Sharif Digital Repository

Thermal barrier coatings (TBCs) are used for increasing the efficiency and reducing pollutants of internal combustion engines (ICEs). In this paper, an optimization framework is developed in order to obtain the optimal dimensions for conventional coat, and the optimal dimensions and material property for functionally graded (FG) coat of a partially coated piston. A thermo mechanical analysis is investigated for Nano coat by finite element method. The conventional and Nano coats are made of MgZrO_3 as the insulating ceramic overlay and NiCrAl as the metallic bond-coat. The properties of the FG coat is assumed to vary according to power law through the thickness. For all tree conventional, FG... 

Among various impacts on environment, the noise problem arising from the expansion of technology has been an important factor, especially in recent years. The noise level in the automotive industry is also considered as a desirability coefficient. One of the most important factors which are causing noise in the vehicle is an automotive gearbox system. The gearbox is major component of automotive powertrain. In the gearbox system, gears pairs generates mechanical noises in the gearbox that transfer to other parts of the car by gearbox housing. Therefore, reduction and isolation this vibration in gearbox housing have crucial role in reducing the noise level of the vehicle. The aim of this... 

Reduction in the oil reserves level and the increasing of fossil fuel prices and GHG has led to growing value of attention to biodiesel. Reserves of fossil fuels are running out and should have proper alternative for them. Environmental benign and renewable properties of biodiesel make it consider suitable candidate to replace fossil fuels.
In this study, continuous production of biodiesel and optimization of important and influential parameters have been investigated. The method is concluded of trans esterification of soya oil with methanol as feed in presence of homogeneous catalyst of NaOH. The reactor was simple with high efficiency and low operational and investment cost. The... 

Increase in energy consumed by buildings, which constitute about 40% of the global final energy consumption and their respective contribution to CO2 emmission has led the building owners and users toward using on–site energy production systems and especially clean energy sources. The present research aims to find the optimal solution to the building energy supply problem under current and other possible circumstances. Energy Engineering Department of Sharif University of Technology has been selected in representation of educational buildings in Iran for case study. ESM software which is based on the MESSAGE model has been used as the modeling tool. Results state that under the current... 

Network structures have many applications in everyday life. For example, we can refer to the real world systems in which clients are indicated by nodes and edges represent their connectivity. Network science has witnessed tremendous progress over the last decade. The field of Network Science and Engineering started by exploring properties of real-world network systems and constructing proper models. Previous studies shows that all real world systems share some common structural features, such as scale free degree distribution and group structure. Analyzing interaction between network structure and its dynamic is a one of the main problem in studying complex dynamical networks. In this study,... 

This thesis presents an inventory control system which is based on Meta-heuristic Algorithms.In this thesis we will optimize the input values of our tree-echelon inventory model (keeping costs,stock worth,reorder costs,...) with these Algorithms. The presented method is able to determine the optimal stock level, costs of system and number of shipments in the system. The method is basically a decision support system (DES) and it is able to provide the order scheduling parameters of goods at operational level. The aim of the current research is to demonstrate that a Meta-heuristic algorithmis capable of solving complex inventory problems and with future improvements it is able to achieve... 

One of the major problems in directional and extended reach wells is poor hole cleaning. Directional and horizontal drilling is more complex than vertical wells. Ineffective particles transport leads to several undesirable issues during drilling. This thesis analyzed all parameters which have directly affected directional hole cleaning. The thesis is based on an experimental set-up designed in Sharif University. In the experimental work, two types of drilling fluid, Newtonian and Non-Newtonian with numerous rheological parameters, three different flow rate, three various nozzle sizes and three individual RPMs in three distinct inclinations 30°, 60° and 90° were used to simulate. Also, to... 

In this study, we synthesized ZSM-5 and doped ZSM-5 applying cations such as Zn(II) and Fe(II). Furthermore, we synthesized [Zn,Fe]-ZSM-5 using similar method for the first time. The final products were characterised by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. On the other hand, the hierarchical mesoporous Zn-ZSM-5 zeolite catalyst was prepared by alkali treatment by NaOH and Zn impregnation, and its application in the conversion of methanol to gasoline (MTG) process was studied. The modified zeolite samples after modification were also characterized by FT-IR and XRD methods. Zn impregnated mesoporous catalyst Zn-Alk-Z5 exhibited dramatic improvements in... 

Nowadays, electricity generation technology from renewable resources, especially solar energy has been very popular; specifically off-grid systems which have the ability of decentralized electricity generation. Dish/Stirling system is one of the most efficient technologies with capability of decentralized electricity generation from solar energy. The purpose of this study is design, optimization and analysis of a 10 KW Dish/Stirling system for different working location in Iran.
A mathematical model is introduced to analyze all the heat losses in different system components including parabolic dish, cavity receiver and Stirling engine. All the calculations are done with MATLABTM... 

A gas cyclone is a fixed mechanical device that uses centrifugal force to separate solid particles from gas. Gas containing particles is brought tangentially into the cyclone. This results in the development of a vortex, which applies strong centrifugal forces to the particles. The larger particles move toward the outer wall of the system as a result of centrifugal forces. gases spiral down from a tangential inlet towards the conical section, where the flow is reversed and the particles are collected in a hopper. The gas phase then proceeds upward in an inner vortex towards the gas exit via the vortex finder.
In this study swirling flow of two-phase gas-solid in cyclone separator is... 

