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IMPROVING EIGENVECTORS IN ARNOLDI'S METHOD

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Journal of Computational Mathematics 2000年第3期18卷 265-276页

作者： Zhong-xiao Jia (Department of Applied Mathematics, Dalian University of Technology, Dalian 116024, China) Ludwig Elsner (Fakultat fur Mathematik, University Bielefeld, Postfach 100131, 33501 Bielefeld,Germany) 大连理工大学辽宁大连 116024 Universitt Bielefeld 德国 Bielefeld 33501

The Ritz vectors obtained by Arnoldi's method may not be good approxima- tions and even may not converge even if the corresponding Ritz values do. In order to improve the quality of Ritz vectors and enhance the efficiency of Arnoldi type algorithms, we propose a strategy that uses Ritz values obtained from an m-dimensional Krylov subspace but chooses modified approximate eigenvectors in an (m + 1)-dimensional Krylov subspace. Residual norm of each new approximate eigenpair is minimal over the span of the Ritz vector and the (m+1)th basis vector, which is available when the m-step Arnoldi process is run. The resulting modi- fied m-step Arnoldi method is better than the standard m-step one in theory and cheaper than the standard (m + 1)-step one. Based on this strategy, we present a modified m-step restarted Arnoldi algorithm. Numerical examples show that the modified m-step restarted algorithm and its version with Chebyshev acceleration are often considerably more efficient than the standard (m+ 1)-step restarted ones.

关键词： Large unsymmetric The m-step Arnoldi process The m-step Arnoldi method Eigenvalue Ritz value Eigenvector Ritz vector Modified

Mechanical properties and corrosion behavior of a new RRA-treated Al-Zn-Mg-Cu-Er-Zr alloy

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Rare Metals 2023年第2期42卷 672-679页

作者： Jun-Tai Lu Hui Huang Hao Wu Sheng-Ping Wen Kun-Yuan Gao Xiao-Lan Wu Zuo-Ren Nie School of Materials Science and Engineering Beijing University of TechnologyBeijing100124China

The effect of various retrogression and re-aging(RRA)treatments on mechanical properties and corrosion behavior of a new type Al-Zn-Mg-Cu-Er-Zr alloy was investigated by microhardness testing,tensile testing,intergranular corrosion(IGC)and exfoliation corrosion(EXCO)*** results show that the RRA treatment can effectively improve the IGC and EXCO resistance with less strength sacrificing because the grain interior precipitates and the grain boundary precipitates are similar to that of T6 temper and T73 ***,as the microhardness of the retrogressed alloy reaches the peak value during the retrogression at 170℃,the corresponding RRA-treated alloy possesses the better strength,but the corrosion resistance is poor in comparison with that of the retrogression at 190℃.The optimal combination of strength,IGC and EXCO resistance is obtained after retrogression at 180℃for 60 ***,for different heat treatment tempers,the corresponding micros true tural evolution of the precipitates including Al_(3)(Er,Zr)particles was also discussed in detail.

关键词： Al-Zn-Mg-Cu-Er-Zr alloy RRA treatment Mechanical properties Corrosion behavior

Adaptive Control of a Flexible Manipulator With Unknown Hysteresis and Intermittent Actuator Faults

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IEEE/CAA Journal of Automatica Sinica 2025年第1期 148-158页

作者： Shouyan Chen Weitian He Zhijia Zhao Yun Feng Zhijie Liu Keum-Shik Hong School of Mechanical and Electrical Engineering Guangzhou University the School of Control Science and Engineering Shandong University IEEE the College of Electrical and Information Engineering Hunan University the national Engineering research Center for Robot Visual Perception and Control Technology Hunan University the School of Intelligence Science and Technology University of Science and Technology Beijing (USTB) the Institute for Future the School of AutomationQingdao University the School of Mechanical Engineering Pusan National University

In this study, we consider a single-link flexible manipulator in the presence of an unknown Bouc-Wen type of hysteresis and intermittent actuator faults. First, an inverse hysteresis dynamics model is introduced, and then the control input is divided into an expected input and an error compensator. Second,a novel adaptive neural network-based control scheme is proposed to cancel the unknown input hysteresis. Subsequently,by modifying the adaptive laws and local control laws, a fault-tolerant control strategy is applied to address uncertain intermittent actuator faults in a flexible manipulator system. Through the direct Lyapunov theory, the proposed scheme allows the state errors to asymptotically converge to a specified interval. Finally,the effectiveness of the proposed scheme is verified through numerical simulations and experiments.

