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991.
D. V. Lebedev E. M. Ivan’kova V. A. Marikhin L. P. Myasnikova V. Seydewitz 《Physics of the Solid State》2009,51(8):1744-1752
Physics of the Solid State - A comparative investigation of the surface structure of three ultrahigh molecular weight poly(eth-ylene) (UHMWPE) reactor powders that differ by their ability to be... 相似文献
992.
The impact of transient and steady-state thermal effects on the conversion efficiency of quasi-phasematched second harmonic
generation in periodically poled LiNbO3 fibres is discussed. The response time and wavelength variation of the quasi-phasematching condition depend on the thermal
conductivity of the fibre, its enclosure and the thermal coefficient of the crystal’s refractive index. 相似文献
993.
To establish a compact analytical framework for the preliminary stress-wave identification of material defects, the focus of this study is an extension of the concept of topological derivative, rooted in elastostatics and the idea of cavity nucleation, to 3D elastodynamics involving germination of solid obstacles. The main result of the proposed generalization is an expression for topological sensitivity, explicit in terms of the elastodynamic Green's function, obtained by an asymptotic expansion of a misfit-type cost functional with respect to the nucleation of a dissimilar elastic inclusion in a defect-free “reference” solid. The featured formula, consisting of an inertial-contrast monopole term and an elasticity-contrast dipole term, is shown to be applicable to a variety of reference solids (semi-infinite and infinite domains with constant or functionally graded elastic properties) for which the Green's functions are available. To deal with situations when the latter is not the case (e.g. finite reference bodies or those with pre-existing defects), an adjoint field approach is employed to derive an alternative expression for topological sensitivity that involves the contraction of two (numerically computed) elastodynamic states. A set of numerical results is included to demonstrate the potential of generalized topological derivative as an efficient tool for exposing not only the geometry, but also material characteristics of subsurface material defects through a local, point-wise identification of “optimal” inclusion properties that minimize the topological sensitivity at sampling location. Beyond the realm of non-invasive characterization of engineered materials, the proposed developments may be relevant to medical diagnosis and in particular to breast cancer detection where focused ultrasound waves show a promise of superseding manual palpation. 相似文献
994.
Gunnar Brinkmann Christian Grothaus Ivan Gutman 《Journal of mathematical chemistry》2007,42(4):909-924
In this paper, a method to constructively enumerate fusenes and benzenoids with perfect matchings is given. It is based on
an algorithm for generating all fusenes and benzenoids and introduces new restrictions into the generation process that avoid
the generation of structures without perfect matchings.
相似文献
995.
Juraj ?ernák Janusz Lipkowski Ivan Poto?ňák Alexander Hudák 《Monatshefte für Chemie / Chemical Monthly》2001,40(5):193-202
[Cu(tn)2Ni(CN)4]2ċ4H2O and Cu(tn)2Ni(CN)4 (tn = 1,3-diaminopropane) were prepared and characterized. The hydrate is unstable on air and readily dehydrates to Cu(tn)2Ni(CN)4. Crystal structure analysis of the hydrate at 150 K revealed a novel tetranuclear molecular structure of the tetracyanonickellate. The building elements are two [Cu(tn)2]2+ cations (coordination numbers of Cu: 5 and 6, respectively), two [Ni(CN)4)2− anions, and crystal water. The two cations are linked by one tetracyanonickellate anion via bridging cyano groups placed in cis positions. The second anion is bound weakly (Cu-N = 2.82 ?) via one μ2-bridging cyano ligand. The tetranuclear molecules and pairs of solvate water molecules are linked by strong hydrogen bonds, thus forming infinite planes which are linked in the third dimension by considerably weaker hydrogen bonds. 相似文献
996.
Federico Iori Eleonora Luppi Ivan Marri D. Ninno Stefano Ossicini 《Journal of luminescence》2006,121(2):335-339
There are experimental evidences that doping control at the nanoscale can significantly modify the optical properties with respect to the pure systems. This is the case of silicon nanocrystals (Si-nc), for which it has been shown that the photoluminescence (PL) peak can be tuned also below the bulk Si band gap by properly controlling the impurities, for example by boron (B) and phosphorus (P) codoping. In this work, we report on an ab initio study of impurity states in Si-nc. We consider B and P substitutional impurities for Si-nc with a diameter up to 2.2 nm. Formation energies (FEs), electronic, optical and structural properties have been determined as a function of the cluster dimension. For both B-doped and P-doped Si-nc the FE increases on decreasing the dimension, showing that the substitutional doping gets progressively more difficult for the smaller nanocrystals. Moreover, subsurface impurity positions result to be the most stable ones. The codoping reduces the FE strongly favoring this process with respect to the simple n-doping or p-doping. Such an effect can be attributed to charge compensation between the donor and the acceptor atoms. Moreover, smaller structural deformations, with respect to n-doped and p-doped cases, localized only around the impurity sites are observed. The band gap and the optical threshold are largely reduced with respect to the undoped Si-nc showing the possibility of an impurity-based engineering of the Si-nc PL properties. 相似文献
997.
998.
999.
In this paper, we prove a central limit theorem for a sequence of multiple Skorokhod integrals using the techniques of Malliavin
calculus. The convergence is stable, and the limit is a conditionally Gaussian random variable. Some applications to sequences
of multiple stochastic integrals, and renormalized weighted Hermite variations of the fractional Brownian motion are discussed. 相似文献
1000.
Javier Sastre Torao Ivan A. Gagarinov Gaël M. Vos Frederik Broszeit Apoorva D. Srivastava Martin Palmer James I. Langridge Oier Aizpurua‐Olaizola Victor J. Somovilla Geert‐Jan Boons 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17780-17784
The fucosylation of glycans leads to diverse structures and is associated with many biological and disease processes. The exact determination of fucoside positions by tandem mass spectrometry (MS/MS) is complicated because rearrangements in the gas phase lead to erroneous structural assignments. Here, we demonstrate that the combined use of ion‐mobility MS and well‐defined synthetic glycan standards can prevent misinterpretation of MS/MS spectra and incorrect structural assignments of fucosylated glycans. We show that fucosyl residues do not migrate to hydroxyl groups but to acetamido moieties of N‐acetylneuraminic acid as well as N‐acetylglucosamine residues and nucleophilic sites of an anomeric tag, yielding specific isomeric fragment ions. This mechanistic insight enables the characterization of unique IMS arrival‐time distributions of the isomers which can be used to accurately determine fucosyl positions in glycans. 相似文献