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Approach to MAI cancellation for micro-satellite clusters

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Journal of Systems Engineering and Electronics 2019年第5期30卷 823-830页

作者： HUANG Jiajun ZHANG Chaojie jin xiaojun Micro-Satellite Research Center Zhejiang University

With the development of micro-satellite technology,traditional monolithic satellites can be replaced by micro-satellite clusters to achieve high flexibility and dynamic reconfiguration *** satellite clusters based on the frequency division-code division multiple access(FD-CDMA)communication system,the inter-satellite ranging precision is usually constrained due to the influence ofmulti-address interference(MAI).Themulti-user detection(MUD)is a solution to MAI,which can be divided into two categories:the linear detector(LD)and the non-linear detector(NLD).The general idea of the LD is aiming to make a better decision during the symbol decision process by using the information of all ***,it is not beneficial for the signal phase tracking ***,the principle of the NLD is to rebuild the interference signal and cancel it from the original one,which can improve the ranging performance at the expense of considerable *** order to enable simultaneous ranging and communication and reduce multi-node ranging performance degradation,this paper proposes an NLD scheme based on a delay locked loop(DLL),which simplifies the receiver structure and introduces no delay in the decision *** scheme utilizes the information obtained from the interference channel to reconstruct the interference signal and then cancels it from the original delayed ***,the DLL input signal-to-interference ratio(SIR)of the desired channel can be significantly *** experimental results show that with the proposed scheme,the standard deviation of the tracking steady error is decreased from 5.59 cm to 3.97 cm for SIR=5 dB,and 13.53 cm to 5.77 cm for SIR=-5 dB,respectively.

关键词： micro-satellite satellite clusters multi-user detection(MUD) interference cancellation inter-satellite ranging

Adaptive median threshold algorithm used in FDIS of DSSS receivers

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Journal of Systems Engineering and Electronics 2013年第1期24卷 11-18页

作者： Weijun Yang Chaojie Zhang xiaojun jin Zhonghe jin Tieshan Yuan Department of Information Science and Electronic Engineering Zhejiang University Micro-Satellite Research Center Zhejiang University

For direct sequence spread spectrum （DSSS） receivers, the capability of rejecting narrow-band interference can be significantly improved by a process of frequency-domain interference suppression （FDIS）. The key issue of this process is how to determine a threshold to eliminate interference in the frequency domain, which has been extensively studied. However, these previous methods are tedious or very complex. A simple and ef- ficient algorithm based on medians is proposed. The elimination threshold is only related to the median by a scale factor, which can be obtained by the numerical analysis. Simulation results show that the algorithm provides excellent narrow-band interfer- ence suppression while only slightly degrading the signal-to-noise ratio （SNR）. A one-pass algorithm using logarithmic segmentation is further derived to estimate medians with low computational complexity. Finally, the FDIS is implemented in a field programmable gate array （FPGA） of Xilinx. Experiments are carried out by connecting the FDIS FPGA to a DSSS receiver, and the results show that the receiver has an effective countermeasure for a 60 dB interference-to-signal ratio （ISR）.

关键词： direct sequence spread spectrum (DSSS) discreteFourier transform (DFT) frequency-domain interference suppres-sion (FDIS) adaptive median threshold one-pass approximatemedians.

Approach to inter-satellite time synchronization for micro-satellite cluster

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Journal of Systems Engineering and Electronics 2018年第4期29卷 805-815页

作者： XU Jiuling ZHANG Chaojie WANG Chunhui jin xiaojun Micro-Satellite Research Center Zhejiang University

Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster is important for both cluster sensing capabilities and its autonomous operating. However, the existing time synchronization methods are not suitable for microsatellite cluster, because it requires too many human interventions and occupies too much ground control resource. Although, data post-process may realize the equivalent time synchronization, it requires processing time and powerful computing ability on the ground, which cannot be implemented by cluster itself. In order to autonomously establish and maintain the time benchmark in a cluster, we propose a compact time difference compensation system（TDCS）, which is a kind of time control loop that dynamically adjusts the satellite reference frequency according to the time difference. Consequently, the time synchronization in the cluster can be autonomously achieved on-orbit by synchronizing the clock of other satellites to a chosen one＇s. The experimental result shows that the standard deviation of time synchronization is about 102 ps when the carrier to noise ratio（CNR） is 95 d BHz, and the standard deviation of corresponding frequency difference is approximately0.36 Hz.

