scholarly journals Reconstruction of Simulated Cylindrical Defects in Acrylic Glass Plate Using Pulsed Phase Thermography

2019 ◽  
Vol 9 (9) ◽  
pp. 1854
Author(s):  
Ljubiša Tomić ◽  
Vesna Damnjanović ◽  
Goran Dikić ◽  
Bojan Milanović
Keyword(s):  
Glass Plate ◽  
Intensity Variation ◽  
Basic Sequence ◽  
Fast Fourier Transformation ◽  
Pixel Intensity ◽  
Thermal Images ◽  
Acrylic Glass ◽  
Pulsed Phase Thermography ◽  
The Time Domain ◽  
Second Procedure

The results of testing of acrylic glass, in which cylindrical defects were simulated at different depths by applying Pulsed Phase Thermography, are presented in the paper. To ensure better visibility of the simulated defects, suitable thermal images were selected and then processed by using two different procedures. In the first procedure, reduced thermal image sequences were generated by uniform extraction from the basic sequence, to enable analysis at different sampling frequencies. The second procedure was based on the application of a window function, which ensured that only uniformly selected thermal images took part in the evaluation of the basic sequence. The remaining thermal images were not used, but they did participate in the determination of the length of the analyzed sequence; in other words, their existence was registered through the number of samples used in Fast Fourier Transformation. The second procedure yielded much better results with regard to the estimation of the shape of a defect and the depth at which it was located. To provide better insight into the development of the thermal process in the defect area, an additional analysis of pixel intensity variation in the time domain was undertaken.

A simple approach to determine the polarization coefficient at synchrotron radiation stations

2014 ◽  
Vol 47 (4) ◽  
pp. 1449-1451 ◽  
Author(s):  
Sergei Sulyanov ◽  
Pavel Dorovatovskii ◽  
Hans Boysen
Keyword(s):  
Synchrotron Radiation ◽  
Simple Procedure ◽  
Glass Plate ◽  
Intensity Variation ◽  
Incident Beam ◽  
Azimuth Angle ◽  
Area Detector ◽  
Ccd Detector ◽  
Diffraction Angle ◽  
Polarization Coefficient

A simple procedure for the measurement of the degree of linear polarization at a synchrotron radiation station is described. The diffraction pattern from a glass plate set perpendicular to the incident beam is registered using a two-dimensional area detector. The intensity variation along the azimuth angle ρ at a constant diffraction angle is fitted to the theoretical cos2ρ dependence. The results of measurements performed at a synchrotron radiation station with a CCD detector on the beam from a bending magnet are presented.

Generation of Wave-Field Time Histories by the Modulated Discrete Fourier Transformation

2003 ◽  
Author(s):  
Yousun Li
Keyword(s):  
Wave Field ◽  
Fourier Transformation ◽  
Time Instant ◽  
Discrete Fourier Transformation ◽  
Fast Fourier Transformation ◽  
Structural Members ◽  
Random Waves ◽  
Offshore Structure ◽  
Time Histories ◽  
The Time Domain

In the time domain simulation of the response of an offshore structure under random waves, the time histories of the wave field should be generated as the input to the dynamic equations. Herein the wave field is the wave surface elevation, the water particle velocities and accelerations at structural members. The generated time histories should be able to match the given wave-field spectral descriptions, to trace the structural member motions if it is a compliant offshore structure, and be numerically efficient. Most frequently used generation methods are the direct summation of a limited number of cosine functions, the Fast Fourier Transformation, and the digital filtering model. However, none of them can really satisfy all the above requirements. A novel technique, called the Modulated Discrete Fourier Transformation, has been developed. Under this method, the wave time histories at each time instant is a summation of a few time-varying complex functions. The simulated time histories have continuous spectral density functions, and the motions of the structural members are well included. This method seems to be superior to all the conventional methods in terms of the above mentioned three requirements.

scholarly journals Nearshore Wave Transformation Domains from Video Imagery

2019 ◽  
Vol 7 (6) ◽  
pp. 186 ◽  
Author(s):  
Umberto Andriolo
Keyword(s):  
Sediment Transport ◽  
Intensity Variation ◽  
Wave Transformation ◽  
Physical Processes ◽  
Pixel Intensity ◽  
Wave Characteristics ◽  
Wide Range ◽  
Different Types ◽  
Propagation Properties ◽  
Wave Properties

