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Positive and maximal positive solutions of singular mixed boundary value problem

100%
Agarwal R., O’Regan D., Staněk S.
Open Mathematics
|
2009
|
tom 7
|
nr 4
694-716
EN
The paper is concerned with existence results for positive solutions and maximal positive solutions of singular mixed boundary value problems. Nonlinearities h(t;x;y) in differential equations admit a time singularity at t=0 and/or at t=T and a strong singularity at x=0.
2
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Fractional BVPs with strong time singularities and the limit properties of their solutions

76%
Staněk S.
Open Mathematics
|
2014
|
tom 12
|
nr 11
1638-1655
EN
In the first part, we investigate the singular BVP $$\tfrac{d} {{dt}}^c D^\alpha u + (a/t)^c D^\alpha u = \mathcal{H}u$$, u(0) = A, u(1) = B, c D α u(t)|t=0 = 0, where $$\mathcal{H}$$ is a continuous operator, α ∈ (0, 1) and a < 0. Here, c D denotes the Caputo fractional derivative. The existence result is proved by the Leray-Schauder nonlinear alternative. The second part establishes the relations between solutions of the sequence of problems $$\tfrac{d} {{dt}}^c D^{\alpha _n } u + (a/t)^c D^{\alpha _n } u = f(t,u,^c D^{\beta _n } u)$$, u(0) = A, u(1) = B, $$\left. {^c D^{\alpha _n } u(t)} \right|_{t = 0} = 0$$ where a < 0, 0 < β n ≤ α n < 1, limn→∞ β n = 1, and solutions of u″+(a/t)u′ = f(t, u, u′) satisfying the boundary conditions u(0) = A, u(1) = B, u′(0) = 0.
3
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Properties of the set of positive solutions to Dirichlet boundary value problems with time singularities

76%
Rachůnková I., Staněk S.
Open Mathematics
|
2013
|
tom 11
|
nr 1
112-132
EN
The paper investigates the structure and properties of the set S of all positive solutions to the singular Dirichlet boundary value problem u″(t) + au′(t)/t − au(t)/t 2 = f(t, u(t),u′(t)), u(0) = 0, u(T) = 0. Here a ∈ (−∞,−1) and f satisfies the local Carathéodory conditions on [0,T]×D, where D = [0,∞)×ℝ. It is shown that S c = {u ∈ S: u′(T) = −c} is nonempty and compact for each c ≥ 0 and S = ∪c≥0 S c. The uniqueness of the problem is discussed. Having a special case of the problem, we introduce an ordering in S showing that the difference of any two solutions in S c,c≥ 0, keeps its sign on [0,T]. An application to the equation v″(t) + kv′(t)/t = ψ(t)+g(t, v(t)), k ∈ (1,∞), is given.
4
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Geometric singular approach to Poisson-Nernst-Planck models with excess chemical potentials: Ion size effects on individual fluxes

64%
Zhang M., Zhang J., Acheampong D.
Molecular Based Mathematical Biology
|
2017
|
tom 5
|
nr 1
58-77
EN
We study a quasi-one-dimensional steady-state Poisson-Nernst-Planck model for ionic flows through membrane channels. Excess chemical potentials are included in this work to account for finite ion size effects. This is the main difference from the classical Poisson-Nernst-Planck models, which treat ion species as point charges and neglect ion-to-ion interactions. Due to the fact that most experiments (with some exceptions) can only measure the total current while individual fluxes contain much more information on channel functions, our main focus is to study the qualitative properties of ionic flows in terms of individual fluxes under electroneutrality conditions. Our result shows that, in addition to ion sizes, the property depends on multiple physical parameters such as boundary concentrations and potentials, diffusion coe-cients, and ion valences. For the relatively simple setting and assumptions of the model in this paper, we are able to characterize, almost completely, the distinct effects of the nonlinear interplay between these physical parameters. The boundaries of different parameter regions are identified through a number of critical potential values that are explicitly expressed in terms of the physical parameters.Numerical simulations are performed to detect the critical potentials and investigate the quantitative properties of ionic flows over different potential regions. In particular, a special case is studied in Section 5 without the assumption of electroneutrality conditions.
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