The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospher...The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.展开更多
Cadmium telluride(CdTe),which has a high average atomic number and a unique band structure,is a leading material for room-temperature X/γ-ray detectors.Resistivity and mobility are the two most important properties o...Cadmium telluride(CdTe),which has a high average atomic number and a unique band structure,is a leading material for room-temperature X/γ-ray detectors.Resistivity and mobility are the two most important properties of detector-grade CdTe single crystals.However,despite decades of research,the fabrication of high-resistivity and high-mobility CdTe single crystals faces persistent challenges,primarily because the stoichiometric composition cannot be well controlled owing to the high volatility of Cd under high-temperature conditions.This volatility introduces Te inclusions and cadmium vacancies(V_(Cd))into the as-grown CdTe ingot,which significantly degrades the device performance.In this study,we successfully obtained detector-grade CdTe single crystals by simultaneously employing a Cd reservoir and chlorine(Cl)dopants via a vertical gradient freeze(VGF)method.By installing a Cd reservoir,we can maintain the Cd pressure under the crystal growth conditions,thereby preventing the accumulation of Te in the CdTe ingot.Additionally,the existence of the Cl dopant helps improve the CdTe resistivity by minimizing V_(Cd)density through the formation of an acceptor complex(Cl_(Te)-V_(Cd))^(-1).The crystalline quality of the obtained CdTe(Cl)was evidenced by a reduction in large Te inclusions,high optical transmission(60%),and a sharp absorption edge(1.456 eV).The presence of substitutional Cl dopants,known as Cl_(Te)^(+),simultaneously supports the record high resistivity of 1.5×10^(10)Ω·cm and remarkable electron mobility of 1075±88 cm^(2)V^(-1)s^(-1)simultaneously,has been confirmed by photoluminescence spectroscopy.Moreover,using our crystals,we fabricated a planar detector withμτ_(e)of(1.11±0.04)×10^(-4)cm^(2)∕V,which performed with a decent radiation-detection feature.This study demonstrates that the vapor-pressure-controlled VGF method is a viable technical route for fabricating detector-grade CdTe crystals.展开更多
Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread appli...Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread applications are hindered by low ionic conductivity at room temperature and lithium dendrite growth.Herein,we report a novel solid-state composite membrane electrolyte design that combines the vertically aligned channel structure and copolymer with a radial gradient composition.Within the vertically aligned channels,the composition of poly(vinyl ethylene carbonate-co-poly(ethylene glycol)diacrylate)(P(VEC-PEGDA)varies in a gradient along the radial direction:from the center to the wall of vertically aligned channels,the proportion of vinyl ethylene carbonate(VEC)in the copolymer decreases,while the proportion of poly(ethylene glycol)diacrylate(PEGDA)increases accordingly.It can be functionally divided into a mechanical-reinforcement layer and a fast-ion-conducting layer.The resulting solid-state composite membrane electrolyte achieves a high critical current density of 1.2 mA cm^(-2)and high ionic conductivity of 2.03 mS cm^(-1)at room temperature.Employing this composite membrane electrolyte,a Li//Li symmetric cell exhibits stable cycling for over 1850 h at 0.2 m A cm^(-2)/0.2 m A h cm^(-2),and a Li//LiFePO4(LFP)battery maintains 77.3% capacity retention at 2 C after 300 cycles.Our work provides insight into the rational design of safer and more efficient solidstate batteries through electrolyte structural engineering.展开更多
The prediction of bathymetry has advanced significantly with the development of satellite altimetry.However,the majority of its data originate from marine gravity anomaly.In this study,based on the expression of verti...The prediction of bathymetry has advanced significantly with the development of satellite altimetry.However,the majority of its data originate from marine gravity anomaly.In this study,based on the expression of vertical gravity gradient(VGG)of a rectangular prism,the governing equations for determining sea depths to invert bathymetry.The governing equation is solved by linearization through an iterative process,and numerical simulations verify its algorithm and its stability.We also study the processing methods of different interference errors.The regularization method improves the stability of the inversion process for errors.A piecewise bilinear interpolation function roughly replaces the low-frequency error,and numerical simulations show that the accuracy can be improved by 41.2%after this treatment.For variable ocean crust density,simulation simulations verify that the root-mean-square(RMS)error of prediction is approximately 5 m for the sea depth of 6 km if density is chosen as the average one.Finally,two test regions in the South China Sea are predicted and compared with ship soundings data,RMS errors of predictions are 71.1 m and 91.4 m,respectively.展开更多
In this paper,we study the onset and development of three-dimensional convection in a tilted porous layer saturated with a liquid.The layer is subjected to a gravitational field and a strictly vertical temperature gra...In this paper,we study the onset and development of three-dimensional convection in a tilted porous layer saturated with a liquid.The layer is subjected to a gravitational field and a strictly vertical temperature gradient.Typically,problems of thermal convection in tilted porous media saturated with a liquid are studied by assuming constant different temperatures at the boundaries of the layer,which prevent these systems from supporting conductive(non-convective)states.The boundary conditions considered in the present work allow a conductive state and are representative of typical geological applications.In an earlier work,we carried out a linear stability analysis of the conductive state.It was shown that at any layer tilt angles,the most dangerous type of disturbances are longitudinal rolls.Moreover,a non-zero velocity component exists in z-direction.In the present work,threedimensional non-linear convection regimes are studied.The original three-dimensional problem is reduced to two-dimensional one with an analytical expression for the velocity z-component v_(z)=v_(z)(x,y).It is shown that the critical Rayleigh number values obtained through numerical solutions of the obtained 2D problem by a finite difference method for different layer inclination angles,are in a good agreement with those predicted by the linear theory.The number of convective rolls realized in nonlinear calculations also fits the linear theory predictions for a given cavity geometry.Calculations carried out at low supercriticalities show that a direct bifurcation takes place.With increasing supercriticality,no transitions to other convective regimes are detected.The situation studied in this problem can be observed in oil-bearing rock formations under the influence of a geothermal temperature gradient,where the ensuing fluid convection can affect the distribution of oil throughout the layer.展开更多
