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921.
Li Huifeng Wang Jinliang 《偏微分方程(英文版)》2008,21(4):289-302
In ecological dynamic systems, the competition between species is a very universal phenomenon, which can be described by the well-known Volterra-Lotka model in a diffusion form. Noticing that the living space usually changes in a seasonal manner and the population development of the species may also undergo time-delay im- pact, a developed form of this model is investigated in this article. The main approaches employed here are the upper-lower solution method and the energy-estimate technique. The results show that whether the species may sustain survival or not depends on the relations among the birth rate, the death rate, the competition rate, the diffusivity and the time delay. For the survival case, the population evolutions of the two species may appear asymptotic periodicity with distinct upper bound and this bound depends heavily on the time delay. These results can be also checked by the intuitionistic numerical simulations. 相似文献
922.
Shuxia Pan 《Journal of Mathematical Analysis and Applications》2008,346(2):415-424
This paper is concerned with the existence of traveling wave fronts for delayed non-local diffusion systems without quasimonotonicity, which can not be answered by the known results. By using exponential order, upper-lower solutions and Schauder's fixed point theorem, we reduce the existence of monotone traveling wave fronts to the existence of upper-lower solutions without the requirement of monotonicity. To illustrate our results, we establish the existence of traveling wave fronts for two examples which are the delayed non-local diffusion version of the Nicholson's blowflies equation and the Belousov-Zhabotinskii model. These results imply that the traveling wave fronts of the delayed non-local diffusion systems without quasimonotonicity are persistent if the delay is small. 相似文献
923.
V. V. Sargsyan Z. Kanokov G. G. Adamyan N. V. Antonenko 《Theoretical and Mathematical Physics》2008,156(3):1331-1346
Based on the non-Markovian quantum Langevin equations, we obtain time-dependent transport coefficients for an inverted oscillator
coupled linearly in the coordinate to a thermostat. We comparatively analyze the diffusion coefficients for harmonic and inverted
oscillators and study the role of quantum statistical effects in the passage through a parabolic barrier.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 156, No. 3, pp. 425–443, September, 2008. 相似文献
924.
925.
Yo Han Yoon Seol-Min Yi Ji-Hoon Lee Young-Chang Joo 《Microelectronic Engineering》2010,87(11):2230-481
In this work, a high power continuous-wave (CW) Nd:YAG laser was used for thermal treatment of inkjet-printed Ag films - resulting in the elimination of organic additives (dispersant, binder, and organic solvent) in the Ag ink and annealing of Ag nano-particles. By optimizing laser parameters such as laser power and defocusing value, the laser energy can be totally converted into heat energy, which is used for thermal treatment of inkjet-printed Ag films. This results in the microstructure and the resistivity of the films to be controlled. We investigated the thermal diffusion mechanisms during laser annealing and the resulting microstructures. The impact of high power laser annealing on microstructures and electrical characteristics of inkjet-printed Ag films was compared to those of the films annealed by a conventional furnace annealing. Focused ion beam (FIB) channeling images show that the laser annealed Ag films have large columnar grains and a dense void-free structure, while furnace annealed films have much smaller grains and exhibit void formation. As a result, the laser annealed films have better electrical properties (low resistivity) compared to furnace annealed samples. 相似文献
926.
M. D. Kostin 《Journal of statistical physics》1986,45(3-4):765-767
An equation of diffusional quantum theory which takes into account the finite velocity of propagation is derived from Kelvin's telegraph equation and Fürth's relation. The equation is then used to derive the ground state of quantum systems and to derive the Sommerfeld-Dirac expression for the ionization potential of hydrogen-like ions. 相似文献
927.
A new MBE growth method for the fabrication of a high-quality double hetero-epitaxial Si/γ-Al2O3/Si structure was recently developed. In the present work, characteristics of NMOSFETs fabricated on the Si/γ-Al2O3/Si structure were investigated, and compared with those on a Si/MgAl2O4/Si structure. A γ-Al2O3 layer was created from a MgAl2O4 layer by reaction with Si beams as follows: MgAl2O4 + Si → γ-Al2O3 + SiO ↑ + Mg ↑. The MBE growth of Si on the effectively restructured γ-Al2O3 layer was then performed at a substrate temperature of 700° C, 150° C lower than for the MBE growth of Si on a MgAl2O4/Si substrate. The electron field effect mobility and leakage current between source and drain for the NMOSFETs fabricated
on Si/γ-Al2O3/Si structures were 660 cm2/V · s and 2.8 pA/μm respectively, and exhibited a higher level of performance than those on a Si/MgAl2O4/Si structure. In the Si/MgAl2O4/Si, SIMS measurements confirmed that autodoped Al and Mg atoms near the interface between the Si epi-layer and MgAl2O4/Si substrate diffused anomalously and accumulated at the surface during device fabrication processes. These autodoped Al
and Mg atoms acted as ionized impurities during test operation. Suppression of autodoping from insulator layers during the
MBE growth of Si was thus deemed essential to the improvement of NMOSFET characteristics. In the Si/γ-Al2O3/Si structure, autodoped atoms were scarcely detectable. It was therefore concluded that the Si/γ-Al2O3/Si structure under study was very promising for SOI device applications. 相似文献
928.
Hong Wang Jiangguo Liu Magne S. Espedal Richard E. Ewing 《Numerical Methods for Partial Differential Equations》2005,21(1):89-103
We develop a quasi‐two‐level, coarse‐mesh‐free characteristic nonoverlapping domain decomposition method for unsteady‐state convection‐diffusion partial differential equations in multidimensional spaces. The development of the domain decomposition method is carried out by utilizing an additive Schwarz domain decomposition preconditioner, by using an Eulerian‐Lagrangian method for convection‐diffusion equations and by delicately choosing appropriate interface conditions that fully respect and utilize the hyperbolic nature of the governing equations. Numerical experiments are presented to illustrate the method. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005 相似文献
929.
930.
Choonkeun Lee Yonggun Shul Haksoo Han 《Journal of Polymer Science.Polymer Physics》2002,40(19):2190-2198
For polyimide thin films, the dielectric properties were investigated with the capacitance and optical methods. The dielectric constants of the 4,4′‐oxydianiline (ODA)‐based polyimide thin films varied from 2.49 to 3.10 and were in the following decreasing order: 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA)–ODA > 1,2,4,5‐benzenetetracarboxylic dianhydride (PMDA)–ODA > 4,4′‐hexafluoroisopropylidene diphthalic dianhydride (6FDA)–ODA. According to the absorption of water, the diffusion coefficients in the films varied from 4.8 × 10?10 to 7.2 × 10?10 cm2/s and were in the following increasing order: BPDA–ODA < PMDA–ODA < 6FDA–ODA. The dielectric constants and diffusion coefficients of the polyimides were affected by the morphological structures, including the molecular packing order. However, because of the water uptake, the changes in the dielectric constants in the polyimide thin films varied from 0.49 to 1.01 and were in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. Surprisingly, 6FDA–ODA with bulky hexafluoroisopropylidene groups showed less of a change in its dielectric constant than PMDA–ODA. The total water uptake for the polyimide thin films varied from 1.43 to 3.19 wt % and was in the following increasing order: BPDA–ODA < 6FDA–ODA < PMDA–ODA. This means that the changes in the dielectric constants in the polyimide thin films were significantly related to the morphological structure and hydrophobicity of hexafluoroisopropylidene groups. Therefore, the morphological structure and chemical affinity in the polyimide thin films were important factors in controlling the dielectric properties. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2190–2198, 2002 相似文献