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991.
We investigated the morphological, structural and electronic properties of Pentacene thin films grown by vacuum thermal evaporation on different inert substrates at room temperature. The results of our AFM and STM analysis give an interplanar spacing of 1.54 nm corresponding to the (0 0 1) distance of the so-called “thin film phase”. The STS measurements show an HOMO-LUMO gap of 2.2 eV. 相似文献
992.
A. I. Khachaturov 《Technical Physics》2006,51(2):226-230
The contribution of electrons moving at large angles to the barrier junction plane to the tunnel current is calculated. This contribution turns out to be small only if the Fermi energy of the electrons equals several electron volts. Otherwise, specifically, when the Fermi energy is no higher than 1–2 eV, this contribution dominates in high and thin potential barriers. It is found that the tunnel magnetic resistance in ferromagnet-insulator-ferromagnet contacts correlates with this contribution. It is this correlation that is responsible for a decrease in this contribution as the potential barriers get lower and thicker. 相似文献
993.
The possibilities of controlling the laser beam properties by a deformable mirror introduced into the laser optical cavity
were studied theoretically and experimentally. The experiments were performed under conditions of an industrial high power
transverse flow cw CO2 laser operating with a stable resonator of a folded configuration. A deformable bimorph mirror of a surface profile controlled
by the voltage applied to the mirror electrodes is implemented to the laser system as a back cavity mirror or as a one of
the inner folding mirrors. The near-and far-field characteristics of the laser beam versus the resonator configuration controlled
by the changes of the focal length of the deformable mirror are discussed in the paper. The analysis reveals that the resonator
with an inner deformable mirror is much more sensitive to the mirror curvature variations than the resonator in which the
deformable mirror is used as a back cavity mirror. The presented results show that dynamic and controllable changes in the
resonator properties result in the controlled modification and optimisation of the laser output power and spatial parameters
of the laser radiation. 相似文献
994.
The theory of dielectric space-charge polarization losses describes well both the model of an inhomogeneous dielectric [1]
and the polarization resulting from mosaic blocks of alkali-halide crystals [2]. The Debye frequency dependences ε*(ω) and
tan δ(ω) with non-Arrhenius relaxation time are calculated in the first approximation of perturbation theory [3, 4] with the
use of a nonlinear system of the Fokker-Planck and Poisson equations for the interlayer polarization with allowance for tunnel
transitions of relaxation oscillators. For the Maxwell mechanism of space-charge relaxation, tan δ(ω) also has the Debye form
[5]. It should be noted that in studies cited above the electric field was considered uniform, and the nonlinearity of the
initial system of equations was not investigated. This paper removes these restrictions and elaborates a theory of relaxation
mechanism.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 28–34, November, 2006. 相似文献
995.
In this paper we propose a general integration scheme for a Multi-Criteria Decision Making model of the Multi-Attribute Utility
Theory in Constraint Programming. We introduce the Choquet integral as a general aggregation function for multi-criteria optimization
problems and define the Choquet global constraint that propagates this function during the Branch-and-Bound search. Finally the benefits of the propagation
of the Choquet constraint are evaluated on the examination timetabling problem. 相似文献
996.
S.N. Abdulmadjid M.M. Suliyanti K.H. Kurniawan T.J. Lie M. Pardede R. Hedwig K. Kagawa M.O. Tjia 《Applied physics. B, Lasers and optics》2006,82(1):161-166
We report in this paper the results of an experimental study on hydrogen analysis of solid samples in high pressure helium
ambient gas employing the basic scheme of laser induced breakdown spectroscopy (LIBS). It is shown that the metastable excited
state of helium atom can be utilized to induce delayed excitation of the ablated hydrogen atoms, and thereby avoid the Stark
broadening effect as well as overcoming the undesirable mismatch effect, which are responsible for inefficient excitation
respectively. It is further demonstrated that for samples of high boiling-point materials such as zircaloy, successful hydrogen
analysis can be achieved by a newly introduced double excitation technique employing single laser realized in a modified configuration
of the conventional LIBS method.
PACS 51-52 相似文献
997.
998.
We present a new verified optimization method to find regions for Hénon systems where the conditions of chaotic behaviour
hold. The present paper provides a methodology to verify chaos for certain mappings and regions. We discuss first how to check
the set theoretical conditions of a respective theorem in a reliable way by computer programs. Then we introduce optimization
problems that provide a model to locate chaotic regions. We prove the correctness of the underlying checking algorithms and
the optimization model. We have verified an earlier published chaotic region, and we also give new chaotic places located
by the new technique. 相似文献
999.
Dmitry I. Belov Ronald D. Armstrong 《Computational Optimization and Applications》2006,33(2-3):319-332
This paper introduces a novel approach for extracting the maximum number of non-overlapping test forms from a large collection
of overlapping test sections assembled from a given item bank. The approach involves solving maximum set packing problems
(MSPs). A branch-and-bound MSP algorithm is developed along with techniques adapted from constraint programming to estimate
lower and upper bounds on the optimal MSP solution. The algorithm is general and can be applied in other applications including
combinatorial auctions. The results of computer simulations and experiments with an operational item bank are presented.
An erratum to this article is available at . 相似文献
1000.
Butyltins were analyzed in waters from California river and lake marinas and were detected at the part per trillion (ppt) level in most locations. The tributyltin:dibutyltin (TBT/DBT) ratios in the fresh waters were similar to those in their saline counterparts indicating like rates of degradation in the two salinity regimes. 相似文献