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A dominant height growth model for eucalyptus plantations in Portugal

Ayana Mateus, Margarida Tomé (2009)

Discussiones Mathematicae Probability and Statistics

Eucalyptus globulus Labill is one of the most important economic forest species in Portugal, occupying an area of 875.10³ ha in a total forest area of 3346.10³ ha (Tomé et al., 2007). The main goal of this study is to develop a dominant height growth model for Eucalyptus, applicable throughout the country, representing an improve of the curves that are part of the whole stand model existing in Portugal, the GLOBULUS model (Tomé et al., 2001). The dominant height growth model will be built on a biological...

Almost sufficient and necessary conditions for permanence and extinction of nonautonomous discrete logistic systems with time-varying delays and feedback control

Jiabo Xu, Zhidong Teng, Shujing Gao (2011)

Applications of Mathematics

A class of nonautonomous discrete logistic single-species systems with time-varying pure-delays and feedback control is studied. By introducing a new research method, almost sufficient and necessary conditions for the permanence and extinction of species are obtained. Particularly, when the system degenerates into a periodic system, sufficient and necessary conditions on the permanence and extinction of species are obtained. Moreover, a very important fact is found in our results, that is, the feedback...

Competitive Exclusion in a Discrete Stage-Structured Two Species Model

A. S. Ackleh, P. Zhang (2009)

Mathematical Modelling of Natural Phenomena

We develop a stage-structured model that describes the dynamics of two competing species each of which have sexual and clonal reproduction. This is typical of many plants including irises. We first analyze the dynamical behavior of a single species model. We show that when the inherent net reproductive number is smaller than one then the population will go to extinction and if it is larger than one then an interior equilibrium exists and it is globally asymptotically stable. Then we analyze...

Initial data stability and admissibility of spaces for Itô linear difference equations

Ramazan Kadiev, Pyotr Simonov (2017)

Mathematica Bohemica

The admissibility of spaces for Itô functional difference equations is investigated by the method of modeling equations. The problem of space admissibility is closely connected with the initial data stability problem of solutions for Itô delay differential equations. For these equations the p -stability of initial data solutions is studied as a special case of admissibility of spaces for the corresponding Itô functional difference equation. In most cases, this approach seems to be more constructive...

Mathematical Modeling Describing the Effect of Fishing and Dispersion on Hermaphrodite Population Dynamics

S. Ben Miled, A. Kebir, M. L. Hbid (2010)

Mathematical Modelling of Natural Phenomena

In order to study the impact of fishing on a grouper population, we propose in this paper to model the dynamics of a grouper population in a fishing territory by using structured models. For that purpose, we have integrated the natural population growth, the fishing, the competition for shelter and the dispersion. The dispersion was considered as a consequence of the competition. First we prove, that the grouper stocks may be less sensitive to the...

Positive fixed point theorems arising from seeking steady states of neural networks

Gen Qiang Wang, Sui-Sun Cheng (2010)

Mathematica Bohemica

Biological systems are able to switch their neural systems into inhibitory states and it is therefore important to build mathematical models that can explain such phenomena. If we interpret such inhibitory modes as `positive' or `negative' steady states of neural networks, then we will need to find the corresponding fixed points. This paper shows positive fixed point theorems for a particular class of cellular neural networks whose neuron units are placed at the vertices of a regular polygon. The...

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