检索结果-南通市图书馆

Numerical investigation of transonic flow over deformable airfoil with plunging motion

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Applied mathematics and mechanics(English Edition) 2016年第1期37卷 75-96页

作者： N.NEKOUBIN m.R.H.NOBARI Department of mechanical Engineering Amirkabir University of Technology

In this article, the transonic inviscid flow over a deformable airfoil with plunging motion is studied numerically. A finite volume method based on the Roe scheme developed in a generalized coordinate is used along with an arbitrary Lagrangian-Eulerian method and a dynamic mesh algorithm to track the instantaneous position of the airfoil. The effects of different governing parameters such as the phase angle, the deformation amplitude, the initial angle of attack, the flapping frequency, and the mach number on the unsteady flow field and aerodynamic coefficients are investigated in detail. The results show that maneuverability of the airfoil under various flow conditions is improved by the deformation. In addition, as the oscillation frequency of the airfoil increases, its aerodynamic performance is significantly improved.

关键词： transonic flow inviscid flow fluid-solid interaction deformable airfoil,plunge motion Roe scheme

H∞ Tracking Control for Switched LPV Systems With an Application to Aero-Engines

在线全文

学校读者我要写书评

暂无评论

IEEE/CAA Journal of Automatica Sinica 2018年第3期5卷 699-705页

作者： Kongwei Zhu Jun Zhao Georgi m.Dimirovski State Key Laboratory of Synthetical Automation for Process Industries (Northeastern University) College of Information Science and Engineering Northeastern University Shenyang 110819 China School of Informatics Linyi University Linyi 276000 China School of Engineering Dogus University and also with the School of Electrical-Electronics Engineering and Information Technologies St. Cyril and St. Methodius University Skopje Macedonia Istanbul TR-34722 R. Turkey IEEE

This paper focuses on the H_∞ model reference tracking control for a switched linear parameter-varying(LPV)model representing an aero-engine. The switched LPV aeroengine model is built based on a family of linearized *** parameter-dependent Lyapunov functions technique is used to design a tracking control law for the desirable H_∞ tracking performance. A control synthesis condition is formulated in terms of the solvability of a matrix optimization *** result on the aero-engine model shows the feasibility and validity of the switching tracking control scheme.

关键词： Aero-engine control H_∞ tracking control multiple parameter-dependent Lyapunov functions switched linear parameter-varying(LPV) systems

Pilot studies on two dimensional wave propagation in rock masses

在线全文

学校读者我要写书评

暂无评论

中国有色金属学会会刊：英文版 2005年第4期15卷 949-955页

作者：雷卫东 m.H.Ashraf 赵坚 School of Civil and Environmental Engineering Nanyang Technological University

Pilot studies on two dimensional(2-D) wave propagation through single joint or multiple parallel joints were comprehensively conducted, using a suitable data processing method. The possible factors influencing the transmission ratio in 2-D wave propagation under certain circumstances in rock masses were studied. It is found that in the process of 2-D wave propagation, for any radial line, the amount, the stiffness and the spacing of the joints influence the transmission ratio; by contrast, the transmission ratio at any point is independent of the radial distance from the center of wave source. It is also found that the transmission ratio for every grid-point along a single circle can present the transmission ratio for every grid-point after a certain quantity of joints. For the special radian direction(normal to the joints), it is concluded that the transmission ratio is dominated by the normal stiffness; while the influence of shear stiffness is negligible. The radius of the tunnel or borehole for the source wave does not affect the transmission ratio in 2-D wave propagation.

关键词：矿山岩石力学引航理论二维波传播

Phonon-dependent transport through a serially coupled double quantum dot system

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2014年第5期23卷 510-515页

作者： m.Bagheri Tagani H.Rahimpour Soleimani Department of Physics University of Guilan

Using Keldysh nonequilibrium Green function formalism and mapping a many-body electron-phonon interaction onto a one body problem, the electron transport through a serially coupled double quantum dot system is analyzed. The influence of the electron-phonon interaction, temperature, detuning, and interdot tunneling on the transmission coefficient and current is studied. Our results show that the electron-phonon interaction results in the appearance of the side peaks in the transmission coefficient, whose height is strongly dependent on the phonon temperature. We have also found that the inequality of the electron-phonon interaction strength in two dots gives rise to an asymmetry in the current-voltage characteristic. In addition, the temperature difference between the phonon and electron subsystems results in the reduction of the saturated current and the destruction of the step-like behavior of the current. It is also observed that the detuning can improve the magnitude of the current by compensating the mismatch of the quantum dots energy levels induced by the electron-phonon interaction.

关键词： quantum dot electron-phonon interaction Keldysh nonequilibrium Green function formalism,current-voltage characteristic

Improved hybrid position/force controller design of a flexible robot manipulator using a sliding observer

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2009年第1期20卷 146-158页

作者： Farooq m Wang Daobo Dar N. U Coll. of Automation Engineering Nanjing Univ. of Aeronautics & Astronautics Nanjing 210016 P. R. China Coll. of mechanical Engineering Univ. of Engineering and Technology Taxila Pakistan

An improved hybrid position/force controller design of a flexible robot manipulator is presented using a sliding observer. The friction between the end effector and the environment is considered and compensated. For systematic reasons the controller is designed taking into consideration the rigid link subsystems and the flexible joints. The proposed control system satisfies the stability of the two subsystems and copes with the uncertainty of robot dynamics. A sliding observer is designed to estimate the time derivative of the torque applied as input to the rigid part of the robot. For the stability of the observer, it is assumed that the uncertainty of the observed system is bounded. A mRAC algorithm is used for the estimation of the friction forces at the contact point between the end effector and the environment. Finally simulation and experimental results are given, to demonstrate the effectiveness of the proposed controller.

