Search results for "FREQUENCY"

The influence of the propagation path length on the results of the time–frequency analysis of the acoustic emission generated by partial discharges i…

2006

The paper presents the measurement results of the acoustic emission (AE) signals generated by partial discharges (PDs) at various thickness of the oil insulation layer. For the AE signals registered the time - frequency analysis was carried out based on the use of the short-time Fourier transform (STFT). Two- and three-dimensional spectrograms of the power spectrum density and the amplitude spectrum were determined. The evaluation of the influence of the propagation path length of the AE signal on the results of the time - frequency analysis was performed through the analysis of the spectrograms determined.

A new Frequency Domain Measure of Causality based on Partial Spectral Decomposition of Autoregressive Processes and its Application to Cardiovascular…

2019

We present a new method to quantify in the frequency domain the strength of directed interactions between linear stochastic processes. This issue is traditionally addressed by the directed coherence (DC), a popular causality measure derived from the spectral representation of vector autoregressive (AR) processes. Here, to overcome intrinsic limitations of the DC when it needs to be objectively quantified within specific frequency bands, we propose an approach based on spectral decomposition, which allows to isolate oscillatory components related to the pole representation of the vector AR process in the Z-domain. Relating the causal and non-causal power content of these components we obtain…

2021

Previous work showed that the beginning of a sound is more important for the perception of loudness than later parts. When a short silent gap of sufficient duration is inserted into a sound, this primacy effect reoccurs in the second sound part after the gap. The present study investigates whether this temporal weighting occurs independently for different frequency bands. Sounds consisting of two bandpass noises were presented in four different conditions: (1) a simultaneous gap in both bands, (2) a gap in only the lower frequency band, (3) a gap in only the higher frequency band, or (4) no gap. In all conditions, the temporal loudness weights showed a primacy effect at sound onset. For the…

Frequency comb generation in whispering gallery mode silica microsphere resonators

2021

Optical frequency combs (OFC) using different kinds of whispering-gallery-mode (WGM) microresonators have already shown different applications and especially their applications in fiber optical communication systems as replacements of laser-arrays. For this application the free spectral range (FSR) of 200 GHz or less is desirable. Besides the fabrication material for microspheres, the resonator radius can be modified to change the FSR. In this paper use of silica microspheres for OFC represents an inexpensive alternative over the other microcombs: microring, microdisk, and microtoroid. We experimentally present a microsphere fabrication process from a different kind of silica (SiO2) fibers …

Refined Sellmeier equations from phase-matching measurements over the complete transparency range of KTiOAsO4, RbTiOAsO4 and CsTiOAsO4

2000

Sum- and difference- frequency generation phasematching properties are measured in spheres of KTiOAsO4, RbTiOAsO4 and CsTiOAsO4 for Sellmeier equations refinement over their complete transparency range.

VALIDACIÓN EN CONTEXTO ESPAÑOL DE LA SUBPRUEBA DE INICIO DE LA ESCRITURA DE LA SHELL

2016

Abstract:VALIDATION IN THE SPANISH CONTEXT OF SHELL’S SUBTEST OF EMERGENT WRITING SKILLSBecause of a lack of research examining early learning skills involved in writing and, above all, the lack of tests evaluating it, the main objective of this work is the validation in the spanish context of SHELL’s subscales related to emergent writing skills. Participants were 119 students from the provinces of Castellón and Valencia, who have been evaluated when 4 years old. The administered instrument was a spanish version of the subtests related to early writing of SHELL scale in which the child has to choose between some letters, the one he needs to write some words (his/her name, “sea”, “sun”, “whi…

Development of a Taekwondo Combat Model Based on Markov Analysis

2019

The purpose of the present study was to examine male and female Olympic taekwondo competitors' movement patterns according to their tactical actions by applying a Markov processes analysis. To perform this study, 11,474 actions by male competitors and 12,980 actions by female competitors were compiled and analyzed. The results yielded 32 significant sequences among male competitors and 30 among female competitors. Male competitors demonstrated 11 sequences initiated by an attack, 11 initiated by a counterattack, and 10 initiated by a defensive action. Female competitors demonstrated nine sequences initiated by an attack, 11 initiated by a counterattack, and 10 initiated by a defensive move.…

Contextual diversity favors the learning of new words in children regardless of their comprehension skills

2021

Available online 6 November 2021 Recent research has shown the benefits of high contextual diversity, defined as the number of different contexts in which a word appears, when incidentally learning new words. These benefits have been found both in laboratory settings and in ecological settings such as the classroom during regular hours. To examine the nature of this effect in young readers aged 11–13 years, we analyzed whether these benefits are modulated by the individuals’ reading comprehension scores; that is, would better comprehenders benefit the most from contextual diversity? The manipulation of contextual diversity was done by inserting the novel words into three different contexts/…

Thermally Tunable Surface Acoustic Wave Cavities

2020

We experimentally demonstrate the dynamical tuning of the acoustic field in a surface acoustic wave (SAW) cavity defined by a periodic arrangement of metal stripes on LiNbO3 substrate. Applying a dc voltage to the ends of the metal grid results in a temperature rise due to resistive heating that changes the frequency response of the device up to 0.3%, which can be used to control the acoustic transmission through the structure. The timescale of the switching is demonstrated to be of about 200 ms. In addition, we have also performed finite-element simulations of the transmission spectrum of a model system, which exhibits a temperature dependence consistent with the experimental data. The adv…

Random vibration of linear and nonlinear structural systems with singular matrices: A frequency domain approach

2017

Abstract A frequency domain methodology is developed for stochastic response determination of multi-degree-of-freedom (MDOF) linear and nonlinear structural systems with singular matrices. This system modeling can arise when a greater than the minimum number of coordinates/DOFs is utilized, and can be advantageous, for instance, in cases of complex multibody systems where the explicit formulation of the equations of motion can be a nontrivial task. In such cases, the introduction of additional/redundant DOFs can facilitate the formulation of the equations of motion in a less labor intensive manner. Specifically, relying on the generalized matrix inverse theory, a Moore-Penrose (M-P) based f…