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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 19 (2019): Issue 2 (April 2019)

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

Calculation of the Impedance of an E-cored Coil Placed Above a Conductive Material with a Surface Hole

Published Online: 02 May 2019
Page range: 43 - 47

Abstract

Abstract

In eddy current testing, probe-coils with the E-type pot core are commonly used for detecting defects in test objects. In this paper, an analytical mathematical model of such a probe placed above a two-layered conductive material with a surface hole has been presented. The final formulas in the closed form that make it possible to calculate the coil impedance were worked out using the truncated region eigenfunction expansion (TREE) method and implemented in Matlab. Changes in resistance and reactance were determined for both material without a hole and for space containing no conductor. The results were compared with those obtained for the air-cored coil and the I-cored coil. The correctness of the calculations was confirmed through experimental measurements and with the finite element method (FEM) in the COMSOL Multiphysics package

Keywords

  • Nondestructive testing
  • eddy current
  • coil impedance
  • ferrite core
  • analytical model
  • truncated region eigenfunction expansion
access type Open Access

A Phase Difference Measurement Method Based on the Extended Kalman Filter for Coriolis Mass Flowmeters

Published Online: 02 May 2019
Page range: 48 - 52

Abstract

Abstract

According to the characteristics of stable single-phase flow, a phase difference measurement method based on the extended Kalman filter is proposed in this paper for use with Coriolis mass flowmeters. Firstly, the Mallat algorithm is applied to filter out interference signals. Then, the frequency and phase difference of the two reconstructed signals are detected through the extended Kalman filter. Compared with the sliding Goertzel algorithm or discrete time Fourier transform, the proposed method does not need to predict the signal frequency and avoids quadratic error. Simulations and experiments show that the proposed method has stronger anti-interference, higher measurement accuracy and lower relative error than the existing method based on the Hilbert transformation.

Keywords

  • Coriolis mass flowmeter
  • phase difference
  • extended Kalman filter
  • Mallat algorithm
access type Open Access

The Combined Relative Uncertainty of Measurement Results by Prototype Semi-Automated Calorimetric Chamber

Published Online: 02 May 2019
Page range: 53 - 60

Abstract

Abstract

The paper presents an evaluation of the combined relative uncertainty of the result of direct step temperature measurements aimed at evaluation of the indirect measurements of the specific thermal capacity of the heat insulating concrete by means of a pair of resistive cable thermometers fitted with Pt100 temperature sensors and integrated into a computer-controlled calorimetric chamber. In particular, it is a proposal of evaluation of the overall relative uncertainty of the measurement of partial temperatures measured in equidistant time steps, in a relatively wider time interval. In practice, the uncertainty of the result of step temperature measurements is most often declared only by the instrument uncertainty specified by the manufacturer. The exact evaluation of the result of the measurements of thermal and temperature material parameters measured by the calorimetric comparison method is required by the fact that the investigated samples are made of newly designed non-tabulated building materials and that the measurements are made by a prototype device.

Keywords

  • Combined relative uncertainty
  • step temperature measurement
  • specific thermal capacity
  • semi-automated calorimetric chamber
access type Open Access

A Cumulative-signals-based Method for Time Delay Estimation

Published Online: 02 May 2019
Page range: 61 - 63

Abstract

Abstract

An original method for time delay estimation is presented. It is based on changing input signals into cumulative ones, followed by determination of inflection points of cumulative curves, and estimation of time delay as time difference of these points’ occurrences. To determine the inflection points, a suitable algorithm is proposed. The preliminary results show that the proposed method is sufficiently efficient, especially in the case of flow measurements based on tomography technique when the cross-correlation function of the signals has no evident peak. This method has no limitations on its application for different types of input signals.

