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RISS 인기검색어
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- 저자 : Wang Hai-dou (검색결과 4 건)
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Performance Analysis of a Novel Distributed C-ARQ Scheme for IEEE 802.11 Wireless Networks
( Fan Wang ),( Suoping Li ),( Zufang Dou ),( Shexiang Hai ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.7
It is well-known that the cooperative communication and error control technology can improve the network performance, but most existing cooperative MAC protocols have not focused on how to cope with the contention process caused by cooperation and how to reduce the bad influence of channel packet error rate on the system performance. Inspired by this, this paper first modifies and improves the basic rules of the IEEE 802.11 Medium Access Control (MAC) protocol to optimize the contention among the multi-relay in a cooperative ARQ scheme. Secondly, a hybrid ARQ protocol with soft combining is adopted to make full use of the effective information in the error data packet and hence improve the ability of the receiver to decode the data packet correctly. The closed expressions of network performance including throughput and average packet transmission delay in a saturated network are then analyzed and derived by establishing a dedicated two-dimensional Markov model and solving its steady-state distribution. Finally, the performance evaluation and superiority of the proposed protocol are validated in different representative study cases through MATLAB simulations.
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Microstructures and nano mechanical properties of the metal tungsten film
Zhu Li-na,Li Guo-lu,Wang Hai-dou,Xu Bin-shi,Zhuang Da-ming,Liu Jia-jun 한국물리학회 2009 Current Applied Physics Vol.9 No.3
The W film was prepared on 1045 steel by magnetron sputtering, with the thickness of 2 ㎛, its surface and cross-section morphologies were investigated with SEM, and the phase structure was analyzed with XRD. X-ray stress determinator was utilized to measure its residual stress, and the nano-hardness and elastic modulus of the film were surveyed by nano-indentation tester. The results show that the surface of W film is very compact and smooth; the particles arranged regularly, the granularity of the thin film is about 1 ㎛. The microcracks, cavities and desquamation were not found in the film and interface, and the bonding between the W film and substrate is well. The XRD results showed that the W film had a body-centered cubic structure, the lattice constant: ɑ = 0.316 nm, the growth preferred orientations are (110) and (220). The compressive stress (-169 MPa) was found on the surface. The average nano-hardness and elastic modulus of W film are 15.22 GPa, 176.64 GPa, respectively, and the mechanical properties of W film are well. The W film was prepared on 1045 steel by magnetron sputtering, with the thickness of 2 ㎛, its surface and cross-section morphologies were investigated with SEM, and the phase structure was analyzed with XRD. X-ray stress determinator was utilized to measure its residual stress, and the nano-hardness and elastic modulus of the film were surveyed by nano-indentation tester. The results show that the surface of W film is very compact and smooth; the particles arranged regularly, the granularity of the thin film is about 1 ㎛. The microcracks, cavities and desquamation were not found in the film and interface, and the bonding between the W film and substrate is well. The XRD results showed that the W film had a body-centered cubic structure, the lattice constant: ɑ = 0.316 nm, the growth preferred orientations are (110) and (220). The compressive stress (-169 MPa) was found on the surface. The average nano-hardness and elastic modulus of W film are 15.22 GPa, 176.64 GPa, respectively, and the mechanical properties of W film are well.
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Low Stratospheric Wind Measurement Using Mobile Rayleigh Doppler Wind LIDAR
Zhi-feng Shu,Xian-kang Dou,Hai-yun Xia,Dong-song Sun,Yan Han,Hyunki Cha,김덕현,Guo-cheng Wang,백성훈,Dong-dong Hu 한국광학회 2012 Current Optics and Photonics Vol.16 No.2
A mobile Rayleigh Doppler wind LIDAR at an eye-safe wavelength of 355 nm incorporating double-edge technique with triple-channel Fabry-Perot etalon is developed for wind measurement from 5to 40km. The structure of this LIDAR system is described. An intercomparsion experiment with rawinsonde is made, showing good agreement with expected measurement accuracy. A continuous observation of stratosphere wind field for several days with temporal resolution of 15 min and spatial resolution of 200 m from 5 to 40 km is presented, demonstrating the stability and robustness of the LIDAR. A stratospheric quasi-zero wind layer can be found at around 20 km with a direction change from east to west evident in the continuous observation.
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Baimantuoluosides D-G, Four New Withanolide Glucosides from the Flower of Datura metel L.
Bing-you Yang,Yong-gang Xia,Qiu-hong Wang,De-qiang Dou,Hai-xue Kuang 대한약학회 2010 Archives of Pharmacal Research Vol.33 No.8
In our search for bioactive anti-psoriasis compounds from the flower of Datura metel L, we isolated four new withanolide glucosides, baimantuoluosides D, E, F and G (1-4). The structures of the new compounds are (5α,6α,7β,22R)-5,6,7,27-tetrahydroxy-1-oxowitha-2,24-dien-27-O-β-D-glucopyranoside (1), (5α,6β,7α,22R)-5,6,7,27-tetrahydroxy-1-oxowitha-2,24-dien-27-O-β-D-glucopyranoside (2), (5α,6β,7α,12β,22R)-5,6,7,12,27-pentahydroxy-1-oxowitha-2,24-dien-27-O-β-D-glucopyranoside (3), and (5α,6β,22R)-5,6,27-trihydroxy-1-oxowitha-2,24-dien-27-O-β-D-glucopyranoside (4) on the basis of chemical and physicochemical evidence.
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