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17 results on '"Liu, Jiangkai"'

10. Lunar far side positioning enabled by a CubeSat system deployed in an Earth-Moon halo orbit

Author

Chen, Hongru, Liu, Jiangkai, Long, Long, Xu, Zhenyu, Meng, Yazhe, Zhang, Hao, Chen, Hongru, Liu, Jiangkai, Long, Long, Xu, Zhenyu, Meng, Yazhe, and Zhang, Hao

Abstract

For explorations of the far side of the Moon, it is necessary to tackle the challenge of navigation and communication as the far side is invisible to the Earth. This paper proposes a low-cost mission concept that consists of four CubeSats in an Earth-Moon L2 (EML2) halo orbit. The mission objective is to provide real-time positioning service for lunar far-side assets, taking advantage of the visibility of EML2 halo orbits to both the Earth and lunar far side. Being miniature, CubeSats can be carried by a mother spacecraft and deployed during the mid-course. As CubeSat missions are generally constrained by limited communication, power, and propulsion capacities, this paper presents a feasibility study that takes into account the high-fidelity dynamical environment and system constraints. This paper analyzes the positioning performance in terms of accuracy, and spatial and temporal coverage. In addition, the requirement of deployment in terms of Dv budget and thrust magnitude is also investigated. Results show that (1) a positioning accuracy of 2.7 km is achievable; and (2) several state-of-the-art propulsion systems can meet the requirement of deployment and the stationkeeping for an acceptable duration.

Published
2021

12. High Fidelity Satellite to Satellite Tracking toolkit (HFSST) for Navigation Mission Design

Author

Wenbin Wang, Shu Leizheng, Yang Gao, and Liu Jiangkai

Subjects
Elliptic orbit, GNSS applications, Computer science, Physics::Space Physics, Real-time computing, Satellite, Satellite navigation, Satellite system, Ranging, Noise (video), Visualization
Abstract

The HFSST “High Fidelity Satellite to Satellite Tracking toolkit” is a tool for space navigation mission analysis design. The inputs of the toolkit are the configurations of the mission. The outputs are the ranging data between different satellites for navigation, as well as the reports on the performance of the system. The content of these reports include the physical visibilities, the relative geometry as well as the measurement noise between satellites participating in a mission. Physical visibilities are evaluated based on the geometric relationship between the satellites and the celestial bodies, as well as the power level of the ranging signals. Which concern the attitude pointing of the satellites, the mounting positions, directions and patterns of antennas, the signal travel losses as well as the threshold of the receiver. The toolkit also includes orbital model, attitude model, and signal model as well as visualization module. These make it suitable to develop elaborated analysis of satellite navigation missions whether near Earth or deep into space. Example from an actual mission that a satellite on High Elliptical Orbit (HEO) tracks side lobe signals of the Global Navigation Satellite System (GNSS) for navigation is demonstrated to show the features and usages of the toolkit.

Published
2018

16. α-lipoic acid protects against carbon tetrachloride-induced liver cirrhosis through the suppression of the TGF-β/Smad3 pathway and autophagy.

Author

Liu, Guangwei, Liu, Jiangkai, Pian, Linping, Gui, Songlin, and Lu, Baoping

Subjects
*LIPOIC acid, *ANTIOXIDANTS, *LIVER failure, *CARBON tetrachloride, *ASPARTATE aminotransferase
Abstract

α-lipoic acid (ALA) is a naturally occurring antioxidant with protective effects against various hepatic injuries. The aim of the present study was to investigate the mechanisms by which ALA protects the liver from carbon tetrachloride (CCl4)-induced liver cirrhosis. The widely used liver cirrhosis rat model was established via an intraperitoneal injection of 2 mg/kg 50% CCl4, three times/week for 8 weeks. Simultaneously, 50 or 100 mg/kg ALA was orally administrated to the rats every day for 8 weeks. The activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was detected in the serum. The pathological liver injuries were analyzed using hematoxylin and eosin and Masson's trichrome staining. The principal factors involved in the transforming growth factor-β (TGF-β)/mothers against decapentaplegic homolog 9 (Smad3) and protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathways and in autophagy were examined using reverse transcription-quantitative polymerase chain reaction or western blot analysis. The results demonstrated that the administration of ALA alleviated CCl4-induced liver injury, as demonstrated by decreased ALT and AST activity, improved pathological injuries and reduced collagen deposition. The CCl4-induced increase in TGF-β and phosphorylated-Smad3 expression levels was additionally inhibited by treatment with ALA. Furthermore, the administration of ALA reversed the CCl4-induced upregulation of light chain 3II and Beclin-1, and downregulation of p62. The CCl4-induced suppression of the AKT/mTOR pathway was additionally restored following treatment with ALA. In combination, the results of the present study demonstrated that ALA was able to protect CCl4-induced liver cirrhosis, an effect that may be associated with inactivation of the TGF-β/Smad3 pathway and suppression of autophagy. [ABSTRACT FROM AUTHOR]

Published
2019

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