Rivista e Edizione

Volume 22 (2022): Edizione 6 (December 2022)

Volume 22 (2022): Edizione 5 (October 2022)

Volume 22 (2022): Edizione 4 (August 2022)

Volume 22 (2022): Edizione 3 (June 2022)

Volume 22 (2022): Edizione 2 (April 2022)

Volume 22 (2022): Edizione 1 (February 2022)

Volume 21 (2021): Edizione 6 (December 2021)

Volume 21 (2021): Edizione 5 (October 2021)

Volume 21 (2021): Edizione 4 (August 2021)

Volume 21 (2021): Edizione 3 (June 2021)

Volume 21 (2021): Edizione 2 (April 2021)

Volume 21 (2021): Edizione 1 (February 2021)

Volume 20 (2020): Edizione 5 (October 2020)

Volume 20 (2020): Edizione 4 (August 2020)

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

Volume 20 (2020): Edizione 2 (April 2020)

Volume 20 (2020): Edizione 1 (February 2020)

Volume 19 (2019): Edizione 6 (December 2019)

Volume 19 (2019): Edizione 5 (October 2019)

Volume 19 (2019): Edizione 4 (August 2019)

Volume 19 (2019): Edizione 3 (June 2019)

Volume 19 (2019): Edizione 2 (April 2019)

Volume 19 (2019): Edizione 1 (February 2019)

Volume 18 (2018): Edizione 6 (October 2018)

Volume 18 (2018): Edizione 5 (October 2018)

Volume 18 (2018): Edizione 4 (August 2018)

Volume 18 (2018): Edizione 3 (June 2018)

Volume 18 (2018): Edizione 2 (April 2018)

Volume 18 (2018): Edizione 1 (February 2018)

Volume 17 (2017): Edizione 6 (December 2017)

Volume 17 (2017): Edizione 5 (October 2017)

Volume 17 (2017): Edizione 3 (June 2017)

Volume 17 (2017): Edizione 2 (April 2017)

Volume 17 (2017): Edizione 1 (February 2017)

Volume 16 (2016): Edizione 6 (December 2016)

Volume 16 (2016): Edizione 5 (October 2016)

Volume 16 (2016): Edizione 4 (August 2016)

Volume 16 (2016): Edizione 3 (June 2016)

Volume 16 (2016): Edizione 2 (April 2016)

Volume 16 (2016): Edizione 1 (February 2016)

Volume 15 (2015): Edizione 6 (December 2015)

Volume 15 (2015): Edizione 5 (October 2015)

Volume 15 (2015): Edizione 4 (August 2015)

Volume 15 (2015): Edizione 3 (June 2015)

Volume 15 (2015): Edizione 2 (April 2015)

Volume 15 (2015): Edizione 1 (February 2015)

Volume 14 (2014): Edizione 6 (December 2014)

Volume 14 (2014): Edizione 5 (October 2014)

Volume 14 (2014): Edizione 4 (August 2014)

Volume 14 (2014): Edizione 3 (June 2014)

Volume 14 (2014): Edizione 2 (April 2014)

Volume 14 (2014): Edizione 1 (February 2014)

Volume 13 (2013): Edizione 6 (December 2013)

Volume 13 (2013): Edizione 5 (October 2013)

Volume 13 (2013): Edizione 4 (August 2013)

Volume 13 (2013): Edizione 3 (June 2013)

Volume 13 (2013): Edizione 2 (April 2013)

Volume 13 (2013): Edizione 1 (February 2013)

Volume 12 (2012): Edizione 6 (December 2012)

Volume 12 (2012): Edizione 5 (October 2012)

Volume 12 (2012): Edizione 4 (August 2012)

Volume 12 (2012): Edizione 3 (June 2012)

Volume 12 (2012): Edizione 2 (April 2012)

Volume 12 (2012): Edizione 1 (February 2012)

Volume 11 (2011): Edizione 6 (December 2011)

Volume 11 (2011): Edizione 5 (October 2011)

