The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the ...The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the plasma sheath can be challenging.Obtaining the electron density of the plasma sheath is crucial for understanding and achieving plasma stealth of vehicles.In this work,the relationship between electromagnetic wave attenuation and electron density is deduced theoretically.The attenuation distribution along the propagation path is found to be proportional to the integral of the plasma electron density.This result is used to predict the electron density profile.Furthermore,the average electron density is obtained using a back-propagation neural network algorithm.Finally,the spatial distribution of the electron density can be determined from the average electron density and the normalized derivative of attenuation with respect to the propagation depth.Compared to traditional probe measurement methods,the proposed approach not only improves efficiency but also preserves the integrity of the plasma environment.展开更多
The aim of this study was to explore the associations of moderate-to-vigorous-intensity physical activity(MVPA)time and sedentary(SED)time with a history of cardiovascular disease(CVD)and multifactorial(i.e.,blood pre...The aim of this study was to explore the associations of moderate-to-vigorous-intensity physical activity(MVPA)time and sedentary(SED)time with a history of cardiovascular disease(CVD)and multifactorial(i.e.,blood pressure(BP),body mass index(BMI),low-density lipoprotein cholesterol(LDL-C),and glycated hemoglobin A1c(HbA1c))control status among type 2 diabetes mellitus(T2DM)patients in China.A cross-sectional analysis of 9152 people with type 2 diabetes from the Multifactorial Intervention on Type 2 Diabetes(MIDiab)study was performed.Patients were grouped according to their self-reported MVPA time(low,<150 min·week−1;moderate,150 to<450 min·week−1;high,≥450 min·week−1)and SED time(low,<4 h·d–1;moderate,4 to<8 h·d–1;high,≥8 h·d–1).Participants who self-reported a history of CVD were identified as having a CVD risk.Odds ratios(ORs)and 95%confidence intervals(CIs)of CVD risk and multifactorial control status associated with MVPA time and SED time were estimated using mixed-effect logistic regression models,adjusting for China’s geographical region characteristics.The participants had a mean±standard deviation(SD)age of(60.87±8.44)years,44.5%were women,and 25.1%had CVD.After adjustment for potential confounding factors,an inverse association between high MVPA time and CVD risk that was independent of SED time was found,whereas this association was not observed in the moderate-MVPA group.A higher MVPA time was more likely to have a positive effect on the control of BMI.Compared with the reference group(i.e.,those with MVPA time≥450 min·week−1 and SED time<4 h·d–1),CVD risk was higher in the low-MVPA group:The OR associated with an SED time<4 h·d–1 was 1.270(95%CI,1.040–1.553)and that associated with an SED time≥8 h·d–1 was 1.499(95%CI,1.149–1.955).We found that a high MVPA time(i.e.,≥450 min·week−1)was associated with lower odds of CVD risk regardless of SED time among patients with T2DM.展开更多
A high performance InAlN/GaN high electron mobility transistor(HEMT)at low voltage operation(6-10 V drain voltage)has been fabricated.An 8 nm InAlN barrier layer is adopted to generate large 2DEG density thus to reduc...A high performance InAlN/GaN high electron mobility transistor(HEMT)at low voltage operation(6-10 V drain voltage)has been fabricated.An 8 nm InAlN barrier layer is adopted to generate large 2DEG density thus to reduce sheet resistance.Highly scaled lateral dimension(1.2μm source-drain spacing)is to reduce access resistance.Both low sheet resistance of the InAlN/GaN structure and scaled lateral dimension contribute to an high extrinsic transconductance of 550 mS/mm and a large drain current of 2.3 A/mm with low on-resistance(Ron)of 0.9Ω·mm.Small signal measurement shows an fT/fmax of 131 GHz/196 GHz.Large signal measurement shows that the InAlN/GaN HEMT can yield 64.7%-52.7%(Vds=6-10 V)power added efficiency(PAE)associated with 1.6-2.4 W/mm output power density at 8 GHz.These results demonstrate that GaN-based HEMTs not only have advantages in the existing high voltage power and high frequency rf field,but also are attractive for low voltage mobile compatible rf applications.展开更多
This paper has proposed a new modelling and simulating technique for the echo of the semi-active radar seeker against the sea skimming target. The echo modelling is based on the electromagnetic scattering mechanisms. ...This paper has proposed a new modelling and simulating technique for the echo of the semi-active radar seeker against the sea skimming target. The echo modelling is based on the electromagnetic scattering mechanisms. A modified Four-path model based on the radar detection scene is used to describe the multipath scattering between the target and rough sea surface. A Facet-based Small Slope Approximation (FBSSA) method is employed to calculate the scattering from the sea surface. The Physical Optics (PO) and the Equivalent Edge Current (EEC) Method is used to calculate the target scattering. In the echo simulations. The results present the original echo and the echo processed by the signal processing procedures, where the clutter and multipath effect can be observed.展开更多
