This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajec...This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajectories.Calculations were performed to investigate the propagation of microwaves in the V(40–75 GHz)and W(75–110 GHz)frequency ranges with O-mode polarization for the density profile of the base TRT scenario.Our analysis showed that the DBS system antenna on the TRT would need to be tilted in both the poloidal and toroidal directions in order to meet the condition Kperp/Kpar<10%..For the DBS system located in the equatorial plane it was shown that a wide range of poloidal and toroidal angles is available for the successful implementation of the diagnostic to study the core,pedestal and scrape-off layer(SOL)regions.The DBS system located at 35 cm above the equatorial plane would be more limited in measurements only covering the SOL and pedestal regions.A shift of the cut-offs in the toroidal direction highlighted the need for 3D analysis of the DBS data.展开更多
Backscatter communication(BC)is con-sidered a key technology in self-sustainable commu-nications,and the unmanned aerial vehicle(UAV)as a data collector can improve the efficiency of data col-lection.We consider a UAV...Backscatter communication(BC)is con-sidered a key technology in self-sustainable commu-nications,and the unmanned aerial vehicle(UAV)as a data collector can improve the efficiency of data col-lection.We consider a UAV-aided BC system,where the power beacons(PBs)are deployed as dedicated radio frequency(RF)sources to supply power for backscatter devices(BDs).After harvesting enough energy,the BDs transmit data to the UAV.We use stochastic geometry to model the large-scale BC sys-tem.Specifically,the PBs are modeled as a type II Mat´ern hard-core point process(MHCPP II)and the BDs are modeled as a homogeneous Poisson point process(HPPP).Firstly,the BDs’activation proba-bility and average coverage probability are derived.Then,to maximize the energy efficiency(EE),we opti-mize the RF power of the PBs under different PB den-sities.Furthermore,we compare the coverage proba-bility and EE performance of our system with a bench-mark scheme,in which the distribution of PBs is mod-eled as a HPPP.Simulation results show that the PBs modeled as MHCPP II has better performance,and we found that the higher the density of PBs,the smaller the RF power required,and the EE is also higher.展开更多
The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and obli...The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and oblique backscatter detection.The ionograms obtained by these detection methods can effectively reflect a large amount of effective information in the ionosphere.The focus of this article is on the oblique backscatter ionogram obtained by oblique backscatter detection.By extracting the leading edge of the oblique backscatter ionogram,effective information in the ionosphere can be inverted.The key issue is how to accurately obtain the leading edge of the oblique backscatter ionogram.In recent years,the application of pattern recognition has become increasingly widespread,and the YOLO model is one of the best fast object detection algorithms in one-stage.Therefore,the core idea of this article is to use the newer YOLOX object detection algorithm in the YOLO family to perform pattern recognition on the F and E_(s) layers echoes in the oblique backscatter ionogram.After image processing,a single-layer oblique backscatter echoes are obtained.It can be found that the leading edge extraction of the oblique backscatter ionogram obtained after pattern recognition and image processing by the YOLOX model is more fitting to the actual oblique backscatter leading edge.展开更多
The vectorial evolution of light polarization can reveal the microstructure and anisotropy of a medium beyond what can be obtained from measuring light intensity alone.However,polarization imaging in reflection geomet...The vectorial evolution of light polarization can reveal the microstructure and anisotropy of a medium beyond what can be obtained from measuring light intensity alone.However,polarization imaging in reflection geometry,which is ubiquitous and often preferred in diverse applications,has often suffered from poor and even incorrect characterization of anisotropic media.We present reciprocal polarization imaging of complex media in reflection geometry with the reciprocal polar decomposition of backscattering Mueller matrices enforcing reciprocity.We demonstrate that reciprocal polarization imaging of complex chiral and anisotropic media ac-curately quantifies their anisotropic properties in reflection geometry,whereas traditional approaches encounter difficulties and produce inferior and often erroneous results from the violation of reciprocity.In particular,reciprocal polarization imaging provides a consistent characterization of complex media of different thicknesses,accurately measures the optical activity and glucose concentration of turbid media in reflection,and discriminates between cancerous and normal tissue with even stronger contrast than forward measurement.Reciprocal polarization imaging promises broad applications of polarization optics ranging from remote sensing to bio-medicine in reflection geometries,especially in in vivo biomedical imaging,where reflection is the only feasible geometry.展开更多
In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indic...In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indicators included boundary identification and variant distribution. Moreover, an innovative variant pair analysis method was proposed. The results indicated that the Kurdjumov-Sachs orientation relationship was the most appropriate because it had the smallest refinement error and deviation. In addition, the variant graph reconstruction was more effective in reducing mis-indexing areas than the grain graph, exhibiting a robust capacity to accurately identify austenite grain boundaries. Additionally, the variant graph reconstruction induced the transformation of variants, variant pairs, close-packed plane (CP) groups, and Bain groups. Moreover, various reconstructed datasets (calc-grain data and EBSD data) affected the distribution of variants. The austenite grains reconstructed from the calc-grain data featured two or more variants clustered within the same region due to the preprocessing (calculating, filtering, and smoothing) of the EBSD data. These variations did not impede the microstructural analysis when consistent original data and reconstruction methods were used. The reconstruction of parent austenite grains holds promise for providing a fresh perspective and a deeper understanding of strengthening and toughening mechanisms in the future.展开更多
