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3. Electron beam irradiation effects on the structure and mechanical properties of PEEK. Part 1

Author

Almassov, Nurlan, Rakhadilov, Bauyrzhan, Serik, Nurzhan, Alsar, Zhanna, Sagdoldina, Zhuldyz, Andybayeva, Gaukhar, Zhakiyev, Nurkhat, Spitas, Christos, Kostas, Constantinos, and Insepov, Zeke

Subjects
Condensed Matter - Materials Science
Abstract

Effects of electron-beam processing on the structure and mechanical properties of poly-ether-ether ketone (PEEK) were studied by XRD and tribological tests. An ambiguous change in the mechanical properties of the irradiated samples was found. In particular, the wear rate of sample 1 is higher than that of the unirradiated original sample, while it is lower for samples 2-7. Sample 4 had the lowest wear rate, and most likely the changes in the mechanical properties of the samples were due to the transformation of their amorphous component. Comparison of the X-ray spectra of the irradiated and unirradiated samples did not reveal any differences in their crystal structure., Comment: 6 pages

Published
2021

4. Energy Transport in 1-Dimensional Oscillator Arrays With Hysteretic Damping

Author

Bountis, Tassos, Kaloudis, Konstantinos, Shena, Joniald, Skokos, Charalampos, and Spitas, Christos

Subjects
Mathematics - Dynamical Systems, Nonlinear Sciences - Chaotic Dynamics
Abstract

Energy transport in 1-dimensional oscillator arrays has been extensively studied to date in the conservative case, as well as under weak viscous damping. When driven at one end by a sinusoidal force, such arrays are known to exhibit the phenomenon of supratransmission, i.e. a sudden energy surge above a critical driving amplitude. In this paper, we study 1-dimensional oscillator chains in the presence of hysteretic damping, and include nonlinear stiffness forces that are important for many materials at high energies. We first employ Reid's model of local hysteretic damping, and then study a new model of nearest neighbor dependent hysteretic damping to compare their supratransmission and wave packet spreading properties in a deterministic as well as stochastic setting. The results have important quantitative differences, which should be helpful when comparing the merits of the two models in specific engineering applications., Comment: Submitted

Published
2021
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9. Periodically Forced Nonlinear Oscillators With Hysteretic Damping

Author

Bountis, Anastasios, Kaloudis, Konstantinos, and Spitas, Christos

Subjects
Mathematics - Dynamical Systems, Nonlinear Sciences - Chaotic Dynamics
Abstract

We perform a detailed study of the dynamics of a nonlinear, one-dimensional oscillator driven by a periodic force under hysteretic damping, whose linear version was originally proposed and analyzed by Bishop in [1]. We first add a small quadratic stiffness term in the constitutive equation and construct the periodic solution of the problem by a systematic perturbation method, neglecting transient terms as $t\rightarrow \infty$. We then repeat the analysis replacing the quadratic by a cubic term, which does not allow the solutions to escape to infinity. In both cases, we examine the dependence of the amplitude of the periodic solution on the different parameters of the model and discuss the differences with the linear model. We point out certain undesirable features of the solutions, which have also been alluded to in the literature for the linear Bishop's model, but persist in the nonlinear case as well. Finally, we discuss an alternative hysteretic damping oscillator model first proposed by Reid [2], which appears to be free from these difficulties and exhibits remarkably rich dynamical properties when extended in the nonlinear regime., Comment: Accepted for publication in the Journal of Computational and Nonlinear Dynamics

Published
2020

28. Dynamics of Antimicrobial Peptide Encapsulation in Carbon Nanotubes: The Role of Hydroxylation

Author

Zarghami Dehaghani,Maryam, Yousefi,Farrokh, Seidi,Farzad, Sajadi,S Mohammad, Rabiee,Navid, Habibzadeh,Sajjad, Esmaeili,Amin, Hamed Mashhadzadeh,Amin, Spitas,Christos, Mostafavi,Ebrahim, Saeb,Mohammad Reza, Zarghami Dehaghani,Maryam, Yousefi,Farrokh, Seidi,Farzad, Sajadi,S Mohammad, Rabiee,Navid, Habibzadeh,Sajjad, Esmaeili,Amin, Hamed Mashhadzadeh,Amin, Spitas,Christos, Mostafavi,Ebrahim, and Saeb,Mohammad Reza