The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at a...The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell’s equations coupled with plasma fluid equations.In this model,we adopt the effective electron diffusion coefficient,which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma.The filamentary plasma arrays observed in experiments are well reproduced in the simulations.The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data.The size of plasma filament parallel to the electric field decreases with increasing frequency,and it increases with the electric field amplitude.The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes.The plasma propagation speed shows little change with the frequency,and it increases with the amplitude.The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.展开更多
The energy transmission of the long microwave pulse for the frequency of 2.45 GHz and 5.8 GHz is studied by using the electron fluid model, where the rate coefficients are deduced from the Boltzmann equation solver na...The energy transmission of the long microwave pulse for the frequency of 2.45 GHz and 5.8 GHz is studied by using the electron fluid model, where the rate coefficients are deduced from the Boltzmann equation solver named BOLSIG＋. The breakdown thresholds for different air pressures and incident pulse parameters are predicted, which show good agreement with the experimental data. Below the breakdown threshold, the transmitted pulse energy is proportional to the square of the incident electric field amplitude. When the incident electric field amplitude higher than the breakdown threshold increases,the transmitted pulse energy decreases monotonously at a high air pressure, while at a low air pressure it first decreases and then increases. We also compare the pulse energy transmission for the frequency of 2.45 GHz with the case of 5.8 GHz.展开更多
The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath.In this paper,the ...The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath.In this paper,the phase shift characteristics of electromagnetic wave propagation in plasma were investigated.Firstly,the impact factors of phase shift including electron density,collision frequency and incident frequency were discussed.Then,the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics.In a real case,the plasma sheath around the hypersonic vehicle will affect and even break down the communication.Based on the hypersonic vehicle model,we studied the electromagnetic wave phase shift under different flight altitude,speed,and attack angle.The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle.Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma.展开更多
The attenuation characteristics of obliquely incident electromagnetic(EM) wave in L-Ka frequency band in weakly ionized dusty plasma are analyzed based on the modified Bhatnagar-Gross-Krook(BGK) collision model.Accord...The attenuation characteristics of obliquely incident electromagnetic(EM) wave in L-Ka frequency band in weakly ionized dusty plasma are analyzed based on the modified Bhatnagar-Gross-Krook(BGK) collision model.According to the kinetic equation and the charging theory,the total complex dielectric constant of the weakly ionized dusty plasma is derived by considering that the minimum velocity of the electron accessible to the dust particle surface is non-zero and the second potential part of the collision cross-section contributes to the charging.The attenuation characteristics within the modified model are compared with those within the traditional model.The influence of the dusty plasma parameters and the incident angle of EM waves on the attenuation in weakly ionized dusty plasma is further analyzed.Finally,the influence of different reentry heights on the attenuation characteristics of the obliquely incident EM wave is discussed.The results show that the effect of the minimum electron velocity and the second term of the collision cross-section on the attenuation characteristics of EM waves cannot be ignored.When the dust density and dust radius are changed,the trends of the attenuation of obliquely incident EM waves are consistent,but the influence of dust density is weaker than that of dust radius due to the constraint of orbit-limited motion(OLM) theory.The plasma thickness,electron density,and incident angle are proportional to the attenuation amplitude of EM waves.The effect of different reentry heights on the attenuation obliquely incident EM waves is related to the electron density and plasma thickness.展开更多
The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is describe...The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision(PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons,and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value,when the number of gas atoms desorbed by an incident electron is taken as 0.4.展开更多
The lifetime and luminescenceefficiency o Light emitting diode(LED)tend to drop rapidly with the increasing P-N junction temperature(Tj).To enhancethe heat dissipationofaluminum alloy radiator for LED,a high emissivit...The lifetime and luminescenceefficiency o Light emitting diode(LED)tend to drop rapidly with the increasing P-N junction temperature(Tj).To enhancethe heat dissipationofaluminum alloy radiator for LED,a high emissivity and hydrophobic coatingwas fabricated bymicroarc oxidation(MAO)com-展开更多
