Orbital stabilization of nonlinear systems via the immersion and invariance technique

Immersion and invariance is a technique for the design of stabilizing and adaptive controllers and state observers for nonlinear systems. In all these applications the problem considered is the stabilization of equilibrium points. Motivated by some modern applications, we show that the technique can also be used to solve the problem of orbital stabilization, where the final objective is to generate periodic solutions that are attractive. The feasibility of our result is illustrated by means of some classical mechanical engineering and power electronics examples.     

Event-driven temporal models for explanations - ETeMoX: explaining reinforcement learning

Software and Systems Modeling - Modern software systems are increasingly expected to show higher degrees of autonomy and self-management to cope with uncertain and diverse situations. As a...     

Hydrophilicity of electrospun microfibers of polyethylene oxide with semisoluble polyaniline for biological applications

This work studies the hydrophilicity of electrospun microfibers of polyaniline (PANI) synthesized by plasma combined with polyethylene oxide (PEO). The hydrophilicity was evaluated measuring the contact angles of water, phosphate-buffered saline (PBS) and Krebs-Ringer (KR) biological solutions formed on the polymers. Plasma PANI is usually insoluble due to the crosslinking associated with the electrical discharges of the synthesis conditions; however, PANI was synthesized as semi-soluble films, which were dissolved and mixed with soluble PEO to obtain PANI/PEO electrospun microfibers. Super-hydrophilic (<30°) angles were obtained with water on PEO fibers and hydrophobic (>90°) angles were obtained with the PBS solution on PANI/PEO fibers. PANI films had contact angles, which increased with the salts of KR and PBS solutions, PEO films had sudden increments and reductions with the saline solutions. PANI showed the typical chemical groups of polyanilines and others as CN and CC associated with a high dehydrogenation, which disappeared in PANI fibers. Electromagnetic absorption peaks in the 270–320 nm wavelength range were detected in the fibers and not in the films, which can be associated with transitions between benzoid and quinoid PANI structures. These results indicated that PANI/PEO fibers would not dissolve as rapidly as PEO fibers in biological solutions.     

Modeling,simulation and intensification of hydroprocessing of micro-algae oil to produce renewable aviation fuel

Micro-algae are photosynthetic organisms, which represent a promissory renewable raw material for biofuels production, since they can be cultivated in non-fertile lands, avoiding the competition with food crops for land use. From micro-algae, oil can be obtained oil that can be converted to biodiesel, green diesel and biojet fuel. In particular, the renewable aviation fuel is one of the less explored biofuels; nevertheless, for the aviation sector, this is the best alternative to reduce CO₂ emissions, allowing its sustainable development. In order to produce hydrocarbons in the boiling point range of jet fuel, we need to transform the micro-algae oil. A number of research projects report the use of micro-algae oil for the production of biojet fuel through the hydrotreating process. However, the application of process intensification strategies for the hydroprocessing of micro-algae oil has not been reported. Therefore, in this work we propose the modeling, simulation and intensification of the hydrotreating process to produce biojet fuel, considering micro-algae oil as raw material. The hydroprocessing of micro-algae oil is modeled in Aspen Plus processes simulator, based on data from an experimental study recently reported. The produced renewable hydrocarbons are purified through conventional and intensified distillation sequences; thereby, conventional and intensified hydrotreating processes are defined and evaluated in terms of total annual costs, CO₂ emissions and biojet fuel price. Simulation results show that the implementation of intensification strategies leads to the production of biojet fuel with reduced carbon dioxide emissions, 34% less, and a competitive price per liter, 78% cheaper than fossil jet fuel price.     

Photofermentation of tequila vinasses by Rhodopseudomonas pseudopalustris to produce hydrogen

Hydrogen production by photofermentation of tequila vinasses (VT) was studied using Rhodopseudomonas pseudopalustris DSM 123. To the best of our knowledge this is the first report on hydrogen production by photofermentation on VT. Hydrogen production was doubled on VT (260 m$props_value{literPattern}/L) as compared to a synthetic medium. Storing VT changed its chemical composition; however, in photofermentations of a sixty-day old stock, growth and hydrogen production were similar to fresh VT. The periodic displacement of hydrogen with nitrogen resulted in a three-fold increase in both hydrogen and growth of R. pseudopalustris (860 mL H₂/L and 4.5 g/L respectively) as compared to non-displaced headspace. Hydrogen almost doubled at a light intensity of 270 W/m² (2249 mL H₂) as compared to 68 W/m². In dark-light cycles, biomass and hydrogen production were highest with continuous illumination. The potential of VT to produce hydrogen in high amounts using R. pseudopalustris has been demonstrated.     

The impact of qualitative methods on article citation: an international business research perspective

Scientometrics - Qualitative methods have traditionally been underused in international business, and their research potential in this area has not been widely investigated. The main objective of...