检索结果-南通市图书馆

Numerical study of the auroral particle transport in the polar upper atmosphere

Science china(Technological Sciences) 2008年第10期51卷 1759-1771页

作者： cai hongtao1,2. ma shuying1,{2. pu {2. 1 School of electronic information, wuhan university, wuhan 430079, china 2.Key Laboratory of Geospace Environment and Geodesy, Ministry of Education of PRC, wuhan 430079, china 3 School of Earth and Space Sciences, Peking university, Beijing 100871, china School of electronic information Wuhan University Wuhan China Key Laboratory of Geospace Environment and Geodesy Ministry of Education of PRC Wuhan China School of Earth and Space Sciences Peking University Beijing China

Starting from the Boltzmann equation and with some reasonable assumptions, a one-dimensional transport equation of charged energetic particles is derived by taking account of major interactions with neutral species in the upper atmosphere, including the processes of elastic scattering, the excitation, the ionization and the secondary electron production. The transport equation is numerically solved, for a simplified atmosphere consisting only of nitrogen molecules (N2., to obtain the variations of incident electron fluxes as a function of altitude, energy and pitch angle. The model results can describe fairly the transport characteristics of pre-cipitating auroral electron spectra in the polar upper atmosphere; meanwhile the N2.ionization rates calculated from the modeled differential flux spectra also exhibit good agreements with existing empirical models in terms of several key parameters. Taking the energy flux spectra of precipitating electrons observed by FAST satellite flying over EISCAT site on may 15, 1997 as model inputs, the model-calculated ionization rate profile of neutral atmosphere consists reasonably with that recon-structed from electron density measurements by the radar.

关键词： aurora particle precipitation polar upper atmosphere electron transport equation numerical simulation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Age of information for Short-Packet Covert Communication with Time Modulated Retrodirective Array

引用

china Communications 2024年第4期21卷 23-37页

作者： ma Yue ma Ruiqian Lin Zhi Yang Weiwei cai Yueming Miao Chen Wu Wen Key Laboratory of Near-Range RF Sensing ICs&Microsystems(NJUST) Ministry of EducationSchool of Electronic and Optical EngineeringNanjing University of Science and TechnologyNanjing 210094China College of electronic Engineering National University of Defense TechnologyHefei 230037China College of Communications Engineering Army Engineering University of PLANanjing 210007China

In this paper,the covert age of information(CAoI),which characterizes the timeliness and covertness performance of communication,is first investigated in the short-packet covert communication with time modulated retrodirective array(TMRDA).Specifically,the TMRDA is designed to maximize the antenna gain in the target direction while the side lobe is sufficiently *** this basis,the covertness constraint and CAoI are derived in closed *** facilitate the covert transmission design,the transmit power and block-length are jointly optimized to minimize the CAoI,which demonstrates the trade-off between covertness and *** results illustrate that there exists an optimal block-length that yields the minimum CAoI,and the presented optimization results can achieve enhanced performance compared with the fixed block-length ***,we observe that smaller beam pointing error at Bob leads to improvements in CAoI.

关键词： age of information covert communication retrodirective array time modulation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Re-usable Cd_(0.9)Zn_(0.1)S-ZnO@C/PVDF piezo-photocatalytic film with exceptional hydrogen evolution capability triggered by the synergetic advantages of piezoelectricity and S-Scheme heterojunction

引用

Journal of Energy Chemistry 2024年第9期96卷 164-176页

作者： Ping Su Dong Zhang Minghui Zhu Tengteng Liang Nan Yang Huaihao Zhao Dafeng Zhang Junchang Liu Peiqing cai Xipeng pu School of materials Science and Engineering Shandong Provincial Key Laboratory of Chemical Energy Science and Novel Cell TechnologyLiaocheng UniversityLiaocheng 252000ShandongChina School of Physics Science and information Technology Shandong Key Laboratory of Optical Communication Sciencend TechnologyLiaocheng UniversityLiaocheng 252000ShandongChina College of Optical and electronic Technology China Jiliang UniversityHangzhou 310018ZhejiangChina

