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EXISTENCE OF SOLUTIONS OF NONLOCAL PERTURBATIONS OF DIRICHLET DISCRETE NONLINEAR PROBLEMS

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Acta Mathematica Scientia 2017年第4期37卷 911-926页

作者： Alberto CABADA Nikolay D.DIMITROV instituto de matemdticas Facultade de MatemdticasUniversidade de Santiago de Compostela15782 Santiago de CompostelaSpain department of Mathematical Analysis University of Rousse7017 RousseBulgaria

This paper is devoted to the study of second order nonlinear difference equations. A Nonlocal Perturbation of a Dirichlet Boundary Value Problem is considered. An exhaustive study of the related Green＇s function to the linear part is done. The exact expression of the function is given, moreover the range of parameter for which it has constant sign is obtained. Using this, some existence results for the nonlinear problem are deduced from monotone iterative techniques, the classical Krasnoselski fixed point theorem or by application of recent fixed point theorems that combine both theories.

关键词： Dirichlet boundary value problem nonlocal perturbations Green's function parameter dependence

A plant-pollinator system： How learning versus cost-benefit can induce periodic oscillations

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International Journal of Biomathematics 2018年第2期11卷 189-215页

作者： Virgilio Vazquez Ignacio Barradas instituto de Fisicay matemdticas universidad Tecnologica de la Mixteca Huajuapan de Leon Oaxaca 69000 Mexico Centro de Investigacion en matemdticas Apartado Postal 302 Guanajuato Guanajuato 36000 Mexico

In this paper, we propose a model describing the interaction between two species： a plant population that gets pollinated by an insect population. We assume the plant population is divided into two groups： the first group in mutualistic relationship with the insect and the second group attracting the insects while deceiving them and not delivering any reward. In addition, we assume that the insect population reduces the number of visits to the plants after several unsuccessful visits. We are interested in the conditions for the coexistence of both species, especially in the appearance of damped or sustained oscillations. We focus the analysis on the parameters that measure the balance among deceit, the benefit that the insect gets from the plant, and the learning by the pollinators. We are especially interested in analyzing the effect of learning by the insect population due to unsuccessfully visiting the deceiving plants.

关键词： deceptive pollination mutualism learning oscillations Hopf bifurcation.

Stable gravastars： Guilfoyle＇s electrically charged solutions

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Chinese Physics C 2018年第11期42卷 120-130页

作者： Ayan Banerjee J.R. Villanueva Phongpichit Channuie Kimet Jusufi department of Mathematics Jadavpur University Kolkata-700032 India instituto de Fisica y Astronomia Facultad de Ciencias Universidad de Valparaiso Gran Bretana 1111 Valparaiso Chile School of Science Walailak University Nakhon Si Thammarat 80160 Thailand Physics department State University of Tetovo Ilinden Street nn 1200 Macedonia

Compelling alternatives to black holes, namely, gravitational vacuum stars （gravastars）, which are multilayered compact objects, have been proposed to avoid a number of theoretical problems associated with event horizons and singularities. In this work, we construct a spherically symmetric thin-shell charged gravastar model where the vacuum phase transition between the de Sitter interior and the external Reissner-Nordstrom spacetime （RN） are matched at a junction surface, by using the cut-and-paste procedure. Gravastar solutions are found among the Guilfoyle exact solutions where the gravitational potential We and the electric potential field Ф obey a particular relation in a simple form a（b-εФ）^2＋b1, where a, b and bl are arbitrary constants. The simplest ansatz of Guilfoyle＇s solution is implemented by the following assumption： that the total energy density 8πρm＋Q^2/r^4 is constant, where Q（r） is the electric charge up to a certain radius r. We show that, for certain ranges of the parameters, we can avoid the horizon formation, which allows us to study the linearized spherically symmetric radial perturbations around static equilibrium solutions. To lend our solution theoretical support, we also analyze the physical and geometrical properties of gravastar configurations.