Keywords

  • Cumulative signal
  • time delay
  • inflection point
  • signal processing
access type Open Access

Graphene Langmuir-Schaefer films Decorated by Pd Nanoparticles for NO2 and H2 Gas Sensors

Published Online: 02 May 2019
Page range: 64 - 69

Abstract

Abstract

NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing and decoration of graphene by palladium nanoparticles (NPs). Graphene was deposited onto SiO2 (500 nm)/Si substrates by a modified Langmuir-Schaefer technique. A solution of FLG flakes in 1-methyl-2-pyrrolidone was obtained by a mild sonication of the expanded milled graphite. FLG films were characterized by atomic force microscopy, X-ray diffraction, Raman spectroscopy, and the Brunnauer-Emmett-Teller method. Average FLG flake thickness and lateral dimension were 5 nm and 300 nm, respectively. Drop casting of Pd NP (6–7 nm) solution onto FLG film was applied to decorate graphene by Pd. The room temperature (RT) resistance of the samples was stabilized at 15 kΩ by vacuum annealing. Heating cycles of FLG film revealed its semiconducting character. The gas sensing was tested in the mixtures of dry air with H2 gas (10 to 10 000 ppm) and NO2 gas (2 to 200 ppm) between RT and 200 °C. The response of 26 % to H2 was achieved by FLG with Pd decoration at 70 °C and 10 000 ppm of H2 in the mixture. Pure FLG film did not show any response to H2. The response of FLG with Pd to 6 ppm of NO2 at RT was ≥ 23 %. It is 2 times larger than that of the pure FLG sample. Long term stability of sensors was studied.

Keywords

  • Few-layer graphene
  • Pd nanoparticles
  • gas sensors
  • NO and H sensing
access type Open Access

The Algebraic Structure of Quantity Calculus II: Dimensional Analysis and Differential and Integral Calculus

Published Online: 02 May 2019
Page range: 70 - 78

Abstract

Abstract

In a previous paper, the author has introduced and studied a new algebraic structure which accurately describes the algebra underlying quantity calculus. The present paper is a continuation of that one, which extends the purely algebraic study by adding two more ingredients: an order structure and a topology. The goal is to give a solid justification of dimensional analysis and differential and integral calculus with quantities.

Keywords

  • Quantity calculus
  • algebraic structure
  • dimensional analysis
  • pi-theorem
6 Articles
access type Open Access

Calculation of the Impedance of an E-cored Coil Placed Above a Conductive Material with a Surface Hole

Published Online: 02 May 2019
Page range: 43 - 47

Abstract

Abstract

In eddy current testing, probe-coils with the E-type pot core are commonly used for detecting defects in test objects. In this paper, an analytical mathematical model of such a probe placed above a two-layered conductive material with a surface hole has been presented. The final formulas in the closed form that make it possible to calculate the coil impedance were worked out using the truncated region eigenfunction expansion (TREE) method and implemented in Matlab. Changes in resistance and reactance were determined for both material without a hole and for space containing no conductor. The results were compared with those obtained for the air-cored coil and the I-cored coil. The correctness of the calculations was confirmed through experimental measurements and with the finite element method (FEM) in the COMSOL Multiphysics package

Keywords

  • Nondestructive testing
  • eddy current
  • coil impedance
  • ferrite core
  • analytical model
  • truncated region eigenfunction expansion
access type Open Access

A Phase Difference Measurement Method Based on the Extended Kalman Filter for Coriolis Mass Flowmeters

Published Online: 02 May 2019
Page range: 48 - 52

Abstract

Abstract

According to the characteristics of stable single-phase flow, a phase difference measurement method based on the extended Kalman filter is proposed in this paper for use with Coriolis mass flowmeters. Firstly, the Mallat algorithm is applied to filter out interference signals. Then, the frequency and phase difference of the two reconstructed signals are detected through the extended Kalman filter. Compared with the sliding Goertzel algorithm or discrete time Fourier transform, the proposed method does not need to predict the signal frequency and avoids quadratic error. Simulations and experiments show that the proposed method has stronger anti-interference, higher measurement accuracy and lower relative error than the existing method based on the Hilbert transformation.

