scholarly journals Development of a New Analytical Method for the Electrocardiogram Using Short-Time First Fourier Transforms

1999 ◽  
Vol 63 (12) ◽  
pp. 941-944 ◽  
Author(s):  
Masatoshi Hara ◽  
Katsuhiko Tsuchiya ◽  
Toshihiko Nanke ◽  
Narumi Mori ◽  
Fumihiko Miyake ◽  
...  
Keyword(s):  
Analytical Method ◽  
Fourier Transforms ◽  
Short Time

Identification of Static Unbalance Wheel of Passenger Car Carried out on a Road

2014 ◽  
Vol 214 ◽  
pp. 48-57 ◽  
Author(s):  
Krzysztof Prażnowski ◽  
Sebastian Brol ◽  
Andrzej Augustynowicz
Keyword(s):  
Fourier Transform ◽  
Wavelet Transform ◽  
Constant Velocity ◽  
Fourier Transforms ◽  
Static Condition ◽  
Rotational Frequency ◽  
Acceleration Sensor ◽  
Short Time Fourier Transform ◽  
Road Roughness ◽  
Short Time

This paper presents a method of identification of non-homogeneity or static unbalance of the structure of a car wheel based on a simple road test. In particular a method the detection of single wheel unbalance is proposed which applies an acceleration sensor fixed on windscreen. It measures accelerations cause by wheel unbalance among other parameters. The location of the sensor is convenient for handling an autonomous device used for diagnostic purposes. Unfortunately, its mounting point is located away from wheels. Moreover, the unbalance forces created by wheels spin are dumped by suspension elements as well as the chassis itself. It indicates that unbalance acceleration will be weak in comparison to other signals coming from engine vibrations, road roughness and environmental effects. Therefore, the static unbalance detection in the standard way is considered problematic and difficult. The goal of the undertaken research is to select appropriate transformations and procedures in order to determine wheel unbalance in these conditions. In this investigation regular and short time Fourier transform were used as well as wavelet transform. It was found that the use of Fourier transforms is appropriate for static condition (constant velocity) but the results proves that the wavelet transform is more suitable for diagnostic purposes because of its ability of producing clearer output even if car is in the state of acceleration or deceleration. Moreover it was proved that in the acceleration spectrum of acceleration measured on the windscreen a significant peak can be found when car runs with an unbalanced wheel. Moreover its frequency depends on wheel rotational frequency. For that reason the diagnostic of single wheel unbalance can be made by applying this method.

Independent component analysis of short-time Fourier transforms for spontaneous EEG/MEG analysis

NeuroImage ◽  
2010 ◽  
Vol 49 (1) ◽  
pp. 257-271 ◽  
Author(s):  
Aapo Hyvärinen ◽  
Pavan Ramkumar ◽  
Lauri Parkkonen ◽  
Riitta Hari
Keyword(s):  
Independent Component Analysis ◽  
Fourier Transforms ◽  
Component Analysis ◽  
Independent Component ◽  
Short Time

DETECTING NONLINEAR AND NONSTATIONARY PROPERTIES OF POST-APNEIC SNORING SOUNDS USING HILBERT–HUANG TRANSFORM

2019 ◽  
Vol 31 (03) ◽  
pp. 1950017
Author(s):  
Tsuyoshi Mikami ◽  
Hirotaka Takahashi ◽  
Kazuya Yonezawa
Keyword(s):  
Soft Tissues ◽  
Fourier Transforms ◽  
Sleep Apnea Syndrome ◽  
Hilbert Huang Transform ◽  
Time Frequency ◽  
Obstructive Sleep ◽  
Leibler Divergence ◽  
The Difference ◽  
Frequency Map ◽  
Short Time

This study focuses on patients with severe obstructive sleep apnea syndrome (OSAS), and clarifies the existence of nonlinear and nonstationary properties in post-apneic snoring sounds. Many researchers have tried to discover intrinsic properties of the snoring sounds in OSAS patients for the past decades using linear frequency analysis, but no one has shown any evidence of the existence of nonlinearity and nonstationarity based on the quantitative evaluation of the post-apneic snoring sounds. In this study, Hilbert–Huang transform (HHT), which is designed for analyzing nonlinear and nonstationary signals, is adopted to generate a time-frequency map and the temporal variation in the spectral density is quantitatively evaluated using the averaged Kullback–Leibler divergence (AKL). As a result, for six OSAS patients, there is a tendency that most of AKL calculated from post-apneic snores are higher than those from non-apneic snores, which indicates that post-apneic snores are more nonstationary. In addition, we also evaluated the difference between the HHT time-frequency maps and spectrograms using short-time fourier transforms (STFT). Such analyses revealed that frequency fluctuations inherent to snoring can be adequately represented through HHT, but not with STFT. These nonlinear and nonstationary properties seem to be highly related to the physiological phenomena of OSAS, two of which are the explosive airflow after reopening of the closed airway and the collision vibration of the soft tissues.

