Non-Linear Vibration and Stability Analysis of a Rotor with Rubbing and NonLinear Support

, M.Sc. Thesis Sharif University of Technology Eisvand Chenari, Ashkan (Author) ; Mohammad Navazi, Hossein (Supervisor)

Abstract

The present study aims to achieve two major objectives in the field of Rotordynamics. The first one is to investigate the frequency response function by considering rubbing between fixed and rotating components of the system and also the presence of nonlinear support such as tiling-pad bearings using analytical approach and the second one is to study the stability of the system using both analytical and numerical methods. In first step, by using assumptions and laws of physics, a model for dealing with the rubbing phenomenon and the friction force between fixed and rotating components of the system is presented. In the next step, the rubbing force is modeled. Then using the Jeffcott rotor...

Sustainable-Resilient Supplier Selection Through Fuzzy Multi-Criteria Decision Making Approaches

, M.Sc. Thesis Sharif University of Technology Varchandi, Sahar (Author) ; Akbari Jokar, Mohammad Resa (Supervisor) ; Memari, Ashkan (Co-Supervisor)

Abstract

Today, with the expansion of business relations at international levels, there are many organizations that operate in global supply chains. Activities at such levels face new types of challenges in various fields of "supply chain management" pillars, of which "supplier selection" is one of them. The possibility of unexpected events, the need to comply with environmental protection laws, as well as the need to take into account social considerations, are among the things that have increased by being in larger supply chains, making it challenging to provide the basic resources needed in such chains and forcing their managers to considering considerations other than what they have always...

Minimizing the Level of Damage of Structures and Improving their Performance through Optimal Design of Semi-Active Tuned Mass Damper

, M.Sc. Thesis Sharif University of Technology Chenari, Mohammad Reza (Author) ; Rahimzadeh Rofooei, Fayyaz (Supervisor)

Abstract

The aim of this study is to evaluate the seismic performance of structures using a semi-active tuned mass damper minimizing the amount of structural damage caused by earthquakes. One of semi-active control mechanisms, which has been studied in recent years, is the damper with fluid controlled by a magnetic field (Magnetorehological Damper, MR). These type of dampers react to the magnetic fields that cause significant changes in the behavior of fluid flow. These dampers are acknowledged because of their simplicity, broad operating range as well as not requiring high-power energy sources. In this thesis, a MR damper is used instead of the existing viscous element of tuned mass damper. To...

On the catalysis capability of transition metal oxide nanoparticles in upgrading of heavy petroleum residue by supercritical water

, Article Journal of Supercritical Fluids ; Volume 126 , 2017 , Pages 14-24 ; 08968446 (ISSN) Kosari, M ; Golmohammadi, M ; Ahmadi, S. J ; Towfighi, J ; Heidari Chenari, A ; Sharif University of Technology

Elsevier B.V 2017

Abstract

Vacuum residue cracking has been successfully conducted under supercritical water condition in presence of various metal oxide nanocalysts, namely NiO, CuO, ZnO, Co2O3, and Cr2O3 synthesized at supercritical water. The cracking experiments were carried out at 450 °C. Three species of cracking: maltene, asphaltene, and coke were then weighed and their corresponding speciation was defined. Gas chromatography-mass spectrometry (GC–MS), nuclear magnetic resonance spectroscopy (NMR), thermogravimetric analysis (TGA), and elemental analysis (CHNS) tests were utilized to prove the performance of upgrading reactions. It was revealed that NiO showed the best performance among other catalyst, in which...

Effect of EPS beads in lightening a typical zeolite and cement-treated sand

, Article Bulletin of Engineering Geology and the Environment ; Volume 80, Issue 11 , 2021 , Pages 8615-8632 ; 14359529 (ISSN) Khajeh, A ; Ebrahimi, S. A ; MolaAbasi, H ; Jamshidi Chenari, R ; Payan, M ; Sharif University of Technology

Springer Science and Business Media Deutschland GmbH 2021

Abstract

The current study aims to assess the influence of EPS beads inclusion on the strength properties of stabilized poorly-graded sands. Various contents of zeolite and cement as stabilizing agents, with the total amounts of 4, 8, and 12% by dry soil weight, and also 0, 0.25, and 0.5% weight ratios of EPS beads (η) are examined. Zeolite is opted among a variety of pozzolanic materials so as to replace a part of cement (0, 10, 30, 50, 70, and 90%) due to its superior environmentally friendly properties. The stress–strain behavior, unconfined compressive strength (UCS), peak strain energy (Eu), and California bearing capacity (CBR) of the zeolite and cement-treated sand-EPS beads mixtures are...

Effect of CO2-laser irradiation on properties and performance of thin-film composite polyamide reverse osmosis membrane

, Article Korean Journal of Chemical Engineering ; Volume 33, Issue 3 , 2016 , Pages 1028-1036 ; 02561115 (ISSN) Jahangiri, F ; Mousavi, S. A ; Farhadi, F ; Vatanpour, V ; Sabzi, B ; Chenari, Z ; Sharif University of Technology

Springer New York LLC 2016

Abstract

CO2-laser irradiation was used to modify the surface properties of thin-film composite (TFC) polyamide reverse osmosis (RO) membranes. These membranes were first synthesized via interfacial polymerization of m-phenylenediamine (MPD) monomers and trimesoyl chloride (TMC) over porous polysulfone ultrafiltration support, followed by a CO2-irradiation. AFM, ATR-FTIR, SEM and contact angle measurements were used to characterize the surface properties of these membranes. The ATR-FTIR results indicated that CO2-laser irradiation did not induce any functional groups on the membrane surface. However, it was found that the laser irradiation enhanced the NaCl salt rejection and slightly reduced the...

Numerical Study of Spray Impingement to Solid Wall

, M.Sc. Thesis Sharif University of Technology Abbasi Chenari, Fatemeh (Author) ; Morad, Mohammad Reza (Supervisor) ; Jahannama, Mohammad Reza (Co-Supervisor)

Abstract

Spray-wall impingement is one of the phenomenon that associated in different subject such as spray cooling, combustion chamber and gas turbine. With the impingement of spray to the wall, liquid film begins to form. Wall film characteristics is still an important subject to study. Due to the various stages of liquid film formation from injection of spray till spray-wall impingement, the investigation of this phenomenon is far more complicated. This paper is meant to provide detailed data on spray-wall impingement and wall film formation physics with the help of computational analysis of OpenFOAM . A Lagrangian-Eulerian method based on discrete phase model (DPM) was employed to model...