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A self-supplied circuit that is able to significantly increase the power delivered to a bridge rectifier by a Resonant Piezoelectric Vibration Energy Harvester (RPVEH) is presented and discussed. The proposed circuit, called the Energy Harvester Power Optimizer (EHPO), is implemented by means of a switch-mode converter that emulates a negative capacitance. Unlike switch-mode impedance emulators, based on sophisticated tracking algorithms requiring lossy microcontrollers, EHPO exploits a very light control circuit based on a hysteresis comparator. The EHPO is self-supplied since it does not need an external supply, but it draws the energy for its operation directly from the RPVEH. Moreover, it is developed without the assumption of purely sinusoidal vibrations. Experimental results show that the EHPO can significantly increase the power delivered to a rectifier, both in the case of sinusoidal vibrations (percent gain of the net extracted power up to about 190%) and non-sinusoidal vibrations (percent gain of the net extracted power up to about 245%), regardless of the shape of the forcing acceleration and regardless of the RPVEH resonance frequency.

The effective localization of damage in structural systems and components remains an active research topic in the engineering community. In contrast to damage detection, for which many alternative methods of a certain degree of functionality have already been established, damage localization is considerably more complicated and, in most cases, requires the availa- bility of redundant spatial information. The localization of the exact point where damage, once detected, exists is inherently de- pendent on the adoption of appropriate damage–sensitive features. In general, these should be selected in a way, that allows for the associated feature extraction procedure to take place in a “transformed domain”, where the initial information is significantly amplified for the location of damage. In this respect, vibration–based methods develop damage-sensitive features on the basis of the modal properties of a structure (e.g. natural frequencies, damping ratios and modal and operating shapes), or quantities that are derived from these (e.g. curvatures, flexibility, strain energy, etc.). In this work, we apply and compare the most common vibration–based criteria for damage localization, by considering a small-scale wind turbine blade as a case study (Fig.1). To this end, a 3-dimensional finite element model of the blade is utilized that consists of an exterior laminate composite surface, modelled with shell elements, and an interior foam represented by solid elements. The critical assessment ranks the efficacy of each method in terms of (i) infor- mation availability (e.g. input from all degrees of freedom vs. input from a sparse subset of nodes); (ii) various scenario of damage patterns of increasing severity; and (iii) sensitivity to noise.

AbstractNuclear vibrations play a prominent role in the spectroscopy and dynamics of electronic systems. As recent experimental and theoretical studies suggest, this may be even more so when vibrational frequencies are resonant with transitions between the electronic states. Herein, a vibronic multilevel Redfield model is reported for excitonically coupled electronic two‐level systems with a few explicitly included vibrational modes and interacting with a phonon bath. With numerical simulations the effects of the quantized vibrations on the dynamics of energy transfer and coherence in a model dimer are illustrated. The resonance between the vibrational frequency and energy gap between the sites leads to a large delocalization of vibronic states, which then results in faster energy transfer and longer‐lived mixed coherences.

Significant increase in the demand for freight and passenger transports by trains pushes the railway authorities and train companies to increase the speed, the axle load and the number of train carriages/wagons. All of these actions increase ground-borne noise and vibrations that negatively affect people who work, stay, or reside nearby the railway lines. In order to mitigate these phenomena, many techniques have been developed and studied but there is a serious lack of life-cycle information regarding such the methods in order to make a well-informed and sustainable decision. The aim of this study is to evaluate the life-cycle performance of mitigation methods that can enhance sustainability and efficacy in the railway industry. The emphasis of this study is placed on new methods for ground-borne noise and vibration mitigation including metamaterials, geosynthetics, and ground improvement. To benchmark all of these methods, identical baseline assumptions and the life-cycle analysis over 50 years have been adopted where relevant. This study also evaluates and highlights the impact of extreme climate conditions on the life-cycle cost of each method. It is found that the anti-resonator method is the most expensive methods compared with the others whilst the use of geogrids (for subgrade stiffening) is relatively reliable when used in combination with ground improvements. The adverse climate has also played a significant role in all of the methods. However, it was found that sustainable methods, which are less sensitive to extreme climate, are associated with the applications of geosynthetic materials such as geogrids, composites, etc.

