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Journal Details
Format
Journal
eISSN
1335-8871
First Published
07 Mar 2008
Publication timeframe
6 times per year
Languages
English

Search

Volume 20 (2020): Issue 3 (June 2020)

Journal Details
Format
Journal
eISSN
1335-8871
First Published
07 Mar 2008
Publication timeframe
6 times per year
Languages
English

Search

6 Articles
access type Open Access

FSI Computation and Experimental Verification of Fluid Flow in Flexible Tubes

Published Online: 24 Jul 2020
Page range: 104 - 114

Abstract

Abstract

Presented paper is focused on the experimental and computational study of fluid flow in pipes with flexible walls. One possible real example of this phenomenon is the blood flow in arteries or their substitutes in the human body. The artery material itself should be understood as anisotropic and heterogeneous. Therefore, the experiment was carried out on the deforming tube, made of silicone (polydimethylsiloxane - PDMS). Obtained results and observed events were verified by numerical FSI simulations. Due to the large deformations occurring during loading of the tube, it was necessary to work with a dynamic mesh in the CFD part. Based on experimental testing of the tube material, a non-Hookean and Mooney-Rivlin material model were considered. Blood flowing in vessels is a heterogeneous liquid and exhibits non-Newtonian properties. In the real experimental stand has been somewhat simplified. Water, chosen as the liquid, belongs to the Newtonian liquids. The results show mainly comparisons of unsteady velocity profiles between the experiment and the numerical model.

Keywords

  • Fluid Structure Interaction
  • Particle Image Velocimetry
  • simulations
  • experimental verification
  • flexible tubes
access type Open Access

A Linearized Model of FID Signal for Increasing Proton Magnetometer Precision

Published Online: 24 Jul 2020
Page range: 115 - 125

Abstract

Abstract

A linearized model of frequency measurement for the Free Induction Decay (FID) signal is proposed to increase the Proton Magnetometer (PM) precision. First, the nonlinear model of frequency measurement is set up according to the characteristic of the FID signal. Then, according to the error analysis of the MCFM method, the model is linearized on the condition of precision requirement. Furthermore, to reduce the nonlinear error caused by approximate treatment and the trigger time error caused by the random noise, the Least Squares (LS) method is adopted to estimate the slope of the linearized model, and the frequency to be measured is the inverse of the slope. Finally, a PM Prototype is made to verify the effectiveness of the proposed method. Experimental results show that the precision of frequency measurement is obviously increased if the proposed method is adopted for the noised sine signal. Moreover, the RMSD and the NPSD of magnetic-field measurement are about 0.13 nT and 80 pT/Hz1/2, respectively if the proposed method is adopted by PM, which is better than the comparison method.

Keywords

  • Proton Magnetometer
  • FID signal
  • frequency measurement
  • trigger time error
  • least square
access type Open Access

A Comparison of Non-negative Tucker Decomposition and Parallel Factor Analysis for Identification and Measurement of Human EEG Rhythms

Published Online: 24 Jul 2020
Page range: 126 - 138

Abstract

Abstract

Analysis of changes in the brain neural electrical activity measured by the electroencephalogram (EEG) plays a crucial role in the area of brain disorder diagnostics. The elementary latent sources of the brain neural activity can be extracted by a tensor decomposition of continuously recorded multichannel EEG. Parallel factor analysis (PARAFAC) is a powerful approach for this purpose. However, the assumption of the same number of factors in each dimension of the PARAFAC model may be restrictive when applied to EEG data. In this article we discuss the potential benefits of an alternative tensor decomposition method – the Tucker model. We analyze situations, where in comparison to the PARAFAC solution, the Tucker model provides a more parsimonious representation of the EEG data decomposition. We show that this more parsimonious representation of EEG is achieved without reducing the ability to explain variance. We analyze EEG records of two patients after ischemic stroke and we focus on the extraction of specific sensorimotor oscillatory sources associated with motor imagery during neurorehabilitation training. Both models provided consistent results. The advantage of the Tucker model was a compact structure with only two spatial signatures reflecting the expected lateralized activation of the detected subject-specific sensorimotor rhythms.

