The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope （AFM）. The roughness ...The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope （AFM）. The roughness measured by this new method can reach the order of angstroms with high quality capillaries.展开更多
An Sb delta doping layer in silicon is grown at the temperature of 300℃ by silicon molecular beam epitaxy and characterized by the small angle x-ray reflectivity measurement using synchrotron radiation beam.The oscil...An Sb delta doping layer in silicon is grown at the temperature of 300℃ by silicon molecular beam epitaxy and characterized by the small angle x-ray reflectivity measurement using synchrotron radiation beam.The oscillations of the reflectivity caused by dopant Sb at Q as large as 14.5 are detected.Simulation of this curve as a whole shows that the total amount of dopant Sb is 0.15 monolayer and is restricted to two atomic layers.An extremely narrow Sb delta doping structure without Sb segregation is thus obtained at the growth temperature of 300℃ as verified by the experiment.展开更多
Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried ...Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried out across the L absorption edge of tungsten to perform depth-dependent element-selective analysis sensitive to potential chemical modification of the WS_(2)layer in ambient conditions.Despite the few monolayer thickness of the studied film,the experimentally measured maps of reflectance as a function of incident angle and photon energy turned out to be quite informative showing well-pronounced interference effects near W absorption edge at 10210 eV.The synchrotron studies were complemented with conventional non-resonant reflectance measurements carried out in the laboratory at a fixed photon energy corresponding to Cu Kαemission.The reconstruction of the depth and energy dependent scattering length density within the studied multilayers was carried out using the OpenCL empowered fitting software utilizing spectral shaping algorithm which does not rely on the pre-measured reference absorption spectra.A thin WO_(x) layer has been revealed at the surface of the WS_(2)layer pointing out to the effect of water assisted photo-oxidation reported in a number of works related to ultrathin layers of transition metal dichalcogenides.展开更多
FY-3G is the first polar-orbiting satellite equipped with a precipitation measurement radar(PMR)operating at Ku-andKa-band frequencies in China.In this study,we compare the reflectivity data from the FY-3G PMR Ku prod...FY-3G is the first polar-orbiting satellite equipped with a precipitation measurement radar(PMR)operating at Ku-andKa-band frequencies in China.In this study,we compare the reflectivity data from the FY-3G PMR Ku product and groundbasedradars(GRs)during 2024.Also,the FY-3G PMR is used as a third-party reference to evaluate the reflectivityconsistency among different GRs.The FY-3G PMR and GRs share similarities in their general distribution,characteristics,and intensity of reflectivity in strong precipitation cloud systems,though the former presents less detailed system structure.Systematic deviations between the FY-3G PMR and GRs and between GRs are comparable,albeit the reflectivity of the FY-3G PMR is generally slightly stronger than that of GRs(especially X-band GRs),with a mean bias ranging from 0.7 to 1.7dB.S-band GRs exhibit the smallest systematic deviation(STD=3.09 dB)from the FY-3G PMR,whereas the X-band GRsshow the largest(STD=3.61 dB),indirectly indicating the highest internal consistency among S-band GRs and the lowestamong X-band GRs.Besides,both S-and C-band GRs display similar deviations when paired with the FY-3G PMR as wellas when paired with their adjacent S/C-band GRs,suggesting good consistency between these two bands.In contrast,XbandGRs exhibit relatively poor consistency with S-band GRs and the FY-3G PMR,showing a deviation ranging from 3.0to 4.6 dB.展开更多
The Global Precipitation Measurement(GPM)dual-frequency precipitation radar(DPR)products(Version 07A)are employed for a rigorous comparative analysis with ground-based operational weather radar(GR)networks.The reflect...The Global Precipitation Measurement(GPM)dual-frequency precipitation radar(DPR)products(Version 07A)are employed for a rigorous comparative analysis with ground-based operational weather radar(GR)networks.The reflectivity observed by GPM Ku PR is compared quantitatively against GR networks from CINRAD of China and NEXRAD of the United States,and the volume matching method is used for spatial matching.Additionally,a novel frequency correction method for all phases as well as precipitation types is used to correct the GPM Ku PR radar frequency to the GR frequency.A total of 20 GRs(including 10 from CINRAD and 10 from NEXRAD)are included in this comparative analysis.The results indicate that,compared with CINRAD matched data,NEXRAD exhibits larger biases in reflectivity when compared with the frequency-corrected Ku PR.The root-mean-square difference for CINRAD is calculated at 2.38 d B,whereas for NEXRAD it is 3.23 d B.The mean bias of CINRAD matched data is-0.16 d B,while the mean bias of NEXRAD is-2.10 d B.The mean standard deviation of bias for CINRAD is 2.15 d B,while for NEXRAD it is 2.29 d B.This study effectively assesses weather radar data in both the United States and China,which is crucial for improving the overall consistency of global precipitation estimates.展开更多
A series of Mo/Si multilayers with the same periodic length and different periodic number were prepared by magnetron sputtering, whose top layers were respectively Mo layer and Si layer. Periodic length and interface ...A series of Mo/Si multilayers with the same periodic length and different periodic number were prepared by magnetron sputtering, whose top layers were respectively Mo layer and Si layer. Periodic length and interface roughness of Mo/Si multilayers were determined by small angle X-ray diffraction （SAXRD）. Surface roughness change curve of Mo/Si multilayer with increasing layer number was studied by atomic force microscope （AFM）. Soft X-ray reflectivity of Mo/Si multilayers was measured in National Synchrotron Radiation Laboratory （NSRL）. Theoretical and experimental results show that the soft X-ray reflectivity of Mo/Si multilayer is mainly determined by periodic number and interface roughness, surface roughness has little effect on reflectivity.展开更多
Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,...Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.展开更多
