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排序方式: 共有136条查询结果,搜索用时 31 毫秒
111.
Desyatnikov AS Kivshar YS Shchesnovich VS Cavalcanti SB Hickmann JM 《Optics letters》2007,32(4):325-327
We study Zener tunneling in two-dimensional photonic lattices and derive, for the case of hexagonal symmetry, the generalized Landau-Zener-Majorana model describing resonant interaction between high-symmetry points of the photonic spectral bands. We demonstrate that this effect can be employed for the generation of Floquet-Bloch modes and verify the model by direct numerical simulations of the tunneling effect. 相似文献
112.
The aim of this study was to develop a titanium tetrafluoride (TiF(4)) varnish and evaluate the stability of the formulation and its reactivity with dental enamel. The varnish was prepared in a resinous matrix using ethanol 96% as solvent. Samples (n=45) were aged at 65 degrees C and 30% of relativity humidity (RE n degrees 01/05-ANVISA) and after 3, 6, 9 and 12 months, nine samples were removed for evaluation and compared with fresh samples. Chemical stability of TiF(4) varnish was determinate by (19)F-NMR and the reactivity of the formulation was quantified by formation of fluoride loosely (CaF(2)) and firmly bound (fluorapatite; FA) to enamel. For reactivity comparisons, a varnish without TiF(4) was used as control. The loss of soluble fluoride was about 0.9% after one year of storage. The values of the reactivity (mean+/-S.D.) of fresh, aged at 3, 6, 9 and 12 months and control samples were: CaF(2) (microg F/mm(2)): 89.3+/-27.5(a); 54.5+/-14.3(b); 51.2+/-29.8(b); 69.3+/-21.3(a); 48.0+/-27.4(b); 0.10+/-0.07(c), FA (microg F/g): 2477.5+/-1044.0(a); 2484.8+/-992.0(a); 2580.0+/-1383.9(a); 2517.2+/-929.9(a); 2121.0+/-1059.2(a); 330.0+/-180.0(b), respectively. Means followed by distinct letters were statistically different (p<0.05). After one year of storage, the formulation was chemically stable and the levels of FA were maintained. However there was an initial decrease in the ability to form CaF(2). 相似文献
113.
Krauss TN Barrena E Zhang XN de Oteyza DG Major J Dehm V Würthner F Cavalcanti LP Dosch H 《Langmuir : the ACS journal of surfaces and colloids》2008,24(22):12742-12744
We have determined the full molecular 3D packing of thin organic films of the archetypical organic n-type semiconductor N, N'-dioctyl-3,4:9,10-perylene tetracarboxylic diimide (PTCDI-C 8) by surface X-ray crystallography. We show that PTCDI-C 8 forms smooth layered films on Al 2O 3 (11-20) with an outstanding degree of molecular order. The thin-film structure is found to consist of a triclinic unit cell with the plane of the aromatic core tilted by 67 +/- 2 degrees with respect to the surface plane, which differs significantly from the bulk structure. The 3D crystallites extend with vertical coherent order across the entire film thickness. 相似文献
114.
E. Cavalcanti E. Castro C. A. Linhares A. P. C. Malbouisson 《The European Physical Journal C - Particles and Fields》2017,77(10):711
A scalar model is built, as a quantum field theory defined on a toroidal topology, to describe a phase transition in films subjected to periodic boundary conditions and influenced by an external and constant magnetic field. Criticality is studied and the relations between the critical temperature, the film thickness, the magnetic field strength and the chemical potential are investigated. Since the model describes a second-order phase transition a comparison with the Ginzburg–Landau theory is made. 相似文献
115.
M.M. Cavalcanti V.N. Domingos Cavalcanti 《NoDEA : Nonlinear Differential Equations and Applications》2000,7(3):285-307
This paper is concerned to the existence, uniqueness and uniform decay for the solutions of the coupled Klein-Gordon-Schr?dinger
damped equations
where ω is a bounded domain of R
n
, n≤ 3, F : R
2→R is a C
1-function; γ, β; θ are constants such that γ, β > 0 and 1 ≤ 2θ≤ 2.