In the realm of Intelligent Railway Transportation Systems,effective multi-party collaboration is crucial due to concerns over privacy and data silos.Vertical Federated Learning(VFL)has emerged as a promising approach...In the realm of Intelligent Railway Transportation Systems,effective multi-party collaboration is crucial due to concerns over privacy and data silos.Vertical Federated Learning(VFL)has emerged as a promising approach to facilitate such collaboration,allowing diverse entities to collectively enhance machine learning models without the need to share sensitive training data.However,existing works have highlighted VFL’s susceptibility to privacy inference attacks,where an honest but curious server could potentially reconstruct a client’s raw data from embeddings uploaded by the client.This vulnerability poses a significant threat to VFL-based intelligent railway transportation systems.In this paper,we introduce SensFL,a novel privacy-enhancing method to against privacy inference attacks in VFL.Specifically,SensFL integrates regularization of the sensitivity of embeddings to the original data into the model training process,effectively limiting the information contained in shared embeddings.By reducing the sensitivity of embeddings to the original data,SensFL can effectively resist reverse privacy attacks and prevent the reconstruction of the original data from the embeddings.Extensive experiments were conducted on four distinct datasets and three different models to demonstrate the efficacy of SensFL.Experiment results show that SensFL can effectively mitigate privacy inference attacks while maintaining the accuracy of the primary learning task.These results underscore SensFL’s potential to advance privacy protection technologies within VFL-based intelligent railway systems,addressing critical security concerns in collaborative learning environments.展开更多
The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electrom...The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.展开更多
The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.T...The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes.Building on the anatomical characteristics of bone and interfacial tissues,this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues,specifically focusing on methods used to construct compositional and structural gradients within the scaffolds.The latest applications of gradient scaffolds for the regeneration of bone,osteochondral,and tendon-to-bone interfaces are presented.Furthermore,the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed,as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.展开更多
We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensiv...We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensively evaluate the performance of the model by power spectral comparisons,correlation analyses,sensitivity matrix assessments,and comparisons with existing lithospheric field models.Results showed that using near east–west gradient data from MSS-1 significantly enhances the model correlation in the spherical harmonic degree(N) range of 45–60 while also mitigating the decline in correlation at higher degrees(N > 60).Furthermore,the unique orbital characteristics of MSS-1 enable its gradient data to provide substantial contributions to modeling in the mid-to low-latitude regions.With continued data acquisition from MSS-1 and further optimization of data processing methods,the performance of the model is expected to improve.展开更多
The Zenith Hydrostatic Delay(ZHD)is essential for high-precision Global Navigation Satellite System(GNSS)and Very Long Baseline Interferometry(VLBI)data processing.Accurate estimation of ZHD relies on in situ atmosphe...The Zenith Hydrostatic Delay(ZHD)is essential for high-precision Global Navigation Satellite System(GNSS)and Very Long Baseline Interferometry(VLBI)data processing.Accurate estimation of ZHD relies on in situ atmospheric pressure,which is primarily variable in the vertical direction.Current atmospheric pressure is either site-specific or has limited spatial coverage,necessitating vertical corrections for broader applicability.This study introduces a model that uses a Gaussian function for the vertical correction of atmospheric pressure when in situ meteorological observations are unavailable.Validation with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis(ERA5)reveals an average Bias and RMS for the new model of 0.31 h Pa and 2.96 h Pa,respectively.This corresponds to improvements of 37.5%and 80.3%in terms of RMS compared to two commonly used models(T0and Tvmodels)that require in situ meteorological observations,respectively.Additional validation with radiosonde data shows an average Bias and RMS of 1.85 h Pa and 4.87 h Pa,corresponding to the improvement of 42.8%and 71.1%in RMS compared with T0and Tv models,respectively.These accuracies are sufficient for calculating ZHD to an accuracy of 1 mm by performing atmospheric pressure vertical correction.The new model can correct atmospheric pressure from meteorological stations or numerical weather forecasts to different heights of the troposphere.展开更多
van der Waals(vdW)heterostructures constructed by lowdimensional(0D,1D,and 2D)materials are emerging as one of the most appealing systems in next-generation flexible photodetection.Currently,hand-stacked vdW-type phot...van der Waals(vdW)heterostructures constructed by lowdimensional(0D,1D,and 2D)materials are emerging as one of the most appealing systems in next-generation flexible photodetection.Currently,hand-stacked vdW-type photodetectors are not compatible with large-areaarray fabrication and show unimpressive performance in self-powered mode.Herein,vertical 1D GaN nanorods arrays(NRAs)/2D MoS_(2)/PEDOT:PSS in wafer scale have been proposed for self-powered flexible photodetectors arrays firstly.The as-integrated device without external bias under weak UV illumination exhibits a competitive responsivity of 1.47 A W^(−1)and a high detectivity of 1.2×10^(11)Jones,as well as a fast response speed of 54/71μs,thanks to the strong light absorption of GaN NRAs and the efficient photogenerated carrier separation in type-II heterojunction.Notably,the strain-tunable photodetection performances of device have been demonstrated.Impressively,the device at−0.78%strain and zero bias reveals a significantly enhanced photoresponse with a responsivity of 2.47 A W^(−1),a detectivity of 2.6×10^(11)Jones,and response times of 40/45μs,which are superior to the state-of-the-art self-powered flexible photodetectors.This work presents a valuable avenue to prepare tunable vdWs heterostructures for self-powered flexible photodetection,which performs well in flexible sensors.展开更多
Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was appli...Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.展开更多
The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the ...The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.展开更多
In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradien...In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradient method.Under the condition of standard Wolfe line search,the proposed search direction is the descent direction.For general nonlinear functions,the method is globally convergent.Finally,numerical results show that the proposed method is efficient.展开更多
This article presents four techniques for assessing verticality:the plumb line approach,the total station distance technique,the three-point centering method,and the centroid method.Given the significant error associa...This article presents four techniques for assessing verticality:the plumb line approach,the total station distance technique,the three-point centering method,and the centroid method.Given the significant error associated with the total station horizontal distance technique when measuring circular piers,this paper proposes the centroid method.This method calculates verticality by determining the coordinates of the center points at both ends of the pier.Experimental findings indicate that the centroid method achieves accuracy in measuring the verticality of circular piers comparable to the three-point centering method,while offering a faster inspection process.Furthermore,the paper explores the concept of composite verticality and validates the effectiveness of the centroid method in measuring composite verticality and its practical applications through comparative experiments.展开更多
A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of wa...A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of water with varying concentrations of salt ions.The movement of these ions across a membrane generates electricity.However,the efficiency of these systems faces a challenge due to membrane performance degradation over time,often caused by channel blockages.One potential solution to enhance system efficiency is the use of nanofluidic membranes.These specialized membranes offer high ion exchange capacity,abundant ion sources,and customizable channels with varying sizes and properties.Graphene oxide(GO)-based membranes have emerged as particularly promising candidates in this regard,garnering significant attention in recent literature.This work provides a comprehensive overview of the literature surrounding GO membranes and their applications in RED systems.It also highlights recent advancements in the utilization of GO membranes within these systems.Finally,it explores the potential of these membranes to play a pivotal role in electricity generation within RED systems.展开更多
Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,redu...Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.展开更多
Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodi...Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.展开更多
The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superallo...The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superalloy after gradient thermal deformation to solve the problem of microstructural inhomogeneity.Compression tests involving double cone(DC)samples were conducted at various temperatures to assess the effect of gradient strain on internal grain microstructure variation,which ranged from the rim to the center of the samples.The results demonstrate considerable microstructural inhomogeneity induced by gradient strain in the DC samples.The delay in heat preservation facilitated post-dynamic recrystallization(PDRX)and promoted extensive recrystallization in the DC samples experiencing large gradient strain,which resulted in a homogeneous grain microstructure throughout the samples.During compression at a relatively low temperature,dynamic recrystallization(DRX)was predominantly driven by continuous dynamic recrystallization(CDRX).As the deformation temperature increased,the DRX mechanism changed from CDRX-dominated to being dominated by discontinuous dynamic recrystallization(DDRX).During the delay of the heat preservation process,PDRX was dominated by a static recrystallization mechanism,along with the occurrence of meta-dynamic recrystallization(MDRX)mechanisms.In addition,the PDRX mechanism of twin-induced recrystallization nucleation was observed.展开更多
The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deform...The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deformation of the gradient structure was examined.In this paper,the gradient structure AZ31 Mg-alloy plate with the surface fine grain(FG)to the center coarse grain(CG)was fabricated using hard plate rolling(HPR).The microstructure and strain distribution of Mg-alloy with a gradient structure were analyzed by electron backscatter diffraction(EBSD)and Digital image correlation(DIC)during uniaxial tensile.The findings indicate that the gradient structure sample(GS sample)displays a uniform strain distribution during the tensile process.Coarse-grain sample(CG sample)have obvious strain concentration,which leads to premature fracture.Based on EBSD characterization,low-angle grain boundaries(LAGBs)accumulates in the CG during plastic deformation.Orientation of CG tends to the(0001)basal.At the same time,the density of geometrically necessary dislocations(GNDs)inside CG has changed,which improves the Heterogeneous deformation induced(HDI)stress of gradient structure.During the uniaxial tensile,LAGBs accumulates in CG and changes the strain distribution of the gradient structure,which induces the accumulation of GNDs,and hence improving the properties of the GS Mg-alloy.These findings unveil the mechanism of strength-plasticity synergism of GS alloys from a new perspective and offer insights into the application of GS in Mg-alloys.展开更多
基金supported by the National Key R&D Program of China (Grant No.2022YFF0503700)the special funds of Hubei Luojia Laboratory (Grant No.220100011)+1 种基金supported by the International Space Science Institute–Beijing(ISSI-BJ) project“The Electromagnetic Data Validation and Scientific Application Research based on CSES Satellite”and ISSI/ISSI-BJ project,“Multi-Scale Magnetosphere–Ionosphere–Thermosphere Interaction.”
