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Parameter influence on electron collection efficiency of a bare electrodynamic tether

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Science China(Information Sciences) 2018年第2期61卷 24-35页

作者： Gangqiang LI zheng h.ZhU Department of Earth and Space Science and Engineering York University Department of Mechanical Engineering York University

This study develops a coupled multiphysics finite element method for the dynamic analysis of a bare flexible electrodynamic tether. Contrary to the existing methods, the new method discretizes and solves the orbital motion limited equation and the dynamic equation of an elastic flexible tether ***, the new method is verified via comparison with the existing methods in a straight tether ***, the number of tether elements, tether bending deformation, and two design parameters at the cathodic end affecting the electrical current are investigated. It is determined that the tether bending deformation and the two parameters i.e., the impedance ZT and ΦPWhave a significant impact on the electron collection efficiency of an electrodynamic tether system. The results indicate that the proposed method should be applied in the refined mission analysis.

关键词： multiphysics coupled finite element electrodynamic tether electron collection efficiency

Libration and end body swing stabilization of a parallel partial space elevator system

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Chinese Journal of Aeronautics 2021年第3期34卷 187-199页

作者： Gefei ShI Gangqiang LI zheng h.ZhU School of Aeronautics and Astronautics Sun Yat-Sen UniversityGuangzhou 510275China Department of Mechanical Engineering York UniversityTorontoOntario M3J 1P3Canada

This paper studies the libration and stabilization of a parallel partial space elevator system in circular orbits. The system is made up of two paralleled partial space elevators, each of which consists of one main satellite, one end body and a climber moving along the tether between *** libration characteristics of the elevator are studied through numerical analysis by a new dynamic model, and a novel control strategy is proposed to stabilize the swing of the end body by projecting the climber speeds only. Optimal control method is used to implement the new control strategy in the case where the climbers move in opposite direction. The simulation results validate the effectiveness of the proposed control strategy whose application will neither sacrifice the transport efficiency nor exacerbate libration significantly.

关键词： Libration stabilization Nonlinear dynamics Optimal control Parallel partial space elevator Space tether

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Orbital radius keeping of floating partial space elevator in cargo transposition

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Astrodynamics 2023年第3期7卷 259-269页

作者： Gefei Shi zheng h.Zhu School of Aeronautics and Astronautics Sun Yat-sen UniversityGuangzhou510275China Department of Mechanical Engineering York University4700 Keele StreetTorontoOntarioM3J 1P3Canada

A floating partial space elevator(PSE)is a PSE with a floating main *** work aims to keep the orbital radius of the main satellite of a floating PSE in cargo transposition without the use of thrusts.A six-degree-of-freedom two-piece dumbbell model was built to analyze the dynamics of a floating *** adjusting the climber’s moving speed and rolling of the end body,the main satellite’s orbital radius can be kept.A novel control strategy using a proportional shrinking horizon model predictive control law containing a self-stability modified law is proposed to stabilize both the orbital and libration states to regulate the speed of only the *** results validated the proposed control *** system provides a successful approach to the desired equilibrium by the end of the transposition.

关键词： floating partial space elevator(PSE) self-stability modified law shrinking horizon model predictive control

Convexification of hybrid AC-DC Optimal Power Flow with Line-Commutated Converters

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 617-628页

作者： hongyuan Liang Zhigang Li J.h.zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China

Line-commutated converter (LCC)-based high-voltage DC (hVDC) systems have been integrated with bulk AC power grids for interregional transmission of renewable power. The nonlinear LCC model brings additional nonconvexity to optimal power flow (OPF) of hybrid AC-DC power grids. A convexification method for the LCC station model could address such nonconvexity but has rarely been discussed. We devise an equivalent reformulation for classical LCC station models that facilitates second-order cone convex relaxation for the OPF of LCC-based AC-DC power grids. We also propose sufficient conditions for exactness of convex relaxation with its proof. Equivalence of the proposed LCC station models and properties, exactness, and effectiveness of convex relaxation are verified using four numerical simulations. Simulation results demonstrate a globally optimal solution of the original OPF can be efficiently obtained from relaxed model.

关键词： AC-DC power system convex relaxation linecommutated converter optimal power flow second-order cone programming

Dispatchable Region for Active Distribution Networks Using Approximate Second-order Cone Relaxation

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CSEE Journal of Power and Energy Systems 2023年第6期9卷 1999-2007页

作者： Zhigang Li Wenjing huang J.h.zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510640China

Uncertainty in distributed renewable generation threatens the security of power distribution *** concept of dispatchable region is developed to assess the ability of power systems to accommodate renewable generation at a given operating *** DC and linearized AC power flow equations are typically used to model dispatchable regions for transmission systems,these equations are rarely suitable for distribution *** achieve a suitable trade-off between accuracy and efficiency,this paper proposes a dispatchable region formulation for distribution networks using tight convex *** cone relaxation is adopted to reformulate AC power flow equations,which are then approximated by a polyhedron to improve ***,an efficient adaptive constraint generation algorithm is employed to construct the proposed dispatchable *** studies on distribution systems of various scales validate the computational efficiency and accuracy of the proposed method.

