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排序方式: 共有402条查询结果,搜索用时 15 毫秒
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Mohamed Charif Soufiane El Adraoui Mounirh Khalid Asmaa Zugari Mohamed I. Yaich Mohsine Khalladi 《Optik》2014
The current density (JE), the piecewise linear recursive convolution (PLRC) and the constant convolution recursive (CRC) techniques are developed and integrated into the transmission line matrix (TLM) algorithm. A comparison of these three schemes according to the criteria of accuracy and CPU time is presented. Numerical experiments show that JE provides the most accurate solution and requires the least CPU time; PLRC is nearly as accurate but consumes more CPU time than CRC. 相似文献
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Single-use sensors, incorporating a three-electrode configuration (graphite carbon-working electrode; carbon-counter electrode and silver/silver chloride-reference electrode), have been fabricated on a polyester substrate using low cost screen-printing (thick-film) technology. These electrodes coupled with constant current stripping chronopotentiometry (CCSCP), has provided a convenient screening tool for on-site detection of trace levels of copper. Modification of the graphite carbon surface based on in situ deposition of mercury film has been carried out. By appropriate choice of supporting medium and applied constant stripping current, well-resolved and reproducible response for copper was obtained. The stripping response for copper following 2 min deposition was linear over the concentration range examined (10-2000 ppb) with detection limit of 6 ppb using 2 M hydrochloric acid (HCl). Successful applications of the sensing device to acetic-acid bioavailable fraction of a certified reference material (CRM 601, a lake sediment) and soil samples are demonstrated. 相似文献
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M. Srinivasan J. B. Rampal S. Thiagarajan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):221-226
Abstract A comparative electron impact study on 2-(2′-nitrobenzoyl)thiophene1(1), 2-(2′-nitrobenzoyl)-3-methylthiophene2(2) and the corresponding 4′-nitrobenzoyl derivatives (3 and 4)3,4 is presented. The results suggest that the presence of nitro group β-to the carbonyl affects the general fragmentation pattern recorded in the literature for 2-acyl and 2-aroylthiophenes. 相似文献
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《Physics and Chemistry of Liquids》2012,50(4):337-345
Relaxational and associative aspects of X…HO bond complexes in ternary liquid mixtures of aromatic halogen compounds, namely, chlorobenzene and bromobenzene with ethanol in benzene have been studied at 10 GHz frequency and a temperature range of 30-60°C using dielectric relaxation data. Due to the observed high values of distribution parameter, the relaxation mechanism has been further resolved in terms of two separate relaxation times. The dipole moment, association equilibrium constant and thermodynamic parameters associated with the complexes have also been determined. All the results indicate the occurrence of weak molecular interaction in both the systems. This is in agreement with the ultrasonic results on these systems, reported earlier by Kannappan and Palani. 相似文献
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《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):573-590
To investigate the effects of solvent type and temperature on the interpolymer complexation via hydrogen bonding, a study was made on the complex system of poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) in two kinds of solvent systems, pure water and water-MeOH (30 wt%) mixed solvent, at various temperatures using the Ubbelohde viscometer, pH-meter, and UV spectrophotometer. The repeating unit mole ratio at the most optimum complexation as confirmed by the reduced viscosity measurement was shifted from [PEO]/[PAA] ≈ 1.25:1 to 1.5:1 by the addition of methanol to water. From the UV measurement, the deviation from the “isosbestic point” (where the absorbance of the solution remains constant) has presented another evidence for the solvent effect on complexation. In addition, the analysis of the changes in thermodynamic properties upon complexation as well as the fraction of carboxyls associated with PEO oxygens and the complex stability constant as estimated by potentiometric titration at several temperatures reveals that the complex formation in mixed solvent became more unfavorable compared to that in pure solvent at high temperatures above 30°C. This could be explained by considering that in water the hydrophobic interaction as well as the hydrogen bonding may greatly contribute to the stabilization of the polymer complex formed, while in water-methanol the main stabilizing force would be the hydrogen bonding alone. 相似文献
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