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Rényi's Problem in Short Intervals

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Acta Mathematica Sinica,English Series 2007年第1期23卷 29-36页

作者： Wen guang zhai Department of Mathematics Shandong Normal University Jinan 250014 P R. China

In this paper, we study Rényi＇s problem and other related problems about the additive functions in short intervals. As corollaries, we improve Ivic＇s results.

关键词： additive function Rényi's problem short interval

Tracking the maneuvering spacecraft propelled by swing propulsion of constant magnitude

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Journal of Systems Engineering and Electronics 2020年第2期31卷 370-382页

作者： zhai guang WANG Yanxin ZHAO Qi School of Aerospace Engineering Beijing Institute of TechnologyBeijing 100081China Systems Engineering Research Institute Beijing 100094China

This paper proposes partially norm-preserving filtering for a class of spacecraft in the presence of time-varying, but constant-magnitude maneuver. The augmented state Kalman filter(ASKF) is commonly used to track the maneuvering spacecraft with unknown constant propulsion;however, if the maneuver varies via time, the estimation performance will be degraded. To promote the tracking performance of the ASKF in case of time-invariant,constant-magnitude disturbance, the partially norm-preserving ASKF is developed by applying the norm constraint on the unknown maneuver. The proposed estimator, which is decomposed into two partial estimators and iteratively propagated in turns,projects the unconstrained maneuver estimation onto the Euclidian surface spanned by the norm constraint. The illustrative numerical example is provided to show the efficiency of the proposed method.

关键词： maneuvering spacecraft tracking augmented state norm-preserving Kalman filter

Observer-based control for the platform of a tethered space robot

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Chinese Journal of Aeronautics 2018年第8期31卷 1786-1796页

作者： guang zhai Heming ZHENG Bo ZHANG Aerospace Engineering School Beijing Institute of TechnologyBeijing 100081China Aerospace System Engineering Shanghai Shanghai 201109China

This paper addresses the attitude control problem of a space tethered robot platform in the presence of unknown external disturbance caused by a connecting elastic tether. The tethergenerated unknown disturbance leads to tremendous challenges for attitude control of the *** this work, the perturbed attitude dynamics of the platform are derived with a consideration of the libration of the elastic tether, and then with the purpose of compensating the unknown disturbance, major attention is dedicated to develop a nonlinear disturbance observer based on gyros measurements, after which, an adaptive attitude scheme is proposed by combining the disturbance observer with a sliding mode controller. Finally, benefits from the observer based on an adaptive controller are validated by series of numerical simulations.

关键词： Adaptive control Attitude dynamics Disturbance observerSliding mode controlTethered space robot

Coordinated target localization base on pseudo measurement for clustered space robot

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Chinese Journal of Aeronautics 2013年第6期26卷 1524-1533页

作者： zhai guang Zhang Jingrui Zhou Zhicheng School of Aerospace Engineering Beijing Institute of Technology China Academy of Space Technology

This paper presents a coordinated target localization method for clustered space *** to the different measuring capabilities of cluster members,the master-slave coordinated relative navigation strategy for target localization with respect to slavery space robots is proposed;then the basic mathematical models,including coordinated relative measurement model and cluster centralized dynamics,are established *** employing the linear Kalman flter theorem,the centralized estimator based on truth measurements is developed and analyzed frstly,and with an intention to inhabit the initial uncertainties related to target localization,the globally stabilized estimator is designed through introduction of pseudo ***,the observability and controllability of stochastic system are also analyzed to qualitatively evaluate the convergence performance of pseudo measurement ***,on-orbit target approaching scenario is simulated by using semi-physical simulation system,which is used to verify the convergence performance of proposed *** the simulation,both the known and unknown maneuvering acceleration cases are considered to demonstrate the robustness of coordinated localization strategy.

关键词： Clustered space robot Coordinated target localization On-orbit servicing Pseudo measurements

On-orbit target tracking and inspection by satellite formation

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Journal of Systems Engineering and Electronics 2013年第6期24卷 879-888页

作者： guang zhai Jingrui Zhang Zhicheng Zhou School of Aerospace Engineering Beijing Institute of Technology China Academy of Space Technology

A new type of estimator is developed for the satellite formation to track and inspect on-orbit targets. The follower satellite in the formation works without relative sensors, and its target pointing commands are derived based on relative orbital dynamics. The centralized estimator based on truth measurement is designed, however, this estimator is proved unstable because of the lack of necessary measurement information. After that, an alternative estimator based on pseudo measurement is designed, and its observability and controllability are analyzed to qualitatively evaluate the convergence performance. Finally, an on-orbit target inspection scenario is numerically simulated to verify the performance of the estimator based on pseudo measurement.