The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff...The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff layer in the plasma at an angle oblique to the cutoff layer.A new Q-band multichannel DBS system based on a comb generator has been designed and tested for application on the HL-3 tokamak.With the comb generator and heterodyne scheme,the stability and flexibility of the new DBS system are improved.The new DBS diagnostic has a high output power(~10 dBm),good power flatness(<5 dB in Q-band),and frequency stability,and the inter-frequency separation is tunable remotely.This article introduces the system design,laboratory test results,and initial experimental results from the HL-3 tokamak.With the help of the newly developed multichannel DBS,the turbulence information can be studied with high temporal and spatial resolution.展开更多
Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving mod...Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving model predictions.In this study,we propose a convolutional neural network(CNN)that combines data-driven techniques with physical principles to develop a robust and interpretable parameterization scheme for mesoscale eddies in ocean modeling.We use a highresolution reanalysis dataset to extract subgrid eddy momentum and then applying machine learning algorithms to identify patterns and correlations.To ensure physical consistency,we have introduced conservation of momentum constraints in our CNN parameterization scheme through soft and hard constraints.The interpretability analysis illustrate that the pre-trained CNN parameterization shows promising results in accurately solving the resolved mean velocity and effectively capturing the representation of unresolved subgrid turbulence processes.Furthermore,to validate the CNN parameterization scheme offline,we conduct simulations using the Massachusetts Institute of Technology general circulation model(MITgcm)ocean model.A series of experiments is conducted to compare the performance of the model with the CNN parameterization scheme and high-resolution simulations.The offline validation demonstrates the effectiveness of the CNN parameterization scheme in improving the representation of mesoscale eddies in the MITgcm ocean model.Incorporating the CNN parameterization scheme leads to better agreement with high-resolution simulations and a more accurate representation of the kinetic energy spectra.展开更多
Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relatio...Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relationships of 0.6μm electroplated nickel(Ni)steel following annealing at 580-650℃for 15-30 hours were investigated.A comprehensive analysis was conducted to gain insights into the complex changes in the material's properties due to the annealing process.The results reveal that prolonged annealing led to considerable long-range diffusion of surface Ni atoms into the substrate of the 0.6μm Ni-plated steel.This diffusion process resulted in the formation of an alloy diffusion layer,approximately 4μm in thickness,which altered the material's microstructural characteristics.The extent of diffusion and its effect on the microstructure and structure were meticulously quantified.At the annealing temperature,the diffused Ni in the substrate,acting as an austenite-stabilizing element,expanded the austenite phase region.The alloy layer at this temperature predominantly consisted of the face-centered cubic(FCC)-structuredγ(Fe,Ni)solid solution.Upon cooling to room temperature,the alloy diffusion layer evolved into a dual-layer composite structure.The upper layer mainly comprised the FCC-structuredγ(Fe,Ni)solid solution,interspersed with a minor FCC compound superstructure phase.The lower layer underwent a diffusionless phase transformation during cooling,which led to the formation of the body-centered tetragonal/body-centered cubic-structured martensite.This phase,which is known for its high hardness and numerous variants,maintained the classic Kurdjumov-Sachs orientation relationship with the upper FCC parent phase,and it satisfied the close-packed plane{111}γ//{110}α′and close-packed direction<110>γ//<111>α′.A detailed analysis of the different phases within the alloy layer and their phase transitions was presented,offering an in-depth understanding of the material's characteristics.展开更多
The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lam...The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.展开更多
Existing orthogonal space-time block coding(OSTBC)schemes for backscatter communication systems cannot achieve a full transmission code rate when the tag is equipped with more than two antennas.In this paper,we propos...Existing orthogonal space-time block coding(OSTBC)schemes for backscatter communication systems cannot achieve a full transmission code rate when the tag is equipped with more than two antennas.In this paper,we propose a quasi-orthogonal spacetime block code(QOSTBC)that can achieve a full transmission code rate for backscatter communication systems with a four-antenna tag and then extend the scheme to support tags with 2i antennas.Specifically,we first present the system model for the backscatter system.Next,we propose the QOSTBC scheme to encode the tag signals.Then,we provide the corresponding maximum likelihood detection algorithms to recover the tag signals.Finally,simulation results are provided to demonstrate that our proposed QOSTBC scheme and the detection algorithm can achieve a better transmission code rate or symbol error rate performance for backscatter communication systems compared with benchmark schemes.展开更多
