Sharif Digital Repository

Some of the low-grade titanium resources which are located in the country are titanomagnetite placer deposits. In current study, beneficiation of titanium-bearing concentrate of a placer deposit containing 6.13wt.% TiO2 was investigated by acidic leaching in order to remove impurities. To beneficiate the concentrate, based on the optimum conditions obtained in previous studies, solid-state reduction, magnetic separation, and calcination of non-magnetic product were performed. Afterwards, by studying temperature, time, acid concentration and L:S ratio, the final product was leached under optimal conditions were as follows: H2SO4 concentration of 15wt.%, L:S ratio of 20:1 (mL:g), reaction... 

Due to the technology advancement and the large-scale application of lithium-ion batteries in recent years, the market demand for lithium is growing rapidly and the availability of land lithium resources is decreasing significantly. As such, the focus of lithium extraction technologies has shifted to water lithium resources involving salt-lake brines and sea water. The ion exchange process is a promising method for lithium extraction from brine and seawater having low concentrations of this element. Among various aqueous recovery technologies, the lithium ion-sieve (LIS) technology is considered the most promising one. This is because LISs are excellent adsorbents with high lithium uptake... 

The steam turbines share a significant part of Iran's electricity production. Evidently improving the performance of these steam turbines will improve the performance of power plants and enhance the capability of power production in Iran. Since the behavior of steam turbines is highly nonlinear and that it is affected by various factors, it is difficult to determine the optimum operating conditions for each turbine in specific unit of a power plant. In addition, it is very difficult to model the turbine behavior based on the mathematical equations. Fortunately a large amount of information is collected and stored annually by the data-processing systems in each power plant. These collected... 

The lubricating oil is commonly used to cool down the moving parts of turbine gas systems. In many applications, this oil is cooled down using a recirculating water circuit. The water is then cooled down using an air-cooled heat exchanger. Any deficiency in aerothermodynamic design of such heat exchanger would result in high temperature of gas turbine moving parts such as bearings. Obviously, this mal-performance has adverse effect on the lifetime of these parts and their maintanence aspects. Since the good performance of air-cooled heat exchanger has numerous advantages for the performance of related gas turbine unit, it is mandatory to design these heat exchangers in minimum sizes and... 

The constitution's effect on economy’s performance is a complex and interesting issue. In the labor market economy, The Employment protection legislation (EPL) beside the minimum wage are two important constitutions that considerably determine the main features of the market and affects the efficiency of the economy. The EPL’s strictness varies between different countries and as many argue, it is the main factor that describes the already difference between north American and southern Europe countries labor markets. In this research, the EPL’s influence on speed of adjustment in manufacturing sector of different countries was studied. To analyze the manufacturing sector, labor demand... 

Iran's experience shows that either single or combined power generation cycles, face heavy summer performance deficiencies. The most limitation of power generation in steam cycles is due to their poor condenser performance.The less condenser performance, the more turbine back pressure, and the more turbine back pressure, the less cycle power generation. The main objective of the present study is to reduce steam turbine back pressure in the combined cycle of an organic Rankine-vapor compression refrigeration by installing heat pipes in suitable locations inside the Air cooled condense (ACC). In order to do so, a commercial numerical simulation solver (FLUENT) is used to find the most suitable... 

Human as an important part of the natural environment and can exert their positive or negative effects in the form of long-term and short-term on a natural environment. Human impacts on the natural system are very complex and consist of various components. The most considerable among them from past to now are maybe land use and land cover change, although, the impact of dam construction, water pollution, air pollution and etc, can not be neglected. To quantify the impact of these changes, many researchers have studied meteorological and climatic parameters using statistical relationships, but one major problem always existed, the low spatial accuracy of meteorological data. In recent years,... 

At Lake Urmia (LU) greatest extent, it was the largest lake in the Middle East and the sixth-largest saltwater lake on Earth, with a surface area of approximately 5,200 km2. The lake has shrunk to 10% of its former size due to damming of the rivers that flow into it, and the pumping of groundwater from the surrounding area. Moreover, as the lake shriks its potentional to be a major dust sources increases. A Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used to investigate and track the extent of dust emission and aerosol concentration over Lake Urmia marginal dust spots in order to identify the affected and critical areas. Also, percent movement, propagation... 

In Iran, titanium dioxide is still not produced and imports of titanium dioxide are required by various industries, including dyeing, electrodeposition, plastics and Therefore, according to the Ministry of Industries and Mines objectives, to obtain the technology of extraction Ti and TiO2, a research was carried out on titanomagnetite concentrate, extracted from the minerals of the plancher titanumitent and low-grade kahnoj. In this research, titanium dioxide is produced by sulfate method. Solid state recovery and magnetic separation were used to isolate titanium and iron. The dissolution process was then performed to achieve maximum dissolution. At this stage, the effects of temperature,... 

This dissertation studies the intertemporal decisions on private consumption and its relationship with financial markets. The main focus here is on using micro-data and heterogeneities. The first chapter gives a brief review on the literature. In the second chapter, we present estimates of the Elasticity of Intertemporal Substitution (EIS) for Iranian households using synthetic cohort panels based on household micro-data. Results show significant difference with the common values used in Dynamic Stochastic General Equilibrium (DSGE) models which are originally based on estimated values for developed countries. We show that this difference has important theoretical and practical implications.... 