关键词： gravastar Guilfoyle exact solutions stability analysis

A POSTERIORI ERROR ANALYSIS OF A FULLY-MIXED FINITE ELEMENT METHOD FOR A TWO-DIMENSIONAL FLUID-SOLID INTERACTION PROBLEM

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Journal of Computational Mathematics 2015年第6期33卷 606-641页

作者： Carolina Dominguez Gabriel N. Gatica salim meddahi instituto de Ciencias Fisicas y matemdticas facultad de ciencias universidad austral de chile Avenida Eduardo Morales Miranda - Campus isla teja valdivia chile CI2 MA and departamento de Ingenieria Matematica Universidad de concapcion casilla 160 concepcion chile departamento de matemdticas Facultad de ciencias universidad de oiede calvo satela s/n oviedo espana

In this paper we develop an a posteriori error analysis of a fully-mixed finite element method for a fluid-solid interaction problem in 2D. The media are governed by the elas-todynamic and acoustic equations in time-harmonic regime, respectively, the transmission conditions are given by the equilibrium of forces and the equality of the corresponding normal displacements, and the fluid is supposed to occupy an annular region surrounding the solid, so that a Robin boundary condition imitating the behavior of the sommerfeld condition is imposed on its exterior boundary. Dual-mixed approaches are applied in both domains, and the governing equations are employed to eliminate the displacenent a of the solid and the pressure p of the fluid. In addition, since both transmission conditions become essential, they are enforced weakly by means of two suitable lahrange multipliers The unknowns of the solid and the fluid are then approximated by a conforming galerkin scheme defined in terms of PEERS elements in the solid, Raviart-Thomas of lowest order in the fluid, and continuous piecewise linear functions on the boundary, As the main con-tribution of this work, we derive a reliable and efficient residual-based a posteriori error estimator for the aforedescribed coupled problem. Some numerical results confirming the properties of the estimator are also reported.

关键词： Mixed finite elements Helmholtz equation Elastodynamic equation A poste- riori error analysis

Phase transitions in four-dimensional AdS black holes with a nonlinear electrodynamics source

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Communications in Theoretical Physics 2021年第12期73卷 119-128页

作者： Ramon Becar P A Gonzalez Joel Saavedra Yerko Vasquez Bin Wang departamento de Ciencias Matematicas y Fisicas Universidad Catolica de TemucoMontt 56Casilla 15-DTemucoChile Facultad de Ingenieria y Ciencias Universidad Diego PortalesAvenida Ejercito Libertador 441Casilla 298-VSantiagoChile instituto de Ffsica Pontificia Universidad Catolica de ValparaisoCasilla 4950ValparaisoChile departamento de Ffsica Facultad de CienciasUniversidad de La SerenaAvenida Cistemas 1200La SerenaChile Center for Gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

In this work we consider black hole solutions to Einstein’s theory coupled to a nonlinear powerlaw electromagnetic field with a fixed exponent *** study the extended phase space thermodynamics in canonical and grand canonical ensembles,where the varying cosmological constant plays the role of an effective thermodynamic *** examine thermodynamical phase transitions in such black holes and find that both first-and second-order phase transitions can occur in the canonical ensemble while,for the grand canonical ensemble,Hawking-Page and second-order phase transitions are allowed.

关键词： black hole thermodynamics nonlinear Maxwell

Senarmontite volatilization kinetics in nitrogen atmosphere at roasting/melting temperatures

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Transactions of Nonferrous Metals Society of China 2016年第1期26卷 294-300页

作者： A.ARACENA O.JERE C.ANTONUCCI Escuela de Ingenieria Qufmica Pontificia Universidad Catoolica de ValparaisoGeneral Cruz 34ValparaisoChile instituto de Geologia Econemica Aplicada(GEA) Universidad de ConcepcionCasilla 160-CConcepci6nChile

