The protection zone for biological population in random environment

A biomathematical model is described by stochastic differential equations with Markovian switching. The long‐time dynamical properties are studied both theoretically and numerically. Results show that both the persistence and extinction have close relationship with environmental noises (white and color noises). These results are of important biological significance for biological conservation. Copyright © 2012 John Wiley & Sons, Ltd.     

A robustness analysis of biological population models with protection zone

Establishing protection zone has been widely used to preserve endangered species. We study the effect of protection zone in random environment by a stochastic model. Our results show that the establishment of nature reserves can protect endangered species effectively in good conditions. Under very bad conditions, though protection zone cannot protect species from extinction, it also can slow down the speed of extinction. Based on our results, we give some methods to strengthen the effect of protection zone and provide a method of dividing the protection zone. In addition, we introduce some examples and use several numerical simulations to enhance our main results.     

A diffusive competition model with a protection zone

This paper is concerned with a two species diffusive competition model with a protection zone for the weak competitor. Our mathematical results imply that when the protection zone is above a certain critical patch size determined by the birth rate of the weak competitor, the weak species almost always survives, but it cannot survive when the protection zone is below the critical size and its competitor is strong enough. While this is the main feature of the model, the actual dynamical behavior of the reaction-diffusion system is more complicated. The key to reveal the main feature of the system lies in a detailed analysis of the attracting regions of its steady-state solutions. Our mathematical analysis shows that, compared with the predator-prey model discussed in [Yihong Du, Junping Shi, A diffusive predator-prey model with a protect zone, J. Differential Equations 226 (2006) 63-91], the protection zone has some essentially different effects on the fine dynamics of the competition model.     

A diffusive predator-prey model with a protection zone

In this paper we study the effects of a protection zone Ω₀ for the prey on a diffusive predator-prey model with Holling type II response and no-flux boundary condition. We show the existence of a critical patch size described by the principal eigenvalue of the Laplacian operator over Ω₀ with homogeneous Dirichlet boundary conditions. If the protection zone is over the critical patch size, i.e., if is less than the prey growth rate, then the dynamics of the model is fundamentally changed from the usual predator-prey dynamics; in such a case, the prey population persists regardless of the growth rate of its predator, and if the predator is strong, then the two populations stabilize at a unique coexistence state. If the protection zone is below the critical patch size, then the dynamics of the model is qualitatively similar to the case without protection zone, but the chances of survival of the prey species increase with the size of the protection zone, as generally expected. Our mathematical approach is based on bifurcation theory, topological degree theory, the comparison principles for elliptic and parabolic equations, and various elliptic estimates.     

Effect of a protection zone in the diffusive Leslie predator-prey model

In this paper, we consider the diffusive Leslie predator-prey model with large intrinsic predator growth rate, and investigate the change of behavior of the model when a simple protection zone Ω₀ for the prey is introduced. As in earlier work [Y. Du, J. Shi, A diffusive predator-prey model with a protection zone, J. Differential Equations 229 (2006) 63-91; Y. Du, X. Liang, A diffusive competition model with a protection zone, J. Differential Equations 244 (2008) 61-86] we show the existence of a critical patch size of the protection zone, determined by the first Dirichlet eigenvalue of the Laplacian over Ω₀ and the intrinsic growth rate of the prey, so that there is fundamental change of the dynamical behavior of the model only when Ω₀ is above the critical patch size. However, our research here reveals significant difference of the model's behavior from the predator-prey model studied in [Y. Du, J. Shi, A diffusive predator-prey model with a protection zone, J. Differential Equations 229 (2006) 63-91] with the same kind of protection zone. We show that the asymptotic profile of the population distribution of the Leslie model is governed by a standard boundary blow-up problem, and classical or degenerate logistic equations.     

A population biological model with a singular nonlinearity

We consider the existence of positive solutions of the singular nonlinear semipositone problem of the form $\left\{ \begin{gathered} - div(|x|^{ - \alpha p} |\nabla u|^{p - 2} \nabla u) = |x|^{ - (\alpha + 1)p + \beta } \left( {au^{p - 1} - f(u) - \frac{c} {{u^\gamma }}} \right),x \in \Omega , \hfill \\ u = 0,x \in \partial \Omega , \hfill \\ \end{gathered} \right. $ where Ω is a bounded smooth domain of ? ^N with 0 ∈ Ω, 1 < p < N, 0 ? α < (N ? p)/p, γ ∈ (0, 1), and a, β, c and λ are positive parameters. Here f: [0,∞) → ? is a continuous function. This model arises in the studies of population biology of one species with u representing the concentration of the species. We discuss the existence of a positive solution when f satisfies certain additional conditions. We use the method of sub-supersolutions to establish our results.     