Abstract

Maryam Zarghami Dehaghani,1 Farrokh Yousefi,2 Farzad Seidi,1 S Mohammad Sajadi,3,4 Navid Rabiee,5 Sajjad Habibzadeh,6 Amin Esmaeili,7 Amin Hamed Mashhadzadeh,8 Christos Spitas,8 Ebrahim Mostafavi,9,10 Mohammad Reza Saeb11 1Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources and Joint International Research Lab of Lignocellulosic Functional Materials, Nanjing Forestry University, Nanjing, 210037, People’s Republic of China; 2Department of Physics, University of Zanjan, Zanjan, 45195-313, Iran; 3Department of Nutrition, Cihan University-Erbil, Erbil, Iraq; 4Department of Phytochemistry, SRC, Soran University, Soran, Iraq; 5Department of Physics, Sharif University of Technology, Tehran, Iran; 6Department of Chemical Engineering, Amirkabir University of Technology (Tehran Polytechnic), Tehran, 1591639675, Iran; 7Department of Chemical Engineering, School of Engineering Technology and Industrial Trades, College of the North Atlantic — Qatar, Doha, Qatar; 8Mechanical and Aerospace Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan, 010000, Kazakhstan; 9Stanford Cardiovascular Institute, Stanford University School of Medicine, Stanford, CA 94305, USA; 10Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA; 11Department of Polymer Technology, Faculty of Chemistry, GdaÅ„sk University of Technology, GdaÅ„sk, 80-233, PolandCorrespondence: Amin Hamed MashhadzadehMechanical and Aerospace Engineering, School of Engineering and Digital Sciences, Nazarbayev University, Nur-Sultan, 010000, KazakhstanEmail amin.hamed.m@gmail.com; amin.hamedmashhadzadeh@nu.edu.kzEbrahim MostafaviStanford Cardiovascular Institute, Stanford University School of Medicine, Biomedical Innovation Building, 240 Pasteur Drive, Palo Alto, Stanford, CA 94304, USAEmail ebimsv@Stanford.edu; ebi.mostafavi@gmail.comIntroduction: Carbon nanotubes (CNTs) have been widely employed as biom

Published
2022

33. An insight into thermal properties of BC3-graphene hetero-nanosheets: a molecular dynamics study.

Author

Dehaghani, Maryam Zarghami, Molaei, Fatemeh, Yousefi, Farrokh, Sajadi, S. Mohammad, Esmaeili, Amin, Mohaddespour, Ahmad, Farzadian, Omid, Habibzadeh, Sajjad, Mashhadzadeh, Amin Hamed, Spitas, Christos, and Saeb, Mohammad Reza

Subjects
THERMAL properties, INTERFACIAL resistance, THERMAL shock, THERMAL resistance, MOLECULAR dynamics, BORON carbides, CRYSTAL grain boundaries
Abstract

Simulation of thermal properties of graphene hetero-nanosheets is a key step in understanding their performance in nano-electronics where thermal loads and shocks are highly likely. Herein we combine graphene and boron-carbide nanosheets (BC3N) heterogeneous structures to obtain BC3N-graphene hetero-nanosheet (BC3GrHs) as a model semiconductor with tunable properties. Poor thermal properties of such heterostructures would curb their long-term practice. BC3GrHs may be imperfect with grain boundaries comprising non-hexagonal rings, heptagons, and pentagons as topological defects. Therefore, a realistic picture of the thermal properties of BC3GrHs necessitates consideration of grain boundaries of heptagon-pentagon defect pairs. Herein thermal properties of BC3GrHs with various defects were evaluated applying molecular dynamic (MD) simulation. First, temperature profiles along BC3GrHs interface with symmetric and asymmetric pentagon-heptagon pairs at 300 K, ΔT = 40 K, and zero strain were compared. Next, the effect of temperature, strain, and temperature gradient (ΔT) on Kaptiza resistance (interfacial thermal resistance at the grain boundary) was visualized. It was found that Kapitza resistance increases upon an increase of defect density in the grain boundary. Besides, among symmetric grain boundaries, 5–7–6–6 and 5–7–5–7 defect pairs showed the lowest (2 × 10–10 m2 K W−1) and highest (4.9 × 10–10 m2 K W−1) values of Kapitza resistance, respectively. Regarding parameters affecting Kapitza resistance, increased temperature and strain caused the rise and drop in Kaptiza thermal resistance, respectively. However, lengthier nanosheets had lower Kapitza thermal resistance. Moreover, changes in temperature gradient had a negligible effect on the Kapitza resistance. [ABSTRACT FROM AUTHOR]

Published
2021
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34. Modelling of elasto-hydrodymic lubrication problems in gears

Author

Amani, Amin, Rajabali Nejad, Mohammadreza, and Spitas, Christos

Subjects
Physics::Classical Physics, IR-89087
Abstract

For highly loaded contacts, lubricant pressure can cause elastic deformation of the surface that is in the same order as the film thickness of lubricant. When this occurs, the influence of deformation on lubrication performance becomes an important parameter. Contacts operating under this condition are in the regime of elasto-hydrodynamic lubrication (EHL).In addition, numerical calculations of EHL problems are high-priced belonging to the large quantity of numerical computations needed as a result of their contact domains being much bigger than those of involute gears and bearings [1,2]. To amplify the effortlessness of simulations, Homotopy Perturbation Method (HPM)[3-6,13-17] is used. HPM is an effective and relatively uncomplicated methodology for solving nonlinear thermal problem for lubrication of gears. In this paper, we contrast HPM in related to higher-order approximate solutions for the EHL. It is concluded that the results of HPM provide accurate solution, as an easy methodology for computing the nonlinear differential equations for EHL

Published
2011

35. Analysis of decision making process for a systematic engineering design

Author

Rajabali Nejad, Mohammadreza, Spitas, Christos, Roozenburg, Norbert, Chen, Lin-Lin, and Stappers, Pieter Jan

Subjects
IR-89089
Abstract

In this paper, we present a new methodology for a systematic design process that shows if the acquired knowledge, modeled in the K-space, is enough or further exploration of the C-space is required. We treat the uncertainty [4] and apply it to the Cold Facts project [5] as a distinguished project with contribution of different scientific disciplines.

Published
2011

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