检索结果-南通市图书馆

Multi-Frequency Channel Characterization for Massive miMO Communications in Lobby Environment

在线全文

学校读者我要写书评

暂无评论

China Communications 2019年第9期16卷 79-92页

作者： Jianzhi Li Bo ai Ruisi He mi Yang Zhangdui zhong State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University

In this paper,a massive multiple input multiple output(miMO)channel measurement campaign with two setups is conducted in an indoor lobby *** the first setup,two types of 256-element virtual uniform rectangular arrays(URAs),i.e.,the 4×64 virtual URA and the 64×4 virtual URA are *** carrier frequency is 11 GHz;in the second setup,measurements are performed at 4,6,11,13,15,18 GHz at two different user *** channel characterization is presented by investigating the typical channel parameters,including average power delay profile(APDP),K factor,root mean square(RMS)delay spread,and coherence ***,the channel characteristics in angular domain are investigated by applying the space-alternating generalized expectation-maximization(SAGE)*** extracted multipath components(MPCs)are preliminarily clustered by visual inspection,and related to the interacting objects(IOs)in physical *** structures at multiple frequency bands are *** spread of departure is estimated to evaluate the directional dispersion at the base station(BS)*** results in this paper can help to reveal the propagation mechanisms in massive miMO channels,and provide a foundation for the design and application of the practical massive miMO system.

关键词： 5G Massive miMO channelmeasurement virtual array SAGE K factor RMS delay spread coherence bandwidth scatterer localization direction spread

Multi-Scenario millimeter Wave Wireless Channel Measurements and Sparsity Analysis

在线全文

学校读者我要写书评

暂无评论

China Communications 2022年第11期19卷 16-31页

作者： Hang mi Bo ai Ruisi He Xin Zhou Zhangfeng Ma mi Yang Zhangdui zhong Ning Wang State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China Henan Joint International Research Laboratory of Intelligent Networking and Data Analysis Zhengzhou UniversityZhengzhou 450001China PengCheng Laboratory Shenzhen 518000China National Institute of Metrology of China Beijing 100029China School of Information Engineering Zhengzhou UniversityZhengzhou 450001China

Wireless channel characteristics have significant impacts on channel modeling,estimation,and communication *** the channel sparsity is an important characteristic of wireless *** the sparse nature of wireless channels can reduce the complexity of channel modeling and estimation,and improve system design and performance *** with the traditional sub6 GHz channel,millimeter wave(mmWave)channel has been considered to be more sparse in existing ***,most research only assume that the mmWave channel is sparse,without providing quantitative analysis and ***,this paper evaluates the sparsity of mmWave channels based on mmWave channel measurements.A vector network analyzer(VNA)-based mmWave channel sounder is developed to measure the channel at 28 GHz,and multi-scenario channel measurements are *** Gini index,Rician𝐾factor and rootmean-square(RMS)delay spread are used to measure channel ***,the key factors affecting mmWave channel sparsity are *** is found that antenna steering direction and scattering environment will affect the sparsity of mmWave *** addition,the impact of channel sparsity on channel eigenvalue and capacity is evaluated and analyzed.

关键词： channel sparsity channel measurement mmWave channel measures of sparsity

在线全文

学校读者我要写书评

暂无评论

植物激素对棉花蕾铃脱落的调控研究进展

作物学报 2025年第1期51卷 1-29页

作者：谢章书谢学方屠小菊刘爱玉董合忠周仲华湖南农业大学农学院/作物生理与分子生物学教育部重点实验室湖南长沙410128 中国热带农业科学院橡胶研究所海南海口571101 山东省农业科学院经济作物研究所山东济南250000

棉花蕾铃脱落是一个普遍存在的现象,有对逆境环境胁迫的主动适应性脱落,也有因品种遗传特性、环境条件、栽培措施以及生物和非生物胁迫被动的受损脱落。蕾铃脱落直接影响着棉花的产量,国内外现有公开报道多集中于20世纪50、60年代关于... 详细信息

