Tallinn University of Technology

About: Tallinn University of Technology is a education organization based out in Tallinn, Estonia. It is known for research contribution in the topics: European union & Computer science. The organization has 3688 authors who have published 10313 publications receiving 145058 citations. The organization is also known as: Tallinn Technical University & Tallinna Tehnikaülikool.

Sorption and desorption of Cd2+ and Zn2+ ions in apatite-aqueous systems.

Abstract: As a low-soluble phosphate mineral capable of binding various metal ions, apatite can be used to immobilize toxic metals in soils and waters. In the present research the factors affecting sorption and desorption of Cd2+ and Zn2+ ions on/from apatites are investigated. Batch experiments were carried out using synthetic hydroxy-, fluoride-, and carbonate-substituted apatites having various specific surface area (SSA). Apatite sorption capacity was found to depend mainly on its SSA, ranging from 16 to 78 and from 11 to 79 mmol per 100 g of apatite for Cd2+ and Zn2+, respectively. The solution composition (pH, and presence of Cl- and NO3- ions) had no essential impact on sorption. Desorption of bound cations depended both on the sorption level and solution composition. The amount of desorbed Cd2+ and Zn2+ increased proportionally to the amount of sorbed cations. However, apatites having higher sorption capacity release relatively less sorbed cations. Desorption increases with increasing Ca2+ concentration in the solution, reaching 8-20% of sorbed Cd2+ in 0.002 M, 10-35% in 0.01 M, and 33-45% in 0.05 M Ca(NO3)2 solution. Compared to nitrate solutions, the presence of Cl- ions in the solution promotes the release of bound cations. Desorption of Zn2+ is slightly higher than that of Cd2+. The desorption mechanism was assumed to include both ion-exchange and adsorption of Ca2+ ions on apatite surface.

Creation of Smart-Contracting Collaborations for Decentralized Autonomous Organizations

Abstract: Electronic communities of decentralized autonomous organizations (DAO) that engage in agile business-network collaborations, are enabled by recent blockchain-technology related innovations using smart contracting. DAOs utilize service-oriented cloud computing in a loosely-coupled collaboration lifecycle that commences with the setup phase. The latter supports the selection of services provided and used by DAOs in combination with smart contract negotiations. Such setup phases for DAO-communities use blueprints of business-network models that DAOs populate with tentative service offers. The negotiation phase may result either in a consensual agreement, a counteroffer, or a disagreement. In the latter case, the smart contract negotiation collapses and the lifecycle returns to the beginning of the selected collaboration blueprints. To the best of our knowledge, such a smart-contracting setup lifecycle has not been formalized so far. The paper fills the gap and evaluates the model with means of model-checking methods.

A convex hull approach to counterfactual analysis of trade openness and growth

Abstract: In this paper, we apply a convex hull approach to counterfactual analysis of trade openness and growth. The experiments we choose evaluate the importance of trade openness for growth across African countries. Specifically, we ask the question “what would happen if African countries were more open?”. The evidence indicates that several countries don´t fall within the convex hull of the observed data and therefore counterfactual inferences are risky. This conclusion is at odds with the literature arguing that greater trade openness would unequivocally lead to higher growth in Africa.