Voltammetry of immobilized microparticles (VMP) has been used in this work for the quantitative determination of tin and lead particles in their binary alloys. Carbon paste electrodes, which contained small amounts of tin and lead or their mixtures, were used as working electrodes and square wave voltammograms of each electrode were recorded. Quantification was performed using optimum experimental conditions, obtained by an experimental design technique. The calibration was made by measuring the percentage peak height of each metal taking the sum of peak currents of the both metals as 100 %. The results were compared with quantitative results of X‐ray fluorescence (XRF) technique to evaluate the capability of VMP method in its quantitative determination of solid samples. 相似文献
We have designed a phantom to evaluate mean glandular dose (MGD) as part of the regulatory dosimetry control for mammographic equipment. The phantom is constituted by TLD-100 thermoluminescent dosemeters (TLDs) inserted within semicircular plates of acrylic. Different groups of TLDs are used to determine entrance surface air kerma and half-value layer (HVL). Calibration of both tasks has been performed using a Senographe 2000D system and an ionization chamber. The phantom has been tested in five clinical systems. The HVL and MGD obtained by this method agree, on average, within 3%, with those from standard procedures based on the use of ionization chambers. The phantom MGD measurements have a combined uncertainty better than 10% (k = 1). 相似文献
Let be a compact immersed surface in the unit sphere with constant mean curvature . Denote by the linear map from into , , where is the linear map associated to the second fundamental form and is the identity map. Let denote the square of the length of . We prove that if , then is either totally umbilical or an -torus, where is a constant depending only on the mean curvature .
We consider embedded compact hypersurfacesM in a halfspace of hyperbolic space with boundaryM in the boundary geodesic hyperplaneP of the halfspace and with non-zero constant mean curvature. We prove the following. Let {Mn} be a sequence of such hypersurfaces withMn contained in a disk of radiusrn centered at a point P such thatrn 0 and that eachMn is a large. H-hypersurface,H > 1. Then there exists a subsequence of {Mn} converging to the sphere of mean curvatureH tangent toP at. In the case of smallH-hypersurfaces orH 1, if we add a condition on the curvature of the boundary, there exists a subsequence of {Mn} which are graphs. The convergence is smooth on compact subset of 3
. 相似文献
Theoretical approaches to calculation of work function within jellium model and the problem of extension of this model to include the lattice corrections to the work function are briefly discussed. Lattice corrections to the work function obtained from the experiment are estimated and compared with those calculated theoretically.
It is found that the mean value of the experimental lattice correction <δψhkl>hkl compared to the mean work function is negligible. It is stated that the mean work function can be treated as a material constant characterizing a given metal, such as, e.g., binding energy.An expression for the dependence of jellium work function on rs, valid in a metallic range of rs, is given. A comparison between then theoretical and experimental results is presented and the role of correlation energy is examined. It is shown that more accurate approximations of the correlation energy than that given by Wigner's formula lead to a better agreement with experiment. A simple model is presented for explanation of work function changes on single crystal planes. Some recent results concerning the thermal dependence of work function are given. The dependence of the work function on the degree of coverage is discussed both for alkali and non-alkali atoms adsorption. Theoretical models are briefly reviewed and comparison between theory and experiment is made. A simple model is presented for explanation of the work function variation on rough planes in metallic non-alkali atoms chemisorption. 相似文献
This paper presents an online procedure that produces the smallest feasible size of two-dimensional FIR filters with prescribed
magnitude error constraint. The procedure uses the mean square normalized error of constrained and unconstrained least-square
filters to produce the initial and the subsequent sizes that converge to the smallest feasible one in a few iterations, where
the constrained least-square filters are defined as the least-square filters satisfying the magnitude error constraint. The
procedure finally returns a smallest size filter that satisfies the magnitude error constraint and has least total squared
magnitude error. Design examples of diamond-shaped, rectangular, and elliptic filters are provided, and comparisons with an
exhaustive search are given. 相似文献