L-asparaginase enzyme is a well known enzyme due to itschemotherapeutic properties. However, this is not the only feature of the enzyme. L- asparaginase can be also used in food processing to reduce of acrylamide which is a carcinogenic substance. furthermore, acrylamide formation, is prevented by addition of the enzyme before cooking process of some foods such as chips, which contains sugar and asparagine amino acid. Due to use of the enzyme in food industry, we need to produce enzyme with high activity and cheaper raw material. In the present study, Candida utilis ATCC 9950 was used to produce asparaginase enzyme, and beet molasses and yeast extract was used as a carbohydrate and... 

In gas-condensate reservoirs, when pressure reduces to less than dew point pressure, condensate will form out of the gas phase. Gas recycling is one of the most common methods to enhance the production of gas-condensate reservoirs.The purpose of this thesis is to optimize gas recycling process in a gas condensate reservoir in order to produce the accumulated condesate in the reservoir and maximize reservoir economic efficiency.The parameters that need optimization are:
• Injection gas ratio
• Injection gas allocation amongst injection wells
• Bottomhole pressure of production wells
Genetic algorithm was considered as optimization method and Proxy model is used in order to... 

In this thesis, we study the mean graph isoperimetry problem using an optimization approach. The k-th isoperimetric constant of a graph is defined as the minimum of an objective function (p-norm of the vector consisting of normalized flow) over k-subpartitions of vertices. We note that the normalized cut problem can be formulated as a semidefinite programming problem and utilizing the relaxation methods for semidefinite programs, the problem can be solved in approximately polynomial time. Finally, we model the isoperimetry problem as an optimization problem with orthogonality constraints and utilizing Wen and Yin’s efficient method for finding local minima of the problem, we extract a... 

Design of a spiking neural network suitable for electronic hardware implementation has been a hot research topic for a long time, in recent years implementation of spiking neural network in real time and biological scale has become important for scientists. This is due to the proximity of these networks to human brain, and the efforts led to the creation of numerous biological models and hardware which has been proposed in this context. This research includes two main parts, the first part is effort to implement a greater number of neurons per device and the second part proposes a communication system among devices to achieve biological scale. This work investigates novel neural elements and... 

In the past several decades, with the increasing evolution of electricity markets, maintenance philosophy has gradually changed, and maintenance process plays a crucial role on the profitability and effectiveness of companies. Therefore, this leads managers to use modern strategies that their performance has been proved in various industries and therefore, traditional strategies have lost their effectiveness. Reliability-Centered Maintenance (RCM) is one of the most successful strategies wherein the maintenance process of system components is linked to improvements in the system reliability and profit of companies. RCM has not been thoroughly furnished in generation system yet. This thesis... 

There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this paper an optimization procedure is proposed which integrates both processing and accident costs for different design schemes. In this procedure, some of the design variables are chosen with regard... 

According to the Government policy in order to make targeted subsidies and apply it on various sectors in the industrial, commercial, agricultural, household and etc. changes in the energy supply needed resources in this section are required to appear. The agriculture sector is one of the most important parts of the food production is the production of security and health product. In this regard, the production of greenhouse products in terms of the use of high yielding varieties, production of the off-season, better control factors in production and reduce water consumption has increased drastically. The main source of supply in the internal energy of the greenhouse heating is mainly fossil... 

In the modern world, one of the largest concerns is the ever depleting supply of oil. The automotive industry is especially impacted. In recent years the price of gasoline has fluctuated substantially and the price of crude oil has reached record highs. The high price of gasoline coupled with the uncertainty of its availability and future price have put a high priority on fuel economy of an engine. In addition the emissions released from internal combustion (IC) engines are polluting the atmosphere. Many studies have linked the greenhouse gases produced by an automobile engine to the partial destruction of our atmosphere and to global warming. As a result the US government is passing... 

This study investigates a two-echelon supply consists of a vendor and a buyer with deteriorating items. The deterioration rate of product is assumed to be constant and independent of time. The buyer’s order is shipped in equal-sized batches. Moreover, in order to ship products from vendor to buyer, two carrier’s modes with different travelling time and cost are considered. What distinguishes this study from literature is that the deterioration of product continues during the travelling time which depends on the carrier’s mode to ship batches from vendor to buyer.
The objective is to minimize the cost of both buyer and vendor simultaneously. The cost functions of buyer and vendor are... 

Considering the negative effects of contamination on wind turbine blade performance, we investigate aerodynamics performance of a one- Megawatt wind turbine. To achieve this, we compare the performance and power of the wind turbine with and without contaminations. To calculate the wind turbine output power, we use a developed wind turbine calculator, which benefits from the Blade Element Momentum (BEM) theory. Furthermore, the aerodynamics calculations are performed using of a commercial software for clean and rough airfoils. Considering the change of Reynolds number along the blade axis, the airfoil characteristics are calculated for two Reynolds numbers of 0.5 and 3.5 millions to increase...