2)The proposed iterative method has a clear physical sense,and its interpolation,border padding error,and running time are much smaller than those of the conventional kriging and minimum curvature methods.展开更多
文摘To address the problem of multi-missile cooperative interception against maneuvering targets at a prespecified impact time and desired Line-of-Sight(LOS)angles in ThreeDimensional(3D)space,this paper proposes a 3D leader-following cooperative interception guidance law.First,in the LOS direction of the leader,an impact time-controlled guidance law is derived based on the fixed-time stability theory,which enables the leader to complete the interception task at a prespecified impact time.Next,in the LOS direction of the followers,by introducing a time consensus tracking error function,a fixed-time consensus tracking guidance law is investigated to guarantee the consensus tracking convergence of the time-to-go.Then,in the direction normal to the LOS,by combining the designed global integral sliding mode surface and the second-order Sliding Mode Control(SMC)theory,an innovative 3D LOS-angle-constrained interception guidance law is developed,which eliminates the reaching phase in the traditional sliding mode guidance laws and effectively saves energy consumption.Moreover,it effectively suppresses the chattering phenomenon while avoiding the singularity issue,and compensates for unknown interference caused by target maneuvering online,making it convenient for practical engineering applications.Finally,theoretical proof analysis and multiple sets of numerical simulation results verify the effectiveness,superiority,and robustness of the investigated guidance law.
基金National Natural Science Foundation of China(Nos.61773387 and 62022061).
文摘A segmented predictor-corrector method is proposed for hypersonic glide vehicles to address the issue of the slow computational speed of obtaining guidance commands using the traditional predictor-corrector guidance method.Firstly,an altitude-energy profile is designed,and the bank angle is derived analytically as the initial iteration value for the predictor-corrector method.The predictor-corrector guidance method has been improved by deriving an analytical form for predicting the range-to-go error,which greatly accelerates the iterative speed.Then,a segmented guidance algorithm is proposed.The above analytically predictor-corrector guidance method is adopted when the energy exceeds an energy threshold.When the energy is less than the threshold,the equidistant test method is used to calculate the bank angle command,which ensures guidance accuracy as well as computational efficiency.Additionally,an adaptive guidance cycle strategy is applied to reduce the computational time of the reentry guidance trajectory.Finally,the accuracy and robustness of the proposed method are verified through a series of simulations and Monte-Carlo experiments.Compared with the traditional integral method,the proposed method requires 75%less computation time on average and achieves a lower landing error.
基金Open Fund of Zhijian Laboratory,Rocket Force University of Engineering(2024-ZJSYS-KF02-09)National Natural Science Foundation of China(51902028,52272034)+1 种基金Key Research and Development Program of Shaanxi(2023JBGS-15)Fundamental Research Funds for the Central Universities(Changan University,300102313202,300102312406)。
文摘To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis(PIP)method,the low-temperature reactive melt infiltration(RMI)process was used to seal the composites using Zr_(2)Cu as the filler.The microstructure,mechanical properties,and ablation properties of the Zr_(2)Cu packed composites were analyzed.Results show that during Zr_(2)Cu impregnation,the melt efficiently fills the large pores of the composites and is converted to ZrCu due to a partial reaction of zirconium with carbon.This results in an increase in composite density from 1.91 g/cm^(3)to 2.24 g/cm^(3)and a reduction in open porosity by 27.35%.Additionally,the flexural strength of Zr_(2)Cu packed C/C-SiC-ZrC composites is improved from 122.78±8.09 MPa to 135.53±5.40 MPa.After plasma ablation for 20 s,the modified composites demonstrate superior ablative resistance compared to PIP C/C-SiC-ZrC,with mass ablation and linear ablation rates of 2.77×10^(−3)g/s and 2.60×10^(−3)mm/s,respectively.The“selftranspiration”effect of the low-melting point copper-containing phase absorbs the heat of the plasma flame,further reducing the ablation temperature and promoting the formation of refined ZrO_(2)particles within the SiO_(2)melting layer.This provides more stable erosion protection for Zr_(2)Cu packed C/C-SiC-ZrC composites.
