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排序方式: 共有632条查询结果,搜索用时 15 毫秒
1.
Ghodratollah Absalan Mohammad Soleimani Mozaffar Asadi Mohammad Bagher Ahmadi 《Analytical sciences》2004,20(10):1433-1436
A new ammonia optical sensor was designed using bis(acetylacetoneethylendiamine)tributylphosphin cobalt(III) tetraphenylborate complex, coated on transparent triacetylcellulose film as membrane. The change in the absorbance of the optode at the maximum wavelength of 408 nm was related to ammonia concentration in aqueous samples. A buffer solution with a pH of 9 (sodium borate-HCl) was used. The optode was fully regenerated in pH 2. The linear dynamic range for determination of ammonia was 3.3 x 10(-4) to 6.9 x 10(-3) mol l(-1) with a detection limit of 5.0 x 10(-5) mol l(-1) and a response time range of 4 - 6 min. This membrane was successfully applied for determination of ammonia in drinking water. 相似文献
2.
Based on the stress transport model, a rate-dependent algebraic expression for the Reynolds stress tensor is developed. It is shown that the new model includes the normal stress effects and exhibits viscoelastic behavior. Furthermore, it is compatible with recently developed improved models of turbulence. The model is also consistent with the limiting behavior of turbulence in the inertial sublayer and is capable of predicting secondary flows in noncircular ducts. The TEACH code is modified according to the requirements of the rate-dependent model and is used to predict turbulent flow fields in a channel and behind a backward-facing step. The predicted results are compared with the available experimental data and those obtained from the standard k-ε and algebraic stress models. It is shown that the predictions of the new model are in better agreements with the experimental data. 相似文献
3.
In the present work, the cathodic stripping voltammetric methodology using a hanging mercury drop electrode was described for simultaneous determination of lead and zinc in different real samples. The method is based on adsorption of metal ions on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. Optimal conditions were found to be: accumulation time; 70 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s?1, supporting electrolyte; 0.01 M ammonia buffer at pH 8.5, and concentration of carbidopa; 8.0 μM. The relationship between the peak current versus concentration was linear over the range of 0.1–210 and 0.2–170 nM for lead and zinc, respectively. The detection limits are 0.09 and 0.15 nM for lead and zinc ions respectively. The relative standard deviations at a concentration level of 70 nM of both metal ions are found 1.08 and 1.24% for lead and zinc ions respectively. 相似文献
4.
In this paper we, present some MATLAB and GAP programs and use them to find the automorphism group of the Euclidean graph
of the C80 fullerence with connectivity and geometry of I
h
symmetry point group. It is proved that this group has order 120 and is isomorphic to I
h
≊Z2×A5, where Z2 is, a cyclic group of order 2 and A5 is the alternating group on five symbols. 相似文献
5.
R. Dabbagh H. Ghafourian A. Baghvand G. R. Nabi H. Riahi M. A. Ahmadi Faghih 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(1):53-59
The ability of living filamentous cells of the cyanobacterium Oscillatoria homogenea to separate stable strontium and 90Sr from aqueous solution is demonstrated in this study. On a basis of filamentous cell biovolume, the removal were 43.78 nM·ml·(mm3)−1 and 3129.48 mBq·ml·(mm3)−1 after 240 hour incubation. The optimum pH for strontium uptake is 9±0.3. The increasing biovolume of the blue-green alga
elevates sorption. In the liquid culture containing 21.2 mm3·ml−1 filamentous cells and 1000 nM·ml−1 initial strontium concentration, the maximum strontium removal was 455.34 nM·ml·(mm3)−1. At 1200 Lux illumination, the maximum removal value was 58.62 nM·ml·(mm3)−1, and at the initial strontium concentration of 6590 nM·ml−1, 235.40 nM·ml·(mm3)−1 removal was observed. The experimental data fitted to Langmuir isotherm and the model parameters and correlation coefficient
(R
2) were q
max = 7.143 μg·(mm3)−1, b = 0.003 and 0.99, respectively. 相似文献
6.
利用密度泛函理论通过计算吸附能量、HOMO/LUMO能隙变化、电荷转移、结构扭曲等研究二氧化氮分子在B12N12纳米笼的吸附.此外,通过计算B12N12的电子结合能、Gibbs自由能、态密度和分子表面的静电势研究其稳定性和其它特性.B12N12纳米笼吸附二氧化氮显示三种构型.B12N12团簇的HOMO/LUMO能隙变化对二氧化氮分子的存在非常敏感,从自由团簇的6.84 eV降为NO2/团簇稳定团簇的3.23 eV.团簇的导电性被极大地提高,表明B12N12纳米簇可能是潜在的二氧化氮气体分子检测传感器. 相似文献
7.
Razaghi M. Gandomkar M. Ahmadi V. Das N. K. Connelly M. J. 《Optical and Quantum Electronics》2012,44(3-5):255-263
Optical and Quantum Electronics - In this paper, we analyse the picosecond wavelength conversion using semiconductor optical amplifier (SOA) with a novel technique. For an accurate and precise... 相似文献
8.
Following recent experimental works, herein we investigated chemical functionalization of a BN graphene-like sheet with hydrazine (N2H4) molecule based on the density functional theory. We found that the functionalization of the pristine sheet is not possible; while the presence of some structural defects such as Stone–Wales is essential to make it feasible. Functionalization energy of the defected sheet is calculated to be in the range of ?6.1 to ?7.4 kcal/mol at B3LYP/6-31G (d) level. Based on the obtained results, the functionalized BN sheet is found to be more soluble in water in comparison with the pristine sheet which is in good agreement with previous experimental reports. Also, it was found that the electronic properties of the defected sheet are slightly changed upon the chemical functionalization. 相似文献
9.
10.
Ali Ahmadi Peyghan Mohammad Bigdeli Tabar Sirous Yourdkhani 《Journal of Cluster Science》2013,24(4):1011-1020
By using density functional theory calculations, we have investigated the adsorption of OH and OCH3 free radicals on a BC2N nanotube based on the energetic, electronic and geometric properties. The adsorption of radicals on the top of a B atom is more favorable than that on the other sites and reaction energies have been calculated to be in the range of ?0.57 to ?1.48 eV for OH and ?0.27 to ?1.19 eV for OCH3. It was found that the adsorption of radicals may facilitate the electron emission from the BC2N nanotube surface by decreasing the work function due to the charge transfer which occurs between the tube and radicals. Also, HOMO/LUMO gap of the tube is significantly decreased, which may result in the increase of the electrical conductivity of the tube. 相似文献