Free profinite R-trivial, locally idempotent and locally commutative semigroups

This paper is concerned with the structure of implicit operations on R intersection with LJ1, the pseudovariety of all R-trivial, locally idempotent and locally commutative semigroups. We give a unique factorization statement, in terms of component projections and idempotent elements, for the implicit operations on R intersection with LJ1. As an application we give a combinatorial description of the languages that are both R-trivial and locally testable. A similar study is conducted for the pseudovariety DA intersection with LJ1 of locally idempotent and locally commutative semigroups in which each regular D-class is a rectangular band.INVOTAN, grant 4/ A/94/PO.PRC-GdR AM

A novel approach of introducing crystalline protection material and curing agent in fresh concrete for enhancing hydrophobicity

A new line of research to enhance the performance of concrete under adverse (harsh) and normal (air cured) curing conditions is presented. A crystallising hydrophobic admixture and curing agents were added to fresh concrete to improve its resistance against severe environmental conditions. A two-stage approach was pursued by adding the crystallising admixture to fresh concrete followed by curing agents, in a wax and liquid forms, in a separate application process, followed by exposing concrete to normal and adverse curing conditions. Results obtained suggests that protecting concrete with the crystallising admixture followed by applying wax based curing agent improves concrete strength and its resistance to water ingress than concrete cured with the liquid curing agent. When following the crystallising-wax treating system under adverse curing conditions, a more conserved strength was noticed compared to that produced by the crystallising-liquid system. Using the liquid curing agent in concrete with high water to cement ratio (w/c) has increased the cracks in the internal structure, while water permeability has decreased, either under normal curing conditions or adverse conditions. Following this protection-curing system in industry would resolve the problem of applying protection on wet surfaces and increase concrete’s resistance to deterioration. A microscopic study of the crystallising material was attained with a Scanning Electron Microscope (SEM) to check crystal growth with time

Full vs Partial Market Coverage with Minimum Quality Standards

The consequences of the adoption of quality standards on the extent of market coverage is investigated by modelling a game between regulator and low-quality firm in a vertically differentiated duopoly. The game has a unique equilibrium in the most part of the parameter range. There exists a non-negligible range where the game has no equilibrium in pure strategies. This result questions the feasibility of MQS regulation when firms endogenously determine market coverage