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Research into a theoretical mode of coherent structures in the wall region of a turbulent boundary layer induced by a wall local disturbance

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Progress in Natural science:Materials International 2009年第9期19卷 1119-1124页

作者： Changgen Lua,*, Qinjuan Qi b a college of Atmospheric sciences, Nanjing university of Information science & technology, Nanjing 210044, china b college of Public Management, Nanjing university of Information science & technology, Nanjing 210044, china college of Atmospheric sciences Nanjing University of Information Science & Technology Nanjing 210044 China college of Public Management Nanjing University of Information Science & Technology Nanjing 210044 China

The idea of applying direct numerical simulation (DNS), a theoretical mode of coherent structures in the wall region of a turbulent boundary layer, has been discussed in the literature. The various aspects of the formation mechanism of the coherent structures agree well with both DNS and experimental results. In addition, a close relationship has been found between the evolutional characteristics and factors such as the magnitude and structural distribution of the wall local impulse disturbance, and the amount of energy a local disturbance introduces into the wall region. Moreover, these parameters play key roles in the formation of coherent structures near the wall region of a turbulent boundary layer. Therefore, the wall local impulse disturbance provides a theoretical model for triggering the formation of coherent structures in the wall region of a turbulent boundary layer.

关键词： Turbulent boundary layer Wall region Coherent structure Local disturbance

Boundary conditions for the bending of a piezoelectric beam

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science china(Physics,Mechanics & Astronomy) 2008年第7期51卷 847-856页

作者： GAO Yang1, XU SiPeng2 & ZHAO BaoSheng3 1 college of science, china Agricultural university, Beijing 100083, china 2 college of Engineering, Ocean university of china, Qingdao 266071, china 3 School of Mechanical Engineering, university of science and technology Liaoning, Anshan 114044, china college of science China Agricultural University Beijing China college of Engineering Ocean University of China Qingdao China School of Mechanical Engineering University of Science and Technology Liaoning Anshan China

For beam bending in transversely isotropic piezoelectric media, the reciprocal theorem and the general solution of piezoelasticity are applied in a novel way to obtain the appropriate stress and mixed boundary conditions accurate to all orders for the beam of general edge geometry and loadings. By generalizing the method developed by Gregory and Wan, a set of necessary conditions on the edge-data for the existence of a rapidly decaying solution is established. The prescribed edge-data of the beam must satisfy these conditions in order that they could generate a decaying state within the beam. When stress and mixed conditions are imposed on the beam edge, these decaying state conditions for the case of bending deformation of piezoelectric beam are derived explicitly. They are then used for the correct formulation of boundary conditions for the beam theory solution (or the interior solution). Besides, an analytical solution of elastic beam is formulated to verify validity of our boundary conditions. For the stress data, our boundary conditions coincide with those obtained in conventional forms of beam theories. More importantly, the appropriate boundary conditions with two sets of mixed edge-data are obtained for the first time.

关键词： boundary conditions beam bending piezoelectric media decaying states regular states

Chaos correlation optical time domain reflectometry

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science china(Information sciences) 2010年第2期53卷 398-404页

作者： WANG AnBang & WANG YunCai Department of Physics, college of science, Taiyuan university of technology, Taiyuan 030024, china Department of Physics College of Science Taiyuan University of Technology

We propose a novel correlation optical time domain reflectometry (C-OTDR) of using broadband chaotic light. This reflectometry has the advantage over the conventional OTDR and the pseudorandom signal C-OTDR in range-independent spatial resolution. We employ a laser diode with feedback from a long fiber ring cavity as the source of chaotic probe light. Experimental and numerical studies show that the chaotic light has broad and flat spectrum, and excellent correlation properties. Using this broadband chaotic laser, we experimentally demonstrate the proposed chaos C-OTDR for locating the fiber reflection events, and analyze the spatial resolution and dynamic range. The results show that the chaos C-OTDR can realize a range-independent resolution of 6 cm and its dynamic range is at least 25 km.