In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(N...In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.展开更多
A polarized bidirectional reflectance distribution function(pBRDF)matrix is developed from two-scale roughness theory with the aim of providing more accurate simulations of microwave emissions and scattering required ...A polarized bidirectional reflectance distribution function(pBRDF)matrix is developed from two-scale roughness theory with the aim of providing more accurate simulations of microwave emissions and scattering required for ocean-atmosphere coupled radiative transfer models.The potential of the pBRDF matrix is explored for simu-lating the ocean backscatter at Ku-band.The effects of ocean wave spectra including the modified Durden and Vesecky(DV2),Elfouhaily,and Kudryavtsev spectra on the pBRDF matrix backscatter simulations are investi-gated.Additionally,the differences in backscattering normalized radar cross-section(NRCS)simulations between the Ku-band geophysical model function and pBRDF matrix are analyzed.The results show that the pBRDF matrix can reasonably reproduce the spatial distribution of ocean surface backscattering energy,but the distribution pat-tern and numerical values are influenced by ocean wave spectra.The DV2 spectrum is the best one for the pBRDF matrix to simulate horizontally polarized NRCSs,with the exception of scenarios where the incidence angle is below 35°,the wind speed is less than 10 m s^(−1),and in the cross-wind direction.Also,the DV2 spectrum effec-tively characterizes the wind speed and relative azimuth angle dependence for vertically polarized NRCSs.The Elfouhaily spectrum is suitable for simulating vertically polarized NRCSs under conditions of low wind speed(be-low 5 m s^(−1))and incidence angles under 40°.The Kudryavtsev spectrum excels in simulating vertically polarized NRCSs at high incidence angles(>40°)and horizontally polarized NRCSs at low incidence angles(<35°).展开更多
A P-band polarimetric synthetic aperture radar(PolSAR)sensor has deep penetration ability into and through the vegetation canopies in forested environments.Thus,the sensor is of great potential to accurately assess fo...A P-band polarimetric synthetic aperture radar(PolSAR)sensor has deep penetration ability into and through the vegetation canopies in forested environments.Thus,the sensor is of great potential to accurately assess forest parameters such as coverage,stand density,and tree height.Unfortunately,the radar backscatter from complex terrain can adversely impact the backscatter from trees or forests,and forest parameters assessed can be erroneous.Thus,reducing the topographic impact is an urgent must.In this study,a topographic compensation algorithm has been studied.To assess the algorithm’s validity and effectiveness,we applied it to P-band PolSAR datasets in four forested areas in the US.Trees in the forest stands have diverse species,and the topographic conditions of the terrain differ.Significant topographic impact on the P-band PolSAR data exists before the topographic compensation algorithm.After the algorithm,the impact decreases noticeably qualitatively and quantitatively.The algorithm is valid and effective in reducing the topographic influence on the PolSAR data and,consequently,provides a better chance of retrieving accurate forest parameters.展开更多
The rapid evolution of wireless technologies and the advent of 6G networks present new challenges and opportunities for Internet ofThings(IoT)applications,particularly in terms of ultra-reliable,secure,and energyeffic...The rapid evolution of wireless technologies and the advent of 6G networks present new challenges and opportunities for Internet ofThings(IoT)applications,particularly in terms of ultra-reliable,secure,and energyefficient communication.This study explores the integration of Reconfigurable Intelligent Surfaces(RIS)into IoT networks to enhance communication performance.Unlike traditional passive reflector-based approaches,RIS is leveraged as an active optimization tool to improve both backscatter and direct communication modes,addressing critical IoT challenges such as energy efficiency,limited communication range,and double-fading effects in backscatter communication.We propose a novel computational framework that combines RIS functionality with Physical Layer Security(PLS)mechanisms,optimized through the algorithm known as Deep Deterministic Policy Gradient(DDPG).This framework adaptively adapts RIS configurations and transmitter beamforming to reduce key challenges,including imperfect channel state information(CSI)and hardware limitations like quantized RIS phase shifts.By optimizing both RIS settings and beamforming in real-time,our approach outperforms traditional methods by significantly increasing secrecy rates,improving spectral efficiency,and enhancing energy efficiency.Notably,this framework adapts more effectively to the dynamic nature of wireless channels compared to conventional optimization techniques,providing scalable solutions for large-scale RIS deployments.Our results demonstrate substantial improvements in communication performance setting a new benchmark for secure,efficient and scalable 6G communication.This work offers valuable insights for the future of IoT networks,with a focus on computational optimization,high spectral efficiency and energy-aware operations.展开更多
This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-...This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.展开更多