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Carbon deposition in porous nickel/yttria-stabilized zirconia anode under methane atmosphere

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International Journal of Minerals,Metallurgy and Materials 2019年第3期26卷 350-359页

作者： Zhi-yuan Chen Li-jun Wang Xiao-jia Du Zai-hong Sun Fu-shen Li Kuo-Chih Chou State key Laboratory of Advanced Metallurgy University of Science and Technology Beijing Department of Materials Science and Engineering Delft University of Technology Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Suzhou Huatsing Jingkun New Energy Technology Co. Ltd. School of Materials Science and Engineering University of Science and Technology Beijing

A commercial solid oxide fuel cell with a Ni/YSZ anode was characterized under a pure methane atmosphere. The amount of deposited carbon increased with an increase in temperature but decreased when the temperature exceeded 700°C. The reactivity of carbon decreased with increasing deposition temperature. Filamentous carbon was deposited from 400 to 600°C, whereas flake carbon was deposited at 700 and 800°C. With increasing temperature, the intensity ratio of the D band over the sum of the G and D bands was constant at the beginning and then decreased with the transformation of the carbon morphology. The crystallite size increased from 2.9 to 13 nm with increasing temperature. The results also indicated that the structure of the deposited carbon was better ordered with increasing deposition temperature. In comparison with pure Ni powders, the interaction between the YSZ substrate and Ni particles could not only modify the carbon deposition kinetics but also reduce the temperature effect on the structure and reactivity variation of carbon.

关键词： solid oxide fuel cell coking Raman spectrum hydrocarbon fuel anode

Geochemical characteristics and accumulation of marine oil and gas around Halahatang depression,Tarim Basin,China

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Science China Earth Sciences 2008年第S1期51卷 195-206页

作者： LU YuHong,XIAO ZhongYao,GU QiaoYuan&ZHANG QiuCha research Institute of Exploration and Development,Tarim Oilfield Company,PetroChina,Korla 841000,China PetroChina Tarim Oilfield Co Res Inst Explorat & Dev Korla 841000 Peoples R China

There exists a petroleum system rich of oil and gas around Halahatang depression,where the oil and gas possess obvious local distinctions of properties in different *** research proved that the discovered crude oil and natural gas in the region derived mainly from O2+3 source rock,and the differences of its properties were controlled by the oil and gas filling *** comprehensive study result shows the oil and gas reservoirs of the region mainly underwent three important accumulation phases:late Caledonian-Early Hercynian epoch,late Hercynian epoch,and Yanshan-Himalayan epoch. In the first phase,the oil and gas derived mostly from Cambrian source rock,which formed the primary ancient oil reservoirs,then suffered strong degradation and remained a great quantity of pyrobitumen in the high position of Tabei uplift in the *** the second phase,the O2+3 source rock of Manjia'er depression started its generation of hydrocarbon,which accumulated in the high position of Tabei uplift afterwards,and then biodegradated to heavy oil in the late Hercynian *** the last phase,the O2+3 source rock of southern Halahatang depression and margin of Manjia'er depression started its peak of generating liquid hydrocarbon,which mostly accumulated in the trap formed before the Indo-China and Yanshan epoch,and in somewhere the heavy oil suffered dilutions in various degrees or serious gas invading,to lead to obvious crude oil divergence.

关键词： marine facies Mid-Upper Ordovician source rock oil and gas source accumulation stage Halahatang depression Tarim Basin

A compact frequency selective stop-band splitter by using Fabry Perot nanocavity in a T-shaped waveguide

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Chinese Physics B 2013年第4期22卷 513-518页

作者： M Afshari Bavil 孙秀冬 Department of Physics Harbin Institute of Technology

By utilizing a Fabry–Perot （FP） nanocavity adjacent to T-shaped gap waveguide ports, spectrally selective filtering is realized. When the wavelength of incident light corresponds to the resonance wavelength of the FP nanocavity, the surface plasmons are captured inside the nanocavity, and light is highly reflected from this port. The resonance wavelength is determined by using Fabry–Perot resonance condition for the nanocavity. For any desired filtering frequency the dimension of the nanocavity can be tailored. The numerical results are based on the two-dimensional finite difference time domain simulation under a perfectly matched layer absorbing boundary condition. The analytical and simulation results indicate that the proposed structure can be utilized for filtering and splitting applications.

