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- 저자 : Mohamed E. Khedr (검색결과 3 건)
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Mohamed E. Khedr,Amr El-Helw,Mohamed Hossam Afifi 한국통신학회 2015 Journal of communications and networks Vol.17 No.6
The coexistence among different systems is a major problem in communications. Mutual interference between different systems should be analyzed and mitigated before their deployment. The paper focuses on two aspects that have an impact on the system performance. First, the coexistence analysis, i.e. evaluating the mutual interference. Second aspect is the coexistence techniques, i.e. appropriate system modifications that guarantee the simultaneous use of the spectrum by different technologies. In particular, the coexistence problem is analyzed between ultra-wide bandwidth (UWB) and narrow bandwidth (NB) systems emphasizing the role of spectrum sensing to identify and classify the NB interferers that mostly affect the performance of UWB system. A direct sequence (DS)-time hopping (TH) code design technique is used to mitigate the identified NB interference. Due to the severe effect of Narrowband Interference on UWB communications, we propose an UWB transceiver that utilizes spectrum-sensing techniques together with mitigation techniques. The proposed transceiver improves both the UWB and NB systems performance by adaptively reducing the mutual interference. Detection and avoidance method is used where spectrum is sensed every time duration to detect the NB interferer's frequency location and power avoiding it's effect by using the appropriate mitigation technique. Two scenarios are presented to identify, classify, and mitigate NB interferers.
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Amgad I. M. Khedr,Sabrin R. M. Ibrahim,Gamal A. Mohamed,Hany E. A. Ahmed,Amany S. Ahmad,Mahmoud A. Ramadan,Atef E. Abd El-Baky,Koji Yamada,Samir A. Ross 대한약학회 2016 Archives of Pharmacal Research Vol.39 No.7
Phytochemical investigation of Ficus pandurataHance (Moraceae) fruits has led to the isolation of two newtriterpenoids, ficupanduratin A [1b-hydroxy-3b-acetoxy-11a-methoxy-urs-12-ene] (11) and ficupanduratin B [21ahydroxy-3b-acetoxy-11a-methoxy-urs-12-ene] (17), alongwith 20 known compounds: a-amyrin acetate (1), a-amyrin(2), 3b-acetoxy-20-taraxasten-22-one (3), 3b-acetoxy-11amethoxy-olean-12-ene (4), 3b-acetoxy-11a-methoxy-12-ursene (5), 11-oxo-a-amyrin acetate (6), 11-oxo-b-amyrinacetate (7), palmitic acid (8), stigmast-4,22-diene-3,6-dione(9), stigmast-4-ene-3,6-dione (10), stigmasterol (12), b-sitosterol(13), stigmast-22-ene-3,6-dione (14), stigmastane-3,6-dione (15), 3b,21b-dihydroxy-11a-methoxy-olean-12-ene (16), 3b-hydroxy-11a-methoxyurs-12-ene (18), 6-hydroxystigmast-4,22-diene-3-one (19), 6-hydroxystigmast-4-ene-3-one (20), 11a,21a-dihydroxy-3b-acetoxy-urs-12-ene(21), and b-sitosterol-3-O-b-D-glucopyranoside (22). Compound21 is reported for the first time from a natural source. The structures of the 20 compounds were elucidated on thebasis of IR, 1D (1H and 13C), 2D (1H–1H COSY, HSQC,HMBC and NOESY) NMR and MS spectroscopic data, inaddition to comparison with literature data. The isolatedcompounds were evaluated for their anti-microbial, antimalarial,anti-leishmanial, and cytotoxic activities. In addition,their radioligand displacement affinity on opioid andcannabinoid receptors was assessed. Compounds 4, 11, and15 exhibited good affinity towards the CB2 receptor, withdisplacement values of 69.7, 62.5 and 86.5 %, respectively. Furthermore, the binding mode of the active compounds inthe active site of the CB2 cannabinoid receptors was investigatedthrough molecular modelling.
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Ali Hanan,Masschelein P.,Pigeat P.,Dauscher A.,Rinnert H.,Horwat D.,Khedr Mohamed Atta,Giba Alaa E. 한국세라믹학회 2022 한국세라믹학회지 Vol.59 No.5
This work reports on the luminescence properties of cerium and samarium co-doped in yttrium–aluminum–garnet ceramic. Single and co-doped YAG nanocrystals have been prepared at different contents of Ce ions. The X-ray diffraction (XRD) confirms the formation of the crystallites and the phase purity. The ceramic has been fabricated by sintering using spark plasma sintering technique. It is found that the photoluminescence (PL) spectral features of ceramic sample are strongly dependent on the excitation wavelength. Broad emission band from Ce 3+ , is superimposed with the emission lines from Sm 3+ , thanks to significant spectral overlapping of their excitation lines. Consequently, the emitted color parameters can be widely controlled, as demonstrated from the chromaticity diagram. In addition, cathodoluminescence (CL) has been performed and evidenced the superimposed CL signal from both ions. Moreover, the time-resolved photoluminescence (TRPL) result indicates the influence of such spectral overlapping on the luminescence decay kinetics.
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