The current work addresses the challenge of elucidating the performance of fluoroelastomers within the HMX(octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)based polymer-bonded explosives(PBXs).To simulate the confine...The current work addresses the challenge of elucidating the performance of fluoroelastomers within the HMX(octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)based polymer-bonded explosives(PBXs).To simulate the confined interface in PBXs,bilayer films of F2314/HMX and F2311/HMX were designed.Neutron reflectivity(NR),nanoindentation,and X-ray reflectivity(XRR)were employed to examine the layer thickness,interface characteristics,diffusion behavior,and surface morphology of the bilayers.NR measurements revealed interface thicknesses of 45Å and 98Å for F2314/HMX and F2311/HMX,respectively,indicating deeper penetration of F2311 into the HMX matrix.NR also suggested a denser polymer network with a higher scattering length density(SLD)near the HMX interface for both fluoroelastomers,while the bound layer of F2311 was notably thicker.Nanoindentation cross-checks and confirms the presence of a bound layer,highlighting the differences in stiffness and diffusion ability between the two polymers.The consistency between the NR and nanoindentation results suggests that F2311 demonstrates better flexibility and elasticity,whereas F2314 is stiffer and more plastic.Accordingly,the structures and performances of different fluoroelastomers at the HMX interface are discussed,which can provide valuable insights into the selection of binders for PBX formulations tailored to specific applications.展开更多
The grazing incidence X-ray reflectivity(GIXR) technique and atomic force microscopy(AFM) were exploited to obtain an accurate evaluation of the surfaces and interfaces for metalorganic chemical vapor deposition grown...The grazing incidence X-ray reflectivity(GIXR) technique and atomic force microscopy(AFM) were exploited to obtain an accurate evaluation of the surfaces and interfaces for metalorganic chemical vapor deposition grown AlGaN/GaN superlattice structures.The X-ray diffraction results have been combined with reflectivity data to evaluate the layer thickness and Al mole fraction in the AlGaN layer.The presence of a smooth interface is responsible for the observation of intensity oscillation in GIXR,which is well correlated to step flow observation in AFM images of the surface.The structure with a low Al mole fraction(x = 0.25) and thin well width has a rather smooth surface for the R,of AFM data value is 0.45 nm.展开更多
This study aims to investigate the responses of a perovskite-based direct-conversion dual-layer flat-panel detector(DL-FPD)numerically.To this end,the X-ray sensitivity,spatial resolution quantified by the modulation ...This study aims to investigate the responses of a perovskite-based direct-conversion dual-layer flat-panel detector(DL-FPD)numerically.To this end,the X-ray sensitivity,spatial resolution quantified by the modulation transfer function(MTF),and detective quantum efficiency(DQE)of the DL-FPD are evaluated numerically using a linear cascade model.In addition,both the single-crystal(SC)and polycrystalline(PC)structures of MAPbI_(3)are investigated,along with various other key parameters such as the material thickness,electric field strength,X-ray beam spectrum,and electronic readout noise.The results demonstrate that SC perovskite consistently exhibits better performance than PC perovskite owing to fewer material defects.Increasing the layer thickness may decrease the MTF,but can also enhance the sensitivity and DQE.Moreover,appropriately increasing the external electric field within the material can improve the sensitivity,MTF,and DQE.Finally,reducing the electronic readout noise can significantly enhance the DQE for low-dose imaging.This study demonstrates the potential of high-quality dual-energy X-ray imaging using direct-conversion perovskite DL-FPDs.展开更多
With the development of the semiconductor industry below the 7 nm scale,critical dimension small-angle X-ray scattering(CD-SAXS)has emerged as a powerful tool for quantitatively measuring nanoscale deviations.In this ...With the development of the semiconductor industry below the 7 nm scale,critical dimension small-angle X-ray scattering(CD-SAXS)has emerged as a powerful tool for quantitatively measuring nanoscale deviations.In this study,the effects of X-ray beam size and photon energy on the accuracy of critical dimension measurements were investigated.Critical dimensions measured using beams with different spot sizes showed different deviations from the expected values.Beam sizes that were either too large or too small did not improve confidence intervals.As the incident energy increased,the X-ray transmission rate increased,while the scattering cross section decreased,resulting in a gradual decrease in the signal-to-noise ratio of the diffraction peaks,which reduced the accuracy of the CD-SAXS measurements.An optimal accuracy was obtained at 12 keV with a smaller beam size.Using an effective trapezoid model,the results yielded an average pitch of 100.4±0.2 nm,width of 49.8±0.2 nm,height of 130.0±0.2 nm,and a sidewall angle below 1.1°±0.1°.These results provide crucial guidance for the future development of CD-SAXS laboratories and the construction of X-ray machines as well as robust support for research in related fields.展开更多
The unique advantage of x-ray ghost imaging(XGI)is its potential in low dose radiology.One of the practical ways to reduce the radiation exposure is to reduce the measurements while remaining sufficient image quality....The unique advantage of x-ray ghost imaging(XGI)is its potential in low dose radiology.One of the practical ways to reduce the radiation exposure is to reduce the measurements while remaining sufficient image quality.Synthetic aperture x-ray ghost imaging(SAXGI)is invented to achieve megapixel XGI with limited measurements,which is expected to implement XGI simultaneously with large field of view and low radiation exposure.In this paper,we experimentally investigate the effect of measurements reduction on the spatial resolution and image quality of SAXGI with standard sample and biomedical specimen.The results with a resolution chart demonstrated that at 360 measurements,SAXGI successfully retrieved the sample image of 1960×1960 pixels with spatial resolution of 4μm.With measurement reduction,the spatial resolution deteriorates but the sparser structures are still discernable.Even with measurements reduced to 10,a spatial resolution of 10μm can still be achieved by SAXGI.A biomedical sample of a fish specimen is employed to evaluate the method and the fish image of 2000×1000 pixels with an SSIM of 0.962 is reconstructed by SAXGI with 770measurements,corresponding to an accumulative exposure reduction of more than 2 times.With the measurements reduced to 10 which corresponds to 1/160 of the accumulative radiation exposure for conventional radiology,bulky structure like the fish skeleton can still be definitely discerned and the SSIM for the reconstructed image still retained 0.9179.Results of this paper demonstrate that measurements reduction is practicable for the radiation exposure reduction of the sample,which implicates that SAXGI with limited measurements is an efficient solution for low dose radiology.展开更多