关键词： satellite formation on-orbit inspection target tracking pseudo measurement

On the Distribution of Hecke Eigenvalues over Piatetski-Shapiro Prime Twins

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Acta Mathematica Sinica,English Series 2021年第9期37卷 1453-1464页

作者： De Yu ZHANG Wen guang zhai School of Mathematics and Statistics Shandong Normal UniversityJinan 250358P.R.China Department of Mathematics China University of Mining and TechnologyBeijing 100083P.R.China

Letλf(n)be the normalized n-th Fourier coefficient of holomorphic eigenform f for the full modular group and Pc(x):={p≤x|[pc]prime},c∈R+.In this paper,we show that for all 0 详细信息

Letλf(n)be the normalized n-th Fourier coefficient of holomorphic eigenform f for the full modular group and Pc(x):={p≤x|[pc]prime},c∈R+.In this paper,we show that for all 0

关键词： Hecke eigenvalue Piatetski-Shapiro primes asymptotic formula

Narrative review of latest research progress about robotic percutaneous coronary intervention

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Journal of Geriatric Cardiology 2024年第8期21卷 816-825页

作者： Zhen-Yu LIU guang-Yao zhai Department of Clinical Medicine Beijing Luhe HospitalCapital Medical UniversityBeijingChina Department of Cardiology Beijing Luhe HospitalCapital Medical UniversityBeijingChina

Robotic percutaneous coronary intervention(R-PCI)is a novel technology in which operators can manipulate guidewires and catheter devices in interventional *** approach provides great benefits to interventional cardiologists in terms of reducing both radiation exposure and orthopedic *** large,high-quality cohort studies have confirmed the short-term safety and high technical success rate of ***,randomized long-term data are still needed before adopting them as part of standard coronary ***,tele-stenting for complex coronary lesions has significant potential for *** need to overcome the present relevant challenges for its application such as inherent delays,bedside care for unstable patients from R-PCIs to manual PCIs(M-PCIs),incompatibility for a thrombus aspiration catheter and heavily calcified *** is a great future in laboratory workflow teams,3D-printed anatomical models and multiple joint collaborative control *** narrative review summarizes the latest developments in R-PCI,with a focus on developments in robotic technology,and discusses the current and future potential use of R-PCI in clinical practice globally.

关键词： coronary injuries unstable

The corrosion of AA2037 aluminum alloy in alkaline aqueous solution studied using slow positron beam spectroscopy

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Nuclear Science and Techniques 2016年第2期27卷 6-13页

作者： Jiao-Jiao Wang Zhe-Jie Zhu Wei Yang Yi-Chu Wu Tong-guang zhai Hubei Key Laboratory of Nuclear Solid Physics School of Physics and Technology Wuhan University Chemical and Materials Engineering Department University of Kentucky

Corrosion behavior of AA2037 T8 Al alloy in a1 M Na OH aqueous solution was investigated using slow positron beam, together with microscopy techniques and electrochemical tests. The alloy was homogenized at 510℃ for 2 h and 30 s, respectively, before final peak aging, so that one Sample A had more dispersoids than Sample B after homogenization. It was found that S parameter of the Doppler-broadened annihilation was significantly decreased near the surface in both samples in the alkaline solution. With increasing the dissolution time,Sample A showed a slower decrease rate than Sample B,which might imply that the preexistence of more dispersoids might hinder the corrosion process in Sample *** electron microscopy and atomic force microscopy observations found that the surfaces of both samples were uniformly thinned due to intense chemical dissolution by the attack of OH-. With increasing the dissolution time,Sample B was corroded more substantially and produced more and larger pits in a short dissolution time than Sample A. Furthermore, polarization curves showed that Sample A had a lower corrosion current and corrosion rate than Sample B, which revealed that the presence of the dispersoids was responsible for the better corrosion resistance in the alloy.

关键词：慢正电子束碱性水溶液腐蚀行为铝合金扫描电子显微镜光谱溶解时间电化学测试

Structured Computational Modeling of Human Visual System for No-reference Image Quality Assessment

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International Journal of Automation and computing 2021年第2期18卷 204-218页

作者： Wen-Han Zhu Wei Sun Xiong-Kuo Min guang-Tao zhai Xiao-Kang Yang MoE Key Lab of Artificial Intelligence AI InstituteShanghai Jiao Tong UniversityShanghai 200240China Institute of Image Communication and Information Processing Shanghai Jiao Tong UniversityShanghai 200240China

Objective image quality assessment(IQA)plays an important role in various visual communication systems,which can automatically and efficiently predict the perceived quality of *** human eye is the ultimate evaluator for visual experience,thus the modeling of human visual system(HVS)is a core issue for objective IQA and visual experience *** traditional model based on black box fitting has low interpretability and it is difficult to guide the experience optimization effectively,while the model based on physiological simulation is hard to integrate into practical visual communication services due to its high computational *** bridging the gap between signal distortion and visual experience,in this paper,we propose a novel perceptual no-reference(NR)IQA algorithm based on structural computational modeling of *** to the mechanism of the human brain,we divide the visual signal processing into a low-level visual layer,a middle-level visual layer and a high-level visual layer,which conduct pixel information processing,primitive information processing and global image information processing,*** natural scene statistics(NSS)based features,deep features and free-energy based features are extracted from these three *** support vector regression(SVR)is employed to aggregate features to the final quality *** experimental comparisons on three widely used benchmark IQA databases(LIVE,CSIQ and TID2013)demonstrate that our proposed metric is highly competitive with or outperforms the state-of-the-art NR IQA measures.

关键词： Image quality assessment(IQA) no-reference(NR) structural computational modeling human visual system visual feature extraction