This paper discusses both the nonexistence of positive solutions for
second-order three-point boundary value problems
when the nonlinear term $f(t,x,y)$ is superlinear in $y$ at $y=0$
and the existence
of multiple positive solutions for second-order three-point boundary value
problems when the nonlinear term $f(t,x,y)$ is superlinear in $x$ at
$+\infty$.
A genuine variational principle developed by Gyarmati, in the field of thermodynamics of irreversible processes unifying the theoretical requirements of technical, environmental and biological sciences is employed to study the effects of uniform suction and injection on MHD flow adjacent to an isothermal wedge with pressure gradient in the presence of a transverse magnetic field. The velocity distribution inside the boundary layer has been considered as a simple polynomial function and the variational principle is formulated. The Euler-Lagrange equation is reduced to a simple polynomial equation in terms of momentum boundary layer thickness. The velocity profiles, displacement thickness and the coefficient of skin friction are calculated for various values of wedge angle parameter $m$, magnetic parameter $\xi$ and suction/injection parameter $H$. The present results are compared with known available results and the comparison is found to be satisfactory. The present study establishes high accuracy of results obtained by this variational technique.
In this paper the singularly perturbed initial boundary value problems for a nonlocal reaction diffusion system are considered. Using the iteration method and the comparison theorem, the existence and asymptotic behavior of solutions for the problem are studied.
For the single gene network model, there are two basic types. For convenience, we call them Type I and Type II, respectively. The Type I model describes both the dynamics of mRNA and protein. The Type II model is a simplification of the Type I model based on the assumption that the change rate of mRNA is much faster than protein because the half-life of mRNA is short compared with that of protein. the Type II model describes only the dynamics of protein. The analysis of the Type I model is based on the assumption that the ratio of the protein decay rate to the mRNA decay rate is small enough. The main results for Type I model show that the Fano factor of the protein must be bigger than one if there is no negative feedback on the transcription. If there is negative feedback, the relative fluctuation strength in the number of proteins is determined by the size of the feedback regulation strength.
Let $D=(V, E)$ be a primitive digraph. The vertex exponent of $D$ at a vertex $v\in V$, denoted by $\exp_{D}(v)$, is the least integer $p$ such that there is a $v\rightarrow u$ walk of length $p$ for each $u\in V.$ Following Brualdi and Liu, we order the vertices of $D$ so that $\exp_{D}(v_{1})\leq \exp_{D}(v_{2})\leq \cdots \leq \exp_{D}(v_{n})$. Then $\exp_{D}(v_{k})$ is called the $k$-point exponent of $D$ and is denoted by $\exp_{D}(k),$ $1\leq k\leq n.$ In this paper we define $e(n,k):=\max\{\exp_D(k)|\, D\in PD(n,2)\}$ and $E(n,k):=\{\exp_{D}(k)|\, D\in PD(n,2)\},$ where $PD(n,2)$ is the set of all primitive digraphs of order $n$ with girth $2$. We completely determine $e(n,k)$ and $E(n,k)$ for all $n,$ $k$ with $n\geq 3$ and $1\leq k\leq n.$
The long time behavior of the solutions of some partly dissipative reaction diffusion systems is studied. We prove the existence of a compact $(L^2\times L^2-H^1\times L^2)$ attractor for a partly dissipative reaction diffusion system in $R^n$. This improves a previous result obtained by A. Rodrigues-Bernal and B. Wang concerning the existence of a compact $(L^2\times L^2-L^2\times L^2)$ attractor for the same system.
In the paper, we study the positive solutions of a diffusive competition model with an inhibitor involved subject to the homogeneous Dirichlet boundary condition. The existence, uniqueness, stability and multiplicity of positive solutions are discussed. This is mainly done by using the local and global bifurcation theory.
By the variable transformation and generalized Hirota method, exact homoclinic and heteroclinic solutions for Davey-Stewartson II (DSII) equation are obtained. For perturbed DSII equation, the existence of a global attractor is proved. The persistence of homoclinic and heteroclinic flows is investigated, and the special homoclinic and heteroclinic structure in attractors is shown.
This paper deals with the design and analysis of adaptive wavelet method for the Stokes problem. First, the limitation of Richardson iteration is explained and the multiplied matrix $M_0$ in the paper of Bramble and Pasciak is proved to be the simplest possible in an appropiate sense. Similar to the divergence operator, an exact application of its dual is shown; Second, based on these above observations, an adaptive wavelet algorithm for the Stokes problem is designed. Error analysis and computational complexity are given; Finally, since our algorithm is mainly to deal with an elliptic and positive definite operator equation, the last section is devoted to the Galerkin solution of an elliptic and positive definite equation. It turns out that the upper bound for error estimation may be improved.
