Sharif Digital Repository

Improvement of numerical solutions and application of them is very important section of engineering researches. So, there are several numerical methods and procedures for solution of equations or problems. All of them have advantages and disadvantages for selection best method. The efficiency of a method is a function of Limitation parameter like time, software and hardware. One of the recent numerical methods for engineering problems is Direct Discrete Method (DDM). This method prepares modern theory for balance equations; also this method combines some advantages of the other numerical methods like finite element and finite difference. DDM uses a double set of mesh structures namely primal... 

In this study, an arbitrary Lagrangian-Eulerian (ALE) approach is incorporated with a mixed finite- volume-element (FVE) method to establish a novel moving boundary algorithm to simulate unsteady incompressible flow on non-stationary meshes. The method collects the advantages of both finite-volume and finite-element methods as well as the ALE approach in a unified algorithm capable of solving laminar, transient, and turbulent flows in fluid flow problems with moving boundaries. To enhance the robustness of the extended algorithm, we treat the convection terms at the cell faces using a physical influence upwinding scheme, while the diffusion terms are treated using bilinear finite-element... 

Nowadays, the use of numerical methods is very common in solving complex equations, and various methods have been developed in this field. One of the new methods in this field, is the direct discrete method(DDM), Which was initially used to solve the electromagnetic field equations. In the past years, this method has been used to discretization some of the neutronics equations and acceptable results are recorded. So that the convergence order for the neutron diffusion equation in this method is higher than other numerical methods. In this method the geometry of the problem is divided into primary and secondary cell that primary cell platform is fixed but there is the possibility of making... 

Partially submerged propellers are new type of propellers which knowledges ragard them is limited. These propellers found a growing market ahead of them and expertsexpect to use these propellers for big vessels at high speeds. This type of propulsors do not lose their efficiences at high speeds and are assumped to be economical. Meanwhile due to continuosus hit to water surface, huge stresses are extered on tha blade witch needs to be fundamentally studied. Several researchers have studied the partially submerged propellers which unfortunately did not publish their results. Undergo less or more thrust and torques which in both cases the efficiency also increases. The use of numerical methods... 

Nowadays numerical solution of engineering equations and relationships is one of the most efficient and most important parts of scientific research. Hence, various methods have been developed and expanded for this purpose, and the choice of the best method for solving a problem based on its strengths and weaknesses is essential. Direct discrete method is one of the new numerical methods that has been used for solving magnetic equations for the first time and shown promising results in nuclear researches. In this method, after determining an interpolation function for the unknown quantity, the discrete form of mathematical operators such as integral and gradient is obtained in the grid... 

In this study, the mechanical properties of composite sheet polymer matrix reinforced with steel mesh were investigated. This bonding was carried out by rolling of a three layers of steel mesh in between two composite polymer sheets. Then, the effective parameters of process; Sample maintenance temperature inside the furnace, reduction during rolling, rolling speed, rolling direction and Number of rolling passes were investigated to determine the optimized processing conditions. In this way, adding mesh to the polymeric matrix improves the strength and polymer / polymer bond in the sandwich structure. Placing the mesh in the sandwich structure converts the brittle behavior of the polymeric... 

Deployable structures have been used on small satellites since the beginning of such space programmes. Here, the design sequence for a special tensegrity structure, for use as supporting structure for deployable mesh-like antenna will be proposed. The design process is conducted to prevent structural elements from failure, and satisfy the minimum specified natural frequency. In this research, structural modeling is performed based on two external geometric parameters (overall height and diameter), and three internal geometric parameters (elements cross-section properties). The pre-stress in structural element is the last design parameter. Also, materials are pre-assigned. Internal forces of... 

Multicasting has gained a lot of research attentions in facilitating group communications in wireless networks. Applying multicast mechanisms in Wireless Mesh Networks, brings a lot of benefits to these networks. In our research, we have introduced Cost-aware On-Demand Multicast Routing Protocol (C-ODMRP) as an extension of ODMRP that supports QoS provisioning for high quality applications in WMNs. In C-ODMRP, the nodes are prevented from applying the links that do not meet the QoS requirements. The multicast receivers are provided with resource-aware information to efficiently compute the cost of the routes when multiple routes from source to destination nodes are established. C-ODMRP takes... 

Having special advantages over existing networks, mesh networks have attracted much attention. Proposing new MAC protocols which are in compliance with these networks is an interesting field in which many works have been done. Also, Task Group S of the IEEE802.11 is going to release a standard for the mesh networks. Analysis of a simplified version of IEEE802.11s is the first goal of this thesis. The standard is a spectrum sharing algorithm based on scheduling and contention. Although IEEE802.11e manages the contention for accessing the wireless medium in the standard, but for the sake of simplicity, in this thesis we used SlottedALOHA instead. Also, one gateway and six other nodes are...