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21.
In this contribution, the performance of an adaptive least squares channel estimator for a time correlated MIMO-OFDM channel is presented in a closed form relation. As a criterion for performance evaluation, the well-known mean square error (MSE) is employed. The pilot aided channel estimation is used to extract the channel coefficients. To minimize the MSE and arrange phase shift orthogonally, the pilots are constructed with equal power and space. The model of the channel is developed by implementing a first order Markov model, and it is proved that the performance of the system is dependent upon the defined forgetting factor, the number of transmit antennas, the number of multipath channel taps, transmitted power, and Doppler shift. The effect of each parameter on the performance of the system is discussed separately. The computer simulation results follow with the analytical results comprehensively. 相似文献
22.
23.
Nadjet Rezki Salsabeel A. Al-Sodies Mohamed R. Aouad Sanaa Bardaweel Mouslim Messali El Sayed H. El Ashry 《International journal of molecular sciences》2016,17(5)
The present work reports an efficient synthesis of fluorinated pyridinium salts-based hydrazones under both conventional and eco-friendly ultrasound procedures. The synthetic approach first involves the preparation of halogenated pyridinium salts through the condensation of isonicotinic acid hydrazide (1) with p-fluorobenzaldehyde (2) followed by the nucleophilic alkylation of the resulting N-(4-fluorobenzylidene)isonicotinohydrazide (3) with a different alkyl iodide. The iodide counteranion of 5–10 was subjected to an anion exchange metathesis reaction in the presence of an excess of the appropriate metal salts to afford a new series of fluorinated pyridinium salts tethering a hydrazone linkage 11–40. Ultrasound irradiation led to higher yields in considerably less time than the conventional methods. The newly synthesized ILs were well-characterized with FT-IR, 1H NMR, 13C NMR, 11B, 19F, 31P and mass spectral analyses. The ILs were also screened for their antimicrobial and antitumor activities. Within the series, the salts tethering fluorinated counter anions 11–13, 21–23, 31–33 and 36–38 were found to be more potent against all bacterial and fungal strains at MIC 4–8 µg/mL. The in vitro antiproliferative activity was also investigated against four tumor cell lines (human ductal breast epithelial tumor T47D, human breast adenocarcinoma MCF-7, human epithelial carcinoma HeLa and human epithelial colorectal adenocarcinoma Caco-2) using the MTT assay, which revealed that promising antitumor activity was exhibited by compounds 5, 12 and 14. 相似文献
24.
El Sayed H. El Ashry Mahmoud A. M. Nassr Yeldez El Kilany Ahmed Mousaad 《Advanced Synthesis \u0026amp; Catalysis》1986,328(1):1-6
Oxidative cyclization of D -galactose (p-chlorophenyl)thiosemicarbazone gave 2-(p-chloroanilino)-5-( D -galacto-1,2,3,4,5-pentahydroxypentyl)-1,3,4-thiadiazole ( 1 ), whose acetylation afforded 2-[N-acetyl-N-(p-chlorophenyl)]-amino-5-( D -galacto-1,2,3,4,5-pentacetoxypentyl)- 1,3,4-thiadiazole ( 3 ). Its periodate oxidation of the glycol groups gave 2-(p-chloroanilino)-1,3,4-thiadiazole-5-carboxaldehyde ( 4 ), which can be transformed into 1,2-[2-(p-chloroanilino)-1,3,4-thiadiazol-5-yl]-1-hydroxy-2-oxoethane. A number of hydrazones of the formyl thiadiazole was prepared and its reduction with sodium borohydride gave 2-(p-chloroanilino)-5-hydroxymethyl-1,3,4-thiadiazole ( 6 ), whose acetylation gave a mono-O-acetyl derivative ( 7 ). Oxidation of the formyl thiadiazole gave 2-(p-chloroanilino)-1,3,4-thiadiazole ( 9 ). The spectral data of the compounds were discussed. 相似文献
25.
Bioactive glass–ceramic with various zirconia concentrations was applied on stainless steel (SS) by the sol–gel method. Bioactive glass powder was prepared by the sol–gel method, and thermal properties of the prepared powders were studied by differential thermal analysis (DTA). The effects of zirconia were investigated to explore the growth of nanowires. The growth model of nanowires, in this study, is proposed in terms of the surface diffusion. The coatings showed the hardness values to be in the range of 3000–4500 MPa. The hardness values of prepared composite coatings increased with an increase in zirconia amounts. 相似文献
26.
The refining of lubricating oils from waste lubricating oil was examined utilizing a novel blend of solvent extraction and activated alumina adsorbent. The activity of these solvent extraction blends {toluene, butanol and methanol (A)}, {toluene, butanol and ethanol (B)} and {toluene, butanol and isopropanol (C)} was evaluated experimentally, oil to solvent proportions from 1:1 to 1:3 were analyzed for mixture blend (C). The results confirm solvent mixture (A) gave good efficiency with the highest percent sludge removal. The maximum percent of sludge removal improves with the increase of solvent to oil ratios. The physical properties of the recycle oil were measured. The results show the change in the properties of recycling oil and have good efficiency. 相似文献
27.
The corrosion inhibition of steel in a closed system containing sodium sulphite at room temperature has been established. Steady-state potential as well as weight loss measurements indicated that sodium sulphite did not only remove O2 from the solution but also brought complete cathodic protection. It was found also that sodium sulphite could tolerate the presence of Cl?, SO42? and S2?. In case of sulphite—sulphate or sulphite—chloride mixtures a concentration of 5 × 10?3M Na2SO3 was required to tolerate a wide range of concentration of these aggressive ions. A linear relationship was found between log sulphite concentration and log maximum tolerated concentration of sulphide. 相似文献
28.
Hend Omar Mohamed Enas Taha Sayed M. Obaid Yun-Jeong Choi Sung-Gwan Park Siham Al-Qaradawi Kyu-Jung Chae 《International Journal of Hydrogen Energy》2018,43(46):21560-21571
The poor wettability and high cost of the carbonaceous electrodes materials prohibited the practical applications of microbial fuel cells (MFCs) on large scale. Here, a novel nanoparticles of metal sheathed with metal oxide is electrodeposited on carbon paper (CP) to introduce as high-performance anodes of microbial fuel cell (MFC). This thin layer of metal/metal oxide significantly enhance the microbial adhesion, the wettability of the anode surface and decrease the electron transfer resistance. The investigation of the modified CP anodes in an air-cathode MFCs fed by various biocatalyst cultures shows a significant improving in the MFC performance. Where, the generated power and current density was 140% and 210% higher as compared to the pristine CP. Mixed culture of exoelectrogenic microorganism in wastewater exhibited good performance and generated higher power and current density compared to yeast as pure culture. The excellent capacitance with a distinctive nanostructure morphology of the modified-CP open an avenues for practical applications of MFCs. 相似文献
29.
The IEEE Signal Processing Society is introducing a new feature that originated from a suggestion made by my colleague Athina Petropulu and a couple of associate editors. The publication of overview articles in the transactions will be a service to our readers and appeal to the broad signal processing audience. 相似文献
30.
Au fur et à mesure que le développement s'accélère en Arabie saoudite, les matériaux importés deviennent de plus en plus nombreux et entrent en concurrence les uns avec les autres. Le Materials Testing Laboratory de Riyad a procédé, il ny a pas très longtemps, à une étude comparative d'échantillons de ciments importés et de ciments fabriqués dans le pays. S'ils concernent avant tout les chimistes du ciment, les résultats n'en présentent pas moins un intérêt plus général. 相似文献