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81.
A novel, sensitive and selective adsorptive stripping procedure for simultaneous determination of copper, bismuth and lead is presented. The method is based on the adsorptive accumulation of thymolphthalexone (TPN) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the simultaneous determination of copper, lead and bismuth were studied using the Derringer desirability function. The optimum analytical conditions were found to be TPN concentration of 4.0 microM, pH of 9.0, and accumulation potential at -800 mV vs. Ag/AgCl with an accumulation time of 80 s. The peak currents are proportional to the concentration of copper, bismuth and lead over the 0.4-300, 1-200 and 1-100 ng mL(-1) ranges with detection limits of 0.4, 0.8 and 0.7 ng mL(-1), respectively. The procedure was applied to the simultaneous determination of copper, bismuth and lead in the tap water and some synthetic samples with satisfactory results. 相似文献
82.
Sculptured copper thin films were deposited on glass substrates, using different deposition rates. The nano-structure and morphology of the films were obtained, using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Their optical properties were measured by spectrophotometry in the spectral range of 340-850 nm. The real and imaginary refractive indices, film thickness and fraction of metal inclusion in the film structure were obtained from optical fitting of the spectrophotometer data. 相似文献
83.
Mohammad Reza Ganjali Tahereh Poursaberi Leila Haji-agha Babaei Shohre Rouhani Mohammad Yousefi Maryam Kargar-Razi Abolghasem Moghimi Hossein Aghabozorg Mojtaba Shamsipur 《Analytica chimica acta》2001,440(2):5376-87
A PVC membrane electrode based on bis-2-thiophenal propanediamine (TPDA) coated directly on graphite is described. The electrode exhibits a Nernstian response for Cu2+ over a very wide concentration range (1.0×10−1 to 6.0×10−8 M) with a detection limit of 3.0×10−8 M (2.56 ng ml−1). It has a fast response time and can be used for at least 2 months without any major deviation. The proposed sensor revealed very good selectivities for Cu2+ over a wide variety of other metal ions and could be used in the pH range of 3.0–7.0. It was successfully used for direct determination of copper in black tea and as an indicator electrode in potentiometric titration of copper ion. 相似文献
84.
In the present paper, the analytical solution for a radially piezoelectric functionally graded rotating hollow shaft is presented.
The variation of material properties is assumed to follow a power law along the radial direction of the shaft. Two resulting
fully coupled differential equations in terms of the displacement and electric potential are solved directly. Numerical results
for different shaft geometries with different profiles of inhomogeneity are also graphically displayed. 相似文献
85.
An adaptive quadtree grid generation algorithm is developed and applied for tracer and multiphase flow in channelized heterogeneous porous media. Adaptivity was guided using two different approaches. In the first approach, wavelet transformation was used to generate a refinement field based on permeability variations. The second approach uses flow information based on the solution of an initial-time fine-scale problem. The resulting grids were compared with uniform grid upscaling. For uniform upscaling, two commonly applied methods were used: renormalization upscaling and local-global upscaling. The velocities obtained by adaptive grid and uniformly upscaled grids, were downscaled. This procedure allows us to separate the upscaling errors, on adaptive and uniform grids, from the numerical dispersion errors resulting from solving the saturation equation on a coarse grid. The simulation results obtained by solving on flow-based adaptive quadtree grids for the case of a single phase flow show reasonable agreement with more computationally demanding fine-scale models and local-global upscaled models. For the multiphase case, the agreement is less evident, especially in piston-like displacement cases with sharp frontal movement. In such cases a non-iterative transmissibility upscaling procedure for adaptive grid is shown to significantly reduce the errors and make the adaptive grid comparable to iterative local-global upscaling. Furthermore, existence of barriers in a porous medium complicates both upscaling and grid adaptivity. This issue is addressed by adapting the grid using a combination of flow information and a permeability based heuristic criterion. 相似文献
86.
The elastic buckling behavior of quadrilateral single-layered graphene sheets (SLGS) under bi-axial compression is studied
employing nonlocal continuum mechanics. Small-scale effects are taken into consideration. The principle of virtual work is
employed to derive the governing equations. The Galerkin method in conjunction with the natural coordinates of the nanoplate
is used as a basis for the analysis. The buckling load of skew, rhombic, trapezoidal, and rectangular nanoplates considering
various geometrical parameters are obtained. It is shown that nonlocal effects are very important in arbitrary quadrilateral
graphene sheets and their inclusion results in smaller buckling loads. Also the effects of geometrical parameters such as
aspect ratio, angle, and mode number on the buckling load decrease when scale coefficient increases, for all arbitrary quadrilateral
SLGS. 相似文献
87.
Afshin Babaei Seddigheh Banihashemi 《Numerical Methods for Partial Differential Equations》2019,35(3):976-992
This paper has focused on unknown functions identification in nonlinear boundary conditions of an inverse problem of a time‐fractional reaction–diffusion–convection equation. This inverse problem is generally ill‐posed in the sense of stability, that is, the solution of problem does not depend continuously on the input data. Thus, a combination of the mollification regularization method with Gauss kernel and a finite difference marching scheme will be introduced to solve this problem. The generalized cross‐validation choice rule is applied to find a suitable regularization parameter. The stability and convergence of the numerical method are investigated. Finally, two numerical examples are provided to test the effectiveness and validity of the proposed approach. 相似文献
88.
Nanostructured conductive polypyrrole has been prepared electrochemically on the surfaces of Cu/Au interdigital electrodes in the presence of Fe(II) as catalyst and ClO4? as anion dopant by using constant potential amperometry and cyclic voltammetry. The morphology of the conducting films was examined by field emission scanning electron microscopy, indicating a dependence from the processing technique. The synthesized polymer was used to investigate the properties of the gas sensing ability. The effect of the catalyst concentration on the oxidation mechanism of pyrrole was discussed. The PPy‐ClO4 gas sensors had demonstrated fast response time and high sensitivity to VOCs. 相似文献
89.
The present work demonstrates that simultaneous determination of adrenalin (AD) and paracetamol (PAR) can be performed on single‐walled carbon nanotube/chitosan/ionic liquid modified glassy carbon electrode (SWCNT‐CHIT‐IL/GCE). The electro‐oxidations of AD and PAR were investigated with cyclic voltammetry (CV), differential pulse voltammetry (DPV) and also chronoamperometry (CA) methods. DPV experiments showed that the oxidation peak currents of AD and PAR are proportional to the corresponding concentrations over the 1–580 μmol/L and 0.5–400 μmol/L ranges, respectively. The RSD at a concentration level of 15 μmol/L AD and 15 μmol/L PAR were 1.69% and 1.82%, respectively. Finally the modified electrode was used for simultaneous determination of AD and PAR in real samples with satisfactory results. 相似文献
90.
A multiwalled carbon nanotube/chitosan modified glassy carbon electrode (MWCNTs‐CHT/GCE) has been used for simultaneous determination of paracetamol (PAR) and uric acid (UA). The measurements were carried out using differential pulse voltammetry (DPV), cyclic voltammetry (CV) and chronoamperometry (CA). DPV measurements showed a linear relationship between oxidation peak current and concentration of PAR and UA in phosphate buffer (pH 7) over the concentration range 2 µM to 250 µM, and 10 µM to 400 µM, respectively. The analytical performance of this sensor has been evaluated for detection of PAR and UA in human serum and human urine with satisfactory results. 相似文献