The study was focused to develop a novel epoxy pebble (EP) composite based machine tool structures with a higher compressive strength and damping ratio. The impact on compressive strength and damping ratio by the addition of 15%, 25% and 35% (by weight) epoxy resin binder to the EP composite has been determined. The weight percentage of pebble epoxy, aggregate size, curing time and size of microfillers were considered as input process parameters in this study. The results showed the drop in compressive strength with respect to increases in the aggregate size. The composite comprises of 15% (by weight) epoxy resin and 85% pebbles showed the maximum compressive strength at 103. 96 , ±,  , 0. 1 MPa and damping ratio at 0. 0169. The damping ratio has been assessed by an experimental modal analysis using a half power bandwidth approach. The damping ratios of EP composites are found to be 5 to 10 times higher than that of cast iron. The analysis results of variance and S/N ratio indicated the contribution of pebbles in the formation of composites as the most influential factor. Confirmatory experiments have been conducted and the results are in good agreement with the experimental findings. The X-ray diffraction (XRD) results showed the presence of silicone oxide, quartz, nickel oxide, lithium niobium arsenide, cobalt oxide, boron nitride and silver cerium indium as major phases in the EP composites developed. Major elements are presented and peak angles are identified. SEM analysis revealed that pebbles and microfillers were uniformly mixed with epoxy resin. Hence, it is found that the application of EP composite rather than conventional machine tool structures can increase the service life of machine tool structures significantly.

This study aims to obtain pebble and epoxy composites with low thermal conductivity, low water absorption and minimal porosity. The effects of filler size, weight percentage of pebble and epoxy, aggregate size and curing time of the composites were evaluated. The ANOVA of S/N ratio was also performed to determine the effect of thermal conductivity, water absorption and porosity of the composites. The experiments were designed as per the Taguchi L27 orthogonal array. The results indicated that the effect of thermal conductivity improved slightly with 35% (wt) of epoxy resin present in the composite and the higher thermal conductivity was observed in the composite with 15% (wt) of epoxy resin. Water absorption and porosity results were found which showed that this composite with 15% (wt) epoxy resin content yielded better results when compared to the composite with 35% (wt) epoxy resin content. The embedded composites were characterized using Fourier transform infrared (FTIR) spectra to study the effect of chemical treatment of pebble/epoxy composite. The morphological studies of the fractured surfaces of the epoxy composites were performed by scanning electron microscopy.

The purpose of this study was to investigate the effect of applying Pebble-in-the-Pond instructional design model on the students’ problem-solving skills of Training Science department in Arak University. For this purpose، the quasi experimental method with the pre-post-test plan including the control group was used. The research population included 170 students of Bachelor degree in Training Science majoring at educational technology in Arak University in the academic year of 2016-2017 that 30 of them who had chosen the system-based instruction course were selected purposefully. Then، they were randomly assigned to an experimental and a control group each consisting of 15 subjects. The data gathering instrument was Hapner and Petterson problem-solving questionnaire (1982). In order to analyze the data، the multivariate analysis of covariance (MANCOVA) was used. The statistical findings showed that applying the instructional method based on the Pebble-in-the-Pond model did not affect the students’ problem-solving skills significantly، (P<. /05). Nevertheless experimental group performed relatively better than control group in problem-solving skills variable.

Million tons of waste are produced annually in mining and processing of dimension stone in Iran. In most cases, the waste is released in nature that would cause environmental hazards. In this work, artificial stone slabs were manufactured by combination of coarse waste and sludge powder of stone cutting factories. The results show that the manufactured stone slabs have physical and mechanical specifications according to Iranian national standards for building stone. With increasing the amount of resin in the composition, the flexural and tensile strength were increased and the compressive strength and water absorption coefficient were decreased. The slabs produced from granite waste compare to the slabs produced from marble waste had better physical and mechanical specifications. At the optimum condition, with the aim of using more waste, with a composition of 90% marble waste and 10% resin, artificial stone slabs were produced which have compressive strength about 143 MPa, flexural strength of 21 MPa, tensile strength of 25 MPa, water absorption coefficient 1% and density equal to 2. 32 g/cm3.

Molecular diffusion is one of the important contaminant transport mechanisms through soil and rocks. In this study the molecular diffusion coefficient of marl stone and sand stone from the Urmia City landfill site was determined using the best fit method of the observed laboratory data and the predicted theoretical data. The marl stone and sand stone samples were tested under the conditions of “through diffusion” and “in diffusion”, respectively, and the observed chloride concentrations were determined.The computer code of Pollute was used for theoretical calculations. The average diffusion coefficients of 2.48´10-10 (m2/s) and 2.55´10-10 (m2/s) were obtained for marl stone and sand stone, respectively, which show the similarity of this parameter in both samples due to the compatibility of the effect of physical parameters of the samples such as porosity and density. The results of the sensitivity analysis of the affecting parameters in molecular diffusion in modeled stones showed that the parameters of time and diffusion coefficient have more effect on the concentration of chloride ion at the end of the migration path through stone. The good agreement between the data of the experimental and theoretical models shows the accuracy of the adopted experimental methods and theoretical model. The results of this study could be used in contaminant transport calculations in the design of solid waste landfills situated on bed rocks.