关键词： time difference measurement time synchronization dynamical reference frequency adjustment micro-satellite cluster

Application and improvement of wavelet packet de-noising in satellite transponder

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Journal of Systems Engineering and Electronics 2015年第4期26卷 671-679页

作者： Yannian Lou Chaojie Zhang xiaojun jin Zhonghe jin Micro-Satellite Research Center Zhejiang University

The satellite transponder is a widely used module in satellite missions, and the most concerned issue is to reduce the noise of the transferred signal. Otherwise, the telemetry signal will be polluted by the noise contained in the transferred signal, and the additional power will be consumed. Therefore, a method based on wavelet packet de-noising （WPD） is introduced. Compared with other techniques, there are two features making WPD more suit- able to be applied to satellite transponders： one is the capability to deal with time-varying signals without any priori information of the input signals; the other is the capability to reduce the noise in band, even if the noise overlaps with signals in the frequency domain, which provides a great de-noising performance especially for wideband signals. Besides, an oscillation detector and an av- eraging filter are added to decrease the partial oscillation caused by the thresholding process of WPD. Simulation results show that the proposed algorithm can reduce more noises and make less distortions of the signals than other techniques. In addition, up to 12 dB additional power consumption can be reduced at -10 dB signal-to-noise ratio （SNR）.

关键词： wavelet packet de-noising (WPD) satellite transpon-der power consumption reduction real-time de-noising.

Integrated method for measuring distance and time difference between small satellites

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Journal of Systems Engineering and Electronics 2021年第3期32卷 596-606页

作者： ZHU Yaowei XU Zhaobin jin xiaojun GUO Xiaoxu jin Zhonghe Micro-Satellite Research Center Zhejiang UniversityHangzhou 310027China School of Aeronautics and Astronautics Zhejiang UniversityHangzhou 310027China

The advancement of small satellites is promoting the development of distributed satellite systems,and for the latter,it is essential to coordinate the spatial and temporal relations between mutually visible *** now,dual one-way ranging(DOWR)and two-way time transfer(TWTT)are generally integrated in the same software and hardware system to meet the limitations of small satellites in terms of size,weight and power(SWaP)***,studies show that pseudo-noise regenerative ranging(PNRR)performs better than DOWR if some advanced implementation technologies are ***,PNRR has no requirement on time *** apply PNRR to small satellites,and meanwhile,meet the demand for time difference measurement,we propose the round-way time difference measurement,which can be combined with PNRR to form a new integrated system without exceeding the limits of *** new integrated system can provide distributed small satellite systems with on-orbit high-accuracy and high-precision distance measurement and time difference measurement in real *** results show that the precision of ranging is about 1.94 cm,and that of time difference measurement is about 78.4 ps,at the signal to noise ratio of 80 dBHz.

关键词： time difference measurement time synchronization inter-satellite ranging satellite formation autonomous flying

Studies on the edwardsiellosis and characterization of pathogenic bacteria from diseased flounder (Paralichthys olivaceus L.) and turbot (Scophthalmus maximus L.)

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Acta Oceanologica Sinica 2006年第3期25卷 138-147页

作者： FANG Hai ZHANG xiaojun CHEN Cuizhen jin Xiaomin WANG Xiuyun Department of Animal Science Hebei Normal University of Science and Technology Qinhuangdao 066600 China

Edwardsiellosis of flounder and turbot occurring in different mariculture farms during 2001～ 2004 was examined, including the conditions of disease occurrence, clinical signs and pathological changes. The results showed that all diseased fishes expressed bacterial septicaemia. A total of 148 strains were identified using a combination of traditional physiological and biochemical tests and partial 16S rRNA gene analysis. In addition, the mole fraction G ＋ C ratio of the DNA of representative strain of isolates and serum homology were detected, and pathogenicity tests of isolates were conducted by experimental infection. The results revealed that 148 strains were identified as E. tarda of genus Edwardsiella, all the isolates are of serologic similarity, and have strong pathogenicity to flounder and turbot.