Optical metrology is a well-established subject,dating back to early interferometry techniques utilizing light's linear momentum through fringes.In recent years,significant interest has arisen in using vortex ligh...Optical metrology is a well-established subject,dating back to early interferometry techniques utilizing light's linear momentum through fringes.In recent years,significant interest has arisen in using vortex light with orbital angular momentum(OAM),where the phase twists around a singular vortex in space or time.This has expanded metrology's boundaries to encompass highly sensitive chiral interactions between light and matter,three-dimensional motion detection via linear and rotational Doppler effects,and modal approaches surpassing the resolution limit for improved profling and quantification.The intricate structure of vortex light,combined with the integration of artifcial intelligence into optical metrology,unlocks new paradigms for expanding measurement frameworks through additional degrees of freedom,offering the potential for more effcient and accurate sensing and metrological advancements.This review aims to provide a comprehensive overview of recent advances and future trends in optical metrology with structured light,specifically focusing on how utilizing vortex beams has revolutionized metrology and remote sensing,transitioning from classical to quantum approaches.展开更多
To the Editor:Type 2 diabetes(T2DM)is a significant health issue in China,with the age-standardized prevalence rising 2.5-fold from 1990 to 9.96%in 2021.[1]Despite this rise,only 32.9%of patients received treatment,an...To the Editor:Type 2 diabetes(T2DM)is a significant health issue in China,with the age-standardized prevalence rising 2.5-fold from 1990 to 9.96%in 2021.[1]Despite this rise,only 32.9%of patients received treatment,and just 50.1%achieved controlled blood sugar.[1]The Chinese Diabetes Society(CDS)advocates for self-monitoring of blood glucose(SMBG)to help patients track levels and manage their condition.[2]While SMBG has been shown to lower HbA1c in type 1 diabetes and untreated type 2 diabetes(T2D),large-scale evidence for its effect in insulin-treated T2D is still limited.展开更多
The all-inorganic lead-free vacancy-ordered perovskite offers a promising avenue toward nontoxic and stable optoelectronic materials.Herein,we present a first-principles study of the structural stability,optical absor...The all-inorganic lead-free vacancy-ordered perovskite offers a promising avenue toward nontoxic and stable optoelectronic materials.Herein,we present a first-principles study of the structural stability,optical absorption,electronic structure,and mechanical behavior of Cs_(2)BCl_(6) compounds with B-site substitutions(B]Ge,Sn,Pb,Cr,Mo,W,Ti,Zr,and Hf).The structural analysis shows that the Cs_(2)BCl_(6) perovskite with face-centered cubes has a stable chemical environment,especially Cs_(2)HfCl_(6),Cs_(2)WCl_(6),and Cs_(2)PbCl_(6).Hf4^(+) and W4^(+) with high-energy d-state external electron configurations can further lower the valence band maximum position of the Cs_(2)BCl_(6) structures and thus increase the band gap,assisting in tuning the optical absorption and emission properties of these structures in the optoelectronic application.For the light absorption properties of Cs_(2)BCl_(6) materials,the best light absorption properties have been concluded for Ti4^(+),Cr4^(+),and Pb4^(+)-based perovskite in the visible range due to a suitable band gap.Therefore,the excellent optical absorption and electronic properties make these vacancy-ordered perovskites promising candidates for optoelectronic applications.展开更多
In recent years,the prevalence of diabetes in China has increased significantly,and approximately 11.9%of Chinese adults had diabetes in 2020.Moreover,there are several rigorous challenges in diabetes prevention and g...In recent years,the prevalence of diabetes in China has increased significantly,and approximately 11.9%of Chinese adults had diabetes in 2020.Moreover,there are several rigorous challenges in diabetes prevention and glycaemic control,especially at the primary medical care level.In order to guide primary healthcare providers in providing comprehensive and continuous care to affected patients,the Office for Primary Diabetes Care of the National Basic Public Health Service Program and the Chinese Diabetes Society issued national guidelines for the prevention and control of diabetes at the primary care level in 2025.The management objects were adults with type 2 diabetes aged≥18 years.The main contents include basic requirements for management,health management process,diagnosis,screening,evaluation,treatment,recognition and management of acute complications,traditional Chinese medicine,referral and health management and education.展开更多
