检索结果-南通市图书馆

Modified fast Fourier transform in FBMC for satellite communications

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2017年第4期30卷 1519-1527页

作者： Chaosan YANG Rongke LIU Ruifeng DUAN School of Electronic and Information Engineering Beihang University School of Information science and technology Beijing Forestry University

In this paper,a Doppler scaling fast Fourier transform（Doppler-FFT）algorithm for filter bank multi-carrier（FBMC）is proposed,which can efficiently eliminate the impact of the Doppler scaling in satellite *** introducing a Doppler scaling factor into the butterfly structure of the fast Fourier transform（FFT）algorithm,the proposed algorithm eliminates the differences between the Doppler shifts of the received subcarriers,and maintains the same order of computational complexity compared to that of the traditional *** the process of using the new method,the Doppler scaling should be estimated by calculating the orbital data in ***,the inter-symbol interference（ISI）and the inter-carrier interference（ICI）can be completely eliminated,and the signal to interference and noise ratio（SINR）will not be *** results also show that the proposed algorithm can achieve a 0.4 d B performance gain compared to the frequency domain equalization（FDE）algorithm in satellite communications.

关键词： Doppler effect Fast Fourier transforms Filter bank multi-carrier Inter-carrier interference Inter-symbol interference Signal to interference and noise ratio

Enhanced Reconfigurable Intelligent Surface Assisted mmWave Communication: A Federated Learning

在线全文

学校读者我要写书评

暂无评论

China Communications 2020年第10期17卷 115-128页

作者： Lixin Li Donghui Ma Huan Ren Dawei Wang Xiao Tang Wei Liang Tong Bai School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710129China School of Electronic Engineering and Computer science Queen Mary University of LondonLondon E14NSU.K.

Reconfigurable intelligent surface(RIS)has been proposed as a potential solution to improve the coverage and spectrum efficiency for future wireless ***,the privacy of users’data is often ignored in previous works,such as the user’s location information during channel *** this paper,we propose a privacy-preserving design paradigm combining federated learning(FL)with RIS in the mmWave communication *** on FL,the local models are trained and encrypted using the private data managed on each local *** this,a global model is generated by aggregating them at the central *** optimal model is trained for establishing the mapping function between channel state information(CSI)and RIS’configuration matrix in order to maximize the achievable rate of the received *** results demonstrate that the proposed scheme can effectively approach to the theoretical value generated by centralized machine learning(ML),while protecting user’privacy.

关键词： reconfigurable intelligent surface privacy federated learning achievable rate

Fabrication and characterization of laminated Ti-（TiB + La2O3）/Ti composite

在线全文

学校读者我要写书评

暂无评论

Progress in Natural science:Materials International 2015年第5期25卷 453-459页

作者： Yuanfei Han Hongqiang Duan Weijie Lu Liqiang Wang Di Zhang State Key Laboratory of Metal Matrix Composites Shanghai Jiao Tong University

The incorporation of ceramic particulate reinforcements into titanium alloys can improve the specific strength and specific stiffness,while inevitably reduce the plasticity and *** this study,in situ synthesized multilayer Ti-（TiB +La2O3）/Ti composite was designed by learning from the microstructure of nature biological materials with excellent mechanical *** Ti-（TiB + La2O3）/Ti composite with unique characteristic of laminated structure was prepared by combined powder metallurgy and hot *** method has the synthesize advantages with in-situ reaction of Ti and LaB6at high temperature and controllability of reinforcements size and constituent phases in *** result shows that the pores in the as sintered laminated structure composite completely disappeared after hot rolling at 1050℃.The agglomerated reinforcement particles were well dispersed and distributed uniformly along the rolling *** thickness of pure Ti layer and（TiB+La2O3）/Ti composite layer decreased from 1 mm to about 200 μ***,the grains size was refined obviously after rolling *** room temperature tensile test indicates that the elongation of the laminated Ti-（TiB + La2O3）/Ti composite improved from 13%to 17%in comparison with the uniform（TiB + La2O3）/Ti composite,while the tensile strength had little *** provides theoretical and experimental basis for fabricating the novel high performance laminated Ti-（TiB + La2O3）/Ti composites.

