Improvement of Fine Sand Properties with Water Soluble Epoxy Resin Grouts

It is generally accepted, that only chemical grouts or solutions are available to penetrate and fill narrow joints or soils with very small pore size. During the last 30 years, a few hundreds of different compounds have been used for this purpose. Such materials show a wide spectrum of properties. Epoxy resins are some of the common compounds which are used in chemical grouting due to their high strength and durability against mechanical or physical erosion. In this paper, the improvement of physical and mechanical properties of fine sand injected with a water soluble, two component epoxy resin is investigated. The experiments were carried out, either using only epoxy resin(“one shot process”) or, in combination with sodium silicate(“two shot process”). For this reason, two epoxy resin solutions have been employed. The one was thick with water/resin (W/R) ratio of 1 and the other was more dilute with W/R of 2. The grouting was performed through 10 cm diameter columns, filled with siliceous sand with particle size distribution of 0.149/2.1mm and 0.076/2.1mm. For the two shot grouting, two solutions of sodium silicate were used, with sodium silicate/water ratio of 3 and 2, respectively. Results of a comparison between the above two processes, showed that the compressive strength and durability of injected sand specimens of the one shot process is much lower than that of the two shot process. On the contrary, the permeability and the porosity of the sand were lowered much more in the first case

Patterns of teacher-child relationships quality: Young children’s perspectives

Examining children’s perspectives about the quality of teacher-child relationships can contribute significantly to our understanding of how the quality of these relationships is developed. The Child Appraisal of the Relationship with the Teacher Scale (CARTS) is a newly developed measure that assesses the quality of teacher-child relationships from children’s perspectives. The purpose of this study was a) to confirm the factor structure of the Greek version of CARTS, b) to examine whether any patterns of teacher-child relationships exist, and c) if they are associated with children’s gender and age. The sample consisted of 365 preschool children from Greece. Results confirmed the construct validity of the CARTS scale. Consistent with attachment-based research, results revealed four types of teacher-child relationships. In addition, results showed that patterns of teacher-child relationships based on children’s perspectives, similar to those of teachers’ perspectives, are existent from the early years

Controle biopolítico de corpo em O Conto da Aia: a ciência ficção e o agenciamento de significados

Este trabalho é uma análise da representação do corpo feminino e de seu controle na obra O Conto da Aia, a partir da qual se produzem reflexões sobre as significações possíveis criadas por meio da ciência ficção. Inicia-se com contextualização e genealogia da ciência ficção e seu papel para produção de sentidos, desnaturalização de estruturas materiais postas no real e desterritorialização de sujeitos. O conto da Aia será analisado por uma perspectiva bio e necropolítica, a partir da qual são agenciados sentidos que possibilitam refletir sobre a representação das estruturas sociais e desnaturalizar suas significações. Argumenta-se que a partir do recurso da ciência ficção é possível produzir agenciamentos que desnaturalizam estruturas de poder do real que estão representadas na narrativ

On the positive solutions of a higher order functional differential equation with a discontinuity

The n-th order nonlinear functional differential equation [r(t)x(n−υ)(t)](υ)=f(t,x(g(t)))is considered; necessary and sufficient conditions are given for this equation to have: (i) a positive bounded solution x(t)→B>0 as t→∞; and (ii) all positive bounded solutions converging to 0 as t→∞. Other results on the asymptotic behavior of solutions are also given. The conditions imposed are such that the equation with a discontinuity [r(t)x(n−υ)(t)](υ)=q(t)x−λ,   λ>0is included as a special case