Atmospheric turbulence degrades the performance of free-space optical(FSO)communication and remote sensing systems by introducing phase and intensity distortions.While a majority of research focuses on mitigating thes...Atmospheric turbulence degrades the performance of free-space optical(FSO)communication and remote sensing systems by introducing phase and intensity distortions.While a majority of research focuses on mitigating these effects to ensure robust signal transmission,an underexplored alternative is to leverage the transformation of structured light to characterize the turbulent medium itself.Here,we introduce a deep learning framework that fuses post-propagation intensity speckle patterns and orbital angular momentum(OAM)spectral data for atmospheric turbulence parameter inference.Our architecture,based on a modified InceptionNet backbone,is optimized to extract and integrate multi-scale features from these distinct optical modalities.This multimodal approach achieves validation accuracies exceeding 80%,substantially outperforming conventional single-modality baselines.The framework demonstrates high inference accuracy and enhanced training stability across a broad range of simulated turbulent conditions,quantified by varying Fried parameters(r_(0))and Reynolds numbers(Re).This work presents a scalable and data-efficient method for turbulence characterization,offering a pathway toward robust environmental sensing and the optimization of dynamic FSO systems.展开更多
Vortex splitting is one of the main causes of instability in orbital angular momentum(OAM) modes transmission. Recent advances in OAM modes free-space propagation have demonstrated that abruptly autofocusing Airy vort...Vortex splitting is one of the main causes of instability in orbital angular momentum(OAM) modes transmission. Recent advances in OAM modes free-space propagation have demonstrated that abruptly autofocusing Airy vortex beams(AAVBs) can potentially mitigate the vortex splitting effect. However, different modes of vortex embedding will affect the intensity gradients of the background beams, leading to changes in the propagation characteristics of vortex beams. This study presents the unification of two common methods of coupling autofocusing Airy beams with vortices by introducing a parameter(m), which also controls the intensity gradients and focusing properties of the AAVBs. We demonstrate that vortex splitting can be effectively reduced by selecting an appropriate value of the parameter(m) according to different turbulence conditions. In this manner,the performance of OAM-based free-space optical systems can be improved.展开更多
The recent development of synthesis processes for three-dimensional （3D） graphene-based structures has tended to focus on continuous improvement of porous nanostructures, doping modification during thin-film fabrica...The recent development of synthesis processes for three-dimensional （3D） graphene-based structures has tended to focus on continuous improvement of porous nanostructures, doping modification during thin-film fabrication, and mechanisms for building 3D architectures. Here, we synthesized novel snowflake- like Si-O/Si-C nanostructures on 3D graphene/Cu foam by one-step low-pressure chemical vapor deposition （CVD）. Through systematic micromorphological characterization, it was determined that the formation mechanism of the nanostructures involved the melting of the Cu foam surface and the subsequent condensation of the resulting vapor, 3D growth of graphene through catalysis in the presence of Cu, and finally , nudeation of the Si-O/Si-C nanostructure in the carbon-rich atmosphere. Thus, by tuning the growth temperature and duration, it should be possible to control the nucleation and evolution of such snowflake-like nanostructures with precision. Electrochemical measurements indicated that the snowflake-like nanostructures showed excellent performance as a material for energy storage. The highest specific capacitance of the Si-O/Si-C nanostructures was - 963.2 mF/cm2 at a scan rate of 1 mV/s. Further, even after 20,000 sequential cycles, the electrode retained 94.4% of its capacitance.展开更多
基金Project supported by the Natural Science Foundation of Henan Province,China(Grant No.242300420634)the Cultivative Plan of Henan University of Technology(Grant No.2024PYJH035)+3 种基金the Research Foundation for Advanced Talents of Henan University of Technology(Grant Nos.2022BS067 and 2022BS068)the National Natural Science Foundation of China(Grant No.62301211)the Key Research and Development and Promotion Special Project(Science and Technology Research)in Henan Province,China(Grant No.232102211068)the Innovative Funds Plan of Henan University of Technology(Grant No.2022ZKCJ15)。
文摘The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the plasma sheath can be challenging.Obtaining the electron density of the plasma sheath is crucial for understanding and achieving plasma stealth of vehicles.In this work,the relationship between electromagnetic wave attenuation and electron density is deduced theoretically.The attenuation distribution along the propagation path is found to be proportional to the integral of the plasma electron density.This result is used to predict the electron density profile.Furthermore,the average electron density is obtained using a back-propagation neural network algorithm.Finally,the spatial distribution of the electron density can be determined from the average electron density and the normalized derivative of attenuation with respect to the propagation depth.Compared to traditional probe measurement methods,the proposed approach not only improves efficiency but also preserves the integrity of the plasma environment.
基金supported by the National Key Research and Development Program of China(2017YFC1309800)the“Outstanding University Driven by Talents”Program and Academic Promotion Program of Shandong First Medical University(2019LJ007)the Key Research and Development Program of Shandong Province(2017CXGC1214).
