Must obtained from Airén grapes was fermented in the presence of wood chips (4 and 7 g/L) of either French oak (from Vosges, central France, and Allier zones) or American oak. Fermentation yields were higher than in the control fermentations carried out in the absence of wood, and production of volatile substances during fermentation (alcohols, esters, and acetates) was also higher. The volatile substances that leached out of the wood were analyzed by GC-MS-SIR. The results showed that their concentrations depended on the type and amount of the oak; some of these substances were consumed in part by the yeasts during fermentation. A taste panel favorably assessed the wines produced by fermentation in the presence of oak chips, which retained part of the must original fruity aroma.

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The symmetry breaking of the loads of a matrix converter (MC) generated an imbalance that induced a quasiperiodic behavior at the input side of the MC.In addition, the load imbalance generated a negative-sequence current at the input side. This paper adopts the time-delayed feedback control (TDFC) to attenuate the quasiperiodic oscillation and the negative-sequence component caused by the symmetry breaking. The results indicate that the attenuation of the quasiperiodic behavior directly leads to a decrease of the negative-sequence current component. As a result, the TDFC improves the operation of the MC under unbalanced loads and part of the periodic symmetry is regained at the input side.

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This article presents the measurements and experiments conducted on the external receiver: the so-called Advanced Sodium Receiver (ASR) of the Small Solar Power Systems (SSPS) Project of the International Energy Agency (IEA) in southern Spain. The basis of this experiment was to provide loss measurements for later use in determining receiver performance. The tests to evaluate thermal losses consisted in operating the receiver with the doors open and circulating the sodium in normal and reverse flow without providing any incident power from the heliostat field (flux-off technique). In this way, total thermal losses are calculated as the energy lost by the sodium. Radiative losses have been calculated based on theoretical calculations and some results have been compared with infrared thermography measurements. Conductive losses are small and have been estimated by flux-off experiments with the receiver doors closed. Convective losses were evaluated subtracting radiative and conductive losses from the total thermal losses. Optical losses were assessed using absorptance measurements of the receiver coating. A simplified analytical model has been developed to calculate losses and ASR efficiency during operation. In spite of the method’s simplicity, the results are very similar to those found by other investigators, verified simulation programs, and test results.

In this work, a method for controlling chaotic systems by means of pulses, with four variants, is presented, and its real time application to a particular electronic chaotic circuit (Kiers-Schmidt-Sprott, KSS) is analyzed. Periodic behavior (periodic orbit, PO) is obtained from chaotic dynamics, with a control law depending on a variable event condition, which is automatically adjusted for each particular chaotic process. No previous knowledge of the mathematical model of the system to control is needed, which is considered as a black-box process. Sample data of only one measurement variable and three tuning parameters (proportional gain, pulse width, and hold-off time) are used. Satisfactory real time experimentation results have been obtained using dSPACE 1104 target for the KSS circuit.

ResumenEn este trabajo se propone un sistema de control equivalente a un método numérico para el cálculo de los puntos de equilibrio de sistemas dinámicos, donde dichos equilibrios pueden ser empleados como señal de referencia en diversas técnicas de control. El procedimiento propuesto está basado en la sincronización adaptativa entre un oscilador y un modelo de referencia conducido por las variables de estado del oscilador. Se realiza un análisis de estabilidad y se propone un algoritmo de cálculo simplificado. Finalmente, se muestran resultados satisfactorios de simulación numérica. Palabras Clave:Control adaptativo, caos, estabilización, modelo de referencia, punto de equilibrio, sincronización, sistema dinámico. Calculation Method for Equilibrium Points in Dynamical Systems Based on Adaptive Sinchronization AbstractIn this work, a control system is proposed as an equivalent numerical procedure whose aim is to obtain the natural equilibrium points of a dynamical system. These equilibrium points may be employed later as setpoint signal for different control techniques. The proposed procedure is based on the adaptive synchronization between an oscillator and a reference model driven by the oscillator state variables. A stability analysis is carried out and a simplified algorithm is proposed. Finally, satisfactory simulation results are shown.