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Performance Improvement of Delay-Tolerant Networks with Mobility Control under Group Mobility
( Ling Fu Xie ),( Peter Han Joo Chong ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.6
This paper considers mobility control to improve packet delivery in delay-tolerant networks (DTNs) under group mobility. Based on the group structure in group mobility, we propose two mobility control techniques; group formation enforcement and group purposeful movement. Both techniques can be used to increase the contact opportunities between groups by extending the group`s reachability. In addition, they can be easily integrated into some existing DTN routing schemes under group mobility to effectively expedite the packet delivery. This paper is divided into 2 parts. First, we study how our proposed mobility control schemes reduce the packet delivery delay in DTNs by integrating them into one simple routing scheme called group-epidemic routing (G-ER). For each scheme, we analytically derive the cumulative density function of the packet delivery delay to show how it can effectively reduce the packet delivery delay. Then, based on our second proposed technique, the group purposeful movement, we design a new DTN routing scheme, called purposeful movement assisted routing (PMAR), to further reduce the packet delay. Extensive simulations in NS2 have been conducted to show the significant improvement of PMAR over G-ER under different practical network conditions.
Lingli Xie,Litao Kang,Yae Li,Mangwei Cui,Bo Chang,Haiwei Jiang,Lili Gao,Xiaomin Wang,Shan Yun 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2017 NANO Vol.12 No.4
Micro-porous activated carbons (ACs) with a narrow pore size distribution of 0.4–0.6 nm and high specific surface areas (1160–1315 m2 · g-1) are prepared from environment-friendly, lowgrade potassium humate (HA-K, carbon resource) and mild activating agent potassium acetate (CH3COOK). Microstructure characterizations indicate that the introduction of activating agent CH3COOK is a key step to achieve high specific surface area and carbonization degree. These ACs contain small amount of oxygen and nitrogen, and show obvious pseudo-capacitance besides double layer capacitance. As a result, the optimized ACs achieve high specific capacitances of 311 F · g-1 and 317 F · g-1 at 0.1 A · g-1 in 2 M KOH and 1 M H2SO4 aqueous electrolytes, respectively. This sample also shows a good charge-discharge cycling stability within 10 000 cycles.
Ling-Ling Xie,Ren-Xi Gong,Hao-Ze Zhuo,Jiong-Quan Wei 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.4
An investigation of the mechanism of period-doubling bifurcation in a voltage mode controlled buck-boost converter operating in discontinuous conduction mode is conducted from the viewpoint of nonlinear dynamical systems. The discrete iterative model describing the dynamics of the close-loop is derived. Period-doubling bifurcation occurs at certain values of the feedback factor. Results from numerical simulations and experiments are provided to verify the evolution of perioddoubling bifurcation, and the results are consistent with the theoretical analysis. These results show that the buck-boost converters exhibit a wide range of nonlinear behavior, and the system exhibits a typical period-doubling bifurcation route to chaos under particular operating conditions.
Ling-Ling Xie,Xiao-Yu Cao,Li-Xu Zhang,Zhong-Xu Dai,Ling-Bo Qu 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.2
A LiV3O8/polyaniline (PAn) composite was prepared by the in-situ polymerization method assisted by sodium dodecyl sulfate and ammonium persulfate. The as-prepared powders were investigated by XRD, SEM, and galvanostatic discharge/charge analysis. It was found that the introduction of PAn to LiV3O8 can effectively buffer the mechanical stress and restrain the number of phase changes of composite material during the electrochemical cycling. Compared with pristine LiV3O8, LiV3O8/PAn composite maintains a reversible capacity of 212.1 mAh g−1 at the current density of 30 mA g−1 after 50 cycles, approximately 22.6%, much higher than the former.
Ling-Ling Xie,Yuan-Dong Xu,Jie-Jie Zhang,Cheng-Peng Zhang,Xiao-Yu Cao,Ling-Bo Qu 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.4
Er-doped LiV3O8 as cathode material for secondary lithium batteries was prepared through a rheological phase reaction method. The as-prepared materials were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and galvanostatic discharge/charge measurements. The results indicate that Er doped phase preserves the layered structure of the pristine LiV3O8 and has an enlarged interlayer spacing. Compared to LiV3O8 sample, Er-doped LiV3O8 sample displays more uniform particles and large surface area. The electrochemical test shows that Er doping does not change the process of Li+ insertion/deinsertion. Er-doped LiV3O8 electrode exhibits an initial discharge capacity of 294.2 mAh g−1 and maintains a stable capacity of 220.7 mAh g−1 after 50 cycles, indicating a greatly improved good cycleability comparing with the undoped one.
Xie, Ling-Ling,Gong, Ren-Xi,Zhuo, Hao-Ze,Wei, Jiong-Quan The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.4
An investigation of the mechanism of period-doubling bifurcation in a voltage mode controlled buck-boost converter operating in discontinuous conduction mode is conducted from the viewpoint of nonlinear dynamical systems. The discrete iterative model describing the dynamics of the close-loop is derived. Period-doubling bifurcation occurs at certain values of the feedback factor. Results from numerical simulations and experiments are provided to verify the evolution of perioddoubling bifurcation, and the results are consistent with the theoretical analysis. These results show that the buck-boost converters exhibit a wide range of nonlinear behavior, and the system exhibits a typical period-doubling bifurcation route to chaos under particular operating conditions.