文摘The aim of this study was to explore the associations of moderate-to-vigorous-intensity physical activity(MVPA)time and sedentary(SED)time with a history of cardiovascular disease(CVD)and multifactorial(i.e.,blood pressure(BP),body mass index(BMI),low-density lipoprotein cholesterol(LDL-C),and glycated hemoglobin A1c(HbA1c))control status among type 2 diabetes mellitus(T2DM)patients in China.A cross-sectional analysis of 9152 people with type 2 diabetes from the Multifactorial Intervention on Type 2 Diabetes(MIDiab)study was performed.Patients were grouped according to their self-reported MVPA time(low,<150 min·week−1;moderate,150 to<450 min·week−1;high,≥450 min·week−1)and SED time(low,<4 h·d–1;moderate,4 to<8 h·d–1;high,≥8 h·d–1).Participants who self-reported a history of CVD were identified as having a CVD risk.Odds ratios(ORs)and 95%confidence intervals(CIs)of CVD risk and multifactorial control status associated with MVPA time and SED time were estimated using mixed-effect logistic regression models,adjusting for China’s geographical region characteristics.The participants had a mean±standard deviation(SD)age of(60.87±8.44)years,44.5%were women,and 25.1%had CVD.After adjustment for potential confounding factors,an inverse association between high MVPA time and CVD risk that was independent of SED time was found,whereas this association was not observed in the moderate-MVPA group.A higher MVPA time was more likely to have a positive effect on the control of BMI.Compared with the reference group(i.e.,those with MVPA time≥450 min·week−1 and SED time<4 h·d–1),CVD risk was higher in the low-MVPA group:The OR associated with an SED time<4 h·d–1 was 1.270(95%CI,1.040–1.553)and that associated with an SED time≥8 h·d–1 was 1.499(95%CI,1.149–1.955).We found that a high MVPA time(i.e.,≥450 min·week−1)was associated with lower odds of CVD risk regardless of SED time among patients with T2DM.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2018M640957)the Fundamental Research Funds for the Central Universities,China(Grant No.20101196761)+2 种基金the National Natural Science Foundation of China(Grant No.61904135)the National Defense Pre-Research Foundation of China(Grant No.31513020307)the Natural Science Foundation of Shaanxi Province of China(Grant No.2020JQ-316).
文摘A high performance InAlN/GaN high electron mobility transistor(HEMT)at low voltage operation(6-10 V drain voltage)has been fabricated.An 8 nm InAlN barrier layer is adopted to generate large 2DEG density thus to reduce sheet resistance.Highly scaled lateral dimension(1.2μm source-drain spacing)is to reduce access resistance.Both low sheet resistance of the InAlN/GaN structure and scaled lateral dimension contribute to an high extrinsic transconductance of 550 mS/mm and a large drain current of 2.3 A/mm with low on-resistance(Ron)of 0.9Ω·mm.Small signal measurement shows an fT/fmax of 131 GHz/196 GHz.Large signal measurement shows that the InAlN/GaN HEMT can yield 64.7%-52.7%(Vds=6-10 V)power added efficiency(PAE)associated with 1.6-2.4 W/mm output power density at 8 GHz.These results demonstrate that GaN-based HEMTs not only have advantages in the existing high voltage power and high frequency rf field,but also are attractive for low voltage mobile compatible rf applications.
文摘This paper has proposed a new modelling and simulating technique for the echo of the semi-active radar seeker against the sea skimming target. The echo modelling is based on the electromagnetic scattering mechanisms. A modified Four-path model based on the radar detection scene is used to describe the multipath scattering between the target and rough sea surface. A Facet-based Small Slope Approximation (FBSSA) method is employed to calculate the scattering from the sea surface. The Physical Optics (PO) and the Equivalent Edge Current (EEC) Method is used to calculate the target scattering. In the echo simulations. The results present the original echo and the echo processed by the signal processing procedures, where the clutter and multipath effect can be observed.
基金supported by China National Natural Science Foundation of Shaanxi Province(No.2020JQ-643)China Postdoctoral Science Foundation funded project(No.2019M653545)the Fundamental Research Funds for the Central Universities,China(No.JB210510)。
文摘The structure and propagation of the plasma in air breakdown driven by high-power microwave have attracted great interest.This paper focuses on the microwave amplitude and frequency dependence of plasma formation at atmospheric pressure using one two-dimensional model,which is based on Maxwell’s equations coupled with plasma fluid equations.In this model,we adopt the effective electron diffusion coefficient,which can describe well the change from free diffusion in a plasma front to ambipolar diffusion in the bulk plasma.The filamentary plasma arrays observed in experiments are well reproduced in the simulations.The density and propagation speed of the plasma from the simulations are also close to the corresponding experimental data.The size of plasma filament parallel to the electric field decreases with increasing frequency,and it increases with the electric field amplitude.The distance between adjacent plasma filaments is close to one-quarter wavelength under different frequencies and amplitudes.The plasma propagation speed shows little change with the frequency,and it increases with the amplitude.The variations of plasma structure and propagation with the amplitude and frequency are due to the change in the distribution of the electric field.