文摘The Michelson Interferometer for Global High-resolution Thermospheric Imaging(MIGHTI)onboard the Ionospheric Connection Explorer(ICON)satellite offers the opportunity to investigate the altitude profile of thermospheric winds.In this study,we used the red-line measurements of MIGHTI to compare with the results estimated by Horizontal Wind Model 14(HWM14).The data selected included both the geomagnetic quiet period(December 2019 to August 2022)and the geomagnetic storm on August 26-28,2021.During the geomagnetic quiet period,the estimations of neutral winds from HWM14 showed relatively good agreement with the observations from ICON.According to the ICON observations,near the equator,zonal winds reverse from westward to eastward at around 06:00 local time(LT)at higher altitudes,and the stronger westward winds appear at later LTs at lower altitudes.At around 16:00 LT,eastward winds at 300 km reverse to westward,and vertical gradients of zonal winds similar to those at sunrise hours can be observed.In the middle latitudes,zonal winds reverse about 2-4 h earlier.Meridional winds vary more significantly than zonal winds with seasonal and latitudinal variations.According to the ICON observations,in the northern low latitudes,vertical reversals of meridional winds are found at 08:00-13:00 LT from 300 to 160 km and at around 18:00 LT from 300 to 200 km during the June solstice.Similar reversals of meridional winds are found at 04:00-07:00 LT from 300 to 160 km and at 22:00-02:00 LT from 270 to 200 km during the December solstice.In the southern low latitudes,meridional wind reversals occur at 08:00-11:00 LT from 200 to 160 km and at 21:00-02:00 LT from 300 to 200 km during the June solstice.During the December solstice,reversals of the meridional wind appear at 20:00-01:00 LT below 200 km and at 06:00-11:00 LT from 300 to 160 km.In the northern middle latitudes,the northward winds are dominant at 08:00-14:00 LT at 230 km during the June solstice.Northward winds persist until 16:00 LT at 160 and 300 km.During the December solstice,the northward winds are dominant from 06:00 to 21:00 LT.The vertical variations in neutral winds during the geomagnetic storm on August 26-28 were analyzed in detail.Both meridional and zonal winds during the active geomagnetic period observed by ICON show distinguishable vertical shear structures at different stages of the storm.On the dayside,during the main phase,the peak velocities of westward winds extend from a higher altitude to a lower altitude,whereas during the recovery phase,the peak velocities of the westward winds extend from lower altitudes to higher altitudes.The velocities of the southward winds are stronger at lower altitudes during the storm.These vertical structures of horizontal winds during the storm could not be reproduced by the HWM14 wind estimations,and the overall response to the storm of the horizontal winds in the low and middle latitudes is underestimated by HWM14.The ICON observations provide a good dataset for improving the HWM wind estimations in the middle and upper atmosphere,especially the vertical variations.
基金supported by the National Key R&D Program(Nos.2023YFE0108500 and 2023YFF0719500)the National Natural Science Foundation of China(Nos.52072300 and 52302199)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515110538)Key Research and Development Program of Shaanxi(No.2023-GHZD-48)the Fundamental Research Funds for the Central Universities.
文摘Cadmium telluride(CdTe),which has a high average atomic number and a unique band structure,is a leading material for room-temperature X/γ-ray detectors.Resistivity and mobility are the two most important properties of detector-grade CdTe single crystals.However,despite decades of research,the fabrication of high-resistivity and high-mobility CdTe single crystals faces persistent challenges,primarily because the stoichiometric composition cannot be well controlled owing to the high volatility of Cd under high-temperature conditions.This volatility introduces Te inclusions and cadmium vacancies(V_(Cd))into the as-grown CdTe ingot,which significantly degrades the device performance.In this study,we successfully obtained detector-grade CdTe single crystals by simultaneously employing a Cd reservoir and chlorine(Cl)dopants via a vertical gradient freeze(VGF)method.By installing a Cd reservoir,we can maintain the Cd pressure under the crystal growth conditions,thereby preventing the accumulation of Te in the CdTe ingot.Additionally,the existence of the Cl dopant helps improve the CdTe resistivity by minimizing V_(Cd)density through the formation of an acceptor complex(Cl_(Te)-V_(Cd))^(-1).The crystalline quality of the obtained CdTe(Cl)was evidenced by a reduction in large Te inclusions,high optical transmission(60%),and a sharp absorption edge(1.456 eV).The presence of substitutional Cl dopants,known as Cl_(Te)^(+),simultaneously supports the record high resistivity of 1.5×10^(10)Ω·cm and remarkable electron mobility of 1075±88 cm^(2)V^(-1)s^(-1)simultaneously,has been confirmed by photoluminescence spectroscopy.Moreover,using our crystals,we fabricated a planar detector withμτ_(e)of(1.11±0.04)×10^(-4)cm^(2)∕V,which performed with a decent radiation-detection feature.This study demonstrates that the vapor-pressure-controlled VGF method is a viable technical route for fabricating detector-grade CdTe crystals.