Lightning modeling and protection zone of conducting rod using Monte Carlo technique

Lightning strike is a harmful process and protection from lightning using conducting rods has been a subject of discussion for decades. In particular, there have been a lot of researches regarding the protection zone of a single conducting rod. This is important for the purpose of installing them to protect complex building structures. In the present article, the protection zone of a conducting rod has been obtained by Monte Carlo simulation method. The lightning process has been modeled for computer simulation. The authors have presented a new Monte Carlo modeling of lightning path. The origin of the downward stepped leader and the magnitude of peak current of the return stroke have appropriate random distributions. The obtained results are compared with already available experimental results present in various literatures. It is shown that this technique is reliable and in fair agreement with the established theories for finding protection zone of conducting rods.     

一类具有保护区域的Leslie-Gower捕食-食饵模型的分歧分析

研究了一类Neumann边界条件下带有保护区域的Leslie-Gower捕食-食饵模型,分析稳态系统从半平凡解处发生分歧的条件,得到了分歧方向及分歧值的唯一性,得到了在确定参数范围内,从半平凡解出发的分支解曲线的稳定性.     

The role of protection zone on species spreading governed by a reaction–diffusion model with strong Allee effect

It is known that a species dies out in the long run for small initial data if its evolution obeys a reaction of bistable nonlinearity. Such a phenomenon, which is termed as the strong Allee effect, is well supported by numerous evidence from ecosystems, mainly due to the environmental pollution as well as unregulated harvesting and hunting. To save an endangered species, in this paper we introduce a protection zone that is governed by a Fisher–KPP nonlinearity, and examine the dynamics of a reaction–diffusion model with strong Allee effect and protection zone. We show the existence of two critical values $0<L_{?}\le L^{?}$, and prove that a vanishing-transition-spreading trichotomy result holds when the length of protection zone is smaller than $L_{?}$; a transition-spreading dichotomy result holds when the length of protection zone is between $L_{?}$ and $L^{?}$; only spreading happens when the length of protection zone is larger than $L^{?}$. This suggests that the protection zone works when its length is larger than the critical value $L_{?}$. Furthermore, we compare two types of protection zone with the same length: a connected one and a separate one, and our results reveal that the former is better for species spreading than the latter.     

Effect of cross-diffusion on the stationary problem of a prey-predator model with a protection zone

This paper is concerned with the stationary problem of a prey-predator cross-diffusion system with a protection zone for the prey. We discuss the existence and non-existence of coexistence states of the two species by using the bifurcation theory. As a result, it is shown that the cross-diffusion for the prey has beneficial effects on the survival of the prey when the intrinsic growth rate of the predator is positive. We also study the asymptotic behavior of positive stationary solutions as the cross-diffusion coefficient of the prey tends to infinity.     

Effect of cross-diffusion on the stationary problem of a Leslie prey-predator model with a protection zone

In this work, we study the change of behavior of positive solutions in a Leslie predator-prey model when a simple protection zone and cross-diffusion for the prey are introduced. We analyze the effects of cross-diffusion and protection zone on the bifurcation continuum of positive solutions. The asymptotic behavior of positive solutions is also discussed as the cross-diffusion and the birth rate of the predator tend to infinity, respectively. Finally, for small birth rates of two species and large cross-diffusion for the prey, the detailed structure and stability of positive solutions are established. Our results indicate that the environmental heterogeneity, together with large cross-diffusion, can produce much more complicated stationary patterns, moreover, our research here reveals significant difference from those studied in Du et al. (J Differ Equ 246:3932-3956, 2009), Oeda (J Differ Equ 250:3988-4009, 2011) and Wang and Li (Nonlinear Anal Real World Appl 14:224-245, 2013).     

