Sharif Digital Repository

The issue of fluid sloshing in vessels is of paramount importance in aerospace engineering. To suppress sloshing Baffles are used and one kind of baffles is “Perforated Baffle” that is good in weight efficiency. When fluid passes through Perforated Baffle, the energy dissipates and sloshing induces. The purpose of this study is to develop a model for linear sloshing in presence of a Perforated Baffle in the vessel. In this project, the flow is modeled by potential function. The Flow may be rotational in the nearby of baffle due to viscosity when it passes through-out perforations, so Laplace's equation for the velocity potential is useless in this region. To simulate the flow in such zones,... 

Todays, heat recovery steam generator (HRSG) systems are used extensively in combined power plant cycles (consisting of Rankine cycles and Brighton gas cycle) to maximize their efficiencies. The role of HRSG is essential in providing additional energy needed in the steam cycle part. The HRSG has many pipes or harps. They recover the heat from the incoming gas from the gas turbine outlet, which may be boosted up by the duct burner unit. The main challenge in simulating heat recovery units such as tube bundles is to provide ultra-large and cost-efficient grids. In such situations, alternative models are used to simplify the simulation of the steam generator in full scale, including the... 

Accurate prediction of myocardial infarction complications is one of the major challenges in the management of cardiac patients, as the occurrence of such complications can lead to severe consequences for quality of life, length of hospitalization, treatment costs, and mortality. This study aims to develop a data-driven, machine learning-based framework to predict 12 critical post-infarction outcomes using modern algorithms. In the first step, patients were stratified into more homogeneous groups based on treatment effects through a causal clustering algorithm. Subsequently, machine learning models, including logistic regression, random forest, and gradient boosting, were trained and... 

Radiation evaluation in non-gray gaseous media is a very complicated issue. Previous researches have shown that the radiation properties of non-gray gases would strongly depend on the wavelengths. The gray gas assumption is the simplest model to calculate the radiation properties. Dispite simplicity, it is widely used in various industrial applications. In this model the gas radiation properties are assumed no to chang across all wavelengths. Evidently this would results in an inaccurate radiation modeling. Using the Spectral Line-based Weighted-sum-of-gray-gases model, SLW, the spectral behavior of radiation properties of gas is almost taken into account in computations. So the use of this... 

Lithium is one of the most commonly used metals in industry with a wide variety of applications including batteries, lubricating grease and pharmaceutical products. Demand for lithium is expected to rise with the increasing adoption of electric vehicles. Market reports have predicted that world lithium demand will increase by 2.5 times from 2010 to 2020. Therefore, there is a pressing need to develop new sources of lithium to support this anticipated increase in demand. Lithium can be extracted from salt brine and lithium containing minerals as lithium compounds.
Salt brines are the most abundant lithium sources available in the world, comprising about 60% of all known lithium deposits.... 

Emission control, especially Carbon Monoxides (CO) as one of the major by-products of combustion processes, is one of the most serious challenges in burning waste-gases with high amounts of humidity and Carbon Monoxide. We investigated an oil waste-gas incinerator serving to a bitumen production line located in Pasargad Oil Company, Shazand, Arak, Iran. The aforementioned incinerator was criticized seriously for its high CO emissions. We were requested to find a solution to reduce the undesirable CO emission from that. Following the environmental standards, there is an upper limit of 150 ppm for the CO produced by an industrial waste oil incinerator. To present an inclusive solution for such... 

The value added service industry as in emergent and profitable industry has gained mane attentions by corporate owners especially in the segment of telecommunication and information technology. For launching value added services, communication infrastructure must combined with attractive and high quality contents. For this purpose, mobile network operators have collaborated with content providers to launch services, cooperative advertisements and shared the earned revenue. Interaction between operators and content providers has many complex stages that starts before contract assignment and ends at the revenue sharing stage. For analysis this problem, first, we investigated this interactions... 

Composite film PLA/PVDF and nanocomposite films PLA/PVDF/MWCNT with a solution method by solvent Dimethyl formamide was prepared at 65◦c. poly vinylidene fluoride as matrix phase and poly lacticacid was used an amplifier. In the next sextion multiwalled carbon nanotubes were added to the PLA/PVDF composite.Scaning Electron microscope results, showed that the PLA/PVDF composite and PLA/PVDF/MWCNT nanocomposites, non porous structure and carbon nanotubes in the polymer matrix have been well dispersed. The impact of nanoparticles in the polymer matrix by X-Ray Diffraction and Differential Scaning Calorimetry was investigated. With differential scaning calorimeter (DSC) and stress strain test,... 

The method of nonlinear time history analysis is well known as one of the most accurate techniques in seismic analysis of structures. However, this method needs much effort in terms of required data and computational cost. Within the time constrains of design consulting firms, more simple analysis tools are also desirable. One of the simple methods which have been gaining ground, as an alternative to time history analysis, is nonlinear static pushover analysis. In this method, the capacity curve of the structure with respect to the roof displacement is established. In nonlinear static pushover analysis, disproportionate increases in the roof displacement and even outright reversals the... 