基金Project supported by the National Natural Science Foundation of China(Grant No.61501358)the Fundamental Research Funds for the Central Universities,China
文摘The energy transmission of the long microwave pulse for the frequency of 2.45 GHz and 5.8 GHz is studied by using the electron fluid model, where the rate coefficients are deduced from the Boltzmann equation solver named BOLSIG＋. The breakdown thresholds for different air pressures and incident pulse parameters are predicted, which show good agreement with the experimental data. Below the breakdown threshold, the transmitted pulse energy is proportional to the square of the incident electric field amplitude. When the incident electric field amplitude higher than the breakdown threshold increases,the transmitted pulse energy decreases monotonously at a high air pressure, while at a low air pressure it first decreases and then increases. We also compare the pulse energy transmission for the frequency of 2.45 GHz with the case of 5.8 GHz.
基金supported by National Natural Science Foundation of China(Nos.U20B2059,62071353,61627901 and 62071348)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.61621005)the Key Laboratory Foundation(No.6142502190203).
文摘The phase shift characteristics reflect the state change of electromagnetic wave in plasma sheath and can be used to reveal deeply the action mechanism between electromagnetic wave and plasma sheath.In this paper,the phase shift characteristics of electromagnetic wave propagation in plasma were investigated.Firstly,the impact factors of phase shift including electron density,collision frequency and incident frequency were discussed.Then,the plasma with different electron density distribution profiles were employed to investigate the influence on the phase shift characteristics.In a real case,the plasma sheath around the hypersonic vehicle will affect and even break down the communication.Based on the hypersonic vehicle model,we studied the electromagnetic wave phase shift under different flight altitude,speed,and attack angle.The results indicate that the phase shift is inversely proportional to the flight altitude and positively proportional to the flight speed and attack angle.Our work provides a theoretical guidance for the further research of phase shift characteristics and parameters inversion in plasma.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U20B2059 and 61627901)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.61621005)+4 种基金the Natural Science Foundation of Shaanxi Province of China(Grant No.2019JM-206)the National Key Laboratory Foundation of China(Grant No.HTKJ2019KL504014)the Fundamental Research Funds for the Central Universities,Chinathe Innovation Fund of Xidian University and the 111 Project(Grant No.B17035)。
文摘The attenuation characteristics of obliquely incident electromagnetic(EM) wave in L-Ka frequency band in weakly ionized dusty plasma are analyzed based on the modified Bhatnagar-Gross-Krook(BGK) collision model.According to the kinetic equation and the charging theory,the total complex dielectric constant of the weakly ionized dusty plasma is derived by considering that the minimum velocity of the electron accessible to the dust particle surface is non-zero and the second potential part of the collision cross-section contributes to the charging.The attenuation characteristics within the modified model are compared with those within the traditional model.The influence of the dusty plasma parameters and the incident angle of EM waves on the attenuation in weakly ionized dusty plasma is further analyzed.Finally,the influence of different reentry heights on the attenuation characteristics of the obliquely incident EM wave is discussed.The results show that the effect of the minimum electron velocity and the second term of the collision cross-section on the attenuation characteristics of EM waves cannot be ignored.When the dust density and dust radius are changed,the trends of the attenuation of obliquely incident EM waves are consistent,but the influence of dust density is weaker than that of dust radius due to the constraint of orbit-limited motion(OLM) theory.The plasma thickness,electron density,and incident angle are proportional to the attenuation amplitude of EM waves.The effect of different reentry heights on the attenuation obliquely incident EM waves is related to the electron density and plasma thickness.
基金supported by the National Key Laboratory Foundation 2021-JCJQ-LB-006,China(No.6142411132116)the Natural Science Basic Research Program of Shaanxi Province,China(Nos.2023-JC-YB-512 and 2023-JC-YB-042)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.ZYTS23075)the China Postdoctoral Science Foundation(No.2019M653545)。
文摘The gas desorbed from the dielectric surface has a great influence on the characteristics of microwave breakdown on the vacuum side of the dielectric window. In this paper, the dielectric surface breakdown is described by using the electromagnetic particle-in-cell-Monte Carlo collision(PIC-MCC) model. The process of desorption of gas and its influence on the breakdown characteristics are studied. The simulation results show that, due to the accumulation of desorbed gas, the pressure near the dielectric surface increases in time, and the breakdown mechanism transitions from secondary electron multipactor to collision ionization. More and more electrons generated by collision ionization drift to the dielectric surface, so that the amplitude of self-organized normal electric field increases in time and sometimes points to the dielectric surface. Nevertheless, the number of secondary electrons emitted in each microwave cycle is approximately equal to the number of primary electrons. In the early and middle stages of breakdown, the attenuation of the microwave electric field near the dielectric surface is very small. However, the collision ionization causes a sharp increase in the number density of electrons,and the microwave electric field decays rapidly in the later stage of breakdown. Compared with the electromagnetic PIC-MCC simulation results, the mean energy and number of electrons obtained by the electrostatic PIC-MCC model are overestimated in the later stage of breakdown because it does not take into account the attenuation of microwave electric field. The pressure of the desorbed gas predicted by the electromagnetic PIC-MCC model is close to the measured value,when the number of gas atoms desorbed by an incident electron is taken as 0.4.
