Construction of Ship Target Image Library Based on 3DS MAX and AP Algorithm

To achieve accurate classification and recognition of ship target types,it is necessary to establish a sample library of ship targets to be identified.On the basis of exploring the principles of building a ship target image library,the paper determines the sample set.Using 3DS MAX software as the platform,combined with the accurate 3D model of the ship in an offline state,the software fully utilizes its own rendering and animation functions to achieve the automatic generation of multi-view and multi-scale views of ship targets.To reduce the storage capacity of the image database,a construction method of the ship target image database based on the AP algorithm is presented.The algorithm can obtain the optimal cluster number,reduce the data storage capacity of the image database,and save the calculation amount for the subsequent matching calculation.

Strategy of preparing SmCo based films with high coercivity and remanence ratio achieved by temperature and chemical optimization

SmCo based films with excellent intrinsic magnetic properties have promising applications in micro-electro-mechanical system(MEMS).However,due to the complexity of phase composition and uncontrollable crystallization degree of SmCo hard magnetic phase in the film,both the coercivity(Hc)and remanence(Mr)of films are difficult to enhance simultaneously.In this paper,SmCo based films were deposited with a Cr underlayer and capping layer on single crystal Si substrates via magnetron sputtering process.The effects of annealing parameters and Sm/Co atomic ratio on the phase structure and coercivity of films are discussed.By adjusting the Sm/Co atomic ratio from 1:5 to 1:4,Co soft magnetic phase disappears and the single phase SmCo5 is obtained,leading to the increase of coercivity of the films from 30 to 34 kOe.The influence of deposition temperature and Cu doping on magnetic properties of SmCo based films was investigated.When the deposition temperature increases from room temperature to 250℃,the coercivity will further increase from 34 to 51 kOe.However,a severe kink is observed in the demagnetization curves due to the poor exchanged coupling.An analysis of transmission electron microscopy(TEM)confirms that the average size of non-hard magnetic amorphous phase exceeds the effective exchanged coupling length of SmCo5,which contributes to the decoupling and low remanence ratio.Therefore,doping Cu and applying a post-annealing process can significantly improve the crystallization degree of the films.Both the coercivity and the remanence ratio of the demagnetization curves are greatly enhanced.We propose a plausible strategy to prepare the SmCo based films with high coercivity and remanence ratio by temperature and chemical optimization,which can be utilized in high performed MEMS devices.

Coercivity mechanism of high-performance anisotropic heterostructure SmCo_(5)magnets

Due to its large magnetocrystalline anisotropy field and high Curie temperature,SmCo-based magnets are irreplaceable in high-temperature applications,The hot-deformed SmCo-based magnets are especially attractive for their excellent corrosion resistance,making them more suitable for harsh environments.However,it is still challenging for hot-deformed SmCo-based magnets to obtain high magnetization and high coercivity simultaneously.Therefore,it is necessary to analyze the relationship between its microstructure and magnetic properties and explore its magnetic hardening mechanism to guide the further improvement of magnetic properties.In this paper,the anisotropic heterostructure SmCo_(5)magnet was prepared by combining large height-reduction and introducing a nano-grained Smrich phase.Strong c-axis texture,(BH)m of 16.1 MGOe,and H_(ci)of 9.6 kOe were obtained via the heterostructure with SmCo_(5)micron-grain and Sm-rich nano-scale precipitates.The magnetic domain observation and technical magnetization analysis demonstrate that the coe rcivity mechanism is dominated by nucleation.The results also show that the smooth and Sm-rich precipitated grain boundary provides weak pinning effects.It provides a reference for the development of high-pe rformance nanocrystalline SmCo_(5)magnets.

Massive water production from lunar ilmenite through reaction with endogenous hydrogen

Finding water resources is a crucial objective of lunar missions.However,both hydroxyl(OH)and natural water(H2O)have been reported to be scarce on the Moon.We propose a potential method for obtaining water on the Moon through H2O formation via endogenous reactions in lunar regolith(LR),specifically through the reaction FeO/Fe2O3+H/Fe+H2O.This process is demonstrated using LR samples brought back by the Chang’E-5 mission.FeO and Fe2O3 are lunar minerals containing Fe oxides.Hydrogen(H)retained in lunar minerals from the solar wind can be used to produce water.The results of this study reveal that 51–76 mg of H2O can be generated from 1 g of LR after melting at temperatures above 1,200 K.This amount is10,000 times the naturally occurring OH and H2O on the Moon.Among the five primary minerals in LR returned by the Chang’E-5 mission,FeTiO3 ilmenite contains the highest amount of H,owing to its unique lattice structure with sub-nanometer tunnels.For the first time,in situ heating experiments using a transmission electron microscope reveal the concurrent formation of Fe crystals and H2O bubbles.Electron irradiation promotes the endogenous redox reaction,which is helpful for understanding the distribution of OH on the Moon.Our findings suggest that the hydrogen retained in LR is a significant resource for obtaining H2O on the Moon,which is helpful for establishing a scientific research station on the Moon.

