A closed-form approximate expression for the solution of a simple pendulum in terms of elementary functions is obtained. To do this, the exact expression for the maximum tension of the string of the pendulum is first considered and a trial…

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In this review, a comparison between the Lewis acid catalysed and organocatalysed 1,3-dipolar cycloaddition is presented with special focus on the enantioselective synthesis of five-membered hetero- or carbocyclic systems, is described. These reactions exhibit very interesting features, but the most…

Technical teaching often requires the use of expensive laboratory materials which are frequently beyond the reach of many students. Students are also required to go to laboratories, which offer the appropriate facilities, according to a strict timetable. For these reasons,…

The aim of this study was to evaluate the worldwide effect of state downsizing policies on achievement of U.N. Millennium Development Goal 4 (MDG4) on infant mortality rates. In an ecological retrospective cohort study of 161 countries, from 1978 to…

Nowadays robots are being created that interact with human beings in order to satisfy certain social needs. Following this trend, the development of the social robot Probo has started. The robot will be used in hospitals, as a tele-interface for…

In this paper we study the distribution of the zeros of each function G_{n}(z)≡1+2^{z}+...+n^{z}, n≥2, which approaches the Riemann zeta function for Rez<-1, and is closely related to the solutions of the functional equations f(z)+f(2z)+...+f(nz)=0. We determine the density of…

The different transitions and reactions involved in the thermal processing of ternary EVA-PE-ADC mixtures, with different concentrations of polyethylene (PE) and azodicarbonamide (ADC), used as foaming agent, have been studied by means of differential scanning calorimetry (DSC).
The effect of…

Porous materials are gaining interest due to their potential for storing hydrogen via physisorption. In the present work, two carbon fibres, carbonised at 973 and 1273 K, have been chemically activated with KOH and NaOH, in order to obtain materials…

Nowadays, the material disassembly is an important issue for the industry. This paper presents an algorithm to sequence the task to be performed in the disassembly of a specific material from a product or to separate all the materials of…