基金Supported by Young Talent Project of Air Force Medical Center,No.2022YXQN008and Rapid Response Project of Air Force Medical University,No.2023KXKT041.
文摘BACKGROUND Depression,anxiety,and insomnia were found out that were significant relevance to the mental health impact of the coronavirus disease 2019(COVID-19)lock-down.AIM To examine the interrelationships among perceived severity,anxiety,depression,insomnia,and sense of security in Chinese community residents during the COVID-19 lockdown period.METHODS Participants were selected using simple random sampling from four large gated communities in Chengdu,China.All participants were invited to complete a survey that included the Perceived Severity Questionnaire,Security Question-naire,Patient Health Questionnaire-9,Generalized Anxiety Disorder 7-item,and Insomnia Severity Index-7.In total,568 valid questionnaires were gathered.Co-rrelation analysis and structural equation models were used to explore the rela-RESULTS The observed prevalence rates of anxiety,depression,and insomnia among residents during lockdown were 27.5%,17.6%,and 16.0%,respectively.Correlation analysis showed that both perceived severity and sense of security were positively correlated with anxiety,depression,and insomnia[Pearson’s r was perceived severity and anxiety r=0.44(P<0.01);with depression r=0.48(P<0.01);with insomnia r=0.43(P<0.01);security with anxiety r=-0.65(P<0.01);with depression r=-0.65(P<0.01);with insomnia r=-0.53(P<0.01)].Structural equation modeling and bootstrap tests revealed that sense of security acted as a significant mediator in the relationship between perceived severity and emotional and sleep disorders(anxiety,depression,and insomnia).CONCLUSION This study demonstrates that sense of security is a significant predictor of emotional and sleep disorders(namely,depression,anxiety,and insomnia)among residents during the COVID-19 lockdown,with sense of security acting as a mediating factor.These findings suggest that mental health interventions for Chinese community residents during lockdowns may benefit from developing community-based educational programs to reduce perceived severity and ensuring the stable supply of essential resources and promoting social support networks to enhance the sense of security.
基金Supported by National Natural Science Foundation of China(Grant Nos.52375028,52205040)Hebei Provincial Natural Science Foundation(Grant Nos.E2024203052,E2024203105)Science and Technology Project of Hebei Education Department(Grant No.QN2023206).
文摘Origami mechanisms are extensively employed in various engineering applications due to their exceptional folding performance and deformability.The key to designing origami mechanisms lies in the design of the creases.The crease design is often derived from experience and inspiration,so it is crucial to have a systematic approach to crease design.In this paper,a novel synthesis approach based on graph theory is proposed,which effectively addresses the challenge of designing the creases in origami mechanisms.The essence of this method lies in the acquisition of the double symmetrical crease pattern through the directed graph product operation of two subgraphs.The crease pattern can be simplified by employing a technique that eliminates certain creases while preserving the non-isomorphism and symmetry of the pattern.An improved mixed-integer linear programming model is developed to achieve an automatic distribution of the peak_valley creases of the origami.The proposed method ultimately generates 12 unique double symmetrical crease patterns.The new method proposed in this paper,through systematic design,significantly improves the efficiency of mechanism design while opening up broad prospects for exploring new mechanism structures,thereby greatly expanding its application potential in cutting-edge fields such as aerospace engineering and intelligent robots.
