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A 2-step GPS carrier tracking loop for urban vehicle applications

Journal of Systems Engineering and Electronics 2017年第5期28卷 817-826页

作者： Hongyang Zhang Luping Xu Yue Jian xiaochen ma School of Aerospace Science and Technology Xidian University Xi'an Flight Automatic Control Research Institute Aviation Industry Corporation of China Xi'an Aeronautics Computing Technique Research Institute Aviation Industry Corporation of China

Global positioning system (GPS) for vehicle applications in the urban area is challenged by low signal intensity. The carrier loop based on fast Fourier transform (FFT) can obtain a high signal to noise ratio (SNR) gain by increasing the observation time. However, this leads to a major problem that the acceleration cannot be ignored. The performance of the FFT-based loop will decline with the acceleration increasing. This paper discusses the effect of the dynamic on FFT first. Then a high performance carrier tracking loop for weak GPS L5 signals is proposed. It combines discrete chirp-Fourier transform (DCFT) and the phase fitting method to estimate Doppler frequency and Doppler rate simultaneously. First, a sequence of integration results is used to perform DCFT to estimate coarse Doppler frequency and Doppler rate. Second, the phase of the sequence is calculated and used to perform linear fitting. By the phase fitting method, the fine Doppler frequency and Doppler rate can be estimated. The computation cost is small because the integration results are used and the phase fitting method needs only coarse estimates of Doppler frequency and Doppler rate. Compared with FFT and DCFT, the precision of the phase fitting method is not limited by the resolution. Thus the proposed loop can get high precision and low carrier to noise ratio (C/N-0) tracking threshold. Simulation results show this loop has a great improvement than conventional loops for urban weak-signal applications.

关键词： satellite navigation receiver signal processing frequency lock loop

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A New Phosphine-Amine-Oxazoline Ligand for Ru-Catalyzed Asymmetric Hydrogenation of N-Phosphinylimines

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Chinese Journal of Chemistry 2018年第12期36卷 1151-1155页

作者： xiaochen ma Lin Qiao Guixia Liu Zheng Huang State Key laboratory of Organometallic Chemistry Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of Sciences345 Lingling RdShanghai 200032China

A series of chiral phosphine‐amine‐oxazoline (PAO) ligands with an NH moiety were synthesized and applied to the ruthenium‐catalyzed asymmetric hydrogenation of N ‐phosphinylimines. The ligand bearing phenyl groups at the phosphorus moiety and isopropyl at the oxazoline moiety exhibits good activity and excellent enantioselectivity (up to 99% ee ). This catalytic system provides an efficient and mild approach to access enantioriched amines.

关键词： amines chiral ligand hydrogenation imines ruthenium

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Exposure to polycyclic aromatic hydrocarbons and risk for premature ovarian failure and reproductive hormones imbalance

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Journal of Environmental Sciences 2020年第5期32卷 1-9页

作者： Xiaoqing Ye Wuye Pan Chunming Li xiaochen ma Shanshan Yin Jianhong Zhou Jing Liu College of Medical Technology Zhejiang Chinese Medical UniversityHangzhou 310053China MOE Key Laboratory of Environmental Remediation and Ecosystem Health College of Environmental and Resource SciencesZhejiang UniversityHangzhou 310058China Womens Reproductive Health Key Laboratory of Zhejiang Province Womens HospitalZhejiang University School of MedicineHangzhou 310006China Research Center for Air Pollution and Health Zhejiang UniversityHangzhou 310058China

Polycyclic aromatic hydrocarbons(PAHs)are a typical class of persistent organic pollutants that is ubiquitous *** animal studies suggested that PAHs had adverse effects on female ***,the human data regarding relationship of PAHs exposure with women reproductive health,such as ovarian dysfunction,are *** this case-control study,the associations of serum levels of PAHs with the risk of premature ovarian failure(POF)and reproductive hormones in Chinese women were investigated,with recruiting 157 POF patients and 217 healthy *** serum levels of 12 types of PAHs,as well as reproductive hormones,including follicle-stimulating hormone,luteinizing hormone and anti-mullerian hormone,were *** the logistic regression models,most individual PAH congeners showed significantly positive correlations with the risk of POF(pmass index,educational levels and household income,per one-unit increase in the log-transformed BaP concentration was significantly correlated with 2.191-fold increased risk of POF(OR=2.191,95%CI:1.634-2.938,p<0.05).To the best of our knowledge,this is the first study to report an association between internal exposure levels of PAHs and the increased risk of POF in women.

