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DFF-EDR:An Indoor Fingerprint Location Technology Using Dynamic Fusion Features of Channel State Information and Improved Edit Distance on Real Sequence

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China Communications 2021年第4期18卷 40-63页

作者： Ke Han yunfei xu Zhongliang Deng Jiawei Fu School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

Positioning technology based on wireless network signals in indoor environments has developed rapidly in recent years as the demand for locationbased services continues to *** state information(CSI)can be used as location feature information in fingerprint-based positioning systems because it can reflect the characteristics of the signal on multiple ***,the random noise contained in the raw CSI information increases the likelihood of confusion when matching fingerprint *** this paper,the Dynamic Fusion Feature(DFF)is proposed as a new fingerprint formation method to remove the noise and improve the feature resolution of the system,which combines the pre-processed amplitude and phase ***,the improved edit distance on real sequence(IEDR)is used as a similarity metric for fingerprint *** on the above studies,we propose a new indoor fingerprint positioning method,named DFF-EDR,for improving positioning *** the experimental stage,data were collected and analyzed in two typical indoor *** results show that the proposed localization method in this paper effectively improves the feature resolution of the system in terms of both fingerprint features and similarity measures,has good anti-noise capability,and effectively reduces the localization errors.

关键词： channel state information indoor positioning edit distance on real sequence dynamic parameters feature resolution

An Area Optimization Based Cooperative Localization Algorithm with Node Selection

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China Communications 2021年第12期18卷 178-195页

作者： Ke Han Chongyu Zhang Huashuai Xing yunfei xu School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications) Beijing 100876China

In recent years,position information has become a key feature to drive location and context aware services in mobile *** from all over the world have proposed many solu-tions for indoor positioning over the past several ***,due to weak signals,multipath or non-line-of-sight signal propagation,accurately and efficiently localizing targets in harsh indoor environments re-mains a challenging *** improve the perfor-mance in harsh environment with insufficient anchors,cooperative localization has *** this paper,a novel cooperative localization algorithm,named area optimization and node selection based sum-product al-gorithm over a wireless network(AN-SPAWN),is de-scribed and *** alleviate the high compu-tational complexity and build optimized cooperative cluster,a node selection method is designed for the cooperative localization *** experi-ment results indicate that our proposed algorithm has a higher accuracy and is less impacted by NLOS errors than other conventional cooperative localization algo-rithms in the harsh indoor environments.

关键词： cooperative localization node selection PDR indoor localization

A Three-phase Integrated Power Electronic Transformer with the Capability of DC Fault Clearance

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CSEE Journal of Power and Energy Systems 2021年第4期7卷 785-796页

作者： yunfei xu Guangfu Tang Weiguo Li Guoliang Zhao Zhanfeng Deng State Key Laboratory of Advanced Transmission Technology(Global Electricity Interconnection Research Institute Co.Ltd.) Changping DistrictBeijing 102211China

This paper presents a three-phase integrated power electronic transformer(PET)topology with the capability of DC fault clearance based on the investigation of PET *** proposed PET has three ports of high-voltage AC,high-voltage DC and low-voltage DC,which can achieve the flexible access of distributed energy resources・The power unit of the PET adopts a three-phase integrated topology,and the single-phase fluctuating power in the DC-link capacitor is reduced by a 4-port DC/DC converter,thereby reducing the capacitance of the DC-link capacitor;Meanwhile,the power unit uses the clamp double sub-module(CDSM)to allow for self-clearing of the short-circuit fault on the high-voltage DC ***,this paper verifies the proposed PET through an EMT simulation and experimental prototype.

关键词： DC fault clearing experimental verification power electronic transformer three phase integration

Voltage sag compensation strategy for unified power quality conditioner with simultaneous reactive power injection

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Journal of Modern Power Systems and Clean Energy 2016年第1期4卷 113-122页

作者： yunfei xu Xiangning XIAO Yamin SUN Yunbo LONG State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power UniversityBeijing 102206China

Unified power quality conditioner(UPQC)holds the capability of solving power quality problems,especially shows good performance in the voltage sag compensation. In this paper, a compensation strategy based on simultaneous reactive power injection for UPQC(namely UPQC-SRI) is proposed to address the issue of voltage sag. The proposed UPQC-SRI determines the injection angle of compensation voltage with consideration of optimal configuration of UPQC ***, the compensation strategy also considers the current-carrying limit of UPQC, and then the zero active power injection region of UPQC-SRI(also called UPQCSRI region) is obtained. Under the conditions which exceed the UPQC-SRI region, the limit value of shunt current is determined by this proposed strategy. Finally, the proposed strategy and the corresponding algorithm are verified under the PSCAD/EMTDC platform. The result indicates the proposed UPQC-SRI strategy in this paper can provide more persistent voltage sag compensation than the previous strategies for the sensitive load.