Piezoelectric materials have advantages of fine-tuning photocatalytic performance through harvesting mechanical energy and open a new avenue in facilitating green catalytic ***,polyvinylidene fluoride(PVDF),a flexible piezoelectric material,was introduced to synthesize a novel Cd_(0.9)Zn_(0.1)S-ZnO@C/PVDF(CZS-ZO@C/PVDF)piezo-photocatalytic film by spin coating and immersion phase conversion *** from the piezoelectricity of PVDF and the internal electric field(IEF)of CZS-ZO@C Step-scheme(S-Scheme)heterojunction,CZS-ZO@C/PVDF was able to induce a hydrogen generation rate of 34.9 mmol g^(−1)h^(−1)activated by ultrasound and visible light(U-L),which is∼17.5 times of Cd_(0.9)Zn_(0.1)S/PVDF(CZS/PVDF)and∼7.4 times of the photocatalysis rate activated by visible light only(L).Piezoelectric measurements and COMSOL simulation illustrated the excellent piezoelectricity of CZS-ZO@C/PVDF film,which exhibits a piezoelectric coefficient(d33)of 9.9 pm V−1 and a piezoelectric potential of 874 mV(under 0.5 MPa).The reaction mechanism for the exceptional piezo-photocatalytic performance was finally disclosed through density functional theory(DFT)calculation and electrochemical *** study enriches the application scope of piezoelectric materials in sustainable energy catalysis and provides a new direction to develop efficient piezoelectric photocatalysts.

关键词： Piezo-photocatalysis Heterojunction Cd_(0.9)Zn_(0.1)S Zno@c PVDF

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Using an improved lightweight YOLOv8 model for real-time detection of multi-stage apple fruit in complex orchard environments

引用

Artificial Intelligence in Agriculture 2024年第1期11卷 70-82页

作者： Baoling ma Zhixin Hua Yuchen Wen Hongxing Deng Yongjie Zhao Liuru pu Huaibo Song College of Mechanical and electronic Engineering Northwest A&F UniversityYanglingShaanxi 712100China Key Laboratory of Agricultural Internet of Things Ministry of Agricultureand Rural AffairsYanglingShaanxi 712100China Shaanxi Key Laboratory of Agricultural information Perception and Intelligent Services YanglingShaanxi 712100China

For the purpose of monitoring apple fruits effectively throughout the entire growth period in smart orchards.A lightweight model named YOLOv8n-ShuffleNetv2.Ghost-SE was *** ShuffleNetv2.basic modules and down-sampling modules were alternately connected,replacing the Backbone of YOLOv8n *** Ghost modules replaced the Conv modules and the C2.Ghost modules replaced the C2. modules in the Neck part of the ***2.reduced the memory access cost through channel splitting *** Ghost module combined linear and non-linear convolutions to reduce the network computation *** Wise-IoU(WIoU)replaced the CIoU for calculating the bounding box regression loss,which dynamically adjusted the anchor box quality threshold and gradient gain allocation strategy,optimizing the size and position of predicted bounding *** Squeeze-and-Excitation(SE)was embedded in the Backbone and Neck part of YOLOv8n to enhance the representation ability of feature *** algorithm ensured high precision while having small model size and fast detection speed,which facilitated model migration and *** 9652.images validated the effectiveness of the *** YOLOv8n-ShuffleNetv2.Ghost-SE model achieved Precision of 94.1%,Recall of 82.6%,mean Average Precision of 91.4%,model size of 2.6 MB,parameters of 1.18 M,FLOPs of 3.9 G,and detection speed of 39.37 *** detection speeds on the Jetson Xavier NX development board were 3.17 *** with advanced models including Faster R-CNN,SSD,YOLOv5s,YOLOv7‑tiny,YOLOv8s,YOLOv8n,MobileNetv3_small-Faster,MobileNetv3_small-Ghost,ShuflleNetv2.Faster,ShuflleNetv2.Ghost,ShuflleNetv2.Ghost-CBAM,ShuflleNetv2.Ghost-ECA,and ShuflleNetv2.Ghost-CA demonstrated that the method achieved smaller model and faster detection *** research can provide reference for the development of smart devices in apple orchards.

关键词： Multi-stage apple fruit Deep learning Real-time detection Lightweight model

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rational construction of CuFe_(2.O_(4)@C/Cd_(0.9)Zn_(0.1)S S-scheme heterojunction photocatalyst for extraordinary photothermal-assisted photocatalytic H_(2. evolution

引用

Journal of Energy Chemistry 2024年第5期92卷 240-249页

作者： Dong Zhang Minghui Zhu Ran Qin Peixian Chen maoye Yin Dafeng Zhang Junchang Liu Hengshuai Li Xipeng pu Peiqing cai School of Physics Science and information Technology Shandong Key Laboratory of Optical Communication Science and TechnologyLiaocheng UniversityLiaocheng 252000ShandongChina School of materials Science and Engineering Shandong Provincial Key Laboratory of Chemical Energy Storage and Novel Cell TechnologyLiaocheng UniversityLiaocheng 252000ShandongChina College of Optical and electronic Technology China Jiliang UniversityHangzhou 310018ZhejiangChina