Received January 1999 – Accepted October 1999 相似文献
116.
117.
Heldeney Rodrigues Sousa Idglan S Lima Lucas Matheus Lima Neris Albert Santos Silva Ariane Maria Silva Santos Nascimento Francisca Pereira Araújo Rafael Felippe Ratke Durcilene Alves Silva Josy Anteveli Osajima Leilson Rocha Bezerra Edson Cavalcanti Silva-Filho 《Molecules (Basel, Switzerland)》2021,26(9)
Agricultural production is influenced by the water content in the soil and availability of fertilizers. Thus, superabsorbent hydrogels, based on polyacrylamide, natural cashew tree gum (CG) and potassium hydrogen phosphate (PHP), as fertilizer and water releaser were developed. The structure, morphology, thermal stability and chemical composition of samples of polyacrylamide and cashew tree gum hydrogels with the presence of fertilizer (HCGP) and without fertilizer (HCG) were investigated, using X-ray diffractometry (XRD), Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA/DTG) and Energy Dispersive Spectroscopy (EDS). Swelling/reswelling tests, textural analysis, effect of pH, release of nutrients and kinetics were determined; the ecotoxicity of the hydrogels was investigated by the Artemia salina test. The results showed that PHP incorporation in the hydrogel favored the crosslinking of chains. This increased the thermal stability in HCGP but decreased the hardness and adhesion properties. The HCGP demonstrated good swelling capacity (~15,000 times) and an excellent potential for reuse after fifty-five consecutive cycles. The swelling was favored in an alkaline pH due to the ionization of hydrophilic groups. The sustained release of phosphorus in HCGP was described by the Korsmeyer–Peppas model, and Fickian diffusion is the main fertilizer release mechanism. Finally, the hydrogels do not demonstrate toxicity, and HCGP has potential for application in agriculture. 相似文献
118.
119.
Marcelo M. Cavalcanti Valéria N. Domingos Cavalcanti Ryuichi Fukuoka Daniel Toundykov 《Journal of Evolution Equations》2009,9(1):143-169
This paper is devoted to the study of uniform energy decay rates of solutions to the wave equation with Cauchy–Ventcel boundary
conditions:
where Ω is a bounded domain of (n ≥ 2) having a smooth boundary , such that with , being closed and disjoint. It is known that if a(x) = 0 then the uniform exponential stability never holds even if a linear frictional feedback is applied to the entire boundary of the domain [see, for instance, Hemmina (ESAIM, Control Optim Calc Var 5:591–622, 2000, Thm. 3.1)]. Let be a smooth function; define ω
1 to be a neighbourhood of , and subdivide the boundary into two parts: and . Now, let ω
0 be a neighbourhood of . We prove that if a(x) ≥ a
0 > 0 on the open subset and if g is a monotone increasing function satisfying k|s| ≤ |g(s)| ≤ K|s| for all |s| ≥ 1, then the energy of the system decays uniformly at the rate quantified by the solution to a certain nonlinear ODE dependent
on the damping [as in Lasiecka and Tataru (Differ Integral Equ 6:507–533, 1993)].
Research of Marcelo M. Cavalcanti was partially supported by the CNPq Grant 300631/2003-0.
Research of Valéria N. Domingos Cavalcanti was partially supported by the CNPq Grant 304895/2003-2. 相似文献
120.
Marcelo?M.?CavalcantiEmail author Valéria?N.?Domingos?Cavalcanti Andrei?Faminskii Fábio?Natali 《Applied Mathematics and Optimization》2012,65(2):221-251
In the present paper we establish results concerning the decay of the energy related to the damped Korteweg–de Vries equation
posed on infinite domains. We prove the exponential decay rates of the energy when a initial value problem and a localized
dissipative mechanism are in place. If this mechanism is effective in the whole line, we get a similar result in H
k
-level, k∈ℕ. In addition, the decay of the energy regarding a initial boundary value problem posed on the right half-line, is obtained
considering convenient a smallness condition on the initial data but a more general dissipative effect. 相似文献