During daylight laser polarization sensing of high-level clouds(HLCs),the lidar receiving system generates a signal caused by not only backscattered laser radiation,but also scattered solar radiation,the intensity and...During daylight laser polarization sensing of high-level clouds(HLCs),the lidar receiving system generates a signal caused by not only backscattered laser radiation,but also scattered solar radiation,the intensity and polarization of which depends on the Sun’s location.If a cloud contains spatially oriented ice particles,then it becomes anisotropic,that is,the coefficients of directional light scattering of such a cloud depend on the Sun’s zenith and azimuth angles.In this work,the possibility of using the effect of anisotropic scattering of solar radiation on the predictive ability of machine learning algorithms in solving the problem of predicting the HLC backscattering phase matrix(BSPM)was evaluated.The hypothesis that solar radiation scattered on HLCs has no effect on the BSPM elements of such clouds determined with a polarization lidar was tested.The operation of two algorithms for predicting the BSPM elements is evaluated.To train the first one,meteorological data were used as input parameters;for the second algorithm,the azi-muthal and zenith angles of the Sun’s position were added to the meteorological parameters.It is shown that there is no significant improvement in the predictive ability of the algorithm.展开更多
Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distri...Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.展开更多
Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained micro...Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.展开更多
This paper presents a novel impedance matching approach for passive UHF RFID transponder ICs,which are compatible with the ISO/IEC 18000-6B standard and operate in the 915MHz ISM band. The passive UHF RFID transponder...This paper presents a novel impedance matching approach for passive UHF RFID transponder ICs,which are compatible with the ISO/IEC 18000-6B standard and operate in the 915MHz ISM band. The passive UHF RFID transponder with complex impedances is powered by received RF energy. The approach uses the parasitic inductance of the antenna to implement ASK modulation by adjusting the capacitive reactance of the matching network, which changes with the backscatter circuit. The impedance matching achieves maximum power transfer between the reader, antenna, and transponder. The transponder IC,whose operating distance is more than 4m with the impedance matching approach,is fabricated using a Chartered 0.35μm two-poly four-metal CMOS process that supports Schottky diodes and EEPROM.展开更多
基金financial support of the Ministry of Science and Higher Education of the Russian Federation in the framework of the state contract in the field of science(No.FSEG-2024-0005)。
文摘This study discusses the scope of application of the Doppler backscattering(DBS)diagnostic for the tokamak with reactor technologies(TRT)project.This involved numerical modeling of the three-dimensional(3D)beam trajectories.Calculations were performed to investigate the propagation of microwaves in the V(40–75 GHz)and W(75–110 GHz)frequency ranges with O-mode polarization for the density profile of the base TRT scenario.Our analysis showed that the DBS system antenna on the TRT would need to be tilted in both the poloidal and toroidal directions in order to meet the condition Kperp/Kpar<10%..For the DBS system located in the equatorial plane it was shown that a wide range of poloidal and toroidal angles is available for the successful implementation of the diagnostic to study the core,pedestal and scrape-off layer(SOL)regions.The DBS system located at 35 cm above the equatorial plane would be more limited in measurements only covering the SOL and pedestal regions.A shift of the cut-offs in the toroidal direction highlighted the need for 3D analysis of the DBS data.
文摘Backscatter communication(BC)is con-sidered a key technology in self-sustainable commu-nications,and the unmanned aerial vehicle(UAV)as a data collector can improve the efficiency of data col-lection.We consider a UAV-aided BC system,where the power beacons(PBs)are deployed as dedicated radio frequency(RF)sources to supply power for backscatter devices(BDs).After harvesting enough energy,the BDs transmit data to the UAV.We use stochastic geometry to model the large-scale BC sys-tem.Specifically,the PBs are modeled as a type II Mat´ern hard-core point process(MHCPP II)and the BDs are modeled as a homogeneous Poisson point process(HPPP).Firstly,the BDs’activation proba-bility and average coverage probability are derived.Then,to maximize the energy efficiency(EE),we opti-mize the RF power of the PBs under different PB den-sities.Furthermore,we compare the coverage proba-bility and EE performance of our system with a bench-mark scheme,in which the distribution of PBs is mod-eled as a HPPP.Simulation results show that the PBs modeled as MHCPP II has better performance,and we found that the higher the density of PBs,the smaller the RF power required,and the EE is also higher.
基金Supported by the National Natural Science Foundation of China(42104151,42074184,42188101,41727804)。
文摘The ionosphere is an important component of the near Earth space environment.The three common methods for detecting the ionosphere with high frequency(HF)radio signals are vertical detection,oblique detection,and oblique backscatter detection.The ionograms obtained by these detection methods can effectively reflect a large amount of effective information in the ionosphere.The focus of this article is on the oblique backscatter ionogram obtained by oblique backscatter detection.By extracting the leading edge of the oblique backscatter ionogram,effective information in the ionosphere can be inverted.The key issue is how to accurately obtain the leading edge of the oblique backscatter ionogram.In recent years,the application of pattern recognition has become increasingly widespread,and the YOLO model is one of the best fast object detection algorithms in one-stage.Therefore,the core idea of this article is to use the newer YOLOX object detection algorithm in the YOLO family to perform pattern recognition on the F and E_(s) layers echoes in the oblique backscatter ionogram.After image processing,a single-layer oblique backscatter echoes are obtained.It can be found that the leading edge extraction of the oblique backscatter ionogram obtained after pattern recognition and image processing by the YOLOX model is more fitting to the actual oblique backscatter leading edge.
