Resonance | EPFL Graph Search

Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscillating force is applied at a resonant frequency of a dynamic system, the system will oscillate at a higher amplitude than when the same force is applied at other, non-resonant frequencies. Frequencies at which the response amplitude is a relative maximum are also known as resonant frequencies or resonance frequencies of the system. Small periodic forces that are near a resonant frequency of the system have the ability to produce large amplitude oscillations in the system due to the storage of vibrational energy. Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, orbital resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of

An Efficient Piezoelectric Energy Harvesting Interface Circuit Using a Sense-and-Set Rectifier

Yimai Peng

Piezoelectric energy harvesters (PEHs) are widely deployed in many self-sustaining systems, and proper rectifier circuits can significantly improve the energy conversion efficiency and, thus, increase the harvested energy. Various active rectifiers have been proposed in the past decade, such as synchronized switch harvesting on inductor (SSHI) and synchronous electric charge extraction (SECE). This article presents a sense-andset (SaS) rectifier that achieves maximum-power-point-tracking (MPPT) of PEHs and maintains optimal energy extraction for different input excitation levels and output voltages. The proposed circuit is fabricated in the 0.18-μm CMOS process with a 0.47-mm 2 core area, a 230-nW active power, and a 7-nW leakage power. Measured with a commercial PEH device (Mide PPA-1022) at 85and 60-Hz vibration frequency, the proposed circuit shows 512% and 541% power extraction improvement [figure of merit (FoM)] compared with an ideal full-bridge rectifier (FBR) for ON-resonance and OFF-resonance vibrations, respectively, while maintaining high efficiency across different input levels and PEH parameters.

IEEE2019

FIRST RESULTS OF SPACE CHARGE SIMULATIONS FOR THE NOVEL MULTI-TURN INJECTION

Matthieu George

Recently, a novelmulti-turn injection technique was proposed. It is based on beam merging via resonance crossing. The various beamlets are successively injected and merged back by crossing a stable resonance generated by non-linear magnetic fields. Space charge is usually a crucial effect at injection in a circular machine and it could have an adverse impact on the phase space topology required for merging the various beamlets. Numerical simulations were performed to assess the stability of the merging process as a function of injected beam charge. The results are presented and discussed in this paper.

2010

Focused electron- and ion-beam induced processes

Vinzenz Friedli

Focused electron- and ion-beam induced processing are well established techniques for local deposition and etching that rely on decomposition of precursor molecules by irradiation. These high-resolution nanostructuring techniques have various applications in nanoscience including attach-and-release procedures in nanomanipulation and fabrication of sensors (magnetic, optical and thermal) for scanning probe microscopy. However, a complete physical and chemical understanding of the process is hampered by the lack of suitable means to monitor and to access the numerous interrelated and time-varying process parameters (deposition and etch rate, yield, molecule flux and adsorption/desorption). This thesis is a first attempt to fill this gap. It is based on experimental and simulative approaches for the determination of process conditions and mechanical properties of deposited materials: Mass and force sensors: The use of tools merging micromechanical cantilever sensors and scanning electron microscopy was demonstrated for in situ monitoring and analysis. A cantilever-based resonant mass sensing setup was developed and used for real-time mass measurements. A noise level at the femtogram-scale was achieved by tracking the resonance frequency of a temperature stabilized piezoresistive cantilever using phase-locking. With this technique the surface coverage and residence time of (CH3)3PtCpCH3 molecules, the mass deposition rate, the yield, and the material density of corresponding deposits were measured. In situ cantilever-based static force sensing and mechanical modal vibration analysis were employed to investigate the Young's modulus and density of individual high aspect ratio deposits from the precursor Cu(hfac)2. Precursor supply simulations and experiments: A prerequisite to understand and quantify irradiative precursor chemistry is the knowledge of the local flux of molecules impinging on the substrate. Therefore, Monte Carlo simulations of flux distributions were developed and gas flows injected into a vacuum chamber were analyzed experimentally for the precursors Co2(CO)8, (hfac)CuVTMS, and [(PF3)2RhCl]2. The process parameters extracted from the mentioned approaches are valuable input for numerical focused electron- and ion-beam induced process models (Monte Carlo, continuum). We evaluated the precursor surface diffusion coefficient and the electron impact dissociation cross-section by relating deposit shapes to a continuum model.

EPFL2008

Focused electron- and ion-beam induced processes

Vinzenz Friedli

EPFL2008