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OPTIMUM CONTROL TO A PARTIALLY CONTROLLED TURBOGENERATOR SHAFT TORSIONAL VIBRATION SYSTEM

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Chinese Journal of mechanical engineering 2002年第1期15卷 66-68页

作者： Hao Zhiyong Gao Wenzhi school of mechanical engineering，tianjin university，tianjin 300072，china school of mechanical engineering Tianjin University 天津 300072

The optimal control to a partially controlled turbogenerator shaft torsionalvibration system is investigated. The principle of input feedforward control is presented to achievethe minimum of the average vibration energy in a system, and the optimal control matrix of thesystem is derived. A turbogenerator shaft system is taken as an example to simulate the optimalcontrol process of the torsional vibration. Results from this simulation indicate that the vibrationcan be effectively controlled by a partial control strategy.

关键词： Optimal control Partially controlled system Torsional vibration Turbogenerator

Simplest Normal Forms of Generalized Neimark-Sacker Bifurcation

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Transactions of tianjin university 2009年第4期15卷 260-265页

作者：丁玉梅张琪昌 school of mechanical engineering Tianjin University school of Sciences Tianjin University of Science and Technology

The normal forms of generalized Neimark-Sacker bifurcation are extensively studied using normal form theory of dynamic system. It is well known that if the normal forms of the generalized Neimark-Sacker bifurcation are expressed in polar coordinates, then all odd order terms must, in general, remain in the normal forms. In this paper, five theorems are presented to show that the conventional Neimark-Sacker bifurcation can be further simplified. The simplest normal forms of generalized Neimark-Sacker bifurcation are calculated. Based on the conventional normal form, using appropriate nonlinear transformations, it is found that the generalized Neimark-Sacker bifurcation has at most two nonlinear terms remaining in the amplitude equations of the simplest normal forms up to any order. There are two kinds of simplest normal forms. Their algebraic expression formulas of the simplest normal forms in terms of the coefficients of the generalized Neimark-Sacker bifurcation systems are given.

关键词： generalized Neimark-Sacker bifurcation simplest normal form near identity nonlinear transformations

Mechanism of Breakdown in Laminar-Turbulent Transition of Incompressible Boundary Layer on a Flat Plate

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Transactions of tianjin university 2007年第2期13卷 79-87页

作者：唐洪涛罗纪生周恒 school of mechanical engineering Tianjin University

Temporal mode direct numerical simulation was done for the process of laminar-turbulent transition in an incompressible boundary layer on a flat plate. The analysis of the results showed that during the breakdown process of laminar-turbulent transition, the modification of the mean flow profile by the disturbances led to a remarkable change in its stability characteristics, manifested in the significant enlargement of the linear unstable zone and the maximum amplification rate, and led to that many more disturbances were excited and enhanced rapidly, correspondingly the turbulent energy also increased rapidly, and the mean flow profiles evolved swiftly from laminar to turbulent. It was also found that if the oblique waves in the initial disturbances did not form symmetrical pairs, the subsequent span-wise mean velocities would, in general, be nonzero due to nonlinear interaction, which would have a great effect on the stability characteristics and also implied that the turbulence obtained by direct numerical simulation might not be fully a random process.

关键词： boundary layer transition direct numerical simulation breakdown

Impulsive Homoclinic Chaos in Van der Pol Jerk System

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Transactions of tianjin university 2010年第6期16卷 457-460页

作者：丁玉梅张琪昌 school of mechanical engineering Tianjin University school of Sciences Tianjin University of Science and Technology

A 3D continuous autonomous chaotic system is reported, which contains a cubic term and six system parameters. Basic dynamic properties of the new Van der Pol Jerk system are studied by means of theoretical analysis and numerical simulation. Based on the Silnikov theorem, the chaotic characterisitics of the dynamic system are discussed. Using Cardano formula and series solution of differential equation, eigenvalue problem and the existence of homoclinic orbit are studied. Furthermore, a rigorous proof for th...

关键词： chaotic system homoclinic orbit Silnikov theorem

A study on odd-parity high-lying states of the Sm atom with three-color resonant excitation

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Science china(Physics,Mechanics & Astronomy) 2011年第6期54卷 1124-1130页

作者： LI Ming 1,2,DAI ChangJian 1,2 & XIE Jun 1,2 1 Key Laboratory of Display Materials and Photoelectric Devices,Ministry of education,tianjin 300191,china 2 school of Science,tianjin university of technology,tianjin 300384,china 1. Key Laboratory of Display Materials and Photoelectric Devices Ministry of Education Tianjin 300191 China2. School of Science Tianjin University of Technology Tianjin 300384 China

The odd-parity high-lying states of the Sm atom are investigated systematically by a three-color resonant excitation scheme with two different excitation *** two intermediate states,4f 6 6s7s 7 F 0 and 4f 6 6s7s 7 F 1 are employed for paths I and II,***-seven bound states are detected with paths I and II in the energy range between 44188 and 45515 cm 1,while 64 autoionizing states are found in the energy range from 45528 to 45761 cm *** only the level energies of all observed states,but also the line widths of autoionizing states are *** possible impact of configuration interaction on the line shape of autoionizing states is also *** addition,the total angular momentum is assigned uniquely to most of the states,whereas the information about the relative line intensity of all states is also presented.