基金upported by the Natural Science Foundation of Zhejiang Province(Grant No.LZ16H180002)the National Natural Science Foundation of China(Grant No.61905181)+1 种基金the Wenzhou Municipal Science and Technology Bureau(Grant No.ZS2017022)the National Science Foundation of the U.S.(Grant No.1607664).
文摘The vectorial evolution of light polarization can reveal the microstructure and anisotropy of a medium beyond what can be obtained from measuring light intensity alone.However,polarization imaging in reflection geometry,which is ubiquitous and often preferred in diverse applications,has often suffered from poor and even incorrect characterization of anisotropic media.We present reciprocal polarization imaging of complex media in reflection geometry with the reciprocal polar decomposition of backscattering Mueller matrices enforcing reciprocity.We demonstrate that reciprocal polarization imaging of complex chiral and anisotropic media ac-curately quantifies their anisotropic properties in reflection geometry,whereas traditional approaches encounter difficulties and produce inferior and often erroneous results from the violation of reciprocity.In particular,reciprocal polarization imaging provides a consistent characterization of complex media of different thicknesses,accurately measures the optical activity and glucose concentration of turbid media in reflection,and discriminates between cancerous and normal tissue with even stronger contrast than forward measurement.Reciprocal polarization imaging promises broad applications of polarization optics ranging from remote sensing to bio-medicine in reflection geometries,especially in in vivo biomedical imaging,where reflection is the only feasible geometry.
基金the National Natural Science Foundation of China(Grant Nos.52325406,52374331,and U1960203)the Program of Introducing Talents of Discipline to Universities(Grant No.B21001).
文摘In this study, novel reconstruction methods, including grain graph and variant graph, were established to reconstruct parent austenite on the basis of electron backscatter diffraction (EBSD) data. The evaluation indicators included boundary identification and variant distribution. Moreover, an innovative variant pair analysis method was proposed. The results indicated that the Kurdjumov-Sachs orientation relationship was the most appropriate because it had the smallest refinement error and deviation. In addition, the variant graph reconstruction was more effective in reducing mis-indexing areas than the grain graph, exhibiting a robust capacity to accurately identify austenite grain boundaries. Additionally, the variant graph reconstruction induced the transformation of variants, variant pairs, close-packed plane (CP) groups, and Bain groups. Moreover, various reconstructed datasets (calc-grain data and EBSD data) affected the distribution of variants. The austenite grains reconstructed from the calc-grain data featured two or more variants clustered within the same region due to the preprocessing (calculating, filtering, and smoothing) of the EBSD data. These variations did not impede the microstructural analysis when consistent original data and reconstruction methods were used. The reconstruction of parent austenite grains holds promise for providing a fresh perspective and a deeper understanding of strengthening and toughening mechanisms in the future.
基金supported by National Natural Science Foundation of China(Nos.12105087,12275096,and 11922503)the Joint Funds of the National Natural Science Foundation of China(No.U21A20440)the Science and Technology Planning Project of Sichuan Province(No.2023YFG0139)。
文摘The Doppler backscattering(DBS)diagnostic is widely used to measure the localized density fluctuations and the propagation velocity of turbulent structures.Microwave is launched at a frequency that approaches a cutoff layer in the plasma at an angle oblique to the cutoff layer.A new Q-band multichannel DBS system based on a comb generator has been designed and tested for application on the HL-3 tokamak.With the comb generator and heterodyne scheme,the stability and flexibility of the new DBS system are improved.The new DBS diagnostic has a high output power(~10 dBm),good power flatness(<5 dB in Q-band),and frequency stability,and the inter-frequency separation is tunable remotely.This article introduces the system design,laboratory test results,and initial experimental results from the HL-3 tokamak.With the help of the newly developed multichannel DBS,the turbulence information can be studied with high temporal and spatial resolution.
基金The National Key Research and Development Program of China under contract No.2021YFC3101602the National Natural Science Foundation of China under contract Nos 42176017 and 41976019.
文摘Mesoscale eddies play a pivotal role in deciphering the intricacies of ocean dynamics and the transport of heat,salt,and nutrients.Accurate representation of these eddies in ocean models is essential for improving model predictions.In this study,we propose a convolutional neural network(CNN)that combines data-driven techniques with physical principles to develop a robust and interpretable parameterization scheme for mesoscale eddies in ocean modeling.We use a highresolution reanalysis dataset to extract subgrid eddy momentum and then applying machine learning algorithms to identify patterns and correlations.To ensure physical consistency,we have introduced conservation of momentum constraints in our CNN parameterization scheme through soft and hard constraints.The interpretability analysis illustrate that the pre-trained CNN parameterization shows promising results in accurately solving the resolved mean velocity and effectively capturing the representation of unresolved subgrid turbulence processes.Furthermore,to validate the CNN parameterization scheme offline,we conduct simulations using the Massachusetts Institute of Technology general circulation model(MITgcm)ocean model.A series of experiments is conducted to compare the performance of the model with the CNN parameterization scheme and high-resolution simulations.The offline validation demonstrates the effectiveness of the CNN parameterization scheme in improving the representation of mesoscale eddies in the MITgcm ocean model.Incorporating the CNN parameterization scheme leads to better agreement with high-resolution simulations and a more accurate representation of the kinetic energy spectra.
