No abstract

In this paper we propose a method for investigating the solvability and iterative solution of a nonlinear fully fourth order boundary value problem. Namely, by the reduction of the problem to an operator equation for the right-hand side function we establish the existence and uniqueness of a solution and the convergence of an iterative process. Our method completely differs from the methods of other authors and does not require the condition of boundedness or linear growth of the right-hand side function on infinity. Many examples, where exact solutions of the problems are known or not, demonstrate the effectiveness of the obtained theoretical results.

In this paper we study a boundary value problem for a nonlinear biharmonic equation, which models a bending plate on nonlinear elastic foundation. We propose a new approach to existence and uniqueness  and numerical solution of the problem. It is based on the reduction of the problem to finding fixed point of a nonlinear operator for the nonlinear term. The result is that under some easily verified conditions we have established the existence and uniqueness of a solution and the convergence of an iterative method for the solution. The positivity of the solution and the monotony of iterations are also considered. Some examples demonstrate the applicability of the obtained theoretical results and the efficiency of the iterative method.

Hàm Green có ứng dụng rộng rãi trong nghiên cứu các bài toán giá trị biên. Đặc biệt, hàm Green là công cụ quan trọng để chỉ ra sự tồn tại và duy nhất nghiệm của các bài toán. Trong bài báo này, chúng tôi nghiên cứu tính giải được của bài toán biên phi tuyến đối với phương trình vi phân có sử dụng hàm Green. Khác với cách tiếp cận của các tác giả khác, chúng tôi đưa bài toán ban đầu về phương trình toán tử đối với hàm vế phải. Xét hàm này trong miền bị chặn xác định, với một số điều kiện dễ kiểm tra chứng tỏ rằng toán tử này có tính chất co. Điều này bảo đảm bài toán gốc có nghiệm duy nhất.

In this work we propose a novel approach to investigate boundary value problems (BVPs) for fully third order differential equations. It is based on the reduction of BVPs to operator equations for the nonlinear terms but not for the functions to be sought. By this approach we have established the existence, uniqueness, positivity and monotony of solutions and the convergence of the iterative method for approximating the solutions under some easily verified conditions in bounded domains. These conditions are much simpler and weaker than those of other authors for studying solvability of the problems before by using different methods. Many examples illustrate the obtained theoretical results.