Knowledge-based VisualQuestion Answering(VQA)requires the integration of visual information with external knowledge reasoning.Existing approaches typically retrieve information from external corpora and rely on pretra...Knowledge-based VisualQuestion Answering(VQA)requires the integration of visual information with external knowledge reasoning.Existing approaches typically retrieve information from external corpora and rely on pretrained language models for reasoning.However,their performance is often hindered by the limited capabilities of retrievers and the constrained size of knowledge bases.Moreover,relying on image captions to bridge the modal gap between visual and language modalities can lead to the omission of critical visual details.To address these limitations,we propose the Reflective Chain-of-Thought(ReCoT)method,a simple yet effective framework inspired by metacognition theory.ReCoT effectively activates the reasoning capabilities ofMultimodal Large LanguageModels(MLLMs),providing essential visual and knowledge cues required to solve complex visual questions.It simulates a metacognitive reasoning process that encompasses monitoring,reflection,and correction.Specifically,in the initial generation stage,an MLLM produces a preliminary answer that serves as the model’s initial cognitive output.During the reflective reasoning stage,this answer is critically examined to generate a reflective rationale that integrates key visual evidence and relevant knowledge.In the final refinement stage,a smaller language model leverages this rationale to revise the initial prediction,resulting in amore accurate final answer.By harnessing the strengths ofMLLMs in visual and knowledge grounding,ReCoT enables smaller language models to reason effectively without dependence on image captions or external knowledge bases.Experimental results demonstrate that ReCoT achieves substantial performance improvements,outperforming state-of-the-art methods by 2.26%on OK-VQA and 5.8%on A-OKVQA.展开更多
Numerical simulations and theoretical models are developed in this paper for the Detonation-Wave/Boundary-Layer Interactions(DWBLIs)under reflections.Transient flow fields demonstrate the highly non-stationarity of th...Numerical simulations and theoretical models are developed in this paper for the Detonation-Wave/Boundary-Layer Interactions(DWBLIs)under reflections.Transient flow fields demonstrate the highly non-stationarity of the DWBLIs when Mach Reflection(MR)occur,and subsequent analyses show that the subsonic region introduced by the boundary layer exacerbates the instability.Further quantitative analyses show that viscosity has little effect on propulsive performance and the separation wave can be considered as an oblique detonation wave.Influence parameters to DWBLIs such as combustion chamber height,incoming Mach number,equivalence ratio,and inlet channel length are categorized and studied.Besides simulations,theoretical analytical modeling is established for Regular Reflection(RR)and MR of DWBLIs.Multiple formulas for the separation zone length are obtained according to the mass conservation under different transformation type between inviscid and viscid reflections.Comparison with the numerical simulations verifies the validity of the model and it can be further generalized to the curved DWBLIs.The developed model makes the theoretical solution process of DWBLIs possible and provides the key foundation for further analysis and solution.展开更多
The advancement of next-generation high-frequency communication systems and stealth detection technologies necessitate the development of efficient,multi-spectrum compatible shielding materials.However,the achievement...The advancement of next-generation high-frequency communication systems and stealth detection technologies necessitate the development of efficient,multi-spectrum compatible shielding materials.However,the achievement of simultaneous high efficiency and low reflectivity across microwave,terahertz,and infrared spectra remains a formidable challenge.Herein,a carbonized MXene/polyimide(C-MXene/PI)aerogel material integrating a spatially coupled hierarchically anisotropic structure with stepwise conductivity gradients was constructed.Electromagnetic waves propagate through the top-down vertical disordered horizontal architecture and progressive conductivity gradient of C-MXene/PI aerogel,undergoing stepwise absorption-dissipation-re-dissipation processes.The C-MXene/PI aerogel exhibits an average electromagnetic interference(EMI)shielding effectiveness of91.0 dB in X-band and a reflection coefficient of 0.40.In the terahertz frequency band,the average EMI shielding performance reaches66.2 dB with a reflection coefficient of 0.33.Furthermore,the heterolayered porous architecture of C-MXene/PI aerogels exhibits low thermal conductivity and reduced infrared emissivity,enabling exceptional infrared stealth capability across the 2-16μm wavelength spectrum.This study provides an feasible strategy for constructing low-reflectivity multi-spectrum compatible shielding materials.展开更多
A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-d...A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.展开更多