基金supported by the National Natural Science Foundation of China(No.52002305)Natural Science Basic Research Program in Shanxi Province of China(Nos.202403021221184,202403021222281)+1 种基金Natural Science Basic Research Plan in Shaanxi Province of China(Nos.2025JC-YBMS-478,23JK0424)College Students’Innovation Program of Taiyuan Normal University(No.CXCY2443)。
文摘Iron carbodiimide(Fe NCN)anode demonstrates significant potential for rapid sodium-ion storage owing to its high reaction activity and near-metallic conductivity.However,further development of Fe NCN is hindered by inherent structural instability and ambiguous structure-kinetics correlation.In this study,Fe NCN crystallites with selectively exposed(002)and{010}facets were precisely engineered and synthesized.Notably,the sodium storage kinetics and electrochemical performance of Fe NCN exhibit facet-dependent variations.Polyhedral-Fe NCN(P-Fe NCN)dominated by{010}facets exhibited a pseudocapacitance-driven storage mechanism and delivered exceptional rate capability(372 m Ah/g at5 A/g)and long cyclability(95.8%capacity retention after 300 cycles at 0.5 A/g).In contrast,sheet-like Fe NCN(S-Fe NCN)with predominant(002)facet exposure displayed diffusion-limited kinetics due to sluggish ion diffusion rate.Crucially,time-resolved operando XRD analysis and DFT simulation bridge this performance gap to mechanistic origins:Fe NCN as an intercalation-conversion type anode,the solid-state diffusion is the rate-determining step during charge/discharge process.Active{010}facets possess numerous broad hexagonal tunnels,coupled with a low diffusion barrier of 0.168 e V along{010}directions.This unique architectural configuration enables rapid sodium-ion transport,thereby shifting the diffusioncontrolled kinetics to intercalation-pseudocapacitive behavior.This discovery establishes active facet exposure as a storage kinetic switch,offering a generalized paradigm for optimizing the rate performance and stability of sodium-ion batteries.
基金Supported by the Youth Fund of Lanzhou Jiaotong University(1200061328)。
文摘A proper conflict-free k-coloring of a graph is a proper k-coloring in which each nonisolated vertex has a color that appears ex-actly once in its open neighborhood.A graph is PCF k-colorable if it admits a proper conflict-free k-coloring.The PCF chromatic number of a graph G,denoted by χ_(pcf)(G),is the minimum k such that G is PCF k-colorable.Caro et al conjectured that for a connected graph G with maximum degreeΔ≥3,χ_(pcf)(G)≤Δ+1.One case in this conjecture,a connected graph with maximum degree 3 is PCF 4-colorable,can be derived from the result of Liu and Yu.Jiménez et al stated that the upper bound of PCF chromatic number of a graph G is max{5,x(G)}without a proof.In this paper,we give new proofs of the two results above and derive that for a connected graph G with maximum degreeΔ≥3,its complete subdivision is PCF(Δ+1)-colorable.
文摘In the design problem of low earth orbit(LEO) reconnaissance satellite constellation, optimization of coverage performance is the design goal in most current methods. However,in the using process, the user only concerns with the detection capabilities rather than coverage performance. To establish the relationship between these two aspects, the reconnaissance processes of normal stochastic targets are considered and the mathematic models of detection processes are built. The indicators of coverage performance are used to evaluate the detection probability and expectation of detection time delay, which are important factors in reconnaissance constellation estimation viewed from military intelligence discipline. The conclusions confirmed by the final simulation will be useful in LEO reconnaissance constellation design, optimization and evaluation.
基金National Natural Science Foundation of China (Grant No.52075541)Shaanxi Province Natural Science Foundation (Grant No. 2022JM-243) to provide fund for conducting experiments。
文摘The corrosion properties of aluminum-lithium(Al-Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to manifest the corrosion resistance of the 2195 Al-Li alloy in practical propellant tanks filled with N2O4, the alloy was soaked in 30% nitric acid solution, an accelerating corrosion environment, to test its corrosion behavior. Scanning electron microscopy(SEM) and transmission electron microscopy(TEM)were used to characterize microstructure and corrosion morphology of the alloy. Focused ion beam(FIB),combined with SEM, was used to demonstrate localized corrosion features and the propagation of corrosion pathways beneath the alloy surface. It was found that the corrosion network was formed with most intergranular corrosion and sparse intragranular corrosion. Additionally, the distribution and number of intermetallic particles influenced the localized corrosion degree and the direction of corrosion pathways. Aggregated particles made corrosion pathways continuously and caused more severe corrosion. The results from this work were valid and useful to corrosion prevention and protection for storage safety on propellant tanks in N_(2)O_(4).
