Deِtermination of the Stiffness and the Damping of a Duplex Back to Back Ball Bearing by using Modal Testing

, M.Sc. Thesis Sharif University of Technology Sedgh Amiz, Gohar (Author) ; Mohammad Navazi, Hossein (Supervisor)

Abstract

This thesis aims to provide a method for obtaining the dynamic properties, including stiffness and damping, of rolling bearings in radial and axial directions using an experimental approach. Experimental and laboratory methods such as modal testing, vibration testing, and static tests are recognized as practical approaches to obtain these properties. In this research, all three of these methods were employed to determine these properties. After studying the theoretical relationships governing bearing stiffness coefficients, a test setup was designed and constructed for conducting experiments. Subsequently, various tests were conducted, and data was collected, including shaft displacement...

The Effect of The Reservation Price Increase Policy on Online Advertising Auction A Case Study of The Auctions of Yektant Company

, M.Sc. Thesis Sharif University of Technology Hosseini Gohar, Mohammad Mahdi (Author) ; Rahmati, Mohammad Hossein (Supervisor)

Abstract

Auction is one of the most important and oldest institutions in economics, enabling resource allocation and trade of goods in the economy. Investigating the effects of changes in reservation price in auctions is an important question in auction theory research. In this study, focusing on a policy implemented by Yektanet, which involved altering the reservation price in auctions for advertising slots, we assessed its impact on advertiser costs. The implemented policy led to the activation of two distinct mechanisms, resulting in conflicting effects on the company's revenue. The first mechanism involved an increase in bid and intensified competition for ad placements on average, while the...

Biodegradation of Polycyclic Aromatic Hydrocarbons in a New Reactor

, M.Sc. Thesis Sharif University of Technology Samiee Gohar, Mohammad Reza (Author) ; Molaei Dehkordi, Asghar (Supervisor) ; Arabian, Daryoush (Co-Advisor)

Abstract

TPPB are characterized by a cell-containing aqueous phase, and an immiscible and biocompatible organic phase that partitions toxic/insoluble substrates to the cells base on their metabolic demand and the thermodynamic equilibrium of the system. Surface areas, Mass transfer coefficient, Hydrophobicity of polycyclic aromatic hydrocarbons (PAH) are considered as limitation in two phase partition bioreactors (TPPB). For solving of this challenge, in this project used solid particle for increment of mss transfer and surface area, and also solid particles can eliminate limitation of initial concentration of polycyclic aromatic hydrocarbon and ratio of aqueous/organic phases. Naphthalene is used as...