Abstract Edgewise vibrations with low aerodynamic damping are of particular concern in modern multi-megawatt wind turbines, as large amplitude cyclic oscillations may significantly shorten the life-time of wind turbine components, and even lead to structural damages or failures. In this paper, a new blade design with active controllers is proposed for controlling edgewise vibrations. The control is based on a pair of actuators/active tendons mounted inside each blade, allowing a variable control force to be applied in the edgewise direction. The control forces are appropriately manipulated according to a prescribed control law. A mathematical model of the wind turbine equipped with active controllers has been formulated using an Euler–Lagrangian approach. The model describes the dynamics of edgewise vibrations considering the aerodynamic properties of the blade, variable mass and stiffness per unit length and taking into account the effect of centrifugal stiffening, gravity and the interaction between the blades and the tower. Aerodynamic loads corresponding to a combination of steady wind including the wind shear and the effect of turbulence are computed by applying the modified Blade Element Momentum (BEM) theory. Multi-Blade Coordinate (MBC) transformation is applied to an edgewise reduced order model, leading to a linear time-invariant (LTI) representation of the dynamic model. The LTI description obtained is used for the design of the active control algorithm. Linear Quadratic (LQ) regulator designed for the MBC transformed system is compared with the control synthesis performed directly on an assumed nominal representation of the time-varying system. The LQ regulator is also compared against vibration control performance using Direct Velocity Feedback (DVF). Numerical simulations have been carried out using data from a 5-MW three-bladed Horizontal-Axis Wind Turbine (HAWT) model in order to study the effectiveness of the proposed active controlled blade design in reducing edgewise vibrations. Results show that the use of the proposed control scheme significantly improves the response of the blade and promising performances can be achieved. Furthermore, under the conditions considered in this study quantitative comparisons of the LQ-based control strategies reveal that there is a marginal improvement in the performances obtained by applying the MBC transformation on the time-varying edgewise vibration model of the wind turbine.

AbstractIn this article, we described concepts for improving the shock reliability of MEMS electrostatic vibration energy harvesters. The harvester is based on silicon mass spring system supporting an electret. We determined experimentally that the primary cause of failure of the harvester under shock excitation is impact between the anchors of the springs. The impact creates chipping damages on the anchors which induces breakage of the springs. The springs are vital for proper functioning of the harvester, so that when they are broken, the device losses all its functionalities. Avoiding impact between moving parts of the harvester is difficultly feasible. However, avoiding impact on vital parts of the device is easily feasible with the use of shock absorbing bumpers. The concept of rigid bumpers is first investigated. While this approach improves the survival chances of the springs under a shock excitation, chipping damages are observed on the rigid bumpers. The residue from the chipping damages may hinder the functionality of the harvester. To limit the chances of chipping damages on the bumpers, flexible in place from rigid bumpers are investigated. By using Hertz contact model approach, it is shown that flexible bumpers allow reducing the risk of chipping damages by a factor five.

Phospholipids self-assembled into reverse micelles in benzene are introduced as a new model system to study elementary processes relevant for energy transport in hydrated biological membranes. Femtosecond vibrational spectroscopy gives insight into the dynamics of the antisymmetric phosphate stretching vibration ν(AS)(PO(2))(-), a sensitive probe of local phosphate-water interactions and energy transport. The decay of the ν(AS)(PO(2))(-) mode with a 300-fs lifetime transfers excess energy to a subgroup of phospholipid low-frequency modes, followed by redistribution among phospholipid vibrations within a few picoseconds. The latter relaxation is accelerated by adding a confined water pool, an efficient heat sink in which the excess energy induces weakening or breaking of water-water and water-phospholipid hydrogen bonds. In parallel to vibrational relaxation, resonant energy transfer between ν(AS)(PO(2))(-) oscillators delocalizes the initial excitation.

The solid-state region of the Ni-Al phase diagram is predicted from first-principles calculations and Monte Carlo simulations through the cluster expansion formalism. In addition to the formation enthalpy and to the configurational entropy, the vibrational entropy and the magnetic enthalpy are included to calculate the Gibbs free energy of each phase. The computed phase diagram is in excellent agreement with the experimentally accepted phase diagram and provides information about the phase boundary between AlNi3 and Ni below 300 K. These results demonstrate the potential of this methodology to determine accurately the phase diagram of alloys of technological interest. Finally, the contributions of vibrational entropy and magnetic effects to the overall stability and solubility of the different phases are analyzed independently This investigation was supported by the European Union’s Horizon 2020 research and innovation program through a Marie SklodowskaCurie Individual Fellowship (Grant Agreement 893883) and also by the project (MAD2D-CM)-IMDEA Materials funded by Comunidad de Madrid, by the Recovery, Transformation and Resilience Plan, and by NextGenerationEU from the European Union, as well as by the Innovation Ability Promotion Program of Hebei (22567609H). Additional support from rom the Comunidad de Madrid under the Multiannual Agreement with UC3M in the line of Excellence of University Professors (EPUC3M23), in the context of the 5th PRICIT is also acknowledged. Computer resources and technical assistance provided by the Centro de Supercomputacion ´ y Visualizacion ´ de Madrid (CeSViMa) and by the Spanish Supercomputing Network (project FI-2021–3–6) are gratefully acknowledged. Wei Shao also acknowledges the support from the China Scholarship Council