文摘Employing experimental equipment and techniques,such as electron backscatter diffraction,transmission Kikuchi diffraction,and transmission electron microscopy,the microstructure,phase structure,and orientation relationships of 0.6μm electroplated nickel(Ni)steel following annealing at 580-650℃for 15-30 hours were investigated.A comprehensive analysis was conducted to gain insights into the complex changes in the material's properties due to the annealing process.The results reveal that prolonged annealing led to considerable long-range diffusion of surface Ni atoms into the substrate of the 0.6μm Ni-plated steel.This diffusion process resulted in the formation of an alloy diffusion layer,approximately 4μm in thickness,which altered the material's microstructural characteristics.The extent of diffusion and its effect on the microstructure and structure were meticulously quantified.At the annealing temperature,the diffused Ni in the substrate,acting as an austenite-stabilizing element,expanded the austenite phase region.The alloy layer at this temperature predominantly consisted of the face-centered cubic(FCC)-structuredγ(Fe,Ni)solid solution.Upon cooling to room temperature,the alloy diffusion layer evolved into a dual-layer composite structure.The upper layer mainly comprised the FCC-structuredγ(Fe,Ni)solid solution,interspersed with a minor FCC compound superstructure phase.The lower layer underwent a diffusionless phase transformation during cooling,which led to the formation of the body-centered tetragonal/body-centered cubic-structured martensite.This phase,which is known for its high hardness and numerous variants,maintained the classic Kurdjumov-Sachs orientation relationship with the upper FCC parent phase,and it satisfied the close-packed plane{111}γ//{110}α′and close-packed direction<110>γ//<111>α′.A detailed analysis of the different phases within the alloy layer and their phase transitions was presented,offering an in-depth understanding of the material's characteristics.
基金financially supported by the European Coal and Steel Community(RFCS-2015.No.709828).
文摘The microstructure development of 55VNb1 microalloyed steel after warm deformation via multi-pass biaxial compression tests was studied,and the effect of thermomechanical conditions on spheroidisation of cementite lamellae and ferrite recrystallisation for a range of deformation temperatures(600–700℃),cooling/soaking time(water quenching,air cooling,10 and 30 min of soaking time)and interpass time(0–10 s)was analysed.During deformation,the spheroidisation of pearlite is dynamically accelerated mainly by boundary splitting mechanism together with the rapid dissolution of cementite,while ferrite softening is attributed to dynamic recovery and continuous dynamic recrystallisation.The strong microstructural evolution during cooling/soaking time indicates that deformation energy accumulated is sufficient to activate metallurgical phenomena in both phases also statically.Static spheroidisation is a diffusive process,with rate controlled by the diffusion of vacancies,as suggested by the estimated activation energy.Ferrite refinement is the result of the evolution of continuous recrystallisation and pinning effect exerted by fine,globulised and homogeneously dispersed cementite particles.Increasing temperature causes accelerated kinetics in metallurgical phenomena;therefore,cooling/soaking time becomes key parameters to achieve ultrafine grained and spheroidised microstructures.Interpass time favours spheroidisation and promotes continuous recrystallisation;however,it must be carefully controlled to find a balance between recrystallisation and Ostwald ripening to optimise microstructural development.
基金supported by Beijing Municipal Natural Science Foundation(L222002)the Natural Science Foundation of China(U22B2004).
文摘Existing orthogonal space-time block coding(OSTBC)schemes for backscatter communication systems cannot achieve a full transmission code rate when the tag is equipped with more than two antennas.In this paper,we propose a quasi-orthogonal spacetime block code(QOSTBC)that can achieve a full transmission code rate for backscatter communication systems with a four-antenna tag and then extend the scheme to support tags with 2i antennas.Specifically,we first present the system model for the backscatter system.Next,we propose the QOSTBC scheme to encode the tag signals.Then,we provide the corresponding maximum likelihood detection algorithms to recover the tag signals.Finally,simulation results are provided to demonstrate that our proposed QOSTBC scheme and the detection algorithm can achieve a better transmission code rate or symbol error rate performance for backscatter communication systems compared with benchmark schemes.