scholarly journals Functional Application of G-Functions of Lorenzo and Hartley on the Free Convection Flow of Oldroyd-B Fluid with Ordinary and Fractional Techniques

Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Imran Siddique ◽  
Sehrish Ayaz ◽  
Dalal Alrowaili ◽  
Sohaib Abdal
Keyword(s):  
Free Convection ◽  
Fourier Transforms ◽  
Special Functions ◽  
Rectangular Channel ◽  
Convection Flow ◽  
Physical Parameters ◽  
Free Convection Flow ◽  
Closed Form Solutions ◽  
Generalized Boundary Conditions ◽  
Short Time

In this article, free convection flow of an Oldroyd-B fluid (OBF) through a vertical rectangular channel in the presence of heat generation or absorption subject to generalized boundary conditions is studied. The fractionalized mathematical model is established by Caputo time-fractional derivative through mechanical laws (generalized shear stress constitutive equation and generalized Fourier’s law). Closed form solutions for the velocity and temperature profiles are obtained via Laplace coupled with sine-Fourier transforms and have been embedded with regards to the special functions, namely, the generalized G-functions of Lorenzo and Hartley. Solutions of the known results from recently published work (Nehad et al. Chin. J. Phy., 65, (2020) 367–376) are recovered as limiting cases. Finally, the effects of fractional and various physical parameters are graphically underlined. Furthermore, a comparison between Oldroyd-B, Maxwell and viscous fluids (fractional and ordinary) is depicted. It is found that, for short time, ordinary fluids have greater velocity as compared to the fractional fluids.

scholarly journals STUDY OF TIME FREQUENCY TRANSFORMS APPLIED TO POWER QUALITY SIGNALS

2020 ◽  
Vol 5 (2) ◽  
Author(s):  
Richard Bini Almeida ◽  
Kenji Watanabe ◽  
Silvia Mara da Costa Campos Victer
Keyword(s):  
Power Quality ◽  
Fourier Transforms ◽  
Spectral Content ◽  
Time Frequency ◽  
Quality Signals ◽  
S Transform ◽  
C Programming ◽  
The Fourier Transform ◽  
Short Time ◽  
Over Time

This work presents a scientific study on Short-Time Frequency Transforms (STFT) with different windows, also called Windowed Fourier Transforms, applied to power quality signals.   Additionally, it deals with S transforms, with its frequency-dependent window.  The disturbances related to energy quality have non-stationary nature, in which the spectral content varies over time.   So, the Fourier Transform is not appropriate for such analysis, because it doesn’t show time locations, only information about existing frequencies in the signal.  Therefore, the spectral analysis by windowed transforms helps to identify and detect a series of defects associated to these power signals.  The motivation behind this document is to verify which window will provide a more precise identification of the characteristics of the disturbances in time-frequency domain.    For this work, synthetic signals were generated for some of these disturbances, and their spectra were compared considering Gaussian, Hann and Blackman windows, as well as the S transform. Based on the obtained results, it was verified that each transform presents different behaviours acording to the input signal,  except for the ones with Hann and Blackman windows, that showed similar spectra. For all of them, there is always a tradeoff between time and frequency resolutions. Therefore, the choice of the window must be done according to the desired outputs.  The Dev-C ++ ® IDE was used for C ++ programming, and the Gnuplot ® program for graphics generation.

Heart Sound Monitor for Biomedical Instrumentation

2013 ◽  
Vol 303-306 ◽  
pp. 650-653
Author(s):  
Sirimonpak Sutdipong ◽  
Khanchai Tunlasakun
Keyword(s):  
Fourier Transforms ◽  
Heart Sound ◽  
Digital Signal ◽  
Electrical Signal ◽  
Sound Card ◽  
Sound Processing ◽  
Biomedical Instrumentation ◽  
Condenser Microphone ◽  
Processing Program ◽  
Short Time

This research presents the design and development of the heart sound monitor for biomedical instrumentation which can be worked with a personal computer. The prototype will receive the heart sound via the condenser microphone built-in the stethoscope. The condenser microphone will be conversed the air pressure from heart beats to electrical signal that signal will transformed to computer via sound card. The sound card will be conversed the analog signal to digital signal for process by heart sound processing program developed by LabVIEW program. The signal will be analyzed with short time Fourier transforms in heart sound processing program by graphical user interface. The user is able to select a band pass of signal for filter and choose the frequency spectrum of heart sound for display. The output database from this prototype is necessary for Medical Education or Clinical Practice.

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