Search results for "VIBRATION"
showing 10 items of 823 documents
Efectos de la vibración sobre la actividad del rectus abdominis y sobre la transmisión de aceleraciones durante la realización de un puente frontal. …
2012
Durante las dos ultimas decadas se ha incrementado notablemente la utilizacion de la vibracion como medio complementario de ejercicio fisico. La literatura cientifica muestra distintos efectos positivos, aunque la mayor parte de ensayos se han centrado en el analisis del ejercicio de squat. El objetivo del presente estudio fue analizar la actividad muscular del rectus abdominis y la transmision de la vibracion en el cuerpo humano durante la realizacion de un puente frontal sobre una plataforma vibratoria oscilante vibrando a diferentes frecuencias (5, 16, 20 Hz) y a una amplitud constante (3 mm). Las aceleraciones maximas en la cabeza (ejes X, Y, Z) y la actividad electromiografica media de…
STUDY OF THE INTERNAL DYNAMICS OF NON PLANAR PYRAMIDAL MOLECULES IN VIBRATIONALY VERY EXCITED STATES.
2007
From the U (p+1) formalism, we built a Hamiltonian adapted to the stretching modes of nonplanar XY3 molecules having the C3v group of geometrical invariance. This Hamiltonian is then coupled with two possible Hamiltonians describing the bending modes of these molecular system: a) based on the U (p+1) approach, a bending Hamiltonian is developed and the interaction between the bending and the stretching modes is taking into account through adapted 2:1 resonance coupling operator defined as a Us(4) x Ub(4) enveloping algebra operator ; b) based on the standard normal modes formalism, a bending modes Hamiltonian is expanded and the 2:1 interaction is taken into account as a tensorial product o…
Identification Techniques I
2012
Infrared (IR) and Raman spectroscopy have a high potential for characterisation of material. Extensive series of wet chemical analysis may be substituted by a single spectroscopic measurement followed by detailed chemometric data evaluation. Topics of this chapter are: (i) basics of IR and Raman spectroscopy, (ii) the registration of “correct” spectra, and (iii) spectra evaluation. Dedicated applications in the area of conservation science are collected in separate chapters. The infrared (IR) spectrum is often called the fingerprint of a substance. An IR spectrum identifies a substance like a human fingerprint. Due to their origin the features of an IR spectrum are bands, not peaks. They in…
Effect of Acoustic Wave Reflections on Space Charge Measurements with PEA Method
2018
The Pulsed Electro-Acoustic (PEA) method is the most used technique for space charge detection in solid dielectrics. The methodology is largely employed in the field of High Voltage Direct Current (HVDC) transmission and is based on the detection of acoustic waves generated by charges vibration. One of the most common problems arising during the detection is the presence of multiple reflections taking place due to the presence of means discontinuity in the different PEA cell components. This reflection phenomenon, if not well taken into account, could cause incorrect interpretation of the PEA output signal. It is easy to understand that a simulation model is a basic tool to understand the w…
Evaluation of Support in Singing
2005
Summary This study searched for perceptual, acoustic, and physiological correlates of support in singing. Seven trained professional singers (four women and three men) sang repetitions of the syllable [pa:] at varying pitch and sound levels (1) habitually (with support) and (2) simulating singing without support. Estimate of subglottic pressure was obtained from oral pressure during [p]. Vocal fold vibration was registered with dual-channel electroglottography. Acoustic analyses were made on the recorded samples. All samples were also evaluated by the singers and other listeners, who were trained singers, singing students, and voice specialists without singing education (a total of 63 liste…
Passive-damping design for vibration control of large structures
2013
In this work, a systematic strategy to design passive damping systems for structural vibration control is presented. The proposed design methodology is based on the equivalence between decentralized static velocity-feedback controllers and passive damping systems. By using recent developments in static output-feedback control, the design of passivedamping systems can be formulated as a single optimization problem with Linear Matrix Inequality constraints. Moreover, this optimization problem can be efficiently solved with standard numerical tools, even for large dimension systems. Due to its computational effectiveness, the proposed methodology can be applied to the design of passive damping…
Isoelectronic series of oxygen deficient centers in silica: experimental estimation of homogeneous and inhomogeneous spectral widths
2008
We report nanosecond time-resolved photoluminescence measurements on the isoelectronic series of oxygen deficient centers in amorphous silica related to silicon, germanium and tin atoms, which are responsible of fluorescence activities at approximately 4 eV under excitation at approximately 5 eV. The dependence of the first moment of their emission band on time and that of the radiative decay lifetime on emission energy are analyzed within a theoretical model able to describe the effects introduced by disorder on the optical properties of the defects. We obtain separate estimates of the homogeneous and inhomogeneous contributions to the measured emission line width, and we derive homogeneou…
Fast response vibration sensor based on Bragg gratings written in tapered core fibres
2007
Bragg gratings written in tapered core fibres permit a direct measure of mechanical vibrations with a time response better than 10 µs. The intrinsic properties of the sensors lead to a simple interrogation technique and wavelength multiplexing capacity. The sensor system is operated at 800 nm and is compact and low-cost.
Immediate Effects of Vibration Transmitted to the Hand
1981
Summary Three different research projects have been accomplished on the problems: biomechanical behaviour of the hand-arm-system; subjective sensation; physiological changes. Some of the main results were:—the wrist and—with smaller amplifications—the elbow show resonances at low vibration frequencies (10–20 Hz);—with constant acceleration subjective perception decreases with increasing frequency;—application of static grip force—without vibration—causes significant reduction of the skin temperature, which under vibration stress remains at the same lowered level.
Discrete-time static output-feedback semi-decentralized H<inf>&#x221E;</inf> controller design: An application to structural vibratio…
2012
In this work, we present a new and effective method to design discrete-time static output-feedback H ∞ controllers. This new method, based on a Linear Matrix Inequality (LMI) formulation, introduces a suitable transformation of the LMI variables that allows to obtain an explicit expression for the output-feedback gain matrix. Moreover, for problems involving a set of subsystems with information exchange constraints, a convenient structure on the LMI variables can be imposed in order to design semi-decentralized controllers, where the corresponding output-feedback gain matrix has a prescribed zero-nonzero structure. To illustrate the proposed methodology, discrete-time static velocity-feedba…