Characteristics of the phase-separated state in manganites: Relationship with transport and magnetic properties

Journal of Experimental and Theoretical Physics - The temperature and magnetic field dependence of the resistivity, magnetoresistance, and magnetic susceptibility of phase-separated manganites in...     

Shortest Path Problem on a Network with Imprecise Edge Weight

A network with its arc lengths as imprecise number, instead of a real number, namely, interval number and triangular fuzzy number is considered here. Existing ideas on addition and comparison between two imprecise numbers of same type are introduced. To obtain a fuzzy shortest path from a source vertex to all other vertices, a common algorithm is developed which works well on both types of imprecise numbers under consideration. In the proposed algorithm, a decision-maker is to negotiate with the obtained fuzzy shortest paths according to his/her view only when the means are same but the widths are different of the obtained paths. Otherwise, a fuzzy optimal path is obtained to which the decision-maker always satisfies with different grades of satisfaction. All pairs fuzzy shortest paths can be found by repeated use of the proposed algorithm.     

Synthesis and photoluminescence of Zinc(II) complexes with tetrafluoroterephthalic acid (H2L). Crystal structure of coordination polymer [Zn(H2O)4(L) · 4H2O]n

Complexes Zn(H₂O)₄(L) (I) and Zn(H₂O)(L) (II) (H₂L = p-HOOCC₆F₄COOH) are synthesized. Single crystals of compound [Zn(H₂O)₄(L) · 4H₂O] _n (III) are grown. According to the X-ray diffraction data, the crystal structure of compound III is built of zigzag chains of coordination polymer Zn(H₂O)₄(L) and molecules of water of crystallization. The chain contains ions Zn²⁺, whose octahedral coordination sphere includes the O atoms of four water molecules and two O atoms of the deprotonated carboxyl groups. The chains in structure III are joined by a system of hydrogen bonds of coordinated water molecules and molecules of water of crystallization. The photoluminescence spectrum of H₂L exhibits the band with λ_max = 368 nm. The spectra of compounds III, I, and II contain bands at 322, 340, and 353 nm, respectively.     

Analysis of the nonlinear vibration of a two-mass–spring system with linear and nonlinear stiffness

An analytical approach is developed for areas of nonlinear science such as the nonlinear free vibration of a conservative, two-degree-of-freedom mass–spring system having linear and nonlinear stiffnesses. The main contribution of this research is twofold. First, it introduces the transformation of two nonlinear differential equations for a two-mass system using suitable intermediate variables into a single nonlinear differential equation and, more significantly, the treatment of a nonlinear differential system by linearization coupled with Newton’s method. Secondly, the major section is the solving of the governing nonlinear differential equation where the displacement of the two-mass system can be obtained directly from the linear second-order differential equation using a first-order variational approach. The aforementioned approach proposed by J.H. He, who actually developed the method, is exactly He’s variational method. This approach is an explicit method with high validity for resolving strong nonlinear oscillation system problems. Two examples of nonlinear two-degree-of-freedom mass–spring systems are analyzed, and verified with published results and exact solutions. The method can be easily extended to other nonlinear oscillations and so could be widely applicable in engineering and science.     

High-temperature properties of the manganites: Manifestation of a paramagnetic-phase inhomogeneity?

An analysis was made of the magnetic susceptibility, electrical resistivity, and magnetoresistance of (La_1?yPr_y)_0.7Ca_0.3MnO₃ samples differing in Pr content and enriched in the oxygen isotope ¹⁸O. At high temperatures, all samples were paramagnetic insulators, while below 60 K, part of them transferred to a ferromagnetic metallic state. All the samples exhibit practically identical behavior of the susceptibility, resistivity, and magnetoresistance in the high-temperature region, despite a noticeable difference between their properties at low temperatures; more specifically, the magnetoresistance grows quadratically with magnetic field within a broad range of temperatures and magnetic fields and scales with increasing temperature close to 1/T⁵. A combined analysis of the magnetic susceptibility and magnetoresistance indicates the possible existence of an inhomogeneous state with considerable ferromagnetic correlations in the paramagnetic region.     

Efficient Transformation of Furfuryl Alcohol Into Ethyl Levulinates via Alcoholysis Reaction Catalyzed by SnO2/H-Mordenite Catalyst

Catalysis Surveys from Asia - Catalytic production of ethyl levulinate by alcoholysis of furfuryl alcohol with ethanol was investigated over H-mordenite supported Sn catalyst under atmospheric N2...