文摘The lifetime and luminescenceefficiency o Light emitting diode(LED)tend to drop rapidly with the increasing P-N junction temperature(Tj).To enhancethe heat dissipationofaluminum alloy radiator for LED,a high emissivity and hydrophobic coatingwas fabricated bymicroarc oxidation(MAO)com-
基金support from the 111 Project(B17035)National Natural Science Foundation of China(Grant no.U20B2059,62231021,61621005,62201613)+2 种基金Shanghai Aerospace Science and Technology Innovation support from the 111 Project(B17035)National Natural Science Foundation of China(Grant no.U20B2059,62231021,61621005,62201613)Shanghai Aerospace Science and Technology Innovation Foundation(SAST-2022-069)。
文摘Optical metrology is a well-established subject,dating back to early interferometry techniques utilizing light's linear momentum through fringes.In recent years,significant interest has arisen in using vortex light with orbital angular momentum(OAM),where the phase twists around a singular vortex in space or time.This has expanded metrology's boundaries to encompass highly sensitive chiral interactions between light and matter,three-dimensional motion detection via linear and rotational Doppler effects,and modal approaches surpassing the resolution limit for improved profling and quantification.The intricate structure of vortex light,combined with the integration of artifcial intelligence into optical metrology,unlocks new paradigms for expanding measurement frameworks through additional degrees of freedom,offering the potential for more effcient and accurate sensing and metrological advancements.This review aims to provide a comprehensive overview of recent advances and future trends in optical metrology with structured light,specifically focusing on how utilizing vortex beams has revolutionized metrology and remote sensing,transitioning from classical to quantum approaches.
文摘To the Editor:Type 2 diabetes(T2DM)is a significant health issue in China,with the age-standardized prevalence rising 2.5-fold from 1990 to 9.96%in 2021.[1]Despite this rise,only 32.9%of patients received treatment,and just 50.1%achieved controlled blood sugar.[1]The Chinese Diabetes Society(CDS)advocates for self-monitoring of blood glucose(SMBG)to help patients track levels and manage their condition.[2]While SMBG has been shown to lower HbA1c in type 1 diabetes and untreated type 2 diabetes(T2D),large-scale evidence for its effect in insulin-treated T2D is still limited.
基金supported by the National Key Research and Development Program of China(Grant 2021YFA0715600,2018YFB2202900)the National Natural Science Foundation of China(62304171,52192610,62274127,62274125,62374128)+2 种基金the China Postdoctoral Science Foundation(2022M722500,2023TQ0255)Key Research and Development Program of Shaanxi Province(Grant 2024GX-YBXM-512)the High-Performance Computing Platform of Xidian University,Guangdong Basic and Applied Basic Research Foundation(2023A1515030084).
文摘The all-inorganic lead-free vacancy-ordered perovskite offers a promising avenue toward nontoxic and stable optoelectronic materials.Herein,we present a first-principles study of the structural stability,optical absorption,electronic structure,and mechanical behavior of Cs_(2)BCl_(6) compounds with B-site substitutions(B]Ge,Sn,Pb,Cr,Mo,W,Ti,Zr,and Hf).The structural analysis shows that the Cs_(2)BCl_(6) perovskite with face-centered cubes has a stable chemical environment,especially Cs_(2)HfCl_(6),Cs_(2)WCl_(6),and Cs_(2)PbCl_(6).Hf4^(+) and W4^(+) with high-energy d-state external electron configurations can further lower the valence band maximum position of the Cs_(2)BCl_(6) structures and thus increase the band gap,assisting in tuning the optical absorption and emission properties of these structures in the optoelectronic application.For the light absorption properties of Cs_(2)BCl_(6) materials,the best light absorption properties have been concluded for Ti4^(+),Cr4^(+),and Pb4^(+)-based perovskite in the visible range due to a suitable band gap.Therefore,the excellent optical absorption and electronic properties make these vacancy-ordered perovskites promising candidates for optoelectronic applications.
基金funded by the Noncommunicable Chronic Diseases-National Science and Technology Major Project(2024ZD0523300)the National Key Clinical Specialty Capacity Building for Endocrine and Metabolic Diseases(Z155080000004)+1 种基金the Shanghai Key Laboratory of Diabetes Mellitus(20DZ2270300)the Sanming Project of Medicine in Shenzhen(SZSM202311019).