Microstructure evolution of hot-deformed SmCo-based nanocomposites induced by thermo-mechanical processing

Nanocomposite permanent magnets have ultra-high theoretical magnetic energy products,due to cou-pling of the soft/hard magnetic phases,inciting strict microstructural requirements.In this study,the microstructure evolution,including the phase transition,morphological changes,and texture formation,of hot-deformed SmCo-based nanocomposites under thermal-stress-strain coupling was characterized to determine a possible strategy for achieving high performance.The SmCo_(5)/α-Fe nanocomposites precursor contained fine and dispersed Sm(Fe,Co)_(5)and Fe-Co grains and exhibited a two-stage phase transforma-tion accompanied by grain growth.In the early stage of deformation at relatively low temperature,the adjacent Sm(Co,Fe)5 and Fe-Co phase formed the Sm_(2)(Co,Fe)_(17)-H phase,which was stable only with small grain sizes.In the high-temperature deformation stage,the Sm_(2)(Co,Fe)_(17)-H phase transformed into the Sm_(2)(Co,Fe)_(17)-R phase with large grain sizes.In addition,the strong c-axis texture formed in the Sm(Co,Fe)_(5)phase but not in the Sm_(2)(Co,Fe)_(17)-R phase.Subsequently,the phase transition process and texture formation mechanism were systematically analyzed by transmission electron microscopy.The ini-tiation of a slip system and/or preferential grain growth explained the formation of texture under the action of uniform stress and strain and assisted by dispersed Sm-rich nanograins.The Sm_(2)(Co,Fe)_(17)-R grains with poor orientations and large grain sizes did not achieve magnetic hardening,which also dam-age the magnetic properties.According to the results of this work,we also presented a new strategy to prepare high-performance SmCo-based nanocomposites magnets.

Excellent thermal stability and high energy storage performances of BNT-based ceramics via phase-structure engineering

Herein,a novel strategy for regulating the phase structure was used to significantly enhance the recoverable energy storage density(Wrec)and the thermal stability via designing the(1-x)[(Bi_(0.5)Na_(0.5))_(0.7)Sr_(0.3)TiO_(3)]-xBiScO_(3)((1-x)BNST-xBS)relaxor ferroelectric ceramics.The incorporation of BS into BNST ceramics markedly increases the local micro-structure disorder,causing a high polarization and inhibiting polarization hysteresis for 0.95BNST-0.05BS ceramics,leading to a large Wrec of 5.41 J/cm^(3)with an ideal efficiency(h)of 78.5%.Meanwhile,transmission electron microscope(TEM)results further proved that the nano-domain structure and the tetragonal(P4bm)phase superlattice structure of 0.95BNST-0.05BS ceramics possess an excellent thermal stability(20-200℃).An outstanding Wrec value of 3.18×(1.00±0.03)J/cm^(3)and an h value of 74.500±0.025 are achieved under a temperature range from 20℃to 200℃.This work provides a promising method for phase-structure design that can make it possible to apply temperature-insensitive ceramic dielectrics with a high energy storage density in harsh environments.

Zirconium content induced mitigation of mechanical anisotropy in 2:17 type SmCo magnets

The mitigation of mechanical anisotropy is observed in 2:17 type SmCo magnets by adjusting the Zr content This behavior is supposed to be closely related to the density of lamellar phase,the density of which is enhanced obviously with increasing Zr content.The other reasons which could cause the reduction of the mechanical anisotropy is discussed from the Zr-rich impurity phase to the atom substitutions and crystal lattice distortion.The observation of crack in nano scale that dearly forms angles of 60° and 90° with respect to the lamellar phase,indicates that the probable cleavage planes are crystal faces(1011) and(1010).The results of investigation can deepen the understanding of mechanical anisotropy and cleavage fracture in the SmCo magnets.

Magnetic-electric composite coating with oriented segregated structure for enhanced electromagnetic shielding

Manipulation of the internal architecture is essential for electromagnetic interference(EMI)shielding performance of metal-based coatings,which can address the electromagnetic pollution in large-size,complex geometries,and harsh environments.In this work,oriented segregated structure with conductive networks embedded in magnetic matrix was achieved in Fe-based amorphous coatings via Ni-Cu-P functionalization of(Fe_(0.76)Si_(0.09)B_(0.1)P_(0.05))_(99)Nb_(1)amorphous powder precursors and then thermal spraying them onto aluminum(Al)substrate.Benefiting from the unique magnetic-electric structure,the coating@Al composite delivered prominent EMI shielding performance.The EMI shielding effectiveness(SE)of modified coating@Al composite is~41 dB at 8-12 GHz,doubling the value of Al substrate and is 15 dB greater than that of Ni-Cu-P-free coating@Al composite.Microstructure analysis showed that the introduced Ni−Cu−P insertions forcefully suppress the serious oxidation of the magnetic precursors during thermal spraying and form a dense conductive network in the magnetic matrix.Electron holography observation and electromagnetism simulation clarified that the modified coating can effectively trap and attenuate the incident radiations because of the electric loss from Ni−Cu−P conductive network,magnetic loss from Fe-based amorphous coating,and the electromagnetic interactions in the oriented segregated architectures.Moreover,the optimized thermal isolation and mechanical properties brought by structural improvement enable the coating to shield complex parts in thermal shock and mechanical loading environments.Our work gives an insight on the design strategies for metal-based EMI shielding materials and enriches the fundamental understanding of EMI shielding mechanisms.