Keywords

  • multichannel electroencephalogram
  • sensorimotor oscillatory brain activity
  • parallel factor analysis
  • Tucker model
access type Open Access

High-resolution Three-dimensional Surface Imaging Microscope Based on Digital Fringe Projection Technique

Published Online: 24 Jul 2020
Page range: 139 - 144

Abstract

Abstract

The three-dimensional (3-D) micro-scale surface imaging system based on the digital fringe projection technique for the assessments of microfiber and metric screw is presented in this paper. The proposed system comprises a digital light processing (DLP) projector, a set of optical lenses, a microscope, and a charge coupled device (CCD). The digital seven-step fringe patterns from the DLP projector pass through a set of optical lenses before being focused on the target surface. A set of optical lenses is designed for adjustment and size coupling of fringe patterns. A high-resolution CCD camera is employed to picture these distorted fringe patterns. The wrapped phase map is calculated by seven-step phase-shifting calculation from these distorted fringe patterns. The unwrapping calculation with quality guided path is introduced to compute the absolute phase values. The dimensional calibration methods are used to acquire the transformation between real 3-D shape and the absolute phase value. The capability of complex surface measurement for our system is demonstrated by using ISO standard screw M1.6. The experimental results for microfiber with 3 μm diameter indicate that the spatial and vertical resolutions can reach about 3 μm in our system. The proposed system provides a fast digital imaging system to examine the surface features with high-resolution for automatic optical inspection industry.

Keywords

  • Digital imaging
  • fringe projection
  • micro-scale measurement
access type Open Access

Analysis of Periodicities in Surface Topography of Cold rolled sheets Using Data Captured by Camera System

Published Online: 24 Jul 2020
Page range: 145 - 149

Abstract

Abstract

A method for surface analysis of cold rolled sheets is proposed in this paper. The approach is based on a low-cost specially built camera system followed by spectral analysis of the data captured from metal surfaces. The focus is on the changes in the surface topography caused by cold rolling with emphasis towards periodicities in the processed surface. Angular profile of the spectrum is calculated and used to display periodicities in surface topography and show their direction. The results obtained by using the proposed system were compared with results obtained from the optical profilometer MicroProf FRT. The experiments show that cold rolling creates marks on the surface of the material, which represent periodicities that can be effectively detected by the proposed method and camera system. Even though the camera system is not able to measure precise surface roughness, it is able to detect periodicities and the results of spectral analysis are comparable with the results from the optical profilometer.

Keywords

  • Surface analysis
  • cold rolling
  • optical profilometer
  • camera system
  • periodicities
access type Open Access

Novel Method of Contactless Sensing of Mechanical Quantities

Published Online: 24 Jul 2020
Page range: 150 - 156

Abstract

Abstract

This article addresses the method of sensing mechanical quantities, in particular force and pressure, without the electrical connection of the sensing element and the electronics. The information about the mechanical quantity is transmitted only by evaluating the changes in the electromagnetic field created around the sensor. The sensor is designed on the basis of a flexible micro-electro-mechanical element (MEMS), the resonance of which carries the information about the measured quantity.

Keywords

  • Measurement of physical quantities
  • MEMS
  • electromagnetic field
  • reflection parameters
  • S parameters
6 Articles
access type Open Access

FSI Computation and Experimental Verification of Fluid Flow in Flexible Tubes

Published Online: 24 Jul 2020
Page range: 104 - 114

Abstract

Abstract

Presented paper is focused on the experimental and computational study of fluid flow in pipes with flexible walls. One possible real example of this phenomenon is the blood flow in arteries or their substitutes in the human body. The artery material itself should be understood as anisotropic and heterogeneous. Therefore, the experiment was carried out on the deforming tube, made of silicone (polydimethylsiloxane - PDMS). Obtained results and observed events were verified by numerical FSI simulations. Due to the large deformations occurring during loading of the tube, it was necessary to work with a dynamic mesh in the CFD part. Based on experimental testing of the tube material, a non-Hookean and Mooney-Rivlin material model were considered. Blood flowing in vessels is a heterogeneous liquid and exhibits non-Newtonian properties. In the real experimental stand has been somewhat simplified. Water, chosen as the liquid, belongs to the Newtonian liquids. The results show mainly comparisons of unsteady velocity profiles between the experiment and the numerical model.

Keywords

  • Fluid Structure Interaction
  • Particle Image Velocimetry
  • simulations
  • experimental verification
  • flexible tubes
access type Open Access

A Linearized Model of FID Signal for Increasing Proton Magnetometer Precision

Published Online: 24 Jul 2020
Page range: 115 - 125

Abstract

Abstract

A linearized model of frequency measurement for the Free Induction Decay (FID) signal is proposed to increase the Proton Magnetometer (PM) precision. First, the nonlinear model of frequency measurement is set up according to the characteristic of the FID signal. Then, according to the error analysis of the MCFM method, the model is linearized on the condition of precision requirement. Furthermore, to reduce the nonlinear error caused by approximate treatment and the trigger time error caused by the random noise, the Least Squares (LS) method is adopted to estimate the slope of the linearized model, and the frequency to be measured is the inverse of the slope. Finally, a PM Prototype is made to verify the effectiveness of the proposed method. Experimental results show that the precision of frequency measurement is obviously increased if the proposed method is adopted for the noised sine signal. Moreover, the RMSD and the NPSD of magnetic-field measurement are about 0.13 nT and 80 pT/Hz1/2, respectively if the proposed method is adopted by PM, which is better than the comparison method.

