检索结果-南通市图书馆

Joint Continuity of Lyapunov Exponent for Finitely Smooth Quasi-periodic Schrodinger Cocycles

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2021年第7期37卷 1131-1142页

作者： jin hao LIANG Lin Lin FU Department of Applied Mathematics Nanjing Forestry UniversityNanjing 210037P.R.China Department of Mathematics Sun Yat-sen UniversityGuangzhou 510275P.R.China

We prove the joint continuity of Lyapunov exponent in the energy and the Diophantine frequency for quasi-periodic Schrodinger cocycles with the C^(2)cos-type *** particular,the Lyapunov exponent is log-Holder continuo... 详细信息

关键词： Schrodinger cocycle Lyapunov exponent C^(2)cos-type potential

Hydrodynamic Response of A Fully Coupled TLP Hull-TTR System with Detailed Modeling of A Hydraulic Pneumatic Tensioner and Riser Joints

在线全文

学校读者我要写书评

暂无评论

China Ocean Engineering 2022年第3期36卷 451-463页

作者： hao shuai YU Yang YU Jian-xing YUAN Zhi-ming XU Li-xin Maritime College Tianjin University of TechnologyTianjin 300384China State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Port and Ocean Engineering Tianjin UniversityTianjin 300072China Department of Naval Architecture Ocean&Marine EngineeringUniversity of StrathclydeGlasgow G40LZUK

Tension Leg Platform(TLP)in deepwater oil and gas field development usually consists of a hull,tendons,and top tension risers(TTRs).To maintain its top tension,each TTR is connected with a tensioner system to the *** to the complicated configuration of the tensioners,the hull and TTRs form a strong coupled ***,some simplified tensioner models are applied to analyze the TLP *** is a large discrepancy between their analysis results and the actual mechanism behaviors of a *** is very necessary to develop a more detailed tensioner model to consider the coupling effects between TLP and *** the present study,a fully coupled TLP hull-TTR system for hydrodynamic numerical simulation is established.A specific hydraulic pneumatic tensioner is modeled by considering 4 *** production TTR model is stacked up by specific riser *** simulation is also extended to analyze an array of *** regular and irregular waves are *** behaviors of different cylinders are *** results show that it is important to consider the specific configurations of the tensioner and TTRs,which may lead to obviously different response behaviors,compared with those from a simplified model.

关键词： top tension riser(TTR) fully coupled hull-tendon-TTR-tensioner model hydraulic pneumatic tensioner hydrodynamic response 3D potential flow theory

Research on Control Strategy of Grid-connected Brushless Doubly-fed Wind Power System Based on Virtual Synchronous Generator Control

在线全文

学校读者我要写书评

暂无评论

CES Transactions on Electrical Machines and Systems 2022年第4期6卷 404-412页

作者： shuai Liang Shi jin Long Shi Shenyang University of Technology Shenyang110870China IEEE

The brushless doubly-fed wind power system based on conventional power control strategies lacks ‘inertia’ and the ability to support grid,which leads to the decline of grid ***,a control strategy of brushless doubly-fed reluctance generator(BDFRG) based on virtual synchronous generator(VSG) control is proposed to solve the problem in this *** output characteristics of BDFRG based on VSG are similar to a synchronous generator(SG),which can support the grid frequency and increase the system ‘inertia’.According to the mathematical model of BDFRG,the inner loop voltage source control of BDFRG is *** addition,the specific structure and parameter selection principle of outer loop VSG control are *** voltage source control inner loop of BDFRG is combined with the VSG control outer loop to establish the overall architecture of BDFRG-VSG control ***,the effectiveness and feasibility of the proposed strategy are verified in the simulation.

关键词： Virtual synchronous generator Brushless doubly-fed relutance generator Grid support ability Voltage source control

Magnetometer-only linear attitude estimation for bias momentum pico-satellite

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第6期11卷 455-464页

作者： Ke HAN hao WANG Zhong-he jin Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

Satellite attitude information is essential for pico-satellite applications requiring light-weight,low-power,and fast-computation *** objective of this study is to provide a magnetometer-only attitude estimation method for a low-altitude Earth orbit,bias momentum *** on two assumptions,the spacecraft spherical symmetry and damping of body rates,a linear kinematics model of a bias momentum satellite's pitch axis is derived,and the linear estimation algorithm is *** algorithm combines the linear Kalman filter(KF) with the classic three-axis attitude determination method(TRIAD).KF is used to estimate satellite's pitch axis orientation,while TRIAD is used to obtain information concerning the satellite's three-axis *** tests confirmed that the algorithm is suited to the time-varying model errors resulting from both *** estimate result keeps tracking satellite attitude motion during all damping,stable,and free rotating control *** with nonlinear algorithms,such as extended Kalman filer(EKF) and square root unscented Kalman filer(SRUKF),the algorithm presented here has an almost equal performance in terms of convergence time and estimation accuracy,while the consumption of computing resources is much lower.

