This paper introduces a new methodology for the development of appropriate technology that allows satisfying energy needs in rural communities. The methodology integrates the technological development, taking particularly into account the assessment of environmental impacts as well as evaluation of the functionality of the technology. Therefore, it is implemented as a case study in the development of a solar wood-dryer in an artisan community in Mexico. Relevant issues were identified for the success of the methodology, which includes identifying key participants in the community, as well as the use of specialized simulation- and computer-based design tools, and a prior evaluation of the potential environmental impacts through Life-Cycle Assessment (LCA) of the solar wood-dryer. Three geometries of a solar wood-dryer prototype were proposed and analyzed with computer-based simulations, which showed better interior heat transfer than the traditional wood brick-dryer. LCA revealed that the new solar wood-dryer prototype has environmental impacts in all analyzed categories that are 5% or smaller than those of the traditional dryer. Therefore, it was demonstrated that the solar wood-dryer developed with our introduced methodology leads to less environmental impacts compared to those of the traditional wood brick-dryer previously used by the rural community.

The time-dependent flow driven by electromagnetic forcing of an electrolytic fluid in the gap of a concentric spheres set-up is studied experimentally and theoretically. The driving Lorentz force is generated by the interaction of an alternating current radially injected through electrodes located at the equatorial zone of the spheres and a dipolar magnetic field produced by a permanent magnet inside the inner sphere. Experimentally, the time-dependent flows were explored in the laminar regime with a Reynolds number .

This article presents a topological data analysis of the Lagrangian orbits occurring in natural convection flows inside cylindrical containers heated from below. The fluid motions are calculated via the numerical integration of the mass, momentum, and energy conservation equations using the Fourier-Chebyshev pseudospectral method. The study focuses on steady-state flows, and their qualitative properties are described in terms of the Rayleigh number. The Lagrangian orbits are calculated using the Eulerian velocity fields and their features are analyzed with Poincaré maps placed at the horizontal central plane of the cylinder. The qualitative features of the Lagrangian orbits calculated are closely related to those predicted by Hamiltonian theory, with the phase space being the real space in our case and considering the Rayleigh number as the driving parameter. The orbits are embedded in nested tori surfaces for low Rayleigh numbers ($\mathrm{Ra}=8\times {10}^3$). Some orbits seem to be dense in the tori and others form sets of points divided into segments in the Poincaré maps. At larger Rayleigh numbers ($\mathrm{Ra}={10}^4$, $2\times {10}^5$) the orbits form increasingly complicated structures, including loop islands in the Poincaré maps. Also, large areas in the maps show irregular or chaotic distributions of points. Topological data analysis (TDA) was used to define parameters that quantify the geometrical properties of the points distributions in the Poincaré maps. The number of segments in the sets of points and the occurrence of holes were determined with the 0- and 1-persistent homologies, respectively. Pairs of relatively prime numbers are used to characterize quasiperiodic orbits; the pairs are naturally identified with torus knots. It is found that the ratio of toroidal to the poloidal number of turns follows a simple rule for each Rayleigh number explored. The most important advantage of using TDA is the quantification and accurate identification of topological features found in the Poincaré maps.