Volume 11 (2011): Edizione 4 (August 2011)

Volume 11 (2011): Edizione 3 (June 2011)

Volume 11 (2011): Edizione 2 (April 2011)

Volume 11 (2011): Edizione 1 (February 2011)

Volume 10 (2010): Edizione 6 (December 2010)

Volume 10 (2010): Edizione 5 (October 2010)

Volume 10 (2010): Edizione 4 (August 2010)

Volume 10 (2010): Edizione 3 (June 2010)

Volume 10 (2010): Edizione 2 (April 2010)

Volume 10 (2010): Edizione 1 (February 2010)

Volume 9 (2009): Edizione 6 (December 2009)

Volume 9 (2009): Edizione 5 (October 2009)

Volume 9 (2009): Edizione 4 (August 2009)

Volume 9 (2009): Edizione 3 (June 2009)

Volume 9 (2009): Edizione 2 (April 2009)

Volume 9 (2009): Edizione 1 (February 2009)

Volume 8 (2008): Edizione 6 (December 2008)

Volume 8 (2008): Edizione 5 (October 2008)

Volume 8 (2008): Edizione 4 (August 2008)

Volume 8 (2008): Edizione 3 (June 2008)

Volume 8 (2008): Edizione 2 (April 2008)

Volume 8 (2008): Edizione 1 (February 2008)

Dettagli della rivista
Formato
Rivista
eISSN
1335-8871
Pubblicato per la prima volta
07 Mar 2008
Periodo di pubblicazione
6 volte all'anno
Lingue
Inglese

Cerca

Volume 18 (2018): Edizione 6 (October 2018)

Dettagli della rivista
Formato
Rivista
eISSN
1335-8871
Pubblicato per la prima volta
07 Mar 2008
Periodo di pubblicazione
6 volte all'anno
Lingue
Inglese

Cerca

6 Articoli
Accesso libero

Confidence Region for Calibration Function Coefficients

Pubblicato online: 30 Nov 2018
Pagine: 227 - 235

Astratto

Abstract

The paper deals with the comparative calibration model, i.e. with a situation when both variables are subject to errors. The calibration function is supposed to be a polynomial. From the statistical point of view, the model after linearization could be represented by the linear errors-in-variables (EIV) model. There are two different ways of using the Kenward and Roger’s type approximation to obtain the confidence region for calibration function coefficients. These two confidence regions are compared on a small simulation study. Calibration process and process of measuring with calibrated device are described under the assumption that the measuring errors are normally distributed.

Parole chiave

  • Calibration
  • calibration function parameters
  • confidence region
  • measurements with calibrated device
Accesso libero

Digital Demodulator of the Quadrature Amplitude Modulation Signals

Pubblicato online: 30 Nov 2018
Pagine: 236 - 242

Astratto

Abstract

In this paper, the digital algorithm and the device for the demodulation of the quadrature amplitude modulation signals are considered. The fundamental advantages of our approach are simple hardware implementation, minimal number of arithmetic operations required over the signal period as well as the potential interference immunity in the presence of Gaussian noise. The expressions have been found for the error probability and their inaccuracy has been estimated. By means of the statistical simulation methods, the practical interference immunity of the introduced demodulator, together with the influence of phase locking errors have been tested. The introduced demodulator can be implemented either as a device independent from the programmable logic devices, or as an installation unit of the receiver equipment.