Urmia Lake is a strong electrolyte containing various salts, with a thermodynamic identity. Changes in the temperature and volume of lake water cause a change in the concentration of ions in this brine as well as the composition and precipitation of salts in the lake. As a result of these changes, the thermodynamic properties of brine are also changed. The purpose of this study was to investigate the effect of mixing the rivers entering the lake and calculate and analyze the changes in the quality and hydrogeochemical characteristics of Urmia Lake and the amount of precipitation and dissolution of the main minerals in Urmia Lake during the period of 2007-2013 per month. For this purpose,... 

The co-existance of rarefied and near-continuum flow regimes is widelyencountered in analyzing the multiscale flow problems, e.g., micro-and nanoflows. Previous investigations have revealed that the continuum-based simulation methods would suffer from the lack of accuracy to predict the rarefied flow regimes. On the other hand, the molecular simulation methods are not computationally efficient in simulating the near-continuum flow regimes. Therefore, the use of hybrid simulation methods has been recommended as a serious alternative to simulate the multiscale flow problems. These methods apply the molecular methods in solving the rarefied flow regions and the continuum methods in solving the... 

In this research, factors affecting the behavior of reduced-cross section steel (RBS) connection to the compound column (CFT) has been investigated. After verifying the accuracy of the numerical simulations performed by finite element software, with a compatible three-dimensional model, several steel beam-to-column connections are modeled to the composite column and the distance effect of the reduced cross section on the column and reduction radius was studied on the behavior of the beam connection with the cross section reduced to the composite column. The results show that in all connections, in which the cross section of the beam is reduced, compared to the connections in which the beam... 

Guilt aversion, the process of avoiding guilt, when guilt indicates the human sense which is present when they let down other's expectations. As the definition suggests, guilt is related to what one thinks of the others’ thoughts; i.e. the second-order beliefs. Incomplete information models of guilt aversion are the most reliable ones in the literature due to economic experiments. Based on these models, the dictator game and the trust game are applied to measure the degree of guilt aversion. In both the above psychological games, there are two players where Player A has the power to decide about the split of the money. We use the amount of transferred money to Player B is as a sign of guilt... 

In this study, we investigate the effect of the macroeconomic volatility on the income distribution of Iranian households from two descriptive and causal aspects. In the descriptive section, by using the national accounts and the data on urban household expenditures and income, from the years 1997 to 2018, the relationship between macroeconomic variables and household budget is extracted, and the "Income Distribution-Business Cycle" is portrayed. In the causal section, a two-step reduced form model with fixed effects is used to estimate the effect of GDP fluctuations on inequality and income distribution fluctuations of Iranian households. This is done using the panel data from the... 

In the Iranian economy, the unemployment rate has always been volatile and double-digit, and this has had a devastating effect on people's livelihoods and the welfare of society. Therefore, job creation has always been the main concern of policymakers. To increase employment, based on the Okun's law, the output must be increased. Since from an economic point of view, economic growth should be accompanied by employment growth and there should be a positive relationship between the employment growth rate and the country's economic growth rate. But in 1384 to 1398, the Iranian labor market has experienced a puzzling behavior in terms of the growth of the total number of employees and the growth... 

Today, recycling lithium as a valuable metal from brine plays an important role in various applications such as battery manufacturing, computers, aerospace and automobiles. Among the aqueous methods available for the extraction of the lithium element in brines, ion exchange by TiO2 nanosorbents is one of the most efficient methods. In this study, first the titanium dioxide nanotubes were well synthesized by anodizing method and the nanograss created after the anodizing process were completely eliminated. Then, the effect of three cathodes of aluminum, graphite and stainless steel in order to select the best cathode and achieve a regular morphology as well as their replacement with platinum... 

Abstract
In this research, the effect of irregularity in the plan floor of structures, including geometric and torsional irregularity on the seismic behavior of steel moment frames braced with chevron knee braces (CKBs) has been investigated. To achieve this, three–dimensional 5-, 8-, 12-story steel buildings models with regular and irregular plan floors were built in OpenSees software and subjected to nonlinear static (pushover) and nonlinear incremental dynamic analysis (IDA) under 22 ground motion records. The performance of each model was then examined by calculation of three seismic design parameters: response modification (R), structural over strength (Ω), and structural ductility... 

Solvent extraction of vanadium (V) from sulfated leaching solution of the converter slag of the Isfahan steel company followed by stripping of this element from the organic solvent were examined in this study. In the experimental section, 2-ethyl-1-hexanol extractor was utilized for selective separation of V(V) from the acidic medium containing Si, Na, Fe, Al, Ca, and P ions. Ammonium chloride solution was also used for stripping V from the organic phase. Under optimal condition (pH=1.9, T=65℃, extractor concentration of 68% and organic phase volume fraction of 0.66), 91% was extracted in solvent extraction stage. Under optimal stripping conditions (pH=7.5, T=25℃, organic phase volume... 

This study aims for investigating a novel type of Steel Plate Shear Wall (SPSW) system in which the plate to boundary column connections are eliminated and the plate is reinforced with side, horizontal or cross stiffeners. SPSWs are one of the best lateral load resisting systems specially in high-rise buildings which makes it to be widely used in modern construction projects. SPSW system was first used in Japan and United States and found its way to other countries through the next years. In contrary to United States, stiffened SPSWs are more popular in Japan as it is a high seismic area. Despite the numerous advantages of this system, the main drawback of SPSWs is the large column sections...