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.

Reverse logistics network design using simulated annealing

Abstract: Reverse logistics is becoming more important in overall industry area because of the environmental and business factors. Planning and implementing a suitable reverse logistics network could bring more profit, customer satisfaction, and a nice social picture for companies. But, most of logistics networks are not equipped to handle the return products in reverse channels. This paper proposes a mixed integer linear programming model to minimize the transportation and fixed opening costs in a multistage reverse logistics network. Since such network design problems belong to the class of NP-hard problems, we apply a simulated annealing (SA) algorithm with special neighborhood search mechanisms to find the near optimal solution. We also compare the associated numerical results through exact solutions in a set of problems to present the high-quality performance of the applied SA algorithm.

Fabrication of composite PVDF-ZnO nanofiber mats by electrospinning for energy scavenging application with enhanced efficiency

Abstract: Composite electrospun nanofibers mats, as a nano- generator, were fabricated through one-step electrospinning method. The structure of fibers is composed of Poly(vinylidene fluoride), PVDF, as the matrix, and Zinc ox- ide (ZnO) nanoparticles; the nanocomposite were produced using electrospinning technique in order to have the benefit of piezoelectric properties and non-brittle behavior of ZnO and PVDF for the application in wearable electronic devices. Characteristics of these structures were evaluated by using X- ray diffraction (XRD), Fourier Transform Infrared (FTIR), Differential Scanning Calorimetry (DSC) and Scanning Elec- tron Microscopy (SEM). Impedance and the electrical con- ductivity of the fabricated composites were also evaluated by Keithley instruments. Electrical response of samples was measured using an impedance analyzer made in Aims Lab (http://aims.aut.ac.ir) at room temperature. Results showed that incorporating the ZnO nanoparticles into the PVDF nanofibers improved the piezoelectric properties of samples compared to PVDF samples. The electrical output of composite samples was improved as high as 1.1 V compared with 0.351 V for the pure PVDF samples. These results imply promising applications, as an enhanced- efficiency energy-scavenging interface, for various wearable self-powered electrical devices and systems.

Unit Commitment Problem Solution Using Shuffled Frog Leaping Algorithm

Abstract: A new evolutionary algorithm known as the shuffled frog leaping algorithm is presented in this paper, to solve the unit commitment (UC) problem. This integer-coded algorithm has been developed to minimize the total energy dispatch cost over the scheduling horizon while all of the constraints should be satisfied. In addition, minimum up/down-time constraints have been directly coded not using the penalty function method. The proposed algorithm has been applied to ten up to 100 generating units, considering one-day and seven-day scheduling periods. The most important merit of the proposed method is its high convergence speed. The simulation results of the proposed algorithm have been compared with the results of algorithms such as Lagrangian relaxation, genetic algorithm, particle swarm optimization, and bacterial foraging. The comparison results testify to the efficiency of the proposed method.

Recent progress in extrusion 3D bioprinting of hydrogel biomaterials for tissue regeneration: a comprehensive review with focus on advanced fabrication techniques

Abstract: Over the last decade, 3D bioprinting has received immense attention from research communities for developing functional tissues. Thanks to the complexity of tissues, various bioprinting methods have been exploited to figure out the challenges of tissue fabrication, in which hydrogels are widely adopted as a bioink in cell printing technologies based on the extrusion principle. Thus far, there is a wealth of literature proposing the crucial parameters of extrusion-based bioprinting of hydrogel biomaterials (e.g., hydrogel properties, printing conditions, and tissue scaffold design) toward enhancing performance. Despite the growing research in this field, numerous challenges that hinder advanced applications still exist. Herein, the most recently reported hydrogel-based bioprinted scaffolds, i.e., skin, bone, cartilage, vascular, neural, and muscular (including skeletal, cardiac, and smooth) scaffolds, are systematically discussed with an emphasis on the advanced fabrication techniques from the tissue engineering perspective. The methods covered include multiple-dispenser, coaxial, and hybrid 3D bioprinting. The present work is a unique study to figure out the opportunities of the novel techniques to fabricate complicated constructs with structural and functional heterogeneity. Finally, the principal challenges of current studies and a vision of future research are presented.