关键词： force control sliding control Lyapunov stability robot end effector friction force.

Evolution of IPv6 Internet topology with unusual sudden changes

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2013年第7期22卷 602-609页

作者：艾均赵海 Kathleen m. Carley 苏湛李辉 College of Information Science and Engineering Northeastern University Institute for Software Research Carnegie Mellon University

The evolution of Internet topology is not always smooth but sometimes with unusual sudden changes. Consequently, identifying patterns of unusual topology evolution is critical for Internet topology modeling and simulation. We analyze IPv6 Internet topology evolution in IP-level graph to demonstrate how it changes in uncommon ways to restructure the Internet. After evaluating the changes of average degree, average path length, and some other metrics over time, we find that in the case of a large-scale growing the Internet becomes more robust; whereas in a top–bottom connection enhancement the Internet maintains its efficiency with links largely decreased.

关键词： scale-free network Internet topology evolution unusual evolution of Internet topology complex network analysis

Telomeres:Linking stress and survival,ecology and evolution

在线全文

学校读者我要写书评

暂无评论

Current Zoology 2010年第6期56卷 714-727页

作者： mark F.HAUSSmANN Nicole m.mARCHETTO Department of Biology Bucknell University

Telomeres are protective structures at the ends of eukaryotic chromosomes. The loss of telomeres through cell division and oxidative stress is related to cellular aging, organismal growth and disease. In this way, telomeres link molecular and cellular mechanisms with organismal processes, and may explain variation in a number of important life-history traits. Here, we discuss how telomere biology relates to the study of physiological ecology and life history evolution. We emphasize current knowledge on how telomeres may relate to growth, survival and lifespan in natural populations. We finish by examining interest- ing new connections between telomeres and the glucocorticoid stress response. Glucocorticoids are often employed as indices of physiological condition, and there is evidence that the glucocorticoid stress response is adaptive. We suggest that one way that glucocorticoids impact organismal survival is through elevated oxidative stress and telomere loss. Future work needs to establish and explore the link between the glucocorticoid stress response and telomere shortening in natural populations. If a link is found, it provides an explanatory mechanism by which environmental perturbation impacts life history trajectories [Current Zoology 56 （6）： 714-727, 2010].

关键词： Corticosterone Stress Survival Telomeres

Domino Tiling:A New method of Real-Time Conforming mesh Construction for Rendering Changeable Height Fields

在线全文

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2011年第6期26卷 971-987页

作者： Dorde m. Durdevi Igor I. Tartalja School of Electrical Engineering University of Belgrade

In this paper we present a novel GPU-oriented method of creating an inherently continuous triangular mesh for tile-based rendering of regular height fields. The method is based on tiling data-independent semi-regular meshes of non-uniform structure, a technique that is quite different from other mesh tiling approaches. A complete, memory efficient set of mesh patterns is created by an off-line procedure and stored into the graphics adapter＇s memory at runtime. At rendering time, for each tile, one of the precomputed mesh patterns is selected for rendering. The selected mesh pattern fits the required level of details of the tile and ensures seamless connection with other adjacent mesh patterns, like in a game of dominoes. The scalability potential of the proposed method is demonstrated through quadtree hierarchical grouping of tiles. The efficiency is verified by experimental results on height fields for terrain representation, where the method achieves high frame rates and sustained triangle throughput on high resolution viewports with sub-pixel error tolerance. Frame rate sensitivity to real-time modifications of the height field is measured, and it is shown that the method is very tolerant and consequently well tailored for applications dealing with rapidly changeable phenomena represented by height fields.

关键词： graphics data structures and data types height field surface representation level of details real-time heightfield manipulation view-dependent rendering

Nonlinear Dust Acoustic Waves in a magnetized Dusty Plasma with Trapped and Superthermal Electrons

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2014年第6期16卷 545-551页

作者： S.Ahmadi ABRISHAmI m.Nouri KADIJANI Islamic Azad University Torbateheydarieh Branch Torbateheydarieh Young Researchers and Elite Club Kashmar Branch Islamic Azad University

In this work, the effects of superthermal and trapped electrons on the oblique propa- gation of nonlinear dust-acoustic waves in a magnetized dusty （complex） plasma are investigated. The dynamic of electrons is simulated by the generalized Lorentzian （k） distribution function （DF）. The dust grains are cold and their dynamics are simulated by hydrodynamic equations. Using the standard reductive perturbation technique （RPT） a nonlinear modified Korteweg-de Vries （mKdV） equation is derived. Two types of solitary waves; fast and slow dust acoustic solitons, exist in this plasma. Calculations reveal that compressive solitary structures are likely to propagate in this plasma where dust grains are negatively （or positively） charged. The properties of dust acoustic solitons （DASs） are also investigated numerically.

关键词： dust acoustic wave trapped electrons superthermal electrons kappa distribution function