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SOME GENERAL THEOREMS AND GENERALIZED AND PIECEWISE GENERALIZED VARIATIONAL PRINCIPLES FOR LINEAR ELASTODYNAMICS
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作者 邢京堂 郑兆昌 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 1992年第9期825-840,共16页
From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displace... From the concept of four-dimensional space and under the four kinds of time limit conditions, some general theorems for elastodynamics are developed, such as the principle of possible work action, the virtual displacement principle, the virtual stress-momentum principle, the reciprocal theorems and the related theorems of time terminal conditions derived from it. The variational principles of potential energy action and complementary energy action, the H-W principles, the H-R principles and the constitutive variational principles for elastodynamics are obtained. Hamilton's principle, Toupin's work and the formulations of Ref. [5], [17]-[24] may be regarded as some special cases of the general principles given in the paper. By considering three cases: piecewise space-time domain, piecewise space domain, piecewise time domain, the piecewise variational principles including the potential, the complementary and the mixed energy action fashions are given. Finally, the general formulation of piecewise variational principles is derived. If the time dimension is not considered, the formulations obtained in the paper will become the corresponding ones for elastostatics. 展开更多
关键词 Boundary value problems Dynamics Mathematical models piecewise linear techniques Stresses Theory Time domain analysis Variational techniques
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Orbital maneuver strategy design based on piecewise linear optimization for spacecraft soft landing on irregular asteroids 被引量:1
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作者 Zhiwei HAO Yi ZHAO +1 位作者 Ying CHEN Qiuhua ZHANG 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第10期2694-2706,共13页
Recently,asteroid exploration becomes an important branch of human’s deep space activities.In this paper,a piecewise linear optimal orbital maneuver strategy is designed for a spacecraft soft landing on irregular-sha... Recently,asteroid exploration becomes an important branch of human’s deep space activities.In this paper,a piecewise linear optimal orbital maneuver strategy is designed for a spacecraft soft landing on irregular-shaped asteroids.First,the space around an irregular asteroid is converted into several grid units,and the gravitational field of the asteroid is linearly fitted in each unit.Then,the soft-landing orbital maneuver strategy design problem is formulated as a piecewise linear optimal problem,and further transferred into a family of two-point boundary value problems,which can be solved using collocation method.Finally,a corresponding algorithm is developed to obtain the piecewise linear optimal maneuver strategy,which is proved to be able to achieve the soft-landing mission well.Simulation results show that the error of the model linearization is small enough,while the calculation efficiency is remarkably improved,and the robustness of maneuver strategy is also improved. 展开更多
关键词 Irregular gravitational field Optimal control Orbital locations piecewise linear techniques Soft landing
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Study of periodic band gap structure of the magnetized plasma photonic crystals 被引量:3
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作者 章海峰 马力 刘少斌 《Optoelectronics Letters》 EI 2009年第2期112-116,共5页
The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-doma... The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-domain (FDTD) method. In frequency-domain, the transmission coefficients of electromagnetic Gaussian pulses are computed, and the effects of the periodic structure constant, plasma layer thickness and parameters of plasma on the properties of periodic band gaps of magnetized photonic crystals are a... 展开更多
关键词 Crystal structure Energy gap Finite difference time domain method Frequency domain analysis MAGNETOPLASMA Method of moments Photonic band gap Photonic crystals piecewise linear techniques Time domain analysis
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STREAMLINE-EQUIVORTICITY-LINE ITERATION METHOD FOR CALCULATING STEADY FLOW OF NONUNIFORM STREAM PAST A CIRCULAR CYLINDER
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作者 Zhai, Da-xi Zhao, Han-zhong 《Journal of Hydrodynamics》 SCIE EI CSCD 1991年第2期1-4,共4页
In this paper, an iteration method is presented to calculate the steady noseparation flow past a circular cylinder with brokenline-shaped velocity profile. At each iteration step, the streamlines of the last step are ... In this paper, an iteration method is presented to calculate the steady noseparation flow past a circular cylinder with brokenline-shaped velocity profile. At each iteration step, the streamlines of the last step are considered as equivorticity lines to determine the new flow field. The iterative process is stopped when certain convergence criterion is reached. Several examples are given which show the effectiveness of the method. 展开更多
关键词 Fluid Mechanics HYDRODYNAMICS Mathematical techniques piecewise Linear techniques Stream Flow
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