The volatilization kinetics of senarmontite（Sb_2O_3） was analyzed in a neutral atmosphere in two temperature ranges： 550-615 °C（roasting temperature） and 660-1100 °C（melting temperature） by using a thermogravimetric analysis method under various gas flow rates and using a 1.3 m L ceramic crucible（11 mm in internal diameter and 14 mm in height）. The effect of particle size was also analyzed. The experimental results of mass loss data, X-ray diffraction（XRD） analysis of partially reacted samples and thermodynamic studies indicate that the senarmontite becomes volatile in the form of Sb_4O_6（g） without the formation of any intermediary compound in the entire temperature range. At roasting temperatures, the volatilization kinetics of Sb_2O_3 was analyzed using the model X=kappt. The volatilization reaction was controlled by the surface chemical reaction and an activation energy value of 193.0 k J/mol was obtained in this temperature range. Based on the volatilization kinetics at the melting temperatures, for linear behaviour in nitrogen gas, kinetic constants were determined, and an activation energy of 73.9 k J/mol was calculated for the volatilization reaction with a surface area of 8.171×10^（-5）m^2.

关键词： senarmontite volatilization rate roasting temperature melting temperature kinetics

Obesity, Body Fat Distribution, and Physical Activity in School-age Children: an Urban and Rural Comparison in Valparaíso, Chile

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Biomedical and Environmental Sciences 2016年第11期29卷 834-839页

作者： Pablo A Lizana Paula Cisternas-Vallejos Leonel Araya Francisco Aguilera Manuel Mora Laboratory of Morphological Sciences Instituto de BiologfaPontificia Universidad Cat61ica de ValparaisoValparaiso2373223Chile

This study analyze the relation between body composition, physical activity （PA）, and sex in Chilean children from rural and urban public educational institutions. The prevalence of obesity （according to BMI） was 30.88% in urban children and 28.93% in rural children. Central obesity presented mainly in the rural girls. Approximately 90% of the participants reported 〈7 h of PA/week, regardless of residential area. In addition, central fat was strongly associated with rural residence; the children reported lower PA levels, and they presented a higher prevalence of central fat. The results reflect the need to implement programs to improve PA conditions in the child urban-rural population.

关键词： an Urban and Rural Comparison in Valpara and Physical Activity in School-age Children so Chile Obesity

The holographic fermions dual to massive gravity

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Science China(Physics,Mechanics & Astronomy) 2016年第10期59卷 49-57页

作者： Li-Qing Fang[[ Xiao-Mei Kuang Jian-Pin Wu School of Physics and Electronic Information Shangrao Normal UniversityShangrao 334000China department of Physics and Astronomy Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Key Laboratory of High Temperature Superconductors Shanghai 200444China instituto de Fisica Pontificia Universidad Catolica de ValparaisoCasilla 4059ValparaisoChile Institute of Gravitation and Cosmology Department of PhysicsSchool of Mathematics and PhysicsBohai UniversityJinzhou 121013China

We investigate the properties of the spectral function of the fermionic operator in the field theory which is dual to a 4-dimensional massive gravity. We first study the Fermi surface and the dispersion relation in the dual boundary theory. We find that as the massive parameters is decreased, the Fermi momentum becomes lower and the low energy excitation near Fermi surface behaves more like non-Fermi liquid. Then, we introduce a dipole coupling in the bulk theory and explore the emergence of a gap in the fermionic spectral function. It is found that larger critical dipole coupling is needed to open the gap than that in Einstein gravity. Accordingly,in the field theory dual to massive gravity, it requires stronger negative dipole coupling to generate the marginal Fermi liquid.

关键词： holography duality AdS/CFT correspondence holographic fermions

On the existence of traveling wave solutions and upper and lower bounds for some Fisher-iolmogorov type equations

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International Journal of Biomathematics 2014年第5期7卷 51-65页

作者： Juan Belmonte-Beitia departamento de matemdticas E. T. S. de Ingenieros Industriales and Instituto de Matemdtica Aplicada a la Ciencia y la Ingenierla (IMA CI) Universidad de Castilla-La Mancha 13071 Ciudad Real Spain

In this paper, we use a dynamical systems approach to prove the existence of traveling waves solutions for the Fisher-Kolmogorov density-dependent equation. Moreover, we prove the existence of upper and lower bounds for these traveling wave solutions found previously. Finally, we present a particular example which has several applications in the mathematical biology field.

关键词： Fisher-Kolmogorov equations nonlinear diffusion heteroclinic orbits upperand lower solutions center manifold.