Sharif Digital Repository

One of the problems in vessels is the marine oscillations that occur due to the collision of sea waves with the vessel. These oscillations in small yachts can cause passengers to seasick upside down and overturn objects in the boat, or in industrial ships can cause problems in the operation of cranes on vessel, and in military vessels can cause errors in targeting weapons and radar systems. The purpose of this research is to design and simulate a robotic compensating table that can actively compensate the vessel fluctuations by using control algorithms in three directions of Roll, Pitch and Heave and create a level that can be used in Medium-sized boats were used to eliminate harmful... 

The main objective of this project is to take the first step in designing torsional vibration damper (TVD) for engines in Iran. To this end a complete dynamic model of a 4 cylinder internal combustion engine comprising of all reciprocating parts plus the crankshaft was developed using Bond Graph method. Real firing data of the engine was used as input to the system and output torque to gearbox shaft as the output. The system equations in two cases, with TVD and without TVD were derived. MATLAB software was used to solve these equations in finding the quality of performance of the torsional vibration damper. Dynamic properties of crankshaft and designed TVD were obtained using finite element... 

Due to the excessive failures of tires used on mining trucks, which lead to significant economic and environmental damages, mine operators are seeking replacements for them. The ASW mechanical wheel, introduced by the American company Global Air Cylinder Wheel, is recognized as the most well-known alternative to pneumatic tires for mining trucks. Although this company has been active since 2004, it has not yet released a commercial product. This study examines the structural, behavioral, and operational characteristics of the mechanical wheel and its impact on the performance of mining trucks. The structure of the mechanical wheel consists of a set of hydro-pneumatic actuators that connect a... 

A high percentage of patients with lower extremities disability are consist of paraplegic patients, hemiparetic patients, spinal cord injuries and chronic stroke patients. Currently, a variety of methods are developed and being used for gait rehabilitation of these patients. Recently, beside physiotherapy and different types of exercises, gait trainers are used to help patients to obtain their walking abilities. The main goal of this work is to modeling, analysis and comparison of two different types of power transmission system for a gait training robot. A familiar gearbox and a cable mechanism for power transmission are studied and mechanical impedance and accuracy of systems in... 

In This project the most important phenomena for design of Vibration Isolation Module is investigated and modeled. These isolators are used in mooring Arrays. One of the most important problems in design of these isolators is lacking of suitable information in resources. Vortex Induced Vibration in Towed Cable and Flutter of Drogue are the most important source of vibrations. They are modeled and frequency band for a typical Sonar Array is calculated. Then by investigating of Normal and Tangantional Vibration in towed cables, it was found that normal vibration is damped, so the Isolators must be damped transactional vibrations. Before final design, for better understanding of the problems... 

In this Thesis, an unmanned multicopter with a new structure is modeled and a nonlinear controller is designed for it to track the trajectories precisely. The multicopter in this thesis, has six propellers with a hybrid propulsion system (a combination of fuel and electric propulsion system) that has the ability to carry more payload and maintain more flight duration compared to electric multicopters. In the beginning, the performance characteristics and technical specifications of the hexacopter are presented. For modeling, first the equations of six degrees of freedom movement of the hexacopter are derived by the Newton-Euler method. In the next step, the forces and torques applied to the... 

Diabete is disability in the body to produce insulin or use it. Body insulin hormone needed to convert starch, sugar and other foods to energy and thus the body is functioning properly. Considering this incurable disease and its complications, many doctors and researchers trying to control the disease, reduce complications and to create favorable conditions and appropriate solutions for preventing its expanding and also strengthening patients mentally. Be destroyed in digestive system, insulin can not through tablets or similar cases received. The best way known to enter insulin to the body, is injection. This project is about a device to reduce the level of blood glucose in patients with... 

Fatigue life and crack growth retardation due to periodic tensile overload that superposed on constant amplitude cycles has been investigated. The tests were performed using C(T) specimens made of 7075 aluminium. All periodic overload tests were carried out at the same spacing between overloads and the effect of overload ratio on fatigue life has been investigated. Results of experiments revealed that the at low and high overload ratios, crack growth rate is relatively high and there is an optimum OLR that maximize interaction and thus minimize FCGR. Whit OCR-1=50, overload ratio of 1.85 led to maximum interaction and resulted in 219% increase in specimen's life relative to CA loading. Also... 

In recent decades, emission from automobiles is considered one of the main reasons for global warming. One of the ways to decrease the fuel consumption of the vehicle, increase the power train efficiency and vehicle acceleration is to use Continuously Variable Transmission (CVT) and infinitely variable transmission (IVT). Previous inquiries include investigate miscellaneous types of continuously variable transmissions and their efficiency and different ways of combination of CVT and other power trains in order to create an IVT. The aim of this research is to optimize one kind of IVT transmission. At first, different state of combination of IVT portions will be investigated. Then, a model is... 