关键词： Pico-satellite Attitude estimation Bias momentum Magnetometer Kalman filter(KF)

Spectral Coexistence between LEO and GEO Satellites by Optimizing Direction Normal of Phased Array Antennas

在线全文

学校读者我要写书评

暂无评论

China Communications 2018年第6期15卷 18-27页

作者： Chen Zhang jin jin hao Zhang Ting Li Tsinghua Space Center Tsinghua University Technology and Engineering Center for Space Utilization Chinese Academy of Sciences

This paper addresses the spectral coexistence between LEO constellation and GEO belt for global distributed earth stations. A specific method is introduced to mitigate the in-line interference by tilting the direction normal of phased array antennas of LEO satellites, and the optimal direction is found by solving a non-linear programming problem. The simulation results prove that the proposed approach leads to greater link availability while guaranteeing the desired received signal level especially for low-latitude earth stations.

关键词： satellite constellation satellite communication spectral coexistence interference mitigation phased array

Comparison of different techniques for time-frequency analysis of internal combustion engine vibration signals

在线全文

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2011年第7期12卷 519-531页

作者： Yang jin Zhi-yong hao Xu ZHENG Department of Energy Engineering Zhejiang University Hangzhou 310027 China Department of Automotive Engineering Hubei University of Automotive Technology Shiyan 442002 China

In this study,we report an analysis of cylinder head vibration signals at a steady engine speed using short-time Fourier transform(STFT).Three popular time-frequency analysis techniques,i.e.,STFT,analytic wavelet transform(AWT) and S transform(ST),have been *** and ST are often applied in engine signal *** particular,an AWT expression in terms of the quality factor Q and an analytical relationship between ST and AWT have been *** time-frequency resolution of a Gaussian function windowed STFT was studied via numerical *** on the simulation,the empirical limits for the lowest distinguishable frequency as well as the time and frequency resolutions were *** can provide insights for window width selection,spectrogram interpretation and artifact *** function windowed STFTs were applied to some cylinder head vibration *** spectrograms of the same signals from ST and AWT were also determined for *** results indicate that the uniform resolution feature of STFT is not necessarily a disadvantage for time-frequency analysis of vibration signals when the engine is in stationary state because it can more accurately localize the frequency components excited by transient excitations without much loss of time resolution.

关键词： Short-time Fourier transform(STFT) Gaussian window Time-frequency resolution limits Internal combustion(IC) engine Vibration signals Analytic wavelet transform(AWT) S transform(ST)

Effects of the band-filling and Fe/Mo disorder on physical properties of Ca_2FeMoO_6

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第12期27卷 444-449页

作者： jin-Feng Wang Zhao-Tong Zhuang shuai-shuai Liu Qian-Qian Gao College of Physics and Materials Science National Demonstration Center for Experimental Physics EducationHenan Normal University and Henan Key Laboratory of Photovoltaic Materials

Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca2FeMoO6. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization(Ms) with the Fe/Mo disorder. Interestingly, magnetoresistance(MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature(TC) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.

关键词： band filling effect Fe/Mo disorder Ca_2FeMoO_6 physical property

Charge transfer in plasma assisted dry reforming of methane using a nanosecond pulsed packed-bed reactor discharge

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2021年第6期23卷 59-66页

作者： shuai ZHANG Yuan GAO hao SUN Zhe FAN Tao Shao Beijing International S&T Cooperation Base for Plasma Science and Energy Conversion Institute of Electrical EngineeringChinese Academy of SciencesBeijing 100190People's Republic of China University of Chinese Academy of Sciences Beijing 100049People's Republic of China

This paper is aimed to investigate the effect of packing material on plasma characteristic from the viewpoint of charge transfer *** the charge accumulation and release processes in the dielectric barrier discharge reactor and packed-bed reactor were investigated by measuring voltage and current waveforms and taking ICCD *** packing material was ZrO2 pellets and the reactors were driven by a parameterized nanosecond pulse *** quantity of transferred charges in the dielectric barrier discharge reactor was enhanced when decreasing pulse rise time or increasing pulse width(within 150 ns),but reduced when the gas gap was packed with *** quantity of accumulated charges in the primary discharge was larger than the quantity of released charges in the secondary discharges in the dielectric barrier discharge reactor,but they were almost equal in the packed-bed *** indicates that the discharge behavior has been changed from the view of charge transfer process once the gas gap was packed with pellets,and the ICCD images confirmed it.

关键词： non-thermal plasma packed-bed reactor dry reforming plasma catalysis charge transfer

Colloidal AgCl induced-growth of thorny gold nanoparticles and their SERS activity

在线全文

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2019年第6期30卷 1266-1268页

作者： shuai Zeng Hong Yuan Lin Gan jin Huang Key Laboratory of Pesticide and Chemical Biology of Ministry of Education College of Chemistry Central China Normal University Wuhan 430079 China Chongqing Key Laboratory of Soft-Matter Material Chemistry and Function Manufacturing School of Chemistry and Chemical Engineering Southwest University Chongqing 400715 China

In this paper,we exploited a unique procedure for obtaining thorny gold nanoparticles(Au NPs)with controllable length of thorns without using seeds and surfacta nts.A larger number of Ag+ions was added into the reaction system containing with HAuCI4 and NH2 OH·HCl,so as to forming colloidal *** could induce the growth of thorny Au *** morphology of Au NPs changed from short-thorns,longthorns to no-thorns,as the amount of AgNO3 *** obtained Au NPs exhibited shapedetermined surface-enhanced Raman spectroscopy(SERS)activity toward rhodamine 6 G(R6 G);indicating their potential for use in SERS-based detections and analysis.

关键词： Thorny nanoparticles Gold Colloidal AgCl SERS Controllable growth