This comprehensive study investigates the formation and evolution of intermetallic compounds during the solidification process of magnesium alloys using advanced micro X-ray computed tomography.By analyzing both commo...This comprehensive study investigates the formation and evolution of intermetallic compounds during the solidification process of magnesium alloys using advanced micro X-ray computed tomography.By analyzing both common industrial Mg-Al-Zn alloys and a novel rare earth-containing Mg-Ni-Gd-Y alloy,we aim to characterize the nucleation,growth,and distribution of Al-Mn and eutectic intermetallics across various stages of solidification.The non destructive imaging technique employed in this research provides high-resolution,three-dimensional insights into the microstructural development,allowing for a detailed examination of the morphology,spatial arrangement,and interconnectivity of intermetallic phases.This approach overcomes limitations of traditional two-dimensional metallographic methods,offering a more comprehensive understanding of the complex three-dimensional structures formed during solidification.展开更多
Objectives This study aimed to explore and clarify the concept of reflective supervision as a professional self-care strategy to create a positive Intensive Care Unit(ICU)practice environment.Methods Walker and Avant...Objectives This study aimed to explore and clarify the concept of reflective supervision as a professional self-care strategy to create a positive Intensive Care Unit(ICU)practice environment.Methods Walker and Avant’s eight-step concept analysis approach was utilized to identify and define the attributes,antecedents,and consequences of reflective supervision in the ICU.An extensive literature search was conducted across various databases,including Google Scholar,CINAHL,PubMed.Articles published from 2005 to 2025 were identified.We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)2020 statement to indicate the included articles and extract related data based on relevance.Results Forty articles were included in the analysis.The identified attributes included the supervisor-supervisee relationship,effective communication,teamwork,collaborations,reflection,competencies,feedback,continuous support,and autonomous choice.The identified antecedents included participation,supportive supervision,flexibility,open-door policy,training,and motivation.Consequences impacting the success of reflective supervision were identified as promotion of resiliency,autonomy,work-life balance,self-awareness,increased self-esteem,professional development,critical thinking,increased job satisfaction,and enhanced commitment.Conclusions Reflective supervision is a complex professional self-care strategy that enhances ICU practice,by promoting nurses’well-being,self-awareness,therapeutic skills,and professional development.展开更多
In clinical diagnosis,conventional X-ray absorption-contrast computed tomography(XACT)technology cannot effectively differentiate diseased tissues from the healthy ones.X-ray phase-contrast CT(XPCT)and dual-energy CT(...In clinical diagnosis,conventional X-ray absorption-contrast computed tomography(XACT)technology cannot effectively differentiate diseased tissues from the healthy ones.X-ray phase-contrast CT(XPCT)and dual-energy CT(DECT),emerging X-ray imaging technologies with superior diagnostic capabilities,address this issue through different principles.While both XPCT and DECT have advantages and disadvantages in medical applications,their systematic comparison is lacking.Using GEANT4 and MATLAB,in this study,we established an X-ray phase-contrast imaging(XPCI)model based on single-mask and single-shot edge illumination for fast XPCT imaging,comparing it with DECT on soft-tissue phantom.XACT served as a reference for comparison.The study introduces an evaluation system using statistical measures including absolute error,mean absolute error,structure similarity index measure,peak signal-to-noise ratio,and contrast-to-noise ratio.Results show XPCT images are superior to DECT.The XPCI model can be improved on existing medical CT for widespread medical application.展开更多
Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics...Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.展开更多
基金supported by the Natural Science Foundation of Beijing,China (Grant No. 1102019)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20100003120010)
文摘The inner surface roughness of a capillary is investigated by the reflectivity of x-rays penetrating through the capillary. The results are consistent with the data from atomic force microscope （AFM）. The roughness measured by this new method can reach the order of angstroms with high quality capillaries.
基金Supported by the National Natural Science Foundation of China under Grant No.69476008the Key Project of the State Commission of Science and Technology of China.
文摘An Sb delta doping layer in silicon is grown at the temperature of 300℃ by silicon molecular beam epitaxy and characterized by the small angle x-ray reflectivity measurement using synchrotron radiation beam.The oscillations of the reflectivity caused by dopant Sb at Q as large as 14.5 are detected.Simulation of this curve as a whole shows that the total amount of dopant Sb is 0.15 monolayer and is restricted to two atomic layers.An extremely narrow Sb delta doping structure without Sb segregation is thus obtained at the growth temperature of 300℃ as verified by the experiment.
基金supported by the Ministry of Science and Higher Education of the Russian Federation(agreement No.075-15-2021-1349)。
文摘Synchrotron method of resonant X-ray reflectivity 2D mapping has been applied to study ultrathin epitaxial layers of WS_(2)grown by pulsed laser deposition on Al_(2)O_(3)(0001)substrates.The measurements were carried out across the L absorption edge of tungsten to perform depth-dependent element-selective analysis sensitive to potential chemical modification of the WS_(2)layer in ambient conditions.Despite the few monolayer thickness of the studied film,the experimentally measured maps of reflectance as a function of incident angle and photon energy turned out to be quite informative showing well-pronounced interference effects near W absorption edge at 10210 eV.The synchrotron studies were complemented with conventional non-resonant reflectance measurements carried out in the laboratory at a fixed photon energy corresponding to Cu Kαemission.The reconstruction of the depth and energy dependent scattering length density within the studied multilayers was carried out using the OpenCL empowered fitting software utilizing spectral shaping algorithm which does not rely on the pre-measured reference absorption spectra.A thin WO_(x) layer has been revealed at the surface of the WS_(2)layer pointing out to the effect of water assisted photo-oxidation reported in a number of works related to ultrathin layers of transition metal dichalcogenides.