基金supported by the General Project of Liaoning Provincial Department of Education(NO:JYTMS20231199)Project of Liaoning Education Department(No:LKMZ20220462 and No:LJKMZ20220467)+1 种基金Basic scientific research project of Liaoning Provincial Department of Education(key research project)(No:JYTZD2023108)Liaoning Nature Fund Guidance Plan(No:42022-BS.179)。
文摘In this study,the twinning-detwinning behavior and slip behavior of rolled AZ31 magnesium-alloy plates during a three-step intermittent dynamic compression process along the rolling direction(RD)and normal direction(ND),are investigated via quasi-in situ electron backscatter diffraction,and the causes of the twinning and detwinning behavior are explained according to Schmid law,local strain coordination,and slip trajectories.It is found that the twins are first nucleated and grow at a compressive strain of 3%along the RD.In addition to the Schmid factor(SF),the strain coordination factor(m’)also influences the selection of the twin variants during the twinning process,resulting in the nucleation of twins with a low SF.During the second and third steps of the application of continuous compressive strains with magnitudes and directions of 3%RD+3%ND and 3%RD+3%ND+2.5%ND,detwinning occurs to different extents.The observation of the detwinning behavior reveals that the order in which multiple twins within the same grain undergo complete detwinning is related to Schmid law and the strain concentration,with a low SF and a high strain concentration promoting complete detwinning.The interaction between slip dislocations and twin boundaries in the deformed grains as well as the pinning of dislocations at the tips of the {1012} tensile twins with a special structure result in incomplete detwinning.Understanding the microstructural evolution and twinning behavior of magnesium alloys under different deformation geometries is important for the development of high-strength and high-toughness magnesium alloys.
基金funded by the National Key Research and Development Program[grant number 2022YFC3004200]the National Natural Science Foundation of China[grant number U2142212]the Hunan Provincial Natural Science Foundation of China[grant number 2021JC0009]。
文摘A polarized bidirectional reflectance distribution function(pBRDF)matrix is developed from two-scale roughness theory with the aim of providing more accurate simulations of microwave emissions and scattering required for ocean-atmosphere coupled radiative transfer models.The potential of the pBRDF matrix is explored for simu-lating the ocean backscatter at Ku-band.The effects of ocean wave spectra including the modified Durden and Vesecky(DV2),Elfouhaily,and Kudryavtsev spectra on the pBRDF matrix backscatter simulations are investi-gated.Additionally,the differences in backscattering normalized radar cross-section(NRCS)simulations between the Ku-band geophysical model function and pBRDF matrix are analyzed.The results show that the pBRDF matrix can reasonably reproduce the spatial distribution of ocean surface backscattering energy,but the distribution pat-tern and numerical values are influenced by ocean wave spectra.The DV2 spectrum is the best one for the pBRDF matrix to simulate horizontally polarized NRCSs,with the exception of scenarios where the incidence angle is below 35°,the wind speed is less than 10 m s^(−1),and in the cross-wind direction.Also,the DV2 spectrum effec-tively characterizes the wind speed and relative azimuth angle dependence for vertically polarized NRCSs.The Elfouhaily spectrum is suitable for simulating vertically polarized NRCSs under conditions of low wind speed(be-low 5 m s^(−1))and incidence angles under 40°.The Kudryavtsev spectrum excels in simulating vertically polarized NRCSs at high incidence angles(>40°)and horizontally polarized NRCSs at low incidence angles(<35°).
基金supported by the National Natural Science Foundation of China under Grants No.41771401 and No.42350710201.
文摘A P-band polarimetric synthetic aperture radar(PolSAR)sensor has deep penetration ability into and through the vegetation canopies in forested environments.Thus,the sensor is of great potential to accurately assess forest parameters such as coverage,stand density,and tree height.Unfortunately,the radar backscatter from complex terrain can adversely impact the backscatter from trees or forests,and forest parameters assessed can be erroneous.Thus,reducing the topographic impact is an urgent must.In this study,a topographic compensation algorithm has been studied.To assess the algorithm’s validity and effectiveness,we applied it to P-band PolSAR datasets in four forested areas in the US.Trees in the forest stands have diverse species,and the topographic conditions of the terrain differ.Significant topographic impact on the P-band PolSAR data exists before the topographic compensation algorithm.After the algorithm,the impact decreases noticeably qualitatively and quantitatively.The algorithm is valid and effective in reducing the topographic influence on the PolSAR data and,consequently,provides a better chance of retrieving accurate forest parameters.
基金funded by the deanship of scientific research(DSR),King Abdukaziz University,Jeddah,under grant No.(G-1436-611-225)。
文摘The rapid evolution of wireless technologies and the advent of 6G networks present new challenges and opportunities for Internet ofThings(IoT)applications,particularly in terms of ultra-reliable,secure,and energyefficient communication.This study explores the integration of Reconfigurable Intelligent Surfaces(RIS)into IoT networks to enhance communication performance.Unlike traditional passive reflector-based approaches,RIS is leveraged as an active optimization tool to improve both backscatter and direct communication modes,addressing critical IoT challenges such as energy efficiency,limited communication range,and double-fading effects in backscatter communication.We propose a novel computational framework that combines RIS functionality with Physical Layer Security(PLS)mechanisms,optimized through the algorithm known as Deep Deterministic Policy Gradient(DDPG).This framework adaptively adapts RIS configurations and transmitter beamforming to reduce key challenges,including imperfect channel state information(CSI)and hardware limitations like quantized RIS phase shifts.By optimizing both RIS settings and beamforming in real-time,our approach outperforms traditional methods by significantly increasing secrecy rates,improving spectral efficiency,and enhancing energy efficiency.Notably,this framework adapts more effectively to the dynamic nature of wireless channels compared to conventional optimization techniques,providing scalable solutions for large-scale RIS deployments.Our results demonstrate substantial improvements in communication performance setting a new benchmark for secure,efficient and scalable 6G communication.This work offers valuable insights for the future of IoT networks,with a focus on computational optimization,high spectral efficiency and energy-aware operations.
