Two sets of nine different silicon carbide particulate (SiCp) reinforced Al 7075 Metal Matrix Composites (MMCs) were fabricated using liquid metallurgy stir casting process. Mean particle size and weight percentage of the reinforcement were varied according to Taguchi L9 Design of Experiments (DOE). One set of the cast composites were then heat treated to T6 condition. Optical micrographs of the MMCs reveal consistent dispersion of reinforcements in the matrix phase. Mechanical properties were determined for both as-cast and heat treated MMCs for comparison of the experimental results. Linear regression models were developed for mechanical properties of the heat treated MMCs using list square method of regression analysis. The fabrication process parameters were then optimized using Taguchi based grey relational analysis for the multiple mechanical properties of the heat treated MMCs. The largest value of mean grey relational grade was obtained for the composite with mean particle size 6.18 µm and 25 weight % of reinforcement. The optimal combination of process parameters were then verified through confirmation experiments, which resulted 42% of improvement in the grey relational grade. Finally, the percentage of contribution of each process parameter on the multiple performance characteristics was calculated through Analysis of Variance (ANOVA).
Powder mixed electro discharge machining (PMEDM) is a hybrid machining process where electrically conductive powder is suspended into a dielectric medium, for enhancing the material removal as well as the surface finish. In this investigation, electro discharge machining (EDM) has been performed for the machining of AISI 304 stainless steel by using the tungsten carbide electrode, when silicon carbide (SiC) powder is suspended into kerosene dielectric medium. Peak current, pulse on time, gap voltage, duty cycle and powder concentration are considered as process parameter while the surface roughness (Ra) is the only response. The effect of significant process parameters on the response has been studied. A regression analysis has been performed to describe the correlation of data between the machining parameter, and the response. Microstructural analysis has been done for the PMEDMed surface. The result shows that peak current is the most influential parameter for surface roughness. Surface roughness decreases with the increase of powder concentration.
Knowledge management plays an essential role on developing efficient systems in educational systems. However, there are different factors influencing the success of knowledge management. In this paper, we present an empirical study to measure the impact of six cultural based factors including management support, organizational affiliation, employee participation in decision-making, staff welfare organization and establishment, adaptation of new policies and organizational and internal organizational climate on establishment of knowledge management. The proposed study of this paper is implemented in 114 selected educational organizations in city of Tehran, Iran. A questionnaire is designed in Likert scale, it is distributed among experts, and using regressions analysis and structural equation modeling, we have analyzed the data. The results of regression analysis indicate that management support, staff welfare organization and internal organizational climate are among the most important factors while other component did not represent any significance on knowledge management implementation.
E-learning has recently attracted many people specially those who cannot attend traditional educational programs for different reasons such as busy schedule, long distance, etc. There is also a growing interest among many public universities to develop such programs in addition to their regular business activities. The primary question is to know how much a program cost and what is the most important factors affecting the cost of e-learning. In this paper, we present an empirical study the measure the effects of different items on the cost of e-learning programs. The proposed study of this paper gathers the necessary cost components of three governmental universities located in city of Tehran/Iran. We choose ten different cost items for our analysis and using some statistical test determine the most important ones. The preliminary study of this paper indicates that seven cost items play essential role on determining the cost of e-learning, which includes utilities, internet connection and network, employee payment, software & licensing, payments of instructors and their assistants, hardware equipments and other overhead expenditures. This could help us determine the precise cost of e-learning using activity cost method.
Sugar is one of the strategic goods in the basket of households in each country and it plays an important role in supplying the required energy. On the other hand, it is one of the goods, which Iranian government is about to change its subsidy strategies. To design useful sugar subsidy strategies, it is necessary to know sugar position in the basket of households and be familiar with households & apos; sugar demand or consumption behavior. This research estimates sugar demand for Iranian households by using time series of 1984-2008, which is taken from central bank of Iran. In this paper, first independent and dependent variables of household sugar demand model are chosen based on the literature review and theory of demand. Then, sugar demand is estimated by OLS technique and linear regression. The preliminary statistical observations such as Durbin-Watson, F statistic and R2 indicate that the regression is admissible. The results seem plausible and consistent with theory and show that sugar demand in Iranian households is associated with household expenditure, relative sugar price, family size and indicate that demand of sugar is affected during the war time. The results also show the income elasticity is 0.8 and price elasticity is -0.2 which means sugar is essential good for Iranian households and is inelastic to price.