Sharif Digital Repository

Using Functionally Graded Materials (FGMs) in hot sections of aged aircrafts is one of the most important ways for life extending of Thermal Barrier Coatings (TBCs). Sudden variation of thermal stresses in interface of bond coat and ceramic coat layers could be changed to gradual variation with use of FGMs. The stress in FGMs has been the subject of several researches. Both macro and micromechanical modeling approaches have been used in these studies. In the macro mechanical approach, FGM is modeled as a multi-layer composite in which mechanical properties of each layer is found by averaging the properties and volume fraction of FGM constituents through the thickness of the layer. In this... 

Cloud Computing can be defined as a distributed set of virtual resources in order to be configured dynamically as an integrated system. One of the significant aspects of such systems is the method of task assignment which can affect the performance and efficiency of the whole system. The vast area of the size and complexity of the requests combined with the variable nature of the requested tasks, essence the use of the new smart strategies for the activity assignment. The main challenge of addressing non-functional requirements of the customers is in fact the software and/or hardware failures. The proposed failure-aware resource provisioning methods take into account failure probability... 

One of the advantage of the mutual funds is their liquidity. They should pay back investor’s money based on Net Asset Value (NAV) anytime they request. Sometimes, NAV computed by fund is different from the real value of it. This error in pricing could be more intense in Iran because Iran stock market liquidity is low, ticker become closed frequently, and stocks can’t be traded and the change of price in one day has the limitation. All of these reasons make the price of stock in Iran stale which doesn’t contain the latest market information. The staleness of stock price makes the return of funds predictable and provide the opportunity of arbitrage which causes the transfer of the wealth among... 

Businesses are dependent on mining of their Big Data more than ever and configuring clusters and frameworks to reach the best performance is still one of the challenges. An accurate performance prediction of the Big Data application helps reduce costs and SLA-violations with better tuning of the configuration parameters. Among the Big Data frameworks, Hadoop, Tez, and Apache Spark are the widely used and popular ones, with the MapReduce and graph-based workflows, usually running on top of the YARN cluster. While a great number of attempts have been made to predict the execution time of Big Data applications, to the best of our knowledge, none of them considered multiple simultaneous YARN... 

Plasma electrolytic oxidation is the novel surface engineering technology that used as the low cost and eco-friendly method for improvement of corrosion resistance and wear resistance of Mg and Ti alloys. The aim of this investigation is firstly joint the Ti and Mg, then optimization of coating process condition of Ti-Mg couple for achieve the best corrosion and wear resistance of coating. For this purpose, initially Ti and Mg were joint together by friction stir welding treatment and then the effect of coating variable such as type of electrolyte, coating voltage, coating time and the concentration of the bath constitute, on the coating properties were investigated, and then the effect of... 

Nowadays application of metallic catalysts in many of the organic reactions has been developed; therefore, different types of catalysts have been produced and used. In this way, in the first part of this thesis magnetic cobalt ferrite and nickel ferrite nanocatalysts were synthesized using co-precipitation method and their activity as catalyst was investigated in C-O bond formation reaction. This reaction was carried out between different types of aryl alcohols and aryl halides with good to excellent yields. The results showed that using N,N-dimethyl formamide as solvent, potassium carbonate as base and 5mol% of nanocatalysts at 80°C are the optimized condition for this reaction. In the... 

Vehicular tunnels are very prone to excess of air pollution due to their enclosed nature. Inadequate ventilation combined with high traffic flow result in elevated concentration of vehicle-induced air pollutants, which can pose serious health hazards. This study was carried out in the longest vehicular tunnel in Tehran, locally referred to as Tohid tunnel. Traffic flow characteristics, carbon monoxide level and it's dispersion along the tunnel were investigated in this project. Data were collected in 4 days and 3 times a day, 7-8 in the morning, 11-12 and 17-18 in the evening. Measurements were conducted at fixed locations, outside the tunnel,... 

Designing efficient and secure electronic voting protocols without the presence of trusted authorities, which are known as decentralized voting protocols, is one of the most interesting and challenging problems in cryptography. In these protocols the outcome of the protocol is determined by voters collaborating with each other. Since voting is a significant concept in every society, the correctness and security of voting protocols are important. For security analysis of electronic voting protocols, an intuitive proof is not enough and we require a comprehensive approach that provides provable security. In this thesis, we use universal composition framework to analyze a decentralized e-voting... 

Ever-increasing energy consumption and consequent extensive greenhouse gas (GHG) emissions have become two major global challenges for all human beings in the 21st century. If this trend of increasing energy consumption continues, our primary energy reserves willbe exhausted very soon.One solution is, shift of primary energy resources from fossil fuels to renewable energy could greatly reduce the current heavy dependence upon fossil fuels. Renewable energies have small share in the global energy market, therefore couldn't be a main method in the mid-term. Because of the low efficiency and consequent extensive GHG emissions of the conventional power generation that producing major amount of...