Sharif Digital Repository

The friction stir welding of AA2024-T6 to AA6061-T6 plates with a 4 mm thickness has been studied at constant traverse and rotational speeds of 1000 rpm and 100 mm/min, respectively. The position of alloys and the effects of precipitation hardening heat treatment in retreating and advancing side in the friction stir welding were analyzed. The tool with taper threaded pin was used for welding. Macro and microstructural analysis were investigated by using Optical and Field Emission-Scanning Electron Microscopes (FE-SEM) to check out the welded joints. Micro-hardness and Tensile tests were also done to study mechanical attributes of the joints. Microstructural analysis revealed some grain... 

In this work, a corresponding-states correlation is presented for prediction of crude oil density in an undersaturated state. The correlation is the extension of corresponding-states liquid densities correlation. The modified corresponding states liquid densities method for predicting saturated liquid densities was coupled with the Tait equation to predict undersaturated densities. Correlations are proposed for the temperature-dependence of Tait equation parameters. Applying proper mixing and combining rules, we calculated the density of 26 crude-oil samples, mainly from Iranian reservoirs. The mixtures included a variety of compositions including N2, H 2S, CO2, and hydrocarbons. The AAD%... 

Aims. EROS (Expérience de Recherche d'Objets Sombres) has searched for microlensing toward four directions in the Galactic plane away from the Galactic center. The interpretation of the catalog optical depth is complicated by the spread of the source distance distribution. We compare the EROS microlensing observations with Galactic models (including the Besançon model), tuned to fit the EROS source catalogs, and take into account all observational data such as the microlensing optical depth, the Einstein crossing durations, and the color and magnitude distributions of the catalogued stars. Methods. We simulated EROS-like source catalogs using the HIgh-Precision PARallax COllecting Satellite... 

In this work the titanium dioxide powder was prepared by the optimized and simple Sol-Gel method and then characterized. The gelling pH was set to values of 3 (TiO2-A), 7 (TiO2-N) and 9 (TiO2-B) to observe the effect on the properties of the material. In these three cases nanoparticulated materials were obtained with particle sizes between 10nm and 20nm. The larger surface areas were obtained at pH 3, which is several times larger than the others. Furthermore, with the gelling condition pH 3, it was possible to synthesize pure anatase phase titania. Some preliminary results on the test of the photocatalytic activity of the synthesized materials in the reduction of nitric oxide are presented.... 

The prepared colloidal silica via ion exchange was modified by adding Mg+2 ions in the surface growth process of colloidal silica. The particle size of the modified colloidal silica was decreased by increasing the seed concentration, whereas that of colloidal silica was slightly increased as the seeds concentration exceed 15 wt%. But the trend of changes in surface area was completely reversed. Magnesium ions on surface of the modified colloidal silica were identified by the measurement of energy-dispersive X-ray spectrometry (EDS). After modifying with Mg+2 ions, the iso-electric point (IEP) of colloidal silica in pH ∼ 2 without modification, disappears over the whole pH range. © 2008... 

In a glance, more than three billion people live in the rural areas of low and middle income countries. In most cases, rural households have many unmet energy needs including cooking, lighting, heating, transportation and telecommunication needs. The main goal of this study is Implementing Conceptual Model Using Renewable Energies in Rural Area of Iran. In this study, the Weibull and Angestrom distribution methods were used to assess the potential of wind and solar energy range in Chaharmahal va Bakhtiari province of Iran (The Case study). After determining the values calculated based on meteorological stations' data, the IDW interpolation method in GIS software was used for the entire... 

We investigate the resistance of reinforced concrete panels (RCPs) due to explosive loading using nonlinear finite element analysis and surrogate models. Therefore, gene expression programming model (GEP), multiple linear regression (MLR), multiple Ln equation regression (MLnER), and their combination are used to predict the maximum deflection of RCPs. The maximum positive and negative errors, mean of absolute percentage error (MAPE), and statistical parameters such as the coefficient of determination, root mean square error (RMSE). Normalized square error (NMSE), and fractional bias are utilized to evaluate and compare the performance of the models. We also present a novel statistical table... 

Solar systems are the most promising technologies to reduce building energy consumption. In recent years, one of the popular solar technologies is building integrated photovoltaic-thermal collectors, because of profitability and no need for separate architectural space. In this study, a new combination of glazed building integrated photovoltaic thermal solar collectors and an absorption cooling system, as a trigeneration system, to provide thermal and electrical energy demands of a case study residential building, is proposed. Dynamic simulation of the proposed system is performed using the TRNSYS-MATLAB co-simulator. Because there is no model for the glazed photovoltaic thermal solar... 

A series of Cr-substituted Fe-Ti compounds were prepared by the co-precipitation method and were systematically investigated as catalysts for the selective catalytic reduction (SCR) of NO by NH 3. A variety of analytical techniques revealed that the Cr substitution amount affects the N 2 selectivity, SCR activity, redox behavior of NH 3/NO x, adsorption ability, and structure of catalysts in terms of surface properties, porosity, mobility of lattice oxygen, oxidative ability of Cr species, ratio of Bronsted acid sites and Lewis acid sites, NO x adsorption capacity, and structural disorder and distortion. In a series of Fe aCr 1-aTiO x (a = 1, 0.75, 0.5, 0.2, 0) catalysts, Fe 0.5Cr 0.5TiO x... 

Among major components of LiBr-H 2O absorption chillers is the absorber, which has a direct effect on the chillier size and whose characteristics have significant effects on the overall efficiency of absorption machines. In this article, heat and mass transfer process in absorption of refrigerant vapor into a lithium bromide solution of water-cooled incline plate absorber in the Reynolds number range of 5