基金supported by the Youth Science Fund Project of the National Natural Science Fund of China(No.51401070)the Program for New Century Excellent Talents in Universities(No.NCET-12-0849)the Fundamental Research Funds for the Central Universities(No.2014ZZD03)
文摘In this paper,a large-sized ingot of Mg–9Gd–3Y–1.5Zn–0.5Zr(wt%) alloy with a diameter of 600 mm was successfully prepared by the semi-continuous casting method.The alloy was subsequently annealed at a relatively low temperature of 430°C for 12 h as a homogenization treatment.The microstructure and room-temperature mechanical properties of the alloy were investigated systematically.The results show that the as-cast alloy contained a mass of discontinuous lamellar-shaped 18 R long-period stacking ordered(LPSO) phases with a composition of Mg10 Zn Y and an α-Mg matrix,along with net-shaped Mg5(Y,Gd) eutectic compounds at the grain boundaries.Most of the eutectic compounds dissolved after the homogenization treatment.Moreover,the amount and dimensions of the lamellar-shaped LPSO phase obviously increased after the homogenization treatment.The structure of the phase transformed into 14H-type LPSO with composition Mg12Zn(Y,Gd).The mechanical properties of the heat-treated large-sized alloy ingot are uniform.The ultimate tensile strength(UTS) and tensile yield strength(TYS) of the alloy reached 207.2 MPa and 134.8 MPa,respectively,and the elongation was 3.4%.The high performances of the large-sized alloy ingot after the homogenization treatment is attributed to the strengthening of the α-Mg solid solution and to the plentiful LPSO phase distributed over the α-Mg matrix.
基金supported by the Program for National Defense Science and Technology Foundation Strengtheningthe Youth Foundation of Rocket Force University of Engineering(Grant No.2021QN-B014)。
文摘A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.
文摘This paper studies a multi-unmanned aerial vehicle(UAV)enabled wireless communication system,where multiple UAVs are employed to communicate with a group of ground terminals(GTs)in the presence of potential jammers.We aim to maximize the throughput overall GTs by jointly optimizing the UAVs’trajectory,the GTs’scheduling and power allocation.Unlike most prior studies,we consider the UAVs’turning and climbing angle constraints,the UAVs’three-dimensional(3D)trajectory constraints,minimum UAV-to-UAV(U2U)distance constraint,and the GTs’transmit power requirements.However,the formulated problem is a mixed-integer non-convex problem and is intractable to work it out with conventional optimization methods.To tackle this difficulty,we propose an efficient robust iterative algorithm to decompose the original problem be three sub-problems and acquire the suboptimal solution via utilizing the block coordinate descent(BCD)method,successive convex approximation(SCA)technique,and S-procedure.Extensive simulation results show that our proposed robust iterative algorithm offers a substantial gain in the system performance compared with the benchmark algorithms.
基金This work was supported by the National Natural Science Foundation of China(NO.52175069).
文摘Bionic-based robotic legs enable the legged robots with elegant and agile mobility in multi-terrain environment,just like natural living beings.And the smart design could efficiently improve the performance of a robotic leg.Inspired by the simplified human leg structure,we present a 3-DOF robotic leg—OmniLeg,that is capable of making omnidirectional legged locomotion while keeping constant posture of the foot.Additionally,the concentrated drive mode,in which all the motor actuators are installed in the torso and do not move with the leg,minimizes the inertia of the robotic leg.In this paper,the modular design,the kinematics model,the structural analysis,the workspace,and the performance evaluation of the OmniLeg are discussed.Furthermore,we build a prototype based on the proposed design,and the precision of it is verified by the error calibration experiment which is conducted by tracking the trajectory of the prototype’s endpoint.Then,we present an OmniLeg-based single legged mobile robot.The capability of omnidirectional legged locomotion of the OmniLeg is demonstrated by the experiments.
