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1.
Using a density-functional method that employs linear combinations of atomic orbitals as basis sets, nonlocal norm-conserving pseudopotentials and the generalized gradient approximation for exchange and correlation, we found that at 0 K the atoms of an Fe monolayer on the Ni (111) surface occupy hcp rather than fcc sites, in keeping with previous predictions made using the ab initio all-electron full-potential linearized augmented plane wave method with the local spin density approximation. 相似文献
2.
S. Riechel U. Lemmer J. Feldmann T. Benstem W. Kowalsky U. Scherf A. Gombert V. Wittwer 《Applied physics. B, Lasers and optics》2000,71(6):897-900
We report on the laser modes in optically pumped solid-state lasers using an electroluminescent organic semiconductor as the
active medium. Mechanically flexible distributed-feedback lasers are fabricated by depositing a thin film of an active material
onto a nano-patterned polyester substrate either via spin-coating of a soluble ladder-type poly(p-phenylene) or via vacuum
co-sublimation of small organic molecules. The different surface texture resulting from the fabrication process causes different
feedback mechanisms. In both lasers higher lateral modes give rise to a broadening of the laser spectra at higher pumping
levels.
Received: 7 August 2000 / Revised version: 12 September 2000 / Published online: 8 November 2000 相似文献
3.
A new structure of GaAs photocathode was introduced. The Be-doping concentration is variable in the new structure compared with the constant concentration of Be in the normal photocathode. Negative electron affinity GaAs photocathodes were fabricated by alternate input of Cs and O. The spectral response results measured by the on-line spectral response measurement system show that the integrated photosensitivity of the photocathodes with the new structure is enhanced by at least 50% as compared to those with the monolayer structure. Accordingly, two main factors leading to the enhanced photosensitivity of the photocathodes were discussed. 相似文献
4.
Liquid sulfur is a well-known liquid which exhibits a polymerization transition at Tp=159 °C. Recently, it was found from our experiments that such a transition can be induced below Tp through laser illumination and that an iridescent pattern appears under strong illumination with a pulsed laser of more than
60 mJ/cm2 pulse. It is proposed that the visible change in iridescence is due to a macroscopic reconstruction of laser-generated polymers
and that a laser-induced phase transition takes place from a freely expanded polymer phase to an ordered polymer phase when
increasing the laser illumination. To further examine this possibility, the time variation of the iridescent pattern has been
fully investigated using a macro lens, a polarized microscope and an optical microscope. In an analysis of the iridescent
pattern, a rapid decrease in the area was observed after an initial slow decrease, suggesting a type of phase transition.
Results from the observation of a quenched sulfur sample with a polarized microscope gave evidence that the iridescent region
consists of polymers. Through observation of the liquid with a microscope, a striped pattern with micrometer sized spacing
was noted in the iridescent pattern. A drastic color change was observed in the pattern from its generation to its disappearance.
Sample thickness dependence of the pattern was also observed. These results were well explained by assuming the self-arrangement
of laser-generated colloidal polymers. 相似文献
5.
Fernanda Vera Cruz de Vasconcelos Paulo Fernandes Barbosa de Souza Jr. Maria Fernanda Pimentel Márcio José Coelho Pontes Claudete Fernandes Pereira 《Analytica chimica acta》2012
This work evaluates the use of near-infrared (NIR) overtone regions to determine biodiesel content, as well potential adulteration with vegetable oil, in diesel/biodiesel blends. For this purpose, NIR spectra (12,000–6300 cm−1) were obtained using three different optical path lengths: 10 mm, 20 mm and 50 mm. Two strategies of regression with variable selection were evaluated: partial least squares (PLS) with significant regression coefficients selected by Jack-Knife algorithm (PLS/JK) and multiple linear regression (MLR) with wavenumber selection by successive projections algorithm (MLR/SPA). For comparison, the results obtained by using PLS full-spectrum models are also presented. In addition, the performance of models using NIR (1.0 mm optical path length, 9000–4000 cm−1) and MIR (UATR – universal attenuated total reflectance, 4000–650 cm−1) spectral regions was also investigated. The results demonstrated the potential of overtone regions with MLR/SPA regression strategy to determine biodiesel content in diesel/biodiesel blends, considering the possible presence of raw oil as a contaminant. This strategy is simple, fast and uses a fewer number of spectral variables. Considering this, the overtone regions can be useful to develop low cost instruments for quality control of diesel/biodiesel blends, considering the lower cost of optical components for this spectral region. 相似文献
6.
Two fluorescent monomers having a quinoxaline skeleton, N-(2,3-dimorpholinoquinoxalin-6-yl)acrylamide (QxA) and N-(1-(2,3-dimorpholinoquinoxalin-6-ylamino)prop-2-yl)methacrylamide (QxAlaMA), were synthesized. Thermo-responsive copolymers of N-isopropylacrylamide (NIPAM) and a small amount of a fluorescent monomer were synthesized and their fluorescence properties investigated. The fluorescent monomers showed intense solvatochromism in their fluorescence. The wavelength at the maximum fluorescence intensity of the QxAlaMA-labeled PNIPAM dramatically blue-shifted and the fluorescence intensity of the QxA-labeled PNIPAM significantly increased around the transition temperature. It was found that these fluorescent dyes can sense and report the thermo-responsive behavior of the PNIPAM in water. Both QxAlaMA and QxA were demonstrated to be applicable to new intramolecular fluorescent probes. 相似文献
7.
GÉRARD Laumon 《Compositio Mathematica》1997,105(3):267-359
In this paper we compute the cohomology with compact supports of a Siegelthreefold as a virtual module over the product of the Galois group of
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and the Hecke algebra. We use a method which has been developed by Ihara, Langlands and Kottwitz: comparison of the Grothendieck--Lefschetz formula and the Arthur--Selberg trace formula. 相似文献
8.
B. Park H.S. Kim J.Y. Bae J.G. Lee H.S. Woo S.H. Han J.W. Wu M. Kakimoto H. Takezoe 《Applied physics. B, Lasers and optics》1998,66(4):445-451
∞v to C1v by the photo-isomerization process, with the azobenzene conformation retained as trans-isomer.
Received: 5 April 1997 相似文献
9.
A thin film of triphenylamine dimer, N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), doped with fac tris(2-phenylpyridine) iridium (Ir(ppy)3) and platinum octaethyl porphine (PtOEP) is characterized by photoluminescence emission measurements at several excitation wavelengths and photoluminescence excitation measurements at relevant emission wavelengths in the temperature range from 10 K to room temperature. The investigated film is a phosphorescent OLED material with singlet absorbing host (TPD) and triplet emitting guests [Ir(ppy)3 and PtOEP]. At short wavelength excitation simultaneous triple band emission from singlet TPD, triplet Ir(ppy)3 and TPD, and from triplet PtOEP is observed. Förster-type singlet-singlet state energy transfer from TPD to Ir(ppy)3 and PtOEP, intra-component intersystem crossing, and Dexter-type triplet-triplet energy transfer between the substituents are studied. 相似文献
10.
Structural changes in the layered compound γ-NaxCoO2 (x=0.74) are studied by in situ Raman scattering and energy-dispersive X-ray diffraction methods at pressures up to 41 GPa. The pressure dependence of the lattice parameters indicate that γ-NaxCoO2 has a strong anisotropic compressibility before 15 GPa and the unit cell is easily compressed between layers. The discontinuity of the lattice parameters and Raman observations reveal that a phase transition occurred at pressures between 10 and 12 GPa. The high-pressure phase has the same hexagonal symmetry and the phase transition may be due to the pressure-induced rearrangement of one of the Na cations in the unit cell. 相似文献