基金supported by the Innovation and Development Special Project of the China Meteorological Administration(Grant No.CXFZ2024J058)the Guangdong Province Basic and Applied Basic Research Foundation Meteorological Joint Fund Project(Grant No.2024A1515510036)+1 种基金the National Key R&D Program of China(Grant No.2022YFC3004101)the Technical Innovation Team Project of Guangzhou Meteorological Satellite Ground Station(Grant No.CXTD202401).
文摘FY-3G is the first polar-orbiting satellite equipped with a precipitation measurement radar(PMR)operating at Ku-andKa-band frequencies in China.In this study,we compare the reflectivity data from the FY-3G PMR Ku product and groundbasedradars(GRs)during 2024.Also,the FY-3G PMR is used as a third-party reference to evaluate the reflectivityconsistency among different GRs.The FY-3G PMR and GRs share similarities in their general distribution,characteristics,and intensity of reflectivity in strong precipitation cloud systems,though the former presents less detailed system structure.Systematic deviations between the FY-3G PMR and GRs and between GRs are comparable,albeit the reflectivity of the FY-3G PMR is generally slightly stronger than that of GRs(especially X-band GRs),with a mean bias ranging from 0.7 to 1.7dB.S-band GRs exhibit the smallest systematic deviation(STD=3.09 dB)from the FY-3G PMR,whereas the X-band GRsshow the largest(STD=3.61 dB),indirectly indicating the highest internal consistency among S-band GRs and the lowestamong X-band GRs.Besides,both S-and C-band GRs display similar deviations when paired with the FY-3G PMR as wellas when paired with their adjacent S/C-band GRs,suggesting good consistency between these two bands.In contrast,XbandGRs exhibit relatively poor consistency with S-band GRs and the FY-3G PMR,showing a deviation ranging from 3.0to 4.6 dB.
基金funded by the National Key Research and Development Program of China(Grant No.2023YFB3907500)the National Natural Science Foundation(Grant No.42330602)the“Fengyun Satellite Remote Sensing Product Validation and Verification”Youth Innovation Team of the China Meteorological Administration(Grant No.CMA2023QN12)。
文摘The Global Precipitation Measurement(GPM)dual-frequency precipitation radar(DPR)products(Version 07A)are employed for a rigorous comparative analysis with ground-based operational weather radar(GR)networks.The reflectivity observed by GPM Ku PR is compared quantitatively against GR networks from CINRAD of China and NEXRAD of the United States,and the volume matching method is used for spatial matching.Additionally,a novel frequency correction method for all phases as well as precipitation types is used to correct the GPM Ku PR radar frequency to the GR frequency.A total of 20 GRs(including 10 from CINRAD and 10 from NEXRAD)are included in this comparative analysis.The results indicate that,compared with CINRAD matched data,NEXRAD exhibits larger biases in reflectivity when compared with the frequency-corrected Ku PR.The root-mean-square difference for CINRAD is calculated at 2.38 d B,whereas for NEXRAD it is 3.23 d B.The mean bias of CINRAD matched data is-0.16 d B,while the mean bias of NEXRAD is-2.10 d B.The mean standard deviation of bias for CINRAD is 2.15 d B,while for NEXRAD it is 2.29 d B.This study effectively assesses weather radar data in both the United States and China,which is crucial for improving the overall consistency of global precipitation estimates.
文摘A series of Mo/Si multilayers with the same periodic length and different periodic number were prepared by magnetron sputtering, whose top layers were respectively Mo layer and Si layer. Periodic length and interface roughness of Mo/Si multilayers were determined by small angle X-ray diffraction （SAXRD）. Surface roughness change curve of Mo/Si multilayer with increasing layer number was studied by atomic force microscope （AFM）. Soft X-ray reflectivity of Mo/Si multilayers was measured in National Synchrotron Radiation Laboratory （NSRL）. Theoretical and experimental results show that the soft X-ray reflectivity of Mo/Si multilayer is mainly determined by periodic number and interface roughness, surface roughness has little effect on reflectivity.
基金support from the National Natural Science Foundation of China(52373077,52003106,52103074,52233006,52161135302)the Research Foundation Flanders(G0F2322N)Innovation Program of Shanghai Municipal Education Commission(2021-01-07-00-03-E00108).
文摘Designing and fabricating a compatible low-reflectivity electromagnetic interference(EMI)shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military.Hence,a hierarchical polyimide(PI)nonwoven fabric is fabricated by alkali treatment,in-situ growth of magnetic particles and"self-activated"electroless Ag plating process.Especially,the hierarchical impedance matching can be constructed by systematically assembling Fe_(3)O_(4)/Ag-loaded PI nonwoven fabric(PFA)and pure Ag-coated PI nonwoven fabric(PA),endowing it with an ultralowreflectivity EMI shielding performance.In addition,thermal insulation of fluffy three-dimensional(3D)space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance.More importantly,the strong bonding interaction between Fe_(3)O_(4),Ag,and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance.Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy,and inhibit external infrared detection.