关键词： Unified power quality conditioner(UPQC) Voltage sag Simultaneous reactive power injection Zero active power injection compensation region

A General Bayesian Model for Speaker Verification

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Chinese Journal of Electronics 2016年第6期25卷 1045-1051页

作者： xu yunfei YANG Hai YANG Lin ZHOU Ruohua YAN Yonghong Key Laboratory of Speech Acoustics and Content Understanding Institute of AcousticsChinese Academy of Sciences

This paper presents a general Bayesian model for speaker verification tasks. It is a generative probability model. Due to its simple analytical property, a computationally efficient expectation-maximization algorithm can be derived to obtain the model parameters. A closedform solution, which allows the scalable size of enrollment set, is given in a full Bayesian way for making speaker verification decisions. Factor analysis technique is employed to model the speaker-specific components, then the redundant information in this model will be dropped. Experimental results are evaluated by both equal error rate and minimum detection cost function. The proposed approach shows promising results on the National institute of standards and technology(NIST) Speaker recognition evaluation(SRE) 2010 extended and 2012 core tasks. Significant improvement is obtained when comparing with Gaussian probabilistic linear discriminant analysis, especially under phone-call conditions and mismatched train-test channel conditions. Contrast experimental results with other popular generative probability models are also presented in this paper.

关键词： Bayesian model Speaker verification I-Vector

Crystal facet-dependent CO_(2) cycloaddition to epoxides over ZnO catalysts

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Frontiers of Chemical Science and Engineering 2024年第5期18卷 49-59页

作者： Yongjian Wei Ying Li yunfei xu Yinghui Sun Tong xu Haiou Liang Jie Bai Inner Mongolia Key Laboratory of Industrial Catalysis Hohhot 010051China College of Chemical Engineering Inner Mongolia University of TechnologyHohhot 010051China

With regard to green chemistry and sustainable development,the fixation of CO_(2) into epoxides to form cyclic carbonates is an attractive and promising pathway for CO_(2) *** oxides,renowned as promising eco-friendly catalysts for industrial production,are often undervalued in terms of their impact on the CO_(2)addition *** this work,we successfully developed ZnO nanoplates with(002)surfaces and ZnO nanorods with(100)surfaces via morphology-oriented regulation to explore the effect of crystal faces on CO_(2) *** quantitative data obtained from electron paramagnetic resonance spectroscopy indicated that the concentration of oxygen vacancies on the ZnO nanoplate surfaces was more than twice that on the ZnO nanorod *** functional theory calculations suggested that the(002)surfaces have lower adsorption energies for CO_(2) and epichlorohydrin than the(100)*** a result,the yield of cyclochloropropene carbonate on the ZnO nanoplates(64.7%)was much greater than that on the ZnO nanorods(42.3%).Further evaluation of the reused catalysts revealed that the decrease in the oxygen vacancy concentration was the primary factor contributing to the decrease in catalytic *** on these findings,a possible catalytic mechanism for CO_(2) cycloaddition with epichlorohydrin was *** work provides a new idea for the controllable preparation of high-performance ZnO catalysts for the synthesis of cyclic carbonates from CO_(2) and epoxides.

