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41.
Per Helvig Christensen Steen Mørup Henrik Topsøe Bjerne Steffen Clausen 《Hyperfine Interactions》1986,28(1-4):945-948
Bimetallic Fe-Co alloy catalysts supported on silica have been studied by use of combined Mössbauer absorption and emisson spectroscopy. Effects of carburization on samples with different particle size are discussed. 相似文献
42.
43.
Steen Markvorsen 《Geometriae Dedicata》2008,133(1):7-34
For a given combinatorial graph G a geometrization (G, g) of the graph is obtained by considering each edge of the graph as a 1-dimensional manifold with an associated metric g. In this paper we are concerned with minimal isometric immersions of geometrized graphs (G, g) into Riemannian manifolds (N
n
, h). Such immersions we call minimal webs. They admit a natural ‘geometric’ extension of the intrinsic combinatorial discrete Laplacian. The geometric Laplacian on
minimal webs enjoys standard properties such as the maximum principle and the divergence theorems, which are of instrumental
importance for the applications. We apply these properties to show that minimal webs in ambient Riemannian spaces share several
analytic and geometric properties with their smooth (minimal submanifold) counterparts in such spaces. In particular we use
appropriate versions of the divergence theorems together with the comparison techniques for distance functions in Riemannian
geometry and obtain bounds for the first Dirichlet eigenvalues, the exit times and the capacities as well as isoperimetric
type inequalities for so-called extrinsic R-webs of minimal webs in ambient Riemannian manifolds with bounded curvature.
相似文献
44.
45.
Jens Martin Knudsen Steen Mørup Jolanta Galazka-Friedman 《Hyperfine Interactions》1990,57(1-4):2231-2235
Both the USSR and US have plans of performing rover missions and sample return missions to the planet Mars in the coming decade. There may be possibilities of performingin situ Mössbauer spectroscopy on Mars or on fresh samples returned to a space station. 相似文献
46.
Dr. Xin-Ming Hu Magnus H. Rønne Prof. Dr. Steen U. Pedersen Prof. Dr. Troels Skrydstrup Prof. Dr. Kim Daasbjerg 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6568-6572
In a comparative study of the electrocatalytic CO2 reduction, cobalt meso-tetraphenylporphyrin (CoTPP) is used as a model molecular catalyst under both homogeneous and heterogeneous conditions. In the former case, employing N,N-dimethylformamide as solvent, CoTPP performs poorly as an electrocatalyst giving low product selectivity in a slow reaction at a high overpotential. However, upon straightforward immobilization of CoTPP onto carbon nanotubes, a remarkable enhancement of the electrocatalytic abilities is seen with CO2 becoming selectively reduced to CO (>90 %) at a low overpotential in aqueous medium. This effect is ascribed to the particular environment created by the aqueous medium at the catalytic site of the immobilized catalyst that facilitates the adsorption and further reaction of CO2. This work highlights the significance of assessing an immobilized molecular catalyst from more than homogeneous measurements alone. 相似文献
47.
H. J. J. Hardy C. H. Massen C. van der Steen J. A. Poulis 《Applied Scientific Research》1973,27(1):129-132
In the preceeding paper on this subject a method was described which enabled the measurement of magnetic susceptibilities in constant magnetic fields. In the present paper it is demonstrated that the application of an alternating magnetic field instead of a constant field is advantageous.Many environmental disturbances are eliminated, the measurement time is highly reduced and the amplitude of the magnetizing field can be brought back to 60 Oersted at which fields the sensitivity is still a few percent for diamagnetic substances. 相似文献
48.
Resonant vibration control of rotating beams 总被引:3,自引:0,他引:3
Martin Nymann Svendsen Steen Krenk Jan Høgsberg 《Journal of sound and vibration》2011,330(9):1877-1256
Rotating structures, like e.g. wind turbine blades, may be prone to vibrations associated with particular modes of vibration. It is demonstrated, how this type of vibrations can be reduced by using a collocated sensor-actuator system, governed by a resonant controller. The theory is here demonstrated by an active strut, connecting two cross-sections of a rotating beam. The structure is modeled by beam elements in a rotating frame of reference following the beam. The geometric stiffness is derived in a compact form from an initial stress formulation in terms of section forces and moments. The stiffness, and thereby the natural frequencies, of the beam depend on the rotation speed and the controller is tuned to current rotation speed to match the resonance frequency of the selected mode. It is demonstrated that resonant control leads to introduction of the intended level of damping in the selected mode and, with good modal connectivity, only very limited modal spill-over is generated. The controller acts by resonance and therefore has only a moderate energy consumption, and successfully reduces modal vibrations at the resonance frequency. 相似文献
49.
Jansen K van der Steen AF van Beusekom HM Oosterhuis JW van Soest G 《Optics letters》2011,36(5):597-599
We demonstrate intravascular photoacoustic imaging of human coronary atherosclerotic plaque. The data was obtained from two fresh human coronary arteries ex vivo, showing different stages of disease. A 1.25?mm diameter intravascular imaging catheter was built, comprising an angle-polished optical fiber adjacent to a 30?MHz ultrasound transducer. Specific photoacoustic imaging of lipid content, a key factor in vulnerable plaques that may lead to myocardial infarction, is achieved by spectroscopic imaging at different wavelengths between 1180 and 1230?nm. Simultaneous imaging with intravascular ultrasound was performed. 相似文献
50.
We show that the Temperley–Lieb algebra of type A and the blob algebra (also known as the Temperley–Lieb algebra of type B) at roots of unity are \(\mathbb{Z}\) -graded algebras. We moreover show that they are graded cellular algebras, thus making their cell modules, or standard modules, graded modules for the algebras. 相似文献