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31.
The results obtained when a laser microprobe is adapted to imaging detectors for multiwavelength detection are described. Detectors evaluated are a silicon-intensified target vidicon and a second-generation photodiode array. Data are presented to illustrate how the combined system can be used to monitor both surface and depth profiles of elemental content of a variety of sample types including a ruby rod and ceramic material with blemishes, electrical capacitors, integrated circuits, and surface-coated electrical conductors. It is also shown how the gating capability of the intensified vidicon can be used to monitor time-dependent changes in the several nanosecond range during the laser microprobe excitation process. Detection limits obtained with both detectors are in the range 2–500 ppm depending on the element, the wavelength used, the matrix, and other variables. The uncertainty associated with the measurement step can be improved by a factor of 2–3 by using ratios of spectral lines. Principal limitations of the laser microprobe method are the nonlinear response of intensity vs. concentration and the resulting need for reference materials with matrices similar to samples for calibration purposes. 相似文献
32.
We consider the convex feasibility problem (CFP) in Hilbert space and concentrate on the study of string-averaging projection (SAP) methods for the CFP, analyzing their convergence and their perturbation resilience. In the past, SAP methods were formulated with a single predetermined set of strings and a single predetermined set of weights. Here we extend the scope of the family of SAP methods to allow iteration-index-dependent variable strings and weights and term such methods dynamic string-averaging projection (DSAP) methods. The bounded perturbation resilience of DSAP methods is relevant and important for their possible use in the framework of the recently developed superiorization heuristic methodology for constrained minimization problems. 相似文献
33.
In this paper we present a super-resolved Raman spectroscopy configuration where, due to the proposed resolution improvement, more chemical species can be simultaneously detected. The idea includes usage of the basic property of Raman in which shifting the excitation wavelength will shift the absolute wavelength of the Raman spectral lines. Thus, encoding the spectra prior to analysis by the spectrometer allows obtaining spectral super-resolved sensing via time multiplexing super-resolution concepts applied over the spectral domain. 相似文献
34.
Journal of Solid State Electrochemistry - 相似文献
35.
Patra A Wijsboom YH Zade SS Li M Sheynin Y Leitus G Bendikov M 《Journal of the American Chemical Society》2008,130(21):6734-6736
The first highly conductive polyselenophene, namely, poly(3,4-ethylenedioxyselenophene) (PEDOS), was synthesized by taking advantage of a novel method for efficiently contracting the selenophene ring. PEDOS shows a relatively low band gap (1.4 eV), very high stability in the oxidized state, and a well-defined spectroelectrochemistry. 相似文献
36.
In the context of cognition, categorization is the process through which several elements (i.e., words) are grouped into a single set which by naming becomes an abstraction of its elements. For example, tiger, kitty, and max can be categorized as Cats. In this article, we aim to show how the physical, biological and cognitive dimensions are related in the process of categorization or abstraction through the physics of computation. Drawing on Landauer's principle, we show that the price paid in terms of entropy is higher when grouping elements of low ranking (high probability) than when grouping elements of high ranking (low probability). Therefore, the logic of the cognitive process of abstraction is explained through constraints imposed by memory on the computation of categories. © 2015 Wiley Periodicals, Inc. Complexity 21: 269–274, 2016 相似文献
37.
In this paper we investigate some properties of forcing which can be considered “nice” in the context of singularizing regular cardinals to have an uncountable cofinality. We show that such forcing which changes cofinality of a regular cardinal, cannot be too nice and must cause some “damage” to the structure of cardinals and stationary sets. As a consequence there is no analogue to the Prikry forcing, in terms of “nice” properties, when changing cofinalities to be uncountable. 相似文献
38.
Abelev E Starosvetsky D Ein-Eli Y 《Langmuir : the ACS journal of surfaces and colloids》2007,23(22):11281-11288
The ability of dissolved potassium monocarboxylate salts to produce surface passivation and to inhibit aqueous corrosion of copper was studied. The electrochemical measurements indicate that the inhibiting efficiency of these compounds, with a general formula Cn-1H2n-1COOK or CnK (n=3...12), is dependent on the hydrocarbon chain length. The inhibiting efficiency was higher for a longer hydrocarbon chain of n-alkanoic acid. The degree of copper protection was found to increase with an increase in n-alkanoic acid potassium salt concentration; the optimum concentration of potassium dodecanoate (C12K) in sulfate solutions was found to be 0.07 M. The protective layers formed at the copper surface subsequent to exposure in various n-alkanoic acid potassium salt solutions were characterized by contact angle measurements, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared reflection spectroscopy. Pronounced copper protection was attributed to the growth of a protective film on the copper surface, containing both copper oxides and copper carboxylate compounds. It is suggested that the organic molecules enhance copper protection by covering copper oxides with a thin and dense organic layer, which prevents water molecules or aggressive anions from interacting with the copper surface. 相似文献
39.
Yair Shapira Moshe Israeli Avram Sidi Uzi Zrahia 《Numerical Methods for Partial Differential Equations》1999,15(5):535-543
Spectral element schemes for the solution of elliptic boundary value problems are considered. Preconditioning methods based on finite difference and finite element schemes are implemented. Numerical experiments show that inverting the preconditioner by a single multigrid iteration is most efficient and that the finite difference preconditioner is superior to the finite element one for both definite and indefinite problems. A multigrid preconditioner is also derived from the finite difference preconditioner and is found suitable for the CGS acceleration method. It is pointed out that, for the finite difference and finite element preconditioners, CGS does not always converge to the accurate algebraic solution. © 1999 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 15: 535–543, 1999 相似文献
40.
By modifying von Neumann’s alternating projections algorithm, we obtain an alternating method for solving the recently introduced Common Solutions to Variational Inequalities Problem (CSVIP). For simplicity, we mainly confine our attention to the two-set CSVIP, which entails finding common solutions to two unrelated variational inequalities in Hilbert space. 相似文献