Sharif Digital Repository

Metal foams are considered as a group of new materials and are applied widely in various areas due to their particular properties such as low density, high strength-to-weight ratio and appropriate mechanical, thermal, physical, electrical and magnetic properties. The aim of the present study is acquiring the technical knowledge of Zinc foam production by melting route and also optimizing the effective parameters on the foam stability. For this reason, 4 Zinc foams were produced at different times and temperatures. The amount of Calcium as the melt fluidity reducing agent and Titanium hydride and Zinc carbonate as the blowing agent were the same in all the specimens. The effect of heat... 

Li-ion batteries have been widely applied as power sources for portable electronic devices. Recently, Li-ion batteries are considered as the most promising energy storage technology for electric vehicle applications however, fundamental improvements are needed. TiO2 (B) is attractive candidate for anodes in rechargeable Li-ion batteries, due to their low cost, non-toxicity and favorable channel structure for fast lithium mobility. It is predicted that synthesis of doped nanostructure of this material, through reducing the diffusion pathway and formation of crystal defects, will increase the capacity of TiO2(B). In this investigation, Co and V doped TiO2(B) nanowires are synthesized by... 

Most of the surface and ground water resources are allocated to agriculture in Iran. Even though lots of water is used in this field, the level of crop production is not satisfactory due to mismanagement. Besides, environmental issues caused by surface and ground water overuse has brought the crucial situation into the governers’ attention. Over the past two decades, Lake Urmia water basin has encountered lots of environmental issues such as decrease in lake water surface. Any effort to improve water reources consumption can be very helpful to lake restoration process. Miandoab plain known as one of the main sub basins of Lake Urmia provides the lake with more than half of its surface water... 

The procyclical behavior of public investment expenditure in OECs is one of the main channels through which the blessing of the natural resource abundance turns into a curse. The focal issue about the public investment expenditures in OECs is the misallocation and the inefficiency of these expenditures which often appear in the form of white elephants- i.e. government investment projects with large scale and high social/political prestige for the politicians implementing theme, but with negative economic return- especially in the oil booms. Moreover, the imprical evidence shows that the efficiency of public investment management in OECs is positively and significantly correlated with the... 

In this study, leaching of Sarcheshmeh Reverberatory Furnace Dust was investigated in the H2SO4-O3 media. Response surface methodology based on central composite face-centered design (RSM-CCF), was applied to optimize the operating parameters. The optimum conditions to obtain the main goal of maximum copper and minimum iron dissolution from dust were identified to be temperature of 30˚C, leaching time of 3hr, initial pH of 0.5, pulp density of 20% and ozone flow rate of 1g/h. The copper and iron concentrations of leaching solution were found to be 27.11 and 0.89983 g/L under the optimum conditions, respectively. The results showed that selective copper extraction from the dust could be... 

Micro/Nano science has obtained enormous applications in aerospace engineering especially in the propulsion system of micro/nano satellites. The satellite attitude control is a vital part of every space mission. Different thruster systems have been already suggested and utilized to achieve this important mission correctly. Considering the future perspectives of space missions for small satellites, the development of micro/nano thrusters has been attracted more attention since the last decades. The scope of this research is to analyze hybrid hot/cold laboratory supersonic micro-thrusters especially for the micro-satellite implementations. The ultimate goal of the current research is to... 

In the present study it was intended to evaluate the seismic performance of multi-story EBF structures for designing. When adopting this method, parametric studies are carried out based on the nonlinear performance of such systems whiting the framework of nonlinear static and dynamic analyses. In lines with seismic strengthening of such structures, this study tries to reassess the performance of these systems through increasing ductility and replacing bracing frames with energy damper and special seismic systems. As a result, a fuse type performance is created to protect the other elements of the structure. This study describes the seismic strengthening of this type of dampers using simple... 

An aerodynamical model for studying asymmetric and three-dimensional flow fields about wind turbine rotors is presented. The developed algorithm combines a asymmetric and three-dimensional Navier-Stokes solver with a so-called actuator disc technique in which the loading is distributed along lines representing the blade forces. The loading is determined iteratively using a bladeelement approach and tabulated airfoil data. Computations are carried out for a 5MW NREL wind turbine equipped with three blades. The computed power production is found to be in good agreement with measurements. The computations give detailed information about basic features of wind turbine wakes, including... 

Titanomagnetites are resources of iron and titanium. high level of titanium in titanomagnetites makes using them in iron making processes very difficult. In this work an attempt was made to produce an iron bearing and a titanium bearing product using solid state reduction of Fanouj mine titanomagnetite concentrate. For this purpose, the concentrate was reduced using coal and then was subjected to magnetic separation. In this work, effect of temperature, time, added coal amount, and additive amount on reduction was studied. The result showed that the optimum conditions are 1325 celsius degree, 2.5 hours, 25 percent added coal and 2 percent additive. In optimum conditions a magnetic product... 

Urmia Lake is one of the largest permanent hypersaline lakes in the world. Since Urmia Lake is faced with drying phenomena, the release of dust from its surface is expected. The most appropriate technique on dust storms is the remote sensing technique. One of the most popular parameter that provides the integrated information over a vertical column of unit cross section of this phenomenon is aerosol optical depth (AOD). Satellite remote sensing has been used to retrieve AOD over land and ocean at spatial resolutions of several to several tens of km. However, higher spatial resolution aerosol products for local scale areas have not been well-researched mainly due to the difficulty of... 