Within the nearshore area, three wave transformation domains can be distinguished based on the wave properties: shoaling, surf, and swash zones. The identification of these distinct areas is relevant for understanding nearshore wave propagation properties and physical processes, as these zones can be related, for instance, to different types of sediment transport. This work presents a technique to automatically retrieve the nearshore wave transformation domains from images taken by coastal video monitoring stations. The technique exploits the pixel intensity variation of image acquisitions, and relates the pixel properties to the distinct wave characteristics. This allows the automated description of spatial and temporal extent of shoaling, surf, and swash zones. The methodology was proven to be robust, and capable of spotting the three distinct zones within the nearshore, both cross-shore and along-shore dimensions. The method can support a wide range of coastal studies, such as nearshore hydrodynamics and sediment transport. It can also allow a faster and improved application of existing video-based techniques for wave breaking height and depth-inversion, among others.

scholarly journals Confirmation of Thermal Images and Vibration Signals for Intelligent Machine Fault Diagnostics

2012 ◽  
Vol 2012 ◽  
pp. 1-10 ◽  
Author(s):  
Achmad Widodo ◽  
Djoeli Satrijo ◽  
Toni Prahasto ◽  
Gang-Min Lim ◽  
Byeong-Keun Choi
Keyword(s):  
Vibration Signal ◽  
Rolling Element Bearing ◽  
Self Organizing Map ◽  
Fault Diagnostics ◽  
Vibration Signals ◽  
Thermal Images ◽  
Outer Race ◽  
Intelligent Machine ◽  
Machine Fault ◽  
The Time Domain

This paper deals with the maintenance technique for industrial machinery using the artificial neural network so-called self-organizing map (SOM). The aim of this work is to develop intelligent maintenance system for machinery based on an alternative way, namely, thermal images instead of vibration signals. SOM is selected due to its simplicity and is categorized as an unsupervised algorithm. Following the SOM training, machine fault diagnostics is performed by using the pattern recognition technique of machine conditions. The data used in this work are thermal images and vibration signals, which were acquired from machine fault simulator (MFS). It is a reliable tool and is able to simulate several conditions of faulty machine such as unbalance, misalignment, looseness, and rolling element bearing faults (outer race, inner race, ball, and cage defects). Data acquisition were conducted simultaneously by infrared thermography camera and vibration sensors installed in the MFS. The experimental data are presented as thermal image and vibration signal in the time domain. Feature extraction was carried out to obtain salient features sensitive to machine conditions from thermal images and vibration signals. These features are then used to train the SOM for intelligent machine diagnostics process. The results show that SOM can perform intelligent fault diagnostics with plausible accuracies.

scholarly journals An illustration of harmonic regression based on the results of the fast Fourier transformation

2002 ◽  
Vol 12 (2) ◽  
pp. 185-202 ◽  
Author(s):  
Imre Bertfai
Keyword(s):  
Time Series ◽  
Fourier Analysis ◽  
Fourier Transformation ◽  
Point Of View ◽  
Fast Fourier Transformation ◽  
Harmonic Model ◽  
Additional Advantage ◽  
Starting Point ◽  
Harmonic Regression ◽  
The Time Domain

The well-known methodology of the Fourier analysis is put against the background in the 2nd half of the century parallel to the development of the time-domain approach in the analysis of mainly economical time series. However, from the author's point of view, the former possesses some hidden analytical advantages which deserve to be re-introduced to the toolbox of analysts. This paper, through several case studies, reports research results for computer algorithm providing a harmonic model for time series. The starting point of the particular method is a harmonic analysis (Fourier-analysis or Lomb-periodogram). The results are optimized in a multifold manner resulting in a model which is easy to handle and able to forecast the underlying data. The results provided are particularly free from limitations characteristic for that methods. Furthermore, the calculated results are easy to interpret and use for further decisions. Nevertheless, the author intends to enhance the procedure in several ways. The method shown seems to be very effective and useful in modeling time series consisting of periodic terms. An additional advantage is the easy interpretation of the obtained parameters.

scholarly journals Fault Diagnosis and Tolerant Control of Three-Level Neutral-Point Clamped Inverters in Motor Drives

