检索结果-南通市图书馆

Unsteady rotating flows of a viscoelastic fluid with the fractional Maxwell model between coaxial cylinders

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2006年第4期22卷 301-305页

作者： haitao qi Hui Jin Department of Applied Mathematics and Statistics Institute of Applied Mathematics Shandong University at Weihai Weihai 264209 Shandong China School of Mathematics and Systematical Science Shandong University Jinan 250100 Shandong China

The fractional calculus is used in the constitutive relationship model of viscoelastic fluid. A generalized Maxwell model with fractional calculus is considered. Based on the flow conditions described, two flow cases are solved and the exact solutions are obtained by using the Weber transform and the Laplace transform for fractional calculus.

关键词： Viscoelastic fluid Unsteady flow Fractional Maxwell model Exact solution

An inverse problem to estimate an unknown order of a Riemann-Liouville fractional derivative for a fractional Stokes' first problem for a heated generalized second grade fluid

在线全文

学校读者我要写书评

暂无评论

Acta Mechanica Sinica 2015年第2期31卷 153-161页

作者： Bo Yu Xiaoyun Jiang haitao qi School of Mathematics Shandong University School of Mathematics and Statistics Shandong University

In this paper,we propose a numerical method to estimate the unknown order of a Riemann-Liouville fractional derivative for a fractional Stokes＇ first problem for a heated generalized second grade *** implicit numerical method is employed to solve the direct *** the inverse problem,we first obtain the fractional sensitivity equation by means of the digamma function,and then we propose an efficient numerical method,that is,the Levenberg-Marquardt algorithm based on a fractional derivative,to estimate the unknown order of a Riemann-Liouville fractional *** order to demonstrate the effectiveness of the proposed numerical method,two cases in which the measurement values contain random measurement error or not are *** computational results demonstrate that the proposed numerical method could efficiently obtain the optimal estimation of the unknown order of a RiemannLiouville fractional derivative for a fractional Stokes＇ first problem for a heated generalized second grade fluid.

关键词： Riemann-Liouville fractional derivative Generalized second grade fluid Inverse problem Implicit numerical method Fractional sensitivity equation

Numerical analysis for viscoelastic fluid flow with distributed/variable order time fractional Maxwell constitutive models

在线全文

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 2021年第12期42卷 1771-1786页

作者： Yanli qiAO Xiaoping WANG Huanying XU haitao qi School of Mathematics and Statistics Shandong UniversityWeihai 264209Shandong ProvinceChina

Fractional calculus has been widely used to study the flow of viscoelastic fluids recently,and fractional differential equations have attracted a lot of ***,the research has shown that the fractional equation with constant order operators has certain limitations in characterizing some physical *** this paper,the viscoelastic fluid flow of generalized Maxwell fluids in an infinite straight pipe driven by a periodic pressure gradient is investigated *** the complexity of the material structure and multi-scale effects in the viscoelastic fluid *** modified time fractional Maxwell models and the corresponding governing equations with distributed/variable order time fractional derivatives are *** on the L1-approximation formula of Caputo fractional derivatives,the implicit finite difference schemes for the distributed/variable order time fractional governing equations are presented,and the numerical solutions are *** order to test the correctness and availability of numerical schemes,two numerical examples are established to give the exact *** comparisons between the numerical solutions and the exact solutions have been made,and their high consistency indicates that the present numerical methods are ***,this paper analyzes the velocity distributions of the distributed/variable order fractional Maxwell governing equations under specific conditions,and discusses the effects of the weight coefficient(α)in distributed order time fractional derivatives,the orderα(r,t)in variable fractional order derivatives,the relaxation timeλ,and the frequencyωof the periodic pressure gradient on the fluid flow ***,the flow rates of the distributed/variable order fractional Maxwell governing equations are also studied.

关键词： distributed order time fractional derivative variable order time fractional derivative finite difference scheme viscoelastic fluid

Electrical impedance tomography for clinical application

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2022年第6期65卷 1433-1434页

作者： XU ShaoFeng SHI Yan CAI MaoLin qi haitao WANG YiXuan School of Automation Science and Electrical Engineering Beihang UniversityBeijing 100191China Engineering Training Centre Beihang UniversityBeijing 100191China

In the course of the disease,the functional changes of the tissues and organs associated with the condition often predate the disease of its organic *** these functional changes can be detected and confirmed by the specific imaging means in the incubation period or the functional compensation period of the disease,that is,before the structural changes in the tissues or organs。

关键词： organs clinical impedance

Flow characteristics of integrated motor-pump assembly with phosphate ester medium for aerospace electro-hydrostatic actuators

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第9期36卷 392-407页

作者： Jiangao ZHAO Jian FU Yuchen LI haitao qi Yan WANG Yongling FU The Laboratory of Aerospace Servo Actuation and Transmission Beijing 100191China Research Institute for Frontier Science Beihang UniversityBeijing 100191China School of Mechanical Engineering and Automation Beihang UniversityBeijing 100191China

Motor-pump assembly is the core component of the Aerospace Electro-hydrostatic Actuator(EHA).Thus,the design of the motor pump can be very challenging under conditions of high speed and wide pressure range,especially in particular working *** ultimate goal is to pursue better flow characteristics under a wide range of working *** this paper,we built a sub-model of the main friction interfaces and a model of single-shaft coaxial motor-pump assembly adopting the method of hierarchical *** experimental investigation of the output characteristics was mainly carried out in a phosphate ester medium ***,the flow characteristics were compared and analyzed with the simulation *** indicated that the flow characteristics of the motor-pump assembly could be accurately simulated by the model and quite severe in a low speed and high-pressure environment.