文摘This study examines the effects of friction stir welding(FSW)and post-weld heat treatment(PWHT)on the grain boundary character distribution and corrosion resistance of cross sectional(top and bottom)regions of nickel-and molybdenum-free high-nitrogen austenitic stainless steel(HNASS).FSW at 400 rpm and 30 mm/min resulted in finer grains(4.18μm)and higher coincident site lattice(CSL)boundaries(32.3%)at the top of the stir zone(SZ)due to dynamic recrystallization(DRX).PWHT at 900℃for 1 h led to grain coarsening(12.91μm the bottom SZ)but enhanced CSL boundaries from 24.6%to 30.2%,improving grain boundary stability.PWHT reduced the kernel average misorientation(KAM)by 14.9%in the SZ-top layer and 20.4%in the SZ-bottom layer,accompanied by a 25%decrease in hardness in the SZ-top layer and 26.7%in the SZ-bottom layer,indicating strain recovery and reduced dislocation density.Potentiodynamic polarization tests(PDP)showed a 18%increase in pitting potential and a 76%reduction in corrosion rate after PWHT.The improvement in corrosion resistance is attributed to the increase inΣ3 twin boundaries,which enhance grain boundary stability and reduce susceptibility to localized corrosion.These findings highlight the role of PWHT in refining the microstructure and strengthening corrosion resistance,making HNASS a promising material for demanding applications.
基金supported by the Government of the Russian Federation grant number 075-15-2025-009 of 28 February 2025 and by the Russian Science Foundation,Grant No.24-72-10127.
文摘During daylight laser polarization sensing of high-level clouds(HLCs),the lidar receiving system generates a signal caused by not only backscattered laser radiation,but also scattered solar radiation,the intensity and polarization of which depends on the Sun’s location.If a cloud contains spatially oriented ice particles,then it becomes anisotropic,that is,the coefficients of directional light scattering of such a cloud depend on the Sun’s zenith and azimuth angles.In this work,the possibility of using the effect of anisotropic scattering of solar radiation on the predictive ability of machine learning algorithms in solving the problem of predicting the HLC backscattering phase matrix(BSPM)was evaluated.The hypothesis that solar radiation scattered on HLCs has no effect on the BSPM elements of such clouds determined with a polarization lidar was tested.The operation of two algorithms for predicting the BSPM elements is evaluated.To train the first one,meteorological data were used as input parameters;for the second algorithm,the azi-muthal and zenith angles of the Sun’s position were added to the meteorological parameters.It is shown that there is no significant improvement in the predictive ability of the algorithm.
文摘Nanoindentation and high resolution electron backscatter diffraction（EBSD） were combined to examine the elastic modulus and hardness of α and β phases,anisotropy in residual elastic stress strain fields and distributions of geometrically necessary dislocation（GND） density around the indentations within TA15 titanium alloy.The nano-indention tests were conducted on α and β phases,respectively.The residual stress strain fields surrounding the indentation were calculated through crosscorrelation method from recorded patterns.The GND density distribution around the indentation was calculated based on the strain gradient theories to reveal the micro-mechanism of plastic deformation.The results indicate that the elastic modulus and hardness for α p hase are 129.05 GPas and 6.44 GPa,while for β phase,their values are 109.80 GPa and 4.29 GPa,respectively.The residual Mises stress distribution around the indentation is relatively heterogeneous and significantly influenced by neighboring soft β phase.The region with low residual stress around the indentation is accompanied with markedly high a type and prismatic-GND density.
基金Projects(50674067,51074106,51374145)supported by the National Natural Science Foundation of ChinaProject(09JC1408200)supported by the Science and Technology Commission of Shanghai Municipality,China+1 种基金Project(2011BAE22B01-5)supported by the National Key Technology R&D Program of ChinaProjects(182000/S10,192450/I30)supported by the Research Council of Norway
文摘Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.
文摘This paper presents a novel impedance matching approach for passive UHF RFID transponder ICs,which are compatible with the ISO/IEC 18000-6B standard and operate in the 915MHz ISM band. The passive UHF RFID transponder with complex impedances is powered by received RF energy. The approach uses the parasitic inductance of the antenna to implement ASK modulation by adjusting the capacitive reactance of the matching network, which changes with the backscatter circuit. The impedance matching achieves maximum power transfer between the reader, antenna, and transponder. The transponder IC,whose operating distance is more than 4m with the impedance matching approach,is fabricated using a Chartered 0.35μm two-poly four-metal CMOS process that supports Schottky diodes and EEPROM.