Parole chiave

  • Quadrature amplitude modulation
  • coherent signal processing
  • noise interference
  • interference immunity
  • phase locking
Accesso libero

Blade Tip-timing Technology with Multiple Reference Phases for Online Monitoring of High-speed Blades under Variable-speed Operation

Pubblicato online: 30 Nov 2018
Pagine: 243 - 250

Astratto

Abstract

High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

Parole chiave

  • BTT technology
  • variable speed
  • online monitoring
  • multiple reference phases (MRP)
Accesso libero

Proposed Use of Monte Carlo Simulated Images to Evaluate the Accuracy of Measurements on X-Ray Computed Tomography

Pubblicato online: 30 Nov 2018
Pagine: 251 - 255

Astratto

Abstract

X-ray computed tomography (CT) is increasingly recognized as a promising measuring technique for dimensional metrology. Various methods are being developed to improve measurement accuracy. Tests of new methods for such applications include accuracy evaluation with the use of calibrated workpieces; however, the internal algorithms of image acquisition and data processing might influence the experimental error, and then also the comparison of methods at different CTs. The accuracy of the results of tomographic measurements is influenced by many factors, one of which is the setting of the threshold value. The article presents the results of an attempt to use Monte Carlo simulated images to estimate deviations to determine threshold values to improve measurement accuracy and additionally, to estimate the impact of data processing. The differences of the results obtained from the simulated images were up to 4 % larger than those from tomographic images. It was caused by degradation of the image contrast by scattered radiation.

Parole chiave

  • Monte Carlo Methods
  • X-ray computed tomography
  • accuracy of measurements
  • threshold values
Accesso libero

Electrostatic Force Microscopy Measurement System for Micro-topography of Non-conductive Devices

Pubblicato online: 30 Nov 2018
Pagine: 256 - 261

Astratto

Abstract

A home-made electrostatic force microscopy (EFM) system is described which is directed toward assessment of the microscopic geometry of the surface of specimens made of non-conductive material with a large thickness. This system is based on the variation in the electrostatic force between the conductive probe and the non-conductive specimen in order to get its surface morphology. First, based on the principle of dielectric polarization, the variation rules of the electrostatic force between the charged probe and the non-conductive specimen were studied. Later, a special tuning fork resonant probe unit made of quartz crystal was fabricated for measurement of the electrostatic force, and the scanning probe microscopic system in the constant force mode was constructed to characterize the three-dimensional micro-topography of the surface of the specimen. Finally, this system was used to perform scanning measurement experiments on the indented surface of the specimen made of the polyvinyl chloride (PVC) material with thickness 3 mm. In the present experimental system, when the external voltage was 100 V and the distance from the probe tip to the specimen surface approximately 100 nm, the variance in the resonant frequency of the probe unit was around 0.5 Hz. These results indicate that this home-made EFM system can effectively characterize the micro-topography of the non-conductive specimen with very large thickness which is above several millimeters.

Parole chiave

  • Electrostatic force microscopy
  • surface morphology
  • precise measurement
  • scanning probe microscopy
Accesso libero

Time-Efficient Perfusion Imaging Using DCE- and DSC-MRI

Pubblicato online: 30 Nov 2018
Pagine: 262 - 271

Astratto

Abstract

Dynamic contrast enhanced MRI (DCE-MRI) and dynamic susceptibility contrast MRI (DSC-MRI) are perfusion imaging techniques used mainly for clinical and preclinical measurement of vessel permeability and capillary blood flow, respectively. It is advantageous to apply both methods to exploit their complementary information about the perfusion status of the tissue. We propose a novel acquisition method that combines advantages of the current simultaneous and sequential acquisition. The proposed method consists of a DCE-MRI acquisition interrupted by DSC-MRI acquisition. A new method for processing of the DCE-MRI data is proposed which takes the interleaved acquisition into account. Analysis of both the DCE- and DSC-MRI data is reformulated so that they are approximated by the same pharmacokinetic model (constrained distributed capillary adiabatic tissue homogeneity model). This provides a straightforward evaluation of the methodology as some of the estimated DCE- and DSC-MRI perfusion parameters should be identical. Evaluation on synthetic data showed an acceptable precision and no apparent bias introduced by the interleaved character of the DCE-MRI acquisition. Intravascular perfusion parameters obtained from clinical glioma data showed a fairly high correlation of blood flow estimates from DCE- and DSC-MRI, however, an unknown scaling factor was still present mainly because of the tissue-specific r2*$r_2^*$ relaxivity. The results show validity of the proposed acquisition method. They also indicate that simultaneous processing of both DCE- and DSC-MRI data with joint estimation of some perfusion parameters (included in both DCE- and DSC-MRI) might be possible to increase the reliability of the DCE- and DSC-MRI methods alone.

