The Effect of Thickness of Filling on Shear Behavior of Discontinuous

, M.Sc. Thesis Sharif University of Technology Nafisi, Ashkan (Author) ; Sadaghiani, Mohammad Hossin (Supervisor)

Abstract

The need to build underground structures like tunnels, oil reservoirs are increasing and it requires a good knowledge of behavior of mass rock, exact data and parameters for safe and economic design. Filling materials which usually transfer with water into the joints reduce shear strength of joints significantly and change the behavior of the joints. To evaluate shear behavior of filled joints, 24 tests were conducted with large scale direct shear test apparatus on model rock joints with a regular “saw tooth” surface profile with the dimensions of 15cmx15cmx18cm. Filled material had specified specifications like particles size and strength parameters.
Infill thickness, moisture content...

Extending protection selectivity in low voltage DC microgrids using compensation gain and artificial line inductance

, Article Electric Power Systems Research ; Volume 188 , 2020 Shamsoddini, M ; Vahidi, B ; Razani, R ; Nafisi, H ; Sharif University of Technology

Elsevier Ltd 2020

Abstract

Vulnerability of power electronic converters in DC microgrids in case of fault occurrence in DC cables necessitates using a fast fault detection and isolation scheme. In this paper, a modified, fast and selective protection scheme has been presented, which provides the required tripping of low voltage DC (LVDC) microgrids. This protection scheme has been developed based on the natural characteristics of the fault current, in which the first and second derivatives of the fault current have been employed to define thresholds for discriminating between faulted and non-faulted situations. To enhance fault detection capability of the protection scheme, definition of thresholds have been improved...

Transmission Radius Games on Wireless Networks

, M.Sc. Thesis Sharif University of Technology Nafisi Asl, Hossein (Author) ; Abam, Mohammad Ali (Supervisor)

Abstract

With the daily increase in the volume of information and due to the growth and pervasiveness of wireless networks, the structures and the way of connection of intermediate nodes have become very important in terms of energy, communication speed and communication overhead. In this thesis, we examine the structure of directionless wireless networks assuming nodes are selfish. In these networks, nodes seek to minimize their costs while being required to access all nodes with limited path length. Due to the selfishness of nodes, we used game theory to analyze the structure and behavior of nodes by calculating the Nash equilibrium state and to compare these networks with networks that are managed...

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...