Microstructure,magnetic domain and dynamic loss of surface-textured Fe-based nanocrystalline alloy

Heterogeneous coarse surface crystallites induced in the industrial Fe-rich nanocrystalline alloy is an obstacle for high-frequency and high-power commercial applications.Herein,the phase,crystal orientation,nanostructure and magnetic domain evolution of the surface-crystallized Fe-rich alloy were systematically investigated.Microstructure and inverse pole figures analysis confirms that the DOordered dendriticcrystallites bear<001>-oriented fiber texture before and after annealing at the free surface,while ultrafine nanocrystals are randomly oriented in the interior and wheel surface after annealing.As compared to zero magnetic-field-annealing,the transverse magnetic-field-annealing induces weakly oriented fiber texture and relatively uniform dendritic-crystallites at the surface,and uniform anisotropy in the interior and surface,which promotes smooth wall motion at the surface and magnetization rotation in the interior.This synergetic effect reduces the excess loss and leads reduction in dynamic loss at 1.0 T and10 kHz by 36%.

Analysis on deformation and texture formation mechanism of hot-deformed Nd-Fe-B magnets based on heterogeneous structure evolution

In this paper, microstructure, micromagnetic structure, texture, together with magnetic properties of the hot-deformed(HD) Nd-Fe-B magnets were systematically studied to understand the deformation process and the formation mechanism of c-axis texture. The results show that the platelet grains are formed in the fine-grain regions at the initial stage of the deformation. As the amount of deformation increases, the proportion of platelet grains increases and arranges gradually, causing the formation of c-axis texture, till the grain merging occurres when the deformation is excessive. It should be noted that the rare earth-rich phase in the fine-grained region slowly diffuses to the coarse-grained region where only grain growth can be observed during deformation. The deformation mechanism and formation of c-axis texture in HD Nd-Fe-B magnets can be deduced to be accomplished by the processes of dissolution-precipitation diffusion, grain rotation and grain arrangement, based on the characterization of microstructure and texture evolution. Also, approaches to optimize the preparation process and magnetic properties of the hot-deformed Nd-Fe-B magnets were discussed.

A novel strategy for the fabrication of highperformance nanostructured Ce-Fe-B magnetic materials via electron-beam exposure

Ce_(2)Fe_(14)B compound has a great potential to serve as a novel permanent magnet alternative thanks to the abundant and inexpensive rare-earth element(cerium),while its low magnetocrystalline anisotropy and energy product severely restrict its applications.In this work,a novel strategy combining melt-spinning and electron-beam exposure(EBE)aiming for fabricating high-performance Ce-Fe-B magnetic materials is reported to solve the above-mentioned problem.Remarkably,this strategy facilitates developing a suitable grain boundary configuration without using any additional heavy rare-earth element.Under the optimal EBE condition,the maximum energy product((BH)max)of pure Ce-Fe-B alloy is 6.5 MGOe,about four times higher than that obtained after conventional rapid thermal processing method for the same precursor.The enhanced intergranular magnetostatic coupling effect in the EBE sample is validated by mapping the first-order-reversal-curve(FORC)diagrams.The in-situ observation of magnetic domain wall motion for Ce-Fe-B alloy using Lorentz transmission electron microscopy reveals that the boundary layers are very effective in pinning the motion of domain walls,leading to the increased coercivity under EBE,and this pinning effect is further verified by micromagnetic simulations.Our results suggest that Ce Fe B materials using EBE could be a promising candidate after further processing,which could fill the performance“gap”between hexaferrite and Nd-Fe-B-based magnets.

Air stable Fe nanostructures with high magnetization prepared by reductive annealing

Monodispersed Fe nanospindles and nanoparticles were successfully synthesized through environmentfriendly reductive annealing ？-Fe OOH nanorods. Effects of annealing temperature and reaction atmosphere on microstructure, phase, and magnetic property of Fe nanostructures were investigated.The as-obtained pure Fe nanoparticles with mean size of 45 nm had a high saturation magnetization up to 207 emu/g, close to that of bulk material（218 emu/g）, which exhibited high air stability. After exposing in air for 2 and 7 days, the as synthesized Fe nanoparticles still showed high magnetization of 182 and141 emu/g, respectively.