Parole chiave

  • Perfusion imaging
  • contrast agents
  • brain tumors
  • DCE-MRI
  • DSC-MRI
6 Articoli
Accesso libero

Confidence Region for Calibration Function Coefficients

Pubblicato online: 30 Nov 2018
Pagine: 227 - 235

Astratto

Abstract

The paper deals with the comparative calibration model, i.e. with a situation when both variables are subject to errors. The calibration function is supposed to be a polynomial. From the statistical point of view, the model after linearization could be represented by the linear errors-in-variables (EIV) model. There are two different ways of using the Kenward and Roger’s type approximation to obtain the confidence region for calibration function coefficients. These two confidence regions are compared on a small simulation study. Calibration process and process of measuring with calibrated device are described under the assumption that the measuring errors are normally distributed.

Parole chiave

  • Calibration
  • calibration function parameters
  • confidence region
  • measurements with calibrated device
Accesso libero

Digital Demodulator of the Quadrature Amplitude Modulation Signals

Pubblicato online: 30 Nov 2018
Pagine: 236 - 242

Astratto

Abstract

In this paper, the digital algorithm and the device for the demodulation of the quadrature amplitude modulation signals are considered. The fundamental advantages of our approach are simple hardware implementation, minimal number of arithmetic operations required over the signal period as well as the potential interference immunity in the presence of Gaussian noise. The expressions have been found for the error probability and their inaccuracy has been estimated. By means of the statistical simulation methods, the practical interference immunity of the introduced demodulator, together with the influence of phase locking errors have been tested. The introduced demodulator can be implemented either as a device independent from the programmable logic devices, or as an installation unit of the receiver equipment.

Parole chiave

  • Quadrature amplitude modulation
  • coherent signal processing
  • noise interference
  • interference immunity
  • phase locking
Accesso libero

Blade Tip-timing Technology with Multiple Reference Phases for Online Monitoring of High-speed Blades under Variable-speed Operation

Pubblicato online: 30 Nov 2018
Pagine: 243 - 250

Astratto

Abstract

High-speed blades form core mechanical components in turbomachines. Research concerning online monitoring of operating states of such blades has drawn increased attention in recent years. To this end, various methods have been devised, of which, the blade tip-timing (BTT) technique is considered the most promising. However, the traditional BTT method is only suitable for constant-speed operations. But in practice, the rotational speed of turbomachine blades is constantly changing under the influence of external factors, which lead to unacceptable errors in measurement. To tackle this problem, a new BTT method based on multi-phases is proposed. A plurality of phases was arranged as evenly as possible on the rotating shaft to determine the rotation speed. Meanwhile, the corresponding virtual reference point was determined in accordance with the number of blades between consecutive phases. Based on these reference points, equations to measure displacement due to blade vibrations were deduced. Finally, mathematical modeling, numerical simulation and experimental tests were performed to verify the validity of the proposed method. Results demonstrate that the error in measurement induced when using the proposed method is less than 1.8 %, which is much lower compared to traditional methods utilized under variable-speed operation.

Parole chiave

  • BTT technology
  • variable speed
  • online monitoring
  • multiple reference phases (MRP)
Accesso libero

Proposed Use of Monte Carlo Simulated Images to Evaluate the Accuracy of Measurements on X-Ray Computed Tomography

Pubblicato online: 30 Nov 2018
Pagine: 251 - 255

Astratto

Abstract

X-ray computed tomography (CT) is increasingly recognized as a promising measuring technique for dimensional metrology. Various methods are being developed to improve measurement accuracy. Tests of new methods for such applications include accuracy evaluation with the use of calibrated workpieces; however, the internal algorithms of image acquisition and data processing might influence the experimental error, and then also the comparison of methods at different CTs. The accuracy of the results of tomographic measurements is influenced by many factors, one of which is the setting of the threshold value. The article presents the results of an attempt to use Monte Carlo simulated images to estimate deviations to determine threshold values to improve measurement accuracy and additionally, to estimate the impact of data processing. The differences of the results obtained from the simulated images were up to 4 % larger than those from tomographic images. It was caused by degradation of the image contrast by scattered radiation.