关键词： Titanium matrix composites Laminated structure Microstructure Mechanical properties

Ergodic sum rate for uplink NOMA transmission in satellite-aerial-ground integrated networks

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2022年第9期35卷 58-70页

作者： Huaicong KONG Min LIN Jian ZHANG Jian OUYANG Jun-Bo WANG Prabhat K.UPADHYAY College of Telecommunications and Information Engineering Nanjing University of Posts and TelecommunicationsNanjing 210003China National Mobile Communications Research Laboratory Southeast UniversityNanjing 210096China Discipline of Electrical Engineering Indian Institute of Technology IndoreIndore 453552India

The application of Non-Orthogonal Multiple Access(NOMA) technology into satelliteaerial-ground integrated networks can meet the requirements of ultra-high rate and massive connectivity for the Sixth-Generation(6G) communication systems. We consider an uplink NOMA scenario for such a satellite-aerial-ground integrated network where multiple users communicate with satellite under the help of an Unmanned Aerial Vehicle(UAV) as an aerial relay equipped with a phased array. Supposing that buffer-aided decode-and-forward protocol is adopted at the UAV relay, we first formulate an optimization problem to maximize Ergodic Sum Rate(ESR) of the considered system subject to individual power constraint and quality-of-service constraint of each ***, with known imperfect channel state information of each user, we propose a joint power allocation and robust Beam Forming(BF) iterative algorithm to maximize ESR for the user-to-UAV link. Besides, to take the advantages of Free-Space Optical(FSO) and millimeter Wave(mmWave)communications, we present a switch-based hybrid FSO/mmWave scheme and a robust BF algorithm for the UAV-to-satellite link to achieve higher rate. Moreover, a closed-form ESR expression is derived. Finally, the effectiveness and correctness of the proposed solutions are verified by numerical simulations, and the performance evaluation results show that the proposed solutions not only achieve performance enhancement and robustness, but also outperform the orthogonal multiple access significantly.

关键词： BeamForming(BF) Ergodic Sum Rate(ESR) Hybrid FSO/mmWave Non-Orthogonal Multiple Access(NOMA) Satellite-aerial-ground integrated network The Sixth-Generation(6G)communication system

DCP法W/ZrC金属陶瓷的激光烧蚀行为研究（英文）

在线全文

学校读者我要写书评

暂无评论

无机材料学报 2017年第12期32卷 1332-1336页

作者：余艺平王松李伟国防科学技术大学新型陶瓷纤维及其复合材料重点实验室长沙410073

采用DCP法制备了W/Zr C金属陶瓷,然后研究了在不同激光能量和烧蚀时间下W/Zr C金属陶瓷的激光烧蚀行为。研究表明:W/Zr C金属陶瓷在激光烧蚀过程中产生了一个较小的烧蚀坑,烧蚀坑的深度随着激光能量的增加和烧蚀时间的延长而增大。在烧... 详细信息

采用DCP法制备了W/Zr C金属陶瓷,然后研究了在不同激光能量和烧蚀时间下W/Zr C金属陶瓷的激光烧蚀行为。研究表明:W/Zr C金属陶瓷在激光烧蚀过程中产生了一个较小的烧蚀坑,烧蚀坑的深度随着激光能量的增加和烧蚀时间的延长而增大。在烧蚀坑的周围,许多不同种类和结构的氧化物堆积组成了几个同心环。铜的挥发和氧化锆层的形成对防止W/Zr C金属陶瓷进一步氧化有着重要作用。

关键词： W/ZrC金属陶瓷激光烧蚀微观结构

超高温热处理对不同工艺制备的W/ZrC金属陶瓷微观结构的影响（英文）

在线全文

学校读者我要写书评

暂无评论

稀有金属材料与工程 2017年第1期46卷 63-67页

作者：余艺平王松李伟蒋进明国防科学技术大学新型陶瓷纤维及其复合材料重点实验室湖南长沙410073

分别采用置换填充工艺(DCP)和热压烧结工艺(HP)制备了W/Zr C金属陶瓷,然后在2600℃下对其进行热处理1 h。研究了热处理前后2种W/ZrC金属陶瓷的组织结构变化。研究表明,热处理后2种材料都出现开孔率增大、线膨胀及质量损失。其中DCP法W/Z... 详细信息

分别采用置换填充工艺(DCP)和热压烧结工艺(HP)制备了W/Zr C金属陶瓷,然后在2600℃下对其进行热处理1 h。研究了热处理前后2种W/ZrC金属陶瓷的组织结构变化。研究表明,热处理后2种材料都出现开孔率增大、线膨胀及质量损失。其中DCP法W/Zr C金属陶瓷在热处理后仍由分散分布的W颗粒相和连续的Zr C相组成,但原始材料中残留的WC、W_2C及Zr-Cu合金相都消失,取而代之的是大量的孔隙,同时W相含量也急剧减小。而HP法W/Zr C金属陶瓷在热处理后则有新相W_2C生成,同时其W颗粒相有聚集的趋势,形成了大块团状相。

