Sharif Digital Repository

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 the present study, the numerical simulation of incompressible laminar and turbulent flows using a high-order finite difference lattice Boltzmann method is presented. To handle curved geometries with non uniform grids, the incompressible form of lattice Boltzmann equation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting equation are discretized using the fifth-order WENO scheme. The advantage of using the WENO-LBM developed is that it needs less number of grid points and remains stable even at high Reynolds number flows. For the temporal term, the fourth-order explicit Rung-Kutta scheme is adopted for laminar flow calculations and... 

Reducing noise, vibration and damage to the vehicle's passenger compartment was always a problem that has been investigatedin many researches. Here engine mounts as connecting members between engine and chassis play a big role. Because both of engine and road vibration put on it. Many studies have been done to optimize the engine mounts. As a result, many of hydraulic engine mounts with different variety of system control. But a few researches did about optimization of location and orientation of engine mounts. Therefore this project is to provide a process to optimize the location and orientation of engine mounts. The optimization process is First the dynamic equations of dynamic system are... 

Unmanned Aerial Vehicles have been used for different applications despite their short life. In last recent years, the developements in technology which leads to producing smaller electronical and electromechanical deveices, attract more attention to the researches in these fields. Among these vehicles, unmanned helicopters are more important because of their special abilities and capabilities. However there are some drawbacks which makes using them more difficult.
In this project, the first principle modeling of a RC helicopter has been accomplished and a parametric model including different sections effects has been created. This model has been implemented for a Trex600 CF helicopter.... 

In recent years health monitoring and prognostics of complex systems have been considered more than ever.. In the present researh, data - based approach has been selected among various prognostics and health monitoring approaches. One of the most challenging issues in data-based methods is how to map system sensor information to its health status. In this research, different methods of mapping are discussed. The results show that sensor fusion by principal component analysis (PCA) offers acceptable performance. This pattern produces a single-dimensional signal for health monitoring with high reliability.The second challenge is to predict the status and design of the prognostics module. For... 

Multiscale modeling is performed within the framework of homogenization methods for problems in which the scales are separated. The existence of representative volume element (RVE) is one of the main ingredients of homogenization methods. Due to non-existence of RVE and macroscale mesh sensitivity, the continuous homogenization method is not applicable for softening materials. Despite the non-existence of RVE for softening materials, it has been demonstrated that by performing the average over the active damage zone rather than the entire domain, objective responses with respect to RVE size could be obtained. That is why discontinuous homogenization is used instead of continuous... 

Nowadays, hybrid electric vehicles get more attention, not only for decreasing fossil fuel resources, but also for increasing environmental pollution. Using multi-propulsion system in hybrid vehicles causes, the low efficient performance of combustion engine is reduced compare to conventional vehicles. Fuel consumption and pollution that reduced in hybrid vehicles is related to how the multi-propulsion system works. Some researches that have been done about hybrid control algorithms, are completely software modeling and development. Despite importance of these researches in development and evaluation of power distribution algorithms, hardware-based evaluations are also necessary. In all... 

One of the most important unit operations in the production of dry powder biological products involves a freeze dryer apparatus. In this process, Liqueur, which is containing the α-amylase enzyme, undergoes a frigidity condition in which loses its moisture during sublimation. Under these circumstances, applying an adequate supply of sublimation enthalpy without raising the temperature of the frigid material up to melting, plays an important role in the quality of the product and preventing degradation of the α-amylase enzyme. Freeze drying depends on two main factors; time and energy. Furthermore, it is necessary to obtain an optimal temperature and pressure for different steps and... 

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... 

Gearbox is one of the important components of power transmission chain in the car which the engagement of the gears inside it causes noise. The following thesis, is in line with the project that was defined as "NVH reduction of the Tiba X200 gearbox" and to increase the correlation between university and industry, the aim of which was to improve all the noise sources in the mentioned vehicle. The purpose of this project is to reduce the noise of the gearbox shell by using reinforcing blades called ribs. For this purpose, first the desired changes were made in Solidworks software on the 3D model of the gearbox shell, and then the finite element model of the gearbox shell was prepared in... 

With the environmental concerns and scarce supply of the crude oil, a revival in the development of bio-based and compostable materials is coming. They are in general being called the ''green'' materials, among which poly(lactic acid) (PLA) got the most extensive attention due to its good combined properties, including the renewable feedstock, the compostability, and its good mechanical properties, especially the young's modulus and stiffness. PLA has found numerous applications. It is considered having the highest potential to replace some regular petroleum based plastics. However PLA has its own shortcomings, its brittleness, low heat distortion temperature and relatively high cost witch... 

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... 

Statistical studies indicate the fact that in Iran, like many other developing countries, a significant percentage of buildings are made of traditional materials and most of them are adobe buildings especially in rural areas. Furthermore, geological data indicates that Iran is located in alps-Himalayas seismic zone and exposed by destructive earthquakes and adobe buildings suffer the most damages comparing with other type of the structures. According to these explanations, this research deals with adobe buildings behavior and provides solutions for reinforcing them and improving the seismic response of these buildings. These studies include numerical modeling with finite elements methods by... 

In this thesis we consider the problem of distributed computation by many processors.We mainly concentrate on matrix multiplication problem in this thesis because of its importance. A distributed system consists of N worker processors and one master processor. The master processor should distribute the computation between workers and after computation in each of them, collect the results. In this thesis, we are going to mitigate the effect of straggler processors by using coding methods. Straggler processors can cause delays in the computation time.In this thesis, we firstly introduce a method to multiply any number of matrices in each other. The proposed method occurred in one shot without... 

The main goal of current investigation was partial reduction of Fe2O3 available in Hematite-rich ore to Magnetite by Fludization Bed method. The reductive gas, CO, was produced by incomplete combustion of Acetylene and Airmixed in inappropriate ratio. X-Ray Diffraction and X-Ray Florescence analyses were implemented in order to conducting qualitative analysis of present phases before and after reduction of the ore. Quantitative analysis of the same phases was also conducted by Titration. The latter analysis revealed the precise magnitude of available iron in each of the oxide containing phases. The chemical composition of the reactor gas was also determined before and after reduction... 

Both handling and ride comfort play an important role in the performance and quality of a vehicle, and all the vehicle companies in addition to power and transmission system, pays special attention to these properties in the way of improving their products. This thesis is performed with the aim of study on effects of rubber bushing's characteristics of suspension system on handling behavior of a homeland built vehicle (pride). Role angle, slip angle, yaw rate and lateral acceleration are interrelated and are important quantities in studying on handling behavior of a vehicle. We have chosen slip angle as one these quantities and studied on effects of rubber bushing's characteristics on slip... 

Abstract The problem of competetive facility location can be defined as follows: There are a number of customers in the form of points in space, and two players arrange a number of facilities in the form of points in space, given some limitations, respectively. Each customer’s connection to each facility has a cost for the customer and an advantage for the facility, and each customer wants to be connected to at most one of the facilities which has the lowest cost for him. The goal is to find the strategy of placing the facilities and determining the cost which the facility receives from the customer, in such a way that the player’s profit is maximised.In this thesis, we first sought to...