关键词： carbon dioxide cycloaddition zinc oxide crystal face oxygen vacancy

Periodic atomization characteristics of an impinging jet injector element modulated by Klystron effect

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Chinese Journal of Aeronautics 2018年第10期31卷 1973-1984页

作者： Anlong YANG Bin LI Shangrong YANG yunfei xu Longfei LI Science and Technology on Liquid Rocket Engine Laboratory Xi'an Aerospace Propulsion Institute

An experimental study on the Klystron effect of periodic injection modulated by pressure drop fluctuations on subsequent atomization is conducted. Time-resolved atomization backlit images and atomization Mie scatter images are captured by using the high speed camera. It is found that periodicity of forced atomization relies on pressure drop fluctuation amplitude and phase differences between atomization and pressure drop fluctuations relate to fluctuation frequencies. This feature of periodic atomization induced by Klystron effect corresponds to periodicities and high amplitudes of pressure fluctuations in unstable combustion chambers and chaos and low amplitudes of pressure fluctuations in stable combustions chambers. Drastically periodic varying of gross surface area of droplets with time was shown in Mie scatter images. The importance of periodic impinging jet atomization modulated by pressure drop fluctuations for acoustic liquid propellant combustion instabilities is illustrated.

关键词： Atomization Combustion stability Impinging jet injector Klystron effect Liquid rocket engine Mie scatter

A Simplified Model for Buckling and Post-Buckling Analysis of Cu Nanobeam Under Compression

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Computer Modeling in Engineering & Sciences 2020年第11期125卷 611-623页

作者： Jiachen Guo yunfei xu Zhenyu Jiang Xiaoyi Liu Yang Cai Department of Engineering Mechanics South China University of TechnologyGuangzhou510640China The Peac Institute of Multiscale Sciences Chengdu610031China

Both of Buckling and post-buckling are fundamental problems of geometric nonlinearity in solid *** the rapid development of nanotechnology in recent years,buckling behaviors in nanobeams receive more attention due to its applications in sensors,actuators,transistors,probes,and resonators in nanoelectromechanical systems(NEMS)and *** this work,buckling and post-buckling of copper nanobeam under uniaxial compression are investigated with theoretical analysis and atomistic *** cross sections are explored for the consideration of surface *** avoid complicated high order buckling modes,a stressbased simplified model is proposed to analyze the critical strain for buckling,maximum deflection,and nominal failure strain for *** effects should be considered regarding critical buckling strain and the maximum post-buckling *** critical strain increases with increasing nanobeam cross section,while themaximumdeflection increases with increasing loading strain but stays nearly the same for different cross sections,and the underlying mechanisms are revealed by our *** maximum deflection is also influenced by surface *** nominal failure strains are captured by our simulations,and they are in good agreement with the simplified *** results can be used for helping design strain gauge sensors and nanodevices with self-detecting ability.

关键词： Nanobeam buckling post-buckling simplified model atomistic simulation

Real-time Abnormal Detection of GWAC Light Curve based on Wavelet Transform Combined with GRU-Attention

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Research in Astronomy and Astrophysics 2024年第5期24卷 151-168页

作者： Hao Li Qing Zhao Long Shao Tao Liu Chenzhou Cui yunfei xu College of Artifcial Intelligence Tianjin University of Science and TechnologyTianjin 300457China National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Nowadays, astronomy has entered the era of Time-Domain Astronomy, and the study of the time-varying light curves of various types of objects is of great significance in revealing the physical properties and evolutionary history of celestial bodies. The Ground-based Wide Angle Cameras telescope, on which this paper is based, has observed more than 10 million light curves, and the detection of anomalies in the light curves can be used to rapidly detect transient rare phenomena such as microgravity lensing events from the massive data. However, the traditional statistically based anomaly detection methods cannot realize the fast processing of massive data. In this paper, we propose a Discrete Wavelet(DW)-Gate Recurrent Unit-Attention(GRU-Attention) light curve warning model. Wavelet transform has good effect on data noise reduction processing and feature extraction, which can provide richer and more stable input features for a neural network, and the neural network can provide more flexible and powerful output model for wavelet transform. Comparison experiments show an average improvement of 61% compared to the previous pure long-short-term memory unit(LSTM) model, and an average improvement of 53.5% compared to the previous GRU model. The efficiency and accuracy of anomaly detection in previous paper work are not good enough, the method proposed in this paper possesses higher efficiency and accuracy,which incorporates the Attention mechanism to find out the key parts of the light curve that determine the anomalies. These parts are assigned higher weights, and in the actual anomaly detection, the star is detected with83.35% anomalies on average, and the DW-GRU-Attention model is compared with the DW-LSTM model, and the detection result f1 is improved by 5.75% on average, while having less training time, thus providing valuable information and guidance for astronomical observation and research.

关键词： methods data analysis-stars variables general-techniques photometric