基金supported in part by the National Natural Science Foundation of China(Nos.12335018,12105264,and 12275248)NSAF Joint Fund Project(Nos.U2230107,U1730244,U2130207)+1 种基金Innovation and Development Fund of China Academy of Engineering Physics(No.CXKS20240052)Central Guidance for Local Science and Technology Development Fund Project(No.2023ZYDF075).
文摘The current work addresses the challenge of elucidating the performance of fluoroelastomers within the HMX(octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine)based polymer-bonded explosives(PBXs).To simulate the confined interface in PBXs,bilayer films of F2314/HMX and F2311/HMX were designed.Neutron reflectivity(NR),nanoindentation,and X-ray reflectivity(XRR)were employed to examine the layer thickness,interface characteristics,diffusion behavior,and surface morphology of the bilayers.NR measurements revealed interface thicknesses of 45Å and 98Å for F2314/HMX and F2311/HMX,respectively,indicating deeper penetration of F2311 into the HMX matrix.NR also suggested a denser polymer network with a higher scattering length density(SLD)near the HMX interface for both fluoroelastomers,while the bound layer of F2311 was notably thicker.Nanoindentation cross-checks and confirms the presence of a bound layer,highlighting the differences in stiffness and diffusion ability between the two polymers.The consistency between the NR and nanoindentation results suggests that F2311 demonstrates better flexibility and elasticity,whereas F2314 is stiffer and more plastic.Accordingly,the structures and performances of different fluoroelastomers at the HMX interface are discussed,which can provide valuable insights into the selection of binders for PBX formulations tailored to specific applications.
基金Project supported by the National Natural Science Foundation of China(No60876008)the Science and Technology Program of the Educational Office of Fujian Province,China(NoJA 10249)
文摘The grazing incidence X-ray reflectivity(GIXR) technique and atomic force microscopy(AFM) were exploited to obtain an accurate evaluation of the surfaces and interfaces for metalorganic chemical vapor deposition grown AlGaN/GaN superlattice structures.The X-ray diffraction results have been combined with reflectivity data to evaluate the layer thickness and Al mole fraction in the AlGaN layer.The presence of a smooth interface is responsible for the observation of intensity oscillation in GIXR,which is well correlated to step flow observation in AFM images of the surface.The structure with a low Al mole fraction(x = 0.25) and thin well width has a rather smooth surface for the R,of AFM data value is 0.45 nm.
基金supported in part by the National Natural Science Foundation of China(Nos.12305349,12235006,12027812)Shenzhen Science and Technology Program(No.JSGGKQTD20210831174329010)Guangdong Basic and Applied Basic Research Foundation(No.2021TQ06Y108).
文摘This study aims to investigate the responses of a perovskite-based direct-conversion dual-layer flat-panel detector(DL-FPD)numerically.To this end,the X-ray sensitivity,spatial resolution quantified by the modulation transfer function(MTF),and detective quantum efficiency(DQE)of the DL-FPD are evaluated numerically using a linear cascade model.In addition,both the single-crystal(SC)and polycrystalline(PC)structures of MAPbI_(3)are investigated,along with various other key parameters such as the material thickness,electric field strength,X-ray beam spectrum,and electronic readout noise.The results demonstrate that SC perovskite consistently exhibits better performance than PC perovskite owing to fewer material defects.Increasing the layer thickness may decrease the MTF,but can also enhance the sensitivity and DQE.Moreover,appropriately increasing the external electric field within the material can improve the sensitivity,MTF,and DQE.Finally,reducing the electronic readout noise can significantly enhance the DQE for low-dose imaging.This study demonstrates the potential of high-quality dual-energy X-ray imaging using direct-conversion perovskite DL-FPDs.
基金supported by the National Natural Science Foundation of China(No.12175295)the National Key R&D Program of China(2021YFA1601000)the Shanghai Municipal Science and Technology Major Project。
文摘With the development of the semiconductor industry below the 7 nm scale,critical dimension small-angle X-ray scattering(CD-SAXS)has emerged as a powerful tool for quantitatively measuring nanoscale deviations.In this study,the effects of X-ray beam size and photon energy on the accuracy of critical dimension measurements were investigated.Critical dimensions measured using beams with different spot sizes showed different deviations from the expected values.Beam sizes that were either too large or too small did not improve confidence intervals.As the incident energy increased,the X-ray transmission rate increased,while the scattering cross section decreased,resulting in a gradual decrease in the signal-to-noise ratio of the diffraction peaks,which reduced the accuracy of the CD-SAXS measurements.An optimal accuracy was obtained at 12 keV with a smaller beam size.Using an effective trapezoid model,the results yielded an average pitch of 100.4±0.2 nm,width of 49.8±0.2 nm,height of 130.0±0.2 nm,and a sidewall angle below 1.1°±0.1°.These results provide crucial guidance for the future development of CD-SAXS laboratories and the construction of X-ray machines as well as robust support for research in related fields.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1603601,2021YFF0601203,and 2021YFA1600703)。
文摘The unique advantage of x-ray ghost imaging(XGI)is its potential in low dose radiology.One of the practical ways to reduce the radiation exposure is to reduce the measurements while remaining sufficient image quality.Synthetic aperture x-ray ghost imaging(SAXGI)is invented to achieve megapixel XGI with limited measurements,which is expected to implement XGI simultaneously with large field of view and low radiation exposure.In this paper,we experimentally investigate the effect of measurements reduction on the spatial resolution and image quality of SAXGI with standard sample and biomedical specimen.The results with a resolution chart demonstrated that at 360 measurements,SAXGI successfully retrieved the sample image of 1960×1960 pixels with spatial resolution of 4μm.With measurement reduction,the spatial resolution deteriorates but the sparser structures are still discernable.Even with measurements reduced to 10,a spatial resolution of 10μm can still be achieved by SAXGI.A biomedical sample of a fish specimen is employed to evaluate the method and the fish image of 2000×1000 pixels with an SSIM of 0.962 is reconstructed by SAXGI with 770measurements,corresponding to an accumulative exposure reduction of more than 2 times.With the measurements reduced to 10 which corresponds to 1/160 of the accumulative radiation exposure for conventional radiology,bulky structure like the fish skeleton can still be definitely discerned and the SSIM for the reconstructed image still retained 0.9179.Results of this paper demonstrate that measurements reduction is practicable for the radiation exposure reduction of the sample,which implicates that SAXGI with limited measurements is an efficient solution for low dose radiology.
