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15 results on '"Liu, Xuewen"'

8. Research and Implementation of Mathematical Model for Solar Running Fixing

Author

Liu Xuewen and Tian Rui

Subjects
Engineering drawing, Visual Basic, Computer science, Process (computing), Line (text file), computer, computer.programming_language
Abstract

This paper mainly expounds the mathematical model and implementation method of the solar shift line positioning. First, the process of sun-line positioning is modeled step by step. Finally, a program is written in Visual Basic language to realize the sun-line positioning based on the data recorded by the driver. A verification program is provided. I hope this article will make it easier to locate the sun's line.

Published
2020

11. Collision-Free Trajectory Design for Long-Distance Hopping Transfer on Asteroid Surface Using Convex Optimization.

Author

Liu, Xuewen, Yang, Hongwei, and Li, Shuang

Subjects
*ANT algorithms, *ASTEROIDS, *SPACE trajectories, *CONVEX surfaces, *ORBITAL transfer (Space flight), *TAYLOR'S series, *GRAVITATIONAL fields
Abstract

The irregular shapes and gravitational fields of asteroids challenge the design of collision-free asteroid surface hopping trajectories. A novel collision-free long-distance transfer trajectory design algorithm based on the convex optimization is presented in this article. A combinatorial keepout zone consisting of three spheres is defined to avoid the spacecraft colliding with the asteroid surface during the transfer. The boundary of the keepout zone is close to the surface of the target asteroid. With the Taylor expansion approximation, the nonconvex keepout zone constraint becomes convex. Two convex glide-slope constraints are employed for avoiding colliding during the ascent and descent. Thereafter, a convex optimization problem for solving a collision-free long-distance transfer trajectory between arbitrary two surface points is formulated. Moreover, an ant colony optimization algorithm combined with the proposed method is used to solve the optimal hopping sequence problem for exploring multiple points on the asteroid surface. Finally, several numerical simulation examples for the asteroid 433 Eros validate the feasibility and effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

Published
2021
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13. Multi-scale processing for network traffic with long-range dependence based on fractional differencing

Author

Liu Xuewen and Shen Lei

Subjects
Sequence, Scale (ratio), Computer science, Range (statistics), Network performance, Traffic generation model, Algorithm, Simulation, Network traffic simulation
Abstract

Network study finds simultaneous presentation of long-range dependence and short-range dependence in Network traffic., which makes the performance of the traditional model used to describe the short-range dependence for prediction lower. And in different scales of these two characteristics of network traffic have different impact for network performance. In small enough scale the short-range dependence has a greater impact on network performance, while in large enough scale, long-range dependence characteristics play a leading role. Therefore, in order to obtain better prediction this paper makes network traffic sequence more smooth and easy to be fitted by the traditional model, through weakening the dependence not affording a major role in small scale and enhancing the dependence playing a leading role in the impact of network.

Published
2010

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