Low-Frequency and High-Frequency Moving Anharmonic Localized Modes in a One-Dimensional Lattice with Quartic Anharmonicity

1992 ◽  
Vol 61 (12) ◽  
pp. 4263-4266 ◽  
Author(s):  
Kazunari Hori ◽  
Shozo Takeno
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Localized Modes ◽  
Dimensional Lattice ◽  
One Dimensional ◽  
Quartic Anharmonicity

scholarly journals Temperature oscillation in one-dimensional superlattice induced by phonon localization

2021 ◽  
Author(s):  
Longkai Lu ◽  
Dengke Ma ◽  
Ming Zhong ◽  
Lifa Zhang
Keyword(s):  
Temperature Gradient ◽  
High Frequency ◽  
Temperature Oscillation ◽  
Thermodynamic Quantities ◽  
Localized Modes ◽  
One Dimensional ◽  
Oscillation Phenomenon ◽  
Low Dimensional ◽  
Phonon Localization ◽  
Good Agreement

Abstract Thermal transport properties and thermodynamic quantities often present anomalous behaviors in low-dimensional systems. In this paper, we find that temperature oscillates spatially in one dimensional harmonic and weakly anharmonic superlattice. With the increase of anharmonicity, the temperature oscillation gradually disappears and a normal temperature gradient forms. Further analysis reveals that the formation of temperature oscillation is due to the localization of high frequency phonons which cannot be thermalized. Moreover, the localized modes interact weakly with heat reservoirs, thus, their contributions to local temperature remain negligible while varying the temperatures of heat reservoirs. The oscillated temperature profile is in a good agreement with Visscher's formula. These discoveries of temperature oscillation phenomenon have great potential in applications of phononic devices for heat manipulation.

scholarly journals ABOUT CLASSIFICATION OF ECG SIGNALS BASED ON HIGH-FREQUENCY WAVELET COMPONENTS

2016 ◽  
pp. 63-71
Author(s):  
Paulina Podkur ◽  
Paulina Podkur ◽  
Nikolay Smolentsev ◽  
Nikolay Smolentsev
Keyword(s):  
Myocardial Infarction ◽  
High Frequency ◽  
Wavelet Decomposition ◽  
Low Frequency ◽  
Feature Space ◽  
Frequency Component ◽  
High Frequency Component ◽  
Ecg Signal ◽  
One Dimensional ◽  
Frequency Components

The new design method of the automated classifying system for electrocardiograms recognition (ECG) of healthy and ill patients, based only on high-frequency components of ECG signal with the use of statistical images recognition is offered. Cardiograms of two groups of patients were studied: healthy and those who came through myocardial infarction. The first step of classification method is ECG wavelet decomposition to the 4th level and allocation of four high-frequency ECG components. The choice of the 4th decomposing level is explained by the fact that the first four high-frequency components represent high ECG frequencies from 30 to 350 Hz, and low-frequency component represents the undistorted smoothed ECG signal cleared of high-frequency oscillations. In case of more deep signal expansion the following high-frequency component has frequency spectrum to 30 Hz, and low frequency component is significantly distorted. For each of the first four components of wavelet decomposition there is a number of ECG numerical signs, including energy, entropy and frequency characteristics, 21 signs in total. During the second step reduction of the dimensionality of the feature space by using scatter matrix is made for two chosen ECG groups. It has turned out that the reduced feature space is one-dimensional. Histograms of values of this one-dimensional feature for groups of healthy and ill patients are constructed. The third step is finding of the dividing constant which is able to distinguish both groups of ECG records. For testing 96 ECG records of patients with normal cardiograms and 120 ECG records of the patients who came through myocardial infarction are used. Only three features (3%) of 96 given features values of the first group are referred by the classifier to patients group and only 20 features (< 17%) of 120 given features values of the second patients group are referred by the classifier to ECG group of healthy patients. Considering that for each patient the system determines 12 features by 12 standard assignments, testing results show well classification accuracy.

scholarly journals Nonlinear Behaviour of Concrete Buttress Dams under High-Frequency Excitations Taking into Account Topographical Amplifications

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Roghayeh Abbasiverki ◽  
Richard Malm ◽  
Anders Ansell ◽  
Erik Nordström
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
High Frequency ◽  
Free Field ◽  
Low Frequency ◽  
Nonlinear Behaviour ◽  
One Dimensional ◽  
Field Modelling ◽  
Stream Direction ◽  
Modelling Approach

Concrete buttress dams could potentially be susceptible to high-frequency vibrations, especially in the cross-stream direction, due to their slender design. Previous studies have mainly focused on low-frequency vibrations in stream direction using a simplified foundation model with the massless method, which does not consider topographic amplifications. This paper therefore investigates the nonlinear behaviour of concrete buttress dams subjected to high-frequency excitations, considering cross-stream vibrations. For comparison, the effect of low-frequency excitations is also investigated. The influence of the irregular topography of the foundation surface on the amplification of seismic waves at the foundation surface and thus in the dam is considered by a rigorous method based on the domain-reduction method using the direct finite element method. The sensitivity of the calculated response of the dam to the free-field modelling approach is investigated by comparing the result with analyses using an analytical method based on one-dimensional wave propagation theory and a massless approach. Available deconvolution software is based on the one-dimensional shear wave propagation to transform the earthquake motion from the foundation surface to the corresponding input motion at depth. Here, a new deconvolution method for both shear and pressure wave propagation is developed based on an iterative time-domain procedure using a one-dimensional finite element column. The examples presented showed that topographic amplifications of high-frequency excitations have a significant impact on the response of this type of dam. Cross-stream vibrations reduced the safety of the dam due to the opening of the joints and the increasing stresses. The foundation modelling approach had a significant impact on the calculated response of the dam. The massless method produced unreliable results, especially for high-frequency excitations. The free-field modelling with the analytical method led to unreliable joint openings. It is therefore recommended to use an accurate approach for foundation modelling, especially in cases where nonlinearity is considered.

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