基金supported by the National Natural Science Foundation of China(Nos.62572017,62441232,62206007)R&D Program of Beijing Municipal Education Commission(KZ202210005008).
文摘Knowledge-based VisualQuestion Answering(VQA)requires the integration of visual information with external knowledge reasoning.Existing approaches typically retrieve information from external corpora and rely on pretrained language models for reasoning.However,their performance is often hindered by the limited capabilities of retrievers and the constrained size of knowledge bases.Moreover,relying on image captions to bridge the modal gap between visual and language modalities can lead to the omission of critical visual details.To address these limitations,we propose the Reflective Chain-of-Thought(ReCoT)method,a simple yet effective framework inspired by metacognition theory.ReCoT effectively activates the reasoning capabilities ofMultimodal Large LanguageModels(MLLMs),providing essential visual and knowledge cues required to solve complex visual questions.It simulates a metacognitive reasoning process that encompasses monitoring,reflection,and correction.Specifically,in the initial generation stage,an MLLM produces a preliminary answer that serves as the model’s initial cognitive output.During the reflective reasoning stage,this answer is critically examined to generate a reflective rationale that integrates key visual evidence and relevant knowledge.In the final refinement stage,a smaller language model leverages this rationale to revise the initial prediction,resulting in amore accurate final answer.By harnessing the strengths ofMLLMs in visual and knowledge grounding,ReCoT enables smaller language models to reason effectively without dependence on image captions or external knowledge bases.Experimental results demonstrate that ReCoT achieves substantial performance improvements,outperforming state-of-the-art methods by 2.26%on OK-VQA and 5.8%on A-OKVQA.
基金support of the National Natural Science Foundation of China(Nos.U20A2069,U21B6003,12302389 and 12472337)the Advanced Aero-Power Innovation Workstation,China(No.HKCX2024-01-017)。
文摘Numerical simulations and theoretical models are developed in this paper for the Detonation-Wave/Boundary-Layer Interactions(DWBLIs)under reflections.Transient flow fields demonstrate the highly non-stationarity of the DWBLIs when Mach Reflection(MR)occur,and subsequent analyses show that the subsonic region introduced by the boundary layer exacerbates the instability.Further quantitative analyses show that viscosity has little effect on propulsive performance and the separation wave can be considered as an oblique detonation wave.Influence parameters to DWBLIs such as combustion chamber height,incoming Mach number,equivalence ratio,and inlet channel length are categorized and studied.Besides simulations,theoretical analytical modeling is established for Regular Reflection(RR)and MR of DWBLIs.Multiple formulas for the separation zone length are obtained according to the mass conservation under different transformation type between inviscid and viscid reflections.Comparison with the numerical simulations verifies the validity of the model and it can be further generalized to the curved DWBLIs.The developed model makes the theoretical solution process of DWBLIs possible and provides the key foundation for further analysis and solution.
基金supported by the Fundamental Research Funds for the Central Universities under No.2024KQ130the National Natural Science Foundation of China(No.52373259)。
文摘The advancement of next-generation high-frequency communication systems and stealth detection technologies necessitate the development of efficient,multi-spectrum compatible shielding materials.However,the achievement of simultaneous high efficiency and low reflectivity across microwave,terahertz,and infrared spectra remains a formidable challenge.Herein,a carbonized MXene/polyimide(C-MXene/PI)aerogel material integrating a spatially coupled hierarchically anisotropic structure with stepwise conductivity gradients was constructed.Electromagnetic waves propagate through the top-down vertical disordered horizontal architecture and progressive conductivity gradient of C-MXene/PI aerogel,undergoing stepwise absorption-dissipation-re-dissipation processes.The C-MXene/PI aerogel exhibits an average electromagnetic interference(EMI)shielding effectiveness of91.0 dB in X-band and a reflection coefficient of 0.40.In the terahertz frequency band,the average EMI shielding performance reaches66.2 dB with a reflection coefficient of 0.33.Furthermore,the heterolayered porous architecture of C-MXene/PI aerogels exhibits low thermal conductivity and reduced infrared emissivity,enabling exceptional infrared stealth capability across the 2-16μm wavelength spectrum.This study provides an feasible strategy for constructing low-reflectivity multi-spectrum compatible shielding materials.
