Sharif Digital Repository

In this research a model is developed which calculates the torque transmission efficiency of a half-toroidal CVT as a function of variator geometry, gear ratio and input torque. The different criteria which are considered to be important in a half toroidal CVT performance are torque transmission efficiency, variator weight, roller fatigue life and bearing torque loss. Variation of geometrical characteristics such as roller curvature, number of power rollers, aspect ratio and half cone angle affect these criteria in different ways. Therefore, in order to find the optimal quantity for each geometrical parameter an optimization problem should be developed. The objective function of this... 

Supplier selection is a multi-criteria problem which includes both tangible and intangible factors. In these problems when suppliers have capacity or other different constraints, two questions persist: which suppliers are the best and how much should be purchased from a selected supplier? Here, we propose an integrated approach of analytic hierarchy process (AHP), Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS), and multi-objective nonlinear programming to consider both tangible and intangible factors in choosing the best suppliers and define the optimum quantities among selected suppliers to maximize the total value of purchasing and minimize the budget, total...