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21.
Rafał Jakieła Marta Galicka Piotr Dziawa Gunther Springholz Adam Barcz 《Surface and interface analysis : SIA》2020,52(3):71-75
Substitutional alloy Pb1 − xSnxSe is a new class of electronic materials called topological crystalline insulators, which at the temperature range from 0 K to 300 K exhibit topological state at compositions in the range 0.18 < x < 0.40 (in the rock-salt structure). In this report, we present a secondary ion mass spectrometry (SIMS) analysis technique to provide accurate Pb and Sn composition based on the measurement of PbCs+ and SnCs+ cluster ions intensities. Studies of Pb1 − xSnxSe bulk samples with various values of x show that x/(1 − x) is linear in relation to the intensity ratio of PbCs+/SnCs+ over the range from x = 0.15 to x = 0.41. This technique allows us to obtain an accurate Sn content for multilayered heterostructures, quantum wells containing Pb1 − xSnxSe with different x values for each layer. 相似文献
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Hennrich G Lynch VM Anslyn EV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(10):2274-2278
The conversion of 1,3,5-substituted benzene and mesitylene by electrophilic aromatic substitution and Sonogashira cross-coupling, respectively, furnished the C3-symmetric, hexasubstituted benzene derivatives 1 and 2 with an alternating substitution pattern. Based on the molecular scaffolds obtained, the two systems serve as model compounds for novel receptor molecules with distinct geometric features. X-ray structures have been obtained for 1 and 2, which are discussed in regard to their aptitude as receptor platforms or supramolecular building blocks. By looking at the rotational barriers for the functional groups placed around the molecular scaffolds by variable temperature 1H NMR spectroscopy, 1 and 2 turn out to exist in rapidly interconverting conformations. The alignment of these potential binding groups around the molecular scaffolds should be strongly biased by specific interactions with suitable guest molecules. 相似文献
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Gunther Pabst 《Discrete Mathematics》1976,16(1):53-56
All axiom systems are derived which define finite affine planes and consist of certain combinatorial inequalities or equalities involving the number of lines connecting two distinct points the number of lines through a point the number of points on a line, the total number of points or the total number of lines. The result given in Dembowski book Finite Geometries are corrected. 相似文献
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Gunther E. Molau 《Journal of membrane science》1981,8(3):309-330
The field of heterogeneous ion exchange membranes is reviewed briefly. Specific advantages and disadvantages of heterogeneous ion exchange membranes are discussed compared with those of homogeneous ion exchange membranes. p]The development of heterogeneous ion exchange membranes is presented in historical perspective. The electrochemistry of ion-selective membranes began with Ostwald in 1890. After the classical work of Michaelis (1925) with collodion membranes, the first fully synthetic ion exchange membranes were prepared by Zhukov (1933) and Wassenegger (1940), based on sulfonated phenol—formaldehyde resins. These initial membranes, which were of the homogeneous type found no practical uses. The era of commercially useful ion exchange membranes began with the work of Wyllie (1948), Juda (1950), Bodamer (1953) and their collaborators who prepared heterogeneous ion exchange membranes by embedding ion exchange particles into polymer matrices. p]Methods for making heterogeneous ion exchange membranes include compression-molding of polymer powders, compounding on hot rolls, latex or solvent blending in situ generation of either the matrix or the ion exchange material. Microheterogeneous ion exchange membranes can be made from block and graft copolymers, interpolymers snake-cage resins, similar techniques and materials. p]Even though the first commercial ion exchange membranes were heterogeneous, the interest in this type of membranes subsided later. As polymer science progressed, speciality monomers and polymers were being made which opened the way to the preparation of quite sophisticated homogeneous ion exchange membranes of satisfactory mechanical strength. However, the possibilities of heterogeneous ion exchange membranes are by no means exhausted and this field may warrant further exploration, applying modern methods and materials and thus progressing beyond the relatively crude heterogeneous ion exchange membranes of the pioneer times. 相似文献
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A multiplier method with automatic limitation of penalty growth 总被引:3,自引:0,他引:3
This paper presents a multiplier method for solving optimization problems with equality and inequality constraints. The method realizes all the good features that were foreseen by R. Fletcher for this type of algorithm in the past, but which suffers from none of the drawbacks of the earlier attempts.Research sponsored by the National Science Foundation (RANN) Grant ENV76-04264 the National Science Foundation Grant ENG73-08214-A01 and the Sweden-American Foundation. 相似文献
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The paper studies quasi-interpolation by scaled shifts of a smooth and rapidly decaying function. The centers are images of a smooth mapping of the hZn-lattice in Rs, sn, and the scaling parameters are proportional to h. We show that for a large class of generating functions the quasi-interpolants provide high order approximations up to some prescribed accuracy. Although in general the approximants do not converge as h tends to zero, the remaining saturation error is negligible in numerical computations if a scalar parameter is suitably chosen. The lack of convergence is compensated for by a greater flexibility in the choice of generating functions used in numerical methods for solving operator equations. 相似文献