基金supported by the National Natural Science Foundation of China(No.52075541)the Natural Science Foundation of Shaanxi Province,China(No.2020JM-354)。
文摘This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%HNO3.The microstructure was observed and determined by the scanning electron microscopy and the transmission electron microscopy.The typical corrosion features,i.e.,regular or irregular corrosion pits and sub/intergranular corrosion,were investigated,and the role of stress were analyzed.The statistical results of the number and area of corrosion pits in various sizes were studied using an improved image processing method.Experimental results demonstrate that stress affects the intergranular corrosion or sub-intergranular corrosion of the alloy most,and promotes them to evolve into cracks under stress corrosion.Stress also plays a role in accelerating corrosion severity of certain corrosion feature.The number of corrosion pits with an area of 0–50μm~2 can be seen as an index to reflect the degree of corrosion.Besides,a corrosion phenomenon,i.e.,the pit bottom in the site with the maximum stress locally suffering from no severe corrosion,was observed and discussed.
基金supported by the National Natural Science Foundation of China(61703410,61873175,62073336,61873273,61773386,61922-089)the Basic Research Plan of Shaanxi Natural Science Foundation of China(2022JM-376).
文摘Remaining useful life(RUL)prediction is one of the most crucial components in prognostics and health management(PHM)of aero-engines.This paper proposes an RUL prediction method of aero-engines considering the randomness of failure threshold.Firstly,a random-coefficient regression(RCR)model is used to model the degradation process of aeroengines.Then,the RUL distribution based on fixed failure threshold is derived.The prior parameters of the degradation model are calculated by a two-step maximum likelihood estimation(MLE)method and the random coefficient is updated in real time under the Bayesian framework.The failure threshold in this paper is defined by the actual degradation process of aeroengines.After that,a expectation maximization(EM)algorithm is proposed to estimate the underlying failure threshold of aeroengines.In addition,the conditional probability is used to satisfy the limitation of failure threshold.Then,based on above results,an analytical expression of RUL distribution of aero-engines based on the RCR model considering random failure threshold(RFT)is derived in a closed-form.Finally,a case study of turbofan engine is used to demonstrate the effectiveness and superiority of the RUL prediction method and the parameters estimation method of failure threshold proposed.
基金co-supported by the National Natural Science Foundation of China(No.61773387)Tianjin Natural Science Foundation,China(No.20JCYBJC00880)。
文摘Aimed at improving the real-time performance of guidance instruction generation,an analytical hypersonic reentry guidance framework is presented.The key steps of the novel guidance framework are the parameterization of reentry guidance problems and the optimization of parameters.First,a quintic polynomial function of energy was designed to describe the altitude profile.Then,according to the altitude-energy profile,the altitude,velocity,flight path angle,and bank angle were obtained analytically,which naturally met the terminal constraints.In addition,the angle of the attack profile was determined using the velocity parameter.The swarm intelligent optimization algorithms were used to optimize the parameters.The path constraints were enforced by the penalty function method.Finally,extensive simulations were carried out in both nominal and dispersed cases,and the simulation results showed that the proposed guidance framework was effective,high-precision,and robust in different scenarios.
基金supported by the National Natural Science Foundation of China(61773387)the China Postdoctoral Fund(2016M5909712017T100770)。
文摘A consensus-distributed fault-tolerant(CDFT)control law is proposed for a class of leader-following multi-vehicle cooperative attack(MVCA)systems in this paper.In particular,the switching communication topologies,stochastic multi-hop timevarying delays,and actuator faults are considered,which may lead to system performance degradation or on certain occasions even cause system instability.Firstly,the estimator of actuator faults for the following vehicle is designed to identify the actuator faults under a fixed topology.Then the CDFT control protocol and trajectory following error are derived by the relevant content of Lyapunov stability theory,the graph theory,and the matrix theory.The CDFT control protocol is proposed in the same manner,where a more realistic scenario is considered,in which the maximum trajectory following error and information on the switching topologies during the cooperative attack are available.Finally,numerical simulation are carried out to indicate that the proposed distributed fault-tolerant(DFT)control law is effective.
