Sharif Digital Repository

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... 

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... 

Since the beginning of human civilization, improving the methods of measuring and identifying changes in order to improve the level of comfort and safety of human civilization is inevitable. The intrinsic property of high sensitivity to system conditions in chaos phenomena has led some researchers to use this feature for purposes of identifying and measuring changes. The most important bugs of previous researches in this area are the complexity, lack of coherence and dependence on the nominal parameters. By analyzing the effect of the type and magnitude of the initial deviation in a system parameter on all the characteristics of the Duffing system response in the chaotic regime, was observed... 

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... 

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... 

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... 

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... 

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... 

Dynamic and vibration behavior of AFM microcantilever beam subject to the tip-sample interaction and/or contact is systematically investigated. An Euler-Bernoli microcantilever in 2D plane is considered with longitudinal and bending displacements. Inextensibility assumption and extended Hamilton’s principle is utilized to extract the single-variable integro partial equation of motion under: 1) tip-nanoparticle interactions, 2) tip-surface interactions in non-contact mode and 3) tip-surface interactions and contacts in intermittent-contact mode. Galerkin’s first mode approximation is then used to discretize the derived equations; and multiple time scales method is adopted to analyze the... 

In this thesis a 2-3PRS hybrid mechanism is presented. This manipulator is consisted of two serially connected parallel 3PRS mechanisms, each mechanism has three degrees of freedom, so that the overall degrees of freedom of the manipulator are six. The relations for position, velocity and acceleration of the mechanism in both forward and inverese kinematics are derived and then singular points are determined. After that, the inverse dynamic equations for one of the 3PRS mechanisms are derived through the Newton-Euler and aslo Lagrange approach and the results are verified. Then the derived Newton-Euler equations are implemented for inverse and forward dynamics of the hybrid manipulator. The... 

Vibrational modeling of a gas turbine considering simultaneous faults is considered. Faults including: unbalance, misalignment, and rotor crack are selected to be modeled. Oil film forces of hydrodynamic bearings are chosen as the supports of the rotor. Modeling starts with choosing an appropriate finite element model for the rotor which includes the effects of shear deflection, rotary inertia, gyroscopic moment, and rotor cross section variation. Modeling of unbalance is in fact a part of rotor finite element modeling. The forces that origniate form misalignment are computed using the static relations of a rigid coupling. Modeling of bearing faults along with bearing forces is performed... 

The application of manipulators is becoming more and more popular in objects handling especially when it is desired to have access to remote areas in destructive or hazardous taskspaces. For this purpose, a hand-like mechanism must be designed to be used as an end-effector, which can grasp objects. In this paper a cable driven grasping mechanism has been presented. In the proposed mechanism each finger consists of three phalanxes which are actuated by a single motor. Also, locking and unlocking constraints are used in the mechanism in order to generate an anthropomorphic motion, in which, the order of reaching phalanxes to the object is sequential, in such a way that each phalanx starts... 

Cable-driven robots are referred to as parallel robots actuated with cables. In fact,in such robots rigid links are replaced by cables, which may be extended to desired lengths without making mechanism much heavy. This robot possesses a number of unique properties that makes it suitable for many industrial applications. The main factor which makes cable robots analysis different from other parallel robots is the incapability of cables to push objects. Hence, obtaining the workspace of a cable robot is one of the most important subjects associated with this type of robot.The goal of this thesis is to design a spatial translational cable driven robot, which may be used for object handling. For... 

Separate analysis of modern systems by continuous or discrete theories is not possible, because they cannot solely express the detailed descriptions of a system. As a result of this, researchers are motivated to study hybrid systems. Specific class of hybrid systems which consists of several continuous subsystems and a rule that specifies how to switch between them, is called a switched system. Recently, many studies have been done on the stability and control of switched systems. In this regard, the goal of present study is presenting applications of switched systems using two control methods. The first application is control of a chemical reactor system with multiple modes. We presented... 

In this thesis, the equations of motion of a beam with tip mass on flying support, based on Euler-Bernoulli and Timoshenko beam theories is derived. To attempt for having accurate model in high rotational speeds, stretch variable is considered and employed in the equations of motion. For a planar and a spatial rotating beam, equations of motion are lineralized and simulated. Finite Element Method and Newmark direct integration scheme are employed for the analysis of the governing equations. To support the numerical results, an experimental setup is designed and based on which different tests are performed. A cantilever beam on a flying support free to vibrate in three dimensions is...