109 research outputs found

    Distribution pattern of phytoplankton (Chrysophyta and Pyrrophyta) in the southern Caspian Sea

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    In regard to study the distribution pattern of phytoplanktons (with emphasize on chrysophyta and pyrrophyta), a series of 4 cruises were carried out seasonlly in 1996. A total of 93 species belong to 2 main phyllums of chrysophyta (mainly diatoms) and pyrrophyta were identified consist of73 and 20 species, respectively. The diatoms have an important role in the whole Caspian Sea from point of species diversity and on the other hand contain the most abundance and biomass in all seasons. There are two main species of Rhizosolenia calcaravis (belong to chrysophyta) and Exuviealla cordata (from Pyrrophyta) inhabit in the southern Caspian Sea. Comparing the density and biomass of different phyllums of phytoplanktons showed that chrysophyta with 75% and pyrrophyta with 17% are the most abundant phytoplanktons in the said region

    Gypsum: prospects for recycling

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    The impact of variation in chemical and physical properties of PFA and BPD semi-dry cement paste on strength properties

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    The effect of Pulverised Fuel Ash (PFA) and By-Pass-Dust (BPD) in ternary semi-dry cement pastes was reported. As well as this, the variability over 6 months in chemical composition and particle distribution was reviewed to determine impact on strength. The addition of BPD in ternary pastes resulted in a reduced strength when combined with PFA. PFA and BPD samples obtained over a 6 month period showed variability in both chemical composition and particle distribution. For PFA, it was reported that at 14 days the particle size distribution had greatest impact on strength and at 28 days the SiO2 content had greatest impact. The high variability in BPD particle size distribution resulted in finer particles achieving the greatest strength

    Recycled materials in concrete barriers

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    Use of recycled gypsum in road foundation construction

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    Scale Effects of Footings on Geocell Reinforced Sand Using Large-Scale Tests

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    The scale effect on bearing capacity of shallow footings supported by unreinforced granular soils has been evaluated extensively. However, the subject has not been addressed for shallow footings on geocell-reinforced granular soils. In this study, load-settlement characteristic of large square footings is investigated by performing large-scale loading tests on unreinforced and geocell-reinforced granular soils. The effects of footing width (B), soil relative density of soil (Dr), and reinforcement depth (u) have been investigated. The test results show that the scale effects exist in geocell-reinforced soils, like unreinforced soils, and the behavior of small-scale models of footings cannot be directly related to the behavior of full-scale footings due to the difference between initial conditions of tests and the initial state of mean stresses in the soil beneath the footings having different dimensions. Large footings create higher mean stresses in the soil, resulting in low soil friction angle and initial conditions of the test approach to the critical state lines. The results of tests indicate that model experiments should be conducted on low-density soil for better prediction of the behavior of full-scale footings, otherwise, the predicted behavior of full-scale footings does not seem conservative
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