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排序方式: 共有110条查询结果,搜索用时 15 毫秒
41.
We construct a second order elliptic equation in divergence form in3, with a nonzero solution which vanishes in a half-space.The coefficients are -Hölder continuous of any order < 1. This improves a previous counterexample of Miller (1972, 1974).Moreover, we obtain coefficients which belong to a finer class ofsmoothness, expressed in terms of the modulus of continuity. 相似文献
42.
In this paper, we report some experimental results concerning several types of loss measurements of Er3+:Ti:LiNbO3 optical waveguides by using optical methods. Using the Fabry-Pérot interferometry method, we evaluated the attenuation coefficient
of an optical waveguide resonator for a laser radiation having λ = 1.55 μm. We also evaluated the insertion losses, polarization dependent losses, and coupling with external losses. Additionally,
from the transmitted spectra of the symmetrical monomode Fabry-Pérot optical waveguide resonator, we were able to evaluate
the value of the group effective refractive index. 相似文献
43.
Tiberiu Rosenzveig Petur Gordon Hermannsson Alexandra Boltasseva Kristjan Leosson 《Applied Physics A: Materials Science & Processing》2010,100(2):341-346
We demonstrate the feasibility of fabricating thermo-optic plasmonic devices for variable optical attenuation and/or low-frequency
(kHz) signal modulation. Results of finite-element simulations and experimental characterization of prototype devices indicate
that a plasmonic device can reach specifications similar to or better than commercially available thermo-optic integrated
optical components. Specifically, we have considered the insertion loss, power consumption, footprint, polarization-dependent
loss, extinction ratio, and frequency response of the plasmonic devices, in addition to fabrication and material-related issues.
The most serious fabrication challenge is to realize metallic nanowire waveguides with a sufficiently accurate cross-section
to ensure low polarization-dependent loss at high extinction ratios. 相似文献
44.
Tiberiu Harko Francisco S. N. Lobo 《The European Physical Journal C - Particles and Fields》2010,70(1-2):373-379
We generalize the f(R) type gravity models by assuming that the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar R and of the matter Lagrangian L m . We obtain the gravitational field equations in the metric formalism, as well as the equations of motion for test particles, which follow from the covariant divergence of the energy-momentum tensor. The equations of motion for test particles can also be derived from a variational principle in the particular case in which the Lagrangian density of the matter is an arbitrary function of the energy density of the matter only. Generally, the motion is non-geodesic, and it takes place in the presence of an extra force orthogonal to the four-velocity. The Newtonian limit of the equation of motion is also considered, and a procedure for obtaining the energy-momentum tensor of the matter is presented. The gravitational field equations and the equations of motion for a particular model in which the action of the gravitational field has an exponential dependence on the standard general relativistic Hilbert–Einstein Lagrange density are also derived. 相似文献
45.
Vasile Georgescu Gianina Dobrescu Florica Papa Niculae I. Ionescu 《Reaction Kinetics and Catalysis Letters》2008,94(2):345-350
Benzene total oxidation on a Cu-Cr supported catalyst was investigated using the work function method. Above 300°C, the majority
of the oxygen species on the surface was O2− in the absence or in the presence of hydrocarbon. 相似文献
46.
Vlad Tiberiu Alexa Camelia Szuhanek Antoanela Cozma Atena Galuscan Florin Borcan Diana Obistioiu Cristina Adriana Dehelean Daniela Jumanca 《Molecules (Basel, Switzerland)》2020,25(23)
Since ancient times complementary therapies have been based on the use of medicinal plants, natural preparations and essential oils in the treatment of various diseases. Their use in medical practice is recommended in view of their low toxicity, pharmacological properties and economic impact. This paper aims to test the antimicrobial effect of natural preparation based on clove, orange and bergamot essential oils on a wide range of microorganisms that cause infections in humans including: Streptococcus pyogenes, Staphylococcus aureus, Shigella flexneri, Candida parapsilosis, Candida albicans, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhimurium and Haemophilus influenza. Three natural preparations such as one-component emulsions: clove (ECEO), bergamote (EBEO), and orange (EOEO), three binary: E(BEO/CEO), E(BEO/OEO), E(CEO/OEO) and a tertiary emulsion E(OEO/BEO/CEO) were obtained, characterized and tested for antimicrobial effects. Also, the synergistic/antagonistic effects, generated by the presence of the main chemical compounds, were studied in order to recommend a preparation with optimal antimicrobial activity. The obtained results underline the fact that the monocomponent emulsion ECEO shows antimicrobial activity, while EOEO and EBEO do not inhibit the development of the analyzed strains. In binary or tertiary emulsions E(BEO/CEO), E(CEO/OEO) and E(OEO/ BEO/CEO) the antimicrobial effect of clove oil is potentiated due to the synergism exerted by the chemical compounds of essential oils. 相似文献
47.
Tiberiu Popoviciu 《Aequationes Mathematicae》1969,2(1):128-129
Sans résumé 相似文献
48.
Sorin D. Anghel Tiberiu Frentiu Eugen Darvasi Ana-Maria Rusu Alpar Simon E. A. Cordos 《Fresenius' Journal of Analytical Chemistry》1996,355(3-4):250-251
The excitation temperatures of Ar and Fe, the ionization temperatures of Ar and Ca and the electron number densities have been determined for a radiofrequency capacitively coupled plasma in the tip-ring electrode geometry. The temperatures and the electron number densities possess their maximum value close to the electrodes. 相似文献
49.
Tiberiu Dumitrescu 《代数通讯》2013,41(3):1115-1123
50.