Technological Educational Institute of Western Macedonia

About: Technological Educational Institute of Western Macedonia is a based out in . It is known for research contribution in the topics: Symplectic geometry & Numerical integration. The organization has 291 authors who have published 522 publications receiving 7682 citations. The organization is also known as: TEI of West Macedonia & TEI of Western Macedonia.

An optimized two-step hybrid block method for solving general second order initial-value problems

Abstract: A new optimized two-step hybrid block method for the numerical integration of general second-order initial value problems is presented. The method considers two intra-step points which are selected adequately in order to optimize the local truncation errors of the main formulas for the solution and the derivative at the final point of the block. The new method is zero-stable and consistent with fifth algebraic order. Numerical experiments used revealed the superiority of the new method for solving this kind of problems, in comparison with methods of similar characteristics in the literature.

Superhydrophobic films for the protection of outdoor cultural heritage assets

Abstract: A very simple method that can be used to impart superhydrophobicity to stone surfaces of monuments using common and low-cost materials that are already employed or are easy to be found by conservators is presented. A siloxane-nanoparticle dispersion is sprayed on a stone, and this process can result in the formation of a rough two-length-scale hierarchical structure that exhibits water repellent properties, provided that the nanoparticle concentration in the dispersion is higher than a critical value. Superhydrophobicity (static contact angle >150° and contact angle hysteresis <7°) is achieved, by this simple method (i) on the surfaces of three types of stones, Opuka, Božanovský and Hořický, which have been used for the restoration of the castle of Prague, (ii) using two poly (alkyl siloxane) products such as Rhodorsil 224 and Porosil VV plus, which are utilized by conservators and (iii) using common nanoparticles such as silica (SiO2), alumina (Al2O3), tin oxide (SnO2) and titanium oxide (TiO2). It is shown that the stone substrate and the nanoparticle size (5–50 nm) or type have almost no effect on the wettability of the superhydrophobic surfaces, as comparable contact angles were measured on the three stone substrates, treated with any siloxane-particle composite. Treatments of the stones with pure (hydrophobic) siloxanes and siloxane-SiO2 (superhydrophobic) composites result in comparable reductions of the water vapor permeability and the water amounts absorbed by capillarity. Consequently, the use of nanoparticles in the protective coatings does not have any obvious effect on the results of the aforementioned tests. However, the aesthetic appearance of the three stones, included in this study, is highly affected by the nanoparticles.