Effect of cross-diffusion on the stationary problem of a diffusive competition model with a protection zone

This paper is concerned with the positive stationary problem of a Lotka–Volterra cross-diffusive competition model with a protection zone for the weak competitor. The detailed structure of positive stationary solutions for small birth rates and large cross-diffusion is shown. The structure is quite different from that without cross-diffusion, from which we can see that large cross-diffusion has a beneficial effect for the existence of positive stationary solutions. The effect of the spatial heterogeneity caused by protection zones is also examined and is shown to change the shape of the bifurcation curve. Thus the environmental heterogeneity, together with large cross-diffusion, can produce much more complicated stationary patterns. Finally, the asymptotic behavior of positive stationary solutions for any birth rate as the cross-diffusion coefficient tends to infinity is given, and moreover, the structure of positive solutions of the limiting system is analyzed. The result of asymptotic behavior also reveals different phenomena from that of the homogeneous case without protection zones.     

Confident estimation for density of a biological population based on line transect sampling

Line transect sampling is a very useful method in survey of wildlife population. Confident interval estimation for density D of a biological population is proposed based on a sequential design. The survey area is occupied by the population whose size is unknown. A stopping rule is proposed by a kernel-based estimator of density function of the perpendicular data at a distance. With this stopping rule, we construct several confidence intervals for D by difference procedures. Some bias reduction techniques are used to modify the confidence intervals. These intervals provide the desired coverage probability as the bandwidth in the stopping rule approaches zero. A simulation study is also given to illustrate the performance of this proposed sequential kernel procedure.     

Mathematical modeling and control of population systems: Applications in biological pest control

The aim of this paper is to apply methods from optimal control theory, and from the theory of dynamic systems to the mathematical modeling of biological pest control. The linear feedback control problem for nonlinear systems has been formulated in order to obtain the optimal pest control strategy only through the introduction of natural enemies. Asymptotic stability of the closed-loop nonlinear Kolmogorov system is guaranteed by means of a Lyapunov function which can clearly be seen to be the solution of the Hamilton–Jacobi–Bellman equation, thus guaranteeing both stability and optimality. Numerical simulations for three possible scenarios of biological pest control based on the Lotka–Volterra models are provided to show the effectiveness of this method.     

Convergence analysis of the fractional decomposition method with applications to time-fractional biological population models

In this study, we present convergence analysis along with an error estimate for time-fractional biological population equation in terms of the Caputo derivative using a new technique called the fractional decomposition method (FDM). Further, we present exact solutions to four test problems of nonlinear time-fractional biological population models to show the accuracy and efficiency of the FDM. This method based on constructing series solutions in a form of rapidly convergent series with easily computable components and without the need of linearization, discretization and perturbations. The results prove that the FDM is very effective and simple for solving fractional partial differential equations in multi-dimensional spaces, special cases of which we have described in this paper.     

The Markov structure of population growth

Some problems concerning the development of general models of population growth are examined, with particular reference to Markovian modelling. The tenet of the paper is that such models can be more realistically attempted by focusing on temporal rather than spatial modifications. Specifically, the time concept considered is linked to the dependent structure inherent in the partial order of descent from mother to child. The author attempts to develop "a general theory of populations of individuals under what might be called free reproduction. Hence, the only dependence assumed between individuals is that from mothers to children." He suggests that the results "can be translated into assertions about evolution in real, physical time and also about the final, stable or balanced, composition of populations, over ages, types, family structure, and many other aspects of populations."     

The zone of flow establishment for plumes with significant buoyancy

The self-similar assumption used in jet and plume models is only valid for distances of greater than about six stack diameters downstream, in the zone of established flow (ZEF). The ‘Gaussian’ profile, observed at the beginning of the ZEF, must be related to source ‘top hat’ parameter values. However, previously used formulae are shown here to be approximations, being valid only for non-buoyant sources (‘pure jets’). Extensions to sources of significant buoyancy are described in terms of the densimetric Froude number, based on recently published experimental work.     

Study of a one-dimensional model,accounting for cell division,of regulation of the renewing zone size in a biological tissue

We describe the modeling of the dynamics of renewing zone structure in biological tissues in the formalism of parameterized L-systems on an example of the shoot apical meristem. Under study is the influence of the ratio of the characteristic times of the cell cycle and diffusion of morphogens on the stability of some spatially distributed molecular-genetic control system. We show that cell division is a perturbing factor for the system regulating the renewing zone structure. Some conditions are found for the loss of stability of the regulation.