基金supported by the National Natural Science Foundation of China(52372099,52202328,22461142135,22479046)the Shanghai Sailing Program(22YF1455500)the Shanghai Magnolia Talent Plan Pujiang Project(24PJD128)。
文摘Solid-state polymer electrolytes are crucial for advancing solid-state lithium-metal batteries owing to their flexibility,excellent manufacturability,and strong interfacial compatibility.However,their widespread applications are hindered by low ionic conductivity at room temperature and lithium dendrite growth.Herein,we report a novel solid-state composite membrane electrolyte design that combines the vertically aligned channel structure and copolymer with a radial gradient composition.Within the vertically aligned channels,the composition of poly(vinyl ethylene carbonate-co-poly(ethylene glycol)diacrylate)(P(VEC-PEGDA)varies in a gradient along the radial direction:from the center to the wall of vertically aligned channels,the proportion of vinyl ethylene carbonate(VEC)in the copolymer decreases,while the proportion of poly(ethylene glycol)diacrylate(PEGDA)increases accordingly.It can be functionally divided into a mechanical-reinforcement layer and a fast-ion-conducting layer.The resulting solid-state composite membrane electrolyte achieves a high critical current density of 1.2 mA cm^(-2)and high ionic conductivity of 2.03 mS cm^(-1)at room temperature.Employing this composite membrane electrolyte,a Li//Li symmetric cell exhibits stable cycling for over 1850 h at 0.2 m A cm^(-2)/0.2 m A h cm^(-2),and a Li//LiFePO4(LFP)battery maintains 77.3% capacity retention at 2 C after 300 cycles.Our work provides insight into the rational design of safer and more efficient solidstate batteries through electrolyte structural engineering.
基金funded jointly by the National Nature Science Funds of China(No.42274010)the Fundamental Research Funds for the Central Universities(Nos.2023000540,2023000407).
文摘The prediction of bathymetry has advanced significantly with the development of satellite altimetry.However,the majority of its data originate from marine gravity anomaly.In this study,based on the expression of vertical gravity gradient(VGG)of a rectangular prism,the governing equations for determining sea depths to invert bathymetry.The governing equation is solved by linearization through an iterative process,and numerical simulations verify its algorithm and its stability.We also study the processing methods of different interference errors.The regularization method improves the stability of the inversion process for errors.A piecewise bilinear interpolation function roughly replaces the low-frequency error,and numerical simulations show that the accuracy can be improved by 41.2%after this treatment.For variable ocean crust density,simulation simulations verify that the root-mean-square(RMS)error of prediction is approximately 5 m for the sea depth of 6 km if density is chosen as the average one.Finally,two test regions in the South China Sea are predicted and compared with ship soundings data,RMS errors of predictions are 71.1 m and 91.4 m,respectively.
基金financial support from the Ministry of Science and Higher Education of the Russian Federation(Topic No.121031700169-1).
文摘In this paper,we study the onset and development of three-dimensional convection in a tilted porous layer saturated with a liquid.The layer is subjected to a gravitational field and a strictly vertical temperature gradient.Typically,problems of thermal convection in tilted porous media saturated with a liquid are studied by assuming constant different temperatures at the boundaries of the layer,which prevent these systems from supporting conductive(non-convective)states.The boundary conditions considered in the present work allow a conductive state and are representative of typical geological applications.In an earlier work,we carried out a linear stability analysis of the conductive state.It was shown that at any layer tilt angles,the most dangerous type of disturbances are longitudinal rolls.Moreover,a non-zero velocity component exists in z-direction.In the present work,threedimensional non-linear convection regimes are studied.The original three-dimensional problem is reduced to two-dimensional one with an analytical expression for the velocity z-component v_(z)=v_(z)(x,y).It is shown that the critical Rayleigh number values obtained through numerical solutions of the obtained 2D problem by a finite difference method for different layer inclination angles,are in a good agreement with those predicted by the linear theory.The number of convective rolls realized in nonlinear calculations also fits the linear theory predictions for a given cavity geometry.Calculations carried out at low supercriticalities show that a direct bifurcation takes place.With increasing supercriticality,no transitions to other convective regimes are detected.The situation studied in this problem can be observed in oil-bearing rock formations under the influence of a geothermal temperature gradient,where the ensuing fluid convection can affect the distribution of oil throughout the layer.
基金supported by Systematic Major Project of Shuohuang Railway Development Co.,Ltd.,National Energy Group(Grant Number:SHTL-23-31)Beijing Natural Science Foundation(U22B2027).
文摘In the realm of Intelligent Railway Transportation Systems,effective multi-party collaboration is crucial due to concerns over privacy and data silos.Vertical Federated Learning(VFL)has emerged as a promising approach to facilitate such collaboration,allowing diverse entities to collectively enhance machine learning models without the need to share sensitive training data.However,existing works have highlighted VFL’s susceptibility to privacy inference attacks,where an honest but curious server could potentially reconstruct a client’s raw data from embeddings uploaded by the client.This vulnerability poses a significant threat to VFL-based intelligent railway transportation systems.In this paper,we introduce SensFL,a novel privacy-enhancing method to against privacy inference attacks in VFL.Specifically,SensFL integrates regularization of the sensitivity of embeddings to the original data into the model training process,effectively limiting the information contained in shared embeddings.By reducing the sensitivity of embeddings to the original data,SensFL can effectively resist reverse privacy attacks and prevent the reconstruction of the original data from the embeddings.Extensive experiments were conducted on four distinct datasets and three different models to demonstrate the efficacy of SensFL.Experiment results show that SensFL can effectively mitigate privacy inference attacks while maintaining the accuracy of the primary learning task.These results underscore SensFL’s potential to advance privacy protection technologies within VFL-based intelligent railway systems,addressing critical security concerns in collaborative learning environments.