Keywords

  • Proton Magnetometer
  • FID signal
  • frequency measurement
  • trigger time error
  • least square
access type Open Access

A Comparison of Non-negative Tucker Decomposition and Parallel Factor Analysis for Identification and Measurement of Human EEG Rhythms

Published Online: 24 Jul 2020
Page range: 126 - 138

Abstract

Abstract

Analysis of changes in the brain neural electrical activity measured by the electroencephalogram (EEG) plays a crucial role in the area of brain disorder diagnostics. The elementary latent sources of the brain neural activity can be extracted by a tensor decomposition of continuously recorded multichannel EEG. Parallel factor analysis (PARAFAC) is a powerful approach for this purpose. However, the assumption of the same number of factors in each dimension of the PARAFAC model may be restrictive when applied to EEG data. In this article we discuss the potential benefits of an alternative tensor decomposition method – the Tucker model. We analyze situations, where in comparison to the PARAFAC solution, the Tucker model provides a more parsimonious representation of the EEG data decomposition. We show that this more parsimonious representation of EEG is achieved without reducing the ability to explain variance. We analyze EEG records of two patients after ischemic stroke and we focus on the extraction of specific sensorimotor oscillatory sources associated with motor imagery during neurorehabilitation training. Both models provided consistent results. The advantage of the Tucker model was a compact structure with only two spatial signatures reflecting the expected lateralized activation of the detected subject-specific sensorimotor rhythms.

Keywords

  • multichannel electroencephalogram
  • sensorimotor oscillatory brain activity
  • parallel factor analysis
  • Tucker model
access type Open Access

High-resolution Three-dimensional Surface Imaging Microscope Based on Digital Fringe Projection Technique

Published Online: 24 Jul 2020
Page range: 139 - 144

Abstract

Abstract

The three-dimensional (3-D) micro-scale surface imaging system based on the digital fringe projection technique for the assessments of microfiber and metric screw is presented in this paper. The proposed system comprises a digital light processing (DLP) projector, a set of optical lenses, a microscope, and a charge coupled device (CCD). The digital seven-step fringe patterns from the DLP projector pass through a set of optical lenses before being focused on the target surface. A set of optical lenses is designed for adjustment and size coupling of fringe patterns. A high-resolution CCD camera is employed to picture these distorted fringe patterns. The wrapped phase map is calculated by seven-step phase-shifting calculation from these distorted fringe patterns. The unwrapping calculation with quality guided path is introduced to compute the absolute phase values. The dimensional calibration methods are used to acquire the transformation between real 3-D shape and the absolute phase value. The capability of complex surface measurement for our system is demonstrated by using ISO standard screw M1.6. The experimental results for microfiber with 3 μm diameter indicate that the spatial and vertical resolutions can reach about 3 μm in our system. The proposed system provides a fast digital imaging system to examine the surface features with high-resolution for automatic optical inspection industry.

Keywords

  • Digital imaging
  • fringe projection
  • micro-scale measurement
access type Open Access

Analysis of Periodicities in Surface Topography of Cold rolled sheets Using Data Captured by Camera System

Published Online: 24 Jul 2020
Page range: 145 - 149

Abstract

Abstract

A method for surface analysis of cold rolled sheets is proposed in this paper. The approach is based on a low-cost specially built camera system followed by spectral analysis of the data captured from metal surfaces. The focus is on the changes in the surface topography caused by cold rolling with emphasis towards periodicities in the processed surface. Angular profile of the spectrum is calculated and used to display periodicities in surface topography and show their direction. The results obtained by using the proposed system were compared with results obtained from the optical profilometer MicroProf FRT. The experiments show that cold rolling creates marks on the surface of the material, which represent periodicities that can be effectively detected by the proposed method and camera system. Even though the camera system is not able to measure precise surface roughness, it is able to detect periodicities and the results of spectral analysis are comparable with the results from the optical profilometer.

Keywords

  • Surface analysis
  • cold rolling
  • optical profilometer
  • camera system
  • periodicities
access type Open Access

Novel Method of Contactless Sensing of Mechanical Quantities

Published Online: 24 Jul 2020
Page range: 150 - 156

Abstract

Abstract

This article addresses the method of sensing mechanical quantities, in particular force and pressure, without the electrical connection of the sensing element and the electronics. The information about the mechanical quantity is transmitted only by evaluating the changes in the electromagnetic field created around the sensor. The sensor is designed on the basis of a flexible micro-electro-mechanical element (MEMS), the resonance of which carries the information about the measured quantity.

Keywords

  • Measurement of physical quantities
  • MEMS
  • electromagnetic field
  • reflection parameters
  • S parameters

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