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Buckling analysis of the shell of a refuge chamber in a coal mine under uniform axial compression

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International Journal of Mining Science and Technology 2012年第1期22卷 85-88页

作者： Fang Haifeng Ge Shirong Cai Lihua Hu Eryi School of mechanical and electrical engineering China University of Mining&TechnologyXuzhou 221116China

A stiffened cylindrical shell is normally used in refuge chambers of a coal mine. Based on the method of application and shape characteristics of a refuge chamber, we simplified its shell as an orthotropic cylinder. The basic buckling equation of the stiffened cylindrical shell under uniform axial compression was deduced by using a Donnell function. The factors affecting its buckling capacity were studied by theoretical analysis and numerical calculations. The results reveal that the torsional rigidity of the longitudinal stiffener had little effect on the buckling capacity of the shell and that the critical load of an externally stiffened cylindrical shell is higher than that of an internally stiffened cylindrical shell.

关键词： Refuge chamber Buckling Axial compression Stiffened cylindrical shell

Research on the cutting force of a pick

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Mining Science and Technology 2009年第4期19卷 514-517页

作者： LIU Song-yong DU Chang-long CUI Xin-xia School of mechanical and electrical engineering China University of Mining ＆ Technology Xuzhou Jiangsu 221008 China

Cutting tests were done using a test bed designed to measure pick cutting forces when cutting coal and *** test equipment has a drum with two starting helical *** forces on a pick were measured as a function of coal compressive strength,pick carbide tip diameter and the cutting depth per drum *** results show that the cutting force is linearly related to the compressive *** relationship between the cutting force and both the carbide tip diameter and the cutting depth are *** in the cutting force does not increase with coal compressive strength but it has a linear relationship to tip diameter.A plot of cutting force fluctuations versus the cutting depth follows a sigmoidal *** on the analysis of these test results a theoretical basis is supplied for design and effective use of shearer drums.

关键词： pick cutting force shearer cutting theory carbide tip diameter cutting depth

Approximate policy iteration:a survey and somenew methods

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控制理论与应用（英文版） 2011年第3期9卷 310-335页

作者： Dimitri P.BERTSEKAS Department of electrical engineering and Computer Science Massachusetts Institute of Technology

We consider the classical policy iteration method of dynamic programming(DP),where approximations and simulation are used to deal with the curse of *** survey a number of issues:convergence and rate of convergence of approximate policy evaluation methods,singularity and susceptibility to simulation noise of policy evaluation,exploration issues,constrained and enhanced policy iteration,policy oscillation and chattering,and optimistic and distributed policy *** discussion of policy evaluation is couched in general terms and aims to unify the available methods in the light of recent research developments and to compare the two main policy evaluation approaches:projected equations and temporal differences(TD),and *** the context of these approaches,we survey two different types of simulation-based algorithms:matrix inversion methods,such as least-squares temporal difference(LSTD),and iterative methods,such as least-squares policy evaluation(LSPE) and TD(λ),and their scaled *** discuss a recent method,based on regression and regularization,which recti?es the unreliability of LSTD for nearly singular projected Bellman *** iterative version of this method belongs to the LSPE class of methods and provides the connecting link between LSTD and *** discussion of policy improvement focuses on the role of policy oscillation and its effect on performance *** illustrate that policy evaluation when done by the projected equation/TD approach may lead to policy oscillation,but when done by aggregation it does *** implies better error bounds and more regular performance for aggregation,at the expense of some loss of generality in cost function representation *** aggregation provides the connecting link between projected equation/TD-based and aggregation-based policy evaluation,and is characterized by favorable error bounds.

关键词： Dynamic programming Policy iteration Projected equation Aggregation Chattering Regularization

Reactive wetting behaviors of Sn/Cu systems: A molecular dynamics study

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Nano-Micro Letters 2010年第2期2卷 60-67页

作者： J.Y.Hsieh J.L.Chen C.Chen H.C.Lin S.S.Yang C.C.Hwang Department of mechanical engineering Ming Hsin University of Science and Technology institute of Precision Mechatronic engineering Ming Hsin University of Science and Technology Department of mechanical engineering Wu Feng Institute of Technology Department of Information Management Meiho Institute of Technology Department of engineering Science National Cheng Kung University

Influences of temperature and Sn-Cu droplet's composition on reactive wettings of Cu(100), Cu(110), and Cu(111) surfaces were analyzed, by using molecular dynamics(MD) calculations. As a result, the spreading on Cu(110)(Cu(100)) has the fastest(slowest) wetting kinetics. A higher temperature or a diluter Cu content in the Sn-Cu alloy droplet results in a higher wettability. Moreover, this work has addressed a theory for positioning the interface separating the liquidus and solidus alloys in the spreading film to confirm the hypothesis that the reactive wetting will come to the end when the interface saturates with the temperature-dependent solidus weight fraction of Cu.

关键词： Wetting Surface alloying Molecular dynamics Droplet

Fatigue crack propagation of new aluminum lithium alloy bonded with titanium alloy strap

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Chinese Journal of Aeronautics 2013年第3期26卷 601-605页

作者： Sun Zhenqi Huang Minghui School of mechanical and electrical engineering Central South University State Key Laboratory of High Performance Complex Manufacturing Central South University

A new type of aluminum lithium alloy （Al–Li alloy） Al–Li–S–4 was investigated by test in this paper. Alloy plate of 400 mm · 140 mm · 6 mm with single edge notch was made into samples bonded with Ti–6Al–4V alloy （Ti alloy） strap by FM 94 film adhesive after the surface was treated. Fatigue crack growth of samples was investigated under cyclic loading with stress ratio （R） of 0.1 and load amplitude constant. The results show that Al–Li alloy plate bonded with Ti alloy strap could retard fatigue crack propagation. Retardation effect is related with width and thickness of strap. Flaws have an observable effect on crack propagation direction.