关键词： Dispatchable region distribution system renewable power generation second-order cone relaxation uncertainty

A Facile Convergent Approach to Octopus Polyestrone

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Chinese Chemical Letters 1997年第6期8卷 487-490页

作者： Chen, YC Weng, LL zheng, h W ChINA UNIV MED SCI SCH PHARMCHENGDU 610041PEOPLES R CHINA

Dendrimers have attracted attention in abroad area of chemistry. In this paper, octopus polyestrones were easily synthesized in a novel convergent strategy.

关键词： OCh Mhz hMR A Facile Convergent Approach to Octopus Polyestrone IR

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Bi-block positive semidefiniteness of bi-block symmetric tensors

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Frontiers of Mathematics in China 2021年第1期16卷 141-169页

作者： zheng-hai h UANG Xia LI Yong WANG School of Mathematics Tianjin UniversityTianjin 300354China

The positive definiteness of elasticity tensors plays an important role in the elasticity *** this paper,we consider the bi-block symmetric tensors,which contain elasticity tensors as a ***,we define the bi-block M-eigenvalue of a bi-block symmetric tensor,and show that a bi-block symmetric tensor is bi-block positive(semi)definite if and only if its smallest bi-block M-eigenvalue is(nonnegative)***,we discuss the distribution of bi-block M-eigenvalues,by which we get a sufficient condition for judging bi-block positive(semi)definiteness of the bi-block symmetric tensor ***,we show that several classes of bi-block symmetric tensors are bi-block positive definite or bi-block positive semidefinite,including bi-block(strictly)diagonally dominant symmetric tensors and bi-block symmetric(B)*** give easily checkable sufficient conditions for judging bi-block positive(semi)definiteness of a bi-block symmetric *** a byproduct,we also obtain two easily checkable sufficient conditions for the strong ellipticity of elasticity tensors.

关键词： Bi-block symmetric tensor bi-block symmetric Z-tensor bi-block symmetric B 0-tensor diagonally dominant bi-block symmetric tensor bi-block M-eigenvalue

Rapid Growth of TiNi intermetallic compound within undercooled Ti_(50)Ni_(50)alloy under electrostatic levitation condition

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Journal of Materials Science & Technology 2021年第18期77卷 82-89页

作者： P.F.Zou C.h.zheng L.hu h.P.Wang School of Physical Science and Technology Northwestern Polytechnical University.Xi'an710072China

The undercooling dependence of the solidification mechanism was systematically explored by the electrostatic levitation(ESL)*** the experiments,the maximum undercooling reached up to 406 K(0.26 T_L)and the growth velocity of the primary TiNi phase was in-situ determined at various *** the initial increase of alloy undercooling,the value of growth velocity sluggishly rose followed by a power *** this case,the primary TiNi phase preferentially developed as the equiaxed dendrite,then the remnant liquid participated as Ti_(2)Ni andα-Ti phases on the grain *** the undercooling exceeded the critical value of 350 K,the growth velocity of the primary phase displayed a sharply increase ***,the TEM results demonstrated that the precipitation of the intermetallic Ti_(2)Ni compound was gradually restrained during the rapid solidification and the R-phase existing in the TiNi matrix at large undercooling implied that the martensitic transformation was incomplete.

关键词： Undercooling Ti-Ni alloy Solidification Growth kinetics

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ThE SYNThESIS OF STEROID-OLIGOPEPTIDE

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Chinese Chemical Letters 1995年第8期6卷 663-666页

作者： Zhang, X Weng, LL zheng, h Guangdong Med Coll Dept Biochem Zhanjiang 524023 Peoples R China W China Univ Med Sci Sch Pharm Chengdu 610041 Peoples R China

Six new compounds-steroid-oligopeptide were designed and synthesized with active ester method,their structures (CA-G(1), DCA-G(1), CA-G(2), DCA-G(2), CA-G(3), DCA-G(3)) were confirmed by spectra and elemental analysis. Preliminary study on their bioactivities showed that the DCA-G(3) his the ability of acid-inhibition and the others have the ability of promoting acid-secretion. The metabolic time of six title compounds are longer than the positive control(Boc-G(2)).

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