Search

Copyright of Bulletin of Volcanology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a modification is proposed in the conventional finite control set model predictive controller (FCS-MPC) applied in the three-phase voltage source inverter's (VSI's) output current control with resistive-inductive (RL) load. It comprises the introduction of the novel type of hysteresis-based comparator in the cost function evaluation implemented with a single-step prediction horizon, which represents an improvement when compared to existing solutions. In this way, effective reduction of the VSI output voltage high switching frequency is achieved, by implementing a simplified predictive current control algorithm. Also, an effective disturbance estimator algorithm is proposed, which enables the operation of a hysteresis FCS-MPC with RL load and with unmeasurable external disturbances. Simulation and experimental tests are used in the paper to prove the effectiveness of the proposed solution, showing the extent of the impact that the chosen cost evaluation comparator hysteresis value has on the resulting average power converter switching frequency, for the model predictive control current controller operating with the zero steady-state error. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Volcanology is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work proposes a new method to probe the hidden magmatic evolution of quiescent Andean volcanoes from the Pb isotope composition of gases. The method is based on an assimilation-fractional crystallisation-degassing model linking the Pb isotope composition of gases with the SiO2 content of their magmatic source. The model is applied to El Misti volcano that threatens Arequipa, the second most densely populated city of Peru. Gas condensates and Pb-rich solid deposits (PbS, PbCl2, PbSO4) collected in 2018 in the bottom of El Misti crater at 260–150°C fumarole vents were used to reconstruct the mean composition of degassing magmas (60.8–61.8 wt% SiO2). These compositions are slightly more evolved than the lavas from the last AD 1440–1470 eruption, suggesting either the secular differentiation of the main magma reservoir, or the contribution of more evolved magmas to volcanic gases. On the other hand, the slight but significant difference between the instantaneous composition recorded in gas condensates and the time-integrated composition recorded in solid deposits points to the degassing of less evolved magmas over the last decades. This trend is ascribed to a recent recharge of El Misti reservoir with hot mafic magmas, in agreement with the evolution of fumarolic deposit mineralogy in the last half a century. The Pb isotope composition of gas appears to be a promising tool for probing the hidden magmatic evolution of quiescent volcanoes where assimilation-fractional crystallisation operates. [ABSTRACT FROM AUTHOR]

In this paper, we report experimental results showing the generation of rotational motion in a non-autonomous Mercury Beating Heart system. Using an electrochemical cell under potentiostatic conditions, a traveling chemomechanical wave can be created on the periphery of the surface of a mercury drop, placed on a concave glass surface, and completely immersed in an acidic media. Due to the spherical geometry of the container, this chemomechanical wave deforms continuously the surface of the drop to induce a variety of rotatory dynamics with different topological structures. In the present study, the applied potential was systematically varied to observe the different dynamical structures. Since the time series of the generated current does not provide useful information, the corresponding image analysis of the bidimensional projection of the surface of the drop was performed in order to verify the existence of the traveling waves. [ABSTRACT FROM AUTHOR]

This study proposes a finite-state model predictive controller to regulate the load current and balance the DC-link capacitor voltages of a four-leg neutral-point-clamped converter. The discrete-time model of the converter, DC-link, inductive filter, and load is used to predict the future behavior of the load currents and the DC-link capacitor voltages for all possible switching states. The switching state that minimizes the cost function is selected and directly applied to the converter. The cost function is defined to minimize the error between the predicted load currents and their references, as well as to balance the DC-link capacitor voltages. Moreover, the current regulation performance is improved by using a two-step prediction horizon. The feasibility of the proposed predictive control scheme for different references and loads is verified through real-time implementation on the basis of dSPACEDS1103. [ABSTRACT FROM AUTHOR]

The growth dynamics of bacterial populations are usually represented by the classical S-shaped profiles composed of lag, exponential and stationary growth phases. Although exceptions to this classical behavior occur, they are normally produced under non-standard conditions such as supply of two carbohydrates as sole carbon source. However, we here report variations in the classic S-shaped growth profiles of Escherichia coli under standard culturing conditions; explicitly, we found growth during transition to the stationary phase wherein the bacterial growth rate inversely depended on the volume-to-surface ratio of cultures ( V/ S); the reasons for this behavior were experimentally explored. To complement our experimental analysis, a theoretical model that rationalizes the bacterial response was developed; simulations based on the developed model essentially reproduced experimental growth curves. We consequently conclude that the effect of V/ S on E. coli growth reflects an interplay between auto-catalytic bacterial growth, bacterial growth auto-inhibition, and, the relief of that inhibition. [ABSTRACT FROM AUTHOR]

In this paper, different methods for cessation of oscillations in a chemo-mechanical oscillator [mercury beating heart (MBH)] are presented. The first set of experiments were carried out on a single MBH oscillator. To achieve cessation of oscillations, two protocols, namely, inverted feedback and delayed feedback were employed. In the second set of experiments, two quasi-identical MBH oscillators are considered. They are first synchronized via a bidirectional attractive coupling. These two synchronized oscillators are thereafter coupled with a unidirectional repulsive coupling and the system dynamics were observed. Subsequently, in the next protocol, the effect of a unidirectional delay coupling on the two synchronized oscillators was explored. The cessation of oscillations in all the above experimental setups was observed as the feedback/coupling was switched on at a suitable strength. Oscillatory dynamics of the system were restored when the feedback/coupling was switched off. [ABSTRACT FROM AUTHOR]