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Frontiers of Mathematics in China 2020年第3期15卷 467-489页

作者： Linlin fu Jiahao xu Fan WU Department of Mathematics Sun Yat-sen UniversityGuangzhou 510275China Chern Institute of Mathematics and LPMC Nankai UniversityTianjin 300017China Department of Mathematics Nanjing UniversityNanjing 210093China

We reconsider the continuity of the Lyapunov exponents for a class of smooth Schrödinger cocycles with a C2 cos-type potential and a weak Liouville *** propose a new method to prove that the Lyapunov exponent is conti... 详细信息

关键词： Schrodinger cocycle Lyapunov exponent(LE) weak Liouville frequency C2 cos-type potential large deviation theorem(LDT)

C^(*)-Isomorphisms Associated with Two Projections on a Hilbert C^(*)-Module

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Chinese Annals of Mathematics,Series B 2023年第3期44卷 325-344页

作者： Chunhong fu Qingxiang xu Guanjie YAN Health School Attached to Shanghai University of Medicine&Health Sciences Shanghai 200237China Department of Mathematics Shanghai Normal UniversityShanghai 200234China Department of Basic Education Shanghai Urban Construction Vocational CollegeShanghai 201415China

Motivated by two norm equations used to characterize the Friedrichs angle,this paper studies C^(*)-isomorphisms associated with two projections by introducing the matched triple and the semi-harmonious pair of projections.A triple(P,Q,H)is said to be matched if is a Hilbert C^(*)-module,P and Q are projections on H such that their infimum P∧Q exists as an element of L(H),where L(H)denotes the set of all adjointable operators on *** C^(*)-sub algebras of L(H)generated by elements in{P-P∧Q,Q-P∧Q,I}and{P,Q,P∧Q,I}are denoted by i(P,Q,H)and o(P,Q,H),*** is proved that each faithful representation(π,X)of o(P,Q,H)can induce a faithful representation(π,X)of i(P,Q,H)such that π~(P−P∧Q)=π(P)−π(P)∧π(Q),π~(Q−P∧Q)=π(Q)−π(P)∧π(Q)..When(P,Q)is semi-harmonious,that is,R(P+Q) and R(2I−P−Q) are both orthogonally complemented in H,it is shown that i(P,Q,H)and i(I-Q,I-P,H)are unitarily equivalent via a unitary operator in L(H).A counterexample is constructed,which shows that the same may be not true when(P,Q)fails to be ***,a counterexample is constructed such that(P,Q)is semi-harmonious,whereas(P,I-Q)is not *** additional examples indicating new phenomena of adjointable operators acting on Hilbert C^(*)-modules are also provided.

关键词： Hilbert C^(*)-module Projection Orthogonal complementarity C^(*)-Isomorphism

Understanding Tunneling Ionization of Atoms in Laser Fields using the Principle of Multiphoton Absorption

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Chinese Physics Letters 2019年第4期36卷 19-23页

作者： Long xu Li-Bin fu Graduate School of China Academy of Engineering Physics

The elaborate energy and momentum spectra of ionized electrons from atoms in laser fields suggest that the ionization dynamics described by tunneling theory should be modified. Although great efforts have been carried out within semiclassical models, there are few discussions describing the multiphoton absorption process within a quantum framework. Comparing the results obtained with the time-dependent Schr?dinger equation(TDSE)and the Keldysh–Faisal–Reiss(KFR) theory, we study the nonperturbative effects of ionization dynamics beyond the KFR theory. The difference in momentum spectra between multiphoton and tunneling regimes is understood in a unified picture with virtual multiphoton absorption processes. For the multiphoton regime, the momentum spectra can be obtained by coherent interference of each periodic contribution. However, the interference of multiphoton absorption peaks will result in a complex structure of virtual multiphoton bands in the tunneling regime. It is shown that the virtual spectra will be almost continuous in the tunneling regime instead of the discrete levels found in the multiphoton regime. Finally, with a model combining the TDSE and the KFR theory,we try to understand the different effects of virtual multiphoton processes on ionization dynamics.

关键词： Laser Multiphoton Absorption ionized electrons

A Uniform Reference Line Based Differential Phase Shifter with Wide Phase Range and Wide Bandwidth

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China Communications 2022年第5期19卷 102-111页

作者： Canrong fu Bowei xu Shaoyong Zheng School of Electronics and Information Technology Sun Yat-sen UniversityGuangzhou 51006China

To implement the multi-way phase shifting maintaining the compact size and simplicity in structure,the uniform reference line concept was proposed for the differential phase ***,the performance in bandwidth and phase range deteriorates with the additional requirements *** solve this problem,a quarter wavelength coupled line section loaded with open/short stubs is proposed as the basic element to implement the main line and also reference *** to the theoretical analysis on this basic element,the loading stubs can be used to control the phase shift and also the phase slope of the basic element without affecting the amplitude *** the predetermined parameters of the uniform reference line,only two parameters are required for the implementation of different differential phase *** demonstrates the high simplicity of the proposed *** demonstration,an eight-way differential phase shifter operating at 3.5 GHz was implemented using the vertically installed planar *** prototype was further fabricated and *** agreement between simulation and measurement can be *** implemented phase shifter can provide a wide range of phase shifting values from 45°to 315°with reference to the uniform reference line over a relative bandwidth of 62.3%.