基金Funded by the Natural Science Foundation of Shaanxi Province of China(2018JM5002)the Key Research and Development Program of Shaanxi Province(2019GY-182)+2 种基金the Postdoctoral Science Foundation Funded Project of China(2018M631152,2018T111051)the Postdoctoral Science Foundation Funded Project of Shaanxi Province of Chinathe Fundamental Research Funds for the Central Universities of China(xzy012019001)
文摘Based on the experimental analysis and theoretical calculation, the self-propagating high temperature synthesis of TiB2/Fe composite was studied. The experimental results show that the interfacial between TiB2 and Fe was smooth and clear, and the composite bending strength increased with the addition of Fe, however, the hardness decreased accordingly. The thermodynamics of the composites preparation process was calculated. The calculation results show that the primary chemical reaction was the reaction between Ti and B. The extra B can react with Fe, producing the brittle phase Fe2 B. By increasing Ti, the production of Fe2B will decrease and a few of Ti-Fe intermetallic compound will be produced by the reaction between Ti and Fe in the composites. Finally, according to the Merzhanov condition of the adiabatic system, it is concluded that the Fe content must be selected between 16.3% and 54.3% by the thermodynamics temperature of reaction calculation.
基金the Major Research Plan of the National Natural Science Foundation of China (No. 92060106)the National Natural Science Foundation of China (No. 52075541)+1 种基金the China Postdoctoral Science Foundation (No. 2019M650262)the Natural Science Foundation of Shaanxi Province, China (No. 2020JM-354)
文摘The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on simultaneously.This study aims to investigate the low-velocity impact response and infrared radiation characteristics of the glass fiber reinforced thermoplastic polypropylene and carbon fiber reinforced thermosetting epoxy resin laminates wildly used in the aircraft industry.The impact tests were conducted at five energy levels.Characterization parameters such as impact load,displacement,and absorbed energy were measured.The damage evolution and damage modes of the laminates were analyzed through active and passive thermography,ultrasonic C-scan,and optical microscope.The results indicate that Thermosets(TS)laminates exhibit better impact resistance,while Thermoplastics(TP)laminates show higher delamination ductility,and the maximum contact force of TP laminates is much smaller than that of the TS laminates under lowvelocity impacts,but the low bending stiffness and low ductility of the TP matrix cause the difference in energy absorption level between the two not significant.The temperature characteristic changes of passive infrared thermography heat maps could characterize the damage mode of the laminates.The correlation between the heat maps and the impact characteristic curves is explained;the fluctuation of the impact characteristic curves is directly related to the hot spot characteristics changes of the heat maps.More frequent curve fluctuations correspond to a larger and brighter hot spot on the heat map,which peaks at the maximum impact load after the impact force versus time curve fluctuation cutoff point,the maximum center displacement of the impact force versus displacement curve,and the maximum absorbed energy of the absorbed energy versus time curve.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41804136, 41774156, 61773389)the Young Talent Fund of University Association for Science and Technology in Shaanxi,China (Grant No.20180702)
文摘Gravity and magnetic exploration areas are usually irregular,and there is some data defi ciency.Missing data must be interpolated before the vertical derivative conversion in the wavenumber domain.Meanwhile,for improved processing precision,the data need to be edge-padded to the length required by the fast Fourier transform algorithm.For conventional vertical derivative conversion of potential fi eld data(PFD),only vertical derivative conversion is considered,or interpolation,border padding,and vertical derivative conversion are executed independently.In this paper,these three steps are considered uniformly,and a vertical derivative conversion method for irregular-range PFD based on an improved projection onto convex sets method is proposed.The cutoff wavenumber of the filter used in the proposed method is determined by fractal model fi tting of the radial average power spectrum(RAPS)of the potential fi eld.Theoretical gravity models and real aeromagnetic data show the following:(1)The fitting of the RAPS with a fractal model can separate useful signals and noise reasonably.(2)The proposed iterative method has a clear physical sense,and its interpolation,border padding error,and running time are much smaller than those of the conventional kriging and minimum curvature methods.