关键词： Polycyclic aromatic hydrocarbons Persistent organic pollutants Premature ovarian failure Women reproductive health Reproductive hormones

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Blockchain‑oriented approach for detecting cyber‑attack transactions

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Financial Innovation 2023年第1期9卷 2190-2227页

作者： Zhiqi Feng Yongli Li xiaochen ma School of Economics and management Harbin Institute of TechnologyHarbin 150001China

With the high-speed development of decentralized applications,account-based blockchain platforms have become a hotbed of various financial scams and hacks due to their anonymity and high financial *** security has become a top priority with the sustainable development of blockchain-based platforms because of an increasing number of cyber attacks,which have resulted in a huge loss of crypto assets in recent ***,it is imperative to study the real-time detection of cyber attacks to facilitate effective supervision and *** this end,this paper proposes the weighted and extended isolation forest algorithms and designs a novel framework for the real-time detection of cyber-attack transactions by thoroughly studying and summarizing real-world ***,this study develops a new detection approach for locating the compromised address of a cyber attack to resolve the data scarcity of hack addresses and reduce time ***,three experiments are carried out not only to apply on different types of cyber attacks but also to compare the proposed approach with the widely used existing *** results demonstrate the high efficiency and generality of the proposed ***,the lower time consumption and robustness of our method were validated through additional *** conclusion,the proposed blockchain-oriented approach in this study can handle real-time detection of cyber attacks and has significant scope for applications.

关键词： Blockchain Cyber-attack detection Extended isolation forest Decentralized application Financial security Fintech

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A Stellar Ranging Scheme Based on the Second-order Correlation Measurement

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Research in Astronomy and Astrophysics 2022年第1期22卷 229-236页

作者： Jian Li Can Xu Yinshen Liu Yaqi ma Xinyao Liu xiaochen ma Run Fan An-Ning Zhang Center for Quantum Technology Research and Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements(MOE) School of PhysicsBeijing Institute of TechnologyBeijing 100081China School of Astronomy&Space Science Nanjing UniversityNanjing 210023China

Stellar ranging is the basis for stellar dynamics research and in-depth research on astrophysics. The parallax method is the most widely used and important basic method for stellar ranging. However, it needs to perform highprecision measurement of the parallax angle and the baseline length together. We aim to propose a new stellar ranging scheme based on second-order correlation that does not require a parallax angle measurement. We hope our solution can be as basic as the parallax method. We propose a new stellar ranging scheme by using the offset of second-order correlation curve signals. The optical path difference between the stars and different base stations is determined by the offset of the second-order correlation curve signals. Then the distance of the stars could be determined by the geometric relation. With the distance to stars out to 10 kpc away, our astrometric precision can be better compared to Gaia by simulation. We also design an experiment and successfully demonstrate the feasibility of this scheme. This stellar ranging scheme enables further and more accurate stellar ranging without requiring any prior information or angle measurement.

关键词： astrometry techniques:miscellaneous methods:observational methods:miscellaneous instrumentation:miscellaneous

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Pathogenic Surveillance of Foodborne Illness-Related Diarrhea—Beijing Municipality,China,2013-2023

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China CDC weekly 2024年第24期6卷 568-573页

作者： Chao Wang Tongyu Wang Yanlin Niu Yangbo Wu Jinru Jiang xiaochen ma Institute for Nutrition and Food Hygiene Beijing Center for Disease Prevention and ControlBeijingChina

What is already known about this topic?Foodborne diseases present a significant public health concern,particularly in China,where they represent a significant food safety ***,there is a need for a thorough and systematic analysis of the extended epidemiological patterns of foodborne diseases in Beijing *** is added by this report?Monitoring results show that Norovirus and diarrheagenic Escherichia coli(DEC)are the most commonly identified foodborne diarrheal *** aged 19–30 are at a higher risk of foodborne diarrhea in Beijing,with Salmonella infection being associated with fever *** are the implications for public health practice?This study analyzes 11 years of consecutive monitoring data to enhance understanding of the epidemiological and clinical features of foodborne diarrhea in *** aims to identify high-risk populations,assist in clinical pathogen identification and treatment,and support the development of tailored preventive strategies.

关键词： Beijing safety borne

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Tracing the Methane Events by Stable Carbon Isotopes of Benthic Foraminifera at Glacial Periods in the Andaman Sea

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Journal of Earth Science 2022年第6期33卷 1571-1582页

作者： Yue Cen Jiasheng Wang Xuan Ding Dorrik Stow Zhou Wang Can Chen xiaochen ma Hubei Key Laboratory of marine Geological Resources College of Marine Science and TechnologyState Key Laboratory of Biogeology and Environmental GeologyChina University of GeosciencesWuhan430074China School of the marine Sciences China University of GeosciencesBeijing100083China Institute of Geo-Energy Engineering Heriot-Watt UniversityEdinburghEH 144ASUK State Key Laboratory of marine Geology Tongji UniversityShanghai200092China

