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- 저자 : ( Jianhua Ge ) (검색결과 3 건)
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Jianhua Ge,Jing Xu,Yujie Liu,Long Zhang,Lan Wang,Dehan Wu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.11
Nitrogen photo fixation mediated by various photocatalysts has received extensive concerns in recent years. In this work, a general strategy is proposed to enhance nitrogen photo fixation performance with some W18O49-based photocatalysts under visible-light irradiation. A series of photocatalysts were successfully synthesized in the presence of some noble-metal-free transition metals (Fe, Co and Ni) to modify the urchin-like W18O49. The resulting photocatalysts were systematically characterized using XRD, SEM, EDS, XPS, PL, N2 adsorption–desorption isotherms, and DRS. Structural characterization of the photocatalysts revealed that the crystal morphology features were preserved, optional harvesting properties were enhanced, BET specific surface area was extended, and migration efficiency of the photo-induced charge carriers was significantly improved in the modified-W18O49 materials. Therefore, a progressed nitrogen photo fixation performance was observed. The maximum production of NH4 + was approximately reached to 2752 μg · g -1 catal. under the optimum reaction conditions. Furthermore, a plausible nitrogen photo fixation mechanism in the presence of the synthesized composites is also proposed.
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Slotted ALOHA Based Greedy Relay Selection in Large-scale Wireless Networks
( Fengchen Ouyang ),( Jianhua Ge ),( Fengkui Gong ) 한국인터넷정보학회 2015 KSII Transactions on Internet and Information Syst Vol.9 No.10
Since the decentralized structure and the blindness of a large-scale wireless network make it difficult to collect the real-time channel state or other information from random distributed relays, a fundamental question is whether it is feasible to perform the relay selection without this knowledge. In this paper, a Slotted ALOHA based Greedy Relay Selection (SAGRS) scheme is presented. The proposed scheme allows the relays satisfying the user`s minimum transmission request to compete for selection by randomly accessing the channel through the slotted ALOHA protocol without the need for the information collection procedure. Moreover, a greedy selection mechanism is introduced with which a user can wait for an even better relay when a suitable one is successfully stored. The optimal access probability of a relay is determined through the utilization of the available relay region, a geographical region consisting of all the relays that satisfy the minimum transmission demand of the user. The average number of the selection slots and the failure probability of the scheme are analyzed in this paper. By simulations, the validation and the effectiveness of the SAGRS scheme are confirmed. With a balance between the selection slots and the instantaneous rate of the selected relay, the proposed scheme outperforms other random access selection schemes.
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A Survey on Spectrum Sharing in Cognitive Radio Networks
( Tangwen Xu ),( Zhenshuang Li ),( Jianhua Ge ),( Haiyang Ding ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.11
With the rapid development of wireless communication, the confliction between the scarce frequency resources and the low spectral efficiency caused by the stationary spectrum sharing strategies seriously restricts the evolution of the future mobile communication. For this purpose, cognitive radio (CR) emerges as one of the most promising inventions which can overcome the spectrum shortage. As the key technology and main objective of CR, spectrum sharing can make full use of the limited spectrum, alleviate the scarcity of frequency resources and improve the system utilities, playing thereby an important role in improving the system performance of cognitive radio networks (CRNs). In this survey, the spectrum sharing in CRNs is discussed in terms of the sharing process, mainstream sharing technologies and spectrum sharing models. In particular, comparisons of different spectrum sharing strategies are concluded, as well as that of different spectrum sensing schemes in sharing procedure. Moreover, some application examples of the spectrum sharing in CRNs, such as smart grid, public safety, cellular network and medical body area networks are also introduced. In addition, our previous related works are presented and the open research issues in the field of spectrum sharing are stated as well.
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