Rational design of photocatalyst to maximize the use of sunlight is one of the issues to be solved in photocatalysis *** this study,the CuFe_(2.O_(4)@C/Cd_(0.9)Zn_(0.1)S(CFO@C/CZS)S-scheme photocatalyst with photothermal effect was synthesized by ultrasonic self-assembly combined with *** dark CFO@C absorbed visible light and partly converted into heat to promote the hydrogen evolution *** presence of heterojunctions inhibited the photogenerated electron-hole *** graphite-carbon layer provided a stable channel for electron transfer,and the presence of magnetic CFO made recycle *** the action of photothermal assistance and heterojunction,the hydrogen evolution rate of the optimal CFO@C/CZS was 80.79 mmol g^(-1) h^(-1),which was 2.55 times and 2.0.61 times of that of pure CZS and CFO@C,***,the composite samples also exhibit excellent stability and a wide range of environmental *** experimental tests and first-principles simulation calculation methods,the plausible mechanism of photoactivity enhancement was *** work provided a feasible strategy of photothermal assistance for the development of heterojunction photocatalysts with distinctive hydrogen evolution.

关键词： Photothermal effect S-scheme heterojunction Photocatalytic hydrogen evolution First-principles calculations

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Genetic algorithm assisted meta-atom design for high-performance metasurface optics

引用

Opto-electronic Science 2024年第9期3卷 15-28页

作者： Zhenjie Yu Moxin Li Zhenyu Xing Hao Gao Zeyang Liu Shiliang pu Hui mao Hong cai Qiang ma Wenqi Ren Jiang Zhu Cheng Zhang School of Optical and electronic information&{2. National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China Hikvision Research Institute Hangzhou 310051China

Metasurfaces,composed of planar arrays of intricately designed meta-atom structures,possess remarkable capabilities in controlling electromagnetic waves in various ways.A critical aspect of metasurface design involves selecting suitable meta-atoms to achieve target functionalities such as phase retardation,amplitude modulation,and polarization *** design processes often involve extensive parameter sweeping,a laborious and computationally intensive task heavily reliant on designer expertise and ***,we present an efficient genetic algorithm assisted meta-atom optimization method for high-performance metasurface optics,which is compatible to both single-and multiobjective device design *** first employ the method for a single-objective design task and implement a high-efficiency Pancharatnam-Berry phase based metalens with an average focusing efficiency exceeding 80%in the visible *** then employ the method for a dual-objective metasurface design task and construct an efficient spin-multiplexed structural beam *** device is capable of generating zeroth-order and first-order Bessel beams respectively under right-handed and left-handed circular polarized illumination,with associated generation efficiencies surpassing 88%.Finally,we implement a wavelength and spin co-multiplexed four-channel metahologram capable of projecting two spin-multiplexed holographic images under each operational wavelength,with efficiencies over 50%.Our work offers a streamlined and easy-to-implement approach to meta-atom design and optimization,empowering designers to create diverse high-performance and multifunctional metasurface optics.

关键词： metasurface metalens Bessel beam metahologram genetic algorithm

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Prediction of SYM-H index by NARX neural network from IMF and solar wind data

引用

Science china(Technological Sciences) 2009年第10期52卷 2877-2885页

作者： cai Lei ma shuying cai hongtao ZHOU YunLiang LIU RuoSi Department of Space Physics College of Electronic InformationWuhan UniversityWuhan 430079China

SYM-H is one of the important indices for space weather. It indicates the intensity of magnetic storm, similarly to Dst index but with much higher time-resolution. In this paper an artificial neural network (ANN) of Nonlinear Auto Regressive with eXogenous inputs (NARX) has been developed to predict SYM-H index from solar wind and IMF data. In comparison with usual BP and Elman network, the new NRAX model shows much better prediction capability. For 15 testing great storms including 5 super-storms of Min. SYM-H 2.0 nT, the cross-correlation of SYM-H indices between NARX network predicted and really observed is 0.91 as a whole. For the 5 individual super-storms, the lowest coefficients is 0.91 relating to the super-storm of march 2.01 with ***-H of -434 nT; while for the two super-storms with Min. SYM-H ranging from -300 nT to -400 nT, the correlations reach as high as 0.93 and 0.96 respectively. The remarkable improvement of the model performance can be attributed to such a key feedback from the network output of SYM-H with a suitable length (about 12. min) to the input, which implies that some information on the quasi real-time ring currents with a proper length of history does its work in the prediction. It tells us that, in addition to the direct driving by solar wind and IMF, the own status of the ring current plays an important role in its evolution especially for recovery phase and must properly be considered in storm-time SYM-H prediction by ANN. The neural network model of NARX developed in this paper provides an effective way to achieve it.