Keywords

  • Coriolis mass flowmeter
  • phase difference
  • extended Kalman filter
  • Mallat algorithm
access type Open Access

The Combined Relative Uncertainty of Measurement Results by Prototype Semi-Automated Calorimetric Chamber

Published Online: 02 May 2019
Page range: 53 - 60

Abstract

Abstract

The paper presents an evaluation of the combined relative uncertainty of the result of direct step temperature measurements aimed at evaluation of the indirect measurements of the specific thermal capacity of the heat insulating concrete by means of a pair of resistive cable thermometers fitted with Pt100 temperature sensors and integrated into a computer-controlled calorimetric chamber. In particular, it is a proposal of evaluation of the overall relative uncertainty of the measurement of partial temperatures measured in equidistant time steps, in a relatively wider time interval. In practice, the uncertainty of the result of step temperature measurements is most often declared only by the instrument uncertainty specified by the manufacturer. The exact evaluation of the result of the measurements of thermal and temperature material parameters measured by the calorimetric comparison method is required by the fact that the investigated samples are made of newly designed non-tabulated building materials and that the measurements are made by a prototype device.

Keywords

  • Combined relative uncertainty
  • step temperature measurement
  • specific thermal capacity
  • semi-automated calorimetric chamber
access type Open Access

A Cumulative-signals-based Method for Time Delay Estimation

Published Online: 02 May 2019
Page range: 61 - 63

Abstract

Abstract

An original method for time delay estimation is presented. It is based on changing input signals into cumulative ones, followed by determination of inflection points of cumulative curves, and estimation of time delay as time difference of these points’ occurrences. To determine the inflection points, a suitable algorithm is proposed. The preliminary results show that the proposed method is sufficiently efficient, especially in the case of flow measurements based on tomography technique when the cross-correlation function of the signals has no evident peak. This method has no limitations on its application for different types of input signals.

Keywords

  • Cumulative signal
  • time delay
  • inflection point
  • signal processing
access type Open Access

Graphene Langmuir-Schaefer films Decorated by Pd Nanoparticles for NO2 and H2 Gas Sensors

Published Online: 02 May 2019
Page range: 64 - 69

Abstract

Abstract

NO2 and H2 gas sensing by few-layer graphene (FLG) were studied in dependence on the annealing and decoration of graphene by palladium nanoparticles (NPs). Graphene was deposited onto SiO2 (500 nm)/Si substrates by a modified Langmuir-Schaefer technique. A solution of FLG flakes in 1-methyl-2-pyrrolidone was obtained by a mild sonication of the expanded milled graphite. FLG films were characterized by atomic force microscopy, X-ray diffraction, Raman spectroscopy, and the Brunnauer-Emmett-Teller method. Average FLG flake thickness and lateral dimension were 5 nm and 300 nm, respectively. Drop casting of Pd NP (6–7 nm) solution onto FLG film was applied to decorate graphene by Pd. The room temperature (RT) resistance of the samples was stabilized at 15 kΩ by vacuum annealing. Heating cycles of FLG film revealed its semiconducting character. The gas sensing was tested in the mixtures of dry air with H2 gas (10 to 10 000 ppm) and NO2 gas (2 to 200 ppm) between RT and 200 °C. The response of 26 % to H2 was achieved by FLG with Pd decoration at 70 °C and 10 000 ppm of H2 in the mixture. Pure FLG film did not show any response to H2. The response of FLG with Pd to 6 ppm of NO2 at RT was ≥ 23 %. It is 2 times larger than that of the pure FLG sample. Long term stability of sensors was studied.

Keywords

  • Few-layer graphene
  • Pd nanoparticles
  • gas sensors
  • NO and H sensing
access type Open Access

The Algebraic Structure of Quantity Calculus II: Dimensional Analysis and Differential and Integral Calculus

Published Online: 02 May 2019
Page range: 70 - 78

Abstract

Abstract

In a previous paper, the author has introduced and studied a new algebraic structure which accurately describes the algebra underlying quantity calculus. The present paper is a continuation of that one, which extends the purely algebraic study by adding two more ingredients: an order structure and a topology. The goal is to give a solid justification of dimensional analysis and differential and integral calculus with quantities.

Keywords

  • Quantity calculus
  • algebraic structure
  • dimensional analysis
  • pi-theorem

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