关键词： high-lying states odd-parity the Sm atom resonant excitation

Effect of Lead Contents on the Properties of PMSZT Piezoelectric Ceramics

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Journal of Wuhan university of technology(Materials Science) 2007年第2期22卷 311-314页

作者：陆翠敏 school of Materials Science and engineering Tianjin University of Technology

The effects of Pb content on crystallographic phase, microstructure, electric-properties of PMSZT piezoelectric ceramics were studied. The crystallographic phase and microstructure of the ceramics were examined by using X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The experimental result shows that the samples consist of a mixture of tetragonal and rhombohedral phases in the range of lead contents x=0.95-1.06, grains grow up homogeneously and the minimum value of Curie temperature was obtained with x-=1.02. With Pb content x〈l.02 or x〉1.02, the Curie temperature moves towards a high temperature. A well-situated electric-properties of ET33/E0 （1660）, d33 （344pC/N）, Kp （0.684）, Qm （2350）,tan 3（0.0030） were obtained when lead content x=1.02.

关键词： piezoelectric ceramics crystallographic phase microstructure electric-properties

GENERALIZED SIMULATION MODEL FOR MILLED SURFACE TOPOGRAPHY-APPLICATION TO PERIPHERAL MILLING

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Chinese Journal of mechanical engineering 2001年第2期14卷 121-126页

作者： Xu Anping Qu Yunxia Li Weimin school of mechanical engineering, Hebei university of technology Zhang Dawei Huang Tian tianjin university 河北工业大学机械学院天津天津大学天津

Based on analyzing various factors influencing milled surface topography, firstly, a generalized model for milled surface topography is proposed. Secondly, using the principles of transformation matrix and vector operation, the trajectory equation of cutting edge relative to workpiece is derived. Then, a three dimensional topography simulation algorithm is constructed through dividing the workpiece into regular grids. Finally, taking the peripheral milling process as an example, the generalized model is simplified, and the corresponding simulation examples are given. The results indicate that it is very efficient for the generalized model to be used to analyze and simulate the peripherally milled surface topography.

关键词： Generalized simulation model Arbitrary contour mill Peripheral milling process Surface topography

Piezoelectric Actuator/Sensor Wave Propagation Based Nondestructive Active Monitoring Method of Concrete Structures

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Journal of Wuhan university of technology(Materials Science) 2011年第3期26卷 541-547页

作者：朱劲松 school of Civil engineering Tianjin University Key Laboratory of Coast Civil Structure Safety(tianjin university) Ministry of Education

In order to monitor the basic mechanical properties and interior damage of concrete structures,the piezoelectric actuator/sensor based wave propagation method was investigated experimentally in the laboratory using a specifically designed test *** energy attenuation of stress waves was measured by the relative index between the output voltage of sensors and the excitation voltage at the *** on the experimental results of concrete cube and cylinder specimens,the effect of excitation frequencies,excitation amplitude,wave propagation paths and the curing age on the output signals of sensors are *** results show that the relative voltage attenuation coefficient RVAC is an effective indicator for measuring the attenuation of stress waves through the interior of concrete.

关键词： piezoceramics actuator/sensor wave propagation method non-destructive evaluation (NDE) active monitoring concrete

X-ray and Magnetoresistance Measurements of Electrodeposited Cu-Co Granular Films

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Journal of Materials Science & technology 2005年第3期21卷 307-310页

作者： Suwei YAO, Haixia WU, Weiguo ZHANG and Hongzhi WANG Sugiyama Laboratory of Surface technology, Department of Applied Chemistry, school of Chemical engineering and technology, tianjin university, tianjin 300072, china Department of Applied Chemistry School of Chemical Engineering and Technology Tianjin University Tianjin 300072 China

Granular CoxCu1-x alloy films were prepared by electrodeposition at room temperature directly onto semiconducting Si substrate. X-ray diffraction (XRD) revealed that the as-deposited films formed single phase metastable fcc alloy structure. The fcc lattice parameter α was found to decrease linearly with increasing Co concentration x in the studied range. The giant magnetoresistance (GMR) of the films was improved after annealing. Pure Co fcc diffraction peaks were observed in the diffractogram of the annealed sample, indicating phase separation occurred upon annealing. The optimal annealing temperature was 450℃. The maximum of magnetoresistance (MR) ratio 8.21% was obtained for the Co20Cu80 thin film after annealing at 450℃ for 1 h. The saturation field decreased upon annealing in the MR curves of Co20Cu80 film.

关键词： Electrodeposition Giant magnetoresistance (GMR) Granular Phase separation