We study the existence of positive solutions to a class of singular nonlinear fourth-order boundary value problems in which the nonlinearity may lack homogeneity. By introducing suitable control functions and applying cone expansion and cone compression, we prove three existence theorems. Our main results improve the existence result in [Z. L. Wei, Appl. Math. Comput. 153 (2004), 865-884] where the nonlinearity has a certain homogeneity.

We provide a theoretical study of the iterative hard thresholding with partially known support set (IHT-PKS) algorithm when used to solve the compressed sensing recovery problem. Recent work has shown that IHT-PKS performs better than the traditional IHT in reconstructing sparse or compressible signals. However, less work has been done on analyzing the performance guarantees of IHT-PKS. In this paper, we improve the current RIP-based bound of IHT-PKS algorithm from ${\delta }_{3s-2k}<\frac{1}{\sqrt{32}}\approx 0.1768$ to ${\delta }_{3s-2k}<\frac{\sqrt{5}-1}{4}\approx 0.309$, where ${\delta }_{3s-2k}$ is the restricted...

We consider the singular boundary value problem $${\left(t^n{u}^{\text{'}}\left(t\right)\right)}^{\text{'}}+t^{n}f(t,u\left(t\right))=0,\underset{t\to 0+}{lim}{t}^n{u}^{\text{'}}\left(t\right)=0,a_{0}u\left(1\right)+a_1{u}^{\text{'}}(1-)=A,$$ where $f(t,x)$ is a given continuous function defined on the set $(0,1]\times (0,\infty )$ which can have a time singularity at $t=0$ and a space singularity at $x=0$. Moreover, $n\in \mathbb{N}$, $n\ge 2$, and $a_0$, $a_1$, $A$ are real constants such that $a_0\in (0,\infty )$, whereas $a_1,A\in [0,\infty )$. The main aim of this paper is to discuss the existence of solutions to the above problem and apply the general results to cover certain classes of singular problems arising in the theory of shallow membrane caps, where we are especially interested in...

In this paper we investigate the problem of existence and asymptotic behavior of solutions for the nonlinear boundary value problem $$ϵy^{\text{'}\text{'}}+ky=f(t,y),t\in \langle a,b\rangle ,k<0,0<ϵ\ll 1$$ satisfying three point boundary conditions. Our analysis relies on the method of lower and upper solutions and delicate estimations.

We design shifted $LR$ transformations based on the integrable discrete hungry Toda equation to compute eigenvalues of totally nonnegative matrices of the banded Hessenberg form. The shifted $LR$ transformation can be regarded as an extension of the extension employed in the well-known dqds algorithm for the symmetric tridiagonal eigenvalue problem. In this paper, we propose a new and effective shift strategy for the sequence of shifted $LR$ transformations by considering the concept of the Newton shift....

The paper discusses the existence of positive solutions, dead core solutions and pseudodead core solutions of the singular Dirichlet problem ${\left(\phi \left(u^{\text{'}}\right)\right)}^{\text{'}}=\lambda f(t,u,u^{\text{'}})$, $u\left(0\right)=u\left(T\right)=A$. Here $\lambda$ is the positive parameter, $A>0$, $f$ is singular at the value $0$ of its first phase variable and may be singular at the value $A$ of its first and at the value $0$ of its second phase variable.

We consider a Strang-type splitting method for an abstract semilinear evolution equation $${\partial }_{t}u=Au+F\left(u\right).$$ Roughly speaking, the splitting method is a time-discretization approximation based on the decomposition of the operators $A$ and $F.$ Particularly, the Strang method is a popular splitting method and is known to be convergent at a second order rate for some particular ODEs and PDEs. Moreover, such estimates usually address the case of splitting the operator into two parts. In this paper, we consider the splitting...

In the paper, we obtain the existence of symmetric or monotone positive solutions and establish a corresponding iterative scheme for the equation ${\left({\phi }_p\left(u^{\text{'}}\right)\right)}^{\text{'}}+q\left(t\right)f\left(u\right)=0$, $0<t<1$, where ${\phi }_p\left(s\right):={\left|s\right|}^{p-2}s$, $p>1$, subject to nonlinear boundary condition. The main tool is the monotone iterative technique. Here, the coefficient $q\left(t\right)$ may be singular at $t=0,1$.