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81.
Rafael P. Bianchin Mariovane S. Donini Cesar F.C. Cristaldo Fernando F. Fachini 《Proceedings of the Combustion Institute》2019,37(2):1903-1910
The present work analyzes cylindrical diffusion flames (Tsuji burner) under low stretch condition, considering fuel injection also from the backward region of the burner. To highlight the fundamental aspects of this flame, some assumptions are imposed, like constant thermodynamic and transport coefficients, unitary Lewis number and no radiative heat loss. It is also considered potential flow model and incompressible Navier–Stokes model. Despite the simplicity of the former model, results from both models show good agreement. Also, an asymptotic analysis describing the problem far from the burner is able to capture the most important mechanisms controlling the flame, then the flame shape is determined and the dependence of the characteristic length scales on Peclet number (based on the burner properties), free stream velocity and stoichiometry is revealed. The results show that the flame width is proportional to the mass stoichiometric coefficient and reciprocal to the Peclet number the 1/4 power and free stream velocity the 3/4 power, and that the flame height is proportional to the square of the mass stoichiometric coefficient and to the square root of the ratio of Peclet number to free stream velocity. In addition, an asymptotic stability analysis reveals low-stretch flame extinction to be caused by reduction in fuel and oxidizer concentrations, which provides the range of the stoichiometric coefficient for stable regime, and at the same time the range of heat released. 相似文献
82.
Pablo A. D. Castro Fernando J. Von Zuben 《Journal of Mathematical Modelling and Algorithms》2009,8(2):151-173
Recently, we have proposed a Multi-Objective Bayesian Artificial Immune System (MOBAIS) to deal effectively with building
blocks (high-quality partial solutions coded in the solution vector) in combinatorial multi-objective problems. By replacing
the mutation and cloning operators with a probabilistic model, more specifically a Bayesian network representing the joint
distribution of promising solutions, MOBAIS takes into account the relationships among the variables of the problem, avoiding
the disruption of already obtained high-quality partial solutions. The preliminary results have indicated that our proposal
is able to properly build the Pareto front. Motivated by this scenario, this paper better formalizes the proposal and investigates
its usefulness on more challenging problems. In addition, an important enhancement regarding the Bayesian network learning
was incorporated into the algorithm in order to speed up its execution. To conclude, we compare MOBAIS with state-of-the-art
algorithms taking into account quantitative aspects of the Pareto front found by the algorithms. MOBAIS outperforms the contenders
in terms of the quality of the obtained solutions and requires an amount of computational resource inferior or compatible
with the contenders. 相似文献
83.
Fernando Charro Enea Parini 《Calculus of Variations and Partial Differential Equations》2013,46(1-2):403-425
We investigate the asymptotic behaviour as p → ∞ of sequences of positive weak solutions of the equation $$\left\{\begin{array}{l}-\Delta_p u = \lambda\,u^{p-1}+ u^{q(p)-1}\quad {\rm in}\quad \Omega,\\ u = 0 \quad {\rm on}\quad \partial\Omega,\end{array} \right.$$ where λ > 0 and either 1 < q(p) < p or p < q(p), with ${{\lim_{p\to\infty}{q(p)}/{p}=Q\neq1}}$ . Uniform limits are characterized as positive viscosity solutions of the problem $$\left\{\begin{array}{l}\min\left\{|\nabla u (x)| - \max\{\Lambda\,u (x),u ^Q(x)\}, -\Delta_{\infty}u (x)\right\} = 0 \quad {\rm in} \quad \Omega,\\ u = 0\quad {\rm on}\quad \partial\Omega.\end{array}\right.$$ for appropriate values of Λ > 0. Due to the decoupling of the nonlinearity under the limit process, the limit problem exhibits an intermediate behavior between an eigenvalue problem and a problem with a power-like right-hand side. Existence and non-existence results for both the original and the limit problems are obtained. 相似文献
84.
Daniel Girela José Ángel Peláez Fernando Pérez-González Jouni Rättyä 《Integral Equations and Operator Theory》2008,61(4):511-547
In this paper we study the positive Borel measures μ on the unit disc in for which the Bloch space is continuously included in , 0 < p < ∞. We call such measures p-Bloch-Carleson measures. We give two conditions on a measure μ in terms of certain logarithmic integrals one of which is a necessary condition and the other a sufficient condition for μ being a p-Bloch-Carleson measure. We also give a complete characterization of the p-Bloch-Carleson measures within certain special classes of measures. It is also shown that, for p > 1, the p-Bloch-Carleson measures are exactly those for which the Toeplitz operator , defined by , maps continuously into the Bergman space A
1, . Furthermore, we prove that if p > 1, α >-1 and ω is a weight which satisfies the Bekollé-Bonami -condition, then the measure defined by is a p-Bloch-Carleson-measure.