Cache memory is one of the most important parts of the microprocessors. Caches improve performance by bringing data and instructions near the processors and decreasing the access time to data and instructions. But caches are also vulnerable to some kind of error called soft error. When an error happens in a cache, suddenly can propagate throughout the system and affect the integrity and reliability of the overall system. There are actually two types of errors in cache memories, permanent (hard) errors and transient (soft) errors. Previous studies have shown that about 92% of system reboots are initiated by soft-error occurring in cache memory. Soft-errors have two main sources, alpha... 

In this research, the effect of variable stiffness and damping, in suspension system, on car performance was studied. The optimization of car performance was obtained by minimization of an objective function including the body acceleration, suspension travel and tire deflection. Firstly, considering the stochastic input for a quarter car model, minimization of the objective function was done by changing the stiffness and damping coefficients in the frequency domain. The Linear Quadratic Regulator (LQR) method was implemented to minimize the objective function. In order to supply the active force obtained by optimization, different semi-active designs, in which stiffness and damping were... 

Hydrophilic polymers are widely used in enhanced oil recovery (EOR) processes to increase water viscosity during polymer flooding. However, these polymers increase the viscosity of injected water in undesirable strands, before reaching considerable positions that make some problems in polymer flooding process such as thermal, mechanical, bacterial degradation, surface absorption and undesirable plugging. In this study, a novel core-shell structure of polyacrylamide as an active polymer and nanoscale coating polystyrene as a shell polymer was designed and prepared to intelligently control mobility ratio in oil reservoirs and overcome weakness and limitations of classical polymer flooding.... 

Pyroshock Test is one of important environment tests in satellite design process.pyroshock or pyrotechnic shock is one of loads that exerted on spacecraft and it's subsystems during launch process. pyroshock can cause failure in some subsystems like sensitive electronic parts, solar cells and so on. For this reason it's necessary to make sure about strength of component under pyroshock which can be done by pyroshock simulator.The purpose of this research is to design a pyroshock simulator that can simulate a pyroshock with given SRS (Shock Response Spectrum) for satellite components.Requirements and constraints for design have been defined such as test item dimensions,weight range and also... 

In recent years passenger cars have been known as the main source of air pollution in urban areas. Despite all the research and efforts in minimizing the fuel consumption and emissions of internal combustion engines (ICE), this is merely a temporary solution. The permanent solution to overcome these disavantages is the use of electric vehicles (EV). The main downside of using electric vehicles is their short driving range. Multi-speed transmissions can be adopted to overcome this problem. Continuously variable transmissions (CVT) and infinitely variable transmissions (IVT) have been proven to enhance fuel economy in ICE vehicles and a great deal of research is being conducted to maximize... 

In this research the vibration of rotating and non-rotating shells was investigated. In the non-rotating shells field, the vibration of joined cylindrical shells and joined conical shells that each sections of them has independent material, thickness, length and angle were investigated. By analyzing the free vibration of joined conical shells, we can perform the free vibration analysis on every complex thin-walled geometry.In the rotating shells field, first the governing equations of the rotating conical shells are derived and then, the vibration of rotating cylindrical-conical shells and joined conical shells were investigated. The governing equations of rotating conical shells and... 

Modern science and technology’s desire is increasing for Control Algorithms Testing Instruments which allow testing autonomics due to advancement in robotic science and increased application for autonomics. In this Thesis, a manufactured tester is equipped with sensors to allow data acquisition and Control algorithms tests for RC helicopters, which are a variety of autonomics. For this purpose; a manufactured 3-DOF tester was used and for control application purposes one degree of freedom was added and it was made to 4-DOF. Also, Mechanical defections which cause vibration resonance failing was solved. In the end, a data acquisition system with an appropriate rate for signal gathering and... 

Propylene Copolymers and terpolymers with small amount of 1-butene& ethylene can greatly improve the properties of polypropylene material such as low temperature toughness, printing performance, transparency, process ability and so on, leading to expanding of its application. Poly(propylene-co-1-butene) performance intensely relies on its composition and chain structure. The copolymerization catalyzed by Ziegler-Natta catalyst, which is a multy-active central system. The Ziegler-Natta catalyst TiCl4/ Mg(OEt)2/ DIBP was used for copolymerization. The microstructure of copolymers were characterized by FTIR. The influence of different comonomer ratios on the copolymerization has been...