关键词： differential phase shifter uniform reference line wideband wide phase range vertically installed planar

Atomic-scale mechanism of effect of co-separation of elements at interface of ferrite and austenite on Cr-depleted zone of duplex stainless steel

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Journal of Iron and Steel Research International 2024年第3期31卷 710-718页

作者： Yan-hui Hou ze-kun xu Shi-long Zhou Guang-qiang Li The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and TechnologyWuhan 430081HubeiChina

Three-dimensional atom-probe tomography and first-principles calculation combined with density functional theory were used to study the effect of the co-segregation of different elements formed during the solidification process of S32205 duplex stainless steel on the Cr-depleted zone at the interface between ferrite and *** was found that the co-segregation of different elements formed during the solidification process of duplex stainless steel can also form Cr-depleted zone at the interface between ferrite and ***,Mo,Si,B,C and P atoms promote co-segregation with Cr atoms,which promotes the formation of Cr-depleted zone at the interface between ferrite and austenite in duplex stainless *** and Si strongly promote the segregation of Cr at the interface between ferrite and austenite,thereby promoting the formation of Cr-depleted zone.B,C and P elements also promote the segregation of Cr element at the interface between ferrite and austenite and the formation of Cr-depleted zone,but their effect is weaker than that of Mo and Si *** conclusions provide a new theoretical basis for improving the intergranular corrosion performance of duplex stainless steel.

关键词： Duplex stainless steel Cr-depleted zone Intergranular corrosion Co-segregation First-principles calculation

Paleoglacial and paleoclimate reconstructions during the global Last Glacial Maximum in the Longriba area, eastern Tibetan Plateau

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Journal of Mountain Science 2021年第2期18卷 307-322页

作者： YANG Wei-lin HAN Ye-song PENG xu RAN ze-ze LIU Qing LIU Geng-nian College of Urban and Environmental Sciences Peking UniversityBeijing 100871China

Owing to the remoteness of the Longriba area and the lack of dating records,it is extremely challenging to reconstruct the chronology and extent of the paleoglaciers in this *** this paper,we combined limited observational data with automated modelling for paleoglacial *** first identified a broadly distributed paleoglacier from satellite imagery and field investigation based on the sediment-landform assemblage principle and dated it to 23.1±1.4~19.5±1.2 ka by ^(10)Be exposure dating,corresponding to the global Last Glacial Maximum(gLGM).Then,we reconstructed the extent and ice surface of 171 paleoglaciers formed during the similar period based on geomorphological evidence and‘ice surface profile’*** results showed that the paleoglacial coverage was 426.5 km2,with an ice volume of 38.1 km^(3),in the Longriba *** reconstructed equilibrium line altitudes(ELAs)based on modelled ice surfaces yielded an average of 4245±66 m above sea level(asl),~725±73 m lower than the present ELA(4970±29 m asl).The temperature was~5.51-6.68℃lower,and the precipitation was~30-34%less in Longriba,during the gLGM compared to the present *** glacial advance was mainly driven by colder climate that was synchronous with Northern Hemisphere cooling events.

关键词： Ice surface profile ^(10)Be surface exposure dating Paleoglacial reconstruction Paleoclimate reconstruction Global Last Glacial Maximum Eastern Tibetan Plateau

Nest survival rate of Reeves＇s pheasant(Syrmaticus reevesii) based on artificial nest experiments

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Zoological Research 2017年第1期38卷 49-54页

作者： xu Luo Yu-ze Zhao Jing Ma Jian-Qiang Li Ji-Liang xu School of Nature Conservation Beijing Forestry University Beijing 100083 China

To explore the nest survival rate of Reeves＇ s pheasant（Syrmaticus reevesii） and the nest-site factors that affect it, we conducted artificial nest experiments with reference to natural nests at Dongzhai National Nature Reserve（DNNR）, Henan Province and Pingjingguan, Hubei Province from April to June 2014 simulating the situation in its early and later breeding season. We also determined distance characteristics of the nest sites by Arc GIS 10.0. Nest survival models were constructed in Program MARK for data analysis. Results indicated that in the early breeding season, the apparent survival rate（ASR） in DNNR（52.4%） was significantly greater than that in Pingjingguan（13.5%）, and the ASR in the later breeding season in DNNR（26.7%） was not indistinctively correlated with Pingjingguan（3.2%）. The daily survival rate（DSR） in the later breeding season was 93.8% in DNNR and 92.0% in Pingjingguan, respectively. The DSRs were both negatively correlated with nest distance to forest edges and settlements. The DSR in Pingjingguan was positively correlated with nest distance to paths and negatively correlated with nest distance to water sources. However, the DSR in DNNR was negatively correlated with nest distance to paths but positively correlated with nest distance to water sources.