棉花蕾铃脱落是一个普遍存在的现象,有对逆境环境胁迫的主动适应性脱落,也有因品种遗传特性、环境条件、栽培措施以及生物和非生物胁迫被动的受损脱落。蕾铃脱落直接影响着棉花的产量,国内外现有公开报道多集中于20世纪50、60年代关于乙烯和脱落酸对棉花蕾铃脱落影响的初步发现。结合其他植物的研究结果来看,蕾铃脱落似乎与生长素、赤霉素和细胞分裂素等促生长类激素的下降以及乙烯和脱落酸等抑制生长类激素的升高密切相关,激素在植物体内不仅介导新陈代谢过程,还协调着与信号通路相关的调控因子,在脱落过程中起着关键作用。本文从植物激素调控入手,综述了近年来包括脱落区形成和作用的分子调控机制以及各激素在棉花蕾铃脱落以及其他植物(生殖)器官脱落过程中的响应和调控机制等。发现目前以棉花蕾铃脱落为对象的研究非常匮乏,且多集中于少数激素对棉花生殖生长影响的有限研究,缺乏对导致蕾铃脱落的深层次机制的探究和解析。因此,未来研究方向应着重于探究棉花蕾铃脱落的遗传基础、发掘新的抗脱落基因资源和培育抗脱落棉花品种,同时加强在以棉花为模型植物下,蕾铃脱落与植物激素调节的关系研究,为提高棉花产量提供理论依据和技术支持。

关键词：棉花植物激素蕾铃脱落研究现状研究方向

V2V Channel Characterization and Modeling for Underground Parking Garages

在线全文

学校读者我要写书评

暂无评论

China Communications 2019年第9期16卷 93-105页

作者： mi Yang Bo ai Ruisi He Liang Chen Xue Li Jianzhi Li Zhangdui zhong The State Key Lab of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China Huawei Technologies Xi’an 710075China

As an important part of the intelligent transportation system(ITS),vehicle-to-vehicle(V2V)communication will improve the safety and efficiency of the transportation system by realizing the information transmission between *** underground parking garage is a typical scenario in V2V communication,but as an indoor environment,it is different from the conventional outdoor road scenarios ***,the purpose of this paper is to analyze and model the V2V channel characteristics of an underground *** this paper,a novel channel measurement carried out in the underground garage is first *** that there are a lot of obstacles in an underground garage,the non-line-of-sight(NLoS)condition is taken into account during the ***,channel characteristic parameters,including large-scale fading,delay spread,and K-factor,are analyzed based on the measured *** addition,we also carry out channel angle of arrival analysis,show the distribution of azimuth of arrival(AOA)and elevation of arrival(EOA)of multipath components(MPC),and conduct a statistical analysis of the angular *** the process of analysis and modeling,we focus on the differences between line-of-sight(LoS)and NLoS *** analysis and conclusions presented in this paper will enrich the understanding of V2V channel and benefit the design of V2V communications.

关键词： V2V channel modeling channel characterization

Generative Adversarial Networks Based Digital Twin Channel Modeling for Intelligent Communication Networks

在线全文

学校读者我要写书评

暂无评论

China Communications 2023年第8期20卷 32-43页

作者： Yuxin Zhang Ruisi He Bo ai mi Yang Ruifeng Chen Chenlong Wang Zhengyu Zhang Zhangdui zhong State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China Institute of Computing Technologies China Academy of Railway Sciences Co.Ltd.Beijing 100081China

Integration of digital twin(DT)and wireless channel provides new solution of channel modeling and simulation,and can assist to design,optimize and evaluate intelligent wireless communication system and *** DT channel modeling,the generated channel data can be closer to realistic channel measurements without requiring a prior channel model,and amount of channel data can be significantly *** intelligence(ai)based modeling approach shows outstanding performance to solve such *** this work,a channel modeling method based on generative adversarial networks is proposed for DT channel,which can generate identical statistical distribution with measured *** validation is conducted by comparing DT channel characteristics with measurements,and results show that DT channel leads to fairly good agreement with measured ***,a link-layer simulation is implemented based on DT *** is found that the proposed DT channel model can be well used to conduct link-layer simulation and its performance is comparable to using measurement *** observations and results can facilitate the development of DT channel modeling and provide new thoughts for DT channel applications,as well as improving the performance and reliability of intelligent communication networking.