This paper develops a theoretical model based on economic misconceptions to explain the stylized facts of unsatisfactory long-term economic growth rates. Should the economic agents lack sufficient public understanding of economics, office-seeking politicians can take advantage of the situation and adopt populistic policies to get elected into office. Undermined economic growth is the price society pays for its ignorance. This mechanism is most relevant in democratic resource-abundant countries suffering from weak institutions. That is because natural resource price fluctuations make it more challenging to distinguish politicians’ performance and exogenous economic shocks, translating... 

One way to increase the power and efficiency of the gas turbines is to cool their incoming air. There are different methods to cool down the inlet air. One of the most widely used and suitable method is spraying or fogging the water droplets into the air at the gas turbine air inlet. In this research and for the first time, the effect of fogging system on the performance of a combined cycle incorporated with a J-class gas turbine (M-501J) is investigated using the computational fluid dynamics (CFD). There are so many parameters, which affect the amount of achieved efficiency. A few of them includes the average temperature and humidity at the outlet, the evaporation efficiency of the water... 

Desiccation of different salty lakes around the world has been considered as one of the most critical environmental events. Gradual desiccation of the Lake Urmia and retreatment of its shoreline with respect to ecological level (1274.1 meters) have resulted in new hotspots for dust outbreaks, especially in east and south-east peripheries, which were previously under water. These areas, part of which are salty, are now exposed to open air and susceptible to wind-erosion. Soil moisture, as one of the most important parameters for dust prevention, determines the threshold friction wind speed over playa because it increases the cohesion between soil particles. Therefore, compared with dry soil,... 

This research presents an innovative analytical solution to static, free vibration and buckling of an isotropic, homogeneous Mindlin plate with uniform thickness. This method satisfies all classical boundary conditions including free, simply supported and clamped as well as non-classical ones. Moreover, Mindlin plates on Winkler foundation of arbitrary stiffness function are investigated. In this study, the deflection and rotation of straight normal line of the plate about x and y axes are represented as the functions of sine and cosine Fourier series, accompanied by auxiliary functions. These auxiliary functions are of great importance because these functions satisfy arbitrary boundary... 

Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to... 

Today a significant portion of the world magnesia supply is produced by approximately 20 manufacturers by precipitation of magnesium hydroxide either from seawater or brine sources, which amounts to about 14% of the world magnesia production. The first synthetic magnesia production occurred along the French coast of the Mediterranean Sea, near Aiques-Mortes, operating sometime before 1885. Magnesium hydroxide was precipitated from seawater by reacting it with milk of lime in a continuous fashion using three sequential agitated reactors. Because of the abundance of brine resources enrich in Magnesium in our country, in this project, was tried to precipitate Magnesium Hydroxide from brine... 

In this paper we answer to the following questions: First, whether we obseve conditional convergance indicating that the poor Iranian provinces tend to grow faster than the rich ones? Second, has inter-provinces migration helped the convergence? Three different indices are used for examining inter-province convergance. These include: per capita expenditure and per capita income both from the household survey since 1364 to 1394 and per capita regional GDP since 1379 to 1393. Our results support the convergance phenomena based on all three different indices. For the second question, we use instrumental variable to resolve the potential endogeneity problem caused by the reversed causality... 

This project aims to determine seismic performance coefficients of Off-Center Braced lateral load resisting system (OBS) equipped with Buckling-Restrained Braces (BRBs), along with comparing its seismic performance in extreme seismicity level with those of Special Moment Frame (SMF). For this intent, the structural design of 24 regular-in-height residential OBS-BRB models was first carried out following ASCE7-16. Then, Static (Pushover) and Incremental Dynamic Analysis (IDA) were performed on the models using the methodology of FEMA P-695 to obtain the target coefficients. Furthermore, the coefficients were used for Pushover and IDA analysis of 27 irregular-in-height OBS-BRB models with soft... 

In the present project, in order to be self-sufficient and optimal use of boron mines in Iran, a study entitled “The effect of process variables on the production of boric acid” has been conducted, This project has two main objectives: the first objective is the production of boric acid from boron sources and mines in Iran and the second objective is to analyze the effect of variables such as temperature, time, acid concentration, solid to liquid ratio and particle size on the purity of boric acid produced. And finally achieve the optimal conditions for the production of boric acid.In this study, boric acid was made from leaching hydrobracite (magnesium-calcium ore with boron) with sulfuric... 

One main problem in many numerical simulations is the lack of sufficient infrastructure data to precisely model and analyze the flow through complex geometries. Since experimental procedures are generally very expensive; and sometimes impossible, it becomes necessary to find alternative ways such as numerical approaches to predict the flow behavior through complex geometries. The heat exchangers can be categorized as geometries with complex configuration and apparently expensive to solve numerically. They are widely used in different industries including the aerospace. The restrictions in design and implementation of aviation’s heat exchangers have promoted the related companies to converge... 

The problem of LQR design based on full state feedback is solved completely in the subject of Optimal Control. So far, however, despite the fact that use of output feedback in many applications of Control is desirable or even necessary, designing optimal controllers using output feedback in general does not seem to have received much attention in the existing literature. Of course, special cases of designing simple controllers using analytical or numerical-analytical methods do exist in the literature. A new algorithm for tuning an optimal controller (P, PI, PID, etc) for a low-order system without delay, and also in the presence of delay, has been introduced in this thesis using the LQR...