文摘In recent years,the prevalence of diabetes in China has increased significantly,and approximately 11.9%of Chinese adults had diabetes in 2020.Moreover,there are several rigorous challenges in diabetes prevention and glycaemic control,especially at the primary medical care level.In order to guide primary healthcare providers in providing comprehensive and continuous care to affected patients,the Office for Primary Diabetes Care of the National Basic Public Health Service Program and the Chinese Diabetes Society issued national guidelines for the prevention and control of diabetes at the primary care level in 2025.The management objects were adults with type 2 diabetes aged≥18 years.The main contents include basic requirements for management,health management process,diagnosis,screening,evaluation,treatment,recognition and management of acute complications,traditional Chinese medicine,referral and health management and education.
基金111 Project(B17035)National Natural Science Foundation of China(U20B2059,62575227,62231021,61621005,62201613)+1 种基金Shanghai Aerospace Science and Technology Innovation Foundation(SAST-2022-069)Fundamental Research Funds for the Central Universities(ZYTS25121).
文摘Atmospheric turbulence degrades the performance of free-space optical(FSO)communication and remote sensing systems by introducing phase and intensity distortions.While a majority of research focuses on mitigating these effects to ensure robust signal transmission,an underexplored alternative is to leverage the transformation of structured light to characterize the turbulent medium itself.Here,we introduce a deep learning framework that fuses post-propagation intensity speckle patterns and orbital angular momentum(OAM)spectral data for atmospheric turbulence parameter inference.Our architecture,based on a modified InceptionNet backbone,is optimized to extract and integrate multi-scale features from these distinct optical modalities.This multimodal approach achieves validation accuracies exceeding 80%,substantially outperforming conventional single-modality baselines.The framework demonstrates high inference accuracy and enhanced training stability across a broad range of simulated turbulent conditions,quantified by varying Fried parameters(r_(0))and Reynolds numbers(Re).This work presents a scalable and data-efficient method for turbulence characterization,offering a pathway toward robust environmental sensing and the optimization of dynamic FSO systems.
基金supported by the Innovation Fund of Xidian University(No.20108183448)the Key Industrial Innovation Chain Project in Industrial Domain(No.2017ZDCXL–GY–06–02)+2 种基金the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.61621005)the National Natural Science Foundation of China(No.41806210)the Fundamental Research Funds for the Central Universities(No.CJT150502)
文摘Vortex splitting is one of the main causes of instability in orbital angular momentum(OAM) modes transmission. Recent advances in OAM modes free-space propagation have demonstrated that abruptly autofocusing Airy vortex beams(AAVBs) can potentially mitigate the vortex splitting effect. However, different modes of vortex embedding will affect the intensity gradients of the background beams, leading to changes in the propagation characteristics of vortex beams. This study presents the unification of two common methods of coupling autofocusing Airy beams with vortices by introducing a parameter(m), which also controls the intensity gradients and focusing properties of the AAVBs. We demonstrate that vortex splitting can be effectively reduced by selecting an appropriate value of the parameter(m) according to different turbulence conditions. In this manner,the performance of OAM-based free-space optical systems can be improved.
基金The work was supported by the National Natural Science Foundation of China （Nos. 61604115 and 61334002）, the Natural Science Basic Research Plan in Shaanxi Province of China （No. 2016ZDJC-09）, the Key Research and Development program in Shaanxi Province （No. 2017ZDCXL-GY-11-03）, the China Postdoctoral Science Foundation （No. 2015M580814）,the Postdoctoral Science Research Plan in Shaanxi Province of China and the Fundamental Research Funds for the Central Universities （Nos. XJS15066 and JB161103）.
文摘The recent development of synthesis processes for three-dimensional （3D） graphene-based structures has tended to focus on continuous improvement of porous nanostructures, doping modification during thin-film fabrication, and mechanisms for building 3D architectures. Here, we synthesized novel snowflake- like Si-O/Si-C nanostructures on 3D graphene/Cu foam by one-step low-pressure chemical vapor deposition （CVD）. Through systematic micromorphological characterization, it was determined that the formation mechanism of the nanostructures involved the melting of the Cu foam surface and the subsequent condensation of the resulting vapor, 3D growth of graphene through catalysis in the presence of Cu, and finally , nudeation of the Si-O/Si-C nanostructure in the carbon-rich atmosphere. Thus, by tuning the growth temperature and duration, it should be possible to control the nucleation and evolution of such snowflake-like nanostructures with precision. Electrochemical measurements indicated that the snowflake-like nanostructures showed excellent performance as a material for energy storage. The highest specific capacitance of the Si-O/Si-C nanostructures was - 963.2 mF/cm2 at a scan rate of 1 mV/s. Further, even after 20,000 sequential cycles, the electrode retained 94.4% of its capacitance.