关键词：钨/碳化锆金属陶瓷微观结构变化热处理

A Consensus-based Filtering Algorithm with State Constraints 36

在线全文

学校读者我要写书评

暂无评论

A Consensus-based Filtering Algorithm with State Constraints

高铌TiAl合金钎焊接头组织和性能研究（英文）

第36届中国控制会议

作者： Yajing Ma Song Guo Shuyi Lin Yunze Cai Department of Automation Shanghai Jiao Tong Universityand Key Laboratory of System Control and Information ProcessingMinistry of Education of China shanghai Academy of Spaceflight technology

ISBN: (纸本)9781538629185

This paper proposes a consensus-based filtering algorithm to solve a nonlinear information fusion problem in multi-agent system that the state vector of the target is *** method is based on the Kalman-Consensus filtering algorithm,Extended Kalman filter and null space *** on target tracking prove the feasibility of the algorithm in dealing with state estimation of nonlinear systems under linear and nonlinear *** is demonstrated that a significant increase in the tracking precision can be expected via the proposed method compared with traditional Kalman-Consensus filter.

关键词： State Estimation Constrained Filtering Consensus Algorithm Kalman Filter Multi-agent System

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

稀有金属材料与工程 2018年第1期47卷 52-58页

作者：宋晓国司晓庆曹健王志权赵洪运冯吉才哈尔滨工业大学先进焊接与连接国家重点实验室黑龙江哈尔滨150001

采用Ti-28Ni(质量分数,%)共晶钎料在1100℃实现了高铌Ti Al合金(Ti-45Al-8.5Nb-(W,B,Y)(at%),TAN)的真空钎焊连接。钎焊接头的典型界面结构为TAN/τ_3-Al_3Ti_2Ni+B2/α_2-Ti_3Al layer/α_2-Ti_3Al+δ-Ti_2Ni/α_2-Ti_3Al layer/τ_3-Al_3Ti_2Ni+B2/TAN。深入研究了保温时间对钎焊接头界面组织和连接性能的影响。结果表明:Ni元素从熔融钎料向TAN母材的扩散决定了界面组织的演化,随着保温时间的延长促进了扩散层的增厚,同时导致钎缝宽度逐渐减小。接头剪切强度测试结果显示,当保温时间为15 min时,获得的最大接头室温剪切强度和高温(600℃)剪切强度分别是248.6和166.4 MPa。接头断口分析表明在剪切试验中裂纹主要沿着连续的金属间化合物层产生和扩展。

关键词： TiAl金属间化合物真空钎焊界面组织力学性能断口

Thermoelastic Dissipation in Diamond Micro Hemispherical Shell Resonators

在线全文

学校读者我要写书评

暂无评论

Journal of shanghai Jiaotong university(science) 2020年第3期25卷 281-287页

作者： FENG Jun ZHANG Weiping LIU Zhaoyang GU Liutao CHENG Yuxiang National Key Laboratory of science and technology on Micro/Nano Fabrication Shanghai Jiao Tong UniversityShanghai 200240China Department of Micro/Nano Electronics School of Electronic Information and Electrical EngineeringShanghai Jiao Tong UniversityShanghai 200240China shanghai aerospace Control technology Institute Shanghai 200233China

Maximizing quality factor (Q) is essential to improve the performance of micro hemispherical shell resonators (μHSRs) which can be used in microelectromechanical system (MEMS) gyroscopes to measure angular *** energy dissipation mechanisms limit Q,where thermoelastic dissipation (TED) is the major one and studied in this *** coupled thermo-mechanical equations for calculating TED are formulated,and then temperature distribution in a deformed μHSR and its quality factor related to TED (QTED) are obtained by solving the equations through a finite-element method (FEM).It has been found that different fabrication process conditions can obtain various geometrical parameters in our previous *** order to provide guidelines for the design and fabrication of μHSRs,the effects of their geometry on resonant frequency (f0) and QTED are *** change of anchor height and small enough anchor radius have no effect on both f0 and QTED,but the shell size including its radius,thickness and height has significant impact on f0 and *** is found that whether a μHSR has lower f0 and higher QTED or higher f0 and higher QTED can be achieved by changing these geometrical *** results presented in this paper can also be applied to other similar resonators.

关键词： microelectromechanical system(MEMS) diamond hemispherical shell resonators quality factor thermoelastic dissipation(TED)