1,721,168 research outputs found
Morello (Giovanni) Pieri (Francesco) éds Documenti pontifici sullo scautismo
No full textDurand Jean-Dominique. Morello (Giovanni) Pieri (Francesco) éds Documenti pontifici sullo scautismo. In: Archives de sciences sociales des religions, n°86, 1994. p. 325
Morello (Giovanni) Pieri (Francesco) éds Documenti pontifici sullo scautismo
No full textDurand Jean-Dominique. Morello (Giovanni) Pieri (Francesco) éds Documenti pontifici sullo scautismo. In: Archives de sciences sociales des religions, n°86, 1994. p. 325
Geometric optimization of magnetically actuated MEMS micromirrors
Full text linkIn this paper we develop a set of self-consistent equations describing the static and resonance characteristics of a rectangular micromirror actuated by driving a current into a multicoil inductor fabricated on the micromirror surface. Under fairly general assumptions, these equations can be solved analytically for the most common design targets, such as the driving current, deflection angle, resonance frequency, and overall dimensions. We use this solutions to optimize the micromirror geometry by minimization of a linear objective function. The tradeoffs that emerge from optimization data allow simple quantitative design of low current, low size mirrors
A transmission line model for the calculation of phononic band gaps in perforated mems structures
No full textAbstractIn this paper an acoustic transmission line model for the calculation of phononic band gaps is presented. We study the propagation of longitudinal waves in thin, rectangular perforated rods. We show that the 1D nature of the rod vibrations allows the modeling of the system by a series of acoustic transmission lines with different characteristic impedance, where the perforated section is modeled as an equivalent filled material with Young's modulus and mass density depending from the size of the holes. Once this model is defined, the derivation of the transmission matrix and transmission coefficient (in matching conditions) of the entire rod is straightforward by using the classical transmission line theory. Finally, the phononic band gap predicted by this model is verified by means of an ANSYS harmonic analysis
Design of Piezo-Actuated MEMS Flexural Phononic Crystals for Mass Sensing Applications
Full text linkIn this work, we present a method for the design of piezoelectrically actuated flexural phono-nic crystal beam devices, targeted at the development of innovative biochemical sensors in a MEMS technology. The method exploits the Timoshenko transmission matrices. The calcu-lated transmission spectra are shown to be in excellent agreement with FEM simulations
An analytical model for the resonance frequency of square perforated Lamé-mode resonators
Full text linkIn this work, simple analytical models based on the concept of an equivalent material are used to describe the mechanical behavior of resonators perforated by a regular array of square holes, a common occurrence in several MEMS devices and sensors. This description is applied to the determination of the resonance frequency of Lamé-mode square resonators, which are frequently pursued as high-Q MEMS resonators. The models predictions are compared with FEM simulations and experimental data both from the literature and from measurements obtained by the authors on thick SOI MEMS resonators. The models predictions are in good accordance both with FEM results and with experimental data
An analytical model for the determination of resonance frequencies of perforated beams
No full textIn this paper, we develop closed expressions for the equivalent bending and shear stiffness of beams with regular square perforations, and apply them to the problem of determining the resonance frequencies of slender, regularly perforated clamped–clamped beams, which are of interest in the development of MEMS resonant devices. We prove that, depending on the perforation size, the Euler–Bernoulli equation or the more complex shear equation needs to be used to obtain accurate values for these frequencies. Extensive finite element method simulations are used to validate the proposed model over the full practical range of possible hole sizes. An experimental verification of the model is also presented
A refined model for piezoelectric composite beams
Full text linkThis work presents and compares few simple one-dimensional models for the piezoelectric actuation and detection of beams. The 1D nature, which allows an easy embedding of the model in the classical Euler-Bernoulli beam equations, is obtained by adopting simplifying assumptions along directions of the cross-sectional plane. By changing such assumptions, different models can be built. Their validity is discussed and compared with results of FEM simulations for varying geometries. We show that commonly adopted models fail in a series of practical cases and propose a new model capable of accurately describing wide beams
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