基金support for this work by Key Research and Development Project of Henan Province(Grant.No.241111232300)the National Natural Science Foundation of China(Grant.No.52273085 and 52303113)the Open Fund of Yaoshan Laboratory(Grant.No.2024003).
文摘The morphological distribution of absorbent in composites is equally important with absorbents for the overall electromagnetic properties,but it is often ignored.Herein,a comprehensive consideration including electromagnetic component regulation,layered arrangement structure,and gradient concentration distribution was used to optimize impedance matching and enhance electromagnetic loss.On the microscale,the incorporation of magnetic Ni nanoparticles into MXene nanosheets(Ni@MXene)endows suitable intrinsic permittivity and permeability.On the macroscale,the layered arrangement of Ni@MXene increases the effective interaction area with electromagnetic waves,inducing multiple reflection/scattering effects.On this basis,according to the analysis of absorption,reflection,and transmission(A-R-T)power coefficients of layered composites,the gradient concentration distribution was constructed to realize the impedance matching at low-concentration surface layer,electromagnetic loss at middle concentration interlayer and microwave reflection at high-concentration bottom layer.Consequently,the layered gradient composite(LG5-10-15)achieves complete absorption coverage of X-band at thickness of 2.00-2.20 mm with RL_(min) of-68.67 dB at 9.85 GHz in 2.05 mm,which is 199.0%,12.6%,and 50.6%higher than non-layered,layered and layered descending gradient composites,respectively.Therefore,this work confirms the importance of layered gradient structure in improving absorption performance and broadens the design of high-performance microwave absorption materials.
基金supported by the National Natural Science Foundation of China(Grant No.52473121,52403370 and 52221006)Fundamental Research Funds for the Central Universities(buctrc202020,buctrc202312).
文摘The intricate hierarchical structure of musculoskeletal tissues,including bone and interface tissues,necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes.This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes.Building on the anatomical characteristics of bone and interfacial tissues,this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues,specifically focusing on methods used to construct compositional and structural gradients within the scaffolds.The latest applications of gradient scaffolds for the regeneration of bone,osteochondral,and tendon-to-bone interfaces are presented.Furthermore,the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed,as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.
基金the support of the National Natural Science Foundation of China (Nos. 42250103, 41974073, and 41404053)the Macao Foundation and the preresearch project of Civil Aerospace Technologies (Nos. D020308 and D020303)funded by China’s National Space Administration, the Specialized Research Fund for State Key Laboratories。
文摘We combine gradient data from the Macao Science Satellite-1(MSS-1),CHAllenging Minisatellite Payload(CHAMP),Swarm-A,and Swarm-C satellites to develop a 110-degree lithospheric magnetic field model.We then comprehensively evaluate the performance of the model by power spectral comparisons,correlation analyses,sensitivity matrix assessments,and comparisons with existing lithospheric field models.Results showed that using near east–west gradient data from MSS-1 significantly enhances the model correlation in the spherical harmonic degree(N) range of 45–60 while also mitigating the decline in correlation at higher degrees(N > 60).Furthermore,the unique orbital characteristics of MSS-1 enable its gradient data to provide substantial contributions to modeling in the mid-to low-latitude regions.With continued data acquisition from MSS-1 and further optimization of data processing methods,the performance of the model is expected to improve.
基金supported by the National Natural Science Foundation of China(42304018)the National Natural Science Foundation of China(42330105,42064002,42074035)+3 种基金the Guangxi Natural Science Foundation of China(Guike AD23026177,2020GXNSFBA297145)the Foundation of Guilin University of Technology(GUTQDJJ6616032)Guangxi Key Laboratory of Spatial Information and Geomatics(21238-21-05)the Innovation Project of Guangxi Graduate Education(YCSW2023341)。
文摘The Zenith Hydrostatic Delay(ZHD)is essential for high-precision Global Navigation Satellite System(GNSS)and Very Long Baseline Interferometry(VLBI)data processing.Accurate estimation of ZHD relies on in situ atmospheric pressure,which is primarily variable in the vertical direction.Current atmospheric pressure is either site-specific or has limited spatial coverage,necessitating vertical corrections for broader applicability.This study introduces a model that uses a Gaussian function for the vertical correction of atmospheric pressure when in situ meteorological observations are unavailable.Validation with the fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis(ERA5)reveals an average Bias and RMS for the new model of 0.31 h Pa and 2.96 h Pa,respectively.This corresponds to improvements of 37.5%and 80.3%in terms of RMS compared to two commonly used models(T0and Tvmodels)that require in situ meteorological observations,respectively.Additional validation with radiosonde data shows an average Bias and RMS of 1.85 h Pa and 4.87 h Pa,corresponding to the improvement of 42.8%and 71.1%in RMS compared with T0and Tv models,respectively.These accuracies are sufficient for calculating ZHD to an accuracy of 1 mm by performing atmospheric pressure vertical correction.The new model can correct atmospheric pressure from meteorological stations or numerical weather forecasts to different heights of the troposphere.
