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排序方式: 共有121条查询结果,搜索用时 0 毫秒
1.
We investigate decay properties of correlation functions in a class of chaotic billiards. First we consider the statistics of Poincaré recurrences (induced by a partition of the billiard): the results are in agreement with theoretical bounds by Bunimovich, Sinai, and Bleher, and are consistent with a purely exponential decay of correlations out of marginality. We then turn to the analysis of the velocity-velocity correlation function: except for intermittent situations, the decay is purely exponential, and the decay rates scale in a simple way with the (uniform) curvature of the dispersing arcs. A power-law decay is instead observed when the system is equivalent to an infinite-horizon Lorentz gas. Comments are given on the behaviour of other types of correlation functions, whose decay, during the observed time scale, appears slower than exponential. 相似文献
2.
We prove that, under appropriate assumptions on the domain Ω and on the datumg, any optimal partition of Ω (minimizing the sum of the total perimeter and the approximation term
is finite. Finiteness result for the problem of image segmentation in Artificial Vision can be deduced.
Sunto Dimostriamo che, in opportune ipotesi sul dominio Ω e sul datog, ogni partizione ottimale di Ω (minimizzante il perimetro totale in Ω più il termine di approssimazione è finita. Se ne deducono risultati di finitezza per il problema della segmentazione di immagini in Visione Artificiale.相似文献
3.
We prove some facts concerning surfaces of minimal area bounding regions of prescribed volume in n. The main result we prove is that the mean curvature of such a surface is constant, if possibly a discontinuous function of the enclosed volume. The boundary behaviour of the solutions is also discussed. 相似文献
4.
Combining Experimental and Computational Studies to Understand and Predict Reactivities of Relevance to Homogeneous Catalysis 下载免费PDF全文
Dr. Althea S.‐K. Tsang Italo A. Sanhueza Prof. Dr. Franziska Schoenebeck 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(50):16432-16441
This article showcases three major uses of computational chemistry in reactivity studies: the application after, in combination with, and before experiment. Following a brief introduction of suitable computational tools, challenges and opportunities in the implementation of computational chemistry in reactivity studies are discussed, exemplified with selected case studies from our and other laboratories. 相似文献
5.
Leonardo Puppulin Yasuhito Takahashi Wenliang Zhu Giuseppe Pezzotti 《Journal of Raman spectroscopy : JRS》2011,42(3):482-487
The complex orientation dependence in space of Raman active vibrations in the orthorhombic structure of polyethylene (PE) is discussed in terms of Raman tensor elements as intrinsic physical parameters of the lattice. Building upon the symmetry assignment of these vibrational modes, we systematically studied, from both theoretical and experimental viewpoints, the changes of polarized intensity for the Ag and the B2g + B3g vibrational modes with respect to PE molecular orientation. After explicitly expanding the Raman selection rules associated with the Ag and the B2g + B3g modes, introducing them into general expressions of the orientation distribution function, and validating them by means of a least‐square fitting procedure on experimental data, we compare here two mesostructural models for a highly crystallized and self‐aligned PE fiber structure. Stereological arguments are shown concerning the arrangement of orthorhombic fibrils in such a sample that unfold the correct values of five independent Raman tensor elements for orthorhombic PE. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
6.
Martina Palomba Italo Franco Coelho Dias Ornelio Rosati Francesca Marini 《Molecules (Basel, Switzerland)》2021,26(11)
In recent years, vinyl selenones were rediscovered as useful building blocks for new synthetic transformations. This review will highlight these advances in the field of multiple-bond-forming reactions, one-pot synthesis of carbo- and heterocycles, enantioselective construction of densely functionalized molecules, and total synthesis of natural products. 相似文献
7.
E. Marin F. Boschetto M. Zanocco W. Zhu T. Adachi N. Kanamura T. Yamamoto B.J. McEntire E.N. Jones C. Powell J. Hendry R.M. Bock B.S. Bal G. Pezzotti 《Materials Today Chemistry》2021
Most structural bioceramics are comprised of metallic oxides such as alumina and zirconia. They are generally considered to be completely bioinert, but a non-oxide ceramic, silicon nitride, achieves equivalent levels of mechanical reliability while being bioactive. Silicon nitride can not only stimulate cellular proliferation but it is also antipathogenic with demonstrated efficacy against Gram-positive and Gram-negative bacteria, fungi, and viruses. In this work, three physical vapor deposition coatings with different Si:N ratios (silicon-rich, stoichiometric, and nitrogen-rich) were deposited on mirror-polished silica glass substrates. The coatings were characterized by spectroscopic and microscopic techniques and tested in vitro against E. coli and KUSA-A1 mesenchymal cells. Results showed that nitrogen-enriched SixNy has a strong antibacterial effect against E. coli and contributes to cellular proliferation while silicon-enriched SixNy stimulates the production of bone tissue, with higher indexes for mineralization and quality. These results suggest that SixNy's biological properties can be optimized for specific applications by carefully tuning its surface chemistry. 相似文献
8.
Calorimetric measurements of molar excess enthalpies, HE, at 298.15 K, of mixtures containing aromatic aldehydes of general formula C6H5(CH2)mCHO (with m = 0, 1 and 2) + n-hexane, n-heptane or benzene are reported, together with the values of HE at equimolar composition compared with the corresponding values of HE for the aromatic ketones in the same solvents. The experimental results clearly indicate that the intermolecular interactions between the carbonyl groups (CHO) are influenced by the intramolecular interactions between the carbonyl and phenyl groups, particularly for the mixtures containing benzaldehyde. 相似文献
9.
A theory for stabilization of quantum resonances by a mechanism similar to one leading to classical resonances in nonlinear systems is presented. It explains recent surprising experimental results, obtained for cold cesium atoms when driven in the presence of gravity, and leads to further predictions. The theory makes use of invariance properties of the system allowing for separation into independent kicked rotor problems. The analysis relies on a fictitious classical limit where the small parameter is not Planck's constant, but rather the detuning from the frequency that is resonant in the absence of gravity. 相似文献
10.
Maria Giorgia Cutrufello Italo Ferino Elisabetta Rombi Vincenzo Solinas Gerardo Colón José Antonio Navío 《Reaction Kinetics and Catalysis Letters》2003,79(1):93-99
A ceria-lanthana catalytic system prepared by the sol-gel technique proved to be active in 4-methylpentan-2-ol conversion,
mainly leading to 4-methylpent-1-ene, a monomer for manufacturing polymers of high technological properties. The product distribution
strongly depends on the acid-base features of the catalyst. The catalytic behavior of the samples was examined in the light
of their acid-base properties.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献