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911.
Time dependent magnetic fields can be used to produce exact rotations of spin wavefunctions. This avoids the inherent approximations encountered in experiments performed with static fields to demonstrate the effect of 2π-rotations on fermions. Two of the experiments proposed explicitly will use forthcoming interferometers for ultra cold neutrons. 相似文献
912.
Aequationes mathematicae - 相似文献
913.
Günther Beer Prof. Dr. Anton Meller Maria Wojnowska 《Monatshefte für Chemie / Chemical Monthly》1975,106(2):567-569
S-Methyl-N-phenyl-iminothiocarbonic acid-tri-O.O′.O″-isopropylsilicic acid anhydride,1 is obtained from the reaction of phenyl isocyanate and methylthiotriiso-propoxysilan.1 readily hydrolyses forming S-methylthiocarbanilide. Substances are characterized by their mass and1H-NMR spectra. 相似文献
914.
915.
Anton Evgrafov 《Applied Mathematics and Optimization》2005,52(3):263-277
We consider a problem concerning the distribution of a solid material
in a given bounded control volume with the goal to minimize the potential power
of the Stokes flow with given velocities at the boundary through the material-free
part of the domain.We also study the relaxed problem of the optimal distribution of
the porous material with a spatially varying Darcy permeability tensor, where the
governing equations are known as the Darcy–Stokes, or Brinkman, equations. We
show that the introduction of the requirement of zero power dissipation due to the
flow through the porous material into the relaxed problem results in it becoming a
well-posed mathematical problem, which admits optimal solutions that have extreme permeability properties (i.e., assume only
zero or infinite permeability); thus, they are also optimal in the original (non-relaxed) problem. Two numerical techniques
are presented for the solution of the constrained problem. One is based on a sequence of optimal Brinkman flows with increasing
viscosities, from the mathematical point of view nothing but the exterior penalty approach applied to the problem. Another
technique is more special, and is based on the “sizing” approximation of the problem using a mix of two different porous materials
with high and low permeabilities, respectively. This paper thus complements the study of Borrvall and Petersson (Internat.
J. Numer. Methods Fluids, vol. 41, no. 1, pp. 77–107, 2003), where only sizing optimization problems are treated. 相似文献
916.
Anton Smolianski 《国际流体数值方法杂志》2005,48(3):231-269
The present work is devoted to the study on unsteady flows of two immiscible viscous fluids separated by free moving interface. Our goal is to elaborate a unified strategy for numerical modelling of two‐fluid interfacial flows, having in mind possible interface topology changes (like merger or break‐up) and realistically wide ranges for physical parameters of the problem. The proposed computational approach essentially relies on three basic components: the finite element method for spatial approximation, the operator‐splitting for temporal discretization and the level‐set method for interface representation. We show that the finite element implementation of the level‐set approach brings some additional benefits as compared to the standard, finite difference level‐set realizations. In particular, the use of finite elements permits to localize the interface precisely, without introducing any artificial parameters like the interface thickness; it also allows to maintain the second‐order accuracy of the interface normal, curvature and mass conservation. The operator‐splitting makes it possible to separate all major difficulties of the problem and enables us to implement the equal‐order interpolation for the velocity and pressure. Diverse numerical examples including simulations of bubble dynamics, bifurcating jet flow and Rayleigh–Taylor instability are presented to validate the computational method. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
917.
Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent‐ and Metal‐Free Anodic Cross‐Coupling Reaction
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Anton Wiebe Dr. Dieter Schollmeyer Dr. Katrin M. Dyballa Prof. Dr. Robert Franke Prof. Dr. Siegfried R. Waldvogel 《Angewandte Chemie (International ed. in English)》2016,55(39):11801-11805
The oxidative cross‐coupling of aromatic substrates without the necessity of leaving groups or catalysts is described. The selective formation of partially protected nonsymmetric 2,2′‐biphenols via electroorganic synthesis was accomplished with a high yield of isolated product. Since electric current is employed as the terminal oxidant, the reaction is reagent‐free; no reagent waste is generated as only electrons are involved. The reaction is conducted in an undivided cell, and is suitable for scale‐up and inherently safe. The implementation of O‐silyl‐protected phenols in this transformation results in both significantly enhanced yields and higher selectivity for the desired nonsymmetric 2,2′‐biphenols. The use of a bulky silyl group to block one hydroxyl moiety makes the final product less prone to oxidation. Furthermore, the partially silyl‐protected 2,2′‐biphenols are versatile building blocks that usually require tedious or low‐yielding synthetic pathways. Additionally, this strategy facilitates a large variety of new substrate combinations for oxidative cross‐coupling reactions. 相似文献
918.
Antonín Klásek Antonín Lyčka Filip Křemen Aleš Růžička Michal Rouchal 《Helvetica chimica acta》2016,99(1):50-62
3‐Butylaminoquinolinediones ( 1 ) react with NaNO2 in AcOH to give the corresponding N‐nitrosoderivatives ( 2 ). The analogous reactions of 4‐hydroxy‐3‐butylaminoquinolinediones ( 5 ), prepared by the reduction of 1 with NaBH4, produce the corresponding nitrosamines ( 4 ). The reduction of both 2 and 4 with Zn under different conditions was non‐productive, but the reduction of both compounds with LiAlH4 at the oxo and lactame groups yielded impure products, generating new tricyclic benzoxadiazocines ( 9 ) by a reaction with HNCO. All compounds were characterized by IR, 1H‐, and 13C‐NMR (in some cases, 15N‐NMR also) spectroscopy and EI and/or ESI mass spectrometry. The X‐ray structure of compound 9g was determined. 相似文献
919.
The ability to control propagation of electromagnetic guided modes lies at the heart of integrated nanophotonics. Surface plasmon‐polaritons are a class of guided modes which can be employed in integrated optical systems. Here, we present a theoretical design of a coherent surface plasmon absorber which can perfectly harvest energy of coherently incident surface plasmons without parasitic scattering into free space modes. Excitation of free space modes which usually accompanies scattering of a surface plasmon by an interface boundary is avoided due to specially tailored anisotropy of the absorber. The concept of coherent SPP absorber is analyzed numerically for spatially non‐uniform and finite‐size structures. We believe that our results will be important for the development of integrated nanoplasmonic systems. 相似文献
920.
Matthias Vogelgesang Tomas Farago Thilo F. Morgeneyer Lukas Helfen Tomy dos Santos Rolo Anton Myagotin Tilo Baumbach 《Journal of synchrotron radiation》2016,23(5):1254-1263
Real‐time processing of X‐ray image data acquired at synchrotron radiation facilities allows for smart high‐speed experiments. This includes workflows covering parameterized and image‐based feedback‐driven control up to the final storage of raw and processed data. Nevertheless, there is presently no system that supports an efficient construction of such experiment workflows in a scalable way. Thus, here an architecture based on a high‐level control system that manages low‐level data acquisition, data processing and device changes is described. This system is suitable for routine as well as prototypical experiments, and provides specialized building blocks to conduct four‐dimensional in situ, in vivo and operando tomography and laminography. 相似文献