关键词： magnetic storm SYM-H index space weather prediction artificial neural network

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Numerical Simulation of Ionization Enhancement in the Topside Ionosphere of Cusp Foot-Point Region Caused by Low Energy Particle Precipitation

引用

wuhan university Journal of Natural Sciences 2008年第2期13卷 185-190页

作者： cai hongtao ma {2. G Kirchengast School of electronic information/Key Laboratory ofGeospace Environment and Geodesy of Ministry of Education Wuhan University Wuhan 430072 China Institute for Geophysics Astrophysics and MeteorologyUniversity of Graz Graz A-8010 Austria

The Graz Ionospheric Flux Tube Simulations （GIFTS） has been improved. The improved GIFTS model was used to numerically investigate the energy particle precipitation on the distribution of electron density in the ionospheric cusp foot-point region under conditions of large plasma convection during magnetic storm. After including the effects of low energy incident particles, the ionospheric electron densities increase remarkably above altitude of -2.0 km, showing a peak at about 350 km. The percent enhancements of electron densities increase gradually with altitude, exceed- ing 60% near the upper boundary of the calculation. The calculated ionospheric F2.peak was remarkably enhanced and lifted up by the incident low energy electrons.

关键词： magnetic storms particle precipitation cusp ionization enhancement ionospheric physical model numerical simulation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

RM-CSTV:An effective high-resolution method of non-line-of-sight millimeter-wave radar 3-D imaging

引用

National Science Open 2024年第5期3卷 36-52页

作者： Xinyuan Liu Shunjun Wei Wei pu Xiang cai Yanbo Wen Shisheng Guo Lingjiang Kong Xiaoling Zhang School of information and Communication Engineering University of Electronic Science and Technology of ChinaChengdu 611731China

Non-line-of-sight(NLOS)imaging is a novel radar sensing technology that enables the reconstruction of hidden ***,it may suffer from synthetic aperture length reduction caused by ambient *** this study,a complex total variation(CTV)regularization-based sparse reconstruction method for NLOS three-dimensional(3-D)imaging by millimeter-wave(mm W)radar,named RM-CSTV method,is proposed to improve imaging quality and *** this scheme,the NLOS imaging model is first introduced,and associated geometric constraints for NLOS objects are ***,an effective high-resolution NLOS imaging method based on the range migration(RM)kernel and complex sparse joint total variation constraint,dubbed as modified RM-CSTV,is proposed for 3-D high-resolution imaging with edge *** experiments with multi-type NLOS targets show that the proposed RM-CSTV method can provide effective and high-resolution NLOS targets 3-D imaging.

关键词： NLOS imaging 3-D-SAR 3-D imaging sparse reconstruction

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Cluster observations of high-altitude cusp during multiple fast-turning IMF

引用

Chinese Science Bulletin 2010年第12期55卷 1178-1185页

作者： cai hongtao ma {2. DUNLOP M W BOGDANOVA Y DAVIES J A PITOUT F School of electronic information Wuhan University Wuhan 430079 China Key Lab of Geospace Environment and Geodesy CNEM Wuhan 430079 China SSTD Rutherford Appleton Laboratory Chilton OX11 OQX UK Department of Physics La Trobe University Melbourne Victoria 3086 Australia max-Planck-lnstitut fiir Extraterrestrische Physik Garching D-37191 Germany

Using coordinated observations from the Cluster,DMSP and ESR radar,high-altitude cusp was investigated for a time period characterized by four fast reversals of the IMF *** February 12.2.03,Cluster was flying sunward at duskside over the Northern Hemisphere,across the high-altitude northern cusp *** the two crossings are during steady northward IMF interval,whereas ion fluxes detected during the time period are quite *** cusp in the first crossing is a "typical" northward-IMF one,with short-lived ion injections of evident "reversed" dispersion *** the second crossing,however,the cusp appears to be a region reminiscent of the Stagnant Exterior Cusp (SEC).In addition,evident upward-flowing O+ ion bursts,possibly original from polar ionosphere,are also detected during the second cusp crossing,together with enhancement of trapped magnetospheric-like electron *** suggest that the SEC-like cusp is likely on newly closed field lines,which were first reconnected (being opened) at low latitudes and later reconnected again (being closed) poleward of the northern cusp.

关键词：国际货币基金组织高海拔群集观测十字路口离子检测低纬度地区气象卫星

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：