A periodic difference predator-prey model with Holling-$(m+1)(m>2)$ type functional response and impulses is established. Sufficient conditions are derived for the existence of periodic solutions by using a continuation theorem in coincidence degree.
A $(v, k, \lambda)$ difference family ($(v, k, \lambda)$-DF in short) over an abelian group $G$ of order $v$, is a collection ${\cal F}=\{B_i| i\in I\}$ of $k$-subsets of $G$, called base blocks, such that any nonzero element of $G$ can be represented in precisely $\lambda$ ways as a difference of two elements lying in some base blocks in ${\cal F}$. A $(v, k, \lambda)$-DDF is a difference family with disjoint blocks. In this paper, by using Weil's theorem on character sum estimates, it is proved that there exists a $(p^n, 4, 1)$-DDF, where $p\equiv 1 \ (mod \ 12)$ is a prime number and $n\geq 1$.
Considering the classical model with risky investment, we are interested in the ruin probability that is minimized by a suitably chosen investment strategy for a capital market index. For claim sizes with common distribution of extended regular variation, starting from an integro-differential equation for the maximal survival probability, we find that the corresponding ruin probability as a function of the initial surplus is also extended regular variation.
In this paper we examine two classes of correlated aggregate claims distributions, with univariate claim counts and multivariate claim sizes. Firstly, we extend the results of Hesselager [ASTIN Bulletin, 24: 19--32(1994)] and Wang $\&$ Sobrero's [ASTIN Bulletin, 24: 161--166 (1994)] concerning recursions for compound distributions to a multivariate situation where each claim event generates a random vector. Then we give a multivariate continuous version of recursive algorithm for calculating a family of compound distribution. Especially, to some extent, we obtain a continuous version of the corresponding results in Sundt [ASTIN Bulletin, 29: 29--45 (1999)] and Ambagaspitiya [Insurance: Mathematics and Economics, 24: 301--308 (1999)]. Finally, we give an example and show how to use the algorithm for aggregate claim distribution of first class to compute recursively the compound distribution.
Let $B_{0}^{H}=\{B_{0}^{H}(t), t\in R_{+}^{N}\}$ be a real-valued fractional Brownian sheet. Define the $(N,d)-$ Gaussian random field $B^{H}$ by $$B^{H}(t)=\big(B_{1}^{H}(t), \cdots, B_{d}^{H}(t)\big)\qquad t\in R_{+}^{N} ,$$ where $B_{1}^{H}, \cdots, B_{d}^{H}$ are independent copies of $B_{0}^{H}$. The existence and joint continuity of local times of $B^{H}$ is proven in some given conditions in [22]. We then study further properties of the local times of $B^{H},$ such as the moments of increments of local times, the large increments and the maximum moduli of continuity of local times and as a result, we answer the questions posed in [22].
In this paper we investigate cycle base structures of a (weighted) graph and show that much information of short cycles is contained in a MCB (minimum cycle base). After setting up a {\it Hall type theorem} for base-transformation, we give a sufficient and necessary condition for a cycle base to be a MCB. Further more, we show that the structure of MCB in a (weighted) graph is unique. In the case of nonnegative weight, every pair of MCB have the same number of $k-$cycles for each integer $k\geq 3$. The property is also true for those having longest length (although much work has been down in evaluating MCB, little is known for those having longest length).
Image restoration is a fundamental problem in image processing. Blind image restoration has a great value in its practical application. However, it is not an easy problem to solve due to its complexity and difficulty. In this paper, we combine our robust algorithm for known blur operator with an alternating minimization implicit iterative scheme to deal with blind deconvolution problem, recover the image and identify the point spread function(PSF). The only assumption needed is satisfy the practical physical sense. Numerical experiments demonstrate that this minimization algorithm is efficient and robust over a wide range of PSF and have almost the same results compared with known PSF algorithm.
By means of the undetermined assumption method, we obtain some new exact solitary-wave solutions with hyperbolic secant function fractional form and periodic wave solutions with cosine function form for the generalized modified Boussinesq equation. We also discuss the boundedness of these solutions. More over, we study the correlative characteristic of the solitary-wave solutions and the periodic wave solutions along with the travelling wave velocity's variation.