Hong Duc University

About: Hong Duc University is a based out in . It is known for research contribution in the topics: Magnetic refrigeration & Magnetization. The organization has 176 authors who have published 259 publications receiving 1932 citations.

Coupled fixed points in partially ordered metric spaces and application

Abstract: In this paper, we prove some coupled fixed point theorems for mappings having a mixed monotone property in partially ordered metric spaces. The main results of this paper are generalizations of the main results of Bhaskar and Lakshmikantham [T. Gnana Bhaskar, V. Lakshmikantham, Fixed point theorems in partially ordered metric spaces and applications, Nonlinear Anal. TMA 65 (2006) 1379–1393]. As an application, we discuss the existence and uniqueness for a solution of a nonlinear integral equation.

Quadruple fixed point theorems for nonlinear contractions

Abstract: The notion of coupled fixed point is introduced by Gnana-Bhaskar and Lakshmikantham. Very recently, the concept of tripled fixed point was introduced by Berinde and Borcut. In this manuscript, a quadruple fixed point is considered and some new related fixed point theorems are obtained. We also give some examples to illustrate our results.

Structural, magnetic and magnetotransport behavior of La0.7SrxCa0.3−xMnO3 compounds

Abstract: A systematic investigation of the structural, magnetic and electrical properties of a series of nanocrystalline La 0.7 Sr x Ca 0.3− x MnO 3 materials, prepared by high energy ball milling method and then annealed at 900 °C has been undertaken. The analysis of the XRD data using the Win-metric software shows an increase in the unit cell volume with increasing Sr ion concentration. The La 0.7 Sr x Ca 0.3− x MnO 3 compounds undergo a structural orthorhombic-to-monoclinic transition at x =0.15. Electric and magnetic measurements show that both the Curie temperature and the insulator-to-metal transition temperature increase from 259 K and 253 K correspondingly for La 0.7 Ca 0.3 MnO 3 ( x =0) to 353 K and 282 K, respectively, for La 0.7 Sr 0.3 MnO 3 ( x =0.3). It is argued that the larger radius of Sr 2+ ion than that of Ca 2+ is the reason to strengthen the double-exchange interaction and to give rise to the observed increase of transition temperatures. Using the phenomenological equation for conductivity under a percolation approach, which depends on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the resistivity versus temperature data measured in the range of 50–320 K and found that the activation barrier decreased with the raising Sr 2+ ion concentration.