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 & Finite element method. The organization has 15254 authors who have published 31165 publications receiving 487551 citations. The organization is also known as: Tehran Polytechnic & Tehran Polytechnic University.

New high performing heuristics for minimizing makespan in permutation flowshops

Abstract: The well-known NEH heuristic from Nawaz, Enscore and Ham proposed in 1983 has been recognized as the highest performing method for the permutation flowshop scheduling problem under the makespan minimization criterion. This performance lead is maintained even today when compared against contemporary and more complex heuristics as shown in recent studies. In this paper we show five new methods that outperform NEH as supported by careful statistical analyses using the well-known instances of Taillard. The proposed methods try to counter the excessive greediness of NEH by carrying out re-insertions of already inserted jobs at some points in the construction of the solution. The five proposed heuristics range from extensions that are slightly slower than NEH in most tested instances to more comprehensive methods based on local search that yield excellent results at the expense of some added computational time. Additionally, NEH has been profusely used in the flowshop scheduling literature as a seed sequence in high performing metaheuristics. We demonstrate that using some of our proposed heuristics as seeds yields better final results in comparison.

Numerical solution of fractional differential equations with a collocation method based on Müntz polynomials

Abstract: This paper presents a computational technique based on the collocation method and Muntz polynomials for the solution of fractional differential equations. An appropriate representation of the solution via the Muntz polynomials reduces its numerical treatment to the solution of a system of algebraic equations. The main advantage of the present method is its superior accuracy and exponential convergence. Consequently, one can obtain good results even by using a small number of collocation points. The accuracy and performance of the proposed method are examined by means of some numerical experiments.

Composition and compressibility of typical samples of Mexico City clay

Abstract: Composition and compressibility characteristics of Mexico City clay were investigated using samples with natural water contents in the range of 421–574%. The composition study included scanning electron microscopy, X-ray diffraction and chemical analyses, as well as measurements of physical properties. Compressibility characteristics were investigated by means of one-dimensional consolidation tests run on specimens in the following states: natural undisturbed, artificially sedimented, remoulded at natural water content, remoulded-aged, and hydrogen peroxide treated. The primary objective was to study the secondary compressibility of Mexico City clay with special reference to the effects of previous secondary compression and thixotropic hardening. Compositional analysis indicated 5–10% sand-sized particles, most of which are calcareous ooliths (the remainder of this size fraction is a suite of heavy minerals); 55–65% of the whole sample is composed of silt-sized siliceous microfossils, mostly diatoms; 20–3...