关键词： T-shaped splitter Fabry–Perot nanocavity spectrally selective splitting finite difference time domain (FDTD) simulation

Late Cenozoic magnetic polarity stratigraphy in the Jiudong Basin,northern Qilian Mountain

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Science China Earth Sciences 2001年第S1期44卷 243-250页

作者：赵志军方小敏李吉均 1. Faculty of Geography Nanjing Normal University 210097 Nanjing China 2. national Laboratory of Western China’s Environmental Systems & College of Resources and Environment Lanzhou University 730000 Lanzhou China

Late Cenozoic sediments in the Hexi Corridor, foreland depression of the Qilian Mountain preserved reliable records on the evolution of the Northern Tibetan Plateau. Detailed magnetic polarity dating on a 1150 m section at Wenshushan anticline in the Jiudong Basin, west of Hexi Corridor finds that the ages of the Getanggou Formation, Niugetao Formation and Yumen Conglomerate are>11-8.6 Ma, 8.6-4.5 Ma and 4.5-0.9 Ma respectively. Accompanying sedimentary analysis on the same section suggests that the northern Tibetan Plateau might begin gradual uplift since 8.6-7.6 Ma, earlier than the northeastern Tibetan Plateau but does not suppose that the plateau has reached its maximum elevation at that time. The commencement of the Yumen Conglomerate indicates the intensive tectonic uplift since about 4.5 Ma.

关键词： Hexi Corridor paleomagnetic stratigraphy Tibetan Plateau uplift.

Problems in wavelet analysis of hydrologic series and some suggestions on improvement

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Progress in Natural Science:Materials International 2007年第1期17卷 80-86页

作者： WANG Hongrui, YE Letian, LIU Changming, YANG Chi and LIU Peng ( College of Water Sciences, Beijing Normal University, Beijing 100875, China key Laboratory for Water and Sediment Sciences, Ministry of Education, Beijing 100875, China School of Mathematical Sciences, Peking University, Beijing 100089, China College of Engineering Sciences, University of Region, Canada) [a]College of Water Sciences Beijing Normal University Beijing China [b]key Laboratory for Water and Sediment Sciences Ministry of Education Beijing China [c]School of Mathematical Sciences Peking University Beijing China [d]College of Engineering Sciences University of Region Canada

Applying the wavelet theory and methods to investigate the hydrologic processes such as precipitation and runoff is a hot field. However, several aspects in research are usually ignored: the effect of admissible condition of wavelet functions and the disturbance of noises for the detection of periods, the effect of the length of a hydrologic time-series on the final result, and the choice between the anomaly and the original time series for wavelet analysis. In this paper, these issues are fully discussed. Precipitation data from Lanzhou Precipitation Station are taken for case study. The result indicates that in the wavelet analysis of hydrologic series, denoise methods should be used to eliminate the influence of noises. The MexHat wavelet function satisfies the admissible condition, which ensures that the periodic properties of hydrologic processes can be well represented by using the MexHat wavelet for decomposition. The affected range of hydro-logic series which should be discarded before analysis is given. It is also suggested that the anomaly series should be used to highlight the actual undulation of the hydrologic series.

关键词： wavelet analysis hydrologic process admissible condition noise period.

A CRITERION FOR TESTING WHETHER A DIFFERENCE IDEAL IS PRIME

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Journal of Systems Science & Complexity 2009年第4期22卷 627-635页

作者： Chunming YUAN Xiao-Shan GAO key Laboratory of Mathematics Mechanization,Institute of Systems Science Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100190,China. key Laboratory of Mathematics Mechanization Institute of Systems Science Beijing China Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China

This paper presents a criterion for testing the irreducibility of a polynomial over an algebraicextension *** this criterion and the characteristic set method,the authors give a criterion fortesting whether certain difference ascending chains are strong irreducible,and as a consequence,whetherthe saturation ideals of these ascending chains are prime ideals.

关键词： Characteristic set difference prime ideal irreducibility strong irreducibility.