基金funded by the National Natural Science Foundation of China(NNSFC)under Grant Numbers 42322408,42188101,and 42441809Additional support was provided by the Climbing Program of the National Space Science Center(NSSC,Grant No.E4PD3005)as well as the Specialized Research Fund for State Key Laboratories of China.
文摘A large-scale view of the magnetospheric cusp is expected to be obtained by the Soft X-ray Imager(SXI)onboard the Solar wind Magnetosphere Ionosphere Link Explorer(SMILE).However,it is challenging to trace the three-dimensional cusp boundary from a two-dimensional X-ray image because the detected X-ray signals will be integrated along the line of sight.In this work,a global magnetohydrodynamic code was used to simulate the X-ray images and photon count images,assuming an interplanetary magnetic field with a pure Bz component.The assumption of an elliptic cusp boundary at a given altitude was used to trace the equatorward and poleward boundaries of the cusp from a simulated X-ray image.The average discrepancy was less than 0.1 RE.To reduce the influence of instrument effects and cosmic X-ray backgrounds,image denoising was considered before applying the method above to SXI photon count images.The cusp boundaries were reasonably reconstructed from the noisy X-ray image.
基金Project(2023YFB4606200)supported by the National Key Research and Development Program of ChinaProject(2023-SSRF-HZ-503114-2)supported by Shanghai Synchrotron Radiation Facility,Instrument BL16U2,China。
文摘This comprehensive study investigates the formation and evolution of intermetallic compounds during the solidification process of magnesium alloys using advanced micro X-ray computed tomography.By analyzing both common industrial Mg-Al-Zn alloys and a novel rare earth-containing Mg-Ni-Gd-Y alloy,we aim to characterize the nucleation,growth,and distribution of Al-Mn and eutectic intermetallics across various stages of solidification.The non destructive imaging technique employed in this research provides high-resolution,three-dimensional insights into the microstructural development,allowing for a detailed examination of the morphology,spatial arrangement,and interconnectivity of intermetallic phases.This approach overcomes limitations of traditional two-dimensional metallographic methods,offering a more comprehensive understanding of the complex three-dimensional structures formed during solidification.
文摘Objectives This study aimed to explore and clarify the concept of reflective supervision as a professional self-care strategy to create a positive Intensive Care Unit(ICU)practice environment.Methods Walker and Avant’s eight-step concept analysis approach was utilized to identify and define the attributes,antecedents,and consequences of reflective supervision in the ICU.An extensive literature search was conducted across various databases,including Google Scholar,CINAHL,PubMed.Articles published from 2005 to 2025 were identified.We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)2020 statement to indicate the included articles and extract related data based on relevance.Results Forty articles were included in the analysis.The identified attributes included the supervisor-supervisee relationship,effective communication,teamwork,collaborations,reflection,competencies,feedback,continuous support,and autonomous choice.The identified antecedents included participation,supportive supervision,flexibility,open-door policy,training,and motivation.Consequences impacting the success of reflective supervision were identified as promotion of resiliency,autonomy,work-life balance,self-awareness,increased self-esteem,professional development,critical thinking,increased job satisfaction,and enhanced commitment.Conclusions Reflective supervision is a complex professional self-care strategy that enhances ICU practice,by promoting nurses’well-being,self-awareness,therapeutic skills,and professional development.
基金supported by the National Natural Science Foundation of China(No.12105267)National Natural Science Foundation of China(No.11975006)+2 种基金Major Special Program of Science and Technology of Gansu Province(No.1ZD8JA002)the Fundamental Research Funds for the Central Universities(No.lzujbky-2020-pd02)the China Postdoctoral Science Foundation(No.2019M653792)。
文摘In clinical diagnosis,conventional X-ray absorption-contrast computed tomography(XACT)technology cannot effectively differentiate diseased tissues from the healthy ones.X-ray phase-contrast CT(XPCT)and dual-energy CT(DECT),emerging X-ray imaging technologies with superior diagnostic capabilities,address this issue through different principles.While both XPCT and DECT have advantages and disadvantages in medical applications,their systematic comparison is lacking.Using GEANT4 and MATLAB,in this study,we established an X-ray phase-contrast imaging(XPCI)model based on single-mask and single-shot edge illumination for fast XPCT imaging,comparing it with DECT on soft-tissue phantom.XACT served as a reference for comparison.The study introduces an evaluation system using statistical measures including absolute error,mean absolute error,structure similarity index measure,peak signal-to-noise ratio,and contrast-to-noise ratio.Results show XPCT images are superior to DECT.The XPCI model can be improved on existing medical CT for widespread medical application.
基金supported by National Natural Science Foundation of China(61921002 and 92163204)。
文摘Van der Waals(vdW)heterostructures have attracted much attention due to their distinctive optical,electrical,and thermal properties,demonstrating promising potential in areas such as photocatalysis,ultrafast photonics,and free electron radiation devices.Particularly,they are promising platforms for studying thermionic emission.It is illustrated that using vdW heterostructure-based thermionic emission can enhance heat transfer in vacuum devices.As a proof of concept,the approach is demonstrated to offer a promising solution for the long-standing overheating issue in X-ray tubes.Specifically,it is shown that the saturated target temperature of a 2000 W X-ray tube can be reduced from around 1200℃ to 490℃.Additionally,it is also demonstrated that by reducing the height of the Schottky barrier formed in the vdW heterostructures,the thermionic cooling performance can be enhanced.The findings pave the way for the development of high-power X-ray tubes.