Stable isotopes of carbon and oxygen variations in foraminiferal shells have been widely used in paleo-environment ***,studies about the shells of benthic foraminifera in methanehydrate-bearing sediments as reliable geochemical proxies to reconstruct the potential methane release events in the geologic past are *** this study,we present the stable carbon and oxygen isotopes of fossil benthic foraminifera including one epifaunal species(Cibicidoides wuellerstorfi)and two infaunal species(Bulimina mexicana and Uvigerina peregrina)from the Site U1447 of IODP 353 Expedition to trace methane events in the Andaman Sea,where one of the thickest and deepest gas hydrate stability zones was ***δ^(13)C values of benthic foraminifera show that there are eight distinct intervals with negative values in the last~10 Myr,interpreted as a record of long-term fluctuations in methane *** of these methane events occurred during the glacial sea-level lowstands in the last~1.1 ***,therefore,infer that the trigger mechanism for these events might be the hydrate destabilization caused by sea level *** methane events that occurred at~2.11 and~5.93 ma are more likely related to the sudden changes in sedimentation,either slide events or marked variations in sedimentation rate.

关键词： benthic foraminifera stable carbon and oxygen isotopes methane events gas hydrates IODP 353 Site U1447 Andaman Sea

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Synthesis of Si3N4 Powder Using Sawdust as Carbon Source

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China's Refractories 2016年第2期25卷 29-34页

作者： ma xiaochen YIN Hongfeng ZHANG Junzhan REN Yun Hua Qing College Xi'an University of Architecture and TechnologyXi'an 710043China Xi'an University of Architecture and Technology Xi'an 710055China

Si3N4 powder was synthesized by carbothermal re- duction nitridation reaction using sawdust as carbon source and introducing SiO2 by silica sol immersion. Effects of SiO2 content of silica sol, molding pressure, reaction temperature, reaction duration, and N2 flow rate on phase compositions and microstructure of result- ants were studied. The results show that using 7. 5 mass% SiO2 containing silica sol immersed sawdust as raw materials, the prepared Si3N4 powder is featured with high α-Si3N4 content, few impurities, etc. in the conditions of 1 450 ℃ of reaction temperature, 9 h of reaction duration, 400 mL ·min- 1 of N2 flow rate and 10 MPa of molding pressure.

关键词： silicon nitride powder carbothermal re-duction nitridation reaction silica sol molding pres-sure reaction temperature reaction duration nitrogenflow rate

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Epidemiological Insights into Foodborne Pathogens Through qPCR Exploration of Prevalence—Beijing Municipality,China,January 2022-April 2023

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China CDC weekly 2024年第18期6卷 385-389,I0001-I0004页

作者： Penghang Zhang xiaochen ma Yuzhu Liu Tongyu Wang Shuning Huo Xiaoai Zhang Beijing Key Laboratory of Diagnostic and Traceability Technologies for Food Poisoning Institute for Nutrition and Food HygieneBeijing Center for Disease Prevention and ControlBeijingChina Yanjing Medical College of Capital Medical University BeijingChina

Summary What is already known on this topic?Foodborne diseases present a substantial global health *** diagnostic methods have constraints,but advancements in molecular techniques,like quantitative polymerase chain reaction(qPCR),provide a hopeful *** is added by this report?We examined 1,011 stool samples from individuals suspected of foodborne illnesses.

关键词： solution constraints advancement

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Measurement of the absorption coefficient for acoustical coating samples using multi-channel inverse filter

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Chinese Journal of Acoustics 2020年第3期39卷 372-386页

作者： SONG Hao ma xiaochen LI Jun LI Jianlong Systems Engineering Research Institute of Chinese Shipbuilding Industry Beijing 100036 College of Information Science and Electronic Engineering Zhejiang UniversityHangzhou 310027 Key Laboratory of Ocean Observation-Imaging Testbed of Zhejiang Province Zhoushan 316021

A method of measuring the absorption coefficient for acoustical coating samples by use of the multi-channel inverse filter based on the least square method was ***,the responses of the circuit channels and the underwater acoustical channels are estimated,the retransmitted inverse signals for the multiple transducers can be estimated using the least square method,and the cost function constructed by the multi-channel inverse filtering theory can be ***,by retransmitting the inverse signals,the incident signal at the position of the acoustical coating sample is focused with high resolution,low level of side lobes and a narrow pulse signal in temporal domain,which improves the measurement accuracy of the absorption coefficient for acoustical coating samples at low *** performance of the spatio-temporal focusing for the proposed method is demonstrated by *** validity of the method is verified by experiments carried out in a cylindrical tank for a steel plate sample in the frequency range 0.8-5.0 *** experimental results show that the proposed method is effective to the measurement of the absorption coefficient for acoustical coating samples in non-free field,and is especially applicable to low-frequency measurements.

关键词： coating steel inverse

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