Amirkabir University of Technology

About: Amirkabir University of Technology is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Nonlinear system & Fuzzy logic. The organization has 15254 authors who have published 31165 publications receiving 487551 citations. The organization is also known as: Tehran Polytechnic & Tehran Polytechnic University.

Megastability: Coexistence of a countable infinity of nested attractors in a periodically-forced oscillator with spatially-periodic damping

Abstract: In this paper, we describe a periodically-forced oscillator with spatially-periodic damping. This system has an infinite number of coexisting nested attractors, including limit cycles, attracting tori, and strange attractors. We are aware of no similar example in the literature.

Characterization of hot deformation behavior of 410 martensitic stainless steel using constitutive equations and processing maps

Abstract: Hot deformation behavior of AISI 410 martensitic stainless steel was investigated by conducting hot compression tests at the temperatures of 900–1150 °C and the strain rates of 0.001–1 s −1 . The relation between the flow stress and Zener–Hollomon parameter was successfully analyzed via the hyperbolic sine function under the whole range of deformation condition. Therefore, the value of apparent activation energy and the empirical materials constants of A and n were determined. The values of both strain and stress of peak and steady state flow were related to Zener–Hollomon parameter and pertaining relations were proposed. On the basis of dynamic materials model the power dissipation map and the instability map were developed. The processing map was obtained by superimposition of the power dissipation and the instability maps and the regions having the lowest strain rate sensitivity added for more clarification of low and high workability regions. Optical microscopy observations of prior austenite grains showed that dynamic recrystallization grain size had an adverse relation with Zener–Hollomon parameter. According to grain size measurements, the best relation between dynamic recrystallization grain size and Zener–Hollomon parameter was proposed.

Incidence energy of a graph

Abstract: The energy of a graph E(G), is the sum of the singular values of its adjacency matrix. We define incidence energy of the graph G, denoted by IE (G), as the sum of the singular values of its incidence matrix. We are interested to find the relation between the energy and the incidence energy of graphs. For any graph G we obtain a bipartite graph 3 G such that IE (G )= E( 3 G) 2 . Moreover we find some similar upper and lower bounds of energy for incidence energy. Finally we show that for any proper subgraph H of the graph G, IE (G) >I E(H).