We also consider the Banach space of those functions f which are analytic in and satisfy , as . The Bloch space is contained in . We describe the p-Carleson measures for and study weighted composition operators and a class of integration operators acting in this space. We determine which of
these operators map continuously to the weighted Bergman space and show that they are automatically compact.
This research is partially supported by several grants from “the Ministerio de Educación y Ciencia, Spain” (MTM2005-07347,
MTM2007-60854, MTM2006-26627-E, MTM2007-30904-E and Ingenio Mathematica (i-MATH) No. CSD2006-00032); from “La Junta de Andalucía”
(FQM210 and P06-FQM01504); from “the Academy of Finland” (210245) and from the European Networking Programme “HCAA” of the
European Science Foundation. 相似文献
85.
86.
P.?Madejczyk A.?Piotrowski K.?K?os W.?Gawron J.?Rutkowski A.?Rogalski 《Opto-Electronics Review》2010,18(3):271-276
The acceptor doping of mercury cadmium telluride (HgCdTe) layers grown by MOCVD are investigated. (111)HgCdTe layers were
grown on (100)GaAs substrates at 350°C using horizontal reactor and interdiffused multilayer process (IMP). TDMAAs and AsH3
were alternatively used as effective p-type doping precursors. Incorporation and activation rates of arsenic have been studied.
Over a wide range of Hg1−xCdxTe compositions (0.17 < x < 0.4), arsenic doping concentration in the range from 5×1015 cm−3 to 5×1017 cm−3 was obtained without postgrowth annealing. The electrical and chemical properties of epitaxial layers are specified by measurements
of SIMS profiles, Hall effect and minority carrier lifetimes. It is confirmed that the Auger-7 mechanism has decisive influence
on carrier lifetime in p-type HgCdTe epilayers. 相似文献
87.
88.
Execution time optimization is one of the most important objectives to accomplish for experiments launched on grid environments. However, the computing community is becoming more conscious about energy savings, seeking their optimization. In this work, both execution time and energy consumption are optimized through two swarm and multi-objective algorithms based on both physics and biology fields. On the one hand, multi-objective gravitational search algorithm (MOGSA) is inspired by the gravity forces between the planet masses. On the other hand, Multi-Objective Firefly Algorithm is based on the light attraction between the fireflies. These swarm algorithms are compared with the standard multi-objective algorithm non-dominated sorting genetic algorithm II to study their efficiency as multi-objective algorithms. Moreover, the best algorithm proposed, MOGSA, is compared with MOHEFT (a multi-objective version of one of the most-used algorithms in workflow scheduling, HEFT), and also with two real grid schedulers: Workload Management System and deadline budget constraint. Results show the superior performance of MOGSA regarding the others. 相似文献
89.
Fernando C. Silva 《Linear and Multilinear Algebra》2013,61(3-4):269-277
Let A and B be n × n nonsingular matrices over a field F, and c 1,…,c n ∈ F. We give a necessary and sufficient condition for the existence of matrices A′ and B′ similar to A and B, respectively, such that A′ B′ has eigenvalues c 1,…,c n. 相似文献
90.
Hongliang Wang Fernando Lusquiños Y. Lawrence Yao 《Applied Physics A: Materials Science & Processing》2012,107(2):307-320
Hydrogenated amorphous silicon (a-Si:H) thin films have been considered for use in solar cell applications because of their
significantly reduced cost compared to crystalline bulk silicon. However, their overall efficiency and stability are lower
than that of their bulk crystalline counterpart. Limited work has been performed on simultaneously solving the efficiency
and stability issues of a-Si:H. Previous work has shown that surface texturing and crystallization on a-Si:H thin film can
be achieved through a single-step laser processing, which can potentially alleviate the disadvantages of a-Si:H in solar cell
applications. In this study, hydrogenated and dehydrogenated amorphous silicon thin films deposited on glass substrates were
irradiated by KrF excimer laser pulses and the effect of hydrogen on surface morphologies and microstructures is discussed.
Sharp spikes are focused only on hydrogenated films, and the large-grained and fine-grained regions caused by two crystallization
processes are also induced by presence of hydrogen. Enhanced light absorptance is observed due to light trapping based on
surface geometry changes of a-Si:H films, while the formation of a mixture of nanocrystalline silicon and original amorphous
silicon after crystallization suggests that the overall material stability can potentially improve. The relationship between
crystallinity, fluence and number of pulses is also investigated. Furthermore, a step-by-step crystallization process is introduced
to prevent the hydrogen from diffusing out in order to reduce the defect density, and the relationship between residue hydrogen
concentration, fluence and step width is discussed. Finally, the combined effects show that the single-step process of surface
texturing and step-by-step crystallization induced by excimer laser processing are promising for a-Si:H thin-film solar cell
applications. 相似文献