基金supported by the National Key Research and Development Program of China(No.2022YFB3604500,No.2022YFB3604501)the National Natural Science Foundation of China(No.52172141)the Technology Development Project of Shanxi-Zheda Institude of Advanced Materials and Chemical Engineering(No.2022SX-TD017).
文摘van der Waals(vdW)heterostructures constructed by lowdimensional(0D,1D,and 2D)materials are emerging as one of the most appealing systems in next-generation flexible photodetection.Currently,hand-stacked vdW-type photodetectors are not compatible with large-areaarray fabrication and show unimpressive performance in self-powered mode.Herein,vertical 1D GaN nanorods arrays(NRAs)/2D MoS_(2)/PEDOT:PSS in wafer scale have been proposed for self-powered flexible photodetectors arrays firstly.The as-integrated device without external bias under weak UV illumination exhibits a competitive responsivity of 1.47 A W^(−1)and a high detectivity of 1.2×10^(11)Jones,as well as a fast response speed of 54/71μs,thanks to the strong light absorption of GaN NRAs and the efficient photogenerated carrier separation in type-II heterojunction.Notably,the strain-tunable photodetection performances of device have been demonstrated.Impressively,the device at−0.78%strain and zero bias reveals a significantly enhanced photoresponse with a responsivity of 2.47 A W^(−1),a detectivity of 2.6×10^(11)Jones,and response times of 40/45μs,which are superior to the state-of-the-art self-powered flexible photodetectors.This work presents a valuable avenue to prepare tunable vdWs heterostructures for self-powered flexible photodetection,which performs well in flexible sensors.
基金The financial supports by the Chinese Academy of Sciences(Nos.XDC04030300 and XDB0510303)CAS-HK Joint Laboratory of Nanomaterials and MechanicsShenyang National Laboratory for Materials Science are acknowledged.
文摘Rolling contact fatigue performance is among the most important issues for applications of bearing steels.In this work,a recently developed surface modification technique,surface mechanical rolling treatment,was applied on a rare-earth addition bearing steel.And rolling contact fatigue behavior of treated samples was compared with that of as-received counterparts at different contacting stresses.The results demonstrated that a 700μm-thick gradient nanostructured surface layer is produced on samples by surface mechanical rolling treatment.The grain size decreases while the microhardness increases gradually with decreasing depth,reaching~23 nm and~10.2 GPa,respectively,at the top surface.Consequently,the rolling contact fatigue property is significantly enhanced.The characteristic life of treated samples is~3.2 times that of untreated counterparts according to Weibull curves at 5.6 GPa.Analyses of fatigue mechanisms demonstrated that the gradient nanostructured surface layer might not only retard material degradation and microcrack formation,but also prolong the steady-state elastic response stage under rolling contact fatigue.
基金supported by the National Key R&D Program of China(No.2022YFB2404400)the National Natural Science Foundation of China(Nos.U23A20577,52372168,92263206 and 21975006)+1 种基金the“The Youth Beijing Scholars program”(No.PXM2021_014204_000023)the Beijing Natural Science Foundation(Nos.2222001 and KM202110005009).
文摘The cobalt-free Mn-based Li-rich layered oxide material has the advantages of low cost,high energy density,and good performance at low temperatures,and is the promising choice for energy storage batteries.However,the long-cycling stability of batteries needs to be improved.Herein,the Mn-based Li-rich cathode materials with small amounts of Li2 MnO3 crystal domains and gradient doping of Al and Ti elements from the surface to the bulk have been developed to improve the structure and interface stability.Then the batteries with a high energy density of 600 Wh kg^(-1),excellent capacity retention of 99.7%with low voltage decay of 0.03 mV cycle^(-1) after 800 cycles,and good rates performances can be achieved.Therefore,the structure and cycling stability of low voltage Mn-based Li-rich cathode materials can be significantly improved by the bulk structure design and interface regulation,and this work has paved the way for developing low-cost and high-energy Mn-based energy storage batteries with long lifetime.
基金Supported by the Science and Technology Project of Guangxi(Guike AD23023002)。
文摘In this paper,we propose a three-term conjugate gradient method for solving unconstrained optimization problems based on the Hestenes-Stiefel(HS)conjugate gradient method and Polak-Ribiere-Polyak(PRP)conjugate gradient method.Under the condition of standard Wolfe line search,the proposed search direction is the descent direction.For general nonlinear functions,the method is globally convergent.Finally,numerical results show that the proposed method is efficient.
文摘This article presents four techniques for assessing verticality:the plumb line approach,the total station distance technique,the three-point centering method,and the centroid method.Given the significant error associated with the total station horizontal distance technique when measuring circular piers,this paper proposes the centroid method.This method calculates verticality by determining the coordinates of the center points at both ends of the pier.Experimental findings indicate that the centroid method achieves accuracy in measuring the verticality of circular piers comparable to the three-point centering method,while offering a faster inspection process.Furthermore,the paper explores the concept of composite verticality and validates the effectiveness of the centroid method in measuring composite verticality and its practical applications through comparative experiments.
基金Key Research and Development Program of Zhejiang Province,Grant/Award Number:2021C04019National Natural Science Foundation of China,Grant/Award Number:U20A20338Natural Science Foundation of Zhejiang Province,Grant/Award Number:LQ21H180012.