Parole chiave

  • Monte Carlo Methods
  • X-ray computed tomography
  • accuracy of measurements
  • threshold values
Accesso libero

Electrostatic Force Microscopy Measurement System for Micro-topography of Non-conductive Devices

Pubblicato online: 30 Nov 2018
Pagine: 256 - 261

Astratto

Abstract

A home-made electrostatic force microscopy (EFM) system is described which is directed toward assessment of the microscopic geometry of the surface of specimens made of non-conductive material with a large thickness. This system is based on the variation in the electrostatic force between the conductive probe and the non-conductive specimen in order to get its surface morphology. First, based on the principle of dielectric polarization, the variation rules of the electrostatic force between the charged probe and the non-conductive specimen were studied. Later, a special tuning fork resonant probe unit made of quartz crystal was fabricated for measurement of the electrostatic force, and the scanning probe microscopic system in the constant force mode was constructed to characterize the three-dimensional micro-topography of the surface of the specimen. Finally, this system was used to perform scanning measurement experiments on the indented surface of the specimen made of the polyvinyl chloride (PVC) material with thickness 3 mm. In the present experimental system, when the external voltage was 100 V and the distance from the probe tip to the specimen surface approximately 100 nm, the variance in the resonant frequency of the probe unit was around 0.5 Hz. These results indicate that this home-made EFM system can effectively characterize the micro-topography of the non-conductive specimen with very large thickness which is above several millimeters.

Parole chiave

  • Electrostatic force microscopy
  • surface morphology
  • precise measurement
  • scanning probe microscopy
Accesso libero

Time-Efficient Perfusion Imaging Using DCE- and DSC-MRI

Pubblicato online: 30 Nov 2018
Pagine: 262 - 271

Astratto

Abstract

Dynamic contrast enhanced MRI (DCE-MRI) and dynamic susceptibility contrast MRI (DSC-MRI) are perfusion imaging techniques used mainly for clinical and preclinical measurement of vessel permeability and capillary blood flow, respectively. It is advantageous to apply both methods to exploit their complementary information about the perfusion status of the tissue. We propose a novel acquisition method that combines advantages of the current simultaneous and sequential acquisition. The proposed method consists of a DCE-MRI acquisition interrupted by DSC-MRI acquisition. A new method for processing of the DCE-MRI data is proposed which takes the interleaved acquisition into account. Analysis of both the DCE- and DSC-MRI data is reformulated so that they are approximated by the same pharmacokinetic model (constrained distributed capillary adiabatic tissue homogeneity model). This provides a straightforward evaluation of the methodology as some of the estimated DCE- and DSC-MRI perfusion parameters should be identical. Evaluation on synthetic data showed an acceptable precision and no apparent bias introduced by the interleaved character of the DCE-MRI acquisition. Intravascular perfusion parameters obtained from clinical glioma data showed a fairly high correlation of blood flow estimates from DCE- and DSC-MRI, however, an unknown scaling factor was still present mainly because of the tissue-specific r2*$r_2^*$ relaxivity. The results show validity of the proposed acquisition method. They also indicate that simultaneous processing of both DCE- and DSC-MRI data with joint estimation of some perfusion parameters (included in both DCE- and DSC-MRI) might be possible to increase the reliability of the DCE- and DSC-MRI methods alone.

Parole chiave

  • Perfusion imaging
  • contrast agents
  • brain tumors
  • DCE-MRI
  • DSC-MRI

Pianifica la tua conferenza remota con Sciendo