关键词： flounder (Paralichthys olivaceus L. ) turbot (Scophthalmus maximus L. ) edwardsiellosis pathogenic bacteria

Two-Stage Client Selection Scheme for Blockchain-Enabled Federated Learning in IoT

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Computers, Materials & Continua 2024年第11期81卷 2317-2336页

作者： xiaojun jin Chao Ma Song Luo Pengyi Zeng Yifei Wei Beijing Key Laboratory of Work Safety Intelligent Monitoring School of Electronic EngineeringBeijing University of Posts and TelecommunicationsBeijing100876China Institute of Industrial Internet and Internet of Things China Academy of Information and Communications TechnologyBeijing100191China

Federated learning enables data owners in the Internet of Things(IoT)to collaborate in training models without sharing private data,creating new business opportunities for building a data ***,in practical operation,there are still some problems with federated learning *** has the characteristics of decentralization,distribution,and *** blockchain-enabled federated learning further improve the security and performance of model training,while also expanding the application scope of federated *** has natural financial attributes that help establish a federated learning data ***,the data of federated learning tasks may be distributed across a large number of resource-constrained IoT devices,which have different computing,communication,and storage resources,and the data quality of each device may also ***,how to effectively select the clients with the data required for federated learning task is a research *** this paper,a two-stage client selection scheme for blockchain-enabled federated learning is proposed,which first selects clients that satisfy federated learning task through attribute-based encryption,protecting the attribute privacy of *** blockchain nodes select some clients for local model aggregation by proximal policy optimization *** show that the model performance of our two-stage client selection scheme is higher than that of other client selection algorithms when some clients are offline and the data quality is poor.

关键词： Blockchain federated learning attribute-based encryption client selection proximal policy optimization

Assessment of water quality using benthic diatom and macroinvertebrate assemblages:A case study in an East China canal

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Water Biology and Security 2024年第1期3卷 80-86页

作者： xiaojun jin Xuan Lan Heqin Sun Baowei Hu Binliang Wang Tongchuang Engineering Design Co. Ltd.ShaoxingZhejiangChina School of Life and Environmental Sciences Shaoxing UniversityShaoxingZhejiangChina Shaoxing Jianhu Lake Research Society ShaoxingZhejiangChina Jianhu Provincial Wetland Park Management Committee ShaoxingZhejiang312000China

The East Zhejiang Canal is an artificial waterway located in the plains of East *** of its role in providing social services,it is frequently subjected to human activities affecting its *** improve the water resource management and condition of this canal,assessment of its ecological health is *** measured water quality variables and benthic diatom and macroinvertebrate assemblages to evaluate the ecological status of the *** found that the canal was eutrophic with an average chemical trophic level index of 64.3 and an average trophic diatom index of 68.1(with Nitzschia palea,Melosira varians,and Navicula rostellata,Encyonema minutum abundant).Macroinvertebrate assemblages also showed that the canal was eutrophic based on the dominance of Limnodrilus sp.A low BMWP(Biological Monitoring Working Party)score further indicated the poor water quality of the *** analysis indicated that phosphorus was the main driver of eutrophication in the ***,more attention should be paid to reduce phosphorus loadings.

关键词： Artificial canal Biomonitoring Eutrophication Multivariate analysis

ModiΡed pseudo-noise code regeneration method

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Journal of Systems Engineering and Electronics 2010年第3期21卷 370-374页

作者： xiaojun jin Zhonghe jin Chaojie Zhang Jianwen Jiang Yangming Zheng Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 R R. China

A modiΡed pseudo-noise（PN） code regeneration method is proposed to improve the clock tracking accuracy without impairing the code acquisition time ***,the method can meet the requirement of high accuracy ranging measurements in short time periods demanded by radio-science *** tracking error variance is derived by linear *** some existing PN codes,which can be acquired rapidly,the tracking error variance performance of the proposed method is about 2.6 dB better than that of the JPL scheme（originally proposed by Jet Propulsion Laboratory）,and about 1.5 dB better than that of the traditional double loop scheme.

关键词： regenerative pseudo-noise (PN) ranging chip tracking loop tracking error variance code acquisition time.