文摘A widely employed energy technology,known as reverse electrodialysis(RED),holds the promise of delivering clean and renewable electricity from water.This technology involves the interaction of two or more bodies of water with varying concentrations of salt ions.The movement of these ions across a membrane generates electricity.However,the efficiency of these systems faces a challenge due to membrane performance degradation over time,often caused by channel blockages.One potential solution to enhance system efficiency is the use of nanofluidic membranes.These specialized membranes offer high ion exchange capacity,abundant ion sources,and customizable channels with varying sizes and properties.Graphene oxide(GO)-based membranes have emerged as particularly promising candidates in this regard,garnering significant attention in recent literature.This work provides a comprehensive overview of the literature surrounding GO membranes and their applications in RED systems.It also highlights recent advancements in the utilization of GO membranes within these systems.Finally,it explores the potential of these membranes to play a pivotal role in electricity generation within RED systems.
基金Supported by the National Key Research and Development Program(2023YFC3107602)。
文摘Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.
基金supported by the National Natural Science Foundation of China(Grant Nos.12274313,62275184,and 62411540033)Collaborative Innovation Center of Suzhou Nano Science and Technology,Suzhou Basic Research Project(Grant No.SJC2023003)+1 种基金the Gusu Leading Talent Plan for Scientific and Technological Innovation and Entrepreneurship(Grant No.ZXL2024400)the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Perfect anomalous reflections have been demonstrated in optical phase gradient metasurfaces(PGMs),but they suffer from single-frequency(narrow-band)response due to the intrinsic limitation of natural geometric periodicity.Here,we provide both numerical and analytical evidence that a depth gradient metasurface can achieve discrete ultra-broadband perfect anomalous reflection in the microwave range in the absence of geometric periodicity.Remarkably,by adjusting the operating frequency of the incident wave,the same effect can be steadily obtained via a physically equivalent phase periodicity in the PGM.Based on this mechanism,a perfect retroreflector with a broadband response ranging from 1 GHz to 40 GHz is realized.Our work has promising applications in communication,source tracking,and military satellites.
基金supported by Shandong Provincial Natural Science Foundation of China(Nos.ZR2024JQ020 and ZR2021QE102)the Taishan Scholars Program of Shandong Province,China(Nos.tsqn202211115,tsqn201909081,and tsqn202306162)+2 种基金the National Natural Science Foundation of China(No.52274397)Yantai high-end talent introduction“Double Hundred Plan”,China(2021)the Graduate Innovation Foundation of Yantai University,China(No.KGIFYTU2520).
文摘The GH141 superalloy ring-rolled parts often face microstructural inhomogeneity during production.This work investigated the effect of post-dynamic recrystallization on the microstructural evolution of GH141 superalloy after gradient thermal deformation to solve the problem of microstructural inhomogeneity.Compression tests involving double cone(DC)samples were conducted at various temperatures to assess the effect of gradient strain on internal grain microstructure variation,which ranged from the rim to the center of the samples.The results demonstrate considerable microstructural inhomogeneity induced by gradient strain in the DC samples.The delay in heat preservation facilitated post-dynamic recrystallization(PDRX)and promoted extensive recrystallization in the DC samples experiencing large gradient strain,which resulted in a homogeneous grain microstructure throughout the samples.During compression at a relatively low temperature,dynamic recrystallization(DRX)was predominantly driven by continuous dynamic recrystallization(CDRX).As the deformation temperature increased,the DRX mechanism changed from CDRX-dominated to being dominated by discontinuous dynamic recrystallization(DDRX).During the delay of the heat preservation process,PDRX was dominated by a static recrystallization mechanism,along with the occurrence of meta-dynamic recrystallization(MDRX)mechanisms.In addition,the PDRX mechanism of twin-induced recrystallization nucleation was observed.
基金supported by the Natural Science Foundation of Heilongjiang Province(JQ2022E004)。
文摘The changes in strain gradient induced by grain boundaries are crucial for enhancing the plasticity of gradient magnesium(Mg)alloys.The change of strain distribution influence by grain boundaries during plastic deformation of the gradient structure was examined.In this paper,the gradient structure AZ31 Mg-alloy plate with the surface fine grain(FG)to the center coarse grain(CG)was fabricated using hard plate rolling(HPR).The microstructure and strain distribution of Mg-alloy with a gradient structure were analyzed by electron backscatter diffraction(EBSD)and Digital image correlation(DIC)during uniaxial tensile.The findings indicate that the gradient structure sample(GS sample)displays a uniform strain distribution during the tensile process.Coarse-grain sample(CG sample)have obvious strain concentration,which leads to premature fracture.Based on EBSD characterization,low-angle grain boundaries(LAGBs)accumulates in the CG during plastic deformation.Orientation of CG tends to the(0001)basal.At the same time,the density of geometrically necessary dislocations(GNDs)inside CG has changed,which improves the Heterogeneous deformation induced(HDI)stress of gradient structure.During the uniaxial tensile,LAGBs accumulates in CG and changes the strain distribution of the gradient structure,which induces the accumulation of GNDs,and hence improving the properties of the GS Mg-alloy.These findings unveil the mechanism of strength-plasticity synergism of GS alloys from a new perspective and offer insights into the application of GS in Mg-alloys.