关键词： EHA Friction interfaces More electric aircraft Motor-pump Multidisciplinary modeling

Architecture Optimization of More Electric Aircraft Actuation System

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2011年第4期24卷 506-513页

作者： qi haitao FU Yongling qi Xiaoye LANG Yan School of Mechanical Engineering and Automation Beihang University Beijing 100191 China Beijing Institute of Control Engineering Beij'ing 100190 China

The optional types of power source and actuator in the aircraft are more and more diverse due to fast development in more electric technology, which makes the combinations of different power sources and actuators become extremely complex in the architecture optimization process of airborne actuation system. The traditional ＂trial and error＂ method cannot satisfy the design demands. In this paper, firstly, the composition of more electric aircraft （MEA） flight control actuation system （FCAS） is introduced, and the possible architecture quantity is calculated. Secondly, the evaluation criteria of FCAS architecture with respect to safe reliability, weight and efficiency are proposed, and the evaluation criteria values are calculated in the case that each control surface adopts the same actuator configuration. Finally, the optimization results of MEA FCAS architecture are obtained by applying genetic algorithm （GA）. Compared to the traditional actuation system architecture, which only adopts servo valve controlled hydraulic actuators, the weight of the optimized more electric actuation system architecture can be reduced by 6%, and the efficiency can be improved by 30% based on the safe reliability requirements.

关键词： more electric aircraft power-by-wire actuation system architecture multiobjective optimization genetic algorithms

Reconstruction Of The Energy Formulae Of The Fractional Viscoelastic Element

在线全文

学校读者我要写书评

暂无评论

Reconstruction Of The Energy Formulae Of The Fractional Visc...

Morphology and crystalline property of an AlN single crystal grown on AlN seed

第五届国际自动控制联合会分数阶导数及其应用会议

作者： Jiaguo Liu haitao qi School of Mathematics and Statistics Shandong University at WeihaiWeihai 264209 P.R. China School of Mathematics and Statistics Shandong University at Weihai Weihai 264209 P.R. China

＜正＞In this paper we consider the stored and dissipated energy of the fractional viscoelastic element under the sinusoidal stress *** the fractional viscoelastic element can be approximated by a sequence series Kelv... 详细信息

关键词： Stored energy Dissipated energy Fractional element Viscoelasticity Loss angle. Dielectric losses stress state Element Energy sources formula COMPLEX MODULUS rationality Sinusoidal

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Journal of Semiconductors 2021年第5期42卷 64-69页

作者： Li Zhang haitao qi Hongjuan Cheng Yuezeng Shi Zhanpin Lai Muchang Luo China Electronics Technology Group Corp 46th Research Institute Tianjin 300220China China Electronics Technology Group Corp 44th Research Institute Chongqing 400060China

AlN single crystal grown by physical vapor transport (PVT) using homogeneous seed is considered as the most promising approach to obtain high-quality AlN *** this work,the morphology of AlN single crystals grown under different modes (3D islands and single spiral center) were *** is proved that,within an optimized thermal distribution chamber system,the surface temperature of AlN seed plays an important role in crystal growth,revealing a direct relationship between growth mode and growth ***,a high-quality AlN crystal,with (002) and (102) reflection peaks of 65and 36 arcsec at full width at half maximum (FWHM),was obtained grown under a single spiral center *** on which,a high-quality Al_x Ga_(1–x) N epitaxial layer with high Al content (x=0.54) was also *** FWHMs of (002) and (102) reflection of Al_x Ga_(1–x) N were 202 and 496 arcsec,respectively,which shows superiority over their counterpart grown on SiC or a sapphire substrate.

关键词： AlN crystal surface morphology growth mechanism crystalline quality

在线全文

学校读者我要写书评

暂无评论

双余度电静液作动器力均衡控制

北京航空航天大学学报 2017年第2期43卷 270-276页

作者：齐海涛滕雅婷北京航空航天大学工程训练中心北京100083 北京航空航天大学机械工程及自动化学院北京100083

随着多电飞机技术的发展,电静液作动器(EHA)被更多地用于机载作动系统。双余度电静液作动器(DREHA)更易于实现余度控制,推进EHA在飞机上的应用。本文给出了一种新型DREHA的结构组成,并对其工作原理和固有的力纷争现象进行了分析。理想... 详细信息

随着多电飞机技术的发展,电静液作动器(EHA)被更多地用于机载作动系统。双余度电静液作动器(DREHA)更易于实现余度控制,推进EHA在飞机上的应用。本文给出了一种新型DREHA的结构组成,并对其工作原理和固有的力纷争现象进行了分析。理想情况下,通过流量补偿进行修正,力纷争会消失。由于实际系统的参数不可能与仿真模型完全一致,通过人为引入两通道参数误差,复现实际的力纷争。针对上述力纷争现象,基于两通道左右腔压差提出了差值力补偿力均衡控制策略和交叉耦合力均衡控制策略,以减小力纷争。MATLAB和AMESim联合仿真结果表明,本文所设计的力均衡控制器能大大减小力纷争峰值,同时提高系统的响应速度。

关键词：双余度电静液作动器力纷争力均衡控制差值力补偿交叉耦合