Sharif Digital Repository

One of the key issues in the operations of on orbit servicing to unmanned satellites is to provide a safe and reliable docking process. In this thesis, the dynamic behavior of a flexible probe in the central docking mechanism of unmanned satellites is investigated. For this purpose, first a dynamic analysis software has been applied to build a three dimensional model with the assumption of flexible clamped beam as a shock absorber, finally, the impact phenomone is simulated. therefore, in addition to solving a three-dimensional problem and studying the impact phenomenon between chaser and target satellite, it is possible to consider the parameters such as the type of connection between the... 

Joint price and service capacity decisions and integrated pricing and queuing problems with finite or infinite buffers are two remarkable issues of pricing research. In this thesis we consider a joint price and service capacity determination problem in a single server, finite buffer queuing system. Customers arrival and serving occur as Poisson processes. Because of finite buffer capacity, customers finding the system full upon their arrival would be rejected. Customers differ with respect to their reservation prices and time sensitivities. This study focuses on investigating the effect of finite buffer capacity and customers reservation prices and time sensitivities on optimal policy and... 

This research considers coordination of pricing and scheduling decisions in a make-to-order environment. We consider a two machine flowshop environment. The objective is to maximize the total net profit, i.e. revenue minus scheduling cost resulting from pricing and scheduling decisions. Prices of orders are set by the manufacturer and demand is a non-increasing function of price. Two mixed integer linear programming models have been developed for the research problem. As the problem is shown to be NP-Hard, a Metaheuristic algorithm is developed which is combination of two tabu search sub algorithms, one for pricing and the other for scheduling. And to evaluate performance, results from... 

A special steel beam-to-column connection, named Khor-jini, is commonly used for steel framing system in Iran. In this system, two continuous beams are passed next to the columns and are connected to the column side using seated brackets.This type of connection has been common in Iran from the late past. Unfortunately, the seismic behavior of Khorjini frames had not been sufficiently studied prior to Manjil Earthquake of 1990. Due to very large damages which occurred in steel structures especially in connections during the said earthquake, the seismic behavior of this type of connection was studied and some of its weak points were recognized.In this study non-linear... 

With intensified concerns of rising fuel vehicles that reduce fossil fuel globally and also prescript strict rules by standard institutes, vehicle manufacturers try to find a way for reducing the fuel of their products. One these methods use a continuously variable transmission (CVT) instead of manual and automatic gearboxes. Various CVT’s have been proposed in recent year.
One of the proposed systems is traction infinitely variable transmission (TIVT) that is type of traction drive continuously variable transmission and has been presented in 2007. Research on this system showed that average efficiency is about 96% that is high efficiency. Completed research in 2011 showed that despite... 

In this research, we consider a network of distiribution channels and a central warehouse to deliver the products to distribution centers. We assume the price of products are fixed and the central warehouse is authorized to change the delivery amount for each DC in a reasonable interval. The main idea is authorizing the central warehouse to be flexible in delivery of ordered amounts of DCs in a reasonable interval in order to reduce the transportation cost and then maximizing the profit.
The problem is formulated as a linear integer programming model and the properties of optimal solution is analyzed. Based on the properties of the model a solution algorithm is developed to solve the... 

Employing array of antennas in amny signal processing application has received considerable attention in recent years due to major advances in design and implementation of large dimentional antennas. In many applications we deal with such large dimentional antennas which challenge the traditional signal processing algorithms. Since most of traditional signal processing algorithms assume that the number of samples is much more than the number of array elements while it is not possible to collect so many samples due to hardware and time constraints.
In this thesis we exploit new results in random matrix theory to charachterize and describe the properties of Sample Covariance Matrices... 

Today, many surgical procedures such, gallbladder, gastric bypass, placement of a ring around the stomach, partial removal of colon, removal of tumors use laparoscopic techniques. In this surgery, a variety of tools to capture and remove the internal organs can be used. Sometimes the surgeon selects the proper tools and replacement during surgery, so the surgeon had to do different things with the operation. These tools generally cannot be used because of the large internal organs device is small and does not have enough degrees of freedom. In laparoscopic surgery, the surgeon operate in the abdominal cavity using a thin instrument that is inserted through the trocar hole would do. If... 

This thesis investigated a two-echelon supply chain consists of one retailer and several manufacturers that faces a price and lead time sensitive demand. We use a Stackelberg game for decision analysis of prices and lead times determined by manufacturers as Leader and retailer as a Follower. We assume that demand depends to the retailer’s price. Market share of each manufacturer, is also price and lead time sensitive. Objective of each firm is to determine price and planned lead time to maximize her own profit. We first determine the best response of the retailer to manufacturers’ decision and next at manufacturers’ level, we will solve the problem for one manufacturer at first and then we... 

This study presents a developed successive boundary element method to determine the sloshing natural frequencies, mode shapes and equivalent mechanical models for multi baffled 2D and axisymmetric containers with arbitrary geometries. The developed fluid model is based on the Laplace equation and Green's theorem. The governing equations of fluid dynamic and free surface boundary condition are also applied to proposed model. A zoning method is presented to model arbitrary arrangement of baffles in multi baffled axisymmetric tanks. The influence of each zone on neighboring zones is applied by introducing interface influence matrix which correlates the velocity potential of interfaces to their... 

In Mechanical systems there is always possibility of statical and dynamical following force. These forces are generated due to aerodynamic pressure, temperature gradient, and jet thrusters. In unstabel systems, if the value of this force exceeds a certaim amount the system becomes unstable. This value is called as critical force. In order to analyse these systems, fisrt of all, the governing dynamic equations are obtained by using the Galerkin-Ritz method. Then, by utilising the modal analysis, these equation are uncoupled. And then, the Ito set of equations are derived. By utilising the Lyapanov method, Ito equations are transfered to another state. and using the fokker-planc equation the... 

In this thesis a mutliScale model based on the Cauchy-Born hypothesis and via usage of XFEM is proposed for crack modeling. By solving an example, the important of surface effects in the surface stresses region is shown. Considering not being able to model the surface effects with the Cauchy-Born method, the boundary Cauchy-Born method for modeling crack effects is used. Moreover, three Molecular Dynamics method for modeling crack will be proposed. According to the obtained results from these methods, it was deduced that for calculating the correct surface stresses in Molecular Dynamics the mutual interaction of upper and lower atoms of crack should be omitted. Finally, the validation of... 

In this project, the landing process is simulated by using of multi-body dynamics commercial software. Various factors, including landing situations, aircraft structures and climate are used in this simulation. The purpose of this project is to determine the forces exerted on the aircraft landing gears in landing process in various landing conditions. For this purpose, the ADAMS multi-body dynamics software is used. At first, different scenarios based on FAR-25, including level landing, tail-down landing, crab landing are simulated. Results of dynamic simulation software with landing load factor obtained from the analytical solution are compared. Then for the level landing, different...