关键词： digital twin channel modeling generative adversarial networks intelligent communication networking

Radio Communication Scenarios in 5G-Railways

在线全文

学校读者我要写书评

暂无评论

China Communications 2023年第9期20卷 235-246页

作者： Ruisi He Bo ai Zhangdui zhong mi Yang Chen Huang Ruifeng Chen Jianwen Ding Hang mi Zhangfeng Ma Guiqi Sun Changzhu Liu State Key Lab of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China Pervasive Communication Research Center Purple Mountain LaboratoriesNanjing 211111China Institute of Computing Technology China Academy of Railway SciencesBeijing 100081China College of Information Engineering Shaoyang UniversityShaoyang 422000China National Research Center of Railway Safety Assessment Beijing Jiaotong UniversityBeijing 100044China Key Laboratory of Railway Industry of Broadband Mobile Information Communications Beijing Jiaotong UniversityBeijing 100044China Beijing Engineering Research Center of High-speed Railway Broadband Mobile Communications Beijing Jiaotong UniversityBeijing 100044China

With the rapid development of railways,especially high-speed railways,there is an increasingly urgent demand for new wireless communication system for *** the mature 5G technology as an opportunity,5G-railways(5G-R)have been widely regarded as a solution to meet the diversified demands of railway wireless *** the design,deployment and improvement of 5GR networks,radio communication scenario classification plays an important role,affecting channel modeling and system performance *** this paper,a standardized radio communication scenario classification,including 18 scenarios,is proposed for *** paper analyzes the differences of 5G-R scenarios compared with the traditional cellular networks and GSM-railways,according to 5G-R requirements and the unique physical environment and propagation *** proposed standardized scenario classification helps deepen the research of 5G-R and promote the development and application of the existing advanced technologies in railways.

关键词： 5G-R scenario classification smart rail-ways

Asymmetric Synthesis of N-(Diphenylphosphinyl)furfurylamine by the Enantioselective Alkylation of Furfurylimine

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2005年第9期16卷 1147-1150页

作者： Hai Le ZHANG Xiao Mei ZHANG Xin LI ai Qiao mi Xin CUI Yao zhong JIANG Key Laboratory of Asymmetric Synthesis and Chirotechnology of Sichuan Province and Union Laboraotry of Asymmetric Synthesis Chengdu Institute of Organic Chemistry Chinese Academy of Sciences Chengdu 610041

Optically active N-（diphenylphosphinyl）furfurylamines 2 with good ee values were obtained by the enantioselective addition of dialkylzincs to furfuryl imine 1 in the presence of chiral aminoalcohol derivatives and o... 详细信息

关键词： Asymmetric dialkylzinc N-(diphenylphosphinyl)furfurylarnine.

Effect of inorganic salt on the thermal degradation of nitrocellulose and reaction mechanism of its mixture

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2023年第9期27卷 111-118页

作者： Guo-zhong Xu Xu Gao mi Li zhong-xuan Han Lin Jiang School of Mechanical Engineering Nanjing University of Science and TechnologyChina

In this study,to better understand the reaction mechanism between inorganic salts and nitrocellulose,CaCO_(3) and Li_(2)CO_(3) were evaluated with respect to their effects on the thermal degradation of NC in nitrogen atmosphere using TG/DSC at three different heating rates(2,5,10 K/min).The numerical relationship between activation energy(E)and conversion rate was obtained by FWO and KAS method,and it was discovered that CaCO_(3) could improve the thermal stability of *** energy values were calculated by Kissinger method,and it was found that NC that contain Li2CO3had the highest activation energy while NC containing CaCO3had the lowest E *** combining the thermal analysis data with Malek method,the most probable mechanism model of thermal degradation is obtained as Sesták-Berggren model,which expression is f(α)=α^(m)(1-α)^(n).As a result of this study,there are certain guiding principles that can be applied to the pyrolysis reaction model and to the actual production process of nitrocellulose.

关键词： Thermal analysis Thermal decomposition mechanism Malek method Nitrocellulose Inorganic salt

To Color or to Decolor:that Is the Question

在线全文

学校读者我要写书评

暂无评论

Molecular Plant 2019年第9期12卷 1173-1175页

作者： Jianing mi Salim ai-Babili King Abdullah University of Science and Technology(KAUST) Biological and Environmental Sciences and Engineering DivisionThe BioActives LabThuwal 23955-6900Kingdom of Saudi Arabia

The bright yellow,orange,and red colors of many fruits and flowers are the result of accumulating carotenoids in a specialized type of plastids,the chromoplasts(Fraser and Bramley,2004).Besides this ecological function,carotenoids exert a vital role in photosynthesis by preventing destructive photooxidation of chlorophylls and other cellular components and by contributing to the light-harvesting ***,these lipophilic pigments are synthesized in all photosynthetic organisms and many non-photosynthetic organisms that use them as antioxidants.

关键词： process. orange flowers