关键词： optical time domain reflectometry chaos laser diode optical feedback

Application of annexation principle to the study of thermodynamic properties of Ag-Bi-In metallic melts

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Journal of university of science and technology Beijing 2003年第1期10卷 18-20页

作者： Jian ZhangMetallurgy school, university of science and technology Beijing, Beijing 100083, china Metallurgy school University of Science and Technology Beijing Beijing 100083 China

Based on the measured activities, the phase diagrams and the annexation principle, the calculating models of mass action concentrations for Ag-Bi and Ag-Bi-In melts have been formulated. The calculated results agree with practice and obey the mass action law, showing that the models formulated can reflect the structural characteristics of both melts. Meanwhile, it confirms that annexation principle is applicable to the Ag-Bi-In metallic melts. The melts involving eulectic which give rise to phase separation, and in which activities exhibit positive deviation from Raoult's law is the basic cause of melts transforming from homogeneous to heterogeneous ones.

关键词： the mass action law annexation principle two phase melts activity, mass action concentration

TYPE X MONOTONE SYSTEMS WITH AN ORDER-INCREASING INVARIANT FUNCTION

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Chinese Annals of Mathematics,Series B 1996年第3期17卷 335-342页

作者： JIANG JIFA(Department of Mathematics, The university of science and technology of china, Hefei 230036, china.) Department of Mathematics University of Science and Technology of China Hefei 230036 China

The author considers the asymptotic behavior of solutions of a class of ordinary dmerentialequations x = F(x) in the nonnegative orthant R7. Suppose that F(o) = o, Fi(x1,..., xn) isnondecreasing in xk for all k≠ i and that F possesses an order-increasing invarian *** it is shown that every bounded solution to such a system converges to a single equilibrium.

关键词： Type K monotone system Monotone flow Invariant function Equilibrium Convergence

Laser-field-induced magnon amplification in a magnetic semiconductor quantum well under an external magnetic field

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Journal of university of science and technology Beijing 2003年第5期10卷 69-72页

作者： Peng FengPhysics Department, university of science and technology Beijing, Beijing 100083, china Phys. Dept. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The laser-field induced magnon amplification in a magnetic semiconductorquantum well under an external magnetic field was discussed, it is shown that when the laserfrequency is near to the electron cyclotron frequency, no matter how weaker the laser field is, themagnon amplification always occurs. In case of fixed laser frequency, the optical absorption ofmagnons obeys the definite selection rule to the laser field strength. The rate of change of magnonoccupation is calculated, and the amplification condition is given.

关键词： magnon amplification magnetic semiconductor quantum well laser field

SINE TRANSFORM MATRIX FOR SOLVING TOEPLITZ MATRIX PROBLEMS

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Journal of Computational Mathematics 2001年第2期19卷 167-176页

作者： Li-zhi Cheng (Department of Mathematics & System sciences, National university of Defence technology, changsha 410073, china) 国防科技大学湖南长沙 410073

Provides information on a study which discussed the properties of eigenvalues for the solutions of symmetric positive definite Toeplitz systems, skew circulant and sine transform based properties. Eigenvalues of various preconditioners; Design of positive sine transform based preconditioners; Clustering property of the preconditioners; Numerical results.

关键词： preconditioner Toeplitz systems the fast sine transform conjugate gradient algorithm

Calculating model of mass action concentrations for Ag-Au-Cu melts

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Rare Metals 2002年第1期21卷 43-47页

作者： ZHANG Jian Metallurgy School, university of science and technology Beijing, Beijing 100083, china Metallurgy School University of Science and Technology Beijing 北京 100083

Based on phase diagrams and measured activities, the calculatingmodel of mass action concentrations for het- erogeneous meltsAg-Au-Cu was formulated. Calculated results agree with the improvedresults of recent research work, Showing that the model formulatedcan reflect the structural characteristics of these melts. In thismodel, without the help Of any empirical parameters, only threeequilibrium constants are used, hence it is simple, lear, andfavorable to the sim- Plification of calculation.

关键词： activity mass action concentration eutectic Solid solution

Application of the annexation principle to the study of thermodynamic properties of ternary metallic melts In-Pb-Ag and In-Bi-Sb

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Rare Metals 2002年第2期21卷 142-151页

作者： ZHANG JianMetallurgical Engineering school.university of science and technology Beijing, Beijing 100083, china Metallurgical Engineering School University of Science and Technology Beijing 北京 100083

Based on the phase diagrams, measured activities an the annexationprinciple, the calculating models of mass action concentrations forin-Pb-Ag and In-Bi-Sb ternary metallic melts have been *** results of calculation both agree with practice, and obey the lawof mass action, showing that the models formulated can reflect thestructural reality of the corresponding melts and the annexationprinciple is applicable to the them.

关键词： activity mass action concnetration th annexation principle In-PB-Ag