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6302
Author(s):  
Kuei-Hsiang Chao ◽  
Chen-Hou Ke
Keyword(s):  
Fault Diagnosis ◽  
Fault Tolerant ◽  
Fault Tolerant Control ◽  
Assessment Method ◽  
Neutral Point ◽  
Fast Fourier Transformation ◽  
Diagnosis System ◽  
Power Transistors ◽  
Fault Diagnosis System ◽  
The Time Domain

This paper presents an extension theory-based assessment method to perform fault diagnosis for inverters in motor driving systems. First, a three-level neutral-point clamped (NPC) inverter is created using the PSIM software package to simulate faults for any power transistor in the NPC-type inverter. Fast Fourier transformation is used to transform the line current signals in the time domain into a spectrum in the frequency domain for analysis of the corresponding spectrum of features of the inverter for faults with different power transistors. Then, the relationships between fault types and specific spectra are established as characteristics for the extension assessment method, which is then used to create a smart fault diagnosis system for inverters. Fault-tolerant control (FTC) is used here when the rated output of a faulty inverter is decreased in order to maintain balanced output in three phases by changing the framework of the transistor connection. This is performed to reinforce the reliability of the inverter. Finally, by the simulation and experimental results, the feasibility of the proposed smart fault diagnosis system is confirmed. The proposed fault diagnosis method is advantageous due to its minimal use of data and lack of a learning process, which thereby reduces the fault diagnosis time and makes the method easily used in practice. The proposed fault-tolerant control strategy allows both online and smooth switching in the wiring structure of the inverter.

A Finite Element Tire Model and Vibration Analysis: A New Approach

1998 ◽  
Vol 26 (3) ◽  
pp. 149-172 ◽  
Author(s):  
Y. Zhang ◽  
T. Palmer ◽  
A. Farahani
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Dynamic Mechanical Properties ◽  
Fast Fourier Transformation ◽  
Tire Model ◽  
New Approach ◽  
The Time Domain ◽  
Dynamics Analyses ◽  
Free Drop

Abstract A complete finite element tire model was developed for the purposes of vehicle dynamics analyses and full vehicle finite element model real time proving ground simulations. The tire model was validated through simulations of some of the very important global, static and dynamic mechanical properties such as the tire radial and lateral stiffnesses, free-drop test, and low-speed rolling cornering stiffness. The three-dimensional free vibration and harmonic/randomly forced vibrations with ground contact of the tire model were studied here. One of the main purposes for the present study is to provide a new approach toward tire and vehicle NVH studies. All the analyses were nonconventional in the sense that, instead of NASTRAN-type modal analysis, the explicit nonlinear dynamic finite element code LS/DYNA3D was used to conduct all the analyses in the time domain, and the vibration modes were decomposed via fast fourier transformation.

Reproducibility of Resting Heart Rate Variability With Short Sampling Periods

1999 ◽  
Vol 24 (4) ◽  
pp. 337-348 ◽  
Author(s):  
Bonita L. Marks ◽  
J. Timothy Lightfoot
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Frequency Domain ◽  
Time Domain ◽  
Repeated Measures ◽  
Sampling Period ◽  
Fast Fourier Transformation ◽  
Resting Heart Rate ◽  
Resting Heart Rate Variability ◽  
The Time Domain

The purpose of this study was to determine whether resting heart rate variability (HRV) is reproducible with short sampling measurement periods using an office-based personal computer measurement system. Eight healthy active women participated in ECG analyses on 2 days within 1 week under controlled environmental and physiological conditions. After they rested for 10 minutes, a 10-min ECG was recorded. HRV was determined from a 2.5- and 5-min sample period using both time domain variables (meanRR and SDNN) and frequency domain variables (LF, HF, LF:HF). Repeated measures ANOVA found no significant differences between Day 1 and Day 2 for either sampling period (p >= 0.23). For both the 2.5- and 5-min sampling periods, the intraclass correlations between days for the time domain variables showed good reproducibility (R = 0.86-0.90). The reproducibility of the frequency domain variables was only average (R = 0.67-0.96), with the LF:HF ratio yielding the higher R values. Key words: fast Fourier transformation, frequency domain, spectral analysis, time domain, women

Sign in / Sign up

Export Citation Format

Share Document