Midrex sponge iron is an active product and there are several problems with store and export it.Cold briquetting sponge iron method is a new method to protect sponge iron from oxidation and provides the possibility of its storage and transportation. Iran as one of the biggest countries that produce sponge iron, has a lot of sponge iron pilots that equipped with cold briquetted machines,but their production capacity is limited and is about 5 percent of their production capacity. With regard to no need for country to these amount of sponge iron, most of these pilots have to store and transport large volumes of sponge iron and the risk of oxidation and fire threatens these units.By using cold... 

According to the climates of the country, using natural draft dry air cooling systems at the power plant is one of the proposed solutions for lower water consumption, but strong wind can make drop in performance of power plant cooling systems based on Rankine Cycle. This means that wind disrupted the order of the normal flow of air intake around the tower by creating areas of low pressure, preventing the flow of air into the cooling system. In the world, many researches and solutions have been proposed to solve the problem. The most common of these solutions is using of windbreaks as aerodynamic devices to compensate for the pressure drop in the cooling tower when the wind blows. But... 

The direct impact of rainfall in human life and its fundamental role in water resources management cause the development of methods and algorithms to estimate the rainfall among the researchers. In the past decades the traditional methods were used to measure the amount of rainfall until the advent of Meteorological Satellites has sparked a revolution in this field. Significant temporal and spatial changes of rainfall and the small number of the synoptic stations caused negative impact on the actual distribution of the amount of rainfall in a vast area. The rainfall satellite data were somewhat overcome by existing deficiencies in Synoptic methods by providing a better rainfall distribution... 

Numerical simulations of participating media need careful solution of the radiation transfer equation (RTE) along the fluid flow governing equations. Evidently, the accuracy of achieved solutions highly depends on the accuracy of radiation transfer calculations. Despite numerous efforts performed in the previous researches, the RTE calculation still faces with several challenges from both accuracy and computational cost perspectives. The main objective of this research is to present new contributions in overcoming such challenges. So, a finite-volume (FV) solver is suitably developed to solve the RTE numerically. This extended solver is then coupled with an existing FV flow solver. The... 

The AISC Seismic Design Provisions now include capacity design requirements for steel plate shear walls,which consist of thin web plates that infill frames of steel beams, denoted horizontal boundary elements)HBEs), and columns, denoted vertical boundary elements (VBEs). The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the... 

Lake Urmia is the largest inner lake in Iran that has been dessicated continuously over the past two decades, and most of it has dried up. Urmia Lake basin is one of the country's agricultural and industrial pillars and has more than 5 million inhabitants. The conflict between people’s interests and the environmental ones besides increased demand for water harvesting has led to a reduction in water inflow to the lake. As the water resources management issues became more complex in last two decades with the entrance of political and socio-economical, the concept of water resources management has been promoted in the broader sense of water governance. The solution to the problem of Lake Urmia... 

The construction industry is one of the most important economic sectors, which shares a major part of Gross Domestic Product (GDP) and employment. In Iran many development projects are designed and implemented annually which billions of Rials are due as a result of construction and operation for executive bodies. The Organization for Development, Renovation and Equipping Schools (ODRES) as the executive branch of the Ministry of Education, is one of the largest construction bodies which undertakes construction of hundreds of educational, cultural and athletic projects annually. Given that the project delivery methods and the need to choose the correct method of contract payments exerts great... 

Previously, numerous studies were carried out on the shear walls and important information are available in various fields, including wall design with various sections, wall design in areas with high seismicity risk, issues related to the reinforcement of boundary element and etc. In the design codes of reinforced concrete structures in the field of seismic design, some criteria for reinforcement of boundary element in the walls were conducted, but these codes do not answer to designers to arrange the wall with or without eccentricity with respect to column or the effect of separation of wall from the column. Due to the fact that we have a powerful software such as ETABS, design of shear... 

Nanodiamond (ND)/polylactic acid (PLA) nanocomposites have the potential for biomedical applications and bone tissue engineering. In this research, nanodiamond/poly lactic acid nanocomposites were prepared by mechanical mixing solution method and applying ultrasonication. Also, PLA-based nanofiber scaffold reinforced by nanodiamond were prepared by electrospinning methods. To find the optimum value of parameters to prepare this nanocomposite sample, the effect of nanofiller concentration, mixing rate and duration, the role of solute and ultrasonication, and solvent evaporation conditions were investigated and then it compared to the neat polylactic acid sample. By means of Fourier transform... 

The level of water at Lake Urmia has decreased dramatically in the last two decades. Lake-Urmia basin is one of the regions in which most of the consumption of water is based on groundwater resources. The annual withdrawal of groundwater in the Urmia Plain is about 468 MCM which is the highest rate of water extraction throughout the basin. In this research, interaction between surface and groundwater flow is simulated using MODFLOW and remote-sensing. METRIC algorithm is used for estimating the amount of recharge to groundwater. The model is calibrated in 24 months of 2008 and 2009. The results show that the main input to the aquifer is the return flow of agricultural lands and the main...