关键词： Reeves's pheasant SyrmaUcus reevesfi Nest survival rate Artificial nest experiments.

Total Synthesis of Nucleoside Antibiotics Amicetin,Plicacetin,and Cytosaminomycin A-D

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Chinese Journal of Chemistry 2021年第10期39卷 2679-2684页

作者： Jiqiang fu Peng xu Biao Yu State Key Laboratory of Bioorganic and Natural Products Chemistry Center for Excellence in Molecular SynthesisShanghai Institute of Organic ChemistryUniversity of Chinese Academy of SciencesChinese Academy of Sciences345 Lingling RoadShanghai200032 China School of Chemistry and Materials Science Hangzhou Institute for Advanced StudyUniversity of Chinese Academy of Sciences1 Sub-lane XiangshanHangzhouZhejiang310024 China

Main observation and conclusion Amicetin and congeners constitute a small family of complex pyrimidine nucleosides,which exhibit strong antibiotic activities against Gram-positive bacteria and notably against strains of Mycobacterium ***,we report chemical synthesis of a series of disaccharide congeners of the amicetin family,including amicetin,plicacetin,and cytosaminomycin A—*** is the first time for successful synthesis of amicetin,the prototypical member,and *** synthetic approach employs glycosyl N-phenyltrifluoroacetimidate and thioglycoside donors to construct the characteristic aminodeoxydisaccharides consisting ofα-(1→4)-glycosidic linkage,uses gold(I)-catalyzed N-glycosylation to furnish 2-deoxy-β-nucleosides,and finally exploits amidation and global deprotection to complete the *** is noteworthy that the 3-O-protecting group in the 2-deoxydisaccharide donors is found to be crucial for a successful N-glycosylation to assemble the cytosaminomycin disaccharide nucleosides.

关键词： Total synthesis Glycosylation Nucleoside Amicetin Cytosaminomycin

Anomaly detection of control rod drive mechanism using long short-term memory-based autoencoder and extreme gradient boosting

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Nuclear Science and Techniques 2022年第10期33卷 53-67页

作者： Jing Chen ze-Shi Liu Hao Jiang Xi-Ren Miao Yong xu College of Electrical Engineering and Automation Fuzhou UniversityFuzhou 350108China The Department of Automation Shanghai Jiao Tong UniversityShanghai 200240China fujian fuqing Nuclear Power Co. Ltd.Fujian 350318China

Anomaly detection for the control rod drive mechanism(CRDM) is key to enhancing the security of nuclear power plant equipment. In CRDM real-time condition-based maintenance, most existing methods cannot deal with long sequences and periodic abnormal events and have poor feature extraction from these data. In this paper,a learning-based anomaly detection method employing a long short-term memory-based autoencoder(LSTM-AE)network and an extreme gradient boosting(XGBoost)algorithm is proposed for the CRDM. The nonlinear and sequential features of the CRDM coil currents can be automatically and efficiently extracted by the LSTM neural units and AE network. The normal behavior LSTM-AE model was established to reconstruct the errors when feeding abnormal coil current signals. The XGBoost algorithm was leveraged to monitor the residuals and identify outliers for the coil currents. The results demonstrate that the proposed anomaly detection method can effectively detect different timing sequence anomalies and provide a more accurate forecasting performance for CRDM coil current signals.

关键词： Anomaly detection CRDM LSTM-AE Residuals XGBoost

full-scale tests of wind effects on a long span roof structure

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Earthquake Engineering and Engineering Vibration 2015年第2期14卷 361-372页

作者： fu Jiyang Zheng Qingxing Wu Jiurong xu An Guangzhou University-Tamkang University Joint Research Center for Engineering Structure Disaster Prevention and Control Guangzhou University

full-scale measurements are regarded as the most reliable method to evaluate wind effects on large buildings and structures. Some selected results are presented in this paper from the full-scale measurement of wind effects on a long-span steel roof structure during the passage of Typhoon Fanapi. Some fi eld data, including wind speed and direction, acceleration responses, etc., were continuously and simultaneously recorded during the passage of the typhoon. Comprehensive analysis of the measured data is conducted to evaluate the typhoon-generated wind characteristics and its effects on a long-span steel roof. The fi rst four natural frequencies and their vibration mode shapes of the Guangzhou International Sports Arena(GISA) roof are evaluated by the stochastic subspace identifi cation(SSI) method and comparisons with those from fi nite element(FE) analysis are made. Meanwhile, damping ratios of the roof are also identifi ed by the SSI method and compared with those identifi ed by the random decrement method; the amplitude-dependent damping behaviors are also discussed. The fullscale measurement results are further compared with the corresponding wind tunnel test results to evaluate its reliability. The results obtained from this study are valuable for academic and professional engineers involved in the design of large-span roof structures.

关键词： long-span steel roof wind effect field measurement