关键词： Aluminum lithium alloy Bonding Fatigue crack growth Fatigue life Stiffness ratio

Gaussian broadcast channel with lossy state reconstruction

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Digital Communications and Networks 2019年第3期5卷 176-182页

作者： Viswanathan Ramachandran Department of electrical engineering Indian Institute of Technology Bombay India

We consider a state reconstruction problem where the additive state process of a Gaussian Broadcast Channel (GBC) is to be reconstructed at both receivers, subject to some distortion constraints. The state process we consider is Gaussian, independently and identically distributed, and known fully a-priori at the encoder. Each receiver has to perform a lossy estimation, to within some prescribed distortion tolerance under a squared error distortion criterion. The set-up also involves communicating messages across to the receivers, in addition to the estimation. The optimal trade-off between the distortions incurred at the receivers and the rates at which messages can be communicated, is of interest. We provide a complete characterization of the optimal rate vs. distortion performance.

关键词： Broadcast channel State transmission Dirty paper coding MMSE estimation

Optimal Control of Nonlinear Inverted Pendulum System Using PID Controller and LQR: Performance Analysis Without and With Disturbance Input

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International Journal of Automation and computing 2014年第6期11卷 661-670页

作者： Lal Bahadur Prasad Barjeev Tyagi Hari Om Gupta Department of electrical engineering Indian Institute of Technology Roorkee Uttarakhand 247667 India

Linear quadratic regulator(LQR) and proportional-integral-derivative(PID) control methods, which are generally used for control of linear dynamical systems, are used in this paper to control the nonlinear dynamical system. LQR is one of the optimal control techniques, which takes into account the states of the dynamical system and control input to make the optimal control *** nonlinear system states are fed to LQR which is designed using a linear state-space model. This is simple as well as robust. The inverted pendulum, a highly nonlinear unstable system, is used as a benchmark for implementing the control methods. Here the control objective is to control the system such that the cart reaches a desired position and the inverted pendulum stabilizes in the upright position. In this paper, the modeling and simulation for optimal control design of nonlinear inverted pendulum-cart dynamic system using PID controller and LQR have been presented for both cases of without and with disturbance input. The Matlab-Simulink models have been developed for simulation and performance analysis of the control schemes. The simulation results justify the comparative advantage of LQR control method.

关键词： Inverted pendulum nonlinear system proportional-integral-derivative (PID) control optimal control linear quadratic regulator (LQR)

Multiple recollisions in nonsequential double ionization below the recollision-ionization threshold

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Chinese Physics B 2021年第12期30卷 392-398页

作者： Xiao-Meng Ma Ai-Hong Tong Zhuo Wang Chun-Yang Zhai Department of Physics and mechanical&electrical engineering Hubei University of EducationWuhan 430205China institute of Optoelectronic Materials and Components Hubei University of EducationWuhan 430205China College of Physics and Electronic engineering Xinyang Normal UniversityXinyang 464000China

By using the three-dimensional classical ensemble model,the recollision dynamics in nonsequential double ionization(NSDI)of Ar by 780-nm laser pulses at(6-1.2)×10^(14)W/cm^(2) was extensively *** revealed the picture of multiplerecollision in the double ionization events at the laser intensity region below the recollision-ionization *** tracing the NSDI trajectories,it was found that the contribution of these multiple-recollision events increases as the laser intensity *** this low intensity region,many multiple-recollision induced NSDI trajectories occur through the doubly excited *** decay speed of the doubly excited state decreases with the decreasing laser intensity.

关键词： nonsequential double ionization multiple recollision

Investigation of Ionic Polymer Metal Composite Actuators Loaded with Various Tetraethyl Orthosilicate Contents

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Journal of Bionic engineering 2012年第1期9卷 75-83页

作者： Qingsong He Min Yu Yuxiu Li Yan Ding Dongjie Guo Zhendong Dai institute of Bio-inspired Structure and Surface engineering Nanjing University of Aeronautics ＆ Astronautics Nanjing 210016 P. R. China College of mechanical and electrical engineering Nanjing University of Aeronautics ＆ Astronautics Nanjing 210016 P. R. China

Ionic Polymer Metal Composite （IPMC） can be used as an electrically activated actuator, which has been widely used in artificial muscles, bionic robotic actuators, and dynamic sensors since it has the advantages of large deformation, light weight, flexibility, and low driving voltage, etc. To further improve the mechanical properties of IPMC, this paper reports a new method for preparing organic-inorganic hybrid Nafion/SiO2 membranes. Beginning from cast Nation membranes, IPMCs with various tetraethyl orthosilicate （TEOS） contents were fabricated by electroless plating. The elastic moduli of cast Nation membranes were measured with nano indenters, the water contents were calculated, and the cross sections of Nation membranes were observed by scanning electron microscopy. The blocking force, the displacement, and the electric current of IPMCs were then measured on a test apparatus. The results show that the blocking force increases as the TEOS content gradually increases, and that both the displacement and the electric current initially decrease, then increase. When the TEOS content is 1.5%, the IPMC shows the best improved mechanical properties. Finally, the IPMC with the best improved performance was used to successfully actuate the artificial eye and tested.

关键词： IPMC TEOS mechanical property artificial eye